JP2001183805A - Halftone phase shift mask and blank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a halftone phase shift mask having a single layer film or multilayered film containing metals and silicon as the main structural elements on a glass substrate in such a manner that the latitude for the optical constants used for designing the film is large, that minute defects are hardly caused in the film after the film is formed and that the film has resistance against laser light. SOLUTION: The shift mask has a region containing a metal silicide produced by coupling a metal and silicon as the main structural element in the substances constituting the single layer film or multilayered film, and at least one of the metal not silicified and silicon not forming a compound with metal elements is incorporated into the aforementioned region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask for exposure transfer used in a photolithography step in a semiconductor manufacturing process and a photomask blank for manufacturing the same, and more particularly to a halftone phase shifter. The present invention relates to a mask or a halftone type phase shift mask blank.

[0002]

2. Description of the Related Art With the recent miniaturization of semiconductors, the use of photomasks provided with a technique for improving resolution when transferring a pattern onto a Si wafer is becoming active. The phase shift method is one of the resolution improving techniques, and has been actively developed. In principle, a phase shift portion is provided on one side of an adjacent opening, and the phase difference between projection lights passing through adjacent patterns is set to 180 degrees, so that light at a boundary portion when transmitted light is diffracted and interferes with each other. The strength is reduced, and as a result, the resolution of the transfer pattern is improved. As a result, the resolution of fine patterns and the depth of focus can be greatly improved compared to ordinary photomasks.

[0003] The phase shift method described above is based on IBM's Leve.
Proposed by nson et al., JP-A-58-173744,
The principle is described in JP-B-62-50811, and Levenson type and halftone type are known. In particular, the halftone phase shift mask has a sharp edge shape of transmitted light intensity by making the translucent film have a phase inversion function of transmitted light and a role of light shielding below the sensitivity of the resist to achieve resolution. And the effect of improving the depth of focus characteristic and faithfully transferring the mask pattern onto the wafer. Among them, in JP-A-11-15132 and JP-A-10-186632, as a film material of a halftone type phase shift mask blank (hereinafter referred to as a halftone blank or blank), it has excellent points such as spectral characteristics. Proposed a method using a compound of Zr or ZrSi. A photomask on which a pattern for transfer is formed by enlarging a pattern dimension formed by exposure transfer to a predetermined magnification is conventionally referred to as a reticle.
In the field of the phase shift mask according to the present invention, this is referred to as a reticle, and is included in the category defined as the phase shift mask.

[0004]

With the rapid miniaturization of semiconductors in recent years, lithography techniques for achieving the same have been advanced at the same time. In a reduction projection exposure apparatus (stepper) for transferring a mask pattern onto a wafer, the wavelength has been shortened in order to improve the resolution, and KrF has been used after the i-line
Light in the ultraviolet region such as an excimer laser and an ArF excimer laser has been put to practical use. Various proposals have also been made on the surface of the mask in order to cope with the shortening of the wavelength of the exposure light.Because the mask material is excellent in spectral characteristics, it is excellent in various resistances such as a chemical solution or exposure laser light or abrasion resistance. Masks and blanks using a metal and silicon compound as main constituent elements have been proposed.

A metal element (denoted by Me) and silicon (S
The method for producing a halftone phase shift mask mainly comprising the compound of i) is a compound such as MeSi ₂ or MeSi, which is a material (expressed as MeSi or Me _x Si _y ) in which a metal element is silicided as a target. It was formed by performing reactive sputtering in an atmosphere of Ar and O ₂ or N ₂ , N ₂ O, CO ₂ or the like using a target. Since sputtering film formation generally tends to reflect the target composition, Me and Si in the film are formed of silicide (M
eSi) exists in the film in a converted state.

However, when the film composition is generally formed of metal silicide, there are some problems. The first is that the degree of freedom of optical constants used for film design is narrowed. FIG. 1 shows optical constants (refractive index n, extinction coefficient k) for each oxygen partial pressure in a sputtering atmosphere when a Zr _x Si _y O _z film is formed by reactive sputtering using a ZrSi ₂ target. ) Is shown. From this result, it can be confirmed that the points indicated by the optical constants are distributed on a certain curve. Therefore, it has conventionally been difficult to form a film having an optical constant far away from the curve as a halftone blank. Was.

Second, M is also considered from the surface of the film after film formation.
A problem arises when the ratio of silicidation between e and Si is high. In the case of a metal silicide having a high hardness, if the content of the metal silicide compound alone or the content of the metal silicide is high, minute defects easily occur in the target or the film after the film formation.

