JPH05304078A - Focusing mechanism of exposure device - Google Patents

Abstract

PURPOSE:To enable exposure light to be more accurately focused even if the surface of a wafer is rugged. CONSTITUTION:A focusing mechanism is equipped with a light source 21, a light projecting lens 31, a detection lens 41, and a photodetector 51, where a diaphragm mechanism 91 which diminishes the spot of the projected light is provided in an optical path between a wafer 7 and the light projecting lens 31, and then a focusing operation is executed changing the spot of the projected light in size corresponding to the size of an exposure region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focusing mechanism in an exposure apparatus, and more particularly, when exposing on a semiconductor substrate,
The present invention relates to a focusing mechanism in an exposure apparatus that presets a focus of exposure to be transferred by irradiating light to which a photoresist is not sensitive.

[0002]

2. Description of the Related Art Generally, as a focusing method in an exposure apparatus, a method has been used in which light having a wavelength (500 nm to 800 nm) in a region where a photoresist is not exposed is used. The light source used for this focusing is a diode (LE that emits light in the infrared region).
D) is the best known.

Such a focusing mechanism has, for example, 1
It was mounted on a Nikon exposure apparatus (trade name NSR-1010G) that was commercially available in 981. Recently, a report using a He-Ne laser (wavelength 631 nm) as a light source has been reported to be SPIE Vo1.1264 Optical.
/ Laser Micro lithography
3, 1990, P244-251.

8 and 9 are views showing different states of a conventional focusing mechanism in different states. Conventionally, a focusing mechanism (hereinafter, simply referred to as a focusing mechanism) in an exposure apparatus of this type is an LED that irradiates a wafer 7 which is a semiconductor substrate mounted on a stage 8 as shown in FIGS. 8 and 9, for example. Light source unit 25 for generating light 65
And a projection lens system 35 for converting the LED light 65 into parallel rays
And a focusing device including a detection lens system 45 for capturing the laser light reflected from the wafer 7 and a light receiving section 55.

The operation of this focusing mechanism is as follows.
The LED light is emitted from the light source unit 25 in a state close to a point light source. The emitted LED light 65 passes through the light projecting lens system 35 and is corrected to parallel light having a circular cross section and a constant diameter. Then, in an oblique direction (about 4
The LED light which is emitted from the surface of the wafer 7 after being irradiated from an angle of 5 ° enters the detection lens system 45. The LED light that has passed through the detection lens system 45 is collected and collected by the light receiving unit 4.

Of course, in order to stabilize the relationship between the focal position of the transfer pattern light by the projection lens 5 and the position of this LED light spot, the light source unit 25, the light projecting lens system 35, the detecting lens system 45 and the light receiving unit 55 are provided. , And is securely fixed to a predetermined place in the exposure apparatus (around the projection lens 1).

Next, the focusing method will be described. First, the wafer 7 is irradiated with LED light, and the stage 8 is moved up and down so that the reflected light is captured by the light receiving unit 55, and the reflected light captured by the light receiving unit 55 is maximized. By deciding the position of the wafer 7 in this manner, the surface of the wafer 7 is brought into a state of being optimally focused on the surface of the wafer 7 as shown in FIG.
This state means that the LED illuminated on the wafer 7
This is because the focusing optical system is designed so that the center of the spot of the light substantially coincides with the center of the area to be exposed later. In other words, a mechanism is provided for vertically moving the stage 8 so that the wafer 8 moves up and down in order to adjust the surface of the wafer 7 to the optimum focus position.

On the other hand, the state where the surface of the wafer 7 is not at the optimum focus position is the state shown in FIG. In this state,
The height position of the surface of the wafer 7 is different from that shown in FIG. Therefore, the area of the surface of the wafer 7 irradiated with the laser light is different. Therefore, the optical path of the light passing through the detection lens system 45 is also different, and the light is projected on a portion different from the light receiving portion 55.

As described above, by driving the stage up and down, the optical path of the laser light reflected from the wafer surface passing through the detection lens system changes, so that the laser reflected from the wafer while the stage is driven up and down. The light signal intensity is highest at the position where the most light is captured by the light receiving unit, and this position is the optimum focus position. This method was a conventional focusing method using an optical method.

[0010]

Conventionally, the size of the exposure area to be transferred to the wafer surface in the exposure apparatus is different depending on the size of the semiconductor chip, whereas the LED light used for focusing is different. , Spot area (irradiation area)
Is always a constant size.

