JP2011038895A - Film quality evaluation device and method of evaluating film quality - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain spatial resolution not more than a diffraction limit in measurement using incoherent light. <P>SOLUTION: A film quality evaluation device 1 forms interference light of infrared light by a Michelson interferometer 3 and then branches the interference light into first measurement light and second measurement light by a beam splitter 12. The first measurement light and the second measurement light are applied to the surface of an object W to be measured while shifting their positions, thus forming a region where the two beams of measurement light overlap and a region whether they do not overlap. A difference between light intensity signals when receiving two beams of measurement light is calculated by a difference processing section 21, and infrared spectra are obtained by performing Fourier transform based on the data. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a film quality evaluation apparatus and a film quality evaluation method.

  A Fourier transform infrared spectrophotometer (hereinafter referred to as FT-IR) is known as a spectroscopic method using infrared light, and an infrared transmission spectrum or reflection spectrum in the infrared region of a substance using Fourier transform. To measure the state and molecular structure of the object to be measured. As an object to be measured in the FT-IR analysis, semiconductor materials can be cited in addition to organic chemical materials. When the object to be measured is a semiconductor material, FT-IR can be used to measure the concentration of impurities such as phosphorus and boron in a silicon wafer, the concentration of hydrogen in a silicon nitride film, and the density of voids formed in an oxide film. Used for measurement.

  A conventional FT-IR apparatus has a light source that emits incoherent infrared light and a Michelson interferometer, and performs measurement by converting infrared light into interference light (interferogram). . The interference light is irradiated onto the measurement object, and the transmitted light or reflected light is received by the infrared detector. The electric signal output from the infrared detector is amplified and converted into a digital signal. When this digital signal is Fourier transformed, an infrared transmission spectrum or reflection spectrum of the measurement object is obtained.

  Here, when infrared light is used for FT-IR analysis, since the wavelength of infrared light is about 2 μm to 10 μm, the spatial resolution is about 10 μm. Therefore, for example, when measuring the density of voids formed in an oxide film, the measurement sensitivity is low when the density of voids is very small and the number of voids contained in infrared rays is very small.

  On the other hand, in the case of performing spectroscopy using visible light, a technique for obtaining information below the line limit using two light beams has been developed, which is called a super-resolution technique. As an analyzer using super-resolution technology, for example, two coherent light sources irradiate a measurement object with two beams whose polarization directions are orthogonal to each other, and irradiate the measurement object with polarized light. Some are separated by a beam splitter and detected by two detectors. When the beam profile of one of the two beams is formed in a bimodal shape such that the power of the central portion is 0, the diffraction limit is about ½ from the difference between the signals output from the two detectors. The information of the area is obtained.

JP 7-234382 A

However, when incoherent light is used as measurement light, it is difficult to control the polarization direction. Therefore, it has been difficult to improve spatial resolution using a super-resolution technique using coherent light.
The present invention has been made in view of such circumstances, and has as its main object to obtain a spatial resolution below the diffraction limit in measurement using incoherent light.

According to one aspect of the present application, an infrared light source that outputs incoherent infrared light, an interferometer that forms interference light from the infrared light, and the interference light into the first measurement light and the second measurement light. Branch off and
An optical system that causes the first measurement light and the second measurement light to be incident on the surface of the measurement object such that the first measurement light and the second measurement light partially overlap each other, and the first that is transmitted through the measurement object or reflected by the measurement object. And a second detector light that is transmitted through or reflected by the measurement object is incident, and the measurement light is incident on the first detector. A second detector that outputs a signal in accordance with the amount of light; a difference between a signal output from the first detector and a signal output from the second detector; and at least one of overlapping portions of the signals. A film quality evaluation apparatus including a data processing unit that calculates and outputs a processed signal and a Fourier transform unit that Fourier-transforms the processed signal output from the data processing unit is realized.

  According to another aspect of the present application, incoherent infrared light is output from an infrared light source to form interference light from the infrared light, and the interference light is converted into the first measurement light and the second measurement light. A step of causing the first measurement light and the second measurement light to be incident on the surface of the measurement object so that a part of the first measurement light and the second measurement light overlap with each other; The step of detecting the reflected first measurement light with the first detector and outputting a signal according to the amount of light, and the second of the measurement object transmitted or reflected by the measurement object A step of detecting measurement light with a second detector and outputting a signal according to the amount of light; and a difference between a signal output from the first detector and a signal output from the second detector; Calculating at least one of the overlapping portions of the signals and outputting as a processed signal; Film quality evaluation method characterized by comprising the step of calculating the infrared spectrum, the processed signal by Fourier transform is realized.

