JP2017134213A - Phase shift mask blank and phase shift mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a halftone type phase shift mask blank having surface reflectance of equal to or less than binary blank for multi-wavelengths of i-line, h-line, and g-line.SOLUTION: Provided is a halftone type phase shift mask blank 100 used for manufacturing a halftone type phase shift mask. The halftone type phase shift mask blank includes a transparent substrate 101 and a phase shifter layer 105 disposed on one face 101a side of the transparent substrate, in which the phase shifter layer has a phase difference of substantially 180° with respect to three wavelengths of i-line, h-line, and g-line. The phase shifter layer includes a region B103 having a higher refractive index than those of upper and lower regions A104 and C102 at a prescribed depth position D1 between a surface 105a thereof to the center of the thickness of the layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a halftone phase shift mask blank having a phase difference with respect to a composite wavelength, and a halftone phase shift mask using the same.

In the semiconductor field, circuit patterns are being miniaturized in order to achieve high-density mounting. In connection with this, shortening of an exposure wavelength, improvement of an exposure method, etc. are examined.
In order to cope with such miniaturization of the circuit pattern, in the photomask, from a binary mask formed only with a simple light-shielding film pattern, light interference at the pattern edge is used and a single wavelength is used to obtain a finer pattern. Phase-shifting masks (PSM) capable of pattern formation have been used.

  As the above-described semiconductor phase shift mask, a combination of exposure light consisting of an i-line single wavelength and an edge-enhanced phase shift mask (for example, Patent Document 1), or ArF single wavelength for further miniaturization. A combination of exposure light consisting of the above and a halftone phase shift mask (Attenuated PSM) (for example, Patent Document 2) is used.

On the other hand, in the flat panel display (FPD) field, in order to realize cost reduction, it is necessary to perform production at a high throughput, and the exposure light wavelength is i-line (wavelength 365 nm), h-line (wavelength 403 nm). ), Pattern formation is performed by exposure using a composite wavelength composed of g-line (wavelength 436 nm).
Recently, in the FPD field as well, the pattern profile tends to be miniaturized in order to form a high-definition screen. Instead of a photomask (binary mask) patterned with a conventional light-shielding film, a halftone phase is used. Use of a shift mask has been studied (for example, Patent Document 3).

  As shown in FIG. 9, a halftone phase shift mask blank (also called a halftone phase shift mask blank) 900 is basically provided with a single-layer shifter film 902 on one surface 901a side of a quartz substrate 901. Thus, the phase shift effect is expressed. The optical characteristics required for the shifter film 902 are a phase shift effect (a phase angle of 180 degrees at the exposure wavelength) and a predetermined transmittance. For example, when the shifter film 902 is formed of a chromium-based film (oxynitride film), the surface reflectance at the surface 902a of the shifter film 902 is about 23% (wavelength 365 nm) in the halftone phase shift mask blank. In a binary blank using a normal chromium film, the surface reflectance is 15% or less (wavelength 365 nm).

In the FPD field, the exposure light quantity is increased by using a composite wavelength composed of i-line, h-line, and g-line as the wavelength of exposure light. At each wavelength, the phase angle shifts from 180 degrees, but it has been confirmed that there is a total phase shift effect.
However, as described above, the halftone phase shift mask blank has a problem that a sufficient resolution cannot be obtained because the surface reflectance is twice or more that of the binary blank.
Further, the halftone phase shift mask blank has a tendency that the back surface reflectance tends to be high, and the reflection of the exposure light incident from the transparent substrate side cannot be prevented, and there is a problem that sufficient resolution cannot be obtained.

  Therefore, a halftone phase shift mask blank having a surface reflectance or a rear surface reflectance equal to or lower than that of a binary blank for a composite wavelength composed of i-line, h-line, and g-line, and a halftone-type phase shift using the same The development of the mask was expected.

JP-A-8-272071 JP 2006-078953 A JP 2010-128003 A

  The present invention has been devised in view of such conventional circumstances, and has a surface reflectance or back surface reflectance of a binary blank or lower for a composite wavelength composed of i-line, h-line, and g-line, It is an object to provide a halftone phase shift mask blank and a halftone phase shift mask using the same.

