JPH01285806A - Measuring device shaped in groove - Google Patents

Abstract

PURPOSE:To enable the highly precise measurement of pattern grooves of minute pitches, by converting a coherent light before application into a straight polarized light having a plane of polarization in the parallel direction (TE) or vertical direction (TM) to the groove of a pattern. CONSTITUTION:A light oscillated from a laser 1 enters a polarizing optical element 2 and it is converted thereby into TE-polarized or TM-polarized light in relation to a groove of an object 3 to be inspected. A detector 4 detecting a diffracted light from the object 3 photoelectrically is supported by a supporting member 41 fitted to a driving motor 5, and an angle detecting means 6 is disposed behind the motor 5. The detector 4 moves on a circular-arc line with the rotation of the motor 5, and thus diffracted lights from the minus secondary to the plus primary can be detected by one detector 4. CPU 7 receives as inputs an intensity signal at its peak at a position of each order from the detector 4 and a signal of an angle of rotation detected from an angle detecting means 6 and subjects them to an arithmetic processing, and thus can calculate an averaged shape of grooves of a pattern of the object 3 to be inspected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for non-contact measuring the groove shape of a test object having a regular uneven shape, such as an optical disk substrate.

[Conventional technology]

In a device that measures the groove shape of a test object non-contact,
For example, it is disclosed in Japanese Patent Application Laid-Open No. 57-187604.

In the apparatus disclosed in this publication, a monochromatic light such as a laser beam is irradiated onto a test object having a regular pattern, and n-th order light ( The intensity and diffraction angle of the diffracted light (including the zero-order light) were detected, the intensity ratio of each order of the diffracted light was taken, and the average groove shape was estimated and calculated.

[Problem to be solved by the invention]

However, in the above-mentioned conventional technology, if the pitch of the regular pattern on the object to be inspected is less than several times the wavelength of the irradiated light, the measurement results become inaccurate, making it difficult to perform high-performance groove shape measurements. It becomes difficult.

This phenomenon is thought to be because the diffraction efficiency varies depending on the polarization state of the irradiated light.

Therefore, the present invention can always maintain high accuracy with respect to the shape of the pattern groove of the test object without changing the measurement results even for a test object having a fine pinch pattern of several times the wavelength of the irradiated light beam or more. The purpose is to provide a high-performance groove shape measuring device that can perform measurements.

[Means to solve the problem]

As shown in FIG. a linearly polarized light irradiation means 'r for irradiating coherent light onto the test object with linearly polarized light having a polarization plane in the direction of the grooves in the pattern of the test object 3 or in a direction perpendicular to the grooves; and the linearly polarized light irradiation means '1 Illuminated by J7
a photoelectric detection means 4 for photoelectrically detecting the intensity of the diffracted light generated from tL of the pattern of the object to be inspected; and a calculation for calculating the average groove shape of the object to be inspected based on the photoelectric signal from the photoelectric detection means 4. The apparatus is configured to have a processing means.

0 effect] In the present invention, linearly polarized light having a plane of polarization in the plane fj direction (abbreviated as 1゛E polarization) or linearly polarized light having a polarization plane in the perpendicular direction (abbreviation as 1゛M polarization) is used in the present invention. By arranging a linearly polarized light irradiation means that irradiates the object to be examined (5 points), the polarization direction of the irradiated light beam can be set in a specific state, and the diffracted light can be detected in a stable state at all times. This facilitates the theoretical analysis of the groove shape and improves the measurement accuracy of the groove shape.

To illustrate the comparison between the present invention and the prior art, FIG. 6 shows the average pitch P of 1.6 μW and the average groove width W of 0°i3. u
Using a test object with a pattern of regular uneven grooves at
When the station L5-zer is used as a light source, a certain distance D at 7 and the intensity ratio l+-+ of the -1st-order diffracted light and the 0th-order diffracted light
, / I ta , is a graph showing the correlation with .

Here, the broken line indicates the theoretical value of the prior art, the solid line indicates the theoretical value of the present invention, and the black dots indicate the measured value of the present invention.

As shown in the graph of FIG. 6, the measurement of pattern grooves based on the theoretical values of the prior art indicated by the broken line is as follows: Obviously, there is a large difference between the measured values and the measured values, and it is not possible to detect such fine pattern grooves.

