JP2989995B2 - Positioning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning apparatus for adjusting a positional relationship between an object to be illuminated and illumination light in a laser tomography apparatus or a microscope.

[0002]

2. Description of the Related Art Conventionally, as a laser tomography apparatus for evaluating a defect or the like of a test object such as a semiconductor wafer,
For example, as shown in FIG. 7, the inside of a sample 105 is illuminated by a laser beam 101 condensed by a condenser lens 103.
7 and scattered light from the portion illuminated by the portion 913 near the focal point is observed from the observation surface 113 side by a microscope via an observation lens 115. No. 151243). In this apparatus, the position of the laser beam 101 is fixed, and the distance L1 from the illumination surface 107 to the focal point is determined by a precision position detector 915 whose position is fixed relative to the laser beam 101 or based on an image of a microscope. Alignment is performed. The distance L2 from the observation surface 113 to the observation portion is determined by using the autofocus function of the microscope to determine the distance between the position when the microscope is on the observation surface 113 and the position when the laser beam is at the focal point of the laser beam. Positioning is performed with the distance set to L2.

[0003]

However, in this prior art, the position of the focal point of the laser beam fluctuates due to thermal expansion or the like due to temperature fluctuations over a long period of time, and the jig for fixing the object to be inspected. This causes a problem that the positional relationship of each part must be reset before using the apparatus in order to prevent the deterioration of the alignment accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a positioning apparatus which can perform positioning with a simpler configuration and method without the need for complicated setting of the positional relationship of each part. Is to do.

[0005]

In order to achieve the above object, an alignment apparatus according to the present invention converges illumination light from a light source by a condensing means, and moves an object to be illuminated from a direction substantially perpendicular to the illumination surface. An alignment device for adjusting the positional relationship between illumination light and an object to be illuminated in a device for illuminating and observing scattered light from the interior due to the illumination light from a direction at an angle of 90 degrees with respect to an illumination optical axis, the alignment device comprising: Reflecting means interposed in the optical path to the light means for reflecting illumination light from the light source toward the light condensing means; and a part of the illumination light reflected on the illumination surface, which returns through the light condensing means and is reflected by the reflection means. Photoelectric conversion means for detecting light transmitted through the means, and a position adjustment means for adjusting the positional relationship between the illumination light and the illuminated object based on the output of the photoelectric conversion means, the photoelectric conversion means, The illumination surface in the direction perpendicular to the illumination light If you are moving, when a focusing position or the vicinity thereof by the focusing means of the illumination light crosses the end of the illumination plane, which output varies discontinuously,
Further, when the light condensing position is located on the illumination surface, its output is maximum. Here, as the reflection means, a reflection mirror using a dielectric film can be used.

In the positioning apparatus of the present invention, illumination light from a light source is condensed by a light condensing means to illuminate an object to be illuminated from a direction substantially perpendicular to the illumination surface. What is claimed is: 1. A positioning device for adjusting a positional relationship between illumination light and an object to be illuminated in a device for observing scattered light from a direction at an angle of 90 degrees with respect to an illumination optical axis, comprising a light source interposed in an optical path from a light source to the condensing means. Reflecting means for reflecting the illumination light from the light source toward the light condensing means; and photoelectric conversion for detecting light transmitted through the light condensing means and returned from the light condensing means in the illumination light portion reflected on the illumination surface. Means, and a position adjusting means for adjusting the positional relationship between the illumination light and the object to be illuminated based on the output of the photoelectric conversion means, and a polarization rotator provided between the reflecting means and the condensing means. The reflecting means is adapted to respond in accordance with the polarization direction of the light. A prism having a changing rate, the illumination light emitted from the light source is polarized in a predetermined direction, and the prism has a high reflectance to the illumination light, and is irradiated and returned through the polarization rotator. Thus, the illumination light portion has a low reflectance with respect to the illumination light portion whose polarization direction has been rotated.

Further, in the case of application to laser tomography, for example, an object to be illuminated is one in which the inside is observed through an adjacent observation surface through an end of the illumination surface, and illumination light is emitted. A laser beam for illuminating the observed interior in the vicinity of the converging position, wherein the adjusting unit adjusts the illuminating light and the illuminated light so that the converging position is located at a desired depth from the illuminating surface and the observing surface. This is for adjusting the positional relationship between objects.

