WO2022230694A1

WO2022230694A1 - Phase shift mask blank, phase shift mask, light exposure method, and device manufacturing method

Info

Publication number: WO2022230694A1
Application number: PCT/JP2022/017946
Authority: WO
Inventors: 賢利林; 茂彦宮城; 高史八神
Original assignee: 株式会社ニコン
Priority date: 2021-04-30
Filing date: 2022-04-15
Publication date: 2022-11-03
Also published as: JPWO2022230694A1; TW202303260A; KR20240003435A; CN116670583A

Abstract

Provided is a phase shift mask blank that allows for manufacture of a phase shift mask having a highly accurate pattern. A phase shift mask blank (100) comprises a base material (10) and a phase shift layer (20) formed on the base material (10) and containing zirconium (Zr), silicon (Si), and nitrogen (N). The phase shift layer (20) has a nitrogen concentration of greater than or equal to 51 atom%.

Description

PHASE SHIFT MASK BLANKS, PHASE SHIFT MASK, EXPOSURE METHOD, AND DEVICE MANUFACTURING METHOD

The present invention relates to phase shift mask blanks, phase shift masks, exposure methods, and device manufacturing methods.

A phase shift mask is known in which a phase shift layer made of chromium oxynitride is formed on a transparent substrate (Patent Document 1). It has been desired to improve the quality of phase shift masks.

JP 2011-013283 A

According to a first aspect, a phase shift mask blank comprising a substrate and a phase shift layer containing zirconium (Zr), silicon (Si) and nitrogen (N) formed on the substrate. and a nitrogen concentration of 51 atomic % or more in the phase shift layer.

According to a second aspect, there is provided a phase shift mask in which a part of the phase shift layer of the phase shift mask blank of the first aspect is removed and a predetermined pattern is formed on the surface of the phase shift layer. be.

According to the third aspect, there is provided an exposure method for exposing a photosensitive substrate through the phase shift mask of the second aspect.

According to a fourth aspect, there is provided a device manufacturing method including the exposure method of the third aspect.

FIG. 1 is a schematic cross-sectional view of a phase shift mask blank according to an embodiment. FIG. 2 is a schematic cross-sectional view of a phase shift mask blank according to a modification. FIG. 3 is a schematic cross-sectional view of the phase shift mask according to the embodiment. 4A to 4E are diagrams for explaining the method of manufacturing the phase shift mask according to the embodiment. FIG. 5 is a schematic diagram of an exposure apparatus used in the exposure method of the embodiment. FIG. 6 is a graph showing the relationship between the nitrogen concentration in the phase shift layer and the refractive index and extinction coefficient of the phase shift layer for light with a wavelength of 365 nm in Examples. FIG. 7 is a graph showing the relationship between the nitrogen concentration in the phase shift layer and the transmittance of the phase shift layer to light with a wavelength of 365 nm in Examples. FIGS. 8A to 8J are SEM photographs of cross sections of phase shift layers in Examples. FIG. 9 is a graph showing the relationship between the nitrogen concentration in the phase shift layer and the tilt angle of the cross section of the phase shift layer in Examples. FIG. 10 is a graph showing the relationship between the introduction ratio of nitrogen in the sputtering gas and the refractive index and extinction coefficient of the phase shift layer for light with a wavelength of 365 nm in Examples. FIG. 11 is a graph showing the relationship between the introduction ratio of nitrogen in the sputtering gas and the transmittance of the phase shift layer to light with a wavelength of 365 nm in Examples.

[Phase shift mask blanks]
A phase shift mask blank 100 of this embodiment shown in FIG. 1 will be described. A phase shift mask blank 100 includes a substrate 10 and a phase shift layer (semi-transmissive layer or phase shift film) 20 formed on a surface (substrate surface) 10a of the substrate 10 . A phase shift mask 300 (see FIG. 3) can be manufactured from the phase shift mask blanks 100 by forming a predetermined pattern 50 on the phase shift layer 20 . The phase shift mask 300 is used when manufacturing display devices such as FPDs (Flat Panel Displays) and semiconductor devices such as LSIs (Large Scale Integration).

