KR101139189B1 - Plasma etching method, plasma processing apparatus, control program and computer redable storage medium - Google Patents

Abstract

The present invention provides a plasma etching method capable of etching a silicon layer in a laminated film using a resist as a mask while ensuring a sufficient mask selection ratio and an etching rate.

In the processing chamber of the plasma processing apparatus 100, a fluorocarbon gas and a hydrofluoric acid are applied to a silicon layer containing silicon as a main component and a workpiece formed by laminating at least a silicon oxide film, a silicon nitride film and a resist film on the upper layer than the silicon layer. The silicon nitride film, silicon oxide film and silicon layer are collectively etched using a plasma generated from a processing gas containing a carboxyl gas, a rare gas and an O ₂ gas.

Description

Plasma Etching Method, Plasma Processing Apparatus and Computer-readable Storage Media {PLASMA ETCHING METHOD, PLASMA PROCESSING APPARATUS, CONTROL PROGRAM AND COMPUTER REDABLE STORAGE MEDIUM}

1 is a cross-sectional view showing a magnetron RIE plasma etching apparatus, which is preferred for implementing the method of the present invention;

2 is a structural diagram of a processing gas supply system in FIG. 1;

3 is a horizontal sectional view schematically showing a dipole ring magnet disposed around a chamber of the apparatus of FIG. 1;

4 is a schematic diagram for explaining an electric field and a magnetic field formed in the chamber,

5 is a schematic view of a cross section showing a laminated structure of a semiconductor wafer to which the method of the present invention is applied;

6 is a view showing a cross section of a semiconductor wafer after etching;

7 is a schematic view of a cross section showing a laminated structure of a semiconductor wafer of another example to which the method of the present invention is applied;

8 is a cross-sectional view of a semiconductor wafer after etching;

9 shows a sample wafer used for the test, (a) shows a cross section before etching, (b) shows a cross section after etching, (c) shows a measurement position of CD on the surface of the sample wafer,

10 is a view showing an etching selectivity with respect to a resist mask of a silicon nitride film when the gas flow rate and pressure are changed;

11 is a view showing an etching rate of a silicon nitride film when the gas flow rate and pressure are changed;

12 is a view showing an etching selectivity ratio of a resist mask of silicon when the gas flow rate and pressure are changed;

13 is a view showing etching rate of silicon when gas flow rate and pressure are changed;

14 is a view showing a change in the side wall inclination angle difference due to the roughness of the pattern when the pressure is changed;

15 is a view showing a change in the side wall inclination angle difference due to the roughness of the pattern when the CHF ₃ / Ar flow rate ratio is changed;

16 is a view showing a change in sidewall inclination angle difference due to the roughness of the pattern when the CF ₄ flow rate is changed;

Figure 17 is shown a change in the side wall slope angle difference by the density of the pattern in the case where changes in the flow rate of O _2,

18 is a view showing a change in the critical dimension difference due to the in-plane position when the pressure is changed;

19 is a view showing a change in the critical dimension difference due to the in-plane position of the wafer when the CHF ₃ / Ar flow rate ratio is changed;

20 is a view showing a change in a critical dimension difference due to a wafer in-plane position when the CF ₄ flow rate is changed;

FIG. 21 is a view showing a change in the critical dimension difference due to a wafer in-plane position when the O ₂ flow rate is changed. FIG.

(Explanation of symbols about main parts of drawing)

1 chamber 2 device isolation region

12 exhaust system 15 high frequency power supply

17: refrigerant chamber 18: gas introduction mechanism

20: shower head (electrode) 25: process gas supply system

30: dipole ring magnet 101: silicon substrate

102 silicon oxide film (SiO ₂ ) 103 silicon nitride film (Si ₃ N ₄ )

106: antireflection film (BARC) 107: resist (PR)

110: to-be-processed object 201: silicon substrate

202: silicon oxide (SiO ₂ ) film 203: silicon nitride (Si ₃ N ₄ ) film

204: silicon oxynitride (SiON) film 205: silicon oxide (SiO ₂ ) film

206: resist (PR) 301: silicon substrate

302: silicon oxide (SiO ₂ ) film 303: silicon nitride (Si ₃ N ₄ ) film

304: resist (PR) W: wafer

 Patent Document 1: Japanese Patent Laid-Open Publication No. 1995-263415 (paragraphs 0006 to 0010)

The present invention relates to a plasma etching method comprising a step of etching a target object using plasma.

In the manufacturing process of a semiconductor device, the process of etching a laminated film using a mask, such as a patterned resist film, is performed repeatedly. For example, in the process of manufacturing the gate electrode, a silicon oxide film, a silicon nitride film, a polycrystalline silicon layer serving as a gate electrode, and a hard mask layer made of silicon nitride, or the like, which are sequentially formed on the semiconductor substrate from below, are made of silicon oxide, or the like. A laminate of an antireflection film and a resist film is prepared. The antireflection film and the hard mask were dry-etched using the resist film patterned by photolithography as a mask, and then the resist film was removed by ashing, and then the polycrystalline silicon layer was etched using the hard mask film as a mask. Gate electrode formation has been performed.

In this case, a plasma etching apparatus dedicated to insulation film etching was used to etch the antireflection film and hard mask film, and a plasma etching apparatus dedicated to silicon etching was used to etch polysilicon. In addition, ashing removal of the resist was performed using the dedicated ashing apparatus.

In addition, in STI (Shallow Trench Isolation) forming a trench for device isolation with respect to a silicon substrate, for example, a silicon oxide film, a silicon nitride film, a silicon oxynitride (SiON) film, and an oxide mask film are sequentially formed from below on a silicon substrate. And what laminated | stacked and formed the resist film is prepared. Then, an oxide mask layer, a silicon oxynitride (SiON) film, a silicon nitride film and a silicon oxide film are etched using a resist patterned by photolithography as a mask, and then the oxide mask layer and a silicon oxynitride (SiON) film And the silicon substrate was etched using the silicon nitride film as a mask to form trenches in the silicon substrate. Also in this case, an etching device dedicated to insulation film etching was used to etch an oxide mask film, a silicon oxynitride (SiON) film, a silicon nitride film, and a silicon oxide film, and an etching device dedicated to silicon etching was used to etch a silicon substrate. . In addition, ashing removal of the resist was performed using the dedicated ashing apparatus.

