JPS58202449A - Reduce-projecting exposure device - Google Patents

Abstract

PURPOSE:To correct automatically a reducing magnification error, by measuring a mark on a substrate through a reduce-projecting lens and a reticle, operating the reducing magnification error, and moving slightly the reduce-projecting lens in the optical axis direction. CONSTITUTION:A pattern on a reticle 22 being an original picture is illuminated by condensing the illuminating light from a light source by a condensing lens 21, and is reduce-projected onto a substrate 24 through a reducing lens 23. The shaded portion in the figure shows a reference member of an immovable state. The substrate 24 is installed on a moving base constituted of a Z moving base 30 being movable in the optical axis direction and an XY moving base 31 being movable on the plane falling at a right angle with the optical axis, and is provided with an automatic focusing mechanism so that the substrate 24 face is always held at a focal position where an image is formed by the reducing lens 23. A relative position of the substrate 24 can be derived by an operating circuit 35 by measuring a position of the moving base by a laser measuring meter 39.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvement of a reduction projection exposure apparatus used in the process of creating semiconductor devices, and particularly in the production of high-precision semiconductor devices in which dimensional accuracy is strictly required in this type of device. The present invention relates to a means for fully automatically correcting the reduction ratio difference that occurs.

A conventional reduction projection exposure apparatus is based on an optical system whose principle configuration is shown in FIG. 3, and projects the pattern of an original image 42 onto a substrate 44 using a reduction lens 43. Distance between reduction lens 43 and substrate 44 tas reduction lens 43
and the distance Ib from the original image 42, as long as the refractive index distribution within the optical system is constant, the reduction factor m is m = a / b,
The focal length f is expressed as 1/f=1/a+1/b. In the conventional reduction projection exposure apparatus, since the distances a and b are fixed, the refractive index changes as the conditions of the medium in the optical path of the optical system from the original ui 42 to the substrate 44 change. When the distribution of changes, the above-mentioned distances a and b on the optical system change.
is a function of the refractive index, and as a result, the reduction @ m changes, which has the drawback of deteriorating the dimensional accuracy of the pattern projected onto the substrate 44. Therefore, the object of the present invention is to
This prevents deterioration of the absolute dimensional accuracy of the pattern reduced and projected from the original onto the substrate due to reduction magnification errors caused by changes in the refractive index distribution of the medium in the reduction projection optical system, and always
High f! It is an object of the present invention to provide a reduction projection exposure apparatus that makes it possible to automatically produce a semiconductor element having an absolute size of 111f.

In order to achieve all of the above objectives, the present invention measures marks on a substrate through a reduction projection lens and a reticle, calculates a reduction magnification error, and automatically reduces the marks by slightly moving the reduction projection lens in the optical axis direction. The present invention is characterized in that the reduction projection exposure apparatus is configured to correct magnification errors.

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

A pattern on a reticle 22, which is an original image, is illuminated by condensing illumination light from a light source (not shown) using a condenser lens 21, and is reduced and projected onto a substrate 24 through a reduction lens 23. The shaded portion in FIG. 2 is a fixed and immovable reference member.

The substrate 24 is installed on a movable stage composed of a Z movable stage 3o movable in the optical axis direction and an XY movable stage 31 movable within a plane perpendicular to the optical axis, and the focal position imaged by the reduction lens 23. To ensure that the 24th side of the board is always held,
An autofocus mechanism as shown in No. 18043 is provided. The relative position of the substrate 24 can be determined by measuring the position of the movable base with a laser length measuring meter 39 and using an arithmetic circuit 35.

The reduction lens 23 is supported by a guide member 32 relative to a reference member so as to be movable only in the optical axis direction, and can be moved slightly in the optical axis direction by a drive motor 33. The fine movement is, for example, measured by a differential coil 34. Lens vertical control circuit 3
He will be returned on 8th.

Here, regarding the method of measuring the reduction magnification, see Figure 1 (Hiron,
This will be explained using (b) and (C).

This reduction projection exposure bag vIt is composed of a condenser lens 1, a reticle 2, a reduction projection lens 3, a substrate 4, a first pattern detector 5, and a second pattern detector 6. A predetermined interval L (
A square light-transmissive window 7.8 is provided at a position separated by a distance (see FIG. 1(b)). FIG. 1(b) shows the window 7 mentioned above.
．． 8 shows an enlarged view of No. 8. Mark 9 on board 4
When viewed through the reduction lens 3 and the window 7t of the reticle 2, it becomes a mark 9', and when the substrate 4 is moved by a predetermined distance t and viewed from the window 8, it becomes a mark 9# (first (See figure (b)).