Synthetic quartz glass, for example, is used as the material of the base material 10 . Note that the material of the substrate 10 is not limited to synthetic quartz glass. The substrate 10 may sufficiently transmit the exposure light of the exposure apparatus in which the phase shift mask 300 is used.

The phase shift layer 20 contains zirconium (Zr), silicon (Si) and nitrogen (N). The nitrogen concentration in the phase shift layer 20 is 51 atomic % or higher, preferably 52 atomic % or higher, or 53 atomic % or higher. As shown in FIG. 3, in the phase shift mask 300, a part of the phase shift layer 20 is removed from the substrate surface 10a by wet etching or the like, and the removed part forms a predetermined pattern 50 on the surface of the phase shift layer 20. do. The pattern 50 (removed portion, concave portion) is defined by the side surface 21 of the phase shift layer 20 exposed by wet etching or the like and the exposed substrate surface 10a. FIG. 3 shows a cross section of the phase shift layer 20 perpendicular to the substrate surface 10a. In the cross section shown in FIG. 3, the closer the inclination angle θ of the side surface 21 of the phase shift layer 20 that partitions the pattern 50 from the substrate surface 10a to 90°, the higher the accuracy of the pattern 50 formed on the phase shift mask 300. can be determined to be high. The angle of inclination θ is the angle formed between the substrate surface 10a and the side surface 21 defining the pattern 50 (recess) of the phase shift layer 20 in the cross section of the phase shift layer 20 perpendicular to the substrate surface 10a. is an angle containing Therefore, the closer the inclination angle θ is to 90°, the better. Specifically, the inclination angle θ is preferably 45° to 90°, and the lower limit is more preferably 60°, and still more preferably 70°. The upper limit may be 85° or 75°. FIG. 3 shows the state of θ=90°. The present inventors found that by setting the nitrogen concentration in the phase shift layer 20 to 51 atomic % or more, the tilt angle θ in the phase shift mask 300 manufactured from the phase shift mask blank 100 increases (approaches 90° ), the pattern accuracy of the phase shift mask 300 is improved. From the viewpoint of nitrogen introduction efficiency, the upper limit of the nitrogen concentration in the phase shift layer 20 is more preferably 56 atomic % or less, and even more preferably 55 atomic % or less.

The zirconium concentration in the phase shift layer 20 is, for example, 20 atomic % to 27 atomic %, and the lower limit is preferably 21 atomic %, more preferably 22 atomic %. The upper limit is preferably 25%, more preferably 24.5%. The silicon concentration in the phase shift layer is, for example, 20 atomic % to 27 atomic %, and the lower limit is preferably 21 atomic %, more preferably 22 atomic %. The upper limit is preferably 26%, more preferably 25%.

The phase shift layer 20 may contain no elements other than Zr, Si and N, or may contain a small amount of impurities that do not affect the effect. In addition, in the specification of the present application, the atomic concentration of the phase shift layer 20 can be measured using X-ray photoelectron spectroscopy (XPS), which will be described in Examples below.

In addition, in the phase shift mask blanks of this embodiment, the refractive index and extinction coefficient of the phase shift layer 20 are stabilized by setting the nitrogen concentration in the phase shift layer 20 to 51 atomic % or more. When the nitrogen concentration in the phase shift layer 20 is less than 51 atomic %, the refractive index and extinction coefficient of the phase shift layer 20 vary greatly depending on the nitrogen concentration in the phase shift layer 20 . The refractive index tends to increase as the nitrogen concentration increases. The extinction coefficient tends to decrease as the nitrogen concentration increases. On the other hand, when the nitrogen concentration is 51 atomic % or more, the refractive index is stable at a high value and the extinction coefficient is stable at a low value even if the nitrogen concentration is changed. That is, by setting the nitrogen concentration to 51 atomic % or more, stable optical properties (refractive index and extinction coefficient) can be obtained. The stable optical properties facilitate optical design based on this. Also, in the process of forming the phase shift layer 20 (film formation process), the optical properties including the values of the refractive index and the extinction coefficient are stabilized, so the film formation conditions can be easily controlled.

