Semiconductor processing method

Abstract

The invention provides a semiconductor processing method. The semiconductor processing method comprises the following steps. The semiconductor ingot is cut to obtain a semiconductor wafer including a first face and a second face opposite to the first face. And performing a double-sided grinding process to simultaneously grind the first surface and the second surface of the semiconductor wafer by using a diamond grinding liquid. The diamond grinding fluid contains diamond particles with the median particle size of 0.1-3 microns.

Description

Technical Field

[0001] The present invention relates to a method for processing semiconductors, and more particularly to a method for grinding semiconductor wafers. Background Art

[0002] Semiconductor wafers are widely used and are the core materials for manufacturing various chips. During the process of fabricating chips, the surface of semiconductor wafers usually needs to be ground and polished to ensure that subsequent semiconductor processes can be carried out on a flat surface. Generally, the grinding process is divided into three stages: rough grinding, medium grinding, and fine grinding, to ensure the uniformity of the wafer thickness. After grinding, rough polishing and fine polishing are also required to further reduce the surface roughness of the wafer. However, this series of grinding and polishing processes not only take time but also are costly. Summary of the Invention

[0003] The present invention provides a method for processing semiconductors, which can reduce the time and cost required for grinding and polishing processes.

[0004] At least one embodiment of the present invention provides a method for processing semiconductors, including the following steps. Cut a semiconductor ingot to obtain a semiconductor wafer, where the semiconductor wafer includes a first surface and a second surface opposite to the first surface. Perform a double-sided grinding process to simultaneously grind the first surface and the second surface of the semiconductor wafer using a diamond grinding fluid. The diamond grinding fluid contains diamond particles with a median particle size of 0.1 to 3 micrometers. Description of the Drawings

[0005] Figures 1A to 1D are various schematic diagrams of a method for processing semiconductors according to an embodiment of the present invention;

[0006] Figure 2 is a flowchart of a method for processing semiconductors according to an embodiment of the present invention. Detailed Description

[0007] Figures 1A to 1D are various schematic diagrams of a method for processing semiconductors according to an embodiment of the present invention. Figure 2 is a flowchart of a method for processing semiconductors according to an embodiment of the present invention. Please refer to Figure 1A and Figure 2In step S1, a semiconductor ingot 100 is cut to obtain a semiconductor wafer 110. In some embodiments, the semiconductor ingot 100 includes, for example, an elemental semiconductor (such as silicon, germanium, or other suitable materials), a compound semiconductor (such as silicon carbide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide, indium antimonide, or other suitable materials), an alloy semiconductor (such as SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, GaInAsP, or other suitable materials), or other types of semiconductor materials.

[0008] In some embodiments, each semiconductor wafer 110 includes a first surface 110a and a second surface 110b opposite to the first surface 110a. At this stage, both the first surface 110a and the second surface 110b of the semiconductor wafer 110 are preliminarily polished surfaces and still have some roughness. For example, the surface roughness Ra of the first surface 110a and the second surface 110b is from 1000 nanometers to 5000 nanometers. In addition, at this stage, the bow of the semiconductor wafer 110 is from +80 micrometers to -80 micrometers, and the warp is from 0 micrometers to 80 micrometers. In some embodiments, the semiconductor wafer 110 includes silicon carbide, and one of the first surface 110a and the second surface 110b is a silicon surface, and the other is a carbon surface. In some embodiments, the semiconductor wafer 110 is a 6-inch to 8-inch wafer.

[0009] In some embodiments, the thickness of the semiconductor wafer 110 is from 200 micrometers to 1600 micrometers.

[0010] Next, please refer to Figure 1B and Figure 2 In step S2, a double-sided grinding process is performed on the semiconductor wafer 110. In this embodiment, the semiconductor wafer 110 is placed in a double-sided grinding device, and the grinding process is performed on the first surface 110a and the second surface 110b simultaneously. The double-sided grinding device includes a first grinding disk 210, a second grinding disk 220, a first grinding pad 230, a second grinding pad 240, a sun gear 250, a first carrier 260a, a second carrier 260b, an internal gear 270, and an adjustment structure 280.