  According to the present invention, a processing signal for a region where two measurement lights overlap or a region where they do not overlap is calculated by the data processing unit, and an infrared spectrum is obtained by Fourier transforming this processing signal. Thereby, spatial resolution below the diffraction limit of incoherent infrared light can be realized.

FIG. 1 is a diagram showing a schematic configuration of a film quality evaluation apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram schematically showing a beam spot formed on the surface of the measurement object while the measurement object and its vicinity are enlarged. FIG. 3 is an enlarged view of an object to be measured and its vicinity, and is a view for explaining a preferable film thickness of a thin film that is an object to be measured. FIG. 4 is a diagram showing a modification of the film quality evaluation apparatus according to the first embodiment of the present invention. FIG. 5 is an enlarged view of the measurement object and its vicinity. FIG. 6 is a diagram showing a schematic configuration of a film quality evaluation apparatus according to the second embodiment of the present invention. FIG. 7 is an enlarged view of the measurement object and its vicinity. FIG. 8 is a diagram schematically showing a beam spot formed by two measuring lights on the surface of the measuring object. FIG. 9 is a diagram showing a schematic configuration of a film quality evaluation apparatus according to the third embodiment of the present invention. FIG. 10 is a diagram schematically showing a beam spot formed by two measurement lights on the surface of a measurement object. FIG. 11 is a diagram showing a schematic configuration of a film quality evaluation apparatus according to the fourth embodiment of the present invention. FIG. 12 is a diagram showing a schematic configuration of the beam forming mechanism. FIG. 13 is a diagram schematically showing a beam spot formed by two measurement lights on the surface of the measurement object. FIG. 14 is a diagram showing a schematic configuration of a film quality evaluation apparatus according to the fifth embodiment of the present invention. FIG. 15 is a diagram schematically showing a beam spot formed by two measurement lights on the surface of the measurement object while enlarging the measurement object and its vicinity. FIG. 16 is a diagram when the measurement object is irradiated with the two measurement lights closer to each other from FIG. 15.

The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not intended to limit the invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the drawings, similar components are given the same reference numerals.
(First embodiment)
FIG. 1 shows a schematic configuration of a film quality evaluation apparatus capable of FT-IR analysis. The film quality evaluation apparatus 1 includes an infrared light source 2 that outputs incoherent infrared light. For the infrared light source 2, a configuration capable of outputting infrared light having a wavelength of 2 μm to 10 μm, such as a high-luminance ceramic light source or a halogen lamp, is selected. A Michelson interferometer 3 is provided on the optical axis of the infrared light output from the infrared light source 2.

  The Michelson interferometer 3 includes a beam splitter 4, a fixed mirror 5, and a movable mirror 6. The beam splitter 4 is arranged with an inclination of 45 ° with respect to the optical axis of the infrared light output from the infrared light source 2, and branches the infrared light into two optical paths. A fixed mirror 5 which is a total reflection mirror is disposed on the optical axis of the optical path of one of the infrared light beams branched into two. A movable mirror 6, which is a total reflection mirror, is arranged on the optical axis of the other infrared light path branched by the beam splitter 4. The movable mirror 6 is fixed on, for example, a uniaxial moving stage (not shown) and can be reciprocated along the infrared optical axis as shown by an arrow in FIG. 1 by a stepping motor, that is, a beam splitter. 4 is configured to be able to approach and separate.

  Here, since the total reflection mirror is used for each of the fixed mirror 5 and the movable mirror 6, the infrared light reflected by each of the fixed mirror 5 and the movable mirror 6 is incident on the beam splitter 4 again. Superimposed. Since the movable mirror 6 reciprocates along the infrared optical axis, an optical path difference occurs in the reflected light of the two infrared lights input to the beam splitter 4. As a result, the two lights interfere with each other based on the optical path difference between the reflected lights of the two infrared lights to form interference light (interferogram). The interference light formed in this way is output from the Michelson interferometer 3. Note that in the Michelson interferometer 3, two infrared lights are superimposed in a state where an optical path difference determined by the position of the movable mirror 6 is generated, so that an interference spectrum is measured as a function of the position of the movable mirror 6 and Fourier transform is performed. It is possible to obtain a spectrum by performing.

  Further, on the optical path of the interference light output from the Michelson interferometer 3, a fixed mirror 11 for bending the optical path of the interference light and a beam splitter 12 are sequentially arranged. On the optical axis L1 of one interference light (first measurement light) branched into two by the beam splitter 12, a fixed mirror 13 and a fixed mirror 14 are arranged in order. On the other hand, a fixed mirror 15 and a fixed mirror 16 are sequentially arranged on the optical axis L2 of the other interference light (second measurement light) branched into two by the beam splitter.

