JPH09201750A - Surface grinding equipment - Google Patents

Abstract

(57) An object of the present invention is to provide a surface grinding apparatus capable of easily adjusting the inclination of a grinding surface of a grindstone and improving TTV of a wafer. A surface grinding apparatus is provided with a grindstone rotating shaft having a grindstone attached to a tip thereof, and a wafer chuck having an axis substantially parallel to the grindstone rotating shaft and chucking a wafer. On the grinding surface 10a, a point O on the axis of the grindstone rotating shaft, a point P2 located on the outer circumference of the grindstone 10 on the axis of the wafer chuck, and the grinding surface 10a
A- defined by the intersection P1 between the outer periphery of the wafer 24 and the outer periphery of the grindstone 10 projected on the grinding surface 10a
The tilting means is capable of tilting the grinding surface 10a of the grindstone 10 about each coordinate axis of the orthogonal coordinate system including the A'axis and the BB 'axis orthogonal to the A'axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface grinding apparatus suitable for processing a flat surface of a wafer used for a semiconductor device.

[0002]

2. Description of the Related Art As VLSI becomes highly integrated and has a high density and a wafer on which elements are formed has a large diameter, it is strongly desired to improve the surface precision of the wafer such as TTV (total thickness variation). . In addition, TTV means a height difference of a wafer when the wafer is attracted to a flat attraction surface. By the way, SOI (Silicon On Ins) for forming a transistor in a single crystal silicon layer on an insulating film such as an oxide film is used.
Since the modulation technology has excellent radiation resistance and latch-up characteristics and is suitable for suppressing the short channel effect, research has been advanced. In particular, an SOI substrate manufacturing method using wafer bonding is one of the techniques that have received the most attention in recent years because an SOI layer with extremely few defects can be obtained. In the substrate manufactured by this SOI substrate manufacturing method, the thinning of the Si layer can be achieved by surface grinding and polishing after bonding, but the variation in the thickness of the thinned Si layer is determined by the TTV during the surface grinding. Especially, it is strongly desired to develop a surface grinding machine capable of improving the TTV of a workpiece.

Here, as a conventional surface grinding apparatus, for example, as shown in FIG. 3, a chuck having a grindstone rotating shaft 4 having a cup-shaped grindstone 3 at its tip and a shaft parallel to the grindstone rotating shaft 4 is used. The table 5 is provided, and during processing, the workpiece 6 is chucked on the chuck table 5, grinded by the grindstone 3, and then removed from the chuck table 5.
After measuring the surface accuracy, the process of adjusting the grindstone rotating shaft 4 and the like is repeated to suppress TTV.

However, in the processing method using such a surface grinding machine, it takes a huge amount of time to adjust the rotary shaft 4 of the grindstone, and an error occurs in the TTV due to the change of the chuck table between the grinding and the measurement. In the case of an inch wafer, there is a problem that it is difficult to suppress the thickness to 2 to 3 μm or less.

As a surface grinding apparatus for solving such a problem, there is one shown in FIG. 4, for example.

In FIG. 4, the support member 14 is the motor 1
For example, the bolts 16 rotated by 5 are attached to the support column 17 at four positions, up, down, left, and right, and it is possible to finely adjust the tilt angle of the grindstone rotating shaft 11 by adjusting the tightening of the bolts 16. .

The grindstone rotating shaft 1 to which the grindstone 10 is attached via the chuck table 18 and the grindstone holder 12
1 means that the distance between the axes is substantially equal to the radius of the grindstone 10.

The wafer 24 vacuum-sucked on the chuck table 18 is ground by rotating the grindstone rotating shaft 11 by the grindstone rotating shaft drive motor 13.

At this time, the chuck table 18 can be moved left and right as shown in the drawing, and an electrostatic capacitance type thickness sensor 19 is provided at the moved position. The thickness sensor 19 is a thickness measuring device and an image processing device 2.
1, a calculator 22, and a motor controller 23 are connected to a feedback means, which is connected to the motor 15.

In the surface grinding apparatus thus constructed, after grinding, the thickness of the entire wafer is measured by the thickness sensor 19, and the measured data is processed by the measuring apparatus 20 and the image processing apparatus 21 to obtain the TTV value a. .

Next, the TTV value a is calculated by the computer 22.
The inclination angle of the grindstone rotating shaft 11 is calculated so as to be 0, the motor 15 is driven through the motor control device, and the bolt 16
Adjust the tightening amount of.

