JPH07120212A - Position detector - Google Patents

Abstract

PURPOSE:To achieve a quick position measurement by providing a reference reflection surface obliquely to a surface crossing the traveling direction and then constituting a detector with an area sensor. CONSTITUTION:Radiation beams from a white color light source 21 are split into two fluxes of light by a beam splitter 23 and one flux of light 24 is applied to a mask M and a wafer W and the other flux of light 25 is applied to a reference reflection surface 27 of a reflection mirror 26 which can travel freely in Y-axis direction. The fluxes of reflection light of the mask M and wafer W and the flux of reflection light of the reflection surface 27 are matched by the splitter 23 and the flux of light is detected by a detector 28. Then, based on the position of the reflection surface 27 and the interference position of the detector 28 when both reflection lights interfere with each other, the position of a sample surface is measured. In this case, the reflection surface 27 is formed on the surface which is inclined by an angle of theta to the surface crossing the Y axis which is the traveling direction and the angle theta is set to an angle where the reflection light passes the same inverse path as the incidence path. Also, the detector 28 is constituted by, for example, a CCD area sensor, thus simultaneously measuring the spacing length between a mask and a wafer without traveling on the reflection surface 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interferometer type position detecting device, and more particularly to a position detecting device suitable for detecting a gap length between two samples.

[0002]

2. Description of the Related Art Recently, an attempt has been made to form a circuit pattern of a VLSI by an equal-magnification exposure using an X-ray exposure apparatus. X-ray exposure is a pattern forming technique with high resolution and is one of the techniques for realizing a minimum line width of 0.2 μm.

A minimum line width of 0.2μ is obtained by using an X-ray equal-magnification exposure apparatus.
In order to form a fine pattern of m, it is necessary to obtain an accuracy of ± 0.05 μm or less when the mask and the wafer are superposed. In order to realize this, not only accurate alignment in a plane orthogonal to the facing direction of the mask and the wafer but also the gap length between the mask and the wafer is set in order to minimize penumbra blurring and runout error. Accurate settings are required.

By the way, various techniques for setting the gap length between the mask and the wafer have been conventionally considered. As typical examples, there are a position aligning device using an optical heterodane interferometric position detecting device using a diffraction grating and a position aligning device using an interferometer type position detecting device.

An alignment device using an optical heterodyne interferometric position detection device is provided with stripe-shaped diffraction gratings on a mask and a wafer so as to face each other so that the stripes are orthogonal to each other, and the radiation emitted from one light source is used. The coherent light beam is divided into two, and two light beams with different frequencies obtained by modulating these are symmetrically arranged with respect to the diffraction grating provided on the mask with the plane perpendicular to the mask surface as a boundary. Irradiation is performed at a predetermined incident angle, and the gap information is obtained from the phase difference between the diffracted lights of a specific order among the diffracted lights obtained by this irradiation.

However, in this alignment device, the range of the gap length that can be detected by the optical heterodyne interference position detection device is about ± 5 μm, so that the above range is previously driven by using, for example, a capacitance type sensor. After that, it is necessary to take the procedure of setting the target gap length using the optical hetero-dyne interferometric position detection device. For this reason, there is a problem that the alignment is not swiftly performed.

On the other hand, as shown in FIG. 13, the alignment device using the interferometer type position detection device converts the light emitted from the white light source 1 into a parallel light beam by the lens 2 and then the beam splitter 3 The light beam 4 is divided into two light beams, and one of the separated light beams 4 is applied to the mask M and the wafer W, which are sample surfaces, and the other light beam 5 is applied to the reference reflecting surface 7 of the reflecting mirror 6 which is movable in the Y-axis direction in the figure. Then, the reflected light flux reflected by the mask M or the wafer W and the reflected light flux reflected by the reference reflection surface 7 are detected by the detector 8, and the sample surface is determined based on the position of the reference reflection surface 7 when both reflected lights interfere with each other. Is configured to measure the position of.

