JPS63201516A - position detection device - Google Patents

Abstract

PURPOSE:To perform automatic focusing with high accuracy by shifting an irradiation system which projects detection light on an object slantingly and a photodetection system which detects its reflected light according to the deviation of the object and accurately inputting the photodetection signal to a signal processing system. CONSTITUTION:The detection light L1 from the irradiation system K1 is projected on the top surface 5A of a semiconductor wafer 5 slantingly. The photodetection system K2 passes the reflected light L2 from a vibration mirror 6 through a photodetection slit 7, converts 9 the detection light L3 passed through the photodetection slit 7 photoelectrically, and inputs its output signal S1 to a signal processing circuit 10. Triangular photoelectric converting elements 21 and 22 in the mutually opposite directions are provided on the input-side surface 7B of the photodetection slit 7 and their outputs D1 and D2 are supplied to the signal processing circuit 10. If the reflecting surface shifts, the reflected light from the mirror 6 deviates from a reference position P0 to a position P1 or P2 to generate a difference between the outputs D1 and D2 of the photoelectric converting elements 21 and 22. The signal processing circuit 10 shifts the irradiation system K1 and photodetection system K2 so that the difference between the outputs D1 and D2 is eliminated. Consequently, the automatic focusing is performed with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a position detection device, and is suitable for application to, for example, a position detection device in semiconductor manufacturing equipment and inspection equipment.

[Conventional technology]

Conventionally, as a position detection device in semiconductor manufacturing equipment, as disclosed in Japanese Patent Application Laid-open No. 56-42205,
An oblique-incidence type position detection device is used that obliquely irradiates detection slit light onto a semiconductor wafer as a target object disposed at a position where a mask pattern is transferred by a projection lens.

FIG. 6 shows this conventional oblique incidence type position detection device, in which a light beam LO generated by a light source 1 passes through a condenser lens 2 and illuminates a slit 3. The slit 3 has an opening 3A that extends perpendicularly to the plane of the paper, and the image of this opening 3A is formed on the surface 5A of the semiconductor wafer 5 by the light-transmitting imaging lens 4A, thus exposing the surface to be detected. Detection slit light LL consisting of a slit-shaped imaging light beam is irradiated onto the constituting surface 5A.

Thus, the light source 1, the condensing lens 2, the slit 3, and the light-transmitting side imaging lens 4A constitute an irradiation system 1.

The slit reflected light L2 obtained by being reflected by the surface 5A passes through the light-receiving side imaging lens 4B, is reflected by the vibrating mirror 6, and is re-imaged on the light-receiving slit 7, during which time the lower A
The light that has passed is focused as detection light L3 on, for example, a photoelectric conversion element 9 as a photoelectric conversion means.

The reflection slit image formed on the open lower A of the light receiving slit 7 is vibrated by the vibrating mirror 6, and when the semiconductor wafer 5 is in the focused position, the center of vibration of the reflection slit image is on the open lower A.
is configured to coincide with the center of The reflected slit image light that has passed through the open lower A of the light receiving slit 7 is converted into a detection signal S1 by the photoelectric conversion element 9, and is subjected to synchronous phase detection at the vibration period of the vibrating mirror 6 in the signal processing circuit IO.

Thus, the light-receiving side imaging lens 4B, the vibrating mirror 6, the light-receiving slit 7, and the photoelectric conversion element 9 constitute a light-receiving system 2, and the signal processing circuit 10 constitutes a signal processing system 3.

As shown in FIG. 7, the synchronous phase detection signal S2 is generated when the height Z of the surface 5A of the semiconductor wafer 5 is from 2=+21 to 2=
-2, the vibration center of the reflected slit image shifts from the center of the open lower A, and the signal level ■ changes from V = +V to V = -V. do.

Thus, the signal processing circuit 10 performs autofocusing control to bring the projection light from the projection lens into focus by adjusting the position of the semiconductor wafer 5 so that the signal level V of the synchronous phase detection signal S2 becomes V-0. do.

