JPH0381769A - Phase difference reticule - Google Patents

Abstract

PURPOSE:To enhance the accuracy of the position of a phase shifter layer and the inspection of defects by forming the phase shifter layer of plural light transmittable films which vary in refractive index and providing a low reflectivity to an exposing wavelength and a high reflectivity to an inspecting wavelength. CONSTITUTION:Light shielding patterns 12 consisting of Cr, etc., are formed on a substrate 11 consisting of glass, etc., and the phase shifter layer 14 consisting of the plural light transmittable films which vary in the refractive index is formed in one of the aperture patterns 13. This layer 14 is formed of the three layers; the upper layer 14a consisting of, for example, CeF3, the intermediate layer 14b consisting of CeO2 and the lower layer 14c consisting of MgF2. A distinct light transmission pattern 15 of a pattern 13 is obtd. when this phase difference reticule is irradiated with exposing light of a prescribed wavelength. A pattern 13 of the point exclusive of the layer 14 is obtd. as a light transmission pattern 16 when the reticule is irradiated with transmission type detecting light of a prescribed wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a phase difference reticle used in a phase difference method in a photolithography process related to semiconductor device manufacturing.

(Prior art) Conventionally, as a technology in this field, for example, "IEE
IEEE Transactions on Electron Devices
ECTRON DEVICE) J, ED-29
[12] (1982-12) (US) P, 1828
There was one described in -1836. The configuration will be explained below.

FIGS. 2(a) to 2(d) show the configuration and characteristics of the conventional phase difference reticle described in the above-mentioned document, and FIG.
) is a cross-sectional view of the phase difference reticle, (b) is the amplitude of light on the reticle, (C) is the amplitude of light on the wafer, and (d) is the intensity of light on the wafer. It shows.

In FIG. 2(a), this retardation reticle has a light-transmissive substrate 1 made of glass, on which a light-shielding pattern 2 of chromium (Cr) is selectively formed. On the substrate 1 exposed between the light shielding patterns 2, a phase shifter layer 3 is formed at one of the opposing light transmitting parts.

The phase shifter layer 3 is a light-transmissive film made of photoresist, SiO, M g F 2 or the like after exposure to a single layer structure. The thickness d of the phase shifter layer 3 is set so that the relationship d=λ/2(n-1> holds), where n is the refractive index and λ is the exposure wavelength.

When a wafer (not shown) is irradiated with light 4 having a wavelength λ through the phase difference reticle having the above configuration, the amplitude of the light on the phase difference reticle after passing through the phase shifter layer 3 is as shown in FIG. is obtained. That is, a phase difference of 180° is given to the amplitude of the light.

As a result, the amplitude of the light on the wafer becomes as shown in FIG. 2(C), and the light intensity on the wafer increases as shown in FIG. 2(d).

In this way, for example, in a repeating pattern as shown in FIG. 2(a), by providing the phase shifter layer 3 on one of the opposing light transmitting parts on the retardation reticle, the light intensity on the wafer is increased, The contrast of the projected image can be fundamentally improved.

(Problems to be Solved by the Invention) However, in the phase difference reticle having the above configuration,
In general, the reflectance of the phase shifter layer 3 due to the single layer structure is uniformly low for all wavelengths. Therefore, when inspecting the phase difference reticle, there is a problem that the amount of light transmitted uniformly increases in the light transmitting parts other than the light shielding pattern 2, making it difficult to inspect the positional accuracy and defects of the phase shifter layer 3.
The solution was difficult.

The above problem will be explained using FIGS. 3 to 5.

FIG. 3 shows a spectral reflectance curve in the phase shifter layer. Moreover, FIG. 4 shows an example of a plan view corresponding to the phase difference reticle of FIG. 2, and FIG. 5 shows a light transmission pattern and pattern by the phase difference reticle.

