JP2652341B2 - Method for manufacturing phase inversion mask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift mask and, more particularly, to a method for manufacturing a phase shift mask suitable for manufacturing ultra-precision semiconductor circuits.

[0002]

2. Description of the Related Art In recent years, as semiconductor devices have been highly integrated and the package density has increased, a photomask having a fine line width has been demanded, and a specially improved manufacturing technique has been announced.

In general, photolithography is a technique in which light having a wavelength such as ultraviolet light is transmitted to the surface of a photoresist applied on a semiconductor substrate through a photomask to form an image pattern. A general photomask is composed of an opaque pattern and a transmissive pattern,
Although selective exposure can be performed, a diffraction phenomenon occurs due to an increase in pattern density, and there is a limit to improvement in resolution.

That is, when exposure is performed using a general photomask, the resolution and the depth of focus are as follows. R (resolution) = κ ₁ λ / NA (1) where κ ₁ is a proportional constant, λ is a light source wavelength at the time of exposure, and NA
Is the aperture (Numerical Apertur)
e). D. O. F (depth of focus) = κ ₂ −λ / (NA) ² (2) where κ ₂ is a proportionality constant.

In this resolution, as shown in FIG. 1, as the repetition period becomes smaller, the amplitude on the wafer becomes indistinguishable because the difference between valleys and peaks becomes smaller due to light diffraction between adjacent patterns. . Therefore, research for improving the resolution using phase inversion lithography has been conducted in various fields.

[0006] In phase inversion lithography, a light-transmitting region that transmits irradiated light as it is and a light-transmitting region that makes a 180 ° phase transition by using a phase-inverting substance are arranged by interposing a light-shielding pattern and combined. This is a technique in which the light-transmitting region is used as an entire light-transmitting region, and the light-shielding region can offset the diffraction between the light-transmitting regions, thereby reducing the problem due to light diffraction. Accordingly, various lithography techniques have been developed so that a pattern image close to a mask image can be formed by steeply modulating the light intensity, and a very complicated pattern can be transferred.

The phase inversion mask includes a Levenson type mask in which a light transmitting film for inverting the phase of light is formed in one of the light transmitting regions adjacent to each other, and an edge portion of two different light transmitting regions. There is an edge emphasis type mask or the like that inverts the phase to lower the light sensitivity.

An edge-enhancement type phase inversion mask has a pattern of a phase inversion material formed wider than a width of a light shielding layer formed below the phase inversion material, and the pattern of the phase inversion material is used as an edge mask. By manufacturing by selectively wet etching the sidewalls on both sides, the effect of the phase inversion layer can be exhibited by the width of the etched light shielding layer.

Such a conventional phase inversion mask will be described below with reference to the drawings. 2 and 3
2A is a sectional view showing a process of a conventional edge-enhancement type phase inversion mask. As shown in FIG. 2A, chromium (Cr) 2 which is a light-shielding metal is vapor-deposited on a transparent substrate 1. (1) The photosensitive film 3 is deposited. Then, the light shielding pattern area is limited as shown in FIG.
As shown in (c), the chromium 2 layer is selectively removed so that the chrome layer remains only in the light shielding region. As shown in FIG. 2 (d), the first photosensitive film 3 is removed, the second photosensitive film 4 is thickly deposited on the entire surface, and exposed and developed on the substrate side, and light is shielded as shown in FIG. 3 (e). The photosensitive film 4 is patterned so as to remain only between the regions. Then, as shown in FIG. 3F, a phase inversion layer 5 such as a silicon oxide film is deposited. At this time, the step is large because the patterned photosensitive film 4 is formed thick. For this purpose, the phase inversion layer 5 is discontinuously deposited. Therefore, as shown in FIG. 3G, the photosensitive film 4 and the phase inversion layer 5 formed thereon are selectively removed by the lift-off method. Then, as shown in FIG. 3 (h), the chromium 2 formed in the light shielding region by the wet etching process is over-etched.

On the other hand, FIGS. 4 and 5 are sectional views showing steps of a conventional spatial frequency modulation type phase inversion mask. A conventional method of manufacturing a spatial frequency modulation type phase inversion mask is shown in FIG.
As shown in FIG. 4A, a chromium layer 2 and a first photosensitive film 3 are sequentially deposited on a transparent substrate 1 and selectively exposed and developed with an electron beam only in a light-transmitting region. Is patterned so that the first photosensitive film 3 remains only on the light-shielding region.
As shown in FIG. 4C, the exposed chrome layer 2 is selectively removed using the patterned first photosensitive film 3 as a mask. As shown in FIG. 4 (d), the first photosensitive film 3 is removed, the second photosensitive film 4 is thickly deposited on the entire surface, and the light-transmitting region is selectively exposed with an electron beam. At this time, instead of exposing the entire light-transmitting area, every other light-transmitting area is exposed. As shown in FIG. 5E, the portion of the second photosensitive film 4 which has been developed and exposed is removed. As shown in FIG. 5F, a phase inversion layer 5 such as a silicon oxide film (SiO ₂ ) is deposited. At this time, the second photosensitive film 4 is also deposited thickly and a large step is generated, so that the phase inversion layer 5 is deposited on the entire surface but discontinuously. As shown in FIG. 5G, the second photosensitive film 4 and the phase inversion layer 5 formed thereon are selectively removed by a lift-off method to manufacture a conventional spatial frequency modulation type phase inversion mask. I do.

