阅读说明：本技术 相移掩模坯料、相移掩模、曝光方法以及器件制造方法 (Phase shift mask blank, phase shift mask, exposure method, and device manufacturing method ) 是由 小泽隆仁 宝田庸平 林贤利 八神高史 于 2019-05-20 设计创作，主要内容包括：一种相移掩模坯料,其是具有基板及形成于上述基板上的相移层的相移掩模坯料,上述相移层含有铬及氧,上述相移层的表面的算术平均高度的值为0.38nm以上。(A phase shift mask blank comprising a substrate and a phase shift layer formed on the substrate, wherein the phase shift layer contains chromium and oxygen, and the arithmetic mean height of the surface of the phase shift layer is 0.38nm or more.)

1. A phase shift mask blank having a substrate and a phase shift layer formed on the substrate,

the phase-shift layer contains chromium and oxygen,

the arithmetic average height of the surface of the phase shift layer is 0.38nm or more.

2. The phase shift mask blank according to claim 1, wherein the value of the arithmetic mean height of the surface of the phase shift layer is greater than the value of the arithmetic mean height of the surface of the substrate by 0.04nm or more.

3. A phase shift mask blank having a substrate and a phase shift layer formed on the substrate,

the phase-shift layer contains chromium and oxygen,

the arithmetic average height of the surface of the phase shift layer is greater than the arithmetic average height of the surface of the substrate by 0.04nm or more.

4. The phase shift mask blank of any one of claims 1 to 3, wherein the phase shift layer is comprised of CrOCN or a material with a higher than stoichiometric oxygen ratio in CrOCN.

5. The phase shift mask blank according to any one of claims 1 to 4, wherein the phase shift layer has an oxygen atom number concentration of 42.6% or more at a depth of 1.25nm from the surface.

6. The phase shift mask blank according to any one of claims 1 to 5, wherein the oxygen atom number concentration on the surface side of the phase shift layer is larger than the oxygen atom number concentration on the substrate side.

7. The phase shift mask blank of any one of claims 1 to 6, wherein a ratio of the concentration of the number of oxygen atoms at a depth of 1.25nm from the surface of the phase shift layer to the concentration of the number of oxygen atoms at a depth of 85nm from the surface of the phase shift layer is 1.59 or more.

8. The phase shift mask blank according to any one of claims 1 to 7, wherein the surface of the phase shift layer is wet etched or dry etched.

9. The phase shift mask blank according to any one of claims 1 to 8, wherein the substrate has a size of 520mm x 800mm or more.

10. A phase shift mask, wherein the phase shift layer of the phase shift mask blank according to any one of claims 1 to 9 is formed in a predetermined pattern.

11. An exposure method, wherein, through the phase shift mask according to claim 10, coated with photoresist photosensitive substrate exposure.

12. A method for manufacturing a device, comprising the steps of:

an exposure step of exposing the photosensitive substrate by the exposure method according to claim 11; and

and a developing step of developing the exposed photosensitive substrate.

Technical Field

The invention relates to a phase shift mask blank, a phase shift mask, an exposure method and a device manufacturing method.

Background

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

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2011-013283

Disclosure of Invention

According to the 1 st aspect of the present invention, a phase shift mask blank comprises a substrate and a phase shift layer formed on the substrate, wherein the phase shift layer contains chromium and oxygen, and the arithmetic mean height of the surface of the phase shift layer is 0.38nm or more.

According to the 2 nd aspect of the present invention, a phase shift mask blank is a phase shift mask blank having a substrate and a phase shift layer formed on the substrate, wherein the phase shift layer contains chromium and oxygen, and the arithmetic mean height of the surface of the phase shift layer is greater than the arithmetic mean height of the surface of the substrate by 0.04nm or more.

According to the 3 rd aspect of the present invention, a phase shift mask is a phase shift mask formed by forming the phase shift layer of the phase shift mask blank according to the 1 st or 2 nd aspect into a predetermined pattern.

According to the 4 th aspect of the present invention, in the exposure method, the photosensitive substrate coated with the photoresist is exposed through the phase shift mask of the 3 rd aspect.

According to the 5 th aspect of the present invention, a method for manufacturing a device includes: an exposure step of exposing the photosensitive substrate by the exposure method according to the 4 th aspect; and a developing step of developing the exposed photosensitive substrate.

Drawings

Fig. 1 is a diagram illustrating an example of a configuration of a phase shift mask blank according to an embodiment.

Fig. 2 is a schematic diagram showing an example of a manufacturing apparatus used for manufacturing a phase shift mask blank.