That is, the reference reflecting surface 7 is brought close to the beam splitter 3, for example, and the driving mechanism 9 is used to move the reference reflecting surface 7 away from the beam splitter 3 from this position. When moved in this manner, FIG.
The optical path length between the beam splitter / reference reflection surface and the optical path length between the beam splitter / mask coincide with each other at the time point of moving to the position indicated by A, and the detector 8 detects strong interference light. Reference reflection surface 7 when this interference light is detected
The position sensor 10 detects the position of. When the reference reflecting surface 7 further moves to the position indicated by B in FIG. 14, the optical path length between the beam splitter / reference reflecting surface and the optical path length between the beam splitter / wafer match and the detector 8 Strong coherent light is detected. The position of the reference reflection surface 7 when the interference light is detected is determined by the position sensor 1
Detect with 0. Then, from the difference between the position B of the reference reflection surface 7 where the interference light is obtained for the wafer W and the position A of the reference reflection surface 7 where the interference light is obtained for the mask M, the gap length between the mask and the wafer is obtained. Find Z ₁ . By driving the mask table driving mechanism 11 or the wafer table driving mechanism 12 based on the gap length thus measured, the gap length between the mask and the wafer can be set accurately.

A positioning device using such an interferometer-type position detecting device can have a wide measuring range.
However, since it is necessary to move the reference reflecting surface 7 to sequentially measure the mask position and the wafer position and finally obtain the gap length Z ₁ from the difference between the two positions, there is still a problem in that the alignment speed is insufficient. It was

[0010]

As described above, in the conventional optical heterodyne interferometer type position detecting device and interferometer type position detecting device used in the aligning device, the range in which the position can be measured is narrow. In addition, it takes time to obtain the measurement result, and there is a problem in that it is not easy to use and quick in measurement.

Therefore, the present invention is to provide a position detecting device which has a wide range of position measurement and can obtain a measurement result in a short time, and which has a great effect when incorporated in, for example, a positioning device. Has an aim.

[0012]

In order to achieve the above object, the present invention separates a light beam emitted from a white light source into two light beams by a beam splitter, and one of the separated light beams is directed to a sample surface and the other is directed to the other surface. The luminous flux of is radiated to the reference reflecting surface of the reflecting mirror that is movable in the direction along this luminous flux, and the light that interferes with the reflected luminous flux reflected on the sample surface and the reflected luminous flux reflected on the reference reflecting surface is electrically detected by the detector. In a position detecting device for converting into a signal, the reference reflecting surface is composed of at least one reflecting surface inclined with respect to a surface orthogonal to the moving direction, and the detector is a line sensor. Alternatively, it is characterized by being configured by an area sensor.

[0013]

In the range where the inclination angle of the reference reflecting surface is small, most of the light that has entered the reference reflecting surface through the beam splitter becomes reflected light that follows the same path as the incident path in the opposite direction, and travels to the beam splitter side.

Taking the case where the reference reflecting surface is composed of one reflecting surface as an example, the optical path length between the beam splitter and the sample surface is determined by the tilt angle of the reference reflecting surface. The interfering light is detected by the detector when it is between the shortest optical path length and the maximum optical path length therebetween. The position on the detector where this interference light is detected is the position of the reference reflection surface with respect to the beam splitter, the inclination angle of the reference reflection surface,
It depends on the arrangement of detectors. The position of the reference reflecting surface with respect to the beam splitter can be known by the position sensor, the inclination angle of the reference reflecting surface is known, and the detector arrangement is known at the time of assembly. Therefore, it is possible to measure the optical path length that causes interference, that is, the position of the sample surface, from the position on the detector where the interference light is detected. In other words, the optical path length between the beam splitter and the sample surface is
When it is between the shortest optical path length and the maximum optical path length between the reference reflecting surfaces, the position of the sample surface can be measured without moving the reference reflecting surface.