The conventional edge-enhancement type phase inversion mask manufactured as described above inverts the phase at the edge of the light-shielding pattern, and the spatial frequency modulation type phase-inversion mask is used for the light in one of the light-transmitting regions adjacent to each other. Is inverted.

FIG. 6 shows a conventional auxiliary pattern enhancement type (Ou
This is a layout of a phase inversion mask (trigger sub resolution), in which fine auxiliary patterns B and B ′ are formed in the periphery of the light transmitting region A in a portion where an actual pattern is formed, and the Interference development due to diffraction is prevented.

A method of manufacturing such a conventional auxiliary pattern emphasis type phase inversion mask will be described as follows. First, when an attempt is made to prevent interference development due to light diffraction using an auxiliary pattern, the width between the light-transmitting region A, which is a part for forming an actual pattern, and the fine auxiliary patterns B, B 'around the light-transmitting region A is considered. Must have a ratio of 3: 1, and a light-shielding area between the light-transmitting area A, which is a part for forming an actual pattern, and each of the fine auxiliary patterns B, B 'around the area. C and C 'must have the same width as the light-transmitting region A of the portion for forming the actual pattern. Therefore, the ratio of each area B ', C', A, C, B must be 1: 3: 3: 3: 1. With such a ratio, optical characteristics for canceling the diffraction of light generated from the edge portion of the light transmitting region A, which is a portion for forming an actual pattern, can be obtained.

At present, in the manufacture of a phase inversion mask of the auxiliary pattern emphasis type, when a portion of a light-transmitting region where an actual pattern is to be formed is about 0.4 μm, the fine auxiliary pattern has a width of about 0.15 μm. Formed. Since the width of the pattern is fine, patterning must be performed using an electron beam.

According to the manufacturing method, chromium (Cr), which is a light-shielding metal, is deposited on a transparent glass substrate, and a photoresist film for an electron beam is adhered thereon. Then, the photoresist film is developed by selectively irradiating the electron beam to the light transmitting region A, which is a portion for forming an actual pattern, and the fine auxiliary patterns B, B 'around the light transmitting region A. After the region is limited, the chromium layer is selectively removed using the remaining photoresist film as a mask, thereby manufacturing an auxiliary pattern emphasis type phase inversion mask.

[0016]

However, such a conventional method for manufacturing a phase shift mask has the following problems. (1) In the case of an edge emphasis type phase inversion mask, an undercut phenomenon occurs when isotropic wet etching is performed on an edge portion of a light-shielding region, so that it is difficult to expect an accurate phase inversion effect. (2) The pattern of the phase inversion layer and the pattern of the light shielding metal layer formed on the transparent substrate are reverse CD (Reverse
Since the mask has a critical dimension (Critical Dimension) structure, it is difficult to correct a defect generated in the mask. (3) In the case of a spatial frequency modulation type phase inversion mask, the phase inversion effect is better than that of the edge emphasis type, but a photomask step is further added to selectively form a phase inversion layer in the light transmitting region. Is complicated.

(4) When forming the auxiliary pattern emphasis type phase inversion mask, as described above, the light transmitting region A for forming the actual pattern and the fine auxiliary patterns B and B 'around the light transmitting region A are provided. The light-shielding regions C, between the light-transmitting region A, which is a portion for forming the actual pattern, and the fine auxiliary patterns B, B 'around the region.
The width of each of the regions B ', C', A, C and B such as C 'must have a predetermined ratio (1: 3: 3: 3: 1).
Considering that the width of the pattern is narrow, a repulsion or affinity between electrons charged up in the photoresist due to the electron beam occurs when the electron beam is exposed, so that it is difficult to form an accurate pattern width, Further, there are disadvantages such as a rise in price and a decrease in yield.

An object of the present invention is to solve such a problem, and an object of the present invention is to control the width of a pattern by the thickness of deposition without using an electron beam, thereby achieving ultra-precision. An object of the present invention is to provide an auxiliary pattern emphasis type phase inversion mask capable of manufacturing a semiconductor circuit.

