JP2013123763A - Polishing method for object to be polished - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing method of an object to be polished by which the object to be polished can be polished at high polishing speed.SOLUTION: The polishing method for the object to be polished includes a test working step for obtaining a grinding direction of the grinding of a precedent step of chemical mechanical polish in which the polishing speed of chemical mechanical polish is made higher using a test object 1 to be polished and a usual working step for grinding the surface 1 a of the object 1 to be polished in the grinding direction obtained in the test working step and performing the chemical mechanical polish. In the test working step, the surface 1a of the test object 1 to be polished is ground using a grinding wheel 11 rotated around a central axis 12 as a center by relatively moving the test object 1 to be polished and the grinding wheel 11 in one direction. The surface of the test object 1 to be polished is then subjected to chemical mechanical polish to obtain the polishing speed of the chemical mechanical polish. The polishing and the grinding are repeated, and the grinding direction in which the polishing speed of the chemical mechanical polish is accelerated is obtained.

Description

  The present invention relates to a method for polishing an object to be polished for polishing the surface of the object to be polished. More specifically, the present invention relates to a polishing method including chemical mechanical polishing.

  Conventionally, chemical mechanical polishing (CMP) has been performed to flatten the surface of an object to be polished such as a semiconductor wafer. In CMP, the polishing amount of the surface of the object to be polished is likely to be non-uniform in the surface, and a high polishing rate is required while uniformly polishing to improve flatness.

  Patent Document 1 discloses a working fluid used for modifying a wafer surface. Patent Document 2 discloses a chemical mechanical polishing pad having a high material removal rate. Further, Patent Document 3 discloses surface modification by plasma treatment.

Special table 2010-537404 gazette Special table 2009-505397 JP 2002-009151 A

  For the hydraulic fluid of Patent Document 1 and the chemical mechanical polishing pad of Patent Literature 2, it is necessary to prepare a hydraulic fluid and a pad suitable for the wafer. In addition, the plasma processing of Patent Document 3 requires a dedicated device.

  An object of the present invention is to provide a polishing method for an object that can polish the object to be polished at a high polishing rate.

  The present inventor has found that the polishing rate of chemical mechanical polishing in the subsequent process can be increased by performing relative grinding in which a workpiece and a grindstone are moved relative to each other in a specific direction. That is, according to the present invention, the following polishing method for an object to be polished is provided.

[1] By relatively moving the test object to be polished and the grindstone in one direction, the surface of the test object to be polished is ground with the grindstone rotating about a central axis, Determine the polishing rate of the chemical mechanical polishing by chemical mechanical polishing the surface, or examine the state of the surface, repeat the same by changing the direction of relative movement between the test workpiece and the grindstone, In the test processing step for obtaining a grinding direction in which the polishing speed of the chemical mechanical polishing is increased, and after grinding the surface of the workpiece with the grindstone in the grinding direction obtained in the test processing step, And a normal processing step of chemically and mechanically polishing the surface of the polished object.

[2] The object to be polished is a Y35 to 55 degree single crystal wafer of lithium tantalate, and the grinding direction in which the polishing speed of the chemical mechanical polishing is increased is relative to the orientation flat of the single crystal wafer. The object to be polished according to [1], wherein the object to be polished is a direction of 100 to 110 degrees, and the surface of the object to be polished is polished by relatively moving the object to be polished and the grindstone in the grinding direction. Polishing method.

  By performing the grinding by moving the workpiece and the grindstone relative to each other in a specific direction, the polishing rate of chemical mechanical polishing in the subsequent process can be increased.

