JPS61256636A - Reduction stepper - Google Patents

Abstract

PURPOSE:To automatically correct the variation of a magnification and distor tion of the image of each exposure range by providing a position measurement mechanism, a position alignment mechanism, a distance adjustment mechanism which changes a relative distance between an exposure mask and a reduction projection lens, and a controller which controls the operations of the respective mechanisms. CONSTITUTION:A distance adjustment mechanism 5 moves a mask-holding mechanism 4 in accordance with the instruction from a controller 9 and changes the relative distance between a mask 1 and a reduction projection lens 3 to correct magnification and distortion. A stage 8 which moves to the XY directions is provided directly under the contract projection lens 3 and its posi tion is measured by a stage position measurement mechanism 8a such as a laser interferometer which counts the magnitude of the movement of the stage 8. The position of a semiconductor substrate 2 is aligned by a position alignment mechanism 8b in such a manner that a laser beam from a laser tube 6 is applied to an alignment mark and the reflected light is detected by a light detection element 7 and the stage 8 is moved by the instruction from the controller 9.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a reduction projection exposure apparatus, and in particular to an apparatus that automatically corrects variations in magnification and image distortion for each exposure range (hereinafter referred to as distortion). The present invention relates to a reduction projection exposure apparatus that can be used.

[Conventional technology]

Conventionally, multiple reduction projection exposure systems have been used in the semiconductor device manufacturing process, and depending on the process, reflective exposure systems (mirror projection aligners) and contact exposure systems have been used to increase the number of sheets processed (throughput). (contact aligners) and reduction projection devices are also used together.

[Problem that the invention seeks to solve]

The conventional method described above has the following problems: (1) When multiple reduction projection exposure devices are used, there may be differences in distortion due to differences in the lens characteristics of the individual devices, or the magnification may change over time. There is also.

(2) When using a reflective batch exposure device, a contact exposure device, and a reduction projection exposure device, the exposure methods are different, so the alignment accuracy of the elements and the way the image is distorted are different, so alignment must be performed with high precision. However, the problem was that the superposition of images was not good (Fig. 3(a)).

The present invention provides an apparatus that solves the above problems.

[Means for solving problems]

The present invention measures the position of a stage for mounting a semiconductor substrate in a reduction projection exposure apparatus that exposes a photoresist coated on a semiconductor substrate by passing light that has passed through an exposure mask through a reduction projection lens and exposing the photoresist coated on the semiconductor substrate. A position measurement mechanism, an alignment mechanism that performs alignment using alignment marks attached to a semiconductor substrate on a stage, and a distance adjustment mechanism that changes the relative distance between the exposure mask and the reduction projection lens.

This reduction projection exposure apparatus is characterized by having a control section that controls the operation of each of these mechanisms.

〔Example〕

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

In FIG. 1, an exposure mask 1 is held by a mask holding mechanism 4. As shown in FIG. The mask holding mechanism 4 is equipped with a piezo element 5, and the piezo element (distance adjustment mechanism) 5 moves the mask holding mechanism 4 in the vertical direction in response to a command from the control unit 9, and the piezo element 5 moves the mask 1 and the reduced projection. By changing the relative distance to the lens 3, the 1 magnification and distortion are corrected. A stage 8 that moves in the XY directions is installed directly below the reduction projection lens 3, and the position of the stage 8 is measured by a stage position measuring mechanism 88 such as a laser interferometer that counts the amount of stage movement. As shown in FIG. 2, the semiconductor substrate 2 has alignment marks 10 at the four corners of the exposure area.
Use one with . The alignment of the semiconductor substrate 2 is as follows:
Radar light from the laser tube 6 is irradiated onto the mark 1O, a reflected signal thereof is received by the light receiving element 7, and the alignment mechanism 8b moves the stage 8 according to a command from the control section 9. 10 is a light source.

In the embodiment, when the first exposure is carried out using a reflection-type batch exposure device, there are positioning marks 10 in both the X and Y directions at the four corners of each exposure area of the reduction projection exposure device that performs the second exposure, as shown in FIG. Perform first exposure using a suitable exposure mask.

