Method of forming photoresist pattern and baking apparatus

Abstract

A method of forming a photoresist pattern and a baking apparatus are provided. A photoresist layer may be formed on a substrate. An exposure process may be performed on the photoresist layer. A post exposure bake (PEB) process may be performed on the photoresist layer with a temperature gradient in the photoresist layer in a vertical direction substantially perpendicular to the upper surface of the substrate. A developing process may be performed on the photoresist layer.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority of Korean Patent Application No. 10-2023-0084165 filed in the Korean Intellectual Property Office on June 29, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] Example embodiments of the present disclosure relate to a method of forming a photoresist (photoresist) pattern and a baking apparatus. Background Art

[0004] The photoresist pattern is formed by forming a photoresist layer on a base (substrate), performing an exposure process on the photoresist layer, performing a post-exposure baking (PEB) process on the photoresist layer, and performing a development process on the photoresist layer. The photoresist layer includes a photoacid generator (PAG), and when the exposure process is performed, an acid is generated by the PAG in an exposed portion of the photoresist layer. During the PEB process, the acid can diffuse to act as a catalyst in a deprotection reaction of a polymer included in the photoresist layer, so that the polymer is easily removed during the development process.

[0005] The acid diffuses in a random (random) direction during the PEB process and thus diffuses into the unexposed portion of the photoresist layer adjacent to the exposed portion in the horizontal direction as well as the exposed portion. Therefore, the sidewall of the opening formed in the photoresist layer by removing the exposed portion of the photoresist layer during the development process has a random slope in the vertical direction and a random shape in the horizontal direction. Summary of the invention

[0006] Example embodiments provide a method of forming a photoresist pattern having enhanced characteristics.

[0007] Example embodiments provide a baking apparatus having enhanced characteristics.

[0008] According to an example embodiment of the inventive concept, a method for forming a photoresist pattern is provided. In the method, a photoresist layer may be formed on a substrate. The photoresist layer may be subjected to an exposure process. The photoresist layer may be subjected to a post-exposure bake (PEB) process in a vertical direction substantially perpendicular to an upper surface of the substrate with a temperature gradient in the photoresist layer. The photoresist layer may be subjected to a development process.

[0009] According to an example embodiment of the inventive concept, a method for forming a photoresist pattern is provided. In the method, a photoresist layer can be formed on a substrate. The photoresist layer can be subjected to an exposure process. The photoresist layer can be subjected to a post-exposure baking (PEB) process by providing the substrate in a space between a heat sink (heat sink) and a heat source in a baking chamber. The photoresist layer can be subjected to a development process.

[0010] According to an example embodiment of the inventive concept, a baking device is provided. The baking device may include a baking chamber, a heat sink in a lower portion of the baking chamber, a heat source in an upper portion of the baking chamber, and a controller configured to control the heat sink and the heat source so that a temperature gradient can be formed between an upper surface and a lower surface of a photoresist layer formed on a substrate provided in a space between the heat source and the heat sink.

[0011] The photoresist pattern according to example embodiments may have an enhanced line edge roughness (LER) characteristic and an enhanced line width roughness (LWR) characteristic. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figures 1 to 4 is a perspective view showing a method of forming a photoresist pattern according to a comparative embodiment, and Figure 5 is a plan view illustrating a method of forming a photoresist pattern.

[0013] Figure 6 is a cross-sectional view illustrating a baking apparatus according to an example embodiment of the inventive concept.

[0014] Figure 7 To illustrate a flowchart of a method of forming a photoresist pattern according to an example embodiment of the inventive concept, Figures 8 to 11 is a perspective view illustrating a method of forming a photoresist pattern according to an example embodiment of the inventive concept, and Fig.12 is a plan view illustrating a method of forming a photoresist pattern according to an example embodiment of the inventive concept. DETAILED DESCRIPTION

[0015] The above and other aspects and features of the inventive concept will become easily understood by the following detailed description with reference to the accompanying drawings. It will be understood that although the terms "first", "second" and / or "third" can be used to describe various elements, parts (components), regions, layers and / or parts in this article, these elements, parts (components), regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish an element, component (component), region, layer or part from another element, component (component), region, layer or part. Therefore, the first element, component (component), region, layer or part discussed below can be referred to as the second or third element, component (component), region, layer or part, without departing from the teaching of the inventive concept.

