JP2008064691A - Apparatus for measuring optical anisotropy parameter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent measuring accuracy from being lowered even if light having a large irradiation diameter is used when optical parameters such as film thickness, refractive index, and refractive index anisotropy are measured through the use of polarization. <P>SOLUTION: In the optical anisotropy parameter measuring apparatus (wherein a surface to be measured of a sample 2 is an XY surface; the direction of the axis of incident light is α; and the direction of the axis of reflected light is β), an irradiation optical system 3 for irradiating the sample 2 with incident light flux B<SB>L</SB>of linear polarization is provided with both a light source device 5 for irradiating spot-shaped parallel light flux according to a region to be measured and a reflecting type polarizer 6 for extracting incident light flux of linear polarization by reflecting the parallel light flux at a prescribed angle, and a measuring optical system 4 for measuring the intensity of reflected light of P-polarization or S-polarization contained in reflected light flux B<SB>R</SB>is provided with both a reflecting type optical analyzer 8 for extracting P-polarization or S-polarization by reflecting the reflected light flux B<SB>R</SB>at a prescribed angle at a reflecting surface intersecting with a Yβ surface or an Xβ surface at right angles and a one-dimensional or two-dimensional optical sensor 10 for detecting the optical intensity of the polarization. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical anisotropy parameter measuring apparatus used when measuring optical parameters such as film thickness, refractive index, and refractive index anisotropy of a substance using polarized light.

Optical parameters such as the film thickness, refractive index, refractive index anisotropy, etc. of the thin film formed on the surface of the electronic device affect the electrical and optical characteristics of the device, and the uniformity is the quality of the electronic device. Determine pass or fail.
Therefore, it is essential to measure and inspect the distribution characteristics of these parameters for quality improvement.

As a method for inspecting these optical parameters by measuring the film thickness and refractive index of the thin film in a non-contact / non-destructive manner, when the light irradiated to the measurement point of the sample is reflected by the sample or transmitted through the sample, There is known an optical anisotropy parameter measuring apparatus that performs measurement using a phenomenon in which a polarization state changes.
Japanese Patent No. 3425923

However, in this case, since only the reflected light intensity at one point on the sample can be measured at a time, the optical anisotropy parameter that can measure the reflected light intensity of the entire region of the sample to be measured with high efficiency. A measuring device has been proposed.
Japanese Patent Laid-Open No. 7-72013

FIG. 10 shows such a conventional optical anisotropy parameter measuring device 51. The irradiation optical system 53 irradiates the thin film sample 52 with an incident light beam of P-polarized light or S-polarized light, and the reflected light beam reflected from the thin film sample 52. A measurement optical system 54 that detects a reflected light intensity distribution of S-polarized light or P-polarized light orthogonal to the polarization direction of the incident light beam among the included polarization components is provided.
Then, the irradiation optical system 53 expands or widens the incident light beam according to the shape of the measurement region 52a of the laser light source 55, the polarizer 56, and the thin film sample 52 along the optical axis L of the incident light beam to obtain a parallel light beam. A beam expander 57 is arranged.
Then, the measurement optical system 54, along the optical axis A _R of the reflected light beam, the light sensor 59 composed analyzer 58 and from the two-dimensional light receiving element is arranged.

According to this, after the laser light emitted from the laser light source 55 of the irradiation optical system 53 is polarized into P-polarized light or S-polarized light by the polarizer 56, the beam expander 57 expands the light beam to a predetermined irradiation diameter. Then, the entire measurement area 52a of the thin film sample 52 is irradiated at once.
Then, the reflected light beam reflected from the entire measurement region 52a passes through the analyzer 58, and among the polarized components, S-polarized light or P-polarized light orthogonal to the polarization direction of the incident light beam is transmitted, and the reflected light intensity distribution is light. It is measured by each light receiving element of the sensor 59.
Therefore, there is an advantage that the reflected light intensity from a number of measurement points corresponding to the number of light receiving elements can be measured at a time.

However, in this case, after the light is polarized, the light is refracted by the lens serving as the beam expander 57 and the light beam is greatly expanded, so that the polarization state of the incident light beam is changed by the lens and the measurement accuracy is increased. There was a problem that decreased.
Further, even if the order of the beam expander 57 and the polarizer 56 is reversed to polarize the expanded light beam, the polarizer 56 used for such optical measurement generally has the following advantages in order to improve measurement accuracy. A material having a high extinction ratio is used, such as a Gran Thompson prism made of natural calcite, but it is difficult to obtain a material for producing a Glan Thompson prism having a side of 20 mm or more in size. Therefore, it was practically impossible to measure with a light beam having an irradiation diameter of 20 mm or more.
Similarly, if the analyzer 59 tries to detect the polarization state of the reflected light beam with a large diameter, a large-diameter analyzer with a high extinction ratio is required. If the analyzer 59 is made to pass through after being reduced in diameter, the polarization state changes at the point of transmission through the lens before passing through the analyzer 59, so that there is still a problem that the measurement accuracy is lowered.

  Therefore, the present invention can measure light parameters with a large irradiation diameter without reducing measurement accuracy when measuring optical parameters such as film thickness, refractive index and refractive index anisotropy using polarized light. To make it a technical issue.

