JPH0769154B2 - Shape measurement method of resist pattern - Google Patents

Description

The present invention relates to a resist pattern shape measuring method, and more particularly to a resist pattern shape measuring method used for manufacturing semiconductors, ICs and the like.

(Prior Art) As one of methods of manufacturing a semiconductor element, a method of forming a resist pattern on a substrate and performing etching using this resist pattern is known. When a semiconductor element is manufactured by this method, it is necessary to remove the solvent after development and baking, and this removal is generally performed by evaporation in a high temperature drying chamber. Therefore, the resist is also exposed to high temperature, and therefore the resist is required to have heat resistance.

The heat resistance test of this resist is usually performed by measuring the change in the shape of the resist pattern before and after heating, and the measurement of the shape of this resist pattern has conventionally been performed by an optical microscope or a scanning electron microscope (SEM). ) Etc. were observed by direct observation.

(Problems to be solved by the invention) However, in the case of directly observing with the microscope, the resist pattern is only observed with the naked eye, so that the shape of the resist pattern cannot be quantified, and the shape change of the resist pattern with time is also impossible. Cannot be observed continuously. Furthermore, in order to observe with SEM, it is a destructive measurement that requires a sample to be a small section, and there is a problem that it is very troublesome.

Therefore, an object of the present invention is to provide a method for measuring the shape of a resist pattern, which solves the above-mentioned problems of the conventional method.

(Means for Solving Problems) The present invention is a method for measuring a change in shape of a resist pattern formed on a substrate by heat treatment, which is performed after heating a substrate having a predetermined resist pattern formed on the surface or The resist pattern is irradiated with coherent light while being heated, the coherent light is diffracted by the resist pattern, and the diffracted light intensity of the diffracted light other than the 0th order light is measured. The feature is that the shape of the resist pattern is measured by measuring the diffracted light intensity other than the 0th order light in the same method and comparing the diffracted light intensity other than the 0th order light.

That is, the method for measuring the shape of the resist pattern of the present invention is based on the fact that the intensity distribution of the diffracted light depends on the transmittance distribution or the shape of the diffractive surface. When a resist pattern formed on a silicon wafer, which can be regarded as a mirror surface, is irradiated with laser light, light diffraction occurs in accordance with the shape of the resist pattern. By observing the diffracted light with an image sensor or the like, the resist pattern can be regarded as an intensity distribution of the diffracted light.

(Operation and Effect of the Invention) In the resist pattern shape measuring method of the present invention,
As described above, by irradiating the coherent light on the resist pattern, diffracting the coherent light by the resist pattern, and measuring the intensity distribution of the diffracted light, the shape of the resist pattern is measured. Since it is not necessary to prepare a sample of a special shape, the shape of the resist pattern can be easily measured in a non-contact manner, and the shape of the resist pattern can be quantified and measured. There is no deviation, and moreover, the change with time of the resist pattern can be continuously observed, so that a good test can be conducted on the heat resistance of the resist.

(Embodiment) A preferred embodiment of the resist pattern shape measuring method of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of an example of an apparatus for carrying out a resist pattern shape measuring method according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 indicates a laser light source, and a half mirror 3 is arranged on an optical path 2 of laser light emitted from the laser light source 1. The half mirror 3 partially transmits the laser light from the laser light source 1 and reflects the rest. A sample 5 is disposed on the optical path 4 of the transmitted light while being supported by a support 6. As shown in FIG. 2, this sample 5 is composed of a substrate 7 which is a silicon wafer, and a resist layer 8 applied on the substrate 7. On the resist layer 8, for example, a grid-shaped resist is formed. A pattern 9 is formed. The reason why the grid pattern is selected as the resist pattern is that the optical axis alignment is easy and the reproducibility is good, but it goes without saying that another pattern may be selected. In addition, the support 6 is a sample 5
It can be moved up and down, left and right, front and back, that is, in the Z, X and Y directions.

The laser light diffracted and reflected on the surface of the sample 5 is reflected on the back surface of the half mirror 3 this time. A lens 11 is arranged on the optical path 10 of the reflected light, and an image sensor 12 is arranged on the focal plane of the lens 11. An oscilloscope 13 is connected to the output terminal of the image sensor 12, and the oscilloscope 13
Is adapted to receive an image signal from the image sensor 12 at the timing of the timing signal generated by the timing signal generator 14 and display it. In addition,
Similarly to the sample 5, the image sensor 12 is also supported by the support 15 so that it can be finely moved up and down, left and right, front and back, that is, in the Z, X and Y directions.