[0016] In the specification (and not necessarily in the claims), two directions substantially parallel to the upper surface of the substrate in the horizontal direction may be referred to as a first direction D1 and a second direction D2, respectively, and a vertical direction substantially perpendicular to the upper surface of the substrate may be referred to as a third direction D3.

[0017] Figures 1 to 4 is a perspective view showing a method of forming a photoresist pattern according to a comparative embodiment, and Figure 5 is a plan view illustrating a method of forming a photoresist pattern.

[0018] Reference Figure 1 , a photoresist layer 10 is formed on a substrate 100 .

[0019] The photoresist layer 10 includes a photo acid generator (PAG) 20 inside the photoresist layer 10 .

[0020] Reference Figure 2 , a photomask 30 is disposed over the photoresist layer 10 , and an exposure process in which light 40 is irradiated onto the photoresist layer 10 is performed.

[0021] When the exposure process is performed, the photoresist layer 10 includes an exposure portion 14 to which the light 40 is irradiated through the photomask 30 , and an unexposed portion 12 to which the light 40 is not irradiated through the photomask 30 .

[0022] The exposure portion 14 has a first width W1 in the first direction D1.

[0023] When the exposure process is performed, the acid 25 is generated by the PAG 20 in the exposed portion 14 of the photoresist layer 10 .

[0024] Reference Figure 3 , the photoresist layer 10 is subjected to a post-exposure baking (PEB) process.

[0025] When the PEB process is performed, the acid 25 in the exposed portion 14 of the photoresist layer 10 diffuses. The acid 25 diffuses in random directions, and thus some of the acid 25 also diffuses into a portion of the unexposed portion 12 adjacent to the exposed portion 14 in the first direction D1. Therefore, the acid 25 exists in a portion of the photoresist layer 10 having a second width W2 greater than the first width W1 in the first direction D1.

[0026] When the acid 25 diffuses in the exposed portion 14 and the portion of the unexposed portion 12 adjacent to the exposed portion 14, the acid 25 acts as a catalyst for the deprotection reaction of the polymer and thus removes the polymer in the exposed portion 14 and the portion of the unexposed portion 12 during a subsequent development process.

[0027] Reference Figure 4 , the photoresist layer 10 is developed to form a photoresist pattern 15 .

[0028] The developing process is performed using an alkaline developer, and during the developing process, not only the exposed portion 14 but also the portion of the unexposed portion 12 adjacent to the exposed portion 14 in which the acid 25 exists is removed. Therefore, the first opening 17 extending through the photoresist pattern 15 has a second width W2 in the first direction D1 that is greater than the first width W1.

[0029] The acid 25 diffuses in random directions in the PEB process, and thus opposite sidewalls of the first opening 17 in the photoresist pattern 15 in the first direction D1 each have not a uniform slope in the third direction D3 but have an irregular slope.

[0030] Reference Figure 5 , opposite side walls of the first opening 17 in the photoresist pattern 15 in the first direction D1 are not respectively formed in straight lines in the second direction D2, but the second width W2 of the first opening 17 in the first direction D1 varies irregularly in the second direction D2.

[0031] Therefore, the photoresist pattern 15 according to the comparative embodiment includes the first opening 17 having the second width W2 greater than the first width W1 of the initial design, and the second width W2 of the first opening 17 in the first direction D1 varies along both the second direction D2 and the third direction D3. Therefore, the photoresist pattern 15 has a degraded line edge roughness (LER) characteristic and a degraded line width roughness (LWR) characteristic.

[0032] Figure 6 1 is a cross-sectional view showing a baking apparatus according to an exemplary embodiment of the present inventive concept. As used herein, the term "apparatus" is interchangeable with "device".

