WO2018220973A1

WO2018220973A1 - Etching method

Info

Publication number: WO2018220973A1
Application number: PCT/JP2018/012689
Authority: WO
Inventors: 麗紅笹原; 戸田　聡; 阿部　拓也; 祖虹黄; 淑恵小澤; 健中込; 賢一中畑; 健史郎旭
Original assignee: 東京エレクトロン株式会社
Priority date: 2017-05-30
Filing date: 2018-03-28
Publication date: 2018-12-06
Also published as: TW201907473A; TWI756425B

Abstract

Provided is an etching method having: a step for disposing a substrate to be processed in a chamber, the substrate having a silicon nitride film, a silicon oxide film, silicon, and silicon germanium; a step for bringing the pressure inside the chamber to 1,333 Pa or more; and a step for supplying hydrogen fluoride gas into the chamber and selectively etching the silicon nitride film with respect to the silicon oxide film, the silicon, and the silicon germanium.

Description

Etching method

The present disclosure relates to an etching method.

Recently, fine etching is performed in the manufacturing process of a semiconductor device. As a dry etching technique that replaces the conventional plasma etching, a chemical etching technique capable of performing low damage etching has attracted attention. For example, for etching a silicon oxide (SiO ₂ ) film, a chemical oxide removal process (Chemical Oxide Removal; using a mixed gas of hydrogen fluoride (HF) gas and ammonia (NH ₃ ) gas as a processing gas; COR) technology is used (for example, Patent Documents 1 and 2).

Recently, application of such a chemical etching technique to etching of a silicon nitride (SiN) film has been studied.

Since it is often SiN film which is adjacent to the SiO ₂ film, a selectively technique for etching the SiN film against the SiO ₂ film, Patent Document 3, and HF gas, and _{F 2} gas, inert It describes that etching is performed by supplying a gas and O ₂ gas in an excited state.

JP 2005-39185 A JP 2008-160000 A Japanese Patent Laid-Open No. 2015-73035

The present disclosure provides an etching method capable of etching a silicon nitride (SiN) film with high selectivity to a silicon oxide (SiO ₂ ) film, silicon (Si), and silicon germanium (SiGe).

An etching method according to one embodiment of the present disclosure includes a step of placing a substrate to be processed having a silicon nitride film, a silicon oxide film, silicon, and silicon germanium in a chamber, a step of setting the pressure in the chamber to 1333 Pa or more, Supplying hydrogen fluoride gas into the chamber, and selectively etching the silicon nitride film with respect to the silicon oxide film, silicon, and silicon germanium.

According to the present disclosure, there is provided an etching method capable of etching a silicon nitride (SiN) film with high selectivity with respect to a silicon oxide (SiO ₂ ) film, silicon (Si), and silicon germanium (SiGe). .

It is process sectional drawing at the time of etching a SiN film | membrane with respect to an example of the structure where the etching method of 1st Embodiment is applied. It is process sectional drawing at the time of etching a SiN film | membrane with respect to the other example of the structure where the etching method of 1st Embodiment is applied. It is a schematic block diagram which shows an example of the processing system used for the etching method of 1st Embodiment. It is sectional drawing which shows the etching apparatus mounted in the processing system of FIG. The SiN film adjacent to the SiO ₂ film containing an impurity at the time of etching by HF gas, which is a diagram for explaining the mechanism of damage is generated in the SiO ₂ film. It is a flowchart which shows the 1st example of the etching method of 2nd Embodiment. It is a figure for demonstrating the function of surfactant used for a surface modification process. It is sectional drawing which shows an example of the structure where the 2nd example of the etching method of 2nd Embodiment is applied. It is a flowchart which shows the 2nd example of the etching method of 2nd Embodiment. It is process sectional drawing in the 2nd example of the etching method of 2nd Embodiment. It is a schematic block diagram which shows an example of the processing system used for the etching method of the 2nd example of 2nd Embodiment. It is sectional drawing which shows the oxide film etching apparatus mounted in the processing system of FIG. It is sectional drawing which shows the surface modification processing apparatus mounted in the processing system of FIG. It is sectional drawing which shows the other example of a surface modification processing apparatus. It is sectional drawing which shows the further another example of a surface modification processing apparatus. In the experimental example, when the SiN film, the thermal oxide film, and the polysilicon film were etched while changing the pressure at a temperature of 70 ° C., the pressure, the etching amount (nm) of each film, and the selection of the SiN film with respect to the thermal oxide film It is a figure which shows the relationship between the ratio and the selective ratio of the SiN film to the polysilicon film. In the experimental example, when the SiN film, the thermal oxide film, and the polysilicon film were etched while changing the temperature at a pressure of 50 Torr, the temperature, the etching amount of each film (nm), and the selectivity ratio of the SiN film to the thermal oxide film It is a figure which shows the relationship with the selection ratio with respect to the polysilicon film of SiN film.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Background>
First, the background to the etching method of the present disclosure will be described.
As described above, recently, etching of the SiN film by chemical etching similar to the COR technique has been studied. For example, in Patent Document 3, HF gas, F ₂ gas, inert gas, and O ₂ gas are supplied in an excited state, and the SiN film is selectively etched with respect to the SiO ₂ film. The technology is described.

However, in the case of etching a SiN film in a semiconductor device using Si and SiGe such as a CMOS transistor, for example, the technique disclosed in Patent Document 3 has sufficient selectivity for all of the SiO ₂ film, Si and SiGe. It is difficult to etch the SiN film.

Further, when the SiO ₂ film contains impurities such as H and N, the SiO ₂ film may be damaged when the SiN film is etched in Patent Document 3 described above.

Therefore, the inventors have conducted various studies to eliminate these points. As a result, it is possible to etch with high selectivity to a silicon oxide (SiO ₂ ) film, silicon (Si) and silicon germanium (SiGe) by etching the silicon nitride film at a high pressure using HF gas. I found it. Further, when the SiN film is etched on the substrate to be processed having the SiN film and the SiO ₂ film, it is effective to perform a surface modification process for removing impurities and the like in the film prior to the etching of the silicon nitride film. I found out.

<First Embodiment>
Next, a first embodiment of the present invention will be described.
In the present embodiment, a method for etching and removing a SiN film formed adjacent to SiO ₂ , Si and SiGe will be described.

[Structural example to which the etching method of the first embodiment is applied]
FIG. 1 is a process cross-sectional view when an SiN film is etched with respect to an example of a structure to which the etching method of the first embodiment is applied. FIG. 1A is an example of a structure to which the etching method of this embodiment is applied. In the structure (a), a pole-like Si film 12 and a SiGe film 13 are formed on a silicon substrate 11. The first SiO ₂ film 14 is formed around the periphery and SiGe film 13 of the Si film 12, on the first ambient and Si film 12 and the SiGe film 13 of SiO ₂ film 14, SiN film 15 Is formed. Further, a second SiO ₂ film 16 is formed between the SiN film 15 around the Si side and the SiN film 15 around the SiGe side. The SiN film 15 having the structure shown in FIG. 1A is etched to form a desired semiconductor device. In this case, ideally, only the SiN film 15 is removed as shown in FIG. That is, it is required to etch the SiN film 15 with a high selectivity with respect to the Si film 12, the SiGe film 13, and the first and second SiO ₂

films

14 and 16.