Further, like the relationship between the mask and the wafer,
When the sample surface has a two-stage structure, both the optical path length between the beam splitter and the mask and the optical path length between the beam splitter and the wafer are between the shortest optical path length and the maximum optical path length between the beam splitter and the reference reflection surface. At some time, the mask position and the wafer position, that is, the gap length between the mask and the wafer can be measured at once without moving the reference reflecting surface.

Further, the reference reflecting surface is composed of a plurality of reflecting surfaces having the same inclination angle and a step, or a plurality of reflecting surfaces having different inclination angles, so that the movement amount of the reference reflecting surface is increased. It is possible to measure the gap length over a wide range between the mask and the wafer in a suppressed state.

[0017]

Embodiments will be described below with reference to the drawings. FIG. 1 shows an example of measuring a gap length Z ₁ between a mask M and a wafer W by a position detecting device according to an embodiment of the present invention.

In this position detecting device, after the light emitted from the white light source 21 is converted into a parallel light flux by the lens 22, it is split into two light fluxes by the beam splitter 23, and one of the split light fluxes 24 is reflected on the sample surface. Certain mask M and wafer W
Then, the other light flux 25 is applied to the reference reflection surface 27 of the reflecting mirror 26 that is movable in the Y-axis direction in the figure, and the reflection light flux reflected by the mask M or the wafer W and the reflection light flux reflected by the reference reflection surface 27 are reflected. The detector 28 detects the light fluxes matched by the beam splitter 23, and the position of the sample surface is measured based on the position of the reference reflection surface 27 and the interference position on the detector 28 when both reflected lights interfere. It is configured. In FIG. 1, 29 indicates a drive mechanism for moving the reflecting mirror 26, 30 indicates a position sensor for detecting the position of the reference reflection surface 27, 31 indicates a mask table drive mechanism, and 32 indicates. The wafer table drive mechanism is shown.

Here, the point that the position detecting apparatus according to this embodiment is largely different from the conventional position detecting apparatus shown in FIG. 13 is the structure of the reference reflecting surface 27. As shown in FIG. 2, the reference reflecting surface 27 is formed on a surface inclined by θ with respect to a surface orthogonal to the moving direction (Y-axis direction). The tilt angle θ is set to an angle that allows most of the light that has entered the reference reflecting surface 27 through the beam splitter 23 to travel to the beam splitter 23 side as reflected light that follows the same path as the incident path but in the opposite direction. In the following figures, the tilt angle θ is shown large for easy understanding.

As shown in FIG. 3, the detector 28 includes a light receiving element 33 having vertical and horizontal dimensions of several μm in the X-axis direction and the Y-axis direction.
For example, CCs arranged in a predetermined pitch in the axial direction
It is composed of a D area sensor.

With this configuration, the gap length between the mask and the wafer can be measured in a state in which the movement amount of the reference reflecting surface 27 is minimized or without moving the reference reflecting surface 27.

That is, the beam splitter 23 is shown in FIG.
And the reference reflection surface 27 and the optical path between the beam splitter 23, the mask M and the wafer W are shown. The optical path length of the light beam 25 traveling between the beam splitter 23 and the reference reflecting surface 27 becomes a value between Lβ1 and Lβ2 due to the influence of the inclination of the reference reflecting surface 27. Reference reflective surface 2
When the inclination angle of 7 is θ and the position of the optical path length Lβ1 is used as a reference, the optical path length LβP at the position of P is expressed by equation (1), where x is the distance to the arbitrary point P.

LβP = Lβ1-x · tan θ (1) On the other hand, the optical path length of the light beam 24 traveling between the beam splitter 23 and the wafer W is Lα1, and the light beam 24 traveling between the beam splitter 23 and the mask M is The optical path length is Lα2, and the optical path lengths at arbitrary two points on the reference reflecting surface 27 are Lβ1,
If Lβ2 is set and the wavelength of light is set to λ, interference occurs and the amount of light increases when the following expressions (2) to (5) are satisfied from the principle of light interference.

| Lα1-Lβ1 | = nλ / 2 (2) | Lα2-Lβ2 | = nλ / 2 (3)
| Lα1-Lβ2 | = nλ / 2 (4) | Lα2-Lβ1 | = nλ / 2 (5) In the formulas (2) to (5), n is the interference order, and in this example, white Since a light source is used, interference occurs only when n = 0.