By repeating this operation several times, the TT
It is possible to suppress the V value.

By the way, the positional relationship between the grindstone 10 and the wafer 24 in such a surface grinding apparatus is as shown in FIG. 5 (a). Further, as shown in FIG. 5B, the chuck table 18 for chucking the wafer 24 has a conical shape with a height of about 4 μm, and the wafer 24 is vacuum-sucked to this.

When the wafer 24 is ground,
The grindstone 10 has the wafer 24 only between the arcs P1 and P2.
Fine adjustment is performed by adjusting the inclination of the grindstone rotating shaft 11 by tightening the bolt 16 so that the above grinding is performed. The points P1, P2 and P3 are points on the grinding surface of the grindstone 10, and the points P1 and P3 are the outer circumference of the grindstone 10 and the wafer 24 when the wafer 24 is superposed on the grinding surface of the grindstone 10. Of the wafer 24.
Is the center of.

That is, the inclination of the grinding surface for grinding the grindstone 10 with respect to the horizontal plane is finely adjusted so that the wafer 24 and the grinding surface of the grindstone 10 contact each other only between the arcs P1 and P2. The portion ground between P2 and P2 is circular arc P2, P as the chuck table 18 rotates.
It prevents the machine from being ground again (double grinding) when it reaches the interval of 3.

Therefore, the fine adjustment of the inclination of the grinding surface of the grindstone 10 with respect to the horizontal plane is performed by the wafer 24 at the points P1 and P2.
The distances to are adjusted so that they are equal.

Further, the fine adjustment of the inclination of the grinding surface of the grindstone 10 is for preventing the above double grinding, and at the same time, the inclination of the grinding surface has a great influence on the TTV value of the wafer 24. Is needed from. Therefore, in addition to making the relative distances to the wafer 24 at the points P1 and P2 equal, it is necessary to finely adjust the relative distance to the wafer 24 at the point P3.

For example, under the conditions shown in FIG. 5, it is necessary to make the relative distance to the wafer 24 at the point P3 longer than the relative distance to the wafer 24 at the point P1 by about 7 μm.

[0019]

However, conventionally,
For the fine adjustment of the inclination of the grinding surface of the grindstone 10 with respect to the horizontal plane, that is, the fine adjustment of the relative distance to the wafer 24 at the points P1, P2 and P3, the motor 15 is driven via the motor control device 23, and the bolt The grindstone rotating shaft 10 is tilted by adjusting the tightening amount. This roughly means that, as shown in FIG. 5, the grinding surface of the grindstone 10 is tilted about the XX ′ axis and the YY ′ axis defined on the grinding surface of the grindstone 10. It is the same.

Therefore, for example, after adjusting the relative distance relationship between the points P1 and P2 about the XX 'axis and the YY' axis, the relative distance relationship between the points P1 and P3 is changed to the XX 'axis and If the adjustment is performed around the YY 'axis, the relative distance relationship between the adjusted points P1 and P2 changes, so
It is necessary to repeat readjustment. Therefore, there is a problem that it takes a considerable time to finely adjust the inclination of the grinding surface of the grindstone 10 with respect to the horizontal plane.

Further, there is a problem that the TTV of the wafer is deteriorated because the precision of the fine adjustment of the inclination is poor.

The present invention has been made in view of the above problems, and an object thereof is to provide a surface grinding apparatus capable of easily adjusting the inclination of the grinding surface of a grindstone and improving the TTV of a wafer. To do.

[0023]

DISCLOSURE OF THE INVENTION A surface grinding apparatus according to the present invention is a chuck for chucking a wafer, which has a grindstone rotating shaft having a grinding grindstone attached to its tip and an axis substantially parallel to the grindstone rotating shaft. A surface grinding device comprising a table, on the grinding surface of the grindstone, a point on the axis of the grindstone rotation axis, and a point on the outer circumference of the grindstone on the axis of the chuck table. And between the outer circumference of the wafer and the outer circumference of the grindstone projected on the grinding surface.
An inclination means is provided which is capable of inclining the grinding surface of the grindstone around each coordinate axis of a predetermined orthogonal coordinate system defined on the grinding surface by one of the intersections.

