JPH04302130A - Exposure method and system - Google Patents

Abstract

PURPOSE:To align a pattern to be exposed with a wafer even if the wafer is mounted on an exposure stage slipping out of the reference positions corresponding to an exposure optical system in relation to the title method and system mounting the wafer on the exposure stage capable of shifting along the exposure surface to be exposed to the photoirradiation from the exposure optical system. CONSTITUTION:As for the exposure method, a photosensor 4 detecting the slippage of a mounted wafer W out of the reference positions corresponding to the exposure optical system 3 is provided so that an exposure stage 1 may be shifted while monitoring the wafer W by the photosensor 4 to correct the position of the wafer W for performing the exposure when the photosensor 4 detects said positional slippage at the time of mounting the wafer W. On the other hand, the exposure system is composed of the photosensor 4 capable of detecting said positional slippage by passing light fluxes 7a-7d in the upward and downward directions in multiple positions around the wafer W on said reference positions by the shade distribution of the light fluxes.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method and an exposure apparatus for manufacturing semiconductor devices. In the manufacture of semiconductor devices, various patterns are stacked on a wafer, and photolithography technology is used to form the patterns, and this technology includes an exposure process.

The exposure method and exposure apparatus according to the present invention are applied to this exposure.

0003

[Prior Art] An exposure apparatus exposes a pattern by irradiating a wafer placed on an exposure stage with light from an exposure optical system, and the exposure stage is movable along the exposure surface. In order to align the position of the wafer on the exposure stage with the reference position corresponding to the exposure optical system, there is a pre-alignment mechanism that aligns the wafer outside the exposure stage, and a pre-alignment mechanism that moves the wafer from the pre-alignment mechanism to the exposure stage. It is equipped with a transport mechanism for transferring and loading. Wafer alignment using the pre-alignment mechanism aligns the direction of the orientation flat and the wafer position using the wafer periphery as a guide.

Conventional exposure is performed as follows. First, in exposure for forming a first layer pattern on a wafer, the wafer is placed on the exposure stage by the above-mentioned transport mechanism, and the exposure operation starts from this state. Positioning marks are provided in this pattern.

In the subsequent exposure for forming the second layer pattern, the wafer on which the first layer pattern has been formed is placed on the exposure stage by the above-mentioned transport mechanism, and the first layer is moved by moving the exposure stage or controlling the exposure optical system. After aligning the patterns using the alignment marks of the patterns in each layer as indexes, the exposure process begins. If the alignment mark of the first layer pattern is hidden by the second layer pattern,
Positioning marks are also provided on the layer patterns.

[0006] Hereinafter, exposure for forming patterns in the third and subsequent layers is performed in the same manner as exposure for forming patterns in the second layer.

[0007]

[Problems to be Solved by the Invention] By the way, when the transport mechanism transfers the wafer from the pre-alignment mechanism to the exposure stage, slippage may occur between the transport mechanism and the wafer, causing the wafer to move away from the reference position. It may come off and be placed on the exposure stage.

In such a case, the pattern is corrected by aligning the patterns with each other in the exposure for forming the pattern on the second layer and thereafter, but the pattern is not placed on the wafer during the exposure for forming the pattern on the first layer. This will cause a positional shift.

As is well known, patterns formed on a wafer are laid out so that as many semiconductor chips as possible can be obtained from the wafer. Therefore, if the above-mentioned large positional deviation occurs during exposure for forming the first layer pattern, some semiconductor chips placed around the pattern will be formed defectively, and the manufacturing yield of semiconductor chips will decrease. do.

Accordingly, the present invention relates to the above-mentioned exposure, and provides a correction method that prevents the pattern to be exposed from being misaligned with respect to the wafer even if the wafer is placed on the exposure stage deviating from the reference position corresponding to the exposure optical system. The purpose of the present invention is to provide an exposure method and an exposure apparatus that enable the following.