Thirdly, the resistance to an exposure light source when transferring onto a wafer is increased. However, as the wavelength of the light source becomes shorter due to the miniaturization of semiconductors, the energy received by the mask increases. In the case of i-line, the energy per photon is 3.40 [e
V], whereas KrF excimer laser is 5.00
[eV], and 6.43 [eV] in the case of an ArF excimer laser. When the wavelength of the exposure light becomes shorter in this way, the reticle on the stepper is not only a thermal energy,
It is required that there is no change in characteristics with respect to optical energy. Here, when a high-energy exposure light such as an ArF excimer laser is continuously irradiated, when a component of a film in a halftone blank (halftone mask) is formed of a single metal silicide compound, laser light irradiation is performed. Therefore, there is a problem that characteristic values such as transmittance and phase difference change in a certain direction. Therefore, it is necessary to examine the resistance to laser light also from the viewpoint of the film composition ratio.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a photomask, particularly a halftone type phase shift mask and a halftone type phase shift mask blank, provided on a glass substrate. The content of the non-silicide compound relative to the content of the metal silicide compound in the layer component of the translucent single-layer film or the multilayer film is defined in view of the optical characteristics and the film characteristics.

Hereinafter, means for solving the problems in the present invention will be listed.

According to a first aspect of the present invention, there is provided a halftone type phase shift mask comprising a glass substrate provided with a single-layer film or a multilayer film containing metal and silicon as main constituent elements. Among the constituent substances, in a region having metal silicide bonded between metal and silicon as a main component, at least one of a metal that is not silicided and silicon that is not a compound with a metal element is contained. This is a half-tone type phase shift mask characterized in that:

According to a second aspect of the present invention, in the halftone phase shift mask according to the first aspect, the non-silicided metal and the metal element are compounded with respect to the content of the metal silicide. A halftone phase shift mask characterized in that the ratio of the total silicon content is 20 atomic% or more.

According to a third aspect of the present invention, in the halftone phase shift mask according to the first or second aspect, the content of the unsilicided metal is 5%.
This is a halftone type phase shift mask characterized by being at least atomic%.

According to a fourth aspect of the present invention, in the halftone phase shift mask according to the first or second aspect, the content of silicon which is not compounded with the other metal element is 5 atomic% or more. This is a halftone phase shift mask characterized by the following.

According to a fifth aspect of the present invention, in the halftone phase shift mask according to the third aspect, the metal which is not silicided is a single metal or an oxygen compound, a nitrogen compound, This is a halftone type phase shift mask characterized by being a fluorine compound.

According to a sixth aspect of the present invention, in the halftone phase shift mask according to the fourth aspect, silicon which is not compounded with another metal element is a silicon element or an oxygen compound or a nitrogen compound of silicon; This is a halftone type phase shift mask characterized by being a fluorine compound.

According to a seventh aspect of the present invention, there is provided the halftone phase shift mask according to the first or second aspect, wherein the metal silicide as a main component includes a non-silicided metal, Further, a halftone type phase shift mask characterized in that the metal is zirconium.

According to an eighth aspect of the present invention, in the halftone phase shift mask according to the third or fifth aspect, the metal which is not silicided is zirconium. This is a phase shift mask.

According to a ninth aspect of the present invention, there is provided the halftone phase shift mask according to the first or second aspect, wherein the region having metal silicide as a main component contains a non-silicided metal, Further, a halftone type phase shift mask characterized in that the metal is molybdenum.

According to a tenth aspect of the present invention, in the halftone type phase shift mask according to the third or fifth aspect, the metal which is not silicided is molybdenum. This is a phase shift mask.

According to an eleventh aspect of the present invention, there is provided a halftone type phase shift mask blank according to any one of the first to tenth aspects.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of a halftone type phase shift mask and a halftone type phase shift mask blank according to the present invention will be described. The halftone type phase shift mask of the present invention and the mask blank according to the manufacturing method of the present invention are not formed of a single metal silicide compound but a metal silicide compound in the film composition of the translucent film provided on the glass substrate. Characterized in that a non-silicidized compound of Me or Si is present in the region formed by the above method. This can solve the above-mentioned problems. Note that when Me is specifically illustrated in a preferred order,
Zr, Mo, Ti, and W are mentioned.

