JP2002296026A - Method and instrument for measuring warp in semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and instrument for measuring a warp in a semiconductor wafer, enhancing accuracy in warp measuring. SOLUTION: Air is blown into the front and rear faces of a silicon wafer W erected on a measuring reference surface, thereby keeping the wafer W vertical. Then, a warp in the wafer W is measured under this condition. Since the warp is measured in a torque-free state not causing any load for gripping the wafer W to act on the peripheral part of the wafer, the possibility of enlarging the warp due to differences in wafer grip positions can be removed, which has been a problem in gripping a wafer by using a conventional gripper. As a result, accuracy in warp measuring can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring warpage of a semiconductor wafer, and more particularly, to a method for vertically holding a semiconductor wafer in a state where a load for holding the wafer is not acting on an outer peripheral portion of the semiconductor wafer. The present invention relates to a semiconductor wafer warpage measuring method and apparatus for measuring the warpage (warp, bow) of a semiconductor wafer in this state.

[0002]

2. Description of the Related Art In a general device for measuring the warpage of a silicon wafer, the center of the silicon wafer is held horizontally by a wafer holding plate having a horizontal holding surface, and then the wafer holding plate is rotated. While rotating about the axis, a pair of capacitance sensors or laser sensors arranged outside (up and down) on the front and back surfaces of the silicon wafer are scanned to measure the warpage of the silicon wafer. . However, in this general-purpose (horizontal) warpage measuring device, the silicon wafer is rotated in a horizontal plane while holding the center of the silicon wafer, so that the outer peripheral portion of the silicon wafer is easily bent by its own weight, and a measurement error is likely to occur. There was a problem. Such a phenomenon becomes more remarkable as the diameter of the silicon wafer becomes larger than 300 mm.

Therefore, as a conventional technique for solving this,
Vertical warpage measuring devices are known. The vertical measuring device grips the outer peripheral portion of the silicon wafer by a gripper for vertically placing the wafer and stands upright, and a pair of electrostatic devices arranged as it is on each side (left and right direction) of the front and back surfaces of the wafer as it is This is to measure the warpage of the silicon wafer by scanning a capacitance sensor or a laser sensor. The gripper is pressed against the outer periphery of the silicon wafer by the force of a built-in spring, and holds the silicon wafer vertically.

[0004]

However, in the conventional warpage measuring device, when the silicon wafer is gripped by the gripper, the warpage of the silicon wafer expands depending on the direction of gripping by the gripper, and the warpage increases. There was a possibility that the reliability of the measurement of the sample may decrease. This phenomenon will be described with reference to FIGS. FIG. 5 is a contour diagram showing the relationship between the gripping direction and the warpage of the outer peripheral portion of the semiconductor wafer. FIG. 6 is a cross-sectional view showing the relationship between the gripping direction and the warpage of the outer peripheral portion of the semiconductor wafer. 5 and 6
As shown in the figure, the silicon wafer W is warped all over. This warp is curved in a substantially horizontal S-shape when viewed in cross section along a virtual line b orthogonal to a virtual line a connecting the wafer center point and the notch n.

Therefore, when the silicon wafer W is gripped by a pair of grippers (not shown), if the gripping direction (the pressing direction of the gripper) is from both sides of the imaginary line a, expansion of the warp hardly occurs. This is because the warp acts as a reinforcing structure for the silicon wafer W. On the other hand, when this gripping direction is the direction of the virtual line b,
Since the pressing direction of the gripper matches the direction of the warpage of the silicon wafer W, the allowable range of the bending stress of the silicon wafer W is reduced. As a result, even if a comparatively small external force acts, it bends. As a result, the warpage was likely to expand, and the reliability of the measurement results was low.

Therefore, as a result of a long-term study, the inventor has sprayed a posture holding gas on each of the front and back surfaces of the wafer standing on the measurement reference plane, and held the wafer vertically to measure the warpage. The present inventors have found that it is possible to measure warpage in a state where a load for holding the wafer does not act on the outer peripheral portion (hereinafter, torque-free state), and completed the present invention.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and an apparatus for measuring the warpage of a semiconductor wafer, which can improve the measurement accuracy of the warpage. Another object of the present invention is to provide a semiconductor wafer warpage measuring method and apparatus capable of automatically vertically holding a semiconductor wafer.

[0008]

According to a first aspect of the present invention, there is provided a method of holding a semiconductor wafer vertically by spraying a posture holding gas on each of the front and back surfaces of the semiconductor wafer standing on a measurement reference plane. Measuring the warpage of the semiconductor wafer held in a non-contact state. The type of the semiconductor wafer is not limited. For example, a silicon wafer, a gallium arsenide wafer, or the like can be used. The type of the posture holding gas is not limited. In addition to air, an inert gas such as an argon gas or a nitrogen gas may be used. The flow rate of the posture holding gas is not limited. In short, it is only necessary that the semiconductor wafer can be held upright when sprayed on the front and back surfaces of the semiconductor wafer. At this time, the flow rate of the attitude maintaining gas normally blown to the front and back surfaces of the semiconductor wafer is equal.

