Device and method for pressing upper polishing cloth against upper polishing plate of machine for simultaneously polishing front side and back side of semiconductor wafer

Abstract

The invention relates to an apparatus and a method for pressing an upper polishing cloth against an upper polishing plate of a machine for simultaneously polishing a front side and a back side of a semiconductor wafer between the upper polishing plate and a lower polishing plate. The device comprises two parallel linear tracks which are parallel to the middle radius of the lower polishing plate and are arranged above the lower polishing plate at a small distance from the lower polishing plate; a body to which the linear track is attached; two driven carriages, which are movable along the linear track; an actuator carried by the carriage for raising and lowering a roller attached to the actuator and arranged between the linear rails; and a controller for synchronously moving the carriage back and forth between the outer pin crown and the inner pin crown of the machine and for synchronously moving the actuator.

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 side (front side) and the back side (back side) of a semiconductor wafer. The present invention also provides a corresponding method of using the apparatus. Background Art

[0002] Polishing both sides of a workpiece such as a semiconductor wafer is also referred to as double-side polishing (DSP). The basic principle of DSP of semiconductor wafers is described, for example, in US 2003 0054 650 A1 and DE 100 07 390 A1.

[0003] Typically, the polishing cloth is adhesively bonded to the two polishing plates of the DSP system. The polishing cloth will be adhesively bonded without any bubbles in order to eliminate sources that negatively affect the desired polishing result. The (corresponding) polishing cloth in question will also adhere equally firmly to the polishing plates. In order to achieve the necessary adhesion, the polishing cloths can be pressed together between the polishing plates (cloth pressing). As a result of the pressing, the adhesive flows and adheres better. Methods for producing an adhesive bond between a polishing cloth and a corresponding polishing plate are known from US 2007 0 087 671 A1, JP 2006 289 523 A, JP 2006 346 808 A and DE 102 39 774 A1.

[0004] Prior to cloth pressing, the upper polishing cloth in the shape of a ring is adhesively bonded to the upper polishing plate. Such a method is described, for example, in EP 4 000 806 A1. Air bubbles in the space between the upper polishing plate and the upper polishing cloth must then be removed, which may be insufficient with cloth pressing alone. Such air bubbles can be pushed manually with the aid of a scraper or a roller to the outer or inner edge of the upper polishing cloth, from where they can be pushed out of the space.

[0005] This operation is laborious and difficult, since it has to be performed while working overhead. Although it is suggested in EP 4000 806 A1 that this operation can also be performed by a machine, it is not clear how this can be achieved.

[0006] US2007 0 087 671A1 recommends clamping a roller unit having radially arranged rollers between the lower polishing plate and the upper polishing plate after the polishing cloth has been adhesively bonded thereto, and rotating the polishing plates in opposite directions. Because the radially arranged rollers move the bubbles in the space between the polishing plate and the polishing cloth mainly in the circumferential direction, they are only able to inadequately remove the bubbles from the space. Summary of the invention

[0007] The invention is based on the object of providing a more effective solution for removing air bubbles from the space between the upper polishing plate and the upper polishing cloth.

[0008] The object of the present invention is achieved by a device for pressing an upper polishing cloth against an upper polishing plate of a machine for simultaneously polishing the front side and the back side of a semiconductor wafer between an upper polishing plate and a lower polishing plate, the device comprising:

[0009] two parallel linear rails, the two parallel linear rails being arranged above the lower polishing plate at a short distance from the lower polishing plate and parallel to a middle radius of the lower polishing plate;

[0010] a base body to which the linear track is fastened;

[0011] two driven slides, the two driven slides being movable along the linear track;

[0012] an actuator carried by the carriage for raising and lowering a roller secured to the actuator and disposed between the linear rails; and

[0013] A controller for synchronously moving the carriage back and forth between the inner and outer pin crowns of the machine and for synchronously moving the actuator.

[0014] The linear rails are preferably fastened to a ring or plate as a base body. The ring or plate is located on the lower polishing cloth and has teeth that mesh with the outer and inner pin crowns of the machine. The linear rails can protrude beyond the edge of the lower polishing plate. However, it is also feasible to shorten them to a length corresponding to the distance between the inner and outer pin crowns.