The angles of the fixed mirrors 13 and 14 are adjusted so that the first measurement light is incident on the measurement object W at a predetermined first angle θ1. Further, the fixed mirrors 15 and 16 are configured so that the second measurement light is incident on the measurement object W at a predetermined second angle θ2 and intersects the first measurement light inside the measurement object W. The angle has been adjusted. The position where the two measurement lights intersect, that is, the position where the two optical paths L1 and L2 intersect is not limited to the inside of the measurement object W, but may be in front of or behind the measurement object W.

  Further, a first detector 17 is arranged on the optical axis L1 of the first measurement light that has passed through the measurement object W, and the output of the first detector 17 is sent to the first variable gain amplifier 18. It is connected. A second detector 19 is arranged on the optical path L2 of the second measurement light that has passed through the measurement object W, and the output of the second detector 19 is connected to the second gain variable amplifier 20. Has been. For these detectors 17 and 19, for example, a DTGS (Deuteriated triglycine sulfate) detector is used and configured to output a light intensity signal proportional to the intensity of infrared light. Each of the variable gain amplifiers 18 and 20 is configured to amplify the signals so that the output signals of the two detectors 17 and 19 have the same level.

  Outputs of the two variable gain amplifiers 18 and 20 are connected to a difference processing unit 21 which is a data processing unit. The differential connection unit 21 has a configuration for calculating a difference between analog signals output from the two gain variable amplifiers 18 and 20, and differential data (processed signal) as a calculation result is A / D (Analog / Digital). ) After being converted into a digital signal by the converter 22, it is input to the computer 23 for data processing. The computer 23 can function as a Fourier transform unit that calculates an infrared spectrum by acquiring difference data and performing Fourier change. Furthermore, it is possible to display, output and record infrared spectra. The difference processing unit 21, the A / D converter 22, and the computer 23 can constitute one processing device.

  Next, a film quality evaluation method using the film quality evaluation apparatus 1 will be described. As the measurement object W, for example, as shown in FIG. 2, a measurement object having a configuration in which a thin film W2 to be a measurement object for measuring a void density is provided on a substrate W1 having a known composition is used. The measurement object W is not limited to the configuration shown in FIG.

  First, the measuring object W is placed at a predetermined inspection position, and infrared light is emitted from the infrared light source 2. The Michelson interferometer 3 forms interference light from the infrared light, and the interference light is split into first measurement light and second measurement light by the beam splitter 12. These measurement lights are folded back by the fixed mirrors 13 to 16 and applied to a predetermined position of the thin film W2 of the measurement object W.

  Further, as shown in FIG. 2, the first measurement light having the optical axis L1 forms a beam spot BS1 on the surface of the thin film W2. The second measurement light having the optical axis L2 forms a beam spot BS2 on the surface of the thin film W2. In this film quality evaluation apparatus 1, the intersection position and the incident angle are set so that the beam spot BS1 of the first measurement light and the beam spot BS2 of the second measurement light partially overlap. In the example of FIG. 2, the two measurement lights are incident on the surface of the thin film W2 at an angle, so that the beam spots BS1 and BS2 on the surface of the thin film are elliptical. Further, the central portions of the two measuring beams are overlapped so that a part of the outer peripheral portion does not overlap. Thereby, an area AR1 where the two measurement lights overlap is formed in the center, and two areas AR2 where the measurement light does not overlap are formed at both ends thereof. The areas AR2 that do not overlap each have a substantially crescent shape, and the total area of the two areas AR2 is smaller than the area of the overlapping area AR1. The size and shape of the beam spots BS1 and BS2 and the size, shape and arrangement of the areas AR1 and AR2 can be changed by setting the incident angles and light diameters of the two measurement lights.

And the 1st measurement light permeate | transmits the thin film W2 and the board | substrate W1, The thin film W2 of the area | region
And light including information on the substrate W1 is input to the first detector 17. Similarly, when the second measurement light passes through the thin film W2 and the substrate W1, light including information on the thin film W2 and the substrate W1 in that region is input to the second detector 19.

  The output signals of the detectors 17 and 19 are level-adjusted by the gain variable amplifiers 18 and 20 and then input to the difference processing unit 21. The difference processing unit 21 calculates the difference between the two output signals. The information obtained at this time is obtained by removing information included in both the first measurement light and the second measurement light. That is, as shown in FIG. 2, information on the area AR2 where the first measurement light and the second measurement light do not overlap is obtained. Furthermore, if the infrared spectrum in the case of only the substrate W1 is measured in advance, and the information resulting from the substrate W1 is removed from the obtained information as the background, information on the region of the thin film W2 indicated by hatching in FIG. Is obtained. In this embodiment, since light transmitted through the measurement object W is used, information inside the thin film W2 can also be obtained.

