KR100497443B1 - Attenuating Embedded Phase Shift Photomask Blanks - Google Patents

Abstract

At least 0.001 at a predetermined lithography wavelength of 400 nm and at least 0.001 at a predetermined lithography wavelength of 400 nm, resulting in a 180 Hz phase transition comprising at least one aluminum compound layer and at least one component having a greater light absorption than the aluminum compound at a predetermined lithography wavelength of less than 400 nm. Attenuated embedded phase shift photomask blanks that may have are prepared by depositing on the substrate at least one aluminum compound layer and at least one component having greater light absorption than the aluminum compound.

Description

Attenuating Embedded Phase Shift Photomask Blanks

The present invention relates to a phase shift photomask blank in photolithography technology using short wavelength (ie less than 400 nm) light. More specifically, the present invention relates to a phase shift photomask blank that attenuates transmitted light with respect to light transmitted in the same path length in air and changes its phase by 180 Hz. Such photomask blanks are commonly known in the art as attenuated (embedded) phase shift photomask blanks or halftone phase transition photomask blanks.

The electronics industry seeks to expand optical lithography technology to fabricate high density integrated circuits with critical dimensions of 0.25 mm or less. To this end, photomask blanks for lithography will need to be operated with short wavelength light, ie less than 400 nm. The two wavelengths targeted for future optical lithography are 248 nm (KrF laser wavelength) and 193 nm (ArF laser wavelength). The phase shift photomask increases the patterning contrast of the small circuit linewidth by evanescent light interference.

The concept of phase shift photomasks and photomask blanks that attenuate light and change its phase is disclosed in US Pat. No. 4,890,309 to HI Smith ("Lithography Mask with p-Phase Shifting Attenuator"). Known attenuated embedded phase shift photomasks fall into two broad categories: (1) Cr-based photomask blanks comprising Cr, Cr-oxide, Cr-carbide, Cr-nitride, Cr-fluoride, or combinations thereof, and (2) It is divided into SiO ₂ or Si ₃ N ₄ based photomask blanks comprising SiO ₂ or Si ₃ N ₄ together with mainly opaque materials such as MoN or MoSi ₂ . Typically the latter material is generally referred to as 'MoOSiN'.

Cr-based photomask blanks have the advantage of being chemically durable and capable of using most conventional processing steps developed for opaque Cr photomask blanks. The second category of SiO ₂ or Si ₃ N ₄ based photomask blanks utilizes transparency to deep ultraviolet and ease of dry etching using more harmless fluorine based compounds. However, photomask blanks based primarily on Cr (i.e. oxides, nitrides, carbides, fluorides or combinations thereof) absorb excessively even at shorter wavelengths (less than 200 nm), so that the photomask blanks for these wavelengths The need for development makes Cr compounds less desirable. A disadvantage of 'MoSiON' photomask blanks in short wavelength regimes is that they are too rich in Si and have poor etch selectivity compared to quartz (SiO ₂ ) substrates. Therefore, they require an etch stop, which is an additional layer of material that is poorly etched with a fluorine etchant.

Furthermore, there is a reference to attenuated embedded phase shift photomask blanks comprising one or more layers of hydrogenated amorphous carbon layers, complexes with tantalum and Cr metal layers, or hafnium compounds.

Summary of the Invention

The present invention results in a 180 Hz phase transition comprising at least one aluminum compound layer and at least one component that is more light absorbing than the aluminum compound at a given lithography wavelength of less than 400 nm and at least 0.001 at a predetermined lithography wavelength of less than 400 nm. Attenuated embedded phase shift photomask blank capable of having light transmittance.

Aluminum nitride, aluminum oxynitride and aluminum oxide are examples of preferred aluminum compounds. These compounds are relatively transparent, strong, etchable at short wavelengths, and have etching selectivity for quartz substrates. The component with higher light absorption is preferably selected from the group consisting of elemental metals, metal oxides, metal nitrides and mixtures thereof. Most preferably, the more light absorbing component is an oxide of Ti, Fe, In, Co, Bi, Mn, Cu, Sn, Cr, Ni, V, Nb, Ta, Mo, lanthanide-based metals and W; Or nitrides of Ti, Nb, Mo, Cr, W, Ta, Zr, Hf or V, and elemental metals.

