JP7490687B2 - Substrate processing method - Google Patents

Description

This invention relates to a substrate processing method, and in particular to a substrate processing method in which a substrate to be processed placed on a substrate placement part is etched by plasma.

Conventionally, a substrate processing method is known in which a substrate placed on a substrate placement unit is etched using plasma (see, for example, Patent Document 1).

The above-mentioned Patent Document 1 discloses a technique in which a process gas is supplied into a process chamber and a high-frequency voltage is applied to turn the process gas into plasma, and a high-frequency voltage is also applied to a substrate holding device, and a silicon substrate held by the substrate holding device in the process chamber is etched by radicals and ions generated by the plasma. In the above-mentioned Patent Document 1, the upper surface of the outer peripheral edge of the silicon substrate held by the substrate holding device is covered with an annular protective member. The protective member has the function of preventing the upper surface of the outer peripheral edge of the silicon substrate, which does not have a protective film such as a resist film or an oxide film, from being etched, and is made of aluminum with an anodized coating or ceramic made of aluminum oxide.

Japanese Patent No. 5250445

However, when performing a non-Bosch dry etching process as in Patent Document 1, it is known that a dimensional difference occurs between the center of the substrate and the outer periphery of the substrate (near the protective member) in the etching portion (the processing portion to be etched) that is on the inner side of the annular protective member. In other words, there is a problem in that the etching shape is not uniform between the center of the substrate and the outer periphery of the substrate (near the protective member).

This invention has been made to solve the above problems, and one object of the invention is to provide a substrate processing method that can improve the uniformity of the shape near the center and near the periphery of the substrate being processed in a non-Bosch dry etching process.

In order to achieve the above object, the inventors of the present application conducted intensive research and came to the conclusion that under the conditions of etching silicon using _SF6 gas and _O2 gas, the distribution of substances involved in etching is non-uniform due to the difference in position between the center and the outer periphery of the substrate to be processed, which affects the uniformity of the etching shape. That is, in the etching part (processing part to be etched) in the center of the substrate to be processed, other etching parts are densely present around it, so the silicon surface area reacting with radicals is relatively large, whereas in the etching part in the outer periphery of the substrate to be processed, there are fewer or no etching parts on the outer periphery side, and furthermore, the outer periphery edge is covered with a protective member such as aluminum oxide, which has high etching resistance, so the silicon surface area reacting with radicals is relatively small. For this reason, in the center of the substrate to be processed, the reaction products with radicals are generated relatively in large amounts, and the radicals are reduced accordingly. Conversely, in the outer periphery of the substrate to be processed, the reaction products with radicals are relatively small, and the radicals are distributed relatively in large amounts. The inventors of the present application have discovered that such non-uniform distribution of the material involved in etching affects the formation of a protective film in the etched portion, and is one of the factors that impair the uniformity of the shape in the dry etching process of the non-Bosch process. In order to eliminate this factor, the inventors of the present application have come up with the following invention.

That is, the substrate processing method according to the first aspect of the present invention includes the steps of: arranging a substrate to be processed made of silicon on the mounting surface of a substrate mounting part; arranging an annular protective member so as to cover the outer peripheral edge of the substrate to be processed arranged on the mounting surface from above; introducing SF ₆ gas and O ₂ gas into a processing chamber that accommodates the substrate mounting part and the protective member, and applying high-frequency power to form plasma; etching the substrate to be processed on the mounting surface with the plasma, and generating a reaction product from a reaction part containing silicon provided on the surface of the protective member with the plasma; and forming a protective film on the etching part in the outer peripheral part of the substrate to be processed by reacting the reaction product generated from the reaction part with the plasma , the material of the reaction part is SiO ₂ , and the reaction product contains silicon fluoride and oxygen radicals . Note that the "outer peripheral part" of the substrate to be processed in this specification means a region on the outer peripheral side of the substrate to be processed and on the inner peripheral side of the protective member where an etching part (processing part) exists, and is a concept that does not include the outer peripheral part of the substrate to be processed.
A substrate processing method according to a second aspect of the present invention includes the steps of: placing a substrate to be processed made of silicon on the mounting surface of a substrate mounting part; placing an annular protective member so as to cover the outer peripheral edge of the substrate to be processed placed on the mounting surface with a gap therebetween from above; introducing SF6 gas and O2 gas into a processing chamber that accommodates the substrate mounting part and the protective member, _and applying _high -frequency power to form plasma; etching the substrate to be processed on the mounting surface with the plasma, and generating a reaction product from a reaction part containing silicon provided on the surface of the protective member with the plasma; and forming a protective film on the etching part at the outer peripheral part of the substrate to be processed by reacting the reaction product generated from the reaction part with the plasma, the material of the reaction part being _SiO2 .
A substrate processing method according to a third aspect of the present invention includes the steps of: placing a substrate to be processed made of silicon on the mounting surface of a substrate mounting part; placing an annular protective member so as to cover from above the outer periphery of the substrate to be processed placed on the mounting surface; introducing SF6 gas and O2 gas into a processing chamber that accommodates the substrate mounting part and the protective member, _and applying _high -frequency power to form plasma; etching the substrate to be processed on the mounting surface with the plasma, and generating a reaction product from a reaction section containing silicon provided on the surface of the protective member with the plasma; and forming a protective film on the etching section in the outer periphery of the substrate to be processed by reacting the reaction product generated from the reaction section with the plasma, wherein the protective member includes an annular first member that covers the outer periphery of the substrate to be processed and has a reaction section on its upper surface, and an annular second member that detachably supports the outer periphery end of the first member and does not have a reaction section.