  Then, if the difference data is acquired while moving the movable mirror 6 of the Michelson interferometer 3 and the difference data is Fourier transformed, an infrared transmission spectrum of the thin film W2 using infrared light can be obtained.

  Here, if the crossing position and crossing angle of the measurement light are set so that the size of the area AR2 is smaller than the diffraction limit of the infrared light used for the measurement, the film quality evaluation apparatus 1 uses the infrared light. An infrared absorption spectrum having a spatial resolution less than or equal to the diffraction limit is obtained. For example, when measuring the density of voids formed on the thin film W2 as a film quality evaluation, even if the size of the void is smaller than the diffraction limit of infrared light, the void is determined from the infrared absorption spectrum obtained by the film quality evaluation apparatus 1. The presence / absence and density can be measured.

  As shown in FIG. 3, when the thickness of the thin film W2 to be measured is thick, the back surface side (substrate) of the thin film W2 from the area AR2 where the two measurement lights formed on the front surface side of the thin film W2 do not overlap each other. The area AR3 in which the two measurement lights formed on the (W1 side) do not overlap may be larger. Here, it is considered that the spatial resolution of the infrared transmission spectrum in the film quality evaluation apparatus 1 is determined by the area (length) of the region where the two measurement lights do not overlap. Therefore, the spatial resolution of the infrared transmission spectrum in the example of FIG. 3 becomes the size of the back surface side of the thin film W2. For this reason, actual spatial resolution becomes lower than the spatial resolution assumed from the surface side of the thin film W2.

  In order to avoid such a situation, the incident angles θ1 and θ2 of the measurement light with respect to the measurement object W are reduced to reduce the difference in size between the areas AR2 and AR3 on the front surface side and the back surface side of the thin film W2. Is preferred.

  Furthermore, it is preferable that the thin film W2 to be measured is thin. In particular, as shown in FIG. 3, the ideal film thickness dw is preferably set to D1 / tan θ1 and / or D1 / tan θ2 or less. Here, D1 is the amount of deviation between the two measurement lights on the surface of the thin film W2.

  As described above, in this embodiment, the two measurement lights are used, and the beam spots BS1 and BS2 of the two measurement lights are irradiated on the measurement target W so as to be partially shifted, and the two measurement lights are irradiated. The infrared transmission spectrum was calculated by removing the common information included. Thereby, an infrared transmission spectrum is obtained for a region narrower than the beam spots BS1 and BS2 of the measurement light. Therefore, the spatial resolution can be increased compared to the conventional case. By increasing the spatial resolution, for example, it is possible to measure the density of minute voids formed in the thin film W2.

  Here, the optical system of the film quality evaluation apparatus 1 may be configured to condense the first and second measurement lights and enter the measurement object W. For example, as shown in FIG. 4, an infrared condenser lens 25 is inserted on the front side of the measurement object W on the optical axis L1 of the first measurement light, and the measurement object W and the first detector are inserted. 17 and the infrared objective lens 26 are inserted between them. Similarly, an infrared condenser lens 27 is inserted on the front side of the measurement object W on the optical axis L2 of the second measurement light, and between the measurement object W and the second detector 19, An infrared objective lens 28 is inserted. Thereby, since the beam diameter of the measuring light incident on the thin film W2 can be further reduced, the spatial resolution can be further increased. The infrared condenser lenses 25 and 27 and the objective lenses 26 and 28 are manufactured using a material that transmits infrared light, such as germanium.

  As shown in FIG. 5, if the incident angles of the two measurement lights are the same, the infrared attenuation due to transmission through the measurement object W is substantially the same in the two measurement lights. The light intensity of the infrared light measured at is approximately the same level. For this reason, it is not necessary to individually adjust the amplification factors by the two variable gain amplifiers 18 and 20. Further, in normal FT-IR, the transmitted light may interfere with the light reflected from the back surface (the surface opposite to the incident surface) of the measurement object W and the incident surface. In this case, the undulation depending on the film thickness of the measurement object W occurs in the infrared spectrum. On the other hand, if the incident angles of the two measurement beams are the same, the undulation period is the same for the two measurement beams. Thereby, it becomes possible to easily determine whether or not the measurement object W is affected by reflection on the back surface or the like.

(Second Embodiment)
FIG. 6 shows a schematic configuration of the film quality evaluation apparatus. In the film quality evaluation apparatus 31, the outputs of the first and second variable gain amplifiers 18 and 20 are connected to the addition processing unit 32 and the first difference processing unit 33, respectively. The processing unit 21 constitutes a data processing unit.