As described above, in the conventional etching process, before etching the silicon layer, the hard mask layer is first etched using the resist film to transfer the resist pattern to the hard mask layer, and then silicon etching is performed using the hard mask. At least two steps of etching were required. This is because when the silicon is to be etched using the resist as a mask, the mask selection ratio is not sufficiently obtained, and it is difficult to secure the etching rate, or the roughness of patterns such as line and space and the center portion of the semiconductor wafer. This is because a difference occurs in etching shapes such as angles of trench sidewalls formed by etching and critical dimensions (CD) depending on the in-plane positions of the edges and the periphery.

In addition, depending on the object of etching, the gas system used for insulating film etching and silicon etching is different, and silicon etching mainly uses a highly corrosive gas, and the etching accuracy decreases due to the mixing of each gas. It was necessary to distinguish and use the etching apparatus for exclusive use of the insulating film, and the etching apparatus for exclusive use of silicon (for example, patent document 1).

It is an object of the present invention to provide a plasma etching method capable of etching a silicon layer in a laminated film using a resist as a mask while ensuring a sufficient mask selection ratio and etching rate. Another object of the present invention is to provide a plasma etching method in which the etching shape does not occur due to the pattern roughness or the position on the workpiece.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the 1st viewpoint of this invention is a fluorocarbon gas and hydrofluoric acid about the to-be-processed object which has the silicon layer which has silicon as a main component, and the resist film formed in the upper layer rather than this silicon layer, and previously patterned. Provided is a plasma etching method comprising the step of etching the silicon layer using a plasma generated from a processing gas containing a carbon gas, a rare gas, and an O ₂ gas, using the resist film as a mask.

In addition, a second aspect of the present invention is directed to an object to be processed in which a silicon layer containing silicon as a main component and at least a silicon oxide film, a silicon nitride film, and a resist film formed in advance on the silicon layer are laminated in the processing chamber of the plasma processing apparatus. The silicon nitride film, the silicon oxide film and the silicon layer were formed by using a plasma generated from a processing gas containing a fluorocarbon gas, a hydrofluorocarbon gas, a rare gas and an O ₂ gas. Provided are a plasma etching method characterized by collectively etching.

In the first and second aspects, the fluorocarbon gas is preferably a CF ₄ gas, a C ₂ F ₆ gas, a C ₃ F ₈ gas, or a C ₄ F ₈ gas. In addition, the hydrofluorocarbon gas is preferably a CHF ₃ gas, a CH ₂ F ₂ gas or a CH ₃ F gas.

Moreover, it is preferable that the flow volume of the said fluorocarbon gas is 10-50 ml / min. Further, the flow rate of the O ₂ gas is preferably 1 ~ 30㎖ / min. The flow rate ratio (hydrofluorocarbon gas flow rate / rare gas flow rate) of the hydrofluorocarbon gas and the rare gas is preferably 0.019 to 0.173.

Moreover, it is preferable that a process pressure is 8-12 kPa.

In addition, in the first and second aspects, the pattern is small (coarse) and dense (density) by the flow rate of the fluorocarbon gas or O ₂ gas. It is preferable to control the critical dimension after the etching in. Moreover, it is preferable to control the critical dimension after the etching in surface inside of a to-be-processed object by the flow volume of the said fluorocarbon gas.

Further, in the second aspect, the hydrofluorocarbon gas when lowering the processing pressure when etching the silicon layer or etching the silicon nitride film with respect to the processing pressure when the silicon nitride film is etched. It is preferable to reduce the flow volume of the hydrofluorocarbon gas at the time of etching the silicon layer with respect to the flow rate.

Further, from the first and second aspects, it is preferable that the silicon layer is composed mainly of polycrystalline silicon or single crystal silicon.

A third aspect of the present invention provides a control program that operates on a computer and controls the plasma processing apparatus such that, when executed, the plasma etching method of the first aspect or the second aspect is executed.

A fourth aspect of the present invention is a computer-readable storage medium storing a control program operating on a computer, wherein the control program is executed such that the plasma etching method of the first or second aspect is executed when executed. It provides a computer readable storage medium to control the.

A fifth aspect of the present invention provides a processing chamber for performing a plasma etching process on a target object, a support on which the target object is mounted in the processing chamber, exhaust means for depressurizing the interior of the processing chamber, and a processing gas in the processing chamber. It provides a plasma processing apparatus having a gas supply means for supplying a gas, and a control unit for controlling the plasma etching method of the first or second aspect to be executed in the processing chamber.

According to the plasma etching method of the present invention, by using a gas containing a fluorocarbon gas, a hydrofluorocarbon gas, a rare gas, and an O ₂ gas as a processing gas, silicon etching is performed using a resist as a mask while ensuring a sufficient etching rate. You can run

In addition, by adjusting the flow rates of the fluorocarbon gas and the O ₂ gas, the angular difference between the sidewalls of the etching groove due to the roughness of the pattern and the critical dimension difference after the etching due to the position on the workpiece can be eliminated, thereby making it possible to uniformize the etching shape. Done.

Therefore, according to the plasma etching method of the present invention, a significant reduction in the number of steps and a shortening of the processing time can be realized in the silicon etching process. In addition, the plasma etching method of the present invention can be advantageously used for manufacturing highly reliable semiconductor devices because the etching shape can be uniformized, and the design rules of the semiconductor devices can be made finer and more integrated. Do.

EMBODIMENT OF THE INVENTION Hereinafter, the preferred form of this invention is demonstrated, referring drawings.

