CN115727772A - Wide-spectrum scanning type film thickness detection optical path system - Google Patents

Abstract

The invention provides a wide spectrum scanning type film thickness detection optical path system, which comprises a spectrum scanning optical path, a Y-shaped branched optical fiber and an illumination optical path, wherein the spectrum scanning optical path, the Y-shaped branched optical fiber and the illumination optical path are sequentially connected through an optical path; the spectrum scanning light path outputs monochromatic light with different wavelengths; the Y-shaped branched optical fiber outputs monochromatic light with different wavelengths to the illumination light path, receives reflected light of the surface of the sample and outputs the reflected light of the sample, so that the thickness of the sample film is measured according to the energy of the monochromatic light with different wavelengths of the reflected light of the surface of the sample; the illumination light path converges monochromatic light with different wavelengths on the surface of the sample, and converges the reflected light of the sample into the Y-shaped branched optical fiber. The invention adopts the spectrum scanning light path to obtain monochromatic light, thereby effectively lowering the cost, being easy for production line integration and calibration; the spectrum scanning light path can rapidly and accurately output monochromatic light, the full spectrum scanning time of 1400-1600 nm is 0.5s, and the spectrum resolution is 5nm. The film thickness measuring speed and accuracy are effectively improved.

Description

A Wide Spectrum Scanning Film Thickness Detection Optical Path System

technical field

The invention relates to the field of optical measurement, in particular to a wide-spectrum scanning film thickness detection optical path system.

Background technique

In the semiconductor integrated circuit wafer production process, the thickness of the wafer needs to be controlled online. In this process link, in terms of equipment detection accuracy requirements, a higher measurement rate is required to cope with data fluctuations caused by silicon wafer rotation during on-line detection.

Silicon wafers are opaque in conventional wavelength bands, and the conventional thickness is between tens of microns and hundreds of microns. At present, the commonly used detection methods are optical methods and non-optical methods. Among them, the most commonly used non-optical method is the probe method, which has the advantage of wide measurement range and fast measurement speed. The disadvantage is that it is greatly affected by the measurement environment, and the sample will be contacted and damaged during the measurement process. Optical methods mainly include ellipsometry and spectrometry. Among them, the advantages of the ellipsometer measurement method are non-destructive, easy to integrate, high precision, and can achieve sub-nanometer film thickness measurement. The disadvantages are relatively high cost, complex data processing, and high requirements for measurement personnel. Compared with ellipsometer measurement, spectrometry has no polarization factor, simple operation, fast measurement speed, small equipment size and low cost.

Contents of the invention

Aiming at the technical problems existing in the prior art, the present invention provides a spectral scanning type film thickness detection optical path system, which includes a spectral scanning optical path, a Y-shaped bifurcated optical fiber, and an illumination optical path connected by sequential optical paths;

The spectral scanning optical path is used to generate and output monochromatic light of different wavelengths;

The Y-shaped bifurcated optical fiber is used to output monochromatic light of different wavelengths to the illumination optical path, and receive the reflected light of the monochromatic light of different wavelengths irradiated on the surface of the sample, and output the reflected light of the sample, so that according to the sample The energy of monochromatic light with different wavelengths of reflected light on the surface measures the film thickness of the sample;

The illumination light path is used for converging the monochromatic light of different wavelengths output by the Y-shaped bifurcated optical fiber on the surface of the sample, and converging the reflected light of the sample into the Y-shaped bifurcated optical fiber. On the basis of the above technical solution, the present invention can also make the following improvements.

Optionally, the spectral scanning optical path includes a light source, a first slit, a high-speed scanning galvanometer mirror, a concave diffraction grating, and a second slit;

The light source is used to provide light energy required to cover the measurement wavelength band, and passes through the first slit;

The high-speed scanning galvanometer mirror is used to collimate the light beam passing through the first slit and sequentially shoot it to the concave diffraction grating;

The concave diffraction grating is used for converging monochromatic light of different wavelengths on different positions of the focal plane of the grating, through the rotation of the mirror of the high-speed scanning galvanometer, the monochromatic light of different wavelengths sequentially passes through the second narrow slits to output monochromatic light of different wavelengths.