Fig. 3 is a table showing measurement results of phase shift mask blanks of examples and comparative examples.

Fig. 4 is a schematic diagram illustrating a cross section of a mask pattern formed using the phase shift mask blank of the embodiment.

Fig. 5 is a conceptual diagram illustrating a case where a photosensitive substrate is exposed through a phase shift mask.

Fig. 6 is a diagram showing an example of the configuration of a phase shift mask blank of a comparative example.

Fig. 7 is a schematic diagram illustrating a cross section of a mask pattern formed using a phase shift mask blank of a comparative example.

Detailed Description

(embodiment mode)

Fig. 1 is a diagram showing an example of the configuration of a phase shift mask blank 10 according to the present embodiment. The phase shift mask blank 10 includes a substrate 11 and a phase shift layer 12. In this embodiment, the phase shift layer 12 is formed on the surface of the substrate 11 by sputtering. At this time, by setting the oxygen content (oxygen atom number concentration) in the phase shift layer 12 according to the sputtering conditions, fine irregularities (concave-convex portions 12a) of a predetermined degree (predetermined arithmetic mean height) are formed on the surface of the phase shift layer 12 as shown in fig. 1.

The phase shift mask blank 10 of the present embodiment will be described in further detail below.

As a material of the substrate 11, for example, synthetic quartz glass is used. The material of the substrate 11 is not limited to synthetic quartz glass. The phase shift mask is used for manufacturing a Display device such as an FPD (Flat Panel Display) or a semiconductor device such as an LSI (Large Scale Integration). The substrate 11 may be formed by sufficiently transmitting exposure light in an exposure step of exposing an exposure target base material such as a wafer using a phase shift mask.

The phase shift layer 12 is formed on the surface of the substrate 11 as a film made of a material containing chromium (Cr) and oxygen (O). The phase shift layer 12 of the present embodiment is formed of a film made of CrOCN. A desired pattern is formed in the phase shift layer 12 to become a phase shift mask. This pattern functions as a phase shifter that locally changes the phase of the exposure light to be irradiated in the exposure step.

When the device substrate is exposed to exposure light through a phase shift mask having a phase shift layer 12 formed to a desired thickness and a desired pattern, a phase difference (phase shift amount) of about 180 ° occurs between light transmitted through a portion where the phase shift layer 12 is present and light transmitted through a portion where the phase shift layer 12 is not present. This suppresses the intensity of the exposure light applied to the region other than the exposure pattern region to be low, thereby improving the contrast of the exposure pattern. As a result, the defect rate in the exposure step can be reduced.

In the above, it is described that the thickness (film thickness) of the phase shift layer 12 is set so that the phase of the exposure light is shifted by about 180 °. However, the phase shift amount of the exposure light is not limited to 180 ° as long as it is within a range in which a desired contrast is obtained in the exposure step. The phase shift layer 12 may be formed of a single film or a plurality of films may be laminated.

A phase shift mask in which a desired pattern is formed in the phase shift layer 12 of the phase shift mask blank 10 is produced, for example, by the process described below.

A photoresist layer is formed by coating a photoresist on the surface of the phase shift layer 12. The formed photoresist layer is irradiated with energy rays such as laser light, electron beam, or ion beam to draw a pattern. By developing the photoresist layer on which the pattern is drawn, the drawn portion or the non-drawn portion is removed, and a pattern is formed in the photoresist layer. Phase shift layer 12 is wet etched using the patterned photoresist layer as a mask. By this wet etching, a shape corresponding to the pattern formed in the photoresist layer is formed (transferred) in the phase shift layer 12. The photoresist layer is removed to complete the phase shift mask.

The present inventors examined the correlation between the arithmetic mean height of the surface of the phase shift layer 12 and the oxygen atom number concentration of the phase shift layer 12, and further examined the interface between the phase shift layer 12 and the photoresist layer when patterning the photoresist layer formed on the phase shift layer 12. As a result, the following findings were obtained. The arithmetic average height in this specification is the arithmetic average height specified in ISO 25178.

(1) The present inventors have found that, when the arithmetic mean height of the surface of the phase shift layer 12 is greater than a predetermined value, for example, 0.38nm or more, in the step of forming a pattern of the phase shift layer 12 using such a phase shift mask blank, permeation of the etching solution does not occur at the interface between the phase shift layer 12 and the photoresist layer.

