JP2001525613A - Titanium chemical vapor deposition on wafer including in-situ pre-cleaning step - Google Patents

Abstract

  (57) [Summary] A multi-step chemical vapor deposition method for depositing a titanium film on a substrate. The first step of the deposition process includes a plasma pretreatment step in which a pretreatment gas including a hydrogen-containing gas and an inert gas are flowed into a deposition area of the substrate processing chamber. During the first deposition step, a plasma is formed from the pre-treatment gas and maintained for at least about 5 seconds to etch any remaining insulating material in the contact areas of the substrate and to clean the contact areas before depositing the titanium layer. Next, during a second deposition step, a titanium-containing source and a reducing agent are introduced into the deposition area, the plasma formed in the first step is maintained, and a titanium layer on the substrate is deposited. In a preferred embodiment, the hydrogen-containing source contained in the pretreatment gas and the reducing agent in the treatment gas of the second deposition step are H _TwoIs the same continuous flow.   

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION The present invention relates to the deposition of a refractory metal layer on a semiconductor substrate. More specifically,
The present invention relates to an improved chemical vapor deposition method and apparatus for depositing a titanium layer with improved sheet resistance uniformity and good contact bottom coverage.
INDUSTRIAL APPLICABILITY The present invention is applicable to various titanium deposition processes, and is practically applicable to a process including titanium tetrachloride (TiCl ₄ ) as a titanium source.

[0002] One of the main manufacturing steps of a current semiconductor device is a step of forming various layers including an insulating layer and a metal layer on a semiconductor substrate. As is known, these layers are formed, among other methods, by chemical vapor deposition (CVD).
Deposition) or physical vapor deposition (PVD)
). In a conventional thermal CVD process, a reactive gas is supplied to the substrate surface, and a heat-induced chemical reaction occurs to form a desired film. In a conventional plasma CVD process, a controlled plasma is formed to decompose and / or excite a reactive species to form a desired film. Generally, the reaction rates of heat treatment and plasma treatment are as follows:
It may be controlled by controlling one or more of temperature, pressure, plasma density, reactant gas flow, power frequency, power level, physical shape of the chamber, and the like.

In a PVD system, for example, a target (a plate of material to be deposited) is connected to a negative voltage supply (direct current (DC) or high frequency (RF)) and faces the target. The substrate holder is grounded, floating, biased, heated, cooled, or provided in some combination. A gas such as argon is introduced into the PVD system and is typically a few millitorr (mt)
(orr) to about 100 mtorr, and glow discharge occurs in the medium and is maintained. When the glow discharge starts, positive ions collide with the target, and the target atoms are removed by momentum transport. These target atoms are sequentially deposited on the substrate placed on the substrate holder to form a thin film.

For several decades since the semiconductor device was first introduced, the shape size of the semiconductor device has been rapidly reduced. Today's wafer fabs routinely produce 0.5 μm and smaller 0.35 μm feature size devices, and in the near future factories will produce smaller feature sizes. There will be. As feature sizes shrink and integration densities increase, there is a growing interest in very important issues not previously considered in the semiconductor industry. For example, features with significantly higher integration densities have higher aspect ratios (e.g.,
Such problems are about 6: 1 for devices with 0.35 μm feature size). (The aspect ratio is the ratio of the height and width of two adjacent steps.)
High aspect ratio features, such as gaps, require that layers be deposited and properly filled in many applications.

[0005] The demands for the manufacture of such highly integrated devices are of course quite stringent, and conventional substrate processing systems are insufficient to meet such demands.
In addition, as device designs evolve, more sophisticated capabilities are required of substrate processing systems used to deposit films with the properties required to implement these devices. For example, the use of titanium has been more integrated into integrated circuit manufacturing processes. For use in semiconductor devices, titanium has many desirable features. For example, titanium may act as a diffusion barrier between a gold bonding pad and a semiconductor, preventing one atomic species from migrating to an adjacent atomic species.
In addition, titanium may be used to increase the adhesion between two layers such as silicon and aluminum. Furthermore, by using titanium, by mixing with the silicon by alloying of titanium silicide (TiSi _x), for example, ohmic contact is formed. One common deposition system used to deposit such titanium films is a titanium sputtering deposition (PVD) system. However, such sputtering systems are often insufficient to perform device formation with more sophisticated processing and manufacturing requirements. In particular, sputtering can damage already deposited layers and structures of such devices, leading to reduced performance and / or yield. Also, in the titanium sputtering system,
Sputtering produces a shadowing effect, which may make it impossible to deposit a uniform conformal layer in a gap having a high aspect ratio.

[0006] Compared to sputtering systems, plasma enhanced chemical vapor deposition (PECVD)
: Plasma-Enhanced Chemical Vapor Deposition) system may be more suitable for forming titanium films on substrates with high aspect ratio gaps. As is well known, plasma is a mixture of ions and gas molecules,
For example, it may be formed by applying energy, such as radio frequency (RF) energy, to a process gas in a deposition chamber under appropriate conditions, such as chamber pressure, temperature, and RF power. When the plasma reaches a threshold density, it becomes self-sustaining, known to form a glow discharge (often referred to as "bombardment" or "ignition" of the plasma). This RF energy raises the energy state of the molecules of the processing gas, and forms ionic species from the molecules. Both excited molecules and ionic species
Since the reactivity is higher than that of the normal processing gas, a desired film can be easily formed. Plasma also enhances the mobility of reactive species across the substrate surface during the formation of a titanium film,
There is an advantage that a film having a good gap filling ability can be obtained.

[0007] One known CVD method for depositing titanium films includes standard PECVD.
The process includes forming a plasma from a process gas including a TiCl ₄ source gas and a hydrogen (H ₂ ) reactive gas. The P of such TiCl ₄ / H ₂
The ECVD process allows the deposition of a titanium film with good via fill, uniformity, and contact resistance characteristics, creating a film that can be suitably used in the manufacture of many different commercially available integrated circuits. Whether or not these processes are suitable for certain manufacturing uses, further enhance via fill, uniformity and contact resistance of titanium films such as those deposited from TiCl ₄ and H ₂ precursor gases. It is still required.

SUMMARY OF THE INVENTION The present invention relates to a CVD process with an improved method of depositing a titanium film and an improved apparatus for performing this deposition. According to the method of the present invention, a chemical vapor deposition method including multi-steps for depositing a titanium film on a substrate is taught. Usually, the titanium layer of the present invention is deposited as a first layer in a contact region formed by etching an insulating film such as a silicon oxide film on a substrate, but can be used in other titanium deposition applications. It is.

The first step of the multi-step deposition method includes a plasma pre-treatment step,
A pre-processing gas including a hydrogen-containing gas and an inert gas flows into the deposition area of the substrate processing chamber. During this first deposition step, a plasma is formed from the pre-treatment gas and maintained for at least about 5 seconds to etch away any insulating material remaining in the contact area of the substrate and to remove the contact area before depositing the titanium layer. Wash. Next, during the second deposition step after the completion of the first step, a raw material containing titanium and a reducing agent are introduced into the deposition area, and the plasma formed in the first step is maintained, so that the plasma is formed on the substrate. Deposit a titanium layer. In a preferred embodiment, the hydrogen-containing material included in the pre-treatment gas, the reducing agent within the process gas in the second step is the same continuous flow of H _2. In another preferred embodiment, the plasma pretreatment step lasts about 5 to 60 seconds.

[0010] Optionally, the titanium layer may be passivated so as not to be contaminated with air-borne impurities such as oxygen and / or carbon. To passivate,
Either (1) flowing nitrogen and / or (2) implanting nitrogen plasma into the deposition area close to the titanium layer are performed.
By exposing the titanium layer to nitrogen, a thin layer of titanium nitride is formed on the surface of the titanium layer. The titanium nitride layer passivates the titanium layer so that impurities do not adsorb into the titanium layer. As described above, the properties of the titanium layer such as surface resistance are stable, and the surface for continuously depositing the titanium nitride barrier layer is in a clean state. Furthermore, by creating a stable and passivated titanium layer, the wafer can be exposed to the atmosphere without the risk of contamination of the titanium layer when moving to another processing chamber for further processing. . For this reason, the chamber of the present invention can be used as a stand-alone titanium film deposition chamber.

[0011] According to another embodiment of the method of the present invention, the flow of the titanium source is started at least 6 to 8 seconds before the second deposition step. However, instead of flowing into the chamber in this way, it flows into the front line. In this way, the inflow of the titanium source is stabilized prior to the deposition step, further improving the film uniformity of the titanium film deposited on the plurality of wafers of the extended wafer run.

[0012] These and other embodiments of the present invention, as well as its advantages and features, are described in more detail in conjunction with the following description and the accompanying drawings.