Optionally, the light source is a high infrared radiation SLED light source with a wavelength of 1400nm-1600nm.

Optionally, the high-speed scanning galvanometer mirror includes a single-axis galvanometer motor with a mirror and a matching drive card, wherein the radius of curvature of the mirror is 50mm-500mm, the base of the mirror is quartz glass, and the surface The coating is aluminum film with protective layer or silver film with protective layer, the aperture is 10mm-40mm, the scanning angle range of the mirror is 5-11°, and the scanning time is 0.5s.

Optionally, the concave diffraction grating is produced in a holographic manner, the substrate is soda-lime glass, the surface coating is an aluminum film with a protective layer or a silver film with a protective layer, the aperture is 10mm-40mm, and the radius of curvature is 300mm-1000mm. The number of lines is 0.7 lines/um.

Optionally, the size of the first slit is 100um×400um, and the size of the second slit is 400um×4000um.

Optionally, the Y-shaped bifurcated optical fiber includes A, B, and C ends, and the A end is formed by arranging six optical fibers with a core diameter of 50um-600um, and is used to collect the second signal of the spectral scanning optical path. Monochromatic light of different wavelengths output by the slit;

The B end is arranged by 6 optical fibers with a core diameter of 50um-600um surrounding one optical fiber with a core diameter of 50um-600um, among which, the 6 outer ring optical fibers output monochromatic light of different wavelengths, and one central optical fiber receives the sample reflected light;

The C end is arranged in the center of an optical fiber with a core diameter of 50um-600um, which is used to output reflected light from the sample received by the B end.

Optionally, the illumination optical path includes two achromatic lenses arranged symmetrically, the surface coating of the achromatic lens is an anti-reflection dielectric film of 1400nm-1600nm, and the gluing process is to deepen optical glue. The illumination optical path is used to The monochromatic light of different wavelengths output from the B-end of the Y-shaped bifurcated fiber converges on the sample surface, and the reflected light from the sample surface is converged into the C-end of the Y-shaped bifurcated fiber.

The invention provides a wide-spectrum scanning film thickness detection optical path system, which adopts the spectral scanning optical path to obtain monochromatic light, which effectively reduces the cost, is easy to integrate in the production line, and is easy to calibrate; the spectral scanning optical path can quickly and accurately output monochromatic light. Light, 1400nm-1600nm full spectrum scanning time is 0.5s, spectral resolution is 5nm. Effectively improve the film thickness measurement speed and accuracy.

Description of drawings

Fig. 1 is a schematic structural view of a wide-spectrum scanning film thickness detection optical path system provided by the present invention;

Fig. 2 is the 1550nm and 1555nm light beam separation situation diagram at the second slit place when the high-speed scanning galvanometer reflector scanning angle (relative to the incident light optical axis) in the spectrum scanning optical path proposed by the present invention is 8 °;

Fig. 3 is the 1600nm and 1595nm light beam separation situation diagram at the second slit place when the high-speed scanning galvanometer reflector scanning angle (relative to the optical axis of the incident light) in the spectral scanning optical path proposed by the present invention is 5 °;

Fig. 4 is a diagram of separation of 1400nm and 1405nm light beams at the second slit when the scanning angle of the high-speed scanning galvanometer reflector in the spectrum scanning optical path proposed by the present invention (relative to the optical axis of the incident light) is 11°;

Fig. 5 schematic diagram of the Y-shaped bifurcated optical fiber proposed by the present invention;

Fig. 6 is a schematic diagram of the illumination light path proposed by the present invention.