FIG. 2 is a process cross-sectional view when the SiN film is etched with respect to another example of the structure to which the etching method of the first embodiment is applied. FIG. 2A shows another example of a structure to which the etching method of this embodiment is applied. In the structure of (a), a first Si film 22a, a second Si film 22b, and a third Si film 22c having a pole shape from the left side are provided on the silicon substrate 21, and a pole shape is formed on the right side. A formed SiGe film 23 is formed. A hard mask 24 remains on the first to third Si films 22 a to 22 c and the SiGe film 23. An SiO ₂ film 25 is formed on the silicon substrate 21 from the periphery of the first Si film 22a and the end on the first Si film 22a side to the third Si film 22c. A SiN film 26 is provided on the SiO ₂ film 25 and around the second Si film 22b. The SiN film 26 having the structure shown in FIG. 2A is etched to form a desired semiconductor device. At this time, ideally, only the SiN film 26 is removed as shown in FIG. That is, it is required to etch the SiN film 26 with a high selectivity with respect to the first to third Si films 22a to 22c, the SiGe film 23, and the SiO ₂ film 25. Specifically, the selection ratio to SiO ₂ is required to be 5 or more, and the selection ratio to Si and SiGe is required to be 50 or more.

As the Si film 12, the first to third Si films 22a to 22c, and the

SiGe films

13 and 23, for example, those formed by epitaxial growth or polycrystalline films formed by CVD can be used. Further, even if the first and second SiO ₂ films 14 and 16 and the SiO ₂ film 25 are formed by chemical vapor deposition (CVD), they are formed by atomic layer deposition (ALD). Or may be a thermal oxide film. There are various methods for forming a SiO ₂ film by CVD, and the amount of hydrogen (H), carbon (C), nitrogen (N), etc. contained as impurities differs depending on the method, and low grade CVD. The -SiO ₂ film contains a relatively large amount of impurities. Similarly, the ALD-SiO ₂ film contains these impurities. On the other hand, in the case of a thermal oxide film, there are few such impurities.

The SiN film to be etched is formed by thermal CVD, plasma CVD, silane-based gas such as SiH ₄ gas, SiH ₂ Cl ₂ , Si ₂ Cl ₆ and nitrogen-containing gas such as NH ₃ gas or N ₂ gas. The film is formed by ALD or the like.

[SiN film etching of the first embodiment]
When the SiN film shown in the above device example is formed adjacent to SiO ₂ , Si and SiGe, as an attempt to etch the SiN film with a high selectivity, (1) HF gas or HF gas + NH ₃ A method of etching with a COR device using a gas, (2) a method of etching by adding F ₂ to the gas system, and (3) a method by radical SiN etching have been performed.

In the case of the COR treatment of (1), it is usually carried out at a relatively low pressure of 4 Torr (532 Pa) or less, but the SiN / SiO ₂ selection ratio is smaller than 2. In the case of (2), although the SiN / SiO ₂ selection ratio is improved, the selection ratio for Si cannot be obtained. Furthermore, in the case of (3) radical SiN etching, the SiN / SiO ₂ selectivity can be obtained, but the SiN / SiGe selectivity cannot be obtained.

Therefore, when a method capable of etching the SiN film with a high selection ratio with respect to all of SiO ₂ , Si, and SiGe was examined, the pressure was increased to 1333 Pa (10 Torr) or higher using HF gas. It was found to be effective. The reason why a high selection ratio can be obtained by setting the high pressure state in this way is that an effect of increasing the adsorption efficiency of the HF gas can be obtained by setting the high pressure.

This will be described in detail below.
In the SiN etching of the present embodiment, for example, a semiconductor wafer having the above-described structure (also simply referred to as a wafer) is accommodated in a chamber, and only HF gas or a mixed gas of HF gas and inert gas is contained in the chamber. It is done by introducing. As the inert gas, N ₂ gas or a rare gas such as Ar or He can be used.

The gas flow rate at this time is preferably HF gas: 200 to 3000 sccm, and inert gas: 200 to 3000 sccm.

The pressure in the chamber at this time is set to a high pressure of 1333 Pa (10 Torr) or more as described above. It is preferably 1333 to 11997 Pa (10 to 90 Torr). More preferably, it is 1333 to 5332 Pa (10 to 40 Torr).

In this case, the wafer temperature is preferably 10 to 120 ° C. Below 10 ° C. and above 120 ° C., it may be difficult to obtain a desired selection ratio. More preferably, it is 30 to 80 ° C.

After the above etching of the SiN film is completed, etching residues and the like are removed as necessary, and the processing is completed.

Etching of the SiN film is performed for a predetermined time according to the thickness of the SiN film under the above conditions, so that the SiN film has a high selectivity with a selectivity of 5 or more with respect to SiO ₂ and a selectivity of 50 or more with respect to Si and SiGe. The film can be etched. The selection ratio to SiO ₂ is preferably 15 or more and the selection ratio to Si and SiGe is preferably 100 or more.

[An example of a processing system used in the first embodiment]
Next, an example of a processing system used in the first embodiment will be described.
FIG. 3 is a schematic configuration diagram illustrating an example of a processing system used in the first embodiment. The processing system 100 includes a carry-in / out unit 102, two load lock chambers 103, two heat treatment apparatuses 104, two etching apparatuses 105, and a control unit 106. The loading / unloading unit 102 is for loading / unloading the wafer W having the structure shown in the above structure example. The two load lock chambers 103 are provided adjacent to the carry-in / out section 102. The two heat treatment apparatuses 104 are provided adjacent to each load lock chamber 103, and are for performing heat treatment on the wafer W. The two etching apparatuses 105 are provided adjacent to the respective heat treatment apparatuses 104 and perform etching on the wafer W.

The loading / unloading unit 102 has a transfer chamber 112 in which a first wafer transfer mechanism 111 for transferring the wafer W is provided. The first wafer transfer mechanism 111 has two

transfer arms

111a and 111b that hold the wafer W substantially horizontally. On the side of the transfer chamber 112 in the longitudinal direction, a mounting table 113 is provided. For example, three carriers C that accommodate a plurality of wafers W such as FOUP can be connected to the mounting table 113. ing. An alignment chamber 114 for aligning the wafer W is provided adjacent to the transfer chamber 112.

In the loading / unloading unit 102, the wafer W is held by the

transfer arms

111 a and 111 b, and is moved to a desired position by moving straight and moving up and down substantially in a horizontal plane by driving the first wafer transfer mechanism 111. Then, the

transfer arms

111 a and 111 b are moved forward and backward with respect to the carrier C, the alignment chamber 114, and the load lock chamber 103 on the mounting table 113, respectively, so that they can be carried in and out.

The two load lock chambers 103 are connected to the transfer chamber 112 with the gate valve 116 interposed between the two load lock chambers 103. In each load lock chamber 103, a second wafer transfer mechanism 117 for transferring the wafer W is provided. The load lock chamber 103 is configured to be evacuated to a predetermined degree of vacuum.

The second wafer transfer mechanism 117 has an articulated arm structure and has a pick for holding the wafer W substantially horizontally. In the second wafer transfer mechanism 117, the pick is positioned in the load lock chamber 103 with the articulated arm contracted, and the pick reaches the heat treatment apparatus 104 by extending the articulated arm and further extends. It is possible to reach the etching apparatus 105, and the wafer W can be transferred between the load lock chamber 103, the heat treatment apparatus 104, and the etching apparatus 105.

The control unit 106 is typically a computer, and includes a main control unit having a CPU that controls each component of the processing system 100, an input device (keyboard, mouse, etc.), an output device (printer, etc.), and a display device ( Display) and a storage device (storage medium). For example, the main control unit of the control unit 106 causes the processing system 100 to execute a predetermined operation based on a processing recipe stored in a storage medium built in the storage device or a storage medium set in the storage device. .