[Problem that the invention seeks to solve]

However, when detecting the position of the semiconductor wafer 5 using this type of oblique incidence type position detection device, if the amount of deviation from the in-focus position of the semiconductor wafer 5 is small, the signal level of the synchronous phase detection signal S2 Since V is within +y, ~-■, 4, focus detection operation can be performed in the signal processing circuit 10, but
When the amount of deviation of the semiconductor wafer 5 from the in-focus position increases and it deviates outside the detectable range R, the reflected slit image vibrated by the vibrating mirror 6 no longer passes through the open lower A of the light receiving slit 7. The synchronous phase detection signal S2 becomes unresponsive (that is, remains at 0 level).

One possible way to solve this problem is to expand the detectable range R by expanding the amplitude of the slit image, but if you do this, there is a risk that the focus detection sensitivity by the synchronous phase detection signal S2 will decrease. Undesirable.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose a position detection device that can expand the detectable range without deteriorating the focus detection sensitivity.

[Means for solving problems]

In order to solve this problem, the present invention includes an irradiation system 1 that irradiates the detection light L1 obliquely to the object 5, and a light receiving system 2 that receives the detection light L3 reflected from the object 5. , the light receiving system has a signal processing system 3 that receives the output S1 of 2, and the detection light L2 reflected by the object 5 is irradiated to the light regulating system 2 so as to move as the object 5 moves. 1 in the system
and 2 are installed in the light receiving system, 3 is installed in the signal processing system, and 2 is installed in the light receiving system.
In a position detection device that generates a detection signal S1 when a predetermined position is irradiated with detection light L3, a light receiving system 2 includes:
comprising first and second photoelectric conversion means 9.21.22;
The photoelectric conversion means 9 is arranged at a predetermined position, the second photoelectric conversion means 21 and 22 have a larger range for detecting the movement of the detection light L3 than the first photoelectric conversion means 9, and the signal processing system 3 is The output S13 of the second photoelectric conversion means 21 and 22 generates a signal for displacing the object 5 in order to move the detection light L3 toward the first photoelectric conversion means 9.

[Effect]

In the light receiving system, 2 is the first and second photoelectric conversion means 9.21.22
, the first photoelectric conversion means 9 is arranged at a predetermined position,
The second photoelectric conversion means 21.22 has a larger range for detecting the movement of the detection light L3 than the first photoelectric conversion means 9, and the signal processing system 3 detects the movement using the output Sl of the second photoelectric conversion means 21.22. A signal is generated to displace the object 5 in order to move the light L3 toward the first photoelectric conversion means 9.

Therefore, even if the position of the object 5 deviates significantly from the range that can be detected by the first photoelectric conversion means 9, it can be detected by the second photoelectric conversion means 21 and 22 with high accuracy. You can control the focus state with .

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

(1) First Embodiment As shown in FIG. 1, a pair of coarse adjustment photoelectric conversion elements 21 and 22 as coarse adjustment photoelectric conversion means are provided on the surface 7B of the light receiving slit 7 on the vibrating mirror 6 side. It is being

One photoelectric conversion element 21 is formed in a triangular shape so that when the reflective slit image P moves to the right in a direction perpendicular to the open lower A position, the light receiving area of the reflective slit image P increases. ing.

The other photoelectric conversion element 22 is arranged in a triangular shape so that when the reflective slit image P moves to the left in a direction orthogonal to the other side of the open lower A, the light-receiving area of the reflective slit image P increases. It is formed.

In the case of this embodiment, the center of the reflective slit image P is located at the open lower A.
When the light-receiving areas of the reflection slit images P for the pair of photoelectric conversion elements 21 and 22 are approximately equal, the detection signals D1 and D
The configuration is such that the two signal levels are equal to each other and the difference therebetween is approximately zero.

When the reflected slit image P is located at a position PL (or P2) shifted to the right (or left) from this state, the detection signals DI and D of the photoelectric conversion elements 21 and 22
2 changes differentially (the sum thereof becomes a constant value), so that the value of the difference increases in the positive direction or decreases in the negative direction.