Detailed Description of Preferred Embodiments I. INTRODUCTION The present invention allows better deposition of titanium films by pre-treating the substrate on which the titanium film is deposited in a pre-treatment plasma step. The present inventors have determined that such a plasma pre-treatment step involves the formation of a multilayer stack (e.g., a titanium / titanium nitride stack, etc.) in ohmic contact with the semiconductor substrate at a contact region that is etched through an insulating layer, such as a silicon oxide layer. It has been found to be particularly beneficial when a partially deposited titanium layer is used. In the plasma pretreatment step, any residual insulating material remaining in the contact areas of the substrate is etched and the contact areas are cleaned before the titanium layer is deposited. After the plasma pretreatment step is completed, a titanium layer is deposited by introducing a titanium-containing source gas while maintaining the previously formed plasma. The titanium layer deposited by the method of the present invention is suitable for use in manufacturing integrated circuits having feature sizes of 0.35 to 0.11 microns or less. The invention can also be used to deposit titanium films in conventional design CVD chambers using readily available gases.

II. Typical Example of CVD Chamber FIG. 1A shows a simplified parallel plate chemical vapor deposition (C) where a titanium layer is deposited according to the present invention.
1 illustrates one embodiment of a VD) system 10. The CVD system 10 includes a reaction chamber 30 that receives gas from a gas delivery system 89 via gas lines 92A-C (other lines may be present but not shown). A vacuum system 88 is used to maintain the reaction chamber at a particular pressure, removing gaseous by-products and spent gas from the reaction chamber. A radio frequency power is applied to the reaction chamber by a low frequency RF power supply 5 to form a plasma from the deposition gas during titanium deposition and from the reaction chamber cleaning gas during the chamber cleaning operation. The heat exchange system 6 employs a liquid heat transfer medium, such as water or a mixture of water and glycol, to remove heat from the reaction chamber and to keep certain portions of the reaction chamber cool properly. Room temperature can be maintained at a stable process temperature or the reaction chamber portion can be heated if necessary. Processor 85 controls the operation of the reaction chamber and subsystems according to instructions stored in memory 86 via control lines 3, 3A-D (only some of which are shown).

The gas transfer system 89 includes a gas supply panel 90 and gas or liquid sources (sources) 91A to 91C (additional sources may be added as necessary), and is used for a specific application. Gas or liquid depending on the desired process. The temperature of the liquid source is much higher than room temperature to minimize source fluctuations due to room temperature changes. The gas supply panel 90 includes a supply line 92A-C for mixing and transporting to the central gas inlet 44 of the gas supply cover plate 45,
There are mixing systems that receive the deposition process and carrier gas (or vaporized liquid) from sources 91A-C. Fluid source is heated, it may be to generate steam at a pressure above the chamber operating pressure, or He, Ar, or a carrier gas such as N ₂ is then bubbled in the liquid (or heated liquid) steam May be generated. Generally, each process gas supply line has a shutoff valve (not shown) used to automatically or manually shut off the process gas flow, and a gas or liquid flow rate through the supply line. A mass flow controller (not shown) to measure is included. When harmful gases (eg, ozone gas, halogenated gas, etc.) are used in the process, several shut-off valves may be located in the nuclear gas supply line in conventional designs. For example, deposition and carrier gases including titanium tetrachloride (TiCl ₄ ) vapor, hydrogen (H ₂ ), helium (He), argon (Ar), nitrogen (N ₂ ) and / or other dopants and reaction sources. The rate at which is supplied to the reaction chamber 30 is also controlled by a liquid or gas mass controller (MFC) (not shown) and / or valves (not shown). In a preferred embodiment, the gas mixing system (not shown) includes a liquid injection system for vaporizing the reaction liquid (eg, TiCl ₄ ). Liquid injection systems are preferred because they allow better control of the amount of reaction liquid introduced into the gas mixing system as compared to bubbler-type sources. Next, the vaporized gas is mixed with a carrier gas such as helium in a gas panel, and is then conveyed to a supply line. Of course, other compounds may also be used as a deposition source.

The heat exchange system 6 transports coolant to various elements of the reaction chamber 30 to cool these components during high temperature processing. The heat exchange system 6 lowers the temperature of these reaction chamber components so that high temperature processing does not cause undesirable deposition on these components. The heat exchange system 6 includes a coolant manifold (not shown) for delivering coolant to a gas delivery system including a face plate 40 (described below).
And a connection (not shown) for supplying cooling water via the connector. A water flow detector detects water flow from a heat exchanger (not shown) to the housing assembly.

The wafer 36 in the wafer pocket 34 is supported by the resistance-heated pedestal 32. As shown in FIG. 1B schematically showing a cross-sectional view of the pedestal 32,
The pedestal 32 includes an embedded electrode 22 such as an embedded molybdenum mesh, and a heating element 33 such as an embedded molybdenum wire coil. The pedestal 32 is preferably made of aluminum nitride to withstand high processing temperatures, and further has a water-cooled aluminum shaft 28 (not shown in FIG. 1B but shown in FIG. 1C) that meshes with the lift motor. It is preferably diffusion bonded to a ceramic support stem 26 fixed to the support stem 26. The ceramic support stem 26 and aluminum shaft 28 have a central passage occupied by a nickel rod 25 that grounds the electrode 22. The central passage is maintained at atmospheric pressure to prevent corrosion of the metal-to-metal connection.

A ceramic pedestal 32 is manufactured so that the RF electrode 22 is embedded at a uniform depth below the surface of the substrate holder so that the capacitance is constant. The RF electrode 22, depending on the ceramic material, may be located at a minimum depth to prevent the thin ceramic layer covering the RF electrode 22 from cracking or peeling while providing maximum capacitance. preferable. In one embodiment, the RF electrode 22 is embedded about 40 mils below the upper surface of the pedestal 32. The ceramic pedestal 32 is assigned to the same assignee as the present application and Sebastien
Raoux, Mandar Mudholkar, William N. Taylor, Mark Fodor, Judy Huang, David Sil
vetti, David Cheung, Kevin Fairbairn is co-inventor, "mixed frequency CVD process and apparatus (Mixed Frequency CVD Process And Apparatus)" entitled December 1, 1997 U.S. Patent Application No. / No., filed (Attorney Case No. 16301-019900), the entire contents of which are incorporated herein by reference.

The pedestal 32 may be moved vertically between a processing position (the position shown in FIG. 1C) and a further lowered loading position (not shown) using a self-adjusting mechanism. As for the self-regulation mechanism, it is assigned to the same assignee as the present application,
199 entitled "Self-Aligning Lift Mechanism"
It is described in more detail in U.S. patent application Ser. No. 08 / 738,240, filed Oct. 25, 2006, the entire contents of which are incorporated herein by reference. Referring to FIG. 1C, a lift pin 38 (only two shown) is slidably mounted within the pedestal 32, but with a conical head at the upper end of the pin. So that it does not fall off. The lower end of the lift pin 38 is engaged with a vertically movable lift ring 39 and is lifted above the surface of the pedestal. When the pedestal 32 is in the lower loading position (slightly below the slit valve 56), a robot blade (not shown) interlocking with the lift pins and the lift ring transfers the wafer 36 through the slit valve 56 to the reaction chamber. And is carried out of the reaction chamber, and is vacuum-sealed so that gas does not flow into or out of the reaction chamber through the slit valve 56. Lift pins 38 lift the inserted wafer (not shown) from the robot blade, and then the pedestal rises, lifting the wafer away from the lift pins into a wafer pocket on the upper surface of the pedestal. A suitable robot transport assembly
Maydan, U.S. Pat. No. 4,951,601, assigned to the same assignee as the present application.
And the entire contents of which are incorporated herein by reference.

The pedestal 32 lifts the wafer 36 further to a processing position and places it on a gas distribution faceplate (hereinafter “shower head”) 40 that includes a number of holes or passages 42 for injecting processing gas into the processing area 58. Bring them closer. The processing gas passes through the central gas inlet 44 in the gas supply cover plate 45 of the first disc-shaped manifold 48, and then passes through the passage 50 in the deflector (or blocking plate) 52 of the second disc-shaped manifold 54. And is injected into the reaction chamber 30.

As indicated by the arrows, processing gas is injected from holes 42 in the showerhead 40 into a processing area 58 (also referred to as a “deposition area”) between the showerhead and the pedestal, A reaction occurs on the surface of the wafer 36. The wafer 36 and process gas by-products on the flow restrictor ring 46 (described in more detail below) located on the upper periphery of the pedestal 32 when the pedestal is in the process position are both of these. Is immediately drained out from corner to corner. Thereafter, process gas flows into the pump channel 60 through a choke hole 50 formed between the top of the flow restrictor ring 46 and the bottom of the annular isolator 53. Upon entering the pump channel 60, the exhaust gas flows around the processing chamber and is exhausted by the vacuum pump 82. The pump channel 60 is connected to the pump plenum 76 via the exhaust hole 74. Exhaust holes 74 limit the flow between the pump channel and the pump plenum. Valve 78 gates exhaust from exhaust vent 80 to vacuum pump 82. A system controller (not shown in FIG. 3) is a memory that compares a measurement signal from a pressure sensor (not shown) such as a manometer with a desired value stored in the memory or generated by a pressure control program. The throttle valve 83 is controlled in accordance with a pressure control program stored in (not shown).