In the accompanying drawings, the names of the parts represented by each label are as follows:

101, the first slit, 102, the high-speed scanning galvanometer mirror, 103, the concave diffraction grating, 104, the second slit, 105, the light source, 201, the achromatic lens.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention. In addition, the technical features in each embodiment or a single embodiment provided by the present invention can be combined arbitrarily with each other to form a feasible technical solution. This combination is not restricted by the sequence of steps and/or structural composition mode, but it must be Based on the ability of those skilled in the art to realize, when the combination of technical solutions is contradictory or unrealizable, it should be considered that such combination of technical solutions does not exist and is not within the protection scope of the present invention.

The invention provides a wide-spectrum scanning type film thickness detection optical path system, which mainly includes a spectral scanning optical path, a Y-shaped bifurcated optical fiber and an illumination optical path connected in sequence.

Among them, the spectral scanning optical path is used to generate and output monochromatic light of different wavelengths; the Y-shaped bifurcated optical fiber is used to output monochromatic light of different wavelengths to the illumination optical path, and receive monochromatic light of different wavelengths to irradiate the sample The reflected light of the surface, and output the reflected light of the sample, so that according to the energy of the monochromatic light of different wavelengths of the reflected light on the surface of the sample, the film thickness of the sample is measured; the illumination optical path is used to output different The monochromatic light of the wavelength is converged on the surface of the sample, and the reflected light of the sample is converged into the Y-shaped bifurcated optical fiber.

FIG. 1 shows a schematic structural diagram of a spectral scanning optical path, which includes a light source, a first slit 101 , a high-speed scanning galvanometer mirror 102 , a concave diffraction grating 103 and a second slit 104 .

The light source is used to provide light energy required to cover the measurement band, and passes through the first slit 101; the high-speed scanning galvanometer mirror 102 is used to collimate the light beam passing through the first slit 101 Directly and sequentially shoot to the concave diffraction grating 103; the concave diffraction grating 103 is used to converge monochromatic light of different wavelengths on different positions on the focal plane of the grating, and through the rotation of the high-speed scanning galvanometer mirror 102, The monochromatic lights of different wavelengths are sequentially passed through the second slit 104 to output the monochromatic lights of different wavelengths.

It can be understood that the light source outputs light beams, which contain monochromatic light of different wavelengths. The light beams pass through the first slit 101 and reach the high-speed scanning galvanometer mirror 102. The high-speed scanning galvanometer mirror 102 collimates the light beams and enters the Concave diffraction grating 103, the concave diffraction grating 103 converges monochromatic light of different wavelengths at different positions on the focal plane of the grating, and through the rotation of the high-speed scanning galvanometer mirror 102, the monochromatic light of different wavelengths passes through the second slit 104 sequentially , to separate monochromatic light of different wavelengths. Wherein, Fig. 2 is a diagram of the separation of 1550nm and 1555nm beams at the second slit 104 when the scanning angle (relative to the optical axis of the incident light) of the high-speed scanning galvanometer mirror 102 is 8°, and Fig. 3 is the scanning of the high-speed scanning galvanometer mirror 102 Separation of 1600nm and 1595nm beams at the second slit 104 when the angle (relative to the optical axis of the incident light) is 5°;

FIG. 4 is a diagram showing the separation of 1400nm and 1405nm beams at the second slit 104 when the scanning angle (relative to the optical axis of the incident light) of the high-speed scanning galvanometer mirror 102 is 11°.

Wherein, the light source is a high infrared radiation SLED light source with a wavelength of 1400nm-1600nm. The high-speed scanning galvanometer reflector 102 includes a single-axis galvanometer motor with a reflector and a matching drive card, wherein the reflector has a radius of curvature of 150 mm, the base of the reflector is quartz glass, and the surface coating is a protective layer Aluminum film or silver film with protective layer, the aperture is 25mm, the scanning angle range of the mirror is 5-11°, and the scanning time is 0.5s.