  The addition processing unit 32 creates an addition signal including information about a region irradiated with at least one of the two measurement lights. The first difference processing unit 33 creates first difference data including information about a region irradiated with only one of the two measurement beams. Further, the outputs of these two processing units 32 and 33 are connected to the second difference processing unit 34. The second difference processing unit 34 performs processing for subtracting the first difference data from the addition signal. Other configurations are the same as those of the first embodiment.

Next, the measurement direction in the film quality evaluation apparatus 31 will be described.
First, the infrared light output from the infrared light source 2 is used to form interference light by the Michelson interferometer 3. Further, the interference light is split into two measurement lights, and each measurement light is irradiated so that a part of the measurement light W overlaps. Then, the light transmitted through the measuring object W is received by the two detectors 17 and 19. The light intensity signals output from the detectors 17 and 19 are subjected to gain adjustment by the variable gain amplifiers 18 and 20, and then input to the addition processing unit 32 and the first difference processing unit 33, respectively.

  For example, the addition processing unit 32 generates an addition signal including all information in the area AR1 and the two areas AR2 in FIG. On the other hand, the first difference processing unit 33 creates first difference data including information on the two areas AR2 in FIG. Then, the second difference processing unit 34 subtracts the first difference data from the addition signal. As a result, second difference data (process signal) including information about the area AR1 where the two measurement lights overlap is created. When the second difference data is converted into a digital signal by the A / D converter 22 and then Fourier-transformed by the computer 23, an infrared transmission spectrum for the area AR1 is obtained.

Here, as shown in FIGS. 7 and 8, when the measurement object W is irradiated with two measurement lights so that the area AR1 where the two measurement lights overlap is smaller than the area AR2 where they do not overlap, infrared transmission is performed. The spectrum is created for the area AR1 where the measurement light overlaps. In this area AR1, since two measurement lights are obliquely irradiated at a predetermined incident angle, the size of the overlapping area AR1 is smaller than the spot diameter of one measurement light. Therefore, a spatial resolution higher than the diffraction limit of the measurement light can be obtained. Furthermore, since only one region where two measurement lights overlap is formed, the measurement position can be made clear.

  As in the first embodiment, infrared condenser lenses 25 and 27 and objective lenses 26 and 28 may be arranged on the optical paths L1 and L2 of the measurement light. Further, the incident angles of the two measurement lights may be the same or different.

(Third embodiment)
FIG. 9 shows a schematic configuration of the film quality evaluation apparatus. The optical system of the film quality evaluation apparatus 41 has a configuration in which the interference light is branched into the first measurement light and the second measurement light by using the beam splitter 12 as in the above-described embodiment. Further, the fixed mirror 13 and the movable mirror 42 are arranged on the optical axis L1 of the first measurement light, and the first measurement light that is turned back by these optical elements passes through the condenser lens 25 and is measured. It is configured to enter the object W. The movable mirror 42 is supported by a drive mechanism 43 that is an adjustment mechanism, and the operation of the drive mechanism 43 can be controlled by a controller 44. The drive mechanism 43 is configured to be able to change the irradiation angle and the irradiation position of the first measurement light with respect to the measurement object by rotating and linearly moving the movable mirror 42.

  Two fixed mirrors 15 and 16 are arranged on the optical axis L2 of the second measurement light, and the second measurement light reflected by the fixed mirrors 15 and 16 passes through the condenser lens 27 to be measured. It is incident on the object W perpendicularly.

  Further, the objective lens 26 and the first detector 17 are arranged in order on the optical path L1 of the first measurement light after passing through the measurement object W, and the output of the first detector 17 is output. Are connected to the first variable gain amplifier 18. Similarly, on the optical path L2 of the second measurement light after passing through the measurement object W, the objective lens 28 and the second detector 19 are sequentially arranged. The output is connected to the variable gain amplifier 20. Other configurations are the same as those of the first embodiment.

  Here, since the second measurement light is incident on the measurement object W perpendicularly, the first measurement light is incident obliquely, so that the optical path lengths of the two measurement lights must be matched. Therefore, in this film quality evaluation apparatus 41, the position of the condenser lens 25, the position of the objective lens 26, and the position of the detector can be finely adjusted in synchronization with the position and angle of the movable mirror 42. For example, a driving mechanism (not shown) is connected to a support member that supports the condenser lens 25 and the objective lens 26 and is driven so that the optical axis of the first measurement light and the central axes of the lenses 25 and 26 coincide. It is good to operate the mechanism. The first detector 17 is mounted on, for example, a stage that can approach or separate from the measurement object W.

