A method for polishing a flat edge silicon wafer

Abstract

The present application relates to the field of wafer manufacturing, and discloses a flat edge silicon wafer polishing method.The flat edge silicon wafer polishing method comprises the following steps: using a mechanical hand to pick up a silicon wafer from a transport tray, and then moving along a preset track to attach and fix the silicon wafer with the back surface coated with an adhesive to the front surface plane of a base; the transport tray is provided with a flat edge corrector, and the flat edge corrector is used to check and correct the flat edge position of the silicon wafer before the mechanical hand picks up the silicon wafer; the base is fixedly installed on a support seat, and the back surface of the base faces the support seat; the support seat is moved to move the front surface of the base to face a fixed disc, until the front surface of the silicon wafer abuts against a polishing cloth arranged on the surface of the fixed disc; the support seat vertically presses the base and rotates, so that the silicon wafer and the polishing cloth are rubbed against each other, the polishing of the front surface of the silicon wafer is completed, the front surface polishing surface of the silicon wafer is flat, the polishing step of the edge of the silicon wafer can be avoided, and the utilization rate of the silicon wafer is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wafer manufacturing, in particular to a method for polishing a flat edge silicon wafer. BACKGROUND

[0002] Polishing of a silicon wafer is a very important step for wafer manufacturing, and the quality of the wafer surface determines the yield of the subsequent crystal manufacturing. Small-size silicon wafers usually use a flat edge as a reference surface, and in the actual polishing production process of small-diameter wafers, a plurality of silicon wafers are attached to a ceramic disc for polishing processing. Figure 1 As shown in FIG. 1, the flat edge position is prone to shift during the attachment process, and a shifted silicon wafer 1' is generated. During the polishing process, the shifted area of the silicon wafer has less loss of polishing cloth on its polishing track relative to other areas, and the polishing cloth has a faster wear rate and a larger friction removal amount on the silicon wafer, resulting in a step at the edge of the polished silicon wafer, which causes wafer defects. In the early stage, the edge is not the main working area, so most of the defects are accepted by the manufacturers. However, with the development of integrated circuits, the utilization rate of silicon wafers is becoming higher and higher, and the impact of the edge step defect is increasingly prominent. The market has higher requirements for the polishing of silicon wafers, and the edge step problem needs to be solved to improve the overall utilization rate of silicon wafers. SUMMARY

[0003] The present application aims to provide a method for polishing a flat edge silicon wafer, which can make the polished surface of the silicon wafer flat, avoid the generation of an edge step, and improve the utilization rate of the silicon wafer.

[0004] To solve the above technical problems, the embodiments of the present application provide a method for polishing a flat edge silicon wafer, which comprises the following steps:

[0005] After the mechanical hand grabs the silicon wafer from the transport disc, the silicon wafer is attached and fixed along a preset track with the back surface coated with adhesive facing the front surface of the base;

[0006] The transport disc is provided with a flat edge corrector, which is used to inspect and correct the position of the flat edge of the silicon wafer before the mechanical hand grabs the silicon wafer;

[0007] The base is fixedly installed on the support seat, and the back surface of the base faces the support seat;

[0008] The support seat moves the front surface of the base towards the fixed disc until the front surface of the silicon wafer abuts against the polishing cloth arranged on the surface of the fixed disc;

[0009] The support seat vertically presses and rotates the base, so that the silicon wafer and the polishing cloth rub against each other, and the polishing of the front surface of the silicon wafer is completed.

[0010] Further, the flat edge corrector comprises a first laser detection device, and a position adjustment device capable of adjusting the relative position of the silicon wafer and the transport disc according to the indication of the first laser detection device.

[0011] Further, a plurality of silicon wafers are attached to the base, and after the attachment of the plurality of silicon wafers is completed, a second laser detection device is used to inspect the attachment position of the plurality of silicon wafers.

[0012] Further, the fixed disc rotates in the same direction as the support base while the support base drives the base to rotate.

[0013] Further, the polishing cloth is periodically polished, and the polishing frequency is once every 200-400 minutes of work of the polishing cloth.

[0014] Further, the polishing cloth is periodically replaced, and the replacement frequency is once every 60-100 hours of work of the polishing cloth.

[0015] Further, the adhesive is rosin resin.

[0016] The silicon wafer polishing method provided by the present application, compared with the prior art, through the flat edge corrector on the transport disc, ensures that the flat edge of each silicon wafer is in a relatively fixed position when the mechanical hand grabs the silicon wafer for attachment, ensures that the positions of the plurality of silicon wafers on the base plane are uniform and symmetrical after attachment, through the second laser detection device after the silicon wafer is attached, the position of the attached silicon wafer is further inspected, and it is ensured that the silicon wafers are uniformly distributed on a circumference with the center point of the front plane of the base as the center before polishing starts, so that the grinding removal amount of each part of the front surface of each silicon wafer is consistent during polishing, the flatness of the front surface of the silicon wafer after polishing is ensured, edge steps are avoided, and the overall utilization rate of the silicon wafer is improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] One or more embodiments are illustrated by way of example in the figures that form a part of this patent document, these illustrative examples do not limit the embodiments, and elements having the same reference numerals in the figures represent similar elements unless otherwise specified, the figures in the drawings do not constitute a proportional limitation.

