Device and method for improving wafer line width uniformity

Abstract

The invention discloses a device and method for improving wafer line width uniformity, and belongs to the technical field of semiconductor integrated circuit manufacturing. The device comprises a hot plate unit and a cold plate unit which are sequentially arranged; arranging the hot plate unit and the cold plate unit between a gluing process and an exposure process in a photoetching process; the hot plate unit is provided with a plurality of real-time temperature monitoring points. The method comprises the following steps: after the step of gluing a wafer is completed, transferring the wafer (4) to a hot plate unit, controlling the temperature range to be 100-200 DEG C, and controlling the time to be 60-80 seconds; transferring the wafer to a cold plate unit until the wafer is cooled to room temperature; and continuing to finish the exposure step and the developing step. According to the device, the uniform distribution of the photoresist is improved, so that the penetration depth of exposure light rays at each part of the surface of the wafer is more consistent, and the problem of non-uniform line width of the wafer caused by the thickness difference of the photoresist is further reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor integrated circuit manufacturing, and relates to a device and method for improving wafer line width uniformity. Background Art

[0002] I-line photolithography usually refers to a technology that uses I-line (i.e. ultraviolet light of a specific wavelength, usually 365 nanometers) as a light source for photolithography during semiconductor manufacturing. This process is one of the most complex and critical steps in the production process of semiconductor chips, and directly determines the process level and performance level of the chip. The I-line photolithography process mainly includes the following steps: Gluing: Apply a uniform and highly adherent I-line photoresist film on the surface of the semiconductor material (such as silicon wafer). Photoresist is a photosensitive material that can undergo chemical changes under light. Exposure: Use an I-line light source to irradiate the photoresist, so that the photosensitive components in the photoresist undergo chemical changes (such as photolysis or polymerization) in the illuminated area, thereby forming a latent image corresponding to the mask pattern on the photoresist layer. Development: Immerse the exposed silicon wafer in the developer, and use the developer to react with the chemically changed part of the photoresist to remove it, thereby forming a clear pattern on the photoresist layer. Etching: Use an etchant to etch the semiconductor material under the photoresist layer and transfer the pattern to the semiconductor material. The etching process can be wet etching (using chemical solutions) or dry etching (using plasma or high-energy ion beams). Stripping: Finally, the photoresist is completely removed from the surface of the semiconductor material to complete the entire photolithography process. Wafer line width is a crucial concept in wafer production and chip manufacturing. It mainly refers to the line width of the internal circuit of the chip, that is, the minimum wire width that can be achieved by the IC (integrated circuit) production process. This size is one of the main indicators to measure the advanced level of chip technology. The uniformity of the photoresist thickness on the semiconductor material is crucial to the uniformity of the wafer line width.

[0003] In the CMOS product process, polycrystalline lines will cross the active area and the field area, and there will be a step difference between the two areas, such as Figure 6 As shown, the thickness of the photoresist in the active area is d1, and the thickness of the photoresist in the field area is d2. There is a difference in the thickness of the photoresist in the two areas, which will lead to a difference in the line width between the field area and the active area. In the existing coating step, the uniformity of the thickness of the photoresist is difficult to control, resulting in uneven line width of the subsequent wafer, affecting chip performance. The existing methods for controlling the thickness of the photoresist mainly include hardening the film in stages, utilizing the material viscosity and self-leveling properties of the photoresist, rotating the wafer in multiple stages (different rotation angles and durations in each stage), and improving the uniformity of the thickness of the photoresist; using a hot plate including no less than two heating rings for baking after exposure, and the set temperatures of the heating rings are different. The control effect on the uniformity of the thickness of the photoresist is not ideal. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problem in the prior art that the thickness uniformity of the photoresist in the coating process is not ideally controlled, and to provide a device and method for improving the uniformity of the wafer line width.

[0005] In a first aspect, the present invention provides a device for improving the uniformity of wafer line width, comprising a hot plate unit and a cold plate unit arranged in sequence; the hot plate unit and the cold plate unit are arranged between the glue coating process and the exposure process in the photolithography process; the hot plate unit is provided with a plurality of real-time temperature monitoring points.

