JPH08181092A - Holding plate for polishing semiconductor wafer - Google Patents

Abstract

PURPOSE: To enable a semiconductor wafer.polishing process to be lessened in number of processes, easily controlled, to decrease dimples produced on the surface of a wafer in number, and to make a wafer less deformed and improved in flatness by a method wherein a air-permeable and elastic sheet is provided onto the surface of a air-permeable ceramic plate which holds a semiconductor wafer. CONSTITUTION: A sheet 10 which is fibrous or porous, air-permeable, and elastic is pasted on an air-permeable ceramic plate 3 with adhesive agent 9 keeping high in air-permeability. Or a sheet 10 which is fibrous or porous, air-permeable, and elastic is disposed in tension and fixed onto an air-permeable ceramic plate 3 with a jig 12. The sheet 10 is set as thick as 600μm or below. An outer vacuum pump is actuated to generate a suction force for holding a wafer 1 placed on the sheet 10 when the wafer 1 is polished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate for holding a semiconductor wafer used when polishing the semiconductor wafer.

[0002]

2. Description of the Related Art The following three methods are currently used as a method of holding a semiconductor wafer (hereinafter, simply referred to as "wafer") during polishing.

(1) Attaching to a plate with high plane accuracy using wax.

(2) Attaching to a plate with high flatness accuracy by a vacuum suction method.

(3) Holding by the template method (backing plate method).

In the pasting method using the wax of (1), first, the wax is uniformly applied to the back surface of the wafer, and then the wax is melted on a substrate with a heater, and a high-precision plate such as alumina is applied with high pressure. The wafer is attached using a press machine.

The sticking method by the vacuum suction method (2) will be described with reference to FIG. FIG. 8 is a partial vertical cross-sectional view of a vacuum suction plate and a wafer.

In the vacuum suction method, minute holes or minute grooves 2 for drawing a vacuum are provided on the surface of a plate 3 having high plane accuracy, and a vacuum pump (not shown) is operated to cause minute holes or grooves. The suction force generated in 2 is used to uniformly apply a suction force to the entire surface of the wafer 1, and the wafer 1 is attached to the surface of the plate 3 having high plane accuracy. A large number of grooves or holes 2 for vacuuming are uniformly provided on the surface of the plate 3 on which the wafer 1 is placed. Further, the surface of the plate 3 is finished with high plane accuracy.

The holding method by the template (template) method of (3) will be described with reference to FIG. FIG. 9 is a view showing a partial vertical cross section of a template plate and a wafer.

In the template method, a backing plate 5 (a non-woven fabric having soft artificial leather or the like) is attached on the surface of a plate 3 having high flatness accuracy as disclosed in Japanese Patent Laid-Open No. 4-206946, and This is a method in which a resin-made template 4 which is hollowed out along the outer shape of the wafer 1 is installed on the upper side and the wafer 1 is fitted therein.

However, each of the methods for holding these wafers has the following problems.

[0012] The major drawback of the pasting method using wax of (1) is that the number of steps is large and each step must be performed under strict control. In order to carry out this method, it is necessary to perform a step of applying wax to the wafer, a step of heating the applied wafer to attach it to the plate, a step of peeling the wafer from the plate, and a step of removing the wax.

In the step of applying the wax, strict control is required to prevent the mixing of particles into the wax, and attention must be paid to the unevenness of the wax application which leads to deterioration of the flatness of the wafer after polishing. I won't. In the step of adhering to the plate, it is necessary to apply a uniform load to the entire surface while heating the wafer. The process of stripping from the plate is difficult to automate and must be manually removed one by one carefully to avoid chipping the wafer. In the step of removing the wax, cleaning with an organic solvent is performed under severe conditions, so that the surface of the wafer may be adversely affected.

A drawback of the (2) attachment method by vacuum suction is that defects are generated on the surface of the wafer. This will be described with reference to FIG. FIG. 10 is a diagram showing a wafer polishing process by the vacuum suction method.

When an attempt is made to hold the wafer 1 by the suction force generated by pulling a vacuum, since the thickness of the wafer 1 is thin, the wafer 1 is locally bent along the vacuum hole or the vacuum groove 2 provided for vacuum suction. Occurs, and traces of vacuum holes or vacuum grooves remain on the surface of the wafer 1 after polishing.

