JPH09180991A - Aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the superposing accuracy by providing means for parallel moving the optical axis of a light which passes through a mask. SOLUTION: The light of a mercury lamp radiated from a light source 1 is converted into parallel beams via a condenser lens 2, the beams pass through a reticle 3, and then the pattern on the reticle 3 is contraction projected on a wafer 8 on an X-Y stage 5 via a contraction projecting lens 4 to be exposed. In this case, a quartz plate 7 is disposed between the reticle 3 and the lens 4 so as to substantially intersect an optical axis 6. The angle formed between the plate 7 and the axis 6 is varied in the directions X and Y. When the beams enter the plate 7, the beams are refracted and emitted at the same angle as the incident angle, and hence the axis 6 can be parallel moved at a desired amount by varying the angle formed between the plate 7 and the axis 6. Thus, the superposing accuracy can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus for patterning semiconductor elements.

[0002]

2. Description of the Related Art FIG. 4 is a schematic diagram of a conventional general reduction projection exposure apparatus. Light such as g-line (wavelength 436 nm), i-line (365 nm), or KrF excimer laser light (248 nm) emitted from the light source 1 of the mercury lamp is collimated by the condenser lens 2 and passes through the reticle 3. After that, the pattern on the reticle 3 is reduced and projected by the reduction projection lens 4 onto the wafer 8 on the XY stage 5, and exposure is performed. The area exposed at one time is about 15 to 20 mm square, and by moving the XY stage 5, the exposure is repeated over the entire surface of the wafer having a diameter of 6 to 8 inches. A ball screw connected to the motor 11 is used to move the XY stage 5 at this time.

[0003]

In the reduction projection exposure apparatus, overlay accuracy is important together with resolution. Because if the overlay accuracy cannot be guaranteed,
This is because it is necessary to secure an extra overlay margin on the mask pattern, and eventually high integration of the device cannot be realized. Generally, the required overlay accuracy is about 1/5 of the resolution line width, for example, 0.25 μm.
For the line width of, an accuracy of about 0.05 μm is required. Of course, if the overlay accuracy is improved, it is possible to expect further high integration with the same minimum line width by reducing the overlay margin on the mask pattern.

In the reduction projection exposure apparatus of FIG. 4, the greatest factor that determines the overlay accuracy is the position control accuracy of the XY stage 5. This position control is performed by the XY stage 5
The position of the mirror 9 fixed above is measured by the laser interferometer 10, and then the motor 1
It is done mechanically with a ball screw connected to 1. At this time, as a general value, the resolution of the laser interferometer is about 0.01 μm, and the position control accuracy of the XY stage is about 0.05 μm. That is, although there is a margin in the position detection accuracy, there is a problem in that the overlay accuracy is governed by the mechanical position control accuracy of the XY stage. Thus, the limit is that the line width corresponds to 0.25 μm. Considering further miniaturization and high integration of elements in the future, further improvement in overlay accuracy is desired.

[0005]

In order to improve the overlay accuracy, the exposure apparatus of the present invention comprises means for moving the optical axis of light passing through the mask in parallel. As a means for moving the optical axis in parallel, a transparent flat plate arranged between the mask and the projection surface so as to intersect the optical axis substantially perpendicularly, and a mechanism for changing the angle formed by the transparent flat plate and the optical axis. It has and. Further, the mechanism for changing the angle formed by the transparent flat plate and the optical axis utilizes the displacement of the piezoelectric element arranged in contact with the transparent flat plate.

[0006]

1 is a schematic diagram of a reduction projection exposure apparatus according to the present invention. G of mercury lamp emitted from light source 1
Line (wavelength 436nm), i line (365nm) or K
Light such as rF excimer laser light (248 nm) is converted into parallel rays by the condenser lens 2 and, after passing through the reticle 3, the pattern on the reticle 3 is reduced by the reduction projection lens 4 onto the wafer 8 on the XY stage 5. Project and expose. The area exposed at one time is 15-2
Exposure is repeated over the entire surface of a wafer having a diameter of 6 to 8 inches by moving the XY stage 5 having a size of about 0 mm square. A ball screw connected to the motor 11 is used to move the XY stage 5 at this time.

What is characteristic here is that the quartz plate 7 is arranged between the reticle 3 and the reduction projection lens 4 so as to intersect with the optical axis 6 substantially perpendicularly. The angle formed by the quartz plate 7 and the optical axis 6 can be changed in the X direction and the Y direction. The light beam is refracted when it enters the quartz plate 7 and is emitted at the same angle as the incident angle. Therefore, by changing the angle between the quartz plate 7 and the optical axis 6,
Can be translated by a desired amount.