[0006] Further improvements are: The hot plate unit comprises a hot plate, and electric heating wires are evenly arranged inside the hot plate; a hot plate cover is arranged on the upper part of the heating plate; when the hot plate unit is working, the wafer is placed between the upper surface of the heating plate and the hot plate cover.

[0007] The heating wire is in a spiral structure inside the heating plate.

[0008] The heating wire is coiled twice inside the heating plate; the number of real-time temperature monitoring points is 9; one real-time temperature monitoring point is arranged at the center point of the heating wire, and four real-time temperature monitoring points are evenly arranged at the positions of the inner circle heating wire and the outer circle heating wire respectively; the four real-time temperature monitoring points arranged at the positions of the inner circle heating wire and the outer circle heating wire are arranged at staggered intervals.

[0009] The temperature control range of the hot plate unit is 100°C to 200°C, the heating time is 60s to 80s, the temperature control accuracy is ±0.5°C, and the temperature difference at each position of the hot plate unit is less than 1°C.

[0010] The cold plate unit includes a cold plate, and water pipes are evenly arranged inside the heating plate; a cold plate upper cover plate is arranged on the upper part of the cold plate; when the cold plate unit is working, the wafer is placed between the upper surface of the cold plate and the cold plate upper cover plate.

[0011] The water pipe is a spiral structure inside the cold plate; low-temperature medium flows through the water pipe.

[0012] The temperature control range of the cold plate unit is 20°C to 35°C, and the temperature control accuracy is ±3°C.

[0013] In a second aspect, the present invention provides a method for improving wafer line width uniformity based on the above device, comprising the following steps: Step 1: After the wafer is coated with glue, the wafer is transferred to a hot plate unit, the temperature range is controlled at 100°C to 200°C, and the time is controlled at 60s to 80s; Step 2: After completing step 1, transfer the wafer to a cold plate unit until the wafer cools to room temperature; Step 3: After the wafer cools down to room temperature, continue to complete the exposure step and the development step.

[0014] Further improvements are: The wafer was transferred to the hot plate unit at a temperature of 120°C for 60 seconds.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The invention discloses a device for improving the uniformity of wafer line width. By sequentially arranging a hot plate unit and a cold plate unit between the coating process and the exposure process in the traditional photolithography process, the uniformity of the photoresist thickness at different steps is optimized, thereby improving the uniformity of the wafer line width. In the traditional photolithography process, the surface of the wafer often causes uneven photoresist coating due to the undulating terrain (such as steps, grooves, etc.), which directly affects the accuracy of subsequent exposure. The hot plate unit of the invention effectively promotes the flow and spreading of the photoresist on the surface of the wafer by precise temperature control heating, especially for the high step area, it can reduce the accumulation and loss of the photoresist. The cold plate unit immediately following quickly cools the wafer to a suitable temperature, fixes the photoresist shape, and prevents the thickness change caused by temperature fluctuations, thereby significantly improving the uniformity of the thickness of the photoresist on the entire wafer surface. The uniformity of the photoresist thickness directly determines the line width accuracy of the pattern after exposure. The device improves the uniform distribution of the photoresist, so that the penetration depth of the exposure light at various locations on the wafer surface is more consistent, thereby reducing the problem of uneven exposure caused by the difference in photoresist thickness. This greatly improves the ability to accurately control the line width on the wafer, helps to achieve a more sophisticated semiconductor device structure, and meets the needs of high-performance integrated circuit manufacturing. The device of the present invention is flexible in design and can be easily integrated into the existing photolithography process line without making major changes to the overall process flow. At the same time, its temperature control accuracy is high, and it can be optimized and adjusted for different types of photoresists and wafer materials, enhancing the compatibility and adaptability of the process.