The substrate processing method according to the first to third aspects of the present invention includes a step of etching the substrate on the mounting surface with plasma and generating reaction products from the reaction part containing silicon provided on the surface of the protective member with plasma, as described above. As a result, reaction products are generated by excess radicals not only on the substrate to be processed but also on the reaction part of the protective member, so that the distribution amount of reaction products near the outer periphery of the substrate to be processed can be increased. Since both the substrate to be processed and the reaction part contain silicon, the reaction products generated from the substrate to be processed and the reaction part contain silicon fluoride (SiF ₄ , etc.) generated by the reaction between fluorine radicals and silicon by the plasma of SF ₆ gas. This silicon fluoride contributes to the formation of a protective film in the etching part. And, since the method includes a step of forming a protective film on the etching part in the outer periphery of the substrate to be processed by reacting the reaction products generated from the reaction part with plasma, a protective film can be formed in the etching part in the outer periphery of the substrate to be processed as well as in the central part of the substrate to be processed where reaction products are sufficiently secured. As a result, the formation conditions of the protective film can be made similar between the etching portion at the outer periphery of the processed substrate and the etching portion at the center, thereby improving the uniformity of the shape near the center and near the outer periphery of the processed substrate in non-Bosch dry etching processing.

In the substrate processing method according to the first to third aspects of the invention, the step of forming a protective film on the etched portion in the outer periphery of the substrate to be processed preferably includes the steps of dissociating a reaction product containing silicon generated from the reaction portion by plasma, and forming a protective film containing silicon oxide by a reaction between the dissociated silicon and oxygen radicals in the plasma. In this manner, a SiO-based protective film is formed on the etched portion by dissociating a part of silicon fluoride, which is a reaction product, by plasma, and reacting the dissociated silicon with oxygen radicals derived from _O2 gas. As a result, a SiO-based protective film can be effectively formed on the etched portion by the reaction product supplied from the reaction portion of the protective member, even in the outer periphery of the substrate to be processed.

In the substrate processing method according to the first aspect of the invention, the material of the reaction section is _SiO2 , and the reaction products include silicon fluoride and oxygen radicals. As a result , not only silicon fluoride but also oxygen radicals as a material for forming a protective film can be supplied from the reaction section by the reaction between the fluorine radicals and the reaction section. In addition to the reaction products of the radicals, oxygen atoms are also generated from the reaction section by ion collision, and become a material for forming a protective film. The _SiO2 material of the reaction section includes quartz and other _SiO2 crystals.

In the substrate processing method according to the first to third aspects of the invention, preferably, in the step of generating reaction products from the reaction section, the reaction products are generated from the reaction section so that the distribution of radicals and reaction products in the outer periphery of the substrate to be processed is made closer to the distribution of radicals and reaction products in the central part of the substrate to be processed. With this configuration, the distribution of radicals and reaction products in the outer periphery of the substrate to be processed, which includes both the etching section and the reaction section, can be made closer to the distribution of radicals and reaction products in the central part of the substrate to be processed. As a result, the formation conditions of the protective film in the central part and the outer periphery of the substrate to be processed can be made closer to each other, so that the difference in shape of the etching sections in the central part and the outer periphery of the substrate to be processed can be effectively reduced.

In the substrate processing method according to the third aspect of the present invention, the protective member includes an annular first member that covers the outer peripheral edge of the substrate to be processed and has a reaction portion on its upper surface, and an annular second member that detachably supports the outer peripheral end of the first member and does not have a reaction portion. This makes it possible to replace the first member having a reaction portion that is etched together with the substrate to be processed with the second member. Therefore, when the reaction portion is worn out due to etching, the replacement work can be made easier and resource consumption can be reduced compared to when the entire protective member is replaced.

As described above, according to the present invention, it is possible to improve the uniformity of the shape near the center and near the periphery of the substrate to be processed in a non-Bosch dry etching process.

1 is a schematic diagram showing a schematic configuration of a substrate processing apparatus for carrying out a substrate processing method. FIG. 2 is a schematic perspective view showing a protective member and a support structure for the protective member. 4 is an enlarged cross-sectional view of the vicinity of the outer periphery of the substrate to be processed for explaining a protective member. FIG. FIG. 4 is a schematic plan view for explaining the positional relationship between a protection member and a substrate to be processed. FIG. 2 is a flow chart showing a substrate processing method according to the present embodiment. 1A to 1C are diagrams illustrating the formation of a protective film in an etching portion on the outer periphery of a substrate to be processed. 1A to 1C are diagrams illustrating the formation of a protective film in an etching portion in the center of a substrate to be processed. 13 shows an overall image and an enlarged image of the cross section of each etched portion at the periphery and center of a substrate to be processed in a comparative example in which a protective member made of aluminum oxide was used. 13A and 13B are overall and enlarged images of cross sections of etched portions at the periphery and center of a substrate to be processed in an embodiment using a protective member having a first member made of quartz.