In FIG. 3, the phase shifter layer 3 consisting of a single layer film is
As shown in the spectral reflectance curve S, the spectral reflectance with respect to wavelength is uniformly low. Therefore, light is easily transmitted regardless of the wavelength, and, for example, when using different wavelengths A and B, the spectral reflectance is approximately the same.

Therefore, as shown in FIG. 4, in a retardation reticle in which an open pattern 5 is formed by a light shielding pattern 2 and a phase shifter layer 3 is selectively formed on the open pattern 5, regardless of the wavelengths A and B, , the same light transmission pattern 6 as shown in FIG. 5 is obtained.

That is, since the detected light transmission pattern is the same regardless of whether wavelength A or B is used, the phase shifter layer 3
It is not possible to accurately inspect the positional accuracy and defects, etc. of

The present invention provides a phase difference reticle that solves the problem of the prior art, in which it is difficult to conduct inspections because the reflectance of the phase shifter layer is uniformly low regardless of the wavelength. be.

(Means for Solving the Problems) In order to solve the above problems, the present invention includes a substrate having a light transmitting property, a light-shielding pattern selectively formed on the substrate, and a light-shielding pattern exposed between the light-shielding patterns. A phase difference reticle comprising a light-transmitting phase shifter layer selectively provided on a substrate, wherein the phase shifter layer is configured with a multilayer structure consisting of a plurality of light-transmitting films having different refractive indexes. be.

(Function) According to the present invention, since the phase difference reticle is configured as described above, the phase shifter layer, which is prevented from having a multilayer structure of a plurality of light-transmitting films having different refractive indexes, changes significantly with respect to wavelength. Due to the spectral reflectance characteristics, it works to have a low reflectance for the exposure wavelength and a high reflectance for the inspection light wavelength.

Due to this function, the phase shifter layer can be accurately inspected by detecting transmitted light or reflected light of the inspection light. Therefore, the above problem can be solved.

(Embodiment) FIG. 1 is a sectional view of a phase difference reticle showing an embodiment of the present invention.

A light-shielding pattern 12 made of chromium or the like is selectively formed on a light-transmitting substrate 11 made of glass or the like.

The exposed portion of the substrate 11 between the light-shielding patterns 12 has an open pattern 13 as a light-transmitting portion.

For example, a phase shifter layer 14 is formed on one of the opposing portions of the open pattern 13 . This phase shifter layer 14 has, for example, a three-layer structure made of light-transmitting films each having a different refractive index.

That is, the phase shifter layer 14 includes an upper layer 14a made of, for example, CeF3, an intermediate layer 14b made of CeO2, etc.
It is composed of a lower layer 14c including M g F 2 and the like. Such a top phase shifter layer 4 can be easily formed by using a vacuum evaporation method or the like.

Here, in order to bring out the effect of the phase difference, the thickness of the entire phase shifter layer 14 is set to be D-λ/2 (n- above) so that the phase is inverted by 180°. , λ is the exposure wavelength used and n is the refractive index of the entire phase shifter [14].

The spectral reflectance curve for the wavelength of the phase shifter layer 14 having the above configuration is shown by a curve P in FIG. As can be seen from the figure, the spectral reflectance curve P in this case has a lower reflectance than the conventional spectral reflectance curve S near wavelength A, and
It is noticeably higher in the vicinity.

For example, if the upper layer 14a, the intermediate layer 14b, and the lower layer 14c are each made of CeF3, CeO2, and MgF2, the wavelength A is 520 to 550 nm.
Light of about 700 to 800 nm may be used as the wavelength B.

The operation of the phase difference reticle configured as above will be explained using FIG. 6 and FIGS. 7(a) to (C).

FIG. 6 shows an example of a plan view corresponding to the phase reticle shown in FIG. 1. In addition, Fig. 7(a) to (c) shows the sixth
The light patterns obtained from the phase difference reticle shown in the figure are shown; (a) is a light transmission pattern at wavelength A, (b) is a light transmission pattern at wavelength B, and (C) is a light reflection pattern at wavelength B. It's a pattern.