In addition, when the nitrogen concentration in the phase shift layer 20 is 51 atomic % or more, the refractive index becomes a high value and the extinction coefficient becomes a low value, resulting in the following advantages. As the refractive index increases, the formula to be described later: d = λ / (2 (n-1)) (d: thickness of phase shift layer 20, λ: wavelength of exposure light, n: phase shift layer at wavelength λ The thickness of the phase shift layer 20 can be reduced, leading to a refractive index of 20). By reducing the thickness necessary for film formation, the film can be formed more uniformly on the substrate 10 . Further, if the thickness of the phase shift layer 20 can be reduced, the amount of side etching, which will be described later, can be reduced, and the pattern 50 closer to the design dimension can be formed (pattern accuracy is improved). In addition, since the extinction coefficient is lowered, the absorption of light is reduced, and the transmittance of the phase shift layer 20 is increased.

The refractive index of the phase shift layer 20 of the present embodiment for light with a wavelength of 365 nm may be, for example, 2.60 to 2.85. .75.

The extinction coefficient of the phase shift layer 20 of the present embodiment for light with a wavelength of 365 nm may be, for example, 0.13 to 0.18, and a more preferable upper limit of the extinction coefficient is 0.17, It is more preferably 0.16, and still more preferably 0.15.

The phase shift layer 20 functions as a phase shifter that locally changes the phase of exposure light irradiated in the exposure process using the phase shift mask 300 . Therefore, the phase shift layer 20 needs to transmit the exposure light to some extent. The transmittance of the phase shift layer 20 to exposure light (for example, light with a wavelength of 330 nm to 470 nm) is preferably 20% or more, or 30% to 40%. Similar to the refractive index and extinction coefficient described above, the phase shift mask blank 100 of the present embodiment has a nitrogen concentration of 51 atomic % or more in the phase shift layer 20, so that the wavelength of the phase shift layer 20 in the above range is stable at 20% or more. Typical exposure light used in the exposure process using the phase shift mask 300 includes, for example, deep ultraviolet rays (DUV, wavelength: 302 nm, 313 nm, 334 nm), i-line (wavelength: 365 nm), h-line (wavelength: 405 nm). ) and g-line (wavelength: 436 nm). These can be used as monochromatic light or as compound light.

Here, the transmittance of light with a wavelength of 365 nm at the thickness of the phase shift layer 20 that gives a phase shift of 180° with light with a wavelength of 365 nm may be 30% to 40%, and the lower limit is preferably 33%. % is more preferred. Also, the upper limit is preferably 38%, more preferably 37%. In addition, the phase shift layer 20 may have a transmittance of 45% to 55% for light with a wavelength of 405 nm at a film thickness that provides a phase shift of 180° at a wavelength of 405 nm, and the lower limit is preferably 47%. % is more preferred. Furthermore, the upper limit is preferably 53%, more preferably 52%. In addition, the phase shift layer 20 may have a transmittance of 55% to 75% for light with a wavelength of 436 nm at a film thickness that gives a phase shift of 180° with light with a wavelength of 436 nm, and the lower limit is 57%. Preferably, 60% is more preferred. Also, the upper limit is preferably 73%, more preferably 72%.

The phase shift layer 20 preferably changes (shifts) the phase of the exposure light emitted in the exposure process using the phase shift mask 300 by about 180° (phase shift amount: about 180°). That is, the phase shift layer 20 shifts the phase of exposure light (for example, light with a wavelength of 330 nm to 470 nm) transmitted through it to 160° to 200° (180° ± 20°) or 170° to 190° (180° ±10°) is preferably changed.

The phase shift amount can be adjusted by changing the refractive index, thickness (film thickness), etc. of the phase shift layer 20 according to the wavelength of the light (exposure light) that passes through the phase shift mask 300 . The thickness of the phase shift layer 20 can be designed so that the phase shift amount is approximately 180°, taking into account the characteristics of the phase shift layer 20 such as the refractive index and the wavelength of the light (exposure light) transmitted therethrough. That is, the thickness d of the phase shift layer 20 can be designed based on the formula: d=λ/(2(n−1)) (d: thickness of phase shift layer 20, λ: wavelength of exposure light, n : the refractive index of the phase shift layer 20 at the wavelength λ). The thickness of the phase shift layer 20 is preferably, for example, 90 nm to 125 nm, and the lower limit of the thickness of the phase shift layer 20 is more preferably 96 nm, still more preferably 102 nm. More preferably, the upper limit of the thickness of the phase shift layer 20 is 116 nm, more preferably 110 nm.

