JP2001305716A - Photomask blanks, photomasks, and manufacturing methods thereof - Google Patents

Abstract

(57) Abstract: In a photomask blank in which at least one chromium-based film is formed on a transparent substrate, the chromium-based film contains at least one of chromium or oxygen, nitrogen, and carbon as a target. A photomask blank characterized in that a film is formed by a reactive sputtering method using chromium to be used and a sputtering gas containing at least a carbon dioxide gas and an inert gas. According to the present invention, when a chromium-based film is formed by a reactive sputtering method, a sputter gas containing at least a carbon dioxide gas and an inert gas is used, so that the in-plane uniformity of the substrate is high, A high-quality chromium-based photomask blank and a photomask with good controllability during manufacturing can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LSI, a VLSI
And photomask blanks, photomasks, and the like suitably used for high-density semiconductor integrated circuits, color filters for CCDs (Charge Coupled Devices) and LCDs (Liquid Crystal Display Devices), and fine processing such as magnetic heads. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, photomasks have been used for fine processing of high-density semiconductor integrated circuits such as LSIs and VLSIs, color filters for CCDs (charge coupled devices) and LCDs (liquid crystal display devices), and magnetic heads. Photolithography technology is used.

These chromium-based light-shielding films are formed by using a photomask blank in which a light-shielding film generally made of a chromium film is formed on a transparent substrate such as quartz glass or aluminosilicate glass by sputtering or vacuum evaporation. A predetermined pattern is used as a photomask.

In this case, there is known a photomask blank in which CrO is formed on the surface of a chromium film used as a light-shielding film to prevent light reflection and an antireflection film is formed on a substrate side. (Japanese Patent Publication 62-37385)
No.). As such an antireflection film, one using CrON (Japanese Patent Publication No. 61-46821, Japanese Patent Publication No.
2-32782) has also been proposed. Furthermore, Cr
Those using N (JP-B-62-27386 and JP-B-62-27387) have been proposed. A single-layer film using CrN (Japanese Patent Publication No. 4-1339) and a multilayer film using Cr + CrN + CrON (Japanese Patent Publication No. 62-37384) have been proposed.

[0005] In order to perform finer processing, a method of processing into a fine shape by using light interference called a phase shift film has been performed, and a chromium film or a molybdenum silicide film to which oxygen is added is formed. A film used alone as a phase shift film (Japanese Patent Application Laid-Open No. Hei 7-140635), a film used in combination with a light-shielding film and a phase shift film (Japanese Patent Publication No.
59296) and the like. Further, Cr or Cr containing at least one of oxygen, nitrogen and carbon is used as a film material (Japanese Patent Application Laid-Open No. 62-18560), and reactive sputtering is performed using oxygen and CH ₄ as reactive gases. Method for forming a film (JP-A-7-43888)
And so on.

[0006]

As described above, in conventional photomask blanks and photomasks, it is necessary to add oxygen to a chromium film or to form a chromium film containing oxygen on a light-shielding film. As a method of producing these oxygen-containing chromium films, oxygen gas as an oxygen source is introduced into a film formation chamber. However, when oxygen gas is used as an oxygen source, transmittance,
There is a problem that optical characteristics such as a reflectance and a refractive index tend to be non-uniform in a substrate surface. Furthermore, in addition to oxygen gas, nitric oxide gas is used as an oxygen source (Japanese Patent Publication No. Sho 62-3).
No. 7385) has been proposed, but there is a similar problem.

When oxygen gas is used as an oxygen source,
Since this oxygen gas has high reactivity, the optical characteristics are rather sensitive to fluctuations in the gas flow rate, mass production cannot be performed stably, and the yield decreases, and the film characteristics are controlled. Even if it is attempted, when the oxygen flow rate exceeds a certain value, the film rapidly becomes an oxide film, so that not only the film quality cannot be controlled, but also the film forming rate is rapidly reduced.

The present invention has been made in order to solve the above problems, and has high uniformity of optical characteristics in a substrate surface.
High quality photomask blanks, photomasks, which are easy to control and can be manufactured stably even during the formation of chromium-based films.
And a method for producing the same.