In another aspect, the present invention results in a 180 Hz phase transition and involves depositing at least one aluminum compound layer and at least one component of greater light absorption than an aluminum compound at a predetermined lithography wavelength of less than 400 nm on a substrate. And a method for producing an attenuated embedded phase shift photomask blank capable of having a light transmittance of at least 0.001 at a lithography wavelength of less than 400 nm.

All features of the present invention will become apparent from the following description of the specification, with reference to the drawings and the appended claims.

1 is an X-ray diffraction pattern of an Al / AlN cermet photomask blank of the present invention prepared in a 6% N ₂ / Ar gas mixture.

2 is an X-ray diffraction pattern of an Al / AlN cermet photomask blank of the present invention prepared in a 10% N ₂ / Ar gas mixture.

3 is an X-ray diffraction pattern of an Al / AlN cermet photomask blank of the present invention prepared in a 20% N ₂ / Ar gas mixture.

4 is a graph showing the relationship between N ₂ partial pressure and refractive index n during sputtering of a cermet photomask blank.

5 is a graph showing the relationship between the N ₂ partial pressure and the extinction coefficient k during the sputtering of a cermet photomask blank.

6 is a graph showing the light transmittance (% T) of the built-in shifter according to the N ₂ partial pressure on the cermet photomask blank.

FIG. 7 is a graph showing the relationship between the refractive index n and% AlN in AlN / CrN multilayer photomask blanks.

8 is a graph showing the relationship between the extinction coefficient k and% AlN in an AlN / CrN multilayer photomask blank.

9 is a graph showing the light transmittance (% T) of the built-in shifter according to% AlN in an AlN / CrN multilayer photomask blank.

FIG. 10 is a graph showing the relationship between refractive index (n) and% Al ₂ O ₃ in an Al ₂ O ₃ / CrO _x composite photomask blank.

11 is a graph showing the relationship between the extinction coefficient (k) and% Al ₂ O ₃ in an Al ₂ O ₃ / CrO _x composite photomask blank.

12 is a graph showing a light transmittance (% T) of a built-in shifter according to% Al ₂ O ₃ in an Al ₂ O ₃ / CrO _x composite photomask blank.

FIG. 13 is a graph showing a light transmittance (% T) of a built-in shifter according to% AlN in an AlN / CrN composite photomask blank.

As known in the art, "photomask blank" and "photomask" differ in that a photomask is used to describe the photomask blank after being imaged. While every attempt has been made to follow this convention herein, those skilled in the art will recognize that this difference is not an important aspect of the present invention. Accordingly, it should be understood that the term "photomask blank" is used herein in its overall sense including both photomask blanks that are imaged or not imaged.

The phase shift photomask blank of the present invention may take three different forms (1) cermet, (2) multilayer, or (3) composite material. Although the preferred method of making the photomask blank is by physical vapor deposition (eg, sputtering or evaporation), other methods known to those skilled in the art of depositing materials on a substrate may also be used.

Cermet

The term “cermet” is used to refer to a photomask blank comprising elemental metals that are evenly or unevenly dispersed in a ceramic matrix. In the scope of the present invention, the cermet is denoted by M / AlX, where M refers to a slight concentration of metal and AlX refers to a ceramic matrix of aluminum compound.

Cermets such as Al / AlN or Ru / Al ₂ O ₃ are prepared by sputtering or electron beam evaporation. In the case of sputtering, the stainless steel chamber is evacuated to a background pressure of at least 1 × 10 ⁻⁴ Pa using a low temperature pump prior to the sputtering experiment. Turbomolecular pumps or diffusion pumps are also suitable. We use metal targets between 5 cm and 20 cm in diameter. DC electron tubes, RF electron tubes, and RF bipolar vacuum tube sputtering modes are all valid for producing cermets. For sputtering cermets, the target may be a single metal for Al / AlN, or a multicomponent target for Cr-SiO films. In the case of elemental metal targets, the sputtering conditions determine the chemical composition, while in multicomponent materials the ratio of the target constituents determines the chemical composition.

Prior to depositing the film on the substrate, the metal target is presputtered or pretreated by sputtering with pure Ar for at least 30 minutes to create a clean reactive surface. Is then sputtered film on the partial pressure of O _2, O ₂ and N ₂ to form the oxynitride forming the N _2, or Ar, and the oxide to form a nitride. To promote the growth of dense films, a typical total sputtering pressure is 1.3 × 10 ⁻² Pa or less. However, if it is beneficial to change other film properties, such as stress, high pressures can also be used. In general, vacuum conditions, target pretreatment and sputtering conditions are similar for cermets, multilayers, and composites.

