TWI756425B - Etching method - Google Patents

Abstract

[Subject] To provide an etching method capable of etching a silicon nitride film with high selectivity with respect to a silicon oxide film, silicon and silicon germanium. [Solution] Arrange a substrate to be processed including a silicon nitride film, a silicon oxide film, silicon, and silicon germanium in the chamber, set the pressure in the chamber to 1333Pa or more, and supply hydrogen fluoride gas into the chamber, so that the oxidation The silicon film, silicon and silicon germanium are selectively etched to the aforementioned silicon nitride film.

Description

Etching method

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

Recently, in the production process of semiconductor elements, micro-etching is performed, but as a dry etching technology replacing the conventional plasma etching, a chemical etching technology capable of performing low-damage etching has been attracting attention. For example, in the etching of silicon oxide (SiO ₂ ) film, a chemical oxide removal (Chemical Oxide Removal; COR) technique is used, and the chemical oxide removal treatment technique uses hydrogen fluoride (HF) gas and ammonia (NH ₃ ). ) gas mixture as the process 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 often adjacent to the SiO ₂ film, as a technique for selectively etching the SiN film with respect to the SiO ₂ film, Patent Document 3 describes the following: HF gas, F ₂ gas , inert gas, and O ₂ gas are supplied and etched in the excited state. [Prior Art 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 Invention]

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

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

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

Furthermore, it is a problem 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, a first aspect of the present invention is to provide an etching method characterized by disposing a substrate to be processed including a silicon nitride film, a silicon oxide film, silicon and silicon germanium in a chamber, The pressure is set to 1333 Pa or more, and hydrogen fluoride gas is supplied into the chamber to selectively etch the silicon nitride film with respect to the silicon oxide film, silicon, and silicon germanium.

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

Moreover, it is preferable to set the temperature of the said to-be-processed board|substrate to 10-120 degreeC, and it is more preferable to set it to 30-80 degreeC.

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

A second aspect of the present invention provides 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, and the etching method is characterized by: The treated substrate is subjected to a surface modification treatment to remove impurities in the film. Next, 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 substrate to be treated to selectively etch the nitride. Silicon film.

In the above-mentioned second viewpoint, the above-mentioned silicon oxide film may be etched before the above-mentioned surface modification treatment. In addition, the substrate to be processed may further comprise silicon and silicon germanium, and the silicon nitride film may be selectively etched with respect to the silicon and the silicon germanium.

A third aspect of the present invention is to provide an etching method, which firstly etches a silicon oxide film on a substrate to be processed having a silicon nitride film, a silicon oxide film, silicon, and silicon germanium, and then removes impurities and impurities in the film. Surface modification treatment of by-products on the surface of the treated substrate, secondly, 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 is selectively etched membrane.

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

In the above-mentioned second and third viewpoints, the pressure at the time of 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. Moreover, it is preferable to set the temperature of the to-be-processed substrate at the time of etching the said silicon nitride film to 10-120 degreeC, and it is more preferable to set it to 30-80 degreeC.

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 said surface modification process can be performed by the reaction process in the range of 20-100 degreeC using _H2O . In addition, the above-mentioned surface modification treatment can be performed by a process including a process of adsorbing the 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, nitrogen can be etched with high selectivity with respect to silicon oxide (SiO ₂ ) film, silicon (Si) and silicon germanium (SiGe) by using HF gas and etching silicon nitride film under high pressure Silicon (SiN) film. In addition, when selectively etching the silicon nitride film on the substrate to be processed having the silicon nitride film and the silicon oxide film, surface modification to remove impurities and the like 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, embodiments of the present invention will be described with reference to the drawings.

<1st Embodiment> Next, the 1st Embodiment concerning this invention is demonstrated. In this embodiment, a method for removing the SiN film formed adjacent to SiO ₂ , Si and SiGe by etching 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 exemplified. In the structure of FIG. 1(a), a columnar Si film 12 and a SiGe film 13 are formed on a silicon substrate 11, and a first SiO2 film 14 is formed around the Si film 12 and around the SiGe film 13, and a first _SiO2 film 14 is formed on the first _SiO2 A SiN film 15 is formed around the film 14 and on the Si film 12 and the SiGe film 13 . 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. Although the desired semiconductor element is formed by etching the SiN film 15 of the structure of FIG. 1(a), at this time, ideally, as shown in FIG. 1(b), only the SiN film 15 is required to be removed. That is, the SiN film 15 is etched with a high selectivity with respect to the Si film 12, the SiGe film 13, and the first and _{second SiO2} films 14, 16.

As another example of the structure to which the etching of the SiN film of the present embodiment is applied, the one shown in FIG. 2( a ) can be mentioned. In the structure of FIG. 2(a), on the silicon substrate 21, a first Si film 22a, a second Si film 22b, and a third Si film 22c are formed in a column shape from the left, and a columnar Si film 22c is formed on the right SiGe film 23 . The hard mask 24 remains on the first to third Si films 22 a to 22 c and the SiGe film 23 . Then, a SiO ₂ film 25 is formed around the first Si film 22a and on the silicon substrate 21 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), only the SiN film 26 is required to be removed. 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 _SiO2 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 by 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). film, or can also be a thermal oxide film. When forming a SiO ₂ film by CVD, there are various methods, and the amount of hydrogen (H), carbon (C), nitrogen (N), etc. contained as impurities varies depending on the method. In low-quality CVD-SiO ₂ films contain a relatively large amount of impurities. The ALD-SiO ₂ film also contains these impurities in the same manner. On the other hand, in the case of a thermal oxide film, there are few impurities like this.