On the other hand, in the present invention, the theoretical values agree well with the measured values, and it is possible to measure even finer pattern grooves with high precision than before.

〔Example〕

FIG. 1 shows a schematic configuration diagram of an embodiment of the present invention.
This will be explained in detail with reference to this figure.

, 3 is the rule! A le-Ne laser 1 which oscillates light with a wavelength of 632.8 nm diagonally above the test object 3, e.g., with a coherent L. Then, a polarizing optical element converts this laser light into linearly polarized light (TE polarized light) having a polarization plane parallel to the grooves of the pattern of the test object or linearly polarized light (TM polarized light) having a polarization plane perpendicular to the grooves. A linearly polarized light irradiation means 'r' having a linearly polarized light beam 2 is disposed.
The M-polarized light is irradiated onto the test object 3 at a predetermined incident angle θ.

Note that this linearly polarized light irradiation means T may use a light source that supplies a linearly polarized light beam, and in this case, the polarizing optical element 2
can also be excluded.

A coherent laser beam oscillated from a laser 1 enters a polarization optical element 2, and the polarization optical element 2 converts T E polarization or T
M-polarized light is converted to make the light source light beam into a stable and specific polarization state, and this polarized light beam has a regular uneven pattern.
The object to be measured 3 is irradiated with light. Then, a diffracted light is generated by this regular pattern, and a detector 4, which is a photoelectric detection means, is arranged in the direction in which this diffracted light is reflected, and photoelectrically detects the diffracted light from the object 3 to be inspected.

5-, this detector 4 is supported by a support member 41, and a drive motor 5, which is a drive means, is attached to this support member 41, and this motor 5 is moved so that the irradiation point O and the motor axis coincide with each other. It is located. Further, behind the drive motor 5, for example, a rotary encoder 6 (angle detection means) is arranged, which converts information on the rotation angle into an electrical signal based on the amount of rotation of the drive motor 5.

With this configuration, as the drive motor 5 rotates, the detector 4 moves in an arc within the incident plane, with the distance between the detector and the motor shaft as a radius. By moving the detector 4 within this arc range, it is possible to detect from the -2nd order diffracted light to the 1st order diffracted light with one detector.

In addition, there are as many detectors as there are diffracted lights of the order to be detected.
Although it may be arranged in the reflection direction of each order of diffracted light, in order to maintain the detection accuracy by keeping the detection state the same, one detector as described above and the CP of the arithmetic processing means should be used.
By configuring U7 and display section 8, the position of detector 4 can be monitored while automatically detecting diffracted light of a desired order.

As shown, this CPLI 7 positions the detector 4 at the position of each order of diffracted light, and detects the intensity signal at the position where the intensity signal from the detector 4 reaches its peak and the rotary encoder 6. Based on the signal of the detected diffraction angle (rotation angle), the CPU 7 can perform arithmetic processing and calculate the average groove shape of the pattern of the object to be inspected.

Next, a method for calculating the shape of a regular pattern of an object to be inspected by detecting these diffracted lights will be explained with reference to FIG.

First, the average pitch P of the pattern grooves is determined by θ being the incident angle of the illumination light and β being the exit angle of the n-th order light. 1. If the wavelength of the irradiated light is λ, the basic formula of the diffraction grating is nλ-P (sin O+
sin β(, lI I+ -----(1). Therefore, for example, the exit angle βil+ of the first-order diffracted light
If detected, since the incident angle θ and wavelength of the illumination light are known, P−λ/(sin θ →sin β(+,
) (obtained as 21 and obtained by calculating the average pitch P.

Note that this average pitch P can also be determined by detecting diffracted light of any order.

Next, a method for determining the average groove width W and depth D will be explained.

First, based on the theoretical calculation of diffraction efficiency considering TE polarized light or TM polarized light, the groove depth D is determined using the groove width W as a parameter.
and the ratio of the intensity of the -1st-order diffracted light to the 0th-order diffracted light' +-+
, / l +. , and the correlation between the groove depth D and the intensity ratio of the -2nd order diffracted light to the 11st order diffracted light, which is 1, -zl/I, using the groove width W as a parameter. The graph shown is stored in the CPU 7 in advance.

