TW201907473A - Etching method - Google Patents

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 invention relates to an etching method for etching a silicon nitride film.

Recently, in the manufacturing process of semiconductor devices, fine etching has been performed, but as a dry etching technology replacing conventional plasma etching, a chemical etching technology capable of etching with low damage has attracted attention. For example, in the etching of silicon oxide (SiO ₂ ) film, the chemical oxide removal treatment (Chemical Oxide Removal; COR) technology is used. The chemical oxide removal treatment technology uses hydrogen fluoride (HF) gas and ammonia (NH ₃₎ ) The gas mixture is used as the processing gas.

Recently, studies have explored the application of chemical etching techniques like this to the etching of silicon nitride (SiN) films.

Since the SiN film is mostly adjacent to the SiO ₂ film, as a technique for selectively etching the SiN film relative to the SiO ₂ film, Patent Document 3 describes the following: HF gas and F ₂ gas , Inert gas and O ₂ gas are supplied and etched in an excited state. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2005-39185 [Patent Document 2] Japanese Patent Laid-Open No. 2008-160000 [Patent Document 3] Japanese Patent Laid-Open No. 2015-73035

[Problems to be solved by the present invention]

However, recently, for example, a semiconductor device using silicon (Si) and silicon germanium (SiGe) like a CMOS transistor has been developed. When a SiN film is used for such a semiconductor device, not only the SiO ₂ film but also High selectivity is required for Si and SiGe.

However, in the current situation, it is difficult to etch the SiN film with sufficient selectivity with respect to all SiO ₂ films, Si, and SiGe.

In addition, when the SiO ₂ film contains impurities such as H or N, even if it is a technique like the above-mentioned Patent Document 3, when the SiN film is etched, the SiO ₂ film may be damaged.

Therefore, the present invention aims to provide an etching method that can etch a silicon nitride (SiN) film with high selectivity relative to a silicon oxide (SiO2) film, silicon (Si), and silicon germanium (SiGe).

In addition, an object of the present invention is to provide an etching method that can selectively etch the SiN film without damaging the SiO ₂ film adjacent to the SiN film. [Means to solve the problem]

In order to solve the above-mentioned problems, the first aspect of the present invention provides an etching method characterized by disposing a substrate to be processed having a silicon nitride film, a silicon oxide film, silicon, and silicon germanium in a chamber, The pressure is set to 1333 Pa or more, hydrogen fluoride gas is supplied into the chamber, and the silicon nitride film is selectively etched with respect to the silicon oxide film, silicon, and silicon germanium.

In the above-mentioned first viewpoint, the pressure in the chamber is preferably set in the range of 1333 to 11997 Pa, and more preferably set in the range of 1333 to 5332 Pa.

In addition, the temperature of the substrate to be processed is preferably 10 to 120 ° C, and more preferably 30 to 80 ° C.

The selection ratio of the silicon nitride film to the silicon oxide film is preferably 5 or more, and more preferably 15 or more. Moreover, the selection ratio of the silicon nitride film to the silicon and silicon germanium is preferably 50 or more, and more preferably 100 or more.

A second aspect of the present invention is to provide an etching method for selectively etching the silicon nitride film on a substrate to be processed having a silicon nitride film and a silicon oxide film. This etching method is characterized in that The treated substrate is subjected to surface modification to remove impurities in the film. Secondly, the substrate to be treated after the surface modification is maintained at a pressure of 1333 Pa or more, and HF gas is supplied to the substrate to be selectively etched. Silicon film.

In the second aspect, the silicon oxide film may be etched before the surface modification treatment. Furthermore, the substrate to be processed may further include silicon and silicon germanium, and the silicon nitride film is selectively etched with respect to the silicon and the silicon germanium.

A third aspect of the present invention is to provide an etching method for etching a silicon oxide film on a substrate to be processed having a silicon nitride film, a silicon oxide film, silicon, and silicon germanium, and secondly, removing impurities and coatings from the film Surface modification treatment of the by-products on the surface of the treatment substrate. Secondly, the substrate to be treated after the surface modification treatment is maintained at a pressure of 1333 Pa or more, and HF gas is supplied to the treatment substrate to selectively etch the silicon nitride membrane.

In the third aspect described above, the etching of the silicon oxide film can be performed using HF gas and NH ₃ gas. In addition, the etching of silicon oxide can also be performed by radical treatment.

In the second and third aspects described above, the pressure when etching the silicon nitride film is preferably in the range of 1333 to 11997 Pa, and more preferably in the range of 1333 to 5332 Pa. Further, the temperature of the substrate to be processed when etching the silicon nitride film is preferably 10 to 120 ° C, and more preferably 30 to 80 ° C.

The aforementioned surface modification treatment can be performed by heat treatment in the range of 150 to 400 ° C in an inert environment. In addition, the aforementioned surface modification treatment can be performed by a reaction treatment using H ₂ O in the range of 20 to 100 ° C. Moreover, the aforementioned surface modification treatment can be performed by a process of adsorbing a surfactant on the surface of the substrate to be processed and a wet cleaning process by H ₂ O. [Effect of invention]

According to the present invention, by using HF gas and etching the silicon nitride film under high pressure, nitrogen can be etched with high selectivity relative to silicon oxide (SiO ₂ ) film, silicon (Si) and silicon germanium (SiGe) Silicone (SiN) film. In addition, when the silicon nitride film is selectively etched for the substrate to be processed with the silicon nitride film and the silicon oxide film, the surface modification such as removing impurities in the film is performed before the etching of the silicon nitride film Therefore, when HF gas is used and the silicon nitride film is etched under high pressure, damage to the silicon oxide film can be suppressed.

Hereinafter, referring to the drawings, embodiments of the present invention will be described.

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

[Example of the structure to which the etching method of the first embodiment is applied] As an example of the structure to which the etching method of the present embodiment is applied, the one shown in FIG. 1 (a) can be cited. 1 (a), a columnar Si film 12 and a SiGe film 13 are formed on a silicon substrate 11, and a first SiO ₂ film 14 is formed around the Si film 12 and a SiGe film 13 and a first SiO ₂ film is formed on the first SiO ₂ A SiN film 15 is formed around the film 14 and on the Si film 12 and the SiGe film 13. In addition, 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. Although the SiN film 15 of the structure of FIG. 1 (a) is etched to form a desired semiconductor element, at this time, ideally, as shown in FIG. 1 (b), it is required that only the SiN film 15 is removed. That is, the SiN film 15 is etched at a high selectivity with respect to the Si film 12, SiGe film 13, first and _second SiO ₂ films 14, 16.