The position of the mark 9' in the window 7 of the pattern detector 5-piece reticle 2, and the pattern detector 6-piece reticle 2
The position of each mark 9'' within the window 8 of the reticle 2 can be measured, and the amount by which the relative distance between the two marks 9' and 9'' deviates compared to the distance between the windows 7 and 8 of the reticle 2 can be measured. ΔL
t-operation is possible.

Now, if the reduction magnification of the reduction projection optical system is m (m<1), and even though the mark on the board 4 has been moved by 9 spaces, it has shifted by ΔL so that 2 mL becomes 2 mL. Then, t=(
The following relationship is satisfied: m+Δm)(L+ΔL).

Reduce f1 by Δm! * m difference, which means that the optical system has reduced the image too much.

On the other hand, as shown in FIG. 1(C), in the reduction projection optical system, the distance between the reticle 2 and the reduction lens 3 is Δm.
, the mark 9f is larger as described above.
: When moved by t, the relationship t becomes ΔL/Δb-yb
- Marks 9' and 9# are shifted by ΔL.

Therefore, the relative distance between the reduction lens 3 and the reticle 2 is determined by the amount that satisfies the relationship Δb=ΔL−b/L from the positional deviation amount ΔL of the mark 9 detected by the 1% second pattern detector 5.6. If Δm is narrowed, the reduction magnification error Δm becomes zero. ΔL
When is a negative value, it is sufficient to increase the distance between the reduction lens 3 and the reticle 2 by Δm.

As an example, in the case of a 1/10 reduction projection exposure apparatus, m=0.1, f==49.2m a==
54.127m.

The values are b = 541.27m and t = 10sm. At this time, if there is a reduction magnification error as large as Δm=0.000001rlO-'%), the pattern of Lo = 100■ will change from Lo (m+Δm) to (1rO01μm
), resulting in a small dimensional error of 0.1 μm. When such a state is measured by the first and second pattern detectors 5.6, the length t=10wx is L+ΔL=t
/(m+Δm).

ΔL=1 μm is detected larger than l=100 m.

At this time, if the distance between the reduction lens 3 and the reticle 2 is narrowed by Δb=5.4 nm, the reduction magnification error will disappear.

As can be seen from the above description, by simply measuring the displacement amount ΔL of the mark 9 on the substrate 4 that has been moved by a predetermined amount t from the reticle 2 at a predetermined distance through the reduction lens 3, the reduction is 11! The r rate error is found, Δb=ΔL−b/
By finely adjusting the distance between the reduction lens 3 and the reticle 2 so as to satisfy the relationship L, the reduction magnification error can be corrected.

By the way, in the conventional reduction projection exposure apparatus, once the distance between the reticle 2 and the reduction lens 3 is accurately fixed, the reduction ratio does not change.

However, in recent years, with the increasing precision of semiconductor devices, in order to prevent matters from adhering to the original image, that is, the two sides of the reticle,
Reduction projection exposure apparatuses have been developed that operate by covering the reticle 2 with a cover glass or interposing a medium other than air between the reduction lens 3 and the substrate 4. In this way, when a medium other than air is interposed in the reduction projection optical system, as long as the refractive index and thickness of the medium remain constant, the difference in refractive index Although it is possible to correct the reduction magnification error, it is usually extremely difficult to maintain the refractive index and thickness of the medium constant, which results in a reduction magnification error.

Therefore, in the present invention, even if a medium with an arbitrary refractive index or thickness is present between the reduction exposure optical system as described above, the reduction magnification is always determined by using the pattern detector 5.6 as described above. The feature is that it allows errors to be detected and corrected.

The present invention will now be described in more detail by returning to the embodiment shown in FIG. The pattern detector 25 passes through the reticle 22 and the reduction lens 23, and detects the mark 29 on the substrate 24.
t is detected, the detection signal is sent to the detection circuit 37 and the calculation circuit 36, and the reduction lens 23 is slightly moved in the optical axis direction by the lens vertical control circuit 38 and a drive system such as the motor 33.

Although not shown, a medium having an arbitrary refractive index or thickness may be present anywhere between the reticle 22, the reduction lens 23, and the substrate 24, and the functions of the present invention can be utilized.

