Method for applying resin to wafer and manufacturing method of wafer

Abstract

To provide a method for applying a resin to a wafer which inhibits variations in resin thickness, and provide a manufacturing method of a wafer which inhibits variations in wafer shape after grinding or polishing.SOLUTION: A resin apply method for applying a resin to a wafer includes: preparing a wafer having a first major surface and a second major surface opposite to the first major surface; holding the second major surface of the wafer with holding means; supplying a resin to a position which faces the first major surface of the wafer; measuring a temperature of the resin and the periphery of the resin; referring to data of a temperature and a press speed which is obtained in advance and in which a resin thickness and a press load are predetermined values to select the press speed corresponding to the measured temperature; driving the holding means at the selected press speed to push and spread the resin on the first major surface of the wafer; stopping the holding means at a timing at which the press load reaches a predetermined value; and curing the resin to form a flattened resin layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for applying resin to a wafer and a method for manufacturing a wafer. [Background technology]

[0002] A method of applying resin to a wafer and grinding it is known as a method of producing a wafer with good nanotopography. In this method, the viscosity of the resin decreases due to an increase in temperature of the device or resin, so the thickness of the resin formed changes when continuous processing is performed under the same processing conditions. In contrast, in Patent Document 1, a predetermined resin thickness is formed by adjusting the press load (temperature compensation). For example, this is a method in which the relationship between the temperature and press load at which the resin thickness becomes constant is obtained in advance, as shown in Figure 3, and the press load is adjusted according to the temperature. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-168565 A [Patent Document 2] Patent Publication No. 2021-186903 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, in the above-mentioned resin application process, it is known that the holding means (upper platen) tilts due to the press load (Patent Document 2). Therefore, when the press load is changed, the tilt of the holding means changes, and as a result, the in-plane distribution of the resin thickness changes. For this reason, if the press load is temperature-compensated for continuous processing to keep the resin thickness constant, the in-plane distribution of the resin thickness varies between wafers due to temperature, which causes a problem that the wafer shape after the subsequent grinding process varies between wafers.

[0005] The present invention has been made to solve the above problems, and aims to provide a method for applying resin to a wafer while reducing variation in resin thickness, and a method for manufacturing a wafer while reducing variation in wafer shape after grinding or polishing. [Means for solving the problem]

[0006] In order to solve the above problems, a resin coating method of the present invention is a resin coating method for coating a wafer with resin, the method comprising the steps of: preparing a wafer having a first main surface and a second main surface opposite to the first main surface; holding the second main surface of the wafer with a holding means; supplying resin to a position facing the first main surface of the wafer; measuring a temperature of the resin or an area surrounding the resin; selecting a press speed corresponding to the measured temperature by referring to previously obtained data on temperature and press speed at which the resin thickness and press load become predetermined values; driving the holding means at the selected press speed to spread the resin over the first main surface of the wafer; stopping the holding means at a timing when the press load reaches a predetermined value; and hardening the resin to form a planarized resin layer.

[0007] With this method, the press speed can be adjusted according to the temperature of the resin or the area around the resin, so that the resin thickness and press load can be kept at predetermined values, thereby suppressing variations in resin thickness due to temperature changes and variations in the in-plane distribution of resin thickness due to changes in press load.

[0008] In addition, the method for manufacturing a wafer of the present invention preferably includes the steps of adsorbing and holding a planarizing resin layer on a wafer formed using the above-mentioned resin coating method, grinding or polishing the second main surface of the wafer, removing the planarizing resin layer from the wafer, adsorbing and holding the second main surface of the wafer, and grinding or polishing the first main surface of the wafer.