[0011] The first grinding disk 210 and the second grinding disk 220 are disposed opposite to each other. The first grinding pad 230 and the second grinding pad 240 are respectively disposed on the first grinding disk 210 and the second grinding disk 220 and are sandwiched between the first grinding disk 210 and the second grinding disk 220. The sun gear 250, the first carrier 260a, the second carrier 260b, and the internal gear 270 are located between the first grinding pad 230 and the second grinding pad 240. When performing the double-sided grinding process, the first grinding disk 210 and the second grinding disk 220 rotate in opposite directions.

[0012] The peripheries of the first carrier 260a and the second carrier 260b are provided with gears, which are engaged between the internal gear 270 and the sun gear 250, enabling the first carrier 260a and the second carrier 260b to rotate around the sun gear 250 in addition to revolving around it.

[0013] The first carrier 260a has through holes for accommodating a plurality of semiconductor wafers 110, and the plurality of semiconductor wafers 110 are fixed in the through holes of the first carrier 260. In other words, a double-sided grinding process can be performed on the plurality of semiconductor wafers 110 simultaneously. In some embodiments, these semiconductor wafers 110 can be obtained by cutting one or more semiconductor ingots. Optionally, the second carrier 260b has a plurality of through holes for accommodating the adjusting structures 280, and the adjusting structures 280 are fixed in the through holes of the second carrier 260b to adjust the process. In some embodiments, the combination of the second carrier 260b and the adjusting structures 280 can also be replaced by an adjusting ring, which is directly engaged between the internal gear 270 and the sun gear 250. When performing the double-sided grinding process, the internal gear 270 and the sun gear 250 drive the first carrier 260a and the second carrier 260b to rotate.

[0014] In the present embodiment, when performing the double-sided grinding process, a diamond grinding fluid is applied to the first surface and the second surface of the semiconductor wafer 110 to simultaneously grind the first surface and the second surface using the diamond grinding fluid. The diamond grinding fluid contains abrasives and a carrier solution, where the abrasives contain diamond particles with a median particle size (D50) of 0.1 to 3 microns, and the carrier solution contains water, alcohol, or a combination of the above or other solutions.

[0015] In some embodiments, when performing the double-sided grinding process, 1 to 10 (5 in the figure as an example) semiconductor wafers 110 are arranged in each first carrier 260a, and weights are applied to the semiconductor wafers 110 in the first carrier 260a. In some embodiments, the thickness of the semiconductor wafer 110 is reduced by 20 to 28 microns during the double-sided grinding process. In some embodiments, weights are applied to the semiconductor wafers 110 in a plurality of first carriers 260a simultaneously. For example, a load of 100 to 200 kg is applied to the semiconductor wafers 110 in 1 to 5 first carriers 260a. Each first carrier 260a includes, for example, 1 eight-inch semiconductor wafer 110 or 5 six-inch semiconductor wafers 110.

[0016] In some embodiments, after the double-sided grinding process, the semiconductor wafer 110 forms a semiconductor wafer 110' including a first surface 110a' and a second surface 110b' (please refer to Figure 1B and Figure 1C), wherein the surface roughness Ra of the first surface 110a' and the second surface 110b' is from 1.0 nanometers to 5.0 nanometers. In addition, after performing the double-sided grinding process, the bow of the semiconductor wafer 110 is from +50 micrometers to -50 micrometers, and the warp is from 0 micrometers to 50 micrometers.

[0017] In an embodiment of the present invention, a single double-sided grinding process is used to replace the complicated process from rough grinding to fine grinding, thereby greatly saving the time and cost required for processing. By simultaneously grinding the two sides of the semiconductor wafer 110 using the double-sided grinding process, when the two sides reach a balanced roughness at the same time, the bow and warp can be improved; conversely, if the two sides of the semiconductor wafer 110 are separately ground using two single-sided grinding processes, it is easy to cause the surface roughness of the two sides of the semiconductor wafer 110 to be inconsistent after processing, resulting in problems of abnormal processing and obtaining poor bow and warp.