In such a processing system 100, a plurality of wafers W on which the above structure is formed are stored in a carrier C and transferred to the processing system 100. In the processing system 100, a single wafer W is loaded from the carrier C of the loading / unloading unit 102 by the

transfer arms

111 a and 111 b of the first wafer transfer mechanism 111 with the atmosphere-side gate valve 116 opened. To the pick of the second wafer transfer mechanism 117 in the load lock chamber 103.

Thereafter, the gate valve 116 on the atmosphere side is closed and the load lock chamber 103 is evacuated, then the gate valve 154 is opened, the pick is extended to the etching apparatus 105, and the wafer W is transferred to the etching apparatus 105.

Thereafter, the pick is returned to the load lock chamber 103, the gate valve 154 is closed, and the SiN film is etched in the etching apparatus 105 by the etching method described above.

After the etching process is completed, the

gate valves

122 and 154 are opened, the wafer W after the etching process is transferred to the heat treatment apparatus 104 by the pick of the second wafer transfer mechanism 117, and the etching residue and the like are removed by heating.

After the heat treatment in the heat treatment apparatus 104 is completed, it is returned to the carrier C by one of the

transfer arms

111a and 111b of the first wafer transfer mechanism 111. Thereby, processing of one wafer is completed.

If it is not necessary to remove etching residues and the like, it is not necessary to provide the heat treatment apparatus 104. In this case, the wafer W after the etching process is finished is load-locked by the pick of the second wafer transfer mechanism 117. It may be retracted to the chamber 103 and returned to the carrier C by one of the

transfer arms

111a and 111b of the first wafer transfer mechanism 111.

[Etching device]
Next, an example of the etching apparatus 105 for performing the etching method of this embodiment will be described in detail.
FIG. 4 is a cross-sectional view showing an example of the etching apparatus 105. As shown in FIG. 4, the etching apparatus 105 includes a sealed chamber 140, and a mounting table 142 for mounting the wafer W in a substantially horizontal state is provided inside the chamber 140. The etching apparatus 105 also includes a gas supply mechanism 143 that supplies an etching gas to the chamber 140 and an exhaust mechanism 144 that exhausts the inside of the chamber 140.

The chamber 140 includes a chamber main body 151 and a lid 152. The chamber main body 151 has a substantially cylindrical side wall portion 151 a and a bottom portion 151 b, and an upper portion is an opening, and the opening is closed by a lid portion 152. The side wall portion 151a and the lid portion 152 are sealed by a seal member (not shown), and airtightness in the chamber 140 is ensured.

The lid portion 152 includes a lid member 155 that constitutes the outside, and a shower head 156 that is fitted inside the lid member 155 and faces the mounting table 142. The shower head 156 includes a main body 157 having a cylindrical side wall 157a and an upper wall 157b, and a shower plate 158 provided at the bottom of the main body 157. A space 159 is formed between the main body 157 and the shower plate 158.

A gas introduction path 161 is formed through the cover member 155 and the upper wall 157b of the main body 157 to the space 159, and an HF gas supply pipe 171 of a gas supply mechanism 143, which will be described later, is connected to the gas introduction path 161. ing.

A plurality of gas discharge holes 162 are formed in the shower plate 158, and the gas introduced into the space 159 through the gas supply pipe 171 and the gas introduction path 161 is discharged from the gas discharge hole 162 into the space in the chamber 140. .

The side wall 151 a is provided with a loading / unloading port 153 for loading / unloading the wafer W to / from the heat treatment apparatus 104, and the loading / unloading port 153 can be opened and closed by a gate valve 154.

The mounting table 142 has a substantially circular shape in plan view, and is fixed to the bottom 151 b of the chamber 140. Inside the mounting table 142, a temperature controller 165 for adjusting the temperature of the mounting table 142 is provided. The temperature controller 165 includes, for example, a pipe line through which a temperature adjusting medium (for example, water) circulates, and heat exchange is performed with the temperature adjusting medium flowing in the pipe line, thereby the mounting table 142. The temperature of the wafer W on the mounting table 142 is controlled.

The gas supply mechanism 143 includes an HF gas supply source 175 that supplies HF gas and an inert gas supply source 176 that supplies inert gas. These include an HF gas supply pipe 171 and an inert gas supply pipe, respectively. One end of 172 is connected. The HF gas supply pipe 171 and the inert gas supply pipe 172 are provided with a flow rate controller 179 that performs opening / closing operation of the flow path and flow rate control. The flow rate controller 179 includes, for example, an on-off valve and a mass flow controller. The other end of the HF gas supply pipe 171 is connected to the gas introduction path 161 as described above. The other end of the inert gas supply pipe 172 is connected to the HF gas supply pipe 171.

Accordingly, the HF gas is supplied from the HF gas supply source 175 through the HF gas supply pipe 171 into the shower head 156, and the inert gas is supplied from the inert gas supply source 176 to the inert gas supply pipe 172 and the HF gas supply pipe. 171 is supplied to the shower head 156. These gases are discharged from the gas discharge holes 162 of the shower head 156 toward the wafer W in the chamber 140.

Of these gases, HF gas is a reactive gas, and an inert gas is used as a dilution gas and a purge gas. Desired etching performance can be obtained by supplying HF gas alone or by mixing HF gas and inert gas.

The exhaust mechanism 144 has an exhaust pipe 182 connected to an exhaust port 181 formed in the bottom portion 151 b of the chamber 140. The exhaust mechanism 144 further includes an automatic pressure control valve (APC) 183 provided on the exhaust pipe 182 for controlling the pressure in the chamber 140 and a vacuum pump 184 for exhausting the interior of the chamber 140. .

On the side wall of the chamber 140, two

capacitance manometers

186a and 186b are provided so as to be inserted into the chamber 140 as pressure gauges for measuring the pressure in the chamber 140. The capacitance manometer 186a is for high pressure, and the capacitance manometer 186b is for low pressure. A temperature sensor (not shown) for detecting the temperature of the wafer W is provided in the vicinity of the wafer W mounted on the mounting table 142.

In such an etching apparatus 105, the wafer W having the above-described structure is loaded into the chamber 140 and placed on the mounting table 142. The temperature controller 165 of the mounting table 142 sets the wafer W to preferably 10 to 120 ° C., more preferably 30 to 80 ° C. The pressure in the chamber 140 is 1333 Pa (10 Torr) or more, preferably 1333 to 11997 Pa (10 to 90 Torr), more preferably 1333 to 5332 Pa (10 to 40 Torr). Then, HF gas and inert gas are preferably supplied at a flow rate of 200 to 3000 sccm to etch the SiN film.

<Second Embodiment>
Next, a second embodiment of the present invention will be described.
This embodiment includes a step of removing the SiN film by etching, as in the first embodiment. In this embodiment, also contain impurities such as N and H on SiO ₂ film adjacent to the SiN film, damage to the SiO ₂ film when etching the SiN film is described hardly etching method generated .

[First Example of Etching Method of Second Embodiment]
First, a basic example of the present embodiment will be described as a first example of the second embodiment. In this example, the SiN film is etched on the wafer on which the SiN film is formed adjacent to the SiO ₂ film containing a predetermined impurity.

