Wafer processing method

Abstract

This invention discloses a wafer processing method, comprising providing a wafer having a first position and a second position, the first position being oriented toward the second position in a reference direction; coating a photoresist solution onto the wafer; and performing a heating process to heat the wafer coated with the photoresist solution to form a photoresist layer on the wafer; wherein, during the heating process, the temperature of the wafer gradually increases along the reference direction, causing the thickness of the photoresist layer to gradually decrease along the reference direction.

Description

Technical Field

[0001] This invention relates to a wafer processing method, and more particularly to a wafer processing method that enables a photoresist layer with continuously varying thickness on a single wafer. Background Technology

[0002] Semiconductor manufacturing processes typically use linewidth as an indicator of process quality. Linewidth is also known as the critical dimension (CD). A smaller critical dimension means that more electronic components can be placed on a single wafer, resulting in a smaller product size. However, wafers with different photoresist layer thicknesses absorb different amounts of energy and have varying reflectivity throughout the manufacturing process. This instability leads to instability in the manufacturing process and affects the critical dimension. The relationship between the critical dimension and the photoresist layer thickness exhibits a sinusoidal waveform, known as the swing curve.

[0003] Therefore, semiconductor manufacturers conduct critical size sampling to determine the optimal critical size and photoresist layer thickness. The current method involves setting different rotation speeds on a spin coater for photoresist coating; the faster the speed, the thinner the photoresist layer. This produces multiple wafers with different photoresist layer thicknesses. After subsequent exposure and development processes, the critical size is measured. A sinusoidal waveform is fitted based on the photoresist layer thickness and the measured critical size to determine the minimum critical size, i.e., the optimal photoresist layer thickness. However, when the sample size in the sampling experiment is insufficient, the fitted sinusoidal waveform may not accurately represent the true optimal photoresist layer thickness. To obtain more accurate results that closely reflect reality, more wafers with different photoresist layer thicknesses are needed to increase the sample size, resulting in lengthy sampling times and high wafer consumption. Summary of the Invention

[0004] This invention provides a wafer processing method that can significantly reduce the number of wafers required for critical size sampling and improve the accuracy of critical size sampling and measurement.

[0005] The wafer processing method provided by the present invention includes: providing a wafer having a first position and a second position, the first position being oriented toward the second position in a reference direction; coating a photoresist solution onto the wafer; and performing a heating process to heat the wafer coated with the photoresist solution to form a photoresist layer on the wafer; wherein, during the heating process, the temperature of the wafer gradually increases along the reference direction, causing the thickness of the photoresist layer to gradually decrease along the reference direction.

[0006] In one embodiment of the present invention, the length of the interval between the first position and the second position is equal to the diameter of the wafer.

[0007] In one embodiment of the present invention, a heating device is used to perform a heating fabrication process. The heating device includes a first heating unit, a second heating unit, and a third heating unit, which are arranged sequentially along a reference direction. The first set temperature of the first heating unit is lower than the second set temperature of the second heating unit, and the second set temperature is lower than the third set temperature of the third heating unit. After the heating fabrication process, a portion of the photoresist layer at the first position of the wafer has a first thickness, and a portion of the photoresist layer at the second position of the wafer has a second thickness. The first thickness is greater than the second thickness.

[0008] In one embodiment of the present invention, the first set temperature, the second set temperature and the third set temperature are all between 90°C and 110°C.

[0009] In one embodiment of the present invention, a heating device is used to perform a heating fabrication process. The heating device includes a top surface, on which at least one spacer is provided. A wafer is placed on the at least one spacer, such that the wafer is tilted on the top surface. The distance between the wafer and the top surface gradually decreases along a reference direction. After the heating fabrication process, a portion of the photoresist layer at a first position on the wafer has a first thickness, and a portion of the photoresist layer at a second position on the wafer has a second thickness. The first thickness is greater than the second thickness.

[0010] In one embodiment of the invention, the first position of the wafer is placed on a spacer on the top surface of the heating device.

[0011] In one embodiment of the present invention, the height of the spacer is preferably between 0.1 mm and 2 mm, more preferably between 0.1 mm and 1 mm.

