Apparatus and method for pressing an upper polishing cloth against an upper polishing plate of a machine for simultaneously polishing the front and back surfaces of a semiconductor wafer - Patents.com

Abstract

An apparatus and method for pressing an upper polishing cloth against an upper polishing plate of a machine for simultaneously polishing the front and back sides of a semiconductor wafer between an upper polishing plate and a lower polishing plate, the apparatus comprising: two parallel linear rails spaced a short distance above the lower polishing plate, the two parallel linear rails being parallel to the radius of the lower polishing plate between the two parallel linear rails; a base to which the linear rails are fixed; two driven carriages movable along the linear rails; actuators fixed by the driven carriages and fixed to the actuators for raising and lowering rollers disposed between the linear rails; and a controller for synchronously reciprocating slides between inner and outer pin crowns of the machine and synchronously moving the actuators.

Description

[Technical Field]

[0001] The present invention provides an apparatus for pressing an upper polishing cloth against an upper polishing plate of a machine for simultaneously polishing the front and back sides of semiconductor wafers. The present invention also provides a corresponding method of using the apparatus. [Background technology]

[0002] Prior art / problems Polishing both sides of a workpiece, such as a semiconductor wafer, is also called double-sided polishing (DSP). The basic principles of DSP of semiconductor wafers are described, for example, in U.S. Patent Application Publication No. 20030054650 and German Patent Application Publication No. 10007390.

[0003] Generally, polishing cloths are adhesively bonded to both polishing plates of a DSP system. The polishing cloths should be adhesively bonded without any air bubbles to prevent air bubbles from entering, which could adversely affect the desired polishing results. The polishing cloths should also adhere equally firmly to the polishing plates. To achieve the required adhesion, the polishing cloths can be pressed against each other between the polishing plates (cloth pressing). As a result of pressing, the adhesive flows and adheres better. Methods for creating adhesive bonds between polishing cloths and corresponding polishing plates are known from U.S. Patent Application Publication No. 20070087671, JP 2006289523, JP 2006346808, and DE 10239774.

[0004] Before the cloth pressing, an annular upper polishing cloth is adhesively bonded to the upper polishing plate. Such a method is described, for example, in EP 4000806 A1. Air bubbles in the space between the upper polishing plate and the upper polishing cloth must then be removed, since cloth pressing alone is insufficient. Such air bubbles can be manually pushed to the outer or inner edge of the upper polishing cloth using a doctor blade or roller, and then pushed out of the space.

[0005] This task is tedious and difficult as it must be performed while working overhead. EP 4000806 suggests that this task could also be performed by machine, but leaves open the question of how this could be done.

[0006] U.S. Patent Application Publication No. 20070087671 recommends sandwiching a roller unit having radially arranged rollers between a lower polishing plate and an upper polishing plate after the polishing cloth has been adhesively bonded, and rotating the polishing plates in opposite directions. The radially arranged rollers primarily move air bubbles in the space between the polishing plate and the polishing cloth in a circumferential direction, which results in insufficient removal of the air bubbles from the space. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to provide a more efficient solution for removing air bubbles from the space between the upper polishing plate and the upper polishing cloth. [Means for solving the problem]

[0008] The object of the present invention is to provide an apparatus for pressing an upper polishing cloth against an upper polishing plate of a machine for simultaneously polishing the front and back sides of semiconductor wafers between an upper polishing plate and a lower polishing plate, the apparatus comprising: two parallel straight rails positioned a short distance above the lower polishing plate, with two parallel straight rails positioned parallel to the radius of the lower polishing plate between the two parallel straight rails; a base body to which the linear rail is fixed; Two driven carriages that can move along a linear rail; an actuator secured by a driven carriage for raising and lowering a roller secured to the actuator and disposed between the linear rails; This is achieved by an apparatus comprising: a driven carriage for synchronously reciprocating between an inner pin crown and an outer pin crown of the machine; and a controller for synchronously moving the actuator.

[0009] The linear rails are preferably fixed to a ring or plate as a base. The ring or plate rests on the lower polishing cloth and has teeth that engage with the outer and inner pin crowns of the machine. The linear rails can extend beyond the edge of the lower polishing plate. However, they can also be shortened to a length corresponding to the distance between the inner and outer pin crowns.

