JPH01164032A - Alignment device for semiconductor exposure device - Google Patents

Abstract

PURPOSE:To enable an accurate alignment to be made easily by locating an alignment system on the rear side of a substrate as well as providing an alignment mark on the surface of a substrate, and by detecting an alignment mark using light that penetrates a substrate and a sensitive material. CONSTITUTION:An image of a first alignment mark A' provided on an alignment substrate 3 by a projection lens 5 and a first alignment mark A provided on a mask 2 are observed at the same time by using a first alignment detector 7. A positional adjustment of the alignment substrate 3 in the horizontal plane is made using a substrate stage 6 so that both of them overlap. Next, this mark B is detected from the rear side of the substrate using a second alignment detector 8. The position of the alignment mark image produced on the receiving surface of a two-dimensional optoelectronic conversion element 12 is captured photo-electronically. Comparing the reference position stored with the position of the mark image captured at this point is made. The position of a substrate 4 is adjusted using the substrate stage 6 so that these match. Thus, the relationship of positions of the mask 1 and the substrate 4 is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is directed to the alignment of semiconductor exposure equipment used for photolithography, etc. when manufacturing semiconductor devices!
Regarding the ljL position.

[Prior art]

Conventionally, in semiconductor exposure equipment that projects and transfers a circuit pattern drawn on a mask onto a semiconductor substrate, alignment is used to align the two so that the circuit pattern is projected at the correct position on the semiconductor substrate. equipment is provided. In such an alignment device, the alignment mark on the mask and the alignment mark on the semiconductor substrate are imaged on the mask through a projection lens, and the relative positional relationship is determined from the degree of overlap. Determine the degree of consistency,
The location of the semiconductor substrate! 11! ! A method is used. However, this method had several problems as shown below.

(Since the alignment marks on the 115 plate are observed through the photosensitive material, if there is uneven application of the photosensitive material, alignment accuracy will be adversely affected.

(2) The alignment marks on the substrate are observed through a projection lens, but since this projection lens has chromatic aberration, the alignment marks are observed using light with the same wavelength as the light used for pattern transfer. Otherwise, the alignment mark will not be clearly detected and accuracy will be adversely affected.

(3) In order to avoid the problem in (2) above, when observing the alignment mark using light of the same wavelength as the light used for pattern transfer, some photosensitive materials applied to the substrate may not be sensitive to light of the wavelength used for pattern transfer. Because some materials have poor transmittance, it may not be possible to detect alignment marks even if you try to detect them.

Particularly, in apparatuses that perform pattern transfer using a laser as a light source, there are some in which the chromatic aberration of the projection lens is not corrected at all, making the above-mentioned problems even more serious.

In order to solve these problems, for example, there is a method described in JP-A-62-160722 Publication. In this method, an alignment mark is provided in advance on the back surface of the substrate, that is, the surface opposite to the surface to which the pattern is transferred, and an alignment optical system placed on the back surface side of the substrate detects the alignment mark provided on the back surface and performs alignment. It is something to do.

[Problem that the invention seeks to solve]

However, the above method requires a step for providing an alignment mark on the back surface of the substrate and a special device, which poses an obstacle to inexpensive pattern transfer. moreover,
Normally, a pattern is overwritten many times on a single substrate, and different equipment is used to transfer the pattern depending on the roughness of the overwritten pattern. Since alignment is performed using the alignment mark provided on the board, the relative positional relationship between the alignment mark provided on the back side of the board and the alignment mark provided on the front surface of the board is necessary to prevent pattern shift during overwriting. One problem is that they must be aligned very precisely, which is very difficult.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide an alignment device that can easily perform accurate alignment without being affected by the type of photosensitive material coated on a substrate, its coating unevenness, or the chromatic aberration of a projection lens.

c Means and operation for solving the problem] The alignment device according to the present invention observes the position of an alignment mark formed in advance on a substrate using an alignment optical system,
The relative positions of the substrate and the mask are adjusted so that the position of the detected alignment mark matches the reference position determined corresponding to the position of the mask, thereby matching the relative positions. In an alignment device for a semiconductor exposure device, the alignment mark is provided on the surface of the substrate, and the alignment optical system is arranged on the back side of the substrate, and the alignment mark is detected using light transmitted through the substrate and the photosensitive material. It is something.

That is, the alignment mark provided on the pattern transfer surface, which is the front surface of the substrate, is observed from the back side of the substrate by passing through the substrate using an alignment optical system.

Most of the substrates currently used are silicon crystals, which have a high transmittance for light with long wavelengths of 1 μm or more, such as infrared light, so it is possible to use such infrared light even from behind the substrate. For example, alignment marks on the substrate surface can be detected. Furthermore, since a photosensitive material sensitive to this infrared light is hardly used, there is no problem of the photosensitive material being exposed to light during alignment. Furthermore, since the alignment mark is provided on the surface of the substrate, it can be provided in the same process as a conventional alignment mark, and can be easily matched with a conventional transfer device.

