JPH0555105A - Semiconductor printing/exposing equipment - Google Patents

Abstract

PURPOSE:To improve the exposure processing speed and/or the yield, while degrading neither, in a semiconductor printing/exposing equipment on which each of a plurality of wafers is shifted step by step and a plurality of shots are exposed on each wafer. CONSTITUTION:A semiconductor printing/exposing equipment having focus position measuring equipment LD and PD, is provided with a means CB to store measured values of the focus position for each shot and wafer, a processing means CB to, via statistical processing, obtain correction values which give the subsequent right measured values of focus positions based on the values stored in the storing means, and a control means CB to control focus positions based on the resulting correction values.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor printing exposure apparatus, and more particularly to a semiconductor printing exposure apparatus of the type provided with a focus measuring device for focus alignment in a mask aligner such as a stepper.

[0002]

2. Description of the Related Art In recent years, semiconductor devices have changed from ICs to LSs.
I and VLSIs are strikingly finer patterns, higher integration, and larger screens, and various steppers have been developed in the field of semiconductor printing exposure apparatus to meet these demands. The stepper has a drawback that the depth of focus is reduced when the NA is increased in order to enhance the resolving power of the lens. Therefore, efforts are being made to enhance the focus alignment accuracy.

As means for improving the focus alignment accuracy, measurement is performed at multiple points of each shot or on the entire surface of the shot, tilt measurement and drive are performed before focus measurement, or baking is performed in order to remove the tilt of the wafer. The pattern offset is measured in advance in order to cancel the influence of the pattern.

[0004]

However, in the above-mentioned conventional example, since the focus alignment is performed using only the focus measurement value in the measured shot, (1) in a shot with foreign matter on the wafer or uneven coating of the resist, The focus position cannot be measured correctly. (2) Since it is necessary to measure the focus every shot, the throughput is poor.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and semiconductor printing exposure capable of quickly detecting an abnormality in focus measurement due to dust, resist, etc. and reducing defective shots. The purpose is to provide a device.

Another object of the present invention is to provide a semiconductor printing apparatus capable of improving throughput without increasing defective shots.

[0007]

In order to achieve the above object, the present invention provides a semiconductor printing apparatus which exposes a plurality of regions on a wafer while stepwise moving the wafer. The focus value of the same shot on one or a plurality of wafers that have been focus-measured and exposed is stored, statistical processing is performed, and when the focus measurement of a new wafer is performed, it is compared with the value stored and calculated above, To detect the presence or absence,
Alternatively, the focus measurement value for each shot of the preceding wafer is stored, statistical processing is performed, and the focus value is calculated using the value stored and statistically processed for a part of the shots of the new wafer. ing.

[0008]

According to the present invention, for a semiconductor printing exposure apparatus having a focus position measuring device, means for storing the focus position measured value of each shot and each wafer, and a means for storing the focus position measured value for each shot An arithmetic means for obtaining a correction value by which the measured value of the focus position is correct by statistical processing and a control means for controlling the focus position based on the correction value are provided. Therefore, if the focus measurement value of a new wafer is compared with the correction value to evaluate this focus value, it becomes possible to quickly know the abnormality of the focus measurement due to dust, resist, etc. You can reduce shots. Further, for a new wafer, if the number of focus measurement shots is reduced by using the correction value, the throughput of the semiconductor printing apparatus can be improved.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an exposure apparatus according to an embodiment of the present invention. In the figure, ZS is the wafer Z
Z stage which is moved up and down in the direction, 1D and PD are a light emitting unit and a light receiving unit, respectively, in an optical autofocus device, C
B is a control box having a control circuit including a CPU (central processing unit) and memory, WF is a wafer, LN
Is a lens.

Next, a semiconductor wafer exposure method using this apparatus will be described. As an example, we will expose two wafers. Hereinafter, the operation of FIG. 1 will be described in detail with reference to the flowchart of FIG.

