JPH09115822A - Projection exposure apparatus and semiconductor device manufacturing method using projection exposure apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection exposure apparatus capable of projecting a pattern on a reticle surface to a wafer surface in a projection optical system, and to provide a semiconductor device manufacturing method using the projection exposure apparatus. SOLUTION: When a pattern on a surface of a first object 3 illuminated by exposure light from a lighting means 1 is projected onto a surface of a second object 7 by a projection optical system 6, a slit member 36 having at least one light transmission unit, which is arranged on an optically conjugate position on the surface of the first object 3 inclined to the conjugate surface, is illuminated by the exposure light. Thereafter, the slit member 36 is projected onto a second reflecting surface 21 provided on the surface of a stage movable along the axis and perpendicularly to the optical axis of the projection optical system 6 through the first object 3 and the projection optical system 6. As a result, the reflected light is returned through the original optical path, and then directed a light detection means capable of detecting the incident amount and the incident point of the light through the projection optical system 6 and the first object 3. Information about the image-formation point of the projection optical system 6 is detected at a processing unit 50 by using a first signal from the light detection means 44.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus and a semiconductor device manufacturing method using the same, and more particularly to I
When manufacturing a semiconductor device such as C or LSI, the imaging performance of the projection optical system is measured when the electronic circuit pattern on the reticle surface is projected and exposed on the wafer surface through the projection optical system. This is suitable for obtaining a highly integrated semiconductor device by utilizing the correction mechanism.

[0002]

2. Description of the Related Art Conventionally, when a semiconductor device is manufactured through a process of projecting a pattern on a reticle surface onto a wafer surface by a projection optical system, the wafer is accurately positioned on an image plane of the projection optical system. Is becoming important.

A method of detecting the image plane position for positioning the wafer at the image formation position of the projection optical system is disclosed in, for example, Japanese Patent Laid-Open No. 57-21.
No. 2406 is proposed.

In the method for detecting the image plane position of the publication, slits or pinholes are transmitted through a transfer object (reticle) having a circuit pattern set at the object position of a projection lens (projection optical system). The mark is installed. A stage that can move in three dimensions (XYZ stage)
An object to be transferred (wafer) is set near the upper imaging position. Then, a light beam having the same wavelength as the exposure light is incident on the reticle. The light flux that has passed through the slit or pinhole on the reticle is reflected on the wafer after passing through the projection lens, and is transmitted through the projection lens in the opposite direction to be re-imaged on the slit or pinhole on the reticle. .

At this time, the amount of light transmitted through the slit or pinhole and detected by the photodetector becomes maximum when the wafer (reflection surface) is placed at the best focus position (focus position). However, when the wafer position moves away from the focus position on the optical axis, the re-formed image becomes unclear and the image spreads (blurrs), so the number of light beams transmitted by the slits or pinholes increases and the amount of light that passes through decreases. The amount of light detected by the vessel decreases.

Based on such a phenomenon, the stage is moved up and down to a position where the amount of light is maximum to detect the image forming position, that is, focus position adjustment is performed.
At this time, when a reflecting surface is used instead of the wafer, the difference between the upper surface of the reflecting surface and the wafer is corrected to drive the stage, or a focus position detecting device, for example, a tilt position, installed independently of this device is used. By using a gap sensor using an incident optical system, the position of the reflecting surface is adjusted by vertically moving the stage on the surface of the wafer.

[0007]

The method of detecting the position of the imaging plane of the projection optical system proposed in the publication, that is, in the focus detection, a stage provided with a reflecting surface for performing one focus measurement is mounted on an optical axis. There is a drawback in that it has to be moved many times in the direction, which takes time and lowers the throughput.

Further, in the above-mentioned conventional example, a mark of a slit or a pinhole is required on the reticle, so that it is costly, and there is a restriction that measurement can be performed only at a position where the mark is arranged. Further, the reticle has no mark. In this case, the test reticle has to be replaced with a reticle on which a mark is arranged, which has a drawback that throughput is reduced.

According to the present invention, when the pattern on the reticle surface as the first object is projected on the wafer surface as the second object by the projection optical system, the image plane (focus position) of the projection optical system is set in the optical axis direction. A projection exposure apparatus capable of highly accurately detecting a semiconductor device with high integration, which can be detected with high precision in a short time without disposing a reticle mark without moving and scanning the stage on the stage, and An object of the present invention is to provide a semiconductor device manufacturing method using the same.

[0010]

A projection exposure apparatus according to the present invention comprises: (1) When a pattern on a first object plane illuminated by exposure light from an illumination means is projected onto a second object plane by a projection optical system. Illuminating the slit member having at least one light transmitting portion, which is arranged at an optical conjugate position with the first object surface and inclined with respect to the conjugate surface, with the exposure light, and the slit member is provided with the first object. And projecting onto the second reflecting surface provided on the stage surface movable through the projection optical system in the optical axis direction of the projection optical system and in a plane orthogonal to the optical axis, and by the second reflecting surface. The light is reflected, the original optical path is returned, and the light is guided through the projection optical system and the first object to the light detecting means capable of detecting the incident amount and the incident position of the light beam, and the first signal from the light detecting means is sent. It is characterized in that the processing unit is used to detect image formation position information of the projection optical system.

In particular, (1-1) from the light detecting means obtained when the slit member is reflected by the first reflecting surface provided on the first object surface and then guided to the light detecting means. Position information in the optical axis direction between the slit member and the first reflecting surface is obtained from the second signal, and the position in the optical axis direction between the slit member and the second reflecting surface is obtained from the first signal. Obtaining information, and obtaining position information in the optical axis direction between the first object surface and the second reflecting surface from this.

(1-2) The position detecting means detects the position information of the second object plane in the optical axis direction of the projection optical system without passing through the projection optical system, and the processing section outputs from the position detecting means. The image formation position information is calibrated using the signal of.