[0009] With this method, the planarizing resin layer formed on the first main surface by the above-mentioned resin application method, which has little variation in thickness and in-plane thickness distribution, is adsorbed and held, and the second main surface is ground or polished, thereby reducing variation in the shape of the second main surface after grinding or polishing, and since the first main surface is ground or polished by adsorbing and holding the second main surface with reduced shape variation, variation in the shape of the first main surface after grinding or polishing can be reduced, and as a result, variation in the wafer shape after grinding or polishing can be reduced. Effect of the Invention

[0010] With the resin application method of the present invention, the press speed can be adjusted according to the temperature of the resin or the surrounding area of ​​the resin, so that the resin thickness and press load can be set to predetermined values, thereby suppressing variations in resin thickness due to temperature changes and variations in the in-plane distribution of resin thickness due to changes in press load. Furthermore, in the wafer manufacturing method of the present invention, the planarizing resin layer formed on the first main surface by the above-mentioned resin application method, which has little variation in thickness and in-plane thickness distribution, is adsorbed and held, and the second main surface is ground or polished, thereby reducing variation in the shape of the second main surface after grinding or polishing, and the first main surface is ground or polished by adsorbing and holding the second main surface with reduced shape variation, thereby reducing variation in the shape of the first main surface after grinding or polishing, and as a result, reducing variation in the wafer shape after grinding or polishing. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing an example of a resin application device used in a resin application method of the present invention. [Diagram 2] FIG. 4 is a characteristic diagram showing an example of the correlation between the temperature and the press speed used in the resin application method of the present invention. [Diagram 3] FIG. 1 is a characteristic diagram showing an example of the correlation between temperature and press load used in a conventional resin application method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] As described above, there has been a demand for a method of applying resin to a wafer with reduced variation in resin thickness and a method of manufacturing a wafer with reduced variation in wafer shape after grinding or polishing.

[0013] As a result of extensive research into the above-mentioned problems, the inventors discovered that by selecting the press speed according to the temperature of the resin or the temperature around the resin, it is possible to maintain specified values ​​for the resin thickness and press load while suppressing variations in the resin thickness due to temperature changes and variations in the in-plane distribution of the resin thickness due to changes in the press load, and thus completed the present invention.

[0014] That is, the present invention is a resin coating method for coating a resin on a wafer, comprising the steps of: providing a wafer having a first major surface and a second major surface opposite the first major surface; holding the second main surface of the wafer with a holding means; supplying a resin to a position facing the first main surface of the wafer; Measuring the temperature of the resin or an area surrounding the resin; selecting a press speed corresponding to the measured temperature by referring to previously acquired data on temperature and press speed at which the resin thickness and press load are given values; driving the holding means at the selected press speed to spread the resin over the first main surface of the wafer; stopping the holding means when the press load reaches a predetermined value; The resin is cured to form a planarized resin layer.

[0015] Further, the present invention provides a method for forming a planarizing resin layer on a wafer by using the above-described resin coating method, suction-holding the planarizing resin layer and grinding or polishing the second main surface of the wafer; removing the planarizing resin layer from the wafer; The method for manufacturing a wafer includes: suction-holding the second main surface of the wafer; and grinding or polishing the first main surface of the wafer.

[0016] The present invention will be described in detail below with reference to the drawings, but the present invention is not limited thereto.

[0017] FIG. 1 is a schematic diagram showing an example of a resin application device that can be used in the resin application method of the present invention. The resin coating device 1 has a resin supplying means 4 for supplying resin 3 in a plastic state, for example, liquid state, to a position facing the first main surface 2a of the wafer 2, a holding means (upper surface plate) 5 for holding the second main surface 2b of the wafer 2 by vacuum suction, and a motor 6 for driving the holding means 5 in the vertical direction, and a stage (lower surface plate) 7 having a flat surface at the bottom. A light-transmitting film 8 is laid on the stage 7, and the resin 3 is supplied onto the film. The resin 3 is an ultraviolet-curable resin, and the resin 3 can be cured by ultraviolet light radiated from an ultraviolet light irradiation means 9. A temperature measuring means 10 is also arranged on the stage 7, and the temperature of the resin 3 held on the stage 7 can be inferred. The holding means 5 has a press load detecting means 11, which detects the press load when the wafer 2 is pressed against the resin 3. The motor 6 can change the speed of the driving of the holding means 5, and as a result, the press speed can be adjusted. Furthermore, the control means 12 determines the resin temperature based on information from the temperature measurement means 10, determines the press load based on information from the press load detection means 11, and controls the motor 6 to drive and stop the holding means 5 and control the press speed.