In order to solve this problem, the present invention provides a surface through which an incident optical axis and a reflected optical axis pass on an XYZ coordinate whose origin is the intersection of the incident optical axis and the XY plane, and the measurement target surface of the sample is the XY plane. Is the XZ plane, the direction of the incident optical axis toward the origin is α, and the direction of the reflected optical axis reflected from the origin is β,
The irradiation optical system includes a light source device that irradiates a spot-shaped parallel beam according to the shape of the measurement region of the sample, and a linearly polarized incident beam that travels toward the sample along the α direction by reflecting the parallel beam at a predetermined angle. With a reflective polarizer to extract
The measurement optical system reflects a reflected light beam traveling in the β direction from a sample at a predetermined angle by a reflecting surface orthogonal to the Yβ surface or the Xβ surface, thereby extracting a P-polarized light or S-polarized light reflected by the sample. And a one-dimensional or two-dimensional optical sensor for detecting the light intensity of the polarization component.

In the present invention, a planar reflector is used as the reflective polarizer and the reflective analyzer, and the respective reflective surfaces are arranged so as to be orthogonal to the Xα plane and the Yβ plane. Is incident on a planar reflector perpendicular to the Xα plane at a Brewster angle, and the reflected light becomes an incident light beam directed toward the sample along the α direction.
At this time, the incident light beam becomes light including only the S-polarized component with respect to the reflecting surface of the planar reflector, and the vibration direction of the polarized light is in the Yα plane direction orthogonal to the Xα plane. Incident light is incident as polarized light.

Next, the reflected light beam reflected from the sample travels in the β direction, is incident at a Brewster angle on a flat reflector perpendicular to the Yβ plane, and the reflected light travels along the Yβ plane.
At this time, the polarization component of the reflected light beam that becomes S-polarized light with respect to the sample vibrates in the Yβ plane direction, so that it enters the plane reflector as P-polarized light, and the polarization component of the reflected light beam that becomes P-polarized light with respect to the sample is Since it vibrates in the Xβ plane direction, it is incident on the planar reflector as S-polarized light.
Since the reflected light beam is incident on the flat reflector at the Brewster angle, only the S-polarized light, that is, the P-polarized light is reflected on the reflecting surface and reaches the optical sensor. .
Therefore, S-polarized light is incident on the sample, and only P-polarized light orthogonal to the polarization direction of the incident light can be detected from the reflected light.

  As described above, since the reflective polarizer and the reflective analyzer are used as the polarizer and the analyzer, not the transmission type polarizing plate, the sample is irradiated with the S-polarized light regardless of the diameter of the incident light beam and the reflected light beam. Even if the reflected light beam from the sample has a large diameter, it is possible to reliably extract P-polarized light that is orthogonal thereto.

Further, if the reflecting surface of each planar reflector is arranged so as to be orthogonal to the Yα plane and the Xβ plane, and a parallel light beam is irradiated along the Yα plane from the light source device, the Brewster angle with respect to the planar reflector orthogonal to the Yα plane. And the reflected light becomes an incident light beam directed toward the sample along the α direction.
At this time, the reflected light of the planar reflector becomes light containing only the S-polarized component with respect to the reflecting surface, and the S-polarized light vibrates in the Xα plane orthogonal to the Yα plane, so that it becomes P-polarized light with respect to the sample. Incident.

Next, the reflected light beam reflected from the sample travels in the β direction, is incident at a Brewster angle on a planar reflector orthogonal to the Xβ plane, and the reflected light travels along the Xβ plane.
At this time, the polarization component of the reflected light beam that becomes S-polarized light with respect to the sample vibrates in the Yβ plane direction, so that it also enters the planar reflector as S-polarized light, and the polarization component of the reflected light beam that becomes P-polarized light with respect to the sample is Since it vibrates in the Xβ plane direction, it is also incident on the flat reflector as P-polarized light.
Then, since the reflected light beam is incident on the flat reflector at the Brewster angle, only the S-polarized light, that is, the S-polarized light is reflected on the reflecting surface of the polarized light component. Reach the sensor.
Therefore, P-polarized light is incident on the sample, and only S-polarized light orthogonal to the polarization direction of the incident light can be detected from the reflected light.

An optical anisotropy parameter measuring apparatus according to the present invention includes an irradiation optical system that irradiates a sample with a linearly polarized incident light beam, and reflected light of P-polarized light or S-polarized light among polarized components included in a reflected light beam reflected from the sample. A measuring optical system for measuring the intensity,
The surface to be measured of the sample is the XY plane, and on the XYZ coordinates with the origin of the intersection of the incident optical axis and the XY plane, the plane through which the incident optical axis and the reflected optical axis pass is the XZ plane. When the direction is α and the direction of the reflected optical axis reflected from the origin is β,
The irradiation optical system includes a light source device that irradiates a spot-shaped parallel beam according to the shape of the measurement region of the sample, and a linearly polarized incident beam that travels toward the sample along the α direction by reflecting the parallel beam at a predetermined angle. With a reflective polarizer to extract
The measurement optical system reflects a reflected light beam traveling in the β direction from a sample at a predetermined angle by a reflecting surface orthogonal to the Yβ surface or the Xβ surface, thereby extracting a P-polarized light or S-polarized light reflected by the sample. And a one-dimensional or two-dimensional optical sensor for detecting the light intensity of the polarization component.

1 is an explanatory view showing an example of an optical anisotropy parameter measuring apparatus according to the present invention, FIG. 2 is an explanatory view showing a measuring method, FIG. 3 is a graph showing a change in light intensity at a measuring point on the origin, and FIG. FIG. 5 and FIG. 6 are explanatory diagrams showing other embodiments, FIG. 7 is an explanatory diagram showing the measuring method, FIG. 8 is an explanatory diagram showing another embodiment, and FIG. Explanatory drawing showing the measurement results,
FIG. 10 is an explanatory view showing a conventional apparatus.