(1-3) The light detecting means includes a light receiving slit having at least one light transmitting portion provided at a position optically conjugate with the first object plane, and a light transmitting portion of the light receiving slit. It must have a light receiving part that receives the light flux that has passed through. And so on.

In the method of manufacturing a semiconductor device of the present invention, (2) the pattern on the reticle surface illuminated by the exposure light from the illumination means is projected and exposed on the wafer surface by the projection optical system, and then the wafer is developed. When manufacturing a semiconductor device by using the exposure light, a slit member having at least one light transmitting portion that is optically conjugate with the reticle surface and tilted with respect to the conjugate surface is illuminated with the exposure light, and the slit member is illuminated. Through a reticle and the projection optical system onto a second reflecting surface provided on a stage surface movable in the optical axis direction of the projection optical system and in a plane orthogonal to the optical axis, The first signal from the light detecting means is reflected by the reflecting surface, returns the original optical path, and is guided to the light detecting means capable of detecting the incident amount and the incident position of the light flux through the projection optical system and the reticle. The projection light in the processing unit using It is characterized in that the image forming position information of the academic system is detected to align the wafer.

In particular, (2-1) the first slit from the light detecting means obtained when the slit member is reflected by the first reflecting surface provided on the reticle surface and then guided to the light detecting means. Position information in the optical axis direction between the slit member and the first reflecting surface is obtained from two signals, and position information in the optical axis direction between the slit member and the second reflecting surface is obtained from the first signal. Then, the positional information in the optical axis direction between the reticle surface and the second reflecting surface is obtained from this.

(2-2) The position detecting means detects the position information of the wafer surface in the optical axis direction of the projection optical system without passing through the projection optical system, and the processing section outputs a signal from the position detecting means. The image forming position information is calibrated using.

(2-3) The light detecting means passes through the light receiving slit having at least one light transmitting portion provided at a position optically conjugate with the reticle surface, and the light transmitting portion of the light receiving slit. It must have a light receiving part that receives the light flux. And so on.

[0018]

1 is a schematic view of the essential portions of Embodiment 1 of a projection exposure apparatus of the present invention. In the figure, reference numeral 1 denotes an exposure illumination system, which illuminates a reticle 3 as a first object and illuminates a slit member 36 described later. The exposure illumination system 1 includes a diaphragm 2 of the exposure illumination system, an ultrahigh pressure mercury lamp (not shown), a shutter, an optical system, and the like. 3
Is a reticle (photomask) as the first object,
The reticle 3 has a lower surface provided with a reticle reflecting surface (for example, a chromium vapor deposition portion or a first reflecting surface) 4. The chromium vapor deposition portion of the reticle reflecting surface 4 is usually arranged in a blank portion other than the area where an integrated circuit pattern such as an IC is provided. A reticle stage 5 holds the reticle 3.

A projection lens (projection optical system) 6 projects the circuit pattern of the reticle 3 illuminated by the exposure illumination system 1 onto a wafer 7 as a second object. 8 is a wafer stage on which the wafer 7 is mounted,
XYZ drive, θ drive, tilt drive, etc. are performed.

Reference numeral 9 is an interference mirror for monitoring the position of the wafer stage 8 with an interferometer 10. The wafer 7 is driven by the wafer stage drive control system 11 using signals obtained from the interferometer mirror 9 and the interferometer 10.
Is always positioned at a predetermined position, and exposure is performed from this position.

Reference numeral 21 is a reflection reference surface (also referred to as a second reflection surface or a reference reflection surface) provided on the wafer stage 8.
Reference numeral 19 denotes a light projecting means, which is the wafer 7, that is, the reflection reference surface 2.
In order to detect the surface position of the No. 1 in the optical axis direction, the reflection reference surface 21 is obliquely illuminated with a light beam that does not expose the photoresist applied to the wafer 7. Reference numeral 20 denotes a detection means (gap sensor), which measures the distance in the optical axis direction between the projection lens 6 and the wafer 7 or the reflection reference surface 21 without the projection lens 6. In the present embodiment, it is possible to measure the distance between them by leveling measurement.

Reference numeral 30 denotes a focus measuring optical system, which detects the image forming position of the projection lens 6, that is, the best focus position.

Next, each element constituting the focus measurement optical system 30 will be described in order. An optical fiber or a routing optical system 31 guides the light flux from the exposure illumination system 1 to the focus measurement optical system 30. Reference numeral 32 is a shutter, and 33 is an ND filter for adjusting the amount of incident light, which has a structure that can be put in and taken out from the optical path. 34 is an illumination optical system for focus measurement,
The diaphragm 35 is provided inside. The diaphragm 35 has a structure that is changed by the illumination control unit 12 when the diaphragm 2 of the exposure illumination system is changed.

36 is a slit member (slit),
Having one or more transmissive portions or multiple apertures,
It is arranged at a position optically conjugate with the reticle 3 with a predetermined amount (known value) tilted with respect to the conjugate plane (plane perpendicular to the optical axis).

FIG. 2 shows a schematic view of the slit member 36.
In FIG. 2, reference numeral 80 is a light transmitting portion (opening portion), and 81 is a light shielding portion. Returning to FIG. 1, 37 is a relay lens.

Reference numeral 38 denotes a polarization beam splitter or a half mirror, which separates the illumination light beam and the light beam returned from the reflection reference surface 21 on the wafer stage 8.

Reference numeral 39 denotes a 1/4 λ plate, which is inserted to improve the light utilization efficiency. An objective lens 40 forms an image of the slit 36 on the lower surface of the reticle 3. 4
Reference numeral 1 is a mirror, which bends the optical path at 90 °. 4
2 is an erector lens. Reference numeral 43 denotes a light receiving slit (slit member) having one or a plurality of openings (transmission portions), and is arranged at a position optically conjugate with the pattern surface on the reticle 3. Reference numeral 44 denotes an optical sensor (light receiving unit), which is composed of, for example, a linear line sensor.