If it contains impurities such as H and N in the SiO ₂ film, it is etched by SiN film directly HF gas adjacent thereto, the gas components such as H and N in the impurities contained in the SiO ₂ film However, it was found to react with HF during the etching of the SiN film. If such a gas component reacts with HF during etching of the SiN film, the SiO ₂ film is etched unevenly, and damage such as pitting (holes) or surface roughness may occur. For example, in the case of a SiO ₂ film formed by CVD or ALD, H, N, C, etc. derived from the film forming source gas are present in the film, and there is a risk of damage during etching of the SiN film. . In particular, when the annealing temperature of the SiO ₂ interlayer insulating film formed by CVD or ALD is low, in addition to the presence of the impurities, the density is low and the SiN film is susceptible to damage during etching. In addition, the SiO ₂ film formed by fluid chemical vapor deposition (F-CVD) is also susceptible to damage during etching of the SiN film because it contains many impurities as described above and has a low density.

In addition, when the SiO ₂ film adjacent to the SiN film is etched, in addition to the impurities originally contained, the components that enter the film during etching and the wafers W adhere to the wafer W without being completely removed. Gas components are present. When the SiN film is etched, the HF and the attached gas component are easily damaged by the etching of the SiO ₂ film. In particular, when the SiO ₂ film is removed by COR, the film contains NH ₃ and F in the gas component in addition to impurities such as H, N, and C, and further, NH ₄ and HF ₂ , etc. There is a possibility that a highly reactive by-product is attached to the wafer W. Since these coexist with HF during the etching of the SiN film, the SiO ₂ film is easily etched. As described above, when the SiO ₂ film is a CVD film or an ALD film, impurities are present, and depending on the film formation method, there are many impurities in the film and the density tends to be low. Therefore, gas components present during the SiO ₂ film etching or reaction products coupled with damage of the SiO ₂ film by etching the SiN film becomes more larger.

An example is shown in FIG. FIG. 5 is a diagram for explaining a mechanism that causes damage to the SiO ₂ film when the SiN film adjacent to the SiO ₂ film containing impurities is etched with HF gas. (A), the deposited by FCVD on the Si substrate 40, SiO ₂ film 41 is etched by the COR, C as an impurity into the surface layer portion of the film, F, it is included NH ₃ or the like. When the SiN film is etched using HF gas as the etching gas in this state, as shown in (b), HF as the etching gas and NH ₃ in the film react with Si in SiO _2. Ammonium fluorosilicate ((NH ₄ ) ₂ SiF ₆ ; AFS) is produced. By subsequent heat treatment, as shown in (c), ammonium fluorosilicate is volatilized and a pitting 42 is formed in the SiO ₂ film 41. This also causes surface roughness on the surface of the SiO ₂ film 41. Similarly, when a by-product such as NH ₄ or HF ₂ adheres to the SiO ₂ film 41, pitting or surface roughness occurs.

Therefore, in the first example of the present embodiment, as shown in the flowchart of FIG. 6, the wafer is first subjected to surface modification processing (step 1), and then the SiN film is etched with HF gas (step 1). 2).

The surface modification treatment in Step 1 is for removing impurities such as NH ₃ , F, and C in the film and by-products such as NH ₄ and HF ₂ adhering to the wafer W. By removing these by the surface modification treatment, the SiO ₂ film becomes difficult to be etched by the subsequent SiN film etching.

Examples of the surface modification treatment include dry treatment in which heat treatment is performed in an inert atmosphere. The temperature at this time is preferably 150 to 400 ° C., for example, 250 ° C. By this treatment, impurities such as NH ₃ , F, and C in the film and by-products such as NH ₄ and HF ₂ adhering to the wafer W can be removed by thermal decomposition or volatilization. In addition, as a dry process, other processes, such as a radical process, can also be used.

Further, as a surface modification treatment include those to perform the reaction process using H 2 _O. By this treatment, impurities in the film and by-products attached to the wafer W can be removed by reacting with H ₂ O. The temperature at this time is preferably 20 to 100 ° C., more preferably 20 to 80 ° C. The reaction process using of H 2 _O, may be performed in a dry process by an atmosphere containing H 2 _O vapor, or immersed in H _{2 O} (deionized water) of the liquid, the liquid H _{2 O} (deionized You may carry out by the wet process which supplies water.

Further, the surface modification treatment can be performed by a treatment including a step of adsorbing a surfactant on the wafer surface and a wet cleaning step using H ₂ O (pure water).

When surface hydrophobic portion of the SiO ₂ film is present, the wet process by simple H _{2 O,} can not reach the H _{2 O} in the portion of the hydrophobic, it becomes insufficient H _{2 O} treated with the portion In some cases, impurities in the film and reaction products attached to the film cannot be sufficiently removed. On the other hand, the entire surface of the wafer surface can be made hydrophilic by adsorbing the surfactant on the wafer surface. Therefore, cleaning of the time of wet cleaning by subsequent H _{2 O} (pure water) is good, to more effectively remove the reaction product adhering to the impurities and the SiO ₂ film in the film of the SiO ₂ film Can do.

FIG. 7 is a diagram for explaining the function of the surfactant used for the surface modification treatment. As shown in FIG. 7 (a), the surfactant has a hydrophobic group and a hydrophilic group in one molecule, and has a function of making a hydrophobic state compatible with water via the hydrophobic group. Have. Then, (b), the entire surface of the SiO ₂ film surface can be hydrophilic group is adsorbed so as to be arranged in the outside. Therefore, as shown in _(c), and _H 2 O (deionized water) is supplied to the entire surface of the SiO ₂ film surface is performed _{H 2} O washed with a good cleaning properties, impurities in the film of the SiO ₂ film And the reaction product adhering to the SiO ₂ film can be effectively removed.

The step of adsorbing the surfactant onto the wafer can be performed by immersing the wafer in the surfactant or by applying the surfactant. At this time, the surfactant may be a stock solution or an aqueous solution. Further, the wet cleaning step using H ₂ O (pure water) can be performed by immersing the wafer in pure water or supplying pure water to the wafer.

Etching of the SiN film in step 2 is performed by introducing only HF gas or a mixed gas of HF gas and inert gas into the chamber and setting the pressure to a high pressure of 1333 Pa (10 Torr) or more as in the first embodiment. Is called. It is preferably 1333 to 11997 Pa (10 to 90 Torr). More preferably, it is 1333 to 5332 Pa (10 to 40 Torr). As the inert gas, N ₂ gas or a rare gas such as Ar or He can be used.

As in the first embodiment, the gas flow rates at this time are preferably HF gas: 200 to 3000 sccm, inert gas: 200 to 3000 sccm, and the wafer temperature is preferably 10 to 120 ° C., 30 to 80 ° C. is more preferable.

With the above processing, inhibit with an SiN film can be etched at a high selection ratio of 15 or more with respect to the SiO ₂ film, a SiO ₂ film during SiN film etching damage to (such as roughness pitting or surface) be able to.

If Si or SiGe is also present adjacent to the SiN film, the SiN film can be etched with a high selection ratio of 50 or more as in the first embodiment.

[Second Example of Etching Method of Second Embodiment]
Next, an application example of this embodiment will be described as a second example.

(Structural example to which the second example is applied)
As an example of the structure to which the etching method of the second example of the present embodiment is applied, the structure shown in FIG. 8 can be cited. In the structure of FIG. 8, a pole-like Si film 32 and a SiGe film 33 are formed on a silicon substrate 31, and a thin SiN film 34 is formed around the Si film 32 and around the SiGe film 33. An SiO ₂ film 35 is formed so as to fill the entire periphery of the substrate.

(Second Example Etching Method)
The etching method of the second example of this embodiment is performed on the structure of FIG. 8 as shown in the flowchart of FIG. 9 and the process cross-sectional view of FIG.