An optical anisotropy parameter measuring apparatus 1 shown in FIG. 1 includes an irradiation optical system 3 that irradiates a thin film sample 2 disposed on a stage 11 with an incident light beam _BL of S-polarized light, and a reflected light beam B reflected from the sample 2. _And a measurement optical system 4 that detects a reflected light intensity distribution of P-polarized light included in _R.
In order to define the positional relationship, the measurement target surface of the sample 2 and XY plane, the intersection of the incident optical axis A _L and the XY plane on the XYZ coordinate of the origin P _0, the incident optical axis A _L and the reflection a surface through which the optical axis a _R and the XZ plane, the direction of the incident optical axis toward the origin P ₀ alpha, the direction of the origin P ₀ the reflected optical axis a _R reflected from the beta.

Irradiation optical system 3 includes a light source device 5 for irradiating along the optical axis A _S traveling through Xα plane parallel light beam spot shape corresponding to the shape of the measurement region of the sample 2 as the irradiation light beam B _S, the irradiation light beam By reflecting B _S with a Brewster angle θ _B by a reflecting surface orthogonal to the Xα plane, the incident side plane reflector (reflective polarizer) extracts S-polarized light toward the sample 2 along the α direction as an incident light beam _BL. 6).

  The light source device 5 includes a laser light source 5a that emits irradiation light whose optical axis travels along the Xα plane, and expands or widens the irradiation light according to the shape of the measurement region of the sample 2 to obtain a parallel light beam. A beam expander lens 5b is provided.

With the planar reflector 6 is the reflecting surface is disposed perpendicular to the Xα surface, the intersection of two times the irradiation optical axis intersected at an angle of A _S and the incident optical axis A _L of the Brewster angle theta _B on Xα surface It is arranged in a direction orthogonal to the angle bisector.

Further, since the irradiation light beam B _S is incident on the flat reflector 6 at the Brewster angle θ _B , the light that becomes P-polarized light (light that vibrates in the Xα-plane direction) is not reflected on the reflection surface, and the S-polarized light. Only the light (light oscillating in the Yα plane direction) is reflected, and this becomes an incident light beam _BL directed toward the sample 2 along the α direction, so that it enters the measurement target surface of the sample 2 as S-polarized light. Is done.

The incident light beam B _L is the reflected light beam B _R traveling in the β direction is reflected by the measurement target surface of the sample 2. The reflected light beam B _R, because it contains reflected light beams B _R is generally (light vibrating in Xβ plane direction) P-polarized component and S-polarized light component (light vibrating in Yβ surface direction) by the physical properties of the sample 2, the measurement optical the system 4, to extract the P-polarized light component included in the reflected light beams B _R, detects the light intensity.

Measuring optical system 4, by reflecting at the Brewster angle theta _B by the reflecting surface which is perpendicular to the reflected light beams B _R and Yβ surface, P-polarized light orthogonal to the (S-polarized light in the present embodiment) the polarization direction of the incident beam B _L a reflection side flat reflector (reflective analyzer) 8 to extract a measurement beam B _M, and an image forming lens 9 for focusing the measuring beam B _M, and a light sensor 10 for detecting the intensity distribution of the polarization components I have.
At this time, the planar reflector 8 is the reflecting surface is disposed perpendicular to the Yβ surface, the reflected optical axis intersected at twice the angle of the Brewster angle theta _B on Yβ surface A _R and the measurement light axis A It is arranged in a direction perpendicular to the bisector of the crossing angle of _M.

Here, the reflected light beam B _R reflected from the sample 2 because it is incident at the Brewster angle theta _B to the plane reflector 8, vibrates in the light (Ybeta plane direction is P-polarized with respect to the reflecting surface light ) Is not reflected, and only the light that becomes S-polarized light (light that vibrates in the Xβ plane direction) is reflected, and this becomes the measurement light beam B _M toward the optical sensor 10.
At this time, with respect to a plane reflector 8 because S polarized light of the reflected light beam B _R is incident as P-polarized light to the plane reflector 8 because vibrates in Yβ plane direction, P-polarized light of the reflected light beam B _R vibrates in Xβ plane direction Is incident as S-polarized light.
Therefore, in the planar reflector 8, only the light that becomes S-polarized light with respect to the reflection surface thereof, that is, the light that becomes P-polarized light with respect to the measurement target surface of the sample 2 is reflected to become the measurement light beam B _{M. M} reaches the optical sensor 10.

Thus, S-polarized light as the incident light beam B _L to the sample 2 is incident only (light vibrating in Yα plane direction), P-polarized light orthogonal to the polarization component of the incident light beam B _L from the reflected light beam B _R (in Xβ plane direction Only the vibrating light) can be extracted, and the light intensity can be detected by the optical sensor 10.
Further, as a polarizer and an analyzer of the measuring optical system 4 of the illumination optical system 3, since the reflective polarizer and the reflective analyzer rather than a transmission type is used, the incident light beam B _L and the reflected light beams B _R, no matter how Even with a large diameter, the sample 2 can be irradiated with S-polarized light, and P-polarized light perpendicular to the sample 2 can be reliably taken out regardless of how large the reflected light beam from the sample 2 is.

As the optical sensor 10, a CCD image sensor or a CMOS image sensor is used in which a light receiving element corresponding to a pixel is one-dimensionally or two-dimensionally used.
The stage 11 is arranged so that its position can be adjusted in the XYZ directions, and is arranged so as to be adjustable around the X and Y axes, and further rotated by a step motor (not shown) by a predetermined angle around the Z axis. It is arranged as possible.