A processing unit 50 obtains the focus position of the projection lens 6 from the pixel information of the light amount distribution received by the optical sensor 44, and drives the wafer stage 8 in Z according to the obtained focus position. Alternatively, the output value from the gap sensor 20 is compared and calibrated.

In this embodiment, the reticle reflecting surface 4 is used as the first step when detecting the image forming position of the projection optical system 6, and the position in the optical axis direction between the slit 36 and the reticle reflecting surface 4 is used. Is being detected.

Next, in the second step, the transmitting surface of the reticle 3 is used, and the slit 36 and the detecting means 20 detect the position of the first reflecting surface 21 on the wafer stage 8 on the wafer stage 8 in the optical axis direction. doing. From the results of the first step and the second step, how much the position of the first reflecting surface 21 deviates from the image forming position of the reticle pattern surface is obtained, and the deviation amount at this time is added to the detecting means 20. The value obtained by the detection means 20 is corrected.

Therefore, in the first step, the focus measurement optical system 30 moves slightly to the right (X direction) from the position shown in FIG.
That is, the slit image of the slit 36 is the reticle reflection surface 4
It is shifted to the position where it reflects. And light sensor 4
The objective lens 40 or the relay lens 37 and the erector lens 42 are moved in the optical axis direction (X
Direction) or the entire focus measurement optical system 30 is driven in the optical axis direction (Z direction) so that the slit 36 and the reticle reflecting surface 4 are in focus.

In the second step, the entire focusing optical system 30 is driven to a predetermined position on the left side in FIG. 1 while keeping that state, and the slit 36 and the detecting means 20 on the wafer stage 8 are arranged at a known position in advance. The position with the second reflecting surface 21 is obtained by the method described later.

Through the above operation, the position of the second reflecting surface 21 in the optical axis direction and the correction amount of the detecting means 20 are obtained. However, the above-mentioned first step does not have to be performed every time the focus measurement according to the present invention is performed, and may be omitted if the stability of the focus measurement optical system is good.

Next, referring to FIG. 1, an optical path relating to the exposure operation on the surface of the wafer 7 and the focus measurement will be described.

First, the case of a normal exposure operation will be described.
Reticle 3 illuminated by exposure light from exposure illumination system 1.
Via the projection lens 6, the electronic circuit pattern of is on the wafer 7 aligned on the focal plane of the projection lens 6 by the Z drive of the gap sensor 20 and the wafer stage 8,
It is transferred in the same size or reduced size. The gap sensor 20 uses the probe light of non-exposure light to enter the reflection reference surface (reference reflection surface) 21 on the wafer 7 or the wafer stage 8 at a low angle, and the reflected light is received by the light receiving portion. By doing so, the Z position and tilt of the wafer 7 are measured.

Next, the optical path of the focus measurement optical system 30 will be described. First, the optical path used in the method of detecting the positional information in the optical axis direction between the slit 36 and the reticle lower surface 3a using the reticle reflecting surface 4 in the first step will be described.

First, the light flux extracted from the exposure illumination system 1 by a mechanism (not shown) is guided to the focus measurement optical system 30 by the fiber 31. This luminous flux is the shutter 3
2, the light enters the illumination optical system 34 through the ND filter 33.

The incident light beam is emitted from the illumination optical system 34 through the diaphragm 35 which is interlocked with the diaphragm 2 of the exposure illumination system and is condensed on the slit member 36. Then, the light flux that has passed through the transmissive portion of the slit member 36 becomes a parallel light flux by the relay lens 37 and is emitted.

The optical path of this light beam is bent to 90 ° by the polarization beam splitter 38, and is imaged on the reticle lower surface 3a through the 1/4 λ plate 39, the objective lens 40, and the mirror 41 in order, but the reticle reflecting surface 4 is present. Go back to the same optical path again.

That is, the mirror 41 and the objective lens 4 are arranged in this order.
The light flux passing through the 0, 1/4 λ plate 39 is guided onto the light receiving slit 43 via the polarization beam splitter 38 and the erector lens 45, and an image of the slit member 36 is formed on the surface thereof. Then, the light sensor 44 detects the light flux that has passed through the transmitting portion of the light-receiving slit 43. At this time, since the slit member 36 is arranged so as to be inclined with respect to the surface perpendicular to the optical axis, when the image is formed on the surface of the light receiving slit 43, the transmitting portion of the slit member 36 is located at the position in the optical axis direction. It contains the shift information.

The amount of light passing through the transmitting portion of the light receiving slit 43 forms an intensity distribution according to the amount of positional deviation of the slit member 36 in the optical axis direction. The optical sensor 44 detects the intensity distribution at this time. The above is the optical path of the focus measurement optical system used in the method of the first step.

Next, the optical path used in the method of detecting the positions of the slit 36 and the reference reflecting surface 21 on the wafer stage 8 using the transmitting surface of the reticle 3 as the second step will be described.

The optical path until the slit 36 illuminated by the light beam from the illumination optical system 34 forms an image on the reticle lower surface 3a is the same as in the first step. The slit image formed on the lower surface 3a of the reticle is directly incident on the projection lens 6,
An image is formed in the vicinity of the reference reflection surface 21 on the wafer stage 8 after being scaled up or down. By the way, Z of the reference reflecting surface 21
The position (position in the optical axis direction) is known by measuring with the gap sensor 20.

The light beam reflected by the reference reflecting surface 21 again enters the projection lens 6 in the opposite direction, passes through it, and forms an image again near the reticle lower surface 3a. This slit image is a reticle 3,
Via the mirror 41, the objective lens 40, the 1/4 λ plate 39, the polarization beam splitter 38, and the erector lens 45,
An image is formed on the light receiving slit 43.