The sides of the annular pump channel 60 are generally defined by a ceramic ring 64, a chamber lid liner 70, a chamber wall liner 72 and an annular isolator 53. FIG. 1E is a simplified, partially cutaway perspective view of pedestal 32, flow restrictor ring 46, liners 70 and 72, isolator 53, ceramic ring 64 and pump channel 60. FIG. This figure shows a state 84 in which the processing gas flows in the direction of the wafer 36 from the nozzle 42 in the shower head 40 and then flows radially outward on the wafer 36. Thereafter, the gas flow is deflected upward and into the pump channel 60 beyond the upper surface of the restrictor ring 46. In the pump channel 60, gas flows along the circumferential passage 86 in the direction of the vacuum pump.

The pump channel 60 and its components are for directing process gases and by-products into the exhaust system to minimize the effects of unwanted film deposition. A "dead zone" is formed in the exhaust flow where there is little gas movement. These dead zones are close to a purge gas blanket that displaces the reactant gases in that area and reduces unwanted deposits. Also, a purge gas (eg, argon) is introduced from gas nozzles (not shown) into critical portions of the blanket, such as the ceramic portion and the edge and backside of the heater, to further reduce unwanted deposits in those regions. Let it.

Undesired deposits on the pedestal and other components of the reaction chamber are minimized in other ways. More specifically, the flow restrictor ring 46 minimizes the flow of gas past the pedestal to the bottom of the reaction chamber. According to embodiments of the present invention, the deposition of titanium using TiCl ₄ (described in more detail below) is less than conventional methods used in conventional deposition systems for forming other titanium films. Also have a rather large flow rate. In a preferred embodiment suitable for titanium deposition, the flow restrictor ring 46 is made of fused silica because of its relatively low thermal conductivity and non-conductive properties. In another embodiment, the flow restrictor ring may be made of titanium used in a titanium-containing layer deposition process, in that the ring material does not contaminate the deposited layer.

In various embodiments, the restrictor ring covers the top and edge of the pedestal, thus depositing unwanted films on the ring rather than on the pedestal or bottom of the reaction chamber. Flow restrictor rings have the advantage of minimizing the risk of unwanted deposition (and attendant problems) that can occur at such high flow rates. The chamber lid 66 is completely removed using a chemical and / or mechanical process after being lifted to remove it easily for cleaning and approach relatively inexpensive restrictor rings.

Referring again to FIG. 1A, the flow restrictor ring 46 is supported by the pedestal 32 during the process, as described above. When the pedestal is lowered to lower or load the wafer, the restrictor ring rests on the ceramic ring 64 of the shelf 69. As the pedestal supporting the next wafer is raised into the processing position, the pedestal raises the flow restrictor ring. At the pressure of the reaction chamber used for titanium processing according to embodiments of the present invention, gravity is sufficient to hold both the wafer (located in the wafer pocket) and the restrictor ring on the pedestal.

A motor and an optical sensor (not shown) are used to move and determine the position of a movable mechanical assembly, such as throttle valve 83 and pedestal 32. The pedestal 32 and a bellows (not shown) attached to the bottom of the reaction chamber body 76 form a movable hermetic seal around the pedestal. Pedestal lift system, motor, gate valve,
The components of the plasma system, including the optical remote plasma system 4 (which may be capable of cleaning the reaction chamber with a remote plasma formed using a microwave source or the like) and other system components, are here partially described. Although only shown,
Controlled by processor 85 via control lines 3 and 3A-D.

The processor 85 executes system control software which is a computer program stored in a memory 86 connected to the processor 85. The memory 86 is preferably a hard disk drive, but of course the memory 86 may be another type of memory. In addition to a hard disk drive (eg, memory 86), in certain embodiments, the CVD apparatus 10 includes a floppy disk drive and a card rack. Processor 85 operates under the control of system control software, which includes timing, gas mixing, gas flow, room pressure, room temperature, RF power level, heater pedestal position, heater pedestal position for a particular process. A set of instructions requesting the temperature and other parameters of the system. Other computer programs, such as those stored on other memory, such as a floppy disk or other computer program product inserted into a disk drive or other suitable drive, are used to operate the processor 85. It may be done. The system control software is described in detail below. The card rack includes a single board computer, analog and digital input / output boards, interface boards and stepper motor controller boards.
Various components of the CVD apparatus 10 conform to the VME (Versa Modular European) standard that specifies the dimensions and types of boards, card cages, and connectors. The VME standard also defines a bus structure having a 16-bit data bus and a 24-bit address bus.

The interface between the user and the processor 85 includes a CRT monitor 93 a and a light, as shown in FIG. 1D, which is a simplified view of a system monitor using the CVD apparatus 10 shown as one of a plurality of chambers in a multi-chamber system. This is via the pen 93b. The CVD apparatus 10 is preferably mounted on a main frame unit 95 that supplies the apparatus 10 with electrical piping and other support functions. CV
An exemplary mainframe unit consistent with the embodiment of the D-device 10 is Precision 5000 (Applied Materials, Santa Clara, CA).
(Trademark), Centura 5200 (trademark), Dendura 5500 (trademark). The multi-chamber system allows wafers to be transported between chambers without breaking vacuum and exposing the wafers to moisture and other contaminants outside the multi-chamber system. An advantage of a multi-chamber system is that different chambers of the multi-chamber system may be used for different purposes in the overall process. For example, in a preferred embodiment of the invention, some chambers are used for CVD deposition of titanium films, while others are used for CVD deposition of titanium nitride films. In this way, the deposition of the titanium / titanium nitride stack commonly used in forming the contact structures described below with reference to FIG. Stacking processes can prevent wafer contamination that often occurs when transporting wafers between various separate individual chambers (not in multi-chamber systems).

In a preferred embodiment, two monitors 93 a are used, one monitor for the operator and mounted on the clean room wall, and another monitor behind the wall for service technicians. It is provided on the side. Both monitors 9
3a displays the same information at the same time, but only one light pen 93b can be used. The light pen 93b detects light emitted from the CRT display with an optical sensor at the tip of the pen. To select a particular screen or function, the operator touches a designated area of the display screen and presses a button on pen 93b. The color of the touched area becomes lighter or a new menu or screen is displayed to confirm the communication between the light pen and the display screen. Of course, a keyboard, mouse, or other pointing device or communication device may be used in place of, or in addition to, the light pen 93b, which allows the user to communicate with the processor 85.

The process for depositing the film and dry cleaning the reaction chamber is performed using a computer program product executed on processor 85 (FIG. 1A). The computer program code is, for example, 68000 assembly language, C,
Written in any conventional computer readable programming language, such as C ++, Pascal, Fortran or other languages. Suitable program code is entered into a single file or multiple files using a conventional text editor, and stored or embodied in a computer usable medium, such as a computer memory system. If the input code text is a high-level language, the code is compiled, and the resulting compiler code is then linked with the object code of the precompiled Windows library routine. To execute the linked compiled object code, a system user calls the object code, causes the computer system to load the code into memory, from which the CPU reads and executes the code to perform the tasks identified in the program. .

FIG. 1F is a block diagram illustrating a computer program 160 according to a particular embodiment, which is a hierarchical control structure of system control software. Using the light pen interface, a process set number or a process chamber number is input into the process selection subroutine 161 in response to a menu or screen displayed on the CRT monitor. A process set, which is a set of a predetermined number of process parameters required to execute a specific process, is identified by a set number defined in advance. The process selection subroutine 161 includes (i) a desired process chamber and (
ii) Identify the desired set of process parameters required to operate the process chamber to perform the desired process. Process parameters for performing a particular process include, for example, process gas composition and flow rates, temperature, pressure, high and low frequency RF power levels and high and low frequency RF frequencies (as well as remote microwave plasma systems. The embodiment relates to process conditions such as a plasma state such as a microwave generator power level), a cooling gas pressure, and a chamber wall temperature. The process selection subroutine 161 controls which type of process (deposition, wafer cleaning, chamber cleaning, chamber gettering, reflow) is performed at some point in the chamber 30. In some embodiments, there may be more than one process selection subroutine. Process parameters are provided to the user in the form of a recipe and may be entered using a light pen / CRT monitor interface.

The signals for monitoring the process are provided on an analog input board and a digital input board of the system controller, and the signals for controlling the process are output on an analog output board and a digital output board of the CVD system 10. .

