JPS6340316A - Device for manufacturing semiconductor - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to semiconductor manufacturing equipment, and in particular, to semiconductor manufacturing equipment that reduces a pattern onto a wafer and performs projection exposure using a step-and-repeat method for manufacturing VLSIs. Related to semiconductor manufacturing equipment.

[Prior Art] As LSIs become smaller, it is increasingly necessary to improve resolution and overlay accuracy in lithography processes. For this reason, a technique for directly exposing a wafer by step ψ and repeating has been developed for manufacturing VLSIs and the like.

This method is a method in which one IC mask pattern is projected onto a wafer at a certain reduction ratio, and then exposed repeatedly to arrange it on the entire wafer.

Next, wafer alignment (global alignment) in this method will be explained.

In this global alignment, the wafer is previously fixed at approximately a predetermined position on the stage. Next, alignment is performed using a microscope. Here, a mark is fixed inside the microscope used, and the mark of this microscope and the mark on the wafer are aligned. Next, positioning is performed in the rotational direction, and then positioning is performed in the X-Y direction. The stage moves during positioning 1. The amount is measured using a laser length measuring device and stored in the computer. Once the alignment is complete, move the stage to the exposure position and press X.

Expose while moving in the Y direction.

However, when exposure is performed after performing 14 alignments as described above, although the throughput (throughput per time) is large, there is a problem in that sufficient overlay accuracy cannot be obtained. For this reason, a method of performing more accurate positioning after global alignment was adopted. This alignment method is called the LSA (laser step alignment) method. This LS
The configuration for performing method A is shown in FIG. 2, and the principle of alignment is shown in FIGS. 3 and 4.

Next, with reference to FIGS. 2 to 4, alignment using the LSA method will be described in detail. A laser beam from a laser emitting device 1 is converted into a laser beam having an oval cross section by a lens system 2. This laser light is projected onto a wafer 10 via a half mirror 3, a mirror 4, and a projection lens 5.

This state is shown in FIG. Here, the projection lens 5 is also a lens used for exposure. Note that a reticle (mask) 9 on which a pattern is formed is mounted on the projection lens 5.

On the wafer 10, an alignment mark 11 consisting of seven segments as shown in FIG. 3 is provided. Each segment is, for example, a square with a side of 4 μm, and the interval P between each segment is, for example, 8 μm.

Further, a resist 12 is coated on the wafer 10. When the stage 13 moves and the alignment mark 11 moves in the direction of arrow A in FIG. 3, and the laser beam spot 21 irradiates the alignment mark 11, diffracted light is generated. This diffracted light passes through the same optical path as described above and is guided to the spatial filter 6. The spatial filter 6 cuts only the 0th order diffracted light. The remaining diffracted light is received by the light receiving element 7 and amplified by the amplifier 8. In this way, as the stage 13 moves, a signal with a waveform as shown in FIG. 4 is obtained. Therefore, by storing the coordinates of the position where such a waveform is obtained in a memory (not shown) and moving the stage 13 based on these coordinates for each exposure, for example, exposure can be performed with high precision.

[Problems to be Solved by the Invention] However, a portion of the reflected light from the alignment mark area is reflected at the interface between the resist 12 and the outside world, as shown in FIG. In particular, when the film thickness of the resist 12 becomes an integral multiple of the wavelength of the laser beam, a standing wave is generated due to interference.
Since the amount of reflected light is reduced, a clear diffraction pattern cannot be obtained and alignment becomes difficult.

In order to avoid such problems, conventional methods have been to increase the amount of reflected light by changing the resist film thickness, but since there is an optimal resist film thickness from the viewpoint of resolution, It is not preferable to change the thickness of the resist.

Therefore, the main object of the present invention is to provide a semiconductor manufacturing apparatus that performs reduction projection exposure in which strong reflected light can be obtained without changing the thickness of the resist film.

[Means for Solving the Problems] A semiconductor manufacturing apparatus according to the present invention comprises a laser light emitting means so as to be able to change the wavelength of the laser light,
A sufficient amount of reflected light can be obtained from the alignment mark area on the wafer.

