JPH03144452A - Phase difference mask - Google Patents

Abstract

PURPOSE:To inspect the position and the defect of a phase shifter layer by comprising the mask of an organic film containing dye whose transmission factor is set at a high level with first wavelength and a low level with second wavelength and with film thickness capable of discriminating light intensity at the second wavelength for the light intensity of a projection image by the first wavelength. CONSTITUTION:The phase shifter layer 13 consisting of the organic film to supply a phase difference of 180 deg. to the amplitude of light L is formed at a part of the surfaces of a glass layer 11 and a light shielding layer 12. The dye to inspect the position and the defect, etc., is contained in the phase shifter layer 13, and the phase shifter layer 13 is comprised of the organic film having the first wavelength lambda1 with high level of light transmission factor and the second wavelength lambda2 with low level of light transmission factor. Therefore, the phase difference shifter layer 13 can be inspected by using the second wavelength lambda2 with low level of light transmission factor. In such a way, it is possible to easily inspect the position and the defect, etc., of the phase shifter layer without changing a transmission light quantity.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a phase difference mask used when using a phase difference method in a photolithography process in semiconductor manufacturing, and particularly a phase shifter provided for phase inversion. This invention relates to a phase difference mask that allows inspection of layer positions, etc.

(Prior art) Conventionally, there has been a technology in this type of field, for example, as shown in FIG. 2.The configuration thereof will be explained below with reference to the drawings.

FIG. 2 is a longitudinal sectional view showing an example of the configuration of a conventional phase difference mask.

This phase difference mask consists of a glass plate 1 for transmitting light.
On one side of the surface of the glass plate ↓, a light shielding layer 2 made of chromium or the like is formed in a predetermined pattern to shield light. A phase shifter layer 3 is formed on a part of the surface of the glass plate 1 and the light shielding layer 2 to give a phase difference of 80° to the amplitude of light.

The film thickness d of this phase shifter layer 3 is d=λ1/(2(n1)), where n; refractive index λ1; exposure wavelength, and photoresist 1~, S i 02 , S
.

It has a single-layer structure with transparent films such as G and MGF2.

FIG. 3 is a plan view of the phase difference mask shown in FIG. 2 taken from a wafer measurement.

An open pattern 2a is formed on the glass plate and the light shielding layer 2. A phase shifter layer 3 is formed over the four corners of the pattern 2a and a part of the surface of the light shielding layer 2.

When the surface of the phase difference mask configured as described above is irradiated with light, the light reaches the mask through the following state change. The process will be explained using FIGS. 4 and 5.

FIG. 4 is a diagram showing a projection view of FIG. 3. Figure 5 shows
2 is a diagram showing an example of the state of the light in FIG. 2, where (a) is a waveform diagram showing the amplitude of the light after passing through the phase shifter layer 3 in FIG. 2, and (b) is a waveform diagram showing the amplitude of the light on the mask. A waveform diagram showing the amplitude of light on the mask (C> is a waveform diagram showing the light intensity of light on the mask).

First, the light passes over the glass plate, and then the portion other than the top of the light-shielding layer 2, that is, the projected view of the open pattern as shown in FIG. 4 reaches the resist on the wafer (not shown) and is exposed. At this time, the light passing through the phase difference shifter layer 3 is given a phase difference of ↓80° with respect to its amplitude, as shown by La in FIG. 5(a). And Fig. 5 (b
> As shown, the amplitude of the light on the wafer is controlled,
The difference (contrast) in light intensity on the wafer, which is the difference between the maximum value X and the minimum value y shown in FIG. 5(C), is increased.

This improves the contrast of the projected image on the wafer.

(Problems to be Solved by the Invention) However, the phase difference mask having the above configuration has the following problems.

The transmittance of light passing through the phase shifter layer 3 is uniformly high for the wavelength of light used in the optical inspection machine in the shell. Therefore, when light of a certain wavelength is used to inspect the phase shifter layer 3, the amount of transmitted light is large in areas other than the light-blocking portion of the mask, making it difficult to inspect the pattern position of the phase shifter layer 3.