When preparing cermets by electron beam evaporation, the vacuum system is evacuated using a turbomolecular pump at a background pressure of less than 1 × 10 ⁻⁴ Pa prior to deposition of the film. Separate evaporation sources are used for Al compound and metal deposition. The rate of deposition of the material from each of the sources heated with the electron beam is independently monitored and adjusted with a crystal rate controller. The chemical composition of the cermet produced by the present deposition method can be controlled by the relative deposition rate. In general, vacuum and deposition practices are similar for deposition cermets, multilayers, and composites.

Multilayer

The term "multilayer" is used to refer to a photomask blank consisting of alternating layers of Al compound layers and light absorbing component layers. In order to facilitate the production of such multilayers, it is preferred that the Al compound and the component with the higher light absorption are in the same form, for example both nitrides or both oxides. The layers can be very thin (1-2 monolayers) or even thicker. Relative layer thicknesses control the optical properties. The layer formation is periodic or aperiodic, and the layers may all have the same thickness or may be different. Gradually varying layer thicknesses can also be advantageously used to design films with different reflection coefficients in the same light transmission. Multilayer formation is of interest because the optical properties are designed by the choice of individual layer thicknesses while maintaining the same process conditions.

Multilayer photomask blanks are prepared by sputtering from separate metal targets at partial pressures of Ar and other reactive gases such as N ₂ or O ₂ . The targets are physically separated so that their sputtering fluxes do not overlap. Although the power applied to each target, and hence its sputtering rate, is typically different, both targets are operated in the same sputtering gas environment. Multilayer growth proceeds by placing the substrate on a continuously rotatable table below each target. The chemical composition of the films is adjusted by the thickness of the individual layers and controlled by their deposition rate and the time the substrate is placed under each target. Alternatively, the substrates can be rotated continuously at a constant speed so that the individual layer thicknesses are only determined by the sputtering speed. When the substrates are placed under the target, the time at which they stop can be programmed to create a periodic or aperiodic multilayer structure.

Composite material

The term "composite" refers to Al compounds and oxides of Ti, Fe, In, Co, Bi, Mn, Cu, Sn, Cr, Ni, V, Nb, Ta, Mo, lanthanide-based metals and W; Or a photomask blank comprising an atomic or molecular mixture of higher light absorbing components selected from nitrides of Ti, Nb, Mo, Cr, W, Ta, Zr, Hf or V. This mixture can be homogeneous or heterogeneous. As in multiple layers, in order to facilitate the preparation of such composite materials, it is preferred that the Al compound and the component with the greater light absorption are in the same form. Composite materials differ from each other in that they are elemental metals in cermet, while the more light absorbing components are metal oxides or metal nitrides.

Composite photomask blanks are prepared by simultaneous sputtering from two or more targets. Since the target has a confocal geometry, an atomic mixture can be obtained by simultaneously coating an Al compound and a component having a higher light absorbency on the substrate. The chemical composition of these composites is controlled by the relative deposition rate of each target. Alternatively, the composites are also prepared by first growing equivalent multilayers in terms of composition and then heating them to chemical homogenization by internal diffusion of the layers, or by depositing films from multicomponent targets having desirable chemical properties.

Optical properties

Optical properties (refractive index, “n” and extinction coefficient, “k”) together with optical reflectance and transmittance data are measured by variable angle spectroscopic ellipsometry at three incident angles of 186-800 nm corresponding to the energy range 1.5-6.65 eV do. The optical constants are matched in unison with this data using an optical model of the film allowing a less dense (50%) interfacial layer at the top surface of the substrate and the film. From the spectrum dependent knowledge of the optical properties, the thickness, light transmittance and reflectivity of the film corresponding to the 180 Hz phase transition can be calculated. In general, see Optical Properties of Thin Solid Films, pp. 55-62, Dover, NY, 1991, O. S. Heavens, which is incorporated herein by reference.

