JP2979769B2 - Silicon wafer thickness sorting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thickness sorter for automatically selecting a thickness of a silicon wafer, which normally requires a dimensional accuracy of. ± .20 .mu.m or less, using a capacitance type non-contact thickness gauge.
The present invention relates to a method of selecting a thickness of a silicon wafer having a function of correcting a measurement error of a capacitance type non-contact thickness gauge caused by a change in an ambient temperature.

[0002]

2. Description of the Related Art As is well known, a silicon wafer used as a substrate material of a monolithic IC or the like has a thickness of several tens of single-crystal silicon ingots with a diamond cutter.
By slicing into a 0 μm disk, the surface is polished with an abrasive to remove the surface layer with processing distortion, and the surface is mirror-finished to form an extremely flat disk. The tolerance of the thickness is usually ± 2.
Since it is required to control the thickness to 0 μm or less, a silicon wafer with dimensional accuracy less than the allowable error is selected by a thickness sorter using a capacitance type non-contact thickness gauge and used as a substrate material for monolithic ICs. Is done.

FIG. 3 is a block diagram showing a conventional silicon wafer thickness sorting apparatus. A capacitance type non-contact thickness gauge 2 has a pair of probes facing each other while maintaining a predetermined gap length G.
And measuring the capacitance of the test silicon wafer 1 inserted into the gap length G in a non-contact manner with the probe, and using the measured value as the thickness d of the silicon wafer. (Or one gap length g that varies depending on the thickness of the silicon wafer), and outputs the measured value 2 d to the selector 5. The selector 5 determines whether or not the measured value 2d falls within a predetermined allowable thickness range of the silicon wafer, and outputs a determination signal 5d to a handling mechanism of the silicon wafer (not shown). The silicon wafer to be tested is sorted.

In the silicon wafer thickness sorter configured as described above, a commercially available capacitance type non-contact thickness gauge (for example, model ST3525 manufactured by Iwatsu Research Co., Ltd.) measures the thickness measured value. It is known that the temperature changes under the influence of the ambient temperature of the part. To avoid this, the probe and the test silicon wafer are housed in a constant temperature bath 8 and the change in the ambient temperature is ± It is recommended that the temperature be kept at 1 ° C. or less, or that the entire thickness sorting apparatus is housed in a thermostatic chamber 9 and the sorting operation is performed in a thermostatic chamber in which the change in the ambient temperature is controlled to ± 1 ° C. or less. Prior to starting the sorting operation, calibration was performed using a silicon wafer of known thickness so that the measured value of the capacitance-type non-contact thickness gauge correctly indicated the known dimensions, and the ambient temperature at that time was adjusted. Measures have been taken to reduce the measurement error by holding and performing the sorting operation.

[0005]

When a constant temperature bath 8 is used in a conventional thickness sorting apparatus, an apparatus for handling silicon wafers without changing the ambient temperature becomes complicated, and equipment costs rise. In addition to this, there is a problem that it is difficult to obtain high working efficiency due to the restriction of the sorting work. In order to avoid the above-mentioned problems by providing the constant temperature chamber 9, the temperature control and the air conditioner must be advanced to suppress the change of the ambient temperature to ± 1 ° C or less due to the heat generated from the apparatus and the human body. This necessitates an increase in equipment costs and a decrease in work efficiency.

An object of the present invention is to provide a method for selecting a thickness of a silicon wafer which does not require a constant temperature bath or a constant temperature chamber and which can accurately measure the thickness of the silicon wafer while eliminating the influence of the ambient temperature. It is in.

[0007]

In order to solve the above-mentioned problems, according to the present invention, a pair of pro- cesses opposed to each other at a predetermined interval so as to maintain a gap between both surfaces of a silicon wafer. A probe is arranged , the capacitance between the probes is measured, and the measured value is converted into the thickness of the silicon wafer by a capacitance type non-contact thickness gauge and output. The measured value of the contact thickness gauge is selected by comparing it with the allowable thickness value of the silicon wafer which is determined in advance by a sorter.
In the method, the silicon wafer - and Ha temperature arranged in the vicinity of the sensor, and a temperature difference detector for detecting a difference in temperature between the detected temperature and the reference temperature of the temperature sensor, the detected temperature difference of the temperature difference detecting unit the temperature correction device comprising a computing unit for correcting the measured value of the basis of the correction coefficient determined corresponding said capacitive contactless thickness meter, provided in front of the selector, the temperature difference
Based on the correction coefficient determined according to the temperature difference detected by the detector
Correcting the measured value of the capacitance type non-contact thickness gauge
I do.

In the above-described thickness selection method , it is assumed that the correction coefficient is a predetermined constant.

Further, in the above-mentioned thickness selection method , it is assumed that the reference temperature is the ambient temperature when the thickness measuring device is calibrated using a silicon wafer having a known thickness.