When exposure is started, first, in step 101, the first wafer (hereinafter referred to as the first wafer) is carried in, and in step 102, the wafer WF is moved so as to come to the exposure position below the printing projection lens LN. , Step 103
Focus measurement with. After the measurement is completed, the measured shot number, the position of the XY stage XYS, and the focus measurement value are stored in the storage device. And step 1
In step 05, the Z stage is moved to the exposure position, and step 106 is performed.
To expose. Then, in step 107, it is determined whether or not the exposure of the final shot is completed. When exposure of all shots is completed, the process proceeds to step 108, and the average and variance of focus values of all shots of the first wafer are calculated. Then, in step 109, the first wafer is unloaded. In step 110, the second wafer (hereinafter referred to as the second wafer) is loaded. In step 111, the wafer WF is moved to the exposure position, and in step 112, focus measurement is performed. Then, in step 113, the value measured this time is compared with the value measured in the shot at the same position on the first wafer, and if the difference is larger than a preset value, the process proceeds to step 114. In step 114, it is also compared with the average obtained in step 108, and when the difference is larger than a preset value, emergency processing such as temporary stop or warning is performed. If the determination result of step 113 or step 114 is OK, the processing from step 116 onward is continued. The processing of steps 116 to 121 is the same as the processing of steps 104 to 109 described above, except that the statistical processing of step 120 is performed for the focus values of both the first and second wafers for which focus measurement has been completed.

According to such a procedure, when exposing wafers of the same pattern in the same lot, the measurement value of the previous wafer serves as a reference for determining the quality of the measurement value of the next wafer. It is possible to determine whether or not the measured value is obtained by correct measurement, prevent exposure at an incorrect focus position in advance, and know that there is an abnormal shot before development. Further, as the number of exposed wafers is increased, the average value of the focus values of the same shots of all the wafers up to that point and the average value of the focus values of all the shots of all the wafers up to now can be applied as a criterion for determination. ..

In the above description, the case where all the shots are necessarily measured has been exemplified, but the present invention can be applied to the case where a plurality of predetermined shots in the wafer are selected and processed as focus measurement shots. it can.

[0015]

[Other Embodiments] Storing the shot information of the previous wafer can be applied to the check of the focus value as described above, but if the idea is further advanced, if the values up to the previous wafer are used, It is possible to omit the focus measurement in.

First, all shots are always measured on the first wafer, and for the second and subsequent wafers, focus measurement is performed only on predetermined shots. Then, the measured value of each shot is compared with the value of the same shot on the first wafer, and if it is within a predetermined range, focus measurement is omitted for each shot and only exposure is performed. If it is out of the range, measurement and exposure are performed on all the shots of the wafer, and this is reflected in the comparison data for the third and subsequent wafers. By doing so, it is possible to minimize the focus measurement, which was always necessary for each shot in the past, and to achieve high throughput.

[0017]

As described above, according to the present invention, when a plurality of wafers are exposed, statistically processing the measured values of all the shots up to the previous wafer allows (b) dust, resist, etc. It is possible to quickly detect an abnormality in focus measurement due to, and reduce the number of defective shots, or (b) reduce the number of focus measurement shots after the second by using the focus information for each shot on one wafer. By doing so, the effect of improving the throughput of the semiconductor printing apparatus can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the apparatus of FIG.

[Explanation of symbols]

ZS: Z stage, 1D: light emitting part of optical autofocus device, PD: light receiving part of optical autofocus device, CB: control box, WF: wafer, L
N: Lens.

Claims (3)

[Claims] 1. In a semiconductor printing exposure apparatus that exposes a plurality of shots on a plurality of wafers while step-moving the wafer, a focus measurement value of a previously processed single or a plurality of wafers is measured. A semiconductor comprising: a means for storing each shot; a calculating means for statistically processing the value stored by the storing means; and a control means for controlling the focus position based on the value obtained by the statistical processing. Printing exposure equipment. 2. When the control means performs focus measurement of a new wafer, the focus measurement value of the new wafer is compared with a value obtained for the same shot of the preceding wafer by the statistical processing, and an abnormality is detected. The semiconductor printing exposure apparatus according to claim 1, wherein the presence or absence of the above is detected. 3. The focus value of a part of shots of a new wafer is calculated by the control means based on focus measurement values of other shots of the new wafer and the values obtained by the statistical processing. The semiconductor printing exposure apparatus according to claim 1.