Example 1-8 Al / AlN cermet

Produce

Table 1 for summary of the synthesis conditions for Al / AlN cermets, where P is the percentage of N ₂ in the total pressure of Ar + N _2,% N is Ar + N ₂ gas mixture, Pw is the power and, Vs is Is the voltage applied to the Al target, R is the deposition rate for the film and d is its thickness. The target is 7.6 cm in diameter Al and RF tube sputtering in a cold pumped sputtering system at a typical background pressure of about 2.6 x 10 ^-5 Pa. Prior to sputtering the film, the Al target is presputtered at 1.3 Pa Ar at 500 W for about 1 hour. This ensures that the target surface is a highly reactive metal Al before introducing N ₂ . AlN is formed when the film is reactively sputtered from an Al target at a partial pressure of about 20% N ₂ /80% Ar, whereas metal Al film is formed when sp is sputtered alone. Sputtering at medium partial pressure produces a film consisting of AlN and Al phases.

By X-ray diffraction, the film sputtered at 20% or more of N ₂ is a single phase AlN having a wurtzite structure and a c-axis structure. For N ₂ partial pressures less than 10%, both Al and AlN peaks are apparent in the diffraction pattern. At 6% N ₂ , diffraction is dominated by the Al peak and only trace amounts of AlN are detectable. At 10% N ₂ , X-ray diffraction with a sensitivity of about 5% to the crystalline phase only detects AlN, but the increase in optical absorption of the film is suggestive evidence of the presence of Al. This X-ray diffraction pattern is shown in Figures 1-3.

At 14% to 20% N ₂ , the deposition rate of the cermet is constant at about 3 mW / s, indicating that the Al target is saturated with nitrogen, which is indicated by X-ray diffraction as a single phase AlN film. Will coincide with growth. At less than 14% N ₂ , the deposition rate increases rapidly, indicating the onset of metal mode sputtering, i.e., since the sputtering rate is greater than the N reaching rate at the target and substrate surface, the concentration or flux of N Insufficient to form phase AlN film. Under these conditions, cermets of Al and AlN are formed, where the formation of Al / AlN cermets is also consistent with the accompanying increase in optical absorption when the N ₂ partial pressure is less than 14%.

Example P % N Pw R d Vs Pa watts Å / s Å volts One 0.696 20 500 3.0 To 1000 320 2 0.695 18 500 3.1 To 1000 360 3 0.695 16 500 3.1 To 1000 375 4 0.692 14 500 3.2 To 1000 475 5 0.688 13 500 3.96 To 1000 455 6 0.691 12 500 4.41 To 1000 480 7 0.684 11 500 5.81 To 1000 490 8 0.681 10 500 6.16 To 1000 490

Optical and Phase Transition Characteristics

4 and 5 summarize the optical constant dependence of the Al / AlN cermet at 248 nm and 193 nm for the N ₂ partial pressure during sputtering. An important feature of this data is the initiation of a sharp change in the optical constant near 13% N ₂ , exactly where the deposition rate increases, which means that Al is depleted from a nitrogen-saturated mode or in a more nitrogen-free state. Indicates that the target has transitioned. Formation of the Al / AlN cermet of the sputtered film in the N lack target mode decreases n and increases k, which is consistent with the optical constants of Al (n = 0.1 and k = 2.2) at 193 nm. There is a similar trend at 248 nm, where n changes more slowly with respect to N ₂ sputtering gas pressure.

FIG. 6 summarizes the light transmittances at 193 nm and 248 nm calculated for the film thickness corresponding to 180 Hz phase transition in Al / AlN cermet as a function of relative AlN concentration. Cermets with interesting properties for phase transition photomask blanks are obtained at N ₂ partial pressures between 10 and 13%, in which case an Al metal concentration of less than 10% is estimated. Specifically, for 11% N ₂ , 180 ° phase transitions can be achieved in 640 mm thick films of about 6% transmission at 193 nm and 970 mm thick films of 12.4% transmission at 248 nm.

Example 9: Ru / Al ₂ O ₃ Cermet

Produce

Ru / Al ₂ O ₃ cermets are prepared by electron beam evaporation using separate sources for Ru and Al ₂ O ₃ . Prior to deposition, the vacuum chamber is evacuated to a background pressure of about 7 × 10 ⁻⁵ Pa using a turbo molecular pump. The feed material is broken into small pieces of 99.6% 2.5 cm x 2.5 cm x 0.051 cm Al ₂ O ₃ and filled in a carbon embedded water-cooled Cu oven (volume about 8 cm ³ ). Ru buttons of 99.95% purity and about 5 cm ³ in volume are filled directly into other water-cooled Cu ovens. A 2.286 mm thick and 2.5 cm x 3.8 cm quartz substrate is secured with a metal clip to a rotatable aluminum table located equidistantly (about 64 cm away) from the Ru and Al ₂ O ₃ sources.