The following describes an embodiment of the present invention with reference to the drawings.

The substrate processing apparatus 100 that performs the substrate processing method of this embodiment will be described with reference to FIG. 1.

(Substrate Processing Apparatus)
The substrate processing apparatus 100 is a plasma processing apparatus that generates plasma in a processing chamber 10 and performs dry etching on a substrate 1 to be processed. The substrate 1 to be processed is a silicon wafer made of silicon.

The substrate processing apparatus 100 includes a processing chamber 10, a substrate placement unit 20, a gas supply unit 30, a plasma generating unit 40, an exhaust unit 50, a high-frequency power supply 60, and a protective member 70.

The processing chamber 10 has a closed space and houses a substrate placement unit 20 within the closed space. The processing chamber 10 is composed of an upper chamber 11 and a lower chamber 12 that have internal spaces that are connected to each other.

The substrate placement part 20 has a placement surface 20a on which the substrate 1 to be processed is placed. The substrate placement part 20 has a disk shape and includes a base 21, an electrostatic chuck 22 installed on the base 21, and a ring member 23 surrounding the electrostatic chuck 22. The substrate placement part 20 is provided so as to be freely raised and lowered in the processing chamber 10 by a lifting cylinder 25. The base 21 is made of aluminum, and the electrostatic chuck 22 and the ring member 23 are made of aluminum oxide. The electrostatic chuck 22 is connected to an electrostatic adsorption power source (not shown) that applies a voltage for electrostatic adsorption. When a voltage is applied to the electrostatic chuck 22, the substrate 1 to be processed is adsorbed to the placement surface 20a, which is the upper surface of the electrostatic chuck 22, by electrostatic induction. The substrate placement part 20 is provided with an internal pipe (not shown), into which a specified coolant such as Galden (registered trademark) is introduced, and a chiller device (not shown) is attached to circulate the coolant while controlling the coolant temperature (for example, at 5°C). This cools the substrate placement part 20 during plasma processing. Also, during plasma processing, a cooling gas (an inert gas such as He gas) is supplied from a specified cooling gas supply pipe (not shown) to the rear surface of the substrate 1 to cool the substrate 1.

The gas supply device 30 supplies an etching gas and a protective film forming gas into the processing chamber 10. The gas supply device 30 includes an _SF6 gas supply unit 31 that supplies _SF6 gas as an etching gas, and an _O2 gas supply unit 32 that supplies _O2 gas as a protective film forming gas. Each gas supply unit is connected to the processing chamber 10 from the top surface of the upper chamber 11 by a branched supply pipe 33 for gas supply. _SF6 gas and _O2 gas are supplied into the processing chamber 10 through the supply pipe 33.

The plasma generating device 40 is a device that generates inductively coupled plasma (ICP) from gas supplied into the processing chamber 10. The plasma generating device 40 includes a spiral coil 41 provided on the outer periphery of the upper chamber 11, and a high-frequency power source 42 that supplies high-frequency power to the coil 41. The gas supplied into the upper chamber 11 is turned into plasma by supplying high-frequency power to the coil 41 by the high-frequency power source 42.

The exhaust device 50 reduces the pressure inside the processing chamber 10. The exhaust device 50 includes a vacuum pump 51 that exhausts gas inside the processing chamber 10, and an exhaust pipe 52 that connects the vacuum pump 51 to the processing chamber 10. The vacuum pump 51 exhausts gas inside the processing chamber 10 through the exhaust pipe 52, and the processing chamber 10 is brought to a predetermined pressure state close to a vacuum.

The high frequency power supply 60 supplies high frequency power for the bias potential to the substrate placement part 20. The high frequency power supply 60 supplies high frequency power to the base 21 of the substrate placement part 20, thereby providing a bias potential between the substrate placement part 20 (base 21) and the plasma.

The protective member 70 is disposed above the substrate placement portion 20 within the processing chamber 10. The protective member 70 has a circular ring shape and a flat plate shape. The protective member 70 is supported by a number of supports 76 that rise from an annular base portion 75 (see FIG. 2).

When the substrate placement part 20 is in the lowered position (see solid line) by the lifting cylinder 25, the substrate placement part 20 moves away from the protective member 70. When the substrate placement part 20 moves to the raised position (see two-dot chain line) by the lifting cylinder 25, the upper surface of the ring member 23 comes into contact with the lower surface of the protective member 70, and the protective member 70 covers the outer peripheral edge part 1c (see FIG. 3) of the substrate 1 to be processed from above. The protective member 70 may be raised and lowered relative to the substrate placement part 20.