[0011]

[Means for Solving the Problems] In order to achieve the above object, an exposure method according to the present invention includes placing a wafer on an exposure stage that is movable along an exposure surface, and exposing the wafer to an exposure optical system. When performing exposure by light irradiation, a detection means for detecting a positional deviation of a placed wafer from a reference position corresponding to the exposure optical system is provided, and the detection means detects the positional deviation at the time the wafer is placed. At this time, the exposure stage is moved while being monitored by the detection means to correct the position of the wafer, and then exposure is performed.

Further, the exposure apparatus according to the present invention includes an exposure stage that is movable along the exposure surface and on which the wafer is placed, an exposure optical system that irradiates the wafer on the exposure stage with exposure light, and an exposure stage that is movable along the exposure surface. The present invention is characterized by having a detection means for detecting a positional deviation of a wafer on a stage from a reference position corresponding to the exposure optical system. The detection means is an optical sensor that passes a light beam in the vertical direction through a plurality of orientation flat portions and arcuate portions of the wafer periphery at the reference position, and detects the positional deviation based on the shielding distribution of the light beam. It is said that

[0013]

[Operation] Conventionally, when exposing a wafer to form a first layer pattern, there is no index that indicates the positional deviation of the wafer placed on the exposure stage from the above-mentioned reference position, so it is not possible to correct the positional deviation. There wasn't. On the other hand, in the exposure method and exposure apparatus according to the present invention, since the detection means provides the index, desired correction can be made.

If the detection means is the above-mentioned optical sensor, it is obvious that the shielding distribution of the light beam will indicate the presence or absence of the positional deviation and the direction of the positional deviation.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to a plan view (a) and a side view (b) of FIG. 1 showing the main parts of an exposure apparatus.

In FIG. 1, this embodiment of the exposure apparatus is the conventional exposure apparatus described above provided with an optical sensor serving as the detection means, 1 is an exposure stage, and 2 is a wafer support of the exposure stage 1. , 3 is an exposure optical system, 4 is an optical sensor which is the detection means, 5 and 6 are a light emitting part and a light receiving part of the optical sensor 4, and 7a to 7d are luminous fluxes directed from the light emitting part 5 to the light receiving part 6. The alignment mechanism and transport mechanism are not shown. W in the figure is a wafer placed on the exposure stage 1 by a transport mechanism, and the wafer W is fixed to the exposure stage 1 by a wafer support.

The light emitting section 5 and the light receiving section 6 of the optical sensor 4 are as follows:
The wafer W is placed at the aforementioned reference position corresponding to the exposure optical system 3.
Assuming that the orientation of the wafer W is located at four locations (indicated by the light emitting section 5) at two locations each on the flat portion and the circular arc portion of the periphery of the wafer W in FIG. 1(a), the orientation is as shown in FIG. 1(b). The light beams 7a to 7d are arranged so as to pass in the vertical direction. Due to this arrangement, when the wafer W is located at the reference position, the light beams 7a to 7d are partially and evenly blocked by the periphery of the wafer W. The results appear in the outputs of the four light receiving sections 6 of the optical sensor 4.

[0018] Therefore, the optical sensor 4 can detect the light fluxes 7a to 7d.
The positional deviation of the wafer W from the reference position can be detected by the light blocking distribution in which the light blocking is not uniform. The relationship between the direction of positional deviation of the wafer W from the reference position and the change in light shielding due to the positional deviation is, for example, as follows. However, the direction of positional shift indicates the direction seen in FIG. 1(a).

Direction of positional shift Light beam 7a shading Light beam 7b shading Light beam 7c shading Light beam 7d shading Upward Decrease Decrease
increase increase
Right direction Unchanged Unchanged
Decrease Increase
Clockwise Decrease Increase Unchanged Unchanged
Note that the light receiving section 6 disposed above the exposure stage 1 is provided with a large distance to the exposure stage 1, so that it does not get in the way when the wafer W is placed. Needless to say, the vertical relationship between the light emitting section 5 and the light receiving section 6 may be reversed.

