JP2012028602A - Automatic polishing device for semiconductor wafer and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic polishing device and a polishing method capable of automatically measuring the thickness of a wafer being polished with high accuracy and automatically polishing it to a desired thickness.SOLUTION: An automatic polishing device comprises: a polishing surface plate; a plate provided so as to press a workpiece retained at the position facing the polishing surface plate against the polishing surface plate while rotating the workpiece; a workpiece position measurement sensor for measuring workpiece position information; a plate position measurement sensor for measuring plate position information; calculation means for calculating difference information between the workpiece position information and the plate position information; and output means for outputting the difference information calculated by the calculation means.

Description

  The present invention relates to an apparatus and a polishing method for polishing a semiconductor wafer to a predetermined thickness.

A semiconductor chip used for a semiconductor device, a light emitting diode, or the like is used by dividing a semiconductor single crystal into a wafer and forming an integrated circuit on the wafer, and then dividing the semiconductor chip into semiconductor chips for each predetermined circuit.
This method of processing a semiconductor single crystal into a wafer is obtained by processing a semiconductor single crystal into a plurality of wafers using a wire saw, a band saw or the like after processing the semiconductor single crystal into a cylindrical shape with a cylindrical grinding machine. Then, a wafer adjusted to a desired thickness can be obtained by polishing.

As described in Patent Document 1, the conventional polishing method pressurizes a plate on which a semiconductor wafer is attached to a surface plate, and rotates the plate and the surface plate to adjust the wafer to a desired thickness. Yes.
In the method described in Patent Document 1, in order to adjust the wafer to a desired thickness, a sizing device is disposed beside the air cylinder for pressurizing the plate of the polishing device to the surface plate, and the sizing device By measuring the polishing amount of the wafer, it is adjusted to a desired wafer thickness.

  However, in this method, since the amount of change in the thickness of the wafer is measured instead of the amount by which the position of the air cylinder moves, the actual amount of change in the thickness of the wafer is large due to mounting errors of various parts of the polishing apparatus. It is necessary to repeat the measurement and polishing operations until the desired thickness is obtained after measuring the thickness after removing the wafer from the plate and then attaching it to the plate and polishing it again. The productivity has not been greatly improved.

JP-A-9-285959

  The present invention has been made to solve such a problem, and provides an automatic polishing apparatus and a polishing method capable of automatically measuring a wafer thickness during polishing with high accuracy and automatically polishing to a desired thickness. For the purpose.

  The first invention of the present invention for solving this problem is a platen and a plate provided to press the platen while rotating the workpiece held at a position facing the platen, Workpiece position measurement sensor for measuring the position information of the workpiece, plate position measurement sensor for measuring the position information of the plate, calculation means for the difference information between the position information of the workpiece and the position information of the plate, and the calculation means An output means for outputting the difference information obtained by the above, and the distance between the position information acquisition positions of the workpiece position measurement sensor and the plate position measurement sensor is 10 mm or less. It is a polishing apparatus.

  The second invention of the present invention is characterized in that the position measuring sensor in the first invention is a contact sensor, and the contact terminal constituting the contact sensor is further on the contact surface side with the workpiece. An automatic polishing apparatus characterized in that it is a curved surface having a convex curvature, and the workpiece position measuring sensor includes a moving mechanism that contacts the workpiece only when measuring position information. .

  According to a third aspect of the present invention, in a polishing method for polishing a rotating surface plate and a workpiece pressed while rotating on the surface plate, position information of a contact surface of the workpiece with the surface plate is measured. And measuring the position information of the plate holding the workpiece, calculating difference information between the position information of the workpiece and the position information of the plate, and obtaining the thickness of the workpiece from the difference information It is what.

  According to a fourth aspect of the present invention, in the third aspect, an exposed portion of the work piece from the surface plate is formed, position information on the exposed portion is measured, and the position information is measured by the number of rotations of the surface plate. The position information is acquired by contacting the contact terminal of the position measurement sensor with the rotation speed slower than that when polishing the workpiece, and when the position information is not measured, the position measurement sensor moves. The contact terminals are retracted from the workpiece and the plate.

  Furthermore, in the fifth invention of the present invention, the measurement of the position information in the third invention is measured n times, and after the fluctuation of the position information due to the (n−1) th and nth measurements converges within 10%, The polishing method is characterized by calculating difference information.

  According to the present invention, it is possible to easily measure a polishing amount of a workpiece with high accuracy and stably, and thus it is possible to reduce the number of polishing work steps.