Then, the optical sensor 44 detects the light flux passing through the transmitting portion of the light receiving slit 43. At this time, since the slit member 36 is arranged so as to be inclined with respect to the surface perpendicular to the optical axis, when the image is formed on the surface of the light receiving slit 43, the transmitting portion of the slit member 36 is located at the position in the optical axis direction. It contains the shift information.

The amount of light passing through the transmitting portion of the light receiving slit 43 forms an intensity distribution according to the amount of positional deviation of the slit member 36 in the optical axis direction. The optical sensor 44 detects the intensity distribution at this time.

Although a slit image is formed on the light-receiving slit 43, the slit image is an image in which the in-focus portion and the out-of-focus portion are mixed. The reason for such an image will be described later. The above is the optical path of the focus measurement optical system used in the method of the second step.

Next, the focus detection principle of the projection lens 6 of this embodiment will be described. In this embodiment, as described above, both the first step and the second step are performed to measure the focus position of the projection lens 6.

The operation of the first step, that is, the method of using the reticle reflecting surface 4 to detect the positional information in the optical axis direction between the slit 36 and the reticle lower surface 3a is performed by the slit 3
6 is basically the same as detecting the position of the reflecting surface on the wafer stage 8. Therefore, the second step, which is the most important part of this embodiment, will be described here.

FIGS. 5, 6 and 7 are diagrams directly showing the detection principle of the present embodiment, and FIGS. 8, 9 and 10 are diagrams for comparing the principle and confirming its effect. Is.

First, in FIGS. 8, 9 and 10, 6 is a projection lens drawn in a simulated manner, 60 is the object plane of the projection lens, and the slit image on that plane is a plane perpendicular to the optical axis. It corresponds to the position formed when not inclined with respect to the reticle lower surface 3a or the position of the light receiving slit 43. Specifically, the slit image is like the slit image 63 shown in FIG.

Reference numeral 62 denotes an image plane of the projection lens 6, which in this case corresponds to the reflection reference plane (second reflection plane) 21 or the wafer surface 7. When this slit image 63 is incident on the projection lens 6, it is imaged on the reflection reference surface 21 and is reflected, so that it travels the projection lens 6 in the opposite direction again, follows the same optical path 61, and is again imaged on the reticle lower surface 3a. To do. The re-formed slit image becomes a slit image 64.

In this figure, the re-formed slit image 64 is larger than the original slit image 63, but it is originally the same size only by changing the size for convenience of explanation.
The re-formed slit image 64 is shielded by the light receiving slit 43, and the light flux passing through the transmitting portion of the light receiving slit 43 is received by the one-dimensional optical sensor 44.
Naturally, the light amount for the pixel of becomes the rectangular intensity distribution 70 of FIG.

Therefore, the slit image 6 of the slit member 36
3 is displaced from the object plane 60 of the projection lens 6,
The slit image reflected from the reflection reference surface 21 is not re-imaged on the reticle lower surface 60, but is re-imaged at a position displaced from it. Therefore, the slit image at the position of the reticle lower surface 60 is in a state where it is more blurred than the original slit image, and this slit image is shielded by the light receiving slit 43 and passed through the transmitting portion of the light receiving slit 43. When the light beam is received by the optical sensor 44, the light amount distribution remains a rectangle and the light amount is reduced.

Next, the features of the principle of the present embodiment will be described. 5, 6 and 7 is basically different from the above description in that the slit member 36 is inclined with respect to the object plane 60 of the projection lens 6.

As shown in FIG. 7, the slit image 63 is formed so as to be inclined with respect to the lower surface 66 of the reticle as a line segment 60 a, and is incident on the projection lens 6. The light flux at that time becomes like a light flux 61, passes through the projection lens 6, and tries to form an image, but is reflected by a reflection surface near the image plane 62 of the projection lens 6, and the reflected light flux from there is a light flux of the light flux 65. Becomes,
Reverse the projection lens 6 and place an image 6 near the lower surface 66 of the reticle.
The image is re-imaged in a tilted state like 7.

Therefore, when the image 67 is received by the light receiving slit 43 located at a position conjugate with the reticle lower surface 66, a defocus amount 72 is generated, and the slit image 64 is at the focused position as shown in FIG. The sharpest. That is, the central portion of the slit image 64 is the clearest and the image width is narrow,
Both ends of the slit image 64 are most blurred and the image width is widened.

This slit image 64 is used as a light receiving slit 43.
When the light transmitted through the transmitting portion of the light receiving slit 43 is received by the one-dimensional line sensor 44 or the like, a light amount distribution 71 as shown in FIG. 5 is obtained. Then, the light amount distribution 71 is distributed with the focused portion as a peak. By obtaining the pixel position H1 of the peak of the light amount distribution 71 by a method described later, the position H1 is detected as the focus position of the projection lens 6.

Actually, the focus position H0 as the initial state of the apparatus is obtained in advance, and the correlation with the measurement value of the gap sensor 20 is measured, and the pixel of the peak of the light amount distribution in the actual apparatus operating state is measured. How far the position H1 is from this origin H0, that is, H1-
The focus variation of the projection lens 6 is measured by obtaining H0.

Next, assuming that the light sensor 44 has obtained the profile of the light amount distribution, a method of obtaining the pixel position of the peak will be described.

In FIG. 11, it is assumed that focus measurement is performed to obtain the light amount distribution profile 75. At this time, the following methods (a) to (d) can be applied to the method of obtaining the pixel position H1 of the peak.

(A) The pixel position where the light intensity profile 75 has the maximum value is simply found and set as H1.

(B) A slice level is set to a certain ratio with respect to the maximum value of the light quantity profile 75, and the light quantity profile 75 shows the output of this slice level at the pixel position H.
3, H4 is calculated and H1 = (H3 + H4) / 2.

(C) The center of gravity processing is performed on the light intensity profile (Si) and the pixel position (Hi), and H1 = Σ (Hi × Si) / ΣSi.