First, the SiO ₂ film 35 in FIG. 8 is etched (step 11).
The etching of the SiO ₂ film 35 can be performed by COR with a wafer having a structure as shown in FIG. 8 in a chamber and using HF gas and NH ₃ gas. At this time, the pressure is preferably 133 to 400 Pa (1 to 3 Torr), the processing temperature is 10 to 130 ° C., the HF gas flow rate is 20 to 1000 sccm, the NH ₃ gas flow rate is 20 to 1000 sccm, and the inert gas flow rate is 20 to 1000 sccm. By this COR treatment, ammonium fluorosilicate ((NH ₄ ) ₂ SiF ₆ ; AFS) is generated, so that the AFS is sublimated by heating to complete the etching. AFS sublimation may be performed with a separate heating apparatus, or etching and heat treatment may be repeatedly performed in the COR chamber, and AFS may be removed therein.

Further, the etching of the SiO ₂ film 35 may be performed by radical treatment. At this time, F radicals and N radicals formed by activating a mixed gas of NF ₃ and NH ₃ can be used as the radicals.

By the etching in step 11, as shown in FIG. 10A, the SiO ₂ film 35 is etched away to a predetermined height position, and the SiN film 34 remains up to a position higher than the predetermined height position. Therefore, etching (de-footing) for removing the footing region of the SiN film 34 is performed.

At this time, if the SiN film is etched as it is with respect to the wafer W after the etching of the SiO ₂ film 35, a film other than the SiN film 34, mainly the SiO ₂ film 35, is etched to cause damage such as pitting and surface roughness. There is a risk of letting you. This damage, and impurities contained in the SiO ₂ film 35, components and entering in the film during the etching of the SiO ₂ film 35, the gas components adhered to the wafer W without being completely removed, SiN It occurs by reacting with HF during film etching. In particular, when the SiO ₂ film 35 is removed by COR, the film contains NH ₃ and F in the gas component in addition to impurities such as H, N, and C, and further NH ₄ and HF _2. There is a possibility that such a by-product with high reactivity adheres to the wafer W, and the SiO ₂ film 35 is likely to be etched by coexistence with HF during the etching of the SiN film. As described above, when the SiO ₂ film is a film formed by CVD or ALD, depending on the film forming method, there is a tendency that the impurity in the film is large and the density is low, and thus this tendency is remarkable. .

Therefore, also in this example, after the etching of the SiO ₂ film 35, a surface modification process is performed (step 12).

The surface modification treatment is for removing impurities in the film and by-products such as NH ₄ and HF ₂ adhering to the wafer W. This makes it difficult for the SiO ₂ film 35 to be etched during the subsequent etching of the SiN film 34.

As in the first example, the surface modification treatment includes heat treatment in an inert atmosphere, reaction treatment using H ₂ O, a step of adsorbing a surfactant on the wafer surface, and H ₂ O (pure water). And a wet cleaning step. Further, as the surface modification treatment, other treatment such as radical treatment can be used.

After performing such surface modification treatment, etching (de-footing) of the footing region of the SiN film 34 is performed (step 13).

In this etching, a wafer having a structure shown in FIG. 10A is accommodated in the chamber, and, as in the first embodiment, only HF gas or a mixed gas of HF gas and inert gas is introduced into the chamber. The pressure is set at a high pressure of 1333 Pa (10 Torr) or more. It is preferably 1333 to 11997 Pa (10 to 90 Torr). More preferably, it is 1333 to 5332 Pa (10 to 40 Torr). As the inert gas, N ₂ gas or a rare gas such as Ar or He can be used. However, in the present embodiment, since the surface modification process is performed, particularly when the etching of the SiO ₂ film 35 is performed by a radical process, the selectivity ratio is low even if it is lower than 1333 Pa (10 Torr). There is a possibility that high SiN film etching can be performed.

In this etching, as in the first embodiment, the gas flow rates are preferably HF gas: 200 to 3000 sccm, inert gas: 200 to 3000 sccm, and the wafer temperature is 10 to 120 ° C. Preferably, 30 to 80 ° C. is more preferable.

Thereby, as shown in FIG. 10B, the footing region of the SiN film 34 can be removed by etching to obtain a desired semiconductor device.

After the etching of the SiN film as described above is completed, etching residues and the like are removed by heat treatment or the like as necessary, and the processing is completed.

According to this example, after removing the SiO ₂ film 35 by etching, impurities in the film and by-products such as NH ₄ and HF ₂ adhering to the wafer W are removed by a surface modification process. Thus, in the subsequent etching of the SiN film 34, by these effects in a state in which damage SiO ₂ film 35 is etched (roughened pitting or surface) is prevented from occurring, SiO ₂ film 35 SiN film 34 The Si film 32 and the SiGe film 33 can be etched with a high selectivity. The selection ratio at this time is 5 or more, preferably 15 or more with respect to SiO ₂ , and 50 or more, preferably 100 or more, with respect to Si and SiGe. Therefore, a semiconductor element having the structure shown in FIG. 10B can be obtained with high accuracy. In particular, even when the SiO ₂ film 35 is formed by CVD (for example, FCVD), which has a relatively large amount of impurities and a low density, etching of the SiO ₂ film 35 can be suppressed, and the SiN film The selectivity ratio of 34 to the SiO ₂ film 35 can be increased.

[An example of a processing system used to implement the second embodiment]
Next, an example of a processing system used in the second embodiment will be described.
FIG. 11 is a schematic configuration diagram illustrating an example of a processing system used in the etching method of the second example of the second embodiment. The processing system 200 includes a vacuum transfer chamber 201 having a rectangular cross section, and an oxide film etching device 202 for etching a SiO ₂ film on one side of the long side of the vacuum transfer chamber 201, a surface modification processing device 203, And a SiN film etching apparatus 204 are connected via a gate valve G. Similarly, an oxide film etching device 202, a surface modification processing device 203, and a SiN film etching device 204 are connected to the other side of the long side of the vacuum transfer chamber 201 via a gate valve G. The inside of the vacuum transfer chamber 201 is evacuated by a vacuum pump and maintained at a predetermined degree of vacuum.

The oxide film etching apparatus 202 can be configured as a COR apparatus that performs etching of the SiO ₂ film by COR. Further, the oxide film etching apparatus 202 may be a radical processing apparatus.

In addition, the surface modification processing apparatus 203 can be configured as a heat treatment apparatus that heat-treats the wafer W at a relatively high temperature. Further, the wafer W may be the H _{2 O} gas treatment apparatus for heat treatment with H _{2 O} gas atmosphere. Furthermore, as the surface modification treatment apparatus 203, another treatment apparatus such as a radical treatment apparatus can be used.

The SiN film etching apparatus 204 can be configured in the same manner as the etching apparatus 105 in the first embodiment.

Also, two load lock chambers 205 are connected to one side of the short side of the vacuum transfer chamber 201 via a gate valve G1. An atmospheric transfer chamber 206 is provided on the opposite side of the vacuum transfer chamber 201 across the load lock chamber 205. The load lock chamber 205 is connected to the atmospheric transfer chamber 206 via a gate valve G2. The load lock chamber 205 controls the pressure between the atmospheric pressure and the vacuum when the wafer W is transferred between the atmospheric transfer chamber 206 and the vacuum transfer chamber 201.

On the wall portion opposite to the load lock chamber 205 mounting wall portion of the atmospheric transfer chamber 206, there are three carrier mounting ports 207 for mounting a carrier C containing a plurality of wafers W such as FOUP. An alignment chamber 208 for aligning the wafer W is provided on the side wall of the atmospheric transfer chamber 206. A downflow of clean air is formed in the atmospheric transfer chamber 206.