Further, the vacuum suction table having high plane accuracy is
The hardness of the surface must be high, and if foreign matter enters between the wafer 1 and the vacuum suction table, dimples (dents) will be generated on the surface of the wafer 1.

A drawback of the holding method using the template and backing plate of (3) is that the flatness of the wafer is deteriorated. This will be described with reference to FIG. Figure 11
FIG. 4 is a diagram showing a partial vertical cross section of a wafer and a plate of a holding system by a template.

In this system, when foreign matter 7 is mixed between the backing plate 5 and the wafer 1, the backing plate 5 which is an elastic material is locally deformed to prevent the occurrence of dimples. However, since the wafer 1 and the backing plate 5 are held only by the frictional force between them, unevenness in the polishing pressure applied to the wafer 1 during polishing causes a gap between the wafer 1 and the backing plate 5, Bubbles 6 may accumulate there. Since the backing plate 5 has no air permeability, the air bubbles 6 that have once accumulated do not have a place to escape, and as a result, a large non-local bending is generated on the wafer 1,
The flatness of the wafer 1 deteriorates.

[0019]

As described above, each of the conventional methods used for polishing a wafer has drawbacks and is not satisfactory.

The problem to be solved by the present invention is to reduce the number of steps, simplify the step control, reduce the dimples generated on the surface of the wafer, reduce the deflection of the wafer and improve the flatness, as compared with the conventional method. (EN) Provided is a new wafer polishing holding plate which can be manufactured.

[0021]

SUMMARY OF THE INVENTION The gist of the present invention is "a semiconductor wafer polishing holding plate having a breathable and elastic sheet at a position for holding a semiconductor wafer on the surface of a breathable ceramic plate". .

[0022]

FIG. 1 shows a wafer polishing holding plate 1 according to the present invention.
It is a figure showing the longitudinal section of an example.

FIG. 1 (a) shows a sheet 10 which is fibrous or porous and has air permeability and elasticity is attached to an air permeable ceramic plate 3 with an adhesive 9 while keeping air permeability. . FIG. 1 (b) shows that a fibrous or porous sheet 10 having air permeability and elasticity is fixed on a breathable ceramic plate 3 by a jig 12 while applying a constant tension. . Reference numeral 8 is a pipe or a hole from a vacuum pump (not shown), which is connected to the seat 10. Reference numeral 11 is a portion of the seat 10 where ventilation is blocked.

The wafer polishing holding plate of the present invention holds the wafer 1 placed on the sheet 10 by utilizing the suction force generated by operating an external vacuum pump when polishing the wafer.

The holding plate for polishing a semiconductor wafer according to the present invention will be described in detail below.

As the material of the ceramic plate 3, it is necessary to use a material having a small coefficient of thermal expansion and a high rigidity.
Examples of this include ceramics such as alumina, quartz, and low thermal expansion glass.

2 (1), (2) and (3) are enlarged sectional views of the wafer polishing holding plate of the present invention. Near the surface of the ceramic plate 3 is a microscopic hole 15 (see (1) in FIG. 2) or a concentric circle that is connected to a pipe 8 (not shown in FIG. 2) leading to a vacuum pump to draw a vacuum. A large number of grooves 2 (see (2) in FIG. 2) are provided. As shown in (3) of FIG. 2, if the material of the ceramic plate 3 is a porous (porous) material with air permeability, it is not necessary to provide holes or grooves, and a large number of fine air holes are provided. Is obtained and the influence on the wafer is small, which is preferable.

The plane accuracy of the side provided with the sheet 10 affects the plane accuracy of the wafer after polishing, so that it is desirable to be as high as possible.

A fine porous or fibrous sheet 10 having air permeability and elasticity is provided at a position for holding a wafer on the surface of the ceramic plate 3. Sheet
Examples of the 10 materials include non-woven fabric (felt infiltrated with liquid artificial leather material), rubber, resin, paper, leather, artificial leather, and the like. The thickness of the sheet 10 is preferably about 600 μm or less.

In the sheet 10, it is necessary that the portion on which the wafer 1 is placed is breathable and the portion not in contact with the wafer 1 is not breathable. In the example shown in FIG. 1, the reference numeral 10 is a breathable sheet portion, and the reference numeral 11 is a non-breathable sheet portion.