[Function] The laser light emitting means of the present invention can irradiate the alignment mark on the wafer with laser light of a wavelength suitable for the resist film thickness, so that a sufficient amount of reflected light can be obtained.
High positional accuracy can be maintained regardless of the resist film thickness.

Embodiment FIG. 1 is a diagram showing a semiconductor manufacturing apparatus for performing reduction projection exposure according to an embodiment of the present invention. The semiconductor manufacturing equipment shown in FIG. 1 has the following features compared to the conventional semiconductor manufacturing equipment shown in FIG.
Since they have the same configuration except for the laser light emitting device 14 and the wavelength setting section 15, the same reference numbers are given to the same parts and the explanation thereof will be omitted. The laser light emitting device 14 can emit laser light of a set wavelength based on the settings of the wavelength setting section 15.

In FIG. 1, a laser beam emitted from a laser beam emitting device 14 is transmitted through a lens system 2. The light passes through the half mirror 3° mirror 4 and the projection lens 5, is reflected by the alignment mark 11 on the wafer 10, passes through the spatial filter 6 through the same optical path as the incident light, and is received by the light receiving element 7. .

On the other hand, some of the light reflected from the wafer 10 is reflected from the cyst 12.
The light is reflected at the interface between the light and the outside world and returns to the wafer 10 side. At this time, when the film thickness of the resist 12 becomes an integral multiple of the wavelength of the laser beam, this reflected light is attenuated while reflecting randomly at the interface between the upper surface of the wafer 10, the resist 12, and the outside world. The intensity becomes extremely low and the diffraction pattern becomes unclear. At this time, if the wavelength of the laser beam is changed by a command from the wavelength setting section 15, interference will be eliminated and a sufficient amount of reflected light will be obtained.

In the above embodiment, the wavelength setting section 15 is provided and the wavelength is changed based on instructions from the wavelength setting section 15, but the invention is not limited to this. For example, when the output of the light receiving element 7 is insufficient. In this case, the wavelength may be changed automatically.

In the above embodiment, a reduction projection exposure apparatus has been described, but the method of obtaining a sufficient amount of reflected light by changing the wavelength can also be applied to an apparatus having a similar optical system and produces almost the same effect.

[Effects of the Invention] As described above, according to the present invention, since the wavelength of the laser beam is made variable, it is possible to prevent the attenuation of the reflected light intensity due to interference, so that it is possible to always obtain a sufficient reflected light intensity. can. Therefore, the film thickness of the resist can be made optimal for resolution.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a semiconductor manufacturing apparatus for performing reduction projection exposure according to an embodiment of the present invention. FIG. 2 is a diagram showing a conventional semiconductor manufacturing apparatus. FIG. 3 is a diagram showing the relationship between alignment marks and laser beam spots. FIG. 4 is a diagram showing a diffraction pattern of reflected light. FIG. 5 is a diagram showing the state of reflected light. In the figure, 2 is a lens system, 3 is a half mirror, 14 is a mirror, 5 is a projection lens, 6 is a spatial filter, 7 is a light receiving element, 8 is an amplifier, 9 is a reticle,
10 is a wafer, 11 is an alignment mark, 12 is a resist, 13 is a stage, 14 is a wavelength variable laser light emitting device, and 15 is a wavelength setting section. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Figure 1 2: Lens thread 9 Nilletia 1 and 3:
7 mph”

Claims (1)

[Claims] Laser light emitting means for emitting laser light; and a wafer for mounting a wafer on which uneven alignment marks are formed and a resist is coated on an exposed surface including the alignment marks. a movable wafer support; a lens system for irradiating the wafer placed on the wafer support with a laser beam emitted by the laser beam emitting means; and a lens system for irradiating the wafer placed on the wafer support; and a light receiving means for receiving diffracted reflected light from the alignment mark forming area when the alignment mark on the wafer is irradiated, and performs alignment based on the output of the light receiving means and determines the exposure position. 1. A semiconductor manufacturing apparatus that performs reduction projection exposure after determining , wherein the laser light emitting means is capable of changing the wavelength of the emitted laser light.