Megasonic auxiliary polishing device for large-diameter gallium antimonide wafer

Abstract

A megasonic auxiliary polishing device for a large-diameter gallium antimonide wafer relates to the technical field of wafer surface polishing and comprises a wafer carrier head, a polishing disc and a megasonic generator. The polishing solution containing device is arranged above the megasonic generator, a high-frequency oscillation signal sent by the megasonic generator is converted into high-frequency mechanical oscillation to be transmitted into the polishing solution, an agglomerated colloidal solution formed by an abrasive part in the polishing solution is scattered, aggregation of nanoscale micelles is inhibited, and then the uniform distribution of the polishing solution colloidal solution on the polishing disc is promoted. The consistency of the roughness of the surface of the wafer in the polishing process is high; the polishing disc is in a circular ring shape, the wafer carrying heads are evenly distributed on the circumference of the polishing disc, the portion, between the adjacent wafer carrying heads, of the polishing disc is provided with a washing cover, washing pipes are evenly arranged in the washing cover, and liquid discharged from the lower ends of the washing pipes washes the polishing disc to wash away scraps on the surface of the polishing disc. And an adverse influence factor on the polishing quality of the wafer is reduced by one, so that the controllability of the polishing quality is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of wafer surface polishing, and particularly relates to a megasonic auxiliary polishing device for large-diameter gallium antimonide wafers. Background Art

[0002] III-V compound semiconductor materials have attracted extensive attention due to their advantages in the application of optoelectronic devices. Antimonide infrared optoelectronic devices have shown great application prospects in infrared imaging, medical diagnosis, resource exploration, gas detection, optical communication, thermophotovoltaics and other fields with their excellent performance, and have become a current research hotspot. Gallium antimonide (GaSb), as a typical III-V compound semiconductor material, has a bandgap of 0.725 eV and a lattice constant of 6.0959 Å. It matches the lattice of III-V materials and their ternary and quaternary antimony-containing compounds with a lattice constant of 6.1 Å. The wavelength range can cover from near-infrared to far-infrared bands, making it an ideal substrate material for the preparation of antimonide infrared optoelectronic devices. GaSb single crystals have a direct impact on the performance of antimonide infrared optoelectronic devices. The improvement of device performance requires single crystals to have large size, lower defect density and better surface quality. In recent years, antimonide infrared photoelectric technology has developed rapidly, especially the development and application of antimonide type II superlattice infrared focal plane detection technology, which has greatly promoted the development of GaSb materials. More and more institutions and enterprises have also invested in the research and development and production of GaSb single crystals.

[0003] The production of large-diameter GaSb single crystal wafers mainly achieves high-quality surface preparation through processing techniques such as polishing and cleaning. GaSb materials have high chemical activity and are easily oxidized, which requires high surface preparation technology and is more difficult to process than GaAs, InP and other materials. With the development of device epitaxial technology, the requirements for single crystal surface performance are becoming more and more stringent, and high-quality surface preparation has become the key to the development of GaSb single crystal wafers. In order to meet the needs of epitaxial material growth, the surface of the single crystal wafer is required to have low roughness, low surface residual impurities and defects, and low surface oxide layer thickness.

[0004] The traditional polishing method for GaSb wafers is chemical mechanical polishing (hereinafter referred to as CMP). The mechanism of chemical mechanical polishing is that the material removal on the surface of SiC wafers is achieved by combining chemical oxidation and mechanical grinding. During the chemical mechanical polishing process, a soft layer with low hardness is generated on the surface of the wafer due to chemical oxidation, and the softened layer is removed by mechanical grinding. Common chemical mechanical polishing is achieved by using nano-scale silicon oxide or aluminum oxide polishing slurry and matching different polishing machine equipment processes.