[0008]

In this configuration, when the illumination light from the light source is reflected by the reflection means and condensed by the light condensing means and illuminates the illumination surface of the illuminated object from a substantially vertical direction, a part of the illumination light becomes The light is reflected by the illumination surface, passes through the condensing means in reverse, and then passes through the reflecting means. The intensity of the transmitted light becomes maximum when the condensing position of the illumination light coincides with the illumination surface. Also,
When the illuminating surface is moved in a direction perpendicular to the illuminating light, when the vicinity of the convergence position of the illuminating light crosses the end of the illuminating surface, it fluctuates discontinuously. Then, by detecting the maximum value and the discontinuous variation point of the transmitted light intensity through the photoelectric conversion means, the light converging position and the illuminating surface and the illuminating light such that the converging position and the end of the illuminating surface coincide. The positional relationship between the illuminated objects is recognized, and the positional relationship between the illumination light and the illuminated object is adjusted based on the recognized positional relationship. Hereinafter, the present invention will be described in more detail through examples.

[0009]

FIG. 1 is a schematic diagram showing a configuration of a laser tomography apparatus to which a positioning apparatus according to one embodiment of the present invention is applied. As shown in the figure, this alignment device is a device that irradiates a laser beam 101 from a light source with a condenser lens 103 and illuminates a sample 105 from a direction substantially perpendicular to an illumination surface 107 thereof. It adjusts the positional relationship with the sample 105, and intervenes in the optical path from the light source to the condenser lens 103 and emits laser light 101 from the light source.
Mirror 109 that reflects light toward the condenser lens 103
And a light receiving element 111 for detecting light that has returned through the condenser lens 103 and transmitted through the dielectric mirror 109 in the laser light portion reflected by the illumination surface 107, and a light receiving element 111
And a position adjusting means for adjusting the positional relationship between the laser beam 101 and the sample 105 based on the output of the laser beam 101. The dielectric mirror 109 preferably has an appropriate reflectivity. In this case, a dielectric mirror made of a dielectric film having a reflectivity of 99% is used. The beam diameter at the condensing position of the laser beam 101 is about several μm.

The inside of the sample 105 is observed through an observation surface 113 adjacent to the end of the illumination surface 107. At this time, the laser light 101 focuses the inside of the observation on the observation surface 113. The positional relationship between the laser beam 101 and the sample 105 is adjusted so that the light condensing position is located at a desired depth from the illumination surface 107 and the observation surface 113 so that the light is illuminated near the position. For observation, scattered light from the vicinity of the converging position illuminated by the laser light 101 is reflected on the observation surface
3 through the observation lens 115 and the imaging lens 117 to be detected by the image pickup device 119. This observation system is arranged so that its optical axis is substantially perpendicular to the illumination direction of the laser beam 101.

In this configuration, when aligning the sample 105 and the laser beam 101, first, the illumination surface 107 is set to be substantially perpendicular to the illumination direction, and
The sample 105 is arranged so that the condensing position of the laser beam 101 is located near the end of 7. Next, the sample 105 is moved stepwise in the direction of the observation lens 115 by a predetermined distance that is several steps smaller than the analysis capability based on the diameter of the focused beam of the laser beam 101. When the laser beam 101 reaches a position where the laser beam 101 irradiates the illumination surface 107, a part of the laser beam 101 is reflected by the illumination surface 107, returns to the dielectric mirror 109 through the condenser lens 103, and further has a part. Body mirror 1
09.

At this time, assuming that the transmittance of the dielectric mirror 109 is t and the reflectance at the illumination surface 107 is λ, the dielectric mirror 1 is incident on the incident light amount I ₀ of the laser beam 101 from the light source.
The amount of light I passing through 09 is I = I ₀ t (1−t) λ. Therefore, for example, t = 1%, λ = 30%, I ₀
= 300 mW, I = I ₀ 0.01 (0.99)
× 0.3 = 2.97 × 10 ⁻³ I ₀ = about 1 mW.