[0033] Reference Figure 6 , the baking apparatus 200 may include a baking chamber 210 , a heat source 220 , a heat sink 230 , and a controller 240 .

[0034] The heat source 220 may be disposed in an upper portion of the baking chamber 210, and the heat sink 230 may be disposed in a lower portion of the baking chamber 210. Figure 6 As shown in , the heat source 220 and the heat sink 230 may be spaced apart from each other in the vertical direction.

[0035] The heat source 220 may include, for example, a laser generator, a lamp heater, or the like.

[0036] The heat sink 230 may include, for example, a chill plate, a cold plate, a cooling plate, etc.

[0037] The substrate 300 may be mounted on and contact the heat sink 230, and the photoresist layer 310 may be formed on the substrate 300. The vertical direction may be a thickness direction of the photoresist layer 310.

[0038] In example embodiments, the heat sink 230 may function as an electrostatic chuck (ESC) that can fix the substrate 300 using electrostatic force. For example, the heat sink 230 may be disposed in the ESC. In example embodiments, a material having high thermal conductivity, such as helium (He), may be disposed between the heat sink 230 and the substrate 300.

[0039] The controller 240 may control the operations of the heat source 220 and the heat sink 230. Therefore, the controller 240 may control the temperature of the substrate 300 between the heat source 220 and the heat sink 230, particularly, the temperature of the photoresist layer 310.

[0040] In example embodiments, the photoresist layer 310 on the substrate 300 may be provided between the heat source 220 and the heat sink 230 and may have a temperature gradient in a vertical direction. That is, the heat provided by the heat source 220 and the heat discharged by the heat sink 230 may be controlled by the controller 240, and thus a temperature gradient may be formed between the upper surface and the lower surface of the photoresist layer 310 that may be provided between the heat source 220 and the heat sink 230.

[0041] In example embodiments, the difference between the temperature of the upper surface of the photoresist layer 310 and the temperature of the lower surface of the photoresist layer 310 may be in a range of greater than about 0° C. to about 300° C. In some embodiments, the temperature difference between the upper and lower surfaces of the photoresist layer 310 may be greater than 0° C., for example, greater than or equal to 5° C. and up to about 300° C.

[0042] The heat source 220 and the heat sink 230 may be disposed in the upper part and the lower part of the baking device 200, respectively, however, the inventive concept may not be limited thereto. For example, the heat source 220 and the heat sink 230 may be disposed in the lower part and the upper part of the baking device 200, respectively. That is, the heat source 220 and the heat sink 230 may be disposed above and below the substrate 300 on which the photoresist layer 310 is formed, and may be spaced apart from each other in the vertical direction, so that a temperature gradient may be formed in the photoresist layer 310 in the vertical direction.

[0043] Figure 7 To illustrate a flowchart of a method of forming a photoresist pattern according to an example embodiment of the inventive concept, Figures 8 to 11 is a perspective view illustrating a method of forming a photoresist pattern according to an example embodiment of the inventive concept, and Fig.12 is a plan view illustrating a method of forming a photoresist pattern according to an example embodiment of the inventive concept.

[0044] Reference Figure 7 and 8 In step S10 , a photoresist layer 310 may be formed on a substrate 300 .

[0045] The substrate 300 may include silicon, germanium, silicon-germanium, or a III-V compound semiconductor such as GaP, GaAs, or GaSb. In example embodiments, the substrate 300 may be a silicon-on-insulator (SOI) substrate or a germanium-on-insulator (GOI) substrate.

[0046] In example embodiments, the photoresist layer 310 may be formed on the substrate 300 through a spin coating process. In example embodiments, the photoresist layer 310 may be a chemically amplified resist (CAR), and may include a polymer and a PAG 320 therein.

[0047] In step S20 , a pre-baking process may be performed on the photoresist layer 310 .

[0048] In an example embodiment, the pre-bake process may be performed at Figure 6 When the pre-bake process is performed, the solvent and volatile materials included in the photoresist layer 310 may be removed.

