JP2012204522A - DEPOSITION METHOD AND FORMATION METHOD OF Cu WIRE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a deposition method capable of depositing a metal film while suppressing overhang of a frontage of a trench or a hole by heating a processed substrate, and of quickly reducing a temperature of the processed substrate after deposition.SOLUTION: The method includes: a step of mounting a processed substrate on a mounting table without adsorption while keeping the mounting table at a low temperature; a step of generating plasma of a plasma generation gas and taking ions of the plasma generation gas into the processed substrate in a state of applying a high-frequency bias to the mounting table to preheat the processed substrate; a step of applying a voltage to a target to emit metal particles, and taking metal ions ionized together with the ions of the plasma generation gas into the processed substrate to form a metal film; and a step of making the mounting table that is kept at a low temperature adsorb the processed substrate, and supplying the heat transfer gas to between the mounting table and the processed substrate to cool the processed substrate.

Description

  The present invention relates to a film forming method and a Cu wiring forming method.

  In the manufacture of semiconductor devices, various processes such as film formation and etching are repeatedly performed on a semiconductor wafer (hereinafter simply referred to as a wafer) to manufacture a desired device. Corresponding to the demands for pattern miniaturization and high integration, there is a demand for lower wiring resistance and improved electromigration resistance.

  Corresponding to these points, copper (Cu) having higher conductivity (lower resistance) and better electromigration resistance than aluminum (Al) and tungsten (W) is used as the wiring material. It is coming.

  As a method for forming Cu wiring, a barrier film made of titanium (Ti), titanium nitride film (TiN), tantalum (Ta), tantalum nitride film (TaN), etc. is formed on an interlayer insulating film in which trenches and holes are formed. Is formed by PVD plasma sputtering, and a Cu seed film is also formed on the barrier film by plasma sputtering. Further, Cu plating is applied on the barrier film to completely fill trenches and holes. A technique has been proposed in which a copper thin film and a barrier film are removed by polishing by a CMP (Chemical Mechanical Polishing) process and planarized to obtain a Cu wiring (for example, Patent Document 1).

  By the way, semiconductor device design rules are becoming increasingly finer, and the trench width and hole diameter are several tens of nanometers. A barrier film such as a Ti film is formed in such a narrow trench or hole as in plasma sputtering. In the case of forming by ionized PVD (iPVD), an overhang portion is generated at the opening portion of the trench or hole, and the opening width of the trench or hole is narrowed. Even if the trench or hole is buried by subsequent Cu plating, Problems such as generation of voids (cavities) due to insufficient filling of the interior occur.

  In order to solve such problems, a technique has been proposed in which, when a Ti film as a barrier film is formed by plasma sputtering, the wafer is heated by a heater provided on the mounting table to flow the Ti film ( Patent Document 2).

JP 2006-148075 A JP 2009-182140 A

  However, when the wafer is heated by the heater provided on the mounting table during Ti film formation as in Patent Document 2, the wafer must be carried out of the processing container at a high temperature after the film formation process. There is concern about oxidation of the film.

  Further, when the wafer is unloaded after the temperature of the wafer is lowered, the throughput is lowered. In particular, when the temperature of the wafer needs to be lowered, such as when Cu seed is formed by plasma sputtering after the Ti film is formed, the temperature of the heated wafer is lowered to the temperature for forming the Cu seed film. Therefore, it takes a very long time to further reduce the throughput and the device production yield.

  The present invention has been made in view of such circumstances, and a metal film such as a Ti film used as a barrier layer or the like while heating a substrate to be processed by iPVD and suppressing an overhang of a trench or a hole opening. And forming a Cu wiring by forming a Cu film on the barrier layer made of such a metal film, and a method for reducing the temperature of the substrate to be processed immediately after the film formation. It is an object to provide a method for forming a Cu wiring.

  In the first aspect of the present invention, a processing container, a mounting table for mounting the substrate to be processed in the processing container, a cooling mechanism for cooling the mounting table, and an adsorption for adsorbing the processing substrate to the mounting table. A mechanism, a heat transfer gas supply means for supplying a heat transfer gas between the mounting table and the substrate to be processed, a gas introduction mechanism for introducing a plasma generation gas into the processing container, and the above in the processing container A plasma generation mechanism for generating plasma of a plasma generation gas, a metal target formed on the substrate to be processed, a DC power source for applying a voltage to the target, and a high-frequency bias for drawing ions into the mounting table A film forming method for forming a metal film on a substrate to be processed using a film forming apparatus having a bias power source for applying a voltage, wherein the mounting table is held at a low temperature by the cooling mechanism and Description Placing the substrate to be treated on a table without adsorbing the substrate, and then generating plasma of the plasma generating gas and applying the high frequency bias from the bias power source to the table. A step of preheating the substrate to be processed to a relatively high temperature by drawing ions of the plasma generation gas to the substrate, and then applying a voltage from the DC power source to the target in a state where the plasma is formed, Releasing the metal particles from the target, drawing the metal ions ionized by the plasma into the substrate to be processed together with the ions of the plasma generating gas by the bias power source, and stopping the film formation After the film formation is stopped, the substrate to be processed is adsorbed to the mounting table held at the relatively low temperature by the adsorption mechanism. And a step of supplying a heat transfer gas between the mounting table and the substrate to be processed to transfer heat between the substrate to be processed and the mounting table, and cooling the substrate to be processed. And a step of unloading the substrate to be processed from the processing container.

