Substrate processing method

Abstract

A substrate processing method for improving the etching resistance of a resist film is provided. [Solution] A substrate processing method comprising the steps of: preparing a substrate having a resist film with an opening pattern formed on a layer to be etched; exposing the substrate to a metal-containing gas to cause metal to infiltrate the resist film; and exposing the substrate to an etching gas to etch the layer to be etched through the openings in the resist film.

Description

[Technical Field]

[0001] The present disclosure relates to a substrate processing method. [Background technology]

[0002] Patent Document 1 discloses an etching method including a film-forming step of forming a resist film on an etching target, an infiltration step of exposing the formed resist to a metal-containing gas containing the metal, thereby infiltrating the metal into the resist, and an etching step of etching the etching target through the resist infiltrated with the metal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-038929 Summary of the Invention [Problem to be solved by the invention]

[0004] In one aspect, the present disclosure provides a substrate processing method for improving etching resistance of a resist film. [Means for solving the problem]

[0005] In order to solve the above problem, according to one aspect, there is provided a substrate processing method comprising the steps of: preparing a substrate having a resist film on an etching target layer with an opening pattern formed thereon; exposing the substrate to a metal-containing gas to cause metal to infiltrate the resist film; and exposing the substrate to an etching gas to etch the etching target layer through the openings in the resist film. [Effects of the Invention]

[0006] According to one aspect, it is possible to provide a substrate processing method that improves the etching resistance of a resist film. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a flowchart showing an example of a substrate processing method according to the present embodiment. [Figure 2] 5A to 5C are examples of schematic cross-sectional views of a substrate in each step. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant explanations may be omitted.

[0009] An example of a substrate processing method according to this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a flowchart showing an example of the substrate processing method according to this embodiment. Figure 2 is an example of a schematic cross-sectional view of a substrate in each step.

[0010] Here, an example will be described in which a substrate is cut into individual chips by etching (dicing). That is, a plurality of semiconductor devices (not shown) are formed on the substrate. The etching process is performed up to the back surface of the substrate, and the substrate is cut (diced) into individual chips each having a semiconductor device.

[0011] The etching process is not limited to a process (dicing) in which the substrate is cut by etching down to the back surface of the substrate. For example, the etching process may be applied to an etching process in which recesses (deep recesses) with a high aspect ratio (ratio of recess depth to recess width) are formed in the substrate. In this case, the recesses may be, for example, holes, trenches, etc. Furthermore, the thickness of the substrate to be diced and the depth of the recesses formed in the substrate may be, for example, about 150 μm (in the range of 30 μm to 300 μm).

[0012] In step S101, a substrate is prepared. Here, the prepared substrate has an etching target layer. The etching target layer is etched in an etching process (see S106) described below. The etching target layer is formed of, for example, a stacked structure of silicon-containing layers. For example, the etching target layer has a silicon layer 200 of a silicon wafer and a silicon-containing layer 210 formed on the silicon layer 200. The silicon layer 200 is made of, for example, silicon (Si). The silicon-containing layer 210 is made of, for example, silicon oxide (SiO2). The silicon-containing layer 210 may be, for example, SOG (Spin On Glass). Alternatively, the silicon-containing layer may be a film in which silicon oxide and silicon nitride are alternately stacked.

[0013] In step S102, a photoresist film 220 is formed. Here, the photoresist film 220 is formed on the etching target layer (silicon layer 200, silicon-containing layer 210). The photoresist film 220 is, for example, an organic film containing a photosensitive resin as a main component. The photoresist film 220 is porous (has holes). The thickness of the photoresist film 220 is, for example, within a range of 500 nm to 2000 nm.

[0014] For example, a phenyl-based resin can be used for the photoresist film 220. Specifically, the photoresist film 220 is based on PHS (polyhydroxystyrene), and any of alkyl, adamantane, lactone, etc. can be used as a protective group.

[0015] Furthermore, for example, an acrylic resin can be used for the photoresist film 220. Specifically, the photoresist film 220 is based on PMMA (polymethyl methacrylate), and any of alkyl, adamantane, lactone, etc. can be used as a protective group.

[0016] In step S103, exposure and development processes are performed to form a pattern of openings 221 in the photoresist film 220. Here, light is irradiated onto the photoresist film 220 on the substrate through a photomask (not shown) having a predetermined pattern (exposure process). As a result, exposed and unexposed portions are formed in the photoresist film 220. Next, either the exposed or unexposed portions of the photoresist film 220 are selectively removed (development process). The development process can be performed using at least one of a wet process and a dry process.

[0017] 2(a) is an example of a schematic cross-sectional view of a substrate after the processes of steps S101 to S103 are completed. As shown in FIG. 2(a), the substrate has an etching target layer (silicon-containing layer) including a silicon layer 200 and a silicon-containing layer 210. A photoresist film 220 is formed on the etching target layer. A pattern of openings 221 is formed in this photoresist film 220 by exposure and development processing.

