JPH0714589B2 - Lapping machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lapping machine used for mirror polishing a silicon wafer or the like.

[0002]

2. Description of the Related Art In a conventional lapping machine, wafers to be processed are housed in a plurality of carriers arranged between upper and lower lapping disks, and the carriers are revolved and rotated by a planetary mechanism. Co-sliding is performed by a so-called 4-way forced drive method in which the upper and lower lap disks are rotated in opposite directions. By supplying the lapping agent between the upper and lower lapping disks and the workpiece together with this co-sliding, the workpiece is polished. In addition, in order to adjust the amount of polishing of the work piece, a pressure device consisting of an air cylinder etc. is usually installed above the center of the sun gear, and the pressure applied to the upper lapping disk is adjusted according to the lapping process. It

[0003]

In the conventional lapping disc described above, the pressure between the upper and lower lapping discs and the workpiece can be adjusted by the pressurizing device, but the upper and lower lapping discs are entirely covered. Cannot always be pressed uniformly. That is, since a plurality of carriers driven as planets are arranged on the circumferential orbit and a plurality of workpieces are housed in concentric circles centering on the rotation axis of each carrier, each workpiece is uniform. It is necessary to pressurize with various pressures. However, since the conventional pressurizing device has a structure in which the upper lap disc is pushed down at a position at the center of the sun gear via a spherical bearing or the like, it is not possible to pressurize each carrier uniformly with high accuracy. Moreover, if the pressure becomes uneven, it cannot be repaired.

In particular, if there is a large variation in the thickness of the workpiece before polishing set on each carrier, the pressing force concentrates only on the thick workpiece. If the adjustment of the pressure applied to the work piece is insufficient as described above, the parallelism and flatness of the lapped work piece are adversely affected, and the yield decreases. The present invention has been made to solve the above problems, and an object thereof is to make it possible to adjust the pressure applied to each part of the workpiece by the upper and lower lap disks to enable highly accurate polishing. To provide a lap disc.

[0005]

In order to achieve the above object, the first invention is to place a workpiece between the upper and lower lapping disks and press the upper lapping disk downward while In the lapping machine that drives the lower lapping disks to rotate in opposite directions, actuators that are installed at multiple points on the upper lapping disk, press the upper lapping disk downward, and are installed at multiple points on the lower lapping disk. A sensor that detects the pressure applied to the disk and / or the displacement of the lower lap disk due to the pressure, a means for obtaining the pressure distribution of the lower lap disk from the detection value of the sensor, and each part of the workpiece based on the obtained pressure distribution And a means for generating an operation signal of each of the actuators so that the pressure distribution in (1) becomes uniform.

According to a second aspect of the present invention, a workpiece is placed between the upper and lower lapping discs and the upper lapping disc is pressed downward,
In the lapping machine that drives the upper and lower lapping disks to rotate in opposite directions, they are installed at multiple points on the upper lapping disk,
An actuator that presses the upper lap disc downward, a sensor that is installed at multiple locations on the lower lap disc, and that detects the pressure applied to the lower lap disc and / or the displacement of the lower lap disc due to the pressure, and the detected value of the sensor A means for obtaining the pressure distribution and / or displacement distribution of the lower lapping disk, and the pressure distribution of each part of the workpiece to finish each part of the workpiece to a uniform thickness based on the obtained pressure distribution and / or displacement distribution And a means for generating an operation signal of each of the actuators.

[0007]

In the first aspect of the invention, when the sensors installed at a plurality of positions on the lower lap disc detect the pressure or / and the displacement of the lower lap disc, the pressure distribution of the lower lap disc is obtained from the detected values, and Based on the obtained pressure distribution, an actuator operation signal that makes the pressure distribution of each part of the workpiece uniform is generated. By this operation signal, actuators installed at a plurality of positions on the upper lapping disk actuate to press the upper lapping disk downward, and the pressure distribution in each part of the workpiece becomes uniform.

In the second invention, when the sensors installed at a plurality of positions on the lower lap disc detect the pressure or / and the displacement of the lower lap disc, the pressure distribution and / or the displacement distribution of the lower lap disc are detected from the detected values. Based on the obtained pressure distribution and / or displacement distribution, an actuator operation signal for finishing each part of the workpiece to a uniform thickness is generated. By this operation signal,
Actuators installed at a plurality of locations on the upper lap disc actuate to press the upper lap disc downward, and the pressure distribution of each part of the workpiece is adjusted.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view schematically showing the overall structure of the lapping machine according to the first invention. In the figure, 1 is an upper lap disc, 2 is a lower lap disc, and 3 is a carrier, which are connected to a transmission unit 4 via power transmission elements, respectively. The speed change unit 4 is connected to a motor 5, and when the motor 5 is driven, the well-known 4-way forced drive of the upper and lower lap disks 1 and 2 and the carrier 3 is performed. Further, a pressurizing device 6 is connected to the central portion 1c of the upper lapping disk 1 and presses the central portion 1c downward to remove the workpiece 7 stored in the carrier 3 for each lapping process. Pressurize at a specified pressure.