Now, the optical path length between the mask and the wafer is dLα.
When (= Lα1−Lα2), when the difference dLβ (= Lβ1−Lβ2) between the optical path lengths Lβ1 and Lβ2 of the light flux 25 at any two points on the reference reflecting surface 27 is equal to dLα, the reference reflecting surface 27 By adjusting the position in the Y-axis direction, the interference light from the mask M and the interference light from the wafer W can be simultaneously detected by the detector 28. At that time, interference occurs on the reference reflecting surface 27 at a position separated by dLα / tan θ.

In FIG. 5, the relationship between the difference dLβ between the maximum optical path length and the minimum optical path length of the light beam 25, dLα, and θ is 0 <θ,
When dLβ <dLα, the transition of the position Q on the reference reflection surface 27 where interference occurs when the reference reflection surface 27 is moved in the direction away from the beam splitter 23 is shown. m ₁ indicates the range caused by the mask M, and m ₂ indicates the range caused by the wafer W.

Therefore, in this case, the interference position Q is the center on the reference reflecting surface 27, that is, the position A detected by the position sensor 30 when the interference light is detected at the center position of the detector 28, and In addition, when the interference light is detected at the center position of the detector 28, the gap length between the mask and the wafer can be known from the difference from the position B detected by the position sensor 30. In this case, the reference reflection surface 27
It is possible to widen the measurable gap length range with respect to the movement amount of.

In FIG. 6, the relationship between the difference dLβ between the maximum optical path length and the minimum optical path length of the light beam 25, dLα, and θ is 0 <θ,
When dLβ> dLα, transitions of the positions Q _M and Q _W on the reference reflecting surface 27 where interference occurs when the reference reflecting surface 27 is moved away from the beam splitter 23 are shown. Q _M indicates a position caused by the mask M, and Q _W indicates a position caused by the wafer W.

In this case, since the interference light from the mask M and the interference light from the wafer W can be simultaneously observed by the detector 28 within the range m ₃ , the position on the detector 28 at which the interference light is detected is detected. The gap length between the mask and the wafer can be measured from. That is, since the inclination angle of the reference reflecting surface 28 is known, and the arrangement and element pitch of the detector 28 are also known, the gap length between the mask and the wafer is measured from the position on the detector 27 where the interference light is detected. You can do it. Therefore, it is possible to perform quick measurement over a wide range of the gap length while keeping the movement amount of the reference reflecting surface 27 to a minimum.

The present invention is not limited to the above embodiment, but can be variously modified. For example, as shown in FIG. 7, a reference reflecting surface 27a having _two reflecting surfaces J ₁ and J ₂ having the same inclination angle θ with respect to a plane orthogonal to the moving direction and having a step difference of H in the direction parallel to the moving direction. You may make it use the reflecting mirror 26a provided with.

When detecting the gap length between the mask and the wafer,
When the reflecting mirror 26a having the above structure is moved by the driving mechanism, the positions Q _M and Q _W on the reference reflecting surface 27a where interference occurs are shown in FIG.
It changes as shown in (a), (b), and (c).

That is, FIG. 8A shows the case where the gap length between the mask and the wafer is narrower than the step H, and FIG. 8B shows the case where the gap length between the mask and the wafer is equal to the step H. 8
(c) is the case where the gap length between the mask and the wafer is wider than the step H.

As can be seen from these figures, when the mask-wafer gap length is equal to the step H, the positions Q _M and Q _{W at} which interference occurs are equal, and the mask-wafer gap length and the step H are equal to each other. , The positions Q _M and Q _{W at} which interference occurs are shifted to the left and right according to the amount of deviation. Therefore,
By measuring the shift amount between the positions Q _M and Q _W from the output of the detector 28, the shift amount of the gap length with respect to the step H can be known.

