Spin etching apparatus and spin etching method

Abstract

To provide a spin etching apparatus and a spin etching method which can improve an etching rate and uniformity in an etched surface in a substrate surface by etching.SOLUTION: A rotary table; an etching liquid supply nozzle; a substrate suction pad; and a sheet-shaped local heating member placed on the substrate suction pad so as to form at least a circular non-heating portion and an annular non-heating portion, wherein a heating portion of the sheet-shaped local heating member is an etching reaction promoting portion for promoting an etching reaction, in the spin etching apparatus, the non-heating portion includes an etching reaction local acceleration area which is an etching reaction non-acceleration portion which does not accelerate an etching reaction, and a non-contact power transmission mechanism which supplies power to the sheet-shaped local heating member by non-contact power transmission, and the substrate is closely mounted on the sheet-shaped local heating member and contact-heated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a spin etching apparatus and a spin etching method for etching a semiconductor substrate by rotating the substrate while holding it horizontally and supplying an etching solution to the upper surface of the substrate. [Background technology]

[0002] Conventionally, in the semiconductor manufacturing process, there has been an increase in processes (also called spin processes) in which various processes are performed while rotating semiconductor substrates, including semiconductor wafers such as silicon, such as spin etching, spin drying, and spin coating. One such spin process is spin etching.

[0003] In spin etching, a semiconductor substrate is rotated while held horizontally, and an etching solution is supplied to the upper surface of the substrate to etch the substrate. Patent Document 1, for example, describes a wafer rotation and holding device using a non-contact power supply mechanism for a rotary table as an example of an apparatus for performing spin etching. Patent Document 2, which describes a wafer rotation and holding device using a non-contact power supply mechanism for a rotary table, also discloses a wafer rotation and holding device that uses a non-contact power supply mechanism for a rotary table to heat the wafer.

[0004] In Patent Document 2, the heating means is a configuration in which the entire substrate is heated by a far-infrared heater and a reflector. However, with a configuration in which the entire substrate is heated using a far-infrared heater and a reflector, there are problems in that the etching rate is not improved as much as expected, and there is also a problem in that the etching does not improve the in-plane uniformity of the etching process within the substrate surface. Note that the in-plane uniformity of the etching process within the substrate surface refers to the amount of etching being uniform at any position within the substrate surface, and the in-plane uniformity of the etching process is an index that indicates this uniformity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2017 / 183402 [Patent Document 2] WO2017 / 204083 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above-mentioned problems of the conventional technology, and aims to provide a spin etching apparatus and a spin etching method that can improve the etching rate and also improve the in-plane etching uniformity within the substrate surface by etching. [Means for solving the problem]

[0007] In order to solve the above problems, the spin etching apparatus of the present invention is a spin etching apparatus comprising: a turntable; an etching solution supply nozzle that drips etching solution from above the turntable; a substrate suction pad placed on the turntable; a sheet-shaped local heating element placed on the substrate suction pad so as to form at least a circular unheated area and an annular unheated area, whereby the heated area of ​​the sheet-shaped local heating element is an etching reaction promotion area that promotes the etching reaction, and the unheated area is an etching reaction non-promotion area that does not promote the etching reaction; and a non-contact power transmission mechanism that supplies power to the sheet-shaped heating element by non-contact power transmission, wherein a substrate is placed in close contact on the sheet-shaped local heating element and heated by contact.

[0008] The non-heated portion is preferably a gap portion where no heated portion of the sheet-shaped local heating member exists.

[0009] It is preferable that the annular non-heated portion is a first annular non-heated portion, and that a second annular non-heated portion having a larger diameter than the first annular non-heated portion is formed outside the first annular non-heated portion.

[0010] It is preferable that the sheet-shaped local heating member is not present at the outer edge of the substrate placed on the sheet-shaped local heating member, and that the outer edge is left as a non-heated region.