In the embodiment of the present invention, one mark 9 (29) on the substrate 4 (24) is moved by a predetermined distance t, and the position of the reticle 2 (22) relative to the windows 7 and 8 extending by L is measured. However, mark 9#- on board 4 (24)
It is also possible to detect patterns of two marks separated by a predetermined distance Vat at the same time. In addition, the pattern is detected at the same time, and the mark on the substrate 4 (24) is placed at the predetermined position of the two predetermined windows 7.8 without measuring the amount of deviation ΔL of the reticle 2 (22) with respect to the window 7.8. As an example of application, it may be possible to control the reduction lens 3 (23) by moving it downward by -E so that the angle 9 is aligned. Furthermore, the positions of the two windows 7.8 on the reticle 2 (22) may be any location as long as the predetermined distance 4L is known, and if the origins of the two pattern detectors 5.6 have good accuracy, The mark 9 on the substrate 4r24) may not be detected with respect to the window 7.8 on the reticle 2 (22), but may be detected with respect to the origin of the pattern detector 5.6.

In addition, even if the pattern detectors 5 and 6 do not have to be coated independently, one pattern detector can be moved a predetermined distance, or such functions and detection ranges can be integrated into one pattern detector. It is also possible to increase the number by 4.

In the embodiment of the present invention, the relative distance adjustment between the reduction lens 3 (23) and the reticle 2 (22) is performed by adjusting the relative distance between the reduction lens 3 (23) and the reticle 2 (22).
23), but since it is sufficient to adjust the relative distance t between the two,
23), it is also possible to achieve the objective by moving the reticle 2 (22) up and down using a known guide drive means that is movable only in the optical axis direction.

Note that by adjusting the reduction @ ratio, the distance a to the optimum focus position of the imaging plane changes, and the reduction magnification changes slightly accordingly, but normally the reduction lens 3 (23) is a telecentric imaging optical lens. Because of this, the reduction magnification error and defocus due to changes in distance a are slight. Therefore, when the medium changes, first, after focusing on the mark 9 (29) on the substrate 4 (24), the reduction magnification error is corrected by the method described above, and further, If correction for a highly fertile embryo is required, it is easy to think that it is sufficient to repeat the correction of the reduction magnification after focusing again. It is also possible to install all the pattern detectors on the attachment of the reticle, measure marks at predetermined intervals on the original reticle, and adjust the reduction magnification. If you think about it upside down, you can easily make an analogy.

According to the present invention, the reduction magnification error of the original pattern projected onto the substrate, which is caused by a change in the distance of the projection fog light optical system or the presence of a medium having an arbitrary refractive index or thickness, is detected. However, since it can be automatically corrected, it is possible to manufacture semiconductor elements with higher precision than conventional ones using the reduction projection exposure apparatus of the present invention.

[Brief explanation of drawings]

FIGS. 1(a), 1(b), and 1(C) are explanatory diagrams for explaining the present invention in detail. Figure (b) is a schematic diagram of the mark on the substrate seen from the window on the reticle, which is the original image, Figure (C) is a schematic diagram of the optical system for explaining the reduction magnification error, and Figure 2 is the reduction projection according to the present invention. A schematic configuration diagram of an embodiment of the exposure apparatus, and FIG. 3 is a diagram explaining the principle of the reduction projection optical system. 1.21... Condenser lens, 2, 22. 42...
・Reticle, 3.23.43... Reducing lens, 4°24.44... Board, 5, 6.25... Pattern detector, 7.8... Window, 9.9', 9 ", 29...
pattern, 30...2 moving base, 31...XY moving base, 32... guide member, 33... drive motor, 34...
...Differential coil, 35.36...Arithmetic circuit, 37...
・Detection circuit, 38...￥ 1 Item 2 Entrance vJ3 Continuation of figure 1 page 0 Inventor Tsuneo Terasawa 1-280 Higashikoigakubo, Kokubunji City, Hitachi, Ltd. Central Research Laboratory Inventor Sumio Hosaka Kokubunji Hitachi, Ltd. Central Research Laboratory, 1-280 Koigakubo, Ichihigashi

Claims (1)

[Claims] 1. A reduction lens for reducing and projecting the original pattern on the reticle onto the substrate, and a predetermined lens for detecting the position rIt of the predetermined pattern provided on the substrate through the reticle and the reduction lens. first and second pattern detectors installed with a distance apart; and a first pattern detector on the substrate when the first pattern detector detects the predetermined pattern provided on the substrate. and the second position of the substrate when detected by the second pattern detector.
a circuit for measuring and calculating the position of the first circuit on the substrate;
The reduction magnification difference of the original image pattern to be projected using the reduction lens is calculated based on the relative distance value calculated and determined from the position and the second position. Reduction projection exposure comprising a fine movement mechanism for slightly adjusting the relative distance between the position of the reduction lens and the position of the original image, and configured to automatically correct the reduction 5s error. Device.