A method for manufacturing the phase shift mask blanks 100 is not particularly limited, and a general-purpose method can be used. For example, the phase shift mask blanks 100 may be manufactured by depositing the phase shift layer 20 on the substrate 10 using reactive sputtering, which will be described later in Examples.

<Modification>
In this modified example, the phase shift mask blanks 200 shown in FIG. 2 will be described. A phase shift mask blank 200 includes a substrate 10, a phase shift layer 20 formed on the substrate surface 10a, and an etching mask layer (chromium compound layer) 30 containing a chromium compound formed on the phase shift layer 20. Prepare. The configuration of the phase shift mask blank 200 is the same as that of the phase shift mask blank 100 shown in FIG. 1 except for having the etching mask layer 30 . The phase shift mask blank 200 of this modified example has the same effect as the phase shift mask blank 100, and further has the etching mask layer 30, so that it has the effect described below.

A phase shift mask 300 (see FIG. 3) can be manufactured from the phase shift mask blanks 200 by forming a predetermined pattern 50 on the phase shift layer 20 in the same manner as the phase shift mask blanks 100 . When forming the predetermined pattern 50 on the phase shift layer 20 by wet etching, a photoresist layer 40 is formed on the phase shift mask blanks 200 (see FIG. 4A). The phase shift layer (ZrSiN-based layer) 20 of this modified example has low adhesion to the photoresist layer 40 . Therefore, if the photoresist layer 40 is formed directly on the phase shift layer 20, the photoresist layer 40 may peel off during wet etching. Therefore, in the phase shift mask blanks 200, by providing the etching mask layer 30 having adhesion to both the photoresist layer 40 and the phase shift layer 20, peeling of the photoresist layer 40 during wet etching can be suppressed.

The material of the etching mask layer 30 is not particularly limited, and any material that enhances the adhesion between the photoresist layer 40 and the phase shift layer 20 may be used. For example, chromium compounds such as chromium nitride and chromium oxide may be used. In addition, in fabricating the phase shift mask 300, the photoresist layer 40 is exposed to light with a wavelength of 350 nm to 450 nm. For this reason, the etching mask layer 30 provided under the photoresist layer 40 preferably has a low reflectance for light with a wavelength of 350 nm to 450 nm and also functions as an antireflection layer, and chromium oxide is more effective as an antireflection layer. preferable. By suppressing the reflection of the exposure light, the multiple reflection of the exposure light in the photoresist layer 40 is suppressed, and the pattern accuracy of the phase shift mask 300 is improved. For example, the reflectance of the etching mask layer 30 for light with a wavelength of 413 nm is preferably 15% or less. The etching mask layer 30 may be a single layer or may be formed from multiple layers. When the etching mask layer 30 is formed of a plurality of layers, it is preferable that the layer immediately below the photoresist layer 40 has a low reflectance to the exposure light. For example, the etching mask layer 30 may consist of a chromium nitride layer 31 formed on the phase shift layer 20 and a chromium oxide layer 32 formed on the chromium nitride layer 31 . The chromium oxide layer 32 can suppress the reflectance of light with a wavelength of 413 nm to about 11%, for example.

The thickness of the etching mask layer 30 is not particularly limited and can be adjusted as appropriate. For example, it may be 10 nm to 120 nm. When the etching mask layer 30 is composed of the chromium nitride layer 31 and the chromium oxide layer 32, for example, the thickness of the etching mask layer 30 is preferably 80 to 120 nm, the thickness of the chromium nitride layer 31 and the thickness of the chromium oxide layer 32. is preferably 6:4 (3:2) to 8:2 (4:1). If the etching mask layer 30 is too thin, the etching time will be shortened, making it difficult to control the CD (critical dimension) within the plane of the phase shift layer (that is, control the line width of the pattern 50). Also, if the etching mask layer 30 is too thick, the amount of side etching increases, making it difficult to obtain pattern dimensions as designed. When the phase shift layer 20 is wet-etched based on the etching mask layer 30 (see FIG. 4D), the phase shift layer 20 is isotropically etched by the etchant. Therefore, in addition to etching the phase shift layer 20 in the direction perpendicular to the substrate 10, the phase shift layer 20 is also etched in the lateral direction orthogonal to the vertical direction. This phenomenon in which etching progresses in the lateral direction is called side etching. Therefore, if the etching mask layer 30 is too thick, or if the phase shift layer 20 is too thick as described above, there is a risk that the pattern width will be wider than the desired pattern width.