Next, using an exposure mask with alignment marks in both the X and Y directions at the four corners of the exposure area and performing second exposure on one sheet using a reduction projection exposure device, the image shown in Figure 3(b) is formed on the semiconductor substrate.
A superimposed image like this is created.

This semiconductor substrate is developed and set again in the reduction projection exposure apparatus of the present invention.

As shown in Fig. 1, a positioning mechanism 8b that moves the X and Y moving stage 8 and uses a laser to detect the signal output from the positioning mark with the light receiving element 7, a laser interferometer that accurately counts the amount of stage movement, etc. The mechanism 8a accurately measures the positions where the signals of the alignment marks 10 for first exposure and second exposure at the four corners of each exposure area are detected. The distortion and magnification of the first exposure and the second exposure differ for each exposure area as shown in FIG. 3(,). Since the amount of deviation of the positioning mark of the second exposure for each exposure area with respect to the 7th exposure is a relative distortion, it is measured for each exposure area and the relative distortion is stored in the control unit 9. .

Next, the magnification and distortion vary depending on the distance between the reduction projection lens 3 and the exposure mask 1. Based on the relative distortion data of each exposure area obtained from the first semiconductor substrate, the control unit 9 adjusts the distance between the exposure mask l and the reduction projection lens 3 according to an experimentally obtained function. This is changed using piezo elements 5 provided at the four corners of the mask holding mechanism 4, and the second and subsequent sheets are exposed so as to eliminate relative distortion.

In addition, considering that image distortion caused by a reduction projection exposure device is unlikely due to the narrow exposure area, it is possible to measure the distortion of the first exposure without performing a second exposure and development. By having a means to measure the relative distortion and vary the distance between the exposure mask and the projection lens for each chip so as to eliminate the relative distortion based on the measured value, it is possible to It can be used accurately with other types of exposure equipment, such as line exposure equipment, which have different distortions and arrangements of transferred images.
Furthermore, even if the magnification changes over time between reduction projectors of the same model, it can be automatically corrected. In addition, if dust gets between the exposure mask and the exposure mask holding mechanism, it will appear as if distortion has occurred, but even in this case, it can be automatically corrected, and defects in overlay exposure due to distortion or magnification deviation can be corrected. This has the effect of dramatically improving the yield.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of an embodiment of the present invention, Figure M2 is an explanatory diagram of an exposure mask used in a batch exposure device, and Figure 3 (
, ) are explanatory views when overlapping exposure is performed using the conventional method, and FIG. 3(b) is an explanatory view when overlapping exposure is performed using the present invention. 1... Exposure mask, 2... Semiconductor substrate, 3... Reduction projection lens, 4... Exposure mask holding mechanism, 5...
Piezo element, 6... laser tube, 7... light receiving element,
8...-xy moving stage, 8a... Stage position measurement mechanism, 8b... Positioning mechanism, 9... Control unit,
lO... Alignment mark. Figure 1 Figure 2 Procedure:? 1 Yama Seisho (Method) 1. Indication of the case Japanese Patent Application No. 60-98473 2, Name of the invention Reduction projection exposure device 3, Person making the amendment Relationship to the case Patent applicant Address 33-1 Shiba 5-chome, Minato-ku, Tokyo Name (42)
3) Representative of NEC Co., Ltd. Tadahiro Sekimoto 4, Agent address: 1-8 Kanda Sakuma-cho, Chiyoda-ku, Tokyo July 30, 1985 (shipment date) 5. Subject to amendment

Claims (1)

[Claims] (1) Position measurement to measure the position of the stage on which the semiconductor substrate is placed in a reduction projection exposure apparatus that exposes the photoresist on the semiconductor substrate by passing the light that has passed through the exposure mask through the reduction projection lens and exposing the photoresist on the semiconductor substrate. an alignment mechanism that performs alignment using alignment marks attached to a semiconductor substrate on a stage, a distance adjustment mechanism that changes the relative distance between the exposure mask and the reduction projection lens, and the operation of each of these mechanisms. 1. A reduction projection exposure apparatus, comprising: a control section that performs control.