It is explanatory drawing which shows the structure of the automatic grinding | polishing apparatus of this invention. It is explanatory drawing which shows the shape of the contact terminal of a workpiece position measurement sensor.

Hereinafter, embodiments of an automatic polishing apparatus and an automatic polishing method of the present invention will be described with reference to the drawings.
[Automatic polishing equipment]
FIG. 1 is an explanatory view showing an automatic polishing apparatus of the present invention. In FIG. 1, 1 is a surface plate, 2 is a cylinder provided facing the surface plate 1, 3 is a plate, 4 is a workpiece, 5 is a workpiece position measuring sensor, and 6 is a plate position measuring sensor.
The workpiece 4 is fixed to the plate 3 and pressed against the surface plate 1.

  The workpiece position measurement sensor 5 is provided so as to measure the position of the surface 4 a (that is, the polishing surface) of the workpiece 4 that contacts the surface plate 1, and the plate position measurement sensor 6 It is provided to measure the position of the workpiece fixing side surface 3a. Furthermore, the distance between the acquisition positions of the position information (the distance indicated by L in FIG. 1) is set to be 10 mm or less.

These workpiece position measurement sensor 5 and plate position measurement sensor 6 may be either a non-contact sensor or a contact sensor, or a combination of both.
A known displacement meter such as a laser displacement meter or an eddy current displacement meter can be used as the non-contact sensor.

  In order to measure the polishing accuracy of the workpiece 4 with high accuracy, a contact-type sensor that directly contacts the workpiece 4 and the plate 3 and measures the position is desirable. When this sensor is a contact type, as shown in FIG. 2, the shape of the contact 21 of the sensor 20 is an R surface, so that the collision angle with the workpiece 4 can be made low. The measurement error due to the impact can be reduced.

  Then, positional information of the workpiece position measuring sensor 5 and the plate position measuring sensor 6 is input to the arithmetic unit 7, and the difference information is obtained as the polishing amount of the workpiece 4. The difference information (polishing amount) is output to the output device 8.

[Automatic polishing method]
A polishing method using the automatic polishing apparatus of the present invention will be described with reference to FIG.
The workpiece 4 is fixed to the plate 3 with wax or the like, pressure is applied by the cylinder 2, and the workpiece 4 is pressed against the surface plate 1.
Before starting the polishing of the pressed workpiece 4, the workpiece position measuring sensor 5 and the plate position measuring sensor 6 measure the position of the workpiece 4 and the position of the plate 3 before polishing. Position (zero reset).
Next, the surface plate 1 and the plate 3 are rotated together to polish the workpiece 4.

When a contact type sensor is used for the workpiece position measuring sensor 5 and the plate position measuring sensor 6, the sensor moves from the measuring position of the workpiece 4 and the plate 3 and is not in contact with each other except when measuring the polishing amount. The state is desirable for the protection of the sensor.
Further, when measuring the position information, it is possible to suppress variations in the measured values by performing measurement in a state where the rotational speed of the surface plate 1 is slower than the rotational speed of the surface plate 1 when the workpiece 4 is polished. desirable. Desirably, the number of rotations is 5 rpm or less.

  Further, the distance L between the workpiece measurement sensor 5 and the plate position measurement sensor 6 is set to 10 mm or less, which is less susceptible to vertical fluctuations due to the rotation of the surface plate 1 and the plate 3 and the inclination of the plate 3. However, it is desirable to make the difference information more accurate.

Then, the difference information is acquired by measuring the position information a plurality of times, and after the variation of the position information of n-1 times (n is the number of times of measurement, 1 <n) and n times converge within 10%, the difference information is obtained. By acquiring the above, it is possible to reduce the measurement error due to the impact when the contact sensor contacts the workpiece 4 and the plate 3, and to measure the workpiece polishing amount with high accuracy.
The polishing amount of the workpiece is measured during the polishing by the above polishing method, and the polishing is completed when the desired polishing amount is reached.

Hereinafter, the present invention will be described in detail using examples.
In the example, using the automatic polishing apparatus shown in FIG. 1, a sapphire wafer having a diameter of 3 inches was used as a test material, and the polishing test was performed under the condition that the rotation speed of the surface plate 1 at the time of polishing was 45 rpm. It is shown in Table 1. Note that both of the position measuring sensors used contact type sensors.
“ΔD” in Table 1 (the ratio of the difference from the measured value with respect to the set polishing amount) is calculated using the following formula 1, and the measured value is measured by measuring the polished wafer with a thickness meter (manufactured by Keyence) before polishing. The value was subtracted from the thickness of the wafer.