1 is a cross-sectional view showing an outline of a magnetron RIE plasma etching apparatus 100 that can be suitably used for the plasma etching method of the present invention. The plasma etching apparatus 100 is hermetically sealed, and has a cylindrical shape having a stage consisting of an upper portion 1a of a small diameter and a lower portion 1b of a large diameter, and the wall portion of the chamber (processing vessel), for example, made of aluminum ( Have 1)

In this chamber 1, a support table 2 for horizontally supporting a semiconductor wafer (hereinafter simply referred to as "wafer") W, which is a single crystal Si substrate, is provided as an object to be processed. The support table 2 is made of aluminum, for example, and is supported by the support 4 of the conductor via the insulating plate 3. In addition, a focus ring 5 formed of a material other than Si, for example, quartz, is provided on the outer circumference of the upper side of the support table 2. The support table 2 and the support 4 can be lifted by a ball screw mechanism including a ball screw 7, and the driving portion below the support 4 is a bellows made of stainless steel (SUS). 8) covered with The bellows cover 9 is provided on the outer side of the bellows 8. Moreover, the baffle plate 10 is provided in the outer side of the said focus ring 5, and is connected with the chamber 1 via this baffle plate 10, the support stand 4, and the bellows 8. As shown in FIG. The chamber 1 is grounded.

An exhaust port 11 is formed on the side wall of the lower portion 1b of the chamber 1, and an exhaust system 12 is connected to the exhaust port 11. Then, the vacuum pump of the exhaust system 12 is operated to reduce the pressure in the chamber 1 to a predetermined degree of vacuum. On the other hand, at the upper side of the side wall of the lower part 1b of the chamber 1, the gate valve 13 which opens and closes the opening / exit of the wafer W is provided.

The high frequency power supply 15 for plasma formation is connected to the support table 2 via the matcher 14, and a high frequency power of a predetermined frequency, for example, l3.36 MHz is supplied from the high frequency power supply 15. It is supplied to (2). On the other hand, the shower head 20 is provided in parallel with the support table 2 above, and this shower head 20 is grounded. Thus, the support table 2 and the showerhead 20 function as a pair of electrodes.

On the surface of the support table 2, an electrostatic chuck 6 for electrostatically holding and holding the wafer W is provided. The electrostatic chuck 6 is configured with an electrode 6a interposed between the insulators 6b, and a DC power supply 16 is connected to the electrode 6a. When a voltage is applied from the power supply 16 to the electrode 6a, the wafer W is attracted by the electrostatic force, for example, a coulomb force.

A coolant chamber 17 is provided inside the support table 2, and the coolant is introduced into the coolant chamber 17 through the coolant introduction pipe 17a, discharged from the coolant discharge pipe 17b, circulated, and the cold heat thereof. Heat is transferred to the wafer W via the support table 2, whereby the processing surface of the wafer W is controlled to a desired temperature.

In addition, even if the chamber 1 is evacuated by the exhaust system 12 and maintained in a vacuum, the cooling gas is supplied to the gas introduction mechanism () so that the wafer W can be effectively cooled by the refrigerant circulated in the refrigerant chamber 17. 18 is introduced between the surface of the electrostatic chuck 6 and the back surface of the wafer W via the gas supply line 19. By introducing the cooling gas in this way, the cooling heat of the refrigerant can be effectively transmitted to the wafer W, and the cooling efficiency of the wafer W can be increased. As cooling gas, He etc. can be used, for example.

The shower head 20 is provided to face the support table 2 on the ceiling wall portion of the chamber 1. The shower head 20 is provided with a plurality of gas discharge holes 22 in the lower surface thereof, has a gas introducing portion 20a in the upper portion thereof, and a space 21 formed therein. A gas supply pipe 24 having a valve 23 is connected to the gas introduction part 20a, and a processing gas supply system for supplying a processing gas consisting of an etching gas and a dilution gas to the other end of the gas supply pipe 24 ( 25) is connected.

As shown in FIG. 2, the process gas supply system 25 has a CF ₄ gas supply source 41, a CHF ₃ gas supply source 42, an Ar gas supply source 43, and an O ₂ gas supply source 44. The piping from the gas supply source is provided with a mass flow controller (MFC) 45 and a valve 46, respectively. Then, CF ₄ gas / CHF ₃ gas / Ar gas / O ₂ gas as an etching gas is discharged from the respective gas supply sources of the processing gas supply system 25 through the gas supply pipe 24 and the gas introduction part 20a to the shower head ( It reaches the space 21 in 20 and discharges from each gas discharge hole 22.

On the other hand, a dipole ring magnet 30 is arranged concentrically around the upper portion 1a of the chamber 1. As shown in the horizontal sectional view of FIG. 3, the dipole ring magnet 30 is formed by attaching a plurality of anisotropic segment main boxes 31 to a case 32 of a ring-shaped magnetic body. In this example, 16 anisotropic segment main stones 31 forming a columnar shape are arranged in a ring shape. In FIG. 3, the arrow shown in the anisotropic segment main box 31 shows the direction of magnetization. As shown in this figure, the direction of magnetization of the some anisotropic segment main box 31 is shifted little by little, and it is 1 as a whole. A uniform horizontal magnetic field B facing the direction is formed.

Therefore, in the space between the support table 2 and the shower head 20, as shown schematically in FIG. 4, the high-frequency power source 15 forms an electric field EL in the vertical direction, and also the dipole ring magnet 30 ), The horizontal magnetic field B is formed, and the magnetron discharge is generated by the orthogonal electromagnetic field thus formed. As a result, plasma of the etching gas in a high energy state is formed, and the wafer W is etched.

In addition, each component of the plasma etching apparatus 100 is connected to the process controller 50 provided with a CPU, and is controlled by it. The process controller 50 includes a keyboard for the process manager to execute a command input operation for managing the plasma etching apparatus 100, a display for visually displaying the operation status of the plasma etching apparatus 100, and the like. 51 is connected.

The process controller 50 further includes a storage unit 52 which stores recipes in which control programs, processing condition data, and the like, for realizing various processes executed in the plasma etching apparatus 100 are controlled by the process controller 50. Connected.

Then, if necessary, an arbitrary recipe is called from the storage unit 52 by an instruction from the user interface 51 and executed by the process controller 50, thereby controlling the plasma etching apparatus (under the control of the process controller 50). The desired processing in 100) is executed. In addition, the recipe is often transferred to a computer-readable storage medium such as a CD-ROM, a hard disk, a flexible disk, or a flash memory, or is frequently transmitted from another device via, for example, a dedicated line. It can also be used.

Next, the etching method of this invention which performs plasma etching with respect to the wafer W which has a silicon layer (monocrystalline silicon or polysilicon) using the plasma etching apparatus 100 comprised in this way is demonstrated.