  As shown in FIG. 10, the second measurement light forms a circular spot SP2 on the thin film W2 to be measured. On the other hand, the first measurement light incident obliquely on the measurement object W forms an elliptical spot SP1 that is flatter than the spot SP2 on the thin film W2. Since the shapes of the spots SP1 and SP2 formed by the two measurement lights on the thin film W2 are different, an area AR1 where the two measurement lights overlap and an area AR2 where they do not overlap can be formed. In the example of FIG. 10, one crescent-shaped portion is formed as the non-overlapping area AR2.

In this film quality evaluation apparatus 41, the controller 44 controls the irradiation position and irradiation angle of the first measurement light with respect to the measurement object W, whereby the size of the non-overlapping region AR2 can be made equal to or less than the diffraction limit of infrared light. Therefore, the spatial resolution of the infrared spectrum can be made below the infrared diffraction limit. Further, by operating the drive mechanism 43, the size of the area AR2 where the spots SP1 and SP2 do not overlap can be controlled. This makes it possible to change the measurement position and adjust the spatial resolution.

  Furthermore, as shown in FIG. 10, when the measurement object W is irradiated with two measurement lights, the non-overlapping region AR2 can be formed in only one place, so that the measurement position can be clarified. The drive mechanism 43 may be adjusted so that two non-overlapping areas AR2 are formed.

  Further, by providing the processing units 32 to 34 as shown in FIG. 6, an infrared transmission spectrum for the overlapping area AR <b> 1 may be acquired. In this case, the drive mechanism 43 controls the irradiation position and the irradiation angle of the first measurement light with respect to the measurement target W so that the size of the overlapping area AR1 is smaller than the diffraction limit of infrared light.

(Fourth embodiment)
FIG. 11 shows a schematic configuration of the film quality evaluation apparatus. The optical system of the film quality evaluation apparatus 51 includes a second beam forming mechanism 52 between the fixed mirror 14 and the measurement target W on the optical axis L1 of the first measurement light. A second beam shaping mechanism 53 is arranged between the fixed mirror 16 and the measuring object W on the optical axis L2 of the second measuring light. Further, one objective lens 26, 28 is disposed between the measurement object W and each of the first and second detectors 17, 19.

  FIG. 12 shows an example of the beam shaping mechanisms 52 and 53. The beam forming mechanisms 52 and 53 combine two lenses 55 and 56 to expand the spot diameter of the measurement light, and a diaphragm 58 that cuts a part of the measurement light expanded by the beam crosser 57. And a condenser lens 59 that condenses the measurement light after passing through the diaphragm 58.

  Here, in the two beam forming mechanisms 52 and 53, if the shape of the diaphragm 58 is made different, the spot shape on the thin film W2 can be made different. For example, the diaphragm 58 of the first beam shaping mechanism 52 is square, and the diaphragm 58 of the second beam shaping mechanism 53 is a horizontally long rectangle. In this case, as shown in FIG. 13, a substantially square beam spot BS3 and a substantially rectangular beam spot BS4 are formed on the thin film W2. The beam spot BS3 is formed by the first beam shaping mechanism 52, and the beam spot BS4 is formed by the second beam shaping mechanism 53. The beam spot BS4 is formed so as to partially overlap the beam spot BS3, and includes all of the beam spot BS3. For this reason, the area AR1 where the two measurement lights overlap is approximately equal to the shape of the beam spot BS3. One area AR2 where the two measurement lights do not overlap is formed by the beam spot BS4.

  In addition, the kind and combination of the optical element which comprises the beam shaping mechanisms 52 and 53 can be set arbitrarily. For example, the shape of the beam spot on the surface of the measurement target W may be a circle, ellipse, line, two or more lines having various diameters, depending on the shape of the diaphragm 58 and other optical elements.

  In this film quality evaluation apparatus 51, the size of the non-overlapping region AR2 can be made equal to or less than the diffraction limit of infrared light by controlling the irradiation position and the irradiation angle of the two measurement lights on the measurement object W. As a result, the spatial resolution of the infrared transmission spectrum falls below the diffraction limit of infrared light.

Thus, by using the beam shaping mechanisms 52 and 53 having a rectangular stop, it is possible to make the shape of the area AR2 where the two measurement lights do not overlap substantially rectangular. Thereby, a measurement area can be made into a simple shape and it becomes easy to specify a measurement area. Furthermore, as shown in FIG. 13, when only one non-overlapping region AR2 is formed, the measurement position can be clarified. Note that the film quality evaluation apparatus 51 may form two regions AR2 that do not overlap.

In addition, you may add the beam shaping mechanisms 52 and 53 and the objective lenses 26 and 28 to the film quality evaluation apparatus 31 shown in FIG.
Further, the beam shaping mechanisms 52 and 53 do not need to have the diaphragm 58. Without providing the objective lenses 26 and 28, the measurement light transmitted through the measurement object W may be directly taken into the first and second detectors 17 and 19.
The incident angles of the two measurement beams may be the same or different.