In the surface grinding apparatus according to the present invention, first,
On the grinding surface of the grindstone, a point on the axis of the grindstone axis (hereinafter referred to as the grindstone axis of rotation), and a point on the outer circumference of the grindstone on the axis of the chuck table (hereinafter, chuck). A table axis center point) and three points of one of two intersections between the outer circumference of the wafer and the outer circumference of the grindstone projected on the grinding surface define a predetermined orthogonal coordinate system on the grinding surface. It

Then, the relative distance between the chuck table axis center point to the wafer and the distance to the wafer at one of two intersections between the outer circumference of the wafer and the outer circumference of the grindstone projected on the grinding surface. The grinding surface of the grindstone is tilted around a coordinate axis that can adjust such a relationship to adjust the relative relationship between the two.

Next, the distance between the outer periphery of the wafer projected on the grinding surface and the outer periphery of the grindstone to the wafer at the other point of the two intersections is set around the coordinate axis orthogonal to the coordinate axis. The grinding surface is inclined and adjusted appropriately.

At this time, the relative relationship between the two points adjusted first is the other of the two intersections between the outer circumference of the wafer and the outer circumference of the grindstone which are adjusted last and projected on the grinding surface. Even if there is a change in the distance of the point to the wafer, it is maintained.

For this reason, the adjustment of the inclination of the grinding surface of the grindstone with respect to the horizontal plane is completed once, so that it is carried out in a short time.

Further, since the relative distance relationship between each other is not affected by the inclination of the grinding surface around each axis, and the adjustment is possible independently, it is possible to finely adjust the inclination of the grinding surface of the grindstone. Accuracy does not deteriorate.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a surface grinding machine according to the present invention will be described below with reference to the drawings.

FIG. 1 is an auxiliary explanatory view for explaining one embodiment of the surface grinding apparatus according to the present invention. In FIG. 1, the positional relationship between the grindstone 10 and the wafer 24 is the positional relationship shown in FIG. Is the same as.

Here, on the grinding surface 10a shown in the figure, A-
An orthogonal coordinate system consisting of the A ′ axis and the BB ′ axis orthogonal to this is on the grinding surface 10 a of the grindstone 10 at the point O on the axis of the grindstone rotating shaft 11 and on the axis of the chuck table 18. It is defined by a point P2 located on the outer circumference of the grindstone 10 and an intersection point P1 between the outer circumference of the wafer 24 projected on the grinding surface 10a and the outer circumference of the grindstone 10.

That is, the AA 'axis is on the axis P of the chuck table 18 and the intersection point P1 between the outer circumference of the wafer 24 and the outer circumference of the grindstone 10 projected on the grinding surface 10a, and is on the grindstone 10. Is a straight line parallel to the line segment connecting the point P2 located on the outer periphery of the grindstone, and is an axis passing through the point O on the axis of the grindstone rotating shaft 11.

The BB 'axis is the axis on the grinding surface 10a and is orthogonal to the AA' axis, and the grindstone rotation axis 1
It is an axis passing through a point O on the axis center of 1.

The surface grinding apparatus according to the present invention is capable of inclining the grinding surface 10a about the AA 'axis of the orthogonal coordinate system defined as described above and the BB' axis orthogonal thereto. The tilting means is provided.

Here, by the above-mentioned tilting means, BB '
By tilting the grinding surface 10a about the axis, the distance from the chuck table axis center point P2 to the wafer 24 and the grinding surface 10
The relative relationship between the distance to the wafer 24 at the intersection P1 between the outer circumference of the wafer 24 and the outer circumference of the grindstone 10 projected on a is adjusted.

Next, the distance to the wafer 24 at the intersection P3 between the outer periphery of the wafer 24 projected on the grinding surface 10a and the outer periphery of the grindstone 10 is taken along the line AA 'which is orthogonal to the line BB'. The grinding surface 10a of the grindstone 10 is tilted to the center and adjusted appropriately.

At this time, the first two points P1 and P2 adjusted
The relative relationship between the two is adjusted last and is maintained even if there is a change in the distance to the wafer 24 at the intersection P3 between the outer circumference of the wafer 24 and the outer circumference of the grindstone 10 projected on the grinding surface. It

For this reason, the adjustment of the inclination of the grinding surface 10a of the grindstone 10 with respect to the horizontal plane is completed once, so that it is carried out in a short time.

Further, the relative distance relationship between each other is not affected by the inclination of the grinding surface 10a about the BB 'axis and the AA' axis, and the adjustments can be made independently.
The precision of the fine adjustment of the inclination of the grinding surface of the grindstone 10 does not deteriorate. Therefore, it becomes possible to improve the TTV value of the processed surface of the wafer 24.