  In the first aspect, the mounting table is preferably cooled to −30 to 90 ° C. An electrostatic chuck can be suitably used as the adsorption mechanism. In this case, in the preliminary heating step, the substrate to be processed is preferably heated to 100 ° C. or higher, more preferably 100 to 200 ° C. Furthermore, a Ti film can be suitably used as the metal film.

  According to a second aspect of the present invention, there is provided a Cu wiring forming method for forming a Cu wiring by burying Cu in a trench and / or a hole of a predetermined pattern formed on the substrate to be processed. Forming a barrier layer by forming a metal film on the surface of the portion where the trench and / or hole is formed by the film forming method of the first aspect; and the trench having the barrier layer formed thereon and And / or a process of embedding Cu in the hole, and a process of polishing and flattening the Cu portion up to the opening of the trench and / or hole after the Cu is buried. Provide a method.

  In the second aspect, the trench and / or hole may be formed in an insulating film of the object to be processed. It is preferable to further include a step of forming a liner film made of ruthenium on the barrier layer after forming the barrier layer. In the step of burying Cu, it is preferable to bury the trench and / or hole by Cu plating after forming a Cu seed film by PVD. The step of polishing and planarizing is preferably performed by CMP.

  According to a third aspect of the present invention, there is provided a storage medium that operates on a computer and stores a program for controlling a film forming apparatus, and the program is executed when the film forming method according to the first aspect is performed. A storage medium is provided that causes a computer to control the film formation apparatus.

  According to the present invention, the plasma generation gas ions are drawn into the substrate to be processed, the substrate to be processed is preheated to a relatively high temperature, and the metal particles together with the plasma generation gas ions are heated in a relatively high temperature state. Since the metal ions are drawn into the substrate to be processed to form the metal film, it is possible to suppress the occurrence of the overhang at the opening of the trench or the hole due to the movement of the metal particles. In addition, the mounting table itself is kept at a relatively low temperature without being heated, and during preheating and film formation, the substrate to be processed is allowed to be heated in a substantially adiabatic state without being held on the mounting table. After the film formation, the substrate to be processed is attracted to the mounting table by the suction mechanism to transfer the heat between the mounting table and the substrate to be processed, and the substrate is cooled, so that the substrate to be processed can be quickly cooled. Therefore, there is no need to worry about oxidation of the film due to carrying out the substrate to be processed at a high temperature, and the cooling time can be shortened, so that the throughput can be improved.

It is sectional drawing which shows an example of the Ti film | membrane film-forming apparatus for enforcing the film-forming method concerning one Embodiment of this invention. It is a flowchart for demonstrating the process of the film-forming method which concerns on one Embodiment of this invention. It is a chart which shows the temperature profile example of the wafer at the time of enforcing the film-forming method of FIG. It is a graph which shows the relationship between the preheating time by the argon plasma in the case of experiment of this invention, and the minimum opening width of a trench. It is a graph which shows the relationship between the wafer temperature in the case of the experiment of this invention, and the normalized trench opening width. It is a schematic diagram for comparing and explaining the state of the Ti film in the trench portion when the preheating is not performed and when the preheating is performed. It is a figure which shows the X-ray-diffraction pattern of Ti film formed without performing preheating, and Ti film formed after preheating. It is a scanning electron microscope (SEM) photograph when Cu films used as seed films are respectively formed on a Ti film formed without preheating and a Ti film formed after preheating. It is a flowchart for demonstrating the method of forming Cu wiring, using Ti film | membrane formed by the film-forming method of this embodiment as a barrier layer. It is process sectional drawing for demonstrating each process of the method of forming Cu wiring, using Ti film | membrane formed into a film by the film-forming method of this embodiment as a barrier layer.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. Here, the formation of a Ti film as a barrier layer of a Cu wiring and the formation of a Cu wiring including the barrier layer will be described.

<Configuration of Ti Film Deposition Apparatus>
First, an example of a Ti film forming apparatus for performing a film forming method according to an embodiment of the present invention will be described.
FIG. 1 is a sectional view showing an example of a Ti film forming apparatus for performing a film forming method according to an embodiment of the present invention. Here, an ICP (Inductively Coupled Plasma) type plasma sputtering apparatus which is an iPVD (ionized Physical Vapor Deposition) will be described as an example of the Ti film forming apparatus.

