Method for coating variable-speed dynamic RRC (Radio Resource Control) photoresist on wafer

Abstract

The invention provides a method for variable-speed dynamic RRC (Radio Resource Control) photoresist coating on a wafer, which is characterized in that before photoresist coating, conventional dynamic RRC coating is improved into two-step variable-speed coating, firstly, a substrate is rotated at the rotating speed of 30-500rpm, a spraying nozzle spits an RRC solvent, the spraying time is 0.1-5s, then, the substrate is rotated at the rotating speed of 0-100rpm, the spraying nozzle spits the RRC solvent, the spraying time is 0.1-5s, and the spraying nozzle spits the RRC solvent at the rotating speed of 0-100rpm. And the original RRC pre-wetting coating time of 0-20 seconds is shortened to 0.1-5 seconds, and meanwhile, the consumption of the photoresist is reduced by 3-5 times. According to the method, the RRC process time is shortened, the consumption of the photoresist is effectively reduced, and the production process cost is reduced; and the process quality of the photoresist film on the surface of the wafer is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor lithography processes in the integrated circuit manufacturing industry, and particularly relates to a process method for variable-speed dynamic RRC (V-RRC) photoresist coating. Background Art

[0002] Due to the continuous improvement of integrated circuit (IC) design and process technology levels, the scale of integrated circuits is getting larger and the complexity of patterns is getting higher. The output of each device is accompanied by a large consumption of photoresist, which increases the process cost of the chip. Therefore, in order to reduce the amount of photoresist used, ensure process quality, and reduce defects on the photoresist film during the process, a pre-wetting treatment process is often used in the integrated circuit process, that is, an organic chemical reagent is sprayed on the substrate before photoresist coating. This organic chemical reagent is usually the solvent of the photoresist, and according to its principle of action, this reagent is simply referred to as RRC (Reducing Resist Consumption).

[0003] The competition in the semiconductor market has become increasingly fierce. Ultimately, the key to success depends on the high yield index of the emerging new manufacturing capabilities in the operation of the production line. In the initial stage of the new generation of chips entering the market, the faster the yield is improved and the lower the cost is reduced, the more obvious the competitive advantage is and the higher the investment benefit is. Therefore, on the premise of improving the yield, how to reduce production costs has become one of the most important factors for modern IC production lines to improve their own competitiveness. Developing a production process that can effectively reduce production costs while ensuring production quality and yield is particularly important.

[0004] At present, in the process method of photoresist coating on a wafer, the conventional dynamic RRC process is usually adopted for coating. The basic steps of the conventional dynamic RRC process for coating are as follows: during the coating process, the RRC nozzle in the coating arm moves to the center position of the aligned substrate, and the substrate rotates at a speed of 0 - 500 rpm. At this time, the RRC solvent is in a state of being ejected while diffusing outward with the rotation of the substrate. The pre-wetting RRC spraying time is 0 - 20 s, and the photoresist consumption during the process is 3 - 20 ml. Compared with non-RRC coating, the conventional dynamic RRC process for coating significantly saves the process time and reduces the consumption of photoresist. In order to further effectively shorten the RRC process time and reduce the usage of RRC solvent and photoresist, the present invention provides a new process method for dynamic RRC coating, namely variable speed RRC (Variable Reducing Resist Consumption, V-RRC) coating process, which can not only reduce the RRC process time, effectively reduce the consumption of photoresist, and lower the production process cost, but also effectively reduce the process defects such as subsequent development and etching, and meet the requirements of high-performance integrated circuit devices. Summary of the Invention

[0005] The object of the present invention is to solve the problems in the prior art, such as large consumption of photoresist, increased cost, more subsequent process defects, and lower process yield rate, and provide a V-RRC coating process method. Compared with the conventional dynamic RRC coating process, the V-RRC coating process method changes the one-step constant rotation speed of 0 - 500 rpm to two different rotation speeds of 30 - 500 rpm and 0 - 100 rpm, preferably 50 - 150 rpm and 30 - 80 rpm; shortens the original RRC pre-wetting coating time of 0 - 20 s to 0.1 - 5 s, preferably 0.1 - 3 s; and at the same time reduces the consumption of photoresist by 3 - 5 times.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for variable speed dynamic RRC photoresist coating on a wafer, and the specific operation steps are as follows:

[0008] (1) Coat the bottom of a 12-inch wafer to be coated with an adhesion promoter, and then send it into the spin coating unit;

[0009] The adhesion promoter is one or more of hexamethyldisilazane, vinyltrichlorosilane, 1-methoxy-2-propanol, aminopropyltriethoxysilane, etc., preferably hexamethyldisilazane or 1-methoxy-2-propanol.

[0010] (2) Two-step variable-speed coating with RRC solvent. In step 1), the substrate rotates at a speed of 30 - 500 rpm, preferably 50 - 150 rpm, while the spray nozzle ejects the RRC solvent, and the spraying time is 0.1 - 5 s, preferably 0.1 - 3 s, more preferably 0.1 - 0.5 s; in step 2), the substrate rotates at a speed of 0 - 100 rpm, preferably 30 - 80 rpm, while the spray nozzle ejects the RRC solvent, and the spraying time is 0.1 - 5 s, preferably 0.1 - 3 s, more preferably 0.5 - 1 s.

[0011] Among them, the two-step variable-speed coating with RRC solvent includes central fixed-point variable-speed coating or scan variable-speed coating;

[0012] The central fixed-point variable-speed coating means that the RRC spray nozzle coincides with the center point of the substrate, and the position remains unchanged to perform the coating of step 1) and step 2);

[0013] The scan variable-speed coating means that the RRC spray nozzle first reaches the position coinciding with the center point of the substrate, performs the coating of step 1), and then the spraying arm horizontally moves at a speed of 3 - 10 mm / s to a position half of the distance from the edge of the substrate to perform the coating of step 2).

[0014] (3) Coating of photoresist; while the substrate rotates at a speed v1 of 1000 - 4000 rpm, the spray nozzle ejects the photoresist to uniformly coat the entire substrate, and the rotation time is t 1 1 - 10 s; then the substrate rotates at a speed v2 of 50 - 200 rpm for t 2 1 - 10 s to adjust the photoresist film at the center and edge of the substrate to make the photoresist film more uniform; finally, the substrate rotates at a speed v3 of 500 - 3000 rpm for t 3 15 - 40 s to volatilize the photoresist solvent and form a stable photoresist film with a certain thickness.

[0015] (4) The coated wafer is taken out by a robot, baked on a hot plate, sent for exposure and development, and finally the wafer is transferred back to the cassette.

[0016] Among them, at the moment when the RRC solvent coating in step (2) is completed, the substrate rotates at a speed of 1000 rpm for 0.1 s, so that the RRC on the substrate surface forms a liquid film and is quickly ejected from the edge of the substrate, and then the coating process of step (3) photoresist starts.

[0017] The advantages and beneficial effects of the present invention are:

[0018] 1. The purpose of the present invention is to provide a process method of variable-speed RRC (V-RRC) to reduce the RRC process time and reduce the consumption of the photoresist process.

[0019] 2. Optimize the conventional dynamic RRC process with a one-step constant speed into a two-step variable speed dynamic RRC process. In combination with other parameter adjustments, such as the dispensing rotation speed v1 and the reflux rotation speed v2, etc., the uniformity of the photoresist film on the wafer surface approaches the requirement of the layout standard, the thickness fluctuation of the film significantly decreases, and the quality of the original process results is improved. Description of the Drawings

[0020] Figure 1 Comparison curve of the conventional one-step dynamic RRC process steps and the variable speed dynamic RRC process steps.

[0021] Figure 2 Schematic diagram of the film thickness measurement points, where (a) is the schematic diagram of measuring 13 points, (b) is the schematic diagram of measuring 25 points, and (c) is the schematic diagram of measuring 49 points.

[0022] Figure 3 Comparison chart of the results of three coating methods: non-RRC, dynamic RRC, and V-RRC photoresist coating in Example 1.

[0023] Figure 4 Comparison chart of the results of three coating methods: non-RRC, dynamic RRC, and V-RRC photoresist coating in Example 2. Detailed Description of the Invention

[0024] The following implementation examples further illustrate the present invention. The specific implementation manners described herein are only for explaining and interpreting the present invention and are not limited to the present invention.

[0025] Example 1

[0026] Perform a film process on a 12-inch wafer. Use a certain I-line photoresist AZ7920 with a viscosity value of 25 cp, a target film thickness of 9500 Å, a target uniformity requirement of Range (film thickness difference value) ≤ 100 Å, and 3*STD (average value of film thickness fluctuation) ≤ 50 Å. Among them, Range = MAX - MIN, MAX represents the maximum value of the substrate film thickness, and MIN represents the minimum value of the substrate film thickness;

[0027]

[0028] xi represents the thickness value of each measurement point of the film, represents the average value of the film thickness. The film thickness measurement points are 13 points or 25 points or 49 points. The schematic diagram of the measurement points is as shown in Figure 2 shown.

[0029] First, take out the wafer to be coated with glue from the cassette, send it into the primer coating unit, set the temperature at 125°C, spray 1-methoxy-2-propanol for 30 s, and then send the wafer with the primer coating completed into the cold plate unit for cooling at 23°C for 60 s to stabilize the wafer temperature. Then send the wafer with the stabilized temperature into the glue coating unit to prepare for the glue coating process, and select the glue coating process formula: without the RRC process step, v1 = 2003 rpm, t 1 = 6 s, v2 = 50 rpm, t 2 = 5 s, v3 = 1485 rpm, t 3 = 30 s; one-step conventional dynamic RRC process step, set the RRC process duration at 10 s, the wafer rotation speed at 10 rpm, the required consumption of the chemical cabinet RRC is 20 ml, v1 = 1984 rpm, t 1 = 3 s, v2 = 100 rpm, t 2 = 3 s, v3 = 1530 rpm, t 3 = 30 s; V-RRC process step, the RRC solvent coating adopts the center fixed-point variable speed coating method, set the RRC process duration at first 1.5 s, the wafer rotation speed at 35 rpm, then 1 s, the wafer rotation speed at 80 rpm, the required consumption of the chemical cabinet RRC is 10 ml, v1 = 1950 rpm, t 1 = 1.5 s, v2 = 150 rpm, t 2 = 1 s, v3 = 1445 rpm, t 3 = 25 s. Record the RRC process duration, the consumption of photoresist, and the changes in the process indicators of the photoresist film on the wafer surface (range, 3*STD) when the RRC process is not added, the one-step conventional dynamic RRC process, and the V-RRC process respectively. In the experiment, 50 wafers are made for each glue coating process formula, and 49 points are measured for the film thickness, and the experimental data is collected and compared. The experimental results are shown in Table 1, Figure 3 as shown. After the wafer completes the coating process in the glue coating unit, it is taken out by the robot, baked at 110°C on the hot plate for 90 s, sent for exposure, and then developed. Finally, the wafer completes the entire film process and is transferred back to the cassette.

[0030] Table 1

[0031] Without RRC Conventional dynamic RRC V-RRC RRC Time (s) 0 10 2.5 Photoresist Consumption (ml) 5 2.5 1.5 RANGE(A) 380-260 300-150 120-80 STD 150-100 100-80 50-30 Photoresist Saving Rate % 0 50％ 40％

[0032] As can be seen from the data in Table 1: The duration of the conventional dynamic RRC process is 10 s, the duration of the V-RRC process is 2.5 s, the consumption of photoresist is reduced from 5 ml to 2.5 ml, and the consumption of photoresist using the V-RRC process is 1.5 ml. The photoresist saving rate is 50% from no RRC to using the dynamic RRC process, and the V-RRC process further saves 40% of the photoresist. For the process indicators of the photoresist film, with the change of the RRC process, both range and 3*STD are significantly improved and optimized. According to the monthly output of 10,000 pieces, the cost can be saved by 5 million yuan per year.

[0033] Example 2

[0034] A thin film process is carried out on a 12-inch wafer, using a certain BARC-type photoresist DUV141 with a viscosity of about 0.94 cp, a target film thickness of 1500 Å, and a target uniformity requirement of range (film thickness difference value) ≤ 20 Å, 3*STD (average value of film thickness fluctuation) ≤ 40 Å. Among them, the calculation methods of Range and STD, and the film thickness measurement points are the same as those in Example 1.

[0035] First, take out the wafer to be coated with glue from the cassette and send it into the primer coating unit. Set the temperature to 120°C, spray hexamethyldisilazane for 40 s, and then send the wafer with the primer coating completed into the cold plate unit for cooling at 23°C for 60 s to stabilize the wafer temperature. Then send the wafer with the stabilized temperature into the glue coating unit to prepare for the glue coating process. Select the glue coating process formula: without the RRC process step, v1 = 2300 rpm, t1 = 5 s, v2 = 100 rpm, t2 = 3 s, v3 = 1560 rpm, t3 = 35 s; one-step conventional dynamic RRC process step, set the RRC process duration to 6 s, the wafer rotation speed to 30 rpm, the required consumption of the chemical cabinet RRC to be 60 ml, v1 = 2150 rpm, t1 = 2.5 s, v2 = 150 rpm, t2 = 2 s, v3 = 1480 rpm, t3 = 30 s; V-RRC process step, the RRC solvent coating uses the scan variable speed coating method. The spray nozzle first reaches the position coinciding with the center point of the substrate, the RRC coating duration is 1 s first, the wafer rotation speed is 60 rpm, then the spraying arm moves horizontally at a speed of 5 mm / s to a position half of the distance from the edge of the substrate, and then for 0.5 s, the wafer rotation speed is 150 rpm, the required consumption of the chemical cabinet RRC is 10 ml, v1 = 2030 rpm, t1 = 1.5 s, v2 = 100 rpm, t2 = 1 s, v3 = 1455 rpm, t3 = 20 s. Respectively record the RRC process duration, the consumption of photoresist, and the changes in the process indexes of the photoresist thin film on the wafer surface (range, 3*STD) when there is no RRC process, one-step conventional dynamic RRC process, and V-RRC process. In the experiment, 50 wafers are made for each glue coating process formula, and the film thickness is measured at 49 points, and the experimental data is collected and compared. The experimental results are shown in Table 2, Figure 4 as shown. After the wafer completes the coating process in the glue coating unit, it is taken out by the robot, baked at 205°C for 60 s on the hot plate, sent for exposure, and then developed. Finally, the wafer completes the entire thin film process and is transferred back to the cassette.

[0036] Table 2

[0037] Without RRC Conventional dynamic RRC V-RRC RRC Time (s) 0 6 1.5 Photoresist Consumption (ml) 4 2 1.5 RANGE(A) 30±5 20±5 10±5 3*STD 40±5 35±5 15±5 Photoresist Saving Rate % 0 50％ 25％

[0038] It can be seen from the data in Table 2 that the duration of the conventional dynamic RRC process is 6 s, the duration of the V-RRC process is 1.5 s, the consumption of photoresist is reduced from 4 ml to 2 ml, and the consumption of photoresist using the V-RRC process is 1.5 ml. The photoresist saving rate is 50% from no RRC to using the dynamic RRC process, and the V-RRC process further saves 25% of the photoresist. The process indexes of the photoresist thin film are optimized in terms of both range and 3*STD with the change of the RRC process. Calculated according to a monthly output of 10,000 pieces, the cost can be saved by 12.6 million yuan per year.

Claims

1. A method for variable-speed dynamic RRC photoresist coating on a wafer, characterized in that, it includes the following steps: (1) Coating the bottom of a 12-inch wafer to be coated with an adhesion promoter, and then feeding it into the spin coater unit; (2) Two-step variable-speed coating with RRC solvent. In step 1), the substrate rotates at a speed of 30 - 500 rpm, preferably 50 - 150 rpm, while the spray nozzle ejects RRC solvent, and the spraying time is 0.1 - 5 s, preferably 0.1 - 3 s, more preferably 0.1 - 0.5 s; In step 2), the substrate rotates at a speed of 0 - 100 rpm, preferably 30 - 80 rpm, while the spray nozzle ejects RRC solvent, and the spraying time is 0.1 - 5 s, preferably 0.1 - 3 s, more preferably 0.5 - 1 s; (3) Coating of photoresist; (4) The coated wafer is taken out by a robot, baked on a hot plate, fed into exposure and development, and finally the wafer is transferred back to the cassette.

2. The method according to claim 1, characterized in that, the adhesion promoter described in step (1) is one or more of hexamethyldisilazane, vinyltrichlorosilane, 1-methoxy-2-propanol, aminopropyltriethoxysilane, etc., preferably hexamethyldisilazane or 1-methoxy-2-propanol.

3. The method according to claim 1, characterized in that, the two-step variable-speed coating with RRC solvent in step (2) includes center fixed-point variable-speed coating or scan variable-speed coating; The center fixed-point variable-speed coating means that the RRC spray nozzle coincides with the center point of the substrate, and the position remains unchanged to perform the coating in step 1) and step 2); The scan variable-speed coating means that the RRC spray nozzle first reaches the position coinciding with the center point of the substrate, performs the coating in step 1), and then the spraying arm moves horizontally at a speed of 3 - 10 mm / s to a position half of the distance from the edge of the substrate, and performs the coating in step 2).

4. The method according to claim 1, characterized in that, The process of coating the photoresist in step (3) is as follows: while the substrate is rotating at a speed v1 of 1000 - 4000 rpm, the spray nozzle ejects the photoresist to uniformly coat the entire substrate, and the rotation time is t 1 1 - 10 s; then the substrate rotates at a speed v2 of 50 - 200 rpm for t 2 1 - 10 s to adjust the photoresist film at the center and edge of the substrate; finally, the substrate rotates at a speed v3 of 500 - 3000 rpm for t 3 15 - 40 s to volatilize the photoresist solvent and form a stable photoresist film with a certain thickness.

5. The method according to claim 1, characterized in that, the temperature of hot plate baking in step (4) is 90 - 250 °C, and the baking time is 60 - 180 s.

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