The process sequencer subroutine 162 receives the identified set of process chambers and process parameters from the process selection subroutine 161 and includes program code for controlling various process chamber operations.
Multiple users may enter process set numbers and process chamber numbers, or a single user may enter multiple process set numbers and process chamber numbers, so that the sequencer subroutine 162 Operate according to the selected process in the desired sequence. Sequencer subroutine 162 includes (i) monitoring the operation of the process chamber to determine if the chamber is being used, and (ii) determining which process is being performed in the chamber being used. Preferably, it comprises program code for performing the steps and (iii) performing the desired process based on the availability of the process chamber and the type of process to be performed. Conventional methods of monitoring the process chamber, such as polling, are used. When scheduling which process to run, the sequencer subroutine 162
Is the current state of the process chamber being used as compared to the desired process state of the selected process, or the "age"
Or any other relevant factors that the system programmer may want included to determine scheduling priorities.

Once the sequencer subroutine 162 determines which combination of process chamber and process set is to be executed next, the sequencer subroutine 162 uses the process set determined by the sequencer subroutine 162 to perform multi-processing tasks in the process chamber 30. Control subroutine 1 for controlling
The execution of the process set is started by passing specific processing set parameters to 63a to 63c. For example, the chamber management subroutine 163b includes program code for controlling a CVD operation in the processing chamber 30. The chamber management subroutine 163b also controls the execution of various chamber component subroutines that provide the control of the chamber components necessary to execute the selected set of processes. Examples of chamber component subroutines are a substrate positioning subroutine 164, a process gas control subroutine 165, a pressure control subroutine 166, a heater control subroutine 167, and a plasma control subroutine 168. Depending on the specific structure of the CVD chamber, some embodiments may include all of the subroutines described above, while other embodiments may include only some of these subroutines. It will be readily recognized by those skilled in the art that other chamber control subroutines may be included, taking into account which processes to perform in the process chamber 30. In operation, the chamber management subroutine 163b selectively schedules or calls process component subroutines depending on the particular set of operations to be performed. The chamber management subroutine 163b schedules the subroutines of the process components much like the sequencer subroutine 162 schedules the next execution order of the process chamber 30 and the process set. Typically, the chamber management subroutine 163b monitors various chamber components, determines which components need to be operated based on the process parameters of the process set to be performed, and monitors these. Starting the execution of the chamber component subroutine in response to the steps and the determining step.

Regarding the operation of the particular chamber component subroutine shown in FIG. 1F, FIG. 1A
And will be described below. The substrate positioning subroutine 164 includes chamber components used to load the substrate onto the pedestal 32 and, optionally, to raise the substrate to a desired height in the chamber 30 and control the spacing between the substrate and the showerhead 40. Includes program code for controlling. As the substrate is loaded into the process chamber 30, the heater assembly 33 is lowered to receive the substrate in the wafer pocket 34 and then lifted to a desired height. In operation, the substrate positioning subroutine 164 controls the movement of the pedestal 32 in response to the support height process set parameters transferred from the chamber management subroutine 163b.

The processing gas control subroutine 165 has a program code for controlling the composition and flow rate of the processing gas. The process gas control subroutine 165 controls the open / close position of the safety shut-off valve, and also activates / deactivates the mass flow controller to obtain a desired gas flow. The process gas control subroutine 165, like all chamber component subroutines, has a chamber management subroutine 163b.
And receives subroutine process parameters from the chamber management program for the desired gas flow rate. Normally, the processing gas control subroutine 165
Opens the gas supply line, reads (i) the required mass flow controller,
ii) It operates by comparing the readout with the desired flow rate received from the chamber management subroutine 163b, and (iii) adjusting the flow rate of the gas supply line if necessary, repeatedly. Further, the processing gas control subroutine 163
Includes monitoring the gas flow rate for flow out of a safe range and activating a safety shut-off valve if an unsafe condition is detected. The process gas control subroutine 165 also controls the gas composition and flow rate of the clean gas and also the deposition gas, depending on the desired process selected (clean, deposition, etc.). In alternative embodiments, there may be more than one process gas control subroutine, each subroutine controlling a particular type of process or a particular set of gas lines.

In some processes, an inert gas, such as nitrogen or argon, is introduced into the chamber to stabilize the pressure in the chamber before the reaction process gas is introduced. In these processes, the process gas control subroutine 165 is programmed to include a step for flowing an inert gas into the chamber for a time necessary to stabilize the pressure in the chamber, wherein the steps described above are performed. Be executed. Further, if the process gas is to be evaporated from a liquid precursor, such as, for example, TiCl ₄ , the process gas control subroutine 165 may bubble the carrier gas, such as helium, through the liquid precursor of the bubbler assembly, or Rewritten to include the step of introducing a carrier gas, such as helium, into the liquid injection system. If a bubbler is used in this type of process, the process gas control subroutine 165 adjusts the carrier gas flow, bubbler pressure, and bubbler temperature to obtain the desired process gas flow. As described above, the desired flow rate of the processing gas is transferred to the processing gas control subroutine 165 as a process parameter. In addition, the process gas control subroutine 165 accesses a stored table containing the required values for a given process gas flow to obtain the required carrier gas flow, bubbler pressure and bubbler temperature for the desired process gas flow. Step. Once the required values have been obtained, the carrier gas flow rate, bubbler pressure and bubbler temperature are monitored while being compared to the required values and adjusted accordingly.

The pressure control subroutine 166 includes program code for controlling the pressure in the chamber 30 by adjusting the opening size of a throttle valve in the exhaust system of the chamber. The aperture size of the throttle valve is set to control the desired level of chamber pressure in relation to the total flow of process gas, the size of the process chamber, and the pump set pressure of the exhaust system. When the pressure control subroutine 166 is executed, a desired or target pressure level is received as a parameter from the chamber management subroutine 163b. Pressure control subroutine 166
Measures the pressure in chamber 30 by reading one or more conventional pressure manometers connected to the chamber, compares the measured value to a target pressure, and calculates a proportional pressure corresponding to the target pressure from a stored pressure table. , Differential and integral (PID) values and adjust the throttle valve according to the PID values obtained from the pressure table. Alternatively, the pressure control subroutine 166 can be rewritten to open and close the throttle valve to a particular opening size to adjust the pumping capacity of the chamber 30 to a desired level.

The heater control subroutine 167 includes program code for controlling the temperature of the heater coil 33 used to resistively heat the pedestal 32 (and any substrates thereon). The heater control subroutine is also executed by the chamber management subroutine, and receives a target temperature parameter or a set temperature parameter. The heater control subroutine measures the voltage output of the thermocouple installed on the pedestal 32 while comparing the measured temperature with the set temperature, and further increases or decreases the current applied to the heating unit to obtain the set temperature. Measure the temperature by: The temperature is obtained from the measured voltage by looking up the corresponding temperature in a stored conversion table or by calculating the temperature using a fourth order polynomial. If the incorporated loop is used to heat the pedestal 32,
The heater control subroutine 167 gradually controls the rise / fall of the current applied to the loop. In addition, a built-in fail-safe mode may be included to detect the safety status of the process, and if the process chamber 30 is not properly set, the operation of the heating unit can be shut off. An alternative method of heater control that can be used is to use a ramp control algorithm, which is assigned to the same assignee as the present application and allows the inventor to use Jonathan Fra.
nkel, "Systems and Methos for Temperature Control of Vapor Deposition Apparatus"
ds for Controlling the Temperature of a Vapor Deposition Apparatus), filed on November 13, 1996, and filed concurrently with US Patent Application No. 0
No. 8 / 746,657 (Attorney Docket No. 16301-017000), the entire contents of which are incorporated herein by reference.

The plasma control subroutine 168 includes program code for setting low and high frequency RF power levels to be applied to the process electrodes of the chamber 30 and heater assembly 32 and for setting the adopted low RF frequency. Similar to the chamber component subroutine described above, the plasma control subroutine 168 is also executed by the chamber management subroutine 163b. For embodiments that include a remote plasma generator 4, the plasma control subroutine 168 also includes program code for controlling the remote plasma generator.

With respect to the above-described CVD system, it is assigned to the same assignee as the present application and describes, “A high temperature, high-temperature process and apparatus for depositing a titanium layer (A High Temperature, H
igh Deposition Rate Process and Apparatus for Depositing Titanium Layers
)), Which is described in more detail in U.S. patent application Ser. No. 08 / 918,706, filed Aug. 22, 1997 (Attorney Docket No. 16301-017930),
The entire contents of which are incorporated herein by reference. However, the above description of the reactor is given mainly for the purpose of explanation, and other plasma CVD apparatuses such as an electron resonance (ECR) plasma CVD apparatus and an inductively coupled RF high-density plasma CVD apparatus may be used. Good. In addition, variations on the above-described system are possible, such as pedestal designs, heater designs, pump channel designs, locations of RF power connections, and any other variations. The method for forming a titanium layer according to the present invention is not limited to a specific CVD apparatus.