Detection signals D1 and D2 obtained from the photoelectric conversion elements 21 and 22 are input to a coarse adjustment signal forming circuit 23 provided within the signal processing circuit 10.

That is, the detection signals D1 and D2 are sequentially input to the subtraction circuit 29 and addition circuit 30 through the amplification circuits 25 and 26 and the low-pass filters 27 and 28, and the subtraction output 311
and the addition output S12 are given to the division circuit 31.

In the above configuration, since the detection signals D1 and D2 change differentially according to the movement of the reflective slit image P (Fig. 1), the value of the addition output S12 of the adding circuit 30 is It maintains a constant value even when moving, and changes depending on the brightness of the reflected slit image P.

On the other hand, the subtracted output 5llO value of the subtraction circuit 29 differentially changes greatly when the reflected slit image P moves to the left, and also changes depending on the brightness of the reflected slit image P.

Therefore, in the division circuit 31, the subtraction output S of the subtraction circuit 29 is
By dividing ll as the numerator and the addition output S12 of the adding circuit 30 as the denominator, the horizontal position P of the reflective slit image P, without being affected by the change in brightness of the reflective slit image P,
A coarse adjustment signal 313 (FIG. 3(B)) whose signal level changes linearly according to ,P, ,P can be obtained.

In fact, this rough adjustment signal S13 is used as a position adjustment signal for the semiconductor wafer 5 in the Z direction, together with the detection signal Sl obtained from the photoelectric conversion element 9 (used as a fine adjustment signal).

According to the above configuration, when the reflective slit image P is located at a position where the synchronous phase detection signal S2 (FIG. 3) of the photoelectric conversion element 9 falls within the detectable range R, the signal processing circuit 10 detects the synchronous phase detection signal S2 (FIG. 3). Precise autofocusing operation can be performed using the detection signal S2.

In addition to this, when the reflective slit image P moves to a position where the synchronous phase detection signal S2 of the photoelectric conversion element 9 deviates from the detectable range R, the signal processing circuit 10
), the ranges R11 and R of the coarse adjustment signal 313
Detectable range R of reflected slit image P using 12 signals
It is possible to perform a rough autofocusing operation such as pulling back to the range R1 corresponding to .

Thus, according to the embodiment described above, even when the position of the semiconductor wafer 5 is significantly shifted compared to the conventional case,
This can be reliably detected and controlled to be in focus with high precision.

(2) Second Embodiment FIGS. 4 and 5 show a second embodiment of the present invention, and corresponding parts to those in FIGS. 1 and 2 are indicated by the same reference numerals. On one side of the open lower A of the light receiving slit 7, a position detection element (PSD
(position 5 sensitive detect
A photoelectric conversion element 35 for rough adjustment is provided.

The coarse adjustment photoelectric conversion element 35 generates a pair of detection signals that differentially change when the irradiation position of the reflective slit image P shifts to the right (or left) with the open lower A as the center. D
ll and D12, and the detection signals Dll and D1 are transmitted.
2 to the low-pass filter 2 via the amplifier circuits 25 and 26.
7 and 28.

In the configurations shown in FIGS. 4 and 5, the detection signals Dll and D12 obtained from the rough adjustment photoelectric conversion element 35 are
Both have values corresponding to the brightness of the reflected slit image P,
Second, the position of the reflective slit image P is P, -P, ~P,
If you change between the two, it will change accordingly.

Therefore, in this embodiment as well, the same effects as in the above case can be obtained.