In the vacuum transfer chamber 201, two wafer transfer mechanisms 210 are provided. One wafer transfer mechanism 210 includes an oxide film etching apparatus 202, a surface modification processing apparatus 203, a SiN film etching apparatus 204, and one load lock chamber 205 connected to one side of the long side of the vacuum transfer chamber 201. On the other hand, the wafer W can be loaded and unloaded. The other wafer transfer mechanism 210 is connected to the oxide film etching device 202, the surface modification processing device 203, the SiN film etching device 204, and the other load lock chamber 205 connected to the other side of the long side of the vacuum transfer chamber 201. On the other hand, the wafer W can be loaded and unloaded.

In the atmospheric transfer chamber 206, a wafer transfer mechanism 211 is provided. The transfer mechanism 211 transfers the wafer W to the carrier C, the load lock chamber 205, and the alignment chamber 208.

The processing system 200 also has a control unit 212. The control unit 212 is typically a computer, and includes a main control unit having a CPU that controls each component of the processing system 200, an input device (keyboard, mouse, etc.), an output device (printer, etc.), and a display device ( Display) and a storage device (storage medium). The main control unit of the control unit 212 causes the processing system 200 to execute a predetermined operation based on, for example, a processing medium stored in a storage device or a processing recipe stored in the storage medium set in the storage device. .

In such a processing system 200, a plurality of wafers having the structure shown in FIG. 8 are stored in the carrier C and transferred to the processing system 200. In the processing system 200, the wafer W is taken out from the carrier C connected to the atmospheric transfer chamber 206 by the wafer transfer mechanism 211, and the gate valve G2 of any one of the load lock chambers 205 is opened to transfer the wafer W to the load lock chamber 205. Carry in. After the gate valve G2 is closed, the load lock chamber 205 is evacuated.

When the load lock chamber 205 reaches a predetermined degree of vacuum, the gate valve G1 is opened, and the wafer W is taken out of the load lock chamber 205 by the wafer transfer mechanism 210. Then, the gate valve G of the oxide film etching apparatus 202 is opened, the wafer W is loaded into the oxide film etching apparatus 202, and the SiO ₂ film is etched. When the etching of the SiO ₂ film is performed by the COR process, AFS is generated as described above. Therefore, in order to sublimate it, the heat treatment is performed by the surface modification apparatus 203 or a heat treatment apparatus provided separately. Alternatively, etching and heat treatment may be repeatedly performed in the oxide film etching apparatus 202, and AFS may be removed therein.

After the etching of the SiO ₂ film is completed, the wafer W is taken out by the wafer transfer mechanism 210, the gate valve G of the surface modification processing apparatus 203 is opened, and the wafer W is carried into the surface modification processing apparatus 203, and the surface modification is performed. Process.

After the surface modification processing of the wafer W is completed, the wafer is taken out by the wafer transfer mechanism 210, the gate valve G of the SiN film etching apparatus 204 is opened, the wafer W is carried into the SiN film etching apparatus 204, and the SiN film is etched. I do.

After the etching of the SiN film, the etching residue is removed by the surface modification processing apparatus 203 or a heat treatment apparatus provided separately as necessary.

Thereafter, the gate valve G1 of the load lock chamber 205 is opened, the wafer W after the SiN film etching is carried into the load lock chamber 205 by the wafer transfer mechanism 210, the gate valve G1 is closed, and the inside of the load lock chamber 205 is brought to atmospheric pressure. return. Thereafter, the gate valve G2 is opened, and the wafer W in the load lock chamber 205 is returned to the carrier C by the wafer transfer mechanism 211.

The above processing is performed simultaneously on a plurality of wafers W to complete the processing of a predetermined number of wafers W.

Next, an example of the oxide film etching apparatus 202 and the surface modification processing apparatus 203 will be described. Since the SiN film etching apparatus 204 has the same configuration as the etching apparatus 105 of the first embodiment, description thereof is omitted.

[Oxide film etching equipment]
First, an example of the oxide film etching apparatus 202 will be described.
FIG. 12 is a cross-sectional view showing an example of the oxide film etching apparatus 202.
In this example, a COR processing apparatus that etches a SiO ₂ film by COR processing will be described as an example. In this case, since the basic configuration of the apparatus is the same as that of the etching apparatus 105 in the first embodiment, the same components as those in FIG.

In the oxide film etching apparatus 202, a gas introduction path 162 is formed in addition to the gas introduction path 161 through the lid member 155 and the upper wall 157 b of the main body 157 to the space 159 of the shower head 156. An HF gas supply pipe 171 of a gas supply mechanism 143 ′, which will be described later, is connected to the gas introduction path 161. An NH ₃ gas supply pipe 191 is connected to the gas introduction path 162.

The gas supply mechanism 143 ′ includes an HF gas supply source 175 for supplying HF gas and an inert gas supply source 176 for supplying inert gas, which include an HF gas supply pipe 171 and an inert gas supply, respectively. One end of the pipe 172 is connected. A flow rate controller 179 is provided in the HF gas supply pipe 171 and the inert gas supply pipe 172. The other end of the HF gas supply pipe 171 is connected to the gas introduction path 161. The other end of the inert gas supply pipe 172 is connected to the HF gas supply pipe 171.

The gas supply mechanism 143 ′ also has an NH ₃ gas supply source 195 for supplying NH ₃ gas and an inert gas supply source 196 for supplying inert gas, which include NH ₃ gas supply pipe 191 and One end of the inert gas supply pipe 192 is connected. The NH ₃ gas supply pipe 191 and the inert gas supply pipe 192 are provided with a flow rate controller 199 configured similarly to the flow rate controller 179. The other end of the NH ₃ gas supply pipe 191 is connected to the gas introduction path 162. The other end of the inert gas supply pipe 192 is connected to the NH ₃ gas supply pipe 191.

Therefore, HF gas, from the HF gas supply source 175 via a HF gas supply pipe 171 is supplied into the shower head 156, NH ₃ gas, the shower head 156 through the NH ₃ gas supply line 191 from the NH ₃ gas supply source 195 Supplied in. Further, the inert gas is supplied from the inert

gas supply sources

176 and 196 to the HF gas supply pipe 171 and the NH ₃ gas supply pipe 191 through the inert

gas supply pipes

172 and 192, respectively, and is supplied to the shower head 156. . These gases are discharged from the gas discharge hole 162 of the shower head 156 toward the wafer W in the chamber 140.

HF gas and NH ₃ gas are used as reaction gas, and inert gas is used as dilution gas and purge gas. A desired reaction can be caused by supplying HF gas and NH ₃ gas, or a mixture thereof with an inert gas.

In such an oxide film etching apparatus 202, for example, the wafer W having the structure shown in FIG. 8 is loaded into the chamber 140 and mounted on the mounting table 142. The pressure in the chamber 140 is preferably 133 to 400 Pa (1 to 3 Torr), and the processing temperature is preferably 10 to 130 ° C. The HF gas flow rate, NH ₃ gas flow rate, and inert gas flow rate are preferably set to 20 to 1000 sccm, and these gases are supplied to react the HF gas, NH ₃ gas, and SiO ₂ to react with AFS. Generate. Then, the SiO ₂ film is removed by heating the wafer W in an appropriate apparatus.

[Surface modification equipment]
Next, an example of the surface modification processing apparatus 203 will be described.
FIG. 13 is a cross-sectional view showing an example of the surface modification treatment apparatus 203.
In this example, a heat treatment apparatus that removes impurities and by-products in the film by heat treatment will be described as an example of the surface modification treatment apparatus 203.