[0018] As described above, by the processes of steps S101 to S103, a substrate is prepared having a photoresist film 220 in which a pattern of openings 221 is formed on the etching target layer (silicon-containing layer, silicon layer 200, silicon-containing layer 210).

[0019] In step S104, a process for infiltrating metal into the photoresist film 220 (metal infiltration process) is performed. Here, a substrate is placed on a mounting table provided in a process chamber, and a metal-containing gas is supplied into the process chamber, exposing the substrate to the metal-containing gas and causing the metal in the metal-containing gas to infiltrate the photoresist film 220. That is, the metal in the metal-containing gas is allowed to infiltrate the pores (vacancies) of the photoresist film 220.

[0020] The metal-containing gas is a gas containing a metal (metal atom). The metal contained in the metal-containing gas (in other words, the metal to be infiltrated into the photoresist film 220) preferably has a high boiling point (in other words, a low vapor pressure) of a metal fluoride formed with fluorine (F). Specifically, the metal to be infiltrated into the photoresist film 220 preferably has a fluoride whose boiling point is 700°C or higher. Furthermore, in the etching process (S106) using a fluorine-containing gas described below, it is preferable that the metal fluoride has high etching resistance with respect to the silicon-containing layer (silicon layer 200, silicon-containing layer 210) that is the etching target layer. In other words, it is preferable that the etching selectivity of the silicon-containing layer (silicon layer 200, silicon-containing layer 210) that is the etching target layer with respect to the metal fluoride is high.

[0021] Here, when the metal-containing gas is infiltrated into the photoresist film 220, it is preferable that the temperature of the substrate is equal to or higher than the temperature at which the infiltration progresses (e.g., 60°C or higher), and equal to or lower than the temperature at which the pattern of the photoresist film 220 does not deform (e.g., 160°C or lower).

[0022] Specifically, the metal (metal atom) contained in the metal-containing gas is preferably any of Al, Ce, Ga, Hf, In, Zn, Ba, Ho, Sr, Ta, Sn, etc., from the viewpoint of etching selectivity relative to etching using a fluorine-containing gas.

[0023] In this case, the metal fluoride is one of AlF3 (boiling point 1276°C), CeF2 (boiling point 2180°C), GaF3 (boiling point 1000°C), HfF4 (boiling point 970°C), InF3 (boiling point 1200°C), ZnF2 (boiling point 1500°C), BaF2 (boiling point 2260°C), HoF3 (boiling point 2200°C), SrF2 (boiling point 2460°C), TaF5 (boiling point 2295°C), SnF2 (boiling point 850°C), SnF4 (boiling point 705°C), etc.

[0024] In addition, it is more preferable that the fluoride has a boiling point of 2200°C or higher, and the metal (metal atom) contained in the metal-containing gas is any of Ba, Ho, Sr, Ta, etc., from the viewpoint of etching selectivity relative to etching using a fluorine-containing gas.

[0025] The metal-containing gas containing Al may be any of TMA (trimethylaluminum), DMA (dimethylaluminum), TME (triethylaluminum), AlCl3, AlCl(CH3)2, and the like.

[0026] The metal-containing gas containing Ce may be any of Ce(thd)4, Ce(dedmg)3, Ce(iPrCp)3, and the like.

[0027] The metal-containing gas containing Ga may be any of TMGa (trimethylgallium), TEGa (triethylgallium), GaCl3, GaCl(CH3)2, GaCl(C2H5)2, Ga2(N(CH3)2)6, and the like.

[0028] The metal-containing gas containing Hf may be any of TDMAHf (tetrakis(dimethylamido)hafnium), HfCl4, or the like.

[0029] The metal-containing gas containing In can be any of TMIn (trimethylindium), TEIn (triethylindium), InCl 3 , InCl(CH 3 ) 2 , and the like.

[0030] The metal-containing gas containing Zn may be any of DEZ (diethyl zinc), DMZ (dimethyl zinc), ZnCl2, or the like.

[0031] The metal-containing gas containing Ba may be any of Ba(CpMe5)2, Ba(thd)2, or the like.

[0032] The metal-containing gas containing Ho may be Ho(thd)3 or the like.

[0033] The metal-containing gas containing Sr may be any of Sr(thd)2, Sr(CbMe5)2, and the like.

[0034] The metal-containing gas containing Ta may be any of TaCl5, TaF5, Ta(N(CH3)2)5, Ta(N(C2H5)2)5, and the like.

[0035] The metal-containing gas containing Sn may be any of TDMASn (tetrakis(dimethylamido)tin), TMSDMSn (trimethyldimethyltin), bis-DMADMSn (bis-dimethylaminodimethyltin), SnCl4, or the like.

