Etching agent, etching method, and device manufacturing method

Abstract

To provide an etching agent, an etching method, and a device manufacturing method that can form recesses with smooth bottom surfaces. [Solution] An etching agent for etching a semiconductor substrate having a surface partially coated with a precious metal, the etching agent comprising an oxidizing agent, hydrogen fluoride, and ammonium fluoride, wherein the molar concentration of the hydrogen fluoride is m [mol / L] and the molar concentration of the ammonium fluoride is n [mol / L], and the etching agent satisfies 0.5≦n / m≦5.0.

Description

[Technical Field]

[0001] The present invention relates to an etching agent, an etching method, and a method for manufacturing a device. [Background technology]

[0002] Patent Document 1 discloses an etching method in which an etching agent containing hydrofluoric acid, an oxidizing agent, and a buffer is supplied to a semiconductor substrate having a first region coated with a metal layer made of one or more metals other than a noble metal, such as aluminum, and a second region coated with a catalytic layer made of a noble metal, thereby causing etching of the semiconductor substrate at the position of the catalytic layer.With this configuration, when a semiconductor substrate provided with a metal layer is etched by a noble-metal-assisted chemical etching method, the semiconductor can be etched with a high selectivity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-050378 Summary of the Invention [Problem to be solved by the invention]

[0004] The noble metal assisted chemical etching method described in Patent Document 1 has a problem in that when recesses are formed in a workpiece, the smoothness of the bottom surface of the recesses cannot be sufficiently increased.

[0005] Therefore, it is an issue to realize an etching agent and an etching method that can form recesses with smooth bottom surfaces by a noble metal-assisted chemical etching method. [Means for solving the problem]

[0006] The etching agent according to the application example of the present invention is An etching agent for etching a semiconductor substrate having a surface partially covered with a noble metal, an oxidizing agent; Hydrogen fluoride, ammonium fluoride, Including, The molar concentration of the hydrogen fluoride is m [mol / L], When the molar concentration of the ammonium fluoride is n [mol / L], The relationship satisfies 0.5≦n / m≦5.0.

[0007] An etching method according to an application example of the present invention includes: 1. A method for etching a semiconductor substrate, comprising: preparing the semiconductor substrate having, on its surface, a first region where the noble metal is exposed and a second region where the noble metal is not exposed; An etching agent according to an application example of the present invention is supplied to the surface of the semiconductor substrate, and the semiconductor substrate is etched.

[0008] A method for manufacturing a device according to an application example of the present invention includes: 1. A method of manufacturing a device comprising a processed semiconductor substrate, comprising: forming a recess on the surface of the semiconductor substrate by an etching method according to an application example of the present invention, and obtaining the processed semiconductor substrate; The processed semiconductor substrate is used to fabricate the device. [Brief explanation of the drawings]

[0009] [Figure 1] 1A to 1C are process diagrams showing the configuration of a method for manufacturing a device according to an embodiment. [Figure 2] 2A to 2C are cross-sectional views illustrating a method for manufacturing the device shown in FIG. [Figure 3] 2A to 2C are cross-sectional views illustrating a method for manufacturing the device shown in FIG. [Figure 4] 2A to 2C are cross-sectional views illustrating a method for manufacturing the device shown in FIG. [Figure 5] 2A to 2C are cross-sectional views illustrating a method for manufacturing the device shown in FIG. [Figure 6] 2A to 2C are cross-sectional views illustrating a method for manufacturing the device shown in FIG. [Figure 7] 2A to 2C are cross-sectional views illustrating a method for manufacturing the device shown in FIG. [Figure 8] 2A to 2C are cross-sectional views illustrating a method for manufacturing the device shown in FIG. [Figure 9] 2A to 2C are cross-sectional views illustrating a method for manufacturing the device shown in FIG. [Figure 10] 1 is Table 1 showing the preparation conditions and evaluation results of the evaluation samples obtained in Examples 1 and 2. [Figure 11] Table 2 shows the preparation conditions and evaluation results of the evaluation samples obtained in Examples 2 and 3. [Figure 12] Table 3 shows the preparation conditions and evaluation results of the evaluation samples obtained in Comparative Examples 1 and 2. [Figure 13] 1 is a graph showing the relationship between the molar concentration ratio n / m of the etching agent and the etching rate. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an etching agent, an etching method, and a device manufacturing method according to the present invention will be described in detail based on embodiments shown in the accompanying drawings.