Further, as shown in FIG. 9, a reflecting surface J ₁ is larger inclination angle theta ₁ with respect to a plane perpendicular to the moving direction, with a reference reflective surface 27b with an inclination angle theta ₂ is less reflective surface J ₂ Alternatively, the reflecting mirror 26b may be used.

Basically, when the inclination angle of the reflecting surface is small, the resolution in the measuring direction can be obtained, but the measuring range becomes narrow. On the contrary, when the tilt angle of the reflecting surface is large, the resolution in the measuring direction is poor, but the measuring range is wide. Therefore, when detecting the gap length between the mask and the wafer, if the reflecting mirror 26b having the above-mentioned structure is moved by the driving mechanism, the positions Q _M and Q _W on the reference reflecting surface 27b where interference occurs will occur.
As shown in FIG. 10, since the positions Q _M and Q _W on the reflecting surface J ₁ having a large tilt angle are used to move into the measurement area, the position Q _M on the reflecting surface J ₂ having a small tilt angle is used. , Q _W
It becomes possible to accurately measure the gap length by using. In FIG. 10, A indicates the position where the interference due to the mask M occurs at the center on the reflecting surface J ₂ , and B indicates the position where the interference due to the wafer W occurs at the center on the reflecting surface J ₂ .

FIG. 11 shows an example of measuring the inclination of the sample by applying the position detecting device according to the present invention. In this example, a reflecting mirror 26c having a reference reflecting surface 27c in which two reflecting surfaces J ₁ and J ₂ are combined in a mountain shape (a valley shape is also possible) so that the top portion is located on the optical axis of the light flux 25 is provided. I am using.

When such a reflecting mirror 26c is used, as shown by a, b, and c in the figure, when the sample 34 has no inclination and only the height changes, a ', b', and c in the figure. As shown by ′, interference occurs at left and right symmetrical positions Q ₁ and Q ₂ centered on the top position 35 of the reference reflecting surface 27c. But,
When the sample 34 is tilted as shown by d and e in the figure, the center of the left and right interference positions is d ',
As indicated by e ', the reference reflecting surface 27c is displaced from the top position 35. By measuring this amount of deviation from the output of a detector (not shown), it is possible to know how much and in what direction the sample 34 is tilted.

FIG. 12 shows a modification of the reference reflecting surface. Reference reflection surfaces 27d, 2 shown in (a) and (b) in the figure
7e, similar to that shown in FIG. 7, the reflecting surface is provided with steps and the reflecting surfaces J are provided at the same inclination.
When such reference reflecting surfaces 27d and 27e are used, the structure shown in FIG.
As described above, the gap length between the sample surfaces having different heights than the step provided between the reflecting surfaces can be measured at one time. The reference reflecting surface 27f shown in (c) in the figure is provided with two reflecting surfaces J having different inclinations. When such a reference reflecting surface 27f is used, a wide range can be measured with a reflecting surface having a large inclination and precise measurement can be performed with a reflecting surface having a small inclination, as described with reference to FIG. In the reference reflecting surface 27g shown in FIG. 3D, the two reflecting surfaces J are tilted in the opposite directions by the same tilt amount. When such a reference reflection surface 27g is used, the measurement range can be widened, and when the height of the sample surface changes, the interference positions on the respective reflection surfaces move in opposite directions. Therefore, when measuring with one reflection surface. Double the resolution can be obtained. The reference reflection surface 27h shown in (e) in the figure reduces the inclination amount of the central portion of the reflection surface J to improve the resolution and enables precise position detection, and increases the inclination at both ends to widen the measurement range. I am able to do it. The reference reflecting surface 27i shown in (f) in the figure is basically the same as that shown in (e), but the inclination of the reflecting surface J is continuously changed. The reference reflection surface 27j shown in (g) in the figure is an extension of that shown in FIG. 11, and is provided with reflection surfaces J that are inclined from the center vertically and horizontally by the same amount.
The tilt in two directions can be measured.