[0012] In one embodiment of the invention, the thickness of the photoresist layer is between 9,000 angstroms and 11,500 angstroms.

[0013] The wafer processing method provided by this invention gradually increases the temperature of the wafer from a first position toward a second position along a reference direction during the heating process after coating the photoresist solution. This causes the solvent in the photoresist solution on the wafer to evaporate at different degrees, thereby forming a photoresist layer of inconsistent thickness. The thickness of the photoresist layer gradually decreases along the reference direction. This method can form a photoresist layer with a continuously varying thickness on a single wafer, allowing a single wafer to serve as multiple samples for critical size sampling. This method can significantly reduce the number of wafers required for critical size sampling and improve the accuracy of critical size sampling.

[0014] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0015] Figure 1 This is a schematic flowchart of a wafer processing method according to an embodiment of the present invention;

[0016] Figure 2 This is a schematic diagram of a wafer in a wafer processing method according to an embodiment of the present invention;

[0017] Figure 3 This is a schematic diagram of a heating device and a wafer in a wafer processing method according to an embodiment of the present invention;

[0018] Figure 4 This is a schematic diagram of a heating device and a wafer in another embodiment of the wafer processing method of the present invention. Detailed Implementation

[0019] Figure 1 This is a schematic flowchart of a wafer processing method according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a wafer in a wafer processing method according to an embodiment of the present invention. Figure 1 As shown, the wafer processing method includes: providing a wafer 10, which is step S1. The wafer 10 has a first position 11 and a second position 12 (e.g., ...). Figure 2 As shown, the first position 11 faces the second position 12 with a reference direction Dr. In one embodiment of the present invention, the first position 11 and the second position 12 are any two points on the edge of the wafer 10. More preferably, the line connecting the two points of the first position 11 and the second position 12 passes through the center C of the wafer 10, that is, the distance between the first position 11 and the second position 12 is equal to the diameter of the wafer. However, the present invention is not limited thereto. The first position 11 and the second position 12 can be adjusted according to the desired photoresist layer thickness distribution in subsequent steps, and the distance between the first position 11 and the second position 12 can also be less than the diameter.

[0020] Next, a photoresist solution is coated onto the wafer 10; this is step S2. The photoresist solution can be coated by spin coating, extrusion coating, spray coating, or roll coating; preferably, spin coating is selected. When spin coating the photoresist solution onto the wafer 10, the spin coater speed can be adjusted from 1000 rpm to 3000 rpm depending on the properties of the photoresist solution, such as viscosity, and the desired photoresist layer thickness.

[0021] Next, a heating process is performed, which is step S3. The wafer 10 coated with photoresist is heated to form a photoresist layer on the wafer 10. The heating method can be an oven or a hot plate. When heating in an oven, the temperature can be set between 80°C and 90°C for 10 to 30 minutes. When heating with a hot plate, the temperature can be set between 85°C and 150°C, preferably between 90°C and 110°C, for 30 to 90 seconds. The heating process removes the solvent inside the photoresist, allowing the formed photoresist layer to be thinner and have stronger adhesion to the wafer 10.

[0022] Continuing from the above description, the temperature of the wafer 10 in the heating fabrication process affects the rate of solvent evaporation and the amount of solvent removed from the photoresist solution. A higher temperature of the wafer 10 results in more solvent evaporation from the photoresist solution, thus forming a thinner photoresist layer. Conversely, a lower temperature of the wafer 10 results in less solvent evaporation from the photoresist solution, thus forming a thicker photoresist layer. Therefore, the temperature of the wafer 10 in the heating fabrication process can be used to adjust the thickness of the photoresist layer. In one embodiment of the present invention, during the heating fabrication process, the temperature of the wafer 10 is gradually increased along the reference direction Dr, thereby causing the thickness of the photoresist layer to gradually decrease along the reference direction Dr.

