Wafer single-side polishing method based on double-side polishing machine

Abstract

The application discloses a wafer single-side polishing method based on a double-side polishing machine, relates to the technical field of wafer single-side polishing, and specifically comprises the following steps: step one, bonding the back surfaces of two processing pieces together through wax sticking; step two, customizing a wandering star wheel with a thickness of 0.7 mm and suitable for the total height of the two processing pieces; and step three, placing the bonded processing pieces into the wandering star wheel, so that the processing surfaces of the two processing pieces are respectively in contact with the polishing pads of the upper and lower discs of the double-side polishing machine. The wafer single-side polishing method based on the double-side polishing machine places the two processing pieces bonded together through wax sticking into the suitable wandering star wheel, the inner bonding back surfaces of the two processing pieces are mutually isolated, and only the outer processing surfaces are respectively in contact with the polishing pads of the upper disc and the lower disc of the double-side polishing machine to complete single-side grinding, so that the special single-side polishing machine is not needed to be purchased, the existing double-side polishing machine is used to complete processing, the non-processing surface of the wafer is prevented from being scratched and abraded by the polishing pads, and the existing polishing equipment resources in the workshop are activated.

Description

Technical Field

[0001] This invention relates to the field of single-sided wafer polishing technology, specifically to a single-sided wafer polishing method based on a double-sided polishing machine. Background Technology

[0002] Single-sided polishing of semiconductor wafers is a crucial step in wafer fabrication. The quality of single-sided polishing directly determines the yield of subsequent device fabrication, imposing stringent requirements on wafer surface roughness, flatness, and the absence of surface damage layers. Semiconductor device fabrication is highly sensitive to the surface condition of wafers. Defects such as scratches, warping, and residual damage layers on the wafer surface after polishing can directly cause failures in subsequent processes such as photolithography, etching, and thin film deposition, leading to chip leakage, performance degradation, or even device scrapping. Therefore, the stability and processing accuracy of single-sided polishing are key control indicators in wafer manufacturing.

[0003] Among existing wafer processing equipment, double-sided polishing machines are widely used. These machines rely on upper and lower polishing discs in conjunction with a planetary wheel to simultaneously polish both sides of the wafer. The planetary wheel drives the wafer in planetary motion, and combined with the relative rotation of the upper and lower polishing discs and the synergistic effect of the polishing fluid, it can simultaneously complete the removal of material from both sides of the wafer. The equipment is highly versatile, efficient, technologically mature, and has good operational stability, making it suitable for large-scale wafer production and widely used in high-volume double-sided wafer processing scenarios. In actual production, many production lines are equipped with mature double-sided polishing units. However, due to the inherent limitations of the equipment's operating mode, native double-sided polishing machines are only suitable for simultaneous polishing of both sides of the wafer. To achieve single-sided wafer polishing, direct application is not possible; corresponding adjustments to the process are needed to maximize the processing capabilities of existing equipment and reduce production line equipment investment costs.

[0004] However, under certain process requirements, only one surface of the wafer needs to be polished, while the other side remains in its original state. Traditional processes mostly use dedicated single-sided polishing equipment to complete this process, which has the following problems: Specialized single-sided polishing equipment is expensive to purchase. In production scenarios where the number of such equipment is limited, it is impossible to make full use of the existing double-sided polishing machine resources on site. If a double-sided polishing machine is used directly for single-sided polishing, the non-processed surface is easily worn or scratched by the polishing disc, making it difficult to meet the process requirements of single-sided processing.

[0005] Therefore, we propose a single-sided wafer polishing method based on a double-sided polishing machine to solve the problems mentioned above. Summary of the Invention