FIGS. 10A and 10B are sectional views showing a portion of the wafer for explaining the problems in the conventional focusing mechanism. Usually, the wafer undergoes various heat treatment processes up to the exposure step, so that it is locally affected by warpage, distortion, etc. due to thermal stress. Therefore, the surface of the wafer is not always flat and is often uneven. Therefore, for example, as shown in FIG. 10A, the exposure region 212 of the wafer 7 is larger than the focusing region (LED light irradiation region) 112, and the central portion of the exposure region is convex. ing. While driving the stage up and down in such an exposure area, the LED
When irradiating light and attempting to perform focusing, since the focusing area is small, the convex portion which is the central portion of the exposure area is focused so as to have an optimum focus position. However, there is a problem that the peripheral portion is deviated from the optimum focus position.

As another case, for example, FIG.
As shown in (b), the exposure region 213 is smaller than the focusing region 113, and a part of the focusing region is convex. Further, only the convex area is exposed. In such a case, it suffices that only the convex region is adjusted to the optimum focus position. However, since the focusing region is large, the LED light is also applied to the concave portion in the peripheral portion, and the focusing region is There is a problem that optimum focusing is performed at an average position corresponding to the unevenness of the entire wafer surface. These problems have become more and more serious as the effective focal range has become narrower with the recent increase in the numerical aperture of exposure apparatuses.

In view of the above problems, it is an object of the present invention to provide a focusing mechanism in an exposure apparatus that can perform optimal focusing even if the wafer surface in the transfer pattern light region has irregularities.

[0014]

A first focusing mechanism in an exposure apparatus according to the present invention is designed to collimate this light with a light source section for generating light having a wavelength in a region where a photoresist applied to a wafer is not exposed to light. In an exposure apparatus including a light projecting lens system that projects light onto the wafer surface, a detection lens system that collects and collects light reflected from the wafer surface, and a light receiving unit that detects the collected light The focusing mechanism includes a diaphragm mechanism that changes the size of the spot of the light in the optical path between the light source unit and the detection lens system.

The second focusing mechanism in the exposure apparatus of the present invention is characterized in that the diaphragm mechanism is variable in accordance with the size of the region for transferring the photomask pattern onto the wafer.

[0016]

The present invention will be described below with reference to the drawings. FIG. 1 is a view showing a first embodiment of the focusing mechanism of the present invention. This focusing mechanism is, as shown in FIG. 1, provided with a diaphragm mechanism 91 for narrowing the LED light 61 in the optical path between the light projecting lens system 31 and the irradiation surface of the wafer 7. Other than that, it is the same as that described in the conventional example. Further, the cross-sectional area of the spot light of the LED light passing through the light projecting lens system 31 is set to be larger than the maximum transfer area in one exposure area using the projection lens 1, and the light spot is a circle. And is corrected to parallel light having a constant diameter.

FIG. 2 is a diagram showing an outline of the diaphragm mechanism of FIG. As shown in FIG. 2, this diaphragm mechanism includes four blind plates 911, 912, 91 that move in the X and Y directions.
3 and 914. Of these, the two blind plates 911 and 912 are independently movable in the X direction. The remaining two blind plates 913 and 914
Has a mechanism that operates independently in the Y direction.

FIG. 3 is a sectional view of a wafer for explaining a focusing method when the focusing mechanism of the present invention is applied. Generally, the shape of the mask pattern region exposed on the wafer is a square or rectangular shape, although the size varies depending on the type of device. Therefore, as shown in FIG. 3, the diaphragm mechanism has a structure in which the four blind plates 911, 912, 913 and 914 can be moved in respective directions in accordance with the size of the exposure area 211 to be transferred onto the wafer. , The size of the focusing area 111 on the photoresist 10 of the wafer 7 is set to the exposure area 2
That is, the size is changed in accordance with the size of 11 so as to match.

FIG. 4 is a diagram showing a second embodiment of the focusing mechanism according to the present invention. In this focusing mechanism, as shown in FIG. 4, the diaphragm mechanism 92 is arranged in the optical path between the light source unit 22 and the light projecting lens system 32. Even if the diaphragm mechanism 92 is arranged in this way, the same effect as that of the above-described embodiment can be obtained.

Further, in the focusing mechanism in the above-mentioned embodiment, a little light is leaked due to the diffraction of the light from the blind plate, but in this embodiment, the light diffracted by the diaphragm mechanism is again projected by the light projecting lens. It is possible to correct parallel light in the system 32. That is, there is an advantage that the size of the focusing area on the wafer can be changed more faithfully in accordance with the size of the exposure area.