It is estimated that the reason why the penetration of the etching solution at the interface between the phase shift layer 12 and the photoresist layer can be suppressed when the arithmetic mean height of the surface of the phase shift layer 12 is greater than a predetermined value is that appropriate roughness (unevenness) is formed on the surface of the phase shift layer 12, and the adhesion between the photoresist layer and the phase shift layer 12 is increased to such an extent that the penetration of the etching solution is suppressed due to the roughness.

(2) The present inventors have found that when the difference between the arithmetic mean height of the surface of the phase shift layer 12 and the arithmetic mean height of the surface of the substrate 11 is larger than a predetermined value, for example, 0.04nm or more, in the step of forming a pattern of the phase shift layer 12 using such a phase shift mask blank, permeation of the etching solution does not occur at the interface between the phase shift layer 12 and the photoresist layer.

(3) The present inventors have found that roughness (unevenness) of a prescribed arithmetic mean height can be generated on the surface of the phase shift layer 12 in the following manner. The present inventors have found that, when the flow rate of oxygen introduced into the sputtering chamber is adjusted so that a predetermined amount or more of oxygen is contained in the phase shift layer 12 when the phase shift layer 12 is formed by sputtering, the phase shift layer 12 having a surface with a predetermined arithmetic mean height can be formed. That is, the present inventors found that there is a correlation between the arithmetic mean height of the uneven pattern on the surface of the phase shift layer 12 and the oxygen atom number concentration or concentration distribution near the surface of the phase shift layer 12.

(4) The present inventors have found that when the concentration of the number of oxygen atoms formed on the surface of the phase shift layer 12 of the phase shift mask blank 10 is greater than a predetermined value, the etchant does not penetrate into the interface between the phase shift layer 12 and the photoresist layer.

As seen from the above (3), the phase shift layer 12 having the surface with the oxygen atom number concentration higher than the predetermined value has an appropriate roughness (unevenness) because the arithmetic mean height of the surface is equal to or higher than the predetermined value (for example, 0.38 nm). It is known that when a photoresist layer is formed on the surface of the phase shift layer 12, the phase shift layer 12 and the photoresist layer have high adhesion, and thus, the etchant does not penetrate into the interface between the phase shift layer 12 and the photoresist layer during wet etching.

(5) The present inventors have found that when the concentration of the number of oxygen atoms in the phase shift layer 12 formed in the phase shift mask blank 10 is decreased from the surface of the phase shift layer 12 in the depth direction, the etchant does not penetrate into the interface between the phase shift layer 12 and the photoresist layer. An example of the case where the oxygen atom number concentration in the phase shift layer 12 decreases in the depth direction from the surface of the phase shift layer 12 is as follows: the ratio of the oxygen atom number concentration at a position of a depth of 1.25nm from the surface of the phase shift layer 12 to the oxygen atom number concentration at a position of a depth of 85nm from the surface of the phase shift layer 12 is 1.59 or more.

An example of the method for manufacturing the phase shift mask blank 10 according to the present embodiment will be described below.

(method of manufacturing phase Shift mask blank)

Fig. 2 is a schematic diagram showing an example of a manufacturing apparatus used for forming the phase shift layer 12 when manufacturing the phase shift mask blank 10 of the present embodiment. Fig. 2(a) is a schematic view of the inside of the manufacturing apparatus 100 as viewed from the top, and fig. 2(b) is a schematic view of the inside of the manufacturing apparatus 100 as viewed from the side. The manufacturing apparatus 100 shown in fig. 2 is an in-line sputtering apparatus, and includes: a chamber 20 for carrying in the substrate 11 on which the phase shift layer 12 is formed, a sputtering chamber 21, and a chamber 22 for carrying out the substrate 11 on which the phase shift layer 12 is formed. A target 41 for forming the phase shift layer 12 is disposed in the sputtering chamber 21.

The substrate tray 30 is a frame-shaped tray on which the substrate 11 for forming the phase shift layer 12 can be placed, and supports and places the outer edge portion of the substrate 11. The substrate 11 is polished and cleaned on its surface, and is placed on the substrate tray 30 so that the surface on which the phase shift layer 12 is formed is located on the lower side (downward). In the sputtering apparatus 100, as will be described later, the phase shift layer 12 is formed on the surface of the substrate 11 while the substrate tray 30 on which the substrate 11 is placed is moved in the direction indicated by the broken-line arrow 25 in fig. 2, with the surface of the substrate 11 being kept facing the target 41.

Gate valves, not shown, are provided between the loading chamber 20, the sputtering chamber 21, and the unloading chamber 22, and the chambers are communicated and blocked by opening and closing the gate valves. The loading chamber 20, the sputtering chamber 21, and the unloading chamber 22 are connected to an exhaust device, not shown, respectively, and exhaust the interior of each chamber.

