JPH10294300A - Wafer polishing method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve polishing precision of a wafer by modifying polishing conditions for next polishing based on comparison results between a polishing amount calculated from a wafer thickness or film thickness of a wafer before polishing and after polishing and a specified polishing amount. SOLUTION: A control part 18 calculates a polishing amount of a wafer in initial polishing conditions from measurement results of a film thickness of a first wafer before polishing and after polishing. When a polishing amount calculated by the control part 18 does not attain a reference polishing amount, or when it exceeds a reference polishing amount, the control part 18 calculates a polishing amount of a wafer per unit time under initial polishing conditions from a polishing amount calculated in the control part 18. Thereafter, a polishing time for a next wafer to be polished by a reference polishing amount is calculated from a polishing amount per calculated unit time. The control part 18 modifies a polishing time so that the next wafer is polished in the calculated polishing time and outputs the modified polishing conditions to a polishing part 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer polishing method and apparatus, and more particularly, to a wafer polishing method and apparatus applied to a CPM apparatus.

[0002]

2. Description of the Related Art In a polishing apparatus such as a CMP apparatus, it is difficult to directly measure a polishing amount of a wafer during processing. Therefore, conventionally, a polishing amount is controlled by adjusting a polishing time. Was. The setting of the polishing time was set based on the result of polishing the dummy wafer.

[0003]

However, the conditions under which a wafer is polished differ from one wafer to another depending on the state of the polishing pad at that time, and are not necessarily polished under the same conditions as a dummy wafer. Absent. For this reason, the conventional method has a disadvantage that the polishing accuracy is limited.

The present invention has been made in view of such circumstances, and has as its object to provide a wafer polishing method and apparatus capable of polishing a wafer with high accuracy.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a wafer polishing method for polishing a wafer, in which the thickness or thickness of the wafer before and after polishing is measured, and the measurement results are used. Calculate the polishing amount of the wafer,
The calculated polishing amount is compared with a predetermined polishing amount set in advance. Based on the comparison result, the polishing conditions are modified so that the next wafer to be polished is polished at the predetermined polishing amount. It is characterized by the following.

In the present invention, the polishing amount of a wafer is calculated from the measurement results of the thickness or thickness of the wafer before and after polishing, and the polishing conditions for the next wafer to be polished are calculated based on the calculated polishing amount. To correct. That is, the previous polishing result is fed back to correct the next polishing condition.
By performing polishing in this manner, appropriate polishing conditions can be sequentially set according to the polishing state that changes every moment. As a result, a highly accurate wafer can be stably obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a wafer polishing method and apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of a wafer polishing apparatus according to the present invention. As shown in FIG. 1, the wafer polishing apparatus 10 mainly includes the storage unit 1.
2. It comprises a measuring unit 14, a polishing unit 16, and a control unit 18.

The storage section 12 has a supply cassette for storing wafers before polishing and a collection cassette for storing wafers after polishing. The wafer stored in the supply cassette is transferred to the measurement unit 14 by the first transfer device 22. The measuring unit 14 measures the thickness of the wafer before and after polishing. Therefore, the wafer transferred by the first transfer means is firstly measured by the measuring unit 1.
At 4, the film thickness before polishing is measured. And the measurement result is
It is output to the control unit 18 described later.

Here, a method for measuring the film thickness of the wafer will be described. The measurement of the film thickness includes a case where the oxide film is measured and a case where the metal film is measured. First, the case where the film thickness of the oxide film is measured will be described. As shown in FIG. 2, the wafer W is rotatable on a rotatable wafer table 30.
And is fixed on the wafer table 30 by vacuum suction. The motor 3 is mounted on the wafer table 30.
2 spindles 32A are connected, and this motor 3
By driving the wafer 2, the wafer table 30 is rotated. Above the wafer table 30, a white interference film thickness meter 34 that runs along the surface of the wafer table 30 is installed. The film thickness is measured.

The measuring method is as follows.
First, the wafer W is placed on the wafer table 30,
Fix by vacuum suction. Next, the motor W connected to the wafer table 30 is driven to rotate the wafer W, and the surface of the rotating wafer W is scanned by the white interference film thickness meter. Thereby, the film thickness at each point on the wafer surface is measured.

Next, a case where the thickness of the metal film is measured will be described. The thickness of the metal film is determined by measuring the thickness of the wafer W. As shown in FIG. 3, the wafer W is mounted on a rotatable wafer table 40 formed in a ring shape. The wafer table 40 is rotatably supported by a holding ring 42 via a bearing 44, and the holding ring 42 is horizontally supported by a base 46. A driven gear 48 is fixed to the lower surface of the wafer table 40.
A drive gear 52 fixed to the spindle of the motor 50 meshes with the drive gear 8. The wafer table 40 includes:
The motor 50 is rotated by driving the motor 50.

In the vicinity of the wafer table 40, there is provided a slider 54 which slides in parallel with the wafer W placed on the wafer table 40,
The slider 54 has an arm 56 formed in a U-shape.
Is fixed. Capacitive sensors 60, 60 are respectively connected to the distal ends of the arms 56 via piezo elements 58, 58.
Are fixed, and the capacitance sensors 60 are disposed so as to face each other with the wafer W placed on the wafer table 40 interposed therebetween. The thickness (metal film thickness) of the wafer W placed on the wafer table 40 is measured by differential measurement by the pair of capacitance sensors 60.