The calculation here is based on the polarized light component (T
For E-polarized light or TM-polarized light, electromagnetic boundary conditions are set, the diffraction efficiency is calculated by numerical calculation, and the ratio of the respective diffracted light intensities is determined. In addition, since it is more advantageous to use TE polarized light in terms of numerical calculations, 3A shows the correlation between the groove depth l] and the ratio of the intensity of the diffracted light, using the groove width W as a parameter. The figures and FIG. 4A are obtained when the irradiation light flux is TE polarized light.

Then, as described above, from the diffraction angle and intensity of each detected order of diffraction light, the ratio of the intensity of the 11th-order diffracted light to the 0th-order diffracted light + +-11/I (01 and -2nd-order diffracted light and the The average groove width W and the groove depth D can be determined by calculating the intensity ratio 1 (-21/1, -1.) with respect to the first-order diffracted light.

Furthermore, the operation of the embodiment of the present invention will be specifically described based on the flowchart shown in FIG.

In step 1, the CPU 7 determines the diffraction light intensity 1, the diffraction angle β, 7. In order to detect this, the drive motor 5 is driven. For example, 1
Intensity I(1) and diffraction angle β of the next diffracted light, 1. In order to detect this, the CPU 7 issues an output signal to drive the motor 5.

In step 2, the CPU 7 determines the intensity ■ at the position where the first-order diffracted light intensity peaks, 1. The signal of the diffraction angle β(1) at that position is detected by the rotary encoder 6 at the same time.

In step 3, the CPU 7 stores the detected signals of the first-order diffraction intensity I (11) and the diffraction angle β13.

In step 4, CP [J 7 is the diffraction intensity ■ of diffracted light of different orders. l and diffraction angle β. Check whether the desired number of , are detected. In this case, since only the intensity 1 (11 and diffraction angle β) of the first-order diffracted light is detected, the process returns to step 1 and steps 1 to 4 are repeated in sequence, and finally, -second-order diffraction light ~ Diffracted light intensity I up to the first-order diffracted light.

11 and diffraction angle β. , are all detected, step 5
Move to.

In step 5, the CPU 7 calculates the detected first-order diffraction angle β5. Based on the signal, the average pitch P is calculated based on the above equation (2).

In Ste and Pro, CPtJ7 is this average pi.

Memorize 1,000P signals.

Step 1. In Step 7, the CPU 7 calculates the intensity ratio between the -1st order diffracted light and the 0th order (C light) based on the light intensity signals of the 12nd order to 1st order diffracted lights stored in Step 3.
+-n/l (.7, the ratio of the intensity of the -2nd-order diffracted light to the 1st-order diffracted light 1 +-21/I +-11 is calculated, respectively.

In step 8, C)) U 7 is kF-1 of the intensity of the 1st-order diffracted light and the 0th-order diffracted light calculated in step 8.
+-11/lt. The signal of the intensity ratio 1 +-21/I +-++ of the 1st and -2nd order diffracted light and the 11st order diffracted light is memorized.

In step 9, the CPU 7 determines that the range of the average groove width W exists within the range of the average pitch P based on the accuracy of the average pitch P calculated in steps 5 and 5. Here, if the range of the average groove width W is known in advance, it is determined that the average groove width W exists within this range. For ease of explanation, in this case, for example, CPU 7
Assume that it is known in advance that the groove width W is within the range of 0.481 to 0.8 μm.

In step 10, the CPU 7 selects this CP tJ7
The existing range of the average groove depth D can be determined based on the graph shown in FIG. 3A, which is stored in the memory. That is, the intensity ratio of the 11th-order diffracted light and the 0th-order diffracted light stored in step 7 is 1+-1+/■. , for example, is 0.
1, the CPU 7 determines from the graph shown in FIG. 38 that the range of the average groove depth D is 717 to 933 people, as shown by a.

In step 11, the CPU 7, based on the graph shown in FIG. 4A stored in the CPU 7,
A narrower range of average groove width W can be determined. In other words, the intensity ratio I, -0/I C-1 between the 1st-2nd-order diffracted light and the -1st-order diffracted light stored in step 7 is
1 is, for example, 0.4, the CPU 7
Based on the graph in the figure, the range of the average groove width W is determined to be 0.44Jl~0.47μm from the range of 717 to 933 people with the average groove depth D determined in step 10.