[0011] It is preferable that the sheet-shaped local heating element is not present at the outer edge of the substrate placed on the sheet-shaped local heating element, but is configured as an outer edge non-heated area, and that the outer edge non-heated area is the second annular non-heated area.

[0012] The sheet-like local heating member is preferably a polyimide tape heater.

[0013] The spin etching method of the present invention is a spin etching method in which spin etching is performed on a substrate using the spin etching apparatus.

[0014] The method for manufacturing a substrate of the present invention is a method for manufacturing a substrate that includes an etching step using the spin etching method. [Effects of the Invention]

[0015] The present invention has the remarkable effect of providing a spin etching apparatus and a spin etching method that can improve the etching rate and the in-plane etching uniformity within the substrate surface. Furthermore, the present invention also makes it possible to monitor and control the temperature using the supplied power. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram showing one embodiment of a spin etching apparatus of the present invention. [Figure 2] 1 is a block diagram showing one embodiment of a spin etching apparatus of the present invention; [Figure 3] 1A and 1B show a state in which a sheet-shaped local heating member used in a spin etching apparatus of the present invention is placed on a suction pad, where (a) is a plan photograph and (b) is a perspective photograph. [Figure 4] 1A and 1B show one embodiment of a sheet-shaped local heating element used in a spin etching apparatus of the present invention, where (a) is a planar photograph of a first annular sheet-shaped local heating element, and (b) is a planar photograph of a second annular sheet-shaped local heating element. [Figure 5] FIG. 2 is a block diagram of a temperature control mechanism used in the examples. [Figure 6] This is a comparative example in which a substrate is placed in close contact with the spin etching apparatus of the present invention and etched without heating. [Figure 7] 1 is a bar graph showing a comparison of variations within the substrate surface between Comparative Example 1 and Examples 1 to 6. [Figure 8] 1 is a line graph showing a comparison of removal amounts by etching in Comparative Example 1 and Examples 1 to 6. [Figure 9] 10 is a graph showing the in-plane uniformity of pattern A before heating and before etching. [Figure 10] 10 is a graph showing the in-plane uniformity of pattern A before heating and before etching. [Figure 11] 10 is a graph showing the in-plane uniformity of pattern A before heating and before etching. [Figure 12] 10 is a graph showing the in-plane uniformity of pattern A in Comparative Example 1, in which etching was performed without heating (0 V) on a substrate having pattern A in FIG. [Figure 13] 11 is a graph showing the in-plane uniformity of pattern A in Example 5, in which etching was performed on a substrate having pattern A in FIG. 10 while heating at 55 V. [Figure 14] 12 is a graph showing the in-plane uniformity of pattern A in Example 6, in which etching was performed on a substrate having pattern A in FIG. 11 while heating at 55 V. DETAILED DESCRIPTION OF THE INVENTION

[0017] The following describes embodiments of the present invention, but these embodiments are shown by way of example only, and it goes without saying that various modifications are possible without departing from the technical spirit of the present invention. In the drawings, the same members are designated by the same reference numerals.

[0018] 1, the reference numeral 10 denotes a spin etching apparatus of the present invention. The spin etching apparatus 10 comprises a turntable 12 that rotates about a rotary shaft 11, an etching solution supply nozzle 13 that dispenses etching solution from above the turntable 12, a substrate suction pad 14 placed on the turntable 12, and a sheet-like local heating member 15 placed on the substrate suction pad 14 so as to form at least a circular unheated region 16 and an annular unheated region 18. A known substrate suction pad 14 can be used as the substrate suction pad 14.

[0019] In the spin etching apparatus 10, the sheet-shaped local heating member 15 is placed on the substrate suction pad 14 so as to form at least a circular unheated region 16 and an annular unheated region 18, and thus the heated region of the sheet-shaped local heating member 15 is an etching reaction promotion region 17 that promotes the etching reaction, and the unheated region is an etching reaction non-promotion region 19 that does not promote the etching reaction, forming a local etching reaction promotion area 21. The spin etching apparatus 10 also has a non-contact power transmission mechanism 20 that supplies power to the sheet-shaped local heating member 15 by non-contact power transmission. The substrate W is placed in close contact on the sheet-shaped local heating member 15 and heated by contact.