The metal shutter shields the substrate from deposition until the Al ₂ O ₃ and Ru evaporation rates, which are monitored and controlled by the crystal oscillator speed controller, are stabilized. The electron beam flows to the Ru and Al ₂ O ₃ sources at a beam voltage of about 11 kV, gradually increasing by 57 mA and 75 mA, respectively, so that the average deposition rate was 1.5 Å / s for Al metal and Al ₂ O ₃ . About 8.8 dl / s is obtained, which corresponds to about 15% by volume Ru in the grown Ru / Al ₂ O ₃ cermet. After the speed has stabilized, the shutter is opened to expose the rotating (3-5 rpm) quartz substrate to deposition from Al ₂ O ₃ and Ru at the same time. Deposition continues until the film with a total thickness of about 1000 mm 3 uniformly coats the substrate, after which the shutter is closed and the electron beam flow to the source is blocked.

Optical and Phase Transition Characteristics

From the variable angle spectroscopic ellipsometry and the optical refraction and transmission data, the optical properties (refractive index and extinction coefficient) are measured at 193 nm and 248 nm. At 193 nm, the composite refractive index (ni k) is measured as 1.88-i 0.46 and at 248 nm is 1.93-i 0.31. At these two wavelengths, the light transmittance at the film thickness corresponding to the 180 Hz phase transition is calculated. At 248 nm, 180 ㅀ phase transitions can be achieved with a 15% -Ru / Al ₂ O ₃ cermet of 1350 Å thick films with 10.1% light transmittance, and 180 상 with 1116 Å thick films with 3% light transmittance at 193 nm. To achieve the transition. Both designs are within the range of interesting light transmittances for embedded phase shift photomask blanks.

Example 10-17 AlN / CrN multilayer

Produce

Sputtering a periodic multilayer of AlN / CrN by placing the substrate on a continuously rotating table under Cr and Al targets that are physically remote from the vacuum chamber and their sputtering flux does not overlap. Sputtering is carried out in a 25% N ₂ /75% Ar gas mixture at a total pressure of 1.3 x 10 ^-2 Pa. The individual AlN and CrN thicknesses in these multilayers can be determined by programming the time the substrate is placed under each target using static deposition rate measurements (1.5 μs / s for AlN and 2.3 μs / s for CrN). .

AlN sputters RF bipolar tubes from a 15 cm diameter Al target and CrN sputters RF tubes from a 7.6 cm diameter sputtering gun. 450 watts from a typical RF power source is distributed to each target by the target's individual RF matching network. Separate sputtering rates for AlN and CrN from thicker films are measured. Prior to the multilayer experiment sequence, both targets were simultaneously sputtered at 1.3 × 10 ⁻² Pa of pure Ar prior to introducing N ₂ to form a clean reactive metal surface of Al and Cr. During sputtering, the AlN target is biased at 1600 volts, whereas the Cr target is biased at 310 volts. Table 2 summarizes the AlN and CrN layer thicknesses within one cycle, and also the total number (N) of bilayers of the film. The total film thickness maintained near 1000 mW corresponds to the product of the bilayer thickness (AlN + CrN) and the number N of bilayers.

Example N d (AlN), Å d (CrN), Å % CrN 10 20 40 10 80 11 20 35 15 70 12 20 30 20 60 13 20 25 25 50 14 20 50 10 83 15 15 70 10 88 16 10 100 10 91 17 8 150 10 94

Optical and Phase Transition Characteristics

Optical constants (n, k) at 248 nm and 193 nm are given for CrN / AlN multilayers as a function of the relative volume concentrations of CrN and AlN in FIGS. 7 and 8. At 248 nm the extinction coefficient decreases regularly from 0.6 at 50% CrN / AlN to 0.16 at 6% CrN / AlN. Over this composition range, n slowly increases from about 2.0 to 2.25 at 6% CrN / AlN. This trend is consistent with the fact that the absorption of AlN is much smaller and the refractive index is higher. At 193 nm this trend is similar up to 20% CrN / AlN except for very low CrN concentrations.

9 summarizes the light transmittances measured at 193 nm and 248 nm for 180 Hz phase transitions in AlN / CrN multilayers as a function of relative AlN concentration. 180 μs phase transition can be achieved in the range of acceptable light transmittance (5-10%) at both 248 nm and 193 nm. Up to an 80% AlN concentration, there is a smooth and gradual dependence of the composition on the 180 Hz phase transition, a characteristic of the material system in which light transmittance can be ideally adjusted.