[0010] The actuator is preferably pneumatically or electrically operated. The object is further to provide a method for pressing an upper polishing cloth against an upper polishing plate of a machine for simultaneously polishing the front and back surfaces of semiconductor wafers, comprising: adhesively bonding an upper polishing cloth to an upper polishing plate; disposing the device according to any one of claims 1 to 3 above a lower polishing cloth; positioning an upper polishing plate above a lower polishing plate at a distance from each other that allows a roller of the apparatus to press against the upper polishing cloth; This is achieved by a method that includes rotating the upper polishing plate and simultaneously reciprocating the roller between the inner and outer pin crowns of the machine while at least intermittently pressing the roller against the upper polishing cloth.

[0011] The upper polishing cloth is adhesively bonded to the upper polishing plate, leaving an intermediate state in which air bubbles exist in the space between the upper polishing cloth and the upper polishing plate and the upper polishing cloth is not yet uniformly bonded to the upper polishing plate. This can be done, for example, by placing the upper polishing cloth on the lower polishing cloth with the adhesive layer of the upper polishing cloth facing up, i.e., facing away from the lower polishing plate, and pressing the polishing plates together. It is also possible to follow the procedure described in EP 4000806 A1.

[0012] In the next step, the apparatus according to the present invention is used to remove air bubbles from the space between the upper polishing plate and the upper polishing cloth. For this purpose, the apparatus is placed above the lower polishing cloth, and the upper polishing plate is pivoted on the lower polishing plate, so that a small distance exists between the two polishing plates. At this distance, the roller does not yet touch the upper polishing cloth unless the actuator has yet to lift the upper polishing cloth. However, this distance is also small enough so that the actuator can press the roller against the upper polishing cloth. The upper polishing plate is then rotated, preferably at a speed of 0.1 rpm to 1 rpm, particularly preferably 0.2 rpm, and the roller is raised by the actuator, so that it is pressed against the upper polishing cloth. The contact pressure of the roller is preferably 1.8 x 10 5 Pa ~ 2.0 × 10 5 Pa (1.8 bar to 2.0 bar) and can be varied.

[0013] While the roller is pressed against the upper polishing cloth, the roller is moved by the carriage along a linear rail between the inner and outer pin crowns of the polishing machine. This causes the roller to drive the bubbles primarily radially from the inner edge of the upper polishing cloth toward the outer edge, and thus outward from the space between the upper polishing cloth and the upper polishing plate. The speed at which the roller is moved along the linear rail is preferably 0.5 m / s to 1.5 m / s and can be similarly varied.

[0014] The roller is pressed at least intermittently against the upper polishing cloth while the upper polishing plate is rotated and the roller is moved between the inner and outer pin crowns of the machine.

[0015] According to one embodiment, a roller is reciprocated between the inner and outer pin crowns of the polishing machine and pressed against the upper polishing cloth while the upper polishing plate is rotated.

[0016] According to another embodiment, the roller is moved back and forth between the inner and outer pin crowns of the polishing machine and is pressed against the upper polishing cloth only on the outward or return movement while the upper polishing plate is rotated.

[0017] The invention will now be further explained with reference to the drawings. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 illustrates features of a DSP polishing machine in a top view of the lower polishing plate. [Figure 2] 1 illustrates a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS IN ACCORDANCE WITH THE INVENTION Figure 1 shows the features of a DSP polishing machine in a plan view of a lower polishing plate 1 to which an annular lower polishing cloth 2 is adhesively bonded. Parallel to the inner and outer edges 3 and 4 of the lower polishing cloth 2 and lower polishing plate 1 are inner and outer pin crowns 5 and 6, which allow the polishing plates 1, 8 to rotate.

[0020] As shown in FIG. 2, the lower polishing plate 1 is used to support a device for pressing the upper polishing cloth 7 against the upper polishing plate 8. This device comprises two parallel linear rails 9, which are arranged at a small distance above the lower polishing plate 1 and parallel to the radius of the lower polishing plate 1 between the two parallel linear rails. Each linear rail 9 serves as a guide for a carriage 10, which is fixed with an actuator 11 and a roller 12 to which the actuator is fixed, so that the roller is positioned between the linear guides 9. The actuator can raise and lower the roller 12, and the carriage 10 can move the roller along the path between the outer pin crown 6 and the inner pin crown 5. The carriages 10 and the actuators 11 move synchronously, which is ensured by a controller 13.