(3) Other embodiments (a) In the above embodiment, the photoelectric conversion elements 21 and 22 for rough adjustment are placed on the surface 7B of the light receiving slit 7.
The case has been described in which the photoelectric conversion elements 21 and 22 are provided at opposing positions on both sides with the open lower A of the light receiving slit 7 interposed therebetween, and the photoelectric conversion elements 21 and 22 have a triangular shape. A change may be made to provide a pair of photoelectric conversion elements 21 and 22 together on one side, or a shape in which the detection output generated by the pair of photoelectric conversion elements 21 and 22 changes differentially as a result. It is possible to make various changes such as molding, etc., and the point is to detect the deviation of the reflection slit image P with respect to the opening lower A of the light receiving slit 7 and the direction of the deviation by the detection output obtained by the photoelectric conversion elements 21 and 22. All you have to do is make it possible.

(bl Also, in the above embodiment, the vibrating mirror 6
In the above, we have described the case where the reflection slit image P is vibrated and the light receiving slit 7 is fixed, but instead of this, the vibrating mirror is removed or the mirror is fixed and the light receiving slit 7 is moved from the open lower part of the light receiving slit 7. It is also possible to vibrate with a predetermined amplitude in a direction perpendicular to A.

(C) Further, in the above-described embodiment, a case was described in which the second photoelectric conversion elements 21 and 22 were attached to the light receiving slit 7, but instead of this, it is possible to connect the light receiving slit 7 and the vibrating mirror 6. , a second photoelectric transformer (a detector to which negative elements 21 and 22 are attached) may be provided.

(d) Furthermore, in the above embodiment, as a detection method for fine adjustment, the detection light L3 that has passed through the open lower A of the light receiving slit 7 in which the second photoelectric conversion elements 21 and 22 are provided is used.
is detected by the first photoelectric conversion element 9, but instead of the light receiving slit 7, a photoelectric conversion element 9 having almost the same shape as the light receiving slit 7 is placed on the same plane as the second photoelectric conversion elements 21 and 22. Even if it is provided, the same effect as in the above case can be obtained.

(e) Furthermore, in the above embodiment, a case will be described in which the reflection slit image P and the light receiving slit 7 having the open lower A of a predetermined width are relatively vibrated (in other words, repeatedly moved back and forth). However, instead of this, the reflection slit image P and the light receiving slit 7 having the open lower A with a predetermined width are relatively moved to cross the open lower A at least once, and based on the detection results at that time, the semiconductor The position of the wafer 5 may also be detected.

〔Effect of the invention〕

As described above, according to the present invention, when the position of the object to be detected deviates significantly from the in-focus position, it can be reliably detected, thereby increasing the accuracy of the autofocusing operation as in the conventional case. It is possible to easily realize a position detecting device that can maintain a certain value.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing a first embodiment of a photoelectric conversion element according to the present invention, FIG. 2 is a block diagram showing signal processing of the photoelectric conversion element, and FIGS. 3 (8) and (B) are The signal waveform diagram, FIG. 4 is a linear plan view showing the second embodiment of the photoelectric conversion element according to the present invention, FIG. 5 is a block diagram showing signal processing of the photoelectric conversion element, and FIG. 6 is position detection. A route map showing the overall configuration of the device, and FIG. 7 is a waveform diagram of the detection signal. 1...Light source, 5...Semiconductor wafer, 6
... Vibration mirror, 7 ... Light receiving slit, 9 ... First photoelectric conversion element, 10 ...
- Signal processing circuit, 21.22.35... Second photoelectric conversion element.

Claims (1)

[Scope of Claims] An irradiation system that irradiates detection light obliquely to a target object, a light receiving system that receives the detection light reflected from the target object, and a signal processing system that receives the output of the light receiving system. , and as the detection light reflected by the target object moves, the light receiving system
In a position detection device, the irradiation system and the light receiving system are disposed so as to be movable, and the signal processing system generates a detection signal when the light receiving system is irradiated with the detection light at a predetermined position. The system includes first and second photoelectric conversion means, the first photoelectric conversion means being disposed at a predetermined position, and the second photoelectric conversion means having a range in which movement of the detection light is detected. larger than the first photoelectric conversion means, and the signal processing system is larger than the second photoelectric conversion means.
A position detection device characterized in that the output of the photoelectric conversion means generates a signal for displacing the object in order to move the detection light toward the first photoelectric conversion means.