The SiN film to be etched is produced by thermal CVD, plasma CVD, and ALD using silane-based gas such as SiH ₄ gas, SiH ₂ Cl ₂ , Si ₂ Cl ₆ and other nitrogen-containing gases such as NH ₃ gas or N2 gas. Wait for the film maker.

[SiN film etching according to the first embodiment] In the case where 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 with a high selectivity ratio, (1 ) A method of etching with a COR device using HF gas or HF gas + NH ₃ gas, (2) a method of etching by adding F ₂ to the gas system, and (3) a method of radical SiN etching.

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

Therefore, after examining such a method for etching SiN films with high selectivity with respect to all SiO ₂ , Si and SiGe, it was found that using HF gas and setting the pressure to a high pressure of 1333 Pa (10 Torr) or more is effective. The reason why a higher selectivity ratio can be obtained by setting it to a high pressure state in this way is because the effect of improving the adsorption efficiency of HF gas can be obtained by setting it to a high pressure state.

Hereinafter, it demonstrates in detail. In the SiN etching of the present embodiment, for example, a semiconductor wafer (also simply referred to as a wafer) having the above-mentioned structure is housed in a chamber, and only HF gas or HF A mixed gas of gas and inert gas is introduced into the chamber. As the inert gas, N ₂ gas or a rare gas such as Ar and He can be used.

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

The pressure in the chamber at this time is set to 1333 Pa (10 Torr) or more as described above. Preferably it is 1333-11997Pa (10-90 Torr). More preferably, it is 1333-5332Pa (10-40 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 a desired selection ratio. More preferably, it is 30-80 degreeC.

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

Under the above conditions, the SiN film is etched for a predetermined time according to the film thickness of the SiN film, whereby the ratio of 5 or more can be selected with respect to SiO ₂ , and the ratio of 50 or more can be selected with respect to Si and SiGe. Selective etching of the SiN film. 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.

[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 loading/unloading unit 102 for loading and unloading semiconductor wafers (hereinafter, only referred to as wafers) W shown in the above-described structural example; and two load lock chambers 103 corresponding to the loading/unloading unit 102 The heat treatment apparatuses 104 are arranged adjacent to the load lock chambers 103, respectively, to perform heat treatment on the wafer W; the etching apparatus 105, respectively, are arranged adjacent to the heat treatment apparatuses 104, and the wafer W is etched; and control unit 106 .

The loading/unloading unit 102 includes a transport chamber 112 and a first wafer transport mechanism 111 that transports the wafers W is provided therein. The first wafer transfer mechanism 111 includes two transfer arms 111a and 111b that hold the wafer W substantially horizontally. On the longitudinal side of the transfer chamber 112, a mounting table 113 is provided, and to the mounting table 113, for example, three carriers C for accommodating a plurality of wafers W such as FOUPs can be connected. In addition, an alignment chamber 114 for performing alignment of the wafers W is provided adjacent to the transfer chamber 112 .

In the carry-in and carry-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 straightly or vertically in a substantially horizontal plane, thereby being transferred to desired location. Then, the transfer arms 111a and 111b move forward and backward with respect to the carrier C on the mounting table 113, the alignment chamber 114, and the load lock chamber 103, respectively, thereby carrying in and out.

Each of the load lock chambers 103 is connected to the transfer chamber 112 in a state in which the gate valve 116 is respectively interposed between the load lock chamber 103 and the transfer chamber 112 . In each of the load lock chambers 103 , a second wafer transfer mechanism 117 that transfers the wafer W is installed. Also, the load lock chamber 103 is configured to be evacuated up to a predetermined degree of vacuum.

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, the pickup is located in the load lock chamber 103 in the state where the articulated arm is retracted, and the pickup reaches the heat treatment device 104 by extending the articulated arm, and by In a further extended manner, the etching apparatus 105 can be reached, so that the wafer W can be transferred between the load lock chamber 103 , the thermal processing apparatus 104 and the etching apparatus 105 .

The control unit 106 is usually constituted by 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.); a display device (display, etc.); and memory device (memory medium). The main control unit of the control unit 106 causes the processing system 100 to execute predetermined actions according to a processing recipe memorized in a storage medium built in the storage device or a storage medium installed in the storage device, for example.

In such a processing system 100 , the wafers W formed with the above-described configuration are accommodated in a plurality of carriers C, and are transported to the processing system 100 . In the processing system 100, with the gate valve 116 on the atmosphere side open, one wafer is transferred from the carrier C of the transfer unit 102 to 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 is delivered to the pickup of the second wafer transfer mechanism 117 in the load lock chamber 103 .

Then, the gate valve 116 on the atmosphere side is closed, and the load lock chamber 103 is evacuated. Next, the gate valve 154 is opened, and the pickup is extended to the etching apparatus 105 to transfer the wafer W to the etching apparatus 105 .

Then, 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-mentioned etching method.

After the etching process is completed, the gate valves 122 and 154 are opened, and the etched wafer W is transferred to the heat treatment apparatus 104 by the pickup of the second wafer transfer mechanism 117, and the etching residues and the like are removed by heating.

After the heat treatment in the heat treatment apparatus 104 is completed, the wafer is returned to the carrier C by any one of 111 a and 111 b of the first wafer transfer mechanism 111 . Thereby, the processing of one wafer is completed.

