JPH0794983B2 - Position shift detection mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention is, for example, for focusing on a sample surface in a microscope used for film thickness measurement or circuit pattern line width measurement on various substrates, or for a disk surface in an optical disk device. Like a focus shift detection mechanism equipped to automatically adjust the focus of the head (either reading or writing, or both), it detects the position shift state of the sample surface from a predetermined reference position. Regarding the mechanism.

<Prior Art> The focusing deviation detecting mechanism introduced in Japanese Patent Application Laid-Open No. 60-76035 is shown in FIG. 33 as a first conventional example and briefly described below.

The light beam emitted from the light source 21 is reflected by the half mirror 22 and forms a spot on the optical disc 25 via the lenses 23 and 24. The reflected light flux of the spot passes through the lenses 24 and 23 and the half mirror 22, and the half mirror 22 and the two-divided sensor D ₁ , D
After forming an image at a position between ₂ and _2, it is incident on the two-divided sensors D ₁ and D ₂ .

A front light-shielding plate 26 and a rear light-shielding plate 27 are provided at positions symmetrical with respect to the image forming point P ₁₀ of the reflected light flux at the time of focusing and at a position apart from the reflected light axis. optical disk
When 25 is in the in-focus position, the reflected light beam is not shielded by both the light-shielding plates 26 and 27 as shown by the solid line, and an equal amount of light is incident on each of the divided sensors D ₁ and D ₂ and is in the in-focus state. Is detected. The image forming point P _{10 at} this time is located exactly at the center position of both the light shielding plates 26, 27.

When the optical disc 25 moves in the direction away from the lens 24 from the in-focus position, the image formation point P ₁₁ becomes the front light-shielding plate 2 as shown by the broken line.
6 side, the rear side light shield plate 27 shields a part of the light flux above the optical axis, and the amount of light incident on the sensor D ₁ decreases, so that the optical disc 25 is defocused in the direction away from the lens 24. Is determined, and the autofocus mechanism is driven based on this detection signal to control the in-focus state.

Conversely, when the optical disc 25 approaches the lens 24 from the in-focus position, the image formation point P ₁₂ approaches the rear light-shielding plate 27 side as indicated by the chain double-dashed line, and the front light-shielding plate 26 causes the image to be formed above the optical axis. Since a part of the light flux is shielded and the amount of light incident on the sensor D ₂ is reduced, it is determined that the optical disc 25 is out of focus in the direction approaching the lens 24, and the autofocus mechanism is driven based on this detection signal. Control is performed so that the in-focus state is achieved.

Next, a focusing deviation detecting mechanism introduced in Japanese Patent Laid-Open No. 58-60433 is shown in FIG. 34 as a second conventional example and briefly described below.

The light beam emitted from the light source 31 passes through the beam splitter 32 and forms a spot on the optical disc 34 via the lens 33. The reflected light flux of the spot passes through the lens 33, is reflected by the beam splitter 32, and goes toward the edge of the plane mirror 35. The plane mirror 35 is inclined by 45 ° with respect to the optical axis of the reflection optical path, and its edge is arranged at the position where the light beam from the beam splitter 32 converges when focusing.

According to the description of Japanese Patent Application Laid-Open No. 58-60433, the second conventional example described above shows that the reflected light flux is the first as shown in FIG.
It is described that the two-divided sensors D ₅ and D ₆ are made to enter the same amount at a time, and the second two-divided sensors D ₇ and D ₈ are made to enter at a same amount. Further, when the optical disc 34 moves from the in-focus position in the direction away from the lens 33, the amount of incident light of the first one sensor D ₅ and the second one sensor D ₈ increases, and the optical disc 34 is out of focus in the direction away from the lens 33. When a detection signal is output, and conversely, when the optical disk 34 approaches the lens 33, the amount of incident light on the first other sensor D ₆ and the second other sensor D ₇ increases, and the light is not focused in a direction too close. It is described that a certain detection signal is output, and the autofocus mechanism is driven based on these detection signals to perform control so that the in-focus state is achieved.

<Problems to be Solved by the Invention> Since the first conventional example (FIG. 33) is to determine the in-focus state when the amounts of light incident on both sensors D ₁ and D ₂ are the same, If the sample surface has a high contrast, such as a black and white stripe pattern,
Even if the sample surface is at the in-focus position, both sensors D ₁ and D ₂
There is a risk that the amounts of light incident on the light beams do not match and that the light beam is erroneously determined to be out of focus.

Next, in the second conventional example (FIG. 34), the two-divided sensors D ₅ and D ₆ are also used.
Since the focus is detected by comparing the incident light of D ₇ with that of D ₇ or D ₈ , the focus detection is erroneous when the sample surface is a surface having contrast, as in the first conventional technique. There is a risk.

Further, in the first and second conventional examples, when the sample surface is the surface of a transparent substrate such as glass, the light reflected from the back surface of the substrate (hereinafter referred to as back surface reflected light) is confused. Therefore, the focus detection may be erroneous. In other words, even if the sample surface is at the in-focus position and the reflected light from the sample surface is incident on both sensors in equal amounts, the back-surface reflected light is the reflected light from the surface that is not in the in-focus position. Incidently incident on the sensor. Therefore, even if the sample surface is at the in-focus position, the amounts of incident light on both sensors are not equal, and it is difficult to detect the focused state of the sample surface from the balance of the amounts of incident light between both sensors.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a position shift detection mechanism that is not affected by the contrast of the sample surface. It is another object of the present invention to provide a positional deviation detection mechanism capable of detecting the positional deviation of the sample surface from the reference position even when the sample surface is the surface of a transparent substrate.

<Means for Solving the Problems> The present invention has the following configuration in order to achieve such an object.

That is, a position deviation detecting mechanism for detecting a position deviation state of the sample surface from a reference position as a reference, a light source for irradiating the sample surface, an objective lens arranged between the light source and the sample surface, and the reference A light-shielding plate which is arranged between the objective lens and the light source so that the edge coincides with a position conjugate with the position, and which shields a part of the light beam emitted from the light source to the sample surface; Of the reflected light from the sample surface with respect to the light flux that is irradiated including the optical axis of the lens and is not shielded by the light shielding plate and is irradiated onto the sample surface through the objective lens, the sample of the light shielding plate through the objective lens It is composed of a light amount detecting element for detecting the light amount of the reflected light irradiating the surface on the side of the surface, and detects the deviation amount of the sample surface from the reference position by a detection signal from the light amount detecting element. A displacement detection mechanism.

<Operation> The operation of the configuration of the present invention is as follows.

A light shielding plate is arranged between the light source and the objective lens. The edge of the light shielding plate is arranged at a position conjugate with the reference position of the sample surface. The light beam emitted from the light source includes the optical axis of the objective lens, and a part of the light beam is blocked by the light blocking plate. Then, the light flux not shielded by the light shield plate passes through the objective lens and is irradiated on the sample surface. The reflected light from the sample surface passes through the objective lens and proceeds to the side where the light shielding plate and the light source are arranged. Therefore, when the sample surface is at the reference position,
The following difference occurs in the reflected light from the sample surface that irradiates the sample surface side of the light shielding plate with that when it is not at the reference position. In the following description, the optical axis of the projection optical path that guides the light flux from the light source to the sample surface (optical axis of the objective lens)
In an imaginary line that is orthogonal to and passes through the edge of the light shield,
With the edge of the shading plate as a branch point, the side of the shading plate is referred to as a "shading plate existing region" and the opposite side is referred to as a "shading plate absent region".

The light flux guided from the light source to the sample surface is a light ray that has passed through the light-shielding plate absent region in the virtual line. When the sample surface is at the reference position, the reflected light of such a light ray passes through the light shielding plate absent region of the virtual line again because the sample surface and the virtual line are conjugate. That is, the irradiation light flux from the light source to be the reflected light passing through the light shielding plate existing area of the virtual line is a light beam that passes through the light shielding plate existing area in the virtual line and is irradiated to the sample surface,
Since this light beam is blocked by the light blocking plate, there is no reflected light from the sample surface for this light beam. Therefore, the reflected light from the sample surface at the reference position does not illuminate the surface of the light shielding plate on the sample surface side.