[0018] Figure 1 is a structure diagram of the flat edge offset condition of the silicon wafer attached to the base in the prior art;

[0019] Figure 2 is a flowchart of the flat edge silicon wafer polishing method provided by the present application;

[0020] Figure 3 is a structure diagram of the silicon wafer in the flat edge silicon wafer polishing method provided by the present application;

[0021] Figure 4This is a schematic diagram of the structure during polishing in the flat-edge silicon wafer polishing method provided by the present invention.

[0022] Explanation of reference numerals in the attached diagram: 1. Silicon wafer; 11. Flat edge; 1'. Offset silicon wafer; 2. Base; 3. Support base; 31. Connector; 4. Fixing plate; 5. Polishing cloth; 6. Aperture. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the various embodiments of this invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this invention to facilitate a better understanding of this application. However, the technical solutions claimed in the claims of this application can be implemented even without these technical details and with various variations and modifications based on the following embodiments.

[0024] like Figures 1-4 As shown, the flat-edge silicon wafer polishing method provided in this embodiment of the invention includes the following steps:

[0025] First, using a robotic arm, the silicon wafer 1 is picked up from the transport tray and then attached and fixed with the back side coated with adhesive facing the front side of the base 2.

[0026] The transport tray is equipped with a flat edge corrector. The silicon wafer 1 is transported to the designated position of the base 2 via the transport tray. The front side of the silicon wafer 1 is picked up by the suction cup of the robotic arm, and the back side coated with adhesive is attached and fixed to the front plane of the base 2. Preferably, the adhesive is rosin resin. Multiple silicon wafers 1 are attached to the front plane of each base 2. In one embodiment, 7 silicon wafers 1 of 4-inch specification are attached at a time, and 5 silicon wafers 1 of 5-inch specification are attached at a time. The size of the base 2 can be selected in different ways, and the number of silicon wafers 1 attached in different specifications can be selected in different ways, depending on the actual production needs.

[0027] The silicon wafer 1 is transported to the designated position near the base 2 by the transport disc, and before the mechanical hand suction cup absorbs and grabs the silicon wafer 1, the flat edge corrector is started, which checks and corrects the position of the flat edge 11 of the silicon wafer 1 to ensure the accuracy of the position of the flat edge 11 when the mechanical hand grabs the silicon wafer 1 and places it on the base 2, avoiding the offset of the flat edge 11. The flat edge corrector includes a first laser detection device and a position adjusting device. The first laser detection device is fixedly arranged on the transport disc. When the flat edge corrector is started, the first laser detection device emits a laser indication line. When the edge of the flat edge 11 of the silicon wafer 1 coincides with the laser indication line, it indicates that the position of the silicon wafer 1 is correct and does not need to be adjusted. When the edge of the flat edge 11 of the silicon wafer does not coincide with the laser indication line, the position adjusting device is started. The lifting mechanism exerts force on the center point of the silicon wafer 1, which is parallel to the transport disc, and then rotates the silicon wafer 1. At this time, the transport disc remains in a stationary state. The relative position of the silicon wafer 1 and the transport disc is adjusted so that the edge of the flat edge 11 of the silicon wafer 1 coincides with the laser indication line, thereby ensuring the stability of the position of the silicon wafer 1 relative to the transport disc, and further ensuring the accuracy of the relative position of the flat edge 11 of the silicon wafer 1 and the base 2 when the silicon wafer 1 is attached to the base 2.

[0028] Preferably, a plurality of silicon wafers 1 are attached to the base 2, and the silicon wafers 1 on the same base 2 are of the same specification. After the plurality of silicon wafers 1 are attached to the base 2, the attachment position of the silicon wafers 1 is detected. A second laser detection device is arranged above the base 2 to delimit the attachment position area by the second laser detection device, that is, a circular aperture 6 with the center point of the front plane of the base 2 as the center is displayed on the front of the base 2, and the relative positions of the silicon wafers 1 are automatically detected to determine whether they are uniformly arranged within the range of the aperture 6, that is, the plurality of silicon wafers 1 are uniformly and symmetrically distributed on a circumference with the center point of the front of the base 2 as the center. Of course, manual detection can also be used to check whether the distances between the two end points of the flat edges 11 of the plurality of silicon wafers and the aperture 6 are the same. If there is a position deviation, the silicon wafers 1 need to be reattached. When manual detection is used, the diameter of the aperture 6 should be as small as possible to facilitate visual detection of the distance between the two end points of the flat edges 11 of the silicon wafers and the aperture 6.

[0029] Secondly, the base 2 is fixedly installed on the support seat 3, and the back of the base 2 faces the support seat 3.

[0030] One end of the support seat 3 connected with the base 2 is provided with a connecting head 31, which is the same shape as the base 2 and has a size close to that of the base 2. The support seat 3 is detachably and fixedly connected with the back of the base 2 through the connecting head 31.

