JPH10274684A - Gap formation mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure and set a gap in a short time by arranging three gap detection sensors around a mask side target and detecting the wafer height simultaneously for the three. SOLUTION: A gap detection sensor S1 in a wafer 1 side detects a mask target T2 and obtains the measured value. It also measures the three points on the mask 2 in turn with the movement of an XY stage 11, obtains the height and inclination of the mask 2, determines the drive quantity of mask drive mechanisms 8 to 10 and drives them. Next, the target T1 is moved onto the gap detection sensors S2 to S4 on the mask 2 side arranged around the mask 2, and standard values of the gap detection sensors S2 to S4 are measured. Then, the wafer 1 center is adjusted to the center of the gap detection sensors S2 to S4 and three points on the wafer 1 are simultaneously measured with the three sensors. From this measured value and the standard value, the drive quantity of the wafer 1 is calculated to determined the height and angle. Since the height of the mask 2 is already determined, the gap between the wafer 1 and the mask 2 is set in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for maintaining a constant distance between a mask and a wafer, and a gap forming mechanism suitable for setting a gap between the mask and the wafer with a gap of several tens of .mu.m, such as an X-ray exposure apparatus. It is.

[0002]

2. Description of the Related Art When a fine pattern of a semiconductor is formed on a wafer, the pattern formed on the mask is irradiated with ultraviolet rays or X-rays having a shorter wavelength, and the pattern on the mask is transferred to a photosensitive agent on the wafer. I do. At this time, it is important to keep the distance between the mask and the wafer constant to maintain the accuracy of the pattern. The present invention relates to a mechanism for keeping the distance (gap) between the mask and the wafer constant. In particular, in an X-ray exposure apparatus, proximity exposure is performed in which a gap between a mask and a wafer is set at a gap of several tens of μm to perform exposure, and it is important to keep the gap between the mask and the wafer constant.

As a method of forming a gap between a mask and a wafer, a gap forming mechanism having a configuration in which one gap detection sensor is mounted on the mask side and one gap detection sensor is mounted on the wafer side has been used. This gap forming method will be described with reference to FIG. In the figure, 1 is a wafer, 2 is a mask which is a pattern original plate, 3 is a wafer chuck for holding the wafer 1, and 4 is a mask chuck for holding the mask 2. Similarly to the wafer chuck, the piezo actuators 8, 9, and 10 move the wafer mask chuck 4 back and forth and swing. S1 is a mask gap sensor mounted on the wafer side, and S2 is a wafer gap sensor mounted on the mask side. The target T1, the gap detection sensor S1, the wafer 1, and the wafer chuck 3 on the wafer side are all mounted on the XY stage 11. In order to form a gap between a mask and a wafer with the apparatus having such a configuration, the following is performed.

[0004] First, the height and tilt of the mask are positioned using the gap sensor S1. That is, the mask-side target T2 is measured by the wafer-side mask sensor S1, and the target mask height position is determined. Next, XY
The stage is driven and the gap detection sensor S1 is moved to measure three mask heights on the mask. Based on the measured values, the piezo actuators 5, 6, and 7 are driven to set the mask height to the previously determined target height. next,
Determine the height of the wafer. That is, the target T1 on the wafer side is measured by the wafer sensor S2 on the mask side, and the target wafer height position is obtained. Next, the XY stage is moved, the wafer is moved, and three points on the wafer are measured.
Based on this value, the piezo actuators 8, 9, 10
To set the wafer height at the target position. Thus, the inclination and height of the mask and the wafer are determined, and the gap between the mask and the wafer is formed at a predetermined value. However, in such a mechanism, the XY stage has to be moved to measure the height of three points on the wafer, and the measurement requires time.

FIG. 4 shows another conventional embodiment as a gap forming mechanism for solving such a problem. In the figure,
S2, S3, and S4 are three gap detection sensors on the mask side. Unlike the second embodiment, there is no mask target on the wafer side, and reference targets T2, T3, T4 are set around sensors S2, S3, S4. In order to form a gap between a mask and a wafer with the apparatus having such a configuration, the following is performed.

The positioning in the height direction of the mask is the same as in the first embodiment. The height of the wafer is determined by moving the wafer to a position where the front of the three sensors, the center of the triangle formed by the sensors, and the center of the triangle of the driving actuators 5, 6, and 7 coincide. At this position, S2, S3,
In S4, the height of the wafer is measured. The target height of the wafer is determined by operating the drive actuator based on the above value in order to calibrate the sensor sensitivity in advance. In this method, when the height of the wafer is determined, the movement of the XY stage is not involved as in the above-described conventional embodiment, so that positioning can be performed in a short time. However, actually, there are individual differences between the sensors S2, S3, and S4, and it is necessary to compensate for this and accurately match the characteristics of the three sensors. This calibration is performed using respective targets placed around each sensor. That is, a jig corresponding to the target is prepared, one surface A is brought into contact with the target, and the other surface B is measured by a sensor. Using this, calibration is performed to adjust the characteristics of the sensors so that the outputs of the sensors match. Thus, in this device calibration, calibration is performed at a different time from the actual measurement,
It has been difficult to calibrate for changes over time of the sensor and changes in the characteristics of the sensor for each device under test. For this reason, it is difficult to obtain an accurate gap when the object to be measured changes.
Further, even when performing the off-line calibration every time the adjustment is performed, there is a problem that the calibration takes a long time because the wafer side does not have a target serving as a reference on the mask side.