In addition, when it is not necessary to remove the etching residue or the like, the heat treatment device 104 may not be provided, and in this case, the wafer W after the etching treatment is only required to be processed 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 111 a and 111 b of the first wafer transfer mechanism 111 .

[Etching Apparatus] Next, an example of the etching apparatus 105 for carrying out the etching method of the present 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 chamber 140 having an airtight structure. Inside the chamber 140 , a mounting table 142 for mounting the wafer W in a substantially horizontal state is provided. In addition, the etching apparatus 105 includes a gas supply mechanism 143 for supplying the etching gas to the chamber 140 , and an exhaust mechanism 144 for exhausting the inside of the chamber 140 .

The chamber 140 is formed by the chamber body 151 and the cover 152 . The chamber body 151 has a substantially cylindrical side wall portion 151 a and a bottom portion 151 b , the upper portion is formed with 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 constituting an outer side, and a shower head 156 provided so as to be fitted into the inner side of the cover member 155 so as to face the mounting table 142 . The shower head 156 has: a main body 157 with a cylindrical side wall 157 a and an upper wall 157 b; and a shower plate 158 arranged on the bottom of the main body 157 . A space 159 is formed between the main body 157 and the shower plate 158 .

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

A plurality of gas discharge holes 162 are formed in the shower plate 158 , and the gas introduced into the space 159 via the gas supply pipe 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 151 a is provided with a loading and unloading port 153 for loading and unloading the wafer W between the thermal processing apparatus 104 , and the loading and unloading port 153 can be opened and closed by a gate valve 154 .

The stage 142 is substantially circular in plan view, and is fixed to the bottom portion 151b 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 temperature-adjusting medium (for example, water), and adjusts the mounting table 142 by exchanging heat with the temperature-adjusting medium flowing in the pipe. At this temperature, the temperature of the wafer W on the mounting table 142 is controlled.

The gas supply mechanism 143 has an HF gas supply source 175 for supplying HF gas and an inert gas supply source 176 for supplying an inert gas, and one ends of the HF gas supply pipe 171 and the inert gas supply pipe 172 are respectively connected to these. The HF gas supply piping 171 and the inert gas supply piping 172 are provided with a flow controller 179 that performs opening and closing operations and flow control of the flow paths. 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 into the shower head 156 from the HF gas supply source 175 via the HF gas supply pipe 171 , 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 the shower head 156 . In the shower head 156 , the gases are discharged from the gas discharge holes 162 of the shower head 156 toward the wafer W in the chamber 140 .

Among these gases, HF gas is a reactive gas, an inert gas, and is used as a dilution gas and a flushing gas. Desired etching performance can be obtained by supplying the HF gas alone or by supplying the HF gas in a mixture with the inert gas.

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

Two capacitive pressure gauges 186 a and 186 b as pressure gauges for measuring the pressure in the chamber 140 are provided on the side wall of the chamber 140 so as to be inserted into the chamber 140 . Capacitance pressure gauge 186a is for high pressure, and capacitance pressure gauge 186b is for low pressure. A temperature sensor (not shown) that detects the temperature of the wafer W is provided in the vicinity of the wafer W placed on the stage 142 .

In such an etching apparatus 105 , the wafer W formed with the above-mentioned structure is carried into the chamber 140 and placed on the mounting table 142 . Furthermore, the pressure in the chamber 140 is set to 1333Pa (10Torr) or more, preferably 1333-11997Pa (10-90Torr), more preferably 1333-5332Pa (10-40Torr), and is adjusted by the temperature of the mounting table 142 The device 165 sets the wafer W at preferably 10-120° C., more preferably 30-80° C., and preferably supplies both HF gas and inert gas at 200-3000 sccm to etch the SiN film.

<Second Embodiment> Next, a second embodiment of the present invention will be described. In this embodiment, as in the first embodiment, a process for etching and removing the SiN film is included, but in this embodiment, the A description will be given of an etching method in which damage to the SiO ₂ film when the SiN film is etched is unlikely to occur even if impurities such as N or H are contained in the SiO ₂ film adjacent to the SiN film.

[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 a wafer on which a SiN film is formed adjacent to a SiO ₂ film containing a predetermined impurity.

When the SiO ₂ film contains impurities such as H or N, it was found that when the SiN film adjacent to the SiN film is directly etched by the HF gas, the impurities contained in the SiO ₂ film during the etching of the SiN film are found. Among them, gas components such as H and N react with HF, and the SiO ₂ film is etched non-uniformly, thereby causing damage such as pitting (holes) and surface roughness. 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 exist in the film, which may cause 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 above-mentioned impurities, the density is low and the SiN film is easily damaged during etching. In addition, the SiO ₂ film formed by the fluid chemical vapor deposition method (F-CVD) is also prone to damage during etching of the SiN film because the above-mentioned impurities are often present and the density is also low.

Also, when the SiO2 film adjacent to the SiN film is etched, in addition to the impurities originally contained, there are components that penetrate into the film during etching or gas components that adhere to the wafer W without being removed, and When the SiN film is etched, it is easy to be damaged by the etching of the SiO ₂ film due to HF and adhering gas components. In particular, when the SiO ₂ film is removed by COR, in addition to impurities such as H, N, C, etc., the film contains NH ₃ or F among the gas components, and also contains NH ₄ or HF ₂ . There is a possibility that by-products with high reactivity adhere to the wafer W, and the SiO ₂ film is easily etched by coexisting with HF when the SiN film is 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 is a tendency for the impurities in the film to be large and the density to be low. Therefore, it is different from the SiO ₂ film. Gas components and reaction products present during etching interact, and damage to the SiO ₂ film due to etching of the SiN film becomes greater.