Further, a space or another standby chamber (not shown) is provided between each gate valve and the target 41, which is sufficient for the substrate tray 30 to stand by before and after film formation.

As described above, the target 41 is provided inside the sputtering chamber 21. Target 41 is a sputtering target for forming phase shift layer 12, and is formed of a material containing chromium (Cr). Specifically, the material of the target 41 is at least 1 selected from chromium, chromium oxide, chromium nitride, chromium carbide, and the like. In the present embodiment, chromium is selected as the target 41. Power is supplied to the target 41 of the sputtering chamber 21 from a DC power supply not shown.

The sputtering chamber 21 is provided with a 1 st gas inlet 31 and a 2 nd gas inlet 32 for introducing a gas for sputtering into the sputtering chamber 21. The 1 st gas inlet 31 is disposed on a side close to the loading chamber 20, that is, on an upstream side with respect to a traveling direction of the substrate tray 30 indicated by a broken-line arrow 25. On the other hand, the 2 nd gas inlet 32 is disposed on the side closer to the carrying-out chamber 22, that is, on the downstream side with respect to the traveling direction of the substrate tray 30.

In this embodiment, a CrOCN film is formed as the phase shift layer 12. Therefore, a mixed gas of a carbon-containing gas such as nitrogen or carbon dioxide and an inert gas (argon is used in the present embodiment) is introduced into the sputtering chamber 21 through the 1 st gas inlet 31. Further, oxygen gas is introduced through the 2 nd gas inlet 32.

The substrate 11 is transferred from the loading chamber 20 to the sputtering chamber 21, and sputtering is started. At this time, since the nitrogen gas, the carbon-containing gas, and the inert gas are introduced from the 1 st gas inlet 31, the concentrations of these gases are relatively high on the side close to the 1 st gas inlet 31 in the sputtering chamber 21, that is, on the side where sputtering onto the substrate 11 starts. On the other hand, since the oxygen gas is introduced from the 2 nd gas inlet 32, the oxygen concentration is relatively high on the side close to the 2 nd gas inlet 32 in the sputtering chamber 21, that is, on the side where the sputtering onto the substrate 11 is completed. Therefore, in the formed CrOCN film, the oxygen atom number concentration increases as the substrate 11 moves rightward and sputtering proceeds, that is, as the film thickness becomes thicker. As a result, oxygen is relatively more contained on the side closer to the surface of the phase shift layer 12 (the side of the final deposition), while oxygen contained is less on the side closer to the substrate (the side of the initial deposition). Roughness (unevenness) having a predetermined arithmetic mean height is formed on the surface of the phase shift layer 12 formed in this manner. The roughness (arithmetic mean height) of the surface of the phase shift layer 12 can be controlled by adjusting the flow rate of each gas introduced through the 1 st gas inlet 31 and the 2 nd gas inlet 32.

The substrate 11 on which the phase shift layer 12 is formed is transported to the carrying-out chamber 22. Thus, the phase shift layer 12 is formed on the surface of the substrate 11, and the phase shift mask blank 10 is produced.

The material of the target 41 and the type of the gas introduced from each of the 1 st gas inlet 31 and the 2 nd gas inlet 32 may be appropriately selected depending on the material and composition of the phase shift layer 12. As the sputtering method, any of DC sputtering, RF sputtering, and the like can be used.

As described above, in the present embodiment, when the phase shift layer 12 is formed by sputtering, the flow rate of each gas (particularly, the flow rate of oxygen) introduced into the sputtering chamber 21 is adjusted. Thereby, the number of oxygen atoms contained in the phase shift layer 12 is adjusted, and the roughness (arithmetic mean height) of the surface of the phase shift layer 12 is adjusted. This can sufficiently improve the adhesion between the photoresist layer and the phase shift layer 12, and can prevent the etchant from penetrating into the interface between the phase shift layer 12 and the photoresist layer. In addition, by manufacturing a phase shift mask using the phase shift mask blank 10 of the present embodiment, a pattern can be formed with good accuracy. Therefore, the yield of phase shift mask fabrication can be improved.

When a phase shift mask manufactured from the phase shift mask blank 10 of the present embodiment is used to pattern-expose a substrate to be exposed, such as a wafer, circuit pattern defects in the exposure process can be reduced, and the yield in the device manufacturing process with high integration can be improved.

According to the above embodiment, the following operational effects can be obtained.

