JP2005335047A - Plane polishing device and processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plane polishing device which always keeps a plane shape of a polishing pad surface highly flat, realizes a stable improvement in processing precision, and simultaneously polishes both surfaces of a semiconductor substrate such as a silicon wafer, and also to provide its processing method. <P>SOLUTION: Assuming that the upper and lower polishing pad surfaces during polishing are varied into recesses or projections owing to the polishing frictional heat, the upper and lower polishing plate surfaces are finished into opposite projections or recesses. In processing, the shape variation amount of the processing surfaces of the upper and lower polishing pads are read with a non-contact displacement meter 26 assembled in three parts of the inner periphery, center, and the outer periphery of the width of the polishing place, and the flow rate and temperature of cooling water, and the flow rate and temperature of a polishing agent to the polishing plate is controlled so that the upper and lower polishing pads maintains flat surfaces. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to the planar shape of a polishing pad surface of a polishing apparatus for a semiconductor substrate such as a silicon wafer, and in particular, the surface of the pad being polished is always kept high and the processing accuracy is stably improved. It is measured.

  Since the polishing principle of an apparatus that polishes a workpiece such as a silicon wafer into a parallel plane is a processing method that transfers the plane of the polishing plate to the workpiece, maintaining the plane of the plate during the polishing process increases the workpiece. It is said that it is a principle to process into a plane of accuracy. For this reason, in order to prevent deformation of the plate due to frictional heat generated during polishing, a plate made of a material such as a low expansion alloy is used, and cooling water is circulated inside the plate to maintain a flat surface.

  However, in the polishing process in which the processing surface of a silicon wafer or the like is mirror-finished, a pad as a polishing cloth is attached to the processing surface of the upper and lower polishing plates, and the silicon wafer held by the carrier is sandwiched between the upper and lower plates, and PH9-12 This is performed by a chemical and mechanical combined polishing process called a mechanochemical method while supplying an abrasive of colloidal silica in which silicon oxide is turbid in the processing liquid to the processing surface. The details of this processing are as follows. While etching the processing surface of the silicon wafer with a processing solution of PH 9-12, colloidal silicon oxide is solid-phased on the processing surface, and the silicon oxide solid-phased on the processing surface is processed on the upper and lower polishing plates. The processed surface of the silicon wafer is polished by repeating mechanical peeling with a pad which is a non-woven fabric attached to the substrate.

  In the chemical and mechanical combined polishing process called the mechanochemical method, the optimum processing temperature for chemical processing is 35.5 ° C., so that the plane of the processing surface of the polishing plate is maintained while maintaining this temperature. This is a condition for processing a silicon wafer as a workpiece with high accuracy.

  In the conventional method, the temperature of the cooling water supplied to and discharged from the cooling jacket of the upper and lower polishing plates is measured or corrected in order to correct the lowering of the planar accuracy of the upper and lower polishing pads due to the temperature change of the upper and lower polishing plates during this processing. Measure the temperature of the upper and lower polishing pad surfaces during polishing and control the flow rate of cooling water or the flow rate or temperature of the polishing agent provided during polishing processing to set the temperature of the processing surface of the upper and lower polishing plates in advance I was trying to be. Specifically, a polishing apparatus described in Japanese Utility Model Publication No. 5-21320 is known, and FIG. 2 shows a part of a temperature detecting unit and a cooling unit in the configuration. In the figure, 11 is a polishing plate, 19 is a pad, 15 and 16 are pipes for circulating a coolant, 12 is a coolant circulation tank, 14 is a coolant circulation pump, and 13 is a coolant in the circulation tank. It is a cooling coil for cooling. Then, the processing surface temperature of the pad 19 is detected by the temperature sensor 17, and the rotational speed of the electric motor in the coolant circulation pump 14 is controlled via the control circuit 18 in accordance with this temperature to control only the flow rate of the coolant. Thus, the cooling liquid is continuously circulated through the polishing platen 11 to keep the temperature constant, thereby maintaining the plane of the pad 16 of the polishing plate.

In the polishing apparatus described in Japanese Patent Application No. 2003-359081, the amount of displacement of the shape of the processed surface of the upper and lower polishing pads during polishing is set at three locations, the inner periphery, the center, and the outer periphery of the width of the polishing plate. In addition, the surface shape of the pad, the shape of the wafer being polished, and the flatness are measured, so that the upper and lower polishing pad surfaces that change to concave or convex become flat, the inner circumference, center, and outer circumference of the upper and lower polishing plates. The flow rate of the cooling water supplied to these three locations and the flow rate and temperature of the abrasive supplied to the polishing process are individually supplied and controlled.
Reality 5-21320 Japanese Patent Application No. 2003-359081

  However, the method of controlling the temperature of the upper and lower polishing plates is that the pad attached to the polishing plate is made of a material in which a nonwoven fabric is infiltrated with resin, etc., so the heat conduction is poor, and the surface temperature of the pad during processing and the polishing The temperature of the surface of the plate to which the pad is adhered is a slight temperature difference of several degrees. Due to this temperature difference, the processed surface of the pad is slightly displaced in a concave or convex manner, and it is difficult to expect a highly accurate plane.

  For this reason, in the polishing process site, a polishing method may be employed in which the surface temperature of the pad is maintained at a constant temperature that seems to be an appropriate temperature by adjusting the flow rate of the abrasive. However, this method of adjusting the flow rate of the abrasive to keep the pad temperature constant cannot maintain a stable accuracy due to fluctuations in the mechanochemical action of the abrasive. Also, in order to maintain stable accuracy after processing without adjusting the abrasive flow rate as described above, find processing conditions such as the load on the wafer during processing, the number of rotations of the polishing plate, and the processing interval. Must-have.

