JPH0675006B2 - Spectrophotometer - 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 measuring the spectral reflectance of a solid sample in the ultraviolet to near-infrared wavelength range. The present invention relates to a spectrophotometer having a reflection device used in this case.

"Prior Art and Its Problems" This type of spectrophotometer is composed of a main body of a spectrophotometer having a spectroscopic optical system and a light receiving optical system, and a reflecting device arranged in a sample chamber of the spectrophotometer main body. It is used to measure the spectral reflectance of lens coating films in the precision industry such as cameras and copying machines, and to measure the spectral reflectance of various reflecting mirrors. 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. In this spectrophotometer, basically, the bundle emitted from the spectroscopic optical system is made incident on the measurement sample placed on the sample mounting surface of the reflection device, and the reflected light from the measurement sample is received by the light receiving optical system. The incident angle of the light beam on the sample is set in the range of about 7.5 ° to 60 ° according to the purpose of use. FIG. 4 shows an example of a conventional apparatus in which the incident angle of the light beam on the sample is 45 °, and the problem of the conventional apparatus will be described by taking this as an example.

As is well known, the main body 1 of the spectrophotometer includes a spectroscopic optical system 2 including a light source and a spectroscope, and a light receiving optical system 3 that receives the light flux L emitted from the spectrophotometer. A sample chamber 4 is located between the optical systems 3. When a light beam L having a predetermined wavelength is emitted from the spectroscopic optical system 2 by the switch 6 provided in the operation unit 5, the light beam L passes through the emission window 4b opening in the sample chamber 4 and is then stored in the sample chamber 4. The light is once condensed and then diverged to enter the light receiving optical system 3 through the entrance window 4c.

The sample chamber 4 can be opened and closed by a light-shielding lid 7, and a reflecting device 10 is mounted therein. The mounting is performed by the housing 11 of the reflection device 10.
This is due to the engagement of the plurality of positioning pins 12 screwed and fixed to the bottom surface of the and the positioning holes 4a formed in the bottom of the sample chamber 4. Case 11
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 serves as a sample mounting surface 15, and a measurement opening 16 is formed in the center thereof. . Inside the reflecting device 10, there are arranged triangular reflecting mirrors 17 having total reflection coatings on reflecting surfaces 17a and 17b which sandwich 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.

In order to measure the spectral reflectance of the solid measurement sample S with the above conventional spectrophotometer, the lid 7 of the sample chamber 4 of the main body 1 is opened, and the measurement opening 16 is provided on the sample mounting surface 15 of the reflecting device 10. The measurement sample S is placed so as to cover the. The lid 7 is then closed to prevent harmful rays from entering the sample chamber 4. When the luminous flux L is emitted from the spectroscopic optical system 2 in this state, the external luminous flux L is incident on the triangular reflecting mirror 17 through the exit window 4b and the entrance side opening 13 of the reflecting device 10, and is totally reflected by the reflecting surface 17a for measurement. It is incident on the sample S at an angle of 45 °. And the measurement sample S
The light flux L reflected by is totally reflected by the reflecting surface 17b of the triangular reflecting mirror 17, returns to the upper side when the spectroscopic optical system 2 is extended light, is once condensed near the exit side opening 14, and then diverges. Entrance window 4c
Is incident on the light receiving optical system 3.

Therefore, if the measurement value when the standard sample is placed on the sample device surface 15 instead of the measurement sample S and the measurement value of the light incident on the light receiving optical system 3 is calibrated by this measurement value, the measurement sample The reflectance of S is obtained and the result is displayed on the CRT screen 8.

However, in this conventional reflection device 10, there is a complexity that the light-shielding lid 7 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 and germanium wafers with a diameter of about 8 inches (204.2.mm) are used, and for copying machines and the like, a reflecting mirror with a length of about 250 mm is used.
If they were cut every time they were measured and inspected, the yield would be extremely poor.

"Object of the Invention" The present invention solves the problems of the conventional device described above, and enables measurement without cutting a large sample.
An object of the present invention is to obtain a spectrophotometer having a reflecting device which does not require opening and closing of a light shielding lid of a sample chamber of the spectrophotometer.

[Outline of the Invention] In the spectrophotometer of the present invention, the reflection device is a housing that can be inserted into and removed from the sample chamber, and the upper surface of the housing integrally provided on the upper part of the housing is the sample mounting surface. In the state where the housing is set in the sample chamber, the sample mounting surface is projected to the outside of the sample chamber, while the lid for shielding the sample chamber is
It is characterized in that a projecting opening through which the sample stand projects is provided, and an annular light shield located below the sample mounting surface is interposed between the projecting opening and the sample stand.