On the other hand, when the sample surface is not at the reference position, even in such a case, the light guided from the light source to the sample surface is the light that has passed through the light-shielding plate absent region in the imaginary line. Since the sample surface and the imaginary line are not conjugate, the reflected light passes through a range wider than the light-shielding plate absent region on the imaginary line. Therefore, a part of the reflected light from the sample surface not at the reference position passes through the light-shielding plate existing area. Therefore, when the sample surface is not at the reference position, there is a light ray that illuminates the surface of the light shielding plate on the sample surface side.

As described above, when the sample surface is at the reference position, the light rays that irradiate the surface of the light shielding plate on the sample surface side are minimum, and the sample surface is not located at the reference position, that is, the sample surface and the edge of the light shielding plate. The number of light rays that irradiate the surface of the light shield plate on the sample surface side increases as the conjugate relationship of (3) is removed.

Based on the above principle, from the photometric amount of the light amount detection element that detects the amount of light that illuminates the sample surface side of the light shielding plate, it is possible to obtain a signal corresponding to the amount of displacement of the sample surface from the reference position, It is possible to detect the position shift state of the sample surface. It should be noted that since the light amount detection element does not compare the magnitude of the detection signals of the two-divided sensor as in the conventional example but captures the light amount change itself in the light amount detection element itself, even if there is contrast in the sample, the detection of the misalignment state There is no risk of making a mistake.

<Example> Hereinafter, an example of the present invention is described in detail based on a drawing.

[First Embodiment] FIG. 1 is a schematic configuration diagram of a positional deviation detecting mechanism of a first embodiment.

In FIG. 1, 1 is a light source, 2 is a sample surface, 5 is a condenser lens, 6 is an objective lens, 7 is a light shielding plate, and 8 is a light amount detection element. The range enclosed by the broken line in FIG.
2 shows the luminous flux that exits and illuminates the sample surface 2.

The light source 1 is a laser, an LED, a tungsten lamp, a discharge tube, or the like. In addition, in FIG. 1 and the following drawings, the light source 1
The light-emitting surface 1a of is shown larger than it actually is.

The sample surface 2 is a surface which is a target for detecting a positional deviation state, and is a surface of a semiconductor wafer, an optical disk, or the like.

The condenser lens 5 is a lens that is arranged between the light source 1 and the objective lens 6 and that condenses the light emitted from the light source 1.

The objective lens 6 is disposed between the sample surface 2 and the light source 1, and the light from the light source 1 passes through the objective lens 6 and the sample surface 2
Irradiate. Further, the objective lens 6 forms an optical system for forming an image of the sample surface 2 on a means for capturing an image (not shown, for example, corresponding to various imaging devices or the eyes of an observer). The in-focus position of the sample surface 2 is the position of the sample surface 2 in which the image of the sample surface 2 through the objective lens 6 is in a positional relationship of being formed on the means for capturing the image of the sample surface 2. . Therefore, in the first embodiment, the in-focus position is the "reference position" referred to in the configuration of the invention.
Corresponds to. The objective lens 6 and the condenser lens 5 form a projection optical path that guides the light from the light source 1 to the sample surface 2.

The light-shielding plate 7 has its edge 7a arranged at a position P _{0 which} is conjugate with the sample surface 2 at the in-focus position.

The light amount detection element 8 is an element that detects reflected light from the sample surface 2 at the out-of-focus position, as will be described later, and may be any means that can detect at least the light amount, such as a photodiode or PSD. There is no problem even if it is used.

Next, the operation of the focus shift detection mechanism according to the first embodiment will be described.

FIG. 2 to FIG. 4 are diagrams showing a specific light ray, which will be described later, emitted from the light source 1 and reflected by the sample surface 2 in the first embodiment. In FIG. 2, the sample surface 2 is at the in-focus position, and in FIG. 3, the sample surface 2 is displaced from the light-shielding plate 7 in the direction away from the light-shielding plate 7 from the in-focus position indicated by the chain double-dashed line. It is located at the non-focus position in the pin direction), and in FIG. 4, the sample surface 2 is displaced from the focus position shown by the chain double-dashed line toward the light shielding plate 7 (hereinafter,
It is in a non-focus position in the front focus direction). The two-dot chain line parallel to the sample surface 2 in FIGS. 3 and 4 is an imaginary line showing the sample surface 2 at the in-focus position.

As shown in the second diagram, when the sample surface 2 is in the in-focus position, that is, when the sample surface 2 and the edge 7a of the light shielding plate 7 are in the conjugate position, the optical axis LA passes through the edge 7a of the light shielding plate 7. A ray passing through an arbitrary point β ₁ on a line segment α-α ′ orthogonal to
After being reflected by the sample surface 2 as shown by the solid line γ ₁ ,
It will pass the point β ₁ again. Therefore, in order for the light rays reflected by the sample surface 2 to illuminate the surface of the light shielding plate 7 on the sample surface 2 side, the light rays emitted from the light source 1 pass through the condenser lens 5 and then intersect with the line segment α-7a. There is a need to.
However, as is clear from FIG. 2, the light path does not exist because the light path is blocked by the light shielding plate 7. That is, when the sample surface 2 is at a position conjugate with the edge 7a of the light shielding plate 7, the sample surface 2 is included in the light beam emitted from the light source 1.
There is no light beam that irradiates the surface of the light shielding plate 7 on the sample surface 2 side after being reflected by.

Next, when the sample surface 2 is not in a position conjugate with the edge 7a of the light shielding plate 7, for example, as shown in FIG. 3 or 4, the light rays shown by the solid lines γ ₂ or γ ₃ emitted from the light source 1 But the light shield 7
After passing through the vicinity of the edge 7a, the light is reflected by the sample surface 2 and the surface of the light shielding plate 7 on the sample surface 2 side is irradiated. That is, when the sample surface 2 is not in a position conjugate with the edge 7a of the light shielding plate 7, in the light beam emitted from the light source 1,
There is a light ray that irradiates the surface of the light shielding plate 7 on the sample surface 2 side after being reflected by the sample surface 2.

As described above, when the sample surface 2 is at a position conjugate with the edge 7a of the light shielding plate 7, the light rays that irradiate the surface of the light shielding plate 7 on the sample surface 2 side are minimized, and the edge 7a of the light shielding plate 7 is As the position of the sample surface 2 deviates from the conjugate relationship, the number of light rays that illuminate the surface of the light shielding plate 7 on the sample surface 2 side increases.

Based on the above principle, the amount of light that illuminates the surface of the light shield plate 7 on the side of the sample surface 2 is detected by the light amount detection element 8, so that the amount of deviation from the focus position of the sample surface 2 is determined from the light amount detection element 8. A corresponding signal can be obtained.

[Second Embodiment] The second embodiment is an embodiment in which the first embodiment is further specified. In the second embodiment and each of the second and subsequent embodiments, the same components as those in the first embodiment will not be described and the same reference numerals will be given.

FIG. 5 shows a schematic configuration diagram of the second embodiment. In FIG. 5, a range surrounded by a broken line shows a light flux emitted from the light source 1 and irradiating the sample surface 2.

The half mirror 3 constitutes an optical system for observation together with the objective lens 6. The image of the sample surface 2 is imaged on the observation surface 4 corresponding to a means for capturing the image of the sample surface 2 through the optical system for observation. The half mirror 3 and the observation surface 4 do not constitute the positional deviation detection mechanism of the present invention and are not limited to the configuration shown in the fifth illustration.

The condenser lens 5 is located at a point P _{0 which} is conjugate with the sample surface 2,
It is arranged so as to form an image of the light emitting surface 1a of the light source 1. That is, the condenser lens 5 and the light source 1 are arranged such that the sample surface 2 at the focus position and the image of the light emitting surface 1a are conjugated.

