JPH07152142A - Phase shift mask - Google Patents

Abstract

PURPOSE:To provide a halftone type phase shift mask capable of respectively exactly setting both of transmittance of light and phase differences of light between shift parts and non-shifter parts. CONSTITUTION:Translucent phase shifters 2 have partial transmitability to projection exposing light and impart the phase differences to this projection exposing light. A substrate in the non-shifter parts is removed by depth (d) in order to impart the phase difference to the projection exposing light. The phase difference imparted by the removed amt. of the non-shifter parts, defined as phi1 and the phase difference imparted by the translucent phase shifters 2, defined as phi0, are set at phi0<180 deg., phi0+phi1=180 deg.+ or -nX360 deg. (n is an integer). The light transmittance is controlled with good accuracy by film formation of the translucent phase shifters 2 and the phase differences are accuracy controlled by film formation of the translucent phase shifters 2 and digging down of the substrate 1. Both of the light transmittance and the phase differences are eventually exactly controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention enables a high resolution pattern transfer by imparting a phase difference to a photomask having a pattern used in a projection exposure apparatus, and in particular, the projection exposure light passing through the photomask. It relates to a phase shift mask.

[0002]

2. Description of the Related Art Conventionally, various types of phase shift masks have been proposed. For example, a Levenson-type phase shift mask having a structure in which a transparent film is provided to invert the phase in one of the openings on the mask, or a phase shifter below the resolution limit is formed in the peripheral portion of the pattern to be formed. There are a phase shift mask with an auxiliary pattern of a structure, a self-aligned phase shift mask with a structure in which a chrome pattern is formed on a substrate and then overhangs of a phase shifter are formed by overetching.

The phase shift mask of each of the above structures is one in which a chrome pattern and a shifter pattern are provided on a substrate. In addition to this structure, a transmission type phase shift mask is formed as a phase shift mask formed only by the shifter pattern. A shift mask, a halftone type phase shift mask, etc. are also known. The transmissive phase shift mask is a phase shift mask that separates the pattern by utilizing the fact that the light intensity becomes zero at the boundary between the light transmitted through the transparent part and the light transmitted through the phase shifter. Therefore, it is also called a shifter edge type phase shift mask.

The halftone type phase shift mask is a so-called semitransparent phase shifter pattern having partial transmissivity for projection exposure light formed on a substrate and formed at a boundary portion of the phase pattern. The phase shift mask is designed to improve the resolution of the pattern in the portion where the light intensity is zero. Since the transmission type phase shift mask and the halftone type phase shift mask have a simple layer structure, they have an advantage that the manufacturing process is easy and there are few defects on the mask.

[0005]

By the way, in the case of producing a phase shift mask having a single layer structure as one of the methods for producing a halftone type phase shift mask, a semitransparent layer which will be a shifter later is formed on a transparent substrate such as quartz. Film uniformly on
A so-called blank is produced, and the blank is subjected to an etching treatment or the like to form a semitransparent shifter having a desired pattern. When producing the blanks as described above, conventionally, a semi-transparent layer is formed on the substrate by using a film forming method such as sputtering or vacuum deposition,
In this film forming method, it is very difficult to accurately set both the light transmittance of the semitransparent layer and the retardation imparted to the light transmitted through the semitransparent layer to desired values.

The present invention has been made in order to solve the above problems, and sets both the light transmittance and the light phase difference between the shifter portion and the non-shifter portion to desired values. It is an object to provide a halftone type phase shift mask that can be set accurately.

[0007]

In order to achieve the above object, a phase shift mask according to the present invention is provided with a substrate and a pattern formed on the substrate so as to have partial transparency to projection exposure light. And a semitransparent phase shifter for imparting a phase difference between the projection exposure light and the transparent portion. The substrate of the non-shifter portion is removed to a predetermined depth in order to add a phase difference to the projection exposure light. Now, when the phase difference imparted by the removal amount of the non-shifter portion is φ ₁ and the phase difference imparted by the semitransparent phase shifter is φ ₀ , φ ₀ <180 ° φ ₀ + φ ₁ = 180 It is set as follows: ° ± n × 360 ° (n is an integer).

That is, in FIG. 2A, regarding the semi-transparent shifter 2 formed on the substrate 1, only the transmittance T is accurately controlled at the time of film formation, and the transmissivity T is given to the light transmitted therethrough. Regarding the phase difference φ, an appropriate value smaller than 180 °, for example, 50 ° <φ <180 °, preferably 90 °
It is set so that ° <φ <180 °. And 1
As shown in FIG. 2 (b), the phase difference of 80 ° is insufficient, as shown in FIG.
Make up by just digging. At this time, the transmittance T does not change even if the substrate 1 is dug down.