〔Example〕

Hereinafter, the present invention will be described in detail based on an illustrated embodiment.

FIG. 1 shows a first embodiment, in which numeral 1 is a mask provided with a first alignment mark A in addition to the transfer pattern, and numeral 2 is a mask that emits light of a relatively short wavelength (for example, 450 nm or less). 1 is an exposure illumination device that illuminates 1; 3 is an alignment substrate on which a first alignment mark A' and a second alignment mark B' are provided without coating a photosensitive material; 4 is an alignment substrate with a photosensitive material on its surface; A semiconductor substrate 5 is coated with a second alignment mark B, and 5 is a mask 1 on a substrate 3 or a substrate 4 positioned in place of the substrate 3.
a projection lens that projects a pattern image drawn on the projection lens; 6 is a substrate stage that holds the substrate 3 or 4 on its surface and can move the substrate at least in a plane perpendicular to the optical axis of the projection lens 5 (in a horizontal plane); 7 is a first alignment detection device that is placed above the mask 1 and performs observation using light of the same wavelength (relatively short wavelength) as the light emitted by the exposure illumination device; 8 is the bottom side of the substrate stage 6; This is a second alignment detection device that is located at the center and performs observation using light with a relatively long wavelength.

Although the projection lens 5 has aberrations corrected for the wavelength of light emitted by the exposure illumination device, it is not necessary that the aberrations be corrected for light of other wavelengths. Further, the material used for the substrates 3 and 4 is, for example, silicon crystal, which has good transmittance for light with a relatively long wavelength. Also, the board 4
The photosensitive material coated on the fork is sensitive to light with a relatively short wavelength emitted by the exposure illumination device, but is insensitive to light with a relatively long wavelength. The substrate mounting portion (shaded portion) of the substrate stage 6 is made of a material such as synthetic quartz that has high transmittance at least to light with a relatively long wavelength.

Figure 2 shows a part of the substrate stage 6 and the substrate 3 placed on it.
(4) and the internal structure of the alignment detection device 8 are shown. 9 is an alignment illumination optical system, 10 is a beam splitter, 11 is an objective lens, and 12 is a two-dimensional photoelectric conversion element such as a so-called image sensor or a semiconductor device detector (PSD). The alignment illumination optical system 9 emits light having a relatively long wavelength (for example, 101,000 nm), which is reflected by the beam splitter 10, enters the objective lens 11, is condensed by the objective lens 11, and passes through the substrate stage 6 to the substrate. 3 (4) and illuminates the front surface.The image of the second alignment mark B' (, B) provided on the illuminated surface of the substrate 3 (4) is captured by the objective lens 1.
, 1 is captured through the substrate 3 (4) and the substrate stage 6, and the two-dimensional photoelectric conversion element 1 is captured through the beam splinter 10.
The image is formed on the light receiving surface of No. 2. The position of the alignment mark image on the light receiving surface is stored by appropriately processing the electric signal output from the photoelectric conversion element 12 using a computer or the like (not shown).

Now, in many cases, pattern transfer (exposure) is performed by overlapping different patterns over and over again on the same area on the substrate 4, so it is necessary to align the relative positions of the mask 1 and the substrate 4 before exposure. Generally speaking, this alignment consists of two steps.

First, the first step is a step of determining a reference position to be used in the second step based on the first alignment mark A provided on the mask 1.

The second step is a step of adjusting the position of the substrate 4 in the horizontal plane (the position in the plane perpendicular to the optical axis of the projection lens) according to the reference position determined in the first step.

The second step is performed every time before each exposure, but the first step may be performed intermittently as necessary, i.e.
If the entire device is relatively stable and the reference position changes little over time, then the first step does not need to be performed frequently; if not, it must be performed accordingly, as described below. The contents of the first and second steps will be explained.

First Step First, the alignment substrate 3 whose surface is not coated with a photosensitive material or the like is loaded onto the substrate stage 6. Then, using the first alignment detection value M7, the image of the first alignment mark A' provided on the alignment substrate 3 formed on the mask 2 by the projection lens 5 and the first alignment mark provided on the mask 2 is determined. The mark A is observed at the same time, and the position of the alignment substrate 3 in the horizontal plane is adjusted using the substrate stage 6 so that both marks overlap.
Since light with a relatively short wavelength is used, the aberration of the projection lens 2 is in good condition, and the image of the first alignment mark A' on the alignment substrate 3 is also the same as the first alignment mark A on the mask 1. It can be observed clearly as well. As a result, the first alignment detection device 7 can be used as a zero-order alignment base whose position in the horizontal plane is adjusted in this way, which allows the position of the substrate to be adjusted with high precision even when using a conventionally well-used method. [The second alignment mark B' on 3 is now observed by the second alignment detection device 8. For this observation, light with a relatively long wavelength (for example, 1000n*) is used, and the alignment substrate 3
Since the second alignment mark B' provided on the front surface of the substrate is observed from the back side of the substrate 3, the transmittance of the substrate 3 and the substrate stage 6 is good because it uses light with a long wavelength. It becomes possible to observe from Then, the position of the second alignment mark B' observed in this way is photoelectrically captured on the light receiving surface of the two-dimensional photoelectric conversion element 12,
The first step is 0 or more, which is stored as a reference position by a computer or the like.