The concave diffraction grating 103 is produced by holographic method, the substrate is soda lime glass, the surface coating is aluminum film with protective layer or silver film with protective layer, the aperture is 25mm, the radius of curvature is 500mm, and the number of lines is 0.7 lines/um.

The size of the first slit 101 is 100um×400um, and the size of the second slit 104 is 400um×4000um.

Referring to Figure 5, it is a schematic diagram of the structure of the Y-shaped bifurcated optical fiber. The Y-shaped bifurcated optical fiber includes A, B, and C ends. The A end is formed by arranging 6 optical fibers with a core diameter of 50um, which are used to collect the spectral scanning optical path Monochromatic light of different wavelengths output by the second slit 104 of the second slit 104; the B end is arranged by 6 optical fibers with a core diameter of 50um surrounded by an optical fiber with a core diameter of 50um, wherein, the 6 outer ring optical fibers output monochromatic light of different wavelengths For color light, a central optical fiber receives the reflected light of the sample; the C end is arranged in the center of an optical fiber with a core diameter of 50um, which is used to output the reflected light of the sample received by the B end.

Referring to Fig. 6, it is a schematic diagram of the structure of the lighting optical path. The lighting optical path includes two achromatic lenses 201 arranged symmetrically. The monochromatic light of different wavelengths output from the B-end of the Y-shaped bifurcated fiber is converged on the sample surface, and the reflected light from the sample surface is converged into the C-end of the Y-shaped bifurcated fiber. Table 1 below is a table of illumination light path parameters.

Table 1 Parameter table of illumination light path

surface radius of curvature thickness Material caliber Object surface 32.7 13 1 176.19 1.8 N-SF6HT 13 2 22.07 10 N-LAK22 13 3 24.05 5 4 24.05 10 N-LAK22 13 5 -22.07 1.8 N-SF6HT 13 6 -176.19 32.7 13 Image surface

The working principle of the wide-spectrum scanning film thickness detection optical path system is: the spectral scanning optical path outputs monochromatic light of different wavelengths; The output monochromatic light of different wavelengths converges on the surface of the sample, and converges the reflected light of the sample into the Y-shaped bifurcated optical fiber. The Y-shaped bifurcated optical fiber receives the reflected light of the monochromatic light of different wavelengths irradiated on the surface of the sample, and outputs the reflected light of the sample. According to the energy of monochromatic light of different wavelengths reflected on the surface of the sample, the film thickness of the sample is measured.

Compared with the prior art, the wide-spectrum scanning film thickness detection optical path system provided by the present invention has the following beneficial effects:

(1) The spectral scanning optical path is used to obtain monochromatic light, which effectively reduces the cost, is easy to integrate in the production line, and is easy to calibrate.

(2) The spectral scanning optical path can quickly and accurately output monochromatic light, the full-spectrum scanning time of 1400nm-1600nm is 0.5s, and the spectral resolution is 5nm. Effectively improve the film thickness measurement speed and accuracy.

(3) The entire optical path of the spectrum scanning optical path adopts reflective optical elements to achieve 1400nm-1600nm full-band output of monochromatic light without chromatic aberration, effectively improving energy utilization.

(4) The Y-shaped bifurcated fiber realizes the combination of the incident light and the outgoing light, and reducing the core diameter of the C-end can improve the effective measurement resolution of the sample.

(5) The illuminating light path adopts two double glued achromatic lens symmetrical structures, the glued process chooses to deepen the optical glue, and the surface of the lens is coated with an anti-reflection film to reduce the color focus shift and stray light, and improve the measurement accuracy.

It should be noted that, in the foregoing embodiments, descriptions of each embodiment have their own emphases, and for parts that are not described in detail in a certain embodiment, reference may be made to relevant descriptions of other embodiments.

While preferred embodiments of the invention have been described, additional changes and modifications to these embodiments can be made by those skilled in the art once the basic inventive concept is understood. Therefore, it is intended that the appended claims be construed to cover the preferred embodiment as well as all changes and modifications which fall within the scope of the invention.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies thereof, the present invention also intends to include these modifications and variations.