Example 18-20 Al ₂ O ₃ / CrO _x Multi-Layer

Produce

The multilayer of CrO _x / Al ₂ O ₃ was sputtered RF bipolar tube from a 15 cm diameter Al target in a 50% O ₂ / Ar gas mixture (1.3 x 10 ^-2 total pressure), and a CrO _x target of 7.6 cm diameter Prepared by sputtering from an RF tube. The thickness of each oxide layer is calculated from their respective static deposition rates measured from the thick film of each oxide. The rate of Al ₂ O ₃ is 0.36 dl / s, and the rate of CrO _x is 0.54 dl / s. RF power (500 watts) from a single source is distributed to each target by the matching network. The target voltage is 1275 volts on the Al target and 285 volts on the Cr target. Table 3 shows the layer thicknesses of Al ₂ O ₃ and Cr _x O and the total number N of film layers.

Example N d (Al ₂ O ₃ ), Å d (CrO _x ), Å 18 20 20 40 19 15 40 40 20 20 40 20

Optical and Phase Transition Characteristics

The optical constants of CrO _x / Al ₂ O ₃ multilayers as a function of relative volume concentration or thickness are given in FIGS. 10 and 11. For CrN / AlN multilayers, the dependencies of n and k at 248 nm vary regularly depending on the chemical composition. Increasing the Al ₂ O ₃ concentration decreases the extinction coefficient, which is consistent with the measured transparency of the Al ₂ O ₃ film at 5 to 6.5 eV and its large band spacing (about 9 eV).

FIG. 12 summarizes the light transmittance theory in Al ₂ O ₃ / CrO _x multilayers that transition 180 ° out of phase at 193 nm and 248 nm as a function of relative Al ₂ O ₃ concentration or thickness. These data indicate that a 180 Hz phase transition of 5-15% light transmission can be obtained in an Al ₂ O ₃ / CrO _x multilayer with an Al ₂ O ₃ concentration of less than 50%.

Example 21 AlN / MoN _x Multilayers

Produce

AlN / MoN multilayers, 25 _× (40 μs AlN + 10 μs MoN _x ) are physically separated to sputter from Al (5 cm diameter) and Mo (7.6 cm diameter) targets whose sputtering fluxes do not overlap. Initially, the targets were all sputtered simultaneously at 1.3 × 10 ⁻² Pa of Ar, Mo sputtered DC tubes at 150 W (300 V) and Al sputtered RF tubes at 300 W (195 V) for 60 minutes. After presputtering, the AlN / MoN _x multilayers are grown on a quartz substrate in a 25% N ₂ / Ar gas mixture at a total pressure of 1.3 × 10 ⁻² Pa. The deposition rate is 0.86 dl / s for MoN _x and 1.0 dl / s for AlN.

Optical and Phase Transition Characteristics

From the variable angle spectroscopic ellipsometry and the optical refraction and transmission data, the optical properties (refractive index and extinction coefficient) are measured at 193 nm and 248 nm. At 193 nm, the composite refractive index (ni k) is measured as 2.365-i 0.620 and 2.288-i 0.37 at 248 nm. At these two wavelengths, the light transmittance is calculated at the film thickness corresponding to 180 Hz phase transition. At 248 nm, 180 ㅀ phase transitions can be achieved in AlN / MoN _x multilayers of 980 Å thick films with 12.7% light transmittance, and 180 ㅀ phase transitions at 725 Å thick films with 4.1% light transmittance at 193 nm. . Both designs are within the range of interesting light transmittances for embedded phase shift photomask blanks.

Example 22-24 AlN-CrN composite material

Produce

AlN-CrN composites are prepared by reactive sputtering in a 20% N ₂ / Ar gas mixture from a 5 cm diameter target of Al and Cr. Al sputters the RF tube, while Cr sputters the DC tube. The two sputtering guns are aligned in a confocal geometry such that their sputtering flux overlaps the quartz substrate and is located about 15 cm from each target. After pumping the stainless steel chamber to a background pressure of 1.1 × 10 ⁻⁴ Pa, Cr and Al targets are all sputtered at 1.3 × 10 ⁻² Pa (Cr target is 150 W and Al target is 400 W). After pre-sputtering, AlN-CrN composites having three different chemical compositions are deposited by simultaneously reactive sputtering from Cr and Al targets on a single quartz substrate that is held statically. Detailed sputtering experiments are summarized in Table 4. Each film is about 100 mm thick.