It is a figure explaining the process of the grinding | polishing method of the to-be-polished object of this invention. It is a schematic diagram which shows a grinding device. It is a schematic diagram which shows another grinding device. It is a schematic diagram which shows the case where a grinding direction is 0 degree | times with respect to an orientation flat. It is a schematic diagram which shows the case where a grinding direction is 105 degree | times with respect to an orientation flat. It is a schematic diagram which shows a lapping apparatus. It is a schematic diagram which shows a CMP apparatus. It is a schematic diagram which shows the process trace on the surface of a to-be-polished object when a grinding direction is 105 degree | times with respect to an orientation flat. It is a schematic diagram which shows the process trace on the surface of a to-be-polished object when a grinding direction is 0 degree | times with respect to an orientation flat. It is a schematic diagram which shows the conventional grinding device. It is a schematic diagram which shows the process trace of the surface of the to-be-polished object by the conventional grinding apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the invention.

  The method for polishing an object to be polished according to the present invention is a polishing method including chemical mechanical polishing (CMP) for polishing a surface 1a of an object to be polished 1 such as a semiconductor wafer. As shown in FIG. 1, the polishing method for an object to be polished according to the present invention uses a test object to be polished 1 to determine the grinding direction of grinding in the previous process of chemical mechanical polishing, in which the polishing speed of chemical mechanical polishing is increased. A test processing step, and a normal processing step of grinding the surface 1a of the workpiece 1 in the grinding direction determined in the test processing step and performing chemical mechanical polishing. As the grinding, for example, creep feed grinding can be performed using a cup-type grindstone 11 (see FIG. 2A). Creep feed grinding is grinding that uses a large depth of cut, reduces the feed rate, and processes into a target shape in one pass. Or it can also grind using the straight type grindstone 11 by which the abrasive layer 11b was provided in the outer peripheral surface of the base metal 11a (refer FIG. 2B). Grinding may be performed once in one direction or multiple times in one direction.

  In the test processing step, the surface 1a of the test object 1 is ground by the grindstone 11 that rotates about the central axis 12 by moving the test object 1 and the grindstone 11 in one direction relative to each other (grinding). Step: see FIG. 2A). Thereafter, the surface 1a of the test object 1 is subjected to chemical mechanical polishing to obtain the polishing rate of chemical mechanical polishing (chemical mechanical polishing step: see FIG. 4).

  Next, the test object 1 and the grindstone 11 are moved relative to each other in a different direction for grinding, and the surface 1a of the test object 1 is chemically mechanically polished to obtain the polishing rate of chemical mechanical polishing. Thus, grinding and chemical mechanical polishing are repeated while changing the direction of relative movement between the test object 1 and the grindstone 11 to obtain a grinding direction in which the polishing speed of chemical mechanical polishing is increased.

  In the test processing step, when it is known what the surface 1a of the test object 1 is to be polished, the chemical mechanical polishing is not performed and the test after grinding is performed. The state of the surface 1a of the workpiece 1 may be examined. Examples of the method for examining the state of the surface 1a include hardness measurement and X-ray diffraction. In the case of a material in which the polishing rate of chemical mechanical polishing increases as the hardness decreases, a grinding direction that decreases the hardness may be obtained.

  In the normal machining process, after the surface 1a of the workpiece 1 is ground with the grindstone 11 in the grinding direction obtained in the test machining process (grinding process: see FIG. 2A), the surface 1a of the workpiece 1 is treated with a chemical machine. Polishing (chemical mechanical polishing step: see FIG. 4). The test process is a test process for determining grinding conditions, and the normal process is a product manufacturing process.

  In the polishing method for an object to be polished according to the present invention, the surface 1a of the object 1 is ground in one direction before chemical mechanical polishing. By optimizing the grinding direction, the state of the surface 1a is modified. . That is, the entire surface of the object to be polished can be uniformly modified (crystal dislocation) by grinding along a certain crystal orientation in the grinding process preceding the chemical mechanical polishing. The modified surface 1a is softened or fragile and can be easily processed in the subsequent steps (lapping, polishing, CMP), and as a result, high-speed processing can be realized. The modification parameter is only the grinding direction, and no dedicated tool or device is required.

The object to be polished 1 in the method for polishing an object to be polished according to the present invention is, for example, a semiconductor wafer such as Si or SiO ₂ or a single crystal wafer such as LN (lithium niobate), LT (lithium tantalate), or GaN. is there.