[0021] According to the embodiment shown, the linear rail 9 rests on a bar 15 located on and within a ring 14, which has external teeth 16 that engage within the outer and inner pin crowns 6 and 5 of the machine.

[0022] To carry out the method of the present invention, the upper polishing cloth 7 is brought into an intermediate state in which air bubbles exist in the space between the upper polishing cloth 7 and the upper polishing plate 8 and the upper polishing cloth 7 is not yet uniformly adhered to the upper polishing plate 8.

[0023] A device for pressing the upper polishing cloth 7 against the upper polishing plate 8 is then placed above the lower polishing cloth 2, pressing the upper polishing plate 8 against the lower polishing plate 1. The two polishing plates 8, 1 are at a distance from each other that allows the rollers 12 of the device to press the upper polishing cloth 7.

[0024] FIG. 2 shows the situation before the upper polishing plate 8 is placed on the lower polishing plate 1.

[0025] The upper polishing plate 8 is then slowly rotated and the roller 12 is moved back and forth between the outer pin crown 6 and the inner pin crown 5 by the carriage 10, while the actuator 11 presses the roller 12 at least intermittently against the upper polishing cloth 7.

[0026] The advantage of this method is not only that it avoids laborious manual work, but also that it has been shown to favorably influence the polishing results. The geometry of polished semiconductor wafers of single crystal silicon, i.e., flatness and plane parallelism, was measured, and the local geometry at the edge was also measured and combined to form a measurement that was a combination of global flatness back ideal range (GBIR) and edge site front least squares range (ESFQR) measurements. This measurement was, on average, approximately 17.8% smaller when the upper polishing cloth was pressed against the upper polishing plate according to the present invention rather than manually before polishing. [Explanation of symbols]

[0027] List of reference symbols used 1 Lower grinding plate 2 Lower polishing cloth 3 Common-law marriage 4 outer edge 5 Inner pin crown 6. Outer pin crown 7 Upper polishing cloth 8 Upper grinding plate 9 Straight Rail 10 carts 11 Actuator 12 Laura 13 Controller 14 Ring 15 Strip 16 outer teeth

Claims

1. 1. An apparatus for pressing an upper polishing cloth against an upper polishing plate of a machine for simultaneously polishing a front and back side of a semiconductor wafer between an upper polishing plate and a lower polishing plate, comprising: two parallel linear rails positioned above the lower polishing plate with a small distance between them and oriented parallel to the radius of the lower polishing plate; a base to which the linear rail is fixed; two driven carriages movable along the linear rail; an actuator held by the driven carriage, the actuator being fixed to the actuator and configured to raise and lower a roller disposed between the linear rails; a controller for synchronously reciprocating the driven carriages between inner and outer pin crowns of the machine and for synchronously moving the actuators; An apparatus comprising:

2. 2. The apparatus of claim 1, characterized by a ring or plate as the base and a bar located within the ring on which the linear rail is supported, the ring or plate having teeth that engage with the outer pin crowns and the inner pin crowns of the machine.

3. 3. A device according to claim 1 or claim 2, characterized in that the actuator is pneumatically or electrically operated.

4. 1. A method for pressing an upper polishing cloth against an upper polishing plate of a machine for simultaneously polishing a front and back surface of a semiconductor wafer, comprising: adhesively bonding the upper polishing cloth to the upper polishing plate; disposing the device according to any one of claims 1 to 3 above the lower polishing cloth; placing the upper polishing plate above the lower polishing plate at a distance from each other that allows the roller of the apparatus to press against the upper polishing cloth; rotating the upper polishing plate while simultaneously reciprocating the roller between the inner and outer pin crowns of the machine, and at least intermittently pressing the roller against the upper polishing cloth; A method comprising:

5. 5. The method of claim 4, wherein the roller is reciprocated between the outer and inner pin crowns of the polishing machine while being pressed against the upper polishing cloth.

6. 5. The method of claim 4, wherein the roller is moved back and forth between the outer and inner pin crowns of the polishing machine and is pressed against the upper polishing cloth only on its outward or return movement.

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