The above is an example of the present invention, and its operation will be described next.
The light source device 5 uses a semiconductor-pumped YAG-SHG laser (wavelength 532 nm, output 150 mW) as the laser light source 5a, and the light from the laser light source 5 is converted into a Y-axis by a one-dimensional beam expander lens 5b composed of a cylindrical lens. A light beam having a linear beam spot with a length of 30 mm parallel to the surface was formed.
As the incident side plane reflector 6 and the reflection side plane reflector 8, a wedge-shaped glass body having a length × width = 40 × 50 (mm) and a back surface inclined with respect to the surface was used, and the surfaces thereof were formed on the reflection surface.

The α-axis and β-axis are arranged one-dimensionally as the optical sensor 10 by arranging the irradiation optical system 3 and the measurement optical system 4 so that the incident angle and reflection angle to the sample 2 and the reflection angle (angle formed with the Z-axis) are 50 °. A CCD imaging device was used and arranged in such a direction that a linear beam irradiated from the irradiation optical system 3 could be received.
As sample 2, one side of LiNbO ₃ having a longitudinal direction L × width direction W × thickness direction T = 50 × 30 × 2 (mm) was optically polished along the longitudinal direction along one side thereof, and in-plane optical The axial direction and the longitudinal direction L were matched, and the longitudinal direction was fixed on the stage 11 with the Y-axis direction (see FIG. 2A).

After adjusting the tilt of the sample 2, while rotating the sample 2 is irradiated with incident light beam B _L of the S-polarized light to measure the intensity of the reflected light beams B _R of the P-polarized light.
At this time, the position of the measurement point on the origin P ₀ be rotated sample 2 is not changed, the light intensity of the pixels of the CCD image sensor constituting the light sensor 10, the optical axis of the measuring beam B _M It is detected by a detector located on A _M.

Figure 3 is a graph showing the measurement value of the light intensity of the measurement beam B _M and the rotation angle of the stage 11 at that time.
In the graph, the two largest peaks lambda ₁ and lambda _2, two intermediate peaks lambda ₃ and lambda ₄ are present, the minimum point V ₁ ~V ₄ the light intensity between the peaks lambda ₁ to [lambda] ₄ is 0 There is a value angle.
The minimum point V ₁ between the two maximum peaks Λ ₁ and Λ ₂ and the minimum point V ₃ between the two intermediate peaks Λ ₃ and Λ ₄ are the optical axes of the measurement points on the sample 2 located at the origin P _0. Indicating the direction, thus the difference is 180 °.
In this example, since the in-plane optical axis direction coincides with the longitudinal direction L, the minimum points V ₁ and V ₃ are 90 ° and 270 when the stage rotates 90 ° and the longitudinal direction becomes parallel to the X axis. Observed at the position of °.
From this, it can be seen that the direction of the optical axis of the sample 2 coincides with the longitudinal direction.

  Next, the stage 11 is rotated and positioned so that the longitudinal direction L of the sample 2 is parallel to the X axis, and the linear beam irradiated from the irradiation optical system 3 is incident in parallel to the width direction W of the sample 2. By moving the stage 11 in the X-axis direction, the light beam is swept from one end side in the longitudinal direction on the sample 2 to the other end side, and the light intensity is detected by each pixel of the photosensor 10 (FIG. 2 ( b)).

At this time, if the optical axes at the respective points on the sample 2 are all directed in the longitudinal direction L, the light intensity is maintained at 0, so that the portion where the optical axis is shifted is where the light intensity is not 0. I can guess.
Therefore, as shown in FIG. 4, if a three-dimensional graph showing the light intensity in the height direction is drawn, it can be evaluated in a very short time whether or not the direction of the optical axis is uniform from the overall distribution. .
For example, when a portion with high light intensity is observed along the longitudinal direction L in the longitudinal direction L as shown in FIG. 4A, and when the light intensity is parallel to the width direction W as shown in FIG. Depending on the case where a high portion is observed, it can be used for discriminating a defect depending on the pulling direction of crystal growth, that is, a defect generated during crystal growth and a defect caused by processing such as polishing.

FIG. 5 shows another embodiment of the present invention. Is incident S polarized light as the incident light beam B _L with respect to Example 1 in the thin film sample 2, was measured the light intensity of P-polarized light of the reflected light beams B _R, in this example, is incident P polarized light as the incident light beam B _L was to measure the light intensity of S-polarized light of the reflected light beams B _R. In addition, the same code | symbol is attached | subjected about the part which is common in FIG. 1, and detailed description is abbreviate | omitted.

This example optically anisotropic parameter measurement device 21 irradiation optical system of 3, the optical axis A _S traveling through Yα plane parallel light beam spot shape corresponding to the shape of the measurement region of the sample 2 as the irradiation light beam B _S The light source device 5 that irradiates along the light beam B and the irradiation light beam B _S is reflected at the Brewster angle θ _B by a reflecting surface orthogonal to the Yα plane, so that the S-polarized light toward the sample 2 along the α direction is incident on the light beam B _L. The incident side plane reflector (reflection type polarizer) 6 is extracted.

Since the reflecting surface of the flat reflector 6 is orthogonal to the Yα plane, the optical axes of light irradiated from the light source device 5 and reflected by the flat reflector 6 to reach the sample 2 all pass on the Yα plane. .
Then, the irradiation optical axis A _S and the incident optical axis A _L from the light source device 5 is a plan reflector as cross at twice the angle of the Brewster angle theta _B on Yα plane, perpendicular to the bisector 6 is arranged.