Further, actuators 8 for pressing the upper lap disk 1 from above are installed at a plurality of positions on the upper lap disk 1, and the upper lap disk 1 is pressed at each installation position to be processed. Adjust the pressure applied to 7. Although not shown in detail, the actuator 8 may be configured to rotate together with the rotation of the upper lapping disc 1 or may be stationary regardless of the rotation of the upper lapping disc 1. Is. As the actuator 8, a piezoelectric element, a cylinder, a spring mechanism, a magnet mechanism or the like is used.

The lower lap disk 2 is provided with a sensor 11 for detecting the pressure applied to the lower lap disk 2 via the workpiece 7 and the displacement in the pressing direction at a plurality of positions. The sensor 11 is, for example, a 6-component force table using a strain gauge. The detection values of these sensors 11 are sent to the controller 12. In addition, from the sensor 11 to the controller 1
Although not shown, a non-contact communication means such as FM communication is used to send the detected value to the communication unit 2. When the sensor 11 detects a pressure value, the controller 12 uses the pressure value as it is, and when a displacement is detected, it converts the displacement into a pressure using a conversion table or the like prepared in advance, and the lower lapping disk 2 as a whole. For the pressure distribution. It should be noted that the pressure distribution of the entire lower lapping disc 2 is almost the same as that of the upper lapping disc 1.
Can be regarded as the pressure distribution of.

The pressure distribution thus obtained is compared with the set pressure applied by the pressurizing device 6 in that step, and for the portion where the detected pressure is smaller than the set pressure, the actuator corresponding to that position Increase the pressing force of 8. Further, for a portion where the detected pressure is higher than the set pressure, the pressure applied to the actuator 8 corresponding to that position is decreased. That is, the controller 12 performs feedback control of the pressure applied to the actuator 8 so that the detected pressure is always equal to the set pressure with reference to the set pressure. Since the distributions of pressure and displacement in the lower lap disc 2 can be mutually converted, the displacement of the lower lap disc 2 can be controlled to be constant.

Although the sensor 11 is mounted on the lower lapping disk 2 in the embodiment, it may be mounted on the upper lapping disk 1. Further, in the embodiment, the pressurizing device 6 and the actuator 8 for fine pressure adjustment are installed to pressurize the upper lapping disk 1. However, the pressurizing device 6 may be removed and the entire actuator 8 may be pressurized. FIG. 2 is a flowchart systematically showing these operations. In the figure, when preparation for setting the workpiece 7 is completed first, the lapping machine driving motor 5 is started (S1).

Next, the pressurizing device 6 and the actuator 8 are operated to pressurize the upper lapping disk 1 to start lapping (S2). At this time, the total pressure applied to each workpiece 7 between the upper lapping disc 1 and the lower lapping disc 2 is the set pressure. Next, the plurality of sensors 11 installed on the lower lap disk 2 causes the workpiece 7 to be transferred to the lower lap disk 2.
The pressure applied via and the displacement of the lower lap disk 2 caused by the pressure is detected and sent to the controller 12 (S3). If the detected value taken in here is the pressure, it is used as it is, and if it is the displacement, it is converted into pressure, and the pressure distribution for the entire lower lapping disk 2 is obtained (S4).
Further, the obtained pressure distribution is compared with the set pressure at that time to obtain the difference between the two (S5).

Next, according to the difference between the two, the actuator 8 at the corresponding position is driven to adjust the pressure distribution to be equal to the set pressure (S6). Then, the process proceeds to S3.
In this way, in the embodiment of the first aspect of the invention, the workpieces 7 housed in the carrier 3 are always kept at the set pressure under the control of the controller 12, and highly accurate lapping is performed. . As a result, sufficient parallelism and flatness are obtained, and at the same time, the yield is improved.

Next, an embodiment of the second invention will be described. The overall configuration of the second embodiment of the present invention is the same as that of the first embodiment of the present invention shown in FIG. 1, and the difference lies in the control content of the controller 12. Controller 12
Calculates the pressure distribution and the displacement distribution for the entire lower lapping disc 2 from the pressure value and the displacement value detected by the sensor 11, compares the pressure distribution and the target thickness of the non-working object 7 after lapping, and calculates the average of the displacement distribution. Calculate the deviation from the value.

