Pattern formation method and photosensitive hard mask

Abstract

To provide: a pattern forming method capable of forming a pattern in a short time when carrying out EUV exposure; and a photosensitive hard mask.SOLUTION: A pattern forming method includes: forming a photosensitive hard mask composed of a transition metal oxide film on a surface of a substrate; exposing EUV light on the photosensitive hard mask with a desired pattern; causing a change of state in an exposure region by heat generated during exposure; and selectively removing either one of a region where a change of state occurred, and a region where no change of state occurred.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a patterning method and a photosensitive hardmask. [Background technology]

[0002] As a next-generation exposure technology corresponding to the miniaturization of semiconductor devices, one using EUV (extreme ultraviolet) with a very short wavelength of 13.5 nm is being considered. In pattern formation by an EUV exposure device, a chemically amplified resist is used as a photosensitive material. In addition, various proposals have been made to increase the sensitivity of the chemically amplified resist to EUV and shorten the exposure time (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-101593 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a pattern formation method and a photosensitive hard mask that can form a pattern in a short time when EUV exposure is performed. [Means for solving the problem]

[0005] A pattern formation method according to one embodiment of the present disclosure includes forming a photosensitive hard mask made of a transition metal oxide film on a surface of a substrate, exposing the photosensitive hard mask to EUV light in a desired pattern, causing a state change in an exposed region by heat during exposure, and selectively removing either the region where the state change has occurred or the region where the state change has not occurred. The thickness t of the transition metal oxide film constituting the photosensitive hard mask is in the range of λ≦t≦3λ, where λ is the extinction length of the EUV light to be exposed. . Effect of the Invention

[0006] According to the present disclosure, there are provided a pattern formation method and a photosensitive hard mask capable of forming a pattern in a short time when EUV exposure is performed. [Brief description of the drawings]

[0007] [Figure 1] 1 is a flow chart illustrating a pattern forming method for forming a pattern on a photosensitive hard mask. [Diagram 2] 1A to 1C are cross-sectional views showing process steps of a pattern forming method for forming a pattern on a photosensitive hard mask. [Diagram 3] FIG. 1 shows the relationship between photon energy and extinction length for HfO2 and ZrO2, and the extinction length for 13.5 nm light (91 eV). [Figure 4] 1 is a cross-sectional view illustrating a state of an exposed region when the thickness of a transition metal oxide film constituting a photosensitive hard mask is smaller than the extinction length λ of EUV light used for exposure. [Diagram 5] 1 is a cross-sectional view illustrating a state of an exposed region when the thickness of a transition metal oxide film constituting a photosensitive hard mask is too large compared to the extinction length λ of EUV light used for exposure. [Figure 6] FIG. 13 is a diagram for explaining an example of negative patterning when the transition metal oxide film is a HfO 2 film. [Figure 7] FIG. 13 is a diagram for explaining an example of negative patterning when the transition metal oxide is MoO3 (MoOx). [Figure 8] FIG. 13 is a diagram for explaining an example of positive patterning when the transition metal oxide is MoO3 (MoOx). [Figure 9] FIG. 1 is a diagram showing a schematic diagram of the temperature change and the phase transition state in the exposed region in negative patterning and positive patterning when the transition metal oxide is MoO3 (MoOx). [Figure 10] 1 is a flowchart for explaining a pattern forming method for forming a pattern on a processing target film using a photosensitive hard mask. [Figure 11]1A to 1C are cross-sectional views illustrating process steps of a pattern forming method for forming a pattern on a film to be processed using a photosensitive hard mask. [Figure 12] 1A to 1C are cross-sectional views illustrating steps of forming a pattern on a film to be processed using a conventional chemically amplified resist. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment will be described with reference to the accompanying drawings.

[0009] <Method of forming a pattern on a photosensitive hard mask> First, a method of forming a pattern on a photosensitive hard mask by EUV exposure and development will be described. Fig. 1 is a flow chart for explaining the pattern formation method for forming a pattern on a photosensitive hard mask, and Fig. 2 is a cross-sectional view showing the steps of the pattern formation method.

[0010] First, a photosensitive hard mask 101 made of a transition metal oxide film is formed on the surface of a substrate 100 (step ST1, FIG. 2(a)).