Example Pw (Cr) R (CrN) Pw (Al) R (AlN) % CrN (Watts) (Å / s) (Watts) (Å / s) 22 31 0.26 400 0.96 21 23 91 0.68 400 0.96 41 24 139 1.02 400 0.96 52

Optical and Phase Transition Characteristics

From the variable angle spectroscopic ellipsometry and the optical refraction and transmission data, the optical properties (refractive index and extinction coefficient) are measured at 193 nm and 248 nm. FIG. 13 summarizes the light transmittance theoretical values of AlN-CrN composites that transition 180 degrees out of phase at 193 nm and 248 nm as a function of the relative AlN concentration of the composite. These data indicate that a 180 Hz phase transition at 5-15% light transmission can be achieved in AlN-CrN composites with AlN concentrations of greater than about 50%.

Claims (19)

A light transmittance of at least 0.001 at a predetermined lithography wavelength of less than 400 nm, resulting in a 180 Hz phase transition, comprising at least one layer of aluminum compound and at least one component having greater light absorption than the aluminum compound at a predetermined lithography wavelength of less than 400 nm. Attenuated embedded phase shift photomask blank capable of having. The photomask blank of claim 1 which is a cermet photomask blank. The photomask blank of claim 1 which is a multilayer photomask blank. 4. The photomask blank of claim 3, wherein the photomask blank is composed of an alternating layer of an aluminum compound and a light absorbing component. The photomask blank of claim 1 which is a composite photomask blank. The photomask blank of claim 1 wherein the aluminum compound is selected from the group consisting of aluminum nitride, aluminum oxynitride and aluminum oxide. The photomask blank of claim 1 wherein the component with greater light absorption is selected from the group consisting of elemental metals, metal oxides, metal nitrides and mixtures thereof. The component according to claim 1, wherein the component having higher light absorbency is selected from (a) elemental metal, (b) Ti, Fe, In, Co, Bi, Mn, Cu, Sn, Cr, Ni, V, Nb, Ta, Mo, Lanthanide-based metals or oxides of W; (c) nitrides of Ti, Nb, Mo, Cr, W, Ta, Zr, Hf or V; And (d) a mixture thereof. The photomask blank of claim 1, wherein the predetermined lithography wavelength is selected from the group consisting of 193 nm, 248 nm, and 365 nm. Induces a 180 Hz phase transition and a predetermined lithography wavelength of less than 400 nm, comprising depositing on the substrate at least one layer of aluminum compound and at least one component of greater light absorption than the aluminum compound at a predetermined lithography wavelength of less than 400 nm. A method of making an attenuated embedded phase shift photomask blank capable of having a light transmittance of at least 0.001. The method of claim 10, wherein the depositing step comprises physical vapor deposition. The method of claim 11, wherein the physical deposition step is selected from the group consisting of sputtering and evaporation. The method of claim 10, wherein the aluminum compound is selected from the group consisting of aluminum nitride, aluminum oxynitride, and aluminum oxide. The method of claim 10 wherein the component with greater light absorption is selected from the group consisting of elemental metals, metal oxides, metal nitrides, and mixtures thereof. The component according to claim 10, wherein the component having higher light absorbency is selected from (a) elemental metal, (b) Ti, Fe, In, Co, Bi, Mn, Cu, Sn, Cr, Ni, V, Nb, Ta, Mo, Lanthanum-based metals or oxides of W; (c) nitrides of Ti, Nb, Mo, Cr, W, Ta, Zr, Hf, or V; And (d) mixtures thereof. The method of claim 10, wherein the more light absorbing component is an elemental metal and the deposited layer comprises an elemental metal dispersed in an aluminum compound to form a cermet photomask blank. The method of claim 10, wherein alternating layers of aluminum compound and light absorbing component are deposited to form a multilayer photomask blank. The method of claim 10, wherein the component with higher light absorbency is not an elemental metal and the deposited layers comprise a mixture of an aluminum compound and a component with higher light absorbency to form a composite photomask blank. The method of claim 10, wherein the predetermined lithography wavelength is selected from the group consisting of 193 nm, 248 nm, and 365 nm.