[0005] At present, chemical mechanical polishing of large-diameter GaSb has problems such as uneven surface roughness, shallow scratches, NG (texture), and edge dirty. The problems of uneven surface roughness, shallow scratches, NG (texture), and edge dirty of large-diameter GaSb wafers are directly related to the particle size, agglomeration size, solution stratification and precipitation state of the colloidal polishing liquid used in the chemical mechanical polishing process, and the uniform distribution of the solution particle size on the polishing main disk. Utility Model Content

[0006] In order to solve the problem of uneven distribution of abrasive particle size in the polishing liquid, the utility model provides a megasonic assisted polishing device for large-diameter gallium antimonide wafers. The application utilizes a megasonic generator to assist the polishing liquid, with the purpose of converting the high-frequency oscillation signal emitted by the megasonic generator into high-frequency mechanical oscillation through a transducer and transmitting it to the abrasive in the polishing liquid. The abrasive in the polishing liquid can break up part of the colloidal solution that has formed agglomerates through high-frequency oscillation of several hundred kHz, and at the same time inhibit the aggregation of nano-scale colloids without precipitation, thereby achieving uniform distribution of colloidal solution particles, and the defect density of the polished wafer is lower and the surface quality is better.

[0007] The technical solution provided by the utility model is: a megasonic assisted polishing device for large-diameter gallium antimonide wafers, comprising a wafer carrier, a grinding disc, a megasonic generator, a polishing liquid holding device, a peristaltic pump, a solution filtering device and a polishing liquid spraying pipe. The wafer is mounted on the wafer carrier. The wafer carrier can move relative to the grinding disc and can rotate; the grinding disc can rotate. The polishing liquid holding device is placed above the megasonic generator, and the high-frequency oscillation signal emitted by the megasonic generator is converted into a high-frequency mechanical oscillation and transmitted to the polishing liquid, breaking up the colloidal solution that has formed agglomeration in the abrasive part of the polishing liquid, inhibiting the aggregation of nano-scale colloids, and then promoting the uniform distribution of the polishing liquid colloidal solution on the polishing disc, achieving uniform distribution of solution particles, and then making the surface roughness of the wafer during the polishing process more consistent. The peristaltic pump is connected to the polishing liquid holding device through a rubber hose, and the polishing liquid contained in the polishing liquid holding device is pumped to the solution filtering device, and the flow rate of the polishing liquid entering the grinding disc is monitored by controlling the rotation speed of the peristaltic pump to achieve the purpose of quantitatively monitoring the flow rate of the polishing liquid. The outlet end of the solution filtering device is connected to the polishing liquid spraying pipe through a rubber hose, and the filtered polishing liquid is sprayed on the grinding disc through the polishing liquid spraying pipe. The grinding disc is annular, and the wafer carriers are evenly distributed on the circumference of the grinding disc. A flushing cover is provided on the grinding disc between adjacent wafer carriers. The flushing cover is located above the grinding disc and a gap is left between the flushing cover and the grinding disc, so as not to affect the rotation of the grinding disc; flushing pipes are evenly provided in the flushing cover, and the liquid output from the lower end of the flushing pipe is flushed on the grinding disc, so as to wash away the debris on the surface of the grinding disc, and the flushing cover is used to prevent the flushing liquid from splashing.

[0008] A further technical solution is that the upper surface of the grinding disc has an inclined slope, so as to facilitate the flushing liquid to flow down quickly from the grinding disc.

[0009] A further technical solution is: a drying hood is also provided between adjacent chip carriers, and the drying hood is located downstream of the rinsing hood along the rotation direction of the grinding disc, so as to dry the surface of the grinding disc after cleaning, and the drying hood is located above the grinding disc and a gap is left between the drying hood and the grinding disc, so as not to affect the rotation of the grinding disc.

[0010] Compared with the prior art, the beneficial effects of the utility model are:

[0011] 1. The high-frequency oscillation signal emitted by the megasonic generator is converted into high-frequency mechanical oscillation and transmitted to the abrasive in the polishing liquid, promoting the uniform distribution of the colloidal solution molecules and controlling the agglomeration of the colloidal solution, thereby improving the polishing quality and reducing the surface roughness and defects of the wafer.

[0012] 2. During the wafer polishing process, the debris ground off from the wafer surface will remain on the grinding disc, and the debris ground off by the grinding disc will also remain on the grinding disc. Since the polishing liquid is expensive, the prior art generally uses small amounts of polishing liquid for spraying, and the impact of the polishing liquid is not enough to wash away the ground debris. Therefore, the debris retained on the grinding disc greatly affects the polishing quality of the wafer. The present application sets a flushing pipe between the two wafer carriers. The liquid ejected from the flushing pipe has a strong impact and can wash away the debris on the grinding disc. In addition, the flushing liquid uses a lower-priced liquid, which will not cause a significant increase in costs. The rinsed grinding disc part returns to the mechanical polishing work under the action of self-rotation. At this time, there is more polishing liquid between the wafer and the grinding disc, and one of the factors adversely affecting the wafer polishing quality is reduced, so the controllability of the wafer polishing quality is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural diagram of the entire utility model.