[0006] The purpose of this invention is to provide a wafer single-sided polishing method based on a double-sided polishing machine, in order to solve the problems mentioned in the background art, such as the high purchase cost and limited number of dedicated single-sided polishing equipment on the market, the inability to fully utilize the existing double-sided polishing machine resources on site, and the problem that if a double-sided polishing machine is used directly for single-sided polishing, the non-processed surface is easily worn and scratched by the polishing disc, making it difficult to meet the process requirements of single-sided processing.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for single-sided polishing of wafers based on a double-sided polishing machine, specifically including the following steps: Step 1: Glue the backs of the two processing pieces together using a waxing method; Step 2: Customize a planetary wheel with a thickness of 0.7-0.8mm to fit the total height of the two processing pieces; Step 3: Place the bonded pieces into the planetary wheel, so that the processing surfaces of the two pieces contact the polishing pads on the upper and lower discs of the double-sided polishing machine respectively; Step 4: Set the processing pressure and speed of the double-sided polishing machine and perform the polishing process; Step 5: After polishing, place the bonded pieces into a three-tank cleaning machine, and sequentially pass through the first tank with 80 degrees Celsius water and dewaxing agent, the second tank with spray treatment, and the third tank with 65 degrees Celsius clean water and ultrasonic treatment.

[0008] Preferably, in step one, processing sheets of different thicknesses are selected for bonding processing.

[0009] Using the above technical solution, before performing the wax bonding process, two types of processing sheets with different thicknesses are selected according to the production and processing requirements. The back sides of the two types of processing sheets with different thicknesses are placed together and bonded into a whole workpiece through the wax bonding process. The overall thickness of the assembled workpiece matches the internal space of the planetary star. Then it is sent into a double-sided polishing machine to complete the single-sided polishing process, which is suitable for the production needs of simultaneous single-sided polishing of wafers of various thicknesses.

[0010] Preferably, when bonding the processing sheets of different thicknesses, the processing sheet with the greater thickness is placed at the bottom.

[0011] Using the above technical solution, when selecting two processing pieces with different thicknesses for wax bonding, the processing piece with a larger thickness is placed at the bottom, and the processing piece with a smaller thickness is stacked on top of the thicker piece. The backs of the two are fixed with wax to form an integral workpiece. The upper and lower surfaces of the workpiece are used as independent processing surfaces. After being fed into the planetary wheel, they are respectively connected to the upper and lower polishing pads for single-sided polishing.

[0012] Preferably, in step two, the thickness of the planetary wheel is adapted to the total height of the two processed pieces.

[0013] Using the above technical solution, after the two processing pieces are bonded together with wax on their backs to form an integral workpiece, the total height of the two processing pieces is measured. A planetary wheel with a corresponding thickness is made according to the total height, so that the workpiece can be completely embedded in the planetary wheel and will not move up and down, ensuring that the processing surface is stably attached to the polishing pad during polishing.

[0014] Preferably, in step three, the piece to be processed is placed in the internal receiving position of the planetary wheel.

[0015] Using the above technical solution, after the two processing pieces are bonded together with wax to form a complete workpiece, the entire workpiece is vertically placed into the internal cavity reserved by the planetary wheel. The workpiece is radially constrained by the inner wall of the planetary wheel. During the polishing process, the planetary wheel drives the workpiece to revolve and rotate synchronously, limiting the lateral displacement of the workpiece and maintaining continuous contact between the processing surface and the polishing pad.

[0016] Preferably, in step three, the processing surfaces of the two processing pieces respectively contact the upper polishing pad and the lower polishing pad.

[0017] Using the above technical solution, after the bonded workpiece is placed in the planetary wheel receiving position, the orientation of the workpiece is adjusted so that the outer processing surface of the lower processing piece is in contact with the polishing pad of the lower plate of the double-sided polishing machine, and the outer processing surface of the upper processing piece is in contact with the upper plate of the double-sided polishing machine for polishing. The upper and lower polishing plates rotate synchronously to polish a single surface of the two wafers respectively. The inner sides of the two wafers are bonded together and the back sides are isolated from each other and are not rubbed by the polishing pad.

[0018] Preferably, in step four, multiple sets of polishing parameters are configured.

[0019] Using the above technical solution, before starting the polishing operation of the double-sided polishing machine, according to different process conditions such as wafer material, target surface finish, and processing time, multiple sets of mutually distinct processing pressure and spindle speed polishing parameters are set. Each set of parameters is used to polish the bonded wafers of the same specification in sequence, and the finished product status of the wafer corresponding to each set of parameters is recorded.

[0020] Preferably, the multiple sets of polishing parameters are used to conduct yield comparisons.

[0021] By adopting the above technical solution, multiple sets of differentiated polishing process parameters are configured in advance. Each set of parameters is used to complete the single-sided polishing of the corresponding batch of bonded wafers. After the processing is completed, the surface roughness, flatness and surface yield of each batch of wafers are tested in a unified manner. The finished product processing quality corresponding to multiple sets of parameters is compared, and the optimal polishing process parameters are selected.