As another example of the structure for applying the etching of the SiN film of this embodiment, the structure shown in FIG. 2 (a) can be cited. The structure of FIG. 2 (a) is that on the silicon substrate 21, a columnar first Si film 22a, a second Si film 22b, and a third Si film 22c are provided from the left side, and a columnar SiGe film 23. In these first to third Si films 22a to 22c and SiGe film 23, a hard mask 24 remains. Furthermore, an SiO ₂ film 25 is formed on the silicon substrate 21 around the first Si film 22a and from the end on the side of the first Si film 22a to the third Si film 22c. Furthermore, a SiN film 26 is provided on the SiO ₂ film 25 and around the _second Si film 22b. Although the SiN film 26 of the structure of FIG. 2 (a) is etched to form a desired semiconductor element, at this time, ideally, as shown in FIG. 2 (b), it is required to remove only the SiN film 26. That is, the SiN film 26 is etched at 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, it is required that the selection ratio with respect to SiO ₂ is 5 or more, and the selection ratio with respect to Si and SiGe is 50 or more.

As the Si film 12, the first to third Si films 22a to 22c, and the SiGe films 13, 23, for example, a polycrystalline film formed by epitaxial growth or CVD can be used. In addition, the first and _second SiO ₂ films 14 and 16 and the SiO ₂ film 25 may be formed by chemical vapor deposition (CVD), or may be formed by atomic layer deposition (ALD) The film may be a thermal oxide film. When forming the SiO ₂ film by CVD, there are various techniques, and the amounts of hydrogen (H), carbon (C), nitrogen (N), etc. included as impurities differ depending on the technique. In low-quality CVD-SiO _{2 The} film contains relatively many impurities. The ALD-SiO ₂ film also contains these impurities in the same way. On the other hand, in the case of a thermal oxide film, there are few impurities like this.

The SiN film to be etched uses 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 N2 gas by thermal CVD, plasma CVD, and ALD Wait for the filmmaker.

[Etching of SiN Film of First Embodiment] When the SiN film shown in the above element example is formed adjacent to SiO ₂ , Si, and SiGe, as an attempt to etch the SiN film at a high selectivity ratio, it can be performed (1 ) Method of etching with COR gas using HF gas or HF gas + NH ₃ gas, (2) Method of etching by adding F _{2 to} the gas system, (3) Method of radical SiN etching.

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

Therefore, after reviewing such a method that can etch the SiN film with a high selectivity relative to all SiO ₂ , Si, and SiGe, it was found that it is effective to use HF gas and set the pressure to a high pressure of 1333 Pa (10 Torr) or more. The reason why a higher selection ratio can be obtained by setting it to a high-pressure state like this is because the effect of improving the adsorption efficiency of HF gas can be obtained by setting it to a high pressure.

The details will be described below. In the SiN etching of this embodiment, for example, the following is performed: a semiconductor wafer (also referred to as a wafer only) having a structure as described above is housed in a chamber, and only HF gas or HF is stored The mixed gas of gas and inert gas is introduced into the chamber. As the inert gas, a rare gas such as N ₂ gas or Ar, 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 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 addition, the wafer temperature at this time is preferably 10 to 120 ° C. Below 10 ° C and above 120 ° C, it becomes difficult to obtain the desired selection ratio. More preferably, it is 30 to 80 ° C.

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

Under the above conditions, the SiN film is etched for a predetermined time in accordance with the thickness of the SiN film, whereby the ratio of SiO ₂ to 5 or more and the ratio of Si and SiGe to 50 or more can be selected The SiN film is selectively etched. The selection ratio with respect to SiO ₂ is 15 or more, and the selection ratio with respect to Si and SiGe is preferably 100 or more.

[An example of the processing system used in the first embodiment] Next, an example of the processing system used in the first embodiment will be described. FIG. 3 is a schematic configuration diagram showing an example of the processing system used in the first embodiment. The processing system 100 includes: a carry-in / out section 102, which carries in and out a semiconductor wafer (hereinafter, only referred to as a wafer) W shown in the above-described structural example; two load lock chambers 103, which are opposite Adjacent to each other; the heat treatment device 104, which is adjacent to each load lock chamber 103, respectively, to heat treat the wafer W; the etching device 105, which is adjacent to each heat treatment device 104, respectively, to etch the wafer W; and Control unit 106.

The carry-in / out section 102 includes a transfer chamber 112, and a first wafer transfer mechanism 111 for transferring wafers W is provided therein. The first wafer transfer mechanism 111 has two transfer arms 111a and 111b that hold the wafer W substantially horizontally. On a side portion of the transfer chamber 112 in the longitudinal direction, a mounting table 113 is provided, and on the mounting table 113, for example, three carriers C that accommodate a plurality of wafers W of FOUP and the like can be connected. In addition, an alignment chamber 114 that performs alignment of the wafer W is provided adjacent to the transfer chamber 112.

In the carry-in / out section 102, the wafer W is held by the transfer arms 111a, 111b, and driven by the first wafer transfer mechanism 111 to move straight up or down in a substantially horizontal plane, thereby being transferred to The desired location. Furthermore, the transfer arms 111a and 111b advance and retreat with respect to the carrier C, the alignment chamber 114, and the load lock chamber 103 on the mounting table 113, respectively, thereby carrying them in and out.

Each load lock chamber 103 is connected to the transfer chamber 112 with the gate valve 116 interposed therebetween. In each load lock chamber 103, a second wafer transfer mechanism 117 that transfers wafers W is provided. In addition, the load lock chamber 103 is configured to be evacuable to a predetermined vacuum degree.

The second wafer transfer mechanism 117 has a multi-joint arm structure and has a pickup that holds the wafer W substantially horizontally. In the second wafer transfer mechanism 117, in the state where the articulated arm is contracted, the pickup is located in the loading lock chamber 103, and the articulator reaches the heat treatment device 104 by extending the articulated arm. With further extension, the etching device 105 can be reached, so that the wafer W can be transferred between the load lock chamber 103, the heat treatment device 104, and the etching device 105.