  Hereinafter, each process will be described in more detail. Each process is the same in both the test process and the normal process. In the test processing step, what is described as the workpiece 1 means the test workpiece 1. Note that the test object 1 means a test sample, and the same object as the object 1 can be used.

(Grinding process)
FIG. 2A shows a schematic diagram of the grinding apparatus 10. As shown in FIG. 2A, the grinding apparatus 10 includes a grindstone 11 that is rotatable about a central axis 12. The grindstone 11 shown in FIG. 2A is a cup-shaped grindstone 11 provided with a grind layer 11b along the outer peripheral edge of the lower surface of the base metal 11a. Further, the grinding apparatus 10 includes a table 13 for fixing the workpiece 1. Then, the workpiece 1 and the grindstone 11 are relatively horizontally moved in one direction to grind the workpiece 1. In FIG. 2A, the surface 1 a of the single crystal wafer is ground by horizontally moving the single crystal wafer of the workpiece 1 in one direction on the table 13 while rotating the grindstone 11 around the central axis 12. . In the embodiment of FIG. 2A, the workpiece 1 is moved perpendicularly to the central axis 12.

  FIG. 2B shows a schematic diagram of another grinding apparatus 10. The grindstone 11 shown in FIG. 2B is a straight type grindstone 11 in which the abrasive layer 11b is provided on the outer peripheral surface of the base metal 11a, and can be ground by the abrasive layer 11b provided on the outer peripheral surface. The center axis 12 is set in the horizontal direction, the center axis 12 and the workpiece 1 are arranged in parallel, and the workpiece 1 or the grindstone 11 is moved and ground.

  In the method for polishing an object to be polished according to the present invention, the number of revolutions of the grindstone 11 is preferably set to 500 to 5000 rpm in the grinding step. More preferably, it is 2000-4000 rpm, More preferably, it is 2500-3500 rpm. By setting the rotational speed of the grindstone 11 within this range, a uniform modified layer (modified layer) can be obtained on the surface 1a of the workpiece 1. As a kind of grindstone 11 used for the grinding | polishing method of to-be-polished material, a vitrified bond, a metal bond, a resin bond, etc. are mentioned.

  The feed rate of the table 13 to which the workpiece 1 is fixed is preferably 1 to 100 mm / min. Since the workpiece 1 is fixed on the table 13, the table feed speed is the moving speed of the workpiece 1. The feed speed of the table 13 is more preferably 10 to 80 mm / min, and further preferably 20 to 60 mm / min. By setting the feed speed of the table 13 within this range, a uniform modified layer (modified layer) can be obtained on the surface 1a of the workpiece 1.

  The cutting amount in the grinding step is preferably 0.1 to 50 μm. More preferably, it is 1-40 micrometers, More preferably, it is 10-30 micrometers. By setting the cut amount within this range, a uniform modified layer (deformed layer) can be obtained on the surface 1a of the workpiece 1.

  In the test processing step, the grinding direction of the workpiece 1 is ground as a certain direction, which is subjected to chemical mechanical polishing to obtain a polishing rate. Here, the grinding direction will be described. The grinding direction is defined as a direction with respect to the orientation flat 1v when the workpiece 1 is a single crystal wafer. As shown to FIG. 2C, the case where it grinds parallel to the orientation flat 1v is set to 0 degree. As shown in FIG. 2D, an angle at which the grinding direction is shifted counterclockwise is defined as an angle in the grinding direction. FIG. 2D shows the case where the grinding direction is 105 degrees.

  When the workpiece 1 is a Y35 to 55 degree single crystal wafer of lithium tantalate (LT), the grinding direction in which the polishing rate of chemical mechanical polishing is high is relative to the orientation flat 1v of the single crystal wafer. The direction is 100 to 110 degrees, preferably 105 degrees (see FIG. 2D). By grinding a single crystal wafer of lithium tantalate in this direction, the polishing rate by chemical mechanical polishing can be increased.

