JPH07211632A - Exposure equipment - Google Patents

Abstract

(57) [Abstract] [Purpose] After correcting the tilt of the semiconductor wafer, the flatness of the upper surface of the semiconductor wafer is followed, and the exposure is performed while automatically focusing during the exposure. Provided is an exposure apparatus capable of performing exposure with a precise focus even when the flatness is poor or during exposure. A semiconductor wafer moving means 10, a detecting means 19 for detecting a distance to the upper surface of the semiconductor wafer, and driving means 13a, 14a, 1 for correcting the inclination of the upper surface of the semiconductor wafer.
7 and means (10, 19, 22, 17) for exposing while automatically focusing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the field of an exposure method in which an original pattern is step-and-repeated on the upper surface of a semiconductor wafer and is reduced and projected by a reduction lens.

[0002]

2. Description of the Related Art Conventionally, as an exposure method in the above field, the method described in JP-A-52-55472 is known.

This conventional technique is as follows: (1) 4 arranged in a square around the lens on a plane perpendicular to the optical axis of the lens.
Detects four signals according to the distance between the openings of the two air sensors and the upper surface of the semiconductor wafer immediately below these openings,
(2) Using one output value resulting from the sum of the four signals from the air sensor and (3) two output values resulting from the difference in the signals from the two apertures at diagonal positions, respectively, (4) Focusing and tilt adjustment were performed at the same time.

This air sensor has four openings 10 in the optical assembly around the reduction lens, as shown in FIG.
The distances between 1, 102, 103, 104 and the upper surface of the semiconductor wafer immediately below these openings are simultaneously detected. Then, by using the detection signals from the four openings simultaneously measured from the air sensor, by the so-called zero point method,
Feedback is provided to a drive mechanism that adjusts the tilt of the sample holder to correct the tilt of the upper surface of the semiconductor wafer and focus is performed.

In short, according to the conventional method of exposing the upper surface of the semiconductor wafer, the semiconductor device is provided with four openings in the optical assembly so that the distances to the four measurement points to be measured at the same time become a predetermined value. The exposure is performed by correcting the inclination of the upper surface of the wafer for each exposure.

[0006]

SUMMARY OF THE INVENTION In this conventional technique,
As shown in FIG. 1, the air sensor openings 101, 102,
103 and 104 are outside the reduction lens 100. The diameter of the image forming surface of the reduction lens is smaller than that of the reduction lens because it is an image forming optical system. Therefore, the four locations on the upper surface of the semiconductor wafer where the four openings face each other are the four locations on the outer periphery that surround the exposed area on the upper surface of the semiconductor wafer having the same size as the image plane of the reduction lens.

Therefore, as shown in FIG. 2A, when the flatness of the upper surface of the semiconductor wafer is good, the exposed area and the image plane of the reduction lens can be made to coincide with each other.
When unevenness is present on the upper surface of the semiconductor wafer as shown in (b) and the flatness is poor, in order to correct the inclination of the upper surface of the semiconductor wafer by measuring the distance at four locations outside the exposed area, It is not possible to detect the position of a certain exposed area. Therefore, even if the upper surface of the semiconductor wafer and the image forming surface of the reduction lens can be made substantially parallel to each other by the signals from the four detected positions, if the exposed region has uneven portions,
It has been discovered that there are cases in which the upper surface of the semiconductor wafer and the image plane of the reduction lens cannot be made to coincide with each other, and the required resolution cannot often be obtained.

The problem to be solved by the present invention is to detect the distance to the upper surface of the semiconductor wafer just below the image plane of the reduction lens in the above field.

[0009]

In order to solve the above-mentioned problems, the present invention has been devised in the above-mentioned field in at least three different positions on the upper surface of a semiconductor wafer, from the image-forming surface immediately below the image-forming surface of the reduction lens to the upper surface of the semiconductor wafer. The detecting means for detecting the deviation to the exposed region of the semiconductor wafer, the deviation is detected, and the table for mounting the semiconductor wafer in the optical axis direction of the reduction lens is set so that the deviation becomes zero. A step of correcting the inclination of the upper surface of the semiconductor wafer by using driving means corresponding to at least three positions, and thereafter, moving the upper surface of the semiconductor wafer in the optical axis direction by using the detecting means;
And a step of successively exposing the original image pattern while holding the exposed area on the upper surface of the semiconductor wafer on the image forming surface of the reduction lens.