Claims (8)

1. A wide spectrum scanning type film thickness detection optical path system is characterized by comprising a spectrum scanning optical path, a Y-shaped branched optical fiber and an illumination optical path which are connected in sequence through the optical path;

the spectrum scanning light path is used for generating and outputting monochromatic light with different wavelengths;

the Y-shaped branched optical fiber is used for outputting monochromatic light with different wavelengths to the illumination light path, receiving reflected light of the monochromatic light with different wavelengths, which is irradiated to the surface of the sample, and outputting the reflected light of the sample, so that the thickness of the sample film is measured according to the energy of the reflected light of the sample surface, which is the monochromatic light with different wavelengths;

and the illumination light path is used for converging monochromatic light with different wavelengths output by the Y-shaped branched optical fiber on the surface of a sample and converging sample reflected light into the Y-shaped branched optical fiber.

2. The film thickness detection optical path system according to claim 1, wherein the spectrum scanning optical path comprises a light source, a first slit, a high-speed scanning galvanometer mirror, a concave diffraction grating and a second slit;

the light source is used for providing light energy required by covering a measurement waveband and passes through the first slit;

the high-speed scanning galvanometer reflector is used for collimating the light beams passing through the first slit and then sequentially emitting the light beams to the concave diffraction grating;

the concave diffraction grating is used for converging monochromatic light with different wavelengths on different positions of a focal plane of the grating, and the monochromatic light with different wavelengths sequentially passes through the second slit by the rotation of the high-speed scanning galvanometer reflector so as to output the monochromatic light with different wavelengths.

3. The film thickness detection optical path system according to claim 2, wherein the light source is a high infrared radiation SLED light source, and the wavelength is 1400nm-1600nm.

4. The film thickness detection optical path system according to claim 2, wherein the high-speed scanning galvanometer reflector comprises a single-shaft galvanometer motor with a reflector and a matched driving card, wherein the curvature radius of the reflector is 50mm-500mm, the substrate of the reflector is quartz glass, the surface coating is an aluminum film with a protective layer or a silver film with a protective layer, the caliber is 10mm-40mm, the scanning angle range of the reflector is 5-11 degrees, and the scanning time is 0.5s.

5. The film thickness detection optical path system according to claim 2, wherein the concave diffraction grating is produced in a holographic manner, the substrate is soda-lime glass, the surface coating film is an aluminum film with a protective layer or a silver film with a protective layer, the aperture is 10mm to 40mm, the curvature radius is 300mm to 1000mm, and the number of lines is 0.7 line/um.

6. The film thickness detection optical path system of claim 2, wherein the first slit size is 100um x 400um, and the second slit size is 400um x 4000um.

7. The film thickness detection optical path system according to claim 2, wherein the Y-shaped branched optical fiber includes A, B and a C end, and the a end is formed by arranging 6 optical fibers with core diameters of 50um to 600um in a line, and is used for collecting monochromatic light with different wavelengths output by the second slit of the spectrum scanning optical path;

the B end is formed by arranging 6 optical fibers with core diameters of 50um-600um around 1 optical fiber with core diameters of 50um-600um, wherein 6 outer ring optical fibers output monochromatic light with different wavelengths, and 1 central optical fiber receives reflected light of a sample;

the C end is arranged in the center of 1 optical fiber with the core diameter of 50um-600um and is used for outputting the reflected light of the sample received by the B end.

8. The film thickness detection optical path system according to claim 7, wherein the illumination optical path comprises two achromatic lenses arranged symmetrically, the achromatic lens surface is coated with an anti-reflection dielectric film of 1400nm-1600nm, the gluing process is deepening optical cement, and the illumination optical path is used for converging monochromatic light of different wavelengths output by the end B of the Y-shaped branched optical fiber on a sample surface and converging reflected light of the sample surface into the end C of the Y-shaped branched optical fiber.

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