As described above, in order to give air permeability to a part of the sheet and block air passage to the other part, as shown in FIG. The sheet 10 may be covered with a non-breathable template or tape or a sealable material 13 that can be embedded, and the portion of the sheet 10 that is not in contact with the wafer may be covered from above. Alternatively, conversely, a portion of the non-breathable template that is in contact with the wafer may be pierced and a breathable sheet 10 in the form of a wafer may be fitted into that portion.

The point is that a sheet 10 having air permeability and elasticity is provided on the surface of the plate 3 at a position for holding a wafer, and a sheet 11 or a template having no air permeability is used at a position on the plate 3 where the wafer is not held. Any structure may be used as long as it is covered so as to block ventilation. With such a structure, when the vacuum pump is operated, a suction force for holding the wafer can be generated only at the position of the sheet 10.

The sheets 10 and 11 are fixed to the plate 3 with an adhesive 9 as shown in FIG. 1 (a) or the jig 12 with a constant tension applied to the sheets 10 and 11 as shown in FIG. 1 (b). It may be fixed to the plate 3 by.

In order to hold a wafer using the wafer polishing holding plate of the present invention, first, the wafer 1 is placed on the sheet 10, and then a suction force is generated by an external vacuum pump. Since the sheet 10 contracts uniformly over the entire surface of the wafer 1, the surface of the sheet 10 is kept flat. As a result, the wafer 1 can be polished with high planar accuracy.

Since the sheet 10 has elasticity, even if some foreign matter or dust is sandwiched between it and the wafer, the foreign matter is absorbed on the sheet 10 side, and the surface of the wafer is flawed or locally deformed (dimples). Does not occur. Further, as the finer fibrous or porous sheet 10 is used, the diameter of the air holes of the sheet 10 for drawing a vacuum becomes smaller and the number becomes larger, so that the suction force applied to the wafer 1 is the surface of the wafer 1. It will be more evenly distributed and applied. As a result, the surface of the wafer 1 after polishing that was in contact with the sheet 10 does not leave a trace of being held in vacuum, and a high quality wafer can be obtained.

Further, since the wafer polishing holding plate of the present invention holds the wafer 1 by utilizing the suction force when pulling a vacuum, air bubbles do not enter between the wafer 1 and the sheet 10, and Deformation of the wafer due to the above does not occur. After polishing the wafer, the vacuum suction can be stopped to easily remove the wafer from the polishing holding plate.

The steps required to hold the wafer polishing holding plate of the present invention are only the steps of holding the wafer and removing the wafer, which are very few steps as compared with the above-mentioned wax sticking method, and are easy. Since it can be carried out, it is possible to automate the process.

[0038]

EXAMPLE An example in which the wafer polishing holding plate of the present invention is applied to an actual polishing apparatus is shown in FIGS. FIG. 4 is applied to a batch type polishing apparatus. In this example, the wafer polishing holding plate of the present invention (combined reference numerals 3, 10 and 11 in the figure) has a structure capable of holding two or more wafers 1 at a time.

FIG. 5 is applied to a single-wafer polishing apparatus. In this example, the wafer polishing holding plate of the present invention has a structure capable of holding one wafer 1.

Holes and grooves (not shown) on the surface of the wafer polishing holding plate are connected to the pipe 8 from the vacuum pump 14, and are provided on the surface of the plate 3 when the vacuum pump 14 is operated. A force for adsorbing the wafer 1 on the sheet 10 acts. The rotary portion and the stop portion of the vacuum pump 14 are connected by a rotary joint 16.

After the wafer 1 is held by the wafer polishing holding plate of the present invention, the polishing platen 17 is rotated and the surface of the wafer 1 is polished by the polishing pad 18 provided on the surface thereof.

FIG. 6 shows an example in which the wafer polishing holding plate of the present invention is applied to a device for automatically attaching and detaching a wafer on the wafer polishing holding plate for the purpose of streamlining the process in the wafer polishing process. It is shown.

The wafer 1 is transferred to the wafer polishing holding device by the transfer device 21. Auto handler arm
The vacuum chuck 19 attached to the tip of 20 moves to a position where the wafer 1 that has been transferred is attracted by the horizontal, vertical and vertical movements of the auto handler arm 20. Next, the vacuum chuck 19 attracts the wafer 1 by utilizing the suction force when pulling a vacuum. The piping from the vacuum pump (not shown) is the auto handler arm 20.
It is pulled up to the vacuum chuck 19 through. The vacuum chuck 19 that has attracted the wafer moves to a predetermined position (position of the sheet 10) for holding the wafer on the wafer polishing holding plate by the vertical movement, horizontal rotation and vertical rotation of the auto handler arm 20. Next, the vacuum of the vacuum chuck 19 at the tip of the auto-handler arm 20 is released, the vacuum pump 14 on the wafer holding plate side is operated to generate a suction force on the sheet 10 via the pipe 8, and the force is utilized. Hold the wafer 1.

