JPH0675005B2 - Spectrophotometer reflector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a spectrophotometer for measuring the spectral transmittance and the spectral reflectance of a sample, and particularly to the spectral reflectance of a solid sample in the wavelength range from ultraviolet to near infrared. The present invention relates to a reflection device used when

"Prior art and its problems" This type of reflection device installed in the sample chamber of a spectrophotometer having a spectroscopic optical system and a light receiving optical system is a spectral reflection of a lens coating film in a precision industry such as a camera or a copying machine. It is used to measure the reflectance and the spectral reflectance of various reflectors. Further, in the semiconductor industry, it is used for film thickness measurement and refractive index measurement by interference of epitaxial layers such as germanium and silicon wafers. This spectrophotometer reflection device is basically configured such that the light beam emitted from the spectrophotometer is incident on the measurement sample, and the reflected light from the measurement sample is received by the light receiving optical system. The incident angle of the luminous flux with respect to is set in the range of about 7.5 ° to 60 ° according to the purpose of use. FIG. 5 shows an example of a conventional device when the incident angle of the light beam on the sample is 45 °, and the problem of the conventional device will be described by taking this as an example.

The reflection device 10 which is the object of the present invention is mounted in the sample chamber 2 of the spectrophotometer 1. The sample chamber 2 can be opened and closed by a light-shielding lid 3. The mounting of the reflection device 10 is performed by engaging a plurality of positioning pins 12 screwed and fixed to the bottom surface of the housing 11 of the reflection device 10 and a positioning hole 2a formed in the bottom portion of the sample chamber 2. An entrance side opening 13 and an exit side opening 14 are formed on both side surfaces of the housing 11, and a top surface of the housing 11 is a sample mounting surface 15, and a measurement opening 16 is formed in the center thereof. Has been. Inside the reflecting device 10, there is arranged a triangular reflecting mirror 17 in which total reflecting coating is applied to reflecting surfaces 17a and 17b sandwiching an apex angle of 135 °.
The triangular reflecting mirror 17 is fixed to a prism base 18, and the prism base 18 is fixed to the bottom of the housing 11 with a fixing screw 19. As is well known, the spectrophotometer 1 includes a spectroscopic optical system 4 including a light source and a spectroscope, and a switch 6 provided on the operation unit 5 emits a light flux L having a predetermined wavelength. The light flux L passes through the exit window 2b opening to the sample chamber 2,
It is configured such that the light is once condensed in the sample chamber 2 and then diverged to enter the light receiving optical system 7 through the entrance window 2c.

In order to measure the spectral reflectance of the solid measurement sample S by the above-described conventional spectrophotometric system 1 and the reflection device 10, the lid 3 of the sample chamber 2 is opened, and the sample mounting surface 15 of the reflection device 10 is used for measurement. The measurement sample S is placed so as to cover the opening 16. The lid 3 is then closed to prevent harmful light rays from entering the sample chamber 2. When the light beam L is emitted from the spectroscopic optical system 4 in this state, the light beam L is emitted from the emission window 2b and the entrance side opening 13 of the device 10.
The light is incident on the triangular reflecting mirror 17 via, and is totally reflected by the reflecting surface 17a, and then is incident on the measurement sample S at an angle of 45 °. Then, the light flux L reflected by the measurement sample S is reflected by the reflecting surface 17 of the triangular reflecting mirror 17.
The light is totally reflected by b and returns to the extended optical axis of the spectroscopic optical system 4,
The light is once condensed in the vicinity of the exit side opening 14 and then diverges and enters the light receiving optical system 7 through the entrance window 2c.

Therefore, if the measurement value when the standard sample is placed on the sample mounting surface 15 instead of the measurement sample S and the measurement value of the light incident on the light receiving optical system 7 is calibrated by this measurement value, The reflectance of the sample S is obtained, and the result is displayed on the CRT screen 8.

However, in this conventional reflection device 10, there has been a problem that the shielding lid 3 has to be opened and closed each time calibration with a standard sample and measurement of a different measurement sample S are performed. Further, the size of the measurement sample S is limited by the size of the sample chamber 2, and usually only a diameter of about 50 to 80 mmφ can be measured. Therefore, when measuring a large sample, the sample must be cut into small pieces for measurement. . However, in the recent semiconductor industry, large silicon wafers with a diameter of about 8 inches (204.2 mm) and germanium wafers are used, and since a mirror with a length of about 250 mm is used for copying machines, etc. If it was cut every time the measurement and inspection were performed, the yield would be extremely poor. Further, in the above-mentioned conventional apparatus, since the light beam incident on the measurement sample S has a certain spread without being condensed on the sample surface, a microlens or a microreflector used for a small camera, a video, a compact disc, etc. Is difficult to measure. That is, the conventional device could not efficiently measure any large sample.