[0011] 1. Device manufacturing method First, a method for manufacturing a device according to an embodiment will be described.

[0012] Fig. 1 is a process diagram showing the configuration of a method for manufacturing a device according to an embodiment, Fig. 2 to Fig. 9 are cross-sectional views illustrating a method for manufacturing the device shown in Fig. 1.

[0013] The method for manufacturing a device shown in Fig. 1 includes a first resist forming step S102, a catalyst film forming step S104, a first resist stripping step S106, a second resist forming step S108, a first etching step S110, a second resist stripping step S112, a second etching step S114, a catalyst film removing step S116, and an assembly step S118. In this device manufacturing method, etching is performed on the surface of semiconductor substrate 10 shown in Fig. 2 to form recess 15 shown in Fig. 9. Then, a device (not shown) is manufactured using semiconductor substrate 1 (processed semiconductor substrate) in which recess 15 has been formed.

[0014] This method of manufacturing a device has a lower environmental impact and is more productive than methods involving the formation of recesses by dry etching.

[0015] In the first etching step S110 and the second etching step S114, the semiconductor substrate 10 is subjected to noble-metal-assisted chemical etching using an etching agent 9 (etching agent according to the embodiment) described below. This allows the formation of recesses 15 with smooth bottom surfaces. Note that the recesses 15 to be formed in this embodiment include, for example, two types of recesses 152 and 154 with different depths, as shown in FIG. 9 . The recesses 152 are deeper than the recesses 154.

[0016] 1.1. First resist formation process In the first resist formation step S102, first, the semiconductor substrate 10 shown in FIG. 2 is prepared.

[0017] The semiconductor substrate 10 is made of a semiconductor material. Examples of the semiconductor material include Group IV elements such as Si and Ge, compounds of Group III and Group V elements such as GaAs and GaN, and compounds containing Group IV elements such as SiC. Note that the "group" here refers to a "group" in the short periodic table.

[0018] Of these, a single crystal silicon substrate is preferably used for the semiconductor substrate 10, and a (100) plane orientation single crystal silicon substrate is more preferably used.

[0019] The semiconductor material may be doped with impurities. Furthermore, elements such as transistors, diodes, resistors, and capacitors may be formed on the surface of the semiconductor substrate 10.

[0020] When the semiconductor substrate 10 is a crystalline substrate, the surface may be parallel to any crystal plane. In this specification, the term "surface" refers to the surface of the semiconductor substrate 10 on which the recess 15 is to be formed.

[0021] Next, as shown in FIG. 2, a first resist 31 is formed on the surface of the semiconductor substrate 10. The first resist 31 is a protective film that covers a portion of the surface of the semiconductor substrate 10. A photoresist such as a photosensitive resin is preferably used as the first resist 31, and a lift-off photoresist is more preferably used. A lift-off photoresist is a material that can be patterned to form a coating with an inverted tapered shape. Specifically, when a thin line-shaped first resist 31 is formed by patterning, the cross-sectional shape of the first resist 31 is an inverted trapezoid, as shown in FIG. 2. By using such a resist, the first resist 31 and the catalyst film 20 formed thereon can be smoothly lifted off in the first resist stripping step S106, which will be described later. Therefore, the first resist 31 covers the area from which the catalyst film 20 is to be removed in the first resist stripping step S106, which will be described later.

[0022] The first resist 31 is formed by applying a photosensitive resin, for example, and then patterning it by photolithography.

[0023] 1.2. Catalyst film formation process In the catalyst film forming step S104, as shown in FIG. 3, a catalyst film 20 is formed so as to cover the entire surface of the semiconductor substrate 10.

[0024] The catalyst film 20 contains a noble metal that acts as a catalyst in a noble-metal-assisted chemical etching method, such as Au, Ag, Pt, Pd, Rd, Rh, or a combination thereof.