The wafer 1 is polished by bringing the polishing pad 18 on the polishing platen 17 into contact with the wafer and rotating the wafer.

After polishing, vacuum chuck of auto handler
19 holds the wafer 1 and sends the wafer 1 to a transfer system (not shown) after polishing. All of these series of operations can be performed automatically.

FIG. 7 shows the relationship between the sheet thickness and the wafer thickness variation when the wafer is actually held and polished using the wafer holding plate of the present invention. A non-woven fabric (DOLYPAS # 1200 FILM manufactured by Fuji Bow Ehime Co., Ltd.) was used as the sheet. TTV on the vertical axis of FIG.
Is the difference between the thickest part and the thinnest part of the semiconductor wafer after polishing.

The following can be seen from FIG. The thicker the sheet, the higher the TTV value. Therefore, it is desirable that the thickness of the sheet be as thin as possible so that no trace of the vacuum groove is left on the surface of the wafer. When the above non-woven fabric is used as a sheet, for example, the non-woven fabric thickness is set to 0.
It should be 5 mm or less.

[0048]

The wafer polishing holding plate of the present invention comprises:
Since the number of steps required to hold a wafer using it is small and simple, the holding step can be automated, and the work efficiency is improved as compared with the conventional method.

Since the wafer polishing holding plate of the present invention has a thin sheet having air permeability and elasticity attached to the surface of the plate having high plane accuracy, the sheet is brought into contact with the wafer by the force of drawing a vacuum. It is possible to hold the wafer flat by deforming uniformly over the entire surface. Further, since the vacuum is pulled, no air bubbles enter between the wafer and the wafer polishing holding plate. Further, since the sheet has an appropriate elasticity, the sheet is locally deformed even when dust or foreign matter is sandwiched between the wafer and the holding plate, so that the dimples generated on the surface of the wafer can be prevented. it can. The finer the fibrous or porous sheet is, the less traces of vacuum holes and grooves are left on the surface of the wafer after polishing.

[Brief description of drawings]

FIG. 1 is a diagram showing a partial vertical cross section of a wafer polishing holding plate of the present invention.

FIG. 2 is an enlarged vertical cross-sectional view of a wafer polishing holding plate of the present invention.

FIG. 3 is a diagram showing a structure of a sheet of a wafer polishing holding plate of the present invention.

FIG. 4 is a diagram showing a configuration when the wafer polishing holding plate of the present invention is applied to a batch type polishing apparatus.

FIG. 5 is a diagram showing a configuration when the wafer polishing holding plate of the present invention is applied to a single-wafer polishing apparatus.

FIG. 6 is a diagram showing a configuration when the wafer polishing holding plate of the present invention is applied to a polishing apparatus having an automatic wafer transfer device.

FIG. 7 is a diagram showing the relationship between the thickness of the sheet of the wafer polishing holding plate of the present invention and the variation in the thickness of the wafer after polishing.

FIG. 8 is a partial vertical cross-sectional view of a conventional suction-type wafer polishing holding plate.

FIG. 9 is a diagram showing a partial vertical cross section of a conventional template-type wafer polishing holding plate.

FIG. 10 is a diagram showing local deformation of a surface that occurs when a wafer is held by a conventional suction method.

FIG. 11 is a diagram showing a deformation that occurs when a wafer is held by a conventional template method.

[Explanation of symbols]

1 wafer, 2 grooves, 3 ceramics plate, 4 template, 5 backing plate, 6 air bubbles, 7 dust and foreign matter,
8 vacuum piping, 9 adhesive,
10 breathable sheets, 11 non-breathable sheets, 12 jigs, 13 non-breathable templates,
14 vacuum pump, 15 holes, 16
Rotary joint, 17 polishing surface plate,
18 polishing pad, 19 vacuum chuck, 20
Auto handler arm, 21 transfer device,

Claims (1)

[Claims] 1. A holding plate for polishing a semiconductor wafer, comprising a breathable and elastic sheet at a position for holding a semiconductor wafer on the surface of a breathable ceramic plate.