When the deviation of the displacement thus found is positive, that is, when the thickness of the workpiece 7 is large, the pressing force of the actuator 8 corresponding to that position is increased according to the size. When the deviation of displacement is negative, that is, when the thickness of the workpiece 7 is small, the pressing force of the corresponding actuator 8 is decreased accordingly. Further, when the non-workpiece 7 reaches the target thickness due to the displacement of each part of the lower lap disk 2, the pressurization of the actuator 8 at that position is stopped.
That is, the controller 12 pays attention to the initial thickness of the workpiece 7 and the minute displacement in the thickness direction of the lower lap disc 2 that changes with the progress of lapping thereafter.
The pressure of each actuator 8 is feedback-controlled so that the thickness of the actuator is always constant.

FIG. 3 is a flow chart systematically showing these operations. In the figure, when preparation such as setting of the workpiece 7 is completed first, the lapping machine driving motor 5 is started (S11). Next, the pressurizing device 6 and the actuator 8 are operated to pressurize the upper lapping disc 1 to start lapping (S12). Next, the pressure and displacement applied to the lower lap disk 2 via the workpiece 7 are detected by the plurality of sensors 11 installed in the lower lap disk 2 and sent to the controller 12 (S
13).

If the detected value taken in here is a displacement, it is used as it is, and if it is a pressure, it is converted into a displacement to obtain a displacement distribution for the entire lower lapping disk 2 (S14). Further, the obtained displacement distribution is compared with the thickness of the workpiece 7 set in the process to obtain the difference between the two (S
15). Next, the actuator 8 at the corresponding position is driven according to the difference between the two, and the displacement distribution is adjusted so as to correspond to the set thickness (S16). Then, the process proceeds to S13.

In this way, in the embodiment of the second aspect of the invention, the workpieces 7 housed in the carrier 3 are lapped by the control of the controller 12 while always maintaining a uniform thickness. As a result, highly accurate lapping is performed, sufficient parallelism and flatness are obtained, and the yield is also improved. In particular, even if there is a variation in the thickness between the workpieces 7 before lapping, they are uniform and have the same thickness at the end of lapping. Further, it is also possible to switch the control of the first invention and the control of the second invention depending on the lapping process in consideration of the characteristics of each of the above inventions.

[0021]

As described above, according to the first invention,
The pressure and displacement in each part of the workpiece are detected, and the actuator is operated so that the pressure distribution in each part of the workpiece is always uniform, whereby the workpiece is uniformly ground. As a result, the flatness and parallelism of the workpiece are improved, and the yield is improved. According to the second aspect of the present invention, the pressure and displacement in each part of the work piece are detected, and the actuator is actuated based on the detected pressure or displacement to finish each part of the work piece to a uniform thickness. As a result, the flatness and parallelism of the workpiece are improved, and the yield is improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram schematically showing the overall configuration of an embodiment of the first invention.

FIG. 2 is a flow chart showing the operation of the embodiment of the first invention.

FIG. 3 is a flowchart showing the operation of the embodiment of the second invention.

[Explanation of symbols]

 1 Upper Lap Disk 2 Lower Lap Disk 3 Carrier 4 Speed Change Section 5 Motor 6 Pressurizing Device 7 Workpiece 8 Actuator 11 Sensor 12 Controller

Claims (2)

[Claims] 1. A lapping machine in which a workpiece is placed between the upper and lower lapping disks, and the upper and lower lapping disks are rotationally driven in opposite directions while pressing the upper lapping disk downward. Actuators installed at multiple points on the disk to press the upper lap disk downwards, and actuators installed at multiple points on the lower lap disk to detect pressure applied to the lower lap disk and / or displacement of the lower lap disk due to pressure Sensor, a means for obtaining the pressure distribution of the lower lapping disk from the detection value of the sensor, and the operation signal of each actuator is generated based on the obtained pressure distribution so that the pressure distribution in each part of the workpiece becomes uniform. A lapping machine characterized by including a means for doing. 2. A lapping machine in which a workpiece is placed between the upper and lower lapping disks and the upper and lower lapping disks are rotationally driven in opposite directions while pressing the upper lapping disk downward. Actuators that are installed at multiple locations on the disk and press the upper lap disk downward, and pressures applied to the lower lap disk and / or displacement of the lower lap disk due to pressure applied to the lower lap disk are detected. Sensor and a means for obtaining the pressure distribution and / or displacement distribution of the lower lapping disk from the detected value of the sensor, and based on the obtained pressure distribution and / or displacement distribution, for finishing each part of the workpiece to a uniform thickness A lapping machine comprising: means for calculating a pressure distribution of each part of the workpiece and generating an operation signal of each actuator.