First, the gate valve 13 is opened, the wafer W is brought into the chamber 1, mounted on the support table 2, and then the support table 2 is raised to the position shown in the drawing. The inside of the chamber 1 is exhausted via the exhaust port 11 by the vacuum pump.

Then, the processing gas containing the etching gas and the dilution gas is introduced into the chamber 1 from the processing gas supply system 25 at a predetermined flow rate, and the inside of the chamber 1 is set to a predetermined pressure. Predetermined high frequency electric power is supplied to the support table 2 from (15). At this time, the wafer W is sucked and held on the electrostatic chuck 6 by a coulomb force by applying a predetermined voltage from the DC power supply 16 to the electrode 6a of the electrostatic chuck 6, and at the same time, A high frequency electric field is formed between the shower head 20 which is an electrode and the support table 2 which is a lower electrode. Since the horizontal magnetic field B is formed between the shower head 20 and the support table 2 by the dipole ring magnet 30, an orthogonal electromagnetic field is formed in the processing space between the electrodes in which the wafer W exists, thereby creating Magnetron discharges are generated by the drift of electrons. The wafer W is etched by the plasma of the etching gas formed by the magnetron discharge.

As the etching gas, it is preferable to use a gas containing CF ₄ gas, CHF ₃ gas, Ar gas and O ₂ gas from the viewpoint of ensuring a sufficient mask selection ratio and etching rate and controlling the etching shape. . The CF ₄ gas is believed to produce F radicals (F *), which mainly contribute to etching, by a reaction mainly represented by CF ₄ → CF ₃ * + F * in the plasma. F radical advances etching by reacting with a silicon oxide film, a silicon nitride film, and a silicon layer as follows (reaction 1)-(reaction 3).

(Reaction 1) SiO ₂ + 4F * → SiF ₄ ↑ + O ₂

(Reaction 2) Si ₃ N ₄ + 12F * → 3SiF ₄ ↑ + 2N ₂ ↑

(Reaction 3) Si + 4F * + SiF ₄ ↑

When the CHF ₃ gas is added to the CF ₄ gas, HF is generated to reduce F radicals, and at the same time, CH or CF-based polymers are produced, thereby acting as a protective film, thereby improving the resistivity selectivity.

Ar gas has a function of promoting the dissociation reaction for generating the F radical and maintaining the uniformity of the radical distribution in the plasma. It also has the effect of removing the film which is performing the etching reaction by sputtering.

In addition, the O ₂ gas has an action of preventing excessive deposition of the CH or CF polymer at the bottom of the etched groove or hole.

It is also effective to adjust the temperature of the wafer W in order to make the shape of etching favorable. For this reason, a coolant chamber 17 is provided, and a coolant is circulated in the coolant chamber 17, and the cool heat thereof is transferred to the wafer W via the support table 2, whereby the processing surface of the wafer W is desired. Controlled by temperature.

The high frequency power supply 15 for plasma generation is suitably set in frequency and output in order to form a desired plasma. In the silicon etching, from the viewpoint of increasing the plasma density immediately above the wafer W, the frequency is preferably 13.56 MHz or more.

The dipole ring magnet 30 applies a magnetic field to the processing space between the support table 2 and the showerhead 20, which are opposite electrodes, in order to increase the plasma density just above the wafer W, but the effect is effectively applied. In order to exert it, it is preferable that it is a magnet of intensity | strength which forms a magnetic field of 10000 microT (100G) or more in a process space. It is considered that the stronger the magnetic field is, the stronger the effect of increasing the plasma density is. However, from the viewpoint of safety, the magnetic field is preferably 100000 µT (1 kG) or less.

The preferable conditions at the time of collectively etching a laminated film using the plasma etching apparatus 100 are as follows.

For example, the flow rate of the process gas is 10-50 ml / min (sccm) for CF ₄ gas, preferably 20-40 ml / min (sccm), and 10-100 ml / min (sccm) for CHF ₃ gas. 20 to 70 ml / min (sccm), Ar gas is 100 to 2000 ml / min (sccm), preferably 300 to 1200 ml / min (sccm), and O ₂ gas is 1 to 30 ml / min (sccm). ), Preferably 6 to 15 ml / min (sccm).

Further, from the viewpoint of securing the etching rate and securing the uniformity of the etching shape (that is, suppressing the inclination angle difference of the sidewall of the etching groove due to the roughness of the pattern and suppressing the critical dimension difference due to the in-plane position of the wafer), It is preferable to set the flow rate ratio to about CF ₄ / CHF ₃ / Ar / O ₂ = 1 to 3/2 to 4/20 to 40 / 0.5 to 2.

From the viewpoint of securing a large mask selectivity in etching the silicon oxide film, silicon nitride film and silicon layer, the processing pressure is preferably from 1.3 to 40 kPa, more preferably from 5 to 13.3 kPa.

In addition, from the viewpoint of increasing the degree of dissociation of the etching gas, the high frequency power of the high frequency power supply 15 is 13.56 MHz, and the high frequency power is 300 W to 500 W (0.96) divided by the surface area of the substrate by the high frequency power supplied to the lower electrode. W / cm 2 to 1.59 W / cm 2) is preferable.

In addition, it is preferable to adjust the temperature of the wafer W to about 40-70 degreeC from a viewpoint of controlling the etching shape ie anisotropy favorably.

≪ First Embodiment >

FIG. 5: is a figure which shows typically the cross-sectional structure of the to-be-processed object 110, such as the semiconductor wafer W to which the plasma etching method of 1st Embodiment is applied. The object 110 to be processed is a silicon oxide (SiO ₂ ) film 102, a silicon nitride (Si ₃ N ₄ ) film 103, a polycrystalline silicon layer 104, and a silicon nitride on the silicon substrate 101 in order from the bottom. An (Si ₃ N ₄ ) film 105 and an inorganic antireflective film (Barc) 106 are formed, and a resist (PR) 107 patterned in advance is formed thereon. This etching process is one process of forming a gate electrode using the polycrystalline silicon layer 104 as an electrode layer, and the silicon oxide (SiO ₂ ) film 102 and the silicon nitride (Si ₃ N ₄ ) film 103 serve as gate insulating films. .

