JP2012047695A - Pattern width measurement equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide pattern width measurement equipment for performing non-destructive measurement without generating seizure on a mask substrate to be measured, and for accurately measuring a pattern width on the substrate to which microfabrication has been performed under the consideration of individual exposure conditions as an effective pattern width in exposure equipment.SOLUTION: The pattern width measurement equipment includes: an irradiation part 10 for irradiating a mask substrate 2 to be inspected, in which a pattern to be inspected is microfabricated, with coherent rays of light in a space area and/or a time domain; an imaging element 15 for receiving diffraction rays of light from the pattern to be inspected on the mask substrate 2 to be inspected which has been irradiated by the irradiation part 10; a recording unit 16a for recording image information being a result of the light reception by the imaging element 15; and a measurement processing unit 16 for analyzing the image information being the result of the light reception recorded in the recording unit 16a to measure a pattern width on the mask substrate 2 to be inspected to which the microfabrication has been performed.

Description

  The present invention relates to a pattern width measuring apparatus for measuring a pattern width on a substrate that has been subjected to microfabrication processing.

  In recent years, in the semiconductor manufacturing field, with the shortening of design rules, the complexity of the manufacturing process and the reduction in defect size have progressed, and improvement in yield has been an issue. In semiconductors such as LSI, nonuniformity of pattern widths such as wiring and holes affects device characteristics. For this reason, the mask substrate, which is the master disk of the semiconductor pattern, is required to have uniform pattern width. For example, in a 22 nm generation semiconductor to which extreme ultraviolet (EUV) lithography is applied, the allowable measurement uncertainty becomes very severe with a line pattern of 3σ of 0.65 nm or less.

  Here, a scanning electron microscope (hereinafter referred to as SEM) is used for pattern width measurement of a conventional semiconductor mask substrate. The SEM irradiates a pattern with highly accelerated electrons and obtains an image by the generated secondary electron intensity. In the signal intensity distribution of the obtained pattern image, a certain threshold width is evaluated as the pattern width (Non-patent Document 1).

  In addition, what is required for pattern width measurement is not an individual pattern width but a change in an average pattern width. Therefore, SEM averaged and evaluated individual pattern widths measured in detail.

Line width measurement method using SEM, Atsuko Yamaguchi, Yoshinori Momonoi, Ken Murayama, Hiroki Kawada and Junichi Tanaka, “Three-Dimensional Profile Extraction from CD-SEM Top-View”, Proc. Of SPIE 7272, (2009) 7272G- 1.

  In the pattern width evaluation of the mask substrate, for example, all the pattern widths on the mask substrate surface of 150 mm square need to be measured in detail with a small visual field. Therefore, in the evaluation by the electron beam using the SEM described above, the measurement time is long and it is difficult to inspect the entire surface of the mask substrate.

  Further, since the SEM uses highly accelerated electrons, there is a problem that the mask substrate is burned in along with the measurement. Furthermore, since the shape is evaluated by secondary electrons emitted from the pattern, the intensity distribution obtained by the cross-sectional shape of the pattern has changed greatly.

  As a specific example, when the incident angle of the illumination light in the EUV exposure machine is 6 degrees, a shadow is formed depending on the height of the pattern, and thus the actually measured pattern width has changed. For this reason, the SEM cannot measure the effective pattern width in consideration of individual exposure conditions such as the incident angle such as the influence of the oblique incidence illumination unique to the EUV mask.

  As described above, the problem of mask inspection with an electron beam in the SEM is that the region to be irradiated is small, and thus inspection takes time. In addition, due to electron beam irradiation, the mask substrate is charged up, and foreign matter adheres. Therefore, in the EUV mask, since the multilayer film is formed on the glass substrate, the film structure is also destroyed. Furthermore, since the angle of incidence on the EUV mask substrate in an actual exposure machine is 6 degrees, accurate evaluation cannot be performed.

  The present invention has been proposed in view of such circumstances, and enables non-destructive measurement without causing burn-in to the mask substrate to be measured, and is accurate in consideration of individual exposure conditions. It is an object of the present invention to provide a pattern width measuring apparatus capable of measuring an effective pattern width on a mask substrate that has been finely processed.