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, HF, reacts with NH ₃ in the film and Si in SiO ₂ to generate As shown in FIG. 5( c ), the ammonium silicofluoride is volatilized and a pit 42 is formed in the SiO ₂ film 41 by subsequent heat treatment. Further, as a result, surface roughness is generated on the surface of the SiO ₂ film 41 . When by-products such as NH ₄ or HF ₂ adhere to the SiO ₂ film 41 , pitting corrosion and surface roughness are similarly generated.

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 SiN film is etched by HF gas. (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 adhering to the wafer W. These are removed by the surface modification treatment, whereby the SiO ₂ film becomes difficult to be etched by the subsequent SiN film etching.

As the surface modification treatment, drying treatment in which heat treatment is performed in an inert atmosphere is exemplified. 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. Moreover, as a drying process, other processes, such as radical treatment, can also be used.

Moreover, as a surface modification process, the reaction process using _H2O is mentioned. By this treatment, impurities in the film or by-products adhering to the wafer W can be reacted with H ₂ O to be removed. The temperature at this time is preferably 20 to 100°C, more preferably 20 to 80°C. The reaction treatment using H ₂ O may be performed by drying treatment in an atmosphere containing H ₂ O vapor, or by immersing in liquid H ₂ O (pure water) or supplying liquid H ₂ O (pure water) wet treatment.

In addition, the surface modification treatment may be performed by a treatment including a process of adsorbing the surfactant on the wafer surface and a wet cleaning process by H ₂ O (pure water).

If there is a hydrophobic part on the surface of the SiO ₂ film, in the wet treatment by pure H ₂ O, there is a part where the H ₂ O cannot reach the hydrophobic part, and the H ₂ O treatment A situation in which impurities in the film and reaction products adhering to the film cannot be sufficiently removed due to insufficient portions thereof. On the other hand, by adsorbing the surfactant on the wafer surface, the entire surface of the wafer surface can be made hydrophilic. Therefore, in the subsequent wet cleaning by H ₂ O (pure water) The cleanability of the SiO ₂ film is good, and the impurities in the SiO ₂ film or the reaction products attached to the SiO 2 film can be removed more effectively.

That is, as shown in FIG. 7( a ), the surfactant has a hydrophobic group and a hydrophilic group in one molecule, and has the function of making the hydrophobic state hydrophilic through the hydrophobic group, as shown in FIG. 7 ( As shown in b), it can be adsorbed on the entire surface of the SiO ₂ film so that the hydrophilic groups are arranged on the outside. Therefore, as shown in FIG. 7( c ), H ₂ O (pure water) is supplied to the entire surface of the SiO ₂ film to perform H ₂ O cleaning with good cleaning properties, thereby effectively removing the SiO ₂ film The impurities in the film or the reaction products attached to the SiO ₂ film.

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

The etching of the SiN film in Step 2 is performed by introducing only HF gas or a mixed gas of HF gas and an 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. . Preferably it is 1333-11997Pa (10-90 Torr). More preferably, it is 1333-5332Pa (10-40 Torr). As the inert gas, N ₂ gas or a rare gas such as Ar and 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, and 30 to 80°C. ℃ is better.

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

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

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

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

(Example of the structure 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, as shown in FIG. 8 . In the structure of FIG. 8, a columnar 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, and a thin SiN film 34 is formed on the SiN film 34. The SiO ₂ film 35 is formed so as to bury the whole around.

(Etching method of the second example) As shown in the flowchart of FIG. 9 and the process sectional view of FIG. 10 , the etching method of the second example of the present embodiment is performed on the structure of FIG. 8 .

First, the SiO ₂ film 35 of FIG. 8 is etched (step 11). The etching of the SiO ₂ film 35 can be carried out by COR using HF gas and NH ₃ gas by housing the wafer having the structure as shown in FIG. 8 in a chamber. At this time, pressure: 133-400Pa (1-3 Torr), processing temperature: 10-130°C, HF gas flow: 20-1000sccm, NH ₃ gas flow: 20-1000sccm, and inert gas flow: 20-1000sccm is preferred. Since ammonium hexafluorosilicate ((NH ₄ ) ₂ SiF ₆ ; AFS) is generated by the COR treatment, the etching is completed by sublimating the AFS by heating. The sublimation of AFS can also be carried out by a separate heating device, or can also be repeatedly etched and heated in a COR chamber, and the removal of AFS is carried out therein.

In addition, the etching of the SiO ₂ film 35 can also be performed by radical treatment. In this case, as the 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 _SiO2 film 35 is etched away to a predetermined height position, and the SiN film 34 remains until a position higher than the predetermined height position. Therefore, etching (de-footing) for removing the footed region of the SiN film 34 is performed.

At this time, if the SiN film is directly etched on the wafer W after the etching of the SiO ₂ film 35 , impurities contained in the SiO ₂ film 35 or the etching of the SiO ₂ film 35 penetrate into the film during the SiN film etching. The components in it or the gas components adhering to the wafer W without being removed may react with HF to etch the films 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 film contains NH ₃ or F among the gas components in addition to impurities such as H, N, C, etc., and also contains NH ₄ or HF ₂ . There is a possibility that by-products with high reactivity adhere to the wafer W, and the SiO ₂ film 35 is easily etched by coexisting with HF when the SiN film is etched. As described above, when the SiO2 film is formed by CVD or ALD, the film tends to have many impurities and a low density depending on the film formation method, so such a tendency is obvious.