[0020] The contactless power transmission mechanism 20 includes a fixed-side primary coil 24 (power supply coil) wound around the rotary shaft 11, a power supply source 28 (high-frequency power supply device) connected to the fixed-side primary coil 24, and a rotary table-side secondary coil 22 (power receiving coil) provided corresponding to the fixed-side primary coil 24 at a predetermined distance and attached to the rotary table 12. The contactless power supply mechanism for a rotary table shown in Figures 2 to 4 of Patent Document 1 can be applied to this contactless power transmission mechanism 20. Reference numeral 26 denotes a capacitor. The rotary table is equipped with a communication and control circuit 30.

[0021] FIG. 2 is a block diagram illustrating one embodiment of a spin etching apparatus 10 according to the present invention. In the block diagram, the spin etching apparatus 10 includes a power supply 28, which is a high-frequency power supply device, and is a high-frequency power supply board connected to an AC power source 44. The power supply 28 is connected to a fixed-side primary coil 24 (power supply coil), and a turntable-side secondary coil 22 (power receiving coil) is provided a predetermined distance away. The turntable-side secondary coil 22 is connected to a DC power source 32, which is connected to a compact CPU 34 mounted on the turntable 12. A semiconductor relay 42 is connected to the turntable-side secondary coil 22 (power receiving coil), and the sheet-shaped local heating element 15 is heated by power supplied via electromagnetic induction. A temperature sensor 40 is connected to the sheet-shaped local heating element 15, which controls the temperature. The compact CPU 34 communicates wirelessly with an external computer via a wireless communication device 38. Wireless communication may be achieved using wireless communication techniques such as Bluetooth (registered trademark) or Wi-Fi (registered trademark).

[0022] An example of the sheet-shaped localized heating member 15 is shown in Fig. 3. A heat-resistant resin tape heater using a tape-shaped heat-resistant resin is suitable as the sheet-shaped localized heating member 15. For example, a heat-resistant resin tape heater that is made by bonding a metal foil resistance heating element and a heat-resistant resin film and generates heat in a planar manner can be used as the heat-resistant resin tape heater.

[0023] A suitable example of a heat-resistant resin tape heater is a polyimide tape heater made by bonding a stainless steel foil resistance heating element and a polyimide resin film. Furthermore, a sheet-shaped local heating element 15 that is highly acid-resistant is also suitable. An example of an acid-resistant sheet-shaped local heating element 15 is a polyimide tape heater, but any other acid-resistant sheet-shaped local heating element can also be used. In the example shown in FIG. 3, two sheet-shaped local heating elements 15 are placed on the substrate suction pad 14. In the example shown in FIG. 3, an annular gap 46 is formed outside a first annular sheet-shaped local heating element 48, which has a circular gap 52 formed in its center. A second annular sheet-shaped local heating element 50, which has a larger diameter than the first annular sheet-shaped local heating element 48, is placed outside the annular gap 46. Both the first annular sheet-shaped local heating element 48 and the second annular sheet-shaped local heating element 50 have circular gaps 52, 54 in their centers. The examples shown in FIGS. 3 and 4 illustrate an example of a polyimide tape heater.

[0024] The area where the sheet-shaped local heating member 15 is placed becomes a heating area for heating the substrate W. The substrate W is heated at the heating area, and an etching reaction is promoted at the heated area, so the heated area becomes an etching reaction promotion area.