A method for manufacturing the phase shift mask blanks 200 is not particularly limited, and a general-purpose method can be used. For example, the phase shift mask blanks 200 may be manufactured by depositing the phase shift layer 20 and the etching mask layer 30 on the substrate 10 using reactive sputtering, which will be described later in Examples.

[Phase shift mask]
The phase shift mask 300 shown in FIG. 3 will be described. The phase shift mask 300 has a substrate 10 and a phase shift layer 20 formed on the surface 10 a of the substrate 10 , and a predetermined pattern 50 is formed on the phase shift layer 20 . The configuration of the phase shift mask 300 is the same as the phase shift mask blanks 100 shown in FIG. 1, except that the predetermined pattern 50 is formed on the phase shift layer 20 . In the cross section of the phase shift layer 20 orthogonal to the substrate surface 10a, the inclination angle θ of the side surface 21 of the phase shift layer 20 defining the pattern 50 from the substrate surface 10a is preferably 45° to 90°.

A method for manufacturing the phase shift mask 300 is not particularly limited, and a general-purpose method can be used. For example, the phase shift mask 300 may be manufactured using reactive sputtering and wet etching (see FIG. 4), which will be described in Examples below.

[Exposure method]
Next, an exposure method using the phase shift mask 300 produced from the phase

shift mask blanks

100 and 200 will be described. The exposure method using the phase shift mask 300 can be implemented as a photolithography process using an exposure apparatus in the manufacture of devices such as semiconductors and liquid crystal panels.

As shown in FIG. 5, an exposure apparatus 500 used in the exposure method includes a light source LS, an illumination optical system 5
02, a mask stage 503 that holds a phase shift mask 300, a projection optical system 504, a substrate stage 505 that holds a photosensitive substrate 515 that is an exposure target, and a driving mechanism 506 that moves the substrate stage 505 in a horizontal plane. and

First, the phase shift mask 300 is placed on the mask stage 503 of the exposure apparatus 500 . Also, a photosensitive substrate 515 coated with a photoresist is placed on the substrate stage 505 . Then, exposure light is emitted from the light source LS. The emitted exposure light enters an illumination optical system 502 to be adjusted to a predetermined light flux, and is irradiated onto a phase shift mask 300 held on a mask stage 503 . The light passing through the phase shift mask 300 has the same pattern as the device pattern 50 drawn on the phase shift mask 300 , and this pattern passes through the projection optical system 504 onto the photosensitive substrate held on the substrate stage 505 . A predetermined position of 515 is irradiated. Thereby, the photosensitive substrate 515 is exposed at a predetermined magnification by the device pattern of the phase shift mask 300 .

The phase shift mask 300 produced from the phase

shift mask blanks

100 and 200 has high pattern accuracy. Therefore, by performing exposure using the phase shift mask 300, circuit pattern defects in the exposure process can be reduced, and highly integrated devices can be efficiently manufactured.

The phase shift mask blanks and the phase shift mask will be specifically described below using examples and comparative examples, but the present invention is not limited to these examples.

Preparation of Samples As samples 1 to 10, phase shift mask blanks 100 shown in FIG. 1 were prepared. Samples 6 to 10 correspond to Examples, and Samples 1 to 5 correspond to Comparative Examples.

[Sample 1]
First, a circular parallel flat plate made of quartz glass was prepared as the substrate 10 (size: 3 inches in diameter, 0.5 mm in thickness). Using a DC magnetron sputtering apparatus and using a ZrSi alloy target as a sputtering target, reactive sputtering is performed while introducing an Ar—N ₂ mixed gas to form a phase shift layer 20 having a thickness of 101 nm on the substrate 10. , Sample 1 was prepared. The composition (atomic ratio) of the ZrSi alloy target was Zr:Si=1:2. The film formation conditions were a mixed gas total pressure of 0.32 Pa, an introduction ratio of N2 in the mixed gas (sputtering gas): 5.0%, and a DC output of 1.5 kw.