As shown in FIG. 1, the Ti film forming apparatus 10 has a processing container 51 formed into a cylindrical shape with, for example, aluminum. The processing vessel 51 is grounded, and an exhaust port 53 is provided at the bottom 52, and an exhaust pipe 54 is connected to the exhaust port 53. A throttle valve 55 and a vacuum pump 56 for adjusting pressure are connected to the exhaust pipe 54 so that the inside of the processing container 51 can be evacuated. Further, a gas inlet 57 for introducing a predetermined gas into the processing container 51 is provided at the bottom 52 of the processing container 51. A gas supply pipe 58 is connected to the gas inlet 57 for supplying a rare gas such as Ar gas or other necessary gas such as N ₂ gas as the plasma excitation gas. The gas supply source 59 is connected. The gas supply pipe 58 is provided with a gas control unit 60 including a gas flow rate controller and a valve.

  In the processing container 51, a mounting mechanism 62 for mounting a wafer W as a substrate to be processed is provided. The mounting mechanism 62 includes a mounting table 63 formed in a disc shape, and a hollow cylindrical column support 64 that supports the mounting table 63 and is grounded. The mounting table 63 is made of a conductive material such as an aluminum alloy, and is grounded via a support column 64. A cooling jacket 65 is provided in the mounting table 63 as a cooling mechanism so as to supply a refrigerant through a refrigerant channel (not shown). As the refrigerant, Galden can be preferably used, and is controlled at -30 to 90 ° C, for example, 30 ° C.

  On the upper surface side of the mounting table 63, for example, an electrostatic chuck 66 is configured by embedding a thin disk-like electrode 66b in a dielectric member 66a such as alumina, and the wafer W can be attracted and held by an electrostatic force. Yes, it can be detached by releasing the electrostatic force. Further, the lower portion of the support column 64 extends downward through an insertion hole 67 formed at the center of the bottom 52 of the processing vessel 51. The support column 64 can be moved up and down by an elevator mechanism (not shown), whereby the entire mounting mechanism 62 is moved up and down.

  A bellows-like metal bellows 68 configured to be stretchable is provided so as to surround the support column 64, and the upper end of the metal bellows 68 is airtightly joined to the lower surface of the mounting table 63, and the lower end thereof is a processing container. It is airtightly joined to the upper surface of the bottom part 52 of 51, and the raising / lowering movement of the mounting mechanism 62 can be permitted while maintaining the airtightness in the processing container 51.

  Further, for example, three (only two are shown in FIG. 2) support pins 69 are provided on the bottom portion 52 in an upward direction. The support pins 69 correspond to the support pins 69 on the mounting table 63. A pin insertion hole 70 is formed. Therefore, when the mounting table 63 is lowered, the wafer W is received by the upper end portion of the support pin 69 penetrating the pin insertion hole 70, and between the transfer arm (not shown) that enters the wafer W from the outside. Can be transferred. For this reason, a carry-out / inlet 71 is provided in the lower side wall of the processing container 51 in order to allow the transfer arm to enter, and the carry-out / inlet 71 is provided with a gate valve G that can be opened and closed. For example, a vacuum transfer chamber (not shown) is connected via the gate valve G.

In addition, a chuck power source 73 is connected to the electrode 66b of the electrostatic chuck 66 through a power supply line 72. By applying a DC voltage to the electrode 66b from the chuck power source 73, the wafer W is brought into a static state. Adsorbed and held by electric power. Further, the chuck power source 73 can be turned on / off by a switch (not shown), and the wafer W is detached by turning off the chuck power source 73. A bias high frequency power source 74 is connected to the power supply line 72, and bias high frequency power is supplied to the electrode 66 b of the electrostatic chuck 66 via the power supply line 72, and bias power is applied to the wafer W. It has come to be. The frequency of the high frequency power is preferably 400 kHz to 60 MHz, and for example, 13.56 MHz is adopted.

  A heat transfer gas channel 88 for supplying heat transfer gas is formed on the mounting surface of the electrostatic chuck 66 on the back side of the wafer W that has been adsorbed, and a heat transfer gas supply source 89 is provided in the heat transfer gas channel. A heat transfer gas, for example, Ar gas is supplied. As the heat transfer gas, in addition to Ar gas, He gas having better heat transfer than Ar gas may be used. The heat transfer gas flow path 88 passes through the support column 64 from below the processing container 51 and extends through the mounting table 63 and the electrostatic chuck 66. When the electrostatic chuck 66 is turned on and the wafer W is attracted, Heat transfer gas is allowed to flow between W and the electrostatic chuck 66 to effectively transfer the heat of the wafer W.

  On the other hand, a transmission plate 76 that is permeable to high frequencies made of a dielectric material such as alumina, for example, is hermetically provided on the ceiling of the processing vessel 51 via a seal member 77 such as an O-ring. A plasma generation source 78 for generating a plasma by generating a rare gas, for example, Ar gas, as a plasma excitation gas in the processing space S in the processing vessel 51 in the upper portion of the transmission plate 76 is provided. As this plasma excitation gas, other rare gases such as He, Ne, Kr, etc. may be used instead of Ar.