The control unit 106 is usually constituted by a computer, and has: a main control unit, a CPU that controls each component of the processing system 100; an input device (keyboard, mouse, etc.); an output device (printer, etc.); a display device (Display, etc.); and memory devices (memory media). The main control unit of the control unit 106 causes the processing system 100 to perform predetermined actions based on, for example, the processing recipe memorized in the memory medium built in the memory device or the memory medium installed in the memory device.

In the processing system 100 like this, the wafer W formed with the above-mentioned configuration is stored in the plurality of carrier C and is transported to the processing system 100. In the processing system 100, with the gate valve 116 on the atmospheric side opened, the carrier C from the carry-in / out section 102 is moved by one of the transfer arms 111a and 111b of the first wafer transfer mechanism 111. The wafer W is transferred to the load lock chamber 103 and received by the pickup of the second wafer transfer mechanism 117 in the load lock chamber 103.

After that, the gate valve 116 on the atmosphere side is closed and the inside of the load lock chamber 103 is evacuated. Next, the gate valve 154 is opened to extend the pickup to the etching device 105 and transfer the wafer W to the etching device 105.

Thereafter, the pickup is returned to the load lock chamber 103, the gate valve 154 is closed, and the etching process of the SiN film is performed in the etching apparatus 105 by the above-described etching method.

After the etching process is completed, the gate valves 122 and 154 are opened, and the wafer W after the etching process is transferred to the heat treatment device 104 by the pickup of the second wafer transfer mechanism 117 and heated to remove etching residues and the like.

After the heat treatment in the heat treatment device 104 is completed, it returns to the carrier C by any one of 111a and 111b of the first wafer transfer mechanism 111. With this, the processing of one wafer is completed.

In addition, when it is not necessary to remove the etching residue, etc., the heat treatment device 104 may not be provided. In this case, the wafer W after the etching process is completed only by the pickup of the second wafer transfer mechanism 117 It is sufficient to retreat to the load lock chamber 103 and return to the carrier C by any one of the transfer arms 111a and 111b of the first wafer transfer mechanism 111.

[Etching Apparatus] Next, an example of the etching apparatus 105 for implementing 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. FIG. As shown in FIG. 4, the etching apparatus 105 is provided with a chamber 140 having a closed structure. Inside the chamber 140, a mounting table 142 is provided for loading the wafer W in a substantially horizontal state. In addition, the etching apparatus 105 includes a gas supply mechanism 143 that supplies etching gas to the chamber 140 and an exhaust mechanism 144 that exhausts the chamber 140.

The chamber 140 is composed of the chamber body 151 and the cover 152. The chamber body 151 has a substantially cylindrical side wall portion 151a and a bottom portion 151b, the upper portion is formed as an opening, and the opening is closed by the cover portion 152. The side wall portion 151a and the cover portion 152 are sealed by a sealing member (not shown) to ensure airtightness in the chamber 140.

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

The upper wall 157b of the cover member 155 and the main body 157 penetrates into the space 159 to form a gas introduction path 161, and the gas introduction path 161 is connected with an HF gas supply pipe 171 of a gas supply mechanism 143 described later.

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 piping 171 and the gas introduction path 161 is discharged from the gas discharge holes 162 to the space in the chamber 140.

The side wall portion 151a is provided with a loading / unloading outlet 153 for loading and unloading the wafer W between the heat treatment device 104, and the loading / unloading outlet 153 can be opened and closed by a gate valve 154.

The mounting table 142 is substantially circular in plan view, and is fixed to the bottom 151 b of the chamber 140. Inside the mounting table 142, a temperature regulator 165 for adjusting the temperature of the mounting table 142 is provided. The temperature regulator 165 is provided with, for example, a pipe for circulating a medium for temperature adjustment (for example, water, etc.), and adjusts the mounting table 142 by heat exchange with the medium for temperature adjustment flowing in such a pipe 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 for supplying HF gas and an inert gas supply source 176 for supplying inert gas. In these, one end of the HF gas supply pipe 171 and the inert gas supply pipe 172 are respectively connected. The HF gas supply pipe 171 and the inert gas supply pipe 172 are provided with a flow controller 179 that performs the switching operation of the flow path and the flow control. The flow controller 179 is constituted by, 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. In addition, the other end of the inert gas supply pipe 172 is connected to the HF gas supply pipe 171.

Therefore, 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 through the inert gas supply pipe 172 and the HF gas supply pipe 171 to In 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.

Among these gases, HF gas is a reactive gas and an inert gas, and is used as a dilution gas and a flushing gas. The 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 the exhaust port 181 formed at the bottom 151b of the chamber 140, and further has an exhaust pipe 182 provided in the exhaust pipe 182 to control the pressure in the chamber 140 An automatic pressure control valve (APC) 183 and a vacuum pump 184 for exhausting the chamber 140.

On the side wall of the chamber 140, two capacitive pressure gauges 186a and 186b are provided as pressure gauges for measuring the pressure in the chamber 140 so as to be inserted into the chamber 140. The capacitive pressure gauge 186a is used for high pressure, and the capacitive pressure gauge 186b is used for low pressure. In the vicinity of the wafer W placed on the mounting table 142, a temperature sensor (not shown) for detecting the temperature of the wafer W is provided.

In such an etching apparatus 105, the wafer W having the above-described structure is carried into the chamber 140 and placed on the mounting table 142. Moreover, the pressure in the chamber 140 is set to be 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), and adjusted by the temperature of the mounting table 142 In the device 165, the wafer W is set to preferably 10 to 120 ° C, more preferably 30 to 80 ° C, and both the HF gas and the inert gas are preferably supplied at 200 to 3000 sccm to etch the SiN film.

<Second Embodiment> Next, a second embodiment of the present invention will be described. Although this embodiment is the same as the first embodiment and includes an engineer who removes the SiN film by etching, in this embodiment, the system An explanation will be given of an etching method in which it is difficult to damage the SiO ₂ film when the SiN film is etched, even if the SiO ₂ film adjacent to the SiN film contains impurities such as N or H.