In the conventional etching method, the antireflection film 106 and the silicon nitride (Si ₃ N ₄ ) film 105 are first etched with respect to the object to be processed 110 in FIG. 5 using the resist film PR 107 as a mask. Next, after removing the resist film (PR) 107 by ashing, a method of etching the polycrystalline silicon layer 104 using the silicon nitride (Si ₃ N ₄ ) film 105 as a hard mask is employed. come. When etching the antireflection film 106 and the silicon nitride (Si ₃ N ₄ ) film 105, an etching device dedicated to insulating film etching is used, and an etching device dedicated to silicon is used when etching the polycrystalline silicon layer 104. Was doing. In addition, ashing removal of the resist film (PR) 107 was performed using the dedicated ashing apparatus.

In contrast, in the plasma etching method according to the present embodiment, in the plasma etching apparatus 100, a processing gas containing a fluorocarbon gas, a hydrofluorocarbon gas, a rare gas, and O ₂ as a processing gas, for example, CF _4. The antireflection film (Barc) 106, the silicon nitride (Si ₃ N ₄ ) film 105, based on the pattern using the resist (PR) 107 as a mask using / CHF ₃ / Ar / O ₂ , The polycrystalline silicon layer 104, the silicon nitride (Si ₃ N ₄ ) film 103, and the silicon oxide (SiO ₂ ) film 102 are etched at once. By this laminated film batch etching, the recessed part 108 can be formed as shown in FIG. 6 by the one-step etching process.

≪ Second Embodiment >

FIG. 7: is a figure which shows typically the cross-sectional structure of the to-be-processed object 210, such as a semiconductor wafer to which the plasma etching method of 2nd Embodiment is applied. The object to be processed 210 is a silicon oxide (SiO ₂ ) film 202, a silicon nitride (Si ₃ N ₄ ) film 203, and a silicon oxynitride (SiON) film 204 formed on the silicon substrate 201 from below. ), A silicon oxide (SiO ₂ ) film 205 is formed, and a resist film (PR) 206 having a pattern formed thereon is formed thereon. This etching step is one step for forming the trench 207 for embedding the insulating film in the silicon substrate 201 by STI.

In the conventional etching method, the silicon oxide (SiO ₂ ) film 205 and the silicon oxynitride (SiON) film 204 are first made of the resist (PR) 206 as a mask for the workpiece 210 in the state shown in FIG. 7. The silicon nitride (Si ₃ N ₄ ) film 203 and the silicon oxide (SiO ₂ ) film 202 are etched, and then the resist film (PR) 206 is removed by ashing, followed by the silicon oxide film 205. ), A silicon oxynitride (SiON) film 204 and a silicon nitride (Si ₃ N ₄ ) film 203 are used as a mask, and a method of etching the silicon substrate 201 has been adopted. When the silicon oxide (SiO ₂ ) film 205, the silicon oxynitride (SiON) film 204, the silicon nitride (Si ₃ N ₄ ) film 203 and the silicon oxide (SiO ₂ ) film 202 are etched, an insulating film is used. When etching the silicon substrate 201 using an etching apparatus dedicated to etching, an etching apparatus dedicated to silicon was used. In addition, ashing removal of the resist film (PR) 206 was performed using the dedicated ashing apparatus.

In contrast, in the plasma etching method according to the present embodiment, the plasma etching apparatus 100 is used, and a processing gas containing a fluorocarbon gas, a hydrofluorocarbon gas, a rare gas, and an O ₂ gas as the processing gas, for example, By using CF ₄ / CHF ₃ / Ar / O ₂ , a silicon oxide (SiO ₂ ) film 205, a silicon oxynitride (SiON) film 204, a silicon nitride (Si ₃ N ₄ ) film 203, and silicon oxide The (SiO ₂ ) film 202 and the silicon substrate 201 are etched at once. By the multilayer film batch etching, the trench 207 for embedding the insulating film can be formed in the silicon substrate 201 in one etching step.

As is apparent from the above first and second embodiments, by using the above-described combination of processing gases, the laminate including at least the silicon layer and the insulating film is subjected to one etching process using a single etching apparatus. Since an etching process can be performed, the reduction of the apparatus by common use and the drastic reduction of the number of processes and processing time are realized.

Next, although an Example and a test example are given and this invention is demonstrated also, this invention is not restrict | limited by these.

Example 1

The object 110 having the laminated structure shown in FIG. 5 is etched using the plasma etching apparatus 100, using CF ₄ / CHF ₃ / Ar / O ₂ as an etching gas, and a resist film ( The recessed part 108 was formed using PR) 107 as a mask. Here, as the resist film PR 107, a material having a film thickness of 400 nm and elemental composition consisting of C, H, F and O is used. The film thickness of the antireflection film Barc 106 is 58 nm and silicon nitride ( As the film thickness of the Si ₃ N ₄ ) film 105, one having a thickness of 60 nm and a thickness of 65 nm of the polycrystalline silicon layer 104 was used. In addition, the pattern of the resist film (PR) 107 was set as the line and space of a line 0.6 micrometer and a space 0.24 micrometer.

Etching conditions are as follows.

CF ₄ / CHF ₃ / Ar / O ₂ = 20/25/300 / 10ml / min (sccm)

Pressure = 13.3 kPa (100 mTorr)

RF frequency [high-frequency power supply 15] = 13.56 MHz

RF power = 400W (l.27W / ㎠)

Back pressure (center part / edge part) = 1066㎩ / 2000㎩ (8/15 Torr; He gas)

Distance between upper and lower electrodes = 27 mm

Temperature (upper electrode / chamber side wall / lower electrode) = 60 ° C./60° C./30° C.

Etching Time = 111 Seconds

Table 1 shows the results of the etching.

The upper CD (CD: Critical Dimension at the interface between the antireflection film (Barc) 106 and the silicon nitride film 105) is 270 nm in any of the center portion and the edge portion of the wafer W (see Fig. 9 (c)). Uniform etching was possible in the surface of the wafer W. FIG. Moreover, it was confirmed from the remaining film thickness of the resist (PR) 107 that sufficient selection ratio with the resist mask could be ensured. Moreover, "flat" in the resist remaining film thickness in the table means the film thickness (total thickness of the resist) of the flat surface of the resist (PR) 107, and "facet" means the resist PR The film thickness obtained by subtracting the thickness of the shoulder cut portion from the total thickness of the resist (PR) film 107 in the case where shaving (so-called shoulder cut) occurs due to the action of ion sputtering or the like at the corner of 107. Means to be.