<Configuration of protective member>
2, the protective member 70 includes an annular first member 71 and an annular second member 72 that detachably supports the outer peripheral end of the first member 71. The first member 71 is a single member that is continuous around the entire circumference. The outer peripheral side of the second member 72 is supported by a plurality of supports 76. A plurality of through holes 72b for venting gas are formed in the second member 72 along the circumferential direction, penetrating from the front to the back.

3, a circumferential step 72a is formed on the inner peripheral end of the second member 72 to engage with the outer peripheral end of the first member 71. The first member 71 is installed on this step 72a in a state in which it can be moved upward (removed). The lower surface of the second member 72 is provided with an abutment 72c that contacts the upper surface of the ring member 23. The contact keeps the vertical positional relationship between the protective member 70 and the substrate 1 to be processed constant. The first member 71 has an inner diameter (see FIG. 4) that is smaller than the outer diameter of the substrate 1 to be processed by the coverage area of the outer peripheral edge 1c so as to cover the outer peripheral edge 1c of the substrate 1 to be processed. The portion covering the outer peripheral edge 1c of the substrate 1 to be processed is constituted by the first member 71, and the second member 72 is provided almost entirely on the outer peripheral side of the outer peripheral edge 1c. A gap is formed between the protective member 70 (first member 71, second member 72) and the upper surface and outer peripheral surface of the outer peripheral edge 1c of the substrate 1 to be processed.

In this embodiment, a reaction portion 71a containing silicon is provided on the surface of the protective member 70. The material of the reaction portion 71a is selected from Si, SiO ₂ , SiC, and the like. In this embodiment, the material of the reaction portion 71a is SiO ₂ (quartz). As will be described later, the reaction portion 71a has a function of reacting with radicals in the plasma to generate a reaction product 87 (see FIG. 6) when etching the substrate 1 to be processed.

In this embodiment, the first member 71 has a reaction portion 71a, and the second member 72 does not have a reaction portion 71a. Specifically, the entire shape of the first member 71 is made of SiO ₂ (quartz), and the entire upper surface of the first member 71 (see FIG. 4) constitutes the reaction portion 71a. On the other hand, the second member 72 is made of aluminum oxide, and does not constitute the reaction portion 71a. A material having higher etching resistance and mechanical strength (toughness) than the material constituting the reaction portion 71a is selected for the second member 72. The material for the second member 72 may be aluminum nitride or the like.

(Substrate Processing Method)
Next, the substrate processing method of this embodiment will be described. As shown in Fig. 5, the substrate processing method of this embodiment includes the following steps S1 to S5. In the following, for each part of the substrate processing apparatus 100, Figs. 1 to 4 will be referred to.

In step S1, the substrate 1 to be processed is placed on the mounting surface 20a of the substrate mounting part 20. The substrate 1 to be processed is placed on the mounting surface 20a of the substrate mounting part 20 in the lowered position by a transport robot (not shown) or the like. The substrate 1 to be processed is attracted to the mounting surface 20a by the electrostatic chuck 22.

In step S2, an annular protective member 70 is positioned so as to cover from above the outer peripheral edge 1c of the substrate 1 to be processed that is placed on the mounting surface 20a. That is, the substrate mounting part 20 is moved from a lowered position to an elevated position by the lift cylinder 25, so that the protective member 70 is positioned at a predetermined position (see FIG. 3) where the first member 71 covers the upper part of the outer peripheral edge 1c of the substrate 1 to be processed.

In step S3, _SF6 gas and _O2 gas are introduced into the processing chamber 10 that accommodates the substrate placement unit 20 and the protective member 70, and high-frequency power is applied to form plasma. First, _SF6 gas and _O2 gas are supplied into the upper chamber 11 by the gas supply device 30, and high-frequency power is supplied to the coil 41 by the high-frequency power source 42. As a result, _SF6 gas and _O2 gas are excited by the high-frequency power to become plasma 80 (see FIG. 6). The plasma 80 includes radicals 81 such as fluorine radicals derived from _SF6 gas, ions 82 such as fluorine ions derived from _SF6 gas, oxygen radicals 85 and oxygen ions 86 derived from _O2 gas, electrons, etc. In reality, the reaction is complicated, so FIGS. 6 and 7 show representative reaction examples or reaction images.

In step S4, the plasma 80 etches the substrate 1 on the mounting surface 20a, and generates a reaction product 87 (see FIG. 6) from the reaction section 71a provided on the surface of the protective member 70 (first member 71). Specifically, high-frequency power is applied to the substrate mounting section 20 by the high-frequency power source 60, which generates a potential difference (bias potential) between the substrate mounting section 20 and the plasma 80 in the processing chamber 10.