[0025] Examples of methods for forming the catalyst film 20 include various vapor phase film formation methods such as sputtering and vapor deposition. The catalyst film 20 may also be formed by various liquid phase film formation methods, various plating methods, and the like.

[0026] The catalyst film 20 is preferably porous, which facilitates penetration and exchange of the etching agent 9 in the first etching step S110 and the second etching step S114. This improves the etching rate and the etching depth, allowing high aspect ratio processing to be completed in a shorter time.

[0027] Methods for forming the porous catalyst film 20 include, for example, a method using a porous or particulate material, a method of obtaining a discontinuous film by stopping film formation before it becomes a continuous film, and a method of making the film porous by patterning.

[0028] The thickness of the catalyst film 20 is not particularly limited, but is preferably about 3 nm to 100 nm, more preferably about 10 nm to 30 nm, which makes it easier for the etching agent 9 to penetrate and be replaced if the catalyst film 20 is porous.

[0029] 1.3. First resist stripping process In the first resist stripping step S106, the first resist 31 is stripped. This allows the catalyst film 20 formed on the first resist 31 to be lifted off, as shown in FIG. 4. At this time, if the first resist 31 has an inverse tapered shape, it can be lifted off with high precision. By lifting off the catalyst film 20, a patterned catalyst film 20 is obtained, as shown in FIG. 4.

[0030] 1.4. Second resist formation process In the second resist formation step S108, a first region 11A where the catalyst film 20 is exposed and a second region 12A where the catalyst film 20 is not exposed are defined on the surface of the semiconductor substrate 10. That is, as shown in FIG. 5, the first region 11A and the second region 12A are defined by covering a portion of the catalyst film 20 with the second resist 32.

[0031] Here, as an example, the portion where the deep recess 152 is to be finally formed is set as the first region 11A, and the other portion is set as the second region 12A. The first region 11A is covered with a catalyst film 20 containing a precious metal, and the catalyst film 20 is exposed. In other words, it can be said that the precious metal is exposed in the first region 11A. On the other hand, the second region 12A shown in FIG. 5 is a portion where the catalyst film 20 containing a precious metal is not provided, or where the catalyst film 20 containing a precious metal is provided but not in an exposed state. In other words, it can be said that the precious metal is not exposed in the second region 12A.

[0032] The second resist 32 is a protective film that selectively covers the second region 12A shown in Fig. 5. In other words, the second resist 32 is a protective film that has an opening corresponding to the first region 11A.

[0033] By defining the first region 11A and the second region 12A on the semiconductor substrate 10, the catalytic action of the noble metal contained in the catalyst film 20 exposed in the first region 11A can be selectively activated in the first etching step S110 described below, thereby enabling etching to be performed.

[0034] A resin resist is preferably used for the second resist 32. The resin resist is less susceptible to erosion by the etching agent 9 used in the first etching step S110 described below. For this reason, the resin resist is more suitable for the second resist 32 than, for example, a resist using an inorganic material.

[0035] 1.5. First etching step 6 (the etching agent according to the embodiment) is supplied to the surface of the semiconductor substrate 10 having the first region 11A and the second region 12A to etch the semiconductor substrate 10. As a result, a recess 151 is formed in the first region 11A as shown in FIG.

[0036] The first etching step S110 uses noble metal-assisted chemical etching, in which the etching agent 9 and the semiconductor substrate 10 are reacted with each other using the noble metal contained in the catalyst film 20 as a catalyst. In the first region 11A, the semiconductor material adjacent to the catalyst film 20 is oxidized, and the resulting oxide is dissolved and removed. This selectively etches the first region 11A. After being used in the etching, the catalyst film 20 remains chemically unchanged and moves toward the inside of the recess 151 formed in the semiconductor substrate 10 by the etching. The movement and etching of the catalyst film 20 are then repeated. As a result, the first region 11A is anisotropically etched in the thickness direction of the semiconductor substrate 10, forming the recess 151.

[0037] The etching agent 9 contains an oxidizing agent, hydrogen fluoride, and ammonium fluoride. When the molar concentration of hydrogen fluoride in the etching agent 9 is m [mol / L] and the molar concentration of ammonium fluoride is n [mol / L], the etching agent 9 has a molar concentration ratio n / m that satisfies 0.5≦n / m≦5.0, as will be described later.