The halftone phase shift mask blank according to claim 1 of the present invention includes a transparent substrate and a phase shifter layer disposed on one surface side of the transparent substrate, and the phase shifter layer includes i-line, h-line and A halftone phase shift mask blank used for manufacturing a halftone phase shift mask having a phase difference of approximately 180 ° with respect to three wavelengths of g-line, wherein the phase shifter layer is formed from the surface thereof. A portion B having a higher refractive index than the upper and lower portions A and C is provided at a predetermined depth position to the center of the layer thickness. Here, the phase difference of about 180 ° indicates 170 ° or more and 190 ° or less.
The halftone phase shift mask blank according to claim 2 of the present invention is the halftone phase shift mask blank according to claim 1, wherein the depth position where the portion B is disposed is 20 nm or more and 40 nm or less when viewed from the surface side of the phase shifter layer. It is characterized by being.
The halftone phase shift mask blank according to claim 3 of the present invention is characterized in that, in claim 1 or 2, the portion B is a single thin film layer.
The halftone phase shift mask blank according to claim 4 of the present invention includes a transparent substrate and a phase shifter layer disposed on one side of the transparent substrate, and the phase shifter layer includes i-line, h-line and A halftone phase shift mask blank used for manufacturing a halftone phase shift mask having a phase difference of approximately 180 ° with respect to the three wavelengths of the g-line, wherein the phase shifter layer is formed from the back surface thereof. A portion B having a higher refractive index than the upper and lower portions A and C is provided at a predetermined depth position to the center of the layer thickness.
The halftone phase shift mask blank according to claim 5 of the present invention is the halftone phase shift mask blank according to claim 4, wherein the depth position where the portion B is disposed is 15 nm or more and 45 nm or less as viewed from the back side of the phase shifter layer. It is characterized by being.
The halftone phase shift mask blank according to claim 6 of the present invention is characterized in that, in claim 4 or 5, the portion B is a single thin film layer.
A halftone phase shift mask blank according to a seventh aspect of the present invention is the halftone phase shift mask blank according to the third or sixth aspect, wherein the thickness of the thin film layer is 1 nm or more and 10 nm or less.
In the halftone phase shift mask according to claim 8 of the present invention, a predetermined pattern can be obtained from the phase shifter layer in the halftone phase shift mask blank according to any one of claims 1 to 7. It is characterized by having a mask pattern made up of a light transmission part and a phase shifter part, which is obtained by performing a patterning process to be selectively removed.

  The invention according to claim 1 (first halftone phase shift mask blank) includes a transparent substrate and a phase shifter layer disposed on one surface side of the transparent substrate, and the phase shifter layer is formed from the surface thereof. A portion B having a higher refractive index than the upper and lower portions A and C is provided at a predetermined depth position to the center of the layer thickness. Thereby, a halftone phase shift mask blank having a surface reflectance equal to or lower than that of the binary blank with respect to a composite wavelength composed of i-line, h-line, and g-line is obtained. Therefore, the present invention contributes to the provision of a halftone phase shift mask blank in which sufficient resolution can be obtained at the composite wavelength of exposure light having i-line, h-line, and g-line.

  The invention according to claim 3 (second halftone phase shift mask blank) is composed of a transparent substrate and a phase shifter layer disposed on one surface side of the transparent substrate, and the phase shifter layer is formed from the back surface thereof. A portion B having a higher refractive index than the upper and lower portions A and C is provided at a predetermined depth position to the center of the layer thickness. Thereby, the halftone phase shift mask blank which has the back surface reflectance of a binary blank or less with respect to the composite wavelength which consists of i line | wire, h line | wire, and g line | wire is obtained. Therefore, according to the present invention, it is possible to prevent reflection of exposure light incident from the transparent substrate side at a composite wavelength composed of i-line, h-line, and g-line, and a sufficient resolution can be obtained. This contributes to the provision of a halftone phase shift mask blank.

Sectional drawing which shows an example (1st embodiment) of the phase shift mask blank of this invention. Sectional drawing which shows another example (2nd embodiment) of the phase shift mask blank of this invention. The graph which shows the relationship between the position of the site | part B, and surface reflectance. The graph which shows the relationship between the position of the site | part B, and a back surface reflectance. The graph which shows the relationship between the position of the site | part B, and the transmittance | permeability. The graph which shows the relationship between the thickness of the site | part B, surface reflectance, and the transmittance | permeability. Sectional drawing which shows an example (corresponding to 1st embodiment) of the phase shift mask of this invention. Sectional drawing which shows another example (corresponding to 2nd embodiment) of the phase shift mask of this invention. Sectional drawing which shows an example of the conventional phase shift mask blank.

  Hereinafter, an embodiment of a halftone phase shift mask blank according to the present invention will be described with reference to the drawings. In the following description, “phase tone mask blank” to “halftone type” are omitted.

(First embodiment): Surface reflectance (insertion depth dependence of part B, thickness of part B = fixed to 4 nm)
FIG. 1 is a sectional view showing an example (first embodiment) of the phase shift mask blank of the present invention. In this embodiment, the position of the part B103 inserted into the phase shifter layer 105 (the position on the back surface 103b side of the part B103 viewed from the front surface 104a (105a) side of the phase shifter layer 105 = the insertion depth) and the phase A simulation was performed on the relationship with the surface reflectance on the surface 104a (105a) of the shifter layer 105. As a simulation method, the method disclosed in Essential Macleod was used.

  That is, the first phase shift mask blank 100 according to this embodiment includes the transparent substrate 101 and the phase shifter layer 105 disposed on the one surface 101 a side of the transparent substrate 101. The phase shifter layer 105 is configured by overlapping a part A 104, a part B 103, and a part C 102 in this order as viewed from the surface 104 a side, and the part C 102 is in contact with the one surface 101 a of the transparent substrate 101.

  The part B103 is disposed at a predetermined depth position (D1) from the surface 104a of the phase shifter layer 105. The part B103 has a higher refractive index than the part A104 located above the part B103 and the part C102 located below the part B103. That is, when the refractive index of the portion A104 is defined as Na, the refractive index of the portion B103 is defined as Nb, and the refractive index of the portion C102 is defined as Nc, the relationship is Nb> Na, Nb> Nc. At this time, in this embodiment, the part B103 is assumed to be composed of a single thin film layer (thickness T1). The refractive index described here indicates the complex refractive index N.

  In this simulation, the phase shift mask blank 100 is configured such that the transparent substrate 101 is composed of a quartz substrate (thickness 10 mm) and the phase shifter layer 105 is composed of a chromium oxide film (thickness 120 nm). A phase shifter layer 105 is disposed on the transparent substrate 101, and a condition is provided where a portion B103 made of a chromium film (thickness 4 nm) is provided at a predetermined depth from the surface 104a of the phase shifter layer 105. did. At that time, the predetermined depth position where the portion B103 was provided was changed from the surface 104a of the phase shifter layer 105 at an interval of 5 nm. That is, the phase shifter layer 105 is a laminated body in which a chromium film (part B103) is inserted into a chromium oxide film (part A102, part C104).

  In the present embodiment, the surface reflectance of the phase shifter film 105 at three wavelengths, i.e., i-line (wavelength 365 nm), h-line (wavelength 403 nm), and g-line (wavelength 436 nm) was examined. At that time, the numerical values shown in Table 1 were used as the optical constants of the chromium oxide film (part A102, part C104) and the chromium film (part B103). Here, N is a complex refractive index, and is expressed as N = n + ik using the refractive index n and the extinction coefficient k. n and k are collectively referred to as an optical constant. The optical constants (n, k) shown in Table 1 used for the simulation are reliable numerical values confirmed not only by design but also by actual film formation.

FIG. 3 shows the surface reflectivity by changing the position of the part B so that a predetermined insertion depth (also referred to as “distance from the surface”) from the surface 104a of the phase shifter layer 105 to the layer thickness center LC is obtained. It is a graph which shows the result of simulation. The symbol ◇ indicates the result of i-line (wavelength 365 nm), the symbol ◯ indicates the result of h-ray (wavelength 403 nm), and the symbol Δ indicates the result of g-line (wavelength 436 nm). In addition, the ◆ mark, the ● mark, and the ▲ mark plotted at positions where the insertion depth is zero are respectively “when the chromium film (part B) is not provided [reference phase]” [that is, the phase shifter film 205 Is a chromium oxide film (part A102, part C104)].
Table 2 shows the values plotted in the graph of FIG. The result of specifying “Rfa: no thin film” in the evaluation column of Table 2 is a reference (judgment standard).

From Table 2 and FIG. 3, the following points became clear.
(A1) In the two regions (region * 1, region * 2) where the position D1 of the part B excludes the vicinity of the layer thickness center LC from the surface 104a of the phase shifter layer 105, the numerical value of the surface reflectance is a reference ( Rfa) is lower for all three wavelengths (i-line, h-line, and g-line).
(A2) In particular, when the position D1 of the part B is included in the region * 1, the surface reflectance is greatly reduced as compared with the region * 2. The region * 1 is in a “predetermined depth position (insertion depth: D1)” from the surface 104a of the phase shifter layer 105 to the layer thickness center LC.
(A3) The “predetermined depth position D1” to be the region * 1 is a range of 20 nm to 40 nm. When the “predetermined depth position D1” satisfies the region * 1, a phase shift mask blank having a surface reflectance of a binary blank or less is obtained at all three wavelengths (i-line, h-line, and g-line).

  In the present embodiment, the case where the part B103 is formed of a single thin film layer (thickness T1) has been described in detail. However, the refractive index Na of the part A104, the refractive index Nb of the part B103, and the refractive index Nc of the part C102 are described. However, as long as the relations of Nb> Na and Nb> Nc are satisfied, the portion B103 of the present invention is not limited to a single thin film layer. That is, the part B103 may have a structure in which two or more thin films are stacked. In that case, the two or more layers of thin films constituting the portion B103 may be made of the same material or different materials.

  In the present embodiment, the phase shifter layer 105 is described in which the portion C104 and the portion A102 are made of a chromium oxide film and the portion B103 is made of a chromium film. As long as the refractive index Nb and the refractive index Nc of the part C102 satisfy the relationship of Nb> Na, Nb> Nc, the phase shifter layer 105 may be made of other materials. Other materials suitable for the phase shifter layer include, in addition to chromium, one or more materials selected from tantalum, titanium, aluminum, vanadium, zirconium, niobium, molybdenum, tungsten, and silicon, or these materials. Examples thereof include nitrides, oxynitrides, oxides, and silicon compounds.

<Second embodiment>: Back surface reflectance (insertion depth dependence of part B, thickness of part B = 4 nm fixed)
FIG. 2 is a cross-sectional view showing another example (second embodiment) of the phase shift mask blank of the present invention. In this embodiment, the position of the portion B203 inserted into the phase shifter layer 205 (the position on the back surface 203b side of the portion B203 viewed from the front surface 204a (205a) side of the phase shifter layer 205 = the insertion depth) and the phase A simulation was performed on the relationship with the back surface reflectance of the back surface 202b (205b) of the shifter layer 205. As a simulation method, the same method as in the first embodiment was used.

  That is, the second phase shift mask blank 200 according to the present embodiment includes the transparent substrate 201 and the phase shifter layer 205 disposed on the one surface 201a side of the transparent substrate 201. The phase shifter layer 205 is configured by overlapping a part A 204, a part B 203, and a part C 202 in this order when viewed from the surface 204 a (205 a) side, and the part C 202 is in contact with the one surface 201 a of the transparent substrate 201.

  The portion B203 is disposed at a predetermined depth position (D2) from the back surface 202b (205b) of the phase shifter layer 205. The part B203 has a higher refractive index than the part A204 located above the part B203 and the part C202 located below the part B203. That is, when the refractive index of the portion A204 is defined as Na, the refractive index of the portion B203 is defined as Nb, and the refractive index of the portion C202 is defined as Nc, the relationship is Nb> Na, Nb> Nc. At this time, in this embodiment, the part B103 is assumed to be composed of a single thin film layer (thickness T2).

  In this simulation, as in the first embodiment, the phase shift mask blank 200 is configured such that the transparent substrate 201 is composed of a quartz substrate (thickness 10 mm) and the phase shifter layer 205 is composed of a chromium oxide film (thickness 120 nm). did. A phase shifter layer 205 is disposed on the transparent substrate 201, and a portion B203 made of a chromium film (thickness 4 nm) is formed at a predetermined depth position from the back surface 202b (205b) of the phase shifter layer 205. The conditions were provided. At that time, the predetermined depth position where the portion B203 was provided was changed at an interval of 5 nm from the back surface 202b (205b) of the phase shifter layer 205. That is, the phase shifter layer 205 is a laminated body in which a chromium film (part B203) is inserted into a chromium oxide film (part A202, part C204).

  In the present embodiment, the back surface reflectance of the phase shifter film 205 at three wavelengths, i.e., i-line (wavelength 365 nm), h-line (wavelength 403 nm), and g-line (wavelength 436 nm) was examined. At that time, the numerical values in Table 1 were used as the optical constants of the chromium oxide film (part A202, part C204) and the chromium film (part B203), as in the first embodiment.

FIG. 4 shows a case where the position of the part B is changed so that a predetermined insertion depth (also referred to as “distance from the back surface”) from the back surface 202b (205b) of the phase shifter layer 205 to the layer thickness center LC is obtained. It is a graph which shows the result of having simulated the reflectance. The symbol ◇ indicates the result of i-line (wavelength 365 nm), the symbol ◯ indicates the result of h-ray (wavelength 403 nm), and the symbol Δ indicates the result of g-line (wavelength 436 nm). In addition, the ◆ mark, the ● mark, and the ▲ mark plotted at positions where the insertion depth is zero are respectively “when the chromium film (part B) is not provided [reference phase]” [that is, the phase shifter film 205 Is a chromium oxide film (part A202, part C204)].
Table 3 shows numerical values plotted in the graph of FIG. The result of specifying “Rfb: no thin film” in the evaluation column of Table 3 is a reference (judgment standard).

From Table 3 and FIG. 4, the following points became clear.
(B1) The numerical value of the back surface reflectance in two regions (region * 3, region * 4) where the position D2 of the part B excludes the vicinity of the layer thickness center LC from the back surface 202b (205b) of the phase shifter layer 205. Are lower than the reference (Rfb) by 3 wavelengths (i-line, h-line, g-line).
(B2) In particular, when the position D2 of the part B is included in the region * 4, the back surface reflectance is greatly reduced as compared with the region * 3. The region * 4 is in a “predetermined depth position (insertion depth) D2” from the back surface 202b (205b) of the phase shifter layer 205 to the layer thickness center LC.
(B3) The “predetermined depth position D2” to be the region * 4 is a range of 15 nm to 44 nm. When the “predetermined depth position D2” satisfies the region * 4, a phase shift mask blank having a low back surface reflectance is obtained for all three wavelengths (i-line, h-line, and g-line).

  In the present embodiment, the case where the part B203 is composed of a single thin film layer (thickness T2) has been described in detail. However, the refractive index Na of the part A204, the refractive index Nb of the part B203, and the refractive index Nc of the part C202. However, as long as the relationship of Nb> Na, Nb> Nc is satisfied, the portion B203 of the present invention is not limited to a single thin film layer. That is, the part B203 may have a structure in which two or more thin films are stacked. At that time, the thin films of two or more layers constituting the part B203 may be made of the same material or different materials.

  In the present embodiment, the phase shifter layer 205 is described in which the portion C204 and the portion A202 are made of a chromium oxide film and the portion B203 is made of a chromium film. However, the refractive index Na of the portion A204 and the refraction of the portion B203 are described. As long as the refractive index Nb and the refractive index Nc of the part C202 satisfy the relationship of Nb> Na, Nb> Nc, the phase shifter layer 205 may be made of other materials. Other materials suitable for the phase shifter layer include, in addition to chromium, one or more materials selected from tantalum, titanium, aluminum, vanadium, zirconium, niobium, molybdenum, tungsten, and silicon, or these materials. Examples thereof include nitrides, oxynitrides, oxides, and silicon compounds.

<Third embodiment>: Transmittance (insertion depth dependence of part B, thickness of part B = fixed to 4 nm)
In this embodiment, in FIG. 1, the position of the portion B103 inserted into the phase shifter layer 105 (the position on the back surface 103b side of the portion B103 viewed from the front surface 104a (105a) side of the phase shifter layer 105 = insertion depth). ) And the transmittance of the phase shifter layer 105 passing through the front surface 104a (105a) to the back surface 103b (105b). As a simulation method, the same method as in the first embodiment was used.

  This embodiment is based on the first phase shift mask blank 100 having the same layer configuration as that of the first embodiment described above. That is, the first phase shift mask blank includes a transparent substrate 101 and a phase shifter layer 105 disposed on the one surface 101a side of the transparent substrate 101. The phase shifter layer 105 is configured by overlapping a part A 104, a part B 103, and a part C 102 in this order as viewed from the surface 104 a side, and the part C 102 is in contact with the one surface 101 a of the transparent substrate 101.

  The part B103 is disposed at a predetermined depth position (D1) from the surface 104a of the phase shifter layer 105. The part B103 has a higher refractive index than the part A104 located above the part B103 and the part C102 located below the part B103. That is, when the refractive index of the portion A104 is defined as Na, the refractive index of the portion B103 is defined as Nb, and the refractive index of the portion C102 is defined as Nc, the relationship is Nb> Na, Nb> Nc. At this time, in this embodiment, the part B103 is assumed to be composed of a single thin film layer (thickness T1).

  In this simulation, the phase shift mask blank 100 is configured such that the transparent substrate 101 is composed of a quartz substrate (thickness 10 mm) and the phase shifter layer 105 is composed of a chromium oxide film (thickness 120 nm). A phase shifter layer 105 is disposed on the transparent substrate 101, and a condition is provided where a portion B103 made of a chromium film (thickness 4 nm) is provided at a predetermined depth from the surface 104a of the phase shifter layer 105. did. At that time, the predetermined depth position where the portion B103 was provided was changed from the surface 104a of the phase shifter layer 105 at an interval of 5 nm. That is, the phase shifter layer 105 is a laminated body in which a chromium film (part B103) is inserted into a chromium oxide film (part A102, part C104).

  In this embodiment, the transmittance of the phase shifter film 105 at three wavelengths, i.e., i-line (wavelength 365 nm), h-line (wavelength 403 nm), and g-line (wavelength 436 nm) was examined. At that time, as in the first embodiment, the numerical values in Table 1 were used as the optical constants of the chromium oxide film (part A102, part C104) and the chromium film (part B103).

FIG. 5 shows a simulation of the transmittance by changing the position of the part B so that a predetermined insertion depth (also referred to as “distance from the surface”) from the surface 104a of the phase shifter layer 105 to the layer thickness center LC is obtained. It is a graph which shows the result. The symbol ◇ indicates the result of i-line (wavelength 365 nm), the symbol ◯ indicates the result of h-ray (wavelength 403 nm), and the symbol Δ indicates the result of g-line (wavelength 436 nm). Further, the ◆ mark, the ● mark, and the ▲ mark plotted at the positions where the insertion depth is zero are respectively “when the chromium film (part B) is not provided as a reference” [that is, the phase shifter film 105 Is a chromium oxide film (part A102, part C104)].
Table 4 shows the values plotted in the graph of FIG. The result specified as “Rfc: no thin film” in the evaluation column of Table 2 is a reference (judgment standard).

The following points became clear from Table 4 and FIG.
(C1) Regardless of the position (insertion depth) D1 of the part B, the numerical value of the transmittance is lower for all three wavelengths (i-line, h-line, and g-line) than the reference (Rfa). However, the position D1 of the part B is transmitted more than the vicinity of the layer thickness center LC in two regions (region * 5, region * 6) excluding the vicinity of the layer thickness center LC from the surface 104a of the phase shifter layer 105. The numerical value of the rate increases for all three wavelengths (i-line, h-line, and g-line).
(C2) The above two regions (region * 5, region * 6) correspond to the insertion depth regions where the antireflection effect appears on the front and back surfaces shown in the first embodiment and the second embodiment. Therefore, it was confirmed that providing the portion B inside the phase shifter layer 105 produces not only the effect of reducing the reflectance but also the effect of increasing the transmittance.
Therefore, according to the present invention, a phase shift mask blank having a low reflectance on the front and back surfaces and a high transmittance at all three wavelengths (i-line, h-line, and g-line) can be obtained.

  In the present embodiment, the case where the part B103 is formed of a single thin film layer (thickness T1) has been described in detail. However, the refractive index Na of the part A104, the refractive index Nb of the part B103, and the refractive index Nc of the part C102 are described. However, as long as the relations of Nb> Na and Nb> Nc are satisfied, the portion B103 of the present invention is not limited to a single thin film layer. That is, the part B103 may have a structure in which two or more thin films are stacked. In that case, the two or more layers of thin films constituting the portion B103 may be made of the same material or different materials.

  In the present embodiment, the phase shifter layer 105 is described in which the portion C104 and the portion A102 are made of a chromium oxide film and the portion B103 is made of a chromium film. As long as the refractive index Nb and the refractive index Nc of the part C102 satisfy the relationship of Nb> Na, Nb> Nc, the phase shifter layer 105 may be made of other materials. Other materials suitable for the phase shifter layer include, in addition to chromium, one or more materials selected from tantalum, titanium, aluminum, vanadium, zirconium, niobium, molybdenum, tungsten, and silicon, or these materials. Examples thereof include nitrides, oxynitrides, oxides, and silicon compounds.

<Fourth embodiment>: Surface reflectance, transmittance (film thickness dependence of part B, wavelength = 365 nm fixed)
In the present embodiment, the film thickness dependence of the part B103 inserted into the phase shifter layer 105 was examined for the surface reflectance and transmittance of the phase shift mask blank having the configuration shown in FIG.
The phase shifter layer 105 is assumed to have a three-layer structure (part A102, part B103, part C104) when the surface reflectance and transmittance are obtained by the simulation method used in the first to third embodiments. The total thickness of the phase shifter layer 105 is evaluated as “120 nm”, and the position (insertion depth) D1 of the portion B is evaluated as “25 nm” in which the surface reflectance shows an extreme value when the wavelength is 365 nm in FIG. The wavelength to be fixed was fixed at “365 nm”. The thickness of the part B103 was changed in the range of 0 to 20 [nm], and the surface reflectance and transmittance were obtained by the simulation method used in the first to third embodiments. For comparison, surface reflectance and transmittance were obtained by a polynomial approximate curve method.

FIG. 6 is a graph showing the relationship between the thickness of the part B, the surface reflectance, and the transmittance, where (a) is the result of the surface reflectance and (b) is the result of the transmittance. In FIG. 6, the solid line is the simulation value, and the dotted line is the evaluation result of the polynomial approximation curve. In the horizontal axis of FIG. 6, “inserted chrome film thickness” is displayed instead of “position B position (insertion depth) D1”.
The following points became clear from FIG.
(D1) As the film thickness of the part B103 increases, both the surface reflectance and the transmittance tend to decrease monotonously.
(D2) The results of the simulation (solid line) and the polynomial approximation curve (dotted line) show the same decreasing tendency. In particular, when the position (insertion depth) D1 of the part B is in the range of 0 to 10 nm, the curves are almost the same.
(D3) In order to satisfy the characteristics required for the phase shifter layer 105, that is, low surface reflectance and high transmittance, it is preferable that the position (insertion depth) D1 of the portion B is in the range of 1 to 10 nm. In particular, if the range is 1 to 5 nm, the surface reflectance is decreased in the range of 0 to 30% and the decrease in transmittance is within 0 to 30% compared to zero on the horizontal axis (no thin film). This is more preferable.

  Hereinafter, an embodiment of a halftone phase shift mask according to the present invention will be described with reference to the drawings. In the following description, “halftone type” is omitted from “phase shift mask”.

<First phase shift mask>
FIG. 7 is a cross-sectional view showing an example of the phase shift mask according to the present invention (corresponding to the first embodiment). A first phase shift mask 700 shown in FIG. 7 includes a transparent substrate 701 and a phase shifter layer 705 disposed on the one surface 701a side of the transparent substrate 701. The phase shifter layer 705 includes a part A 704, a part B 703, and a part C 702 that are stacked in this order as viewed from the surface 704 a side, and the part C 702 is in contact with one surface 701 a of the transparent substrate 701. In the first phase shift mask 700, the part B703 is arranged so as to have a predetermined insertion depth (also referred to as “distance from the surface”) from the surface 704a of the phase shifter layer 705 to the layer thickness center LC. Yes.

  That is, the first phase shift mask 700 is obtained by performing a patterning process for selectively removing the phase shifter layer in the phase shift mask blank of FIG. 1 so as to obtain a predetermined pattern. It has a mask pattern composed of a light transmission part (area indicated as β) and a phase shifter part (area indicated as α). That is, the light transmission portion (β region) is a portion where the phase shifter layer 705 is completely removed, and the phase shifter portion (α region) is a portion where the phase shifter layer 705 remains entirely.

  In the first phase shift mask 700, the phase shifter layer 705 (105 in FIG. 1) that constitutes the phase shifter portion (α region) is vertically moved at a predetermined depth position from the surface to the layer thickness center LC. A portion B having a higher refractive index than the portions A and C is provided. As a result, a halftone phase shift mask having a surface reflectance equal to or lower than that of a binary blank with respect to a composite wavelength composed of i-line, h-line, and g-line is obtained. Therefore, the first phase shift mask 700 can obtain sufficient resolution at the composite wavelength in which the exposure light wavelength is i-line, h-line, and g-line.

<Second phase shift mask>
FIG. 8 is a cross-sectional view showing another example of the phase shift mask according to the present invention (corresponding to the second embodiment). The second phase shift mask 800 shown in FIG. 8 includes a transparent substrate 801 and a phase shifter layer 805 disposed on the one surface 801a side of the transparent substrate 801. The phase shifter layer 805 is configured by overlapping a portion A804, a portion B803, and a portion C802 in this order as viewed from the surface 804a side, and the portion C802 is in contact with one surface 801a of the transparent substrate 801. In the second phase shift mask 800, the region B 803 has a predetermined insertion depth (also referred to as “distance from the back surface”) from the back surface 802 b (805 b) of the phase shifter layer 805 to the layer thickness center LC. The position is arranged.

  That is, the second phase shift mask 800 is obtained by performing a patterning process for selectively removing the phase shifter layer in the phase shift mask blank of FIG. 2 so as to obtain a predetermined pattern. It has a mask pattern composed of a light transmission part (area indicated as β) and a phase shifter part (area indicated as α). That is, the light transmission part (β region) is a part from which all of the phase shifter layer 805 is removed, and the phase shifter part (α region) is a part from which all of the phase shifter layer 805 remains.

  In the second phase shift mask 800, the phase shifter layer 805 (205 in FIG. 2) constituting the phase shifter portion (α region) is positioned at a predetermined depth position from the back surface to the layer thickness center LC. A portion B having a higher refractive index than the portions A and C is provided. Thereby, a halftone phase shift mask having a back surface reflectance equal to or lower than that of a binary blank with respect to a composite wavelength composed of i-line, h-line, and g-line is obtained. Therefore, the second phase shift mask 800 can obtain sufficient resolution at the composite wavelength in which the exposure light wavelength is i-line, h-line, and g-line.

  Therefore, the present invention contributes to the provision of a halftone phase shift mask having a front-surface reflectance or a back-surface reflectance equal to or lower than that of a binary blank with respect to a composite wavelength composed of i-line, h-line, and g-line.

  The halftone phase shift mask blank and the halftone phase shift mask of the present invention have been described above. However, the present invention is not limited to this, and can be appropriately changed without departing from the spirit of the invention. It is.

  The present invention is widely applicable to a halftone phase shift mask blank used for a composite wavelength composed of i-line, h-line, and g-line, and a halftone-type phase shift mask using the same.

  100 Phase shift mask blank, 101 Transparent substrate, 101a One surface of transparent substrate, 105 Phase shifter layer, 105a Surface of phase shifter layer, A104 upper part, B103 High refractive index part, C102 lower part

Claims (8)

A halftone including a transparent substrate and a phase shifter layer disposed on one side of the transparent substrate, wherein the phase shifter layer has a phase difference of about 180 ° with respect to three wavelengths of i-line, h-line, and g-line. A halftone phase shift mask blank used to manufacture a type phase shift mask,
The phase shifter layer is provided with a portion B having a refractive index higher than that of the upper and lower portions A and C at a predetermined depth position from the surface to the center of the layer thickness.   2. The halftone phase shift mask blank according to claim 1, wherein a depth position where the portion B is disposed is 20 nm or more and 40 nm or less when viewed from the surface side of the phase shifter layer.   The halftone phase shift mask blank according to claim 1, wherein the portion B is a single thin film layer. A halftone including a transparent substrate and a phase shifter layer disposed on one side of the transparent substrate, wherein the phase shifter layer has a phase difference of about 180 ° with respect to three wavelengths of i-line, h-line, and g-line. A halftone phase shift mask blank used to manufacture a type phase shift mask,
The phase shifter layer is provided with a portion B having a refractive index higher than that of the upper and lower portions A and C at a predetermined depth position from the back surface to the center of the layer thickness.   5. The halftone phase shift mask blank according to claim 4, wherein a depth position where the portion B is disposed is 15 nm or more and 45 nm or less when viewed from the back surface side of the phase shifter layer.   6. The halftone phase shift mask blank according to claim 4, wherein the portion B is a single thin film layer.   The halftone phase shift mask blank according to claim 3 or 6, wherein the thin film layer has a thickness of 1 nm or more and 10 nm or less.   A light obtained by performing a patterning process for selectively removing the phase shifter layer in the halftone phase shift mask blank according to claim 1 so as to obtain a predetermined pattern. A halftone phase shift mask having a mask pattern including a transmission portion and a phase shifter portion.

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