As shown in FIG. 6, ions 82 in the plasma 80 are attracted toward the substrate 1 to be processed by the bias potential. The ions 82 collide with the etching portion 90, which physically etches the etching portion 90. In addition, radicals 81 in the plasma 80 chemically react with the silicon in the etching portion 90 to detach reaction products and etch the silicon. The reaction products generated include silicon fluoride 83 (SiF ₄ , etc.). In addition, although not shown, surface oxidation of silicon is also performed by oxygen radicals 85 and oxygen ions 86. At this time, even outside the outer periphery 1a (see FIG. 4) of the substrate 1 to be processed, some of the radicals 81 in the plasma 80 etches the reaction portion 71a of the protective member 70, and reaction products 87 including silicon fluoride 83 (SiF ₄ ) and oxygen radicals 85 are generated from the reaction portion 71a. In addition, physical etching of the reaction portion 71a by the ions 82 in the plasma 80 also occurs. Note that the etching process of this embodiment is a so-called non-Bosch process. Unlike the Bosch process, which repeats the silicon etching process and the sidewall protection film formation process, the non-Bosch process simultaneously performs the etching process and the sidewall protection film formation process. In the Bosch process, a shell-shaped shape (or wavy unevenness) called scallops occurs on the sidewall of the etched part due to isotropic etching, so when the etching sidewall shape is important, the non-Bosch process, which does not generate scallops, is preferable.

In this embodiment, in step S5 of FIG. 4, the reaction product 87 generated from the reaction portion 71a is reacted with the plasma 80 to form a protective film 91 on the etched portion 90 in the outer periphery 1a of the substrate 1 to be processed.

Specifically, step S5 includes a step of dissociating a reaction product 87 (see FIG. 6) containing silicon generated from the reaction section 71a by plasma 80, and a step of forming a protective film 91 (see FIG. 6) containing silicon oxide by a reaction between the dissociated silicon and oxygen radicals 85. Specifically, the reaction product 87 containing silicon is silicon fluoride 83 ( _SiF4 , etc.).

6, most of silicon fluoride 83 (SiF ₄ ) which is a reaction product generated from the etching portion 90 of the substrate 1 to be processed, and silicon fluoride 83 which is a reaction product 87 generated from the reaction portion 71a are exhausted from the processing chamber 10 by the exhaust device 50. Meanwhile, a part of the silicon fluoride 83 generated in each portion is dissociated into Si dissociated species 83a and F dissociated species 83b by the plasma 80. The dissociated Si dissociated species 83a reacts with and bonds to oxygen radicals 85 derived from O ₂ gas or oxygen radicals 85 which are reaction products 87 of the reaction portion 71a, and adheres to the inside of the etching portion 90 to form a SiO-based (silicon oxide) protective film 91. The protective film 91 formed on the bottom surface of the etching portion 90 is physically etched by ions 82, etc., and as a result, the protective film 91 is formed on the side wall of the etching portion 90.

The formation of a SiO-based protective film 91 derived from silicon fluoride 83 occurs in both the outer periphery 1a and the central portion 1b of the substrate 1 to be processed. In the outer periphery 1a shown in FIG. 6, both the silicon fluoride 83 generated from the etching portion 90 and the silicon fluoride 83 generated from the reaction portion 71a as described above contribute to the formation of the protective film 91. In the central portion 1b shown in FIG. 7, since the distance from the reaction portion 71a is large, the silicon fluoride 83 generated mainly from the etching portion 90 contributes to the formation of the protective film 91.

As shown in FIG. 4, the "periphery" of the substrate 1 to be processed is the portion radially outward from the center 1b and radially inward from the protective member 70 (the portion not covered), for example, a range of about 10 mm to 20 mm inward from the outer periphery 1c of the substrate 1 to be processed.

Next, the operation of the substrate processing method of this embodiment will be explained by comparing the etched portion 90 in the central portion 1b of the substrate 1 to the etched portion 90 in the peripheral portion 1a.

7, in the central portion 1b of the substrate 1 to be processed, any one of the etching portions 90 is surrounded by another etching portion 90. Therefore, in the periphery (region within a certain radius) of a certain point in the central portion 1b, the silicon surface area (ratio) reacting with the radicals 81 is larger than that in the peripheral portion 1a. The radicals 81 generate silicon fluoride 83 (SiF ₄ ) in each of the many etching portions 90. In the central portion 1b, since the silicon surface area (ratio) reacting with the radicals 81 is larger, the amount of reaction product (silicon fluoride 83) generated is relatively larger than that in the peripheral portion 1a, and the amount of radicals 81 generated is relatively smaller.