[Samples 2 to 10]
Samples 2 to 10 were produced in the same manner as Sample 1, except that the N ₂ introduction ratio in the mixed gas was changed as shown in Table 1.

Evaluation of Physical Properties of Phase Shift Layer (1) Composition Analysis Composition analysis of the phase shift layers 20 of Samples 1 to 10 was performed by X-ray photoelectron spectroscopy (XPS). Table 1 shows the results. In addition, since the outermost surface of the phase shift layer may be oxidized, the composition analysis was performed after the portion affected by the oxidation of the outermost surface was removed by sputtering. QuanteraAXM manufactured by PHI was used as an analyzer. The analysis conditions were as follows. X-ray source: monochromatic Al (1486.6 eV), detection area: circular area with a diameter of 100 μm, detection depth: about 4 to 5 nm (takeoff angle 45°), measurement spectrum: Zr3d, Si2p, N1s and O1s, sputtering conditions : Ar+2.0 kV, sputtering rate: about 5 nm/min (converted to SiO ₂ ).

(2) Measurement of Refractive Index and Extinction Coefficient, and Transmittance Simulation For the phase shift layers 20 of Samples 1 to 10, the refractive index and extinction coefficient at the i-line (365 nm) were measured by ellipsometry. The results are shown in Table 1 and FIG. Further, with respect to the phase shift layers 20 of samples 1 to 10, the film thickness that gives a phase shift of 180° at each of the three wavelengths (365 nm, 405 nm, and 436 nm) was obtained from the results of refractive index measurement. The transmittance of the phase shift layer 20 was calculated by simulation. The results are shown in Table 1 and FIG. The simulation was performed using the simulation software "TFCalc". From the measurement results of the refractive index and extinction coefficient at the i-line (365 nm) obtained by the ellipsometry method, 180 The transmittance of the phase shift layer 20 was calculated using a film thickness that gives a phase shift of .degree. Here, the transmittance is the external transmittance in consideration of reflection.

Production of Phase Shift Mask A pattern 50 was formed in the phase shift layer 20 of Sample 1 (phase shift mask blanks) to produce a phase shift mask 300 shown in FIG. First, using a DC magnetron sputtering apparatus and using a Cr target as a sputtering target, reactive sputtering was performed while introducing an Ar—N mixed gas, followed by reactive sputtering while introducing an Ar _— O mixed gas. gone. As a result, an etching mask 30 composed of a chromium nitride layer 31 and a chromium oxide layer 32 was formed on the phase shift mask blank 100 to produce a phase shift mask blank 200 (FIG. 2). The thickness of the etching mask 30 was 96 nm (thickness of the chromium nitride layer 31:thickness of the chromium oxide layer 32=7:3). Next, a positive ultraviolet resist (GRX-M237 manufactured by Nagase ChemteX) was applied onto the phase shift mask blank 200 by spin coating to form a photoresist layer 40 (FIG. 4(a)). The thickness of the photoresist layer 40 was set to 660 nm.

Using a mask aligner (PLA-501, manufactured by Canon) using a high-pressure mercury lamp, the photoresist layer 40 was exposed using a light-shielding mask having openings corresponding to the pattern 50 . As a result, a portion of the photoresist layer 40 corresponding to the pattern 50 was exposed. Next, the exposed phase shift mask blanks 200 were immersed in an organic alkaline developer (1.83% tetramethylammonium hydroxide manufactured by Tama Kagaku Kogyo Co., Ltd.). As a result, the exposed portion of the photoresist layer 40 was dissolved and removed, and an opening corresponding to the pattern 50 was formed (FIG. 4(b)).

Next, using the photoresist layer 40 having openings corresponding to the pattern 50 as a mask, the etching mask layer 30 is etched with an etchant containing ceric ammonium nitrate and nitric acid (PureEtchCR101 manufactured by Hayashi Junyaku Kogyo Co., Ltd.). and wet etched. The etching liquid temperature was 23±3° C., and the etching time was 100 sec. and As a result, the exposed portion of the etching mask layer 30 that was not covered with the photoresist layer 40 was removed (FIG. 4(c)).