[0016] The present invention discloses a method for improving the uniformity of wafer line width. After the wafer is coated with glue, the wafer is transferred to a hot plate unit, the temperature range is controlled to be 100°C to 200°C, and the time is controlled to be 60s to 80s; then the wafer is transferred to a cold plate unit until the wafer is cooled to room temperature, and the exposure step and the development step are continued. The method effectively reduces problems such as poor exposure and line width deviation caused by uneven thickness of photoresist, thereby reducing the scrap rate and rework rate, and significantly improving production efficiency and the yield rate of the final product. This not only saves production costs, but also speeds up the product launch and enhances market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A side view of a hot plate unit of a device for improving wafer line width uniformity in the present invention; Figure 2 A top view of a hot plate unit of a device for improving wafer line width uniformity in the present invention; Figure 3 A side view of a cold plate unit of a device for improving wafer line width uniformity in the present invention; Figure 4 A top view of a cold plate unit of a device for improving wafer line width uniformity in the present invention; Figure 5 A schematic diagram of the positions of nine real-time temperature monitoring points in a hot plate unit of a device for improving wafer line width uniformity in the present invention; Figure 6 Schematic diagram of the difference in photoresist thickness in different areas of the wafer; Figure 7 It is a trend diagram of the line width difference between the field area and the active area at different hot plate temperatures in the present invention.

[0019] Among them: 1-hot plate; 2-heating wire; 3-cover plate on hot plate; 4-wafer; 5-cold plate; 6-water pipe; 7-cover plate on cold plate; 8-temperature test board. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0023] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0024] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0025] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings: See also Figure 1 and Figure 3 , an embodiment of the present invention discloses a device for improving the uniformity of wafer line width, including a hot plate unit and a cold plate unit which are arranged in sequence; the hot plate unit and the cold plate unit are arranged between the glue coating process and the exposure process in the photolithography process; the hot plate unit is provided with a number of real-time temperature monitoring points. The hot plate unit includes a hot plate 1, and electric heating wires 2 are evenly arranged inside the hot plate 1; a hot plate cover plate 3 is arranged on the upper part of the hot plate 1; when the hot plate unit is working, the wafer 4 is placed between the upper surface of the hot plate 1 and the hot plate cover plate 3. Figure 2As shown, the heating wire 2 is a spiral structure inside the heating plate 1. The heating wire 2 spirals 2 times inside the heating plate 1; the number of real-time temperature monitoring points is 9; a real-time temperature monitoring point is set at the center of the heating wire 2, and 4 real-time temperature monitoring points are evenly set at the positions of the inner circle heating wire and the outer circle heating wire; the 4 real-time temperature monitoring points set at the positions of the inner circle heating wire and the outer circle heating wire are staggered. The temperature control range of the hot plate unit is 100℃~200℃, the heating time is 60s~80s, the temperature control accuracy is ±0.5℃, and the temperature difference at each position of the hot plate unit is less than 1℃.

[0027] See also Figure 3 The cold plate unit includes a cold plate 5, and water pipes 6 are evenly arranged inside the heating plate; a cold plate upper cover plate 7 is arranged on the upper part of the cold plate 5; when the cold plate unit is working, the wafer 4 is placed between the upper surface of the cold plate 5 and the cold plate upper cover plate 7. The water pipe 6 is a spiral structure inside the cold plate 5; a low-temperature medium is passed inside the water pipe 6. The temperature control range of the cold plate unit is 20℃~35℃, and the temperature control accuracy is ±3℃.