(D) A quadratic function approximation (y = a.x.x) with respect to the light amount profile (Si) and the pixel position (Hi)
+ B · c + c), and H1 = −b / (2 · a).

In this embodiment, the peak pixel position is detected by using the above method. Next, the origin and sensitivity calibration will be described in the present embodiment.

In the present embodiment, the focus position of the projection lens 6 and the focus fluctuation are measured in addition to this operation, and various origins and sensitivity calibrations are performed in advance. Although the necessity has been briefly described in the above explanation, the importance thereof will be summarized and explained again here. The origin and the sensitivity calibration in this embodiment are the following three.

A. Detection of positional information in the optical axis direction between the slit 36, the reticle lower surface 3a, and the light receiving slit 43 using the reticle reflecting surface 4 in the first step B. In the second step, the focus position of the projection lens 6,
Origin detection as a reference for obtaining focus position variation C. Matching with the focus measurement optical system of the present embodiment when a focusing device without the projection lens 6, for example, the above-mentioned gap sensor 20 and the like are used together will be described in order below.

A: As described above, the focus measuring method according to the present invention indirectly determines the position information of the reticle 3 and the reference reflecting surface 21 in the optical axis direction, that is, the projection, based on the measurement results of the first step and the second step. The focus position of the lens 6 can be detected.

Therefore, the focus measuring optical system 30 as a whole or the slit 36, the light receiving slit 43, and the light receiving slit 43, which constitute the focus measuring optical system 30, are affected by some disturbance (for example, temperature and atmospheric pressure fluctuations).
When the position of the optical member or the like changes, the light amount profile received by the optical sensor 44 shifts, and it is determined that the focus of the projection lens 6 has changed, and an extra correction operation is performed to perform proper exposure. May not be done. Therefore, it is necessary to monitor the positions of the slit 36 and the reticle lower surface 3a as necessary,
The first step of detection is required.

B: In the present embodiment, the focal position H0 in the initial state of the apparatus is obtained in advance, and the correlation with the measured value of the gap sensor 20 (for example, when the gap sensor 20 changes by 1 μm, the Sensor 4
Linearity of how much the measured value of 4 changes)
Is measured, how far the pixel position H1 of the peak of the light amount distribution is from this origin H0 in the actual operating state of the device, that is, H1-H0 is obtained, so that the temporal focus fluctuation of the projection lens 6 can be obtained. It will be possible to monitor with TTL.

C: The probe light used for focus measurement according to the present invention has the same wavelength as the exposure light. Therefore, focus measurement cannot be performed on the wafer surface 7 coated with the resist. Therefore, the gap between the projection lens 6 and the wafer surface 7 is measured by using the gap sensor 20 using the conventionally used incident optics system.
This gap sensor 20 has a projection lens 6 in advance.
The measured value when the wafer 7 or the reflection reference surface 21 is located at the image plane position of is the origin of the gap sensor 20, and is frequently calibrated when there is a possibility that it will change over time, so that the correct focus can be obtained. The exposure is done at the position. Also, this gap sensor is T
Since it is not the TL method, it cannot cope with focus fluctuation due to disturbance of the projection lens 6.

Therefore, by using the focus measuring method according to the present invention, the gap sensor 20 can be used in a short time.
It is possible to calibrate. Specifically, the focus measurement is performed at every appropriate interval (shot, wafer, lot, etc.), and the focus variation amount obtained there is sent to the processing unit 50 as a true value, and the gap sensor 20
Offset value.

By performing the above origin and sensitivity calibration in advance, the projection lens 6 can be used even in the actual exposure operation.
Focus measurement.

Next, the operation (flow) of this embodiment will be described. FIG. 12 shows a flowchart relating to the process of exposing the wafer 7 in the present invention. First, a conventional case in which focus position detection is not performed in the present invention will be described.

The wafer 7 to be exposed is supplied (step 1
10) Then, the reticle 3 may be supplied corresponding to the wafer to be exposed, or may be already supplied because it is the same as the previous wafer. The supplied wafer 7 is subjected to pre-alignment (step 111) for rough alignment. Then, in step 112, fine alignment is executed. This positions the wafer 7,
It is determined where the shot position to be exposed is on the XY stage coordinates.

In step 113, the stage 8 moves to the shot position to be exposed according to the determined coordinates. Then, the focus plane of the projection lens 6 (best image plane)
Then, focus drive (step 114) is performed to drive the wafer 7 in the Z direction.

At this time, in order to remove the tilt component of the wafer 7 at the same time, the tilt amount is measured by the gap sensor 20,
Tilt the XY stage so as to cancel the tilt component. As a result, the position of the wafer 7 is adjusted on the focus plane (best image plane) of the projection lens 6, and the wafer 7 is exposed (step 115).

Next, in step 116, it is determined whether or not all shot exposure has been completed. The process returns to step 113 until the exposure of all shots is completed, moves to the next exposure shot, and repeats the exposure loop. When the exposure of all shots is completed, the process proceeds to step 117 to collect the wafer 7.

Next, at step 118, it is judged whether exposure of all wafers is completed. The process returns to step 110 until the exposure of all the wafers is completed, the next wafer is supplied, the alignment and the exposure are repeated. Then, exposure of all wafers is completed, and processing of one lot is completed.

A flow when the focus position of the projection lens 6 is detected and the focus position is corrected by using the present invention will be described. Steps a to e shown in FIG. 13 show the timing of focus position correction.

The timing of correction in steps a to e will be described. The actual correction may be performed at any one of steps a to e. The timing to be selected is determined based on the focus change amount of the projection lens 6, the change amount of the gap sensor 20 over time, and the allowable defocus amount of the wafer 7 to be exposed. The layer sensitive to defocus comes to the timing of step e. Step e is a case where correction is performed for each shot. However, if this is applied to all layers, it takes a long time to process the wafer, the throughput is lowered, and the productivity is deteriorated.

