JP4663334B2 - Line width measurement method - Google Patents

Description

  In the present invention, a line width of a translucent film is formed by simultaneously illuminating both sides of a measurement sample formed with an opaque pattern on a transparent substrate and forming a translucent film across the transparent substrate and the opaque pattern with reflected light and transmitted light. The present invention relates to a line width measuring method in a line width measuring apparatus that measures the above.

  A line width measuring device for measuring the line width of a measurement sample using reflected light and transmitted light is already on the market.

  First, referring to FIG. 3, the luminance waveform obtained when the measurement sample is illuminated with reflected light and transmitted light will be described.

  In FIG. 3, the measurement sample is composed of a metal pattern (non-transparent) 32 formed on a glass 31. When the line width of the metal pattern (non-transparent) 32 is actually measured by turning on the reflected illumination and the transmitted illumination at the same time, the reflected illumination and the transmitted illumination are turned on at the same time. The luminance waveform obtained and the luminance waveform obtained only by transmitted illumination will be described separately. In fact, there are cases where measurements are made with only reflected illumination and cases with only transmitted illumination.

  In the case of only reflected illumination, when the metal pattern (non-transparent) 32 side is illuminated with reflected light 33 from a reflection light source (not shown), the reflected light reflected from the measurement sample is measured. The light is incident on a camera (not shown) via an ND filter (a filter whose transmittance changes continuously) located in the automatic light adjustment adapter (not shown) located above the sample. The luminance waveform 34 obtained as the output of the camera is (b), and the ND filter in the automatic dimming adapter is adjusted so that the peak of the luminance waveform 34 becomes a specified value (video signal 0.7 V).

  In the case of only transmitted illumination, as shown in FIG. 5C, the side opposite to the side where the metal pattern (non-transmitted) 32 is formed on the glass 31 is illuminated with transmitted light 35 from a not-shown transmitted light source. Then, the transmitted light that has passed through the measurement sample is incident on the camera via an ND filter (a filter whose transmittance changes continuously) located in the automatic light adjustment adapter located above the measurement sample. The luminance waveform 36 obtained as the output of the camera is (d), and the transmitted light 35 from the transmissive light source is adjusted so that the peak of the luminance waveform 36 becomes a specified value (video signal 0.7V).

  Accordingly, when the reflected light 33 and the transmitted light 35 are simultaneously turned on as shown in FIG. 5E, the simultaneous lighting luminance waveform 37 obtained as the output of the camera is as shown in FIG. That is, in the synthesis of (b) and (d), the peak due to the reflected light 33 and the peak due to the transmitted light 35 have the same specified value (video signal 0.7 V), and the peak due to the reflected light and the metal pattern (non-transparent) 32 The contrast between the bottom of the groove based on the inclined portion and the contrast between the bottom of the groove and the peak due to the transmitted light are the same, and a luminance waveform corresponding to the shape of the inclined portion of the metal pattern (non-transmissive) 32 is obtained. Obtainable.

  Patent document 1 of our application is given as a patent document regarding a line width measuring device. However, Patent Document 1 describes only reflected light, and is not a line width measuring apparatus that simultaneously illuminates with reflected light and transmitted light, which is a premise of the present invention.

JP 2003-279318 A

  However, in practice, the reflectance of the reflected light and the transmittance of the transmitted light in the measurement sample are often different depending on the sample, and in this case, the simultaneous lighting luminance waveform obtained as the output of the camera differs.

  With reference to FIG. 4, the luminance waveform at the time of simultaneous lighting obtained when the reflectance of the reflected light and the transmittance of the transmitted light in the measurement sample are different will be described.

  (A) is a case where the reflectance of the reflected light 33 is higher than the transmittance of the transmitted light 35. In this case, the peak of the simultaneous lighting luminance waveform 37a shown in FIG. When the ND filter is adjusted, the luminance waveform of the portion of the transmitted light 35 becomes extremely small.

  (C) is a case where the transmittance of the transmitted light 35 is higher than the reflectance of the reflected light 33. In this case, the peak of the simultaneous lighting luminance waveform 37b shown in FIG. When the transmitted light 35 is adjusted, the luminance waveform of the portion of the reflected light 33 becomes extremely small.