[0022] Preferably, in step five, the film is first sent to the first tank for dewaxing, then to the second tank for spraying, and finally to the third tank for ultrasonic treatment with clean water.

[0023] Using the above technical solution, after the polishing process is completed, the wafer assembly that is stuck together is taken out and sent to the first tank of the three-tank cleaning machine. The adhesive wax layer between the wafers is dissolved by soaking in the heated dewaxing water solution. After dewaxing is completed, it is transferred to the second tank, where the wax residue and polishing debris on the wafer surface are washed away by high-pressure water jet. Finally, it is sent to the third tank where the fine residual impurities are cleaned by ultrasonic vibration with heated water.

[0024] Preferably, in step five, the bonded sheets are placed into a three-tank cleaning machine to complete the dewaxing and cleaning process.

[0025] Using the above technical solution, after all polishing processes are completed, the two wafers bonded together with wax are transferred together into the three-tank cleaning machine. They are then subjected to a three-tank segmented cleaning process to dissolve and separate the bonding wax and remove surface polishing residue. After cleaning, the two wafers are automatically separated, and finished wafers with only a single surface polished are obtained.

[0026] Compared with the prior art, the beneficial effects of the present invention are: the wafer single-sided polishing method based on a double-sided polishing machine: 1. Utilize double-sided polishing equipment to achieve single-sided wafer processing, eliminating the need for dedicated single-sided polishing equipment. After the backs of the two processing wafers are coated with wax and bonded together, they are placed into the matching planetary wheel. The inner sides of the two processing wafers are bonded together and isolated from each other. Only the outer processing surfaces contact the upper and lower polishing pads of the double-sided polishing machine to complete single-sided grinding. There is no need to purchase a special single-sided polishing machine. The existing double-sided polishing machine can be directly reused to complete single-sided wafer processing, avoiding scratches and wear on the non-processing surfaces of the wafer by the polishing pads, and making full use of the existing polishing equipment resources in the workshop. 2. Adaptable to various wafer thickness combinations; process parameters can be compared to select the optimal polishing solution. Different thicknesses of processing sheets can be selected for bonding. After placing the thicker processing sheet below, a planetary wheel of the corresponding thickness can be matched to stably clamp and process the wafer. Before polishing, multiple sets of differentiated processing pressure and speed polishing parameters can be configured for batch processing. After processing, the wafer polishing yield corresponding to each set of parameters can be compared to quickly select the optimal polishing process for wafers of different materials and improve the control of wafer surface flatness and smoothness. 3. The three-stage, three-tank cleaning machine removes adhesive wax and polishing impurities in stages, resulting in high cleanliness of the separated wafers. After polishing, the bonded wafers are sent into a three-tank cleaning machine. The first tank is heated with a dewaxing solution to dissolve the inter-wax bonding wax. The second tank is high-pressure sprayed to remove large pieces of wax residue and polishing debris. The third tank is heated with clean water and ultrasonically removed to peel off fine residual dirt. The segmented cleaning thoroughly removes the bonding medium and surface processing impurities. After cleaning, the two wafers are automatically separated, and each wafer retains only the polishing effect on one side, simplifying the wafer separation and cleaning process. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the workflow of the present invention; Figure 2 This is a simulation table of processing parameters for the present invention; Figure 3 This is a comparison table of good products of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Please see Figures 1-3 This invention provides a technical solution: a method for single-sided polishing of wafers based on a double-sided polishing machine, specifically including the following steps: Step 1: Glue the backs of the two processing pieces together using a waxing method; Step 2: Customize a planetary wheel with a thickness of 0.7mm that is compatible with the total height of the two processing plates; Step 3: Place the bonded pieces into the planetary wheel, so that the processing surfaces of the two pieces contact the polishing pads on the upper and lower discs of the double-sided polishing machine respectively; Step 4: Set the processing pressure and speed of the double-sided polishing machine and perform the polishing process; Step 5: After polishing, place the bonded pieces into a three-tank cleaning machine, and sequentially pass through the first tank with 80 degrees Celsius water and dewaxing agent, the second tank with spray treatment, and the third tank with 65 degrees Celsius clean water and ultrasonic treatment.