[0049] Reference Figure 7 and 9 In step S30 , a photomask 330 may be disposed over the photoresist layer 310 , and an exposure process may be performed so that light 340 may be irradiated onto the photoresist layer 310 .

[0050] When performing the exposure process, the photoresist layer 310 may include an exposure portion 314 to which light 340 is irradiated through the photomask 330 and an unexposed portion 312 to which the light 340 is not irradiated through the photomask 330. The exposure portion 314 may have a third width W3 in the first direction D1.

[0051] When the exposure process is performed, an acid 325 may be generated by the PAG 320 in the exposed portion 314 of the photoresist layer 310 .

[0052] Reference Figure 7 and 10 In step S40 , a post exposure bake (PEB) process may be performed on the photoresist layer 310 .

[0053] Available Figure 6 The PEB process is performed by using the baking equipment shown in . Therefore, during the PEB process, the temperatures of the heat source 220 and the heat sink 230 respectively disposed above and below the substrate 300 may be controlled, and a temperature gradient may be formed in the photoresist layer 310 which may be disposed between the heat source 220 and the heat sink 230 in the vertical direction. The PEB process may include providing the substrate 300 on which the photoresist layer 310 is formed into a baking chamber 210 including the heat source 220 and the heat sink 230, and the heat source 220 and the heat sink 230 may be spaced apart from each other in the vertical direction. In other words, the PEB process may include providing the substrate 300 on which the photoresist layer 310 is formed into a space between the heat source 220 and the heat sink 230 which may be spaced apart from each other in the vertical direction.

[0054] When the PEB process is performed with a temperature gradient in the vertical direction in the photoresist layer 310, the acid 325 in the exposed portion 314 of the photoresist layer 310 may diffuse into adjacent regions, however, the acid 325 may diffuse not primarily in random directions but in a vertical direction substantially perpendicular to the upper surface of the substrate 300 through a thermophoresis phenomenon in the photoresist layer 310. In some embodiments, the amount of the acid 325 diffused in the vertical direction may be much greater than the amount of the acid 325 diffused in other directions.

[0055] The thermophoresis phenomenon can be represented by the following mathematical equation.

[0056] <Mathematical equation>

[0057]

[0058] χ is the particle concentration, D is the diffusion coefficient, and D T is the thermal diffusion coefficient.

[0059] Concentration variation of the acid 325 included in the photoresist layer 310 according to time That is, the movement rate of the acid 325 may be proportional to the temperature gradient (▽T) of the photoresist layer 310, and over time, the acid 325 may mainly move to the upper surface of the photoresist layer 310 having a relatively high temperature through the heat source 220, or to the lower surface of the photoresist layer 310 having a relatively low temperature through the heat sink 230.

[0060] Therefore, during the PEB process, the amount of movement of the acid 325 in the vertical direction may be greater than the amount of random movement of the acid 325 in the horizontal direction. The acid 325 may diffuse into the exposed portion 314 and a portion of the unexposed portion 312 adjacent to the exposed portion 314 in the first direction D1 to exist in a portion of the photoresist layer 310 having a fourth width W4 greater than the third width W3 of the exposed portion 314 in the first direction D1. However, the fourth width W4 may be smaller than the second width W2 of the portion of the photoresist layer 10 in the first direction D1 in which the acid 25 exists after the PEB process in the comparative embodiment.

[0061] When the acid 325 diffuses into the exposed portion 314 and the portion of the unexposed portion 312 adjacent to the exposed portion 314 , the acid 325 may act as a catalyst for a deprotection reaction of the polymer.

[0062] Reference Figure 7 and 11 In step S50 , the photoresist layer 310 may be subjected to a development process to form a photoresist pattern 315 .

[0063] The developing process may be performed using an alkaline developing solution, and during the developing process, not only the exposed portion 314 but also the portion of the unexposed portion 312 adjacent to the exposed portion 314 in which the acid 325 is present may be removed. Therefore, the second opening 317 extending through the photoresist pattern 315 may have a fourth width W4 greater than the third width W3 of the exposed portion 314 in the first direction D1.