  The plasma generation source 78 has an induction coil 80 provided so as to correspond to the transmission plate 76. To this induction coil 80, for example, a 13.56 MHz high frequency power source 81 for plasma generation is connected, and the transmission is performed. High frequency power is introduced into the processing space S via the plate 76 to form an induced electric field.

  A baffle plate 82 made of aluminum, for example, is provided directly below the transmission plate 76 to diffuse the introduced high-frequency power. In the lower part of the baffle plate 82, a target 83 made of, for example, an annular (a truncated cone-shell) metal Ti is provided so as to surround the upper side of the processing space S, for example, the cross section is inclined inward. The target 83 is connected to a target variable voltage DC power supply 84 for applying DC power for attracting Ar ions. An AC power supply may be used instead of the DC power supply.

  Further, a magnet 85 for applying a magnetic field to the target 83 is provided on the outer peripheral side of the target 83. The target 83 is sputtered as Ti atoms or atomic groups by Ar ions in the plasma, and is largely ionized when passing through the plasma.

  A cylindrical protective cover member 86 made of, for example, aluminum or copper is provided below the target 83 so as to surround the processing space S. The protective cover member 86 is grounded, and a lower portion thereof is bent inward and is positioned in the vicinity of the side portion of the mounting table 63. Therefore, the inner end of the protective cover member 86 is provided so as to surround the outer peripheral side of the mounting table 63.

  The Ti film forming apparatus 10 is controlled by the control unit 100. This control unit 100 visualizes a process controller 101 composed of a microprocessor (computer) that controls each component, a keyboard for an operator to input commands to manage the device, and the operating status of the device. A control program for realizing processing executed by the user interface 102 including the display and the Ti film forming apparatus 10 under the control of the process controller 101, various data, and processing conditions A program for causing each component of the apparatus to execute processing, that is, a storage unit 103 storing a recipe is provided. Note that the user interface 102 and the storage unit 103 are connected to the process controller 101.

  The recipe is stored in the storage medium 103 a in the storage unit 103. The storage medium may be a hard disk or a portable medium such as a CD-ROM, DVD, BD (Blue-ray Disc), or flash memory. Moreover, you may make it transmit a recipe suitably from another apparatus via a dedicated line, for example.

  Then, if necessary, an arbitrary recipe is called from the storage unit 103 by an instruction from the user interface 102 and is executed by the process controller 101, so that the Ti film forming apparatus 10 can control the process controller 101. The desired processing is performed.

<Ti film forming method>
Next, a Ti film forming method in the Ti film forming apparatus configured as described above will be described with reference to the flowchart of FIG. 2 and the temperature profile example of FIG.

  First, the wafer W is loaded into the processing container 51 shown in FIG. 1, and the wafer W is placed on the mounting table 63 held at a low temperature by the coolant supplied to the cooling jacket 65 that is a cooling mechanism constituting the mounting table 63. Place (Step 1). At this time, the voltage supply to the electrostatic chuck 66 is turned off, the wafer W is not adsorbed, and the heat transfer gas flows through a bypass line (not shown) and is not supplied to the back surface of the wafer W. For this reason, there is almost no heat transfer between the mounting table 63 and the wafer W, and the heat is not actively transferred.

  Then, by operating the vacuum pump 56, the inside of the processing vessel 51 is brought into a predetermined vacuum state. In this state, the gas control unit 60 is operated in the processing container 51 to flow the Ar gas as the plasma generation gas at a predetermined flow rate, and the throttle valve 55 is controlled to maintain the processing container 51 at a predetermined vacuum level. The gas is stabilized by flowing Ar gas at a predetermined flow rate for 3 to 30 seconds, for example, 5 seconds (step 2).

  Next, high-frequency power (plasma power) is supplied from the high-frequency power source 81 of the plasma generation source 78 to the induction coil 80 with Ar gas flowing, while the high-frequency power source 74 for bias is applied to the electrode 66b of the electrostatic chuck 66. A high frequency power for a predetermined bias is supplied. Thereby, in the processing container 51, argon gas is turned into plasma and argon ions are generated. In the state where no DC voltage is applied to the electrode 66b and the wafer W is not adsorbed, the argon ions in the argon plasma are made to collide with the surface of the wafer W by the high frequency power for biasing to give energy to the wafer W in advance. (Step 3).

  At this time, the mounting table 63 is controlled to a relatively low temperature of, for example, about 30 ° C. by supplying the coolant to the cooling jacket 65, but the wafer W is not adsorbed by the electrostatic chuck 66 and transmitted. Since no hot gas is supplied, the wafer W is difficult to be cooled by the minute space between the wafer W and the electrostatic chuck 66. For this reason, the wafer W is heated by the energy of argon ions, and the temperature rises. That is, the wafer W is preheated. By preheating with argon ions in this way, Ti fine particles on the shoulders of trenches and holes move into the trenches and holes during Ti film formation, so overhangs at the openings of the holes and trenches are suppressed. can do.