[0030] In step one, processing sheets of different thicknesses are selected for bonding. Before performing the wax bonding process, two types of processing sheets with different thicknesses are selected according to the production and processing requirements. The back sides of the two types of processing sheets of different thicknesses are placed together and bonded into a whole workpiece through the wax bonding process. The overall thickness of the assembled workpiece matches the internal space of the planetary star. Then it is sent into a double-sided polishing machine to complete the single-sided polishing process, which is suitable for the production needs of simultaneous single-sided polishing of wafers of various thicknesses.

[0031] When bonding processing pieces of different thicknesses, the thicker processing piece is placed at the bottom. When bonding two processing pieces of different thicknesses with wax, the thicker processing piece is placed at the bottom and the thinner processing piece is stacked on top of the thicker piece. The backs of the two are fixed with wax to form a whole workpiece. The upper and lower surfaces of the workpiece are used as independent processing surfaces. After being fed into the planetary wheel, they are respectively connected to the upper and lower polishing pads for single-sided polishing.

[0032] In step two, the thickness of the planetary wheel is matched with the total height of the two processing pieces. After the back of the two processing pieces are waxed and bonded to form an integral workpiece, the total height of the two processing pieces is measured. The planetary wheel with the corresponding thickness is made according to the total height, so that the workpiece can be completely embedded in the planetary wheel and will not move up and down, ensuring that the processing surface is stably attached to the polishing pad during polishing.

[0033] In step three, the workpiece to be processed is placed in the internal receiving position of the planetary wheel. After the two workpieces are bonded together with wax to form a complete workpiece, the entire workpiece is vertically placed into the internal receiving cavity reserved by the planetary wheel. The workpiece is radially constrained by the inner wall of the planetary wheel. During the polishing process, the planetary wheel drives the workpiece to rotate synchronously around the sun and rotate on its own axis, limiting the lateral displacement of the workpiece and maintaining continuous contact between the processed surface and the polishing pad.

[0034] In step three, the processing surfaces of the two processing pieces respectively contact the upper and lower polishing pads. After the bonded workpiece is placed in the planetary wheel's receiving position, the orientation of the workpiece is adjusted so that the outward-facing processing surface of the lower processing piece is in contact with the lower polishing pad of the double-sided polishing machine, and the outward-facing processing surface of the upper processing piece is in contact with the upper polishing pad of the double-sided polishing machine. The upper and lower polishing pads rotate synchronously to polish a single surface of the two wafers respectively. The inner sides of the two wafers are bonded together and isolated from each other, so they are not rubbed by the polishing pads.

[0035] In step four, multiple sets of polishing parameters are configured. Before starting the double-sided polishing machine, multiple sets of different processing pressure and spindle speed polishing parameters are set according to different process conditions such as wafer material, target surface finish, and processing time. Each set of parameters is used to polish the same specification bonded wafers in sequence, and the finished product status of the wafer corresponding to each set of parameters is recorded.

[0036] Multiple sets of polishing parameters are used to conduct yield comparisons. Multiple sets of differentiated polishing process parameters are configured in advance, and each set of parameters is used to complete the single-sided polishing of the corresponding batch of bonded wafers. After processing, the surface roughness, flatness, and surface yield of each batch of wafers are uniformly tested. The finished product processing quality corresponding to multiple sets of parameters is compared, and the optimal polishing process parameters are selected.

[0037] In step five, the wafers are first sent to the first tank for dewaxing, then to the second tank for spraying, and finally to the third tank for ultrasonic cleaning with clean water. After the polishing process, the wafer assemblies that are stuck together are taken out and sent to the first tank of the three-tank cleaning machine. The wax layer between the wafers is dissolved by soaking in the heated dewaxing solution. After dewaxing, the wafers are transferred to the second tank, where high-pressure water jets are used to spray away the wax residue and polishing debris on the wafer surface. Finally, the wafers are sent to the third tank where heated clean water ultrasonic vibration is used to clean away any remaining impurities.

[0038] In step five, the wafers bonded together are put into a three-tank cleaning machine to complete the dewaxing and cleaning process. After all the polishing processes are completed, the two wafers bonded together with wax are transferred together and put into the three-tank cleaning machine. They are then cleaned in three separate tanks to dissolve and separate the bonding wax and remove the surface polishing residue. After cleaning, the two wafers are automatically separated, and finished wafers with only a single surface polished are obtained.