  As means for solving the above-described problems, the present invention is directed to irradiation means for irradiating a test mask substrate on which a test pattern is finely processed with coherent light in a spatial region and / or a time region, and an irradiation unit. Receiving means for receiving the diffracted light from the test pattern on the test mask substrate irradiated by, a recording means for recording image information as a result of light reception by the light receiving means, and analyzing the image information recorded on the recording means And a measurement processing means for measuring a pattern width on the test mask substrate on which the fine processing has been performed.

  The present invention records and analyzes the diffracted light from the pattern on the mask substrate, thereby evaluating the pattern width on the mask substrate on which the fine processing has been performed. In this way, the present invention enables non-destructive measurement without causing burn-in on the mask substrate to be measured, and is a mask that has been subjected to fine processing with high precision in consideration of individual exposure conditions. The effective pattern width on the substrate can be measured.

It is the figure which showed the structure of the pattern width measuring apparatus to which this invention was applied. It is the figure which showed the CCD camera image of an example of a measurement result. It is a figure which shows the line width measurement result in the pattern width measuring apparatus to which this invention was applied, and the measurement result in SEM which is a conventional measuring technique. It is a figure which shows the specific example which measured the pattern width distribution of the line and space (L / S) pattern whose pattern area | region is 50 micrometers square with the pattern width measuring apparatus 1. FIG.

  A pattern width measuring apparatus to which the present invention is applied is a pattern width measuring apparatus that measures an effective pattern width on a mask substrate that has been subjected to a fine processing. Below, the form for implementing this invention using the pattern width measuring apparatus as shown in FIG. 1 is demonstrated.

  As shown in FIG. 1, the pattern width measuring apparatus 1 has the following configuration in order to measure an effective pattern width on a mask substrate on which fine processing has been performed.

  That is, the shape measuring apparatus 1 includes an irradiation unit 10 for irradiating the test mask substrate 2 with extreme ultraviolet light having a coherent wavelength in the spatial domain and / or time domain of about 6 [nm] to 15 [nm]. A stage 14 for fixing the substrate 2, an imaging element 15 for receiving diffracted light from the surface of the mask substrate 2 fixed to the stage 14 and converting it into an electrical signal, and a light reception result converted into an electrical signal by the imaging element 15 A measurement processing unit 16 that measures the shape of the mask substrate 2 from the image information, and a display unit 17 that displays a measurement result by the measurement processing unit 16 so as to be visible to the user.

  The test mask substrate 2 is a measurement target by the shape measuring apparatus 1 described above, and is, for example, a semiconductor mask substrate on which a predetermined repetitive pattern is finely processed.

  The irradiation unit 10 includes a light source 11 that emits extreme ultraviolet light and an optical unit 12 that converts the extreme ultraviolet light emitted from the light source 11 into coherent light.

  The light source 11 is a light source that emits extreme ultraviolet light having a wavelength of about 6 nm to 15 nm. Specific examples include synchrotron radiation, high-order harmonic light sources, laser plasma light sources, discharge-type pinch plasma light sources, and any light source that emits extreme ultraviolet light. Good.

  The optical unit 12 includes a pinhole 12a for making the extreme ultraviolet light emitted from the light source 11 coherent light, and an aperture 12b for adjusting the irradiation region.

  The pinhole 12a is provided between the light source 11 and the stage 14, and allows the extreme ultraviolet light emitted from the light source 11 to pass spatially restricted, thereby allowing coherent in the spatial domain and / or time domain. Extreme ultraviolet light is emitted to the stage 14 side.

  The aperture 12b is provided between the pinhole 12a and the stage 14, and the irradiation area irradiated on the stage 14 and the observation area (Field Of View: FOV) area of the test mask substrate 2 coincide with each other. As described above, the coherent extreme ultraviolet light irradiated from the pinhole 12a is spatially limited and allowed to pass to the test mask substrate 2 side.

  The stage 14 is provided at a position where the extreme ultraviolet light passed from the aperture 12b is irradiated. The mask substrate 2 fixed to the stage 14 is irradiated with coherent extreme ultraviolet light by the irradiation unit 10 including the light source 11, the pinhole 12a, and the aperture 12b. In this way, the FOV region of the test mask substrate 2 irradiated with coherent extreme ultraviolet light emits diffracted light corresponding to the micropatterned test pattern.

  The imaging element 15 is, for example, an X-ray CCD detection element, and receives light reflected from the test pattern on the test mask substrate 2. That is, the image sensor 15 detects this diffracted light from the 0th order diffracted light to the several order diffracted light. Since the light emitted from the FOV region shows the complex amplitude of diffraction corresponding to the test pattern in the FOV region, the image sensor 15 obtains the intensity distribution of the diffraction image corresponding to the FOV region. Certain image information is supplied to the measurement processing unit 16.