[Object of the Invention] The present invention solves the problems of the conventional apparatus, and can measure both large and small samples, and at the time of measurement, opens and closes the light-shielding lid of the sample chamber of the spectrophotometer. SUMMARY OF THE INVENTION The reflecting device of the present invention therefore has a spectroscopic optical system for making a constraint incident on the sample chamber and a light beam incident on the sample chamber and reflected by the measurement sample. In a spectrophotometer including a light receiving optical system for receiving light, a housing that can be inserted into and removed from the sample chamber is provided, and a sample mounting surface located outside the sample chamber is provided on the upper part of the housing. The incident condenser mirror and the exit condenser mirror, which are positioned substantially symmetrically with respect to the normal line of the sample mounting surface, the incident side reflector for making the light flux from the spectroscopic optical meter into a substantially parallel light flux and incident on the incident condenser mirror, as well as,
A light-receiving-side reflector is provided that causes the light beam that has entered and reflected on the measurement sample on the sample mounting surface via this incident-side reflector and the incident light-collecting mirror to enter the light-receiving optical system via the output light-collecting mirror. Is characterized by.

In this way, by providing the sample mounting surface located outside the sample chamber on the upper part of the housing that can be inserted into and removed from the sample chamber, the size of the sample does not matter, and the light flux from the spectroscopic optical system is substantially eliminated. By providing an incident-side reflector that collimates the light into an incident condensing mirror, the optical path length from the spectroscopic optical system to the sample surface can be made arbitrary, and therefore the shape and position of the sample can be adjusted. The degree of freedom increases.

The incident side reflector is specifically, for example, a toric shape,
It can be composed of an elliptical or spherical convex reflecting mirror.

Further, if the incident side reflector and the light receiving side reflector are composed of a single triangular reflecting mirror, it is possible to obtain a reflecting device having a smaller number of parts.

"Examples of the Invention" The present invention will be described below with reference to illustrated examples. 1 to 3 show a first embodiment of the present invention, and FIG. 1 is a sectional view showing a state in which the reflecting apparatus of the present invention is incorporated in a sample chamber of a spectrophotometer, and FIG. FIG. 3 is a cross-sectional view of an essential part of the entire spectrophotometer without showing the reflecting device of the present invention as a cross-section, and FIG. 3 is a perspective view showing how a light beam is reflected by an incident side reflector of a triangular reflecting mirror.

The reflection device 20 of the present invention is similar to the conventional device in the spectrophotometer 1
Which is mounted in the sample chamber 2 of
A plurality of positioning pins 22 that fit into the positioning holes 2a are screwed and fixed. Like the conventional device, the casing 21 has an entrance side opening 23 and an exit side opening 24 formed on both side surfaces thereof. With respect to the spectrophotometer 1, the same parts as those of the conventional device shown in FIG.

A hollow cylindrical sample base 25 protruding upward from the sample chamber 2 is fixed to the upper part of the housing 21 by a set screw 26.
The upper surface of the sample table 25 constitutes a sample mounting surface 27. A measurement opening 28 is formed in the sample mounting surface 27.

In the sample table 25, symmetrical incident condenser mirrors 30 and outgoing condenser mirrors 31 are provided at positions symmetrical with respect to the normal line SL of the sample mounting surface 27 passing through the center of the measurement opening 28. Further, in the optical path from the spectroscopic optical system 4 of the spectrophotometer 1 to the light receiving optical system 7,
An incident-side reflector 32 is provided, and the incident light collecting mirror 30 and the incident-side reflector 32 cooperate with each other so that the light flux L from the spectroscopic optical system 4 is generated.
Is focused on the measurement sample S placed on the sample mounting surface 27 tatami. Further, the exit condenser mirror 31 cooperates with the light-reception-side reflector 35 composed of the third condenser mirror 33 and the plane mirror 34 so that the light flux reflected by the measurement sample S is again reflected on the extended optical axis of the spectroscopic optical system 4. With returning
The light flux L is once condensed within the reflecting device 20 and then diverged to give the light-receiving optical system 7. The entrance-side reflector 32 and the plane mirror 34 are provided on the same triangular reflector 36. Further, the entrance condenser mirror 30 and the exit condenser mirror 31 are respectively attached to the support step portions 38 which are obliquely provided so that the upper sides of the upper opening 37 of the housing 21 are close to each other, and can be attached and detached by the holding ring 39. Is held. The third condenser mirror 33 and the prism base 40 to which the triangular reflector 36 is fixed are fixed to the bottom of the housing 21 with fixing screws 41.

