TW486740B - Improved method for controlling critical dimension during high temperature photoresist reflow process by ultraviolet light irradiation - Google Patents

Abstract

The present invention discloses an improved photoresist reflow process, which comprises (1) irradiating photoresist to form cross-linking on its surface, and (2) no additional processing of any structure or the bottom side of the photoresist required. After the critical dimension of the photoresist is controlled, any follow-up processes such as etching or ion implanting can be utilized to fabricate semiconductor device with small critical dimension.

Description

486740 V. Description of the invention (1) 5-1 Field of invention: The present invention relates to a method for controlling critical dimensions of semiconductor manufacturing (critica 1 dimensi ο η; CD), and in particular to a method for controlling photoresist by ultraviolet light irradiation. In the method, a bond (cr 0 ss 1 inking) is generated on the surface of the photoresist to reach a fixed shape of the photoresist to control the critical size of the photoresist. 5-2 Background of the Invention ... w 41 6¾ Critical dimension (CD) is a critical factor in manufacturing semiconductor components, and it represents the smallest line width that can be achieved by lithographic processes. Obviously, as the size of semiconductor products is constantly controlled, the size of the boundary will also be significantly reduced. The general process of the lithography process from covering photoresist to developing can be summarized as follows: (1) Dehydration bake. (2) Priming. (3) Photoresist coating. (4) soft bake or pre-bake. (5) exposure. (6) P0St exposure bake. (7) Development ^ shadow (development). (8) Hard back. (9) Heat reflow (r e f ο 1 w). Basically, in the process of lithography, from the earliest dewatering baking and coating, to

486740 V. Description of the invention (2)-The purpose of the last 1 hard bake step is to strengthen the photoresist's ability to adhere to the surface of the wafer and define the photoresist profile. The soft bake purpose is to remove the photoresist. After the exposure, baking will reduce the standing wave effect. The final hard roasting can remove the residual solvent and water vapor, and reduce the dutgass i ng. The hot-return machine usually uses a hot pad ( The main operating conditions for hot plate) are time and temperature, especially the mastery of temperature affects the final results. Generally, the temperature of hot reflow is higher than the soft baking and post-exposure baking. At this temperature, the photoresist will soften and begin to produce a viscous flow. This temperature is called the glass breaking temperature ( glass transition temperature). This feature is used in the thermal reflow process to shrink the original hole pattern (contact / Via hole). In the actual process, when the critical size of the photoresist after the pattern transfer is less than 18 μm, such as the first A photomask The critical dimension W1 of the 30 pattern is known by a light source 40, and the transmitted light 401 is transferred to the photoresist layer 30. The critical dimension is W 2. However, the bottleneck is encountered during the thermal reflow step, and the thermal reflow is used for the thermal pad method. The temperature is above the glass transition temperature of the photoresist. Although the photoresist can produce viscous flow and shrink the pattern, it is affected by cohesion. Undercut) phenomenon, as shown in Figure 2B, the critical size w 3 of the photoresist after thermal reflow process will be less than W2 due to the deformation of the photoresist 20, but the critical size control is unstable and the contour control

Page 5 486740 V. Description of the invention (3) The system is not good, and it has a deviation in the selectivity of the blocking ability of subsequent processes such as etching and ion implantation. Therefore, according to the above description, controlling the critical size is an important task in the development of semiconductor device manufacturing processes, and developing a method that can not only control the critical size but also avoid other complex programming techniques has become an urgent topic. 5-3 Purpose and summary of the invention; The main object of the present invention is to propose a method for effectively controlling the critical dimension of a semiconductor device. Another object of the present invention is to control the critical size of the photoresist by irradiating the photoresist with ultraviolet light to cause bonding on the photoresist surface and avoiding excessive viscous flow. Another object of the present invention is to avoid complicated processes and difficulties in improving the lithography system. Another object of the present invention is to effectively control the critical size of the photoresist after all the patterns of the photomask are correctly transferred to the photoresist.

486740 V. Description of the invention (4) Another object of the present invention is to provide a method that can not only control the critical size of semiconductor elements, but also maintain the manufacturing of semiconductor elements at a high capacity. In order to achieve the above-mentioned object of the present invention, the method provides a method for controlling critical dimensions by using ultraviolet light to improve high-temperature photoresistance and thermal reflow, which at least includes forming a photoresist on a substrate through a photomask and a lithography process, so that The pattern of the photomask is all transferred to the photoresist correctly. Then, a thermal reflow process is performed by a hot pad method to generate a viscous flow. At the same time, the photoresist is irradiated with ultraviolet light, and the photoresist surface is bonded to form a fixed profile. Then, the effect of controlling the critical size can be achieved by fixing the photoresist profile. Therefore, the method of the present invention is to control the critical size of the photoresist by irradiating the photoresist with ultraviolet light to form a bond on the surface of the photoresist to fix the contour. Obviously, the method provided by the present invention is an improved photoresistive thermal reflow method, and the main improvements include: (1) using ultraviolet light to irradiate the photoresist to form a bond on its surface. (2) Do not add processes to any structure in the photoresist or its bottom. Of course, when the critical size of the photoresist is controlled, any subsequent process, such as etching and ion implantation, can be used to form a semiconductor device with a small critical size. 5-4 Invention Details:

Page 7 486740 V. Description of the invention (5) The method of the present invention is applied to a semiconductor device, and the ultraviolet light is irradiated on the photoresist, so that the surface of the photoresist forms a bond and fixes the contour to control the critical size of the photoresist. First, as shown in FIG. 2A, a photomask 30 is provided, which has a pattern corresponding to a plurality of lines and a plurality of openings. The pattern of the photomask 30 corresponds to at least one semiconductor structure, among which possible semiconductor structures There are at least contact holes, interconnects and gates. In addition, the critical size of the photomask 30 is W4. Secondly, the lithography process is performed by the light 401 emitted from the light source 40. The source of the light source is ultraviolet light generated by a mercury arc lamp or g line (g 1 ine) or i line (I line) or KrF. Laser or electron beam (e-bean) to transfer all the patterns of photomask 30 to photoresist 20, where photoresist 20 covers the substrate 10, and the photoresist used in this embodiment is usually Positive photoresist, photoresist coating is usually performed by spin coating. Furthermore, each structure 25 in the photoresist 20 has a specific aspect ratio, wherein the pinch energy types of the structure 25 include at least voids, holes, and lines, and the critical size of the photoresist 20 is W 5 , W 5 and W 4 are the same size. In addition, the substrate 10 includes at least one semiconductor element, such as a metal oxide semiconductor, a capacitor, and an element isolation structure. Incidentally, the composition of the photoresist 20 includes a resin, a photosensitizer, and a solvent, and the thickness of the photoresist 20 is about several angstroms to several micrometers.

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450 / 4U 5. Description of the invention (6) As shown in the second figure B, corresponding to the positive photoresist and then removed by hard baking, the normal temperature is controlled to about 1 to 2 minutes in the thermal reflow process, and the result is 2 0 3 'This bond is established, and at the same time, the control temperature is 2 0 2' which uses the purple temperature to reach the photoresistance 2 0 2 'intermolecular transport j W 6. After this treatment, the subsequent processability can also be controlled in this embodiment. Bonding, and opening or simultaneously. Hot steps. Or use the above only to define the present invention of Zhongyanqingzhong, in which the step of irradiating the photoresist with ultraviolet light to heat the photoresist surface with a hot pad to remove residual solvents can be divided into the following steps: first, ultraviolet light irradiation, and then the hot pad Adding ultraviolet light to irradiate the photoresist is performed simultaneously with the heating of the hot pad. In the pattern transfer process, Hu Jinbu ’is developed after exposure and development, and the developer is an alkaline solution such as NaOH or KOH. Residual solvents. This method uses a hot pad 50 ° C, passing 100 ° C to about 130 ° C, for a time of about 1 to 2 minutes. After that, the temperature is controlled at about 130 ° C to about 160 ° C. The time force is used to irradiate the photoresist 20 with ultraviolet light. This ultraviolet light source 60 generates ultraviolet light 6 0 1 to make the photoresist 20 The bond t to the curing effect is generated on the surface, so that the photoresistive contour 70 can be fixed to the dimension W 6, as shown in the second figure C. The external light 6 0 1 irradiates the photoresist 2 0 method. The glass transition temperature during thermal reflow is difficult to cure because of the bond on the surface. Therefore, the photoresist critical size W6 can be controlled. It is equal to the mask critical dimension W4. In order to improve the blocking ability of etching and ion implantation, the critical size of the contact hole or via hole is selected. This is only a preferred embodiment of the present invention, and is not intended to limit the scope of the patent; all others that do not depart from the scope of the present invention

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Page ί 486740 Brief description of the drawing The first A is the exposure method of the general traditional lithography process. The first B diagram is the deformation and undercut of the exposed photoresist obtained according to the first A diagram. The second A picture, like the first A picture, is a photoresist exposure process. Fig. 2B is the invention of baking with a hot pad and increasing the photoresistance of the ultraviolet light source. The second C picture is the representative symbol of the main part of the critical size of the fixed photoresist shape control obtained from the second B picture: 10 substrate 2 0 photoresist 2 5 photoresist 20 structure 2 0 1 Spherical 2 0 2 Undercut 2 0 3 Photoresist surface to form a bond 3 0 Mask 4 0 Light source for exposure 4 0 1 Light for exposure 5 0 Thermal pad

Page 11 486740 Brief description of the drawing 6 0 UV light source 6 0 1 Ultraviolet light rays 7 0 Surface-formed photoresist with fixed shape W1 Critical dimension of photomask pattern W 2 Critical dimension of pattern transfer photoresist W 3 The critical size of the photoresist produced by thermal re-transmission W4 The critical size of the photomask pattern W 5 The critical size of the pattern transfer photoresist W 6 The critical size of the photoresist through ultraviolet light irradiation and thermal reflow treatment

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Claims (1)