[0038] According to this configuration, the molar concentrations of the components in the etching agent 9 are optimized, so that recesses 151 with smooth bottom surfaces can be formed. In this embodiment, the recesses 151 are further etched in a step described later, and finally, recesses 15 with smooth bottom surfaces and a desired depth can be formed.

[0039] Examples of oxidizing agents include H2O2 (hydrogen peroxide), HNO3 (nitric acid), AgNO3, KAuCl4, HAuCl4, K2PtCl6, H2PtCl6, Fe(NO3)3, Ni(NO3)2, Mg(NO3)2, Na2S2O8, K2S2O8, KMnO4, K2Cr2O7, etc., and one or more of these may be used. Of these, H2O2 is preferably used.

[0040] The molar concentration of the oxidizing agent in the etching agent 9 is not particularly limited, but is preferably 0.01 mol / L or more, more preferably 0.1 mol / L to 8.0 mol / L, even more preferably 0.5 mol / L to 5.0 mol / L, and particularly preferably 2.0 mol / L to 4.0 mol / L. If the molar concentration of the oxidizing agent is within the above range, a sufficient etching rate can be obtained while ensuring etching accuracy. If the molar concentration of the oxidizing agent is below the lower limit, the etching rate may be insufficient. On the other hand, if the molar concentration of the oxidizing agent is above the upper limit, the etching accuracy may be reduced.

[0041] The hydrogen fluoride produces hydrofluoric acid in the etching agent 9 and acts to dissolve the oxide produced by the oxidizing agent. The ammonium fluoride produces a complex of the semiconductor material in the etching agent 9 and acts to slightly etch the semiconductor material.

[0042] As described above, the molar concentration m [mol / L] of hydrogen fluoride and the molar concentration n [mol / L] of ammonium fluoride in the etching agent 9 satisfy the relationship 0.5≦n / m≦5.0. By setting the molar concentration ratio n / m within the above range, recesses 151 with smooth bottom surfaces can be formed. If the molar concentration ratio n / m is below the lower limit, the bottom surface of the recesses 151 formed will have an uneven structure, resulting in a decrease in smoothness. In particular, if the catalyst film 20 is porous, needle-like uneven structures, for example, are likely to form. Such uneven structures not only hinder the use of the recesses 151 but may also fall off and become foreign matter. On the other hand, if the molar concentration ratio n / m exceeds the upper limit, the etching rate will decrease due to a shortage of hydrogen fluoride or an excess of ammonium fluoride.

[0043] The molar concentration ratio n / m preferably satisfies 0.6≦n / m≦3.0, which makes it possible to further improve the smoothness of the bottom surface of the recess 151 and ensure a stable etching rate regardless of other conditions.

[0044] The molar concentration ratio n / m more preferably satisfies 1.0≦n / m≦1.5, which makes it possible to further improve the smoothness of the bottom surface of the recess 151 and ensure a particularly good etching rate.

[0045] The etching rate can also be adjusted by the temperature of the etching agent 9. For example, the etching rate can be increased by increasing the temperature of the etching agent 9. The temperature of the etching agent 9 is not particularly limited, but is preferably 20°C or higher and 50°C or lower.

[0046] The molar concentration m [mol / L] of hydrogen fluoride preferably satisfies m≦2.0. This ensures a sufficient etching rate while suppressing side etching and improving etching accuracy. However, if the molar concentration m exceeds the upper limit, etching accuracy may decrease.

[0047] The molar concentration m of hydrogen fluoride more preferably satisfies 1.0≦m≦1.8. This further suppresses side etching while ensuring a sufficient etching rate, thereby particularly improving etching accuracy. If the molar concentration m is below the lower limit, the etching rate may decrease slightly. On the other hand, if the molar concentration m is above the upper limit, the etching accuracy may decrease.

[0048] The molar concentration n [mol / L] of ammonium fluoride preferably satisfies n≦7.0. This can suppress the formation of an uneven structure on the bottom surface of the recess 151, thereby obtaining recess 151 with a smooth bottom surface. Note that if the molar concentration n exceeds the upper limit, the pH of the etching agent 9 increases, which may result in a decrease in the etching rate.