Position on wafer Center part Edge Upper CD [nm] 270 270 Etching Depth [nm] 158 136 Resist Residual Film Thickness (Flat) [nm] 250 252 Resist remaining film thickness (facet) [nm] 214 222

Example 2

The object 210 having the laminated structure shown in FIG. 7 was etched using the plasma etching apparatus 100, using CF ₄ / CHF ₃ / Ar / O ₂ as an etching gas, and a resist (PR) The trench 207 was formed using the 206 as a mask. Here, as the resist (PR) 206, a material having a film thickness of 320 nm and elemental composition consisting of C, H, F and O is used. The silicon oxide (SiO ₂ ) film 205 has a film thickness of 20 nm and silicon oxynitride. The (SiON) film 204 has a film thickness of 32 nm, the silicon nitride (Si ₃ N ₄ ) film 203 has a film thickness of 265 nm, and the silicon oxide (SiO ₂ ) film 202 has a film thickness of 8 nm. In addition, the pattern of the resist (PR) 206 was 0.17 micrometer in line width, and 0.18 micrometer in trench width.

Etching conditions are as follows.

CF ₄ / CHF ₃ / Ar / O ₂ = 20/25/300 / 10ml / min (sccm)

Pressure = 13.3 kPa (100 mTorr)

RF frequency [high-frequency power supply 15] = 13.56 MHz

RF power = 400W (1.27W / ㎠)

Back pressure (center section / edge section) = 933 Pa / 5332 Pa (7/40 Torr; He gas)

Distance between upper and lower electrodes = 27 nm

Temperature (upper electrode / lower electrode) = 60 degrees Celsius / 30 degrees Celsius

Etching Time = 130 Seconds

Table 2 shows the results of the etching.

In any of the center portion and the edge portion of the wafer W, the upper CD (CD at the interface between the silicon oxide film 202 and the silicon nitride film 203 in this test) is 206 nm, and the CD at the bottom of the trench 207 is 174 nm. Since it was nm, uniform etching was possible in the surface of the wafer W.

In addition, the trench depth and sidewall angle (180 ° -θ: see FIG. 8) formed in the silicon substrate 201 are also the same in the center portion and the edge portion of the wafer W, and it has been shown that high in-plane uniformity is obtained with respect to the etching shape. .

Position on wafer Center part Edge Upper CD [nm] 206 206 Trench bottom CD [nm] 174 174 Trench sidewall angle [°] 87.1 87.1 Silicon Etch Depth [nm] 58 58

Next, the effect of etching conditions on etching rate, large mask selectivity, and etching shape was tested. In this test, a sample wafer having a laminated structure shown in Fig. 9A was used. This sample wafer has a structure in which a silicon oxide (S10 ₂ ) film 302, a silicon nitride (Si ₃ N ₄ ) film 303, and a resist film 304 are stacked on a silicon substrate 301. Then, using CF ₄ / CHF ₃ / Ar / O ₂ as the processing gas, as shown in Table 3, etching was performed by changing the etching conditions based on the experimental design method, and the concave portion 305 was formed. The etching rate at that time, the large resist mask selectivity, and the etching shape were measured and compared.

As another condition for etching, the RF frequency (high frequency power supply 15) is 13.56 MHz, the RF power is 300 W (0.96 W / cm 2), and the back pressure (center part / edge part) is 933 kHz / 2666 kHz (7 / 20 Torr; He gas), the distance between the upper and lower electrodes = 27 mm, and the temperature (upper electrode / lower electrode) were performed at 60 ° C / 30 ° C.

The results of the etching rate and the large mask selectivity are shown in Table 4 and FIGS. 10 to 13. Moreover, the result of an etching shape is shown in Table 5 and FIGS. 14-21. 10 to 13, the horizontal axis represents the flow rate ratio of CHF ₃ / Ar, and the vertical axis represents the processing pressure.

Test pressure CF ₄ flow rate
[Ml / min (sccm)] CHF ₃ / Ar
Flow rate ratio CHF ₃ flow
[Ml / min (sccm)] Ar flow
[Ml / min (sccm)] O ₂ flow rate
[Ml / min (sccm)] One 8㎩ (60Torr) 0 0.019 23 1200 3 2 8㎩ (60Torr) 20 0.058 46 800 6 3 8㎩ (60Torr) 40 0.173 69 400 9 4 10㎩ (75Torr) 40 0.019 23 1200 6 5 10㎩ (75Torr) 0 0.058 45 800 9 6 10㎩ (75Torr) 20 0.173 69 400 3 7 12㎩ (90Torr) 20 0.019 23 1200 9 8 12㎩ (90Torr) 40 0.058 46 800 3 9 12㎩ (90Torr) 0 0.173 69 400 6

Test Resist
Etching Rate
[Nm / min] SiO ₂
Etching Rate
[Nm / min] SiO ₂
Large mask selection fee SiN
Etching Rate
[Nm / min] SiN
Large mask selection fee One 17.15 16.45 0.96 57.62 3.36 2 35.08 37.78 1.08 99.60 2.84 3 51.28 68.05 1.33 134.90 2.63 4 46.36 46.50 1.00 85.42 1.84 5 55.50 60.64 1.09 93.08 1.68 6 14.65 18.07 1.23 109.45 7.47 7 45.15 57.78 1.28 75.72 1.68 8 19.28 36.15 1.64 116.26 6.03 9 11.76 36.22 3.08 137.57 11.70

Test Between roughness patterns
Inclination angle difference of side wall [degrees] Difference [CD] of CD in wafer surface One -3.10 26 2 -1.54 8 3 -1.08 -14 4 0.60 2 5 -1.28 18 6 -2.44 2 7 0.00 0 8 -1.92 -8 9 -3.14 16

10 shows the etching selectivity with respect to the resist film 304 of the silicon nitride (Si ₃ N ₄ ) film 303. Since the large mask selectivity at the time of etching the silicon nitride (Si ₃ N ₄ ) film 303 may be one or more, it can be seen from this FIG. 10 that a sufficient large mask selectivity is obtained within the set condition range. In addition, it is understood that the large mask selectivity can be further improved by selecting a condition (region in the upper right part of FIG. 10) in which the flow rate ratio of CHF ₃ / Ar is large and the processing pressure is high.