[0009]

Means for Solving the Problems and Embodiments of the Invention The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that chromium or chromium containing at least one of oxygen, nitrogen and carbon can be obtained. By using a target and performing reactive sputtering using a sputtering gas containing at least a carbon dioxide gas and an inert gas, the uniformity of optical characteristics in the substrate surface is improved, and the chromium-based film is also formed. Easy to control and stable mass production, especially chromium oxycarbide (CrCO) or chromium oxynitride carbide (CrCON)
It was found that a high-quality chromium-based film formed by the method described above could be obtained, and the conventional problems could be effectively solved, and the present invention was accomplished.

That is, the present invention provides the following photomask blanks, photomasks, and methods for manufacturing these. Claim 1: In a photomask blank formed by forming at least one layer of a chromium-based film on a transparent substrate, the chromium-based film uses chromium or oxygen, nitrogen, and chromium containing at least one kind of carbon as a target,
A photomask blank formed by a reactive sputtering method using a sputtering gas containing at least a carbon dioxide gas and an inert gas. Claim 2: The chromium-based film is made of chromium oxycarbide (CrC
The photomask blank according to claim 1, which is O) or chromium oxynitride carbide (CrCON). In a preferred embodiment, the photomask blank according to claim 1 is patterned by lithography. In a fourth aspect of the present invention, in a method of manufacturing a photomask blank having at least one chromium-based film formed on a transparent substrate, chromium or chromium containing at least one of oxygen, nitrogen, and carbon is used as a target, and at least dioxide is used. A method for producing a photomask blank, wherein reactive sputtering is performed using a sputtering gas containing a carbon gas and an inert gas. Claim 5: The chromium-based film is made of chromium oxycarbide (CrC
5. The method for producing a photomask blank according to claim 4, wherein the photomask blank is O) or chromium oxynitride carbide (CrCON). Claim 6: A method for manufacturing a photomask, comprising patterning a photomask blank manufactured by the method according to claim 4 by a lithography method.

According to the present invention, when a chromium-based oxide film is formed on a transparent substrate by a reactive sputtering method, carbon dioxide is used as an oxygen source so that the carbon dioxide is more reactive than oxygen or the like. Is low, the gas can flow uniformly over a wide area in the chamber, and the quality of the chromium-based film to be formed becomes uniform.

It is considered that the non-uniformity of the optical characteristics in the substrate surface can be reduced by forming a film by sputtering using a carbon dioxide gas as an oxygen source for the following reasons. That is, the variation in reflectivity is caused by the fact that when a gas that reacts with chromium such as oxygen gas flows, oxygen is consumed and oxidized sequentially from a portion near the gas inlet, or the degree of oxidation increases. Further, when oxygen is supplied from the outside of the target, oxygen is consumed in a portion corresponding to the outside of the target, and the oxygen concentration becomes lower toward the inside. As a result, the degree of oxidation differs in the plane and the optical constant is changed. This is because a distribution occurs.

On the other hand, in the present invention, since reactive sputtering is performed using carbon dioxide gas as an oxygen source, the carbon dioxide gas having low reactivity is hardly consumed until activated by plasma. Therefore, it is easy to spread uniformly in the chamber, and the uniformity of the degree of oxidation of the film is increased. As a result, the uniformity of the optical characteristics in the substrate surface is dramatically improved, and the inert gas is used as a sputtering gas. The film characteristics can be controlled by simultaneously using carbon dioxide gas and appropriately adjusting the mixing ratio.

The simultaneous use of a carbon dioxide gas and an inert gas as a sputtering gas can improve the controllability of the film composition, and the carbon dioxide gas has a low reactivity. The margin for unexpected fluctuations of various parameters is increased, a chromium-based film can be stably formed with good controllability, and the reflectance can be reduced without a large decrease in the film formation speed. There are advantages.

Hereinafter, the present invention will be described in more detail.
As shown in FIG. 1, a photomask blank of the present invention is formed on a substrate 1 such as quartz or CaF ₂ through which exposure light is transmitted.
As a target, chromium or oxygen, nitrogen, and chromium containing at least one of carbon were used, and a film was formed by reactive sputtering using a sputtering gas containing at least carbon dioxide gas and an inert gas. The chromium-based film 2 is formed by forming a chromium-based film 2 made of chromium oxycarbide (CrCO) or chromium oxynitride carbide (CrCON).