[0010]

In the structure of the present invention, a temperature sensor disposed in the vicinity of a silicon wafer, a temperature difference detecting section for detecting a temperature difference between a temperature detected by the temperature sensor and a reference temperature, and a temperature difference detecting section the temperature correction device comprising a computing unit for correcting the measured value of the capacitance type based on the correction coefficient determined in response to the detected temperature difference between the non-contact thickness meter, provided before the sorter,
Correction coefficient determined according to the temperature difference detected by the temperature difference detector
Based on the configuration to correct the measurement value of the capacitance type non-contact thickness gauge based on, the measurement error of the capacitance type non-contact thickness meter due to the change of the ambient temperature will be corrected by the temperature correction device, A function of eliminating a constant temperature bath or a constant temperature chamber, which is conventionally required to avoid the influence of a change in the ambient temperature, is obtained.

[0011] In the thickness sorting method of the present invention,
By setting the correction coefficient to a predetermined constant, a function of correcting a measurement error of the capacitance type non-contact thickness gauge can be obtained by a simple digitized arithmetic unit.

Further, in the thickness selection method of the present invention, if the reference temperature is the ambient temperature when the thickness measuring device is calibrated using a silicon wafer having a known thickness, the static temperature at the reference temperature is obtained. Since it is possible to correct the measurement error while confirming that the measurement error of the capacitance type non-contact thickness gauge is zero,
The function of improving the measurement accuracy and the sorting accuracy of the thickness of the silicon wafer can be obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. FIG. 1 is a configuration diagram showing a silicon wafer thickness sorting apparatus according to an embodiment of the present invention. The same components as those of the prior art are denoted by the same reference numerals, and redundant description will be omitted. In the figure, a temperature correction device 11 includes a temperature sensor 12, a temperature difference detection unit 13, and a temperature correction calculation unit 1.
And 4. That is, the pair of pro - Bed 3,4 noncontact inserted test silicon wafer between - in the vicinity of the wafer 1, the temperature sensor 12 for detecting the ambient temperature is disposed, the temperature difference is the detected temperature T _I The temperature is compared with the reference temperature T _{O by the} detection unit 13 to obtain a temperature difference T _O −T _{I from} the reference temperature, and is input to the temperature correction calculation unit 14. The thickness measurement value 2d of the silicon wafer 1 obtained by the capacitance type non-contact thickness meter 2 is input to the calculation unit 14, and the correction value determined in accordance with the temperature difference T _O −T _I is a reference temperature. When the temperature difference with respect to T _O is positive, it is subtracted from the thickness measurement value 2d, and when the temperature difference is negative, it is added, so that the corrected thickness measurement value 14d is output to the selector 5. The selector 5 determines whether or not the corrected thickness measurement value 12d falls within a predetermined allowable thickness range of the silicon wafer, for example, a standard thickness d ± 20 μm, and outputs a determination signal to the silicon wafer handling mechanism (not shown). The test silicon wafers are sorted out by outputting to the section.

As described above, the silicon wafer according to the embodiment is
In the thickness sorter C, the measurement error of the capacitance type non-contact thickness gauge due to the change of the ambient temperature is corrected by the temperature corrector, which is necessary to avoid the influence of the change of the ambient temperature. A constant temperature chamber or constant temperature room can be eliminated, so that the cost of equipment can be prevented from rising, and the restriction on the constant temperature chamber or constant temperature room on the sorting operation can be eliminated to improve the efficiency of the sorting operation. can get.

FIG. 2 is a graph showing the relationship between the ambient temperature and the measurement error characteristic of the capacitance type non-contact thickness gauge obtained by the apparatus of the embodiment. The horizontal axis of the figure shows the temperature difference (° C.) with respect to the reference temperature.
On the vertical axis, the measurement error (μ
m) takes the measurement error at the reference temperature as zero. In the figure, it was found that the thickness measurement error caused by the ambient temperature of the capacitance type non-contact thickness gauge showed a linear line with respect to the temperature difference as shown by the error curve 100.
Therefore, the thickness of the temperature-corrected silicon wafer is defined as d _O
(Μm), d _I (μm), the thickness measured by the capacitance type non-contact thickness gauge, and α (μm / ° C.) the temperature correction coefficient, d _o = d _I + α (T _O −T _I The simple calculation is performed by the calculation unit 14 of the temperature correction device 11, whereby the measurement error of the capacitance-type non-contact thickness meter 2 due to the ambient temperature difference can be easily corrected. In particular, the temperature correction coefficient α of the error curve 100 is 1.0 (μm / ° C.), making temperature correction easier.