This light amount is enough to be detected by the light receiving element 111, so that the light transmitted through the dielectric mirror 109 is detected by the light receiving element 111. The position of the sample 105 at the time of this detection is the laser beam 1
01 is located at the end of the sample 105, that is, the observation surface 11
This is the position corresponding to 3. Therefore, next, the sample 105 is further placed on the observation lens 115 based on this position.
Is moved by the depth D from the observation surface 113 at the position where the observation is desired to be performed, so that the alignment between the laser beam 101 and the sample 105 in the direction parallel to the observation surface 113 is completed.

Next, the condenser lens 103 is moved in the direction of the optical axis, and adjusted to a position where the output of the light receiving element 111 is maximized. At this time, the external shape of the reflected light from the illumination surface 107 is shown in FIG.
Changes as shown by the broken line. FIG. 7B shows a case where the light condensing position coincides with the illumination surface 107. At this time, the reflected light returns through the condensing lens 103 as parallel light as in the case of incidence, and the dielectric mirror 109 is transmitted. FIG. 9A shows a case where the distance between the sample 105 and the condenser lens 103 is larger than that in the case of FIG. 9B. In this case, a considerable part of the reflected light returns to the dielectric mirror 109. And the light receiving element 111 is
9, the light transmitted through the dielectric mirror 109 is diverged, and the light intensity at the light receiving element 111 is smaller than that in the case of FIG. FIG. 3C shows a case where the distance between the sample 105 and the condenser lens 103 is smaller than that in the case of FIG. 3B. Less than. Therefore, the output O of the light receiving element 111 changes as shown in FIG. 3 with respect to the distance L between the sample 105 and the condenser lens 103. In FIG. 3, (a) to (c) correspond to FIG.
The distances corresponding to the cases (a) to (c) are shown. The distance (b) corresponds to the focal length f of the condenser lens 103.

The distance between the sample 105 and the observation lens 115 can be set using a normal auto-focus mechanism.

FIG. 4 is a schematic diagram showing a positioning apparatus according to another embodiment of the present invention. FIG. 5 is an explanatory view showing the state of polarization of laser light in this device. This device includes a prism 121 whose reflectance changes in accordance with the polarization direction of light, and a polarization rotator 123 between the prism 121 and the condenser lens 103, instead of the dielectric pair mirror 109. Laser light 101 emitted from the light source is polarized in the x direction in the figure. The prism 121 has a reflectance of almost 100% with respect to the laser beam 101 from the light source, and has a reflectance of approximately 100% with respect to the light whose polarization direction has been rotated by being irradiated through the polarization rotator 123 and returned. 100
% Transmittance. As the polarization rotator 123, a Faraday element or the like can be used.

In this configuration, the alignment between the sample 105 and the laser beam 101 is performed in the same manner as described above. In that case, most of the laser light 101 from the light source whose polarization direction 125 is the x direction in the drawing is reflected by the prism 121, and then passes through the polarization rotator 123, at which time the polarization direction is rotated by 45 °. I do. Then, after that, the light passes through the condenser lens 103, is reflected by the illumination surface 107, passes through the condenser lens 103 again, and passes through the polarization rotator 123 in the opposite direction. At this time, the polarization direction is further rotated by 45 °. . As a result, most of the light whose polarization direction has changed to the y-direction is transmitted through the prism 121 and the light-receiving element 1
11 is detected.

According to this, since there is almost no loss of light in the prism 121, the detection sensitivity of the light receiving element 111 is improved. Further, since all the reflected light is eliminated from the optical path via the prism 121 and does not return to the light source direction, adverse effects such as generation of stray light due to multiple reflection and the like are prevented.

Note that, as shown in FIG.
The position of the reflection means such as 09 and the prism 121 is not limited to the above, and may be anywhere on the optical path of the illumination light as long as the position of the light receiving element 111 and the like is made to correspond. Also, this positioning device
The present invention can be applied not only to laser tomography but also to an ordinary microscope. Further, the present invention can be applied not only to the case where laser light is used as illumination light but also to the case where light from a normal lamp is used.