(1) The phase shift mask blank 10 has a substrate 11 and a phase shift layer 12 formed on the substrate, wherein the phase shift layer 12 contains chromium and oxygen, and the arithmetic mean height of the surface of the phase shift layer 12 is 0.38nm or more. When the photoresist applied to the phase shift mask blank 10 is wet-etched after pattern exposure, the etching solution does not penetrate into the interface between the phase shift layer 12 and the photoresist layer.

(2) The oxygen atom number concentration inside (at a predetermined depth) phase shift layer 12 is greater than a predetermined value. For example, the oxygen atom number concentration of phase shift layer 12 at a depth of 1.25nm from the surface (described later) is 42.6% or more. When the photoresist applied to the phase shift mask blank 10 is wet-etched after pattern exposure, the etching solution does not penetrate into the interface between the phase shift layer 12 and the photoresist layer.

(3) In the process of manufacturing a phase shift mask using the phase shift mask blank 10 of the present embodiment, the phenomenon of permeation of the etching solution does not occur in the phase shift layer 12 at the edge portion of the pattern. That is, the phase shift layer 12 is not inclined due to the penetration of the etching solution. Therefore, the pattern accuracy of the phase shift mask manufactured using the phase shift mask blank 10 of the present embodiment can be improved, and thus the yield of the phase shift mask manufacturing process can be improved. Conventionally, an inclined surface is formed at the edge of a pattern due to permeation of an etching solution, which causes a reduction in yield. By performing the exposure process using the phase shift mask manufactured from the phase shift mask blank 10 of the present embodiment, a device with high integration can be manufactured with high yield.

(example 1)

A substrate 11 made of synthetic quartz glass was prepared. The in-line sputtering apparatus 100 shown in fig. 2 was used to form the phase shift layer 12 on the surface of the glass substrate 11. The method of manufacturing the phase shift layer 12 will be described in more detail below.

Argon (Ar) and carbon dioxide (CO) are introduced into the sputtering chamber 21 from the 1 st gas inlet 31₂) Nitrogen (N)₂) Oxygen (O) is introduced into the sputtering chamber 21 from the 2 nd gas inlet 32₂)。Ar、CO₂、N₂、O₂The flow rate of each gas was set to 240sccm, 42sccm, 135sccm, and 1.5sccm, and the flow rate and the exhaust gas amount of each gas were controlled so that the pressure in the sputtering chamber 21 was maintained at 0.3 Pa. The power of the DC power supply of the sputtering chamber 21 was set to 9kW (the control power was constant), and sputtering was performed while moving the substrate 11 in the direction of the broken-line arrow 25, so that the phase shift layer 12 made of CrOCN was formed on the substrate 11 at a thickness of 170nm, and the phase shift mask blank 10 was produced.

In the phase shift mask blank 10 produced by the above-described procedure, the arithmetic mean height Sa of the surface of the phase shift layer 12 was measured by a coherent scanning interferometer (New View8000 manufactured by Zygo Co., Ltd.) in a range of 220. mu. m.times.220. mu.m. The distribution of the oxygen atom number concentration in the depth direction of the phase shift layer 12 was measured by an X-ray photoelectron spectroscopy apparatus (quantera ii manufactured by PHI corporation).

The measurement of the oxygen atom number concentration distribution in the depth direction of the phase shift layer 12 by the X-ray photoelectron spectroscopy apparatus was performed according to the following procedure. A synthetic quartz glass substrate having SiO formed on the surface thereof by sputtering was prepared in the same manner as the substrate 11₂Reference substrate for film. The reference substrate was set in an X-ray photoelectron spectroscopy apparatus, and a sputtering ion gun provided in the X-ray photoelectron spectroscopy apparatus was used to irradiate SiO₂The film is sputtered and etched. At this time, SiO was obtained₂The etching time of the film and the etching amount (etching depth). Next, the phase shift mask blank 10 produced in example 1 was set in an X-ray photoelectron spectroscopy apparatus, and the oxygen atom number concentration was measured while sputtering the phase shift layer 12 with a sputtering ion gun. At this time, the relationship between the etching time and the etching depth of the phase shift layer 12 is considered to be SiO₂The relationship between the etching time and the etching amount (etching depth) of the film is the same. I.e. the etching depth obtained from a certain etching timeIn SiO₂The film and phase shift layer 12 are considered the same. Based on this process, the oxygen atom number concentration distribution in the depth direction of the phase shift layer 12 is obtained.