[0018] Here, an embodiment of the resin application method of the present invention will be described in which a resin application device as shown in FIG. 1 is used.

[0019] <Resin Coating> Referring to Figure 2, if you apply resin and measure the resin thickness while changing the resin temperature or the temperature around the resin (the temperature of stage 7 in Figure 1) and the press speed in advance, and connect only the conditions under which the resin thickness and press load are constant from the obtained results with a line, you will obtain linear data as shown in Figure 2. This shows the characteristics that satisfy one resin thickness and one press load that realizes it, and a different straight line will be obtained for a different resin thickness and press load. Therefore, the resin application process is carried out by setting the desired resin thickness and press load, grasping the relationship between temperature and press speed as shown in Fig. 2, and selecting the press speed corresponding to the measured temperature. In this way, even if the temperature changes, the press speed corresponding to the measured temperature is selected, and the desired resin thickness can be applied with a specified press load.

[0020] The resin application process is as follows. Referring to FIG. 1, first, a wafer 2 having a first main surface 2a and a second main surface 2b opposite to the first main surface is prepared. A light-transmitting film 8 is laid on a stage (lower surface plate) 7 having a flat surface, and a resin 3 in a plastic state, for example a liquid state, is supplied onto the film 8 by a resin supplying means 4 . The wafer 2 is held by vacuum suction onto a holding means (upper platen) 5 . The temperature of the resin or the temperature around the resin (the temperature of the lower surface plate 7 that holds the resin 3) is measured by the temperature measuring means 10. Set the resin thickness and press load, and refer to the measured temperature and press speed data described above (e.g., Figure 2), and select the press speed at which the resin thickness and press load become constant. The upper platen 5 is lowered at the selected press speed. The lowering of the upper platen 5 is stopped at the timing when the press load detection means 11 detects the set press load. After that, a curing process is performed according to the type of resin used. For example, when an ultraviolet curing resin is used, the resin 3 is cured by ultraviolet rays irradiated from an ultraviolet irradiation means 9. In this manner, a planarizing resin layer (not shown) can be formed on the first main surface 2a of the wafer 2.

[0021] According to this embodiment, by adjusting the press speed according to the temperature of the resin 3 or the temperature surrounding the resin 3 (the temperature of the lower platen 7 that holds the resin 3), the resin thickness and press load are set to predetermined values, thereby suppressing variations in the resin thickness due to temperature changes and variations in the in-plane distribution of the resin thickness due to changes in the press load.

[0022] In the above embodiment, the temperature of the lower platen 7 is measured by the temperature measuring means 10, but a method of directly measuring the temperature of the resin 3 using, for example, an infrared sensor may also be used. Directly measuring the temperature of the resin 3 allows temperature changes in the resin 3 to be detected more quickly than inferring the temperature from the ambient temperature.

[0023] Next, an embodiment of a method for manufacturing a wafer in which a wafer on which a planarizing resin layer has been formed using the above-mentioned resin coating method is ground or polished will be described.

[0024] <Grinding or polishing> A wafer 2 having a flattening resin layer formed thereon using the above-mentioned resin coating method is prepared. The flattening resin layer is held by suction, and the second main surface 2b of the wafer 2 is ground or polished. Next, the planarizing resin layer is removed from the wafer 2 . Next, the second main surface 2b of the wafer 2 is suction-held, and the first main surface 2a of the wafer 2 is ground or polished. Here, the second main surface 2b of the wafer 2 can be held by vacuum suction using a chuck table made of porous ceramic, for example. In this manner, the first principal surface 2a and the second principal surface 2b of the wafer 2 can be ground or polished, respectively.