As described above, Me and S are contained at the element level in the semi-transparent film of the halftone type phase shift mask or blank.
The deliberate presence of each non-silicided elemental compound between i has several advantages. (Less than,
These Me and Si are referred to as free Me and free Si. Although it has been described that the optical constants of MeSi are distributed on a specific curve in the above-mentioned problem to be solved, it is necessary to obtain a film having a refractive index n and an extinction coefficient k other than the curve by using a silicide compound of MeSi. Needs to be reviewed from the compound composition of the target material, and it is necessary to consider from the production of a silicide target having another composition ratio of Me _x Si _y , which is substantially very difficult considering the process from the target development. At this point, if free Me or Si is positively used, the optical constant can be shifted to the Me side or the Si side depending on the mixture ratio of Me and Si, and the degree of freedom of the optical constant is increased.

In terms of the quality of the target used during film formation, some silicide compounds are very hard and low in viscosity, and when processed as a target, many small cracks are formed. There are problems such as causing a film defect after the film. By adding free Si or the like to the target in excess of the stoichiometric ratio of MeSi, the target density can be increased, and micro defects in the target and the film can be reduced.

Further, in terms of resistance to irradiation by laser light, the content of free Me and free Si can contribute to a reduction in transmittance and a change in phase difference. When a film is formed only by a single MeSi, the material constituting the film by irradiation has a certain tendency to change, but there is Me or Si which has not been silicided. In this case, the change is not uniform and the rate of change is reduced. That is, M
The oxidation reaction of eSi is considered to occur by irradiation with laser light. However, Me and Si, which are usually present as oxides in a film, emit O ₂ when they receive the energy of laser light and undergo a silicide reaction. , MeSi
A change in the opposite direction occurs, and changes in transmittance and phase difference are canceled out and reduced.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A halftone type phase shift mask according to the present invention will be described with reference to embodiments. In this embodiment, the halftone phase shift mask blank was formed by reactive sputtering. A magnetron sputtering device is used as a sputtering device, and a ZrSi oxide film is formed on a glass substrate in an atmosphere of Ar and O ₂ gas. Incidentally, by appropriately changing the introduced gas, it is also possible to obtain a thin film similarly nitrided or fluorinated.

Although the target is mainly a silicidized target of ZrSi, Zr and Si are mixed in a powdery state and then pressed to form a mixed target, which does not cause any particular problem. The target used in this example was mainly ZrSi, but the manufacturing method was to first mix Zr and Si from powder at a ratio based on the stoichiometric ratio, and then heated to promote the silicide reaction between Zr and Si. A silicide material such as ZrSi or ZrSi ₂ is obtained. (The compound of Zr and Si is also Zr ₅ Si ₄ and Z
r ₃ Si ₂ , Zr ₅ Si ₃ , Zr ₂ Si or the like may be used. Thereafter, the silicided material is pulverized again, and if necessary, Zr or Si powder is slightly added and mixed, followed by press molding as a target. In order to generate free Zr or Si present in the film after film formation, a target in which Zr or Si contained in the target is not completely silicided over the entire amount is used, or in the second step, The amount of Zr or Si to be added and mixed may be controlled.

In this embodiment, ZrSi
Other ₂ silicided target, Zr: Si =
Elemental powders were mixed at a ratio of 1: 2.2, and ZrSi _2.2
A target having the following composition was also prepared. In this case, since the solid volume limit of ZrSi ₂ is narrow, surplus Si is discharged from the ZrSi ₂ phase during the silicide reaction and exists as free Si, which serves as a binder. Thus, the finish of the target is good, and the minute cracks are reduced. ZrS
The film formed from i ₂ has a relatively high content of metal silicide, and Zr or S present without being silicided exists.
The proportion of i was relatively low. In comparison with this, in the film formed from the latter target, a decrease in film defects after film formation was observed, and at the same time, the content of unsilicided elements in the film was increased. In addition, due to the difference in film formation conditions and the like, as a result, the content of the non-silicided element in the film is approximately 5 atomic% or more as described in the claims. Reduction of defects and the like were confirmed. In an experiment conducted on the ratio of Zr to Si (Zr: Si = 1: 2.0 to 1: 2.4), the content of Si was determined in the present embodiment from the viewpoint of the target surface state and film defects. Good results were obtained when the described Zr: Si = 1: 2.2 or more. This is because the ratio of free Si to ZrSi ₂ is 20%, assuming that Zr and Si form a compound called ZrSi ₂ .