[0036] Furthermore, when the photoresist film 220 is made of a phenyl-based resin, the metal-containing gas can be an amide-based or metal halide-based gas. Specifically, when the photoresist film 220 is made of a phenyl-based resin, the metal-containing gas can be any of TDMAHf, TDMASn, TMSDMSn, bis-DMADMSn, AlCl3, GaCl3, HfCl4, InCl3, SnCl4, etc. This allows the metal-containing gas to infiltrate the photoresist film 220, forming the infiltrated portion 225.

[0037] Furthermore, when the photoresist film 220 is made of an acrylic resin, the metal-containing gas can be an alkyl metal-based or metal halide-based gas. Specifically, when the photoresist film 220 is made of an acrylic resin, the metal-containing gas can be any of TMA, TEA, TMGa, TEGa, TMIn, TEIn, DMZ, AlCl3, GaCl3, HfCl4, InCl3, SnCl4, etc. This allows the metal-containing gas to infiltrate the photoresist film 220, forming the infiltrated portion 225.

[0038] 2(b) is an example of a schematic cross-sectional view of the substrate after the processing of step S104 is completed. As shown in FIG. 2(b), the metal of the metal-containing gas infiltrates into the pores of the photoresist film 220, forming an infiltrated portion 225 on the surface of the photoresist film 220. On the other hand, the metal-containing gas does not infiltrate into the silicon-containing layer 210.

[0039] When the photoresist film 220 is thin, the solution permeates the entire photoresist film 220, forming a permeated portion 225.

[0040] In step S105, the metal infiltrated into the photoresist film 220 is oxidized (oxidation process). Here, a substrate is placed on a mounting table provided in a processing chamber, and an oxygen-containing gas is supplied into the processing chamber, thereby oxidizing the metal infiltrated into the photoresist film 220 and forming a metal oxide.

[0041] The oxygen-containing gas may be any of O2, O3, CO2, etc.

[0042] However, the oxidation treatment is not limited to this method. For example, the substrate that has been treated in step S104 may be exposed to the air atmosphere to naturally oxidize the metal that has infiltrated into the infiltrated portion 225.

[0043] The oxidation treatment in step S105 is not an essential step and may be omitted depending on the conditions of the etching treatment in step S106. In this case, the process proceeds to step S106 after the metal infiltration treatment in step S104.

[0044] In step S106, an etching process is performed. Here, a substrate is placed on a mounting table provided in a processing chamber, an etching gas is supplied into the processing chamber, and the substrate is exposed to the etching gas. Alternatively, plasma of the etching gas is generated or supplied into the processing chamber, and the substrate is exposed to the plasma of the etching gas. As a result, the etching target layer (silicon layer 200, silicon-containing layer 210) is etched using the etching gas or plasma of the etching gas through a mask having openings 221 (photoresist film 220 having infiltrated portions 225).

[0045] The etching gas may be a fluorine-containing gas or a mixed gas containing a fluorine-containing gas.

[0046] The fluorine-containing gas may be any of CF-based gases (containing carbon (C) and fluorine (F)), SF6, NF3, and the like.

[0047] The mixed gas containing the fluorine-containing gas may be a mixed gas of a fluorine-containing gas and an oxygen-containing gas, in which case the fluorine-containing gas may be, for example, SF6, and the oxygen-containing gas may be, for example, O2.

[0048] The etching process may be a cryo-etching process in which the substrate is cooled to a cryogenic temperature range (for example, within a range of −40° C. to −160° C.) Etching the silicon-containing layer (silicon layer 200, silicon-containing layer 210) in a cryogenic temperature range can improve the etching rate.

[0049] FIG. 2(c) is an example of a schematic cross-sectional view of the substrate in the process of step S106.

[0050] The photoresist film 220 is infiltrated with metal to form infiltrated portions 225 (S104, see FIG. 2(b)). As a result, the photoresist film 220 having the infiltrated portions 225 has improved etching resistance compared to a photoresist film without the infiltrated portions.

[0051] Furthermore, the metal that has infiltrated the photoresist film 220 is oxidized (see S105), which further improves the etching resistance of the photoresist film 220.

[0052] Furthermore, in the etching process (see S106), the metal infiltrated into the photoresist film 220 is fluorinated by exposure to a fluorine-containing gas or a plasma of the fluorine-containing gas, and a metal fluoride infiltrated portion 226 (see FIG. 2(c)) is formed. Here, the metal fluoride preferably has a boiling point of 700°C or higher. This further improves the etching resistance of the photoresist film 220 including the metal fluoride infiltrated portion 226. Furthermore, by using a metal (Ba, Ho, Sr, Ta) with a high boiling point (e.g., 2200°C or higher), the etching resistance of the photoresist film 220 including the metal fluoride infiltrated portion 226 is further improved.

[0053] These improve the etching resistance of the photoresist film 220. Therefore, deep openings (recesses) 201 reaching the rear surface of the substrate can be formed in the etching target layers (silicon-containing layer, silicon layer 200, silicon-containing layer 210). This allows the substrate to be cut (diced) into individual chips.

[0054] Furthermore, it is possible to increase the etching selectivity of the etching target layer (silicon-containing layer, silicon layer 200, silicon-containing layer 210) relative to the photoresist film 220 having the metal fluoride infiltrated portion 226. In other words, it is possible to reduce the thickness of the photoresist film 220 formed on the substrate.

[0055] Here, when the substrate is cooled to a cryogenic temperature range (specifically, within a range of −40° C. to −160° C.), if the photoresist film 220 is thick, the porous photoresist film 220 may shrink and crack. In contrast, in this embodiment, the thickness of the photoresist film 220 can be reduced, making it possible to prevent cracks from occurring in the photoresist film 220 during cryogenic cooling. Furthermore, by infiltrating a metal-containing gas into the pores of the photoresist film 220, the pores can be reduced, making it possible to prevent cracks from occurring in the photoresist film 220 during cryogenic cooling.

[0056] Furthermore, by reducing the thickness of the photoresist film 220, the processing time for the exposure and development process (see S102) can be shortened, thereby improving the productivity of substrate processing.

[0057] Furthermore, as the thickness of the photoresist film 220 increases, the aspect ratio of the opening 221 increases, and the etching rate of the silicon-containing layer (silicon layer 200, silicon-containing layer 210) decreases. In contrast, in this embodiment, the thickness of the photoresist film 220 can be reduced, and the aspect ratio of the opening 221 can be reduced, preventing a decrease in the etching rate of the silicon-containing layer (silicon layer 200, silicon-containing layer 210). This makes it possible to improve the productivity of substrate processing.

[0058] The substrate processing method has been described above, but the present disclosure is not limited to the above-described embodiments, and various modifications and improvements are possible within the scope of the gist of the present disclosure described in the claims. [Explanation of symbols]

[0059] 200 Silicon layer (etching target layer, silicon-containing layer) 201 Aperture 210 silicon-containing layer (etching target layer, silicon-containing layer) 220 Photoresist film 221 Aperture 225 Infiltrated area 226 Metal fluoride infiltration area

Claims

1. preparing a substrate having a resist film on a layer to be etched, the resist film having an opening pattern formed thereon; exposing the substrate to a metal-containing gas to infiltrate the resist film with a metal; exposing the substrate to an etching gas to etch the etching target layer through the openings in the resist film; Substrate processing method.

2. The metal to be infiltrated into the resist film has a metal fluoride whose boiling point is 700°C or higher. A substrate processing method according to claim 1.

3. the metal infiltrated into the resist film is any one of Al, Ce, Ga, Hf, In, Zn, Ba, Ho, Sr, Ta, and Sn; The substrate processing method according to claim 1.

4. the metal fluoride of the metal to be infiltrated into the resist film has a boiling point of 2200°C or higher; the metal infiltrated into the resist film is any one of Ba, Ho, Sr, and Ta; The substrate processing method according to claim 1.

5. The etching gas is a fluorine-containing gas or a mixed gas containing a fluorine-containing gas. The substrate processing method according to claim 1.

6. The aforementioned fluorine-containing gas is SF ６ That is, The substrate processing method according to claim 5.

7. The mixed gas containing the aforementioned fluorine-containing gas is SF ６ and O ２ It is a mixed gas of The substrate processing method according to claim 5 .

8. The etching process described above is: generating a plasma of the etching gas and exposing the substrate to the plasma of the etching gas; The substrate processing method according to claim 5.

9. The step of etching the etching target layer includes: forming a metal fluoride of the metal infiltrated into the resist film; The substrate processing method according to claim 5.

10. After the step of infiltrating the resist film with a metal and before the step of etching the etching target layer, The method further comprises a step of oxidizing the metal infiltrated into the resist film to form a metal oxide. The substrate processing method according to claim 1.

11. The step of forming the metal oxide includes: oxidizing the metal with an oxygen-containing gas; The substrate processing method according to claim 10.

12. The step of forming the metal oxide includes: exposing the substrate to the atmosphere to oxidize the metal by natural oxidation; The substrate processing method according to claim 10.

13. The step of infiltrating a metal into the resist film includes: The substrate is infiltrated at a temperature of 60°C or higher and 160°C or lower. The substrate processing method according to claim 1.

14. The etching process described above is: Etching the substrate at a temperature in the range of −40° C. to −160° C. The substrate processing method according to claim 1.

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