Therefore, the correction interval can be lengthened as long as the amount of change in the focus position can be ignored. When step c or step d is selected, the interval becomes longer for each wafer compared to step e. Further, if step b is performed, for example, each lot is completed, and the interval becomes longer. Step b may be one hour later or one day later. Step a is a longer interval, for example, every 10 lots.

The focus correction interval is obtained from the amount of fluctuation of the focus position due to exposure and atmospheric pressure and the allowable value.
By setting the allowable value in advance, the processing unit 50 can automatically set the interval.

When the correction of the present embodiment is not performed for each wafer, the predicted value of the focus position may be controlled by calculation between the corrections. In the process (wafer processing) in which the predicted value control and the actual variation match, the interval may be selected from step a or step b. If the difference is known to be large, the interval may be step c or step d. Step e will be selected.

Further, for example, in the case of performing correction for each wafer, after performing the correction of the present embodiment, the focus position obtained by the predicted value control and the correction using the present embodiment are performed when the correction is performed on the next wafer. The processing unit 50 compares the obtained true focus positions. If the difference from the predicted value is less than the allowable value, it can be changed automatically for each lot, improving the throughput.

Furthermore, since the difference between the process of the processed wafer and the predicted value control of the focus position can be stored correspondingly, even if the process is performed for each wafer in the previous process, the result of the previous process will be used in the next process. Since it can be determined in advance that the difference from the predicted value is small, the setting is automatically changed for each lot. The previous processing result can store not only the previous data but all the past data, and it is possible to make a comprehensive judgment by using a learning function such as statistical processing. Further, it is naturally possible to optimize the parameters for predictive value control.

With the above functions, the optimum correction interval can be automatically selected without always lowering productivity more than necessary.

In this correction, only the focus surface of the projection lens 6 is used. However, by performing the correction of the present embodiment at a plurality of points in the exposure area, it is possible to obtain the curvature of field and the inclination of the field. .

Although not shown in FIG. 1, astigmatism can also be measured only by providing the slit member 36 with a surface which is slightly tilted independently in the X and Y directions. Since these imaging characteristics can also be measured, the change over time can be measured by measuring at the interval of step a, for example. The field curvature and astigmatism can be corrected by driving one or more lenses inside the projection lens 6 or by changing the environment such as the temperature and pressure of the projection lens 6, and the image plane inclination can be corrected by the wafer stage 8. This can be corrected by tilt driving or inputting an offset to the measurement value of the gap sensor 20.

In this way, there is always no change with time, and it becomes possible to correct the focus position according to each process. As a matter of course, the timing for measuring the change over time may be input and set, or may be automatically set using the difference from the predicted measurement value in the same process, the focus change amount, or the like.

Next, FIGS. 13 and 14 show specific correction flows performed in steps a to e. FIG. 13 is the most basic flow.

In step 130 including confirmation, the reticle 3 is positioned at a predetermined position with respect to the optical axis direction of the projection lens 6.

Next, in step 131, the operation of the above-mentioned first step is performed. Focus measurement optical system 3
In order to move the optical axis of 0 to the reticle reflecting surface 4, the entire optical system is moved in the X and Y directions (X direction in the example of FIG. 1). Then, in step 132, in order to focus the reticle reflecting surface 4 and the slit 36, the optical sensor 4
The entire focus optical system 30 is moved in the Z direction so that the light amount of 4 becomes maximum. This completes the first step,
The process proceeds from step 133 to the second step.

In step 133, the transparent surface of the reticle 3 is used to move the focus measurement system 30 to a position where the image plane on the wafer stage 7 can be measured. Step 1
In step 34, the wafer stage 8 is driven in XYZ in order to bring the reference reflection surface 21 to a position where it can be observed by the focus measurement system adjusted in step 133. The drive position at this time is a preset position. As a matter of course, this position is the position when the origin / sensitivity correction is performed. Since the positioning has been performed, the shutter 3 of the focus measurement optical system is adjusted in step 135 for correction measurement.
Open 2 As described above, the light is guided to the slit 36, reflected by the reference reflection surface 21, and the light receiving slit 43.
Through the light sensor 44.

In step 136, the optical sensor 44
The peak pixel position is obtained from the light amount distribution of the incident light, and the correction amount is calculated from the pixel position H0 corresponding to the initial focus position. Since the measurement is completed, the shutter 32 of the focus measurement optical system is closed in step 137. The timing may be immediately if the light intensity distribution can be obtained.
The subsequent calculation process may be performed in parallel with step 137. Now that the correction amount is obtained, in step 138 the correction amount is added to the currently stored focus position,
Find a new focus position.

In the processing section 50, the gap sensor 20 and the wafer stage 8 are controlled so that the wafer 7 will come to a new focus position. At this time, although not shown, the correction amount of the focus change due to the atmospheric pressure is calibrated including the atmospheric pressure when the new focus position is obtained, so the calculated correction amount on the atmospheric pressure side is cleared. Since the shot correction (calibration) is not performed for each shot except when the correction interval is other than the above step e, the focus correction amount for the atmospheric pressure value can be calculated by calculation between the corrections. The same applies to the change in focus position due to exposure. However, as described above, the comparison with the value obtained from the prediction measurement is performed here. The optimum value of the correction interval is also obtained here.

Next, the flow other than that shown in FIG. 14 will be described. FIG. 14 shows the operation of the first step in which the reticle 3 is moved instead of moving the entire focus measurement optical system 30 in XY. In step 140, the reticle 3 is set, and in order to focus the reticle 3 and the slit 36, the reticle 3 set in step 141 is moved by a known amount until the reticle reflecting surface 4 enters the visual field of the focus measurement optical system. . Then, in step 142, the objective lens 40 is moved in the X direction (in the case of FIG. 1) and focused.