Next, using the photoresist layer 40 having openings corresponding to the pattern 50 and the etching mask layer 30 as masks, the phase shift layer 20 is etched using an etchant containing ammonium fluoride (ADEKA's ADEKA CHEMICA WGM-155). was wet etched. The temperature of the etchant was set at 23±3° C., and 40% over-etching was performed in order to uniformly remove the exposed phase shift layer 20 without residue. Thereby, a pattern 50 was formed in the phase shift layer 20 (FIG. 4(d)).

Finally, the photoresist layer 40 and the etching mask layer 30 were removed. Through the above steps, the phase shift mask 300 shown in FIG. 4E was obtained from the sample 1 (phase shift mask blanks).

A phase shift mask 300 shown in FIG. 3 was also manufactured from samples 2 to 10 (phase shift mask blanks) in the same manner as sample 1.

In the process of manufacturing the phase shift mask 300, cross-sectional observation of the patterns 50 formed on the samples 1 to 10 was performed. The cross-sectional observation was performed in the state before removing the etching mask layer 30 and the photoresist layer 40 (the state shown in FIG. 4(d)). 8(a) to (j) show SEM photographs of cross sections perpendicular to the substrate surface 10a of samples 1 to 10. FIG. From FIGS. 8A to 8J, in samples 1 to 10, the inclination angle θ of the side surface 21 of the phase shift layer 20 from the substrate surface 10a was measured. The results are shown in Table 1 and FIG. In FIG. 8A, θ is shown, and the boundary between the phase shift layer 20 and the chromium nitride layer 31 and the boundary between the chromium nitride layer 31 and the chromium oxide layer 32 are shown by dotted lines.

As shown in Table 1, FIGS. 8 and 9, samples 6 to 10 in which the nitrogen concentration in the phase shift layer 20 is 51 atomic % or more have a pattern The inclination angle θ of the side surface 21 of the phase shift layer 20 that partitions 50 from the substrate surface 10a was 45° or more. From this, it can be seen that samples 6 to 10 (phase shift mask blanks) yielded phase shift masks 300 in which patterns were accurately formed (high pattern accuracy).

Further, as shown in Table 1, FIGS. 6 and 7, samples 6 to 10 in which the nitrogen concentration in the phase shift layer 20 is 51 atomic % or more have the optical properties of the phase shift layer 20 (refractive index, extinction coefficient and transmittance) did not differ greatly among the samples and were close values. That is, when the nitrogen concentration in the phase shift layer 20 was 51 atomic % or more, the optical properties (refractive index, extinction coefficient and transmittance) were stable even when the nitrogen concentration in the phase shift layer 20 changed. . In addition, as shown in Table 1, FIGS. 10 and 11, samples 6 to 10 have a nitrogen introduction ratio in the sputtering gas of 35% to 100% in the step of forming the phase shift layer 20 (film formation step). A wide range of variations was made. When the nitrogen introduction ratio is 35% or more (Samples 6 to 10), the optical properties of the phase shift layer 20 are stabilized, so the film forming conditions can be easily controlled.

On the other hand, as shown in Table 1, FIGS. 8 and 9, samples 1 to 5 in which the nitrogen concentration in the phase shift layer 20 was less than 51 atomic % had an inclination angle θ of less than 45°. From this, it can be seen that the pattern accuracy of the phase shift mask 300 produced from Samples 1 to 5 (phase shift mask blanks) is low. Further, as shown in Table 1, FIGS. 6 and 7, samples 1 to 5, in which the nitrogen concentration in the phase shift layer 20 is less than 51 atomic %, have optical properties (refractive index, extinction coefficient and transmittance) fluctuated greatly. Further, as shown in Table 1, Samples 1 to 5 were produced by setting the introduction ratio of nitrogen in the sputtering gas to less than 35% in the step of forming the phase shift layer 20 (film formation step). As shown in FIGS. 10 and 11, when the nitrogen introduction ratio in the sputtering gas is less than 35% (Samples 1 to 5), the optical characteristics of the phase shift layer 20 change greatly depending on the nitrogen introduction ratio. Strict control of conditions is required.