[0009]

In the phase shift mask of the present invention, first, a film for a semitransparent shifter is formed so as to exhibit a phase difference smaller than 180 °, and the remaining phase difference of 180 ° or less is caused by etching the substrate. Complement by processing by.
Thereby, the light transmittance is accurately controlled by forming the semi-transparent shifter film, and the phase difference is accurately controlled by forming the semi-transparent shifter film and substrate processing. As a result, the transmittance and the phase difference are controlled. Both create a halftone phase shift mask with precise control. In this case, it is desirable that the value of the phase difference to be compensated by processing the substrate is set to 90 ° or less. That is, the phase difference φ produced by the blank-state translucent shifter film is 90 ° <φ <18.
It is desirable to set it to 0 °.

The reason is as follows. That is,
If a large phase difference close to 180 ° is to be compensated by processing the substrate, the substrate must be dug down to a considerably deep place by etching or the like. There is a very high possibility that the defect will be transferred as a black spot on an exposure target object, for example, a resist-coated single crystal wafer during the projection exposure using. On the other hand, if the phase difference to be compensated for by the substrate processing is set to 90 ° or less, even if a defect as indicated by the symbol K in FIG. This is because the phase difference is so small that the transfer is hardly performed.

[0011]

1 shows an embodiment of a phase shift mask according to the present invention, that is, a halftone type phase shift mask. This phase shift mask has a substrate 1 formed of transparent glass or transparent synthetic quartz, and a semitransparent shifter 2 formed on the substrate 1 in a predetermined pattern. The portion where the semitransparent shifter 2 is not formed, that is, the non-shifter portion of the substrate 1 is dug down by a depth d by processing such as etching. When an object to be exposed, for example, a single crystal wafer (not shown) is exposed using this phase shift mask, projection exposure light is irradiated from the direction of arrow L, and the light transmitted through the phase shift mask is the object to be exposed. And a desired light image pattern is formed on the object to be exposed.

The semitransparent shifter 2 is formed of, for example, chromium oxide, chromium nitride, chromium fluoride, iron oxide or a mixture thereof, and the transmittance T for projection exposure light is set to 1% <T <30%. . Further, the light La that passes through the semitransparent shifter 2 and the light L that passes through the non-shifter portion
The phase difference with b is set to 180 °, and the action of this phase difference improves the resolution of the light image on the exposure object. In the present invention, the phase difference φ covered by the semitransparent shifter 2 is 50 ° <φ <180 °, preferably 9 °.
The setting is made to 0 ° <φ <180 °, and the remaining phase difference which is not 180 ° is compensated by the depth d of the substrate 1.

Thus, the transmissivity is controlled by the semitransparent shifter 2, and the phase difference is controlled by the semitransparent shifter 2 and the processing depth d of the substrate 1. As a result, both the transmissivity and the phase difference are accurately controlled. ing.

An example of a method of manufacturing the phase shift mask shown in FIG. 1 will be described below in the order of steps.

As shown in FIG. 3, a semitransparent shifter film 2'is uniformly formed on a substrate 1 made of glass, synthetic quartz or the like by sputtering, vacuum deposition or the like, and a blank 3 is formed.
To make. The semi-transparent shifter film 2'is formed of one layer or two layers of chromium oxide, chromium nitride, chromium fluoride, iron oxide or a mixture thereof, and the transmittance T and the phase difference φ for projection exposure light are, for example, , T = 10% φ = 120 ° is set. This setting is performed by adjusting the film thickness of the semitransparent shifter film 2 ′, the mixing ratio of the composition components, and the like.

Next, a resist 4 (for example, manufactured by Toray: trade name EBR-9) is applied (FIG. 4) and a desired pattern is formed as a latent image by electron beam exposure or the like (FIG. 5).
A development process is performed to form the resist 4 in a desired pattern (FIG. 6). Then, an etching process is performed to form a semitransparent shifter 2 having a desired pattern from the semitransparent shifter film 2 '(FIG. 7). For etching chromium-based thin films,
For example, dry etching, wet etching using a ceric ammonium nitrate solution, or the like is applied. Hydrochloric acid is used for the iron oxide thin film.

After that, as shown in FIG. 8, the substrate 1 is processed by wet etching using HF (hydrofluoric acid), dry etching using CF ₄ (carbon tetrafluoride) or the like, and is dug down to a depth d. This digging depth d is set as follows, for example. d = (60/360) × {λ / (n-1)} where λ: wavelength of projection exposure light n: refractive index of the substrate 1 This dug depth d is the phase difference (φ = due to the semitransparent shifter 2). 120 °) is insufficient for 180 °, that is, the depth is enough to give a phase difference of (180 ° −φ).