  Further, by providing the processing units 32 to 34 as shown in FIG. 6, an infrared transmission spectrum for the overlapping area AR <b> 1 may be acquired. In this case, the irradiation position and the irradiation angle of the two measurement lights with respect to the measurement target W are controlled so that the size of the overlapping area AR1 is smaller than the diffraction limit of the infrared light.

(Fifth embodiment)
FIG. 14 shows a schematic configuration of the film quality evaluation apparatus. The optical system of the film quality evaluation apparatus 61 has a mirror drive mechanism 62 that is an adjustment mechanism after the measurement light is branched and before the measurement object W is irradiated. Furthermore, one set of condenser lenses 25 and 27 and objective lenses 26 and 28 are arranged so as to sandwich the measuring object W. The condenser lenses 25 and 27 and the objective lenses 26 and 28 are not essential components.

  The mirror drive mechanism 62 has a base 63, and two sliders 64 and 65 are movably mounted on the base 63. One fixed mirror 14, 16 is fixed to each slider 64, 65 with a predetermined inclination angle with respect to the base 63. These sliders 64 and 65 can move the fixed mirrors 14 and 16 substantially parallel to the optical axis of the fixed mirrors 13 and 15 by an automatic stage or piezo. The movement of the fixed mirrors 14 and 16 is controlled by the controller 66. The position and angle of the condenser lenses 25 and 27 and the objective lenses 26 and 28 and the position of at least one of the detectors 17 and 19 can be adjusted in synchronization with the movement of the fixed mirrors 14 and 16. The mechanism for adjusting the beam irradiation position is not limited to the illustrated configuration.

  In this film quality evaluation apparatus 61, the area of the area AR1 where the spots formed on the thin film W2 overlap can be changed by two measurement lights. That is, when at least one of the two fixed mirrors 14 and 16 is moved away from each other by the mirror driving mechanism 62, the area AR1 where the spots SP1 and SP2 overlap as shown in FIG. 15 can be reduced. On the other hand, when at least one of the two fixed mirrors 14 and 16 is moved in the direction approaching each other by the mirror driving mechanism 62, the area of the region where the spots SP1 and SP2 overlap as shown in FIG. Compared to larger.

  In this way, by controlling the incident positions of the two measurement lights with respect to the measurement object W using the mirror drive mechanism 62, the size of the area AR2 where the spots SP1 and SP2 do not overlap can be made equal to or less than the diffraction limit. it can. Thereby, the spatial resolution of the infrared transmission spectrum can be made below the diffraction limit. Further, by operating the mirror driving mechanism 62, the size of the area AR2 where the spots SP1 and SP2 do not overlap can be controlled. This makes it possible to change the measurement position and adjust the spatial resolution.

In this film quality evaluation apparatus 61, since the difference processing unit 21 takes the difference of the intensity signal, the infrared spectrum of the non-overlapping area AR2 can be obtained. If the configuration of the data processing part is as shown in FIG. An infrared transmission spectrum of the overlapping area AR1 is obtained. In this case, if the size of the overlapping area AR1 is made the diffraction limit or less by the mirror driving mechanism 62, a high spatial resolution can be obtained. In addition, the size of the area AR2 that does not overlap can be controlled by the operation of the mirror drive mechanism 62.

The present invention is not limited to each embodiment and can be widely applied.
For example, in the optical system, the number and arrangement of fixed mirrors can be arbitrarily set. Further, instead of using a condenser lens and an objective lens, an optical system that forms parallel light by combining lenses may be used. A fixed mirror may be provided between the measurement object W and the detectors 17 and 19.

  The condenser lens and objective lens for infrared rays may be silicon, sapphire, zinc selenide, zinc sulfide, thallium bromoiodide, magnesium fluoride, calcium fluoride, barium fluoride, and spinel (MgAl2O3). These materials can be selected according to the range of the wave number (wavelength) of the infrared spectrum. Further, instead of condensing the measurement light with a lens, the measurement light may be condensed using a reflection optical system such as a Cassegrain mirror.

  The detector is a pyroelectric detector using an optical crystal such as TGS (triglycine sulfate) or DLATGS (deuterium-substituted L-alanine triglycine sulfate), or a semiconductor MCT (mercury cadmium telluride) detection. A vessel or the like may be used. In the infrared region, a photodiode using indium gallium arsenide, lead selenide, or the like can be used. In the far infrared region, a detector such as a silicon bolometer or a germanium bolometer may be used.