Next, the operation of the focus shift detection mechanism according to the second embodiment will be described.

FIG. 6 is an optical path diagram of a light beam emitted from the light source 1 in the second embodiment. 6 to 10, broken lines L ₁₁ and L ₁₂ indicate light rays emitted from the upper end position of the light emitting surface 1a of the light source 1, and two-dot chain lines L ₁₃ and L ₁₄ indicate light emitting surface of the light source 1. Shows rays emanating from the lower end of 1a, indicated by the solid lines L ₁₅ and L
Reference numeral ₁₆ denotes a light beam that passes through the edge 7a of the light-shielding plate 7 in the immediate vicinity thereof. Further, in the following description, the expression “upper” or “lower” means the upper and lower sides of the paper of each drawing.

Further, FIG. 7 is an enlarged optical path diagram showing the edge 7a of the light shielding plate 7 in FIG. In FIG. 7, a broken line L ₁₇ perpendicular to the alternate long and short dash line showing the optical axis LA shows the image I ₁ of the light emitting surface 1 a of the light source 1 formed by the condenser lens 5. The solid line L ₁₈ following the vertical broken line L ₁₇ is the light shield plate 7.
The rest of the image I ₁ that is not formed due to light shielding is shown, and the total of the vertical broken line L ₁₇ and the vertical solid line L ₁₈ indicates the entire image I ₁ that would be formed if the light shielding plate 7 were excluded.

8 to 10 are enlarged views of the sample surface 2 in FIG. 6 to irradiate the sample surface 2 with the broken lines L ₁₁ and L ₁₂ and the solid line.
Is a diagram showing an optical path of L ₁₅ and L _16. However, in FIG. 8, the sample surface 2 is in the in-focus position, in FIG. 9, the sample surface 2 is in the out-of-focus position in the rear pin direction, and in FIG.
Is in the out-of-focus position in the front focus direction.

When the sample surface 2 is in the focus position, the light emitting surface 1a of the light source 1
Of the light forming the image I ₁ of FIG. 7, the light rays passing near the edge 7a of the light shielding plate 7 as shown by the solid lines L ₁₅ and L ₁₆ in the seventh illustration are the sample surface 2 at the in-focus position and the light shielding plate. Since the edge 7a of 7 is conjugated, as shown in FIG. 8, an image is formed on the sample surface 2 at a position immediately adjacent to P ₁ which is a position conjugate with the edge 7a of the light shielding plate 7. Further, for example, as indicated by broken lines L ₁₁ and L ₁₂ in the seventh illustration, a light ray that has passed below the immediate vicinity of the edge 7a of the light shielding plate 7 is imaged at a position above the immediate vicinity of the P _1. . on the other hand,
Since the portion below the position P ₁ that is conjugate with the edge 7a of the light shield 7 is conjugate with the upper edge 7a of the light shield 7, the light from the light source 1 is blocked by the light shield 7 and is dark.

In this way, the sample surface 2 at the in-focus position is bright at the upper part and the shadow of the light-shielding plate 7 below the boundary with the position P ₁ conjugate with the edge 7a of the light-shielding plate 7 as the boundary. And it's dark. Therefore, the reflected light from the sample surface 2 at the in-focus position is the light reflected at a position above the position P ₁ which is conjugate to the edge 7a of the light shield plate 7, and is conjugated to the edge 7a of the light shield plate 7 as described above. An arbitrary position in the area above the unique position P ₁ is defined as a point A ₁ .

11 shows a solid line of the reflected light at A ₁ on the sample surface 2 at the in-focus position shown in FIG. 8 at the position of the edge 7a of the light shielding plate 7.
It is an optical path diagram showing in La ₁ and La _2. In Fig. 11, the solid line La
₁ and La ₂ are, as shown by A ₂ below the edge 7a of the light shield plate 7,
It passes through the position conjugate to A ₁ .

In this way, the reflected light from the sample surface 2 at the focus position is
Position P ₁ conjugate with edge 7a of light shield 7 on sample surface 2
The light is reflected in the upper range, passes under the end edge 7a of the light shield plate 7, and travels while hiding the light shield plate 7. Therefore, the surface of the light shield plate 7 on the sample surface 2 side is not irradiated.

On the other hand, when the sample surface 2 is at the non-focused position in the rear pin direction, the sample surface 2 and the edge 7a of the light shielding plate 7 are not conjugate, and therefore, as indicated by solid lines L ₁₅ and L ₁₆ in FIG. The light ray passing near the edge 7a of the light shielding plate 7 is once imaged at a position near the point P ₁ as shown in FIG. . As described above, the sample surface 2 at the non-focused position in the rear focus direction has a thin bright portion between the bright portion and the dark portion. Here, an arbitrary position in the light and bright area that spreads to the dark side in the light and bright portion is defined as a point B ₁ . At this point B ₁ , an imaginary line (which coincides with the optical axis LA in FIG. 9) extending parallel to the optical axis LA from the point P ₁ which is a position conjugate with the edge 7a of the light shielding plate 7 as a starting point This is a position that hits the sample surface 2 at a non-focused position in the direction.
Located below S ₁ . (Note that the edge 7a of the light-shielding plate 7 is the optical axis.
When separated from LA, the imaginary line separates from the optical axis LA in parallel.) FIG. 12 shows the point B _{1 at} the position of the edge 7a of the light shielding plate 7.
FIG. ₃ is an optical path diagram showing reflected light at solid lines Lb ₁ and Lb ₂ . In FIG. 12, a point B ₂ is a position conjugate with the point B _1, and solid lines Lb ₁ and L
The reflected light at the point B ₁ indicated by b ₂ passes through the point B ₂ . In addition,
The position of the point B ₂ is the edge 7a of the light shielding plate 7 in the optical axis direction.
It is closer to the sample surface 2 and above the end edge 7a of the light shielding plate 7 in the direction perpendicular to the optical axis LA. Therefore, some of the reflected light from the sample surface 2 at the non-focused position in the rear focus direction always illuminates the surface of the light shielding plate 7 on the sample surface 2 side.

Next, even when the sample surface 2 is at the non-focused position in the front focus direction, the sample surface 2 and the edge 7a of the light shielding plate 7 are not conjugated. Therefore, as shown by the solid lines L ₁₅ and L ₁₆ in the seventh illustration,
The light beam that passes through the vicinity of the edge 7a of the light shielding plate 7 by passing
As shown in the figure, the image reaches the sample surface 2 before the image is formed near the point P ₁ while the image is still being blurred, and the sample surface 2 is illuminated in a dimly lit state. In this way, a thin bright portion is formed between the bright portion and the dark portion on the sample surface 2 at the non-focused position in the front focus direction. Here, an arbitrary position in the light and bright area that spreads to the dark side in the light and bright portion is defined as a point B ₃ . This point B ₃ is 2
The imaginary line indicated by the dotted chain line L ₁₉ is located below S _2, which is the position that hits the sample surface 2 at the non-focused position in the front focus direction.

FIG. 13 shows the point B _{3 at} the position of the edge 7a of the shading plate 7.
FIG. 7 is an optical path diagram showing reflected light at the solid lines Lb ₃ and Lb ₄ . In FIG. 13, a point B ₄ is a position conjugate with the point B ₃ , and the position is the light source 1 from the edge 7a of the light shielding plate 7 in the optical axis direction.
In the direction close to and perpendicular to the optical axis LA, it is above the edge 7a of the light shield plate 7. Therefore, the reflected light at the point B ₃ indicated by the solid lines Lb ₃ and Lb ₄ illuminates the surface of the light shielding plate 7 on the sample surface 2 side, which is in front of the point B ₄ . Therefore, some of the reflected light from the sample surface 2 at the light focusing position in the front focus direction always irradiates the surface of the light shielding plate 7 on the sample surface 2 side.