In order to realize the inclining means, for example, in the surface grinder shown in FIG. 4, the BB 'axis is parallel to the reference plane of the support 17 and the AA' axis is perpendicular to the reference plane. Then, the positional relationship between the wafer 24 and the grindstone 10 may be changed.

In this case, if the tightening amount of the bolt 16 is adjusted appropriately, the reference plane of the support column 17 can be tilted three-dimensionally. With such a structure, the above-mentioned AA can be approximately obtained. Grinding surface 10a centered on the'axis and BB 'axis
Is the same as tilting.

Next, the surface grinding apparatus shown in FIG. 2 employs, as a bearing, an air bearing 31 for flowing a high pressure air to the bearing holding the grindstone rotating shaft 11 to realize smooth high speed rotation.

In this surface grinding machine, the grindstone rotating shaft 1
1 has an upper end driven by a motor (not shown).

This grindstone rotating shaft 11 has an upper end portion indicated by an arrow CC '.
When moved in the direction, the ground surface 10a is approximately tilted about the EE ′ axis with the air bearing 31 as a fulcrum.

Therefore, A- described in FIG.
By aligning the A ′ axis and the BB ′ axis with the arrow CC ′ direction and the DD ′ direction in the drawing, it is possible to finely adjust the inclination of the grinding surface 10a as described in FIG.

The fine adjustment of the inclination of the grinding surface 10a can be performed by, for example, appropriately adjusting the amount of tightening of the bolt 16.

Here, an example of a method of manufacturing an SOI substrate using the above-described surface grinding apparatus according to the present invention will be briefly described.

First, a Si substrate A having a step formed in advance is bonded to another Si substrate B via an oxide film and a poly-Si film. After that, surface grinding is performed from the back surface of the Si substrate A using the surface grinding apparatus according to the present invention until the Si layer of the Si substrate A reaches about 10 μm.

Then, chemical polishing is carried out using an aqueous solution of ethylenediamine as a polishing liquid. This chemical polishing mainly proceeds by wiping off the reaction product of the ethylenediamine aqueous solution and Si with a polishing cloth, so that the polishing rate is significantly reduced when the oxide film stopper is exposed. As a result, the SOI having a film thickness substantially equal to the step formed at the beginning
A substrate is obtained.

In the SOI substrate manufactured as described above, since the TTV of the wafer is improved after the surface grinding, it becomes easy to achieve the required film thickness accuracy of the Si layer.

[0052]

As described above, according to the surface grinding apparatus of the present invention, it is possible to easily finely adjust the inclination of the grinding surface of the grindstone, and it is possible to greatly reduce the time required for the fine adjustment. Become.

Further, the precision of fine adjustment can be made better than that of the conventional surface grinding machine, and as a result, the TTV value of the processed surface of the wafer can be improved.

[Brief description of drawings]

FIG. 1 is an auxiliary explanatory diagram for explaining a surface grinding apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing an embodiment of a surface grinding apparatus according to the present invention.

FIG. 3 is an explanatory view showing an example of a conventional surface grinding apparatus.

FIG. 4 is an explanatory view showing another example of a conventional surface grinding apparatus.

5 is an explanatory view (FIG. 5A) showing a positional relationship between a grindstone and a wafer in the surface grinding apparatus shown in FIG. 4 and an explanatory view (FIG. 5B) showing a sectional shape of a chuck table.

[Explanation of symbols]

 10 Grinding Stone 10a Grinding Surface 11 Grinding Stone Rotating Axis 12 Grinding Stone Holder 13 Grinding Stone Rotating Axis Driving Motor 14 Supporting Member 15 Motor 16 Bolt 17 Strut 18 Chuck Table 19 Thickness Sensor 20 Thickness Measuring Device 21 Image Processing Device 22 Computer 23 Motor Control Device 24 Wafer

Claims (1)

[Claims] 1. A surface grinding apparatus comprising: a grindstone rotating shaft having a grinding grindstone attached to a tip thereof; and a chuck table having a shaft substantially parallel to the grindstone rotating shaft and chucking a wafer. On the grinding surface, a point on the axis of the grindstone rotating shaft, a point on the outer circumference of the grindstone on the axis of the chuck table, and of the wafer projected on the grinding surface. Inclination means capable of respectively inclining the grinding surface of the grindstone around each coordinate axis of a predetermined orthogonal coordinate system defined on the grinding surface by the one of two intersections between the outer circumference and the outer circumference of the grindstone. Surface grinding machine equipped with.