The structure of the chromium-based film of the present invention comprises at least one chromium-based film formed on a transparent substrate by a reactive sputtering method using a sputtering gas containing a carbon dioxide gas as an oxygen source.
Preferably, the layer is chromium oxycarbide (CrCO) or chromium oxynitride carbide (CrCON).

In this case, chromium oxycarbide (CrCO)
The composition is 20 to 95 at% Cr, especially 30 to 80 at%, 1 to 60 at% C, especially 5 to 50 at%, O 1 to 6 at%.
It is preferably 0 atomic%, particularly preferably 5 to 50 atomic%.
The composition of chromium oxynitride carbide (CrCON) is C
r 20 to 95 at%, especially 30 to 80 at%, C 1 to 2
It is preferably 0 at%, especially 2 to 15 at%, O 1 to 60 at%, especially 5 to 50 at%, N 1 to 30 at%, especially 3 to 20 at%.

The method for forming a chromium-based film of the present invention includes the following:
A reactive sputtering method is used, and chromium is used as a sputtering target at this time. In this case, a target in which any of oxygen, nitrogen, and carbon, or a combination thereof is added to chromium may be used.

In the present invention, the sputtering method comprises:
A DC power supply or a high-frequency power supply may be used, and a magnetron sputtering method or a conventional method may be used.

The composition of the sputtering gas is composed of at least an inert gas such as argon or krypton and a carbon dioxide gas. The flow rate ratio between the two differs depending on the equipment and power used, but cannot be specified unconditionally. As inert gas: carbon dioxide gas = 1: 0.01 to 10
0 is preferable, and more preferably 1: 0.02 to 50. Further, in addition to the inert gas and the carbon dioxide gas, a nitrogen supply gas such as a nitrogen gas or various nitrogen oxide gases may be used so that the chromium-based film to be formed has a desired composition of CrCON.
It can be added as appropriate.

In the photomask blank of the present invention, by using carbon dioxide gas as an oxygen source, the non-uniformity of the optical characteristics of the chromium-based film formed on the substrate surface can be reduced.

That is, the dispersion D of the reflectance of the photomask blank represented by the following equation is preferably 0.1 or less,
More preferably, the thickness is 0.05 or less, and the film has uniform optical characteristics as compared with the conventional CrCO film and CrCON film (variation D is 0.2 or more). (Max-min) / (max + min) = D [where, max represents the maximum value of the reflectance measurement value, and min represents the minimum value of the reflectance measurement value. ]

For example, when the in-plane reflectance distribution at a wavelength of 400 to 450 nm is measured at intervals of 5 mm using Nanometrics manufactured by Nanometrics, etc., the above formula of the in-plane reflectance is obtained. Is 0.1.
Or less, more preferably 0.05 or less.

When a photomask is manufactured using the photomask blank of the present invention, as shown in FIG. 3A, a CrCO layer (or CrCON layer) 12 is formed on a substrate 11 as described above. After that, a resist film 13 is formed, and the resist film 13 is patterned as shown in FIG. 3B, and further, as shown in FIG.
After the O layer (or CrCON layer) 12 is dry-etched or wet-etched, a method of stripping the resist film 13 as shown in FIG. In this case, application of the resist film, patterning (exposure and development), dry etching or wet etching, and removal of the resist film can be performed by known methods.