The measuring method is as follows.
First, the wafer W is placed on the wafer table 30,
The motor 32 connected to the wafer table 30 is driven to rotate the wafer W. Next, the plate thickness of the rotating wafer W is operationally measured by the pair of capacitance sensors 60, 60. Thereby, the plate thickness (metal film thickness) at each point on the wafer surface is measured.

As described above, the wafer whose film thickness has been measured is transferred to the polishing section 16 by the second transfer device 24. The polishing section 16 polishes the wafer transferred by the second transfer device 24. The polishing of the wafer performed here is performed by chemical mechanical polishing (CM) described below.
The wafer is polished by the P) method.

FIG. 4 is a configuration diagram of the polishing section 16. As shown in the figure, the polishing section 16 has a polishing platen 70, and a polishing cloth 72 is adhered to the surface of the polishing platen 70. A spindle 74 is connected coaxially to the lower surface of the polishing platen 70, and a motor (not shown) is connected to the spindle 74. The polishing platen 70 is rotated by driving the motor.

Above the polishing platen 70, a wafer W
Is provided. This head 7
A spindle 78 is connected coaxially with the upper surface of the motor 6, and a motor (not shown) is connected to the spindle 78. The head 76 is driven by this motor to rotate. A polishing liquid supply pipe (not shown) is provided above the polishing platen 70. A polishing liquid is dropped onto the polishing cloth 72 from the polishing liquid supply pipe.

In the polishing section 16 configured as described above, the wafer W is polished as follows. First, a polishing liquid is dropped on the polishing cloth 72 while rotating the polishing platen 70. And this rotating polishing platen 7
The wafer W held by the head 76 is pressed toward zero. Thus, the wafer W is polished under the pressure and the relative speed.

At this time, if the surface of the wafer W has an uneven portion, the convex portion has a high contact pressure with the polishing pad 72 and is polished at a high relative polishing rate. Since the contact pressure with the polishing pad 72 is small, it is hardly polished. As a result, the surface of the wafer W is alleviated and the surface becomes flat. The wafer W polished as described above is again transferred to the measuring unit 14 by the second transfer device 24. The measuring unit 14
Then, the thickness of the polished wafer is measured, and the measurement result is output to the control unit 18 described later. Then, after this measurement, the wafer is transferred again to the first transfer device 22 and stored in the collection cassette of the storage unit 12.

The overall operation of the wafer polishing apparatus 10 configured as described above is controlled by the control unit 18. In particular, the polishing unit 16 based on the measured value of the thickness of the wafer before and after polishing measured by the measurement unit 14,
The driving is controlled as follows. First, for the first polishing of the wafer W, the operator polishes the wafer W according to the initial polishing conditions input to the control unit 18 in advance. At this time, the first wafer W
The film thickness before and after polishing is measured by the measurement unit 14, and the measurement result is output to the control unit 18. As described above, when the measurement target is an oxide film, the film thickness is measured, and when the measurement target is a metal film, the thickness of the wafer is measured.

The controller 18 calculates the polishing amount of the wafer W under the initial polishing conditions from the measurement results of the thickness of the wafer before and after the first polishing of the wafer W. The calculated polishing amount is determined in advance by the controller 18.
In this case, the wafer W to be polished next is also polished under the same conditions as the initial polishing conditions.

On the other hand, if the polishing amount calculated by the control unit 18 does not reach the reference polishing amount or exceeds the reference polishing amount, the polishing conditions of the next wafer W to be polished are corrected. I do. The polishing conditions are corrected, for example, by correcting the polishing time. In this case, first, the control unit 18 calculates the polishing amount of the wafer per unit time under the initial polishing conditions from the polishing amount calculated by the control unit 18. Then, from the calculated polishing amount per unit time, a polishing time for polishing the wafer W to be polished next at the reference polishing amount is calculated.

The control unit 18 corrects the polishing time based on the calculated polishing time so that the next wafer W is polished, and changes the corrected new polishing condition (hereinafter referred to as a modified polishing condition) to the polishing unit. 16 is output. As a result, the wafer to be polished next is polished at a value closer to the reference polishing amount.

The thickness of the wafer to be polished next, that is, the second wafer, is measured in the same manner as the first wafer before and after the polishing, and the control unit is determined from the measurement results. At 18, the polishing amount of the wafer under the modified polishing conditions or the initial polishing conditions is calculated. If the calculated polishing amount matches the reference polishing amount, the next wafer W to be polished, that is, the third wafer is polished under the same conditions as the modified polishing conditions (however, If the initial polishing conditions are not modified when polishing the second wafer, the polishing is performed under the same conditions as the initial polishing conditions.)

On the other hand, if the polishing amount calculated by the control unit 18 does not reach the reference polishing amount or exceeds the reference polishing amount, the wafer to be polished next is processed in the same procedure as described above. W, that is, the modified polishing conditions are modified so that the third wafer is polished by the reference polishing amount (however, when polishing the second wafer,
If the initial polishing conditions have not been modified, the initial polishing conditions are modified. ).