[0014] Figure 2 It is a top view showing the positional relationship of the grinding disc, the wafer carrier, the washing cover and the drying cover in the utility model.

[0015] Figure 3 It is a cross-sectional view of the grinding disc in the utility model.

[0016] In the figure: 1. Megasonic generator; 2. Polishing liquid holding device; 3. Rubber hose; 4. Polishing liquid spraying pipe; 5. Wafer carrier; 6. Grinding disc; 7. Solution filtering device; 8. Peristaltic pump; 9. Flushing hood; 10. Drying hood; 11. Flushing pipe. DETAILED DESCRIPTION

[0017] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] The utility model comprises a wafer carrier 5 and a grinding disc 6. The wafer is mounted on the wafer carrier 5. The wafer carrier can move relative to the grinding disc 6 and can rotate on its own. The grinding disc 6 can rotate on its own. The above is a solution that already exists in the prior art and will not be described in detail here.

[0019] The innovation of the utility model lies in:

[0020] 1. The megasonic assisted polishing device for large-diameter gallium antimonide wafers further comprises a megasonic generator 1, a polishing liquid containing device 2, a peristaltic pump 8, a solution filtering device 7 and a polishing liquid spraying pipe 4. The polishing liquid containing device 2 is placed above the megasonic generator 1. The high-frequency oscillation signal emitted by the megasonic generator 1 is converted into a high-frequency mechanical oscillation and transmitted to the abrasive in the polishing liquid, breaking up the colloidal solution that has formed agglomerates in the abrasive, inhibiting the aggregation of nano-scale micelles, and promoting the uniform distribution of the polishing liquid gel solution on the polishing disk, achieving uniform distribution of solution particles, and thus making the surface roughness of the wafer surface more consistent during the polishing process, reducing the surface roughness and defects of the wafer.

[0021] 2. The peristaltic pump 8 is connected to the polishing liquid containing device 2 through the rubber hose 3, and the polishing liquid contained in the polishing liquid containing device 2 is pumped into the solution filtering device 7. The flow rate of the polishing liquid entering the grinding disc 6 is monitored by controlling the rotation speed of the peristaltic pump 8, so as to achieve the purpose of quantitatively monitoring the polishing liquid flow rate.

[0022] 3. The outlet end of the solution filtering device 7 is connected to the polishing liquid spraying pipe 4 through a rubber hose 3. After the polishing liquid is filtered, it is ensured that there are no large particles. The filtered polishing liquid is sprayed on the grinding disc 6 through the polishing liquid spraying pipe 4.

[0023] 4. The grinding disc 6 is in the shape of a circular ring, and the chip carriers 5 are evenly distributed on the circumference of the grinding disc 6. A flushing cover 9 is provided on the grinding disc 6 between adjacent chip carriers 5. The flushing cover 9 is located above the grinding disc 6 and a gap is left between the grinding disc 6 so as not to affect the rotation of the grinding disc 6; flushing pipes 11 are evenly arranged in the flushing cover 9, and the liquid output from the lower end of the flushing pipes 11 is flushed on the grinding disc 6, so as to wash away the debris on the surface of the grinding disc 6, and the flushing cover 9 is used to avoid splashing of the flushing liquid.

[0024] The reason why the present application sets the flushing pipe 11 is that during the wafer polishing process, the scraps ground off from the wafer surface will remain on the grinding disc 6, and the scraps ground off by the grinding disc 6 will also remain on the grinding disc 6. Since the price of the polishing liquid is relatively expensive, the polishing liquid is generally sprayed in small streams in the prior art, and the impact of the polishing liquid is not enough to wash away the scraps ground off. Therefore, the scraps retained on the grinding disc 6 greatly affect the polishing quality of the wafer. In order to be able to wash away the scraps online, the present application sets a flushing pipe 11 between the two wafer carriers 5. The liquid pierced by the flushing pipe 11 has a strong impact (the impact is adjustable), which can wash away the scraps on the grinding disc 6. In addition, the flushing liquid uses a lower-priced liquid, which will not cause a significant increase in cost. The part of the grinding disc 6 that has been washed returns to the mechanical polishing work under the action of self-rotation. At this time, there is more polishing liquid between the wafer and the grinding disc 6, and the factors affecting the quality of wafer polishing are reduced by one, so the quality of wafer polishing is more controllable.