[0025] According to this embodiment, the planarizing resin layer formed on the first main surface 2a by the above-mentioned resin application method, which has little variation in thickness and in-plane thickness distribution, is adsorbed and held, and the second main surface 2b is ground or polished, so that variation in the shape of the second main surface 2b after grinding or polishing can be reduced. Since the second main surface 2b with reduced shape variation is adsorbed and held, and the first main surface 2a is ground or polished, variation in the shape of the first main surface 2a after grinding or polishing can be reduced, and as a result, variation in the wafer shape after grinding or polishing can be reduced. EXAMPLES

[0026] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[0027] [Experimental content] The raw wafers used were 300 mm diameter P-type Si single crystal wafers that had been sliced ​​and then chamfered. 25 wafers were processed in succession, and the inter-wafer variations in resin thickness and wafer shape after grinding were evaluated.

[0028] <Resin application conditions> -UV-curable resin was used as the resin, and PET film was used as the light-transmitting film. A PET film was placed on a flat glass platen (lower platen), and 10 ml of UV-curable resin was dropped onto the PET film. The second main surface of the wafer was held by suction on a ceramic surface plate (upper surface plate). The temperature of the lower platen that holds the resin was measured. The temperature and press speed data were obtained in advance so that the resin thickness and press load would be the specified values. Here, the specified resin thickness was 100 μm, and the specified press load was 2000 N. By referring to the above data, the press speed corresponding to the measured temperature of the lower platen was selected. The actual measured temperature range was 23 to 28°C, and the press speed range was 1 to 100 μm / s. The pressure control for pressing the wafer against the resin was driven by a servo motor holding a ceramic surface plate, and pressure was applied at the press speed set above until the specified press load was detected. A UV-LED with a wavelength of 365 nm was used as the light source for curing the resin.

[0029] <Conditions for measuring resin thickness> The resin thickness was measured using the KEYENCE optical sensor SI-T80. The sensor was fixed and scanned linearly across the wafer to measure the resin thickness profile. The average value of four resin thickness profiles measured evenly radially from the center of the wafer was used as the average resin thickness value for each wafer. The difference between the maximum and minimum average resin thickness values ​​for each wafer, out of 25 wafers processed in succession, was taken as the wafer-to-wafer variation in the average resin thickness.

[0030] <Surface grinding conditions> For the grinding process, a grinding wheel bonded with diamond grains was used. By adjusting the axis angle of the chuck table, the wafer thickness variation was adjusted to 1 μm or less. The resin side of the wafer (front side, first main surface) was vacuum-adsorbed, and the back side of the wafer (second main surface) was ground. The resin peeled off. The back side of the wafer (second main surface) was vacuum-attached, and the front side of the wafer (first main surface) was ground.

[0031] <Conditions for measuring wafer shape after grinding> A flatness measuring device (Kobelco Research Institute: SBW-330) was used for the measurements. The warp of each wafer was calculated from the profile of four wafers measured evenly in a radial direction. The difference between the maximum and minimum Warp values ​​for each wafer over 25 consecutively processed wafers was taken as the wafer-to-wafer variation in the wafer shape.

[0032] (Example) In the embodiment, as described above, when applying the resin, only the press speed was corrected by temperature, and the conventional temperature correction of the press load was not performed (constant press load).

[0033] Comparative Example 1 In Comparative Example 1, when applying the resin, the temperature correction of the press speed in the above-mentioned Examples was not performed, and the conventional temperature correction of the press load was not performed either (constant press speed and constant press load).

[0034] Comparative Example 2 In Comparative Example 2, when applying the resin, the temperature correction of the press speed in the above-mentioned embodiment was not performed, and only the conventional temperature correction of the press load was performed (constant press speed).

[0035] The results are shown in Table 1.