Thereafter, in the same procedure, when the actual polishing amount does not match the reference polishing amount, the polishing is sequentially performed while correcting the polishing conditions. As described above, the control unit 18 feeds back the previous polishing result and corrects the polishing conditions so that the next wafer to be polished is polished with the predetermined reference polishing amount. By performing polishing in this manner, appropriate polishing conditions can be sequentially set according to the polishing state that changes every moment (the degree of consumption of the polishing cloth, the degree of supply of the polishing liquid, and the like). As a result, the wafer can be accurately polished. Further, since the wafer is always polished with a polishing amount near the reference polishing amount, it is possible to stably obtain a wafer with high polishing accuracy.

Further, since the next polishing condition is automatically corrected, it is not necessary to manually correct the polishing condition. As a result, the operation efficiency of the device is improved, and the throughput is improved. In addition, since the polishing amount is controlled for each polishing pad, the degree of consumption of the polishing pad 72 can be grasped.
Judgment of maintenance time and the like becomes easy.

It should be noted that the current polishing conditions are set, what are the measured values of the film thickness before and after the polishing of the previously polished wafer, and from the measured values. For these items, so that the operator can recognize how much the calculated polishing amount is, etc.
It is displayed on the monitor 20. The operator operates this monitor 2
From the display of 0, the above-mentioned maintenance time and the like are determined.

In this embodiment, the case where the polishing time of the wafer is modified has been described as an example of modifying the polishing conditions. In addition, the polishing pressure is modified, and the polishing platen 70 or the head 76 is modified. Modify the speed, or
The same object can be achieved by modifying the polishing conditions by combining these. Further, in the present embodiment, the wafer polished by the polishing unit 16 is directly transported to the measuring unit 14 to measure the film thickness after polishing. However, as shown in FIG. The cleaning unit 80 may be provided, and after the polishing, the wafer is cleaned by the cleaning unit 80, and then the film thickness of the polished wafer may be measured. As a result, the polishing amount can be grasped with higher accuracy, and the wafer can be polished with higher accuracy.

In addition, as a result of measurement after polishing, a wafer having a polishing defect is collected by the collecting unit 90.
You may comprise so that it may collect | recover at. As a result, the defective wafer can be automatically collected without performing an inspection later. Further, in the present embodiment, an example in which the film thickness is measured has been described, but the same effect can be obtained by measuring the thickness of the wafer.

[0030]

As described above, according to the present invention,
Since the previous polishing result is fed back and the next polishing condition is sequentially corrected, an appropriate polishing condition can be set according to the polishing condition that changes moment by moment. As a result, a highly accurate wafer can be stably obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a wafer apparatus according to the present invention.

FIG. 2 is a configuration diagram of a measurement unit (a measurement unit when measuring an oxide film).

FIG. 3 is a configuration diagram of a measurement unit (a measurement unit when measuring a metal film).

FIG. 4 is a configuration diagram of a polishing unit.

FIG. 5 is a block diagram showing a configuration of another embodiment of the wafer apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Polishing apparatus 12 ... Storage part 14 ... Measuring part 16 ... Polishing part 18 ... Control part 20 ... Monitor 22 ... 1st conveyance apparatus 24 ... 2nd conveyance apparatus W ... Wafer

Continuation of front page (72) Inventor Masaaki Oguri 9-7-1, Shimorenjaku, Mitaka-shi, Tokyo

Claims (5)

[Claims] 1. A wafer polishing method for polishing a wafer, comprising: measuring a thickness or thickness of a wafer before and after polishing; calculating a polishing amount of the wafer from the measurement result; and calculating the calculated polishing amount. And a predetermined polishing amount set in advance, and based on the comparison result, the polishing conditions are modified so that the next wafer to be polished is polished with the predetermined polishing amount. Polishing method. 2. The wafer polishing method according to claim 1, wherein the polishing conditions of the wafer are modified by modifying a polishing time of the wafer. 3. The wafer polishing method according to claim 1, wherein when the calculated polishing amount is smaller than the predetermined polishing amount, the wafer is polished again. 4. A wafer polishing apparatus for polishing a wafer, comprising: a storage section having a supply cassette in which a large number of unpolished wafers are stored; a storage section having a collection cassette in which a large number of polished wafers are stored; Unit, a measuring unit that measures the thickness or thickness of the wafer before and after polishing, a first transport unit that transports the wafer between the storage unit and the measuring unit, the measuring unit and the A second transfer unit that transfers the wafer between the polishing unit and the polishing amount of the wafer polished by the polishing unit from the thickness or thickness of the wafer before and after polishing measured by the measurement unit. The calculated polishing amount is compared with a predetermined polishing amount set in advance, and the polishing is performed based on the comparison result so that the next wafer to be polished is polished at the predetermined polishing amount. Polishing by part A controller for correcting polishing conditions of the wafer to be polished. 5. The wafer polishing apparatus according to claim 4, wherein the correction of the polishing conditions of the wafer is performed by correcting a polishing time of the wafer.