The film was formed under the following conditions. ZrSi
The optical characteristics of the _two targets were as shown in FIG. Also,
For reference, the results of film formation using Zr and Si simple targets are shown in FIGS. 2 and 3, respectively. Film formation condition: Ar + O ₂ = 40 SCCM Power = DC600W The numerical value at each point in the figure represents the oxygen flow rate [SCCM]. Here, when the film was formed at an oxygen flow rate of 1.0 [SCCM] under the above conditions, the optical constants when the film was formed with the ZrSi ₂ target were n = 1.11 and k = 1.55, but ZrSi was mixed with ZrSi. As a result of generating excess free Zr in the film using the target thus obtained, a film having optical constants of n = 1.27 and k = 1.01 was obtained. This film was good in terms of spectral characteristics and stability as a film layer for controlling transmittance in a halftone phase shift mask blank. Conversely, by intentionally increasing Si from the composition of ZrSi ₂ , it is also possible to shift the values of n and k to the Si side. By changing the target composition in advance, the characteristics after film formation can be changed.

Next, a pattern was formed on the thus obtained phase shift photomask blank by performing dry etching through a resist process such as resist application, exposure and development. The dry etching conditions are as follows. An RIE device was used as a dry etching device. Etching gas: BCl ₃ pressure: 1.0 Pa POWER: 200 W Etching is possible even when other chlorine-based gas is used.

[0031]

The present invention can be applied to the current halftone type phase shift mask containing metal and silicon, and improves the design, processing and quality of the mask corresponding to future miniaturization of semiconductors. For example, it is an effective means. As the method, the content of Me or Si present in a non-silicided state contained in a film provided on a glass substrate is defined. By including these elements that are not silicided, it is possible to optimize the optical characteristics of the film, improve the spectral characteristics, and the like depending on the content. In particular, when the transmittance in the inspection wavelength range is suppressed for the purpose of obtaining a contrast in the inspection of a halftone phase shift mask or a blank, it is possible to include a large amount of Me in the film. In addition, by including free Me and free Si, which are non-silicidized elements, in a film in a certain amount or more, the film has an effect of reducing the defects of the film and relaxing the stress. In addition, the mask was actually used on a stepper. It is also effective in improving the resistance to short wavelength laser light in such cases.

[Brief description of the drawings]

FIG. 1 shows ZrSi in a laser beam having a wavelength of 193 nm.
Optical constant distribution diagram of O film

FIG. 2 is an optical constant distribution diagram of a ZrO film in a laser beam having a wavelength of 193 nm.

FIG. 3 is a distribution diagram of optical constants of a SiO film in laser light having a wavelength of 193 nm.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koichiro Kanayama 1-5-1, Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd. F-term (reference) 2H095 BB03

Claims (11)

[Claims] In a halftone type phase shift mask provided with a single-layer film or a multi-layer film containing metal and silicon as main constituent elements on a glass substrate, among the materials constituting the single-layer film or the multi-layer film, metal Characterized in that a region mainly composed of metal silicide bonded between silicon and silicon contains at least one of a metal which is not silicided and silicon which is not a compound with a metal element. Type phase shift mask. 2. The halftone phase shift mask according to claim 1, wherein a ratio of a total content of the metal not silicided and silicon not being a compound with the metal element to the content of the metal silicide. Is 20 atomic% or more. 3. The halftone phase shift mask according to claim 1, wherein the content of the unsilicided metal is 5 atomic% or more. . 4. The halftone phase shift mask according to claim 1, wherein the content of silicon not being a compound with the other metal element is 5 atomic% or more. Tone type phase shift mask. 5. The halftone phase shift mask according to claim 3, wherein the non-silicided metal contained is a single metal or an oxygen compound, a nitrogen compound or a fluorine compound of the metal. Half-tone type phase shift mask. 6. The halftone phase shift mask according to claim 4, wherein the silicon which is not compounded with another metal element is a silicon element or an oxygen compound, a nitrogen compound or a fluorine compound of silicon. Half-tone type phase shift mask. 7. The halftone phase shift mask according to claim 1, wherein a region mainly composed of metal silicide contains a metal which is not silicided, and the metal is zirconium. A halftone type phase shift mask characterized by the following. 8. The halftone phase shift mask according to claim 3, wherein the non-silicided metal is zirconium. 9. The halftone phase shift mask according to claim 1, wherein the region mainly composed of metal silicide contains a metal which is not silicided, and the metal is molybdenum. A halftone type phase shift mask characterized by the following. 10. The halftone phase shift mask according to claim 3, wherein the metal that is not silicided is molybdenum. 11. A halftone type phase shift mask blank according to claim 1, wherein the halftone type phase shift mask blank is manufactured.