As described above, the measurement of the oxygen atom number concentration by the X-ray photoelectron spectroscopy apparatus is performed while etching the phase shift layer 12 by the sputter ion gun. The range of etching by the sputter ion gun was spread to a range of several hundreds of micrometers (μm) in diameter, and the value of the oxygen atom number concentration obtained by the X-ray photoelectron spectroscopy apparatus outputted an average value in the same range. It is considered that the measured oxygen atom number concentration is an average value of the oxygen atom number concentration measured by etching the phase shift layer 12 for a predetermined time in a range including a large number of such fine irregularities on the surface of the phase shift layer 12 by a sputter ion gun. The present inventors measured the various physical quantities described above for a comparative example in which the flow rate of oxygen gas in the phase shift layer formation step was set to zero, example 1 in which the flow rate was set to 1.5sccm, and example 2 in which the flow rate was set to 3 sccm.

Since the outermost surface of the phase shift layer 12 is likely to be contaminated by adsorption of an atmospheric gas or the like, it is preferable to remove the outermost surface of the phase shift layer to some extent in consideration of the degree of surface roughness when actually analyzing the composition of the phase shift layer 12. Therefore, in the present embodiment, the atomic number concentration at the position etched to a depth of 1.25nm from the outermost surface is taken as the surface atomic number concentration of the phase shift layer 12, but the etching depth for obtaining the surface composition is not limited to this value.

The measurement results are shown in the table of fig. 3. According to fig. 3, the arithmetic mean height of the surface of the phase shift layer 12 fabricated in example 1 was 0.402 nm. In addition, the arithmetic mean height of the surface of the phase shift layer 12 is 0.04nm greater than the arithmetic mean height of the surface of the substrate 11. In addition, in this phase shift layer 12, the oxygen atom number concentration at a depth of 1.25nm from the surface was 42.6%, the oxygen atom number concentration at a depth position of 85nm from the surface was 26.8%, and further, the ratio of the oxygen atom number concentration at a depth of 1.25nm from the surface to the oxygen atom number concentration at a depth of 85nm from the surface of the phase shift layer 12 was 1.59.

The produced phase shift mask blank 10 was subjected to UV cleaning for 10 minutes, then to spin cleaning (megasonic cleaning, alkali cleaning, brush cleaning, rinsing, spin drying) for 15 minutes, and a photoresist (GRX-M237 manufactured by Nagase Chemtex corporation) was applied to the surface of the phase shift layer 12 by a spin coater to form a photoresist layer. After exposure to light in a line space pattern of 2 μm pitch using a mask aligner, the photoresist layer was partially removed by development to form a resist pattern. Using this resist pattern as a mask, the phase shift mask blank 10 on which the resist pattern was formed was immersed in an etching solution (Pure Etch CR101 manufactured by linko Pure chemical industries, ltd.) and wet-etched, thereby forming a pattern in the phase shift layer 12.

After the pattern was formed, the pattern was cut, and the cross-sectional shape of the pattern was observed with a Scanning Electron Microscope (SEM), and whether or not the etching solution penetrated into the interface portion between the photoresist layer and the phase shift layer 12 was confirmed from the cross-sectional shape of the pattern. When the photoresist layer formed on the phase shift mask blank 10 produced in example 1 was exposed and then patterned in the phase shift layer 12 by wet etching, it was confirmed that no permeation of the etching solution occurred in the interface portion between the photoresist layer and the phase shift layer 12.

(example 2)

A substrate 11 made of synthetic quartz glass, which was the same as the substrate 11 used in example 1, was prepared. In example 1, when the phase shift layer 12 was formed, oxygen (O) gas was introduced into the sputtering chamber 21₂) The flow rate of (2) was set to 1.5sccm, but in this example, oxygen (O) gas was used₂) Phase shift layer 12 was formed under the same conditions as in example 1 except that the flow rate of (2) was set to 3 sccm. The same items as in example 1 were measured. The measurement results are shown in the table of fig. 3.

According to fig. 3, the arithmetic mean height of the surface of phase shift layer 12 fabricated in example 2 has a value of 0.417 nm. In addition, the arithmetic mean height of the surface of the phase shift layer 12 is 0.05nm greater than the arithmetic mean height of the surface of the substrate 11. In this phase shift layer 12, the oxygen atom number concentration at a depth of 1.25nm from the surface was 43.5%, the oxygen atom number concentration at a depth of 85nm from the surface was 27.2%, and the ratio of the oxygen atom number concentration at a depth of 1.25nm from the surface to the oxygen atom number concentration at a depth of 85nm from the surface of the phase shift layer 12 was 1.60.