As shown in FIG. 6, the etching portion 90 of the outer periphery 1a of the substrate 1 is close to the outer periphery 1c of the substrate 1, so there are few other etching portions 90 around it. Therefore, in the periphery (area within a certain radius) of a certain point of the outer periphery 1a, the silicon surface area (ratio) reacting with the radicals 81 is small compared to the central portion 1b. In addition, the outer periphery 1c of the substrate 1 is covered by the protective member 70. Therefore, if the reaction portion 71a is not provided, the amount of reaction product (silicon fluoride 83) generated in the outer periphery 1a is relatively small compared to the central portion 1b, and the radicals 81 are relatively large relative to the silicon surface area. Note that although each reaction is depicted as one reaction in FIG. 6 and FIG. 7, in reality, an infinite number of reactions occur, and FIG. 6 and FIG. 7 do not show the reaction amount (or reaction ratio) of each reaction. For example, in both Fig. 6 and Fig. 7, only one silicon fluoride 83 is depicted from one etching portion 90, but the number of etching portions 90 (i.e., silicon surface area) including the periphery (area within a certain radius) is greater in the central portion 1b than in the outer peripheral portion 1a, so the amount of reaction products such as silicon fluoride 83 generated from the etching portion 90 including the periphery of one etching portion 90 is greater in the central portion 1b. Furthermore, if there is no reaction portion 71a near the outer peripheral portion 1a shown in Fig. 6 (when only the protective film 91 derived from the reaction product generated from the etching portion 90 is considered), the amount of the protective film 91 that penetrates into the etching portion 90 (i.e., the amount of production) is the same in Fig. 6 and Fig. 7, but as described above, the amount of reaction products generated from the etching portion 90 including the periphery of one etching portion 90 is greater in the central portion 1b, so the amount of the protective film 91 that penetrates into the etching portion 90 (the amount of production) derived from the reaction product generated from the etching portion 90 is also greater in the central portion 1b.

The inventors of the present application have discovered that when the distribution (dense or coarse) of such radicals 81 and the distribution (dense or coarse) of the reaction product (silicon fluoride 83) differ between the central portion 1b and the peripheral portion 1a of the substrate 1 to be processed, the formation of the SiO-based protective film 91 derived from the reaction product differs between the central portion 1b and the peripheral portion 1a, which is one of the factors that cause the difference in shape of the etched portion 90. Because the formation of the protective film 91 in the peripheral portion 1a is weak, the etching rate in the depth direction and the groove width tend to be greater in the peripheral portion 1a compared to the central portion 1b.

Therefore, in this embodiment, a reaction section 71a is provided on the protective member 70 further outside the outer periphery 1a of the substrate 1 to be processed, so that the excess radicals 81 in the outer periphery 1a are used to etch the reaction section 71a and generate a reaction product 87 (silicon fluoride 83). That is, in this embodiment, in step S4 (see FIG. 5), the reaction product 87 is generated from the reaction section 71a so that the distribution of the radicals 81 and the reaction product (silicon fluoride 83) in the outer periphery 1a (see FIG. 6) of the substrate 1 to be processed is made closer to the distribution of the radicals 81 and the reaction product (silicon fluoride 83) in the central portion 1b of the substrate 1 to be processed.

As a result, in this embodiment, the difference in the formation state of the SiO-based protective film 91 resulting from the reaction product between the central portion 1b and the peripheral portion 1a is reduced, and the difference in shape of the etched portion 90 is reduced. In particular, in this embodiment, the reaction product 87 from the reaction portion 71a made of quartz (SiO ₂ ) contains not only silicon fluoride 83 but also oxygen radicals 85, and both Si and O, which are materials for the SiO-based protective film 91, are supplied from the reaction portion 71a. Although not shown in the figure, oxygen atoms (O) are also supplied from the reaction portion 71a due to collision of ions 82 in the plasma 80.

(Effects of this embodiment)
In this embodiment, the following effects can be obtained.

As described above, the substrate processing method of this embodiment includes a step S4 in which the substrate 1 on the mounting surface 20a is etched by the plasma 80, and the reaction product 87 is generated from the reaction section 71a provided on the surface of the protective member 70 by the plasma 80. As a result, in the vicinity of the outer periphery 1a of the substrate 1, the reaction product 87 is generated by excess radicals not only in the etching section 90 of the substrate 1 but also in the reaction section 71a of the protective member 70, so that the distribution amount of the reaction product (silicon fluoride 83) in the vicinity of the outer periphery 1a of the substrate 1 can be increased. The reaction product generated from the substrate 1 and the reaction section 71a both contains silicon fluoride 83 (SiF ₄ , etc.). This silicon fluoride 83 contributes to the formation of the protective film 91 in the etching section 90. Then, the method includes a step S5 of forming a protective film 91 in an etched portion 90 in the outer periphery 1a of the substrate 1 by reacting the reaction product 87 generated from the reaction portion 71a with the plasma 80, so that a sufficient amount of the protective film 91 derived from the reaction product (silicon fluoride 83) can be formed in the etched portion 90 in the outer periphery 1a of the substrate 1, similarly to the central portion 1b where the reaction product is sufficiently secured. As a result, the formation conditions of the protective film 91 can be made similar between the outer periphery 1a and the central portion 1b of the substrate 1, so that the uniformity of the shape between the central portion 1b and the outer periphery 1a of the substrate 1 can be improved in the dry etching process of the non-Bosch process.