[0031] Then, the support seat 3 is moved to move the front of the base 2 towards the fixed disc until the front of the silicon wafer 1 abuts against the polishing cloth 5 arranged on the surface of the fixed disc.

[0032] A polishing cloth 5 is fixedly installed on the fixed plate 4. Under the drive of the support base 3, the front of the base 2 moves towards the fixed plate 4. A silicon wafer 1 is attached to the front of the base 2, so that the front of the silicon wafer 1 comes into contact with the polishing cloth 5.

[0033] Finally, the support base 3 applies vertical pressure to the base 2 and rotates, causing the silicon wafer 1 and the polishing cloth 5 to rub against each other, thus completing the polishing of the front side of the silicon wafer 1.

[0034] like Figure 4 As shown, when polishing begins, under the vertical force of the support base 3, the silicon wafer 1 can apply a uniform force to the polishing cloth 5. The support base 3 rotates around its own central axis, causing the base 2 to rotate. Under a certain pressure, the front surface of the silicon wafer 1 and the polishing cloth 5 rub against each other, thereby quantitatively grinding and removing material from the surface of the silicon wafer 1, making the front surface of the silicon wafer 1 smoother and flatter.

[0035] To improve the utilization rate of the polishing cloth 5, the fixed plate 4 drives the polishing cloth 5 to rotate in the same direction as the support base 3, and at the same time, polishing liquid is injected from the edge of the fixed plate 4 to improve the polishing speed and quality of the silicon wafer 1.

[0036] In one embodiment, to ensure polishing efficiency and quality, multiple bases 2 can be set on each plate 4 simultaneously, allowing multiple sets of silicon wafers 1 to be polished at the same time. At the same time, the polishing cloth 5 needs to be repaired, brushed and replaced regularly. In one embodiment, depending on the specifications of the silicon wafers 1 being polished, the polishing marks on the polishing cloth 5 are cleaned and repaired with a wire brush every 200 to 400 minutes. The polishing cloth 5 is replaced every 60 to 100 working hours.

[0037] The silicon wafer polishing method provided by this invention, compared with the prior art, ensures that the flat edge of each silicon wafer is in a relatively fixed position when the robot arm picks up and attaches the silicon wafer by using a flat edge corrector on the transport tray. This ensures that the positions of multiple silicon wafers on the base plane are uniform and symmetrical after attachment. The position of the attached silicon wafers is further inspected by a second laser detection device after attachment, ensuring that the silicon wafers are evenly distributed on the circumference with the center point of the front plane of the base as the center before polishing. This ensures that the amount of grinding and removal is consistent in each part of the front of each silicon wafer during polishing, ensuring the flatness of the front of the silicon wafer after polishing, avoiding the formation of edge steps, and improving the overall utilization rate of the silicon wafer.

[0038] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.

Claims

1. A method of polishing a flat edge silicon wafer, the method comprising: The method comprises the following steps: After the mechanical arm picks up the silicon wafer from the transport tray, the silicon wafer is attached to the front surface of the base along a preset trajectory with the adhesive-coated back surface of the silicon wafer facing the front surface of the base; The transport tray is provided with a flat edge corrector, and the flat edge corrector is used to check and correct the flat edge position of the silicon wafer before the mechanical arm picks up the silicon wafer; After the plurality of silicon wafers are attached to the base, the attachment position of the silicon wafers is detected, a second laser detection device is arranged above the base, the attachment position area is delimited by the second laser detection device, a circular aperture is displayed on the front surface of the base, and the relative positions of the silicon wafers are detected to determine whether the silicon wafers are uniformly arranged within the aperture range; The base is fixedly installed on the support seat, and the back surface of the base faces the support seat; The support seat is moved to move the front surface of the base towards the fixed disc until the front surface of the silicon wafer abuts against the polishing cloth arranged on the surface of the fixed disc; The support seat vertically presses the base and rotates to make the silicon wafer and the polishing cloth rub against each other, thereby completing the polishing of the front surface of the silicon wafer.

2. The method of claim 1, wherein the polishing pad is a fixed abrasive pad. The flat edge corrector comprises a first laser detection device and a position adjustment device, and the position adjustment device can adjust the relative position of the silicon wafer and the transport tray according to the indication of the first laser detection device.

3. The method of claim 1, wherein the polishing pad is a flat edge pad. The fixed disc rotates in the same direction as the support seat while the support seat rotates the base.

4. The method of claim 1, wherein the polishing pad is a flat edge silicon wafer polishing pad. The polishing cloth is periodically polished to remove polishing marks, and the polishing frequency is once every 200-400 minutes of operation of the polishing cloth.

5. The method of claim 1, wherein the polishing pad is a flat edge silicon wafer polishing pad. The polishing cloth is periodically replaced, and the replacement frequency is once every 60-100 hours of operation of the polishing cloth.

6. The method of claim 1, wherein the polishing pad is a flat edge silicon wafer polishing pad. The adhesive is rosin resin.

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