In the case where a photoresist layer was formed on the phase shift mask blank 10 produced in example 2 and then a pattern was formed on the phase shift layer 12 by wet etching, it was confirmed that the permeation phenomenon of the etching solution did not occur at the interface portion between the photoresist layer and the phase shift layer 12.

The photoresist layer 15 formed on the phase shift mask blank 10 produced in examples 1 and 2 was exposed to light, then patterned by wet etching, and the pattern was cut off, and the cross section of the pattern was observed by a Scanning Electron Microscope (SEM), and fig. 4 is a view schematically showing the observed state. It is shown that no penetration of the etching solution occurs at the interface of the photoresist layer 15 and the phase shift layer 12.

Comparative example 1

A substrate 51 made of synthetic quartz glass, which was the same as the substrate 11 used in example 1, was prepared. Oxygen (O), which is oxygen gas, is not introduced into the sputtering chamber 21 when forming the phase shift layer₂) A phase shift layer was formed under the same conditions as in example 1 except that the introduction amount of (3) was set to 0 sccm. That is, in comparative example 1, no oxygen gas was introduced into the sputtering chamber 21 when forming the phase shift layer. Fig. 6 is a schematic diagram showing the structure of the phase shift mask blank 50 produced in comparative example 1. The surface roughness having the predetermined arithmetic mean height was not formed on the surface of the phase shift layer 52 of the phase shift mask blank 50 produced in comparative example 1. In the phase shift mask blank 50 of comparative example 1, the phase shift layer 52 formed on the surface of the substrate 51 was measured for the same items as in example 1.

The measurement results are shown in the table of fig. 3. According to fig. 3, the arithmetic mean height of the surface of the phase shift layer 52 produced in comparative example 1 has a value of 0.359 nm. In addition, in this phase shift layer 52, the oxygen atom number concentration at a depth of 1.25nm from the surface was 42.1%, the oxygen atom number concentration at a depth position of 85nm from the surface was 31.8%, and the ratio of the oxygen atom number concentration at a depth of 1.25nm from the surface to the oxygen atom number concentration at a depth of 85nm from the surface of the phase shift layer 52 was 1.32. In addition, in the phase shift mask blank 50 having the photoresist layer formed on the phase shift layer 52, which was produced in comparative example 1, when a pattern was formed on the phase shift layer 52 by wet etching, it was confirmed that permeation of the etching solution occurred at the interface portion between the photoresist layer and the phase shift layer 52.

The photoresist layer 55 formed on the phase shift mask blank 50 produced in comparative example 1 was exposed to light, then patterned by wet etching, and the pattern was cut off, and the cross section of the pattern was observed by a Scanning Electron Microscope (SEM), and fig. 7 is a view schematically showing the observed state. It is shown that an inclined surface is formed in the phase shift layer 52 due to permeation of the etching solution at the interface of the photoresist layer 55 and the phase shift layer 52.

In the phase shift mask having such an inclined surface, the area of the phase shift layer having the original film thickness is reduced by the formation of the inclined surface, and thus the phase shift function of the exposure light is reduced. As a result, when a circuit pattern is formed on a device substrate using such a phase shift mask, the accuracy of the circuit pattern is lowered. Therefore, such phase shift masks are not suitable for device fabrication.

From the above experimental results, the arithmetic surface roughness of the phase shift layer 12 is preferably 0.38nm or more. The oxygen atom concentration of the phase shift layer 12 at a depth of 1.25nm from the surface is preferably 42.6% or more. In addition, the oxygen atom concentration at a depth of 1.25nm from the surface of phase shift layer 12 is preferably greater than the oxygen atom concentration at a depth of 85nm, and the ratio thereof is preferably greater than 1.59.

The phase shift mask blank according to the present embodiment having this aspect has a tendency that the etching solution does not easily penetrate between the photoresist and the phase shift layer during wet etching, and an accurate mask pattern can be formed with respect to the pattern of the exposure light during exposure of the photoresist.

The arithmetic average height of the surface of phase shift layer 12 is not particularly limited as long as it is within a range in which desired contrast performance can be obtained. However, if the arithmetic mean height Sa of the surface of the phase shift layer 12 is too large, the scattering of the exposure light at the surface of the phase shift layer 12 increases, and the sharpness at the edges of the exposure pattern decreases, so the upper limit value of the arithmetic mean height Sa of the surface is preferably 1.0 nm.