As described above, when the sample surface 2 is in the in-focus position, the amount of light reflected from the sample surface 2 that illuminates the surface of the light-shielding plate 7 on the sample surface 2 side is larger than that in the non-in-focus position. Few.

Third Example The third example is different from the second example in the position where the condenser lens 5 is arranged. In the second embodiment, the condenser lens 5 is formed so that the image I ₁ of the light emitting surface 1a of the light source 1 formed by the condenser lens 5 is formed at the position of the point P ₀ conjugate with the sample surface 2 at the focus position. In contrast to the above-mentioned point P _0,
The condenser lens 5 is arranged at a position closer to the sample surface 2 so that the image I ₂ of the light emitting surface 1a of the light source 1 formed by the condenser lens 5 is formed.

Next, the operation of the focus shift detection mechanism according to the third embodiment will be described. FIG. 14 is an optical path diagram of a light beam emitted from the light source 1 in the third embodiment. In addition, from FIG.
In FIG. 18, broken lines L ₂₁ and L ₂₂ and a solid line L ₂₅ represent light rays emitted from the upper end position of the light emitting surface 1a of the light source 1, and are indicated by a two-dot chain line L ₂₃ ,
L ₂₄ and the solid line L ₂₆ show the light rays emitted from the lower end position of the light emitting surface 1a of the light source 1, and among them, the solid lines L ₂₅ and L ₂₆ are the light shielding plate 7
Shows a ray passing near the edge 7a.

FIG. 15 is an enlarged optical path diagram showing the edge 7a of the light shielding plate 7 in FIG. In FIG. 15, a wavy line L ₂₇ perpendicular to the one-dot chain line showing the optical axis LA shows the image I ₂ of the light emitting surface 1 a of the light source 1 formed by the condenser lens 5. It should be noted that this image I ₂ is an edge of the light shielding plate 7 as in the second embodiment.
Since it is not formed at the position of 7a, the image I ₂ is not missing.

16 to 18 are enlarged views of the sample surface 2 in FIG. 14 to irradiate the sample surface 2 with the broken line L ₂₂ and the chain double-dashed line L.
Is a diagram showing an optical path of ₂₄ and a solid line L ₂₅ and L _26. However, the 16th
In the figure, the sample surface 2 is in the in-focus position, in FIG. 17, the sample surface 2 is in the out-of-focus position in the rear pin direction, and in FIG. 18, the sample surface 2 is in the out-of-focus position in the front pin direction. is there.

As shown in FIG. 15, as indicated by the broken lines L ₂₁ and L ₂₂ and the solid line L ₂₅ ,
A part of the light beam emitted from the upper end of the light emitting surface 1a of the light source 1 is blocked by the light shielding plate 7 as shown by a broken line L ₂₁ , but a broken line L ₂₂ and a solid line L ₂₅
Others reach the sample surface 2 like. Also, like the two-dot chain lines L ₂₃ , L ₂₄ and the solid line L ₂₆ , the light rays emitted from the lower end of the light emitting surface 1a of the light source 1 are partially blocked by the light shielding plate 7 as the two-dot chain line L _23. Others reach the sample surface 2, such as the two-dot chain line L ₂₄ and the solid line L ₂₆ . Of the light that reaches the sample surface 2, the light that has passed near the edge 7a of the light shielding plate 7 as indicated by the solid lines L ₂₅ and L ₂₆ is at the in-focus sample surface 2 as shown in FIG. An image is formed in the vicinity of the point P ₁ which is a position conjugate with the edge 7a of the light shielding plate 7. The broken line L ₂₂ and the chain double-dashed line L ₂₄
As described above, the light passing below the edge 7a of the light shielding plate 7 reaches above the point P ₁ on the sample surface 2 at the in-focus position.

As described above, also in the third embodiment, the sample surface 2 at the in-focus position has the edge 7a of the light shielding plate 7 as in the second embodiment.
With the position P ₁ conjugate with the boundary as the boundary, the upper part is bright, and the lower part is shaded by the light shielding plate 7 and dark.
Therefore, the reflected light from the sample surface 2 at the focus position is
Light that is reflected above the position P ₁ that is conjugate to the edge 7a of the shading plate 7, and is the same as the light rays shown by solid lines La ₁ and La ₂ in FIG. 11 passing through A _2. Since it passes under the end edge 7a of the substrate and advances by shading the light shielding plate 7, the surface on the sample surface 2 side is not irradiated.

On the other hand, if the sample surface 2 as 17 shown is in-focus position of the rear focus direction, as in the fifteenth solid line shown L ₂₅ and L _26, passes near the edge 7a of the light shielding plate 7 Do the light rays
Once it forms an image at a position near P ₁ , it blurs and spreads,
Illuminate the sample surface 2 lightly and brightly. As described above, the sample surface 2 at the non-focused position in the rear focus direction has a thin bright portion between the bright portion and the dark portion. Where the
17 If the point B ₅ is an arbitrary position in the thin bright area that spreads to the dark side in the thin bright portion shown in the figure, the reflected light at the point B ₅ is the reflected light at the point B ₁ shown in FIG. Similarly to 7
The surface on the sample surface 2 side of is irradiated. Therefore, some of the reflected light from the sample surface 2 at the non-focused position in the rear focus direction always illuminates the surface of the light shielding plate 7 on the sample surface 2 side.

Further, if the sample surface 2, as 18 shown is in the non-focus position of the front focus direction, as in the fifteenth solid line shown L ₂₅ and L _26, passes near the edge 7a of the light shielding plate 7 Do the light rays
Before the image is formed in the vicinity of P ₁ , it reaches the sample surface 2 while it is still blurry and illuminates the sample surface 2 in a dim light. In this way, a thin bright portion is formed between the bright portion and the dark portion on the sample surface 2 at the non-focused position in the front focus direction. Here, if the point B ₆ is an arbitrary position within the thin bright area that spreads to the dark side in the thin bright portion shown in FIG. 18, the reflected light at the point B ₆ is the point B ₃ shown in FIG. The surface of the light shield plate 7 on the side of the sample surface 2 is illuminated in the same manner as the reflected light. Therefore, some of the reflected light from the sample surface 2 at the non-focused position in the front focus direction is always
The surface of the light shielding plate 7 on the sample surface 2 side is irradiated.

As described above, when the sample surface 2 is in the in-focus position, the amount of light reflected from the sample surface 2 that illuminates the surface of the light-shielding plate 7 on the sample surface 2 side is larger than that in the non-in-focus position. Few.

[Fourth Embodiment] In the fourth embodiment, the position where the condenser lens 5 is arranged is different from the second and third embodiments. In the third embodiment, the sample plane 2 is moved from the position of the point P ₀ conjugate to the sample plane 2 at the focus position.
The condensing lens ₅ is arranged so that the image I ₃ of the light emitting surface 1a of the light source 1 is formed by the condensing lens ₅ , whereas in the fourth embodiment, the point P _{0 is different} from the point P ₀ . The condenser lens ₅ is arranged at a position near the light source 1 so that the image I ₃ of the light emitting surface 1a of the light source 1 formed by the condenser lens ₅ is formed.

Next, the operation of the focus shift detection mechanism according to the fourth embodiment will be described. FIG. 19 is an optical path diagram of a light beam emitted from the light source 1 in the fourth embodiment. 19 and 20, the broken lines L ₃₁ , L ₃₂ and the solid line L ₃₅ indicate the light source 1
2 shows the light beam emitted from the upper end of the light emitting surface 1a of
L ₃₃ and L ₃₄ and the solid line L ₃₆ indicate light rays emitted from the lower end position of the light emitting surface 1a of the light source 1, and among them, the solid lines L ₃₅ and L ₃₆ pass near the end edge 7a of the light shielding plate 7. The rays of light to be shown.