  The temperature of the wafer W at this time can be adjusted by the argon gas flow rate, the high frequency power (ICP power) to the induction coil 80, the bias power applied to the electrode 66b, the argon ion irradiation time, and the like. The preheating temperature at this time is preferably 100 ° C. or higher. If it is 100 degreeC or more, Ti can be moved at the time of Ti film formation, and it can suppress that an opening width becomes narrow by the overhang of a trench or a hole. Moreover, even if it exceeds 200 degreeC, an effect is only saturated. For this reason, it is preferable that preheating temperature is 100 degreeC or more and 200 degrees C or less. In the example shown in FIG. 3, the wafer temperature is increased to 170 ° C. by setting the argon ion irradiation time to about 60 seconds.

  Thereafter, with the DC power supply of the electrostatic chuck 66 kept off, high-frequency power is supplied to the induction coil 80 to generate plasma, and high-frequency power is supplied to the electrode 66b of the electrostatic chuck 66 to supply the wafer W. A high frequency bias is applied to the substrate, and Ar gas, which is a heat transfer gas, is bypassed so that the heat transfer gas does not flow between the wafer W and the mounting table 63, and the direct current is supplied from the variable DC power source 84 while maintaining the argon plasma. Electric power is applied to the target 83 made of Ti, and a Ti film is formed on the entire surface including the trenches and holes as described below (step 4).

Specifically, the Ti film is formed as follows.
When DC power is applied to the target 83 from the variable DC power source 84, argon ions in the argon plasma are attracted to the DC voltage and collide with the target 83, and the target 83 is sputtered to release (fly) Ti particles. . At this time, the amount of Ti released by the DC voltage applied to the target 83 is optimally controlled. Further, Ti atoms and Ti atomic groups, which are Ti particles emitted from the sputtered target 83, are mostly ionized when passing through the plasma. Then, the ionized Ti ions and electrically neutral neutral Ti atoms are mixed and drawn into the downward wafer W to which a bias is applied. The ionization rate at this time is controlled by the plasma generated by the high frequency power supplied from the high frequency power supply 81.

  When Ti ions enter the region of an ion sheath having a thickness of about several millimeters formed on the surface of the wafer W by the high frequency power for bias applied from the high frequency power source 74 for bias to the electrode 66b of the electrostatic chuck 66, the Ti ions are strong. The Ti film is formed by being attracted so as to accelerate toward the wafer W with directivity and deposited on the wafer W. At this time, argon ions are also attracted to the wafer W side by the high-frequency power for bias, and the Ti film is formed at a desired film formation speed by adjusting the bias power at this time to adjust the film formation by Ti and the etching by Ar. Form a film.

  In this manner, the electrostatic chuck 66 is also turned off when the Ti film is formed, and the wafer is heated by plasma without supplying a heat transfer gas between the wafer W and the mounting table 63. Since it is difficult to transfer the heat from W to the mounting table 63, the Ti film can be formed while the wafer W is heated by the preliminary heating in the step 2 and the temperature is increased. The Ti film formation process time is appropriately set according to the thickness of the Ti film, but the film formation is completed in a relatively short time of about 10 sec when the film thickness of the normal barrier layer is several nm. . In the example of FIG. 3, it is 12 sec. Note that, as shown in FIG. 3, the temperature of the wafer W slightly rises due to the plasma irradiation even when the Ti film is formed.

  After the Ti film is formed, the power supplies 81, 74, and 84 are turned off, the chuck power supply 73 of the electrostatic chuck 66 is turned on, and the wafer W is attracted to the mounting table 63. During this period, Ar gas, which is a heat transfer gas, is supplied at, for example, 1 to 10 Torr, and the wafer W is cooled by the mounting table 63 (Step 5).

  In this way, the wafer W is adsorbed to the mounting table 63 and the heat transfer gas is supplied between the mounting table 63 and the wafer W, so that the wafer W is held by the mounting table 63 held at a low temperature of 30 ° C., for example. It is cooled quickly and can be brought to a temperature close to the holding temperature of the mounting table 63 in a short time. At this time, for example, Ar gas, which is a heat transfer gas, is caused to flow from the heat transfer gas supply source 89 to the back surface of the wafer W through the heat transfer gas flow path 88, whereby heat transfer between the wafer W and the mounting table 63 is performed. Thus, the wafer W can be cooled in a shorter time. The temperature of the mounting table 63 is preferably -30 to 90 ° C. In the example of FIG. 3, the temperature of the wafer W is cooled from about 180 ° C. to about 50 ° C. in about 10 seconds.

  Thereafter, the supply of the heat transfer gas is stopped, the electrostatic chuck is turned off, the gate valve G is opened, and the wafer W is unloaded (step 6).