[0023] Figure 3 This is a schematic diagram of a heating device and a wafer in a wafer processing method according to an embodiment of the present invention. In one embodiment of the present invention, as shown... Figure 3 As shown, the heating fabrication process can be performed using a heating device 14, which includes multiple heating units, preferably three or more. Temperature control of these multiple heating units achieves a gradual increase in the temperature of the wafer 10 along the reference direction Dr during the heating fabrication process. Figure 3As shown, the heating device 14 has a first heating unit 141, a second heating unit 142, and a third heating unit 143. The first heating unit 141, the second heating unit 142, and the third heating unit 143 are arranged sequentially along the reference direction Dr, that is, the first heating unit 141 corresponds to the first position 11 on the wafer 10 (marked on...). Figure 2 The third heating unit 143 corresponds to the second position 12 on the chip 10 (marked as follows). Figure 2 The first heating unit 141, the second heating unit 142 and the third heating unit 143 are respectively set, and the first heating unit 141, the second heating unit 142 and the third heating unit 143 can be hot plates. To form a photoresist layer 13 with a continuously varying thickness on the wafer 10, the first set temperature of the first heating unit 141 is set to be lower than the second set temperature of the second heating unit 142, and the second set temperature is set to be lower than the third set temperature of the third heating unit 143. Therefore, after the heating process, a portion of the photoresist layer 13 at the first position 11 of the wafer 10 has a first thickness TH1, and a portion of the photoresist layer 13 at the second position 12 of the wafer 10 has a second thickness TH2. The first thickness TH1 is greater than the second thickness TH2, and the thickness of the photoresist layer 13 between the first position 11 and the second position 12 gradually decreases from the first thickness TH1 at the first position 11 along the reference direction Dr to the second thickness TH2 at the second position 12. In one embodiment of the present invention, both the first thickness TH1 and the second thickness TH2 are between 9000 angstroms and 11500 angstroms. Figure 3 The heating device 14 shown is the corresponding Figure 2 The first position 11 and the second position 12 of the chip 10 shown are two points on the edge of the chip 10, and the line connecting the first position 11 and the second position 12 passes through the center C of the chip 10. Figure 3 The heating device 14 shown can have three parallel heating units 141, 142, and 143 of the same size. However, the heating device of the present invention is not limited to this, and the size and shape of each heating unit can be different. In an embodiment not shown, the first position on the wafer can be located at the center of the wafer, and the second position can be any point on the edge of the wafer. In this case, the reference direction is the direction from the center outwards. The multiple heating units of the heating device can be arranged along concentric circles. For example, the first heating unit is a circular heating unit located at the center, the second heating unit is an annular heating unit, and the third heating unit is an annular block corresponding to the outermost periphery of the wafer. A heating device arranged in this way allows the wafer to form a photoresist layer with a center thickness greater than the outer edge thickness after the heating process, meaning that the thickness of the photoresist layer gradually decreases from the center of the wafer to the outer periphery.

[0024] Figure 4 This is a schematic diagram of a heating device and a wafer in another embodiment of the wafer processing method of the present invention. Unlike the hot plate heating method described above, which involves directly placing the entire wafer on the heating device, this method... Figure 4 As shown, in one embodiment of the present invention, a gap 145 is formed between the wafer 10 and the heating device 14A, and the temperature of the wafer 10 in the heating fabrication process is adjusted by the size of the gap 145. In one embodiment of the present invention, the wafer 10 is placed at an angle on the top surface 144 of the heating device 14A, forming a gap 145 with the top surface 144, and the height of the gap 145, that is, the distance D between the wafer 10 and the top surface 144, is determined by a first position 11 (marked at...). Figure 2 ) Along the reference direction Dr towards the second position 12 (marked at Figure 2 The greater the distance D between the wafer 10 and the top surface 144, the lower the temperature of the wafer 10, which affects the degree of solvent evaporation in the photoresist solution. The lower the temperature, the less solvent is removed, thus forming a thicker photoresist layer 13. Furthermore, the distance D between the wafer 10 and the top surface 144 gradually decreases along the reference direction Dr, which means that the temperature on the wafer 10 gradually increases along the reference direction Dr, thereby forming a photoresist layer 13 with a continuous thickness variation on the wafer 10.