FIG. 5 is a view showing a third embodiment of the focusing mechanism in the present invention. This focusing mechanism is, as shown in FIG. 5, provided with a diaphragm mechanism 93 between the wafer 7 and the detection lens system 43. Other than that, it is the same as the above-mentioned embodiment. Further, the same effect can be obtained by providing this diaphragm mechanism between the detection lens system 43 and the light receiving section 53.

Although the present invention has been described with reference to some embodiments, these are applied to a focusing mechanism for optical autofocus in an exposure apparatus.
The focusing mechanism of the present invention can also be applied to a tip leveling mechanism.

FIG. 6 is a perspective view showing an example in which the focusing mechanism of the present invention is applied to a chip leveling mechanism, and FIG. 7 is shown in FIG.
FIG. 6 is a diagram showing a state in which a chip on a wafer is observed for explaining the operation of the chip leveling mechanism of FIG. This tip leveling mechanism, as shown in FIG.
This is a mechanism in which one of the three positions is fixed and the other two are driven vertically to obtain the level of the chip surface of the wafer 7.
And this focusing mechanism detects whether or not the level is set.

Next, the operation of this tip leveling mechanism will be described. First, the size of the aperture of the diaphragm mechanism 94 is adjusted according to the response of the chip area on the wafer. Next, the LED light 64 is generated from the light source unit 24 to irradiate the chip area of the wafer 7. At this time, the light reflected by the chip area of the wafer 7 is captured by the light receiving section 54. The reflected image at this time is, for example, as shown in FIG.
The image of the ED light is a region A in the visual field of the light receiving unit 54,
If the amount of light occupying B, C and A is equal, leveling has been performed correctly. When the focusing mechanism of the present invention is applied to this tip leveling mechanism,
In principle, it is not appropriate to provide a diaphragm mechanism in the optical path between the wafer and the light receiving section.

[0025]

As described above, according to the present invention, means for narrowing the irradiation light for focusing is provided in the optical path between the light source section and the semiconductor substrate or between the semiconductor substrate and the light receiving section to perform the focusing. By changing the size of the area according to the size of the exposure area on the semiconductor substrate, even if there are irregularities on the surface of the semiconductor substrate, the focus can be optimized for the surface condition of the exposure area. There is an effect that a focusing mechanism in an exposure apparatus that can be performed is obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a focusing mechanism of the present invention.

FIG. 2 is a diagram showing an outline of a diaphragm mechanism of FIG.

FIG. 3 is a sectional view of a wafer for explaining a focusing method when the focusing mechanism of the present invention is applied.

FIG. 4 is a diagram showing a second embodiment of the focusing mechanism in the present invention.

FIG. 5 is a diagram showing a third embodiment of the focusing mechanism in the present invention.

FIG. 6 is a perspective view showing an example in which the focusing mechanism of the present invention is applied to a chip leveling mechanism.

FIG. 7 is a diagram showing a state of observing a chip on a wafer for explaining the operation of the chip leveling mechanism of FIG.

8A and 8B are views showing different states for explaining an example of a conventional focusing mechanism.

9A to 9C are views showing different examples of a conventional focusing mechanism in different states.

FIG. 10 is a cross-sectional view showing a portion of a wafer for explaining problems in the conventional focusing mechanism.

[Explanation of symbols]

 1 Projection lens 21, 22, 23, 24, 25 Light source part 31, 32, 33, 34, 35 Projection lens system 41, 42, 43, 44, 45 Detection lens system 51, 52, 53, 54, 55 Light receiving part 61, 62, 63, 64, 65 LED light 7 Wafer 8 Stage 91, 92, 93, 94 Aperture mechanism 911, 912, 913, 914 Blind plate 10 Photoresist 111, 112, 113 Focusing area 211, 212, 213 Exposure region

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G03B 27/34 9017-2K G03F 7/207 H 9122-2H

Claims (2)

[Claims] 1. A light source unit for generating light having a wavelength in a region where a photoresist applied to a wafer is not exposed, a light projecting lens system for collimating the light and projecting the light on the wafer surface, and the wafer surface. In a focusing mechanism in an exposure apparatus, which includes a detection lens system that collects more reflected light and collects the collected light, and a light receiving unit that detects the collected light, an optical path between the light source unit and the detection lens system. A focusing mechanism in an exposure apparatus, comprising a diaphragm mechanism for changing the size of the light spot on the way. 2. The focusing mechanism in an exposure apparatus according to claim 1, wherein the diaphragm mechanism is variable in accordance with a size of a region for transferring a photomask pattern onto the wafer.