With this configuration, since the sample mounting surface is located outside the sample chamber, there is no restriction on the size of the sample, and it is possible to save the time and effort for opening and closing the light shielding lid each time the sample is replaced. Further, since the light shielding of the sample chamber is performed by both the light shielding lid and the annular light shielding body, the influence of external light does not reliably affect the measured value. Further, since the annular light shield is located below the sample mounting surface, there is no risk of contacting and contaminating the sample.

"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. FIG. 1 is a sectional view showing a state in which a reflecting device is incorporated in a sample chamber of a spectrophotometer, and FIG. 2 is a reflecting device. Is a cross-sectional view of the main part of the entire spectrophotometer without showing a cross section, and FIG. 3 is a perspective view of an annular light shield. The same components as those of the conventional apparatus shown in FIG. 4 are designated by the same reference numerals.

Reflector 20 mounted in the sample chamber 4 of the spectrophotometer body 1
A plurality of positioning pins 22 fitted in the positioning holes 4a are screwed and fixed to the lower surface of the housing 21 of the same as the conventional product, and an entrance side opening 23 and an exit side opening 24 are formed on both side surfaces thereof. ing.

A hollow cylindrical sample table 25 protruding upward from the sample chamber 4 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 exit 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. . An incident side reflector 32 is provided in the optical path from the spectroscopic optical system 2 of the spectrophotometer body 1 to the light receiving optical system 3, and the incident condenser mirror 30 and the incident side reflector 32 cooperate with each other. Then, the light flux L from the spectroscopic optical system 2 is focused on the measurement sample S placed on the sample mounting surface 27. The exit condenser mirror 31 includes a third condenser mirror 33 and a plane mirror 34.
After the light flux reflected by the measurement sample S is returned to the extended optical axis of the spectroscopic optical system 2 in cooperation with the light-receiving-side reflector 35 including , And acts on the light receiving optical system 3 by diverging. Incident side reflector
32 and the plane mirror 34 are provided on the same triangular reflector 36. The entrance condenser mirror 30 and the exit condenser mirror 31 are respectively
The support openings 38 are provided so as to be oblique to each other so that the upper sides of the upper openings 37 of the 21 come close to each other, and are detachably held by a holding ring 39. Further, the third condensing mirror 33 and the prism base 40 to which the triangular reflector 36 is fixed are fixed to the housing with a fixing screw 41.
It is fixed at the bottom of 21.

One of the features of the present invention is the light-shielding structure between the sample stage 25 and the sample chamber 4 protruding from the sample chamber 4. A light shielding lid 45 having a circular projecting opening 44 in the center is detachably provided at the upper end of the sample chamber 4, and an annular light shielding body 46 is inserted between the light shielding lid 45 and the sample table 25. There is. The ring-shaped light shield 46 is placed on the light shield cover 45, and the sample table is provided on the inner peripheral surface thereof.
An elastic light shield 47 that elastically contacts with 25 is provided to prevent harmful light from entering the sample chamber 4 through this gap. The ring-shaped light shield 46 is the sample table 25 and the sample mounting surface of the sample table 25.
The diameter is sufficiently larger than the size of the measurement sample S placed on the 27. Then, on the surface of the annular light shield 46, as shown in FIG. 3, the sample mounting surface 27 (measurement opening 2
A plurality of concentric annular V grooves 48 centered on the center of 8) are engraved. The plurality of annular V-shaped grooves 48 serve as guide lines when the center of the measurement sample S placed on the sample mounting surface 27 is aligned with the measurement opening 28.

The spectrophotometer having the above-mentioned configuration is set in the sample chamber 4 as shown in FIGS.
A light beam L having a predetermined wavelength is emitted from the spectroscopic optical system 2 of the spectrophotometer main body 1 with the measurement sample S placed on the sample mounting surface 27 of 25. As described above, the emission of the light flux L is performed by the operation unit 5
Switch 6 of FIG. As shown in the optical path diagram in FIG. 2, the light flux L is condensed once in the sample chamber 4 and then diverges and enters the light receiving optical system 3 without the present reflecting device 20. .

The light flux L emitted from the emission window 4b into the sample chamber 4 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 preferably 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. Luminous flux L
Is a square or circular light beam, the incident side reflector 32 can be an elliptical or spherical convex surface to make the light beam totally reflected by the incident side reflector 32 a substantially parallel light beam.