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

The surface modification treatment is used to remove impurities in the film or by-products such as NH ₄ or HF ₂ adhering to the wafer W. Thereby, the SiO ₂ film 35 becomes difficult to be etched during the subsequent etching of the SiN film 34 .

As the surface modification treatment, as in the first example, heat treatment in an inert atmosphere, treatment using H ₂ O, a process of adsorbing a surfactant on the wafer surface, and H ₂ O (pure water) can be exemplified. ) caused by the wet cleaning process treatment. In addition, as the surface modification treatment, other treatments such as radical treatment can also be used.

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

In this etching, the wafer having the structure shown in FIG. 10(a) is housed in a chamber, and as in the first embodiment, only HF gas or a mixed gas of HF gas and an inert gas is introduced into the chamber, and The pressure was set to a high pressure of 1333 Pa (10 Torr) or more. Preferably it is 1333-11997Pa (10-90 Torr). More preferably, it is 1333-5332Pa (10-40 Torr). As the inert gas, N ₂ gas or a rare gas such as Ar and He can be used. However, in the present embodiment, the surface modification treatment is performed, in particular, when the etching of the SiO ₂ film 35 is performed by radical treatment, even if it is lower than 1333 Pa (10 Torr), it is possible to perform the etching. Possibility of selecting high ratio SiN film etching.

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 preferably 10 to 120° C. It is better, 30～80℃ is better.

Thereby, as shown in FIG. 10(b), the footing 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, as necessary, removal of etching residues and the like is performed by heat treatment or the like, and the treatment is completed.

According to this example, after the SiO ₂ film 35 is removed by etching, impurities in the film and by-products such as NH ₄ or HF ₂ adhering to the wafer W are removed by the surface modification treatment. In the etching of the SiN film 34, under the condition that the _SiO2 film 35 is prevented from being damaged (pitting corrosion or surface roughness) due to the etching of the _SiO2 film 35 due to these influences, the _SiO2 film 35 and the Si film 32 can be and SiGe film 33, the SiN film 34 is etched with a high selectivity ratio (with respect to _SiO2 , with a selectivity ratio of 5 or more, preferably 15 or more; with respect to Si and SiGe, with a selectivity 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 precision. In particular, even when the SiO ₂ film 35 is formed by CVD (eg, FCVD) using a film-forming method with a relatively large amount of impurities and a low density, the etching of the SiO ₂ film 35 can be suppressed and improved The selection ratio of the SiN film 34 to the SiO ₂ film 35 .

[An example of a processing system used for implementing 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 showing 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 SiO ₂ films and a surface modification treatment device are connected to one of the long sides of the vacuum transfer chamber 201 via a gate valve G. 203 and SiN film etching device 204. Moreover, the oxide film etching apparatus 202, the surface modification processing apparatus 203, and the SiN film etching apparatus 204 are similarly connected to the other side of the long side of the vacuum transfer chamber 201 via the gate valve G similarly. The inside of the vacuum transfer chamber 201 is evacuated by a vacuum pump to maintain a predetermined degree of vacuum.

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

In addition, the surface modification processing apparatus 203 may be configured as a thermal processing apparatus for thermally processing the wafer W at a relatively high temperature. Moreover, H ₂ O gas processing apparatus which heat-processes the wafer W in H ₂ O gas atmosphere may be sufficient. In addition, as the surface modification treatment device 203, other treatment devices such as a radical treatment device can also be used.

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

In addition, two load lock chambers 205 are connected to one side of the short side of the vacuum transfer chamber 201 via the gate valve G1. An atmospheric 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 atmosphere transfer chamber 206 via the gate valve G2. The load lock chamber 205 is used to perform 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 portion of the atmospheric transfer chamber 206 opposite to the mounting wall portion of the load lock chamber 205 has three carrier mounting ports 207, and the carrier mounting ports 207 are mounted with carriers C that accommodate a plurality of wafers W such as FOUPs. . In addition, an alignment chamber 208 for performing alignment of the wafer W is provided on the side wall of the atmospheric transfer chamber 206 . In the atmosphere transfer chamber 206, a downflow of clean air is formed.

In the vacuum transfer chamber 201, two wafer transfer mechanisms 210 are installed. One of the wafer transfer mechanisms 210 is capable of processing the oxide film etching device 202 , the surface modification treatment 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 loaded and unloaded, and the other wafer transfer mechanism 210 is capable of processing the oxide film etching device 202 , the surface modification treatment 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 out the loading and unloading of the wafer W.

Inside the atmospheric transfer chamber 206, a wafer transfer mechanism 211 is installed. 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 further includes a control unit 212 . The control unit 212 is usually constituted by 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.); a display device (display, etc.); and memory device (memory medium). The main control unit of the control unit 212 causes the processing system 200 to execute predetermined actions according to a processing recipe memorized in a storage medium built in the storage device or a storage medium installed in the storage device, for example.

In such a processing system 200 , the wafers formed with the configuration shown in FIG. 8 are accommodated in a plurality of carriers 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, the gate valve G2 of any one of the load lock chambers 205 is opened, and the wafer W is transferred to the Load lock chamber 205 . After the gate valve GV2 is closed, the inside of 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, the wafer W is taken out from the load lock chamber 205 by the wafer transfer mechanism 210, the gate valve G of the oxide film etching apparatus 202 is opened, and the wafer W is The circle W is carried into the oxide film etching apparatus 202, and the etching of the _SiO2 film is performed. When the SiO ₂ film is etched by the COR process, since AFS is generated as described above, in order to sublime it, the surface modification treatment device 203 or a heat treatment device provided separately is used for heat treatment. Alternatively, the etching and heat treatment may be repeated in the oxide film etching apparatus 202, and the 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 treatment apparatus 203 is opened, and the wafer W is carried into the surface modification treatment apparatus 203 for surface modification. deal with.