[0025] In one embodiment of the present invention, at least one spacer 146 is provided on the top surface 144 of the heating device 14A. The height H of the spacer 146 is between 0.1 mm and 2 mm, more preferably, the height H of the spacer 146 is between 0.1 mm and 1 mm. The first position 11 of the wafer 10 is placed on the spacer 146, and the second position 12 is placed directly on the top surface 144 of the heating device 14A. Thus, the wafer 10 can be tilted on the top surface 144. After the heating fabrication process, a portion of the photoresist layer 13 on the first position 11 of the wafer 10 has a first thickness TH1, and a portion of the photoresist layer 13 on the second position 12 of the wafer 10 has a second thickness TH2. The first thickness TH1 is greater than the second thickness TH2. In one embodiment of the present invention, both the first thickness TH1 and the second thickness TH2 are between 9000 angstroms and 11500 angstroms.

[0026] The wafer processing method provided by this invention gradually increases the temperature of the wafer from a first position toward a second position along a reference direction during the heating process after coating the photoresist solution. This causes the solvent in the photoresist solution on the wafer to evaporate at different degrees, thereby forming a photoresist layer of inconsistent thickness. The thickness of the photoresist layer gradually decreases along the reference direction. This method can form a photoresist layer with a continuously varying thickness on a single wafer, allowing a single wafer to serve as multiple samples for critical size sampling. This method can significantly reduce the number of wafers required for critical size sampling and improve the accuracy of critical size sampling.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed in conjunction with the above preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the methods and techniques disclosed above without departing from the scope of the present invention to create equivalent embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method of wafer processing, characterized by, Include: A wafer is provided, the wafer having a first position and a second position, the first position being oriented toward the second position in a reference direction; A photoresist solution is applied to the wafer. After the photoresist solution is coated onto the wafer, a heating process is performed to heat the wafer coated with the photoresist solution, thereby forming a photoresist layer on the wafer. During the heating process, the temperature of the wafer gradually increases along the reference direction, causing the thickness of the photoresist layer to gradually decrease along the reference direction.

2. The wafer processing method as described in claim 1, characterized in that, The length of the interval between the first position and the second position is equal to the diameter of the wafer.

3. The wafer processing method as described in claim 1, characterized in that, The heating process is carried out using a heating device, which includes a first heating unit, a second heating unit, and a third heating unit.

4. The wafer processing method as described in claim 3, characterized in that, The first heating unit, the second heating unit, and the third heating unit heat the wafer at a first set temperature, a second set temperature, and a third set temperature, respectively, wherein the first set temperature is lower than the second set temperature, and the second set temperature is lower than the third set temperature.

5. The wafer processing method as described in claim 4, characterized in that, The first heating unit, the second heating unit, and the third heating unit are arranged sequentially along the reference direction. After the heating process is performed, the photoresist layer at the first position has a first thickness, and the photoresist layer at the second position has a second thickness, wherein the first thickness is greater than the second thickness.

6. The wafer processing method as described in claim 4, characterized in that, The first set temperature, the second set temperature, and the third set temperature are all between 90°C and 110°C.

7. The wafer processing method as described in claim 1, characterized in that, The heating fabrication process is performed using a heating device, the heating device including a top surface, the wafer being placed at an angle on the top surface, the distance between the wafer and the top surface gradually decreasing along the reference direction, and after the heating fabrication process, a portion of the photoresist layer at the first position has a first thickness, and a portion of the photoresist layer at the second position has a second thickness, wherein the first thickness is greater than the second thickness.

8. The wafer processing method as described in claim 7, characterized in that, At least one spacer is provided on the top surface, and the first position of the wafer is placed on the at least one spacer.

9. The wafer processing method as described in claim 8, characterized in that, The height of the at least one spacer is between 0.1 mm and 2 mm.

10. The wafer processing method as described in claim 9, characterized in that, The height of the at least one spacer is between 0.1 mm and 1 mm.

11. The wafer processing method as described in claim 1, characterized in that, The thickness is between 9,000 and 11,500 angstroms.

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