In the present embodiment, as described above, the step S5 of forming the protective film 91 on the etched portion 90 in the outer peripheral portion 1a of the substrate 1 to be processed includes a step of dissociating the reaction product 87 containing silicon generated from the reaction portion 71a by the plasma 80, and a step of forming the protective film 91 containing silicon oxide by the reaction between the dissociated silicon and the oxygen radicals 85 in the plasma 80. As a result, a part of the silicon fluoride 83 (SiF ₄ ) which is the reaction product 87 is dissociated by the plasma 80, and the SiO-based protective film 91 is formed on the etched portion 90 in the outer peripheral portion 1a by the reaction between the dissociated silicon (Si) and the oxygen radicals 85 in the plasma 80. Therefore, even in the outer peripheral portion 1a of the substrate 1 to be processed, the SiO-based protective film 91 can be effectively formed on the etched portion 90 by the reaction product 87 supplied from the reaction portion 71a.

In this embodiment, as described above, the material of the reaction section 71a is SiO ₂ (quartz), and the reaction product 87 contains silicon fluoride 83 and oxygen radicals 85. As a result, not only silicon fluoride 83 but also oxygen radicals 85 serving as a material for forming the protective film 91 can be supplied from the reaction section 71a by the reaction between the radicals 81 and the reaction section 71a. Therefore, oxygen radicals 85 serving as a material for forming the protective film 91 can also be supplied from the reaction section 71a. In addition, oxygen atoms (O) are also generated from the reaction section 71a by ion collision, and serve as a material for forming the protective film 91.

In addition, in this embodiment, as described above, in step S4 of generating the reaction product 87 from the reaction portion 71a, the reaction product 87 is generated from the reaction portion 71a so that the distribution of the radicals 81 and the reaction product (silicon fluoride 83) in the outer peripheral portion 1a of the substrate 1 to be processed is made closer to the distribution of the radicals 81 and the reaction product (silicon fluoride 83) in the central portion 1b of the substrate 1 to be processed. This makes it possible to make the distribution of the radicals 81 and the reaction product of both the etching portion 90 and the reaction portion 71a in the outer peripheral portion 1a of the substrate 1 to be processed closer to the distribution of the radicals 81 and the reaction product in the central portion 1b. As a result, the formation conditions of the protective film 91 in the central portion 1b and the outer peripheral portion 1a of the substrate 1 to be processed can be made closer, so that the difference in shape of each etching portion 90 in the central portion 1b and the outer peripheral portion 1a can be effectively reduced.

In addition, in this embodiment, as described above, the protective member 70 includes an annular first member 71 that covers the outer peripheral edge portion 1c of the substrate 1 to be processed and has a reaction portion 71a on its upper surface, and an annular second member 72 that detachably supports the outer peripheral end of the first member 71 and does not have a reaction portion 71a. As a result, when the reaction portion 71a is worn out due to etching, only the first member 71 can be replaced with the second member 72, making the replacement work easier and reducing resource consumption. In addition, in this embodiment, the entire first member 71 is made of quartz, which is a brittle material, and the structure of the first member 71 can be simplified by separately configuring the first member 71 and the second member 72, effectively reducing the risk of damage to the first member 71 (reaction portion 71a).

(Experimental result)
Next, an experiment conducted to confirm the effect of the substrate processing method of this embodiment and the results of the experiment will be described.

The experiment was carried out by using the same substrate processing apparatus 100, performing the same etching process on different materials for the protective member 70 shown in Fig. 3, and comparing the etched shapes formed. As the material of the first member 71, a first member 71 made of quartz ( _SiO2 ) was used in the example, and a protective member in which the first member and the second member were integrally formed of aluminum oxide ( _Al2O3 ) was used as the comparative example. The shapes and dimensions of the first member and the second member were _the same in the example and the comparative example.

Table 1 shows the processing conditions for the etching process.

Table 2 shows the experimental results of the etching process.

In the comparative example, the etching rate in the depth direction, the width dimension of the top end, and the width dimension of the bottom end were all larger in the outer peripheral portion 1a than in the central portion 1b, and the in-plane uniformity of the etching rate was ±3.9%. Figure 8 shows an image of the etched portion 90 in the central portion 1b according to the comparative example side by side with an image of the etched portion 90 in the outer peripheral portion 1a.

Here, the in-plane uniformity is calculated by the following formula (1) based on the maximum etching rate (ER _Max ) and minimum etching rate (ER _Min ) among the etching rates in the depth direction measured at any n locations on the substrate 1 to be processed, and the average etching rate (ER _Ave ) calculated from the etching rates at the n locations. The smaller the calculated value, the better the uniformity.
In-plane uniformity={(ER _Max −ER _Min )/(2×ER _Ave )}×100 (1)

On the other hand, in the embodiment shown in Table 2, the etching rate in the depth direction, the width dimension of the upper end, and the width dimension of the bottom were all equivalent in the central portion 1b and the outer peripheral portion 1a, and the difference between the central portion 1b and the outer peripheral portion 1a tended to be smaller than in the comparative example. It was confirmed that the in-plane uniformity of the etching rate was ±0.3%, which was smaller than in the comparative example. Figure 9 shows images of the etched portion in the central portion 1b of the substrate 1 to be processed according to the embodiment and the etched portion in the outer peripheral portion 1a side by side. Compared to Figure 8, Figure 9 shows a clear improvement in the uniformity of the shape of the etched portion. Also, while Figure 8 shows sidewall roughness due to insufficient formation of the protective film on the outer peripheral portion, Figure 9 shows improvement due to sufficient formation of the protective film.