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

When impurities such as H or N are contained in the SiO ₂ film, it is found that if the SiN film adjacent to it is directly etched by HF gas, the impurities contained in the SiO ₂ film are etched when the SiN film is etched The gas components such as H or N react with HF, and the SiO ₂ film is etched unevenly, which may cause damage such as pitting (holes) or rough surfaces. For example, in the case of the SiO ₂ film formed by CVD or ALD, H, N, and C derived from the film-forming raw material gas exist in the system film, which may cause damage when the SiN film is etched. 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 aforementioned impurities, the density is low and it is easily damaged by etching of the SiN film. In addition, since the SiO ₂ film formed by the fluidized chemical vapor deposition method (F-CVD) often contains impurities as described above and has a low density, it is still susceptible to damage during etching of the SiN film.

In addition, when the SiO2 film adjacent to the SiN film is etched, in addition to the impurities originally contained, there is also a component that penetrates into the film during etching or a gas component that is not removed and adheres to the wafer W, and When the SiN film is etched, it is easily damaged by the etching of the SiO ₂ film due to HF and attached gas components. In particular, when the SiO ₂ film is removed by COR, the system film contains NH ₃ or F in the gas component in addition to impurities, that is, H, N, C, etc., and NH ₄ or HF ₂ exists. the high reactivity of the possibility of by-product adhered to the wafer W, by etching the SiN film in some occasion, to coexist with HF, SiO ₂ film can be easily etched. As aforesaid, since the case where the SiO ₂ film is a CVD film or the ALD film, based impurities present, and, according to the film formation technique, having film-based impurities and the density also tends to be low, thus, the SiO ₂ film The gas components or reaction products existing during the etching interact, and the damage of the SiO ₂ film due to the etching of the SiN film becomes larger.

An example is shown in FIG. 5. As shown in FIG. 5 (a), the SiO ₂ film 41 formed on the Si substrate 40 by FCVD and etched by COR contains C, F, NH ₃ and the like as impurities in the surface layer portion of the film. In this state, when the SiN film is etched using HF gas as an etching gas, as shown in FIG. 5 (b), the etching gas, that is, HF reacts with NH ₃ in the film and Si in SiO ₂ to form Ammonium silicofluoride, and subsequent heat treatment, as shown in FIG. 5 (c), ammonium silicide fluoride volatilizes and forms pitting 42 on the SiO ₂ film 41. Moreover, the surface of the SiO ₂ film 41 is roughened. When a by-product such as NH ₄ or HF _{2 is} attached to the SiO ₂ film 41, pitting corrosion or surface roughness similarly occurs.

Therefore, in the first example of the present embodiment, as shown in the flowchart of FIG. 6, first, the wafer is subjected to surface modification treatment (step 1), and thereafter, the etching of the SiN film by HF gas is performed (Step 2).

The surface modification treatment in step 1 is used to remove impurities such as NH ₃ , F, and C in the film or by-products such as NH ₄ or HF _{2 that are} attached to the wafer W. These are removed by surface modification treatment, whereby the SiO ₂ film becomes difficult to be etched by the subsequent SiN film etching.

As the surface modification treatment, a drying treatment that performs heat treatment in an inert environment can be mentioned. 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 or by-products such as NH ₄ or HF ₂ adhering to the wafer W can be thermally decomposed or volatilized and removed. In addition, as the drying treatment, other treatments such as radical treatment can also be used.

In addition, as a surface modification treatment, a person who performs a reaction treatment using H ₂ O may be mentioned. By this treatment, impurities in the film or 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, and more preferably 20 to 80 ° C. The reaction treatment using H ₂ O may be carried out by drying treatment in an atmosphere containing H ₂ O vapor, or it may be carried out by immersing in liquid H ₂ O (pure water) or supplying liquid H ₂ O (Pure water) wet processing is performed.

Furthermore, the surface modification treatment can also be performed by a process of adsorbing the surfactant on the surface of the wafer and a wet cleaning process caused by H ₂ O (pure water).

If there is a hydrophobic part on the surface of the SiO ₂ film, then in the wet treatment caused by pure H ₂ O, there is a part where H ₂ O cannot reach the hydrophobic part, and the H ₂ O treatment In some cases, it becomes insufficient to sufficiently remove impurities in the film or reaction products attached to the film. In this regard, the entire surface of the wafer surface can be made hydrophilic by adsorbing the surfactant to the wafer surface. Therefore, in the subsequent wet cleaning by H ₂ O (pure water) good cleaning, the film can be more effectively removed in the SiO ₂ film or impurities adhering to the reaction product of the SiO ₂ film.

That is, 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 the hydrophobic state affinity with water through the hydrophobic group, as shown in FIG. 7 ( As shown in b), the hydrophilic group can be adsorbed on the entire surface of the surface of the SiO ₂ film so that the hydrophilic groups are arranged outside. Therefore, as shown in FIG. 7 (c), H ₂ O (pure water) is supplied to the entire surface of the SiO ₂ film surface, and H ₂ O is washed with good detergency, so that the SiO ₂ film can be effectively removed Impurities in the film or reaction products attached to the SiO ₂ film.

The process of adsorbing the surfactant to the wafer can be carried out by soaking the wafer in the surfactant or coating the surfactant. At this time, the surfactant may be a stock solution or an aqueous solution. In addition, the wet cleaning process caused by H ₂ O (pure water) can be performed by soaking the wafer in pure water or supplying pure water to the wafer.

The etching of the SiN film in step 2 is carried out by introducing 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. . 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, a rare gas such as N ₂ gas or Ar, He can be used.

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

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

By the treatment as described above, the SiN film can be etched at a high selectivity ratio of 15 or more relative to the SiO ₂ film, and damage to the SiO ₂ film (pitting corrosion, surface roughness, etc.) during the etching of the SiN film can be suppressed.

In addition, when Si or SiGe is also adjacent to the SiN film, the SiN film can be etched at a high selectivity ratio of 50 or more with respect to these as in the first embodiment.

[Second example of the etching method of the second embodiment] Next, an application example of this embodiment will be described as a second example.

(Structure example to which the second example is applied) As an example of the structure to which the etching method according to the second example of the present embodiment is applied, the one shown in FIG. 8 can be cited. 8, the columnar Si film 32 and the SiGe film 33 are formed on the silicon substrate 31, and the thin SiN film 34 is formed around the Si film 32 and around the SiGe film 33, and the SiN film 34 is formed The SiO ₂ film 35 is formed by burying the entire surrounding.