III. Improved CVD Titanium Process The method of the present invention may be used to deposit better titanium films in substrate processing chambers, as in the example of the CVD chamber described above. As described above, titanium films are frequently used in the production of integrated circuits today. One of the primary uses of such a titanium film is as the first adhesion layer of a titanium / titanium nitride stack that is part of a contact structure. Such a contact structure
FIG. 2A is a cross-sectional view of an exemplary contact structure in an embodiment in which the present invention is used.

As shown in FIG. 2A, an oxide layer 200 (eg, SiO _x film) having a thickness of about 1 μm is deposited on a substrate 205 having a surface of crystalline silicon or polycrystalline silicon. . Oxide layer 200 may act as a pre-metal insulator or interlayer insulator in integrated circuits. To obtain electrical contact between the layers, the contact holes 210 are etched through the oxide layer 200 and filled with a metal such as aluminum.

In most modern integrated circuits, contact holes 210 are narrow,
In many cases, the width is smaller than 0.35 μm, and the aspect ratio is about 6: 1 or larger. Filling such holes is very difficult, but somewhat standard processes have been developed, in which holes 210 are first conformally covered with a layer of titanium 215. Next, titanium (Ti)
Layer 215 is conformally coated with titanium nitride (TiN) layer 220. Thereafter, an aluminum layer 225 is deposited, primarily using physical vapor deposition, to fill the contact hole 225 and form an electrical interconnect line with the upper layer. The titanium layer 215 serves as an adhesive layer for both the underlying silicon and the oxide layer on the side walls. It can also be silicided with underlying silicon to form an ohmic contact. The TiN layer 220 tightly bonds with the Ti layer 215 and the aluminum layer 225
Is wetted to TiN, so that aluminum can satisfactorily fill contact holes 210 without forming voids. The TiN layer 220 also acts as a diffusion barrier, and the aluminum 225 is
To prevent from affecting the conductivity.

To properly achieve this objective, the titanium layer 215 should have good bottom coverage, low resistivity, uniform resistivity and uniform deposition thickness, among other properties.
It must have both the entire bottom of the contact and the entire wafer (from center to edge). It is also preferred that the titanium layer 215 be deposited uniformly along the bottom of the contact 210, but not deposited on the sidewalls at all. By preventing titanium from being deposited on the sidewalls, "silicon creep" where silicon from the contact area reacts with the titanium at the sidewalls and is transported from the bottom of the contacts to the sidewalls
Can be prevented from occurring. The titanium layer deposited by the method of the present invention satisfies all of these characteristics and exhibits significantly better bottom coverage and sheet resistance uniformity when compared to prior art titanium deposition processes. These improvements are achieved by combining new and unique steps that are superior to and follow the primary titanium bulk deposition step.

One of these steps is a new and unique plasma processing step that is performed before the titanium deposition step. In this plasma processing step, the wafer is exposed to a plasma formed from H ₂ and Ar process gases for a relatively short period of time (eg, between 5 and 60 seconds in the preferred embodiment). In this way, a small portion of the top surface of the wafer is etched before the deposition step. The present inventors have determined that this etching step includes (1) removing any oxide (SiO _x ) grown in the contact region of the wafer after forming the contact hole 210, and (2) forming the hole ( It has been found to be particularly effective when further etching any silicon oxide from the layer 200 unintentionally left in the contact hole 210 after the (etching) step. If the wafer is exposed to the atmosphere for a significant period of time before contact formation, an oxide with a thickness of 10-50 Å is typically formed.
The inventors have also found that many commercial manufacturing processes do not completely etch layer 200, leaving a thin unetched silicon oxide layer on the contact area. Such a layer is shown in FIG. 2B as layer 230 and may have a thickness of 100 to 250 Angstroms or more, depending on the process.

Depending on the thickness of such unetched layer 230 or of any oxide formed on the wafer, if the titanium layer 215 is deposited without the advantages of the present invention, an electrical Since no contact is formed on the surface of the underlying substrate, it leads to component failure that reduces the overall yield of the manufacturing process. In another example, the layer 230 or oxide formation is of a thickness that allows electrical contact to be made to the underlying silicon at an increased resistance level. As a result, the manufactured device may not meet the characteristics requirements of the manufacturer. In either of these cases, using the pretreatment step of the present invention can improve the electrical contact with the substrate 200 by etching all or part of the residual layer 230 or oxide formation. Become. This aspect of the invention is described in further detail below with reference to FIG.

FIG. 3 is a flowchart detailing the steps used to deposit a titanium film, according to a preferred embodiment of the present invention. The steps shown in FIG. 3 illustrate only the preferred process, and other embodiments of the present invention may use some of the steps disclosed herein together, or the form or order of these steps. It is to be understood that may be used with a change. As shown in FIG. 3, before beginning the deposition of the titanium layer, a wafer is loaded into the chamber 30 (step 300) and the processor 85 is used for cleaning purposes (N: cleaning purposes as described below). ) Is set to 1 (step 305). After the wafers have been loaded into the chamber, the pedestal 32 is typically removed from the gas distribution showerhead 40 by 250-50.
It is moved to the processing position located between 0 mil. In one particular preferred embodiment,
The pedestal 32 is arranged at a position 329 mil from the shower head 40. During such a wafer positioning step, the chamber is pressurized above a pressure at which deposition occurs with a non-corrosive gas such as argon. The argon is vented so that the chamber pressure continues to be reduced to the deposition pressure (5.0 torr in certain embodiments) to fill the voids and cavities within the chamber, particularly the interior of the heater pedestal. In this way, step 310 minimizes the ingress of process gases that can erode or oxidize the heater pedestal or chamber portions. Ar
The pressurized gas flows through the shower head 40 as an upper Ar flow, and further flows from a location below the wafer 36 as a lower Ar flow. The chamber pressure is
While performing this step, it is preferably set between about 5 to 90 torr.

In step 310, the temperature of the pedestal is set to ± 15 of the actual process temperature.
Set between ° C. The process may be performed at any temperature between about 400-750 ° C., but the temperature of the pedestal is about 630-700 ° C. (about 535-635 ° C.).
Is more preferably set to about 680 ° C. (corresponding to a wafer temperature of about 605 ° C.) in certain embodiments. In certain embodiments, the temperature is initially set at about 690 ° C. (10 ° C. above the process temperature) at step 310 to cool the heater and wafer as the process gas begins to flow. By first heating the wafer above the process temperature, the cycle time of the wafer is further reduced, and the heater element that would otherwise be generated when the heater power is increased to return the heater to the processing temperature after gas begins to flow. Thermal shock to the heater due to the thermal gradient between the heater and the heater surface is reduced.

About 10 seconds after the start of step 310, the temperature is reduced to the actual process temperature (which is preferably maintained thereafter during the entire deposition process) and the flow of the reactant gas (preferably H ₂ ) is reduced to the initial Turning on at the flow rate, the upper argon flow rate is increased (step 315). The reaction gas, the desired thickness loss amount of energy required for the deposition of the raw material gas to form a (introduced later), further it hydrogen chloride in addition to leave a part of the chlorine as Cl or Cl ₂ ( HCl) is also reduced. Then, two seconds after step 320, the gas flow rate further increases, and further increases three seconds after step 325. The flow rate of the gas may be incremented in a stepwise manner (or alternatively, ramped up) from an initial flow rate to a final flow rate during steps 310 to 325 to reduce the thermal shock to the heater. That is, the final flow rate of the gas is extremely large, and if the gas is turned on at once, the wafer may be excessively cooled. Such stepwise or rising start of the gas is particularly important because gases such as helium and hydrogen have high thermal transfer properties.

The next step, Step 325, is the above-described plasma pretreatment step. In plasma pretreatment step, a low frequency (e.g., a 300～450KHz, most preferably from 350 KHz) RF energy is applied to the shower head 40, forming a plasma from H ₂ and argon process gas. As described above, this plasma may completely or partially etch the thin oxide layer grown on the substrate 200 after the formation of the contact hole 210, or the layer 230 left unetched in the contact hole 210. Thereby, electrical contact with the substrate 200 can be improved. Such an etching process
It can be represented by the basic chemical reaction SiO ₂ + H ₂ → SiH ₄ + H ₂ O, where silane (SiH ₄ ) and water (H ₂ O) are both evacuated from the chamber. Of course, other intermediate reactions also take place, and the exhausted compounds will include ions and other molecules from these intermediate reactions.

Step 32 to etch oxide formations and silicon oxide residues
At 0, other gases referred to as pretreatment gases can be used. Since the pretreatment gas must have a high etching selectivity between the silicon oxide and the silicon substrate, it is necessary to etch oxide formations and residual oxides without damaging the silicon contact region. Can be. Other pretreatment gases that can be used in step 320 include ammonia (NH ₃ ) and various halogen species, and are those known for etching silicon oxide. Fluorine-containing gases (eg, CHF ₃ , CF ₄ , C ₂ F ₆ , BF ₃ , NH _3, etc.) are the most preferred halogen species, whereas iodine-containing raw materials are solid at room temperature. It is considered to be the most unfavorable because it is difficult to act.
Bromine-containing species are also generally preferred over chlorine-containing species in that they are less likely to affect the next deposition process. Any of these pretreatment gases can be, and preferably are, mixed with a carrier gas or another inert gas.
This can stabilize the plasma and the resulting etching process.