Second Step First, the substrate 4 on which a photosensitive material or the like is applied and on which the mask pattern is to be actually transferred is loaded onto the substrate stage 6. As described above, the second alignment mark B is provided on the substrate surface of this substrate 4 similarly to the substrate 3. Then, as in the first step, the mark B is detected from the back side of the substrate using the second alignment detection device 11!8. Then, the position of the alignment mark image formed on the light-receiving surface of the two-dimensional photoelectric conversion element 12 is captured photoelectrically. The second step is 0 or more, in which the comparison is made and the position of the substrate 4 is adjusted using the substrate stage 6 so that the comparisons match.

Thus, by performing the first step and the second step, the relative positional relationship between the mask l and the substrate 4 is adjusted (aligned), but the alignment mark is not provided on the substrate surface. Since the alignment marks can be formed in the same process as conventional alignment marks2, matching with conventional transfer equipment is also good.Also, since the alignment marks are observed from the back side of the substrate, it is possible to check the type of photosensitive material and its coating unevenness. Also, it is not affected by chromatic aberration of the projection lens, so accurate alignment can be easily performed.

In this embodiment, independent alignment marks A' and B' are provided on the alignment substrate 3 for the first alignment detection device 7 and the second alignment detection device 8, respectively. This is preferable in that a mark that matches the characteristics of the detection device can be used, but
If you don't care about this, you can set the mark for the rain detection device to - and one.

FIG. 3 shows a second embodiment. Compared to the first embodiment, this embodiment has a structure in which the first alignment detection device 7 is not provided, the alignment substrate 3 is not provided, and the substrate mounting portion (shaded portion) of the substrate stage 6 is relatively large. The alignment detection device 1 is made of a material that has high transmittance not only for long wavelength light but also for short wavelength light, and the optical system is an achromatic optical system instead of the alignment detection device 8.
The difference is that 3 is used. The alignment procedure in this embodiment is also performed in two steps, and the role of each step is the same as in the previous embodiment. In particular, regarding the second step, the alignment detection device 13 performs exactly the function that was performed by the second alignment detection device 8 in the previous embodiment, and the contents are also the same as in the previous embodiment. However, although the first step has the same role of determining the reference position, the method is different, and this will be explained below.

First, the first alignment mark A provided on the mask 1 is illuminated by the exposure illumination device 2, and a clear image A1 of the alignment mark is created in the air by the projection lens 5 (
At this time, the board 4 has not been loaded yet). This image is observed using the alignment detection device 13 to determine the reference position. That is, alignment detection device 1
3 has basically the same configuration as that shown in FIG. The design must also minimize aberrations when observing the substrate surface using light with a long target wavelength. In addition to correcting chromatic aberration, such aberrations of the objective lens 11 are corrected on the one hand, and because observation is performed through the substrate 4 on the one hand and without the substrate 4 on the other hand, the difference in ball recovery occurring at the substrate 4 is corrected on the one hand, and on the other hand. If this is difficult, the transmittance must be sufficient for light with a relatively short wavelength, such that spherical aberration equivalent to the spherical aberration that occurs in the substrate 4 occurs only during the first step. A plane-parallel plate made of a material with good properties (for example, synthetic quartz) may be inserted between the objective lens 11 and the projection lens 5.

〔Effect of the invention〕

As mentioned above, the alignment device for semiconductor exposure equipment according to the present invention has practical importance in that it can easily perform accurate alignment without being affected by the type of photosensitive material coated on the substrate, its coating unevenness, or the chromatic aberration of the projection lens. It has many advantages.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a first embodiment of the alignment device according to the present invention, FIG. 2 is a diagram showing a part of the substrate stage, a part of the substrate, and the internal structure of the alignment detection device of the first embodiment. The figure is a schematic diagram of the second embodiment. 1...Mask, 2...Lighting device for exposure, 3...
... Alignment substrate, 4... Semiconductor substrate, 5.
...Projection lens, 6...Substrate stage, 7...
- First alignment detection device, 8... Second alignment detection device, 9... Alignment illumination optical system, 10... Beam splitter, 11... Objective lens, 12... ...Two-dimensional photoelectric conversion element, 13...
Alignment detection device. Figure 2? 3 0-13 Figure! 4

Claims (1)

[Claims] The position of the alignment mark formed in advance on the substrate is observed by an alignment optical system, and the relative position of the substrate and mask is determined so that the position of the alignment mark matches a reference position determined corresponding to the position of the mask. In an alignment apparatus for a semiconductor exposure apparatus, the alignment mark is provided on the surface of the substrate, the alignment optical system is arranged on the back side of the substrate, and the alignment mark is provided on the surface of the substrate, and the alignment optical system is arranged on the back side of the substrate. An alignment device characterized in that the alignment mark is detected using light that passes through the alignment mark.