11 shows the etching rate of the silicon nitride (Si ₃ N ₄ ) film 303. As shown in Fig. 11, as a condition for improving the etching rate of the silicon nitride (Si ₃ N ₄ ) film 303, the processing pressure is not very effective. Rather, it is effective to increase the flow rate ratio of CHF ₃ / Ar within the set condition range. You can see that.

12 shows the etching selectivity with respect to the resist film 304 of the silicon substrate 301. Since the large mask selectivity of silicon etching should just be 1 or more, it turns out from FIG. 12 that the sufficient large mask selectivity is obtained if it is in the set conditions. In addition, by selecting the conditions (higher region in the upper right part of FIG. 12) where the flow rate ratio of CHF ₃ / Ar is high and the processing pressure is high, the large mask selectivity in silicon etching can be further improved.

13 shows the etching rate of the silicon substrate 301. From this FIG. 13, if the flow rate ratio of CHF ₃ / Ar is larger within the set condition range, the higher etching rate is obtained for the smaller process pressure, and the higher process pressure is smaller for the flow rate ratio of CHF ₃ / Ar. It was shown that this high etching rate was obtained.

To sum up the above results, if the silicon nitride (Si ₃ N ₄ ) film 303 and the silicon substrate 301 are to be further improved in the large mask selectivity, the pressure is set high within the condition range shown in Table 3. In addition, it is effective to set the CHF ₃ / Ar flow rate high. In this case, the etching rate of the silicon nitride (Si ₃ N ₄ ) film 303 can also be increased. On the other hand, when the etching rate of the silicon substrate 301 is important, as shown in FIG. 13, when the flow ratio of CHF ₃ / Ar is large, the processing pressure is smaller, and when the flow rate ratio of CHF ₃ / Ar is small, the treatment is performed. It is preferable to change the flow rate or the processing pressure of CHF ₃ during etching in consideration of the higher pressure.

For example, in the step of etching the silicon nitride (Si ₃ N ₄ ) film 303, the pressure and the CHF ₃ / Ar flow rate ratio are set high within the condition range shown in Table 3 to obtain a sufficient mask selection ratio and etching rate. in the step of the silicon etch after the recess 305 reaches the silicon substrate 301, by which CHF ₃ flow rate as to degrade the processing pressure, or vice versa treatment pressure will remain and lower the CHF ₃ flow rate The etching rate of the silicon substrate 301 can be improved. In these cases, since the large mask selection ratio of silicon etching should just be 1 or more, it is thought that there is no possibility that the large mask selection ratio will be largely impaired from the result of FIG.

In the step of etching the silicon nitride (Si ₃ N ₄ ) film 303, it is also possible to set both the processing pressure and the CHF ₃ / Ar flow rate ratio to be low within the condition range shown in Table 3, in which case the recess 305 ) is, for example CHF ₃ flow rate to as to increase the processing pressure, or vice versa processing pressure as it is, and the silicon substrate by increasing the CHF ₃ flow rate at the stage of the silicon etching after reaching the silicon substrate 301 The etching rate of 301 can be improved.

Next, "the inclination-angle difference of the side wall between roughness patterns" in Table 5, and the result of FIGS. 14-17 corresponding to it are demonstrated.

The result of Table 5 measured the inclination-angle difference of the side wall of the groove | channel in a device in the following method in order to confirm the uniformity of the etching shape on the wafer W. The side wall inclination angle difference measures the inclination angle θ ₁ of the side wall of the concave portion 305 of the dense portion shown in Fig. 9 (b) and the inclination angle θ ₂ of the side wall of the concave portion 305 of the sweeping portion. The side wall inclination angle θ ₂ ) of the sweeping site was calculated from the side wall inclination angle θ ₁ of the dense site.

It is FIGS. 14-17 which performed variance analysis about Table 5 of the result regarding the said side wall inclination-angle difference. Thus it can be seen that each of the process parameters (pressure, flow rate of CF _4, CHF ₃ / Ar flow ratio, O ₂ flow rate) changes sidewall variation trend of the inclination angle difference of about.

More specifically, as shown in Figs. 9 (a) to 9 (c), the inclination angles of the side walls of the portions (iso) in which the patterns in the center portion and the edge portion of the wafer W are sweeped are measured at each of three positions, and the average value thereof is measured. Obtained. Similarly, three side wall inclination angles of the dense part of the pattern in the center part and the edge part of the wafer W were measured, and the average value was calculated | required. And the difference of the average value of the side wall inclination-angle of a sweeping site | part and the average value of the side wall inclination-angle of a dense site | part was calculated | required, and it was set as the vertical axis of the graph of FIGS. 14-17 (unit; FIG.). It is shown that the smaller the absolute value of the vertical axis, the smaller the difference in the sidewall inclination angle.

From Fig. 14, it is shown that the pressure tends to increase from 9.3 to 10.6 kPa (70 to 80 mTorr) within the set condition range, and when the pressure is larger or smaller than that, the side wall inclination angle difference due to the roughness of the pattern increases. It became.

15, with respect to the flow rate ratio CHF ₃ / Ar between CHF ₃ and Ar, when the flow rate ratio increases (that is, increases the flow rate of CHF ₃ ), the side wall inclination angle difference due to the roughness of the pattern tends to increase, and the flow rate ratio CHF ₃ / Ar This proved to be difficult to eliminate the side wall inclination angle difference.

From FIG. 16, it was confirmed that the CF ₄ flow rate tends to decrease as the side wall inclination angle difference due to the roughness of the pattern decreases as the flow rate increases within the set condition range. Similarly, from FIG. 17, it was confirmed that the side wall inclination angle difference decreased as the flow rate was increased within the set condition range for the O ₂ flow rate. Therefore, it was found that by adjusting the CF ₄ flow rate and / or the O ₂ flow rate, the side wall inclination angle difference due to the roughness of the pattern can be controlled.