During step 325, the flow of TiCl ₄ (source gas) and helium is started. However, this time does not introduce these flows into the chamber 30, but diverts them directly to the front line. In this way, the flow, in particular TiC
By diverting the flow of l _4, can and this to stabilize the flow before the deposition begins, the multi-wafer deposition sequence (e.g., 2,000 wafer run)
The processing conditions in various titanium deposition steps can be made more uniform. Optionally,
As part of another step 330, it is possible to start the flow of TiCl ₄ and helium immediately after the start of the plasma. In any case, the deposition step 335
At least 6-8 seconds before, it is preferable to stabilize the flow of TiCl _4.

In the deposition step 335, the flow of TiCl ₄ and helium gas is redirected with the flow of argon and H ₂ , and the plasma continues to provide RF power to the showerhead 40.
Is maintained by applying the TiCl ₄ is a liquid, before being mixed with a helium carrier gas, a gas panel precision liquid injection system (GPLIS) manufactured by STEC Corporation.
It is vaporized using a liquid injection system such as an injection system. As shown in Table 1 below, in the embodiment which is presently preferred, the ratio of H ₂ and TiCl ₄ is 106
: 1. This ratio can be calculated by converting the mgm flow rate of TiCl ₄ given in the table to an equivalent sccm flow rate, as is done by one skilled in the art. In this case, TiCl ₄ is introduced at a rate of 400 mg / m, which corresponds to a gas flow rate of 47.23 sccm.

The deposition step 335 is maintained until the thickness of the film has been deposited to the selected thickness. Due to the high deposition temperature and the increasing gas flow rates and other factors, the titanium films of the present invention are deposited at a deposition rate of at least 100 Å / min to greater than about 400 Å / min. Thus, the overall time of step 335 is generally shorter than that required for the prior art process, which leads to increased wafer throughput.

After the deposition step 335 is completed, the flow of H ₂ , TiCl ₄ and helium is turned off, the RF power is rapidly reduced, and the upper argon flow is rapidly reduced (step 340), Release any large particles that may have formed on the chamber during the deposition step. Then, after about 3 seconds, the RF power is switched off and the titanium layer may be passivated. The passivation of the titanium layer is performed by forming a thin titanium nitride layer on the surface of the titanium layer so that impurities such as carbon and oxygen cannot be adsorbed in the titanium. Such impurities may alter the resistivity of the titanium layer, making the surface on which the titanium nitride barrier layer is deposited an inappropriate surface. Passivation may be achieved by adding a flow of H ₂ and N _{2 to} the flow of argon as a passivation step 345 and / or forming a nitrogen plasma at step 350. Preferably, both steps 345 and 350 are performed together. Thus, when the perform, the chamber is stabilized before the plasma treatment step 350 after deposition in step 345, can be further wiped residues TiCl ₄ from the chamber. Also, the nitrogen reacts with the titanium on the surface and begins to form a thin titanium nitride layer.

After step 345, in step 350, the titanium layer is further passivated by applying RF energy to the H ₂ / N ₂ / Ar passivation gas in the chamber to form a plasma. Alternatively, the passivation plasma may be formed at a remote plasma source and channeled to the chamber. The nitrogen ionized by the passivation plasma reacts with the surface of the titanium layer to complete the formation of the thin titanium nitride layer during about 10 seconds of exposure. RF power is typically applied to the showerhead 40 to form a plasma in the chamber. However, the RF power may be applied to the pedestal electrode 22 or to both the pedestal electrode 22 and the showerhead 40. Both steps 345
In the preferred embodiment using and 350, step 345 lasts about 8 seconds. In other embodiments where only step 345 or step 350 is used, the steps may be used for a longer time, for example, about 10-30 seconds.

After step 350, a second plasma purge step 355 is performed to further liberate any large particles that may be present in the chamber. Plasma purge step 355 is similar to the plasma purge step 340, The difference is that at step 355 the flow of N ₂ and H ₂ is maintained in addition to the flow of argon. Finally, in step 360, all gas flows are shut off, the chamber is evacuated, and the wafer is then removed from the chamber (step 365). Since the wafer is generally passivated, it can be exposed to the atmosphere without the titanium layer absorbing impurities such as oxygen and carbon and becoming harmful. Thus, the properties of the titanium layer do not degrade after prolonged exposure to air, for example for days. Furthermore, the passivation layer of titanium nitride provides a "clean" surface for depositing the titanium nitride barrier layer in subsequent processing. After the wafer is removed, the next wafer is loaded (step 410) and the temperature is preset to about 680 ° C. (step 405) before processor 85 increases the wafer count (step 415).

Plasma purge clean steps 340 and 35 performed after each wafer deposition
In addition to 5, a dry clean process (performed without opening the chamber lid) is performed on the chamber periodically after a predetermined number of wafer deposition processes to further prevent wafer contamination. According to the present invention, there are no wafers (eg, dummy wafers) in the chamber during this clean process. The dry clean process is generally performed on every "X" wafers, and preferably on every 2 to 300 wafers. For example, in certain embodiments, dry clean is performed on every three to five wafers. It is desirable to maintain a dry clean process efficiently so as not to significantly affect the number of wafers produced in the entire system. Suitable dry cleaning processes according to certain embodiments are described in further detail below.

Referring back to FIG. 3, when X (here, X = 3, for example) wafers have been processed (step 370), the chamber is dry-cleaned. At first,
The heater is moved so as to be about 650 mil away from the shower head (step 3).
75), maintained at a processing temperature of 680 ° C. At this time, N ₂ or similar non-reactive gas is flowed into the chamber, the chamber is in the range of about 0.1 to 10 Torr, is preferably less than about 5 torr, further certain embodiments about 0. 6
It is maintained at a cleaning pressure of torr. As a result, the heat flow from the heater to the shower head is reduced, so that the shower head is cooled with respect to the heater.

Three seconds after step 375, chlorine gas (Cl ₂ ) is introduced into the chamber at a flow rate of about 250 sccm, and the pedestal is lifted from shower head 40 to a position of 600 mil (step 380). Next, after 2 seconds, the plasma is about 400 wa.
It is driven with a power of tt (step 385). By maintaining this condition for a period of time, the chlorine species reacts with the unwanted deposits and etches the deposits from the chamber components. Undesired deposits resulting from the deposition process are generally thickest on the hottest exposed portion of the chamber, ie, the top surface of the heater that is not covered by a wafer or protected by a flow restrictor ring. By moving and moving the heater away from the showerhead, all of the components of the chamber, especially the showerhead, can be sufficiently and reliably cleaned in the above condition without over-etching the showerhead.

The length of step 390 depends on the amount of deposit formation in chamber 30, in other words, among other factors, the number of wafers processed during the dry clean operation and the length of the deposition process ( That is, it depends on the thickness of the titanium film deposited on the wafer 36). In one particular embodiment, the duration of step 390 is 15 seconds. Alternatively, the length of step 390 may be determined using a cleaning endpoint technique. This technique is well known and includes optical endpoint detection methods and pressure-based endpoint detection methods. Optical endpoint detection methods require quartz or similarly opaque windows in the walls of chamber 30 for proper operation, and such windows are susceptible to titanium deposition that interferes with proper endpoint detection. Therefore, some embodiments may produce less favorable results. Similarly, with respect to known pressure-based endpoint detection methods, such pressure-based endpoint detection methods can be used individually for each chamber 30 to accurately and accurately identify when clean step 390 is complete. This is not ideal because it must be calibrated to

The present inventors have developed a novel endpoint detection method of step 390 based on the measured reflected RF power. This endpoint detection method measures the power reflected from the chamber 30 to the power supply line of the RF power supply 5 (FIG. 1A) through the entire clean step 390. At the beginning of the clean step 390, the reflected power increases as the deposit is etched from the chamber walls. This increase in reflected power indicates that the density of the cleaning plasma is increasing as ionic species and activated molecules from the etched titanium deposit are incorporated. As the deposited material is etched from the chamber walls, the measured reflected power peaks and then begins to fall. Such results are illustrated in FIG. 4, which is a graph showing the reflected power measured during the clean step 390 as a function of the time and length of the titanium deposition step 335. The data shown in FIG. 4 shows an embodiment in which X = 1, that is, the case where the chamber 30 has undergone a dry clean process after processing of one wafer is completed.

The chamber clean process is terminated when the measured reflected power decreases below a minimum rate. For example, in one embodiment, step 390 is stopped 10 seconds after the measured reflected power has dropped to 0 watts / second. In another embodiment, step 390 is stopped when the rate of decrease of the measured reflected power is less than or equal to 2 watts / sec.