FIG. 6 is a waveform chart showing the spectral transmittance curve of the phase shifter layer 3 in FIG. 2 constructed using, for example, a photoresist after exposure, and FIG. 2 is a waveform diagram showing a spectral reflectance curve of the phase shifter layer 3 in FIG. 2. FIG. As shown in Figure 6, the transmittance is uniformly high for wavelengths in the visible light range, and as Figure 7 shows, the reflectance is low for a single-layer transparent film, so light can easily pass through. . On the other hand, for example, the wavelength λ in FIGS. 6 and 7
1. No matter which one of λ2 is used, the amount of transmitted light increases.

As a result, when the phase shifter layer 3 is formed on the open pattern 2a, the wavelength λ1. The pattern detected at any of the wavelengths λ2 is a projection diagram as shown in FIG. 4, and there is a problem in that the position (overlap accuracy) of the phase shifter layer 3 and defects cannot be inspected.

The present invention provides a phase difference mask that solves the problem of the prior art, which is that it is not possible to inspect the position and defects of the phase shifter layer.

(Means for Solving the Problem) In order to solve the problem, the first invention includes a light transmitting plate that allows light having a predetermined amplitude to pass through the wafer measurement, and a predetermined pattern on the surface of the light transmitting plate. a light-shielding layer formed on a part of the surface of the transparent plate and the light-shielding layer for shielding the light and exposing a projected image of a predetermined pattern on the wafer; The phase difference mask includes a phase shifter layer that increases the contrast of an image according to the phase difference, and the phase shifter layer is configured as follows.

The dye contains a dye whose transmittance of the light is set to a high level depending on the first wavelength of the light and a low level depending on the second wavelength of the light, and the light intensity of the projected image due to the first wavelength is On the other hand, it is constructed of an organic film having a thickness that allows the light intensity at the second wavelength to be determined.

In the second invention, the phase shifter layer is made of a material whose reflectance of the light is set to a low level according to the first wavelength and to a high level according to the second wavelength, and the light shielding layer is , the reflectance of the light is set to a high level according to the first wavelength and to a low level according to the second wavelength.

(Function) According to the first invention, since the phase difference mask is configured as described above, the phase sister layer has high transmittance for the first wavelength during exposure, and the second wavelength during inspection. The transmittance is low. Furthermore, it works to give a phase difference to the amplitude of light during exposure.

According to the second invention, the phase sister layer is
It has a low reflectance for the wavelength of , and a high reflectance for the second wavelength during inspection. The light shielding layer functions to have a high reflectance for the first wavelength during exposure and a low reflectance for the second wavelength during inspection.

Therefore, the above problem can be solved.

(Example) FIG. 1 is a longitudinal sectional view of a phase difference mask showing a first example of the present invention.

This phase difference mask has a glass plate 11 which is a transparent plate for transmitting light having a predetermined amplitude, and on the surface of the glass plate 11 there is a light shielding layer 12 made of chromium Cr etc. that blocks the light. are formed in a predetermined pattern. A phase shifter layer 13 made of an organic film is formed on a part of the surface of the glass plate l↑ and the light shielding layer 2 to give a phase difference of 180° to the amplitude of light.

The phase shifter layer 13 is coated with a dye (for example, a product name Σ manufactured by Nagase Sangyo Co., Ltd.) for inspecting its position and defects.
) is contained in the photoresist, SiO2, SO after exposure.
It has a single-layer structure made of transparent films such as G and MGF2.

FIG. 8 is a plan view of the phase difference mask of FIG. 1 taken from a wafer measurement.

An open pattern 12a is formed by a glass plate 1 which is a transparent plate and a light shielding layer 12. A phase shifter layer 13 containing a dye 13a is formed over the four corners of the pattern 12a and a part of the surface of the light shielding layer 12.

FIG. 9 is a waveform diagram showing a spectral transmittance curve when a photoresist film is used for the phase shifter layer 13 in FIG. 1.

The first wavelength λ at which the spectral transmittance shown in FIG. 9 is at a high level is
1 (for example, 365 nm) is the exposure wavelength for exposing the wafer, and the second wavelength λ2 has a low level of spectral transmittance.
(for example, 436 nm) is used as an inspection wavelength for inspecting the position and defects of the phase shifter layer 13, respectively.