The light flux thus totally reflected by the entrance-side reflector 32 to become parallel light is condensed by the entrance 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. An exiting condensing mirror 31 arranged at a position symmetrical to the mirror 30 returns the light to substantially parallel light, and further, the receiving-side reflector 35 temporarily changes the housing 21.
After condensing inside, it diverges and reaches the light receiving optical system 3. 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 sample mounting surface 27 projects outside the sample chamber 4,
It is possible to measure anything that can be mounted on the sample mounting surface 27 without being restricted by the size of the. Further, since the sample mounting surface 27 is provided on the upper surface of the sample table 25 which is integrated with the housing 21, the housing 21, that is, the entrance-side and exit-side focusing mirrors 30 and 31 inside the housing 21. Positions of reflectors 36 and 35, and sample mounting surface
The positional relationship with 27 does not get out of order, and therefore, it is possible to measure personality. Further, 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 7 unlike the conventional device. Since the light shielding of the sample chamber 4 is performed by the light shielding lid 45 having the projecting opening 44 and the annular light shielding body 46 provided between the light shielding lid 45 and the sample table 25, it can be reliably performed. . In particular, when an elastic light shield 47 is provided on the inner peripheral surface of the annular light shield 46,
It is possible to effectively shield the outer periphery of the sample table 25 where light is most likely to enter. The plurality of concentric annular V-grooves 48 formed on the surface of the annular light-shielding member 46 are effective for correctly aligning the center of a large-sized annular sample such as a silicon wafer or a germanium wafer with the measurement opening 28. The diameter of the annular V groove 48 is preferably formed at intervals according to the wafer diameter, for example, 1 inch intervals (1/2 inch intervals in terms of radius).
The annular reference line 48 may of course be formed from a line drawn on the surface of the annular light shield 46.

Further, according to the optical system of the above-mentioned embodiment, 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. 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. However, the present invention does not ask about the optical system of the light flux given to the measurement sample S, and the above shows one example.

[Advantages of the Invention] As described above, in the spectrophotometer of the present invention, the sample mounting surface is projected to the outside of the sample chamber of the spectrophotometer, so that the sample can be easily replaced and the size of the sample can be increased. There are no restrictions on. That is, it is possible to measure an extremely large measurement sample having a diameter of 8 inches or more without cutting. In addition, since the light shield lid and the annular light shield shield the space between the sample base and the sample chamber, external light does not adversely affect the measurement. Since this annular light shield is located below the sample mounting surface, there is no risk of the sample coming into contact with and contaminating the annular light shield. Further, by providing an elastic light-shielding body that makes elastic contact with the sample base on the inner peripheral surface of the annular light-shielding body, it is possible to shield light more reliably. Even if the sample has a large diameter, the center can be easily placed in the center of the sample mounting surface if the annular light shield has a sufficiently large diameter and an annular guide line concentric with the sample mounting surface is provided on the surface. Can be matched.

[Brief description of drawings]

1 to 3 show a first embodiment of the present invention. FIG. 1 is a sectional view showing a state in which a reflecting device is incorporated in a sample chamber of a spectrophotometer body, and FIG. The apparatus is not a sectional view, and is a sectional view of an essential part of the entire spectrophotometer, and FIG. 3 is a perspective view of an annular light shield. FIG. 4 is a cross-sectional view of a main part showing an example of a reflection device of a conventional spectrophotometer. 1 ... Spectrophotometer body, 2 ... Spectroscopic optical system, 3 ... Receiving optical system, 4 ... Sample chamber, 20 ... Reflector, 23 ... Injection side aperture, 24 ... Exit side aperture, 25 ... … Sample stand, 27 …… Sample mounting surface, 28 …… Measuring opening, 44 …… Projecting opening, 45 …… Light-shielding lid, 46 …… Ring light-shielding body, 47 …… Elastic light-shielding body, 48 …… Ring V groove (circular guide line).

Claims (3)

[Claims] 1. A main body of a spectrophotometer having a spectroscopic optical system and a light receiving optical system, and a reflecting device arranged in a sample chamber of the spectrophotometer, the reflecting device being provided on a sample mounting surface thereof. In a spectrophotometer in which a light beam emitted from the spectroscopic optical system is made incident on a mounted measurement sample, and reflected light from the measurement sample is received by the light receiving optical system, the reflection device is insertable into and removable from a sample chamber. The apparatus is provided with a case and a sample table integrally provided on the upper part of the case and having the upper surface as the sample mounting surface, and the sample mounting surface of the sample table is set in the sample chamber. In the state, the lid that protrudes to the outside of the sample chamber and closes the sample chamber is provided with a projecting opening through which the sample stage projects, and further, between the projecting opening and the sample stage, the sample It is characterized in that an annular light shield located below the mounting surface is interposed. Spectrophotometer. 2. The annular light-shielding body according to claim 1, having a diameter sufficiently larger than that of the sample stand, and an elastic light-shielding body elastically contacting the outer circumference of the sample stand is provided on the inner peripheral surface of the annular light-shielding body. Spectrophotometer. 3. The spectrophotometer according to claim 1 or 2, wherein the annular light-shielding body is provided with a mounting reference line composed of a plurality of concentric circles centered on the center of the sample mounting surface. Total.