The light blocking structure between the sample table 25 and the sample chamber 2 is as follows. A light shielding lid 45 having a circular opening 44 in the center is detachably provided at the upper end of the sample chamber 2, and an annular light shielding body 46 is inserted between the light shielding lid 45 and the sample table 25. The annular light shield 46 is placed on the light shield lid 45, and has an elastic light shield 47 that is in elastic contact with the sample table 25 on the inner peripheral surface thereof.
The harmful light is prevented from entering the sample chamber 2 through this gap. The annular light shield 46 has a diameter sufficiently larger than the size of the measurement sample S mounted on the sample mounting surface 27 of the sample table 25.

In the present reflection device 20 having the above configuration, when the housing 21 is set in the sample chamber 2 as shown in FIGS. 1 and 2, the sample table 25 projects from the sample chamber 2. The measurement sample S is mounted on the sample mounting surface 27 of the projecting sample table 25, and in this state, the light beam L having a predetermined wavelength is emitted from the spectroscopic optical system 4 of the spectrophotometer 1.
As described above, the light flux L is emitted by the switch 6 of the operation unit 5. As shown in the optical path diagram in FIG. 2, the light flux L is condensed once in the sample chamber 2 and then diverges and enters the light receiving optical system 7 without the present reflecting device 20. .

The light beam L emitted from the emission window 2b into the sample chamber 2 is
The light is incident on the incident side reflector 32 through the incident side opening 23, is totally reflected here, and is then condensed on the measurement sample S by the incident condenser mirror 30. The incident angle on the measurement sample S is 45 ° in the illustrated example.

The incident side reflector 32 is formed of a curved surface that makes the light flux from the incident side reflector 32 to the incident condenser mirror 30 substantially parallel. Such a curved surface can be configured by a toric convex surface when the light flux L is a rectangular condensed light flux. FIG. 3 is a conceptual diagram of the reflection by the toric convex surface. The curvatures of the incident side reflector 32 in the x-axis and y-axis directions orthogonal to each other are determined according to the vertical and horizontal luminous flux angles of the rectangular luminous flux L. Side reflector 32
The light flux after being reflected by is set to be substantially parallel light flux in both vertical and horizontal directions. When the light flux L is a square or circular light flux, by making the incident side reflector 32 an elliptical or spherical convex surface, the incident side reflector 32 can make the totally reflected light flux substantially parallel.

The light flux thus totally reflected by the incident-side reflector 32 to become parallel light is condensed by the incident condenser mirror 30 at an incident angle of 45 °. The incident condensing mirror 30 may be composed of a simple concave mirror, but in order to reduce the condensing diameter on the measurement sample S,
It is preferably composed of an elliptical concave surface from which spherical aberration is removed.

The light beam condensed by the measurement sample S is reflected at a reflection angle of 45 ° which is equal to the incident angle according to the reflectance of the measurement sample S and becomes a divergent light beam. The output light collecting mirror 31 arranged at a position symmetrical to the optical mirror 30 returns the light to substantially parallel light, and the light receiving side reflector 35 temporarily changes the state of the housing 21.
After the light is condensed inside, it reaches the divergent light receiving optical system 7. Therefore, the 45 ° reflectance of the measurement sample S with respect to the standard sample can be known on the CRT screen 8 by calibration with the standard sample.

As is clear from the above description, in the present invention, since the light flux L given to the measurement sample S is condensed, the measurement sample S
May be small enough to cover the measurement opening 28, and since the sample mounting surface 27 projects to the outside of the sample chamber 2, there is no restriction on the size of the sample chamber 2 and sample mounting is possible. surface
27 Can measure anything that can be placed on top. Then, the measurement sample S can be exchanged easily on the sample mounting surface 27 exposed to the outside, and there is no need to open and close the light-shielding lid 3 unlike the conventional device.