Then, in step 143, the reticle 3 is moved again so that the transmission surface of the reticle 3 is used so that the image plane on the wafer stage 8 is located at a measurable position.
At this time, the reticle 3 may be returned to the original set position. Since the operations from step 144 to step 148 are the same as step 134 to step 138 in FIG. 13, the description thereof will be omitted.

One of the main purposes of the present invention is to quickly measure the focus, not to define the flow order. Although the above shows two embodiments, it goes without saying that the present invention is not limited to this, and other flows may be used as long as the object of the present invention is satisfied.

Next, a second embodiment of the present invention will be described. 3 and 4 are explanatory views of the slit members 83 and 85 used in the second embodiment of the present invention.

In FIG. 3, the slit 36 has only one opening (transmissive portion) in the first embodiment, but has five openings 82 here. Reference numeral 83 is a light shielding portion. Here, if the optical sensor 44 is a two-dimensional sensor, five light amount distribution profiles can be obtained simultaneously by one focus measurement. Then, the peak position of each profile is obtained and the averaging process is performed, so that the peak position can be obtained more stably and accurately than in the first embodiment. By the way, the number of slit openings may be increased or decreased depending on the accuracy of peak determination.

In the present embodiment, an optical system such as a cylindrical lens is arranged on the light receiving side of the light receiving slit, and y in FIG.
A linear light beam may be received by a linear line sensor that produces a compressed light beam.

In FIG. 4, the opening of the slit 36 has a cross shape 84, and 85 is a light shielding portion. Embodiment 1
Then, with one slit, the focus of the projection lens 6 in either the sagittal direction or the meridional direction is detected. In order to measure both directions at the same time, it is necessary to prepare two sets of focus measurement optical systems 30 and arrange them in each direction.

In order to improve this in the present embodiment, the opening portion 84 of the slit 36 is formed in a cross shape as shown in FIG.

In the present embodiment, the light-receiving slit 43 also has the opening 84 shown in FIG. 4, the slit 36 is tilted in the direction of 45 ° with respect to the optical axis, and the slit 36 is provided behind the light-receiving slit 43. Light may be received using a two-dimensional sensor. According to this, it is possible to measure the light amount distributions in the sagittal direction and the meridional direction.

As described above, by using this slit 36, it is possible to detect both the sagittal direction and the meridional direction of the projection lens 6 by one measurement with one set of focus measurement optical system, and focus with higher precision. The detection is realized.

As described above, in the second embodiment, the focus measurement using the two slit shapes has been described. However, the slit shapes are not limited to these two, and more effective slit shapes can be obtained. You may use it if you like. Further, the flow of the focus measurement operation using this embodiment is exactly the same as the method described in the first embodiment, and will not be described here.

Next, a third embodiment of the present invention will be described with reference to FIG. Although the light-receiving side slit 43 is arranged in front of the optical sensor 44 in the first embodiment, the present embodiment is different from the first embodiment in that the optical sensor 44 substitutes the role of the light-receiving side slit. Others are the same. The optical sensor 44 is composed of, for example, a linear line sensor. By making the size of the linear line sensor itself the same as the size of the opening of the slit on the light receiving side, the same function as that of the slit for receiving light is achieved.

Since the flow of the focus measurement operation using this embodiment is exactly the same as the method described in the first embodiment, it is omitted here.

Next, a fourth embodiment of the present invention will be described. In the embodiments described above, the focus measurement correction of the actual wafer uses the gap sensor 20, so that the focus measurement means of the present invention uses the reference reflection surface 21 for calibration of the gap sensor 20.

However, the focus measuring means of the present invention can also be used for focusing the wafer itself by using the actual reflection of the wafer. By doing so, the wafer can be directly focused without the need to calibrate the gap sensor.

The present invention is characterized in that focus measurement can be performed in a short time by correcting the focus measurement by inclining the slit member 36 of the focus optical system 30 by a known amount in advance with respect to a plane perpendicular to the optical axis. Therefore, the configuration, flow, and shape of each of the above-described embodiments are not limited.

Next, an embodiment of a method of manufacturing a semiconductor device using the above-described projection exposure apparatus will be described.

FIG. 16 is a flow chart for manufacturing a semiconductor device (semiconductor chip such as IC or LSI, or liquid crystal panel, CCD or the like).

In step 1 (circuit design) of the present embodiment, a semiconductor device circuit is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design.

On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer.

The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer manufactured in step 4, including an assembly process (dicing, bonding), a packaging process (chip encapsulation). Etc. are included. In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 17 is a detailed flowchart of the wafer process in Step 4 above. First step 11
In (oxidation), the surface of the wafer is oxidized. Step 1
In 2 (CVD), an insulating film is formed on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted in the wafer. In step 15 (resist processing), a photosensitive agent is applied to the wafer. Step 16
In (exposure), the circuit pattern of the mask is printed and exposed on the wafer by the above-described exposure apparatus.

In step 17 (development), the exposed wafer is developed. In step 18 (etching), parts other than the developed resist are scraped off. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, a highly integrated semiconductor device can be easily manufactured.

[0122]

According to the present invention, by setting each element as described above, when the pattern on the reticle surface as the first object is projected on the wafer surface as the second object by the projection optical system, It is possible to detect with high accuracy in a short time without reticle mark placement, without moving the stage to scan the image plane (focus position) of the projection optical system in the optical axis direction, and to achieve a high degree of integration. It is possible to achieve the projection exposure apparatus capable of easily manufacturing the semiconductor device and the manufacturing method of the semiconductor device using the same.

In addition, according to the present invention, the focus position fluctuation of the projection lens can be effectively measured by TTL by only one measurement in a short time in an actual operating state of the apparatus. At the same time, when a focusing device that does not use a projection lens, such as a gap sensor that uses a radiating incident optical system, is used together, when the detection value of this focusing device changes with time, or when the projection lens is exposed It is possible to detect the focal position shift when a change with time due to the above occurs, and to effectively calibrate.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of a projection exposure apparatus of the present invention.