[0064] As described above, during the PEB process, the amount of vertical movement of the acid 325 may be greater than the amount of random horizontal movement of the acid 325 , and thus opposite sidewalls of the second opening 317 in the photoresist pattern 315 in the first direction D1 may each have an almost uniform slope.

[0065] In addition, refer to Fig.12 , opposite sidewalls of the second opening 317 in the photoresist pattern 315 in the first direction D1 may each be almost straight lines in the second direction D2.

[0066] Therefore, even if the photoresist pattern 315 may have a second opening 317 having a fourth width W4 slightly larger than the initially designed third width W3 in the first direction D1, the fourth width W4 of the second opening 317 in the first direction D1 may be almost constant or uniform along both the second direction D2 and the third direction D3. Therefore, the photoresist pattern 315 may have an enhanced line edge roughness (LER) characteristic and an enhanced line width roughness (LWR) characteristic.

[0067] Since the photoresist pattern 315 may have an enhanced LER characteristic and an enhanced LWR characteristic, a pattern formed by etching a target layer through an etching process using the photoresist pattern 315 as an etching mask may have a desired shape and size.

[0068] While the inventive concept has been shown and described with reference to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the inventive concept as set forth in the following claims.

Claims

1. A method for forming a photoresist pattern, the method comprising: forming a photoresist layer on a substrate; performing an exposure process on the photoresist layer; performing a post-exposure bake (PEB) process on the photoresist layer with a temperature gradient in the photoresist layer in a vertical direction substantially perpendicular to the upper surface of the substrate; and The photoresist layer is subjected to a developing process. 2 . The method of claim 1 , wherein the photoresist layer comprises a photoacid generator (PAG).

3. The method of claim 2, wherein an acid is generated by the PAG during the exposure process, and Wherein during the PEB process, the acid diffuses in the vertical direction.

4. The method according to claim 1, wherein the PEB process comprises providing a substrate on which the photoresist layer is formed into a baking chamber, and Wherein the baking chamber comprises: a heat source above an upper surface of the photoresist layer on the substrate; and A heat sink is below a lower surface of the photoresist layer on the substrate.

5. A method for forming a photoresist pattern, the method comprising: forming a photoresist layer on a substrate; performing an exposure process on the photoresist layer; Performing a post-exposure bake (PEB) process on the photoresist layer by providing the substrate in a space between a heat sink and a heat source in a baking chamber; and The photoresist layer is subjected to a developing process. 6 . The method of claim 5 , wherein the heat source and the heat sink are located in an upper portion and a lower portion of the baking chamber, respectively.

7. The method according to claim 1 or 5, wherein the heat source comprises a laser generator or a lamp heater, and The heat sink comprises a chill plate.

8. The method of claim 7, wherein a lower surface of the substrate contacts an upper surface of the chill plate.

9. The method of claim 5, wherein the photoresist layer comprises a photoacid generator (PAG).

10. The method according to claim 9, wherein the heat sink and the heat source are spaced apart from each other in a vertical direction, and acid is generated by the PAG during the exposure process, and During the PEB process, the acid diffuses in the vertical direction.

11. The method according to claim 1 or 5, wherein: In the PEB process, the temperature difference between the upper and lower surfaces of the photoresist layer is greater than 0°C and up to about 300°C.

12. The method according to claim 1 or 5, further comprising performing a pre-baking process on the photoresist layer before performing the exposure process.

13. The method of claim 1 or 5, wherein the photoresist layer is a chemically amplified resist (CAR).

14. Baking equipment, including: Baking room; a heat sink in a lower portion of the baking chamber; a heat source in an upper portion of the baking chamber; and A controller configured to control the heat sink and the heat source so that a temperature gradient is formed between an upper surface and a lower surface of a photoresist layer formed on a substrate provided in a space between the heat source and the heat sink.

15. The baking apparatus according to claim 14, wherein the heat source comprises a laser generator or a lamp heater, and The heat sink comprises a chill plate.

Images