[0036] [Table 1]

[0037] The evaluation criteria for the variations in the table are as follows: ×: When the variation is 150% or more of the target value △: When the variation is greater than 100% and less than 150% of the target value ○: When the variation is less than 100% of the target value

[0038] In Comparative Example 1, the wafer-to-wafer variation in the average resin thickness and the wafer-to-wafer variation in the wafer shape after grinding did not reach the target value. In continuous processing, the temperature of the device increases, so the resin viscosity decreases and the resin spreads more easily. However, since the press speed and press load were constant, the average resin thickness of the wafer in the latter half of the continuous processing became smaller, and the wafer-to-wafer variation in the average resin thickness worsened. Furthermore, when the wafer-to-wafer variation in the average resin thickness is large, the grinding allowance on the front and back surfaces changes, so the wafer-to-wafer variation in the wafer shape after grinding worsens and does not reach the target value.

[0039] In Comparative Example 2, the wafer-to-wafer variation of the resin thickness average value achieved the target value, but the wafer-to-wafer variation of the wafer shape after grinding did not reach the target value. As described above, in continuous processing, the temperature of the device increases, so the resin viscosity decreases and the resin spreads more easily. Here, the press speed is constant, but the press load is changed by temperature compensation, so the resin thickness average value becomes constant and the wafer-to-wafer variation of the resin thickness average value achieved the target value. On the other hand, the change in the press load caused the inclination of the upper platen to change, and the in-plane distribution of the resin thickness changed between the wafers. As a result, the wafer-to-wafer variation of the wafer shape after grinding worsened and did not reach the target value.

[0040] In the embodiment, the target values ​​were achieved for both the wafer-to-wafer variation of the average resin thickness and the wafer-to-wafer variation of the wafer shape after grinding. As described above, in continuous processing, the temperature of the device rises, so the resin viscosity decreases and the resin spreads more easily. Here, the press load is constant, but the press speed is changed by temperature compensation, so the average resin thickness becomes constant and the wafer-to-wafer variation of the average resin thickness achieves the target value. In addition, since the press load is constant, the inclination of the upper platen is constant and the in-plane distribution of the resin thickness does not change between wafers. Therefore, the wafer-to-wafer variation of the wafer shape after grinding achieves the target value.

[0041] From the above results, it was shown that by performing temperature correction of the press speed when applying the resin (not performing temperature correction of the press load (constant press load)), the inter-wafer variation in the average resin thickness is improved, and the inter-wafer variation in the wafer shape after grinding is also improved.

[0042] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and any configuration that is substantially the same as the technical idea described in the claims of the present invention and that provides similar effects is included in the technical scope of the present invention. [Explanation of symbols]

[0043] 1...resin application device, 2...wafer, 2a...first main surface, 2b...second main surface, 3...resin (liquid resin), 4...resin supply means, 5...holding means (upper platen), 6...motor, 7...stage (lower platen), 8...light-transmitting film, 9...ultraviolet light irradiation means, 10...temperature measurement means, 11...press load detection means, 12...control means.

Claims

1. A resin coating method for coating a wafer with a resin, comprising the steps of: providing a wafer having a first major surface and a second major surface opposite the first major surface; holding the second main surface of the wafer with a holding means; supplying a resin to a position facing the first main surface of the wafer; Measuring the temperature of the resin or an area surrounding the resin; selecting a press speed corresponding to the measured temperature by referring to previously acquired data on temperature and press speed at which the resin thickness and press load are given values; driving the holding means at the selected press speed to spread the resin over the first main surface of the wafer; stopping the holding means when the press load reaches a predetermined value; and curing the resin to form a planarizing resin layer.

2. A wafer on which a planarizing resin layer is formed using the resin coating method according to claim 1, suction-holding the planarizing resin layer and grinding or polishing the second main surface of the wafer; removing the planarizing resin layer from the wafer; 4. A method for manufacturing a wafer, comprising: suction-holding the second main surface of the wafer; and grinding or polishing the first main surface of the wafer.

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