[0011] Examples of transition metal oxides include HfO 2 or ZrO 2 Tetravalent transition metal oxides such as WO x , MoO x , V.O. x Examples of the transition metal oxide that can be used for the photosensitive hard mask 101 include low-melting-point polyvalent oxides such as those shown in FIG. 1. The photosensitive hard mask 101 can be formed by a thin film formation technique such as physical vapor deposition (PVD) such as sputtering, chemical vapor deposition (CVD), or atomic layer deposition (ALD). The transition metal oxide that can be used for the photosensitive hard mask 101 is one that undergoes a state change when irradiated with EUV light. Examples of the state change include a phase transition and a composition change.

[0012] Next, the photosensitive hard mask 101, which is a transition metal oxide film, is exposed to EUV light 102 in a desired pattern to form an exposed region 103 (step ST2, FIG. 2(b)). The exposure at this time is performed through a mask.

[0013] Next, a state change is caused in the exposure region 103 by heat due to exposure, and the exposure region 103 becomes a state change region 104 (step ST3, FIG. 2(c)). This state change is caused by the energy of the EUV light 102 becoming heat and heating the exposure region 103. In this way, an exposure pattern is formed. Note that a thermal diffusion region 103a is formed outside the exposure region 103 by thermal conduction, but this part can be kept below the state change temperature to prevent state change.

[0014] Next, in the photosensitive hard mask 101, either the state change region 104 or the non-state change region 105 that has not been exposed and has not changed state is selectively removed (step ST4, FIG. 2(d)). In this process, selective removal is realized due to the difference in removal characteristics between the state change region 104 and the non-state change region 105. As a result, the exposed pattern is developed, and a pattern is formed in the photosensitive hard mask. Note that, although the example in FIG. 2(d) shows a positive type example in which the state change region 104 is removed to form the removal region 106, a negative type in which the non-state change region 105 is removed may also be used. The state change region 104 or the non-state change region 105 can be removed by, for example, dry etching or wet etching.

[0015] In the conventional photosensitive process using chemically amplified resist, when exposed to EUV light, high-energy photons are incident on the resist, and the electrons generated by the excitation activate a photo acid generator (PAG), which causes the process to proceed. At this time, the number of electrons generated is small, and the sensitivity of the photosensitive material is low, resulting in a problem of long exposure time and low throughput. To overcome this problem, various proposals have been made to increase the sensitivity of chemically amplified resist to EUV and shorten the exposure time. For example, a technology to improve sensitivity, such as doping chemically amplified resist with a metal element that has high absorption of EUV light, to multiply the number of electrons generated by excitation by photons, has been widely tried. However, the effects of these methods are limited, and a photosensitive material that can fundamentally shorten the exposure time is required.

[0016] Therefore, in this embodiment, a photosensitive hard mask made of a transition metal oxide film, which is an inorganic material, is used, and instead of the conventional photosensitive process based on a chemical reaction, a photosensitive process is performed that utilizes the state change caused by heat generated when exposed to EUV light, as described above.

[0017] Among electromagnetic waves, EUV light has a wavelength close to that of X-rays, and the EUV light with a wavelength of 13.5 nm (13.5 nm light) used for exposure has a high energy of 91 eV. When this high-energy photon is incident on a film made of an inorganic material, it excites the valence electrons of the constituent atoms, and this energy is ultimately transferred to the crystal lattice and becomes heat. In this embodiment, this heat is used to cause a local temperature rise in the transition metal oxide film, which is an inorganic material film, causing a change in the state of the material.

[0018] In a photoexposure process using a chemically amplified resist, only a small portion of the energy of the EUV light is used in the chemical reaction, and the remaining energy is dissipated as heat. In contrast, in this embodiment, almost all of the energy of the EUV light, which was previously dissipated as heat, is used to cause a state change, so the energy efficiency is essentially high. This allows the exposure time to be shortened.

[0019] In addition, the unit lattice of inorganic materials is smaller than that of general polymer photosensitive materials, and HfO 2 In the case of , the side length of the unit cell is about 0.5 nm, which can suppress the fluctuation in pattern width caused by molecular size, which is a problem in chemically amplified resists. In addition, although the heat generated during exposure spreads from the exposed area to the outside due to thermal diffusion, moderate thermal diffusion reduces the effect of statistical fluctuation in pattern width.