[0007] In the above-mentioned prior art, there has been a problem that the distance that the sensor moves to the detection position becomes longer and the time for forming the gap becomes longer. Since this operation is performed for each wafer, the throughput is reduced. Further, in another conventional technique, the calibration of the gap sensor is performed off-line and with another calibration jig, and it is difficult to obtain an accurate gap for each object to be measured. further,
Even when performing the off-line calibration every time the adjustment is performed, there is a problem that the calibration takes a long time because the wafer side does not have a target serving as the mask side reference.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a gap forming mechanism capable of measuring and setting a gap in a short time.

[0009]

As a means for solving the above-mentioned problems, the present invention relates to a method for detecting three gaps in a wafer at the same time, three gap detection sensors and one reference target for calibrating the same. In addition, three gap detection sensors are arranged around the target on the mask side, and are arranged so as to minimize the moving distance when calibrating the gap sensor.

A second aspect of the present invention is characterized in that the mask-side target is set inside a triangle formed by three gap detection sensors. like this,
With the configuration of the three gap detection sensors and the target, the movement time for sensor calibration is reduced,
Further, the moving time of the XY stage for measuring the height of the wafer is shortened, so that the gap forming time is shortened and the gap forming accuracy is improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a wafer, 2 is a mask, 3 is a wafer chuck for holding the wafer, and 4 is a mask chuck for holding the mask. The wafer chuck 4 is driven by wafer fine movement mechanisms 5, 6, and 7, and moves the wafer 1 back and forth and swings. Here, a piezo actuator using a piezoelectric element is used for the wafer fine movement mechanisms 5, 6, and 7. The mask chuck 4 is driven by mask fine movement mechanisms 8, 9, and 10, and the mask 2 performs forward and backward movement and tilt drive. A target T2 serving as a mask height reference is mounted on the mask side, and a target T1 serving as a wafer height reference is mounted on the wafer side. The wafer chuck 4, the sensor S1, and the target T1 are mounted on an XY stage 11 that moves perpendicular to the height direction of the wafer.

In order to form a gap between the mask 2 and the wafer 1 with the apparatus having such a configuration, the following steps are performed. First, in order to determine the height of the mask 2, the mask target T2 is detected by the gap sensor S1 mounted on the wafer side, and the measured value of the sensor S1 is detected. Next, three points on the mask are sequentially measured by moving the XY stage by the sensor S1, and the height and inclination of the mask 2 are obtained. Based on this value, the driving amounts of the mask fine movement mechanisms 8, 9, and 10 are obtained, and the mask is driven. At this time, if the three points on the mask are taken as three points on a line connecting the centers of the triangles of the mask fine movement mechanisms 8, 9, and 10, the driving amount of the mask fine movement mechanism can be easily calculated, and the arithmetic processing becomes faster.

Next, when the height of the mask 2 is determined, the height of the wafer 1 is determined. First, the target T1 is moved onto the mask side gap detection sensors S2, S3, S4, and the standard values of the mask side gap detection sensors S2, S3, S4 are measured. Next, the center of the wafer 1 is brought to the center of the gap detection sensors S2, S3 and S4 on the mask side, and three points on the wafer 1 are measured by the three sensors. The driving amount of the wafer is calculated from the measured value and the standard value of the sensor previously obtained, and the height and tilt of the wafer are determined by the wafer fine movement mechanism. Since the height of the mask is already determined, the gap between the mask and the wafer is accurately formed if the height and the tilt of the wafer are determined.

[0014]

As described above, the standard target is mounted on the wafer side, and the measurement characteristics of each sensor are calibrated in this way, so that the wafer height can be measured more accurately. . Further, since the three sensors can simultaneously detect the wafer height without moving the XY stage to measure the height of the wafer, the gap can be measured and set in a short time.

[Brief description of the drawings]

FIG. 1 is a perspective view of a gap generating mechanism according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of sensor arrangement according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of Conventional Example 1.

FIG. 4 is an explanatory diagram of Conventional Example 2.

[Explanation of symbols]

 Reference Signs List 1 wafer 2 mask 3 wafer chuck 4 mask chuck 5, 6, 7 wafer fine movement mechanism 8, 9, 10 mask fine movement mechanism 11 XY stage S1 wafer side gap detection sensor S2, S3, S4 mask side gap detection sensor T1 mask side target T2 , T3, T4 Wafer side target

Claims (2)

[Claims] 1. A mechanism for forming a gap between an original plate of a pattern (hereinafter referred to as a mask) and a semiconductor substrate (hereinafter referred to as a wafer) for forming a pattern, wherein 3
Three gap detection sensors, one gap detection sensor on the wafer side, two gap reference targets serving as gap references on the mask side and the wafer side, three fine movement mechanisms for driving the mask, and three fine movement mechanisms for driving the wafer And a positioning stage for moving the wafer chuck, the gap reference target, and the gap detection sensor in a plane perpendicular to the gap direction. 2. The gap forming mechanism according to claim 1, wherein the mask-side target is set inside a triangle formed by three gap detection sensors.