Prior to starting the automatic sorting of silicon wafers using the thickness sorting apparatus according to the embodiment, the thickness measured by the capacitance type non-contact thickness gauge 2 using a standard sample having a known thickness. 2d is calibrated to indicate correctly the known thickness, but the ambient temperature at this as a reference temperature T _O, after setting the temperature difference detection unit 13 of the temperature correction device 11, silicon wafer - automatic sorting Ha 1 If the operation is started, the measurement error can be corrected in a state where the measurement error of the capacitance type non-contact thickness gauge at the reference temperature T _O is confirmed to be zero, so that the thickness of the silicon wafer can be corrected. The advantage that the measurement accuracy and the sorting accuracy can be improved is obtained.

[0017]

As described above, the present invention provides a temperature sensor disposed in the vicinity of a silicon wafer, a temperature difference detector for detecting a temperature difference between the temperature detected by the temperature sensor and a reference temperature, and the temperature correction device comprising a computing unit for correcting the measured value of the capacitance type noncontact thickness meter based on the correction coefficient determined in response to the detected temperature difference of the temperature difference detection unit, provided in front of the selector, the temperature difference Correction determined according to the temperature difference detected by the detector
Corrects the measurement value of the capacitance type non-contact thickness gauge based on the coefficient.
That as configured. As a result, the measurement error of the capacitance type non-contact thickness gauge due to the change in the ambient temperature is corrected by the temperature correction device, and the constant temperature chamber or the constant temperature chamber that was conventionally required to avoid the influence of the change in the ambient temperature is eliminated. This makes it difficult to handle silicon wafers without changing the ambient temperature, which is a problem with conventional equipment using a thermostat. Reduction of work efficiency due to constraints. Alternatively, ± 1 due to heat generation from a device or a human body in a conventional device having a constant temperature chamber.
Eliminates many problems, such as advanced temperature control and air conditioning equipment that suppress changes in the ambient temperature below ° C, soaring equipment costs, and a reduction in work efficiency. It is possible to provide a silicon wafer thickness sorting method capable of performing a sorting operation without increasing equipment costs. In particular, a silicon wafer is incorporated into a surface polishing line of a silicon wafer by incorporating a thickness sorter.
It is also possible to control the thickness of the c
The advantage that can contribute to the improvement of the yield of C is obtained.

Further, in the thickness sorting method of the present invention,
Since it has been confirmed that the detected temperature difference and the correction value have a linear inverse proportional relationship, the correction coefficient can be a constant determined in advance, and the temperature correction device has a simple digitized arithmetic unit. Thereby, the advantage that the measurement error of the capacitance type non-contact thickness gauge can be corrected can be obtained.

Furthermore, in the thickness sorting method of the present invention, if the reference temperature is the ambient temperature when the thickness measuring device is calibrated using a silicon wafer of a known thickness, the static temperature at the reference temperature can be obtained. Since it is possible to correct the measurement error while confirming that the measurement error of the capacitance type non-contact thickness gauge is zero,
The advantage is that the measurement accuracy and the sorting accuracy of the thickness of the silicon wafer can be improved.

[Brief description of the drawings]

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

FIG. 2 is a graph showing a measurement error characteristic of an electrostatic capacitance-type non-contact thickness gauge obtained by an apparatus according to an embodiment.

FIG. 3 is a configuration diagram showing a conventional silicon wafer thickness sorting apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon wafer 2 Capacitance type non-contact thickness gauge 3 Probe 4 Probe 5 Sorter 11 Temperature correction device 12 Temperature sensor 13 Temperature difference detection part 14 Operation part

Claims (3)

(57) [Claims] A pair of opposed probes are arranged at a predetermined interval so as to maintain a gap between both surfaces of a silicon wafer, and the capacitance between the probes is measured. The measured value was measured by the capacitance type non-contact thickness gauge using the silicon wafer.
In terms of the thickness of the wafer output by the silicon wafer in advance determined by sorter measurement of the capacitance type noncontact thickness meter - How smell of selecting as compared with the allowable thickness value Ha
Te, the silicon wafer - and Ha temperature arranged in the vicinity of the sensor, and a temperature difference detector for detecting a difference in temperature between the detected temperature and the reference temperature of the temperature sensor, corresponding to the detected temperature difference of the temperature difference detecting unit A temperature correction device comprising a calculation unit for correcting the measurement value of the capacitance-type non-contact thickness gauge based on the correction coefficient determined in the preceding stage of the sorter ,
Based on the correction coefficient determined according to the detected temperature difference,
A method for selecting a thickness of a silicon wafer, comprising correcting a measurement value of a capacitive non-contact thickness gauge . 2. A method according to claim 1, wherein the silicon wafer, wherein the correction coefficient is previously determined constant - Ha Thickness sorting method. Wherein the reference temperature silicon wafer of known thickness - is characterized by using a wafer which is ambient temperature when calibrating the thickness gauge according to claim 1, wherein the silicon wafer - Ha Thickness sorting method.