[0025] On the other hand, the gaps 52 and 46 where the sheet-shaped local heating member 15 is not placed are non-heated areas. The gap 46 is part of the circular gap 54. Furthermore, the gap 56 on the outside of the second annular sheet-shaped local heating member 50 is also non-heated because it does not have a sheet-shaped local heating member 15. The gap 56 is an outer edge non-heated area. Since the substrate W is not heated in the non-heated area, the etching reaction is not promoted, and the non-heated area is an etching reaction non-promoted area.

[0026] In the present invention, as described above, by providing heated areas and unheated areas, etching reaction promotion areas and etching reaction non-promotion areas are formed, and etching with a uniform etching removal amount (uniform etching rate) is performed in accordance with the in-plane shape of the substrate while maintaining the in-plane shape of the substrate. In other words, when the entire substrate is heated as in the conventional method, the etching reaction is promoted across the entire surface of the substrate, so even if there are irregularities in the surface of the substrate, the irregularities are not maintained, and the in-plane shape of the substrate is removed by etching. In the present invention, even if there are irregularities in the surface of the substrate, it is possible to perform etching so that the irregular shape is maintained.

[0027] In the example of Fig. 1, one annular sheet-shaped local heating member 15 is placed as the sheet-shaped local heating member 15. In the examples of Figs. 3 and 4, an example of a configuration in which two annular sheet-shaped local heating members 15 are placed is shown. A configuration in which two annular sheet-shaped local heating members 15 are placed (or a configuration in which two or more sheet-shaped local heating members 15 are placed), as in the examples of Figs. 3 and 4, is preferable because it allows for more precise setting of etching reaction promotion areas and etching reaction non-promotion areas.

[0028] In Patent Document 2, the heating means heats the entire substrate without contacting the substrate. In the present invention, at least a circular unheated area and an annular unheated area are provided, and the sheet-shaped local heating member 15 and the substrate W are in contact with each other, thereby directly heating the substrate W locally. In the present invention, by directly heating the substrate W in a contact-type manner as a method for efficiently transferring heat, it is possible to obtain effects not previously obtainable. Furthermore, by using power supplied by the non-contact power transmission mechanism 20, it is possible to monitor and control the temperature via the temperature sensor 40. In this way, in the present invention, the substrate is directly heated locally, rather than heated entirely.

[0029] In the illustrated example, the rotating shaft 11 is made of SUS (stainless steel), and the rotating table 12 is made of synthetic resin such as industrial plastic. There is no particular limit to the rotation speed of the rotating table 12, but a range of 100 to 1000 rpm is preferable. The substrate W used in the present invention is preferably a semiconductor substrate, and examples of suitable substrates include silicon substrates and compound semiconductor substrates such as SiC (silicon carbide), GaN (gallium nitride), and SiN (silicon nitride). Furthermore, the substrate W is preferably a wafer-shaped semiconductor substrate.

[0030] By performing spin etching on the substrate W using the spin etching apparatus 10 described above, the spin etching method of the present invention is achieved.

[0031] The method for manufacturing a substrate of the present invention is characterized by including an etching step using the spin etching method described above. [Example]

[0032] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to these examples, and various modifications are possible as long as they do not deviate from the technical concept of the present invention.

[0033] As shown in Figures 3 and 4, a first annular sheet-shaped local heating element 48 and a second annular sheet-shaped local heating element 50 with a larger diameter were placed in the spin etching apparatus shown in Figures 1 and 2. A diagram of the control block is shown in Figure 5. The temperature of the first annular sheet-shaped local heating element 48 and the second annular sheet-shaped local heating element 50 with a larger diameter were controlled using the control block configuration shown in Figure 5.

[0034] A silicon single crystal wafer with a diameter of 12 inches and a standard thickness of 775 μm ± 25 μm was prepared as a semiconductor substrate. The silicon single crystal wafer has minute variations within its surface, which will be referred to as Pattern A. Using an etching solution of a mixed acid based on hydrofluoric acid and nitric acid, the wafer was subjected to spin etching by oscillating the nozzle under the following etching conditions. The temperature of the wafer at the start of spin etching was approximately 30°C or less.