As shown in FIG. 13, the surface modification processing apparatus 203 has a chamber 220 that can be evacuated and a mounting table 223 on which the wafer W is mounted. A heater 224 is embedded in the mounting table 223, and the wafer W after the etching process of the SiO ₂ film is heated by the heater 224 to heat impurities existing in the film and by-products attached to the surface of the wafer W. Objects are removed by thermal decomposition or volatilization. A loading / unloading port 234 for transferring a wafer to / from the vacuum transfer chamber 201 is provided on the side surface of the chamber 220, and the loading / unloading port 234 can be opened and closed by a gate valve G. A gas supply path 225 is connected to the upper portion of the side wall of the chamber 220, and the gas supply path 225 is connected to an inert gas supply source 230. An exhaust path 227 is connected to the bottom wall of the chamber 220, and the exhaust path 227 is connected to the vacuum pump 233. The gas supply path 225 is provided with a flow rate adjusting valve 231, and the exhaust path 227 is provided with a pressure adjusting valve 232. By adjusting these valves, the inside of the chamber 220 is filled with an N ₂ gas atmosphere at a predetermined pressure. Then, heat treatment is performed. As the inert gas, a rare gas such as N ₂ gas or Ar gas can be used.

In such a surface modification processing apparatus 203, for example, the wafer W having the structure of FIG. 10A is carried into the chamber 220 by the SiO ₂ film etching and placed on the mounting table 223. Then, the wafer W is heated to 150 to 400 ° C., for example, 250 ° C. by the heater 224 while introducing an inert gas such as N ₂ gas into the chamber 220 to make a predetermined reduced pressure atmosphere. Thereby, impurities in the film and by-products such as NH ₄ and HF ₂ adhering to the wafer W can be thermally decomposed or volatilized.

It should be noted that by introducing H ₂ O vapor into the chamber 220 and performing a reaction treatment preferably at 20 to 100 ° C., more preferably at 20 to 80 ° C., impurities in the film and by-products attached to the wafer W can be obtained. The substance may be removed by reacting with H ₂ O gas.

In this example, a cluster type system is used as the processing system 200, and the SiO ₂ film etching, the surface modification process, and the SiN film etching are performed in-situ. It may be used alone and performed ex-situ.

Further, as described above, when the surface modification treatment is performed by wet treatment, an example of the surface modification treatment apparatus shown in FIG. 14 can be used. As shown in this figure, the surface modification processing apparatus 250 has a liquid processing tank 251 for storing and processing the liquid L. A plurality of wafers W held by the wafer holding member 252 are immersed in the liquid L stored in the liquid processing tank 251. The wafer holding member 252 has a plurality of wafer holding bars 252a, and a plurality of wafers W are held by these wafer holding bars 252a. The wafer holding member 252 is moved up and down and horizontally by a transfer device (not shown) so that a plurality of held wafers W are transferred.

A nozzle 253 is provided in the liquid treatment tank 251, and a liquid supply pipe 254 is connected to the nozzle 253. A predetermined liquid can be supplied from the liquid supply mechanism 255 to the liquid supply pipe 254.

A drainage pipe 256 is connected to the bottom of the liquid treatment tank 251, and the liquid in the liquid treatment tank 251 is drained via the drainage pipe 256 by the drainage mechanism 257.

In the case where a treatment with liquid H ₂ O (pure water) is performed as the surface modification treatment, pure water is used as the liquid supplied from the liquid supply mechanism 255. Further, as a surface modification process, when a process including a step of adsorbing a surfactant on the wafer surface and a wet cleaning process using H ₂ O (pure water) is performed, the liquid supplied from the liquid supply mechanism 255 is used. Use pure water and surfactant. Then, these can be selectively supplied, or two types of liquid treatment layers 251 for pure water and a surfactant are prepared.

In the surface modification treatment apparatus 250 configured as described above, when the surface modification treatment is a treatment with liquid H ₂ O (pure water), pure water is supplied into the liquid treatment tank 251 and stored. This is performed by immersing a plurality of wafers W in pure water. In the case where the surface modification process is a process including a step of adsorbing a surfactant on the wafer surface and a wet cleaning step using H ₂ O (pure water), the surface modification treatment is performed as follows. That is, first, a surfactant is supplied into the liquid processing tank 251 and stored, so that a plurality of wafers W are immersed in the surfactant, and then the liquid supplied into the liquid processing tank 251 is purified water. A plurality of wafers W are immersed in pure water in a state where the pure water is stored by switching to the above. Alternatively, a plurality of wafers W are immersed in pure water in a state where pure water is supplied and stored in another liquid processing tank 251.

As another example of the surface modification treatment apparatus when the surface modification treatment is performed by wet treatment, the one shown in FIG. 15 can be used. As shown in this figure, the surface modification processing device 260 includes a chamber 261, a spin chuck 262, a motor 263, a nozzle 264, and a liquid supply mechanism 265. The spin chuck 262 rotatably holds the wafer W in the chamber 261. The motor 263 rotates the spin chuck 262. The nozzle 264 discharges liquid onto the wafer W held by the spin chuck 262. The liquid supply mechanism 265 supplies a liquid to the nozzle 264. Liquid is supplied from the liquid supply mechanism 265 to the nozzle 264 through a liquid supply pipe 266. A predetermined liquid can be supplied from the liquid supply mechanism 265.

As the surface modification treatment, when performing the processing by H _{2 O} (deionized water) of the liquid, pure water is used as the liquid supplied from the liquid supply mechanism 265. In addition, as a surface modification process, when a process including a step of adsorbing a surfactant on the wafer surface and a wet cleaning step using H ₂ O (pure water) is performed, the liquid supplied from the liquid supply mechanism 265 is used. Using pure water and a surfactant, these can be selectively supplied.

A cup 267 for covering the wafer W held by the spin chuck 262 is provided in the chamber 261. An exhaust / drain pipe 268 for exhaust and drainage is provided at the bottom of the cup 267 so as to extend below the chamber 261. On the side wall of the chamber 261, a loading / unloading port 269 for loading and unloading the wafer W is provided.

In the surface modification processing apparatus 260 configured as described above, a single wafer W is loaded into the chamber 261 by a transfer apparatus (not shown) and mounted on the spin chuck 262. In this state, while the wafer is rotated together with the spin chuck 262 by the motor 263, the liquid is discharged from the nozzle 264 from the liquid supply mechanism 265 through the liquid supply pipe 266 to supply the liquid to the entire surface of the wafer W.

When the surface modification process is performed using liquid H ₂ O (pure water), pure water is supplied from the liquid supply mechanism 265 to the rotating wafer W via the liquid supply pipe 266 and the nozzle 264. Then, pure water is spread over the entire surface of the wafer W.

When the surface modification treatment includes a step of adsorbing a surfactant on the wafer surface and a wet cleaning step using H ₂ O (pure water), the surface modification treatment is performed as follows. That is, first, a surfactant is supplied from the liquid supply mechanism 265 to the rotating wafer W via the liquid supply pipe 266 and the nozzle 264, and the surfactant is spread and adsorbed on the entire surface of the wafer W. Next, the liquid supplied from the liquid supply mechanism 265 is switched to pure water, and pure water is supplied onto the wafer to perform wet cleaning.

<Experimental example>
Next, experimental examples of the present invention will be described.