486740 VI. Application Patent Scope 1. A method for controlling critical size in pattern transfer, the method includes at least the following steps: coating a photoresist layer on a substrate; providing a photomask, and providing a pattern on the photomask Providing a light source to expose the pattern on the photomask to the photoresist layer; providing a solvent as a developer to reveal the latent pattern transferred by the photoresist layer, performing an ultraviolet light irradiation process; and performing a thermal reprocessing Reflow process. ❹ 2. The method according to item 1 of the scope of patent application, wherein the coated photoresist layer is formed by the following steps, which at least include de-baking, coating, photoresisting and pre-baking. 3. The method of claim 1, wherein the composition of the photoresist layer is composed of the following components, which include at least a resin, a photosensitizer, and a solvent. 4. The method of claim 1 in which the photoresist layer is applied by spin coating. ❶ 5. The method according to item 1 of the patent application range, wherein the thickness of the photoresist layer is from several angstroms to several micrometers. 6. The method of claim 1 in which the photomask has Page 13 486740 6. Scope of Patent Application The pattern of plural lines and plural openings. 7. The method according to item 1 of the patent application, wherein the exposure light source is ultraviolet light generated by a mercury arc lamp or deep ultraviolet light emitted by a KrF laser. 8. The method according to item 1 of the patent application, wherein This developer corresponds to positive photoresist development and is a test solution such as Na 0 Η or K 0 Η. 9. For the method of applying for the first range of the specialty scope, wherein the light source of the ultraviolet irradiation process is the ultraviolet light generated by a mercury arc lamp. 10. The method according to item 1 of the patent application scope, wherein the thermal reflow process uses a hot pad method. 11. A method for controlling critical dimensions in pattern transfer, the method includes at least the following steps: coating a photoresist layer on a substrate; providing a photomask, providing a pattern on the photomask; providing a light source to A pattern on the photomask is exposed on the photoresist layer; a solvent is provided as a developer to reveal the potential pattern transferred by the photoresist layer; a thermal reflow process is performed; and an ultraviolet light irradiation process is performed. Page 14 486740 VI. Application for Patent Scope 1 2. The method according to item 11 of Patent Application Scope, wherein the coated photoresist layer is formed by the following steps, which at least include dewatering baking, primer coating, Photoresist and pre-bake. 1 3. The method according to item 11 of the scope of patent application, wherein the composition of the photoresist layer is composed of the following components, which include at least a resin, a photosensitizer, and a solvent 1 4. The method according to item 11 of the scope of patent application Method, wherein the photoresist layer is performed by spin coating. 15. The method according to item 11 of the patent application range, wherein the thickness of the photoresist layer is from several angstroms to several micrometers. 16. The method according to item 11 of the patent application, wherein the photomask has a pattern corresponding to a plurality of lines and a plurality of openings. 1 7. The method according to item 11 of the scope of patent application, wherein the exposure light source is ultraviolet light generated by a mercury arc lamp or deep ultraviolet light emitted by KrF laser. 0 1. The method of item, wherein the developer is a basic solution such as NaOH or K0Η, which corresponds to positive photoresist development. 1 Page 15 486740 6. Scope of patent application 1 9. The method according to item 11 of the scope of patent application, wherein the thermal reflow process uses a hot pad method. 20 · The method according to item 11 of the scope of patent application, wherein the ultraviolet light irradiation process light source uses ultraviolet light generated by a mercury arc lamp. 2 1. —A method for controlling a critical dimension in a pattern transfer, the method includes at least the following steps: coating a photoresist layer on a substrate; providing a photomask, providing a pattern on the photomask; providing a light source Expose the pattern on the photomask to the photoresist layer; provide a solvent as a developer to reveal the potential pattern transferred by the photoresist layer, perform an ultraviolet light irradiation process; and simultaneously perform a thermal reflow process. 2 2 · The method according to item 21 of the patent application range, wherein the coated photoresist layer is formed by the following steps, which at least include dewatering baking, coating, photoresisting and prebaking. 2 3. The method according to item 21 of the scope of patent application, wherein the composition of the photoresist layer is composed of the following components, which include at least a resin, a photosensitizer, and a solvent Page 16 486740 6. Application scope of patent 24. The method according to item 21 of the scope of patent application, wherein the photoresist layer is applied by spin coating. 25. The method according to item 21 of the patent application, wherein the thickness of the photoresist layer is about several angstroms to several micrometers. 26. The method of claim 21, wherein the photomask has a pattern corresponding to a plurality of lines and a plurality of openings. 2 7. The method according to item 21 of the scope of patent application, wherein the exposure light source is ultraviolet light generated by a mercury arc tube or deep ultraviolet light emitted by a KrF laser. 28. If so, please apply the method according to item 21 of the patent, wherein the developer corresponds to positive photoresist development and is a test solution such as NaOH or K0Η. 29. The method according to item 21 of the patent application scope, wherein the light source for the ultraviolet irradiation process uses ultraviolet light generated by a mercury arc lamp. 30. The method according to item 21 of the patent application scope, wherein the thermal reflow process uses a thermal pad method. Page 17