After the surface modification treatment 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 apparatus 204 is opened, and the wafer W is carried into the SiN film etching apparatus 204, and the SiN film etching apparatus is carried out. etching.

After the SiN film is etched, the etching residues are removed by the surface modification treatment device 203 or a heat treatment device provided separately as necessary.

After that, the gate valve G1 of the load lock chamber 205 is opened, the wafer W after the etching of 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 inside of the load lock chamber 205 to atmospheric pressure. . After that, 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-described processes are simultaneously performed on a plurality of wafers W in parallel, and the processing of a predetermined number of wafers W is completed.

Next, an example of the oxide film etching apparatus 202 and the surface modification treatment apparatus 203 will be described. In addition, since the SiN film etching apparatus 204 has the same structure as that of the etching apparatus 105 of the first embodiment, the description thereof will be omitted.

[Oxide Film Etching Apparatus] 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 for etching 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 reference numerals are given to the same parts as those in FIG. 4 and the description thereof will be omitted.

In the oxide film etching apparatus 202, the cover member 155 and the upper wall 157b of the main body 157 are formed with the gas introduction path 161 in addition to the gas introduction path 161 penetrating into the space 159 of the shower head 156. To the gas introduction path 161, an HF gas supply pipe 171 of a gas supply mechanism 143' described later is connected. Moreover, the NH ₃ gas supply piping 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, and one end of an HF gas supply pipe 171 and an inert gas supply pipe 172 are connected to these, respectively. The HF gas supply piping 171 and the inert gas supply piping 172 are provided with a flow controller 179 . 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 .

The gas supply mechanism 143' has an NH ₃ gas supply source 195 for supplying NH ₃ gas and an inert gas supply source 196 for supplying inert gas, and NH ₃ gas supply piping 191 and inert gas supply piping 192 are respectively connected to these. one end. The NH ₃ gas supply piping 191 and the inert gas supply piping 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, the HF gas is supplied into the shower head 156 from the HF gas supply source 175 via the HF gas supply pipe 171 , and the NH ₃ gas is supplied into the shower head 156 from the NH ₃ gas supply source 195 via the NH ₃ gas supply pipe 191 . The inert gas is supplied to the shower head 156 from the inert gas supply sources 176 and 196 through the inert gas supply pipes 172 and 192 to reach the HF gas supply pipe 171 and the NH ₃ gas supply pipe 191, respectively. 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 reactive gas and inert gas, which are used as diluent gas and flushing gas. A desired reaction can be produced by supplying HF gas and NH ₃ gas or supplying them in a mixture with an inert gas.

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

[Surface Modification Treatment Apparatus] Next, an example of the surface modification treatment 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, as the surface modification treatment device 203, a heat treatment device for removing impurities or by-products in a film by heat treatment will be described as an example.

The surface modification treatment apparatus 203, as shown in FIG. 13, has: a chamber 220, which can be evacuated; and a mounting table 223, on which the wafer W is mounted. The heater 224 heats the wafer W to which the SiO ₂ film has been subjected to the etching process, so that impurities present in the film or by-products adhering to the surface of the wafer W are thermally decomposed or volatilized and removed. . The side surface of the chamber 220 is provided with a loading and unloading port 234 for transferring wafers between the chamber 220 and the vacuum transfer chamber 201 . The loading and unloading port 234 can be opened and closed by a 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 the 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 a 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 control valve 232. By adjusting these valves, the chamber 220 is set to a predetermined pressure N ₂ gas atmosphere , heat treatment. As the inert gas, a rare gas such as N ₂ gas or Ar gas can be used.

_In such a surface modification treatment apparatus 203, for example, the wafer W having the structure shown in FIG. Then, while introducing an inert gas such as N ₂ gas into the chamber 220 to form a predetermined decompressed atmosphere, the wafer W is heated to 150-400° C., eg, 250° C., by the heater 224 . Thereby, impurities in the film and 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 , and the reaction process is preferably performed at 20 to 100° C., more preferably 20 to 80° C., so that impurities in the film or the wafer W are adhered. The by-products are removed by reacting with H ₂ O.

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

Furthermore, 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 apparatus. As shown in the figure, the surface modification treatment apparatus 250 includes a liquid treatment tank 251, and stores and processes the liquid L. The plurality of wafers W held by the wafer holding member 252 can be 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 holds a plurality of wafers W by the wafer holding bars 252a. The wafer holding member 252 can be moved up and down and horizontally by a transfer device (not shown) to transfer the plurality of wafers W held.

In the liquid processing tank 251 , a nozzle 253 is provided, 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 piping 254 .

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

As the surface modification treatment, when the 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, when performing a process including a process of adsorbing the surfactant on the wafer surface and a wet cleaning process by H ₂ O (pure water) as the surface modification treatment, pure water and Surfactants are selectively supplied as liquids supplied from the liquid supply means 255, or two types of pure water and surfactants are prepared for the liquid treatment layer 251.