FIG. 20 is an optical path diagram showing an enlarged end edge 7a of the light shielding plate 7 in FIG. Note that, in FIG. 20, a broken line L ₃₇ perpendicular to the alternate long and short dash line showing the optical axis LA shows the image I ₃ of the light emitting surface 1 a of the light source 1 formed by the condenser lens 5. It should be noted that this image I ₃ is the edge of the light shielding plate 7 as in the second embodiment.
The image I ₃ is not missing because it is not formed at the position of 7a.

As indicated by the broken lines L ₃₁ and L ₃₂ and the solid line L ₃₅ , the light emitted from the upper end of the light emitting surface 1a of the light source 1 passes through the lower end of the image I ₃ , and part of the light is directed to the light shielding plate 7 as indicated by the broken line L _32. Others reach the sample surface 2 as shown by the broken line L ₃₁ and the solid line L ₃₅ . Also, the two-dot chain line L ₃₃ ,
The light emitted from the lower end of the light emitting surface 1a of the light source 1 as shown by L ₃₄ and the solid line L ₃₆ passes through the upper end of the image I ₃ and is partially blocked by the light shielding plate 7 as shown by the chain double-dashed line L _34. However, like the two-dot chain line L ₃₃ and the solid line L ₃₆ , others reach the sample surface 2.

Of the light reaching the sample surface 2, the light rays that have passed near the edge 7a of the light shielding plate 7 as shown by the solid lines L ₃₅ and L ₃₆ are at a position conjugate with the edge 7a of the light shielding plate P. Image near ₁ . It should be noted that, as indicated by the broken line L ₃₁ and the chain double-dashed line L ₃₃ , the light rays that have passed below the edge 7 a of the light shielding plate 7 reach above the point P ₁ on the sample surface 2 at the in-focus position.

As described above, also in the fourth embodiment, the sample surface 2 at the in-focus position has the edge 7a of the light shielding plate 7 as in the above embodiments.
With the position P ₁ conjugate with the boundary as the boundary, the upper part is bright, and the lower part is shaded by the light shielding plate 7 and dark.
Therefore, the reflected light from the sample surface 2 at the focus position is
It is the light reflected above the position P ₁ which is conjugate to the edge 7a of the shading plate 7 and is similar to the solid lines La ₁ and La ₂ passing through A ₂ in FIG. It passes under 7a, and the surface on the sample surface 2 side is not irradiated.

On the other hand, when the sample surface 2 is at the out-of-focus position in the rear focus direction, the light rays passing near the end edge 7a of the light shielding plate 7 as shown by the solid lines L ₃₅ and L ₃₆ in FIG. The image is once formed in the vicinity of P ₁ and then spreads out in a blurry manner to illuminate the sample surface 2 in a thin and bright manner. As described above, the sample surface 2 at the non-focused position in the rear focus direction has a thin bright portion between the bright portion and the dark portion. The reflected light at an arbitrary position within the thin bright area that spreads to the dark side in the thin bright portion is the same as the reflected light at the point B ₁ shown in FIG.
The surface on the sample surface 2 side of is irradiated. Therefore, some of the reflected light from the sample surface 2 at the non-focused position in the rear focus direction always illuminates the surface of the light shielding plate 7 on the sample surface 2 side.

Further, when the sample surface 2 is at the out-of-focus position in the front focus direction, the light rays passing near the end edge 7a of the light shielding plate 7 as shown by the solid lines L ₃₅ and L ₃₆ in the twentieth illustration are Before the image is formed in the vicinity of P ₁ , it reaches the sample surface 2 while it is still blurred and spreads, and the sample surface 2 is illuminated with a bright light.
In this way, a thin bright portion is formed between the bright portion and the dark portion on the sample surface 2 at the non-focused position in the front focus direction. The arbitrary reflected light in the thin bright area that spreads to the dark side in this thin bright portion is the same as the reflected light at the point B ₃ shown in FIG. Irradiate. Therefore, some of the reflected light from the sample surface 2 at the non-focused position in the front focus direction is always inevitable.
The surface on the sample surface 2 side of is irradiated.

As described above, when the sample surface 2 is in the in-focus position, the amount of light reflected from the sample surface 2 that illuminates the surface of the light-shielding plate 7 on the sample surface 2 side is larger than that in the non-in-focus position. Few.

[Fifth Embodiment] In the fifth embodiment, the position where the condenser lens 5 is arranged is the same as the first embodiment.
Different from the second, third and fourth embodiments. In the fifth embodiment, the light source 1 formed by the condenser lens 5 is located at the focus position F of the objective lens 6.
The condensing lens 5 is arranged so that the image I ₄ of the light emitting surface 1a is formed, that is, the focus F of the objective lens 6 and the light emitting surface 1a of the light source 1 are conjugated. Thereby, the light from the light source 1 illuminates the sample surface 2 with parallel light.

Next, the operation of the focus shift detection mechanism according to the fifth embodiment will be described. FIG. 21 is an optical path diagram of a light beam emitted from the light source 1 in the fifth embodiment. 21 and 22, broken lines L ₄₁ and L ₄₂ and a solid line L ₄₅ indicate the light source 1
2 shows the light beam emitted from the upper end of the light emitting surface 1a of
L ₄₃ and L ₄₄ and the solid line L ₄₆ indicate the light rays emitted from the lower end position of the light emitting surface 1a of the light source 1, and among them, the solid lines L ₄₅ and L ₄₆ are close to the edge 7a of the light shielding plate 7 The rays of light passing through.

FIG. 22 is an enlarged optical path diagram showing the edge 7a of the light shielding plate 7 in FIG. Note that, in FIG. 22, a broken line L ₄₇ perpendicular to the alternate long and short dash line showing the optical axis LA shows an image I ₄ of the light emitting surface 1a of the light source 1 formed by the condenser lens 5. It should be noted that this image I ₄ is the edge of the light-shielding plate 7 as in the second embodiment.
Since it is not formed at the position of 7a, it is not chipped.

A part of the light beam emitted from the upper end of the light emitting surface 1a of the light source 1 is blocked by the light shielding plate 7 as shown by a broken line L ₄₁ , but the other part is broken by a broken line L _42.
And like a solid line L _45, through the lower end of the image I _4, the sample surface 2
Reach. Further, light emitted from the lower end of the light emitting surface 1a of the light source 1, a part like a two-dot chain line L ₄₃ is blocked by the light shielding plate 7, and the other as the two-dot chain line L ₄₄ and solid L _46, It reaches the sample surface 2 through the upper edge of the image I ₄ .

Of the light reaching the sample surface 2, light rays that have passed near the edge 7a of the light shielding plate 7 as indicated by solid lines L ₄₅ and L ₄₆ are points that are conjugate with the edge 7a of the light shielding plate P ₁ The image is formed at a position near. As indicated by the broken line L ₄₂ and the chain double-dashed line L ₄₄ ,
The light that has passed below the edge 7a reaches the point P ₁ on the sample surface 2 at the focus position.

As described above, also in the fifth embodiment, the sample surface 2 at the in-focus position has the edge 7a of the light shielding plate 7 as in the above-described embodiments.
With the position P ₁ conjugate with the boundary as the boundary, the upper part is bright, and the lower part is shaded by the light shielding plate 7 and dark.
Therefore, the reflected light from the sample surface 2 at the focus position is
It is the light reflected above the position P ₁ which is conjugate to the edge 7a of the shading plate 7 and is similar to the solid lines La ₁ and La ₂ passing through A ₂ in FIG. After passing under 7a, the shading plate 7 is scratched and advanced, and the surface on the sample surface 2 side is not irradiated.

On the other hand, when the sample surface 2 is at the out-of-focus position in the rear focus direction, the light rays passing near the end edge 7a of the light shielding plate 7 as shown by solid lines L ₄₅ and L ₄₆ in FIG. The image is once formed in the position closest to P ₁ , then blurred and spread, and the sample surface 2 is illuminated brightly. As described above, the sample surface 2 at the non-focused position in the rear focus direction has a thin bright portion between the bright portion and the dark portion. The reflected light at an arbitrary position within the thin bright area that spreads to the dark side in the thin bright portion is the same as the reflected light at the point B ₁ shown in FIG.
The surface on the sample surface 2 side of is irradiated. Therefore, some of the reflected light from the sample surface 2 at the non-focused position in the rear focus direction always illuminates the surface of the light shielding plate 7 on the sample surface 2 side.