(Etching method of the second example) As shown in the flowchart of FIG. 9 and the engineering cross-sectional view of FIG. 10, the etching method of the second example of the present embodiment is performed on the structure of FIG.

First, the SiO ₂ film 35 of FIG. 8 is etched (step 11). The etching of the SiO ₂ film 35 can be performed by storing a wafer having a structure as shown in FIG. 8 in a chamber, and using COR using HF gas and NH ₃ gas. At this time, the pressure: 133 to 400 Pa (1 to 3 Torr), the processing temperature: 10 to 130 ° C., the HF gas flow rate: 20 to 1000 sccm, the NH ₃ gas flow rate: 20 to 1000 sccm, and the inert gas flow rate: 20 to 1000 sccm are preferred. Since the COR treatment generates ammonium hexafluorosilicate ((NH ₄ ) ₂ SiF ₆ ; AFS), the AFS is sublimated by heating to complete the etching. The sublimation of AFS can also be performed by individual heating devices, or it can be repeatedly etched and heated in the COR chamber, and the AFS can be removed therein.

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

By the etching in step 11, as shown in FIG. 10 (a), the SiO ₂ film 35 is etched and removed up 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) to remove the footed region of the SiN film 34 is performed.

In this case, if the SiN film is etched directly on the wafer W after the etching of SiO ₂ film 35, the SiN film is etched in the occasion, etching the film to invade the impurities contained in the SiO ₂ film 35 or the film 35 of SiO ₂ The component in the gas or the gas component that has not been removed but adhered to the wafer W will react with HF to etch the film other than the SiN film 34, mainly the SiO ₂ film 35, which may cause damage such as pitting or surface roughness. In particular, when the SiO ₂ film 35 is removed by COR, the system film contains NH ₃ or F in the gas component in addition to impurities such as H, N, and C, and NH ₄ or HF _{2 is present} . the high reactivity of the possibility of by-product adhered to the wafer W, by etching the SiN film in some occasion, to coexist with HF, SiO ₂ film 35 is easily etched. As described above, when the SiO2 film is a film formed by CVD or ALD, the film-forming method tends to have many impurities in the film and the density is low, so this tendency is obvious.

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

Surface modification treatment is used to remove impurities in the film or by-products such as NH ₄ or HF ₂ attached to the wafer W. With this, when the subsequent SiN film 34 is etched, the SiO ₂ film 35 becomes difficult to be etched.

As the surface modification treatment, as in the first example, heat treatment in an inert atmosphere, treatment using H ₂ O, and the process of adsorbing the surfactant to the wafer surface and H ₂ O (pure water) ) Disposal of the wet cleaning project. In addition, as the surface modification treatment, other treatments such as radical treatment may be used.

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

In this etching, a wafer having the structure shown in FIG. 10 (a) is housed 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, and The pressure is set to a high pressure of 1333 Pa (10 Torr) or higher. 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, a rare gas such as N ₂ gas or Ar, He can be used. However, in the present embodiment, by performing a surface modification treatment, in particular, in the case where the SiO ₂ film 35 is etched by radical treatment, it may be performed even if it is less than 1333Pa (10 Torr) The possibility to select a SiN film with a higher ratio is etched.

In this etching, as in the first embodiment, the gas flow rate is 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 even better.

As a result, as shown in FIG. 10 (b), the footed region of the SiN film 34 can be removed to obtain a desired semiconductor element.

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

According to this example, after the SiO ₂ film 35 is etched and removed, by surface modification treatment, impurities in the film or by-products such as NH ₄ or HF ₂ adhering to the wafer W are removed. etching the SiN film 34 in preventing the SiO ₂ film 35 damage (pitting or surface roughness) due to the plurality of impact SiO ₂ film 35 is etched occurring state, with respect to the SiO ₂ film 35, Si film 32 , SiGe film 33, a high selectivity etching of the SiN film 34 (with respect to SiO _2, to select the ratio of 5 or more, preferably 15 or more; Si and SiGe, to select a relative ratio of 50 or more, preferably 100 or more). Therefore, the semiconductor element having the structure of FIG. 10 (b) can be obtained with high accuracy. In particular, even if the SiO ₂ film 35 is formed by a CVD (for example, FCVD) using a film formation method with a relatively large amount of impurities and a low density, the etching of the SiO ₂ film 35 can be suppressed and can be improved The selection ratio of the SiN film 34 to the SiO ₂ film 35.

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

The oxide film etching device 202 can be configured as a COR device for etching the SiO ₂ film by COR. In addition, the oxide film etching device 202 may be a radical processing device.

In addition, the surface modification processing device 203 may be configured as a heat treatment device that performs heat treatment on the wafer W at a relatively high temperature. Alternatively, it may be an H ₂ O gas processing apparatus that performs heat treatment on the wafer W in an H ₂ O gas atmosphere. In addition, as the surface modification treatment device 203, another treatment device such as a radical treatment device may be used.

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

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

The wall part opposite to the mounting wall part of the load lock chamber 205 of the atmospheric transfer chamber 206 has three carrier mounting ports 207, and the carrier mounting port 207 is mounted with a carrier C that houses a plurality of wafers W such as FOUP . In addition, an alignment chamber 208 for aligning the wafer W is provided on the side wall of the atmospheric transfer chamber 206. In the atmospheric transfer chamber 206, a downward flow of clean air is formed.

In the vacuum transfer chamber 201, two wafer transfer mechanisms 210 are provided. One wafer transfer mechanism 210 can be connected to the oxide film etching device 202, the surface modification processing device 203 and the SiN film etching device 204 connected to one side of the long side of the vacuum transfer chamber 201 and the one load lock chamber 205 The wafer W is transported in and out, and the other wafer transport mechanism 210 can be used for the oxide film etching device 202, the surface modification processing device 203, and the SiN film connected to the other side of the long side of the vacuum transfer chamber 201 The etching apparatus 204 and the other load lock chamber 205 carry in and out the wafer W.

In the atmospheric transfer chamber 206, a wafer transfer mechanism 211 is provided. The transfer mechanism 211 can transfer 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 usually constituted by a computer, and has a main control unit, 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, etc.); and memory devices (memory media). The main control unit of the control unit 212, for example, causes the processing system 200 to perform a predetermined action according to the processing recipe memorized in the memory medium built in the memory device or the memory medium installed in the memory device.