[0009] The position at which the attitude holding gas is blown on the front and back surfaces of the semiconductor wafer is not limited. The spray position on each surface differs depending on the size and shape of the semiconductor wafer. In short, any position may be used as long as the semiconductor wafer standing on the measurement reference plane can be balanced. Normally, the gas blowing positions on the front and back surfaces of the semiconductor wafer are opposed to each other across the semiconductor wafer. Of course, it is not necessary to be at this facing position. However, in this case, it is necessary to adjust the flow rate difference so that a difference is made between the flow rate of the attitude holding gas sprayed on the wafer front surface and the flow rate of the attitude holding gas sprayed on the back surface of the wafer, and the semiconductor wafer stands upright. There is. The method of spraying the posture holding gas is not limited. For example, an attitude holding gas is blown to each part of the front and back surfaces of the semiconductor wafer through a pair of nozzles respectively arranged outside the front and back surfaces of the semiconductor wafer. The non-contact type measuring means for measuring the warpage of the semiconductor wafer is not limited. Usually, it is a general-purpose type warpage measuring device that scans a pair of capacitance sensors. In addition, a laser interference type, an ultrasonic type, or the like may be used.

According to a second aspect of the present invention, the step of detecting the outer shape of the semiconductor wafer and the position of the attitude maintaining gas blown to the front and back surfaces of the semiconductor wafer are controlled based on the detected outer shape of the semiconductor wafer. 2. The method for measuring warpage of a semiconductor wafer according to claim 1, further comprising the steps of: The configuration of the wafer temporary holding means is not limited. For example, a gripper for gripping the outer peripheral portion of the semiconductor wafer by the spring force of the conventional means can be employed. The wafer shape detecting means is not limited. For example, an optical sensor, a capacitance sensor, or the like can be employed.
The point is that the outer edge of the semiconductor wafer can be detected. The configuration of the gas blowing position control means is not limited. Usually, it is composed of a computer serving as a main body, and nozzle moving means for moving the position of a blowing nozzle for blowing a posture holding gas in accordance with a command from the computer.

According to a third aspect of the present invention, there is provided a gas blowing means for blowing a posture holding gas onto the front and back surfaces of a semiconductor wafer standing on a measurement reference plane to hold the semiconductor wafer vertically, and to hold the semiconductor wafer vertically. A semiconductor wafer warpage measuring device comprising a non-contact type warpage measuring means for measuring the warpage of a semiconductor wafer. As the gas blowing means, for example, in the case of air, an air nozzle or the like that blows the attitude holding gas generated from the compressed air generating device can be employed.

According to a fourth aspect of the present invention, there is provided a temporary wafer holding means for temporarily holding a semiconductor wafer for detecting an outer shape of a semiconductor wafer, and detecting an outer shape of the semiconductor wafer temporarily held by the temporary wafer holding means. 4. The semiconductor wafer according to claim 3, further comprising: a wafer outer shape detecting unit; and a gas blowing position control unit that controls a blowing position of a posture holding gas that is blown onto each of the front and back surfaces of the semiconductor wafer based on the detected outer shape of the semiconductor wafer. Is a warpage measuring device.

[0013]

According to the present invention, a posture maintaining gas is blown onto the front and back surfaces of the semiconductor wafer, respectively, on the semiconductor wafer placed vertically on the measurement reference plane. Thus, the semiconductor wafer is held vertically. After that, the warpage of the semiconductor wafer is measured in the vertical state. In this way, the attitude holding gas is sprayed on the front and back surfaces of the semiconductor wafer, and the wafer is warped (warped or bowed) on the outer periphery of the semiconductor wafer in a torque-free state where no load for holding the semiconductor wafer is applied. To measure,
This eliminates the problem of the increase in the warpage due to the difference in the grip position of the semiconductor wafer, which is a problem when gripping the outer peripheral portion of the wafer with the conventional gripper. This allows
It is possible to improve the reliability of the measurement result, and thus the measurement accuracy of the warpage.