Further, when the sample surface 2 is at the out-of-focus position in the front focus direction, the light rays passing near the end edge 7a of the light shielding plate 7 as shown by the solid lines L ₄₅ and L ₄₆ in the 21st drawing are the same as those in the P Before the image is formed in the vicinity of ₁ , the sample surface 2 reaches the sample surface 2 while it is still blurry, and the sample surface 2 is irradiated with light. In this way, a thin bright portion is formed between the bright portion and the dark portion on the sample surface 2 at the non-focused position in the front focus direction. The arbitrary reflected light in the thin bright area that spreads to the dark side in this thin bright portion is the same as the reflected light at the point B ₃ shown in FIG. Irradiate. Therefore, some of the reflected light from the sample surface 2 at the non-focused position in the front focus direction is always inevitable.
The surface on the sample surface 2 side of is irradiated.

As described above, when the sample surface 2 is in the in-focus position, the amount of light reflected from the sample surface 2 that illuminates the surface of the light-shielding plate 7 on the sample surface 2 side is larger than that in the non-in-focus position. Few.

[Sixth Embodiment] The sixth embodiment differs from the above-described embodiments in that the condenser lens 5 is not arranged.

Next, the operation of the focus shift detection mechanism according to the embodiment of FIG. 6 will be described. FIG. 23 is an optical path diagram of a light beam emitted from the light source 1 in the sixth embodiment. Figure 24 shows
FIG. 20 is an optical path diagram showing an enlarged end edge 7a of the light shielding plate 7 in FIG. 23 to 24, broken lines L ₅₁ , L ₅₂ and a solid line L ₅₅ represent light rays emitted from the upper end position of the light emitting surface 1a of the light source 1, and are indicated by two-dot chain lines L ₅₃ , L ₅₄ and a solid line L _{55. Reference numeral 56} denotes light rays emitted from the lower end position of the light emitting surface 1a of the light source 1, and solid lines L ₅₅ and L ₅₆ among them indicate light rays that pass while grazing the vicinity of the edge 7a of the light shielding plate 7.

The sixth embodiment is the same as the fourth embodiment (FIGS. 19 and 20).
It can be considered to be optically equivalent to disposing the light emitting surface 1a of the light source 1 at the position of the image I ₃ of the light emitting surface 1a of the light source 1 in the drawing).

Therefore, similarly to the fourth embodiment, also in the sixth embodiment, the light amount of the reflected light from the sample surface 2 that illuminates the surface of the light shielding plate 7 on the sample surface 2 side is the focus position of the sample surface 2. In the case of, it is less than in the case of being out of focus.

[Seventh Embodiment] In the seventh embodiment, the light emitting surface of the light source 1 is attached to the edge 7a of the light shielding plate 7.
The arrangement is different from that in each of the above-described examples, in that they are arranged so that 1a is in contact therewith. In order to do so, for example, the edge of the light emitting surface 1a of the light source 1 and the edge 7a of the light shielding plate 7 may be adjacent to each other without a gap. Alternatively, the edge 7a of the light shielding plate 7 is the light emitting surface of the light source 1.
The light source 1 may be arranged at the end edge 7a of the light shielding plate 7 so as to partially cover 1a.

The seventh embodiment is the same as the second embodiment (FIGS. 5 to 5).
It can be considered that it is optically equivalent to disposing the light emitting surface 1a of the light source 1 at the position of the image I ₁ of the light emitting surface 1a of the light source 1 in FIG. 13).

Therefore, similarly to the second embodiment, also in the seventh embodiment, the light amount of the reflected light from the sample surface 2 that irradiates the surface of the light shield plate 7 on the sample surface 2 side is the focus position of the sample surface 2. In the case of, it is less than in the case of being out of focus.

[Supplementary Explanation to the Embodiments] The positions where the light source 1 and the condenser lens 5 are arranged with respect to the sample surface 2 are not limited to the above-mentioned embodiments. Further, the position where the light source 1 and the condenser lens 5 are arranged with respect to the objective lens 6 is not limited to the above embodiment. Further, it is not always necessary to arrange the condenser lens 5. In short, the edge 7a of the light shielding plate 7 is arranged between the light source 1 and the sample surface 2, and a part of the light beam emitted from the light source 1 is blocked by the light shielding plate 7 or in the vicinity of the light beam. 1 may be arranged.

As shown in the twenty-fifth figure, a half mirror 9 is attached between the objective lens 6 and the light shield plate 7, the optical path of the reflected light from the sample surface 2 is folded back by the half mirror 9, and the light shield plate is formed in the folded optical path. The light amount detecting element 8 may be arranged at a position conjugate with the surface of the sample surface 2 on the sample surface 2 side. The “reflected light from the sample surface that illuminates the surface of the light shield plate on the sample surface side” in the configuration of the present invention is, for example, as shown in FIG. 25, not conjugate with the surface of the light shield plate 7 on the sample surface 2 side. The reflected light from the sample surface 2 received by the surface is also included.

As shown in FIG. 26, the light amount detection element 8 may be directly attached to the edge 7a of the light shield plate 7. The light amount detection element 8 may be arranged so as to detect reflected light from the sample surface 2 that is incident on the surface of the light shield plate 7 on the sample surface 2 side regardless of how and where it is attached. In the case of the 26th illustration, the light received by the light amount detecting element 8 is the light before the surface of the light shielding plate 7 on the sample surface 2 side is irradiated, and the light amount is detected from the light shielding plate 7 by irradiating the light shielding plate 7. Although it is different from the light reflected to the element 8, the “reflected light from the sample surface that irradiates the sample surface side of the light shielding plate” in the configuration of the present invention is, for example,
As shown in FIG. 26, the light before the surface of the shading plate 7 on the sample surface 2 side is also irradiated without actually irradiating the surface of the shading plate 7 on the sample surface 2 side.

The light amount detection element 8 may also be used as the light shield plate 7. That is, as shown in FIG. 27, the back surface (non-light-receiving surface) of the semi-circular (not necessarily semi-circular) light amount detecting element 8 is attached to the front surface of the transparent plate 15, and the light source is attached to the back surface. 1
Blocks the light beam from the sample surface 2
You may make it receive the reflected light flux from.

The shape of the edge 7a of the light shielding plate 7 does not need to be a straight line,
Any shape can be adopted as long as it is linear, for example, it can be curved as shown in FIG. 28, bent like a saw tooth, or ring-shaped as shown in FIG. 29. Good.

By the way, when the end edge 7a of the light shielding plate 7 is formed into a curved shape or a polygonal line shape (hereinafter collectively referred to as a non-linear shape), the following effects can be expected.

The position shift detecting mechanism according to the present invention detects a position shift state from the reference position of the sample surface 2 (corresponding to the in-focus position in the above embodiment) from the conjugate relationship between the sample surface 2 and the edge 7a of the light shielding plate 7. Therefore, if the edge 7a of the light shielding plate 7 is linear,
The object for detecting the positional deviation state on the sample surface 2 is linear, and if the edge 7a of the light shielding plate 7 is non-linear, the object for detecting the positional deviation state is also non-linear. By the way, when the sample surface 2 has a pattern with a large contrast like a photomask, for example, the reflected light at the dark portion of the pattern is weak, and therefore the object of position shift state detection on the sample surface 2 is the light amount detection element 8. S / of the signal output from
To improve N, it is desirable to avoid the dark part of the pattern as much as possible. Therefore, in the case where the dark portion of the pattern is linear, if the edge 7a of the light shielding plate 7 is made non-linear as described above, the entire length of the linear portion that is the target of the positional deviation detection is the linear pattern. It is possible to avoid matching with the dark part of.