[0018] Next, please refer to Figure 1C and Figure 2 Step S3 of, after performing the double-sided grinding process, a first single-sided polishing process is performed on the first surface. In this embodiment, the semiconductor wafer 110' is placed in a single-sided polishing apparatus, and a polishing process is performed on the first surface 110a'. The single-sided polishing apparatus includes a polishing carrier 310, an actuator 312, a polishing pad 320, a turntable 330, an actuator 332, and a polishing liquid supply unit 340.

[0019] The polishing carrier 310 is adapted to fix one or more semiconductor wafers 110'. The turntable 330 is disposed at a corresponding position of the polishing carrier 310 for supporting the polishing pad 320. When polishing the semiconductor wafer 110', the surface 320a of the polishing pad 320 is adapted to face the semiconductor wafer 110' and the surface 310a of the polishing carrier 310.

[0020] The actuator 312 drives the whole or part of the polishing carrier 310 to move or rotate in a corresponding direction. In some embodiments, the actuator 312 may include a power supply device, a motor, a belt, a gear, and other related components, but the present invention is not limited thereto. In addition, related components such as communication components, power components, shock-absorbing components, positioning components, or sensing components may also be included in the actuator 312, but the present invention is not limited thereto.

[0021] The actuator 332 drives the turntable 330 and / or the polishing pad 320 thereon to rotate in a corresponding direction. In some embodiments, the rotation direction of the actuator 312 (such as the fourth direction D4) and the rotation direction of the actuator 332 (such as the fifth direction D5) may be the same or different.

[0022] The polishing liquid supply unit 340 can supply the polishing liquid 390 to the semiconductor wafer 110' in a single-sided polishing process to polish the semiconductor wafer 110'. In some embodiments, the polishing liquid 390 contains abrasive, dispersant, water, and lubricant.

[0023] In some embodiments, the thickness of the semiconductor wafer 110' is reduced by 1 to 2 microns in the first single-sided polishing process. In some embodiments, the first surface 110a' of the semiconductor wafer 110' forms a semiconductor wafer 110'' (please refer to Figure 1C and Figure 1D ) including the first surface 110a'' after the first single-sided polishing process, and the surface roughness Ra of the first surface 110a'' is less than 0.5 nanometers.

[0024] Finally, please refer to Figure 1D and Figure 2 Step S4 of to flip the semiconductor wafer 110'' so that the unpolished second surface 110b' faces the polishing pad 320, and perform a second single-sided polishing process on the second surface 110b'.

[0025] In some embodiments, the thickness of the semiconductor wafer 110'' is reduced by 1 to 2 microns in the second single-sided polishing process. In some embodiments, the surface roughness Ra of the second surface 110b' of the semiconductor wafer 110'' after the second single-sided polishing process is less than 0.5 nanometers. In some embodiments, the total thickness lost by the semiconductor wafer in the first single-sided polishing process and the second single-sided polishing process is about 2 to 5 microns.

[0026] In some embodiments, the total thickness variation (TTV) of the semiconductor wafer 110'' after the second single-sided polishing process is less than 2 microns, the bow is +25 microns to -25 microns, and the warp is +50 microns to -50 microns.

[0027] In some embodiments, the semiconductor wafer 110'' can be used as a seed after the second single-sided polishing process and can be used as a raw material for making other semiconductor ingots. In some embodiments, the semiconductor wafer 110'' can be used as a raw material for manufacturing various chips after the second single-sided polishing process.

[0028] Some embodiments and comparative examples are provided below to better describe the present invention. In the embodiments and comparative examples, the grinding wheel used can have a shape with abrasive grains embedded on the surface, and the size of the abrasive grains is represented by mesh. Mesh is a measure of how many openings there are per inch on a sieve.