[0025] The function of the flushing cover 9 in the present application is to prevent the flushing liquid from splashing. During the entire process of the grinding disc 6 rotating, the position of the flushing cover 9 is always fixed.

[0026] In order to facilitate the rapid flow of the flushing liquid from the grinding disc 6, Figure 3 As shown, the upper surface of the grinding disc 6 has an inclined slope. The speed control of the grinding disc 6 of the present application takes 50 seconds to 120 seconds for a single turn.

[0027] A drying hood 10 is also provided between adjacent wafer carriers 5. The drying hood 10 is located downstream of the rinsing hood 9 along the rotation direction of the grinding disc 6, so as to dry the surface of the cleaned grinding disc 6. The drying hood 10 is located above the grinding disc 6 and a gap is left between the grinding disc 6 so as not to affect the rotation of the grinding disc 6. A drying device is provided in the drying hood 10 to dry the rinsing liquid on the grinding disc 6 and reduce the mixing of the rinsing liquid and the polishing liquid.

[0028] In summary, the present application can obtain a large-diameter gallium antimonide wafer with a surface roughness below 0.3NM, with no obvious raglan (NG) observed under strong light, and no shallow scratches or shallow damage observed under sunlight. The technical solution disclosed in the present application has great application prospects in the polishing process of semiconductor material substrate wafers.

Claims

1. A megasonic assisted polishing device for a large diameter gallium antimonide wafer, comprising a wafer carrier (5) and a grinding disc (6), wherein the wafer is mounted on the wafer carrier (5), the wafer carrier can move relative to the grinding disc (6) and can rotate on its own, and the grinding disc (6) can rotate on its own, characterized in that: The megasonic assisted polishing device for large-diameter gallium antimonide wafers further comprises a megasonic generator (1), a polishing liquid containing device (2), a peristaltic pump (8), a solution filtering device (7) and a polishing liquid spraying pipe (4), wherein the polishing liquid containing device (2) is placed above the megasonic generator (1), and the high-frequency oscillation signal emitted by the megasonic generator (1) is converted into a high-frequency mechanical oscillation and transmitted to the polishing liquid; the peristaltic pump (8) is connected to the polishing liquid containing device (2) through a rubber hose (3), and the polishing liquid contained in the polishing liquid containing device (2) is pumped into the solution filtering device (7); and the outlet end of the solution filtering device (7) is connected to the polishing liquid spraying pipe (4) through the rubber hose (3); The grinding disc (6) is in the shape of a ring. The wafer carriers (5) are evenly distributed on the circumference of the grinding disc (6). A flushing cover (9) is provided on the grinding disc (6) between adjacent wafer carriers (5). The flushing cover (9) is located above the grinding disc (6) and a gap is left between the flushing cover (9) and the grinding disc (6), so as not to affect the rotation of the grinding disc (6). Flushing pipes (11) are evenly provided in the flushing cover (9). Liquid discharged from the lower end of the flushing pipe (11) is flushed on the grinding disc (6), so as to flush away the debris on the surface of the grinding disc (6).

2. The megasonic assisted polishing device for large diameter GaSb wafers according to claim 1, characterized in that: The upper surface of the grinding disc (6) has an inclined slope, thereby facilitating the rapid flow of the flushing liquid from the grinding disc (6).

3. The megasonic assisted polishing device for large diameter GaSb wafers according to claim 1, characterized in that: A drying hood (10) is also provided between adjacent wafer carriers (5). The drying hood (10) is located downstream of the rinsing hood (9) along the rotation direction of the grinding disc (6), so as to dry the surface of the grinding disc (6) after cleaning. The drying hood (10) is located above the grinding disc (6) and a gap is left between the drying hood (10) and the grinding disc (6), so as not to affect the rotation of the grinding disc (6).

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