FIG. 10 is a diagram showing the intensity of transmitted light at wavelength λ2 with respect to the photoresist film which is the phase shifter layer 13. As shown in FIG. 10, the intensity of transmitted light decreases as the thickness of the photoresist film increases.

The thickness of the phase shifter layer 13 is set so that the light intensity at wavelength λ2 can be distinguished from the light intensity of the projected image at wavelength λ1, and D=λ1/(2(n-1)
) However, the relationship is set such that n: refractive index λ1: exposure wavelength.

When light is irradiated onto the surface of the phase difference mask configured as described above, the light reaches the mask through the following state change. The process will be explained using FIG. 11 (a>(b)).

FIGS. 11(a) and 11(b) are diagrams showing projection views of FIG. It is a diagram.

When inspecting the position of the phase shifter layer 13, the wavelength λ2
When the light is irradiated from the upper part of the glass plate 11, the light passes through the glass plate 11 and affects the parts other than the light shielding layer 2 and the phase shifter layer 13, that is, as shown in FIG. A projection view is obtained. By inspecting the positions of the thick line parts x1 to x4 in the projected view of FIG. 11(a), the position and defects of the phase shifter layer 13 are inspected.

When exposing a resist on a wafer (not shown), the wavelength λ
Use 1 light. When the light is irradiated from the top of the glass plate 11, the light is transmitted from the glass plate 11 to the light shielding N12.
It passes through the other parts and reaches the resist on the wafer (not shown). That is, a projected view as shown in FIG. 11(b), which has the same shape as the open pattern 12a in FIG. 8, is exposed to the resist. At this time, the light passing through the phase difference shifter scrap 3 is given a phase difference of 180° with respect to its amplitude.

This embodiment has the following advantages.

Since the phase shifter layer 13 is constituted by an organic film containing a dye and having a first wavelength λ1 with a high transmittance and a second wavelength λ2 with a low transmittance, the second wavelength λ2 has a low transmittance.
By inspecting the phase difference shifter 413 using the wavelength λ2, the position of the phase difference shifter layer 13, etc. can be easily inspected without changing the amount of transmitted light.

FIG. 12 is a longitudinal cross-sectional view of a phase difference mask showing a second embodiment of the present invention, in which the same elements are given the same reference numerals.

This retardation mask is provided with a glass plate 11 and a light shielding layer 12A as in FIG. These glass plates 11
And a part of the surface of the light shielding layer 12A has a light amplitude of 180
A phase shifter IW13A is formed to provide a phase difference of .degree.

The phase shifter layer 13A is made of a material such as MGF2 that has a high reflectance (low transmittance) for the exposure wavelength and a low reflectance (high transmittance) for the detection wavelength. There is.

Further, the light shielding layer 12A is made of a material such as 5rTi03 that has a low reflectance (high transmittance) for the exposure wavelength and a high reflectance (low transmittance) for the detection wavelength. There is.

FIG. 13 is a plan view of the phase difference mask shown in FIG. 12 from the wafer side.

As in FIG. 1, a glass plate 11 and a light shielding layer ↑2A are provided, and an open pattern 12a is formed by the glass plate 11 and the light shielding layer 12A.

A phase shifter layer 13A is formed over the four corners of the pattern 12a and a part of the surface of the light shield 112A.

FIG. 14 is a waveform diagram showing spectral reflectance curves of the phase shifter layer 13A and the light shielding layer 12A in FIG. 12.

The curve P in FIG. 14 shows the spectral reflectance curve of the phase shifter layer 13A, and the curve Q shows the spectral reflectance curve of the light shielding layer 112A.
) is the exposure wavelength, and the second wavelength λ2 (for example, 350 nm
) are used as inspection wavelengths.

When the surface of the phase difference mask configured as described above is irradiated with light, the following process occurs. The process will be explained using FIGS. 15 and 16.

FIG. 15 (a>(b) is a usage state diagram when the retardation mask of FIG. 1 is irradiated with light, and FIG. 15 (a) shows the case where the first wavelength λ1 is irradiated. FIG. 3B is a diagram showing the case where the second wavelength λ2 is irradiated.

In addition, FIG. 16 (a>(b) is a diagram showing a projection view of FIG. 15, in which (a) is a projection view obtained with wavelength λ1, and FIG. 16 (b) is a projection view obtained with wavelength λ2. FIG.