[0029] Comparative Example 1

[0030] In Comparative Example 1, a semiconductor wafer was obtained after cutting a semiconductor ingot. Subsequently, a double-sided grinding process was performed on the first side and the second side of the semiconductor wafer. The double-sided grinding process included 30 minutes of rough grinding and 30 minutes of fine grinding. The rough grinding was carried out with a rough grinding wheel of 300 to 800 mesh, and the fine grinding was carried out with a fine grinding wheel of 1000 to 10000 mesh. The thickness of the semiconductor wafer decreased by 20 microns during the rough grinding process and by 10 microns during the fine grinding process. After the grinding process, a single-sided polishing process was performed on the semiconductor wafer. The single-sided polishing process included 120 minutes of rough polishing and 60 minutes of fine polishing. The rough polishing was carried out using Al2O3 particles (or SiO2 particles) with a particle size of 0.1 to 0.3 microns as abrasive grains, and the fine polishing was a chemical polishing without using abrasive grains. The thickness of the semiconductor wafer decreased by 1 to 2 microns during the rough polishing and by 0.1 to 0.5 microns during the fine polishing process. In Comparative Example 1, the total time consumed by the grinding process plus the polishing process was at least 240 minutes.

[0031] Comparative Example 2

[0032] In Comparative Example 2, a semiconductor wafer was obtained after cutting a semiconductor ingot. Subsequently, a double-sided grinding process was performed on the first side and the second side of the semiconductor wafer. The double-sided grinding process included grinding the semiconductor wafer for 10 minutes using a diamond grinding fluid containing diamond particles with a median particle size (D50) of 4 microns. During the grinding process, a load of 170 kg was applied to 5 eight-inch semiconductor wafers. The thickness of the semiconductor wafer decreased by 30 microns during the grinding process. After the grinding process, a single-sided polishing process was performed on the semiconductor wafer. The single-sided polishing process included 100 minutes of polishing. The thickness of the semiconductor wafer decreased by 1 to 2 microns during the polishing process. In Comparative Example 2, the total time consumed by the grinding process plus the polishing process was at least 110 minutes.

[0033] Comparative Example 3

[0034] In Comparative Example 3, a semiconductor wafer was obtained after cutting a semiconductor ingot. Subsequently, a double-sided grinding process was performed on the first side and the second side of the semiconductor wafer. The double-sided grinding process included grinding the semiconductor wafer for 15 minutes using a diamond grinding fluid containing diamond particles with a median particle size of 6 microns. During the grinding process, a load of 170 kg was applied to 5 eight-inch semiconductor wafers. The thickness of the semiconductor wafer decreased by 50 microns during the grinding process. After the grinding process, a single-sided polishing process was performed on the semiconductor wafer. The single-sided polishing process included 100 minutes of polishing. The thickness of the semiconductor wafer decreased by 1 to 2 microns during the polishing process. In Comparative Example 3, the total time consumed by the grinding process plus the polishing process was at least 115 minutes.

[0035] Example 1

[0036] In Example 1, a semiconductor wafer is obtained after cutting a semiconductor ingot. Then, a double-sided grinding process is performed on the first surface and the second surface of the semiconductor wafer. The double-sided grinding process includes grinding the semiconductor wafer for 20 minutes using a diamond grinding fluid containing diamond particles with a median particle size of 3 microns. During the grinding process, a load of 170 kg is applied to 5 eight-inch semiconductor wafers. The thickness of the semiconductor wafer is reduced by 28 microns during the grinding process. After the grinding process, a single-sided polishing process is performed on the semiconductor wafer. The single-sided polishing process includes 100 minutes of polishing. The thickness of the semiconductor wafer is reduced by 1 to 2 microns during the polishing. In Example 1, the total time consumed by the grinding process plus the polishing process is at least 120 minutes.

[0037] Example 2

[0038] In Example 2, a semiconductor wafer is obtained after cutting a semiconductor ingot. Then, a double-sided grinding process is performed on the first surface and the second surface of the semiconductor wafer. The double-sided grinding process includes grinding the semiconductor wafer for 30 minutes using a diamond grinding fluid containing diamond particles with a median particle size of 2 microns. During the grinding process, a load of 170 kg is applied to 5 eight-inch semiconductor wafers. The thickness of the semiconductor wafer is reduced by 26 microns during the grinding process. After the grinding process, a single-sided polishing process is performed on the semiconductor wafer. The single-sided polishing process includes 100 minutes of polishing. The thickness of the semiconductor wafer is reduced by 1 to 2 microns during the polishing. In Example 2, the total time consumed by the grinding process plus the polishing process is at least 115 minutes.