In the processing system 200 like this, a wafer formed with the configuration shown in FIG. 8 is stored in a plurality of carrier C and transported to the processing system 200. In the processing system 200, the wafer W is taken out of the carrier C connected to the atmospheric transfer chamber 206 by the wafer transfer mechanism 211, the gate valve G2 of any load lock chamber 205 is opened, and the wafer W is transferred into the Load lock chamber 205. After closing the gate valve GV2, the inside of the load lock chamber 205 is evacuated.

When the load lock chamber 205 reaches a predetermined vacuum degree, 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, and the gate valve G of the oxide film etching apparatus 202 is opened to turn the crystal The circle W is carried into the oxide film etching apparatus 202, and the SiO ₂ film is etched. When the SiO ₂ film is etched by COR treatment, since AFS is generated as described above, in order to sublime it, a surface modification treatment device 203 or a separately provided heat treatment device is used for heat treatment. Alternatively, the etching and heating treatment may be repeated 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, and the gate valve G of the surface modification processing device 203 is opened to carry the wafer W into the surface modification processing device 203 for surface modification deal with.

After the surface modification process of the wafer W is completed, the wafer is taken out by the wafer transfer mechanism 210, and the gate valve G of the SiN film etching device 204 is opened to carry the wafer W into the SiN film etching device 204 to perform the SiN film Etch.

After the etching of the SiN film, the etching residue is removed by the surface modification treatment device 203 or the separately provided heat treatment device as needed.

Thereafter, the gate valve G1 of the load lock chamber 205 is opened, and the wafer W etched by the SiN film is carried into the load lock chamber 205 by the wafer transfer mechanism 210, and the gate valve G1 is closed to return the load lock chamber 205 to atmospheric pressure . 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 plurality of wafers W are simultaneously processed in parallel as described above to complete the processing of a predetermined number of wafers W.

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

[Oxide Film Etching Device] First, an example of the oxide film etching device 202 will be described. FIG. 12 is a cross-sectional view showing an example of an oxide film etching apparatus 202. In this example, a COR processing apparatus for etching an SiO ₂ film by COR processing will be described as an example. In this case, since the basic configuration of the device is the same as the etching device 105 in the first embodiment, the same symbols as those in FIG. 4 are given and explanations are omitted.

In the oxide film etching apparatus 202, the gas introduction path 162 is formed in addition to the gas introduction path 161 formed in the cover member 155 and the upper wall 157b of the main body 157 in addition to the space 159 penetrating the shower head 156. An HF gas supply pipe 171 connected to a gas supply mechanism 143 'described later is connected to the gas introduction path 161. In addition, 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. In these, one end of the HF gas supply pipe 171 and the inert gas supply pipe 172 are respectively connected. The flow 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. In addition, the other end of the inert gas supply pipe 172 is connected to the HF gas supply pipe 171.

Gas supply mechanism 143 ', lines with NH ₃ gas supply source supplying the NH ₃ gas 195 and the inert gas supply source supplying the inert gas 196, in which some, lines were connected to the NH ₃ gas supply pipe 191 and the inert gas supply pipe 192 At the end. The NH ₃ gas supply pipe 191 and the inert gas supply pipe 192 are provided with a flow controller 199 having the same configuration as the flow controller 179. The other end of the NH ₃ gas supply pipe 191 is connected to the gas introduction path 162. In addition, the other end of the inert gas supply pipe 192 is connected to the NH ₃ gas supply pipe 191.

Therefore, HF gas is supplied from the HF gas supply source 175 through the HF gas supply pipe 171 into the shower head 156, and NH ₃ gas is supplied from the NH ₃ gas supply source 195 through the NH ₃ gas supply pipe 191 into the shower head 156 The inert gas is supplied from the inert gas supply sources 176 and 196 via the inert gas supply pipes 172 and 192 to the HF gas supply pipe 171 and the NH ₃ gas supply pipe 191, respectively, and is supplied to the shower head 156. Furthermore, these gases are discharged from the gas discharge holes 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 as dilution gas and flushing gas. By supplying HF gas and NH ₃ gas or supplying these in a mixture with an inert gas, a desired reaction can be generated.

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

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

The surface modification treatment device 203, as shown in FIG. 13, has: a chamber 220, which can be evacuated; and a mounting table 223, in which the wafer W is mounted, and a heater 224 is embedded in the mounting table 223 The heater 224 heats the wafer W subjected to the etching treatment of the SiO ₂ film to thermally decompose or volatilize the impurities present in the film or by-products adhering to the surface of the wafer W to be removed . On the side of the chamber 220, there is provided a carry-in / out port 234 for transferring wafers with the vacuum transfer chamber 201. The carry-in / out port 234 can be opened and closed by the gate valve G. A gas supply path 225 is connected to the upper part of the side wall of the chamber 220, and the gas supply path 225 is connected to an inert gas supply source 230. In addition, 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 control valve 231, and the exhaust path 227 is provided with a pressure adjustment valve 232. By adjusting these valves, the chamber 220 becomes a predetermined pressure N ₂ gas atmosphere For heat treatment. As the inert gas, a rare gas such as N ₂ gas or Ar gas can be used.

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

In addition, H ₂ O vapor can also be introduced into the chamber 220 to perform a reaction treatment at preferably 20 to 100 ° C, more preferably 20 to 80 ° C, thereby allowing impurities in the film to adhere to the wafer W The by-products react with H ₂ O to be removed.

In addition, in this example, although it is shown that "the cluster type which connects the oxide film etching apparatus 202, surface modification processing apparatus 203, and SiN film etching apparatus 204 to the vacuum transfer chamber 201 is used as the processing system 200, in- situ performs the etching of the SiO ₂ film, the surface modification treatment, and the etching of the SiN film. However, these devices can also be used alone to perform ex-situ.