  As a specific example, a CCD camera image as an example of the measurement result is shown in FIG. Here, as measurement conditions, it is assumed that white light including EUV having a wavelength of 13.5 nm is emitted from the BL-3 synchrotron radiation source 11 of the Newval synchrotron radiation facility. A pattern width measuring device installed at BL-3 of the facility was used. Further, white radiated light was monochromatic to a wavelength of 13.5 nm by a Mo / Si multilayer film and a Zr thin film, and the irradiation area to the test mask substrate 2 was limited to φ5 μm by the pinhole 12a. Furthermore, the incident angle of the irradiated light to the mask substrate was set to 6 °, which is equivalent to EUV lithography. The test pattern on the mask substrate 2 as a measurement sample is an L / S pattern with a half pitch (hp) of 130 nm for a semiconductor 32 nm generation, and the line width is changed from 70 to 135 nm.

  In the five diffracted lights arranged in FIG. 2, the strongest diffracted light at the center is the 0th order, and ± 1st order and ± 2nd order lights appear sequentially in the lateral direction.

  The measurement processing unit 16 includes a recording unit 16a that records image information that is a light reception result by the imaging element 15, and analyzes the image information that is the light reception result recorded in the recording unit 16a and is subjected to a fine processing process. Further, the pattern width on the test substrate 2 is measured. Then, the measurement processing unit 16 outputs the measurement result to the display unit 17.

  Here, the recording unit 16a records diffracted light intensity information indicating the intensity of diffracted light from the test pattern as image information that is a light reception result by the imaging element 15, and the measurement processing unit 16 records the information in the recording unit 16a. By performing a calculation process on the diffracted light intensity information, the pattern width on the mask substrate 2 to be subjected to the fine processing is measured.

Measurement processing unit 16, among the recorded diffracted light intensity information to the recording unit 16a, a 0-order diffracted light intensity I _0, ± m (m is a natural number.) Using a ratio of the order diffracted light intensity I _m Then, the pattern width on the mask substrate 2 to be subjected to the fine processing is measured. Specifically, the measurement processing unit 16 measures the pattern width by performing image formation using the diffraction intensity of each order as frequency information for the two-dimensional diffraction intensity information recorded by the recording unit 16a.

  The display unit 17 displays the measurement result by the measurement processing unit 16, that is, the shape of the FOV region, the pattern width of the test pattern on the mask substrate, and the presence / absence of a defect so as to be visible to the user.

  Here, in the semiconductor manufacturing process, the pattern width to be evaluated is not the pattern width on the mask substrate, but the pattern width on the wafer as the exposure result. Therefore, the pattern width measuring apparatus configured as described above No. 1 records and analyzes the diffracted light from the mask, and evaluates the pattern width on the substrate subjected to the fine processing as an effective pattern width equivalent to the pattern width on the wafer as the exposure result. To do.

  Therefore, in the pattern width measuring apparatus 1, the coherent irradiation light to the test mask substrate 2 is set to the same wavelength as the EUV in the case of an EUV mask, for example, and the incident angle of the coherent light in the exposure machine is the same. And

  Further, in the pattern width measuring apparatus 1, as described above, the measurement processing unit 16 performs calculation processing on the diffracted light intensity information recorded in the recording unit 16a, and on the test mask substrate 2 on which fine processing has been performed. By measuring the pattern width, it is possible to perform nondestructive measurement without causing seizure of the micropatterned test pattern on the test mask substrate 2.

  This is because the diffracted light intensity includes information in the irradiation area, so there is no need to average the area as in the SEM. Further, as described above, the same light as the actual exposure machine is used. This is because measurement is possible with low energy particles compared to SEM.

  In the pattern width measuring apparatus 1, it is preferable to measure the pattern width by analyzing the diffraction intensity ratio between the strong 0th-order light and the first-order light. This is because, in the pattern width close to the resolution limit of the exposure machine, only the 0th order light and the 1st order light contribute to the image formation. This is because an effective pattern width correlated with the pattern width printed on the wafer can be obtained. In addition, since the 0th and 1st order lights have high intensities, the measurement time can be shortened and the entire mask substrate inspection can be realized.