[0039] Example 3

[0040] In Example 3, a semiconductor wafer is obtained after cutting a semiconductor ingot. Then, a double-sided grinding process is performed on the first surface and the second surface of the semiconductor wafer. The double-sided grinding process includes grinding the semiconductor wafer for 30 minutes using a diamond grinding fluid containing diamond particles with a median particle size of 1 micron. During the grinding process, a load of 170 kg is applied to 5 eight-inch semiconductor wafers. The thickness of the semiconductor wafer is reduced by 24 microns during the grinding process. After the grinding process, a single-sided polishing process is performed on the semiconductor wafer. The single-sided polishing process includes 100 minutes of polishing. The thickness of the semiconductor wafer is reduced by 1 to 2 microns during the polishing. In Example 3, the total time consumed by the grinding process plus the polishing process is at least 115 minutes.

[0041] Example 4

[0042] In Example 4, a semiconductor wafer is obtained after cutting a semiconductor ingot. Subsequently, a double-sided grinding process is performed on the first side and the second side of the semiconductor wafer. The double-sided grinding process includes grinding the semiconductor wafer for 30 minutes using a diamond grinding fluid containing diamond particles with a median particle size of 0.1 micrometer. During the grinding process, a load of 170 kilograms is applied to 5 eight-inch semiconductor wafers. The thickness of the semiconductor wafer is reduced by 20 micrometers during the grinding process. After the grinding process, a single-sided polishing process is performed on the semiconductor wafer. The single-sided polishing process includes 100 minutes of polishing. The thickness of the semiconductor wafer is reduced by 1 to 2 micrometers during polishing. In Example 4, the total time consumed by the grinding process plus the polishing process is at least 115 minutes.

[0043] Table 1 shows the geometric performance of semiconductor wafers obtained by the processing techniques of Comparative Examples 1 to 3 and Examples 1 to 4.

[0044] Table 1

[0045]

[0046] As can be seen from Table 1, using a diamond grinding fluid containing diamond particles for the grinding process can significantly shorten the processing time. Additionally, when the median particle size of the diamond grit in the diamond grinding fluid is less than or equal to 3 micrometers, the geometric performance of the semiconductor wafer after the processing technique can be significantly improved.

Claims

1. A semiconductor processing method, comprising: Cutting a semiconductor ingot to obtain a semiconductor wafer, wherein the semiconductor wafer includes a first surface and a second surface opposite to the first surface; And Performing a double-sided grinding process to simultaneously grind the first surface and the second surface of the semiconductor wafer using a diamond grinding fluid, wherein the diamond grinding fluid contains diamond particles with a median particle size of 0.1 to 3 microns.

2. The processing method according to claim 1, wherein one or more semiconductor ingots are cut to obtain a plurality of semiconductor wafers, 1 to 10 of the plurality of semiconductor wafers are placed in a first carrier and the double-sided grinding process is simultaneously performed on the 1 to 10 semiconductor wafers in the first carrier, and when performing the double-sided grinding process, a load is applied to the 1 to 10 semiconductor wafers in the first carrier.

3. The processing method according to claim 1, wherein the thickness of the semiconductor wafer is reduced by 20 to 28 microns in the double-sided grinding process.

4. The processing method according to claim 1, further comprising: After the double-sided grinding process, performing a first single-sided polishing process on the first surface.

5. The processing method according to claim 4, wherein the thickness of the semiconductor wafer is reduced by 1 to 2 microns in the first single-sided polishing process.

6. The processing method according to claim 4, further comprising: After the first single-sided polishing process, performing a second single-sided polishing process on the second surface.

7. The processing method according to claim 6, wherein the thickness of the semiconductor wafer is reduced by 1 to 2 microns in the second single-sided polishing process.

8. The processing method according to claim 6, wherein the total thickness deviation value of the semiconductor wafer after the second single-sided polishing process is less than 2 microns.

9. The processing method according to claim 6, wherein the bow of the semiconductor wafer after the second single-sided polishing process is from +25 microns to -25 microns, and the warp is from +50 microns to -50 microns.

10. The processing method according to claim 4, wherein after the first single-sided polishing process, the surface roughness Ra of the first surface is less than 0.5 nanometers.

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