[0015] The actuator is preferably operated pneumatically or electrically.

[0016] The object is also achieved by a method for pressing an upper polishing cloth against an upper polishing plate of a machine for simultaneously polishing the front side and the back side of a semiconductor wafer, the method comprising:

[0017] adhesively bonding the upper polishing cloth to the upper polishing plate; and

[0018] Arranging the device according to one of claims 1 to 3 above the lower polishing cloth;

[0019] arranging the upper polishing plate above the lower polishing plate at a distance from each other, which allows the rollers of the device to be pressed against the upper polishing cloth; and

[0020] The roller is at least intermittently pressed against the upper polishing cloth while rotating the upper polishing plate and moving the roller back and forth between the inner and outer pin crowns of the machine.

[0021] The upper polishing cloth is adhesively bonded to the upper polishing plate and enters an intermediate state in which there are bubbles in the space between the upper polishing cloth and the upper polishing plate and the upper polishing cloth is not yet uniformly adhered to the upper polishing plate. This can be achieved, 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 4 000 806 A1.

[0022] The device according to the invention is used to remove air bubbles from the space between the upper polishing plate and the upper polishing cloth in a next step. For this purpose, the device is arranged above the lower polishing cloth and the upper polishing plate is pivoted above the lower polishing plate so that there is a small distance between the two polishing plates. With this distance, as long as the actuator has not yet raised the roller, it has not yet touched the upper polishing cloth. However, the distance is also small enough that the roller can be pressed against the upper polishing cloth by means of the actuator. The upper polishing plate is then rotated, preferably at a speed of not less than 0.1 rpm and not more than 1 rpm, particularly preferably at 0.2 rpm, and the roller is raised by means of the actuator so that it is pressed against the upper polishing cloth. The contact pressure of the roller is preferably from 1.8×10 5 Pa to 2.0×10 5 Pa (from 1.8 bar to 2.0 bar) and can vary.

[0023] The roller moves along a linear track between the inner and outer pin crowns of the polishing machine by means of a carriage while the roller is pressed against the upper polishing cloth. Thus, the roller drives the air bubbles mainly in the radial direction from the inner edge to the outer edge of the upper polishing cloth and thus out of the space between the upper polishing cloth and the upper polishing plate. The speed at which the roller moves along the linear track is preferably from 0.5 m / s to 1.5 m / s and can likewise vary.

[0024] As the upper polishing plate rotates and the roller moves between the inner and outer pin crowns of the machine, the roller at least intermittently presses against the upper polishing cloth.

[0025] According to one embodiment, as the upper polishing plate rotates, the roller moves back and forth between the inner and outer pin crowns of the polishing machine and presses against the upper polishing cloth.

[0026] According to another embodiment, the roller moves back and forth between the inner and outer pin crowns of the polishing machine as the upper polishing plate rotates and presses against the upper polishing cloth only on the outward or return stroke.

[0027] The present invention will be further described with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1The following plan view of the polishing plate illustrates the features of the DSP polisher.

[0029] Figure 2 Preferred embodiments of the present invention are shown.

[0030] List of reference symbols used

[0031] 1 lower polishing plate

[0032] 2 polishing cloth

[0033] 3Inside edge

[0034] 4 Outer edge

[0035] 5 Domestic Sales Champion

[0036] 6 Export crown

[0037] 7. Polishing cloth

[0038] 8 Upper polishing plate

[0039] 9 Linear tracks

[0040] 10 Slide

[0041] 11 Actuator

[0042] 12 Rollers

[0043] 13 Controller

[0044] 14 rings

[0045] 15 rods

[0046] 16 external teeth DETAILED DESCRIPTION

[0047] Figure 1 The features of the DSP polishing machine are shown in a plan view of the lower polishing plate 1, to which the annular lower polishing cloth 2 is adhesively bonded. Inner pin crowns 5 and outer pin crowns 6 are arranged parallel to the inner and outer edges 3 and 4 of the lower polishing cloth 2 and the lower polishing plate 1, by means of which the polishing plates 1, 8 can be rotated.