An example of exposure is carried out as follows. First, in exposure for forming a first layer pattern on the wafer W, the wafer W is placed on the exposure stage 1 by the transport mechanism, and the optical sensor 4 detects the presence or absence of the positional shift of the wafer W. A minute positional deviation of, for example, about 20 μm or less may be regarded as no positional deviation from the required accuracy of pattern position with respect to the wafer W. If it is determined that there is no positional shift, the exposure operation starts from that state. If it is determined that there is a positional shift, the exposure stage 1 is moved while being monitored by the optical sensor 4, and a correction is made to move the wafer W to a position where there is no positional shift, and then exposure work begins. The moving direction of the exposure stage 1 in this correction can be determined from the shielding distribution of the light beams 7a to 7d. Needless to say, positioning marks are provided in this pattern.

[0021] By doing this, the pattern will not be misaligned with respect to the wafer W, and the manufacturing yield of semiconductor chips will be reduced, in which some semiconductor chips placed around the pattern are formed defectively. Deterioration is prevented.

The subsequent exposure for pattern formation of the second and subsequent layers is carried out in the same manner as in the conventional case. When the positional deviation at the time when the wafer W is placed on the exposure stage 1 by the above-mentioned transport mechanism becomes so large that the alignment mark of the preceding pattern, which is necessary to align the patterns with each other, cannot be found, It is necessary to move the exposure stage 1 to bring the wafer W closer to the reference position. Conventionally, the operation was performed visually, but in this embodiment, the operation can be performed while being monitored by the optical sensor 4.

It should be noted that the plurality of light beams shown by 7a to 7d of the optical sensor 4 are shielded as described above as the key to detecting the positional deviation of the wafer W, and are arranged so as to perform the function of detecting the positional deviation. If so, the number is not limited to four in the example.

[0024]

As explained above, according to the present invention, there is an exposure method in which a wafer is placed on an exposure stage that is movable along an exposure surface, and the wafer is exposed by light irradiation from an exposure optical system. An exposure method and an exposure apparatus capable of making corrections to prevent positional deviation of the exposed pattern relative to the wafer even if the wafer is placed on the exposure stage deviating from the reference position corresponding to the exposure optical system. This has the effect of making it possible to prevent a decrease in the manufacturing yield of semiconductor chips in which some of the semiconductor chips arranged around the pattern are formed defectively.

[Brief explanation of drawings]

[Fig. 1] A plan view and a side view showing the main parts of an exposure apparatus for explaining an embodiment.

[Explanation of symbols]

1 Exposure stage 2 Wafer support for exposure stage 3 Exposure optical system 4 Optical sensor (detection means) 5 Light emitting section of the optical sensor 6 Light receiving sections 7a to 7d of the optical sensor Light flux W from the light emitting section to the light receiving section Wafer

Claims (3)

[Claims] Claim 1: A wafer is placed on an exposure stage that is movable along an exposure surface, and when the wafer is exposed by light irradiation from an exposure optical system, the exposure optical system of the placed wafer (W) is A detection means (4) for detecting a positional deviation from a reference position corresponding to the system (3) is provided, and when the wafer (W) is placed, the detection means (4)
When the wafer (W) detects the positional deviation, the exposure stage (1) is moved while being monitored by the detection means (4) to correct the position of the wafer (W), and then exposure is performed. exposure method. 2. An exposure stage (1) that is movable along the exposure surface and on which the wafer (W) is placed, and an exposure optical system that irradiates the wafer (W) on the exposure stage (1) with exposure light. system (3), and detection means (4) for detecting a positional deviation of the wafer (W) on the exposure stage (1) from a reference position corresponding to the exposure optical system (3). exposure equipment. 3. The detection means passes vertical light beams (7a to 7d) to a plurality of orientation flat portions and arcuate portions of the wafer periphery at the reference position, and detects light fluxes (7a to 7d) according to a shading distribution of the light beams (7a to 7d). The exposure apparatus according to claim 2, further comprising an optical sensor (4) that detects the positional deviation.