Further, since the irradiation light beam B _S is incident on the flat reflector 6 at the Brewster angle θ _B , the light that becomes P-polarized light (light that vibrates in the Yα-plane direction) is not reflected on the reflection surface, and the S-polarized light. Only the light (light oscillating in the Xα plane direction) is reflected, and this becomes the incident light beam _BL toward the sample 2 along the α direction, and therefore enters the measurement target surface of the sample 2 as P-polarized light. Is done.

Measuring optical system 4, by reflecting at the Brewster angle theta _B by the reflecting surface which is perpendicular to the reflected light beams B _R and Xβ plane, S-polarized light orthogonal to the (P-polarized light in this example) the polarization direction of the incident beam B _L Is provided as a measurement light beam B _M , a reflection-side planar reflector (reflection analyzer) 8, an imaging lens 9, and an optical sensor 10.

At this time, since the planar reflector 8 is orthogonal to the Xβ plane, all the optical axes of light from the sample 2 passing through the planar reflector 8 and the imaging lens 9 to the optical sensor 10 pass on the Xβ plane. .
Then, the reflection optical axis A _R reflected by the sample 2, the measurement optical axis A _M extending from the plane reflector 8 on the light sensor 10, intersect at twice the angle of the Brewster angle theta _B on Xβ plane, the A planar reflector 8 is arranged so as to be orthogonal to the bisector.

Here, the reflected light beam B _R reflected from the sample 2 because it is incident at the Brewster angle theta _B to the plane reflector 8, it vibrates in the light (X? Plane direction is P-polarized with respect to the reflecting surface light ) Is not reflected, and only the light that becomes S-polarized light (light that vibrates in the Yβ plane direction) is reflected, and this becomes the measurement light beam B _M toward the optical sensor 10.
At this time, S polarized light of the reflected light beam B _R is also incident as S-polarized light to the plane reflector 8 because vibrates in Yβ plane direction, P-polarized light of the reflected light beam B _R is the plane reflector 8 because vibrates in Xβ plane direction In contrast, it is incident as P-polarized light.
Therefore, in the planar reflector 8, only the light that becomes S-polarized light with respect to the reflection surface, that is, the light that becomes S-polarized light with respect to the measurement target surface of the sample 2 is reflected to become the measurement light beam B _{M. M} reaches the optical sensor 10.

Thus, P-polarized light as the incident light beam B _L to the sample 2 is incident only (light vibrating in Xα plane direction), S-polarized light orthogonal to the polarization component of the incident light beam B _L from the reflected light beam B _R (in Yβ plane direction Only the vibrating light) can be extracted, and the light intensity can be detected by the optical sensor 10.

FIG. 6 shows another embodiment of the optical anisotropy parameter measuring apparatus according to the present invention. In addition, the same code | symbol is attached | subjected about the part which is common in FIG. 1, and detailed description is abbreviate | omitted.
Irradiation optical system 33 of the optical anisotropy parameter measurement device 31 of the present embodiment, the optical axis A _S traveling through Xα plane parallel light beam spot shape corresponding to the shape of the measurement region of the sample 2 as the irradiation light beam B _S The light source device 35 that irradiates along and the irradiation light beam B _S are reflected at a resonance angle θ _R by a reflection surface orthogonal to the Xα plane, so that the S-polarized light toward the sample 2 along the α direction is set as the incident light beam _BL. An extraction-side prism (reflection type polarizer) 36 for extraction is provided.

Light source device 35 on the optical axis _{B S} that leads to the prism 36 to irradiate light beam _{B L} from the xenon lamp 35a, an interference filter (transmission wavelength 632.8 nm) 35b, collimator 35c to parallel light irradiation light beam _{B L} is distribution Has been.
The prism 36 is formed in a semicircular or triangular cross section, and a metal thin film in which gold is evaporated to a thickness of 50 nm is formed on the bottom surface serving as the reflective surface 36a.
Then, the irradiation optical axis A _S and the incident optical axis A _L is intersected at twice the angle of the resonance angle theta _R on Xα plane, the prism 36, the irradiation optical axis A _S passes through the prism 36 reflecting in a direction leading to the surface 36a, and are arranged so as to be orthogonal to the bisector of the intersection angle of the irradiation optical axis a _S and the incident optical axis a _L.

Light Accordingly, the irradiation light beam B _S Since enters in resonance angle theta _R to the reflection surface 36a passes through the prism 36, which vibrates the light (X [alpha plane direction is P-polarized with respect to the reflecting surface 36a ) Is not reflected, and only the light that becomes S-polarized light (light that vibrates in the Yα plane direction) is reflected, which again becomes an incident light beam _BL that passes through the prism 36 and travels toward the sample 2 along the α direction. The incident light beam _BL is incident on the measurement target surface of the sample 2 as S-polarized light.

The incident light beam B _L is the reflected light beam B _R traveling in the β direction is reflected by the measurement target surface of the sample 2. The reflected light beam B _R, because it contains reflected light beams B _R is generally (light vibrating in Xβ plane direction) P-polarized component and S-polarized light component (light vibrating in Yβ surface direction) by the physical properties of the sample 2, the measurement optical the system 34 extracts P polarized light components included in the reflected light beams B _R, detects the light intensity.

