JPH06332152A - Phase shift mask and phase shift mask blank - Google Patents

Abstract

PURPOSE:To provide the phase shift mask which can be produced while the generation of microdefects is suppressed with relatively simple stages and with which pattern transfer with a high resolution is possible and the phase shift mask blank which is the blank material thereof. CONSTITUTION:The mask patterns to be formed on a transparent substrate 1 of this phase shift mask are composed of light transparent parts 4 which allow the transmission of light of the intensity substantially contributing to exposing and light translucent parts 2 which allow the transmission of the light of the intensity substantially contributing to exposing. The phase shift mask is so formed that the phase of the light past the light translucent parts 2 and the phase of the light past the light transparent parts 4 are varied by shifting the phase of the light passing the light translucent parts 2, by which the light rays passing near the boundary parts of the light transparent parts 4 and the light translucent parts 2 are negated with each other and the contrast in the boundary parts is well maintained. The light translucent parts 2 are composed of thin films consisting of materials consisting of oxygen, molybdenum and silicide as main constituting elements.

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 capable of improving the resolution of a transfer pattern by giving a phase difference between exposure lights passing through the mask, and a phase shift mask blank as a material thereof. In particular, it relates to a so-called halftone type phase shift mask and a phase shift mask blank as a material thereof.

[0002]

2. Description of the Related Art In manufacturing a semiconductor LSI or the like, a phase shift mask is used as one of photomasks for transferring a fine pattern. This phase shift mask is capable of improving the resolution of the transfer pattern by giving a phase difference between the exposure lights passing through the mask. As one of the phase shift masks, the phase shift mask described in Japanese Patent Application Laid-Open No. 4-136854 is known as being particularly suitable for transferring an isolated pattern such as a single hole, dot or line.

In the phase shift mask described in this publication, a mask pattern formed on a transparent substrate is provided with a light transmitting portion that transmits light having an intensity that substantially contributes to exposure and a light transmitting portion that does not substantially contribute to exposure. A light-semitransmissive portion to be transmitted, and the phase of light passing through the light-semitransmissive portion is shifted so that the phase of light passing through the light-semitransmissive portion is the phase of light transmitted through the light-transmissive portion. By arranging so that the light passing through the vicinity of the boundary between the light transmitting portion and the light semi-transmitting portion cancels each other out, the contrast of the boundary is maintained well. It was made possible. This type of phase shift mask is called a so-called halftone type phase shift mask.
In this phase shift mask, since the light semi-transmissive portion has both the light shielding function of substantially blocking the exposure light and the phase shifting function of shifting the phase of the light, the light shielding film pattern and the phase shift mask are provided. It also has a feature that it is not necessary to separately form a film pattern, the structure is simple, and the manufacturing is easy.

By the way, the light semi-transmissive portion in the above-mentioned halftone type phase shift mask needs to have required optimum values for both the light transmittance and the phase shift performance. Here, when the light semi-transmissive portion is made of one kind of material, it is necessary to simultaneously satisfy both conditions by selecting its thickness.
So far, no suitable material has been developed that can sufficiently satisfy such conditions.

For this reason, the light semi-transmissive portion has a multi-layer structure composed of a plurality of kinds of materials of a high transmittance layer and a low transmittance layer,
By adjusting the light transmittance mainly to a predetermined value with the low transmittance layer and mainly adjusting the phase shift amount with the high transmittance layer, both the values of the light transmittance and the phase shift amount are optimized. It is considered to be easy to set. 3 and 4 are partial sectional views of a phase shift mask in which the light semi-transmissive portion has a multi-layer structure. In the example shown in FIG. 3, a stopper film 11 is formed on a transparent substrate 10, and an SOG (coated glass; spin-on-glass) film 1 which is a high transmittance layer is formed on the stopper film 11.
2 is formed, and a chromium film 13 as a low transmittance layer is further formed on the SOG film 12. Further, in the example shown in FIG. 4, the chrome film 13 is formed on the transparent substrate 10, and the SOG film 12 is formed on the chrome film 13.

[0006]

However, the above-mentioned light-semitransmissive part having a multi-layer structure has the following problems.

That is, since SOG is used as the material for the high transmittance layer and chromium is used as the material for the low transmittance layer, high transmittance is achieved when etching is performed to form the mask pattern. It is necessary to use different types of etching media when etching the SOG film 12 that is the high-permeability layer and when etching the chromium film 13 that is the low-transmittance layer. For example, if both are dry etched to suppress side etching, the
As an etching gas for etching the G film 12, C
F ₄ , CHF ₃ , SF ₆ , C ₂ F ₆ , NF ₃ , CF ₄ +
A fluoride-based gas such as H ₂ or CBrF ₃ is used. On the other hand, when the chromium film 13, which is the low transmittance layer, is etched, it is necessary to use a chlorine-based gas such as CCl ₄ and Cl ₂ . If these etchings are performed in the same etching apparatus, the etching gas before may mix with the etching gas after and the etching conditions may be disturbed. Further, in order to prevent this possibility, it is necessary to prepare an extra etching device in order to perform etching with different etching devices, and it is necessary to transfer the substrate from one etching device to the other etching device. Further, there is a problem that foreign matters such as dust may adhere to the substrate during the transfer to cause a pattern defect. Moreover, since SOG having a low refractive index is used, there is a problem that the pattern difference of the photomask is large, which is disadvantageous from the viewpoint of pattern damage during cleaning or cleaning performance such as foreign matter removal.

The present invention has been made under the background described above, and a phase shift mask and a phase shift mask which can be manufactured while suppressing the generation of microdefects by a relatively simple process and which enables high-resolution pattern transfer. The purpose is to provide a phase shift mask blank as the material.

[0009]

In order to solve the above-mentioned problems, a phase shift mask according to the present invention is (Structure 1) a mask for performing fine pattern exposure, which is a mask pattern formed on a transparent substrate. Is composed of a light transmissive portion that transmits light of intensity that substantially contributes to exposure and a light semi-transmissive portion that transmits light of intensity that does not substantially contribute to exposure, and passes through this light semi-transmissive portion. By shifting the phase of the light passing through the light-semitransmissive portion and the phase of light passing through the light-transmissive portion to make the phase difference between the light-transmissive portion and the light-semitransmissive portion. A phase shift mask capable of maintaining good contrast at a boundary portion by canceling out light passing through each other, wherein the light semi-transmissive portion contains oxygen, metal and silicon as main constituent elements. From As a mode of this configuration 1, as a mode of this configuration 1, the phase shift mask of configuration 1 is characterized in that the constituent metal of the substance forming the thin film is molybdenum, (Structure 3) In the phase shift mask of Structure 1 or 2, the thin film has an oxygen content of 35 to 60 atom%, and as an aspect of any one of Structures 1 to 3, Configuration 4) In the phase shift mask of Configuration 1 or 3, the substance that constitutes the thin film is characterized in that its constituent elements also include nitrogen. Further, as an aspect of Configuration 4, (Configuration 5) Configuration In the phase shift mask of No. 4, the ratio between the amount of nitrogen and the amount of oxygen contained in the thin film is 0.2.
To 0.5, and as an aspect of Configuration 4 or 5, (Configuration 6) In the phase shift mask of Configuration 4 or 5, the thin film has another portion near the surface in the thickness direction. The phase shift mask blank according to the present invention is characterized by having a smaller oxygen content, and is used as a material of the phase shift mask of any one of (Structure 7) to (1). A phase shift mask blank, which is characterized in that a thin film made of a substance containing oxygen, metal and silicon as main constituent elements is formed on a transparent substrate. In the phase shift mask blank of configuration 7, the metal as a constituent element of the substance forming the thin film is molybdenum.

[0010]

According to the above-mentioned structure 1, the light semi-transmissive portion is
Since the light-semitransmissive part is composed of a single-layer film composed of one kind of material, it is possible to obtain both the light transmittance and the phase shift performance by forming the light-semitransmissive part by a thin film composed of a material mainly composed of metal and silicon. It has become possible to satisfy the required optimum values at the same time. In addition, like this,
The fact that a thin film made of a substance containing oxygen, a metal (for example, molybdenum, tantalum, or tungsten) and silicon as main constituent elements is suitable as a material forming the light semi-transmissive portion has been found by the present inventors. is there. In addition, since it can be made up of a single layer film, the manufacturing process can be made extremely simple, and since it is made up of a thin film having a high refractive index, the film thickness can be made extremely thin, and therefore the pattern difference of the mask can be made small, so that it is possible to reduce the cleaning time during cleaning. It is also advantageous from the viewpoint of the pattern damage or the cleaning property such as foreign matter removal.
According to the configuration 2, the features of the configuration 1 can be brought out most.

According to the structure 3, it is possible to obtain the light semi-transmissive portion having excellent characteristics.

According to the constitutions 4 to 5, the acid resistance of the thin film forming the light semi-transmissive portion can be improved, and at the same time, the thin film can be made highly selective in dry etching. The effect of doing is also obtained.

According to the sixth aspect, the thin film forming the light transmitting portion is made of a material having a high nitrogen content, which has a property that the surface portion in contact with acid is rich in acid resistance but has a low light transmittance. Since it is composed of a material with a high oxygen content that has poor acid resistance but high light transmittance, it is necessary to obtain a light-transmitting part with sufficient acid resistance while ensuring the required light transmittance. You can

Further, according to the structures 7 to 8, it is possible to obtain a phase shift mask blank which can be used as a material for the phase shift mask of the structures 1 to 6.

[0015]

1 is a partial sectional view showing a phase shift mask according to an embodiment of the present invention, and FIG. 2 is a partial sectional view showing a phase shift mask blank according to the embodiment. Hereinafter, the phase shift mask and the phase shift mask blank according to the embodiment will be described with reference to these drawings.

In FIG. 1, reference numeral 1 is a transparent substrate and reference numeral 2
Is a light semi-transmissive portion formed on the transparent substrate 1, reference numeral 4
Is a light transmitting portion.

The transparent substrate 1 is a quartz glass substrate (dimensions: length 5 inches, width 5 inches, thickness 0.09 inches) whose main surfaces (front and back surfaces) are mirror-polished.

The light-semitransmissive portion 2 is a substance containing oxygen, molybdenum and silicon as main constituent elements, for example, molybdenum oxide silicide (MoSiO), or an oxide containing nitrogen in addition to oxygen, molybdenum and silicon. It is composed of a thin film of molybdenum nitride silicide (MoSiON). In this embodiment, the i-line (wavelength λ = 365 nm) of a mercury lamp is used as the exposure light,
In order for the light semi-transmissive portion 2 to simultaneously obtain a predetermined amount of phase shift and a predetermined light shielding performance with respect to this exposure light,
Oxygen content (atomic%), nitrogen content (atomic%), film thickness d
(Angstrom), select the light transmittance.

In this case, when the phase shift amount is φ, the refractive index is n, and the wavelength of the exposure light is λ, the film thickness d is determined by the following equation (1).

D = (φ / 360) × {λ / (n−1)} (1) In the equation (1), the phase shift amount φ is preferably 180 °, but practically, It may be 160 ° ≦ φ ≦ 200 °. The light transmittance of the light transmitting portion 2 with respect to the exposure light depends on the sensitivity of the resist used for pattern formation, but is generally preferably 2 to 20%. The light transmittance of the light transmitting section 2 can be selected by selecting the oxygen content rate of the thin film forming the light semi-transmission section or the oxygen and nitrogen content rates.

FIG. 5 is a table showing Examples 1 to 9 in which the oxygen content rate or the oxygen and nitrogen content rates of the thin film constituting the light semi-transmission part are changed. In FIG. 5, the acid resistance was evaluated as ◯ when the change was not observed at all by soaking in H ₂ SO ₄ (120 ° C. hot concentrated sulfuric acid) for 2 hours. Was designated as Δ.

In FIGS. 5A and 5B, Examples 1 to 3 are examples in which the light semi-transmissive portion is composed of a thin film of molybdenum oxide silicide (MoSiO), and Examples 4 to 9 are those in which the light semi-transmissive portion is molybdenum oxynitride silicide (MoSiON). This is an example of a thin film. Of these, Example 9 is an example in which the oxygen content in the vicinity of the surface in the thickness direction of the thin film is smaller than that in other portions.

A procedure for manufacturing the phase shift mask having the above-described structure will be described with reference to FIG.

As shown in FIG. 2, first, the transparent substrate 1
A light semi-transmissive film 2a made of a thin film of molybdenum oxide silicide (MoSiO) (Examples 1 to 3) or a thin film of molybdenum oxynitride silicide (MoSiON) (Examples 4 to 9) is formed on the surface of the phase shifter. Obtain a mask blank.

The light semi-transmissive film 2a is formed by
In the case of Examples 1 to 3 in which a is composed of a thin film of molybdenum oxide silicide (MoSiO), it is performed as follows.

Molybdenum (Mo) and silicon (silicon; S
i) mixed target (Mo: Si = 1: 2 mol
%), And a mixed gas atmosphere of argon (Ar) and oxygen (O ₂ ) (Ar; 90-80%, O ₂ ; 10-20)
%, Pressure; 1.5 × 10 ⁻³ Torr) to form a thin film having a thickness of 1400 to 2000 Å on the transparent substrate 1 by reactive sputtering. In the case of Example 2, the film thickness was formed to 2000 angstroms in a mixed gas atmosphere of argon (Ar; 85%) and oxygen (O ₂ ; 15%). In this case, the film thickness is selected so that the phase difference is 180 °.

Further, in the case of Examples 4 to 9 in which the light semi-transmissive film 2a is composed of a thin film of molybdenum oxynitride silicide (MoSiON), it is carried out as follows. Molybdenum (M
o) and silicon (silicon; Si) mixed target (M
o: Si = 1: 2 mol%) and argon (Ar)
Mixed gas atmosphere of nitrogen and nitrous oxide (N ₂ O) (Ar; 8
4-72%, N ₂ O; 16-28%, pressure; 1.5 × 1
It is performed by forming a thin film having a film thickness of 1400 to 2000 angstrom on the transparent substrate 1 by reactive sputtering at 0 ^-3 Torr). In the case of Example 4, the film thickness was 1400 angstroms in a mixed gas atmosphere of argon (Ar; 84%) and nitrogen oxide (N ₂ O; 16%). Further, in this case, NO gas or O ₂ + N ₂ gas may be used instead of the nitric oxide (N ₂ O) gas. Furthermore, in Example 9, in order to make the oxygen content different in the film thickness direction, the partial pressure of Ar gas is controlled. FIG. 6 is a diagram showing the results of analyzing the composition of the light transmitting film of Example 9 by an Auger analyzer. The vertical axis in the figure represents the content (%) of each element, and the horizontal axis represents the sputtering time (minutes), that is, the position in the thickness direction.

Next, a resist film is formed on the light-semitransmissive film 2a of the phase shift mask blank thus obtained, and a series of well-known pattern forming treatments such as pattern exposure, development, etching and washing are carried out, and light is applied. A part of the semi-transmissive portion 2a is removed to obtain a phase shift mask in which a pattern of holes or dots is formed by the light transmissive portion 4 and the light semi-transmissive portion 2. Note that in this case, when the molybdenum oxide silicide film or the molybdenum oxynitride silicide film is etched by dry etching, CF _{4 is used} as an etching gas.
A + O ₂ mixed gas may be used.

As shown in FIG. 1, when the exposure light L0 is applied to the phase shift mask, the exposure light L0 is applied to the phase shift mask.
Is a light L1 which passes through the light semi-transmissive portion 2 and reaches a non-transfer member (not shown), and a light L which passes through the light transmissive portion 4 and reaches the non-transfer member.
Divided into 2. In this case, the intensity of the light L1 that has passed through the light semi-transmissive portion 2 is weak so that it does not substantially contribute to the exposure. On the other hand, the light L2 that has passed through the light transmitting portion 4 is a strong light that substantially contributes to the exposure. Therefore, by this, pattern exposure is performed. At that time, the light passing through the boundary between the light semi-transmissive portion 2 and the light transmissive portion 4 wraps around to the area of the other party due to the diffraction phenomenon, but the phases of the two light beams are substantially inverted, so they cancel each other out. It As a result, the light intensity on the non-transfer member in the boundary area becomes almost zero. Therefore, the boundary becomes very clear and the resolution is improved.

According to one embodiment described above, the light semi-transmissive portion 2
Is composed of a thin film made of a substance containing oxygen, molybdenum, and silicide as main constituent elements. Therefore, even if the light semi-transmissive portion 2 is formed of a single-layer film without having a multi-layer structure, the light transmittance and It has become possible to simultaneously satisfy the optimum values required for both phase shift performances.
Further, since the film is composed of one layer, the manufacturing process can be extremely simplified, and the film can be formed extremely thin because it is composed of a thin film having a high refractive index. Since it can be reduced to about 1/2 to 1/3 of the case of a two-layer structure of a chromium film and a chromium film, it is also advantageous from the viewpoint of pattern damage during cleaning or cleaning performance such as removal of foreign matter. Moreover, a thin film made of a substance having oxygen, molybdenum, and silicon as main constituent elements can be easily formed by a general film forming technique such as vapor deposition in addition to sputtering, and moreover, the oxygen content, or the oxygen and nitrogen contents can be reduced. The light transmittance and acid resistance can be controlled by adjusting and the etching selectivity in dry etching can be improved. Therefore, it is relatively easy to obtain a semi-transmissive portion having desired characteristics.

Further, since the film stress of the above-mentioned thin film is small, it is possible to reduce distortion of the mask and to secure excellent adhesion to a transparent substrate such as a quartz substrate.

In the above embodiment, molybdenum is used as a metal as a constituent element of the substance forming the light semi-transmissive portion, but tantalum or tungsten may be used.

In one embodiment, the i-line (365 nm) of the mercury lamp is used as the exposure light, but the present invention uses exposure light of other wavelengths, such as g-line (4 nm).
36 nm), KrF excimer laser light (248 nm)
Of course, it can be applied to the case of using the above. At this time, the refractive index and the absorptivity of the thin film for each exposure wavelength may be examined to adjust the oxygen and nitrogen content and the film thickness.

[0034]

As described in detail above, according to the present invention,
Since the light-semitransmissive portion is made of a thin film made of a substance whose main constituent elements are oxygen, molybdenum, and silicide, even if the light-semitransmissive portion is made of a single-layer film made of one kind of material, It is now possible to simultaneously satisfy the optimum values required for both the rate and the phase shift performance. In addition, since it can be made up of a single layer film, the manufacturing process can be made extremely simple, and since it is made up of a thin film having a high refractive index, the film thickness can be made extremely thin, and therefore the pattern difference of the mask can be made small, so that it is possible to reduce the cleaning time during cleaning. It is also advantageous from the viewpoint of pattern damage or cleaning properties such as foreign matter removal.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing the structure of a phase shift mask according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing the structure of a phase shift mask blank according to an embodiment of the present invention.

FIG. 3 is a partial cross-sectional view showing the structure of a phase shift mask having a two-layer structure.

FIG. 4 is a partial cross-sectional view showing the structure of a phase shift mask having a two-layer structure.

FIG. 5 is an explanatory diagram of Examples 1 to 9.

FIG. 6 is a diagram showing the results of analyzing the composition of the light semi-transmissive film of Example 9 with an Auger analyzer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transparent substrate, 2 ... Light semi-transmission part, 2a ... Light semi-transmission film, 4
… Light transmitting part.

Claims (8)

[Claims] 1. A mask for performing fine pattern exposure, wherein a mask pattern formed on a transparent substrate and a light transmitting portion for transmitting light having an intensity that substantially contributes to the exposure contributes substantially to the exposure. A light semi-transmissive portion that transmits light of a non-intensity, and shifts the phase of light passing through this light semi-transmissive portion to shift the phase of light passing through the light semi-transmissive portion and the light transmissive portion. By making the phase of the light passing therethrough different, the light passing through the vicinity of the boundary between the light transmitting portion and the light semi-transmitting portion cancels each other out so that the contrast at the boundary can be maintained well A phase shift mask, wherein the light-semitransmissive portion is formed of a thin film made of a substance containing oxygen, metal, and silicon as main constituent elements. 2. The phase shift mask according to claim 1, wherein the constituent metal of the substance forming the thin film is molybdenum. 3. The phase shift mask according to claim 1, wherein the substance forming the thin film has an oxygen content of 35 to 60 atom%. 4. The phase shift mask according to claim 1, wherein the substance forming the thin film includes nitrogen as a constituent element thereof. 5. The phase shift mask according to claim 4, wherein the ratio of the amount of nitrogen contained in the thin film to the amount of oxygen contained in the thin film is 0.2 to 0.5. . 6. The phase shift mask according to claim 4 or 5, wherein the thin film has a smaller oxygen content in the vicinity of the surface than in other portions in the thickness direction. mask. 7. A phase shift mask blank used as a material for the phase shift mask according to any one of claims 1 to 6, comprising: a substance having oxygen, metal and silicon as main constituent elements on a transparent substrate. A phase shift mask blank having a thin film formed thereon. 8. The phase shift mask blank according to claim 7, wherein the constituent metal of the substance forming the thin film is molybdenum.