  Therefore, in such a case, the contrast between the peak due to the reflected light and the bottom of the groove based on the inclined portion of the metal pattern (non-transmissive) 32 and the contrast between the bottom of the groove and the peak due to the transmitted light are the same. In addition, a luminance waveform corresponding to the shape of the inclined portion of the metal pattern (non-transparent) 32 cannot be obtained.

Next, the principle of measuring the line width of the measurement sample will be described with reference to FIG. (A) is a measurement sample, and the pattern 50 is formed on the glass substrate. (B) is a brightness | luminance waveform obtained when the glass substrate of the measurement sample and the pattern 50 are crossed by the scanning line Li by a camera. In the luminance distribution, the maximum luminance level 51 is set to 100%, the minimum luminance level 52 is set to 0%, and the positional difference between the a-th pixel and the b-th pixel corresponding to the luminance level 53 of the intermediate luminance level 50% is Nab. To do. A coefficient determined by the measurement magnification of the camera and the object distance from the camera to the measurement sample is k. At this time, the line width X of the pattern 50 of the measurement sample can be obtained by the following equation (1).
X = k × Nab (1)
Therefore, in order to measure the line width of the pattern 50 of the measurement sample, it is necessary to correctly obtain an intermediate luminance level of the luminance waveform.

  However, if there are samples with different reflectivity and transmitted light transmittance in the measurement sample, as described with reference to FIG. 4, the peak of the reflected light and the groove based on the inclined portion of the metal pattern (non-transmitted) 32 The contrast between the bottom and the contrast between the bottom of the groove and the peak due to the transmitted light are not the same, and a luminance waveform corresponding to the shape of the inclined portion of the metal pattern (non-transmissive) 32 cannot be obtained. Thus, since the intermediate luminance level of the obtained luminance waveform is shifted from the correct position, the accurate line width of the pattern cannot be measured.

  FIG. 6 is a diagram illustrating a measurement waveform that is an actual measurement target and a luminance waveform obtained by a conventional line width measurement apparatus. (A) is a top view of the measurement sample which is an actual measurement object, (b) is the sectional drawing. As shown in FIGS. 4A and 4B, a measurement sample that is an actual measurement target forms an opaque pattern 22 on a transparent substrate 21 typified by an LCD substrate, and straddles the transparent substrate 21 and the opaque pattern 22. This is a sample on which a translucent film (ITO) 23 is formed.

  When the line width of the translucent film (ITO) 23 is measured by illuminating both sides of the measurement sample simultaneously with the reflected light and the transmitted light, conventionally, the output ratio of the reflected light and the output ratio of the transmitted light are fixed. It was. Since the output ratio was determined by relying on the operator's intuition according to the reflectance and transmittance of the sample to be measured, the output ratio may be different due to individual differences and the deterioration of the reflected light source or transmitted light source. In this case, the same luminance waveform cannot always be obtained as described with reference to FIG. 4, and it is therefore difficult to maintain the same contrast state.

  (C) is an example of the luminance waveform 25 to be obtained. In the case of a sample with poor transmittance, the peak of the luminance waveform obtained by the transmitted light is lowered, and as a result, the contrast is the same as the contrast of the luminance waveform obtained by the reflected light. It gets worse.

  Therefore, the line width data varies depending on the sample of the measurement sample, it is difficult to reproduce the measurement, and the line width cannot be measured accurately.

  An object of the present invention is to provide a line width measuring method capable of maintaining a stable contrast state.

  In the present invention, an opaque pattern is formed on a transparent substrate, and a semi-transparent film is formed across the transparent substrate and the opaque pattern. In the line width measuring apparatus for measuring the line width of the translucent film, when measuring the line width of the semi-transparent film, the transparent substrate and the opaque pattern are individually dimmed by specifying dimming areas, and then the semi-transparent film is measured. The line width of the transparent film is measured.