[0035] <Etching conditions> [Table 1]

[0036] <Heating conditions by applying voltage> Comparison example: 0V (no heating) approx. 35°C *Heat generated by etching Example 1: 35V for 60 seconds, approximately 41°C Example 2: 35V for 60 seconds, approximately 41°C Example 3: 45V for 60 seconds, approximately 44°C Example 4: 45V for 60 seconds, approximately 44°C Example 5: 55V for 60 seconds, approximately 49°C Example 6: 55V for 60 seconds, approximately 49°C

[0037] FIG. 6 shows comparative data for a case in which a substrate was placed in close contact with the spin etching apparatus of the present invention and etched without applying a voltage of 0 V or heating. In FIG. 6, the vertical axis represents the etching removal amount (μm). The horizontal axis represents the distance (mm) from the 0 mm center to the outer periphery of the substrate. As shown in FIG. 6, a suction pad with a diameter of 260 mm was used. A first annular sheet-shaped local heating element 48 and a second annular sheet-shaped local heating element 50 with a larger diameter were placed on the suction pad. In other words, only the areas where the first annular sheet-shaped local heating element 48 and the second annular sheet-shaped local heating element 50 with a larger diameter were present were heated.

[0038] On the other hand, in Examples 1 to 6, a semiconductor substrate wafer was placed in close contact with the spin etching apparatus of the present invention, and the above-mentioned voltages were applied to heat the semiconductor substrate wafer, thereby performing spin etching. A comparison between Comparative Example 1 and Examples 1 to 6 is shown in FIG. 7. The variation within the substrate surface (etching uniformity within the substrate surface) shown in FIG. 7 was measured by measuring the thickness at the same position within the substrate surface before and after etching using a capacitance-type thickness meter. Specifically, one line was measured at 1 mm intervals within the substrate surface of a 12-inch wafer (-145 mm to 145 mm: diameter 290 mm), and the removal rate was calculated for each point using the following formula: Before etching - After etching = Removal amount The obtained removal amount was used to calculate the variation [%] within the substrate surface using the following formula. Variation within the board surface [%] = (Maximum removal allowance - Minimum removal allowance) / (Maximum removal allowance + Minimum removal allowance) x 100

[0039] In Comparative Example 1, the variation within the substrate surface (uniformity of etching within the substrate surface) was about 3%. In Examples 1 to 6, in which heating was performed by applying a voltage, the degree of variation within the substrate surface was reduced, as shown in Figure 7, and in Examples 5 and 6, the reduction in variation within the substrate surface was nearly twice as large as in Comparative Example 1.

[0040] FIG. 8 shows a comparison of the removal amount by etching. In FIG. 8, the vertical axis represents the removal amount by etching [μm]. The horizontal axis represents the distance [mm] from 0 mm to the outer periphery of the substrate. In Examples 1 to 6, in which the substrate was heated, the etching rate was improved compared to Comparative Example 1, in which heating was not performed, and the removal amount by etching closely followed Pattern A. In the cases of Examples 1 to 6, the heated portion of the sheet-shaped local heating member was an etching reaction promotion portion that promoted the etching reaction, and the unheated portion was an etching reaction non-promotion portion that did not promote the etching reaction, so the etching reaction was locally promoted.

[0041] In order to show that the etching removal amount is in a shape that faithfully follows pattern A, a comparison is shown in FIGS.

[0042] 9 shows the in-plane uniformity of pattern A before heating and before etching. The horizontal axis represents the horizontal length of the substrate, and the vertical axis represents the vertical thickness of the substrate. Fig. 12 shows the in-plane uniformity of pattern A in Comparative Example 1, in which etching was performed without heating (0 V) on the substrate with pattern A in Fig. 9. In Comparative Example 1, the in-plane etching uniformity within the substrate surface after etching fluctuated significantly compared to before etching.