  However, the shape of the workpiece is not always the same, and the outer shape varies. Therefore, in the present invention, it is assumed that the polishing plate warp shape when polishing is stopped and the polishing plate being polished is deformed by polishing frictional heat in advance so that the flatness after polishing of the polished wafer is minimized. Manufacture with optimally set warp curvature of polishing plate.

  As described above, in the present invention, the surface shape before processing of the polishing plate, which is a workpiece polishing processing surface, is the processing surface of the polishing plate in the chemical and mechanical compound polishing processing in which the silicon wafer is called mechanochemical method. By making the curvature of the polishing plate optimally set on the condition that the flat surface is maintained, the silicon wafer as the workpiece can be accurately obtained while maintaining the optimum processing temperature of chemical processing at 35.5 ° C. And it was able to process with high quality.

Hereinafter, a planar polishing apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a main part of an embodiment of the present invention, in which 25 is a lower polishing pad and is attached to a 20 lower polishing plate. Reference numeral 24 denotes an upper polishing pad, which is attached to the 21 upper polishing plate. The 27 carrier, which is a jig held by the 20 lower polishing plate and the 21 upper polishing plate, holds the silicon wafer 28 as a workpiece, meshes with the 23 central gear and the 22 internal gear, and revolves while revolving. To do. At the beginning of the polishing process, the upper 24 polishing plate is depressurized by the processing pressure adjusting mechanism, and when the lower polishing plate reaches a temperature approaching a plane due to thermal expansion due to the heat generated by the processing, the upper 21 polishing plate changes to the 28 silicon wafer. The processing pressure is increased, and the flow rate and temperature of the abrasive provided to the processing are controlled to maintain the flat surface with the 20 lower polishing plate.

  FIG. 2 is a cross-sectional perspective view showing a conventional method for controlling the temperature of the polishing plate. The temperature of the 21 polishing plate processed surface is detected by a non-contact type 17 temperature sensor, and a transmitter incorporated in the center of the polishing plate is used. The temperature at the time of processing is transmitted to the temperature control device, and the temperature and flow rate of the polishing liquid are controlled.

  FIG. 3 shows the shapes of the processed surfaces of the 20 lower polishing plate and the 21 upper polishing plate before the polishing process incorporated in the polishing apparatus of the present invention. The upper and lower polishing plates are subjected to 19 plane cuttings in advance according to the wafer outer diameter.

  FIG. 4 shows the shapes of the processed surfaces of the 21 upper polishing plate and the 20 lower polishing plate that have started to polish the wafer by this polishing apparatus and have reached a predetermined temperature and load. The upper polishing plate 21 and the outer polishing plate outer periphery 19 of the lower polishing plate 19 are cut in consideration of the outer diameter of the 28 silicon wafer. For example, in the case of a 300 mm wafer, the 19 planing portions of the 21 upper polishing plate and the 20 lower polishing plate are set to 30 mm.

It is sectional drawing of the principal part which shows one Example by this invention. The cross-sectional perspective view which shows the temperature control method of the conventional grinding | polishing plate. The cross-sectional perspective view which shows the shape of the grinding | polishing plate before grinding | polishing processing. Sectional drawing which shows the shape of the upper and lower polishing plate at the time of wafer grinding | polishing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Polishing surface plate 12 Cooling liquid circulation tank 13 Cooling coil 14 Cooling liquid circulation pump 15 Cooling liquid feed circulation pipe 16 Cooling liquid return circulation pipe 17 Temperature sensor 18 Control device 19 Planing part 20 Lower polishing plate 21 Upper polishing plate 22 Internal gear 23 Central gear 24 Upper polishing pad 25 Lower polishing pad 26 Non-contact displacement meter 27 Carrier 28 Silicon wafer 29 Abrasive tray 30 Abrasive agent 31 Abrasive agent distribution pipe 32 Cooling temperature control device 33 Abrasive agent tank 34 Abrasive agent feed pipe 35 Abrasive agent Return pipe 36 Abrasive pump

Claims (3)

  A plurality of carriers holding the workpiece are arranged at equal intervals between the central gear and the internal gear incorporated in the horizontal plane, and the workpiece, which is the workpiece, is inserted, and then the upper plate is lowered. Generated by polishing a workpiece in a parallel plane polishing device that simultaneously rotates and revolves the work carrier while rotating and revolving the workpiece carrier while being sandwiched between the lower plate and the relative rotational movement of the upper and lower plates. Since the processing surface of the upper and lower polishing plates is deformed into a convex or concave shape due to the frictional heat of polishing, the polishing plate before the processing is finished in a concave or convex shape in advance, and the processing surface of the polishing plate is maintained flat during normal operation processing. Surface polishing apparatus and processing method   In order to correct slight deformation of the processing surface of the upper and lower polishing plates to be convex or concave due to the frictional friction heat generated by polishing the workpiece in claim 1, the amount of displacement of the shape of the processing surface of the upper and lower polishing plates is A polishing method for automatically controlling the flow rate of cooling water, the temperature of the upper and lower polishing plates, the flow rate of the abrasive, and the temperature so that the processing surface of the lower polishing plate is maintained flat by reading with a non-contact displacement meter. In claim 1, in order to prevent the surface sag of the work outer peripheral part generated by polishing the work, the work surface of the outer peripheral part of the polishing plate is cut in advance corresponding to the work sag after work, A polishing method and apparatus characterized by preventing generation.

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