In addition, as described above, when the surface modification treatment is performed by wet treatment, the one shown in FIG. 14 can be used as an example of the surface modification treatment device. As shown in the figure, the surface modification treatment device 250 includes a liquid treatment tank 251 that stores and processes the liquid L. The plurality of wafers W held by the wafer holding member 252 may be immersed in the liquid L stored in the liquid processing tank 251. The wafer holding member 252 includes a plurality of wafer holding bars 252a, and the wafer holding bars 252a hold a plurality of wafers W. The wafer holding member 252 can be moved up and down and horizontally by a transfer device (not shown) to transfer a plurality of held wafers W.

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

A liquid discharge pipe 256 is connected to the bottom of the liquid treatment tank 251, and the liquid in the liquid treatment tank 251 can be discharged through the liquid discharge pipe 256 by the liquid discharge mechanism 257.

As the surface modification treatment, when a treatment by liquid H ₂ O (pure water) is performed, pure water is used as the liquid supplied from the liquid supply mechanism 255. In addition, as a surface modification treatment, in the case of performing a process of adsorbing a surfactant on the wafer surface and a wet cleaning process caused by H ₂ O (pure water), pure water and The surfactant is selectively supplied as liquid supplied from the liquid supply mechanism 255, or the liquid treatment layer 251 is prepared for two types of pure water and surfactant.

In the surface modification treatment device 250 configured as above, when the surface modification treatment is caused by liquid H ₂ O (pure water), pure water is supplied to the liquid treatment tank 251 and stored In the state of, it is performed by immersing a plurality of wafers W in pure water. In addition, when the surface modification treatment includes the process of adsorbing the surfactant on the surface of the wafer and the wet cleaning process caused by H ₂ O (pure water), the liquid treatment tank In a state where the surfactant is supplied and stored in the 251, a plurality of wafers W are immersed in the surfactant, and then, the liquid supplied to the liquid treatment tank 251 is switched to pure water and the pure water is stored, or In a state where pure water is supplied and stored in the other liquid processing tank 251, a plurality of wafers W is immersed in pure water.

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

As the surface modification treatment, when a treatment by liquid H ₂ O (pure water) is performed, pure water is used as the liquid supplied from the liquid supply mechanism 265. In addition, as a surface modification treatment, in the case of performing a process of adsorbing a surfactant on the wafer surface and a wet cleaning process caused by H ₂ O (pure water), pure water and The surfactant is selectively supplied as liquid supplied from the liquid supply mechanism 265.

In the chamber 261, a cup 267 for covering the wafer W held by the spin chuck 262 is provided. At the bottom of the cup 267, an exhaust / drain pipe 268 for exhausting and draining is provided so as to extend below the chamber 261. A loading / unloading outlet 269 for loading and unloading the wafer W is provided on the side wall of the chamber 261.

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

As a surface modification treatment, when a treatment due to liquid H ₂ O (pure water) is performed, pure water is supplied to the rotating crystal from the liquid supply mechanism 265 through the liquid supply pipe 266 and the nozzle 264 This is performed by diffusing pure water on the entire surface of the wafer W on the circle W.

As a surface modification treatment, when a process including a process for adsorbing a surfactant on the surface of a wafer and a wet cleaning process due to H ₂ O (pure water) are performed, first, from the liquid supply mechanism 265 The surfactant is supplied to the rotating wafer W through the liquid supply pipe 266 and the nozzle 264, and the surfactant is diffusely adsorbed on the entire surface of the wafer W. Next, the liquid supplied from the liquid supply mechanism 265 is switched to pure Water is supplied to the wafer for wet cleaning.

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

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

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

As shown in FIG. 16, it can be seen that the higher the pressure, the more the etching amount of the SiN film is increased, and the selection ratio of the SiN film to the thermal oxide film and the selection ratio of the SiN film to the polycrystalline silicon film are higher. Also, as shown in FIG. 17, it can be seen that the temperature range of 50 to 120 ° C. is the allowable range of the selection ratio. In particular, at 70 ° C., the etching amount of the SiN film becomes larger, and the selection of the SiN film relative to the thermal oxide film The selectivity ratio of the SiN film to the polysilicon film becomes higher. At a pressure of 50 Torr and a temperature of 70 ° C, the selection ratio of the SiN film relative to the thermal oxide film can be as high as 15 or more, and the selection ratio of the SiN film relative to the polysilicon film can be as high as 100 or more.

In addition, although not shown in FIGS. 16 and 17, the SiGe film shows the same tendency as the polysilicon film. At a pressure of 50 Torr and a temperature of 70 ° C, the selection ratio for the SiGe film of the SiN film can also be obtained at 100 or more. Higher value.

(Experimental Example 2) In this case, the wafer formed with CVD system due to the SiO ₂ film, first using HF gas and NH ₃ gas, a pressure: 333 Pa (2.5 Torr), temperature: 100 ℃ for conduct of SiO ₂ After the COR treatment of the film, the AFS was removed by heat treatment at 250 ° C to etch the SiO ₂ film. After that, "Where the wafer is directly subjected to SiN film etching conditions (HF gas treatment + heat treatment) (Sample 1)" and "After performing pure water treatment, those who are subjected to SiN film etching conditions (Sample 2) "," After the treatment with the process of adsorbing the surfactant and the wet cleaning process caused by H ₂ O (pure water), the person who performed the etching conditions of the SiN film (sample 3) " To investigate the surface state of the SiO ₂ film.

In addition, the SiN film etching conditions are treated as HF gas flow rate: 2000 sccm, pressure: 1333 to 1995 Pa (10 to 15 Torr), temperature: 50 to 75 ° C, and 250 ° C heat treatment.

As a result, in Sample 1, although a large amount of pitting occurred on the surface of the SiO ₂ film and the surface roughness was also poor, in Sample 2, the number of pitting on the surface of the SiO ₂ film was reduced by about 20%, and it was also observed Surface roughness improved. In addition, in Sample 3, no pitting on the surface of the SiO ₂ film was observed and the surface roughness was further improved.

<Other Applications> Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the gist thereof.