In the present invention, the chromium-based film may be a multilayer film as well as a single-layer film. For example, a CrCO film or a CrCON film may be used as an anti-reflection film on a light shielding film by using a CrCO film or a CrCON film as a part of the multilayer film.
A CON film is formed, an anti-reflection film is formed on both the film surface side and the substrate side of the light-shielding film, and a CrCO film or a CrCON film is formed on both or one of the anti-reflection films. And CrCON or CrCO film or Cr
A two-layer or three-layer CON film, each film having a function of a light-shielding film or an anti-reflection film, and an anti-reflection film on a substrate.
A structure in which a light-shielding film and an anti-reflection film are formed in this order, a structure in which a light-shielding film and an anti-reflection film are formed on a substrate, and a structure in which an anti-reflection film and a light-shielding film are formed on a substrate can be used. . Further, on the phase shifter film, a conductive film, or a light shielding film, all or a part of a single layer or two or more layers used as an anti-reflection film is a CrCO film or a CrCON film,
A phase shift type photomask or photomask blank can be used. The film structure may be, for example, a structure in which a phase shift film, an antireflection film, a light-shielding film, and an antireflection film are formed on a substrate in this order, or a structure in which a phase shift film, a light-shielding film, and an antireflection film are formed on a substrate. Alternatively, a structure in which a phase shift film, an antireflection film, and a light shielding film are formed on a substrate in this order can be employed. Further, the present invention is also applied to a halftone type phase shifter film using Cr.

[0026]

EXAMPLES The present invention will be described below in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1] 8 "C on a 6" quartz substrate
r as a target and a total flow rate of 7 sc as a sputtering gas
cm at a gas flow rate of 0.3 Pa, 500 W, and a temperature before film formation of 120 ° C. by changing the flow ratio of Ar and CO _{2 in} cm.
When the C magnetron sputtering method was performed, the discharge characteristics were:
As shown in FIG. 4, it is possible to easily adjust the reflectance of light having a wavelength of 450 nm from about 10% to about 50 to 60% without a rapid change in discharge resistance and a small decrease in film forming rate. Was completed.

[Comparative Example 1] 8 "C on a 6" quartz substrate
r as a target and a total flow rate of 7 sc as a sputtering gas
gas pressure during discharge by changing the flow ratio of Ar and O _{2 in} cm.
When the DC magnetron sputtering method was performed under the conditions of 3 Pa, 500 W, and a film forming temperature of 120 ° C., as shown in FIG. 5, the discharge characteristics showed a jump (a sharp change in the discharge resistance) and a small discharge resistance. Means that the reflectance of light having a wavelength of 450 nm is as high as 50 to 60%, whereas the reflectance is as small as about 10% where the discharge resistance is high,
It was difficult to control the reflectance to an arbitrary value. Furthermore, when the reflectance was high, the deposition rate was as high as 12 ° / sec, but when the reflectance was low, the deposition rate was as low as 2 ° / sec.

[Embodiment 2] 8 "C on a 6" quartz substrate
r was set as a target, Ar was supplied at 4.5 sccm, CO ₂ was supplied at 2.5 sccm, and the gas pressure during discharge was 0.3 Pa, 50
A 300 nm film was formed by DC magnetron sputtering under the conditions of 0 W and a film formation temperature of 120 ° C., and a CrCO film having a reflectance of about 30% was formed. At this time, the film forming speed is 7 ° / s.
ec.

The optical characteristics of the obtained CrCO film were measured at a wavelength of 450 nm at a wavelength of 450 nm using a Nanospec manufactured by Nanometrics Co., Ltd., and the distribution of the reflectance in the substrate plane was measured at intervals of 5 mm. Variation D is 0.0
32. (Max-min) / (max + min) = D [where, max represents the maximum value of the reflectance measurement value, and min represents the minimum value of the reflectance measurement value. As a result of analyzing the film composition of Example 2 by ESCA, C
r: 59 at%, C: 9 at%, and O: 32 at%. Table 1 shows the results.

[Embodiment 3] 8 "C on a 6" quartz substrate
With r as the target, 3.5 sccm of Ar, 2.0 sccm of CO _2, and 1.5 sccm of N ₂ were flowed, and a DC magnetron sputtering method was performed under the conditions of a gas pressure during discharge of 0.3 Pa, 500 W, and a deposition temperature of 120 ° C. With a reflectance of about 30%
An rCON film was formed. At this time, the film forming speed is 8 ° / s.
ec.

With respect to the obtained CrCON film, the optical characteristics were measured at a wavelength of 450 nm using a Nanospec manufactured by Nanometrics, and the distribution of the reflectivity in the substrate plane was measured at intervals of 5 mm. Was 0.019. The film composition of Example 3 was changed to ESCA
As a result of the analysis, Cr: 51 atomic%, C: 6 atomic%,
O: 20 atomic%, N: 23 atomic%. Table 1 shows the results.