[0020] Furthermore, either the exposed region that has undergone a state change is removed, or the non-exposed region is removed, so that both the positive type and the negative type can be selected, providing a high degree of freedom.

[0021] <Photosensitive hard mask> Next, the photosensitive hard mask will be described in detail. As described above, the photosensitive hard mask is made of a transition metal oxide. Examples of transition metal oxides include HfO, which is widely used in the semiconductor field. 2 or ZrO 2 Tetravalent transition metal oxides such as WO x , MoO x , V.O. x Examples of low-melting-point polyvalent metal oxides include HfO. Transition metal oxides have a short extinction length (the length over which the light intensity decays to 1 / e) for 13.5 nm light, which is the EUV light used for exposure. 2 and ZrO 2 In the case of WO, the extinction lengths are 31.5 nm and 70.6 nm, respectively, as shown in Fig. 3(a) and (b). x and MoO x WO 3 and MoO 3The extinction lengths of 13.5 nm light from transition metal oxides are also short, at 18 nm and 69 nm. In other words, the extinction length of 13.5 nm light from transition metal oxides is short, at around 18 to 70 nm, and the light energy attenuates rapidly over that short distance, and the energy is converted into heat, causing a change in state. In contrast, the extinction length of 13.5 nm light from polymer materials such as PMMA is around 0.2 μm, and the energy loss in the lattice occurs with a spatial spread several times larger than that.

[0022] Regarding the film thickness of the transition metal oxide film constituting the photosensitive hard mask, as shown in FIG. 4, if the film thickness t is smaller than the extinction length λ of the EUV light used for exposure, the EUV light may not be sufficiently attenuated by the transition metal oxide film and may reach the undercoat film 107 present under the exposed region 103, resulting in the pattern becoming enlarged due to thermal diffusion. In addition, if the thermal conductivity of the undercoat film 107 is large, the film thickness t is smaller than the extinction length λ, so that the heat generated by the exposure to the EUV light is dissipated to the undercoat film, and the exposed region 103 cannot be sufficiently heated, and the state change region may not be sufficiently formed. On the other hand, as shown in FIG. 5, if the film thickness t is too large than the extinction length λ, the EUV light is extinguished in the middle of the photosensitive hard mask 101, the exposed region 103 is only partially formed, and the state change region cannot be sufficiently formed, resulting in poor development. From the viewpoint of appropriately forming a state change region, the thickness t of the transition metal oxide film constituting the photosensitive hard mask 101 is preferably equal to or greater than the extinction length λ and not much larger than λ, and is preferably in the range of λ≦t≦3λ. It is more preferable that the thickness t is approximately equal to the extinction length λ.

[0023] Of the above transition metal oxides, HfO 2 or ZrO 2 and tetravalent transition metal oxides such as WO x , MoO x , V.O. x The properties are different from those of low melting point polyvalent oxides such as

[0024] Tetravalent transition metal oxide HfO 2 or ZrO 2In the case of , the melting point is high at about 2700 °C and it cannot be melted by exposure to EUV light, but a phase transition occurs at temperatures below about 1000 °C, so this phase transition can be utilized.

[0025] For example, HfO 2 In the case of a HfO2 film, negative patterning can be performed as shown in Figure 6. First, a HfO2 film is prepared by room temperature sputtering or ALD, which is in the amorphous phase as-depo. 2 Membrane (a-HfO 2 A thin film (film) 201 is formed on the substrate (FIG. 6(a)), and then EUV light (13.5 nm light) 202 is pattern-exposed to form an exposed region 203 (FIG. 6(b)). 203a is a thermal diffusion region. The exposed region 203 is heated to a crystallization temperature Tc or higher by the heat of exposure, and undergoes a phase transition (state change) to a crystalline phase, becoming a phase transition region 204, and an exposure pattern is formed (FIG. 6(c)). Next, the non-phase transition region of the amorphous phase is selectively removed by wet etching or dry etching to form (develop) a removed region 206, and negative patterning is performed (FIG. 6(d)). Specifically, in wet etching using DHF or BHF, the etch rate of the amorphous phase is higher than that of the crystalline phase, and negative patterning is realized by selectively etching the amorphous phase. Selective etching of the amorphous phase is performed using HF gas and TiCl 4 This can also be achieved by dry etching using gas.