In the surface modification treatment apparatus 250 configured in this way, in the case of the treatment by the surface modification treatment of liquid H ₂ O (pure water), pure water is supplied and stored in the liquid treatment tank 251 It is performed by immersing a plurality of wafers W in pure water. In addition, when the surface modification treatment includes a process of adsorbing the surfactant on the wafer surface and a wet cleaning process by H ₂ O (pure water), first, in the liquid treatment tank In the state where the surfactant is supplied and stored in the 251, a plurality of wafers W are immersed in the surfactant, and thereafter, the liquid supplied into the liquid processing tank 251 is switched to pure water and the pure water is stored, or The plurality of wafers W are immersed in the pure water while the pure water is supplied and stored in the other liquid processing tank 251 .

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

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

Inside the chamber 261, a cup 267 for covering the wafer W held by the spin chuck 262 is provided. At the bottom of the breast cup 267, an exhaust/drain pipe 268 for exhausting and draining is provided in a manner of extending downward of the chamber 261. The side wall of the chamber 261 is provided with a loading and unloading port 269 for loading and unloading the wafers W. As shown in FIG.

In the thus configured surface modification treatment apparatus 260 , one wafer W is carried into the chamber 261 by a transfer apparatus (not shown), and mounted on the spin chuck 262 . In this state, while the spin 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 the surface modification treatment, when the treatment by 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 spreading pure water over the entire surface of the wafer W on the circle W.

As the surface modification treatment, when performing a process including a process of adsorbing the surfactant on the wafer surface and a wet cleaning process by H ₂ O (pure water), first, the liquid supply mechanism 265 The surfactant is supplied onto the rotating wafer W through the liquid supply pipe 266 and the nozzle 264, and the surfactant is diffused 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, pure water is supplied to the wafer to perform wet cleaning.

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

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

16 is a graph showing the relationship between the pressure at a temperature of 70°C, the etching amount (nm) of each film, the selectivity ratio of SiN film to thermal oxide film, and the selectivity ratio of SiN film to polysilicon film. 17 is a graph showing the relationship between the temperature at a pressure of 50 Torr, the etching amount (nm) of each film, and the selectivity 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 increases, and the selection ratio of the SiN film to the thermal oxide film and the selection ratio of the SiN film to the polysilicon 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 increases, and the selection of the SiN film relative to the thermal oxide film is increased. The ratio and the selection ratio of the SiN film to the polysilicon film become high. At a pressure of 50 Torr and a temperature of 70° C., the selectivity ratio of the SiN film to the thermal oxide film was as high as 15 or more, and the selectivity ratio of the SiN film to the polysilicon film was as high as 100 or more.

In addition, although not shown in FIGS. 16 and 17 , the SiGe film has the same tendency as that of the polysilicon film, and at a pressure of 50 Torr and a temperature of 70° C., the selectivity ratio of the SiGe film to the SiN film can be obtained as 100 or more. the higher value.

(Experimental Example 2) Here, on the wafer on which the SiO ₂ film by CVD was formed, first, HF gas and NH ₃ gas were used to conduct SiO ₂ under the conditions of pressure: 333Pa (2.5 Torr) and temperature: 100°C After the COR treatment of the film, the AFS was removed by heat treatment at 250° C. to perform etching of the SiO ₂ film. After that, "the wafer was directly subjected to the SiN film etching conditions (HF gas treatment + heat treatment) (sample 1)", "after the pure water treatment, the SiN film etching conditions were carried out (sample 1)"2)","For the process with the process of adsorbing surfactant and wet cleaning process by H ₂ O (pure water), and then performing the process of SiN film etching conditions (sample 3)" , to investigate the surface state of the SiO ₂ film.

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

As a result, in sample 1, although a large number of pitting corrosion occurred on the surface of the _SiO2 film and the surface roughness was poor, in sample 2, the number of pitting corrosion on the surface of the _SiO2 film was reduced by about 20%, and it was also observed that Surface roughness improvement. 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> As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist.

For example, the structure example of the above-mentioned embodiment is merely an illustration, and it can be applied as long as it is a structure in which a SiN film coexists with SiO ₂ , Si, and SiGe. In addition, the structure of the above-mentioned processing system or individual apparatuses is merely an example, and the etching method of the present invention can be implemented by various systems or apparatuses.

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 sectional view showing an example of a structure to which the etching method according to the first embodiment of the present invention is applied; (b) is a view showing a semiconductor element after etching the SiN film of the structure of (a) Sectional drawing. [FIG. 2] (a) is a sectional view showing another example of the structure to which the etching method according to the first embodiment of the present invention is applied; (b) is a semiconductor element after etching the SiN film of the structure of (a) sectional view. [ Fig. 3] Fig. 3 is 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] Fig. 4 is a cross-sectional view showing an etching apparatus mounted in the processing system of Fig. 3 . [ Fig. 5] Fig. 5 is a diagram for explaining a 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. 6 is a flowchart showing a first example of the etching method according to the second embodiment of the present invention. [ Fig. 7] Fig. 7 is a diagram for explaining the function of the surfactant used for the surface modification treatment. 8 is a cross-sectional view showing an example of the structure of the second example of the etching method to which 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 is a sectional view of the process in the second example of the etching method according to the second embodiment of the present invention; (a) shows the structure after etching of the SiO ₂ film; (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 the etching method of the second example of the second embodiment of the present invention. 12 is a cross-sectional view showing an oxide film etching apparatus mounted in the processing system of FIG. 11 . [ Fig. 13 ] A cross-sectional view showing a surface modification treatment apparatus mounted in the treatment system of Fig. 11 . [ Fig. 14] Fig. 14 is a cross-sectional view showing another example of the surface modification apparatus. [ Fig. 15] Fig. 15 is a cross-sectional view showing yet another example of the surface modification apparatus. Fig. 16 shows the pressure, the etching amount (nm) of each film, and the difference between the SiN film and the thermal oxide film when the SiN film, the thermally oxidized film, and the polysilicon film are etched at a temperature of 70°C and the pressure is varied in the experimental example. Graph of selectivity ratio and selectivity ratio of SiN film relative to polysilicon film. [Fig. 17] In the experimental example, the temperature and the etching amount (nm) of each film when the SiN film, the thermal oxide film, and the polysilicon film are etched at a pressure of 50 Torr and the temperature is varied, and the selection of the SiN film with respect to the thermal oxide film is shown. Graph showing the relationship between the ratio and the selectivity ratio of SiN film to polysilicon film.