Further, by making the luminous flux from the incident side reflector 32 to the incident condenser mirror 30 and the luminous flux from the emission condenser mirror 31 to the light receiving side reflector 35 substantially parallel luminous fluxes, the curvature and arrangement of these optical members may be slightly different. The incident angle on the measurement sample S can be expanded to angles other than 45 °, such as 60 °, 30 °, 15 °, 7.5 °, etc. simply by changing the above.

FIG. 4 shows a second embodiment of the present invention. This embodiment is different from the first embodiment in that the incident side reflector 32, the third condenser mirror 33, and the plane mirror 34 in the first embodiment are configured by a single triangular reflecting mirror 50. This triangular reflector 50
Is a structure in which the third condenser mirror 33 and the plane mirror 34 in the first embodiment are caused to function by a single reflecting surface 51, and the reflecting surface 51 and the incident side reflector 32 are integrated. is there. The prism base 52 to which the triangular reflecting mirror 50 is fixed is fixed to the bottom of the housing 21 by a fixing screw 53. The other points are the same as those of the first embodiment, and the same portions are denoted by the same reference numerals.

According to this embodiment, the same function can be obtained with a smaller number of parts.

"Effects of the Invention" As described above, in the spectrophotometer reflection device of the present invention, the sample mounting surface located outside the sample chamber is provided in the housing that is inserted into and removed from the sample chamber of the spectrophotometer. Therefore, the sample can be easily replaced, and the size of the sample is not limited. Further, the housing is provided with a condenser mirror and a reflector on the incident side and the emission side, respectively, and the reflector on the incident side converts the light flux from the spectroscopic optical system into a substantially parallel light flux and makes it enter the incident condenser mirror. Therefore, the degree of freedom in the optical path length from the spectroscopic optical system to the sample mounting surface can be obtained. Therefore, a degree of freedom is obtained in the position of the sample mounting surface, and the position and size of the sample are not selected.

[Brief description of drawings]

1 to 3 show a first embodiment of the present invention, and FIG. 1 is a sectional view showing a state in which the reflecting apparatus of the present invention is incorporated in a sample chamber of a spectrophotometer, and FIG. FIG. 3 is a cross-sectional view of an essential part of the entire spectrophotometer without showing the reflecting device of the present invention as a cross-section, and FIG. 3 is a perspective view showing how a light beam is reflected by an incident side reflector of a triangular reflecting mirror. FIG. 4 is a sectional view of an essential part similar to FIG. 1 showing a second embodiment of the present invention, and FIG. 5 is a sectional view of an essential part showing an example of a reflecting device of a conventional spectrophotometer. 1 ... Spectrophotometer, 2 ... Sample chamber, 4 ... Spectroscopic optical system,
7 ... Receiving optical system, 20 ... Reflecting device, 21 ... Housing, 23 ...
… Inlet side aperture, 24 …… Outgoing side aperture, 25 …… Sample stage, 27…
… Sample mounting surface, 28 …… Measuring aperture, 30 …… Injection condensing mirror,
31 …… Exit condensing mirror, 32 …… Injection side reflector, 33 …… Third condensing mirror (reception side reflector), 34 …… Plane mirror (reception side reflector), 35 …… Reception side reflector, 50 …… Triangular reflector.

Claims (3)

[Claims] 1. A spectroscopic optical system for making a light beam enter a sample chamber,
In a spectrophotometer including a light receiving optical system that receives a light beam that enters the sample chamber and is reflected by a measurement sample, a housing that can be inserted into and removed from the sample chamber is provided, and the sample chamber is provided above the housing. A sample mounting surface is provided outside, and an incident condensing mirror positioned substantially symmetrically with respect to the normal line of the sample mounting surface is provided in the housing. The light beam from the spectroscopic optical system is converted into a substantially parallel light beam. An incident side reflector which is incident on the incident condenser mirror, and a light beam which is incident on the measurement sample on the sample mounting surface through the incident side reflector and the incident condenser mirror and reflected by the measurement sample,
A reflection device for a spectrophotometer, comprising: a light-receiving side reflector that makes the light-receiving optical system enter through the emission condenser mirror. 2. The spectrophotometer reflection device according to claim 1, wherein the incident-side reflector comprises a toric, elliptical, or spherical convex reflecting mirror. 3. A spectrophotometer reflecting device according to claim 1 or 2, wherein the incident side reflector and the light receiving side reflector are formed in a single triangular reflecting mirror.