In particular, according to the second and fourth aspects of the present invention, the outer shape of the semiconductor wafer is detected, and based on the inspection result, the position of the position holding gas to be blown onto the front and back surfaces of the semiconductor wafer is determined. Control. Thereby, the semiconductor wafer can be automatically held vertically.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a warp measuring step in a method for measuring a warp of a semiconductor wafer according to one embodiment of the present invention. FIG. 2 is a front view showing a wafer temporary holding step in the semiconductor wafer warpage measuring method according to one embodiment of the present invention. FIG. 3 is an enlarged vertical sectional view of a main part showing a step of detecting an outer shape of a semiconductor wafer according to one embodiment of the present invention. FIG. 4 is a front view showing a warpage measuring step in the method for measuring a semiconductor wafer according to one embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes a semiconductor wafer warpage measuring device (hereinafter, warpage measuring device). The warpage measuring device 10 sprays a posture maintaining gas on each of the front and back surfaces of the silicon wafer W standing up, holds the silicon wafer W vertically in a torque-free state, and keeps the warpage of the silicon wafer W in that state in a non-contact manner. It is measured by a warpage measuring device of the formula. Hereinafter, this warpage measuring device 1
A specific configuration of 0 will be described. That is, as shown in FIGS. 1 to 4, the warp measuring device 10 includes a wafer pedestal 11 having a measurement reference surface of a silicon wafer W, and a silicon wafer W standing on the measurement reference surface of the wafer pedestal 11.
Blow air (posture holding gas) on the front and back of
A pair of air nozzles (gas blowing means) 12 and 12 for vertically holding the silicon wafer W, and a pair of non-contact type capacitance sensors (for measuring the warpage of the vertically held silicon wafer W) Means) 13, 13; four grippers (wafer temporary holding means) 14 for temporarily holding the silicon wafer W to detect the outer shape of the silicon wafer W; and the outer shape of the silicon wafer W temporarily held by the grippers 14 ... And a gas blowing position control means 16 for controlling the blowing position of the air blown to each of the front and back surfaces of the silicon wafer W based on the detected outer shape of the silicon wafer W.

The wafer receiving table 11 is a thick rectangular parallelepiped member, and the inner surface of the groove 11a formed on the upper surface thereof serves as a measurement reference surface of the silicon wafer W. Wafer support 11
Above this, a fall prevention piece 20 for preventing the silicon wafer W from accidentally falling when the silicon wafer W stands up is arranged to be able to move up and down. The lower surface of the fall prevention piece 20 has a groove 2 loosely inserted into the upper end of the silicon wafer W.
0a is formed. The fall prevention piece 20 can be moved up and down by elevating means (not shown). The silicon wafer W is erected with the lower end of the wafer inserted into the groove 11a of the wafer receiving table 11, and then the falling prevention piece 20 is lowered from above by an elevating means (not shown), and the groove 20a is moved to the upper end of the silicon wafer W. It is inserted into the part.
The air nozzles 12, 12 can be vertically moved up and down along the radial direction of the silicon wafer W by a pair of lifting cylinders 17, 17 disposed above both sides of the wafer receiving table 11. A predetermined flow rate of air is supplied from the air nozzles 12 and 12.

The pair of capacitance sensors 13 and 13 are integrated with a silicon wafer W by a scanning drive unit (not shown).
Are scanned along the front and back surfaces of the. The flat tip surface of the grippers 14 is pressed against the outer peripheral surface of the silicon wafer W at 90-degree intervals in the circumferential direction of the wafer by the spring force of the coil springs 14a, and the silicon wafer W is pressed at predetermined pressures from four directions. Pinch. As the wafer outer shape detection sensor 15, an optical sensor including a light emitting unit 15a and a light receiving unit 15b is employed. One pair of the wafer outer shape detection sensors 15 is disposed outside each of the front and back surfaces of the silicon wafer W. The gas blowing position control means 16 includes a pair of elevating cylinders 17, 17,
And a controller 18 that adjusts the amount of protrusion of the rods 17a, 17a to change the height of the air nozzles 12, 12 based on the detection signal from

Next, a method for measuring the warpage of a semiconductor wafer using the warpage measuring apparatus 10 will be described. At the time of the warpage measurement, first, the outer peripheral portion of the wafer is gripped by a clamper of a robot hand (not shown), and the silicon wafer W
Is loaded into the warpage measuring apparatus 10 and the silicon wafer W is vertically placed on the measurement reference plane of the wafer receiving table 11. Next, the silicon wafer W in the upright state is mechanically gripped by the four clampers 14.
The outer shape of the silicon wafer W is detected using the wafer outer shape detection sensor 15. At this time, since each end face of the grippers 14 is flat, each gripper 14 does not hinder the inspection of the outer shape of the silicon wafer W. Then, based on the obtained outer shape detection signal, the control unit 18 issues a height adjustment command for the air nozzles 12 to both the lifting cylinders 17. Thereby, a pair of air nozzles 1
2 and 12 move to the position where the air is blown optimally to hold the silicon wafer W vertically. Thereafter, the air generated by the compressed air generator is transmitted to both air nozzles 12 and 1.
Blow out at the same flow rate from 2. As a result, the silicon wafer W is held vertically on the measurement reference plane of the wafer holder 11.