(Lapping process)
In the polishing method for an object to be polished according to the present invention, a chemical mechanical polishing step is performed after the grinding step of FIG. 2A, but a lapping step may be performed after the grinding step and before the chemical mechanical polishing step. FIG. 3 shows a lapping apparatus for performing the lapping process. As shown in FIG. 3, the lapping apparatus includes an upper surface plate 22, a lower surface plate 23 that is disposed so as to face the upper surface plate 22, and a disk-shaped carrier 24 that is sandwiched therebetween. Have. The object to be polished 1 is arranged on the lower surface of the carrier 24, the object to be polished 1 is sandwiched between the upper surface plate 22 and the lower surface plate 23, and polished with abrasive grains to improve flatness.

(Chemical mechanical polishing process)
FIG. 4 shows a schematic diagram of a CMP apparatus 30 used for chemical mechanical polishing. The CMP apparatus 30 includes a surface plate 32, a polishing head 33, and a slurry supply device 34. A polishing pad 40 is attached to the surface plate 32. The slurry is supplied from the slurry supply device 34 onto the polishing pad 40, the surface plate 32 rotates, and the polishing head 33 presses the workpiece 1 disposed on the polishing pad 40 against the polishing pad 40. While rotating in the same direction as the surface plate 32, the surface 1a of the workpiece 1 is chemically and mechanically polished.

  The polishing pad 40 of the present invention is formed in a disk shape, and a plurality of grooves 45 are processed on the surface thereof, and the polishing pad 40 is attached to the surface plate 32 to polish the object 1 to be polished. It is. The polishing pad 40 is made of, for example, foamed hard urethane, suede or the like. The number, depth, width and the like of the grooves 45 can be appropriately selected depending on the type of the workpiece 1 and the purpose of polishing. However, for example, the groove 45 having a width of 0.2 to 1.5 mm and a pitch of the grooves 45 (a distance between the centers of the grooves 45) of about 1 to 20 mm can be used.

  The number of rotations of the polishing pad 40 in the chemical mechanical polishing step is preferably 10 to 300 rpm. More preferably, it is 20-150 rpm, More preferably, it is 30-100 rpm. By setting the number of rotations of the polishing pad 40 within this range, the polishing amount of the workpiece 1 can be made uniform in the plane.

  The number of rotations of the workpiece 1 in the chemical mechanical polishing step is preferably 10 to 300 rpm. More preferably, it is 20-150 rpm, More preferably, it is 30-100 rpm. By setting the rotational speed of the workpiece 1 within this range, the polishing amount of the workpiece 1 can be made uniform in the plane.

  The load for pressing the workpiece 1 against the polishing pad 40 is preferably 0.5 to 100 kPa. More preferably, it is 5-50 kPa, More preferably, it is 10-30 kPa. By setting the load within this range, the polishing amount of the workpiece 1 can be made uniform in the plane.

  The slurry is supplied onto the surface of the polishing pad 40 from the slurry supply device 34 of the CMP apparatus 30. The slurry includes an abrasive, acid, oxidant, and water. Colloidal silica, fumed silica, alumina, titania, zirconia, and mixtures thereof can be used as the abrasive. Further, as the oxidizing agent, a peroxide, nitrate, or the like can be used. Further, the slurry may contain a pH adjusting agent. As the pH adjuster, an acidic substance or a basic substance is appropriately used in order to adjust the pH of the slurry to a desired value.

  The slurry is supplied from the slurry supply device 34 onto the polishing pad 40, the surface plate 32 rotates, and the polishing head 33 presses the workpiece 1 disposed on the polishing pad 40 against the polishing pad 40. By rotating in the same direction as the surface plate 32, the surface 1a of the workpiece 1 is chemically and mechanically polished.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

  As the work 1, a single crystal wafer of Y40 degree lithium tantalate was prepared.