[Comparative Example 2] 8 "C on a 6" quartz substrate
3.7 sccm Ar and O ₂To
The gas pressure during discharge was 3.3 Pa at a flow rate of 3.3 sccm.
DC magnetron spa at 0W, deposition temperature 120 ° C
A 300 nm CrO film was formed by a sputtering method. At this time
Was 2 ° / sec.

The optical characteristics of the obtained CrO film were 4
The reflectivity at a wavelength of 50 nm was measured using Nanometrics manufactured by Nanometrics Co., Ltd., and the in-plane distribution of the reflectivity was measured at intervals of 5 mm.
It was 3. As a result of analyzing the film composition of Comparative Example 2 by ESCA, it was found that Cr was 37 at% and O was 63 at%. Table 1 shows the results.

[0035]

[Table 1] From the results shown in Table 1, when Examples 2 and 3 are compared with Comparative Example 2, when the carbon dioxide gas is used as the oxygen source gas, the variation in the reflectance in the substrate surface is larger than when the oxygen gas is used. It can be seen that it has improved by almost one digit. Also, as compared with the case where oxygen gas was used for film formation, it was confirmed that by using carbon dioxide gas, the margin for variation of various parameters in the film formation process was increased, and the film could be formed with good reproducibility. .

[0036]

According to the present invention, when a chromium-based film is formed by a reactive sputtering method, a sputtering gas containing at least a carbon dioxide gas and an inert gas is used.
A high-quality chromium-based photomask blank and photomask having high in-plane uniformity and good controllability during manufacturing can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a photomask blank according to one embodiment of the present invention.

FIG. 2 is a sectional view of the photomask.

FIG. 3 is an explanatory view showing a method of manufacturing a photomask.
(A) is a cross-sectional view of a state where a resist film is formed, (B) is a state where a resist film is patterned, (C) is a state where dry etching is performed, and (D) is a cross-sectional view where the resist film is removed.

FIG. 4 is a graph showing the relationship between the flow rate of CO ₂ and the discharge resistance in Example 1.

FIG. 5 is a graph showing the relationship between the flow rate of O ₂ and the discharge resistance in Comparative Example 1.

[Explanation of symbols]

1 11 Substrate 2 12 Chromium oxycarbide film (or chromium oxynitride carbon film) 1a Substrate exposed portion 2a Chromium-based film portion

Continuing on the front page (72) Inventor Tamotsu Maruyama 28-1 Nishifukushima, Nippon-mura, Nakakushijo-gun, Niigata Pref.Shin-Etsu Chemical Co., Ltd. 28-1 Nishifukushima Shin-Etsu Chemical Co., Ltd. Precision Functional Materials Laboratory F-term (reference) 2H095 BB25 BC05 BC08 4K029 AA08 AA24 BA43 BA54 BA55 CA06 DC03 DC34 DC39 EA05

Claims (6)

[Claims] 1. A photomask blank comprising at least one chromium-based film formed on a transparent substrate, wherein the chromium-based film uses chromium or chromium containing at least one of oxygen, nitrogen and carbon as a target. A photomask blank formed by a reactive sputtering method using a sputtering gas containing at least a carbon dioxide gas and an inert gas. 2. The chromium-based film according to claim 1, wherein said chromium-based film comprises
The photomask blank according to claim 1, wherein the photomask blank is rCO) or chromium oxynitride carbide (CrCON). 3. A photomask formed by patterning the photomask blank according to claim 1 by a lithography method. 4. A method for manufacturing a photomask blank comprising at least one chromium-based film formed on a transparent substrate, wherein chromium or chromium containing at least one of oxygen, nitrogen and carbon is used as a target. A method for producing a photomask blank, wherein reactive sputtering is performed using a sputtering gas containing carbon dioxide gas and an inert gas. 5. The chromium-based film according to claim 1, wherein the chromium oxide carbide (C
5. The method for producing a photomask blank according to claim 4, wherein the photomask blank is rCO) or chromium oxynitride carbide (CrCON). 6. A method of manufacturing a photomask, comprising patterning a photomask blank manufactured by the method according to claim 4 by a lithography method.