Measurement optical system 34, by reflecting in the resonance angle theta _R by the reflection surface orthogonal to the reflected light beams B _R and Yβ surface, the P-polarized light orthogonal to the (S-polarized light in the present embodiment) the polarization direction of the incident beam B _L A reflection-side prism (reflection analyzer) 38 that extracts the measurement light beam B _M , an imaging lens 9, and an optical sensor 10 that detects the intensity distribution thereof are provided.
Similar to the incident side prism 36, the reflecting side prism 38 has a semicircular or triangular cross section, and a metal thin film on which gold is deposited to a thickness of 50 nm is formed on the bottom surface which becomes the reflecting surface 38a.
The reflected optical axis A _R and the measurement light axis A _M can be crossed at twice the angle of the resonance angle theta _R on Yβ surface, the prism 38 is reflected optical axis A _R passes through the prism 38 reflecting in a direction leading to surface 38a, it is arranged so as to be orthogonal to the bisector of the intersection angle of the reflected optical axis a _R and the measurement light axis a _M.

Thus, the reflected light beam B _R, so is incident at the resonance angle theta _R to the reflection surface 38a, the light becomes a P-polarized light with respect to the reflecting surface 38a (light vibrating in Xα plane direction) is not reflected, Only light that becomes S-polarized light (light that vibrates in the direction of the Yα plane) is reflected, and this becomes the measurement light beam B _M that passes through the prism 38 and travels toward the optical sensor 10.
At this time, S polarized light of the reflected light beam B _R is incident as P-polarized light to the reflecting surface 38a so that the vibration in the Yβ plane direction, P-polarized light of the reflected light beam B _R whereas the reflection surface 38a so that the vibration in the Xβ plane direction Is incident as S-polarized light.

Therefore, in the prism 38, only the S-polarized light (light oscillating in the Xβ plane direction) with respect to the reflecting surface 38a, that is, the light that becomes P-polarized with respect to the measurement target surface of the sample 2 is reflected, and the measurement light beam B _M The measurement light beam B _M reaches the optical sensor 10.
According to this embodiment, as an incident light beam B _L to the sample 2 is incident only S-polarized light (light vibrating in Yα plane direction) perpendicular to the polarized component of the incident light beam B _L from the reflected light beam B _R P Only polarized light (light vibrating in the Xβ plane direction) can be extracted, and the light intensity can be detected by the optical sensor 10.

Using optical anisotropy parameter measurement device 31 of the present embodiment, the light source device 35 to form a radiation beam B _S having a diameter of about 30 mm, so that the resonance angle θ _{R =} 45 °, the irradiation optical type 33 and measuring optical System 34 was adjusted.
Thereby, the reflected light intensity from the plurality of measurement points Mij included in the measurement area A of 10 mm ² irradiated on the alignment film 3 can be measured simultaneously.

In the same manner as in Example 1, the optical axis direction of the thin film sample 2 was set on the stage 11 so as to coincide with the Y axis.
After adjusting the tilt of the sample 2, while rotating the sample 2 is irradiated with incident light beam B _L of the S-polarized light, to measure the light intensity of P-polarized light included in the reflected beam B _R.
At this time, the position of the measurement point on the origin P ₀ be rotated sample 2 is not changed, the light intensity of the pixels of the CCD image sensor constituting the light sensor 10, the optical axis of the measurement beam B _M It is detected by a detector located on A _M.

FIG. 7A shows measurement points Mij (i, j = 1 to 10) in the measurement area A before rotation.
FIG. 7 (b) shows an image rotated with the rotation of the stage 11. If each measurement point Mij is represented by polar coordinates Mij = (r _n , φ _m ), the rotation table 6 is rotated by an angle γ. The position of Mij is represented by Mij = (r _n , φ _m + γ).
Therefore, if the reflected light intensity is measured in the pixel region of the CCD camera 39 corresponding to Mij = (r _n , φ _m + γ), the individual measurement points are shown in FIG. A simple rotation angle-light intensity diagram can be measured simultaneously.

From this graph, it is possible to obtain an accurate optical axis direction and polar angle direction distribution by a conventionally known calculation method for each measurement point Mij in total of 100 points.
Further, based on this result, the ordinary optical dielectric constant ε ₀ , the extraordinary optical dielectric constant ε _e , and the anisotropic layer thickness t are determined using a conventional ellipsometer in two directions, the direction of the optical axis and the direction orthogonal thereto. If measured, these values can be calculated very easily.

  FIG. 8 shows an embodiment in which the optical anisotropy parameter measuring apparatus according to the present invention is used as an ellipsometer. In addition, the same code | symbol is attached | subjected about the part which is common in FIG. 1, and detailed description is abbreviate | omitted.

Irradiation optical system 43 of the optical anisotropy parameter measurement device 41 of the present embodiment, the optical axis A _S traveling through Xα plane parallel light beam spot shape corresponding to the shape of the measurement region of the sample 2 as the irradiation light beam B _S The light source device 35 that irradiates along and the irradiated light beam B _S is reflected at the resonance angle θ _R to extract only S-polarized light, and linearly polarized light (other than P-polarized light and S-polarized light) is applied to the sample 2 along the α direction. In this example, an incident side prism (reflective polarizer) 36 that extracts approximately 45 ° linearly polarized light) as an incident light beam _BL is provided.

The irradiation optical system 43 has the same configuration as the irradiation optical system 33 except that the irradiation optical system 33 according to the third embodiment is rotated 45 ° counterclockwise about the α axis.
Light Accordingly, the irradiation light beam B _S Since enters in resonance angle theta _R to the reflection surface 36a passes through the prism 36, which vibrates the light (X [alpha plane direction is P-polarized with respect to the reflecting surface 36a ) Is not reflected, and only light that becomes S-polarized light (light that vibrates in the Yα plane direction) is reflected.
Then, the reflected light again passes through the prism 36, becomes an incident light beam _BL toward the sample 2 along the α direction, and is incident as linearly polarized light having a vibration direction of about 45 ° with respect to the Xα plane.
As a result, the sample 2 is irradiated with P-polarized light and S-polarized light having a predetermined intensity.