In the case of making it non-linear, in order to make the entire length of the edge 7a of the shading plate 7 conjugate with the sample surface 2 at the reference position, the surface of the shading plate 7 on the sample surface 2 side is It may be arranged so as to be parallel to the sample surface 2 at the reference position.
However, in the case of such plane parallelization, the optical path of the reflected light from the surface of the light shielding plate 7 on the sample surface 2 side toward the light amount detection element 8 does not have an angle with the optical axis,
If the light amount detection element 8 is arranged at a position suitable for receiving such reflected light, there is a possibility that the light amount detection element 8 may block the light beam emitted from the light source 1 and traveling toward the sample surface 2. As a measure for avoiding such inconvenience, for example, as described above, the light amount detection element 8 may be used also as the light shielding plate 7.

When the shape of the edge 7a of the light-shielding plate 7 is linear, it is expected that the displacement from the reference position can be detected without any trouble even if the sample surface 2 is inclined. On the sample surface 2, if the linear portion that is the object of the positional deviation state detection is linear, the object of the positional deviation state detection on the sample surface 2 is linear, that is, it does not oppose the slope, that is, at a right angle to the tilt direction. This is because the misregistration state can be detected along this direction.

In the method of detecting the focus from the balance of the amount of received light between the two split sensors, like the focus shift detection mechanism using the two split sensors introduced as the prior art, the detection target area is the light source. It is difficult to detect the misalignment state with respect to the inclined sample surface because the entire irradiation area of the light from, that is, the surface is not linear like the present invention.

In the first to sixth embodiments, in order to arrange the light shielding plate 7 and the light amount detecting element 8 so that the light amount detecting element 8 can efficiently receive the reflected light from the sample surface 2, for example, It may be done as shown in FIGS. 30 (a) and 30 (b).

That is, the light blocking plate 7 is fixed to the light blocking plate support 10, and the light amount detecting element 8 is fixed to the light amount detecting element support 11. A bolt 12 and a light amount detection element support screwed to the light shield support 10
The bolt 13 screwed to 11 is engaged with a fixing member (not shown) so as to be guided and moved in an arcuate guide groove 14 centered on a point P ₀ conjugate with the sample surface 2 at the reference position, Therefore, the light-shielding plate 7 and the light amount detecting element 8 can adjust the mounting position by moving around the point P ₀ .

As shown in the enlarged view of the main part of FIG. 30 (b), the vicinity of the edge 7a on the surface of the light shielding plate 7 on the sample surface 2 side is
The mirror surface 7b is formed so as to efficiently reflect the reflected light from the sample surface 2 toward the light amount detection element 8. Also,
The light amount detecting element support 11 is provided with the cylindrical lens 15 so that the light amount detecting element 8 can efficiently receive the light from the mirror surface 7b, but the lens is not necessarily required.

In each of the above-mentioned embodiments, the characteristic curve of the light amount detecting element 8 is shown in FIG. 31, and the position of the sample surface 2 when the amount of received light is the minimum is the in-focus position.

Therefore, the focus detection work in each of the above-described embodiments is performed, for example, as the initial operation in the determination area A of the characteristic curve of FIG.
Inside, try to bring the sample surface 2 and the objective lens 6 relatively close to each other. Due to this relative approach, the light amount detection element 8
When the amount of received light decreases in the front focus state, if the autofocus operation is stopped at the position where the amount of received light is minimized by continuing the approaching operation, the focus state is achieved.

Further, when the amount of received light increases due to the relative approach, it is in the back focus state, so that the amount of received light decreases when switching to the operation of relatively separating the sample surface 2 and the objective lens 6 this time. Then, if the autofocus operation is stopped at the position where the amount of received light is minimized, the in-focus state is achieved.

When the sample surface 2 is, for example, the surface of a transparent substrate such as a glass plate, back surface reflected light is generated. Therefore, when the characteristic curve of the light amount detection element 8 is illustrated, as shown in FIG.
It is a characteristic curve where two valleys, large and small, appear. The bottom of the large valley corresponds to the state where the sample surface 2, that is, the front surface of the transparent substrate is in the reference position, and the small valley corresponds to the state where the back surface of the transparent substrate is in the reference position. As described above, according to the present invention, it is possible to detect the displacement of the transparent substrate from the reference position.

In each of the above-described embodiments, the edge 7a of the light shield plate 7 is arranged so as to be conjugate with the sample surface 2 at the reference position.
May be arranged conjugate with a position displaced from the sample surface 2 at the reference position in the front pin direction or the rear pin direction. When the edge 7a of the light shielding plate 7 is arranged in such a manner, the bottom of the valley in the characteristic curve of the light amount detecting element 8 as shown in FIG. 31 does not correspond to the reference position, and Become.
For example, when the edge 7a of the light shielding plate 7 is arranged in a conjugate position with respect to the reference position, which is deviated from the sample surface 2 in the front pin direction (tentatively, P _X ), the characteristic curve of the light amount detection element 8 is shown. It is the position of P _X that corresponds to the bottom of the valley in.
It should be noted that the reference position is located at a position displaced from the bottom of the valley of the characteristic curve in the rear pin direction in such a characteristic curve.

By the way, the peculiar effect of arranging the edge 7a of the light shielding plate 7 in a conjugate position with the position displaced from the sample surface 2 at the reference position is that the sample surface 2 is moved from the reference position to the front pin direction or the rear pin direction. This is because it becomes easy to detect in which direction the deviation has occurred. That is, in the case where the edge 7a of the light shielding plate 7 is arranged conjugate with the sample surface 2 at the reference position, in which direction the sample surface 2 moves when the sample surface 2 is moved from the reference position. However, since the amount of light detected by the light amount detecting element 8 increases, it is not easy to detect the moving direction. Sample surface 2 at the reference position
When the end edge 7a of the light shield plate 7 is arranged in a conjugate position with respect to the position deviated from the position, the detected light amount increases or decreases depending on in which direction the sample surface 2 is moved, so that the direction can be detected. However, the movement is limited to the range that does not exceed the bottom of the valley of the characteristic curve. This is because, when moving beyond the bottom of the valley of the characteristic curve, the decrease is reversed to the increase.

As described above, the “reference position” referred to in the configuration of the present invention corresponds not only to the in-focus position, but also to the position deviated from the in-focus position as described above.

It is not essential that the edge 7a of the light shielding plate 7 be aligned with the optical axis of the objective lens 6 as in each of the above-mentioned embodiments. Further, when the optical axis is not matched, for example, the light shielding plate 7 may be arranged so as to intersect with the optical axis, or the light shielding plate 7 may be arranged so as to be away from the optical axis. Either way,
The light blocking plate 7 may be arranged between the objective lens 6 and the light source 1 so as to exceed a part of the light beam irradiating the sample surface 2 or in the vicinity of the light beam.

In each of the above-mentioned embodiments, the light shielding plate 7 is arranged so as to be tilted at an appropriate angle with respect to the optical axis, but the angle is a direction that is convenient for receiving the reflected light from the sample surface 2 which is deviated from the reference position. In addition, the reflected light is detected by the light amount detection element 8
Any orientation is suitable for efficient reflection. Further, for example, when the light amount detecting element 8 is also used as the light shielding plate 7 as shown in the above-mentioned 27th drawing, the light shielding plate 7 may be arranged so as to be orthogonal to the optical axis. In short, the angle formed by the light shield 7 and the optical axis is not specified.

The edge 7a of the light shielding plate 7 does not necessarily need to have the entire length of the edge conjugate with the sample surface 2 at the reference position. Compared with the case where the entire length of the edge 7a of the light shielding plate 7 is conjugate with the sample surface 2 at the reference position, when part of the edge 7a is not conjugated with the sample surface 2 at the reference position, the sample surface 2 is The amount of light detected under the condition of the reference position is only slightly increased, and if the sample surface 2 is at the reference position, it must be smaller than that at the reference position. is there.