From the results of measurement of atomic number concentration by an X-ray photoelectron spectroscopy apparatus, in the phase shift layer 12 composed of a CrOCN film formed in the present embodiment, oxygen is higher than the stoichiometric ratio. This improves the adhesion between the photoresist layer and the phase shift layer 12, and suppresses the permeation of the etching solution. For example, the phase shift layer 12 in the present embodiment may be formed of a film made of CrOCN (Cr: O: C: N: 51:27:5:18 atomic%) as a constituent. In the present specification, the composition of the CrOCN film is in a stoichiometric ratio, which means that the atomic ratio is Cr: O: C: N is 1:1:1: 1.

The surface of the substrate 11 of the phase shift mask blank 10 is finished by grinding. On the other hand, phase shift layer 12 is formed by sputtering. Therefore, although the arithmetic mean height of the surface of the phase shift layer 12 is usually larger than the arithmetic mean height of the surface of the substrate 11, the adhesion of the photoresist pattern formed on such a phase shift mask blank can be improved by making the arithmetic mean height of the surface of the phase shift layer 12 larger than the arithmetic mean height of the substrate 11 by a predetermined value. For example, such an effect can be obtained by making the arithmetic mean height of the surface of the phase shift layer 12 larger than the arithmetic mean height of the surface of the substrate 11 by 0.04nm or more. From the viewpoint of scattering of the exposure light on the surface of the phase shift layer 12, the upper limit of the difference between the arithmetic mean height of the surface of the phase shift layer 12 and the arithmetic mean height of the surface of the substrate 11 is preferably 1.0 nm.

The following modifications are also within the scope of the present invention, and one or a plurality of modifications may be combined with the above-described embodiment.

(modification 1)

In the above-described embodiment, when the phase shift layer 12 is formed by sputtering, the flow rate of oxygen introduced into the sputtering chamber is adjusted so that the arithmetic mean height of the surface of the phase shift layer 12 falls within a predetermined range. However, instead of adjusting the flow rate of oxygen gas introduced into the sputtering chamber, the surface irregularities may be formed at a predetermined arithmetic mean height by dry etching or wet etching the surface after the phase shift layer 12 is formed. This improves the adhesion between the photoresist layer formed on the surface of the phase shift layer 12 and the phase shift layer 12.

(modification 2)

The phase shift mask blank 10 described in the above embodiment and modification can be suitably used as a phase shift mask blank for manufacturing a phase shift mask for display device manufacturing applications, semiconductor manufacturing applications, and printed circuit board manufacturing applications. In the case of a phase shift mask blank used for manufacturing a phase shift mask for use in manufacturing a display device, a substrate having a size of 520mm × 800mm or more can be used as the substrate 11. The thickness of the substrate 11 may be 8 to 21 mm.

(Exposure apparatus)

Next, a photolithography process in semiconductor manufacturing or liquid crystal panel manufacturing will be described with reference to fig. 5 as an application example of a phase shift mask manufactured using the phase shift mask blank 10 manufactured in examples 1 and 2. The exposure apparatus 500 was provided with a phase shift mask 513 produced using the phase shift mask blank 10 produced in examples 1 and 2. In addition, a photosensitive substrate 515 coated with a photoresist is mounted in the exposure apparatus 500.

The exposure apparatus 500 includes: a light source LS, an illumination optical system 502, a mask support table 503 holding a phase shift mask 513, a projection optical system 504, an exposure object support table 505 holding a photosensitive substrate 515 as an exposure object, and a drive mechanism 506 moving the exposure object support table 505 in a horizontal plane. The exposure light emitted from the light source LS of the exposure apparatus 500 is incident on the illumination optical system 502, is adjusted to a predetermined light flux, and is irradiated on the phase shift mask 513 held on the mask support table 503. The light having passed through the phase shift mask 513 has an image of a device pattern drawn by the phase shift mask 513, and is irradiated to a predetermined position of the photosensitive substrate 515 held on the exposure object support table 505 via the projection optical system 504. Thereby, the image of the device pattern of the phase shift mask 513 is imagewise exposed on a photosensitive substrate 515 such as a semiconductor wafer or a liquid crystal panel at a predetermined magnification.

By using the phase shift mask of the embodiment, pattern defects in the exposure step can be reduced, and the yield in the exposure step can be improved.

While the various embodiments and modifications have been described above, the present invention is not limited to these embodiments. Other modes contemplated within the scope of the technical idea of the present invention are also included within the scope of the present invention.

The disclosures of the following priority base applications are incorporated herein by reference.

Japanese patent application No. 172898 in 2018 (application on 14/9/2018)

Description of the symbols

10 … phase shift mask blank

11 … baseplate

12 … phase shift layer

100 … manufacturing device