The conditions in the example of FIG. 3 are as follows.
-Preheating pressure in the processing vessel: 10 mTorr
Argon gas flow rate: 130sccm
ICP power supply power: 5.25kW
Bias power: 150W
Time: 60sec
・ Ti film deposition Pressure in the processing vessel: 5 mTorr
Argon gas flow rate: 130sccm
ICP power supply power: 5.25kW
DC power (target): 4kW
Bias power: 100W
Time: 12 sec
・ Wafer cooling Argon gas flow: 500sccm
Heat transfer gas pressure: 6 Torr
Electrostatic chuck voltage: 1650V

  In this embodiment, since the Ti film is formed after the wafer W is preheated by plasma, Ti deposited on the wafer W can be flowed, and overhang is suppressed, and the gap between the trench and the hole is reduced. Narrowing can be prevented. At this time, it was found that the effect of suppressing the overhang can be obtained by moving the deposited Ti even at a low temperature of 100 ° C. as described above. This is an extremely low temperature as compared with the case where the wafer is heated to 300 ° C. or higher in Patent Document 2 above, and this is the first time that the effect of suppressing the overhang even by heating at such a low temperature is present. This is the point that was found.

  At this time, the wafer W is not adsorbed to the mounting table 63 and a heat transfer gas is not supplied between the mounting table 63 and the wafer W, so that argon ions collide with the wafer W to preheat the mounting table 63 itself. Is kept at a low temperature, the Ti film is formed at the preheated temperature, and then the wafer W is adsorbed onto the mounting table 63 and the heat transfer gas is supplied to quickly cool the wafer W. it can. For this reason, there is no need to worry about the oxidation of the film due to unloading the wafer W at a high temperature, and the cooling time can be shortened, so that the resistance can be reduced and the throughput can be improved.

<Experimental result>
Here, for the wafer in which a trench having a width of 25 nm and a height of 90 nm is formed, the apparatus of FIG. 1 is used to turn off the power supply to the electrostatic chuck and to supply no Ar gas as a heat transfer gas. Then, argon gas is introduced into the processing container at a flow rate of 130 sccm, the pressure in the processing container is set to 10 mTorr, 5.25 kW is applied to the ICP power source to generate argon plasma, the bias is 150 W, and argon ions are applied to the wafer for a predetermined time. Preheating is performed while irradiating, and thereafter, similarly, the power supply to the electrostatic chuck is turned off, the heat transfer gas is not supplied, the pressure in the processing container is set to 5 mTorr, the argon gas is set to 130 sccm, and the ICP power source is set to 5. While maintaining at 25 kW, 4 kW of DC power is supplied to the target, and 200 W of high frequency power is supplied to the electrode 66b. A bias is applied to the Fine W, thereby forming a thick 20nm of Ti film than usual to see the influence of the overhang to generate plasma in the processing chamber 51.

  FIG. 4 shows the relationship between the preheating time with argon plasma and the minimum opening width of the trench. The minimum opening width on the vertical axis indicates the opening width of the trench having the narrowest width when the Ti film is formed. From this figure, it can be seen that the longer the preheating time, the wider the trench opening width after the Ti film is formed. The preheating time corresponds to the wafer temperature, and the relationship between the wafer temperature and the minimum trench opening width becomes wider as the temperature increases, as shown in FIG. The vertical axis in FIG. 5 is a value obtained by dividing the actual minimum opening width of the trench by the minimum opening width when the Ti film is formed without heating, and is preheated at 175 ° C. to form the Ti film. In this case, the minimum opening width of the trench is about 1.27 times that in the case where the preheating is not performed. When the preheating is not performed, the Ti film overhangs as shown in FIG. While the opening width of the trench is narrowed, overheating is suppressed by performing preheating as shown in FIG.

  Next, the crystal state of the Ti film formed without preheating and the Ti film formed after 30 seconds of preheating was investigated. FIG. 7 is a diagram showing X-ray diffraction patterns of these Ti films. The thickness of the Ti film was 7 nm. As shown in FIG. 7, the preheated Ti film has a lower peak of the (002) plane of Ti than the nonpreheated Ti film, and the Ti particle size estimated from the half-value width is smaller when preheated. It was confirmed. Thus, preheating is expected to reduce the particle size of the Ti film and improve the barrier properties.

  FIG. 8 shows a scanning electron microscope (SEM) when a Cu film serving as a seed film is formed by iPVD on a Ti film formed without the above-described preheating and a Ti film formed after 30 sec preheating. ) Photo. These are SEM photographs after the Ti film has a thickness of 7 nm, the Cu film has a thickness of 30 nm, and the Cu film has been etched by 25 nm. As shown in these figures, it can be seen that the crystal grains (grains) of the Cu film on the Ti film are reduced by preheating. The Cu barrier layer on the Ti film preferably has smaller crystal grains in the film formation stage, which is also an advantage of preheating.

<Cu wiring formation method>
Next, a method of forming a Cu wiring using the above Ti film as a barrier layer will be described with reference to the flowchart of FIG. 9 and the process cross-sectional view of FIG.

