JP2013043222A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad which can be manufactured in a shorter time than that of a needle punch type, while allowing its polishing surface to be formed of short fibers.SOLUTION: The polishing pad for polishing a plate-like object such as a wafer includes a substrate, and a polishing layer arranged on the substrate with fibers electrostatically implanted therein. Preferably, the fibers are short hydrophilic fibers which are 1 mm or smaller in length.

Description

  The present invention relates to a polishing pad for polishing a workpiece such as a semiconductor wafer.

  For example, in a semiconductor wafer manufacturing process, a chemical mechanical polishing method, so-called CMP (Chemical Mechanical Polishing), is widely adopted as a polishing method capable of forming a surface having excellent flatness.

  In recent years, there has been a demand for thinner semiconductor wafers due to demands for smaller and thinner semiconductor devices. Therefore, after mechanically grinding the back surface of the semiconductor wafer with a grindstone, etc., the back surface of the semiconductor wafer after grinding is polished by CMP for the purpose of removing grinding distortion caused by this grinding and improving the bending strength. doing.

  CMP is performed by relatively sliding the polishing pad and the object to be rotated while supplying a polishing liquid (slurry) between the polishing pad and the object to be polished (see, for example, Japanese Patent Laid-Open No. Hei. No. 3-248532).

  A nonwoven fabric is generally used as the polishing pad, and the surface of an object to be polished such as a semiconductor wafer is polished while supplying a polishing liquid (slurry) containing free abrasive grains such as silica. As a polishing pad for polishing a polishing surface of a plate-like object such as a semiconductor wafer, a polishing pad made of a nonwoven fabric has been widely used. Nonwoven fabrics are generally manufactured using a needle punch method as disclosed in JP-A-61-207654.

JP-A-3-248532 JP-A 61-207654

  There is a problem that it takes a very long time to produce a nonwoven fabric by the needle punch method, and it is difficult to produce a nonwoven fabric with short fibers of 1 mm or less, for example, by the needle punch method. In particular, when the fibers are hydrophilic fibers such as cotton or rayon, it is difficult to produce a nonwoven fabric by the needle punch method.

  The present invention has been made in view of these points, and an object of the present invention is to provide a polishing pad that can be manufactured in a shorter time than the needle punch method and can form a polishing surface with short fibers. It is.

  According to the present invention, there is provided a polishing pad for polishing a plate-like material, comprising: a base material; and a polishing layer in which fibers are arranged by electrostatic flocking on the base material. Is provided.

  Preferably, the fibers are composed of hydrophilic fibers. Furthermore, the fibers are preferably short fibers of 1 mm or less.

  Since the polishing pad of the present invention is manufactured using an electrostatic flocking method, it can be manufactured in a shorter time than the needle punch method. Further, by forming the polishing layer with hydrophilic fibers, it is possible to prevent the polishing liquid from remaining on the upper surface of the plate-like material and forming a stain or the like. Furthermore, when the polishing layer is formed of short fibers of 1 mm or less, the polishing surface can be made very flat.

1 is an external perspective view of a polishing apparatus suitable for mounting the polishing pad of the present invention. 1 is a perspective view of a polishing pad according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a perspective view of a polishing apparatus 2 suitable for mounting the polishing pad of the present invention. Reference numeral 4 denotes a housing of the polishing apparatus 2, and a column 6 is erected on the rear side of the housing 4. A pair of guide rails (only one is shown) 8 extending in the vertical direction is fixed to the column 6.

  A polishing unit (polishing means) 10 is mounted along the pair of guide rails 8 so as to be movable in the vertical direction. The polishing unit 10 is attached to a moving base 12 whose housing 20 moves in the vertical direction along a pair of guide rails 8.

  The polishing unit 10 includes a housing 20, a spindle (not shown) rotatably accommodated in the housing 20, a servo motor 22 that rotationally drives the spindle, and a polishing wheel 24 having a polishing pad 26 fixed to the tip of the spindle. Contains.

  The polishing unit 10 includes a polishing unit moving mechanism 18 including a ball screw 14 and a pulse motor 16 that move the polishing unit 10 up and down along a pair of guide rails 8. When the pulse motor 16 is pulse-driven, the ball screw 14 rotates and the moving base 12 is moved in the vertical direction.