105‧‧‧Etching device

140‧‧‧Chamber

142‧‧‧Place

143‧‧‧Gas supply mechanism

144‧‧‧Exhaust mechanism

151‧‧‧Chamber body

151a‧‧‧Sidewall

151b‧‧‧Bottom

152‧‧‧Cover

153‧‧‧Moving in and out

154‧‧‧Gate Valve

155‧‧‧Cover components

156‧‧‧Sprinkler

157‧‧‧Ontology

157a‧‧‧Sidewall

157b‧‧‧Upper wall

158‧‧‧Sprinkler panels

159‧‧‧Space

161‧‧‧Gas introduction path

162‧‧‧Gas discharge hole

165‧‧‧Temperature Regulators

171‧‧‧Gas supply piping

172‧‧‧Inert gas supply piping

175‧‧‧HF gas supply source

176‧‧‧Inert gas supply source

179‧‧‧Flow Controller

181‧‧‧Exhaust

182‧‧‧Exhaust piping

183‧‧‧Automatic Pressure Control Valve (APC)

184‧‧‧Vacuum Pumps

186a‧‧‧Capacitance Manometer

186b‧‧‧Capacitance Manometer

W‧‧‧Wafer

Claims (14)

An etching method is characterized in that a substrate to be processed having a silicon nitride film, a silicon oxide film, silicon and silicon germanium is arranged in a chamber, and only HF gas or a mixed gas of HF gas and an inert gas is introduced into the chamber, The pressure in the chamber is set to 1333Pa~5332Pa, the temperature of the substrate to be processed is set to 30~70°C, and hydrogen fluoride gas is supplied into the chamber to selectively select the silicon oxide film, silicon and silicon germanium relative to the silicon oxide film, silicon and silicon germanium. The aforementioned silicon nitride film is etched. The etching method of claim 1, wherein the selectivity ratio of the silicon nitride film to the silicon oxide film is 5 or more. The etching method of claim 2, wherein the selectivity ratio of the silicon nitride film to the silicon oxide film is 15 or more. The etching method of claim 1, wherein the selectivity ratio of the silicon nitride film to the silicon and silicon germanium is 50 or more. For the etching method of item 4 of the scope of the patent application, wherein, The selectivity ratio of the silicon nitride film to the silicon and silicon germanium is 100 or more. An etching method for selectively etching the above-mentioned silicon nitride film on a substrate to be processed having a silicon nitride film and a silicon oxide film, the etching method is characterized in that the above-mentioned substrate to be processed is subjected to removal of impurities in the film. Surface modification treatment, secondly, only HF gas or a mixed gas of HF gas and inert gas is introduced into the aforementioned chamber, and the substrate to be treated after the surface modification treatment is maintained at a pressure of 1333Pa~5332Pa, and the aforementioned treated substrate is The temperature of the substrate was set to 30 to 70° C., and HF gas was supplied to the substrate to be processed to selectively etch the silicon nitride film. The etching method of claim 6, wherein the silicon oxide film is etched before the surface modification treatment. The etching method of claim 6 or 7, wherein the substrate to be processed further comprises silicon and silicon germanium, and the silicon nitride film is selectively etched with respect to the silicon and the silicon germanium. An etching method is characterized in that, for a substrate to be processed having a silicon nitride film, a silicon oxide film, silicon and silicon germanium, First, the silicon oxide film is etched, and secondly, a surface modification treatment is performed to remove impurities in the film and by-products on the surface of the substrate to be processed. Second, only HF gas or a mixed gas of HF gas and an inert gas is introduced into the chamber. The substrate to be processed after the surface modification treatment is maintained at a pressure of 1333Pa~5332Pa, the temperature of the substrate to be processed is set to 30~70°C, HF gas is supplied to the substrate to be processed, and the nitridation is selectively etched Silicon film. According to the etching method of claim 9, the etching of the silicon oxide film is performed using HF gas and NH ₃ gas. According to the etching method of claim 9, the etching of the silicon oxide film is performed by radical treatment. The etching method according to any one of Claims 6, 7, 9 to 11, wherein the surface modification treatment is performed in an inert environment by heat treatment in the range of 150 to 400°C. The etching method according to any one of Claims 6, 7, 9 to 11, wherein the surface modification treatment is performed by a reaction treatment in the range of 20 to 100° C. using H ₂ O. The etching method according to any one of claims 6, 7, 9 to 11 in the scope of the application, wherein the surface modification treatment is caused by the process of adsorbing the surfactant on the surface of the substrate to be treated and H ₂ O Wet cleaning process.

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