FIG. 2 is an explanatory view of a slit member according to the present invention.

FIG. 3 is an explanatory view of a slit member according to the present invention.

FIG. 4 is an explanatory view of a slit member according to the present invention.

FIG. 5 is an explanatory diagram of a method for detecting an image plane position according to the present invention.

FIG. 6 is an explanatory view of a method of detecting the image plane position according to the present invention.

FIG. 7 is an explanatory diagram of a method of detecting an image plane position according to the present invention.

FIG. 8 is an explanatory diagram of a method for detecting an image plane position according to the present invention.

FIG. 9 is an explanatory diagram of a method of detecting an image plane position according to the present invention.

FIG. 10 is an explanatory diagram of a method for detecting an image plane position according to the present invention.

FIG. 11 is an explanatory diagram for detecting the peak of the light amount distribution in the present invention.

FIG. 12 is a flowchart of a wafer surface exposure process according to the present invention.

FIG. 13 is a flowchart of focus measurement and correction according to the present invention.

FIG. 14 is a flowchart of focus measurement and correction according to the present invention.

FIG. 15 is a schematic view of a main part of a third embodiment of the present invention.

FIG. 16 is a flowchart of a method for manufacturing a semiconductor device of the present invention.

FIG. 17 is a flowchart of a method for manufacturing a semiconductor device of the present invention.

[Explanation of symbols]

1 Exposure Illumination System 2 Exposure Illumination System Aperture 3 Reticle 4 Reflection Part (Chromium Evaporation Part) 5 Reticle Stage 6 Projection Lens 7 Wafer 8 Wafer Stage 9 Bar Mirror 10 Interferometer 11 Wafer Stage Drive Control System 12 Illumination Control Unit 20 Gap Sensor 21 Reflection reference surface on stage 30 Focus measurement optical system 31 Optical fiber or routing optical system 32 Shutter 33 ND filter 34 Illumination optical system 35 Aperture 36 Slit member having one or a plurality of openings (transmission part) 37 Relay lens 38 Polarization beam splitter or half mirror 39 1/4 λ plate 40 Objective lens 41 Mirror 42 Elector lens 43 Light receiving slit 44 Optical sensor 50 Processing unit

Claims (8)

[Claims] 1. When the pattern on the first object plane illuminated by the exposure light from the illuminating means is projected onto the second object plane by the projection optical system, the conjugate is located at an optically conjugate position with the first object plane. A slit member having at least one light-transmitting portion that is tilted with respect to the plane, is illuminated with the exposure light, and the slit member is passed through the first object and the projection optical system, and the optical axis of the projection optical system. Direction and the projection optical system that projects onto a second reflecting surface provided on a stage surface movable in a plane orthogonal to the optical axis and reflects the second reflecting surface to return the original optical path. The light is guided through a first object to a light detecting means capable of detecting the incident amount and the incident position of the light flux, and the processing unit uses the first signal from the light detecting means to obtain image formation position information of the projection optical system. A projection exposure apparatus characterized by being detected. 2. A second signal from the light detecting means obtained when the slit member is reflected by a first reflecting surface provided on the first object surface and then guided to the light detecting means. Obtaining positional information in the optical axis direction between the slit member and the first reflecting surface, obtaining positional information in the optical axis direction between the slit member and the second reflecting surface from the first signal, The projection exposure apparatus according to claim 1, wherein position information in the optical axis direction between the first object surface and the second reflecting surface is obtained from this. 3. The position detecting means detects the position information of the second object plane in the optical axis direction of the projection optical system without passing through the projection optical system, and the processing section detects the signal from the position detecting means. 3. The projection exposure apparatus according to claim 1, wherein the image forming position information is calibrated by utilizing the image forming position information. 4. The light detecting means includes a light-receiving slit having at least one light-transmitting portion provided at a position optically conjugate with the first object plane, and a light beam passing through the light-transmitting portion of the light-receiving slit. 4. The projection exposure apparatus according to claim 1, further comprising a light receiving section for receiving the light. 5. A reticle surface when a pattern on a reticle surface illuminated by exposure light from an illuminating means is projected and exposed on a wafer surface by a projection optical system, and then the wafer is developed to manufacture a semiconductor device. And illuminating a slit member having at least one light transmitting portion, which is arranged at an optically conjugate position with an inclination with respect to the conjugate surface, with the exposure light, and causes the slit member to pass through the reticle and the projection optical system. Projecting onto a second reflecting surface provided on a stage surface movable in the optical axis direction of the projection optical system and a plane orthogonal to the optical axis, reflecting the light on the second reflecting surface, and returning the original optical path. , Through the projection optical system and the reticle to guide the light to an optical detecting means capable of detecting the incident amount and the incident position of the light beam, and using a first signal from the optical detecting means, a processing unit of the projection optical system. The position of the wafer is detected by detecting the imaging position information. A method of manufacturing a semiconductor device, which is characterized by performing alignment. 6. The slit based on a second signal from the light detecting means obtained when the slit member is reflected by a first reflecting surface provided on the reticle surface and then guided to the light detecting means. Position information in the optical axis direction between the member and the first reflecting surface is obtained, and position information in the optical axis direction between the slit member and the second reflecting surface is obtained from the first signal. 5. The method of manufacturing a semiconductor device according to claim 4, wherein position information in the optical axis direction between the reticle surface and the second reflecting surface is obtained. 7. The position detecting means detects position information of the wafer surface in the optical axis direction of the projection optical system without passing through the projection optical system, and the processing section uses a signal from the position detecting means. 6. The method for manufacturing a semiconductor device according to claim 4, wherein the image formation position information is calibrated. 8. The light detecting means receives a light-receiving slit having at least one light-transmitting portion provided at a position optically conjugate with the reticle surface, and receives a light beam passing through the light-transmitting portion of the light-receiving slit. 8. The method for manufacturing a semiconductor device according to claim 5, 6 or 7, further comprising: