KR100503833B1 - Attenuating embedded phase shift photomask blanks - Google Patents

Abstract

Attenuating embedded phase shift photomask blanks having a light transmittance of at least 0.001 at a wavelength of less than 400 nm and capable of shifting the phase by 180 ° are used to periodically or lightly transmit the light transmitting material and the light absorbing material. Or an alternating layer of aperiodic layers, which layer is formed by alternately depositing a layer of a light transmissive material and a light absorbing material onto the substrate, preferably by vacuum deposition.

Description

Optically Attenuated Built-in Phase Shift Photomask Blank {ATTENUATING EMBEDDED PHASE SHIFT PHOTOMASK BLANKS}

The present invention relates to a phase shift photomask blank in photolithography technology that uses short wavelength light (ie, less than 400 nm). More particularly, the present invention relates to a phase shift photomask blank that attenuates transmitted light and changes its phase by 180 ° for light propagating in the same path length in the atmosphere. Such photomask blanks are commonly known as light attenuated (embedded) phase shift photomask blanks or light attenuated half-tone phase shift photomask blanks. More specifically, the present invention proposes a novel light-attenuated embedded phase-shift photomask blank, in which a plurality of mltilayering of an ultra-thin UV transmitting layer and an ultra-thin UV absorbing layer is performed periodically or aperiodically. This allows the optical properties to be engineered at any wavelength.

The electronics industry has expanded optical lithography technology to precisely manufacture high density integrated circuit areas of 0.25 micrometers or less. To achieve this, the lithographic photomask blank needs to operate at short wavelength light, i.e., less than 400 nm. Two wavelengths for future-oriented optical lithography are 248 nm (KrF laser wavelength) and 193 nm (ArF laser wavelength). Phase shift masks increase the patterned contrast of small circuit features by destructive optical interference.

The concept of phase shift photomask blanks is to attenuate light and change its phase, as disclosed by HI Smith in US 4,890,309 ("Lithography Mask with a π-Phase Shifting Attenuator"). Known light attenuated embedded phase shift photomask blank techniques can be broadly divided into two categories: (1) Cr, Cr-oxide, Cr-carbide, Cr-nitride, Cr-fluoride or combinations thereof Cr-based photomask blanks; There are based photomask blank-and (2) MoN MoSiO ₂ or the like material and excellent transmission with SiO _2, and SiO _2, and Si ₃ N ₄ containing Si ₃ N ₄ in. The latter material is usually referred to generally as "MoOSiN". Cr-based photomask blanks have the advantage of being persistent in chemistry, allowing the use of most familiar manufacturing steps developed for transparent Cr photomask blanks. Photomask blanks belonging to the second category of SiO ₂ , or Si ₃ N ₄ systems penetrate deep into UV light to facilitate dry etching due to the more harmless fluoride-based chemical action. However, developing photomask blanks for shorter wavelengths (less than 200 nm) results in photomask blanks that are primarily based on Cr (ie, oxides, nitrides, carbides, fluorides, or combinations thereof) that produce excessive light at these wavelengths. Absorption will make the chemistry of Cr less desirable. The disadvantage of the 'MoSiON' photomask blank in this short wavelength scheme is that the Si is excessively high, resulting in poor etch selectivity for the quartz (SiO 2) substrate. Thus, they require an etch stop, which is a layer of material etched poorly with a fluorine etchant.

Reference is also made to a light attenuated embedded phase shift photomask blank comprising a hydrogenated amorphous carbon layer, a compound with a layer of tantalum and Cr metals, or one or more layers composed of hafnium compounds. have.

In practice, phase shift photomask blanks require a transmittance that meets the requirements at operating wavelengths (less than 400 nm) and inspection wavelengths (typically 488 nm). Preferred properties also include electrical conductivity, which allows electron beam patterning, selective dry-etchability, environmental, chemical, and radiation stability for photoresist and quartz substrates. Moreover, it is also preferable to be able to manufacture the photomask blank which has a required optical characteristic by the same manufacturing method in another wavelength.

It is known to those skilled in the art that by changing the chemistry of the top layer or by adding a layer to a binary or phase shift photomask blank, reflection is prevented or chemically more robust. Although these photomask blanks include "multiple" layers in the sense of having at least two layers, these added layers do not adjust the light transmittance and transmitted phase of the photomask blank.

Summary of the Invention

In one aspect, the present invention includes a light attenuated embedded phase shift photomask blank having a light transmittance of at least 0.001 at a selected lithography wavelength of less than 400 nm and capable of shifting the phase 180 °, which includes a light transmissive material and light And layers in which the absorbent material is alternately stacked.

In another aspect, the invention includes a method of making a light attenuated embedded phase shift photomask blank capable of shifting a phase 180 ° with a light transmittance of at least 0.001 at a selected lithography wavelength of less than 400 nm, the method comprising: And a method of alternately depositing the light transmitting material and the light absorbing material onto the substrate.

These and other features of the present invention will be better understood by reading this specification with reference to the drawings and the appended claims.

1 is a graph showing the relationship between the index of refraction (n) and the MoNx ratio (% MoNx) of the AlN / MoNx photomask blank of the present invention.

2 is a graph showing the relationship between extinction coefficient (k) and MoNx ratio (% MoNx) in the AlN / MoNx photomask blank of the present invention.

3 is a graph showing the light transmittance (% T) of the AlN / MoNx photomask blank of the present invention as a function of MoNx ratio (% MoNx).

4 is a graph showing the relationship between the refractive index n of the AlN / TiN photomask blank of the present invention and the ratio of TiN (% TiN).

5 is a graph showing the relationship between the extinction coefficient k and the TiN ratio (% TiN) of the AlN / TiN photomask blank of the present invention.

6 is a graph showing the light transmittance (% T) of the AlN / TiN photomask blank of the present invention as a function of the TiN ratio (% TiN).

7 is a graph showing the relationship between the refractive index (n) and the RuO ₂ ratio (% RuO ₂ ) of the RuO ₂ / HfO ₂ photomask blank of the present invention.

8 is a graph showing the relationship between the extinction coefficient k of the RuO ₂ / HfO ₂ photomask blank of the present invention and the RuO ₂ ratio (% RuO ₂ ).

9 is a graph showing the light transmittance (% T) of the RuO ₂ / HfO ₂ photomask blank of the present invention as a function of the RuO ₂ ratio (% RuO ₂ ).

10 is a graph showing the relationship between the refractive index (n) and the RuO ₂ ratio (% RuO ₂ ) of the RuO ₂ / ZrO ₂ photomask blank of the present invention.

11 is a graph showing the relationship between the extinction coefficient k and the RuO ₂ ratio (% RuO ₂ ) of the RuO ₂ / ZrO ₂ photomask blank of the present invention.

12 is a graph showing the light transmittance (% T) of the RuO ₂ / ZrO ₂ photomask blank of the present invention as a function of the RuO ₂ ratio (% RuO ₂ ).

FIG. 13 is a graph showing the light transmittance (% T) as a function of energy (E) for AlN / MoNx photomask blanks according to the present invention.

14 is a graph showing the light reflectance (% R) as a function of energy (E) for AlN / MoNx photomask blanks according to the present invention.

As is known to those skilled in the art, "photomask blank" and "photomask" differ in that "photomask" is used to represent the "photomask blank" after being imaged. While all attempts have been made to understand the prior art herein, those skilled in the art will understand that such features are not an exhaustive interpretation of the invention. Thus, the term "photomask blank" as used herein is used in a broad sense including both imaged and non-imaged photomask blanks.

The optical multilayer of the present invention comprises a layer consisting of successive alternating layers of light absorbing layer (A) and light transmitting layer (T), which has a transmittance of at least 0.001 and is designed to shift the phase by 180 °. Such multilayers can be periodic (T and A remain the same thickness in the stack) or aperiodic (T and A thickness vary in the stack). As an example, the chemistry of the multilayers herein can be expressed as 20x (35Å AlN + 15ÅCrN), which is repeated 20 times over a UV transmissive layer of 35Å AlN and a 15Å thick CrN UV absorbing layer. By laminating | stacking periodically, the thing which made the total film thickness into 1000 micrometers is shown.

As described herein, the “light transmissive” material or layer T is one with an extinction coefficient k <0.3 and within 3eV <E <7eV. Examples of light transmissive materials include oxides of Hf, Y, Zr, Al, Si, and Ge; Nitrides of Al, Si, B, C; And fluorides of Mg, Ba, and Ca. The "light absorbing" material or layer (A) is in the range of 3 eV <E <7 eV with extinction coefficient k> 0.3. Examples of light absorbing materials are oxides of Cr, Ti, Fe, In, Co, Bi, Mn, Cu, Sn, Ni, V, Ta, Mo, Ru and W; And nitrides of Ti, Nb, Mo, W, Ta, Hf, Zr, and Cr.

The thickness ratio of A to T is A / T &lt; 5, preferably the entire stack in the range of A / T &lt; 1 has a transmission of at least 0.001 at the lithographic wavelength. The total thickness d of the stack is selected to shift the phase of the lithographic light wavelength l by 180 °, approximately corresponding to 2 (n-1) d = l / 2 or an odd number thereof. The total number N> 2 of each transmission and absorption layer corresponds to at least four layers. The thickness of each layer A and T is matched with d to design optically.

A photomask blank, a layer of alternating layers of a light transmissive compound and a light absorbing compound, is formed by sputtering from each metal target by applying partial pressure with Ar and other reactive gases such as N ₂ or O ₂ . . These targets are physically separated so that the sputtered flux from these targets does not overlap. Although both targets are operated in the same sputtering gas environment, and power is applied to each target, as a result, the sputtering rate is usually different. Multilayer growth proceeds by continuously placing the substrate on a rotatable table below each target. The chemical composition of the film is adjusted by the thickness of each layer and controlled by their deposition rate and the length of time that the substrate is briefly positioned under each target. Alternatively, the substrate can rotate continuously at a constant speed so that each layer thickness is determined by the sputtering rate. When the substrates are positioned below the target, the time they are stationary can be programmed, resulting in either periodic or non-periodic multilayer structures.

Optical properties

Optical properties (refractive index n, and extinction coefficient k), in combination with light reflection and transmission data, are variable angle spectrometer ellipsometry with three angles of incidence from a wavelength of 186 to 800 nm corresponding to an energy range of 1.5 to 6.65 eV. (variable angle spectroscopic ellipsometry). The optical constants fit together in this data and use an optical model of the film, which can be a (50%) less dense interfacial layer on the substrate and the top layer of the film. As can be seen from the spectrum depending on the optical properties, the film thickness, light transmittance and reflectivity corresponding to shifting the phase by 180 ° can be calculated.

More specifically, the general theory format for calculating the optical properties of a superlattice or multilayer material is described by O, Hundrei in Effective Medium Theory and Nonlocal Effects for Superlattice, J. of Wave Material Interaction, 2 (1987) pp. 29-39, and The Optical Properties of Thin Films and Superlattices, physica A, 157 (1989) pp. By O. Hundrei. 309-322, the disclosure of which is incorporated herein by reference. In defining the long wavelength, Hundrei and colleagues consider the multilayer stack to behave as a single film with an optical axis perpendicular to the film and determine that it has the following common dielectric constant.

Where f _a and f _t are the volume fractions of the absorbing and transmissive layers, respectively, and e _a and e _t are the dielectric constants corresponding to them.

<Example>

Examples 1-5: AlN / MoNx Photomask Blanks

Manufacture and physical properties

Placing a substrate on a rotary table under the Mo and Al targets periodically sputters the periodic multilayers of AlN / MoNx, each target being physically separated in a vacuum chamber, so that the flux sputtered at each target Does not overlap. Sputtering is performed in a 25% N ₂ to 75% Ar gas compound (total pressure 1.3 × 10 −2 Pa) to form nitrides of Al and Mo. The thickness of each of these multilayers of AlN and MoNx determines the time at which the substrate is located under each target, respectively, measured static deposition rate: 1.0 1.0 / s for AlN and 0.86 0.8 / s for MoNx, respectively. It is determined by programming that corresponds to 25W and 284V applied to the Mo target, 250W and 190V applied to the Al target. AlN was rf magnetron sputtered from a 5 cm diameter Al target and MoNx was dc magnetron sputtered from a 7.6 cm diameter Mo target.

And generates a metal target surface of fresh and reactive sputtering (presputtering) - Prior to sputtering a multi-layer, N ₂ is approximately an hour free to Ar of the Mo and Al targets at the same time, 1.3 x 10- ² Pa before the injection. The Al target was presputtered at 300 W (360V) and the Mo target was presputtered at 150W (300V). The total film thickness maintained near 1000 mW corresponds to the multiplication of the double layer thickness (AlN + MoNx) by the double layer number N. Table 1 summarizes each layer thickness, total number of bilayers (N), and electrical sheet resistance for AlN / MoNx multilayers. Even for AlN-rich compositions (Examples 3 and 4), these multilayer films have a relatively low resistance, which is desirable for dissipating charge during electron beam writing.

Yes N d (AlN), Å d (MoNx), Å % MoNx R (Ω / sq) One 20 45 5 10 2 20 40 10 20 3M 3 20 35 15 30 120 K 4 20 25 25 50 30K 5 20 20 30 60

Optical properties

1 and 2 summarize the light constant, refractive index (n) and extinction coefficient (k) determined as a function of MoNx fraction for AlN / MoNx multilayers at 248 nm and 193 nm. At both wavelengths, k increases almost unchanged until the thickness of MoNx increases to match MoNx with higher absorbency than AlN. At 248 nm, the refractive index has little to do with the fraction of MoNx, while n decreases as MoNx increases at 193 nm wavelength. This is consistent with metals in which the energy generated at n for MoNx decreases. At 248 nm, n for AlN and MoNx are nearly identical, while at 193 nm, n for MoNx becomes smaller but larger for AlN, approaching its bandgap energy (-6.5 eV).

Wavelengths of 488 nm (2.54 eV) are commonly used to inspect photomask blanks, and the transmittances of Examples 2 and 3 are -47% and -35%, respectively, which are suitable for inspecting these photomask blanks.

Phase shift characteristics

FIG. 3 summarizes the light transmittance determined by the relative fraction of MoNx relative to the AlN / MoNx multilayer thickness calculated in correspondence with the 180 ° shifted phase at 193 nm and 248 nm wavelengths. At 248 nm, the acceptable transmission (5-10%) is in the range of 0.25 to 0.4 MoNx, while at 193 nm is in the range of approximately 0.1 to 0.2. Thus, the AlN / MoNx multilayer is an ideally adjustable system for phase shift photomask attenuation blanks at 248 nm and 193 nm.

Examples 6-10: AlN / TiN Photomask Blanks

Manufacturing and physical properties

AlN / TiN multilayers are prepared by rf magnetron sputtering from a 5 cm diameter Al target and by dc magnetron sputtering from a 7.6 cm diameter Ti target in a reactive gas compound of Ar and N ₂ . Both targets were presputtered with Ar prior to coating a substrate of quartz 2.5 cm x 3.8 cm x 2.286 mm thick. The static deposition rates for AlN and TiN used to grow a multi-layer of 75% Ar versus 25% N ₂ gas compound at 1.3 × 10 ⁻² Pa are ¹ kW / s and 1.1 kW / s, respectively. To achieve this deposition rate, the Al target was operated at 250 W (210 V) and the Ti target was operated at 150 W (322 V). Table 2 summarizes the thickness of each layer, the total number of bilayers (N), and sheet resistance for AlN / TiN multilayers.

Yes N d (AlN), Å d (TiN), Å % TiN R (Ω / sq) 6 20 29 32 52 160k 7 20 34 26.5 44 1.2M 8 20 44 15.5 26 3.4M 9 20 54 15.5 22 10 20 54 10 15.5

Optical properties

4 and 5 summarize the refractive index and extinction coefficient determined by the ratio of TiN (% TiN) in the AlN / TiN multilayer. This is easy to agree with that n becomes smaller and k becomes larger for TiN than AlN for wavelengths 248 nm and 193 nm. At 488 nm, the wavelength length normally used to inspect the photomask blank, the transmission in Example 7 is preferably low -40%.

Phase shift characteristics

FIG. 6 calculates the light transmittance determined by the TiN ratio with respect to the AlN / TiN multilayer thickness calculated in correspondence with the phase shift of 180 ° at 193 nm and 248 nm. At 248 nm, the acceptable transmission (5-10%) is in the range of 33-45% TiN, while at 193 nm this same transmission is in the range of approximately 15-25%. Thus, the AlN / TiN multilayer is a system that can ideally adjust the phase shift photomask attenuation blank at 248 nm and 193 nm.

Examples 11-14: RuO ₂ / HfO ₂ photomask blank

Manufacture and physical properties

The RuO ₂ / HfO ₂ multilayers were subjected to a total pressure of Ar + O ₂ by dc magnetron sputtering from a 5 cm diameter Ru target and rf magnetron sputtering from a 7.6 cm diameter Hf target at 10 x 1.3 x 10 ^-2 Pa. Reactively prepared at% partial pressure. A 2.5 cm x 3.8 cm x 0.2286 mm quartz substrate is placed briefly under each target to form multiple layers in succession. The static deposition rate measured for each target is used to calculate the time the substrate is briefly positioned under each target to produce a specific layer thickness. The RuO ₂ deposition rate in Examples 11-13 was 0.79 dl / s, while the deposition rate in Example 14 was 3.3 dl / s; This corresponds to 25W (528V) and 50W (619V) applied to the Ru target, respectively. In all these examples, the power applied to the hafnium target was 300W (270V). Prior to depositing the multilayers, both the Hf and Ru targets are presputtered for at least 30 minutes in Ar of 1.3 × 10 ⁻² Pa before the O ₂ gas is injected to form a clean metal surface. Table 3 outlines each layer thickness, total bilayer number (N), and sheet resistance for four RuO ₂ / HfO ₂ multilayers. All the resistors are small enough to dissipate charge during electron beam writing.

Yes N d (RuO ₂ ), Å d (HfO ₂ ), Å % RuO ₂ R (Ω / sq) 11 20 10 40 20 20K 12 20 15 35 30 700 13 20 20 30 40 200 14 20 25 25 50 600

Optical properties

7 and 8 summarize the refractive index and extinction coefficient determined by the ratio of RuO ₂ (% RuO ₂ ) in RuO ₂ / HfO ₂ multilayers at 248 nm and 193 nm wavelengths. It is common to reduce n and increase k in increasing the RuO ₂ content. However, when the extinction coefficient is 50%, because sensitive to deposition conditions, RuO _2, and k is decreased at 193㎚ wavelength, compared to the sputtering at 0.79Å / s of the other RuO ₂ layer is sputtered at 3.3Å / s RuO ₂ layer Reflects the difference in optical properties. That is, films sputtered at higher concentrations of O ₂ are less crystalline than films sputtered at lower concentrations of O ₂ and have a larger extinction coefficient at 193 nm wavelength. As in Example 14, increasing this sputtering rate while maintaining the same O ₂ partial pressure is equivalent to consuming O ₂ at the target surface to reduce the partial pressure. At a wavelength of 488 nm commonly used to inspect the photomask blank, the transmittance for all RuO ₂ / HfO ₂ multilayers was less than 45%, which is desirable to inspect.

Phase shift characteristics

FIG. 9 summarizes the light transmittance determined by the RuO ₂ ratio to RuO ₂ / HfO ₂ multilayer thickness calculated corresponding to 180 ° shifted phase at 193 nm and 248 nm wavelengths. Acceptable transmittances (5-12%) at 248 nm wavelength occur within the 25-30% RuO ₂ range, while at 193 nm the same transmittance occurs within the approximately 17-25% range. Thus at 248 nm and 193 nm RuO ₂ / HfO ₂ multilayers are a system that can ideally adjust the phase shift photomask attenuation blank.

Example 15-18: RuO ₂ / ZrO ₂ Photomask Blanks

Manufacture and physical properties

The RuO ₂ / ZrO ₂ multilayers were subjected to rf magnetron sputtering from a 7.6 cm diameter Zr target and dc magnetron from a 5 cm Ru target at a total pressure of 1.3 × 10 ⁻² Pa at 10% O ₂ to 90% Ar. It is made reactive. In multi-layering synthesis, 515V, 25W was applied to the Ru target, while 280V, 300W was applied to the Zr target. In this state, the static deposition rate on the substrate is 0.79 dl / s for RuO ₂ and 0.77 dl / s for ZrO ₂ . Multiple layers of RuO ₂ / ZrO ₂ are conventionally made by presputtering Ru and Zr targets with Ar of 1.3 × 10 ⁻² Pa and then successively placing a quartz substrate under each target. Table 4 summarizes the composition and sheet resistance of the RuO ₂ / ZrO ₂ multilayers, measuring their optical properties to determine the efficiency as a phase shift photomask attenuation blank. Example 16-18 has a sheet resistance of 1 MΩ / square or less, which is desirable for dissipating charge in electron beam writing.

Yes N d (RuO ₂ ), Å d (ZrO ₂ ), Å % RuO ₂ R (Ω / sq) 15 20 10 40 20 16 20 15 35 30 1M 17 20 20 30 40 20K 18 20 25 25 50 1.4K

Optical properties

10 and 11 is a summary of the refractive index and extinction coefficient that is determined by the ratio of RuO ₂ to the RuO ₂ / ZrO ₂ multilayer and in 248㎚ 193㎚ wavelength. Similar to the multilayer with HfO ₂ , it is common to decrease n and increase k in increasing the RuO ₂ content for ZrO ₂ .

Phase shift characteristics

FIG. 12 summarizes the light transmittance determined by the ratio of RuO ₂ to RuO ₂ / ZrO ₂ multilayer thickness calculated corresponding to 180 ° phase shift at 193 nm and 248 nm. At 248 nm, an acceptable transmission (5-15%) occurs at 35-40% RuO ₂ , while the same light transmission at 193 nm occurs in the range of approximately -20-35%. Thus RuO ₂ / ZrO ₂ multilayers are a system for ideally adjusting phase shift photomask attenuation blanks at 248 nm and 193 nm.

Example 19-20: Aperiodic AlN / MoNx Photomask Blank

Examples 19 and 20 illustrate how it is possible to adjust the optical properties of a multilayer photomask blank by laminating each layer aperiodically. The multilayer of Example 19 periodically deposited AlN / MoNx: 20 x (40 μs AlN + 20 μs MoNx), while Example 20 thickened the MoNX layer more thickly at the membrane / air interface: [12 x (40 μs AlN +) 10 Å MoNx) + 5 (40 Å AlN + 30 Å MoNx) + 3 (40 Å AlN + 50 Å MoNx)]. The two multilayer stacks contain the same amount of AlN (800 kPa) and MoNx (420 kPa), so that their light transmission for energy is almost the same everywhere, as shown in FIG. However, the reflectivity of the more metallic MoNx-rich surface of Example 20 (FIG. 14) is greater than 50% at 2.2 eV (15% compared to the previous 10%) near the inspection energy of 2.54 eV (at 488 nm wavelength). Has a large reflectivity. Thus, it is possible to have specific optical properties such as reflectivity by laminating aperiodically while maintaining the same light transmittance and phase shift.

Claims (18)

For attenuating embedded phase shift photomask blank having a light transmittance of at least 0.001 at a selected lithography wavelength of less than 400 nm and capable of shifting the phase by 180 °. The photomask blank includes an alternating layer of light transmissive material and light absorbing material alternately stacked, The total resistance of the photomask blank is 1 MΩ / square or less based on the light transmissive material and the light absorbing material selected for the photomask blank, and the thickness of the photomask is the light transmissive material and the light absorbent. A light attenuated embedded phase shift photomask blank, characterized in proportion to the thickness of at least one of the materials. The light attenuated embedded phase shift photomask blank of claim 1, wherein the light transmissive material is selected from the group consisting of metal oxides, metal nitrides, alkaline earth metal fluorides, and mixtures thereof. The method of claim 1, wherein the light transmissive material comprises (a) an oxide of Hf, Y, Zr, Al, Si, or Ge; (b) nitrides of Al, Si, B or C; (c) fluorides of Mg, Ba or Ca; And (d) a group consisting of a mixture of these. The light attenuated embedded phase shift photomask blank. The light attenuated embedded phase shift photomask blank of claim 1, wherein the light absorbing material is selected from the group consisting of metal oxides, metal nitrides, and mixtures thereof. The method of claim 1, wherein the light absorbing material is (a) Cr, Ti, Fe, In, Co, Bi, Mn, Cu, Sn, Ni, V, Ta, Mo, Ru, lanthanide series metal or Oxide of W; (b) nitrides of Ti, Nb, Mo, W, Ta, Hf, Y, Zr or Cr; And (c) a group consisting of a mixture of these. The light attenuated embedded phase shift photomask blank. 2. The light attenuated embedded phase shift photomask blank of claim 1, comprising at least two layers of light transmissive material and at least two layers of light absorbing material. The light attenuated embedded phase shift photomask blank of claim 1, wherein the alternately stacked layers are periodic. The light attenuated embedded phase shift photomask blank of claim 1, wherein the alternately stacked layers are aperiodic. A method of making a light attenuated embedded phase shift photomask blank having a light transmittance of at least 0.001 at a selected lithography wavelength of less than 400 nm and capable of shifting the phase by 180 °. Alternately laminating a light transmissive material and a light absorbing material on the substrate, The total resistance of the photomask blank is 1 MΩ / square or less based on the light transmissive material and the light absorbing material selected for the photomask blank, and the thickness of the photomask is the light transmissive material and the light absorbent. A method for forming a light attenuated embedded phase shift photomask blank, characterized in that it is proportional to the thickness of at least one of the materials. 10. The method of claim 9, wherein said alternately stacked layers are periodic. 10. The method of claim 9, wherein said alternately stacked layers are aperiodic. 10. The method of claim 9, wherein at least two layers of light transmissive material are deposited and at least two layers of light absorptive material are deposited. 10. The method of claim 9, wherein the light transmissive material is selected from the group consisting of metal oxides, metal nitrides, alkaline earth metal fluorides, and mixtures thereof. 10. The method of claim 9, wherein the light transmissive material comprises (a) an oxide of Hf, Y, Zr, Al, Si, or Ge; (b) nitrides of Al, Si, B or C; And (c) fluorides of Mg, Ba, or Ca, and (d) mixtures thereof. 10. The method of claim 9, wherein said light absorbing material is selected from the group consisting of metal oxides, metal nitrides, and mixtures thereof. 10. The method of claim 9, wherein the light absorbing material is (a) Cr, Ti, Fe, In, Co, Bi, Mn, Cu, Sn, Ni, V, Ta, Mo, Ru, lanthanum-based metals or oxides of W; (b) nitrides of Ti, Nb, Mo, W, Ta, Hf, Zr or Cr; And (c) a group consisting of a mixture thereof. 10. The method of claim 9, wherein said alternately stacked layers are deposited by vapor deposition. 10. The method of claim 9, wherein said alternately stacked layers are deposited by sputter deposition.