(Example 1, Comparative Example 1)
The surface 1a of the lithium tantalate single crystal wafer was ground in one direction. As the grindstone 11, diamond # 1000 and vitrified bond grindstone were used. The rotational speed of the grindstone 11 was 2500 rpm, the feed speed of the table on which the workpiece 1 was fixed was 20 mm / min, and the cutting amount was 5 μm. The grinding direction of the single crystal wafer with respect to the orientation flat 1v was set to 0,105 degrees (see FIGS. 2C and 2D). FIG. 5 shows a processing mark on the surface of the workpiece 1 (single crystal wafer) when the grinding direction is 105 degrees, and FIG. 6 shows the surface of the workpiece 1 (single crystal wafer) when the grinding direction is 0 degrees. The processing trace of is shown.

(hardness)
The hardness of the surface 1a of the single crystal wafer after grinding was evaluated by Martens hardness (HMT115) using a 115 ° triangular cone indenter.

(Chemical mechanical polishing)
The surface 1a of the single crystal wafer after grinding was subjected to chemical mechanical polishing. The conditions for chemical mechanical polishing are as follows. The rotation speed of the polishing pad 40 was 100 rpm. The rotation speed of the single crystal wafer was 100 rpm. The load for pressing the single crystal wafer against the polishing pad 40 was 15 kPa. A slurry containing colloidal silica as an abrasive was used. The polishing rate of chemical mechanical polishing was determined by measuring the thickness of the single crystal wafer before and after polishing.

(Comparative Example 2)
Grinding was performed with a conventional grinding apparatus 50. FIG. 7A shows a conventional polishing apparatus 50. The object to be polished 1 was ground while being rotated by a grindstone 11 rotating around a central axis 12. In the same manner as in Example 1, the state of the surface and the polishing rate of chemical mechanical polishing were examined. FIG. 7B shows a processing mark on the surface of an object to be polished by a conventional grinding apparatus.

  In Example 1, the hardness was low, and the polishing rate of chemical mechanical polishing was faster than Comparative Example 1 and Comparative Example 2. By changing the grinding method from general in-feed grinding (Comparative Example 2) to creep feed grinding, the entire surface of the single crystal wafer could be uniformly modified. In addition, by setting the grinding direction of creep feed grinding to one specific direction, the polishing rate of chemical mechanical polishing in the subsequent process could be increased.

  The method for polishing an object to be polished according to the present invention can be used for polishing the surface of an object to be polished such as a semiconductor wafer.

1: (test) object to be polished, 1a: surface (of object to be polished), 1v: orientation flat, 10: grinding device, 11: grinding wheel, 11a: base metal, 11b: abrasive layer, 12: central axis, 13: Table: 20: Lapping device, 22: Upper surface plate, 23: Lower surface plate, 24: Carrier, 30: CMP device, 32: Surface plate, 33: Polishing head, 34: Slurry supply device, 40: Polishing pad, 45 : Groove, 50: polishing apparatus.

Claims (2)

By relatively moving the test object and the grindstone in one direction, the surface of the test object is ground with the grindstone rotating around the central axis.
The surface of the test workpiece is chemically mechanically polished to determine the polishing rate of the chemical mechanical polishing, or the state of the surface is examined,
A test processing step for obtaining a grinding direction in which the polishing speed of the chemical mechanical polishing is increased by repeating the same by changing the direction of relative movement between the test workpiece and the grindstone,
In the grinding direction determined in the test processing step, after grinding the surface of the object to be polished with the grindstone, the normal processing step of chemical mechanical polishing the surface of the object to be polished;
A method for polishing an object to be polished. The object to be polished is a single crystal wafer having a Y35 to 55 degree plane of lithium tantalate,
The grinding direction in which the polishing rate of the chemical mechanical polishing is increased is a direction of 100 to 110 degrees with respect to the orientation flat of the single crystal wafer,
The method for polishing an object according to claim 1, wherein the surface of the object to be polished is polished by relatively horizontally moving the object to be polished and the grindstone in the grinding direction.

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