This confirmed that the substrate processing method according to this embodiment improves the uniformity of the shape between the central portion 1b and the outer periphery 1a of the substrate 1 to be processed.

As can be seen from the above experimental results, whether or not a certain etching method includes the steps described in this embodiment can be identified in two ways: (1) to verify whether the reactive portion of the protective member is actually worn out, and (2) to verify whether the etching shape deteriorates when the reactive portion is changed to a material that does not contain Si. In other words, (1) can be verified, for example, by performing a certain amount of etching, measuring the degree of wear of the reactive portion based on the fluctuation in the weight and thickness of the protective member (as a whole) before and after the etching process, and comparing the degree of wear with that of a protective member made of a conventional material that is resistant to etching (such as aluminum oxide). In addition, (2) can be determined by checking the in-plane difference in the etching shape, as described in this embodiment.

[Modification]
It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the description of the embodiments above, and further includes all modifications (variations) within the meaning and scope of the claims.

For example, in the above embodiment, an example of carrying out the substrate processing method using the substrate processing apparatus 100 shown in FIG. 1 has been described, but the present invention is not limited to this. The configuration of the substrate processing apparatus that carries out the substrate processing method of the present invention is not particularly limited, and may be different from the configuration of FIG. 1.

In the above embodiment, the protective member 70 is configured as an assembly of the first member 71 and the second member 72, but the present invention is not limited to this. In the present invention, the protective member 70 may be configured as a single member.

1: substrate to be processed, 10: processing chamber, 20: substrate placement section, 20a: placement surface, 70: protective member, 71: first member, 71a: reaction section, 72: second member, 80: plasma, 81: radicals, 83: silicon fluoride, 85: oxygen radicals, 87: reaction products, 90: etching section, 91: protective film

Claims (5)

A step of placing a substrate to be processed made of silicon on a mounting surface of a substrate mounting part;
a step of disposing an annular protective member so as to cover from above an outer peripheral edge portion of the substrate to be processed placed on the placement surface;
A step of introducing _SF6 gas and _O2 gas into a processing chamber that accommodates the substrate placement part and the protective member, and applying high frequency power to generate plasma;
a step of etching the substrate on the placement surface with the plasma and generating a reaction product from a reaction portion containing silicon provided on the surface of the protective member with the plasma;
and forming a protective film on an etching portion in an outer periphery of the substrate to be processed by reacting the reaction product generated in the reaction portion with the plasma ,
The material of the reaction part is _SiO2 ,
The method for processing a substrate , wherein the reaction products include silicon fluorides and oxygen radicals . A step of placing a substrate to be processed made of silicon on a mounting surface of a substrate mounting part;
a step of disposing an annular protective member so as to cover an outer peripheral edge portion of the substrate placed on the placement surface from above with a gap therebetween;
A processing chamber that accommodates the substrate placement portion and the protective member is provided with SF ₆ Gas and O ₂ introducing a gas and applying high frequency power to form a plasma;
a step of etching the substrate on the placement surface with the plasma and generating a reaction product from a reaction portion containing silicon provided on the surface of the protective member with the plasma;
and forming a protective film on an etching portion in an outer periphery of the substrate to be processed by reacting the reaction product generated in the reaction portion with the plasma,
The material of the reaction part is SiO ₂ The substrate processing method is as follows. A step of placing a substrate to be processed made of silicon on a mounting surface of a substrate mounting part;
a step of disposing an annular protective member so as to cover from above an outer peripheral edge portion of the substrate to be processed placed on the placement surface;
A step of introducing _SF6 gas and O2 _gas into a processing chamber that accommodates the substrate placement part and the protective member , and applying high frequency power to generate plasma;
a step of etching the substrate on the placement surface with the plasma and generating a reaction product from a reaction portion containing silicon provided on the surface of the protective member with the plasma;
and forming a protective film on an etching portion in an outer periphery of the substrate to be processed by reacting the reaction product generated in the reaction portion with the plasma,
The protective member is
a first annular member that covers an outer peripheral edge of the substrate to be processed and has the reaction portion on an upper surface thereof;
a second annular member that detachably supports an outer peripheral end of the first member and does not have the reaction portion. The step of forming the protective film on the etching portion in the outer periphery of the substrate to be processed includes:
dissociating the reaction product containing silicon produced in the reaction portion by the plasma;
The substrate processing method according to claim 1 , further comprising the step of forming the protective film containing silicon oxide by a reaction between dissociated silicon and oxygen radicals in the plasma. 5. The substrate processing method according to claim 1, wherein in the step of generating the reaction products from the reaction section, the reaction products are generated from the reaction section so that a distribution of radicals and reaction products in an outer periphery of the substrate is made closer to a distribution of radicals and reaction products in a central portion of the substrate.

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