A photodetector 17 is arranged on the optical path 16 of the reflected light of the laser light from the half mirror 3. The photodetector 17 measures the reflected light as the intensity reference light and outputs a signal corresponding to the intensity of the light. Is output to the oscilloscope 13. The oscilloscope 13 is usually used as it has a processor function. Oscilloscope 13
Receives the image signal from the image sensor 12 and the intensity reference light signal from the photodetector 17, and standardizes the image signal based on the intensity reference light signal (corrects fluctuations of the laser light itself). The image signal after this processing
Display on CRT. The image signal after this processing may be stored in the storage means or may be recorded on a hard copy. Of course, the processor function may be performed by a computer.

Next, a method of measuring the shape of a resist pattern according to the embodiment of the present invention using the above apparatus will be described.

First, prepare two samples of the above-mentioned form,
One is used as it is and the other is heat-treated and used for measurement. Of these samples, the one as it is is the first sample 5A, and the one subjected to the heat treatment is the second sample 5B.

Then, first, in measuring the shape of the resist pattern of the first sample 5A, the first sample 5A is placed on the support 6,
Align. Then, the laser light source 1 is activated,
Through the half mirror 3, laser light is applied to a predetermined portion of the first sample 5A on the support 6. Then, this laser light is reflected on the resist surface of the predetermined portion of the first sample 5A and also causes diffraction. This reflected diffracted light returns to the half mirror 3 again, and this time, the half mirror 3
Reflected on the back side of. The reflected light from the half mirror 3 is
It is converged by the lens 11 and forms a diffraction image on the image sensor 12.

This image sensor 12 photoelectrically converts the diffraction image,
It is converted into an electric signal and output to the oscilloscope 13. On the other hand, the reflected light first reflected by the half mirror 3 enters the photodetector 17. This photo detector
17 receives the reflected light as intensity reference light, measures it, and outputs an intensity reference light signal to the oscilloscope 13.

As described above, the processor of the oscilloscope 13 first standardizes the image signal based on the intensity reference light signal, and then processes the image signal to digitize the resist pattern data into a desired form. This signal processing is performed by (1) digitizing the data of light intensity distribution and performing FFT.
Etc., there are three methods of performing Fourier transform, (2) measuring the intensity of the diffracted light of the m-th order, and (3) taking the intensity ratio of the diffracted light of the m-th order and the n-th order, whichever method is adopted. Good.
The oscilloscope 13 processes the signal as described above and displays it on the CRT. The photograph is shown in Fig. 3.

Then, the shape of the resist pattern of the second sample 5B was measured in the same manner as the first sample 5A. Of the result
A photograph of the image on the CRT is shown in FIG. By comparing these two photographs, it is possible to detect a change in the resist due to heat, that is, a change in the shape of the resist pattern. That is, as apparent from FIGS. 3 and 4, in the heat-treated second sample, the first-order diffracted light intensity is smaller than that in the non-heat-treated first sample. I understand. This result shows that the method of the present invention is effective as a method for measuring a minute change in the shape of a resist pattern. Moreover, according to this resist pattern shape measuring method, since the shape of the resist pattern is numerically captured as the light intensity distribution of the diffraction image by the resist pattern, the numerical values themselves can be compared.

Further, if the sample 5 is placed in, for example, a heat treatment chamber, it is possible to measure the temporal change of the resist pattern due to heat.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus for carrying out a resist pattern shape measuring method according to an embodiment of the present invention, and FIG. 2 is a perspective view of a sample which is an object to be measured in the above measurement. FIG. 4 is an oscilloscope waveform photograph showing a diffraction pattern of the resist pattern of the first sample that has not been heat-treated, and FIG. 4 is an oscilloscope waveform photograph showing the diffraction pattern of the resist pattern of the second sample that has been heat-treated. 1 …… Laser light source, 5 …… Sample 12 …… Image sensor 13 …… Oscilloscope

Claims (1)

[Claims] 1. A method for measuring a change in shape of a resist pattern formed on a substrate due to heat treatment, the method comprising: heating a substrate having a predetermined resist pattern on its surface after heating or while heating the resist pattern; The coherent light is irradiated with light and diffracted by the resist pattern, and the diffracted light intensity of the diffracted light other than the 0th-order light is measured. The method for measuring the shape of a resist pattern is characterized in that the shape of the resist pattern is measured by measuring the diffracted light intensities and comparing the diffracted light intensities of the two other than the zero-order light.