Next, the "difference of CD in a wafer surface" in Table 5 and the result of FIGS. 18-21 corresponding to it are demonstrated.

The results shown in Table 5 are for measuring the difference of critical dimensions (CD) in the wafer plane in the following manner in order to confirm the uniformity of the etching shape on the wafer W. As shown in Fig. 9 (b), CD was obtained by measuring the width at the interface between the silicon oxide (SiO ₂ ) film 302 and the silicon nitride (Si ₃ N ₄ ) film 303.

More specifically, three CDs at the center part and the edge part of the wafer W were measured, and respective average values were obtained. The difference between the average value of the CD of the center portion and the average value of the CD of the edge portion is " CD difference in wafer surface " 18 to 21 show variance analysis of the results of the CD differences in Table 5. FIG. As a result, it is possible to know the tendency of the difference of the CD in the wafer surface with respect to the variation of each process parameter (pressure, CF ₄ flow rate, CHF ₃ / Ar flow rate ratio, O ₂ flow rate). The vertical axis of each graph was the CD difference in the wafer surface (unit nm).

18 and 21, no significant difference was observed in the treatment pressure and the O ₂ flow rate within the set condition range. From Figure 19, with increasing the flow rate in the flow rate ratio of CHF ₃ / Ar a range of conditions set for (that is, more to the CHF ₃ increases), and confirmed a tendency to difference reduction of the CD, to control the flow rate ratio CHF ₃ / Ar This suggests that the in-plane difference of the CD can be controlled.

Further, there can be confirmed a tendency to shrink the surface of the CD my car in accordance with the increase of the flow rate in a range of conditions set for, CF ₄ flow rate from Fig. Accordingly, it has been found that the in-plane difference of the CD can be controlled by adjusting the CF ₄ flow rate.

Summarizing the above results (FIGS. 14 to 21), it is effective to adjust the flow rate of CF ₄ in order to improve the side wall inclination angle difference due to the roughness of the pattern and the CD difference at the in-plane position. For example, it is preferable to set the flow rate of CF ₄ to 20-40 ml / min (sccm). It is also effective to adjust the flow rate of O ₂ in order to improve the side wall inclination angle difference due to the roughness of the pattern. For this purpose, for example, the flow rate of O ₂ is set to 6-15 ml / min (sccm). It is preferable.

As mentioned above, according to the plasma etching method of this invention, it becomes possible to collectively etch the laminated | multilayer film containing an insulating film and a silicon layer using a resist as a mask. This makes it possible to significantly shorten the process of forming a gate electrode of a transistor, forming a trench for element isolation by STI, for example.

In addition, it is possible to suppress variations in the etching shape in the surface of the wafer W and variations in the etching shape due to the roughness of the pattern, thereby ensuring uniformity of the etching shapes.

Therefore, the plasma etching method of this invention can be used suitably in manufacture of various semiconductors.

As mentioned above, although embodiment of this invention was described, this invention is not restrict | limited to the said embodiment, A various deformation | transformation is possible. For example, in the said embodiment, although the dipole ring magnet was used as a magnetic field formation means of a magnetron RIE plasma etching apparatus, it is not limited to this, Formation of a magnetic field is not essential, either. In addition, as long as the plasma can be formed by the gas species of the present invention, various plasma etching apparatuses such as capacitive coupling type and inductive coupling type can be used regardless of the apparatus.

The present invention can be suitably used in the process of manufacturing various semiconductor devices such as transistors, for example.

Claims (16)

delete In the processing chamber of the plasma processing apparatus, a fluorocarbon gas and hydrofluoro are applied to a workpiece to which a silicon layer containing silicon and a silicon oxide film, a silicon nitride film, and a resist film formed in advance with a pattern are laminated on the upper layer than the silicon layer. The silicon nitride film, the silicon oxide film and the silicon layer are collectively etched using a plasma generated from a processing gas containing carbon gas, rare gas and O ₂ gas, using the resist film as a mask. Plasma etching method. The method of claim 2, The fluorocarbon gas is CF ₄ gas, C ₂ F ₆ gas, C ₃ F ₈ gas or C ₄ F ₈ gas Plasma etching method. The method of claim 2, The hydrofluorocarbon gas is CHF ₃ gas, CH ₂ F ₂ gas or CH ₃ F gas Plasma etching method. The method of claim 2, The flow rate of the fluorocarbon gas is 10 to 50ml / min Plasma etching method. The method of claim 2, The flow rate of the O ₂ gas is 1 to 30 ml / min Plasma etching method. The method of claim 2, The flow rate ratio (hydrofluorocarbon gas flow rate / rare gas flow rate) of the said hydrofluorocarbon gas and the said rare gas is 0.019-0.173 Plasma etching method. The method of claim 2, Processing pressure is 8 ~ 12㎩ Plasma etching method. The method of claim 2, By controlling the flow rate of the fluorocarbon gas or the O ₂ gas, the critical dimension after etching in the region where the pattern is small and the region that is dense is controlled. Plasma etching method. The method of claim 2, By controlling the flow rate of the fluorocarbon gas, the critical dimension after etching in the plane of the object to be controlled is controlled. Plasma etching method. The method of claim 2, The processing pressure at the time of etching the silicon layer is lowered relative to the processing pressure at the time of etching the silicon nitride film. Plasma etching method. The method of claim 2, Reducing the flow rate of the hydrofluorocarbon gas when etching the silicon layer with respect to the flow rate of the hydrofluorocarbon gas when etching the silicon nitride film  Plasma etching method. The method of claim 2, The silicon layer includes polycrystalline silicon or single crystal silicon Plasma etching method. delete A computer-readable storage medium storing a control program running on a computer, The control program controls the plasma processing apparatus such that, when executed, the plasma etching method according to claim 2 is executed. Computer-readable storage media. A processing chamber for performing plasma etching processing on the target object; A support for mounting a target object in the processing chamber; Exhaust means for reducing the pressure inside the processing chamber; Gas supply means for supplying a processing gas into the processing chamber; And a control unit for controlling the plasma etching method according to claim 2 to be executed in the processing chamber. Plasma processing apparatus.

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