  In each embodiment, the infrared transmission spectrum is calculated using light transmitted through the measurement object. However, the infrared reflection spectrum may be calculated using light reflected from the measurement object. In this case, the detector is arranged on the same side as the incident side with respect to the measurement object.

  Further, each of the film quality evaluation devices 1, 31, 41, 51, 61 may be configured to divide the measurement light into three or more and irradiate the measurement object W with each of them. If each of the processing units 32 to 34 as shown in FIG. 6 is used to extract a signal in a region where all three measurement beams overlap and perform Fourier change using this signal, an infrared spectrum with higher spatial resolution can be obtained. It is done. By using three or more measurement lights, it becomes easy to control the size and shape of the measurement region. Alternatively, Fourier transform may be performed by extracting a region where two arbitrary measurement beams overlap from three or more measurement beams, or extracting a region where measurement beams do not overlap.

  A visible light source and an imaging device for imaging the surface of the measurement object W are provided, and visible light is abbreviated as measurement light to the measurement object W using the first and second measurement light optical systems. You may comprise so that irradiation is possible with the same beam shape. If comprised in this way, it will become possible to measure an infrared spectrum, after confirming beforehand the irradiation position of two measurement light, and the amount of overlap using visible light.

  All examples and conditional expressions given here are intended to help the reader understand the inventions and concepts that have contributed to the promotion of technology, such examples and It should be construed without being limited to the conditions, and the organization of such examples in the specification is not related to showing the superiority or inferiority of the present invention. Although embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions and variations can be made thereto without departing from the spirit and scope of the present invention.

1, 31, 41, 51, 61 Film quality evaluation device 2 Infrared light source 3 Interferometer 17 First detector 19 Second detector 21 Difference processing unit (data processing unit)
23 Computer (Fourier transform part)
32 addition processing unit 33 first difference processing unit (data processing unit)
34 Second difference processing unit (data processing unit)
42 Drive mechanism (adjustment mechanism)
52, 53 Beam shaping mechanism 62 Mirror drive mechanism (adjustment mechanism)
AR1 Overlapping area AR2 Non-overlapping area W Object to be measured

Claims (6)

An infrared light source that outputs incoherent infrared light;
An interferometer that forms interference light from infrared light;
An optical system that splits the interference light into a first measurement light and a second measurement light, and that causes the first measurement light and the second measurement light to be incident on the surface of the measurement object so that they partially overlap;
A first detector that is incident on the first measurement light that has passed through the measurement object or reflected by the measurement object, and that outputs a signal according to the amount of light;
A second detector that receives the second measurement light that has passed through the measurement object or reflected by the measurement object, and outputs a signal according to the amount of light;
A data processing unit that calculates a difference between a signal output from the first detector and a signal output from the second detector and at least one of overlapping portions of the signals and outputs the calculated signal as a processing signal;
A Fourier transform unit for Fourier transforming the processing signal output from the data processing unit;
A film quality evaluation apparatus comprising:   The optical system includes a beam shaping mechanism for shaping a beam shape of at least one of the first measurement light and the second measurement light before entering the measurement object. Film quality evaluation device.   The optical system includes an adjustment mechanism capable of changing an incident angle and an incident position when at least one of the first measurement light and the second measurement light is irradiated on the measurement object. 2. The film quality evaluation apparatus according to 1.   The optical system is configured to match an incident angle when the first measurement light is incident on the measurement object and an incident angle when the second measurement light is incident on the measurement object. The film quality evaluation apparatus according to claim 1.   The optical system calculates the shift amount of the optical axis position when each of the first and second measurement lights is irradiated on the measurement object, and the infrared when calculating the difference between detection signals by the data processing unit. The diffraction limit of the infrared light output from the light source is set to be lower than or equal to the diffraction limit of the infrared light output from the infrared light source when the data processing unit calculates the overlapping component of the detection signal. The film quality evaluation apparatus according to any one of claims 1 to 4. Outputting incoherent infrared light from an infrared light source and forming interference light from the infrared light; and
A step of branching the interference light into the first measurement light and the second measurement light and causing the first measurement light and the second measurement light to be incident on the surface of the measurement object so as to partially overlap;
Detecting the first measurement light transmitted through the measurement object or reflected by the measurement object with a first detector, and outputting a signal according to the amount of light;
Detecting a second measurement light transmitted through the measurement object or reflected by the measurement object with a second detector, and outputting a signal according to the amount of light;
Calculating at least one of the difference between the signal output from the first detector and the signal output from the second detector and the overlapping portion of the signals, and outputting as a processed signal;
A process of Fourier transforming the processed signal to calculate an infrared spectrum;
A film quality evaluation method comprising:

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