  A holding table mechanism (chuck table mechanism) 28 having a holding table 50 is disposed at an intermediate portion of the housing 4, and the holding table mechanism 28 is moved in the Y-axis direction by a holding table moving mechanism (not shown). Reference numeral 30 denotes a bellows that covers the holding table mechanism.

  In the front portion of the housing 4, a first wafer cassette 32, a second wafer cassette 34, a wafer transfer robot 36, a positioning mechanism 38 having a plurality of positioning pins 40, and a wafer carry-in mechanism (loading arm) 42 are provided. A wafer unloading mechanism (unloading arm) 44 and a spinner unit 46 are disposed.

  Further, a cleaning water spray nozzle 48 for cleaning the holding table 50 is provided at the approximate center of the housing 4. The cleaning water spray nozzle 48 sprays cleaning water toward the holding table 50 in a state where the holding table 50 is positioned in the wafer loading / unloading area on the front side of the apparatus.

  Referring to FIG. 2, a perspective view of the polishing pad 26 of the present invention is shown. The polishing pad 26 includes a base material 27 formed of a plastic such as PET (polyethylene terephthalate), polyethylene, and vinyl chloride, and a polishing layer 29 in which hydrophilic fibers such as rayon are disposed on the base material 27 by electrostatic flocking. It consists of. Here, the substrate is not limited to plastic, and may be made of metal, for example.

  Preferably, the fiber for electrostatic flocking is preferably rayon having a fiber length of 0.5 to 1 mm. Examples of other hydrophilic fibers include cotton and cupra (copper ammonia rayon). Instead of rayon, electrostatic flocking may be carried out using nylon (polyamide fiber) or polyester.

  The electrostatic flocking process is composed of the steps of applying an adhesive to a substrate → electrostatic flocking → drying → excess fiber removal. The adhesive applied to the substrate is preferably a water-soluble adhesive such as an acrylic emulsion adhesive or a vinyl acetate emulsion adhesive. The excess fiber is removed using an air gun, a brush, an ultrasonic hair removal device, or the like.

  Here, electrostatic flocking will be briefly described. Electrostatic flocking is also called flocking, and basically uses the electrostatic attraction in a high-voltage electrostatic field based on the same principle as electrostatic coating, etc., and a short fiber (pile or flock) on a substrate that has been previously coated with an adhesive. This is a processing method in which the pile piled up is fixed by drying (curing) the adhesive layer to obtain the required strength, and a direct current voltage of 20000 to 100000 V is usually used.

  When a high DC voltage is applied between the flat electrodes and an electrodeposited pile is placed on one electrode plate, the pile is charged to a certain amount of electricity. When a pile having a charge is placed during electrolysis in this way, the pile receives electrostatic force according to Coulomb's law, and the pile flies in a different direction in parallel to the electric field.

  A pile that has reached a different polarity changes its polarity and flies in the opposite direction. By applying an adhesive to a base material to be processed between a pair of electrode plates, the pile is statically placed on the base material by casting the flying pile using an electrostatic attraction force onto the adhesive layer. Electric hair transplanted.

  Since the pile is cast perpendicularly to the adhesive layer, the pile is regularly aligned on the substrate, and a very high flocking density can be obtained. You may give the coating which fixes the fiber transplanted to the finish. Alternatively, electrostatic flocking may be repeated a plurality of times, and a plurality of polishing layers 29 may be laminated on the substrate 27.

  The polishing pad 26 of the present invention is particularly suitable for polishing a silicon wafer sliced from a single crystal silicon ingot by the CMP method. However, the polishing pad 26 is produced by grinding the back surface of the wafer with a grinding wheel. For the purpose of removing grinding distortion and improving bending strength, it can also be used when the back surface of the ground wafer is polished by CMP.

  By forming the polishing layer 26 with a hydrophilic fiber such as rayon, it is possible to prevent the polishing liquid from remaining on the polishing surface and forming a stain or the like. Further, the polishing surface 29 can be made very flat by forming the polishing layer 29 with short fibers of 1 mm or less.

2 Polishing device 10 Polishing unit 26 Polishing pad 27 Base material 28 Holding table 29 Polishing layer 50 Holding table

Claims (3)

A polishing pad for polishing a plate-like object,
A substrate;
A polishing layer in which fibers are arranged by electrostatic flocking on the substrate;
A polishing pad comprising:   The polishing pad according to claim 1, wherein the fibers are composed of hydrophilic fibers.   The polishing pad according to claim 1 or 2, wherein the fibers are composed of short fibers of 1 mm or less.

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