[0043] 10 shows the in-plane uniformity of pattern A before heating and before etching. The horizontal axis represents the horizontal length of the substrate, and the vertical axis represents the vertical thickness of the substrate. Fig. 13 shows the in-plane uniformity of pattern A in Example 5, in which etching was performed on the substrate with pattern A in Fig. 10 while heating at 55 V. In Example 5, the in-plane etching uniformity within the substrate surface after etching showed little change compared to before etching.

[0044] 11 shows the in-plane uniformity of pattern A before heating and before etching. The horizontal axis represents the horizontal length of the substrate, and the vertical axis represents the vertical thickness of the substrate. Fig. 14 shows the in-plane uniformity of pattern A in Example 6, in which etching was performed on the substrate with pattern A in Fig. 11 while heating at 55 V. In Example 6, the in-plane etching uniformity within the substrate surface after etching showed little change compared to before etching.

[0045] As described above, the spin etching method using the spin etching apparatus of the present invention not only improves the etching rate, but also reduces fluctuations in the in-plane etching uniformity within the substrate surface after etching compared to before etching, thereby improving the in-plane etching uniformity within the substrate surface after etching. [Explanation of symbols]

[0046] 10: spin etching device, 11: rotating shaft, 12: rotating table, 13: etching solution supply nozzle, 14: substrate suction pad, 15: sheet-shaped local heating member, 16: non-heated area, 17: etching reaction promotion area, 18: non-heated area, 19: etching reaction non-promotion area, 20: non-contact power transmission mechanism, 21: etching reaction local promotion area, 22: secondary coil on rotating table side, 24: primary coil on fixed side, 28: power supply source, 30: control circuit, 32: DC power supply, 34: small CPU, 38: wireless communication device, 40: temperature sensor, 42: semiconductor relay, 44: AC power supply, 46: gap, 48: first annular sheet-shaped local heating member, 50: second annular sheet-shaped local heating member, 52, 54, 56: gaps, A: pattern, W: substrate.

Claims

1. A rotary table and an etching solution supply nozzle that drips etching solution from above the rotary table; a substrate suction pad placed on the rotary table; a sheet-shaped local heating member placed on the substrate suction pad so as to form at least a circular non-heated area and an annular non-heated area; an etching reaction local promotion area, in which a heated portion of the sheet-shaped local heating member is an etching reaction promotion portion that promotes an etching reaction, and a non-heated portion is an etching reaction non-promotion portion that does not promote an etching reaction; a non-contact power transmission mechanism for supplying power to the sheet-shaped heating element by non-contact power transmission; Including, A spin etching apparatus in which a substrate is placed in close contact with the sheet-like local heating member and heated by contact.

2. 2. The spin etching apparatus according to claim 1, wherein the non-heated portion is a gap portion where no heated portion of the sheet-shaped local heating member exists.

3. 2. The spin etching apparatus of claim 1, wherein the annular non-heated portion is a first annular non-heated portion, and a second annular non-heated portion having a larger diameter than the first annular non-heated portion is formed outside the first annular non-heated portion.

4. 2. The spin etching apparatus according to claim 1, wherein the sheet-shaped local heating member is not present at the outer edge of the substrate placed on the sheet-shaped local heating member, and the outer edge is left as a non-heated region.

5. 4. The spin etching apparatus according to claim 3, wherein the sheet-shaped local heating element is not present at the outer edge of the substrate placed on the sheet-shaped local heating element, but is configured as an outer edge non-heated area, and the outer edge non-heated area is the second annular non-heated area.

6. 2. The spin etching apparatus according to claim 1, wherein the sheet-like local heating member is a polyimide tape heater.

7. A spin etching method, comprising: performing spin etching on a substrate using the spin etching apparatus according to any one of claims 1 to 6.

8. A method for manufacturing a substrate, comprising an etching step by the spin etching method according to claim 7.

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