First, an interlayer insulating film 202 such as a SiO ₂ film is provided on a lower structure 201 (details omitted), and a trench 203 and a via (not shown) for connection to a lower layer wiring are formed in a predetermined pattern therein. The wafer W thus prepared is prepared (step 11, FIG. 10A). Such a wafer W is preferably one obtained by removing moisture on the insulating film surface and residues during etching / ashing by a Degas process or a Pre-Clean process.

  Next, a barrier layer 204 that shields (barriers) Cu is formed on the entire surface including the surfaces of the trench 203 and the via (step 12, FIG. 10B). As the barrier layer 204, a Ti film formed in a high temperature state after preheating as in the above film forming method is used.

  Next, a Ru liner film 205 is formed on the barrier layer 204 (step 13, FIG. 10C). The Ru liner film is preferably formed as thin as 1 to 5 nm, for example, from the viewpoint of increasing the volume of Cu to be embedded and reducing the resistance of the wiring.

  Since Ru has high wettability with respect to Cu, by forming a Ru liner film on the base of Cu, it is possible to ensure good Cu mobility when forming the next Cu film. It is possible to make it difficult to generate an overhang that closes the opening of a trench or a hole during film formation. For this reason, Cu can be reliably embedded without generating voids even in fine trenches or holes.

The Ru liner film 205 can be suitably formed by thermal CVD using ruthenium carbonyl (Ru ₃ (CO) ₁₂ ) as a film forming material. Thereby, a high-purity and thin Ru film can be formed with high step coverage. In addition to ruthenium carbonyl, for example, (cyclopentadienyl) (2,4-dimethylpentadienyl) ruthenium, bis (cyclopentadienyl) (2,4-methylpentadienyl) ruthenium, (2,4-dimethylpenta) Ruthenium pentadienyl compounds such as dienyl) (ethylcyclopentadienyl) ruthenium and bis (2,4-methylpentadienyl) (ethylcyclopentadienyl) ruthenium can also be used. Further, the Ru liner film 205 can be formed by PVD.

  If the trench or via opening is wide and overhang is not likely to occur, it is not always necessary to form the Ru liner film 205, and a Cu seed film described below is directly formed on the barrier layer 204. Also good.

  Next, a Cu seed film 206 is formed by PVD (step 14, FIG. 10 (d)). The film thickness of the Cu seed film 206 is preferably 20 to 40 nm in consideration of the embedding property of subsequent Cu plating. The film formation at this time can be suitably performed using the same iPVD apparatus used for film formation of the Ti film except that the target material is changed from Ti to Cu. In this case, the temperature of the mounting table is preferably as low as -50 to 0 ° C, for example. When the Cu seed film 206 is directly formed after forming the barrier film 204 made of the Ti film, the wafer W carried out in a cooled state from the iPVD apparatus for forming the Ti film is vacuum-transferred. Since the temperature is controlled and kept at a low temperature by the mounting table of the iPVD apparatus for forming the Cu film through the chamber, the throughput improvement effect can be further increased.

  Thereafter, Cu plating 207 is applied on the Cu seed film 206, and the trench 203 is filled to form Cu on the entire surface of the wafer W (step 15, FIG. 10E).

  Thereafter, annealing is performed as necessary (step 16), and then the entire surface of the wafer W is polished and planarized by CMP (chemical mechanical polishing) (step 17, FIG. 10 (f)). As a result, a Cu wiring 208 is formed by the barrier layer 204 (Ru film), the Cu seed film 206 and the Cu plating 207 remaining in the trench 203 and the via (hole).

  Of the above-described series of steps, Step 12 for forming the barrier layer 204, Step 13 for forming the Ru liner film 205, and Step 14 for forming the Cu seed film 206 are performed by an apparatus for forming each film. It is preferable to form a film continuously in a vacuum without exposure to the atmosphere using a cluster tool type processing device connected to a vacuum transfer chamber equipped with a transfer device. Also good. Even if it is not exposed to the atmosphere, after the Ti film is formed, if the wafer W is carried out at a high temperature, the oxidation of the Ti film is inevitable. Therefore, it is effective to carry out the wafer W after cooling it on the mounting table. . When the Ti film is exposed to the atmosphere after the Ti film is formed, the Ti film is remarkably oxidized by carrying it out at a high temperature. Therefore, the effect of carrying out the wafer W after cooling it by the mounting table is extremely large.

<Other applications>
As mentioned above, although embodiment of this invention was described, this invention can be variously deformed, without being limited to the said embodiment. For example, in the above embodiment, an example in which an ICP type plasma sputtering apparatus is used for forming a Ti film has been described. However, the present invention is not limited to this, and other types of plasma sputtering apparatuses may be used, and Cu ions and plasma gas generating ions may be used. Other iPVD devices may be used as long as the pull-in of the device can be adjusted.