Next, the fall prevention piece 20 is lowered from above, and the groove 20a is loosely inserted into the upper end of the silicon wafer W. Then, the gripping state of the silicon wafer W by the four grippers 14 is released. Thus, the silicon wafer W is vertically held in a torque-free state by only the air blown from the air nozzles 12,12. In this state, the pair of capacitance sensors 13 and 13
Is scanned along the front and back surfaces of the silicon wafer W to measure the warpage of the silicon wafer W, specifically, warp or bow in a non-contact state.

As described above, air is blown onto the front and back surfaces of the silicon wafer W, and the wafer is warped in a torque-free state where no load for holding the silicon wafer W is applied to the outer peripheral portion of the silicon wafer W. Since the measurement is performed, it is possible to eliminate the problem that the warpage of the silicon wafer W is expanded by the gripping position of the silicon wafer W, which is a problem when the outer peripheral portion of the wafer is gripped by the conventional gripper. it can. As a result, the reliability of the result of the warpage measurement is increased, and the measurement accuracy of the warpage can be improved. Further, since the outer shape of the silicon wafer W is detected and the positions of the air blown to the front and back surfaces of the silicon wafer W are controlled based on the inspection result, the silicon wafer W is automatically vertically held. Can be.

[0022]

According to the present invention, a posture maintaining gas is blown onto the front and back surfaces of a semiconductor wafer, and the warpage of the wafer is measured in a state where a load for holding the wafer is not applied to the outer peripheral portion of the semiconductor wafer. Therefore, the problem that the warpage of the semiconductor wafer is increased by the gripping direction of the wafer, which is a problem when the outer peripheral portion of the wafer is gripped by the conventional gripper, is solved. Thereby, the measurement accuracy of the warpage can be improved.

In particular, according to the second and fourth aspects of the present invention, the outer shape of the semiconductor wafer is detected, and based on the inspection result, the position at which the position maintaining gas is blown on the front and back surfaces of the semiconductor wafer is controlled. Therefore, the semiconductor wafer can be automatically held vertically.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a warp measuring step in a method for measuring a warp of a semiconductor wafer according to one embodiment of the present invention.

FIG. 2 is a front view showing a temporary wafer holding step in the method for measuring the warpage of a semiconductor wafer according to one embodiment of the present invention.

FIG. 3 is an enlarged vertical sectional view of a main part showing a step of detecting an outer shape of a semiconductor wafer according to one embodiment of the present invention;

FIG. 4 is a front view showing a warpage measuring step in the method for measuring a semiconductor wafer according to one embodiment of the present invention.

FIG. 5 is a contour diagram showing a relationship between a gripping direction and a warp of an outer peripheral portion of a semiconductor wafer.

FIG. 6 is a cross-sectional view illustrating a relationship between a gripping direction and a warp of an outer peripheral portion of a semiconductor wafer.

[Explanation of symbols]

10 semiconductor wafer warpage measuring device, 12 air nozzle (gas blowing means), 13 capacitance sensor, 14 gripper (temporary wafer holding means), 15 wafer outer shape detecting sensor (wafer outer shape detecting means), 17 elevating cylinder (gas blowing position) Control means), 18 control unit (gas blowing position control means), W silicon wafer (semiconductor wafer).

Claims (4)

[Claims] 1. A step of blowing a posture holding gas onto each of the front and back surfaces of a semiconductor wafer standing on a measurement reference plane to hold the semiconductor wafer vertically, and the step of warping the semiconductor wafer held vertically in a non-contact state. Measuring the warpage of a semiconductor wafer, comprising: 2. The method according to claim 1, further comprising the steps of: detecting a contour of the semiconductor wafer; and controlling a blowing position of a posture holding gas to be blown onto each of the front and back surfaces of the semiconductor wafer based on the detected contour of the semiconductor wafer. 3. The method for measuring warpage of a semiconductor wafer according to item 1. 3. A gas blowing means for blowing a posture holding gas onto the front and back surfaces of a semiconductor wafer standing on a measurement reference plane to hold the semiconductor wafer vertically, and measuring the warpage of the semiconductor wafer held vertically. An apparatus for measuring warpage of a semiconductor wafer, comprising: a non-contact type warpage measuring means. 4. A temporary wafer holding means for temporarily holding a semiconductor wafer for detecting an outer shape of the semiconductor wafer, a wafer outer shape detecting means for detecting an outer shape of the semiconductor wafer temporarily held by the temporary wafer holding means, 4. The semiconductor wafer warpage measuring apparatus according to claim 3, further comprising gas blowing position control means for controlling a blowing position of a posture holding gas blown to each of the front and back surfaces of the semiconductor wafer based on the outer shape of the semiconductor wafer.