  Further, the present invention illuminates the translucent film of a measurement sample formed by forming an opaque pattern on a transparent substrate and forming a translucent film across the transparent substrate and the opaque pattern with reflected light from a reflected light source, In the line width measuring device that measures the line width of the translucent film by simultaneously illuminating the side of the measurement sample opposite to the translucent film with transmitted light from a transmission light source, the line width of the translucent film is measured. In this case, a dimming area for transmitted light and a dimming area for reflected light are designated for the transparent substrate and the opaque pattern, respectively, and the peak is a predetermined value for the luminance waveform obtained from the dimming area for the reflected light. The filter in the dimming adapter is dimmed so that the luminance waveform obtained from the dimming area of the transmitted light is dimmed with the transmitted light from the transmitted light source so that the peak is a predetermined value. And then the translucent film And measuring the line width.

  According to the present invention, it is possible to obtain a line width measuring method capable of maintaining a stable contrast state.

  FIG. 1 is a configuration diagram of an embodiment of a line width measuring apparatus using a line width measuring method according to the present invention. In FIG. 1, reference numeral 1 denotes a CCTV camera for measurement, which takes an image of a sample of a measurement sample magnified by a microscope. Reference numeral 2 denotes an automatic dimming adapter disposed in front of the CCTV camera for adjusting the amount of light reaching one imaging device (CCD) 1 to a specified value.

  3 to 6 are components of the microscope, 3 is a straight tube, 4 is a light projecting tube, 5 is a revolver, and 6 is an objective lens. 7 is a light guide, and 11 is a reflected illumination light source unit of a microscope. Light output from the exit of the reflected illumination light source unit 11 passes through the light guide 7, the light projecting tube 4, and the objective lens 6, and on the sample table 8. A measurement sample (not shown) is irradiated and used as reflected illumination.

  Reference numeral 9 denotes a transmission illumination head, 10 denotes a light guide, and 12 denotes a transmission illumination light source unit. Light output from the exit of the transmission illumination light source unit 12 passes through the light guide 10 and the transmission illumination head 9 and passes through the sample table. 8 is used as transmitted illumination by irradiating a measurement sample (not shown) from the back side.

  The light reflected by the measurement sample and the transmitted light are incident on the CCTV camera 1 via the ND filter in the automatic light adjustment adapter 3 and imaged and converted into a video signal.

  The video signal obtained by the CCTV camera 1 is input to the image processing device 13, converted into a format that can be displayed on the video monitor 14, and the image is displayed on the video monitor 14.

  Reference numeral 15 denotes an operation device such as a mouse or a keyboard, which looks at the image displayed on the video monitor 14 and controls the image processing device 13 to specify and display a dimming area.

  FIG. 2 is a diagram showing a measurement sample placed on the sample stage 8 in FIG. 1 and a luminance waveform obtained in the embodiment of the present invention for explaining the line width measurement method in the present invention. (A) is a plan view of a measurement sample that is an actual measurement object, (b) is a sectional view thereof, and (c) is an example of a luminance waveform to be obtained.

  As shown in FIGS. 4A and 4B, the measurement sample is formed by forming an opaque pattern 22 on a transparent substrate 21 typified by an LCD substrate, and translucent film (ITO) across the transparent substrate 21 and the opaque pattern 22. 23 is formed.

  When both sides of the measurement sample are illuminated simultaneously with reflected light and transmitted light, a plan view (a) and an image of the luminance waveform (c) of the measurement sample are displayed on the video monitor 14 (however, at this stage, the sign of (a) is displayed) Areas 26 and 27 are not displayed, and (c) is a waveform in which the peak of the luminance waveform obtained by transmitted light is lowered).

  When measuring the line width of the semi-transparent film (ITO) 23 of the measurement sample, in the embodiment of the present invention, using the operation device 15 of FIG. 1, as shown in FIG. A transmitted light adjustment area 26 is designated and displayed, and a reflected light adjustment area 27 is designated and displayed on the opaque pattern 22.

  Next, in the luminance waveform (c), the automatic dimming of FIG. 1 is performed so that the peak of the luminance waveform obtained from the dimming area 27 of the reflected light has a predetermined specified value (video signal 0.7 V). The ND filter (filter whose transmittance changes continuously) in the adapter 2 is dimmed, and the peak of the luminance waveform obtained from the dimming area 26 of the transmitted light has a predetermined value (video signal 0.7V). ) The transmitted light from the transmitted light source is dimmed in the transmitted illumination light source unit 12 of FIG.