When light with a wavelength λ1 is irradiated from above the glass plate 11, the light shielding layer 12A reflects the light, and the phase shifter layer 13A and the glass plate 11
transmits light. Therefore, a projection view as shown in FIG. 16(a) is obtained.

Furthermore, when the wavelength λ2 is irradiated from the top of the glass plate 11, the phase shifter 113A appears as shown in FIG. 15(b).
reflects the light, light shielding 112A and glass plate 1↑
transmits light. Therefore, a projection view as shown in FIG. 16(b) is obtained. Thereby, the position and defects of the phase sister layer 13A are inspected.

Similar to the second embodiment, this embodiment has the advantage that the position of the phase difference shifter layer 13A can be easily inspected without changing the amount of transmitted light.

Note that the present invention is not limited to the illustrated embodiment, and various modifications are possible.

(I) Although glass 11 was used as the light-transmitting plate, other light-transmitting substrates may be used.

(II) Cr for light shielding layer N12, 5rT for light shielding layer 12A
Although i○3 was used, the material is not limited to these.

(Effects of the Invention) As explained in detail above, in the first invention, an organic film containing a dye and having a first wavelength with a high level of transmittance and a second wavelength with a low level of transmittance is used. Since the shifter layer is configured, the position of the phase difference shifter layer can be easily inspected without changing the amount of transmitted light by inspecting the phase difference shifter layer using the second wavelength with a low level of transmitted light. can.

In the second invention, the phase shifter layer and the light shielding layer are made to have greatly different reflectances at the first and second wavelengths, so when the second wavelength is used, the reflectance of the light shielding layer is Since the reflectance of the phase shifter layer is small, the position and defects of the phase shifter layer can be inspected by detecting the reflected light of the phase shifter layer.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of a phase difference mask showing a first embodiment of the present invention, FIG. 2 is a vertical sectional view of a conventional phase difference mask, and FIG. 3 is a vertical sectional view of a conventional phase difference mask.
The figure is a plan view of the phase difference mask in Figure 2, Figure 4 is a projection view of Figure 2, Figure 5 is a diagram showing an example of the state of light in Figure 2, and Figure 6 is a conventional spectral transmittance. A waveform diagram showing a curve, FIG. 7 is a waveform diagram showing a conventional spectral reflectance curve, FIG. 8 is a plan view of the phase difference mask of FIG. 1, and FIG. 9 is a spectral transmittance curve of the first embodiment. FIG. 10 is a waveform diagram showing the transmitted light intensity at the second wavelength, FIG. 11 is a projection diagram of FIG. 8, and FIG. 12 is a waveform diagram showing the transmitted light intensity at the second wavelength. 13 is a plan view of the retardation mask shown in FIG. 12, FIG. 14 is a diagram showing the spectral transmittance [1j line] of the second embodiment, and FIG. 15 (a> (b) is a usage state diagram when the phase difference mask in FIG. 12 is irradiated with light;
) is a diagram showing the case of the first wavelength, FIG. 16(b) is a diagram showing the case of the second wavelength, and FIG.
It is a figure which shows the projection view of a>(b), respectively. 11...Glass plate, 12.12A...
Light shielding layer, 13° 13A...Phase sister layer, 13a...Dye, L...Light.

Claims (1)

[Scope of Claims] 1. A light transmitting plate that allows light having a predetermined amplitude to pass toward the wafer, and a predetermined pattern formed on the surface of the light transmitting plate,
a light-shielding layer for shielding the light and exposing a projected image of a predetermined pattern on the wafer; A phase shifter layer that provides a phase difference mask, wherein the phase shifter layer has a transmittance of the light set to a high level depending on the first wavelength of the light and a low level depending on the second wavelength of the light. A phase difference comprising an organic film containing a dye and having a thickness such that the light intensity at the second wavelength can be distinguished from the light intensity of the projected image at the first wavelength. mask. 2. The phase difference mask according to claim 1, wherein the phase shifter layer is made of a material whose reflectance of the light is set to a low level according to the first wavelength and to a high level according to the second wavelength. The light shielding layer is a retardation mask made of a material whose reflectance of the light is set to a high level according to the first wavelength and to a low level according to the second wavelength.