In FIG. 6, phase shifter layers 1 having a three-layer structure are placed at the four corners of an open pattern 13 defined by a light-shielding pattern 12.
4 is a formal precept. If light of wavelength A is used as the exposure wavelength for this phase difference reticle, since the reflectance of the phase shifter layer 14 is extremely small, a light transmission pattern E5 of the open pattern 13 can be obtained as shown in FIG. 7(a). It will be done. In this case, the amount of light transmitted through the phase shifter layer 4 is increased compared to when a conventional single layer film is used, and a clearer light transmission pattern 15 is obtained.

Next, if the light of wavelength B is used as the transmission type detection light, the reflectance of the phase shifter layer 14 becomes extremely large, so the seventh
As shown in Figure (b), an open pattern 13 excluding the phase shifter layer 14 is obtained as a light transmission pattern 16.

Furthermore, if the light of wavelength B is used as the reflective detection light, the reflected light from the phase shifter layer 44 and the light shielding pattern 12 will cause
A light reflection pattern 17 shown in FIG. 7(C) is obtained.

In this example, by configuring the phase shifter layer 14 with a multilayer structure, if wavelength A is used as the exposure light, the residual reflection that cannot be reduced with a conventional single layer film can be significantly reduced, and the exposure light can be reduced. The amount of permeation can be increased.

Furthermore, if wavelength B is used as the detection light, the reflectance of the phase shifter layer 14 increases significantly. Inspection for positional accuracy, defects, etc. can be performed easily and with high precision.

Note that the present invention is not limited to the illustrated embodiment, and various modifications are possible. For example, the phase shifter layer 14 may have not only a three-layer structure but also two or more layers. Furthermore, the material, shape, etc. are not limited to those illustrated, and can be changed as appropriate depending on the use of the retardation reticle.

(Effects of the Invention) As explained in detail above, according to the present invention, the phase shifter layer is configured with a multilayer structure consisting of a plurality of light-transmitting films having different refractive indexes, so that a certain wavelength can be used as exposure light. For example, the amount of exposure light transmitted can be increased by significantly reducing residual reflection.

Further, if a detection light having a wavelength different from that of the exposure light is used, the reflectance of the phase shifter layer can be significantly increased.

Therefore, by detecting the transmitted light or reflected light of the detection light, it is possible to easily and accurately inspect the formation position, defects, etc. of the phase shifter layer.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a phase difference reticle showing an embodiment of the present invention, FIGS. 2(a) to 2(d) show the configuration and characteristics of a conventional phase difference reticle, and FIG. A cross-sectional view of
The same figure (b) is a light amplitude diagram on the reticle, the same figure (C> is the light amplitude diagram on the wafer, the same figure (d) is the light intensity diagram on the wafer, and FIG. 3 is the conventional and present invention implementation. 4 is a plan view corresponding to the phase difference reticle in FIG. 2, FIG. 5 is a diagram of the light transmission pattern by the phase difference reticle in FIG. 4, and FIG. A plan view corresponding to the phase difference reticle in FIG. 1, and FIGS. 7(a) to (C) are
A diagram of the light pattern obtained from the phase difference reticle in the figure is shown,
The figure (a) shows the light transmission pattern at wavelength A, and the figure (b) shows the light transmission pattern at wavelength A.
, (C) are a light transmission pattern and a light reflection pattern at wavelength B, respectively. 11... Substrate, ■2... Light shielding pattern, 13... Open pattern, 14... Phase shifter layer.

Claims (1)

[Scope of Claims] A light-transmitting substrate, a light-shielding pattern selectively formed on the substrate, and a light-transmitting light-transmitting pattern selectively formed on the substrate exposed between the light-shielding patterns. A phase difference reticle comprising a phase shifter layer, wherein the phase shifter layer has a multilayer structure composed of a plurality of light-transmitting films having different refractive indexes.