The sample surface 2 does not need to be a mirror surface.
Since it is said that the portion of the sample surface 2 that is illuminated by the light from the light source 1 brightly or to some extent faintly is conjugate to the edge 7a of the light shielding plate 7, the sample surface 2 from the reference position This is because the position shift state of is detected. The sample surface 2 is, for example,
Not only a silicon oxide film such as the surface of a silicon wafer, but also a polysilicon film surface, a metal film surface, a resist surface, a coated surface, a glass plate surface, a polished metal surface or the like may be used.

In the above embodiment, the focus position corresponds to the "reference position" referred to in the configuration of the present invention, and it is used for the focus shift detection mechanism of the present invention, but the application of the present invention is the focus shift detection mechanism. The present invention is not limited to the above, but it can also be used in an apparatus for measuring the unevenness on the sample surface by, for example, providing a means for moving the sample surface in the direction orthogonal to the optical axis of the objective lens. That is, if a specific one point on the sample surface is referred to as the “reference position” in the configuration of the present invention and the sample surface is moved in the direction orthogonal to the optical axis, the positional deviation in the optical axis direction due to the movement is caused. By detecting the state, the height of the other portion of the sample surface 2 with respect to the specific portion can be measured, and thus the device can be used as a device for measuring the uneven state of the sample surface. As described above, the present invention is not limited to the detection of the position shift state with respect to the in-focus position, and can be used for the detection of the position shift state of the sample surface from some reference position.

<Effects of the Invention> According to the present invention, the following effects are exhibited.

The light amount detecting element detects the positional deviation state of the sample surface from the reference position by capturing the light amount itself in the light amount detecting element itself, not by comparing the magnitude of the detection signal between the two sensors as in the conventional example. Therefore, the influence of the contrast can be prevented, and a single element can be adopted as the light amount detecting element.

When the sample surface is the surface of the transparent substrate, the characteristic curve of the light amount detection element has a large valley corresponding to the state where the sample surface, that is, the surface of the transparent substrate is at the reference position,
This is a characteristic curve in which a small valley corresponding to the state where the back surface of the transparent substrate is at the reference position appears, and the state of displacement from the reference position can be detected by distinguishing the front side and the back side of the transparent substrate. In other words, the problem that it is difficult to detect the misalignment state due to the irradiation light on the back surface of the substrate as in the above-described prior art is solved, and the misalignment state of the transparent substrate surface can be detected. It is also possible to detect the position shift state of the back surface of the transparent substrate.

[Brief description of drawings]

FIGS. 1 to 30 relate to an embodiment of the present invention, FIG. 1 is a schematic configuration diagram of the first embodiment, and FIG. 2 is a case where the sample surface is at the in-focus position in the first embodiment. FIG. 4 is a diagram showing light rays reflected by the sample surface of FIG. 4, FIG. 3 is a diagram showing light rays reflected by the sample surface when the sample surface is in a non-focused position in the rear pin direction in the first embodiment, FIG. FIG. 5 is a diagram showing light rays reflected by the sample surface when the sample surface is at a non-focused position in the front focus direction in the first embodiment, and FIG. 5 is a schematic configuration diagram of the second embodiment. FIG. 6 is a diagram showing rays of light from a light source in the second embodiment, and FIG. 7 is a diagram showing rays of light from a light source in which an edge of a light shielding plate is enlarged in the second embodiment. FIG. 9 is a diagram showing a light beam that illuminates the sample surface when the sample surface is at the in-focus position in the second embodiment. FIG. 9 shows the rear surface of the sample surface in the second embodiment. FIG. 10 is a diagram showing light rays irradiating the sample surface when the sample surface is in the non-focused position in the front direction, and FIG. 10 is a sample when the sample surface is in the non-focused position in the front pin direction in the second embodiment. FIG. 11 is a diagram showing light rays illuminating the surface, FIG. 11 is a diagram showing light rays reflected by the sample surface at the in-focus position at the position of the edge of the light shielding plate in the second embodiment, and FIG. 12 is the second embodiment. FIG. 13 is a diagram showing a light ray reflected by a sample surface at a non-focused position in the rear-pin direction at the edge position of the light shielding plate in the example, and FIG. 13 is a diagram showing the light beam at the edge position of the light shielding plate in the second embodiment. The figure which shows the light ray reflected by the sample surface of the non-focus position to the front focus direction, FIG. 14 is the figure which shows the light ray from the light source in the 3rd Example, FIG. 15 is the 3rd Example. The figure which shows the light beam from the light source which expands and shows the edge of a light-shielding plate, and FIG. 16 shows the sample surface in a focus position in the 3rd Example. FIG. 17 is a diagram showing light rays irradiating the sample surface, FIG. 17 is a diagram showing light rays irradiating the sample surface when the sample surface is at a non-focused position in the rear pin direction in the third embodiment, FIG. FIG. 19 is a diagram showing light rays irradiating the sample surface when the sample surface is in a non-focused position in the front focus direction in the third embodiment, and FIG. 19 shows light rays from the light source in the fourth embodiment. Fig. 20 is a diagram showing light rays from a light source showing the edge of the light shielding plate in an enlarged manner in the fourth embodiment, and Fig. 21 is a diagram showing light rays from the light source in the fifth embodiment. FIG. 22 is a diagram showing a light beam from a light source showing an end edge of a light shielding plate in an enlarged manner in a fifth embodiment, and FIG. 23 is a diagram showing a light beam from a light source in a sixth embodiment. FIG. 24 is a diagram showing a light beam from a light source showing an end edge of a light-shielding plate in an enlarged manner in the sixth embodiment, and FIG. 25 is another embodiment showing a half-beam between the objective lens and the light-shielding plate. Is a schematic configuration diagram in which the light amount detection element is arranged at a position conjugate with the sample surface side of the light shielding plate by attaching a light beam, and FIG. 26 is a schematic configuration diagram in which the light amount detection element is directly attached to the light shielding plate as another embodiment, FIG. 27 is a schematic configuration diagram in which the light amount detecting element is also used as a light shielding plate as another embodiment, FIG. 28 is a schematic configuration diagram in which the shape of the edge of the light shielding plate is an arc as another embodiment, and FIG. 29 is As another embodiment, a schematic configuration diagram in which the light amount detecting element is also used as a light shielding plate so that the edge of the light shielding plate has a ring shape, FIG. 30 (a) shows the first embodiment to the fifth embodiment. FIG. 30 (b) is an enlarged view of the main part of FIG. 30 (a), and FIG. 31 is a diagram showing the detection of the light amount detecting element by the light amount detecting element. It is a characteristic curve figure of the amount of light to do. FIG. 32 is a characteristic curve diagram of the light amount detected by the light amount detection element when the sample surface is the surface of a transparent substrate. FIG. 33 is a schematic configuration diagram of the first conventional technique, and FIG. 34 is a schematic configuration diagram of the second conventional technique. 1 ... Light source 2 ... Sample surface 6 ... Objective lens 7 ... Shading plate 7a ... Edge of shading plate 8 ... Light amount detection element

Claims (1)

[Claims] 1. A position deviation detecting mechanism for detecting a position deviation state of a sample surface from a reference position as a reference, comprising a light source for irradiating the sample surface, and an objective lens arranged between the light source and the sample surface. , So that the edge matches the position conjugate with the reference position,
A light-shielding plate that is disposed between the objective lens and the light source and shields a part of the light flux emitted from the light source to the sample surface, and is irradiated from the light source including the optical axis of the objective lens,
Of the reflected light from the sample surface with respect to the light flux that is not shielded by the light shielding plate and is irradiated onto the sample surface through the objective lens, the reflected light that irradiates the sample surface side surface of the light shielding plate through the objective lens. A position deviation detecting mechanism comprising a light quantity detecting element for detecting a light quantity, and detecting a deviation amount of the sample surface from the reference position by a detection signal from the light quantity detecting element.