To obtain the difference information by measuring the distance L between the acquisitions of the position information to 9.5 mm, polishing the surface plate 1 at the time of measurement to 45 rpm and polishing for 20 minutes, and then setting the number of rotations of the surface plate 1 to 2 rpm. When the fluctuation range of the position information of 10% became 10%, the ratio (ΔD) of the difference from the measured value with respect to the set polishing amount was obtained. In addition, the positional information for calculating | requiring difference information made the average value measured 10 times at 1-second intervals after the fluctuation width of positional information became 10% as positional information.
Table 1 shows the polishing conditions according to this example and the results.

  The ratio (ΔD) of the difference from the actual measurement value with respect to the set polishing amount when measurement was performed in a range where the fluctuation range of the position information exceeded 10% was obtained. Polishing was performed under the same conditions as in Example 1 for other conditions. Table 1 shows the conditions and measurement results.

  Polishing was performed under the same conditions as in Example 1 except that an eddy current sensor (manufactured by Keyence) was used as the position measurement sensor. Table 1 shows the conditions and measurement results.

(Comparative Example 1)
Polishing was performed under the same conditions as in Example 1 except that the distance L between acquisitions of sensor position information was set to 15 mm. Table 1 shows the conditions and polishing results.

(Comparative Example 2)
Polishing was performed under the same conditions as in Example 1 except that the distance L between acquisitions of sensor position information was 15 mm, and the rotational speed of the surface plate 1 was measured at the same rotational speed as that during polishing. Table 1 shows the conditions and polishing results.

  As is clear from Table 1, Comparative Example 1 in which the distance L between the acquisitions of the position information exceeds 10 mm, and Comparative Example in which the distance L between the acquisitions of the position information exceeds 10 mm and measured without slowing the rotation of the surface plate at the time of measurement In No. 2, there is a large difference between the set polishing amount and the measured value, and it can be seen that the polishing accuracy is poor. On the other hand, it can be seen that in Examples 1 to 3 where polishing is performed within the conditions of the present invention, the difference between the set polishing amount and the measured value is small and the polishing accuracy is good. In particular, in Example 1 in which the variation in the position information was set to 10% or less when the difference information was output, an actual measurement value corresponding to the set polishing amount was obtained.

DESCRIPTION OF SYMBOLS 1 Surface plate 2 Cylinder 3 Plate 4 Workpiece 5 Workpiece position measurement sensor 6 Plate position measurement sensor 7 Arithmetic processing device 8 Output device 10 Automatic polishing machine 20 Sensor 21 Contact L Distance between acquisition of position information

Claims (9)

A surface plate,
A plate provided to press against the surface plate while rotating the workpiece held at a position facing the surface plate;
A workpiece position measuring sensor for measuring position information of the workpiece;
A plate position measuring sensor for measuring position information of the plate;
Calculation means for calculating difference information between the position information of the workpiece and the position information of the plate;
Output means for outputting difference information obtained by the computing means, and
An automatic polishing apparatus, wherein a distance between position information acquisition positions of the workpiece position measurement sensor and the plate position measurement sensor is 10 mm or less.   The automatic polishing apparatus according to claim 1, wherein the position measurement sensor is a contact sensor.   3. The automatic measuring apparatus according to claim 2, wherein the contact terminal of the contact sensor is a curved surface having a convex curvature on the contact surface side with the workpiece.   The automatic polishing apparatus according to claim 2, wherein the workpiece position measurement sensor includes a moving mechanism that contacts the workpiece only when position information is measured. In a polishing method for polishing a rotating surface plate and a workpiece pressed while rotating on the surface plate,
The position information of the contact surface with the surface plate of the workpiece is measured, the position information of the plate holding the workpiece is measured, and the difference information between the position information of the workpiece and the position information of the plate And a thickness of the workpiece is obtained from the difference information.   The polishing method according to claim 5, wherein an exposed portion of the workpiece from the surface plate is formed, and the position information in the exposed portion is measured.   The position information is measured by making the rotation speed of the surface plate slower than that during polishing of the workpiece, and obtaining the position information by contacting the contact terminals of the position measurement sensor. The polishing method according to 5 or 6.   8. The device according to claim 5, wherein when the position information is not measured, the position measurement sensor moves to retract the contact terminal from the workpiece and the plate. 9. Polishing method.   6. The polishing according to claim 5, wherein the position information is measured n times, and the difference information is calculated after fluctuations in the position information due to the (n-1) th and nth measurements converge within 10%. Method.

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