After the plasma clean, the chlorine gas is turned off, and the plasma power is turned off (step 390). The flow rate of N ₂ is maintained for about 3 seconds chamber in order to purge. The pedestal is then returned to approximately 650 mil intervals (step 395), and the lower argon flow is increased for 10 seconds to further purge the chamber. Finally, the chamber is evacuated for about 5 seconds (step 400). Of course,
A "wet clean" or preventative maintenance cleaning (which occurs every hundreds to thousands of wafers to be processed) is performed by opening the chamber lid and manually cleaning various chamber parts.

Performing a dry clean process periodically during wafer deposition minimizes the number of these time consuming wet clean preventive maintenance operations and further increases the efficiency of the deposition process. A cleaner chamber is provided which is said to contribute to speeding up. In addition, the use of a periodic dry clean process improves the repeatability of the titanium deposition process with extended wafer runs. That is, for example, during an extended wafer run of 2,000 wafers, as compared to an extended wafer run in which such periodic dry cleaning is not used, the deposited on the first plurality of wafers The properties of the titanium layer are quite similar to those of the deposited layers in the last multiple wafers.

The present inventors have also found that after the flow of TiCl ₄ is stopped (step 340), liquid TiCl ₄ remaining in the gas line interferes with the repeatability of the process. That is, when the flow of TiCl ₄ is stopped in the deposition step 340 by shutting off a suitable flow control valve connected to the line, a part of the TiCl ₄ liquid remains in the line. The present inventors have discovered that this amount of residual liquid changes from one deposition process to the next, and that residual TiCl ₄ makes the deposition unstable and adversely affects the deposition process. For example, since the residual amount of TiCl ₄ is change, there is a case where the amount of TiCl ₄ that flows into the chamber of any two individual substrates in extended wafer run is different, somewhat on the particular substrate Accumulation will occur. Also, residual TiCl ₄ may react with moisture present on the new substrate as it is transported into the chamber, forming TiO ₂ and creating unwanted particles. Finally, residual TiCl ₄ leaks into the chamber during the wafer deposition step and changes the color of the coated part by coating parts of the chamber or components of the chamber, thereby changing the color of the chamber or components. The emissivity of the same part also changes. Changes in the emissivity of a surface can change the temperature and other properties of the surface to undesirable states.

This residual TiCl_FourIn order to eliminate the adverse effects of helium, the present inventors have determined that helium or another inert gas source (residual TiCl _Four Gas that does not react with TiCl)_FourNew and dried gas line
Two unique steps have been devised. For example, in each of steps 375-395
Helium flow of 500 sccm_FourRemaining in the line_FourDry and purge. In this way, the method of the present invention ensures that gas lines can be regenerated before depositing on all wafers.
State. Also, TiCl_FourAfter purging the line, the helium that has flowed into the deposition chamber stabilizes the dry cleaning plasma. Helicopter
The flow of um is controlled by appropriate valves and flow controllers, as understood by those skilled in the art.
Using TiCl_FourFollow the line.

The gas flow rates, pressure levels and other information according to the presently preferred embodiment of the present invention described with respect to FIG. 3 are shown in Tables 1 (deposition process) and 2 (cleaning process) below. I have. The gas introduction rates shown in Tables 1 and 2 are based on the use of the process shown in FIG. 3 in a resistively heated TixZ CVD chamber manufactured by Applied Materials, supplied on 8-inch wafers. is there. As will be appreciated by those skilled in the art, the actual rate at which the gas is introduced in other embodiments will be different if other chambers of different designs and / or volumes are used.

[0071]

[Table 1]

[0072]

[Table 2]

The deposition conditions and flow rates shown in Tables 1 and 2 above represent the flow rates used in the presently preferred embodiments of the present invention, but other deposition conditions and other flow rates It should be understood that it can be used. For example, with respect to the rate at which the raw material gas and the reactive gas is introduced into the deposition stage, the present inventors have approximately a ratio of H ₂ and TiCl ₄ 64
: 1 and 2034: 1. The preferred ratio will depend in part on other deposition conditions, including deposition temperature, pressure, pedestal spacing, RF power levels and other factors. However, the inventors use the above ratios to deposit high quality titanium films under suitable deposition conditions including a heater temperature range of at least 630-700 ° C. and a deposition pressure range of at least 1-10 torr. Discovered that you can. In one particular test, a high quality titanium film was
With a flow rate of TiCl ₄ in 000sccm of H ₂ flow and 400 mg / m (corresponding to 47.23sccm) 64: 1 of H ₂ / those deposited at a ratio of TiCl ₄ and, 12,000Sccm of H ₂ with a flow rate of TiCl ₄ flow and 50 mg / m (corresponding to 5.9 sccm) 2034: those which are deposited in a ratio of 1 H ₂ / TiCl _4. If the flow ratio of H ₂ / TiCl ₄ is smaller than 64: 1, the hydrogen during the reaction becomes insufficient and unstable, and if the flow ratio is larger than 2034: 1, the deposited film will have a bottom in the contact. Coverage begins to deteriorate and becomes unacceptable, and furthermore it becomes difficult to control emissions.

IV. Test Results and Measurements To demonstrate the efficiency of the present invention, experiments were conducted to deposit titanium layers with and without the method of the present invention. The experiments were performed in a resistance heated TixZ chamber manufactured by Applied Materials. TixZ chamber is 200m
Supplied for m-wafers, also mounted on a Centura multi-chamber substrate processing system manufactured by Applied Materials.

In one of these experimental sets, prior to the titanium deposition step, various pre-treatment steps (step 3) were performed on the wafer on which the silicon oxide layer was deposited.
25) was performed. The first of these pre-treatment steps formed a plasma from Cl ₂ (125 sccm), N ₂ (500 sccm) and Ar (200 sccm) process gases. The plasma was formed using a 400 W RF power level and was maintained for 40-100 seconds in different tests. According to test results, this step etched the silicon oxide layer at a rate of 1.1 Å / sec, but the etching was not very uniform and was quite uncontrollable, etching not only silicon oxide but also silicon. It was strong.

Further tests have shown that chlorine from the Cl ₂ plasma pretreatment step interferes with the next titanium deposition step. More specifically, residual chlorine is said to be the cause of the slowing down of the deposition rate of the titanium film in step 335. Also, the resulting titanium layer was found to be less uniform than a titanium layer deposited without using the Cl ₂ plasma pretreatment step.

The inventors have also experimented with a plasma pretreatment step using H _{2 according} to a presently preferred embodiment of the present invention. From the results of these tests, H ₂ (12 slm) and Ar (5,500 sccm) plasma (RF power 900 W)
It was found that the silicon oxide was etched uniformly at a rate of about 0.8 Å / sec. Also, the etching process was relatively gentle in that there was no sign of damaging the silicon. FIGS. 5A and 5B show the uniformity of etching obtained using this process. FIG. 5A shows the thickness of the silicon oxide layer deposited on the wafer before the results of the wafer before undergoing the plasma pretreatment of the present invention. The measurement was performed using a Rudolph Focus Ellipsometer known to those skilled in the art, and according to the measurement result, the thickness of the oxide layer before the pretreatment step was 132 ± 15.61 Å. . FIG. 5B shows the thickness of the oxide layer immediately after the 90 second pre-treatment step. In FIG. 5B, the thickness of the oxide layer is 58 ± 16.7 angstroms. 5A and 5B, the change in thickness of the oxide layer in FIG. 5B is almost the same as the change shown in FIG. 5A. Therefore,
From this comparison, it is clear that the etching in this step 325 is very uniform.

The present inventors have also generally used semiconductor manufacturing companies to remove oxides prior to titanium deposition, and have found that similar titanium layers deposited according to the present invention The resistivity of the titanium layer deposited in the process was measured without the plasma pretreatment step and without the standard HF dip step. According to these test results, for a 300 Å titanium layer, the resistivity of the layer of titanium film not treated in the plasma pre-treatment step is 0.5-1. 0 Ω / □ higher.

From these results, it can be seen that the plasma pretreatment step of the present invention is useful for etching unwanted oxides on silicon oxide prior to the deposition of the titanium layer. As previously described, such oxides are regularly formed on the substrate and previously used another processing step, such as immersion in an HF solution, to transfer the substrate to another chamber for deposition of the titanium film. It was necessary to etch what was formed before transferring. In such an HF dip step, the wafer must be subsequently dried and transferred to the deposition chamber immediately before further oxidation occurs. This process is cumbersome and time-consuming and inherently less reliable than the process of the present invention.

From other tests, it has been found that the process of the present invention is performed in the hole 210 (FIG. 2A).
), No titanium is deposited on the side walls of the contact holes, and the bottom coverage exceeds 300%. A membrane exhibiting 300% bottom coverage is:
When a 100 angstrom titanium layer is deposited in the contact, the titanium silicide formed at the bottom of the contact has 300 angstrom.