[0019]

In order to achieve the above object, a method of manufacturing a phase shift mask according to the present invention comprises the steps of sequentially depositing a first light shielding metal layer and a second phase shift material layer on a transparent substrate. Defining a light-transmitting region for forming an actual pattern and a portion including the auxiliary patterns B and B 'of the light-transmitting region,
Selectively removing the first light-shielding metal layer and the first phase inversion material layer in the defined portion; and depositing and etching back the second phase inversion material layer on the entire surface to form the phase inversion material layer. Forming an arbitrary material having a high etching selectivity with respect to the first light-shielding metal layer and the first and second phase inversion material layers over the entire surface; Etching back the arbitrary material so that the surface of the second phase inversion material layer is sufficiently exposed; and etching the first and second phase inversion material layers to the height of the first light shielding metal. Backing and forming a phase inversion layer in the auxiliary patterns B and B 'regions, and depositing and etching back a second light shielding material layer on the entire surface to form a second light shielding material on the side wall of the phase inversion material. It is characterized in that it includes a step of forming a material wall.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a phase shift mask according to the present invention will be described below in more detail with reference to the accompanying drawings. 7 (a) to 7 (d) and FIGS. 8 (e) to 8 (h) are cross-sectional views (along line DD in FIG. 9) showing the manufacturing steps of the phase shift mask of the present invention. FIG. 9 is a plan view of a phase shift mask according to the present invention.

First, in the method of manufacturing a phase shift mask according to the present invention, as shown in FIG. 7A, a chromium (Cr) layer 1 serving as a first light-shielding metal is formed on a transparent substrate (glass or quartz) 11.
2 and a first phase inversion material layer 13 and a photosensitive (photoresist) film 14 are sequentially deposited. At this time, the chrome layer 12
Is determined by a phase inversion layer formed in a later step. The first phase inversion material layer 13 has the same etching characteristics (etch selectivity) as the second phase inversion material layer 15 described later.

That is, the refractive index of the phase inversion layer is n,
Assuming that the wavelength of exposure to be used is λ, the height (thickness) d of the chromium layer 12 is given by the following equation. d = λ / 2 (n−1) (3) Accordingly, the chromium layer 12 is formed by adjusting the height (thickness) of the chromium layer 12 using the equation (3).

As shown in FIG. 7B, a light transmitting area A for forming an actual pattern as described in the prior art is used.
And fine auxiliary patterns B and B 'in the periphery thereof, and light-transmitting regions A and light-shielding regions C and C' between the fine auxiliary patterns B and B 'for forming actual patterns. A light-shielding chrome pattern 12a is formed by defining a portion and selectively removing the chromium (Cr) layer 12 and the first phase inversion material layer 13 as the first light-shielding metal in the defined portion. .

As shown in FIG. 7C, after the photosensitive film 14 is removed, the chromium pattern 12 which is the first light shielding metal is removed.
A second phase inversion material layer 15 is deposited on the entire surface of the transparent substrate 11 on which a is formed. At this time, the second phase inversion material layer 1
5 is deposited uniformly over the entire surface and is deposited to the same thickness as the width of the auxiliary patterns B and B '.

The second phase inversion material layer 15 is etched by an anisotropic etching process such as an ion milling method or an RIE (reactive ion etching) method to form a light-shielding chrome pattern 12a and a first phase inversion material layer. 13
The side wall 16 of the phase inversion material is formed on the side surface as shown in FIG. On the entire surface of the obtained structure, a photosensitive film (photoresist) 17 having a higher etching selectivity than the phase inversion material layers 13 and 15 is deposited so that its surface becomes flat.

The photosensitive film is etched back by an anisotropic etching process such as RIE as follows. That is, as shown in FIG. 8E, the surfaces of the first and second phase inversion material layers 13 and 16 are sufficiently exposed, and the remaining photosensitive film 1 is left.
The photosensitive film is etched back so that 7 remains at the height of the chrome pattern 12a.

As shown in FIG. 8F, using the photosensitive film 17 as a mask, the first and second phase inversion material layers 1 are used.
3 and 16 are etched back by an anisotropic etching process such as RIE. As described above, since the etching characteristics of the first and second phase inversion material layers 13 and 16 are the same, when the entire first phase inversion material layer 13 is removed, the height of the chromium pattern 12a is reduced. Auxiliary pattern B,
The phase inversion layer 15a is formed in the B 'region.

Subsequently, a second light-shielding material layer 18 is deposited on the entire surface of the structure obtained as shown in FIG. At this time, the second light-shielding material layer 18 is formed by depositing a metal such as tungsten or amorphous silicon by a low-pressure CVD method. The thickness of the vapor deposition is the exposure wavelength λ or the light shielding areas C and C ′.
Is deposited in consideration of the size of the substrate.

That is, the desired width of the light-transmitting region A and the light-shielding regions C and C 'is obtained at the time of anisotropic etching in the subsequent step, and the phase is sufficiently inverted between the phase inversion layer and the pattern region. The thickness of the second light shielding material layer is adjusted.