  Furthermore, in the pattern width measuring apparatus 1, the measurement processing unit 16 can use not only the pattern width but also the pattern cross-sectional shape measurement by using high-order diffracted light intensity such as secondary light for analysis.

  When the intensity of incident light by the exposure machine changes, the amount of incident light on the resist changes and the pattern width to be transferred changes. However, the pattern width measuring device 1 takes the diffraction intensity ratio and performs the measurement process to measure the incident light intensity. The pattern width can be evaluated without being influenced by the light source, and can be measured by applying not only to the radiated light which is a stable light source but also to a light source with relatively unstable intensity used in a laboratory, for example. .

  Next, FIG. 3 shows a comparison result in which the line width measurement result in the pattern width measuring apparatus 1 configured as described above is represented on the vertical axis, and the measurement result in the conventional measurement technique SEM is represented on the horizontal axis. Show.

  In FIG. 3, the change in the pattern width is measured when the pattern direction of the L / S pattern is parallel to the incident light incident surface and perpendicular. As shown in FIG. 3, the pattern line width obtained from the measurement result of the pattern width measuring apparatus 1 has a good correlation with the SEM measurement result.

  Moreover, the pattern width measuring apparatus 1 was able to accurately measure the change in the pattern width when the L / S pattern direction was parallel to the incident light incident surface and perpendicular. This is generally referred to as the shadowing effect, and the effective pattern width varies depending on the pattern direction when illuminating from an oblique direction.

  The pattern line width measurement reproducibility when the same point is continuously measured by the pattern width measuring apparatus 1 is 0.24 nm at 3σ, and can sufficiently satisfy, for example, 0.65 nm required by the 22 nm generation semiconductor technology. . In addition, since the measurement reproducibility before correcting the incident intensity fluctuation is 1.05 nm at 3σ, the pattern width measuring apparatus 1 can realize an accuracy improvement of 4 times or more.

  Further, FIG. 4 shows an example in which the pattern width distribution of the L / S pattern whose pattern region is 50 μm square is measured by the pattern width measuring apparatus 1. The horizontal axis is the measurement position, and it was possible to measure that the pattern line width in the peripheral part was small. Specifically, the uniformity of the central portion ± 10 μm is within ± 0.3 nm, and the pattern line width uniformity can be evaluated with this accuracy.

  As described above, the pattern width measuring apparatus 1 records and analyzes the diffracted light from the pattern to be tested on the mask substrate, so that the pattern width on the substrate subjected to the microfabrication processing is effectively obtained in the exposure machine. It is evaluated as a simple pattern width.

  In this way, the pattern width measuring apparatus 1 enables nondestructive measurement without causing seizure on the mask substrate to be measured, and performs fine processing with high accuracy in consideration of individual exposure conditions. The effective pattern width on the mask substrate thus formed can be measured.

  In addition, this invention is not limited only to the above embodiment, Of course, a various change is possible in the range which does not deviate from the summary of this invention.

  DESCRIPTION OF SYMBOLS 1 Shape measuring apparatus, 2 Mask board | substrate, 10 Irradiation part, 11 Light source, 12 Optical part, 12a Pinhole, 12b Aperture, 14 Stage, 15 Image sensor, 16 Measurement processing part, 16a Recording part, 17 Display part

Claims (3)

An irradiation means for irradiating a test substrate on which a test pattern is finely processed, with coherent light in a spatial domain and / or a time domain;
A light receiving means for receiving diffracted light from a test pattern on the test substrate irradiated by the irradiation means;
Recording means for recording image information which is a light reception result by the light receiving means;
A pattern width measuring apparatus comprising: a measurement processing unit that analyzes image information recorded in the recording unit and measures a pattern width on the test substrate that has been subjected to the fine processing. The recording means records diffracted light intensity information indicating the intensity of diffracted light from the test pattern as image information that is a light reception result by the light receiving means,
2. The pattern width according to claim 1, wherein the measurement processing means measures the pattern width on the test substrate subjected to the microfabrication processing by performing a calculation process on the diffracted light intensity information recorded in the recording means. measuring device. It said measurement processing means, in the diffracted light intensity information recorded in the recording means, and 0-order diffracted light intensity I _0, ± m (m is a natural number.) Using a ratio of the order diffracted light intensity I _m The pattern width measuring apparatus according to claim 2, wherein the pattern width on the substrate to be tested that has been subjected to fine processing is measured.

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