[0048] like Figure 2As shown, the lower polishing plate 1 is used to support a device for pressing the upper polishing cloth 7 against the upper polishing plate 8. The device comprises two parallel linear rails 9, which are arranged above the lower polishing plate 1 at a small distance from the lower polishing plate 1 and parallel to the middle radius of the lower polishing plate 1. Each of the linear rails 9 serves as a guide for a carriage 10, wherein each of the carriages 10 carries an actuator 11 and a roller 12, wherein the actuator is fastened to the roller 12 so that the roller is arranged between the linear rails (guides) 9. The actuator is able to raise the roller 12 and lower it again, and the carriage 10 is able to move the roller 12 along the path between the outer pin crown 6 and the inner pin crown 5. The carriage 10 and the actuator 11 each move synchronously, which is ensured by the controller 13.

[0049] According to the embodiment shown, the linear rail 9 rests on a ring 14 and on a rod 15 located in the ring 14 , wherein the ring 14 has external teeth 16 that mesh with the outer pin crown 6 and the inner pin crown 5 of the machine.

[0050] To implement the method according to the present invention, the upper polishing cloth 7 is brought into an intermediate state in which there are bubbles in the space between the upper polishing cloth 7 and the upper polishing plate 8 and the upper polishing cloth 7 has not yet uniformly adhered to the upper polishing plate 8 .

[0051] The device for pressing the upper polishing cloth 7 against the upper polishing plate 8 is then arranged above the lower polishing cloth 2 and the upper polishing plate 8 is pushed over the lower polishing plate 1. The two polishing plates 8, 1 are at a distance from each other, which allows the roller 12 of the device to press against the upper polishing cloth 7.

[0052] Figure 2 The situation is shown before the upper polishing plate 8 has been arranged above the lower polishing plate 1 .

[0053] Then, the upper polishing plate 8 rotates slowly and the roller 12 is moved back and forth by means of the carriage 10 between the outer pin crown 6 and the inner pin crown 5, while the actuator 11 presses the roller 12 against the upper polishing cloth 7 at least intermittently.

[0054] It has been shown that the advantages of this method include not only avoiding laborious manual work, but also having a favorable influence on the polishing result. The geometry of the semiconductor wafer of single-crystalline silicon after polishing (that is to say the flatness and plane parallelism) is measured, the local geometry at the edge is also measured, and the geometry of the semiconductor wafer of single-crystalline silicon after polishing and the local geometry at the edge are combined to form a measurement value, which combines the measurement results of GBIR (global flatness back side ideal range) and ESFQR (edge ​​site front side least squares range). Before polishing, if the upper polishing cloth is not pressed against the upper polishing plate manually but according to the invention, the measured values ​​are on average almost 17.8% smaller.

Claims

1. A device 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 device comprising: two parallel linear tracks, the two parallel linear tracks being arranged above the lower polishing plate at a short distance from the lower polishing plate and parallel to a middle radius of the lower polishing plate; a base body to which the linear track is fastened; two driven slides, the two driven slides being movable along the linear track; an actuator carried by the carriage for raising and lowering a roller secured to the actuator and disposed between the linear rails; as well as A controller for synchronously moving the carriage back and forth between the inner and outer pin crowns of the machine and for synchronously moving the actuator.

2. The device according to claim 1, characterized in that The linear track is supported on a ring or plate as the base body and a rod located in the ring, wherein the ring or plate has teeth that mesh with the outer pin crown and the inner pin crown of the machine.

3. The device according to claim 1 or claim 2, characterized in that: The actuator operates pneumatically or electrically.

4. A 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, comprising: adhesively bonding the upper polishing cloth to the upper polishing plate; as well as Arranging the device according to one of claims 1 to 3 above the lower polishing cloth; Arranging the upper polishing plate above the lower polishing plate at a distance from each other, which allows the rollers of the device to be pressed against the upper polishing cloth; as well as The roller is at least intermittently pressed against the upper polishing cloth while rotating the upper polishing plate and moving the roller back and forth between the inner and outer pin crowns of the machine.

5. The method according to claim 4, characterized in that The roller moves back and forth between the outer pin crown and the inner pin crown of the polishing machine and is pressed against the upper polishing cloth at the same time.

6. The method according to claim 4, characterized in that The roller moves back and forth between the outer pin crown and the inner pin crown of the polishing machine and is pressed against the upper polishing cloth only on the outward stroke or the return stroke.

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