A phase shift mask with high pattern accuracy can be manufactured from the phase shift mask blanks of this embodiment. Phase shift masks are used when manufacturing display devices such as FPDs and semiconductor devices such as LSIs.

10 substrate 20 phase shift layer 30 etching mask layer 31 chromium nitride layer 32 chromium oxide layer 40 photoresist layer 50

patterns

100, 200 phase shift mask blanks 300 phase shift mask 500 exposure apparatus LS light source 502 illumination optical system 504 projection optical system 503 Mask stage 505 Substrate stage

Claims

A phase shift mask blank,
a substrate;
a phase shift layer comprising zirconium (Zr), silicon (Si) and nitrogen (N) formed on the substrate;
A phase shift mask blank, wherein the nitrogen concentration contained in the phase shift layer is 51 atomic % or more.
The phase shift mask blank according to claim 1, wherein the nitrogen concentration contained in the phase shift layer is 51 atomic % to 56 atomic %.
3. The phase shift mask blank according to claim 1, wherein the phase shift layer has a zirconium concentration of 20 atomic % to 27 atomic %.
The phase shift mask blanks according to any one of claims 1 to 3, wherein the silicon concentration in the phase shift layer is 20 atomic % to 27 atomic %.
The phase shift mask blanks according to any one of claims 1 to 4, wherein the phase shift layer has a refractive index of 2.60 to 2.85 for light with a wavelength of 365 nm.
The phase shift mask blanks according to any one of claims 1 to 5, wherein the phase shift layer has an extinction coefficient of 0.13 to 0.18 for light with a wavelength of 365 nm.
The phase shift mask blanks according to any one of claims 1 to 6, wherein the phase shift layer has a transmittance of 20% or more for light with a wavelength of 330 nm to 470 nm.
8. The phase shift layer according to any one of claims 1 to 7, wherein the phase shift layer has a transmittance of 30% to 40% for light with a wavelength of 365 nm in a film thickness that gives a phase shift of 180° with light with a wavelength of 365 nm. Phase shift mask blanks.
8. The phase shift layer according to any one of claims 1 to 7, wherein the phase shift layer has a transmittance of 45% to 55% for light with a wavelength of 405 nm in a film thickness that gives a phase shift of 180° with light with a wavelength of 405 nm. Phase shift mask blanks.
8. The phase shift layer according to any one of claims 1 to 7, wherein the phase shift layer has a transmittance of 55% to 75% for light with a wavelength of 436 nm in a film thickness that gives a phase shift of 180° with light with a wavelength of 436 nm. Phase shift mask blanks.
The phase shift mask blanks according to any one of claims 1 to 10, wherein the phase shift layer shifts the phase of light transmitted through the phase shift layer by 160° to 200°.
The phase shift mask blanks according to claim 11, wherein the phase shift layer shifts the phase of light transmitted through the phase shift layer by 170° to 190°.
The phase shift mask blanks according to any one of claims 1 to 12, further comprising a chromium compound layer formed on said phase shift layer.
14. The phase shift mask blanks according to claim 13, wherein said chromium compound layer contains chromium (Cr) and oxygen (O).
15. The chromium compound layer of claim 13 or 14, wherein the chromium compound layer comprises a chromium nitride (CrN) layer formed on the phase shift layer and a chromium oxide (CrO) layer formed on the chromium nitride layer. Phase shift mask blanks.
A phase shift mask, wherein a part of the phase shift layer of the phase shift mask blanks according to any one of claims 1 to 15 is removed, and a predetermined pattern is formed on the surface of the phase shift layer.
In the cross section of the phase shift layer perpendicular to the substrate surface, the inclination angle, which is an angle including the phase shift layer among the angles formed between the side surface of the phase shift layer defining the pattern and the substrate surface, is 45. 17. The phase shift mask of claim 16, which is between degrees and 90 degrees.
The phase shift mask according to claim 17, wherein the tilt angle is 60° to 90°.
An exposure method for exposing a photosensitive substrate through the phase shift mask according to any one of claims 16-18.
A device manufacturing method comprising the exposure method according to claim 19 .