(Experimental example 1)
Here, the SiN film, the thermal oxide film (SiO ₂ film), and the polysilicon film formed by CVD using dichlorosilane (Si ₂ H ₂ Cl ₂ ) gas and NH ₃ gas as the SiN film are etched. It was. Etching was performed using HF gas as an etching gas and changing the temperature and pressure. The etching conditions were as follows: HF gas flow rate: 1500 sccm, pressure: 30 Torr (4000 Pa) and 50 Torr (6665 Pa), temperature: 50 to 150 ° C.

FIG. 16 is a diagram showing the relationship between the pressure, the etching amount (nm) of each film, the selection ratio of the SiN film to the thermal oxide film, and the selection ratio of the SiN film to the polysilicon film at a temperature of 70 ° C. . FIG. 17 is a diagram showing the relationship between the temperature, the etching amount (nm) of each film, and the selectivity of the SiN film to the thermal oxide film and the polysilicon film when the pressure is 50 Torr.

As shown in FIG. 16, it can be seen that the higher the pressure, the higher the etching amount of the SiN film, and the higher the selectivity ratio of the SiN film to the thermal oxide film and the selectivity of the SiN film to the polysilicon film. In addition, as shown in FIG. 17, the temperature range of 50 to 120 ° C. is an allowable range of the selection ratio. In particular, the etching amount of the SiN film increases at 70 ° C., and the selection ratio of the SiN film to the thermal oxide film and the SiN film It can be seen that the selectivity of the film to the polysilicon film is high. At a pressure of 50 Torr and a temperature of 70 ° C., the SiN film has a high selectivity ratio of 15 or more and the SiN film has a selectivity ratio of 100 or more.

Although not shown in FIGS. 16 and 17, the SiGe film shows the same tendency as the polysilicon film, and the selectivity of the SiGe film to the SiN film is 100 or more at a pressure of 50 Torr and a temperature of 70 ° C. A value was obtained.

(Experimental example 2)
Here, the wafer with the SiO ₂ film formed by CVD is first subjected to COR treatment of the SiO ₂ film using HF gas and NH ₃ gas under the conditions of pressure: 333 Pa (2.5 Torr) and temperature: 100 ° C. It was. Next, AFS was removed by heat treatment at 250 ° C., and SiO ₂ film etching was performed. Thereafter, a sample (sample 1) was prepared by performing the SiN film etching condition treatment (HF gas treatment + heat treatment) on the wafer as it was. In addition, after performing pure water treatment, after performing a SiN film etching condition treatment (sample 2), a step of adsorbing a surfactant, and a wet cleaning step using H ₂ O (pure water) A sample (sample 3) subjected to SiN film etching conditions was also prepared. For these samples, the surface state of the SiO ₂ film was investigated.

The SiN film etching conditions are as follows: gas treatment is performed under the conditions of HF gas flow rate: 2000 sccm, pressure: 1333 to 1995 Pa (10 to 15 Torr), temperature: 50 to 75 ° C., and then heat treatment at 250 ° C. .

As a result, in sample 1, a lot of pitting occurred on the SiO ₂ film surface and the surface roughness was poor, but in sample 2, the number of pitting on the SiO ₂ film surface decreased by about 20%, and the surface roughness was also improved. It was. In sample 3, no pitting was observed on the SiO ₂ film surface, and the surface roughness was further improved.

<Other applications>
Although the embodiment has been described above, the embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The above embodiments may be omitted, replaced, and modified in various forms without departing from the scope and spirit of the appended claims. The various embodiments described above may be implemented in combination as appropriate.

For example, the structural example of the above embodiment is merely an example, and any structure can be applied as long as the SiN film coexists with SiO ₂ , Si, and SiGe. In addition, the structure of the processing system and the individual apparatuses are merely examples, and the etching method of the present disclosure can be performed by systems and apparatuses having various configurations.

11, 21, 31; silicon substrate, 12, 22a, 22b, 22c, 32; Si film, 13, 23, 33; SiGe film, 14, 16, 25, 35; SiO ₂ film, 15, 26, 34; SiN Film, 100, 200; processing system, 105; etching apparatus, 202; oxide film etching apparatus, 203, 250, 260; surface modification processing apparatus, 204; SiN film etching apparatus, W; wafer

Claims

Placing a substrate to be processed having a silicon nitride film, a silicon oxide film, silicon and silicon germanium in the chamber;
Setting the pressure in the chamber to 1333 Pa or higher;
Supplying hydrogen fluoride gas into the chamber, and selectively etching the silicon nitride film with respect to the silicon oxide film, silicon, and silicon germanium;
An etching method comprising:
The etching method according to claim 1, wherein the pressure in the chamber is in the range of 1333 to 11997 Pa.
The etching method according to claim 2, wherein the pressure in the chamber is in the range of 1333 to 5332 Pa.
The etching method according to claim 1, wherein the temperature of the substrate to be processed is 10 to 120 ° C.
The etching method according to claim 4, wherein the temperature of the substrate to be processed is 30 to 80 ° C.
The etching method according to claim 1, wherein a selectivity ratio of the silicon nitride film to the silicon oxide film is 5 or more.
The etching method according to claim 6, wherein a selection ratio of the silicon nitride film to the silicon oxide film is 15 or more.
The etching method according to claim 1, wherein a selection ratio of the silicon nitride film to the silicon and silicon germanium is 50 or more.
The etching method according to claim 8, wherein a selection ratio of the silicon nitride film to the silicon and silicon germanium is 100 or more.
An etching method for selectively etching the silicon nitride film for a substrate to be processed having a silicon nitride film and a silicon oxide film,
Performing a surface modification process to remove impurities in the film on the substrate to be processed;
Next, holding the substrate to be processed after the surface modification treatment under a pressure of 1333 Pa or more, supplying HF gas to the substrate to be processed, and selectively etching the silicon nitride film;
An etching method comprising:
The etching method according to claim 10, wherein the silicon oxide film is etched prior to the surface modification treatment.
11. The etching method according to claim 10, wherein the substrate to be processed further includes silicon and silicon germanium, and the silicon nitride film is selectively etched with respect to the silicon and the silicon germanium.
The etching method according to claim 10, wherein the pressure at the time of etching the silicon nitride film is in the range of 1333 to 11997 Pa.
The etching method according to claim 13, wherein the pressure at the time of etching the silicon nitride film is in the range of 1333 to 5332 Pa.
The etching method according to claim 10, wherein the temperature of the substrate to be processed at the time of etching the silicon nitride film is set to 10 to 120 ° C.
The etching method according to claim 15, wherein the temperature of the substrate to be processed at the time of etching the silicon nitride film is set to 30 to 80 ° C.
The etching method according to claim 10, wherein the surface modification treatment is performed by a heat treatment in a range of 150 to 400 ° C in an inert atmosphere.
The etching method according to claim 10, wherein the surface modification treatment is performed by a reaction treatment in a range of 20 to 100 ° C using H 2 O.
The etching method according to claim 10, wherein the surface modification treatment includes a step of adsorbing a surfactant on the surface of a substrate to be processed and a wet cleaning step using H 2 O.
A method for etching a substrate to be processed having a silicon nitride film, a silicon oxide film, silicon and silicon germanium,
First, etching the silicon oxide film,
Next, a step of performing surface modification treatment to remove impurities in the film and by-products on the surface of the substrate to be processed;
Next, holding the substrate to be processed after the surface modification treatment under a pressure of 1333 Pa or more, supplying HF gas to the substrate to be processed, and selectively etching the silicon nitride film;
An etching method comprising:
21. The etching method according to claim 20, wherein the etching of the silicon oxide film is performed using HF gas and NH 3 gas.
21. The etching method according to claim 20, wherein the etching of the silicon oxide film is performed by radical treatment.