When a reflecting mirror having a reference reflecting surface consisting of one reflecting surface is used as shown in FIG. 1, the detector 28 may be composed of a line sensor. Of course, various modifications can be made without departing from the scope of the present invention.

[0040]

As described above, according to the present invention,
Since the reference reflecting surface of the movably arranged reflecting mirror is tilted with respect to the plane orthogonal to the moving direction, it is possible to measure the position over a wide range while suppressing the moving amount of the reflecting mirror. . Further, by setting the inclination angle of the reference reflecting surface, the gap length between a plurality of samples can be measured without moving the reflecting mirror. Therefore, the measurement range can be expanded and the time required for measurement can be shortened. Further, by configuring the reference reflecting surface with a plurality of reflecting surfaces having different inclination angles, it is possible to easily drive to the measurement position and contribute to further shortening of the time required for measurement. further,
By configuring the reference reflecting surface with a reflecting surface having a step equal to the target gap length, it is possible to contribute to high-speed gap length setting while suppressing the movement amount of the reflecting mirror.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a position detection device according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a reflecting mirror incorporated in the same device as shown in FIG.

FIG. 3 is a diagram showing an arrangement example of light receiving elements in a detector incorporated in the same device.

FIG. 4 is a diagram for explaining a measurement principle of the device.

FIG. 5 is a diagram for explaining the relationship between the movement amount of the reference reflection surface and the transition of the interference position on the reference reflection surface when the mask wafer as the sample is measured by the same apparatus.

FIG. 6 is a diagram for explaining the relationship between the movement amount of the reference reflection surface and the transition of the interference position on the reference reflection surface when the mask wafer as the sample is measured by the same apparatus.

FIG. 7 is a perspective view showing a modified example of a reference reflecting surface provided on a reflecting mirror.

FIG. 8 is a diagram for explaining a relationship between a movement amount of a reference reflection surface and a transition of an interference position on the reference reflection surface when a mask wafer as a sample is measured using a reflection mirror having the reference reflection surface.

FIG. 9 is a perspective view showing another modification of the reference reflecting surface provided on the reflecting mirror.

FIG. 10 is a diagram for explaining the relationship between the movement amount of the reference reflection surface and the transition of the interference position on the reference reflection surface when a mask wafer, which is a sample, is measured using the reflection mirror having the reference reflection surface.

FIG. 11 is a view for explaining still another modification of the reference reflecting surface provided on the reflecting mirror and its operation.

FIG. 12 is a diagram showing different modifications of the reference reflecting surface provided on the reflecting mirror.

FIG. 13 is a diagram showing a schematic configuration of a conventional interferometer-type position detection device.

FIG. 14 is a diagram for explaining a relationship between a reference reflection surface movement amount and an interference position when a mask wafer as a sample is measured using the same apparatus.

[Explanation of symbols]

21 ... White light source 22 ... Lens 23 ... Beam splitter 24 ... One light flux 25 ... Other light flux 28 ... Detector 26, 26a, 26b, 26c ... Reflector 29 ... Drive mechanism 27, 27a-27j ... Reference reflection surface 30 ... Position sensor 31 ... Mask table drive mechanism 32 ... Wafer table drive mechanism 33 ... Light receiving element J, J ₁ , J
₂ … Reflective surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuhiko Higashi 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Toshiba Research and Development Center (72) Inventor Hiroyuki Nagahama 75 Hasunuma-cho, Itabashi-ku, Tokyo No. 1 Topcon Co., Ltd.

Claims (1)

[Claims] 1. A light beam emitted from a white light source is separated into two light beams by a beam splitter, one of the separated light beams is directed to a sample surface, and the other light beam is moved in a direction along the light beam. In the position detecting device, which irradiates the reference reflection surface and causes the reflected light flux reflected by the sample surface and the reflected light flux reflected by the reference reflection surface to interfere with each other, is converted into an electric signal by the detector. The position detecting device, wherein the reflecting surface is composed of at least one reflecting surface inclined with respect to a surface orthogonal to the moving direction, and the detector is composed of a line sensor or an area sensor.