[0049] The molar concentration n of ammonium fluoride more preferably satisfies 0.8≦n≦4.5. This particularly suppresses the formation of an uneven structure on the bottom surface of the recess 151. If the molar concentration n is below the lower limit, the smoothness of the bottom surface of the recess 151 may decrease. On the other hand, if the molar concentration n is above the upper limit, the pH of the etching agent 9 may increase, resulting in a slight decrease in the etching rate.

[0050] The pH of the etching agent 9 is preferably 1.8 or more and 4.0 or less, more preferably 1.9 or more and 3.0 or less, and even more preferably 2.0 or more and 2.4 or less, thereby ensuring a particularly sufficient etching rate and also sufficiently enhancing the smoothness of the bottom surface of the recess 151 to be formed.

[0051] The etching agent 9 may contain additives other than the above components. Examples of additives include alcohols, carboxylic acids, hydroxy acids, amines, amino acids, thiols, organic fluorine compounds, and chelating agents. The concentration of the additives in the etching agent 9, in terms of the total of all components, is preferably 0.001% by mass or more and 5% by mass or less, and more preferably 0.01% by mass or more and 1% by mass or less.

[0052] The surface roughness (arithmetic mean roughness Ra) of the bottom surface of the recess 151 to be formed is preferably 3.0 μm or less, more preferably 2.0 μm or less, and even more preferably 1.0 μm or less. This allows the recess 151 to have a particularly good smoothness of the bottom surface.

[0053] The surface roughness is measured as follows: First, the cross section of the recess 151 is observed with a scanning electron microscope to obtain an observed image. Next, the outline of the bottom surface is identified in the observed image. Then, the arithmetic mean roughness Ra of the outline is calculated by image processing.

[0054] 1.5. Second resist stripping process In the second resist stripping step S112, the second resist 32 is stripped off. As a result, the catalyst film 20 that was covered with the second resist 32 is exposed, as shown in Fig. 7. As a result, on the surface of the semiconductor substrate 10 after the second resist stripping step S112, a first region 11B where the catalyst film 20 is exposed and a second region 12B where the catalyst film 20 is not provided (exposed) are formed.

[0055] In the first region 11B, the catalyst film 20 containing the precious metal is exposed, so it can be said that the precious metal is exposed. On the other hand, in the second region 12B, the catalyst film 20 containing the precious metal is not provided, so it can be said that the precious metal is not exposed.

[0056] By defining the first region 11B and the second region 12B in the semiconductor substrate 10, the catalytic action of the noble metal exposed in the first region 11B can be selectively acted upon to perform etching in the second etching step S114 described later.

[0057] 1.6. Second etching process In the second etching step S114, an etching agent 9 (etching agent according to the embodiment) shown in FIG. 8 is supplied to the surface of the semiconductor substrate 10 having the first region 11B and the second region 12B, and the semiconductor substrate 10 is etched. As a result, the recess 151 shown in FIG. 7 is further dug down, and the recess 152 shown in FIG. 8 is obtained. Furthermore, the portion where the recess 151 was not formed is selectively etched, and a recess 154 is formed.

[0058] Also in the second etching step S114, by performing noble metal assisted chemical etching using the etching agent 9 (etching agent according to the embodiment), recesses 152 and 154 with smooth bottom surfaces can be formed.

[0059] 1.7. Catalyst membrane removal process In the catalyst film removal step S116, the catalyst film 20 is removed. For example, a solution that dissolves noble metals is used to remove the catalyst film 20. As a result, the semiconductor substrate 1 having the recess 15 formed therein shown in FIG. 9 is obtained.

[0060] 1.8.Assembly Process In the assembly step S118, a device (not shown) is manufactured using the semiconductor substrate 1 (processed semiconductor substrate) in which the recess 15 is formed. The semiconductor substrate 1 in which the recess 15 is formed has a smooth bottom surface, and is therefore useful as a component having a cavity for accommodating an element or the like. Therefore, according to the device manufacturing method of the embodiment, a device with high shape accuracy can be efficiently manufactured while minimizing the environmental load. Examples of elements that can be accommodated in the cavity include MEMS (Micro Electro Mechanical Systems) elements, vibration elements, sensor elements, light-emitting elements, and light-receiving elements.

[0061] 2. Etching method Next, the etching method according to the above embodiment will be described again.

[0062] In the method for manufacturing the device shown in FIG. 1, the first etching step S110 and the second etching step S114 each use an etching method according to the embodiment.

[0063] In the first etching step S110, a semiconductor substrate 10 having a first region 11A and a second region 12A on its surface is prepared, and then an etching agent 9 (the etching agent according to the embodiment) is supplied to the surface of the semiconductor substrate 10 to etch the semiconductor substrate 10. In the first region 11A shown in FIG. 5, the noble metal is exposed, but in the second region 12A, the noble metal is not exposed. Therefore, as shown in FIG. 6, a recess 151 is obtained by selectively etching the first region 11A.

[0064] Furthermore, the molar concentration ratio n / m of the etching agent 9 is optimized, which allows the bottom surface of the recess 151 formed in the semiconductor substrate 10 to be smoothed.

[0065] In the second etching step S114, a semiconductor substrate 10 having a first region 11B and a second region 12B on its surface is prepared, and then an etching agent 9 (the etching agent according to the embodiment) is supplied to the surface of the semiconductor substrate 10 to etch the semiconductor substrate 10. In the first region 11B shown in FIG. 7, the noble metal is exposed, but in the second region 12B, the noble metal is not exposed. Therefore, as shown in FIG. 8, recesses 152 and 154 are obtained by selectively etching the first region 11B.

[0066] Furthermore, the molar concentration ratio n / m of the etching agent 9 is optimized, which allows the bottom surfaces of the recesses 152 and 154 formed in the semiconductor substrate 10 to be smoothed.

[0067] 3. Effects of the above embodiment As described above, the etching agent 9 according to the embodiment is an etching agent for etching a semiconductor substrate 10 whose surface is partially covered with a precious metal, and contains an oxidizing agent, hydrogen fluoride, and ammonium fluoride. Furthermore, when the molar concentration of hydrogen fluoride in the etching agent 9 is m [mol / L] and the molar concentration of ammonium fluoride is n [mol / L], the etching agent 9 satisfies 0.5≦n / m≦5.0.

[0068] According to this configuration, an etching agent 9 capable of forming recesses with smooth bottom surfaces can be obtained in a noble metal-assisted chemical etching method.

[0069] In the etching agent 9 according to the embodiment, it is preferable that 0.6≦n / m≦3.0 be satisfied.

[0070] According to this configuration, the smoothness of the bottom surface of the recess can be further improved, and a stable etching rate can be ensured regardless of other conditions.

[0071] In the etching agent 9 according to the embodiment, it is preferable that 1.0≦n / m≦1.5 is satisfied.

[0072] With this configuration, the smoothness of the bottom surface of the recess can be further improved, and a particularly good etching rate can be ensured.

[0073] In the etching agent 9 according to the embodiment, it is preferable that n≦7.0 be satisfied.

[0074] According to this configuration, the generation of an uneven structure on the bottom surface of the recess can be suppressed, and therefore, a recess with a smooth bottom surface can be obtained.

[0075] In the etching agent 9 according to the embodiment, it is preferable that 0.8≦n≦4.5 is satisfied.

[0076] With this configuration, it is possible to particularly suppress the generation of an uneven structure on the bottom surface of the recess.

[0077] In the etching agent 9 according to the embodiment, it is preferable that m≦2.0 be satisfied.

[0078] According to this configuration, it is possible to suppress side etching while ensuring a sufficient etching rate, thereby improving etching accuracy.

[0079] In the etching agent 9 according to the embodiment, it is preferable that 1.0≦m≦1.8 is satisfied.

[0080] According to this configuration, side etching is further suppressed while a sufficient etching rate is ensured, and etching precision can be particularly improved.

[0081] The etching method according to the embodiment is a method for etching a semiconductor substrate 10, in which a semiconductor substrate 10 having, on its surface, first regions 11A, 11B in which a precious metal is exposed and second regions 12A, 12B in which the precious metal is not exposed is prepared, and an etching agent 9 according to the embodiment is supplied to the surface of the semiconductor substrate 10 to etch the semiconductor substrate 10.

[0082] According to this configuration, recesses with smooth bottom surfaces can be formed by the noble metal-assisted chemical etching method.

[0083] In the etching method according to the embodiment, the second regions 12A and 12B may be covered with a resin resist when etching is performed.

[0084] According to this configuration, the resin resist is less susceptible to erosion by the etching agent 9, and is therefore more suitable for covering the second regions 12A and 12B than a resist using an inorganic material, for example.

[0085] The device manufacturing method according to the embodiment is a method for manufacturing a device having a processed semiconductor substrate (semiconductor substrate 1 having a recess 15 formed on its surface), in which recess 15 is formed on the surface of semiconductor substrate 10 by the etching method according to the embodiment, a processed semiconductor substrate is obtained, and the device is manufactured using the processed semiconductor substrate.

[0086] According to this configuration, the semiconductor substrate 1 (processed semiconductor substrate) in which the recess 15 having a smooth bottom surface is formed can be used as, for example, a part having a cavity for accommodating an element, etc. Therefore, devices with high shape accuracy can be efficiently manufactured while reducing the environmental load.

[0087] In the device manufacturing method according to the embodiment, the second regions 12A and 12B may be covered with a resin resist when etching is performed.

[0088] According to this configuration, the resin resist is less susceptible to erosion by the etching agent 9, and is therefore more suitable for covering the second regions 12A and 12B than a resist using an inorganic material, for example.

[0089] The etching agent, etching method, and device manufacturing method of the present invention have been described above based on the illustrated embodiments, but the present invention is not limited to these.

[0090] For example, the etching agent of the present invention may be one in which any component is added to the above-described embodiment, and the etching method and device manufacturing method of the present invention may be one in which any desired step is added to the above-described embodiment. [Example]

[0091] Next, specific examples of the present invention will be described. 4. Preparation of evaluation samples 4.1. Examples 1 to 4 First, a silicon substrate with a P-type conductivity and a (100) surface orientation was prepared.

[0092] Next, a catalytic film was formed on the surface of the silicon substrate, patterned into lines of a specified width. The catalytic film was 16 nm thick and contained Au as the precious metal.

[0093] Next, an etching agent was supplied to the silicon substrate on which the catalyst film had been formed, and noble metal-assisted chemical etching was performed. This resulted in recesses with widths of 0.1 to 0.5 mm and depths of 0.1 to 0.2 mm, and evaluation samples for Examples 1 to 4 were obtained. The temperature of the etching agent in each Example was 23°C ± 1°C. However, the temperature of the etching agent is not limited to this range.

[0094] The molar concentrations of the oxidizing agent, the molar concentrations m of hydrogen fluoride, and the molar concentrations n of ammonium fluoride, the molar concentration ratio n / m, and the pH of the etching agent used are as shown in Table 1 (FIG. 10) and Table 2 (FIG. 11).

[0095] 4.2. Comparative Example 1 A sample for evaluation was obtained in the same manner as in Example 1, except that the molar concentration n of ammonium fluoride in the etching agent used was set to 0. The pH of the etching agent is as shown in Table 3 (FIG. 12).

[0096] 4.3. Comparative Example 2 Evaluation samples were obtained in the same manner as in Example 1, except that the molar concentration n of ammonium fluoride in the etching agent used, the molar concentration ratio n / m, and the pH of the etching agent were changed as shown in Table 3 (FIG. 12).

[0097] 5. Evaluation of the evaluation sample 5.1. Cross-sectional observation of recessed areas The evaluation samples obtained in each example and comparative example were cut so as to intersect with the extending direction of the recesses. The cross sections were then observed using a scanning electron microscope. The observed images are shown in Table 1 (FIG. 10), Table 2 (FIG. 11), and Table 3 (FIG. 12).

[0098] In the evaluation samples obtained in each example, no uneven structure was observed on the bottom surface of the recesses, and they were smooth.

[0099] In contrast, in the evaluation samples obtained in the comparative examples, an uneven structure was observed on the bottom surface of the recesses.

[0100] 5.2. Surface roughness of the bottom of the recess The arithmetic mean roughness Ra of the bottom surface of the recesses was measured for the evaluation samples obtained in each Example and Comparative Example. The measurement results are shown in Table 1. Note that the surface roughness of the evaluation samples obtained in each Comparative Example could not be measured due to the influence of the significant uneven structure.

[0101] In the evaluation samples obtained in each example, it was found that the bottom surfaces of the recesses were smooth, as shown in Table 1 (FIG. 10) and Table 2 (FIG. 11). On the other hand, in the evaluation samples obtained in each comparative example, an uneven structure was present on the bottom surfaces of the recesses, as shown in Table 3 (FIG. 12).

[0102] 5.3.Etching rate The etching rate was calculated when preparing evaluation samples for each example and comparative example. The etching rate was calculated based on the depth of the recess and the required time. The calculation results are shown in FIG. 13. FIG. 13 is a graph showing the relationship between the molar concentration ratio n / m of the etching agent and the etching rate. The horizontal axis of FIG. 13 is the molar concentration ratio n / m, and the vertical axis is the etching rate [μm / min], which represents the depth [μm] of the recess formed by etching for 1 minute.

[0103] 13, a sufficient etching rate was obtained when the molar concentration ratio n / m was 5.0 or less. This tendency was particularly noticeable when the molar concentration ratio n / m was 3.0 or less.

[0104] The same evaluations were carried out with the molar concentration of the oxidizing agent changed to 2.0 mol / L and 4.0 mol / L. As a result, the smoothness of the bottom surface of the recess and the etching rate showed the same tendency as when the molar concentration was 3.0 mol / L.

[0105] The same evaluation was carried out with the hydrogen fluoride molar concentration m changed to 1.0 mol / L and 1.8 mol / L. As a result, the smoothness of the bottom surface of the recess and the etching rate showed the same tendency as when the molar concentration was 1.4 mol / L. [Explanation of symbols]

[0106] 1...semiconductor substrate, 9...etchant, 10...semiconductor substrate, 11A...first region, 11B...first region, 12A...second region, 12B...second region, 15...recess, 20...catalyst film, 31...first resist, 32...second resist, 151...recess, 152...recess, 154...recess, S102...first resist forming step, S104...catalyst film forming step, S106...first resist stripping step, S108...second resist forming step, S110...first etching step, S112...second resist stripping step, S114...second etching step, S116...catalyst film removing step, S118...assembly step

Claims

1. An etching agent for etching a semiconductor substrate having a surface partially covered with a noble metal, an oxidizing agent; Hydrogen fluoride, ammonium fluoride, Including, The molar concentration of the hydrogen fluoride is m [mol / L], When the molar concentration of the ammonium fluoride is n [mol / L], An etching agent characterized by satisfying the condition 0.5≦n / m≦5.

0.

2. The etching agent according to claim 1, wherein n / m satisfies 0.6≦n / m≦3.

0.

3. The etching agent according to claim 2, wherein n / m satisfies 1.0≦n / m≦1.

5.

4. 4. The etching agent according to claim 1, wherein n≦7.0 is satisfied.

5. The etching agent according to claim 4, wherein n satisfies 0.8≦n≦4.

5.

6. 4. The etching agent according to claim 1, wherein m≦2.0 is satisfied.

7. The etching agent according to claim 6, wherein m satisfies 1.0≦m≦1.

8.

8. A method for etching the semiconductor substrate, comprising: preparing the semiconductor substrate having, on its surface, a first region where the noble metal is exposed and a second region where the noble metal is not exposed; 4. The etching agent according to claim 1, wherein the etching agent is supplied to the surface of the semiconductor substrate to etch the semiconductor substrate. An etching method characterized by:

9. 9. The etching method according to claim 8, wherein the second region is covered with a resin resist when the etching is performed.

10. 1. A method of manufacturing a device comprising a processed semiconductor substrate, comprising: forming a recess on the surface of the semiconductor substrate by the etching method according to claim 8, and obtaining the processed semiconductor substrate; manufacturing the device using the processed semiconductor substrate; A method for manufacturing a device comprising the steps of:

11. The method for manufacturing a device according to claim 10 , wherein the second region is covered with a resin resist when the etching is performed.

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