[0020]

According to the present invention, the position between the illuminated object and the illumination light can be directly adjusted without measuring the position of the illuminated object and the illumination light. Therefore, it is not necessary to use a special measuring instrument or to set complicated positional relations of each part, and the alignment can be performed simply by using a simple and inexpensive element such as a light receiving element or a dielectric mirror. Can be. Therefore, the cost of the apparatus can be minimized. In addition, since the alignment is performed directly using the illumination light itself, there is no mutual error that occurs when a sensor probe or the like for measuring the position of each unit is used.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a laser tomography apparatus to which an alignment apparatus according to one embodiment of the present invention is applied.

FIG. 2 is an explanatory diagram showing a state of reflected light from an illumination surface 107 in the apparatus of FIG.

FIG. 3 shows an output O of a light receiving element 111 in the apparatus of FIG.
6 is a graph showing how the distance varies with the distance L between the sample 105 and the condenser lens 103.

FIG. 4 is a schematic diagram showing a positioning device according to another embodiment of the present invention.

FIG. 5 is an explanatory view showing a state of polarization of laser light in the apparatus of FIG.

FIG. 6 is a schematic diagram showing a measurement method in the case of illumination by a plurality of mirrors.

FIG. 7 is an explanatory diagram for explaining a laser tomography apparatus according to a conventional example.

[Explanation of symbols]

101: laser light, 103: condenser lens, 105: sample, 107: illumination surface, 109: dielectric mirror, 111:
Light receiving element, 113: observation surface, 115: observation lens, 11
7: imaging lens, 119: image sensor, 121: prism, 123: polarization rotator.

Claims (4)

(57) [Claims] An illumination light from a light source is condensed by a light condensing means to illuminate an object to be illuminated from a direction substantially perpendicular to the illumination surface.
Then, the scattered light from inside due to the illumination light is
What is claimed is: 1. A positioning device for adjusting a positional relationship between illumination light and an object to be illuminated in a device observing from a direction of 0 degrees, wherein the illumination light from the light source intervenes in an optical path from a light source to the light condensing means. Reflection means for reflecting light toward the light means, photoelectric conversion means for detecting light transmitted through the reflection means and returning through the light condensing means of the illumination light portion reflected on the illumination surface, and the photoelectric conversion means Position adjusting means for adjusting the positional relationship between the illumination light and the illuminated object based on the output of the
And the photoelectric conversion means sets the illumination surface perpendicular to the illumination light.
Direction, the illumination light is collected by the light collecting means.
When the light position or its vicinity crosses the edge of the illumination surface,
Its output fluctuates discontinuously;
When the light position is located on the illumination surface, its output is
A positioning apparatus characterized by being a large one . 2. An apparatus according to claim 1, wherein said reflection means is a reflection mirror using a dielectric film. 3. Illumination light from a light source is condensed by condensing means to illuminate an object to be illuminated from a direction substantially perpendicular to the illumination surface.
Then, the scattered light from inside due to the illumination light is
What is claimed is: 1. A positioning device for adjusting a positional relationship between illumination light and an object to be illuminated in a device observing from a direction of 0 degrees, wherein the illumination light from the light source intervenes in an optical path from a light source to the light condensing means. Reflection means for reflecting light toward the light means, photoelectric conversion means for detecting light transmitted through the reflection means and returning through the light condensing means of the illumination light portion reflected on the illumination surface, and the photoelectric conversion means Position adjusting means for adjusting the positional relationship between the illumination light and the illuminated object based on the output of the
A polarizing rotator between the reflecting means and the condensing means.
The reflection means changes the reflectance according to the polarization direction of light.
The illumination light emitted from the light source is directed in a predetermined direction.
And the prism is
Has a high reflectivity and is illuminated back through the polarization rotator
The illumination light part whose polarization direction has been rotated
An alignment apparatus characterized by having a low reflectance . 4. An object to be illuminated has its interior observed through an adjacent observation surface through an end portion of the illumination surface, and the illumination light illuminates the observed interior in the vicinity of its converging position. The adjusting means adjusts a positional relationship between the illuminating light and the object to be illuminated so as to position the light condensing position at a desired depth from the illuminating surface and the observation surface. The alignment device according to claim 1, wherein: