JP2837807B2 - Phase shift mask and phase shift mask blank - 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 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 its material. In particular, it relates to a so-called halftone type phase shift mask and a phase shift mask blank as its material.

[0002]

2. Description of the Related Art A phase shift mask is used as one of photomasks as a mask for transferring a fine pattern when a semiconductor LSI is manufactured. This phase shift mask is designed to improve the resolution of a transfer pattern by giving a phase difference between exposure lights passing through the mask. As one of the phase shift masks, a phase shift mask described in Japanese Patent Application Laid-Open No. 4-136854 is known as one which is 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 formed by a light transmitting portion that transmits light having an intensity substantially contributing to exposure and light having an intensity not substantially contributing to exposure. A light transmissive portion, and a phase of light passing through the light transmissive portion is shifted by shifting a phase of light passing through the light semitransmissive portion. , The light passing near the boundary between the light transmitting portion and the light semi-transmitting portion cancels each other, thereby maintaining a good contrast at the boundary. It is made possible. This type of phase shift mask is commonly called a halftone type phase shift mask. In this phase shift mask, the light semi-transmissive portion has two functions of a light blocking function of substantially blocking exposure light and a phase shift function of shifting the phase of light.
There is no need to separately form the light-shielding film pattern and the phase shift film pattern, and the feature is that the configuration is simple and the manufacturing is easy.

Incidentally, the light semi-transmissive portion in the above-described halftone type phase shift mask needs to have required optimum values for both light transmittance and phase shift performance. Here, when the light semi-transmissive portion is made of one type of material, both conditions must be satisfied simultaneously by selecting its thickness,
Until now, no suitable material has been developed that can sufficiently satisfy such conditions.

[0005] For this reason, the light semi-transmissive portion has a multi-layer structure composed of a plurality of types of materials of a high transmittance layer and a low transmittance layer,
By adjusting the light transmittance to a predetermined value mainly by the low transmittance layer and adjusting the phase shift amount mainly by the high transmittance layer, the values of both the light transmittance and the phase shift amount are optimized. It is conceived to make it easy to set to. FIGS. 3 and 4 are partial cross-sectional views of a phase shift mask in which a light semi-transmissive portion has a multilayer structure. In the example shown in FIG. 3, a stopper film 11 is formed on a transparent substrate 10, and a low transmittance layer SOG (coated glass; spin-on-glass) film 1 is formed on the stopper film 11.
2 and a chromium film 13 as a high transmittance layer is formed on the SOG film 12. In the example shown in FIG. 4, a chromium film 13 is formed on a transparent substrate 10, and an SOG film 12 is formed on the chromium film 13.

[0006]

However, the above-described light semi-transmissive portion having a multi-layer structure has the following problems.

That is, since SOG is used for the material forming the high transmittance layer and chromium is used for the material forming the low transmittance layer, high etching is performed when etching for forming a mask pattern. It is necessary to use different types of etching media when etching the SOG film 12 as the rate layer and when etching the chromium film 13 as the low transmittance layer. For example, when both are performed by dry etching to suppress side etching, SO 2
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 gas such as H ₂ or CBrF ₃ is used. On the other hand, when etching the chromium film 13 as the low transmittance layer, it is necessary to use a chlorine-based gas such as CCl ₄ or Cl ₂ . If these etchings are performed in the same etching apparatus, there is a possibility that a previous etching gas is mixed into a later etching gas and the etching conditions are disturbed. Further, in order to perform this etching with a separate etching apparatus to prevent this possibility, it is necessary to prepare an extra etching apparatus, and it is necessary to transfer a substrate from one etching apparatus to the other etching apparatus. In addition, there is a problem that foreign matter such as dust adheres to the substrate during the transfer, which may cause a pattern defect. In addition, since SOG having a low refractive index is used, there is a problem that the pattern difference of the photomask is large, and the pattern is disadvantageous from the viewpoint of pattern breakage due to film peeling during cleaning, or cleaning properties such as removal of foreign substances.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and has a phase shift mask which can be manufactured in a relatively simple process while suppressing generation of minute defects, and which can transfer a pattern with high resolution. It is an object of the present invention to provide a phase shift mask blank as the material.

[0009]

Means for Solving the Problems To solve the above-mentioned problems, a phase shift mask according to the present invention comprises: (Constitution 1) a mask for performing fine pattern exposure, which is a mask pattern formed on a transparent substrate; Comprises a light transmitting portion that transmits light having an intensity substantially contributing to exposure and a light semi-transmitting portion that transmits light having an intensity that does not substantially contribute to exposure, and passes through the light semi-transmitting portion. The phase of light passing through the light transmissive portion is shifted to make the phase of light passing through the light transmissive portion different from the phase of light passing through the light transmissive portion, so that the boundary between the light transmissive portion and the light semitransmissive portion is shifted. What is claimed is: 1. A phase shift mask in which light passing through the vicinity cancels each other to maintain a good contrast at a boundary portion, wherein the light semi-transmissive portion is formed of a chromium film containing oxygen and contains the oxygen. Chromium membrane oxygen As an aspect of the first aspect of the present invention, there is provided a phase shift mask according to the first aspect, wherein the thickness of the thin film constituting the light semi-transmissive portion is reduced. (Structure 3) The phase shift mask according to Structure 1 or 2,
The mask pattern is obtained by drying the mask pattern.
When forming by etching, use the etching gas
And formed using a mixed gas of CCl ₄ gas and oxygen gas.
Structure, characterized in that those were, (Configuration 4) Configuration 1 or 2 of the phase shift mask odor
The mask pattern is formed by etching the mask pattern.
When forming by etching, use the etching solution
Containing ceric ammonium nitrate and perchloric acid
Characterized in that it is formed using a
Configuration.

Further, the phase shift mask blank according to the present invention is: (Structure 5) A phase shift mask blank used as a material of the phase shift mask according to any of Structures 1 to 4 , wherein the transparent substrate contains oxygen. A chromium film is formed, and the oxygen content of the chromium film containing oxygen is 30 to 6
The configuration is characterized by being 0 atomic%.

[0011]

According to the above configuration 1, the light semi-transmissive portion is formed of the chromium film containing oxygen, and the oxygen content of the chromium film containing oxygen is set to 30 to 60 atomic%, thereby providing the light semi-transmission portion. Even if the transmitting portion is formed of a single layer film made of one type of material, it is possible to easily satisfy the optimum values required for both the light transmittance and the phase shift performance at the same time. By setting the amount in this range, it is possible to maintain good film adhesion of the light semi-transmissive portion to the substrate, and effectively prevent pattern damage and the like due to film peeling during cleaning or the like. Was. Thus, the present inventors have found out that a chromium film containing oxygen having an oxygen content of 30 to 60 atomic% is suitable as a material constituting the light semi-transmissive portion. Also, 1
Since it can be composed of layer films, the manufacturing process can be extremely simplified, and because it is composed of a thin film having a high refractive index, it can be formed to be extremely thin. Or, it is further advantageous from the viewpoint of cleanability such as foreign matter removal.

Here, if the oxygen content of the chromium film containing oxygen is other than 30 to 60 atomic%, it is difficult to simultaneously satisfy the optimum values required for both the light transmittance and the phase shift performance. In addition, it was found that the film adhesion amount could not be maintained satisfactorily. That is, for example, when the oxygen content is less than 30 atomic%, it is disadvantageous to maintain the phase shift performance while securing the light transmission performance required for the light semi-transmissive portion. If it exceeds, it is disadvantageous to maintain the phase shift characteristic while securing the light shielding performance required for the light semi-transmissive portion. In other words, when the oxygen content of the chromium film containing oxygen is 30 to 60 atomic%, the optimum values required for both the light transmittance and the phase shift performance as the light semi-transmissive portion must be sufficiently satisfied at the same time. And it is possible to obtain an excellent advantage that the film adhesion can be maintained well.

According to the configuration 2, it is possible to obtain a light semi-transmissive portion having excellent characteristics.

According to the third aspect, a phase shift mask blank which can be used as a material of the phase shift mask of the second aspect can be obtained.

[0015]

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

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

The transparent substrate 1 is made of a quartz glass substrate whose main surface is mirror-polished.

The light semi-transmissive portion 2 is composed of a chromium film containing oxygen. In this embodiment, the i-line (wavelength λ = 365 nm) of a mercury lamp is used as the exposure light, and the light semi-transmissive part 2 simultaneously obtains a predetermined phase shift amount and a predetermined light shielding performance with respect to the exposure light. For this purpose, the oxygen content was 45 atomic%, the film thickness d was about 1350 Å, and the light transmittance was about 7% (refractive index; about 2.35).

In this case, assuming that 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 desirably 180 °, but practically, It is sufficient that 160 ° ≦ φ ≦ 200 °. The light transmittance of the light semi-transmissive portion 2 to the exposure light depends on the sensitivity of the resist used in pattern formation, but generally may be about 2 to 20%.
It is desirable to set it to 15%. The light transmittance of the light semi-transmissive portion 2 can be selected by selecting the oxygen content of chromium. Regarding the light semi-transmissive part 2,
The transmittance for light having a wavelength of 365 nm when the oxygen content is changed is as follows.

Oxygen content (atomic%) Light transmittance at 365 nm (%) 55 15 50 10 45 7 40 5 354 4 In this case, when the oxygen content is reduced to lower the light transmittance, the refractive index also increases. When the oxygen content is determined, the refractive index at that time is determined, and the film thickness d is calculated according to the equation (1).
To determine. It should be noted that the adhesive strength of the film also changes depending on the oxygen content.

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 transmissive film 2a made of a chromium film containing oxygen having a thickness of 1350 Å is formed on the surface of the substrate to obtain a phase shift mask blank. The formation of the light semi-transmissive film 2a is performed by sputtering using chromium as a target in an atmosphere of argon gas and oxygen gas. In this case, by changing the ratio of oxygen in the sputtering atmosphere, the oxygen content in chromium can be changed. Other than this, for example, sputtering using chromium oxide (Cr ₂ O ₃ ) as a target may be used, or film formation by vapor deposition in an oxygen atmosphere by resistance heating or electron gun heating using chromium or chromium oxide may be used. Of course.

Next, a resist film is formed on the light translucent film 2a of the phase shift mask blank thus obtained, and a series of well-known pattern forming processes such as pattern exposure, development, etching, and cleaning are performed. A part of the semi-transmissive portion 2a is removed to obtain a phase shift mask in which the light transmissive portion 4 and the light semi-transmissive portion 2 form a pattern such as a hole or a dot. In this case, the etching of the chromium film containing oxygen is performed by using C as an etching gas when dry etching is performed.
In the case of wet etching using a mixed gas of Cl ₄ + O ₂ , an etching solution obtained by adding pure water to 165 g of ceric ammonium nitrate and 42 ml of perchloric acid (70%) to make 1000 ml is used as an etching solution. I just need.

As shown in FIG. 1, when the exposure light L0 is applied to the phase shift mask, the exposure light L0
Are the light L1 passing through the light semi-transmissive portion 2 and reaching the non-transfer member (not shown) and the light L1 passing through the light transmitting portion 4 and reaching the non-transfer member.
Divided into two. In this case, the intensity of the light L1 that has passed through the light semi-transmissive portion 2 is weak light that does not substantially contribute to exposure. On the other hand, the light L2 that has passed through the light transmitting portion 4 is strong light substantially contributing to exposure. Accordingly, the pattern exposure is thereby performed. At this time, the light passing through the boundary between the light semi-transmissive portion 2 and the light transmissive portion 4 wraps around each other due to the diffraction phenomenon. However, since the phases of the two lights are almost reversed, they are canceled each other. You. As a result, the light intensity on the non-transfer member in the boundary region becomes almost zero. Therefore, the boundaries are very clear and the resolution is improved.

According to the above-described embodiment, since the light semi-transmissive portion 2 is formed of a chromium film containing an appropriate amount of oxygen, the light semi-transmissive portion 2 is formed of a single film without having a multilayer structure. However, it has become possible to simultaneously satisfy the optimum values required for both the light transmittance and the phase shift performance, and to maintain the film adhesion well. In addition, since a single-layer film is used, the manufacturing process can be extremely simplified, and the thin film having a high refractive index can be formed to have a very small film thickness. Of a two-layer structure of
Since it can be reduced to 3 or less, it is advantageous from the viewpoint of pattern breakage due to film peeling or the like at the time of cleaning, or cleanability such as removal of foreign matter. Moreover, a chromium film containing an appropriate amount of oxygen
It can be easily formed by a general film forming technique such as normal sputtering or vapor deposition, and furthermore, since the light transmittance can be controlled by adjusting the oxygen content, it is possible to obtain a semi-transmissive portion having desired characteristics. .

In the embodiment, an example is described in which i-line (365 nm) of a mercury lamp is used as the exposure light. However, the present invention uses another wavelength such as a g-line (4
36 nm), KrF excimer laser light (248 nm)
Needless to say, the present invention can be applied to the case where the above is used. In this case, the oxygen content and the film thickness may be adjusted by examining the refractive index and the absorptance of the thin film containing the metal oxide for each exposure wavelength.

[0028]

As described in detail above, according to the present invention,
The light semi-transmissive portion is made of a chromium film containing oxygen, and the oxygen-containing chromium film has an oxygen content of 30 to 60 atomic%. It is easily possible to satisfy the required optimum values for both the light transmittance and the phase shift performance at the same time, even if the film is formed of the above film. Also, since it can be composed of a single layer film,
The manufacturing process can be extremely simplified, and the thin film having a high refractive index can be formed to a very thin film thickness, so that the pattern step of the mask can be reduced. This is advantageous from the viewpoint of sex.

[Brief description of the drawings]

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

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

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

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transparent substrate, 2 ... Semi-transmissive part, 2a ... Semi-transmissive film, 4
... light transmitting part.

Claims (5)

(57) [Claims] 1. A mask for performing fine pattern exposure, comprising: a mask pattern formed on a transparent substrate, a light transmitting portion that transmits light having an intensity substantially contributing to exposure, and a mask that substantially contributes to exposure. And a light transmissive portion that transmits light of an intensity that does not occur, and shifts the phase of light passing through the light semitransmissive portion to shift the phase of light passing through the light semitransmissive portion and the light transmissive portion. By making the phase of the transmitted light different from that of the light transmitting part and the light semi-transmitting part, the light that has passed near the boundary between the light transmitting part and the light semi-transmitting part cancels each other, and the phase of the boundary part can be maintained well. A phase shift mask, wherein the light semi-transmissive portion is formed of a chromium film containing oxygen, and the oxygen content of the chromium film containing oxygen is 30 to 60 atomic%. 2. The phase shift mask according to claim 1, wherein the thickness of the thin film forming the light semi-transmissive portion is from 600 to 200.
A phase shift mask having a thickness of 0 Å. 3. The phase shift mass according to claim 1, wherein:
In the The mask pattern is obtained by dry etching the mask pattern.
When forming by etching, the etching gas is C
Cl _Four Formed using a mixed gas of gas and oxygen gas
A phase shift mask, characterized in that: 4. The phase shift mass according to claim 1, wherein
In the The mask pattern is obtained by wet etching the mask pattern.
When forming by etching, use nitric acid as the etchant.
Etch containing ceric ammonium diacid and perchloric acid
Characterized by being formed using a plating solution
Phase shift mask. 5. A phase shift mask blank used as a material of the phase shift mask according to claim 1 , wherein a chromium film containing oxygen is formed on a transparent substrate, and the chromium film contains the oxygen. A phase shift mask blank, wherein the chromium film has an oxygen content of 30 to 60 atomic%.