[0028] The invention discloses a device for improving the uniformity of wafer line width. By sequentially arranging a hot plate unit and a cold plate unit between the coating process and the exposure process in the traditional photolithography process, the uniformity of the photoresist thickness at different steps is optimized, thereby improving the uniformity of the wafer line width. In the traditional photolithography process, the surface of the wafer often causes uneven photoresist coating due to the undulating terrain (such as steps, grooves, etc.), which directly affects the accuracy of subsequent exposure. The hot plate unit of the invention effectively promotes the flow and spreading of the photoresist on the surface of the wafer by precise temperature control heating, especially for the high step area, it can reduce the accumulation and loss of the photoresist. The cold plate unit immediately following quickly cools the wafer to a suitable temperature, fixes the photoresist shape, and prevents the thickness change caused by temperature fluctuations, thereby significantly improving the uniformity of the thickness of the photoresist on the entire wafer surface. The uniformity of the photoresist thickness directly determines the line width accuracy of the pattern after exposure. The device improves the uniform distribution of the photoresist, so that the penetration depth of the exposure light at various locations on the wafer surface is more consistent, thereby reducing the problem of uneven exposure caused by the difference in photoresist thickness. This greatly improves the ability to accurately control the line width on the wafer, helps to achieve a more sophisticated semiconductor device structure, and meets the needs of high-performance integrated circuit manufacturing. The device of the present invention is flexible in design and can be easily integrated into the existing photolithography process line without making major changes to the overall process flow. At the same time, its temperature control accuracy is high, and it can be optimized and adjusted for different types of photoresists and wafer materials, enhancing the compatibility and adaptability of the process.

[0029] The embodiment of the present invention discloses a method for improving wafer line width uniformity, comprising the following steps: Step 1: After the wafer 4 is coated with glue, the wafer 4 is transferred to a hot plate unit, the temperature range is controlled to be 100° C. to 200° C., and the time is controlled to be 60s to 80s; Step 2: after completing step 1, transfer the wafer 4 to the cold plate unit until the wafer 4 is cooled to room temperature; Step 3: After the wafer 4 is cooled to room temperature, the exposure step and the development step are continued.

[0030] Optimally, wafer 4 is transferred to the hot plate unit at a temperature of 120° C. and a time control of 60 s.

[0031] The present invention discloses a method for improving the uniformity of wafer line width. After the wafer is coated with glue, the wafer is transferred to a hot plate unit, the temperature range is controlled to be 100°C to 200°C, and the time is controlled to be 60s to 80s; then the wafer is transferred to a cold plate unit until the wafer is cooled to room temperature, and the exposure step and the development step are continued. The method effectively reduces problems such as poor exposure and line width deviation caused by uneven thickness of photoresist, thereby reducing the scrap rate and rework rate, and significantly improving production efficiency and the yield rate of the final product. This not only saves production costs, but also speeds up the product launch and enhances market competitiveness.

[0032] The working principle of the present invention is as follows: The glue coating machine and developer used in the present invention are both TEL MARK V, and the photolithography machine model is NSR2005I11D. The high-precision hot plate adopts (but is not limited to) heating wire heating, the temperature control range is 100℃~200℃, the temperature control accuracy is within ±0.5℃, 9-point temperature real-time detection is adopted, and the temperature difference within the chip is less than 1℃. The cold plate adopts normal temperature water temperature control, the temperature control range is 20℃~35℃, and the temperature control accuracy is within ±3℃. The specific method is as follows: Step 1: Complete the gluing process on the TEL MARK V-type gluing machine; Step 2: Perform hot plate process on a high-precision hot plate (process conditions are 120°C, 60 seconds), and then cool to room temperature on a cold plate.

[0033] Step 3: Complete exposure on NSR2005I11D photolithography machine.

[0034] Step 4: Complete development on a TEL MARK V-type developer.

[0035] The key point of the present invention is to apply the high-precision hot plate process to the I-line photolithography process, namely: The original I-line photolithography process is: coating → exposure → development.

[0036] The new I-line lithography process is: glue coating → high-precision hot plate → exposure → development.

[0037] The beneficial effects of the present invention are verified as follows: The difference between the 0.5μm polycrystalline line width of a certain CMOS product field area and active area is about 0.045μm. By using the method of the present invention, after adding a high-precision hot plate process after glue coating and before exposure, the difference between the 0.5μm polycrystalline line width of the field area and active area is reduced to about 0.03μm, and the line width uniformity is improved by about 33%.

[0038] After multiple tests on a certain CMOS product under current process conditions, the polycrystalline line width data of the active area and field area are obtained and shown in Table 1.