FIGS. 2A and 2B are schematic views for explaining a specific method for changing the angle formed by the quartz plate 7 and the optical axis 6, and FIG. 2A is a plan view. Figure, Figure 2 (b)
FIG. 3 is a sectional view taken along the line AA ′ of FIG. Quartz plate 7
Is four piezoelectric elements 1 arranged in contact with the four corners of the lower surface
The piezoelectric elements 121 to 121 are supported by the piezoelectric elements 121 to 124.
The support 124 is fixed to the inner wall 14 of the exposure apparatus by the support member 13. The piezoelectric elements 121 to 124 are adapted to be displaced in the vertical direction, that is, in the direction of pushing up the quartz plate 7 by applying a voltage. Therefore, for example, when it is desired to translate the optical axis in the X direction, the piezoelectric element 1 1
21 and the piezoelectric element 4 124 or the piezoelectric element 2 122
Then, the piezoelectric element 3123 may be displaced. Also,
When it is desired to translate the optical axis in the Y direction, the piezoelectric element 1
121 and the piezoelectric element 2 122 or the piezoelectric element 3 1
23 and the piezoelectric element 4124 may be displaced. Furthermore, by displacing each piezoelectric element by an appropriate amount, it is possible to move the optical axis in parallel in the X and Y directions simultaneously.

Next, the effect of the present invention will be estimated quantitatively. FIG. 3 shows the rotation angle θ of the quartz plate 7, the displacement amount k, when the quartz plate 7 is considered to rotate about the rotation axis Q,
It is a schematic diagram which shows the relationship between the parallel displacement amounts D of an optical axis. The actual required rotation angle is very small, but it is exaggerated in this figure for ease of explanation.

Here, T is the thickness of the quartz plate 7, n ₁ and n ₂
Where D is the refractive index of air and the refractive index of quartz plate 7 is D = T {(n ₂ −n ₁ ) / n ₂ } θ (1), and L is displaced from the rotation axis Q of quartz plate 7. Assuming the distance to the point, the approximate expression of k = Lθ (2) is established. Eliminating θ from equations (1) and (2),
When the parallel movement amount d of the projected image on the wafer is calculated with A as the reduction magnification, d = AD = A (T / L) {(n ₂ −n ₁ ) / n ₂ } k (3). For example, A = 1/5, T = 1 cm, L = 10c
If m, then d = 0.0062k (4) is obtained from the equation (3). By the way, from the equation (4), the parallel movement amount of the projected image equivalent to the resolution of the laser interferometer described above, that is, d
= 0.01 μm, k = 1.6 μm, which is a value that can be realized as the displacement amount of the piezoelectric element. As described above, according to the present invention, when the images are superposed, the displacement of the piezoelectric element is used to move the projected image, so that a mechanical control error does not occur and the superposition accuracy can be improved.

[0011]

As described above, in the exposure apparatus of the present invention, the transparent flat plate is arranged between the mask and the projection surface so as to intersect with the optical axis substantially perpendicularly, and the transparent flat plate and the optical axis form the same. By changing the angle and moving the projected images in parallel, the overlay accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an exposure apparatus of the present invention.

FIG. 2 is a schematic view showing a part of an exposure apparatus of the present invention.

FIG. 3 is a schematic view illustrating the principle of the present invention.

FIG. 4 is a schematic diagram showing a conventional exposure apparatus.

[Description of Reference Signs] 1 light source 2 condenser lens 3 reticle 4 reduction projection lens 5 XY stage 6 optical axis 7 quartz plate 8 wafer 9 mirror 10 laser interferometer 11 motors 121, 122, 123, 124 piezoelectric element 13 support material 14 Inner wall Q Quartz plate rotation axis θ Quartz plate rotation angle k Quartz plate displacement amount D Optical axis translation amount T Quartz plate thickness L Distance between quartz plate support point and displacement point

Claims (3)

[Claims] 1. An exposure apparatus for projecting a pattern on a mask onto a projection surface by light emitted from a light source, comprising means for translating an optical axis of the light passing through the mask. apparatus. 2. A transparent flat plate disposed between the mask and the projection plane so as to intersect the optical axis substantially perpendicularly, as a means for moving the optical axis in parallel, and the transparent flat plate and the optical axis. 2. The exposure apparatus according to claim 1, further comprising a mechanism for changing an angle formed by. 3. A mechanism for changing an angle formed by the transparent flat plate and the optical axis utilizes displacement of a piezoelectric element placed in contact with the transparent flat plate.
Exposure apparatus according to the above.