[0018] Then, for example, removing the resist 4 by 0 ₂ plasma ashing, finished products halftone phase shift mask shown in FIG. 1 is completed. The reflectance of the surface of the semitransparent shifter 2 with respect to the projection exposure light is 2
It is desirable to set it to 0% or less. The reason is to prevent so-called transfer fog, which disturbs the optical image on the exposure object by the light reflected by the surface of the semitransparent shifter 2 when performing projection exposure using the present phase shift mask. is there.

The present invention has been described above with reference to the preferred embodiments, but the present invention is not limited to the embodiments and can be variously modified within the technical scope described in the claims.

For example, a halftone semitransparent phase shifter can be formed by forming a semitransparent layer made of a conductive material on the surface layer of the transparent phase shifter or the layer between the transparent phase shifter and the substrate. By providing this semi-transparent layer,
It can play a role similar to a single-layer translucent phase shifter layer such as chromium oxide or iron oxide. Furthermore,
Due to the charge-up (charging) caused by the charged particles injected during electron beam exposure, the electron beam may be bent during subsequent electron beam exposure and accurate pattern formation may not be possible. Conveniently, a conductive layer is formed to escape to the ground wire. As the conductive material, metal chromium, indium oxide, tin oxide, a mixture of indium oxide to tin oxide, or the like can be used.

Further, the phase difference between the semi-transparent shifter portion and the non-shifter portion is not necessarily limited to 180 °, and theoretically may be any value obtained by adding an integral multiple of 360 °. it can. The light transmittance T of the semitransparent phase shifter is preferably 1 to 30 with respect to the projection exposure light.
It can be set to any value other than 10% within the range of%.

[0022]

According to the phase shift mask of the first aspect, both the light transmittance and the light phase difference between the shifter portion and the non-shifter portion are set to desired values for the halftone type phase shifter. Can be set accurately.

[0023]

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an embodiment of a phase shift mask according to the present invention.

FIG. 2 is a cross-sectional view schematically showing a manufacturing process of the same phase shift mask.

FIG. 3 is a schematic view showing a manufacturing process of the same phase shift mask, in particular, a state in which a film for a semitransparent shifter is formed and a blank is manufactured.

FIG. 4 is a schematic view showing a manufacturing process of the same phase shift mask, particularly a state in which a resist is applied.

FIG. 5 is a schematic view showing a manufacturing process of the same phase shift mask, in particular, a state of pattern exposure of a resist.

FIG. 6 is a schematic view showing a manufacturing process of the same phase shift mask, particularly a state in which a resist is developed into a predetermined pattern.

FIG. 7 is a schematic view showing a manufacturing process of the same phase shift mask, particularly a state in which a semi-transparent shifter having a predetermined pattern is formed.

FIG. 8 is a schematic view showing a process of manufacturing the same phase shift mask, particularly a state in which the substrate is dug down by etching.

[Explanation of symbols]

 1 Substrate 2 Semitransparent shifter 2'Semitransparent shifter film 3 Blanks 4 Resist

Claims (6)

[Claims] 1. A substrate and a semitransparent phase formed on the substrate in a pattern and having partial transparency to projection exposure light and imparting a phase difference to the projection exposure light and a transparent portion. The shifter has a non-shifter portion, and the substrate of the non-shifter portion has been removed by a predetermined depth in order to add a phase difference to the projection exposure light, and the phase difference imparted by the removal amount of the non-shifter portion. Is φ ₁ and the phase difference provided by the semitransparent phase shifter is φ ₀ , φ ₀ <180 ° φ ₀ + φ ₁ = 180 ° ± n × 360 ° (n is an integer) And a phase shift mask. 2. The phase shift mask according to claim 1, wherein the semitransparent phase shifter is formed of chromium oxide, chromium nitride, chromium fluoride, iron oxide or a mixture thereof. 3. The phase shift mask according to claim 1, wherein a layer made of a conductive material is formed on one of the front and back layers of the semitransparent phase shifter. 4. The phase shift mask according to claim 3, wherein the conductive material is metallic chromium, indium oxide, tin oxide, or a mixture of indium oxide and tin oxide. 5. The phase shift mask according to claim 1, wherein the semitransparent phase shifter has a reflectance of 20% or less with respect to projection exposure light. 6. The phase shift mask according to claim 1, wherein the semitransparent phase shifter has a light transmittance of 1 to 30% with respect to projection exposure light.