[0039] Table 1 Polycrystalline line width and difference between field region and active region under baseline conditions (unit: μm)

[0040] The difference in 0.5µm polycrystalline line width between the active area and the field area of ​​this product is close to 0.045μm. Under the condition that other factors such as the test machine and the exposure conditions of the photolithography machine remain unchanged, the temperature of the hot plate after coating is pulled (the hot plate process time remains unchanged), and the specific line width data at each process temperature of the hot plate are shown in Table 2. The influence trend of the hot plate process temperature after coating on the difference in polycrystalline line width between the active area and the field area is shown in Figure 7 .

[0041] Table 2 Polycrystalline line width and difference between field region and active region at different hot plate temperatures (unit: μm)

[0042] See also Figure 7 Through the analysis of the above data, it can be seen that after adding a high-precision hot plate after coating and before exposure (the process conditions are 120℃, 60 seconds), the difference in polycrystalline line width between the active area and the field area is reduced from about 0.045μm to below 0.03μm.

[0043] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A device for improving wafer line width uniformity, characterized in that: It comprises a hot plate unit and a cold plate unit which are arranged in sequence; the hot plate unit and the cold plate unit are arranged between the glue coating process and the exposure process in the photolithography process; the hot plate unit is provided with a plurality of real-time temperature monitoring points.

2. The device for improving wafer line width uniformity according to claim 1, characterized in that: The hot plate unit comprises a hot plate (1), wherein electric heating wires (2) are evenly arranged inside the hot plate (1); a hot plate upper cover plate (3) is arranged on the upper part of the hot plate (1); when the hot plate unit is working, the wafer (4) is placed between the upper surface of the hot plate (1) and the hot plate upper cover plate (3).

3. The device for improving wafer line width uniformity according to claim 2, characterized in that: The heating wire (2) is in a spiral structure inside the heating plate (1).

4. The device for improving wafer line width uniformity according to claim 3, characterized in that: The heating wire (2) is coiled twice inside the heating plate (1); the number of real-time temperature monitoring points is 9; a real-time temperature monitoring point is arranged at the center point of the heating wire (2), and 4 real-time temperature monitoring points are evenly arranged at the positions of the inner circle heating wire and the outer circle heating wire respectively; the 4 real-time temperature monitoring points arranged at the positions of the inner circle heating wire and the outer circle heating wire are arranged at staggered intervals.

5. The device for improving wafer line width uniformity according to claim 1, characterized in that: The temperature control range of the hot plate unit is 100°C to 200°C, the heating time is 60s to 80s, the temperature control accuracy is ±0.5°C, and the temperature difference at each position of the hot plate unit is less than 1°C.

6. The device for improving wafer line width uniformity according to claim 1, characterized in that: The cold plate unit comprises a cold plate (5), water pipes (6) are evenly arranged inside the heating plate; a cold plate upper cover plate (7) is arranged on the upper part of the cold plate (5); when the cold plate unit is working, the wafer (4) is placed between the upper surface of the cold plate (5) and the cold plate upper cover plate (7).

7. The device for improving wafer line width uniformity according to claim 6, characterized in that: The water pipe (6) is a spiral structure inside the cold plate (5); a low-temperature medium flows through the water pipe (6).

8. The device for improving wafer line width uniformity according to claim 1, characterized in that: The temperature control range of the cold plate unit is 20°C to 35°C, and the temperature control accuracy is ±3°C.

9. A method for improving wafer line width uniformity based on the device according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1, after the wafer (4) is coated with glue, the wafer (4) is transferred to a hot plate unit, the temperature range is controlled to be 100° C. to 200° C., and the time is controlled to be 60 s to 80 s; Step 2: after completing step 1, transferring the wafer (4) to a cold plate unit until the wafer (4) is cooled to room temperature; Step 3: After the wafer (4) is cooled to room temperature, the exposure step and the development step are continued.

10. The method for improving wafer line width uniformity according to claim 9, characterized in that: The wafer (4) is transferred to a hot plate unit at a temperature of 120° C. for a time of 60 seconds.

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