[0010]

In the above technical means, since the detecting means for detecting the deviation from the image forming surface of the reducing lens to the exposed area on the upper surface of the semiconductor wafer is provided immediately below the image forming surface of the reducing lens, the reducing lens is used. It is possible to detect the distance to the upper surface of the semiconductor wafer just below the image forming plane.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a schematic view of the apparatus according to this embodiment.
1 is a schematic view of a reduction projection exposure apparatus capable of performing a method of detecting and correcting the tilt of the upper surface of a semiconductor wafer by using one detector provided in a reduction lens, focusing, and exposing the upper surface of the semiconductor wafer. is there. The reduction lens 18 has an optical axis 18
a is provided so as to be perpendicular to the surface of the base plate 11, that is, the moving guide surface 11a of the stage 10, and the lower end of the reduction lens 18 is aligned with the upper surface of the semiconductor wafer to the image plane of the reduction lens, that is, focusing. 1 for detecting the distance to the upper surface of the semiconductor wafer in order to perform
9 is attached. The semiconductor wafer 3 is a semiconductor wafer stage 6
Placed on top. The semiconductor wafer table 6 has a first support mechanism 7
Is provided on the moving table 8 so that the inclination of the upper surface of the semiconductor wafer can be finely adjusted, and the moving table 8 is provided on the stage 10 so that it can be finely moved in the vertical direction by the second support mechanism 9. Further, the stage 10 is configured to be movable back and forth and left and right on the base plate 11 by a moving mechanism (not shown).

The first support mechanism 7 has fulcrums 12, 14, and 13 attached to the three points A, B, and C on the movable table 8 which are substantially point-symmetrical, as shown in the movable table 8 in FIG. Have.
Of these, the fulcrum 12 is a fixed fulcrum, and the other fulcrums 13 and 1
The tip of 4 can be finely moved up and down by drive mechanisms 13a and 14a, respectively. The inclination of the surface of the semiconductor wafer table 6 can be finely adjusted by changing the height of these fulcrums 12, 13, and 14. The second support mechanism 9 is composed of a wedge plate 15 attached to the back surface of the movable table 8 and a wedge plate 16 provided on the stage 10 so as to be movable in the left-right direction. The moving table 8 has a structure that can be appropriately moved only in the vertical direction by a guide (not shown).
By moving the wedge plate 16 in the left-right direction by the drive mechanism 17, the moving table 8 can be finely moved up and down.

A detection signal corresponding to the deviation from the image plane of the reduction lens to the upper surface of the semiconductor wafer is applied from the detector 19 to the discrimination circuit 20 and a predetermined value (focal length of the reduction lens 18, that is, reduction serving as a reference plane). (Value corresponding to the position of the image plane of the lens), a signal corresponding to the deviation is applied from the discrimination circuit 20 to the amplifier 21. Further, the signal is amplified and added to the switching circuit 22, and is distributed to the driving mechanism 13a, 14a, or 17 by switching, and a driving motor built in each (not shown).
Is driven.

Next, using the image forming surface of the reduction lens as a reference plane, the detector for detecting the deviation from the image formation surface of the reduction lens to the upper surface of the semiconductor wafer in the exposed area is used to form the image formation of the reduction lens. If the deviation between the surface and the exposed region is detected and the inclination of the upper surface of the semiconductor wafer is corrected so that the deviation becomes a predetermined value at at least three different positions on the upper surface of the semiconductor wafer, at least three different positions on the upper surface of the semiconductor wafer. Now, the procedure of a correction method in which the upper surface of the semiconductor wafer is substantially parallel to the image plane of the reduction lens will be described.

The semiconductor wafer 3 is placed on the semiconductor wafer base 6 by a transfer mechanism (not shown), and the stage 10 is mounted on the base plate 1.
The position A of the fulcrum 12 on the moving table is positioned directly below the detector 19. Here, the switching circuit 22 is switched to the motor of the driving mechanism 17, and it corresponds to the output of the amplifier 21, that is, the distance from the detector above the fulcrum 12 to the upper surface of the semiconductor wafer, that is, the deviation from the image plane of the reduction lens. The output is added to the drive mechanism 17, and the wedge plate 1
6 moves horizontally to finely move the semiconductor wafer stage up and down, and the point A on the upper surface of the semiconductor wafer comes to the focal position of the reduction lens.

Next, the switching circuit 22 is switched to the motor of the driving mechanism 13a, and the stage 10 is moved to position the position C of the fulcrum 13 just below the detector on the optical axis 18a of the reduction lens. In this state, the drive mechanism 13a is operated to adjust the point C on the upper surface of the semiconductor wafer to the focal position.