As shown in FIG. 8H, the second light-shielding material layer 18 is etched back by an anisotropic etching process such as ion milling or RIE to form the phase inversion layer 15.
A second light-shielding material wall 19 is formed on the side wall of FIG.

Therefore, the phase shift mask of the present invention thus manufactured is formed as shown in FIG. That is,
Between the light transmitting region A for forming the actual pattern and the fine auxiliary patterns B and B 'around the light transmitting region A and the light transmitting region A and the fine auxiliary patterns B and B' for forming the actual pattern The portion including the light-shielding regions C and C ′ is primarily limited, and the light-shielding chrome pattern 12
a, and a phase inversion layer 15a is formed on the side surface of the light-shielding chrome pattern 12a so as to have a width of the auxiliary patterns B and B '.
It has a structure in which the wall 19 of the second light-shielding material layer 18 is formed on the side surface of the phase inversion layer 15a.

The light amplitude and light intensity of such a phase inversion mask of the present invention have characteristics as shown in FIG.

[0033]

As described above, the phase shift mask of the present invention has the following effects. (1) Another mask step for forming a phase inversion layer (ie, electron beam or photolithography step)
Is not required, so that the entire process is simplified. (2) Each region A ', B, B', C, and C, depending on the thickness of the deposition, without using a patterning process using an electron beam.
Since the width of C ′ can be determined and pattern errors due to affinity or repulsion between charged electrons can be prevented, a more precise semiconductor circuit can be designed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a general mask structure and the light amplitude and light intensity resulting therefrom.

FIG. 2 is a process sectional view (first half) of a conventional edge-enhancement type phase shift mask.

FIG. 3 is a process sectional view (second half) of a conventional edge-enhancement type phase shift mask.

FIG. 4 is a process sectional view (first half) of a conventional spatial frequency modulation type phase inversion mask.

FIG. 5 is a process sectional view (second half) of a conventional spatial frequency modulation type phase inversion mask.

FIG. 6 is a layout of a conventional auxiliary pattern B, B ′ emphasized phase inversion mask.

FIG. 7 is a process sectional view (first half) of a phase shift mask of the present invention.

FIG. 8 is a process sectional view (second half) of the phase inversion mask of the present invention.

FIG. 9 is a plan view of the phase shift mask of the present invention.

FIG. 10 is a diagram showing light amplitude and light intensity of the phase inversion mask of the present invention.

[Explanation of symbols]

11 ... substrate, 12 ... chrome layer (as first metal layer for light shielding), 12a ... chrome pattern for light shielding, 13 ... (first
A) phase inversion material layer, 14, 17 ... photosensitive film, 15 ... (second) phase inversion material layer, 15a ... phase inversion layer, 16 ... side wall of phase inversion material layer, 18 ... second light shielding material layer, 19 ...
Second light-shielding material wall, A: light-transmitting region, B, B ': fine auxiliary pattern.

Claims (6)

(57) [Claims] 1. A light-transmitting region for forming an actual pattern and an auxiliary pattern for the light-transmitting region by sequentially depositing a first light-shielding metal layer and a first phase-inversion material layer on a transparent substrate. Defining a portion, selectively removing the first light-blocking metal layer and the first phase inversion material layer in the defined portion; and depositing a second phase inversion material layer on the entire surface Forming a side wall of the phase inversion material by etching back; and an arbitrary etching selectivity greater than the first light shielding metal layer and the first and second phase inversion material layers over the entire surface. A step of depositing a substance evenly and etching back the arbitrary substance so that the surfaces of the first and second phase inversion substance layers are sufficiently exposed; Etching the first and second phase inversion material layers Backing and forming a phase inversion layer in the auxiliary pattern area; and depositing and etching back a second light shielding material layer on the entire surface.
Forming a wall of a second light-shielding substance on a side wall of the phase inversion layer. 2. The height d of the first light-shielding metal layer is represented by a relational expression of d = λ / 2 (n−1), where n is the refractive index of the phase inversion layer, and λ is the exposure wavelength to be used. The method for manufacturing a phase inversion mask according to claim 1, wherein: 3. The method according to claim 1, wherein the arbitrary material is formed of a photosensitive film. Wherein said second light-shielding material, method of manufacturing a phase shift mask according to claim 1, characterized in that it is formed by amorphous Shitsushi silicon or tungsten by low-pressure CVD. 5. The method according to claim 1, wherein the arbitrary substance is etched back to a height of the first light shielding metal layer.
A manufacturing method of the phase inversion mask described in the above. 6. A pattern width ratio of the phase inversion layer, the second metal layer for light shielding, and a light transmitting region for forming an actual pattern to be 1: 3: 3. The method according to claim 1, wherein the method is performed.