  In the above embodiment, the film formation of the Ti film has been described. However, if the particles move when the film is heated by preheating, not only the Ti film but also other metals such as a Ta film, for example. The present invention can also be applied to film formation.

  Furthermore, in the above-described embodiment, an example in which a wafer having a trench and a via (hole) is used when forming a Cu wiring using a Ti film formed after preheating as a barrier layer has been described. Needless to say, the present invention can be applied to cases having holes only. Further, Cu plating may be embedded without providing a Cu seed, or Cu may be embedded with PVD instead of Cu plating.

  Furthermore, in the above embodiment, the semiconductor wafer is described as an example of the substrate to be processed. However, the semiconductor wafer includes not only silicon but also compound semiconductors such as GaAs, SiC, and GaN, and is further limited to the semiconductor wafer. Needless to say, the present invention can also be applied to a glass substrate, a ceramic substrate, and the like used in an FPD (flat panel display) such as a liquid crystal display device.

DESCRIPTION OF SYMBOLS 10; Ti film-forming apparatus 51; Processing container 56; Vacuum pump 59; Gas supply source 63; Mounting stage 65; Cooling jacket 66; Electrostatic chuck 74; High frequency power supply 78 for biasing 78; Plasma generation source 80; 84; DC power supply 85; magnet 88; heat transfer gas flow path 89; heat transfer gas supply source 201; lower structure 202; interlayer insulating film 203; trench 204; barrier layer (Ti film)
205; Ru liner film 206; Cu seed film 207; Cu plating 208; Cu wiring W; Semiconductor wafer (substrate to be processed)

Claims (12)

A processing container; a mounting table for mounting the substrate to be processed in the processing container; a cooling mechanism for cooling the mounting table; an adsorption mechanism for adsorbing the processing substrate to the mounting table; the mounting table; A heat transfer gas supply means for supplying a heat transfer gas to the processing substrate; a gas introduction mechanism for introducing a plasma generation gas into the processing container; and a plasma for generating plasma of the plasma generation gas in the processing container. A generation mechanism, a metal target formed on the substrate to be processed, a direct current power source for applying a voltage to the target, and a bias power source for applying a high frequency bias for attracting ions to the mounting table. A film forming method for forming a metal film on a substrate to be processed using a film apparatus,
Holding the mounting table at a low temperature by the cooling mechanism, and placing the substrate to be processed on the mounting table by the suction mechanism without sucking;
Next, plasma of the plasma generation gas is generated, and with the high frequency bias applied from the bias power source to the mounting table, ions of the plasma generation gas are attracted to the substrate to be processed to relatively move the substrate to be processed. Preheating to a high temperature;
Next, in the state in which the plasma is formed, a voltage is applied to the target from the DC power source, metal particles are discharged from the target, and the metal ionized by the plasma together with ions of the plasma generation gas by the bias power source A step of drawing ions into the substrate to be processed to form a metal film;
After the film formation is stopped, the substrate to be processed is adsorbed to the mounting table held at the relatively low temperature by the suction mechanism, and a heat transfer gas is supplied between the mounting table and the substrate to be processed. Heat transfer between the substrate to be processed and the mounting table, and cooling the substrate to be processed;
And a step of carrying out the cooled substrate to be processed from the processing container.   The film forming method according to claim 1, wherein the mounting table is cooled to −30 to 90 ° C.   The film forming method according to claim 1, wherein the adsorption mechanism is an electrostatic chuck.   4. The film forming method according to claim 1, wherein the preheating step heats the substrate to be processed to 100 ° C. or more. 5.   The film forming method according to claim 4, wherein in the preliminary heating, the substrate to be processed is heated to 100 to 200 ° C.   The film formation method according to claim 1, wherein the metal film is a Ti film. A Cu wiring forming method for forming Cu wiring by burying Cu in trenches and / or holes of a predetermined pattern formed on a substrate to be processed,
Forming a barrier layer by forming a metal film on a surface of at least the trench and / or hole of the substrate to be processed by a film forming method according to claim 1;
Burying Cu in the trench and / or hole in which the barrier layer is formed;
And a step of polishing and flattening a Cu portion up to the opening of the trench and / or hole after the Cu is buried.   8. The method for forming a Cu wiring according to claim 7, wherein the trench and / or the hole is formed in an insulating film of the substrate to be processed.   9. The method for forming a Cu wiring according to claim 7, further comprising a step of forming a liner film made of ruthenium on the barrier layer after forming the barrier layer.   10. The Cu wiring according to claim 7, wherein the Cu burying step buryes the trench and / or the hole by Cu plating after forming a Cu seed film by PVD. 11. Forming method.   The method for forming a Cu wiring according to claim 7, wherein the step of polishing and planarizing is performed by CMP.   A storage medium that operates on a computer and stores a program for controlling a film forming apparatus, wherein the program performs the film forming method according to any one of claims 1 to 6 at the time of execution. And a computer that controls the film forming apparatus.