-,! 3- AQ step 1
In step 2, the CPU 7 confirms whether the average groove width W and groove depth D with an accuracy of one minute have been obtained. In this case, since the average groove width W and groove depth D have not yet been determined with sufficient accuracy, the process returns to step 10 again.

Again in step 10, the CPU 7 calculates the average a width W obtained in step 11 by 0.44 μm-0 based on the memorized graph shown in FIG. 3B (an enlarged view of the part e in FIG. 3A). , 47/jm, the intensity ratio I of the -1st-order diffracted light and the 0th-order diffracted light is -0/1. , is 0
．． The existence range of the average groove depth D at l is 87 as shown by b.
The number is estimated to be between 5 and 897 people.

Then, in step 11 again, the CPU 7 determines the intensity of -2nd order light beam -1st order diffracted light based on the memorized graph shown in Fig. 4B (an enlarged view of the part r in Fig. 4A). Ratio 1 +-21/l +-++ is 0.
In Step 4, the range of the average groove depth D obtained in Step 10 is determined to be 0.450 μm - 0,445 μm for the average groove width W for 875 to 897 people. In Step 12, Check again whether the average groove width W and groove depth D have been obtained with sufficient accuracy. If the average, S width W, and groove depth D obtained in this step are not accurate enough, the CPU 7 again performs steps 10 to 12.
By repeating the steps 4 and 2 in sequence, it is possible to obtain the average groove width W and groove depth p ov values with even higher accuracy. Then, when the values of the average groove width W and the 7s depth D are obtained, the CPIJ 7 stops its operation and outputs the measurement results in a desired format.

Note that FIGS. 3A to 4B show qualitative graphs, and the specific numerical values shown above are just examples.

The present invention can also be applied to cases where the object to be tested is made of a transparent material such as a glass substrate, and cases where the regular pattern groove shape is trapezoidal, sinusoidal, triangular, etc.

Further, although the embodiments of the present invention utilize second-order to first-order diffracted light, it is also possible to use diffracted light of other orders.

Furthermore, it goes without saying that the present invention is not limited to this embodiment.

〔Effect of the invention] According to the present invention, the pins are even finer than before.

It is possible to realize a highly accurate groove shape measuring device that can correspond to the groove shape of an object to be tested having a thousand pattern grooves.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of an embodiment of the present invention, Figure 2 is a diagram showing the principle of diffracted light generated by irradiating an object to be measured with irradiation light, and Figure 3A is a diagram showing the groove width W as a parameter. As, the groove depth D and the intensity ratio of -1st-order diffracted light to 0th-order diffracted light 1 +-
1,/Ii. , FIG. 3B is an enlarged view of the part e shown in FIG. 3A, and FIG. Figure 4B is an enlarged view of the part 1r shown in Figure 4A. Figure 6, a diagram showing flowchart 1 in the example, has an average pitch of 1,000 P of 1.6.
μm, the horizontal axis is the groove depth D when the average groove width W is 0.8 μm,
-Intensity ratio I (-It/
FIG. 3 is a diagram showing the correlation between the theoretical value of the prior art, the theoretical image of the present invention, and the measured value, with l + o) as the vertical axis. [Description of main parts] 4 Detector [Photoelectric detection means] 7 CPU [Arithmetic processing means]

Claims (1)

[Claims] In a groove shape measuring device that measures the shape of a test object by irradiating coherent light onto a test object having a regular pattern and detecting diffracted light, the coherent light is applied to a pattern of the test object. linearly polarized light irradiation means for irradiating a test object with linearly polarized light having a polarization plane in the direction of the grooves or in a direction perpendicular to the grooves; and diffracted light generated by the grooves in the pattern of the test object illuminated by the linearly polarized light irradiation means. A groove shape measuring device comprising: a photoelectric detection means for photoelectrically detecting the intensity of the groove; and an arithmetic processing means for calculating an average groove shape of the object to be inspected based on a photoelectric signal from the photoelectric detection means.