Measurement optical system 44, together with the P-polarized light and S-polarized light quarter-wave plate 47 to 90 ° shifted phase are rotatably arranged on the optical axis A _R around included in the reflected light beams B _R, the reflected light beam B _R the by reflecting in the resonance angle theta _R by the reflecting surface perpendicular to the Yβ surface, and the reflection side prism (reflective analyzer) 38 to extract the S-polarized light included in the reflected light beam B _R as measurement beam B _M, the measurement An imaging lens 9 that forms an image of the light beam B _M and an optical sensor 10 that detects the intensity distribution of the polarization component thereof are provided.

Here, the reflected light beams B _R reflected from the sample 2, since it is incident at the resonance angle theta _R the reflecting surface 38a of the prism 38, the light (X? Plane direction is P-polarized with respect to the bottom surface 38a light vibrating) is not reflected, only light becomes S polarized light (light vibrating in Yβ plane direction) is reflected, which is at this time that the measuring beam B _M toward the optical sensor 10, S-polarized light of the reflected light beams B _R is incident as S-polarized light with respect to the bottom surface 38a of the prism 38 so vibrates in Yβ plane direction, P-polarized light of the reflected light beam B _R is incident as P-polarized light with respect to the bottom surface 38a so that the vibration in the Xβ plane direction.
Therefore, in the prism 38, only the light that becomes S-polarized light with respect to the reflection surface 38a, that is, the light that becomes P-polarized light with respect to the measurement target surface of the sample 2 is reflected to become the measurement light beam B _{M. M} reaches the optical sensor 10.

Accordingly, the linearly polarized light of 45 ° as the incident light beam B _L to the sample 2 is incident (light vibrating in Xα plane direction), the incident light beam B when the reflected light beam B _R rotating the quarter-wave plate 47 Only S-polarized light (light oscillating in the Yβ plane direction) orthogonal to the _L polarization component can be extracted, and its light intensity can be detected by the optical sensor 10.

The light source device 35 to form a radiation beam B _S having a diameter of about 30 mm, the resonance angle θ _{R =} 45 °, so that the incident angle = 50 ° to the sample 2 was adjusted illumination optical type 43 and the measurement optical system 44 .
In Sample 2, a Si wafer was thermally oxidized to form a SiO ₂ film and etched with an HF—NH ₃ aqueous solution.
When measured with a commercially available ellipsometer, the average film thickness was 50.2 nm and the refractive index was 1.46.

FIG. 9 is a graph showing the rotation angle θ-light intensity distribution I measured by the optical anisotropy parameter measuring device 41.
According to the rotational phaser method, fitting is performed by changing the values of constants A, B, and C in Formula (1) in the range of −1 to +1, and optimum values of constants A, B, and C are calculated using Formula (2). ) To (4) to obtain ψ and δ.
I = I ₀ [2 + A−2Bsin (2θ) + Acos (4θ) + Csin (4θ)] (1)
A = cos (2ψ) ………………………………………………………………… (2)
B = sin (2ψ) sinδ ………………………………………………………… (3)
C = sin (2ψ) cosδ ………………………………………………………… (4)

The reflectance ratio is expressed by a function of the refractive index n and the film thickness, and at the same time by a function of the amplitude reflectance ratio tan Ψ and the phase difference Δ, as shown in the equation (5).
_{R p (n, d) /} R s (n, d) = (E p out / E s out) / (E p in / E s in)
= TanΨexp (iΔ) ……………………… (5)
In this example, since 45 ° linearly polarized light is irradiated, E _p ⁱⁿ / E _s ⁱⁿ = 1, and ψ and δ obtained by equations (1) to (4) are used to obtain equation (6). Holds.
R _p (n, d) / R _s (n, d) = tan ψ exp (iδ) (6)

On the other hand, the values of ψ and δ obtained by the equations (1) to (4) are substituted into a conventionally known relational expression using the film thickness d and the refractive index n as variables, and the refractive index n is set to an appropriate value. Then, the film thickness d is calculated.
Based on the obtained film thickness d and refractive index n, when ψ and δ are calculated as ψ _c and δ _c by Equation (6), these values and Equations (1) to (4) The film thickness d and the refractive index n can be obtained by sequentially changing the refractive index n with a computer and searching for the optimum value until the obtained ψ and δ match.

The one measurement point Mij will be described. When ψ and δ are calculated by setting A, B, and C in Equation (1) based on the graph of FIG. 9 and performing fitting, (ψ, δ) = (32 The film thickness d was 50.0 nm and the refractive index n was 1.45 at an incident angle of 50 °.
Since the measurement results using a conventional ellipsometer were a film thickness d = 50.2 nm and a refractive index n = 1.46, it was confirmed that the measurement could be performed with sufficient accuracy even when compared with these.
According to this example, since the rotation angle θ-light intensity distribution I as shown in FIG. 9 can be measured at the same time for a large number of measurement points Mij, the optical anisotropy is similarly performed for the other measurement points Mij. The film thickness d and the refractive index n, which are characteristic parameters, can be measured quickly, and therefore the film thickness distribution and refractive index distribution over a wide range can be measured in a short time.

  The present invention can be applied to products having optical anisotropy, in particular, quality inspection of liquid crystal alignment films.