For example, the structural examples of the above-mentioned embodiments are merely examples, 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 above-mentioned processing system or individual device is also merely an example, and the etching method of the present invention can be implemented by a system or device 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 device

202‧‧‧ oxide film etching device

203, 250, 260‧‧‧surface modification treatment device

204‧‧‧SiN film etching device

W‧‧‧ Wafer

[FIG. 1] (a) is a cross-sectional view showing an example of a structure to which the etching method of the first embodiment of the present invention is applied; (b) is a semiconductor element after etching the SiN film of the structure of (a) Profile view. [FIG. 2] (a) is a cross-sectional view showing another example of the structure to which the etching method of the first embodiment of the present invention is applied; (b) is a semiconductor device after etching the SiN film of the structure of (a) Section view. [Fig. 3] A schematic configuration diagram showing an example of a processing system used in the etching method according to the first embodiment of the present invention. [Fig. 4] A cross-sectional view showing an etching apparatus mounted on the processing system of Fig. 3. [Fig. 5] A diagram for explaining the mechanism of damage to the SiO ₂ film when the SiN film adjacent to the SiO ₂ film containing impurities is etched by HF gas. [Fig. 6] A flowchart showing a first example of the etching method according to the second embodiment of the present invention. [Fig. 7] A diagram for explaining the function of a surfactant used for surface modification treatment. [Fig. 8] A cross-sectional view showing an example of a structure of a second example to which the etching method according to the second embodiment of the present invention is applied. 9 is a flowchart showing a second example of the etching method according to the second embodiment of the present invention. [Fig. 10] An engineering cross-sectional view in a second example of the etching method according to the second embodiment of the present invention; (a) shows the structure of the SiO ₂ film after etching; (b) shows the etching of the SiN film ( cross-sectional view of the semiconductor device after de-footing). 11 is a schematic configuration diagram showing an example of a processing system used in an etching method according to a second example of the second embodiment of the present invention. [Fig. 12] A cross-sectional view showing an oxide film etching apparatus mounted on the processing system of Fig. 11. [Fig. 13] A cross-sectional view showing a surface modification treatment device mounted on the treatment system of Fig. 11. 14 is a cross-sectional view showing another example of the surface modification treatment device. [Fig. 15] A cross-sectional view showing still another example of the surface modification treatment device. [Fig. 16] In the experimental example, the pressure when etching the SiN film, the thermal oxide film, and the polycrystalline silicon film at a temperature of 70 ° C and varying the pressure and the etching amount (nm) of each film and the SiN film relative to the thermal oxide film A graph of the selection ratio and the selection ratio of the SiN film relative to the polysilicon film. [Fig. 17] In the experimental example, the temperature when etching the SiN film, the thermal oxide film, and the polycrystalline silicon film at a pressure of 50 Torr and varying the temperature, the etching amount of each film (nm), and the selection of the SiN film relative to the thermal oxide film It is a graph comparing the selection ratio of the SiN film to the polysilicon film.

Claims (22)

An etching method characterized by: arranging a substrate to be treated with a silicon nitride film, a silicon oxide film, silicon, and silicon germanium in a chamber; setting the pressure in the chamber to 1333 Pa or more and supplying hydrogen fluoride gas to the chamber, The silicon nitride film is selectively etched with respect to the silicon oxide film, silicon, and silicon germanium. For example, the etching method according to item 1 of the patent application scope, wherein the pressure in the chamber is set in the range of 1333 to 11997 Pa. For example, in the etching method of claim 2 of the patent application scope, the pressure in the chamber is set in the range of 1333 to 5332 Pa. An etching method as described in any one of claims 1 to 3, wherein the temperature of the substrate to be processed is set to 10 to 120 ° C. For example, in the etching method of claim 4, the temperature of the substrate to be processed is set to 30 to 80 ° C. An etching method as described in any one of claims 1 to 3, wherein the selection ratio of the silicon nitride film to the silicon oxide film is 5 or more. For example, in the etching method of claim 6, the selectivity ratio of the silicon nitride film to the silicon oxide film is 15 or more. The etching method according to any one of the items 1 to 3 of the patent application range, wherein the selectivity ratio of the silicon nitride film to the silicon and silicon germanium is 50 or more. For example, in the etching method of claim 8, the selectivity ratio of the silicon nitride film to the silicon and silicon germanium is 100 or more. An etching method is to selectively etch the silicon nitride film on a substrate to be processed having a silicon nitride film and a silicon oxide film. This etching method is characterized by removing impurities in the film from the substrate to be processed In the surface modification process, next, the substrate to be treated after the surface modification treatment is maintained at a pressure of 1333 Pa or more, HF gas is supplied to the substrate to be treated, and the silicon nitride film is selectively etched. An etching method as described in item 10 of the patent application scope, wherein, before the surface modification treatment, the silicon oxide film is etched. According to the etching method of claim 10 or 11, the substrate to be processed further includes silicon and silicon germanium, and the silicon nitride film is selectively etched relative to the silicon and the silicon germanium. An etching method characterized by for a substrate to be treated with a silicon nitride film, a silicon oxide film, silicon and silicon germanium, first etching the silicon oxide film, secondly, to remove impurities in the film and by-products on the surface of the substrate to be treated After the surface modification treatment of the object, the substrate to be treated after the surface modification treatment is maintained at a pressure of 1333 Pa or more, HF gas is supplied to the substrate to be selectively etched. For example, in the etching method of claim 13, the etching of the silicon oxide film is performed using HF gas and NH ₃ gas. For example, in the etching method of claim 13, the etching of the aforementioned silicon oxide film is performed by radical treatment. An etching method according to any one of the patent application items 10, 11, 13 to 15, wherein the pressure during etching of the silicon nitride film is set to the range of 1333 to 11997 Pa. For example, in the etching method of claim 16, the pressure during etching of the silicon nitride film is set in the range of 1333 to 5332 Pa. An etching method according to any one of patent application items 10, 11, and 13 to 15, wherein the temperature of the substrate to be processed when etching the silicon nitride film is set to 10 to 120 ° C. For example, in the etching method of claim 18, the temperature of the substrate to be processed when etching the silicon nitride film is set to 30 to 80 ° C. The etching method according to any one of the patent application items 10, 11, 13 to 15, wherein the surface modification treatment is performed by heat treatment in the range of 150 to 400 ° C in an inert environment. The etching method according to any one of the patent application items 10, 11, 13 to 15, wherein the surface modification treatment is performed by a reaction treatment using H ₂ O in the range of 20 to 100 ° C. The etching method according to any one of the patent application items 10, 11, 13 to 15, wherein the surface modification treatment is caused by the process of adsorbing the surfactant on the surface of the substrate to be processed and H ₂ O The wet cleaning project.