Further, the switching circuit 22 is switched to the motor of the driving mechanism 14a, the stage 10 is moved, and the point B on the moving table is positioned directly below the detector of the optical axis 18a of the reduction lens to perform focusing. The point B on the upper surface of the wafer is adjusted to the focal position.

As a result, the three exposed regions on the upper surface of the semiconductor wafer coincide with the image plane of the reduction lens which is the reference surface, so that the three exposed regions on the upper surface of the semiconductor wafer are the light of the reduction lens. The inclination of the upper surface of the semiconductor wafer is corrected so as to be orthogonal to the axis 18a.

Next, the circuit 22 is switched to the motor of the drive mechanism 17, the distance detection signal sent from the detector 19 is applied to the discrimination circuit 20, and the signal corresponding to the deviation of the predetermined value is amplified and applied to the switching circuit 22. The motor of the drive mechanism 17 is driven to move the upper surface of the semiconductor wafer in the optical axis direction of the reduction lens, thereby automatically keeping the upper surface of the semiconductor wafer and the image plane of the reduction lens substantially parallel to each other, It is possible to perform exposure while holding the exposed area of the image at the focal position.

That is, the circuit pattern is formed on the upper surface of the semiconductor wafer while step-and-repeat moving the stage 10 so that the image forming surface of the reduction lens and the exposed region on the upper surface of the semiconductor wafer are always aligned with each other. The exposure can be done at the stop of the step and repeat. The drive mechanisms 13a, 14a, and 17 can be fixed by using ordinary holding means such as short-circuiting the motor circuit when the motor is not connected to the amplifier 21.

[0022]

In order to solve the same technical problem as the present invention, from at least three different positions on the upper surface of the semiconductor wafer, from the image forming surface immediately below the image forming surface of the reduction lens to the exposed region on the upper surface of the semiconductor wafer. Using the detection means to detect the deviation of
Detecting the deviation, and moving each of the mounts for mounting the semiconductor wafer in the optical axis direction of the reduction lens by using driving means corresponding to at least the three positions so that the deviation becomes zero. Even if the technical means of providing only the step of correcting the inclination of the upper surface of the wafer is taken, the technical problem of the present invention can be solved as described in the section of the above action. However, in the present invention, not only this step but also the detection means is used to move the upper surface of the semiconductor wafer in the optical axis direction to hold the exposed region of the upper surface of the semiconductor wafer on the image forming surface of the reduction lens. While
Since the technical means of providing the step of sequentially exposing the original image pattern is taken, as compared with the case of taking the technical means of providing only the first step as described above, the upper surface of the semiconductor wafer is There is more than a supplement to the negative side of the increase in the number of steps by adding the second step of further improving the degree of coincidence of the exposed area on the upper surface of the semiconductor wafer with the image plane of the reduction lens by moving in the optical axis direction. Brings advantages.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an air sensor of a leveling device used in an exposure method in a conventional technique for adjusting the inclination of the upper surface of a semiconductor wafer.

FIG. 2 is a sectional view illustrating a problem in the conventional technique.

FIG. 3 is a configuration diagram for explaining an embodiment of the present invention.

FIG. 4 is an explanatory view showing three points on a moving table.

[Explanation of symbols]

3 ... Semiconductor wafer, 6 ... Semiconductor wafer base, 7 ... First support mechanism, 8 ... Moving base, 9 ... Second support mechanism, 10 ... Stage, 11 ... Base plate, 12, 13, 14 ... Support point, 13a ，
14a ... Driving mechanism, 15, 16 ... Wedge plate, 17 ... Driving mechanism, 18 ... Reduction lens, 18a ... Optical axis, 19 ... Detector.

Front page continuation (72) Inventor Kuniyoshi Shinji, 1-280, Higashi Koikeku, Kokubunji, Tokyo, Central Research Laboratory, Hitachi, Ltd. (72) Inventor, Sumio Hosaka 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi, Ltd. Central Research Laboratory (72) Inventor Tsuneo Terasawa 1-280 Higashi Koigokubo, Kokubunji, Tokyo Inside Hitachi Central Research Laboratory

Claims (1)

[Claims] 1. An exposure apparatus comprising a light source, an original image, and a reduction lens, wherein a detection means for detecting a deviation up to an upper surface of a semiconductor wafer immediately below the reduction lens and at least three deviations are made constant. A correcting means for correcting the inclination of the upper surface of the semiconductor wafer, and an exposing means for successively exposing the original image pattern while automatically focusing the exposed area on the upper surface of the semiconductor wafer after the correction by the correcting means. An exposure apparatus having.