  As a result of the dimming, the peak due to the reflected light and the peak due to the transmitted light have the same specified value (video signal 0.7V).

  Thereafter, the line width of the translucent film (ITO) 23 is measured by measuring the line width as described in FIG.

  Therefore, in this embodiment, a line width measurement method capable of maintaining a stable contrast state can be obtained. As a result, the line width of the translucent film (ITO) 23 can be accurately measured. Moreover, the line width data does not vary depending on the sample of the measurement sample, and the measurement can be easily reproduced.

  In the present embodiment, even if the reflectance of the reflected light and the transmittance of the transmitted light are different depending on the sample of the measurement sample, the control signal is generated by the image processing device 13 in FIG. 2 is fed back to the ND filter (filter with continuously changing transmittance) and the transmitted illumination light source unit 12, so that the same specified value (video signal 0.7V) can always be automatically maintained. This also allows the line width of the translucent film (ITO) 23 to be always accurately measured.

It is a lineblock diagram of an embodiment of a line width measuring device using a line width measuring method by the present invention. It is a figure which shows the luminance waveform obtained by the measurement sample put on the sample stand of FIG. 1, and embodiment of this invention for demonstrating the line | wire width measuring method in this invention. It is a figure which shows the luminance waveform obtained when a measurement sample is illuminated with reflected light and transmitted light. It is a figure which shows the luminance waveform at the time of simultaneous lighting obtained when the reflectance of the reflected light and the transmittance | permeability of transmitted light in a measurement sample differ. It is a figure explaining the principle of measurement of the line width of a measurement sample. It is a figure which shows the luminance waveform obtained with the measurement sample which is an actual measurement object, and the conventional line | wire width measuring apparatus.

Explanation of symbols

1: CCTV camera, 2: automatic dimming unit, 3: straight tube, 4: projector tube, 5: revolver, 6: objective lens, 7: light guide, 8: sample stage, 9: transmission illumination head, 10: light Guide: 11: Reflection illumination light source unit, 12: Transmission illumination light source unit, 13: Image processing device, 14: Video monitor, 15: Controller, 21: Transparent substrate, 22: Opaque pattern, 23: Translucent film (ITO) 24, 25: luminance waveform, 26: dimming area for transmitted light, 27: dimming area for reflected light, 31: glass, 32: metal pattern (non-transmissive), 33: reflected light, 35: transmitted light, 34 , 36, 37, 37a, 37b: luminance waveform, 50: pattern.

Claims (2)

An opaque pattern is formed on a transparent substrate, and both sides of a measurement sample formed by forming a translucent film across the transparent substrate and the opaque pattern are simultaneously illuminated with reflected light and transmitted light to reduce the line width of the translucent film. in line width measuring device for measuring the in measuring the line width of the translucent film, to specify the respective light adjustment area in the opaque pattern and the transparent substrate, the luminance waveform obtained from the respective light adjustment area A line width measuring method , wherein the reflected light and the transmitted light are individually dimmed so that the peaks have the same predetermined value, and then the line width of the translucent film is measured. An opaque pattern is formed on a transparent substrate, and the translucent film of the measurement sample formed by forming a translucent film across the transparent substrate and the opaque pattern is illuminated with reflected light from a reflection light source, and the measurement sample In the line width measuring apparatus that measures the line width of the translucent film by simultaneously illuminating the opposite side of the translucent film with transmitted light from a transmission light source, A light control area for transmitted light and a light control area for reflected light are specified for the substrate and the opaque pattern, respectively, and the brightness waveform obtained from the light control area for the reflected light is adjusted so that the peak is a predetermined value. the filter in the optical adapter tone and light, the transmitted light from the transmission light source dimming and to have the same value as the predetermined value is the peak for the luminance waveform obtained from the light control area of the transmitted light And then of the translucent film Line width measuring method characterized by measuring the width.

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