Explanatory drawing which shows an example of the optical anisotropy parameter measuring apparatus which concerns on this invention. Explanatory drawing which shows the measuring method. The graph which shows the measurement result of rotation angle-light intensity. The graph which shows the measurement result of the uniformity of the direction of an optical axis. Explanatory drawing which shows other embodiment of this invention. Explanatory drawing which shows other embodiment of this invention. Explanatory drawing which shows the measuring method. Explanatory drawing which shows other embodiment of this invention. Explanatory drawing which shows the measurement result. Explanatory drawing which shows a conventional apparatus.

Explanation of symbols

1, 21, 31, 41 Optical anisotropy parameter measuring device 2 Sample 3, 33, 43 Irradiation optical system 4, 34, 44 Measurement optical system 5, 35 Light source device B _L incident light beam
_BR reflected light flux
θ _B Brewster's angle 6 Incident side planar reflector (reflective polarizer)
8 Reflective plane reflector (reflection analyzer)
9 Imaging lens 10 Optical sensor

Claims (10)

An optical optical system comprising an irradiation optical system for irradiating a sample with a linearly polarized incident light beam and a measurement optical system for measuring the reflected light intensity of P-polarized light or S-polarized light among the polarized light components contained in the reflected light beam reflected from the sample. An isotropic parameter measuring device comprising:
The surface to be measured of the sample is the XY plane, and on the XYZ coordinates with the origin of the intersection of the incident optical axis and the XY plane, the plane through which the incident optical axis and the reflected optical axis pass is the XZ plane. When the direction is α and the direction of the reflected optical axis reflected from the origin is β,
The irradiation optical system includes a light source device that irradiates a spot-shaped parallel beam according to the shape of the measurement region of the sample, and a linearly polarized incident beam that travels toward the sample along the α direction by reflecting the parallel beam at a predetermined angle. With a reflective polarizer to extract
The measurement optical system reflects a reflected light beam traveling in the β direction from a sample at a predetermined angle by a reflecting surface orthogonal to the Yβ surface or the Xβ surface, thereby extracting a P-polarized light or S-polarized light reflected by the sample. And an optical anisotropy parameter measuring apparatus comprising a one-dimensional or two-dimensional optical sensor for detecting the light intensity of the polarization component. The reflection type polarizer of the irradiation optical system reflects P-polarized light or S-polarized light toward the sample by reflecting the parallel light beam emitted from the light source device at a predetermined angle by a reflective surface orthogonal to the Xα plane or the Yα plane. Arranged in the direction to extract the luminous flux,
The reflective analyzer of the measurement optical system reflects the reflected light beam traveling in the β direction from the sample at a predetermined angle by the reflection surface orthogonal to the Yβ surface or the Xβ surface, thereby allowing the S-polarized light orthogonal to the polarization direction of the incident light beam or The optical anisotropy parameter measuring device according to claim 1, wherein the optical anisotropy parameter measuring device is arranged in a direction for extracting P-polarized light. The reflection type polarizer of the irradiation optical system receives S-polarized light obtained by reflecting a parallel light beam emitted from a light source device at a predetermined angle as linearly polarized light other than P-polarized light and S-polarized light. Arranged in the direction
In the measurement optical system, the reflected analyzer reflects the reflected light beam traveling in the β direction from the sample at a predetermined angle by a reflection surface orthogonal to the Yβ surface or the Xβ surface, so that S-polarized light orthogonal to the polarization direction of the incident light beam or The optical anisotropy parameter measuring device according to claim 1, wherein the optical anisotropy parameter measuring device is arranged in a direction in which P-polarized light is extracted and a wave plate is rotatably arranged between the sample and the reflection analyzer.   The reflective polarizer is formed to a size capable of irradiating the entire portion to be measured of the sample with parallel light as an incident light beam, and the reflective analyzer reflects the entire reflected light beam toward the optical sensor. 2. The optical anisotropy parameter measuring device according to claim 1, wherein the optical anisotropy parameter measuring device is formed in a size that can be obtained.   2. The optical anisotropy parameter measuring apparatus according to claim 1, wherein the optical sensor comprises a large number of light receiving elements arranged in a one-dimensional or two-dimensional matrix.   An imaging lens for reducing the diameter or width of the reflected light beam reflected by the analyzer according to the size of the optical sensor is disposed between the reflective analyzer and the optical sensor of the measurement optical system. The optical anisotropy parameter measuring apparatus according to 1.   One or both of the reflective polarizer and the reflective analyzer are formed by a planar reflector, and the incident angle on the planar reflector is Brewster so that only light that is S-polarized light is reflected by the planar reflector. 2. The optical anisotropy parameter measuring apparatus according to claim 1, wherein the optical anisotropy parameter measuring apparatus is selected at a corner.   8. The optical anisotropy parameter measuring apparatus according to claim 7, wherein a wedge-shaped transparent body whose back surface is inclined with respect to the front surface is used as the planar reflector, and the front surface is a reflective surface.   One or both of the reflective polarizer and the reflective analyzer is a prism having a metal thin film formed on the bottom surface, and the incident light beam or the reflected light beam is disposed at a position where it passes through the prism and is reflected on the bottom surface. 2. The optical anisotropy parameter measuring apparatus according to claim 1, wherein an incident angle of light incident on the prism bottom surface is selected as a resonance angle so that only light that becomes S-polarized light is reflected on the prism bottom surface. The optical anisotropy parameter measuring apparatus according to claim 9, wherein the prism is a semicircular prism or a triangular prism.

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