[0039] Working Principle: When using this wafer single-sided polishing method based on a double-sided polishing machine, firstly, two wafers are taken and bonded together with wax applied to their backs. Wax-coated wafers of different thicknesses can be used for bonding, with the thicker wafer placed on the bottom. The total height of the two wafers after stacking is measured, and a planetary wheel of corresponding thickness is customized. The bonded wafer is then placed into the receiving position inside the planetary wheel, where the planetary wheel provides radial restraint. The placement of the wafers is adjusted, and the outer surfaces of the two wafers are respectively bonded to the upper and lower polishing pads of the double-sided polishing machine. Multiple sets of processing pressures and rotations are configured within the double-sided polishing machine according to processing requirements. The high-speed polishing parameters are set, and the double-sided polishing machine is started to perform polishing. After multiple sets of polishing parameters are completed, the polishing yield of each batch of wafers is compared. After all polishing processes are completed, the laminated wafer is removed and sent to a three-tank cleaning machine. The wafer first enters the first tank for heated dewaxing agent immersion and dewaxing treatment. After dewaxing, it is transferred to the second tank for high-pressure spray rinsing to remove surface wax residue and polishing debris. Then it is sent to the third tank for heated water ultrasonic cleaning, where fine impurities are removed. After cleaning, the adhesive wax between the two wafers is completely dissolved, and the two wafers automatically separate, each retaining only the outer single-sided polishing shape, thus completing a series of processes. Content not described in detail in this specification belongs to prior art known to those skilled in the art.

[0040] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for single-sided polishing of wafers based on a double-sided polishing machine, characterized in that: Specifically, the following steps are included: Step 1: Glue the backs of the two processing pieces together using a waxing method; Step 2: Customize a planetary wheel with a thickness of 0.7-0.8mm to fit the total height of the two processing pieces; Step 3: Place the bonded pieces into the planetary wheel, so that the processing surfaces of the two pieces contact the polishing pads on the upper and lower discs of the double-sided polishing machine respectively; Step 4: Set the processing pressure and speed of the double-sided polishing machine and perform the polishing process; Step 5: After polishing, place the bonded pieces into a three-tank cleaning machine, and sequentially pass through the first tank with 80 degrees Celsius water and dewaxing agent, the second tank with spray treatment, and the third tank with 65 degrees Celsius clean water and ultrasonic treatment.

2. The wafer single-sided polishing method based on a double-sided polishing machine according to claim 1, characterized in that: In step one, processing sheets of different thicknesses are selected for bonding.

3. The wafer single-sided polishing method based on a double-sided polishing machine according to claim 2, characterized in that: When bonding processing sheets of different thicknesses, the thicker processing sheet is placed at the bottom.

4. The wafer single-sided polishing method based on a double-sided polishing machine according to claim 1, characterized in that: In step two, the thickness of the planetary wheel is matched with the total height of the two processed pieces.

5. A method for single-sided polishing of a wafer based on a double-sided polishing machine according to claim 1, characterized in that: In step three, the piece to be processed is placed in the internal receiving position of the planetary wheel.

6. The wafer single-sided polishing method based on a double-sided polishing machine according to claim 1, characterized in that: In step three, the processing surfaces of the two processing pieces respectively contact the upper polishing pad and the lower polishing pad.

7. The wafer single-sided polishing method based on a double-sided polishing machine according to claim 1, characterized in that: In step four, multiple sets of polishing parameters are configured.

8. A method for single-sided polishing of a wafer based on a double-sided polishing machine according to claim 7, characterized in that: The multiple sets of polishing parameters are used to compare yield rates.

9. A method for single-sided polishing of a wafer based on a double-sided polishing machine according to claim 1, characterized in that: In step five, the film is first sent to the first tank for dewaxing, then to the second tank for spraying, and finally to the third tank for ultrasonic treatment with clean water.

10. A method for single-sided polishing of a wafer based on a double-sided polishing machine according to claim 1, characterized in that: In step five, the bonded sheet is placed into a three-tank cleaning machine to complete the dewaxing and cleaning process.

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