The parameters listed in the processes and experiments described above were claimed as described herein.
It should not be limited in scope. Those skilled in the art will be able to
Use the chemicals, chamber parameters and conditions other than those described here to
The process can be modified. Thus, the above description is illustrative and not restrictive.
Instead, the present invention provides a variety of different deposition and cleaning processes
Applicable for depositing films. For example, the dry cleaning process
Using the remote plasma system 4, Cl_TwoIt is possible to decompose gas molecules and / or other gases. Similarly, using the remote microwave plasma system 4,
It is possible to decompose titanium and other process gas molecules during the deposition process
The collected ions can be sent to the chamber 30. The present invention relates to F_Two, C IF_ThreeIt is also possible to use different cleaning sources including, for example, TiI,_FourIt is also possible to use with different titanium sources such as (solid) and any other titanium halides. Also before the plasma
Processing step 325 heats the wafer and removes the entire wafer prior to the deposition step.
Can be used to stabilize at a uniform temperature. Further, for example, N _Two And NH_ThreePassivate the titanium layer in steps 345 and 350
It can also be used to install. Therefore, the scope of the present invention is
Not limited by reference to the list above, with all equivalent ranges
It should be limited with reference to the appended claims.

[Brief description of the drawings]

FIG. 1A is a vertical cross-sectional view illustrating one embodiment of a simplified plasma enhanced chemical vapor deposition system according to the present invention.

FIG. 1B is a simplified cross-sectional view of the ceramic pedestal 36 shown in FIG. 1A, according to one embodiment of the present invention.

FIG. 1C is a simplified cross-sectional view of the deposition chamber 30 shown in FIG. 1A, according to an embodiment of the present invention.

FIG. 1D illustrates an interface between a user and a processor that can control the deposition system of the present invention.

FIG. 1E is a simplified, partially cut-away perspective view showing gases flowing into an exhaust system across a wafer, according to one embodiment of the invention.

FIG. 1F is an explanatory block diagram illustrating a hierarchical control structure of system control software according to an embodiment of the present invention.

FIG. 2A is a simplified cross-sectional view illustrating an exemplary contact structure using a titanium layer deposited according to the present invention.

FIG. 2B is a simplified cross-sectional view illustrating the formation of defects in the contact structure of FIG. 2A.

FIG. 3 is a flow diagram of a processing sequence used to deposit a titanium layer, according to a presently preferred embodiment of the method of the present invention.

FIG. 4 is a graph showing the measured reflectivity as a function of time and deposition length during a chamber clean step.

FIG. 5A is a film pressure measurement result showing an experimental result of the present invention.

FIG. 5B is a film pressure measurement result showing an experimental result of the present invention.

──────────────────────────────────────────────────の Continuation of front page (72) Inventors: Fu, Frederick, C. United States, California, Cupertino, Orion Place 7771 (72) Inventor Vasdev, Anand United States of America, California, San Jose, Indian Creek Court 1859 (72) Inventor Chan, May United States of America, California, Saratoga, Cote de Algero 12881 (72) 72) Inventor Buclay, Lawrence, D. , Jr. United States, California, Santa Clara, Saratoga Avenue 141 Apartment 1132 (72) Inventor Fu, Lee United States of America, California, San Jose, Birch Meadow Court 1524 (72) Inventor Boyle, Brian, P.S. United States, California, San Francisco, Marietta Driving 193 (72) Inventor Hizume, Shunichi 4-25-1, 4-106, Karabe, Narita-shi, Chiba, Japan Jennings, Patricia United States of America, San Jose, California Phelps Avenue 1311 F-term (reference) 4K030 AA03 AA13 AA17 BA18 BA48 CA04 CA12 DA06 FA03 HA01 JA09 JA10 LA15 4M104 BB14 DD22 DD44 DD45 HH13

Claims (19)

[Claims] 1. A chemical vapor deposition method for depositing a titanium film on a substrate having an insulating layer already formed on the substrate, comprising: (a) placing the substrate in a deposition area; b) during a first deposition step: (i) flowing a pre-treatment gas into the deposition area; (ii) forming a plasma in the deposition area from the pre-treatment gas; (iii) C) maintaining the deposition area in a state suitable for maintaining the plasma to etch an upper portion of an insulating layer from the substrate; and c) during a second deposition step after the first step. (I) flowing a processing gas containing a titanium-containing source gas and a reaction gas into the deposition area; (ii) forming a plasma from the processing gas; and (iii) depositing a titanium layer on the substrate. Maintaining said deposition area in a state suitable for stacking. 2. The pre-treatment gas comprises either H ₂ or NH ₃ , and steps (b) and (iii) are maintained for a time sufficient to etch at least 10 to 50 angstroms of the insulating layer. The method according to claim 1. 3. The method of claim 2, wherein said titanium source comprises TiCl ₄ . 4. The insulating layer is made of undoped silicate glass (USG).
, Phosphorus-doped silicate glass (PSG), borophosphosilicate glass (
The method according to claim 3, wherein the method is selected from the group of BPSG) and fluorine-doped silicate glass (FSG). 5. The substrate is a silicon substrate, the insulating layer has at least one contact opening etched therein, and the titanium layer covers a bottom of the contact opening and has a titanium silicide at the bottom. 5. The method of claim 4, wherein the layer is deposited to form a layer. 6. The method of claim 5, wherein said titanium silicide layer has a thickness at least three times that of said deposited titanium layer. 7. A chemical vapor deposition method for depositing a titanium film on an insulating layer formed on a substrate, comprising: (a) disposing a substrate in a deposition area; (I) flowing a pretreatment gas into the deposition area; (ii) forming a plasma from the pretreatment gas in the deposition area; and (iii) from the substrate. Maintaining the deposition area in a state suitable for maintaining the plasma for at least about 5 seconds to etch an upper portion of an insulating layer; and (c) during a second deposition step after the first step. (I) flowing a process gas containing a titanium-containing source gas and a reactive gas into the deposition area; (ii) forming a plasma from the process gas; and (iii) forming a titanium layer on the substrate. Maintaining said deposition area in a state suitable for deposition. 8. The method of claim 7, wherein said pretreatment gas comprises a hydrogen-containing gas selected from the group of H ₂ and NH ₃ and an inert gas. 9. The method of claim 8, wherein step (b) (iii) maintains the plasma for about 5 to 120 seconds. 10. The method of claim 8, wherein step (b) (iii) maintains the plasma for about 5 to 60 seconds. 11. The first deposition step further comprises: starting a flow of the titanium-containing source gas, diverting the titanium-containing source gas from the deposition area, and entering an exhaust line of a substrate processing chamber. Item 9. The method according to Item 8. 12. The method of claim 7, wherein said titanium-containing source gas comprises evaporated TiCl ₄ . Includes wherein said reactant gas and said hydrogen containing source are both H _2, claim stream H ₂ is maintained until the step (b) (i) ~ Step (c) (iii) 7
The described method. 14. The method of claim 7, wherein said pretreatment gas comprises a halogen-containing gas. 15. A chemical vapor deposition method for depositing a titanium film on silicon oxide formed on a substrate having a portion partially etched in a contact region, the method comprising: (B) during a first deposition step, (i) flowing a pretreatment gas containing H ₂ and an inert gas into the deposition area; Forming a plasma from the pre-treatment gas in a deposition area; and (iii) maintaining the plasma in a state suitable to maintain the plasma for about 5-120 seconds to etch an upper portion of a silicon oxide layer from the substrate. Maintaining said deposition area; and (c) during a second deposition step after said first step, (i) evaporating said pre-processing gas to form a processing gas flowing into said deposition area Done T And applying a flow of Cl _4, (ii) step to deposit a titanium layer on the substrate (b) (i
maintaining the deposition area in a state suitable for maintaining the plasma formed in i). 16. After the deposition of the titanium film is completed, the substrate is transported under vacuum to a second chamber of the multi-chamber substrate processing system, and the chemical vapor deposition method comprises the steps of: 2. The method of claim 1, wherein the titanium film is used to deposit a titanium film.
5. The method according to 5. 17. A chemical vapor deposition method for depositing a titanium layer on a substrate disposed in a deposition area of a substrate processing chamber, the method comprising: (a) heating the wafer to a temperature of about 535-625 ° C. (B) maintaining the deposition zone at a pressure of about 1 to 10 torr; (c) flowing a processing gas and a reaction gas including TiCl ₄ into the chamber, wherein the reaction gas and the TiCl ₄ Comprises a reactant, wherein the flow rate of the raw material is between about 64: 1 to 2034: 1; and (d) forming a plasma from said process gas and depositing a titanium film on the substrate. Applying energy for the application. 18. The method according to claim 17, wherein said reaction gas comprises H ₂ . 19. The plasma comprises a low frequency R
19. The method of claim 18, formed by applying F energy.