[0026] Alternatively, positive patterning may be performed by selectively etching the crystalline phase of the exposed region.

[0027] ZrO as a transition metal oxide 2 When using ZrO, the as-depo state becomes a crystalline phase (low-temperature phase), but 2 Since a high-temperature phase exists in the exposed area, the exposed area is heated to a temperature equal to or higher than the transition temperature to the high-temperature phase, causing the exposed area to transition to the high-temperature phase. Then, due to the difference in etch rate between the low-temperature phase and the high-temperature phase, one of them can be selectively removed.

[0028] WO, a low melting point polyvalent oxidex , MoO x , V.O. x In the case of HfO, the melting point is about 800 to 1500°C. 2 or ZrO 2 In particular, MoO x MoO 3 The melting point of MoO is extremely low at 795°C. 3 can be formed by sputtering, and when the substrate temperature during sputtering is room temperature, the film becomes amorphous as-deposited, and when the substrate temperature is 200°C or higher, the film becomes crystalline as-deposited. This allows for both negative and positive patterning.

[0029] MoO 3 Negative patterning of the film can be performed as shown in FIG. 7. First, MoO, which is in the amorphous phase in the as-depo state, is formed by room temperature sputtering. 3 Film (a-MoO 3 A thin film (film) 211 is formed (FIG. 7(a)), and then EUV light (13.5 nm light) 212 is exposed in a pattern to form an exposed region 213 (FIG. 7(b)). 213a is a thermal diffusion region. The exposed region 213 is heated to above the crystallization temperature Tc by the heat of exposure, and becomes a phase transition region 214 that has undergone a phase transition to a crystalline phase, thereby forming an exposure pattern (FIG. 7(c)). Next, the non-phase transition region of the amorphous phase is selectively removed by wet etching or dry etching to form (develop) a removed region 216, and negative patterning is performed (FIG. 7(d)).

[0030] MoO 3 Positive patterning of the film can be performed as shown in FIG. 8. First, MoO, which is in the crystalline phase in the as-depo state, is formed by sputtering at 200° C. or higher. 3 Membrane (c-MoO 3A thin film (film) 221 is formed (FIG. 8(a)), and then a pattern of EUV light (13.5 nm light) 222 is exposed to form an exposed region 223 (FIG. 8(b)). 223a is a thermal diffusion region. The exposed region 223 is heated to or above the melting point Tm and melts, and then the exposure is turned off, so that the exposed region 223 is rapidly cooled and the molten state is quenched, becoming an amorphous phase phase transition region 224, and an exposure pattern is formed (FIG. 8(c)). Next, the amorphous phase phase transition region 224 is selectively removed by wet etching or dry etching to form (develop) a removal region 226, and positive patterning is performed (FIG. 8(d)).

[0031] In addition, in the case of negative patterning, the amorphous phase MoO 3 The film is exposed to EUV light, and the exposed area is heated to a relatively low crystallization temperature Tc or higher and then slowly cooled, as shown in Figure 9(a). This causes the exposed area to become crystalline. On the other hand, in the case of positive-tone patterning, the crystalline phase of MoO 3 The film is exposed to EUV light, and as shown in Fig. 9(b), the exposed area is heated to a relatively high melting temperature Tm or higher, causing it to melt, and when the exposure is turned off, it is rapidly cooled, causing the exposed area to become amorphous.

[0032] In addition, in an example where the amorphous phase is the non-phase transition region and the crystalline phase is the phase transition region, the etching method may be adjusted to change the portion to be removed to the crystalline phase transition region, thereby forming a positive patterning.In an example where the amorphous phase is the phase transition region and the crystalline phase is the non-phase transition region, the etching method may be adjusted to change the portion to be removed to the crystalline phase non-phase transition region, thereby forming a negative patterning.

[0033] That's all, MoO 3 Although the membrane was used as an example, WO x WO 3 Membrane, VO x The membrane is VO 3 The same patterning can be performed for the WO 3 , V.O. 3 is MoO 3Since it has a higher melting point than Cr, it is necessary to extend the exposure time to EUV light when melting.

[0034] In addition, WO, a low melting point polyvalent oxide, x , MoO x , V.O. x Regarding WO, the state change upon exposure to EUV light is not limited to the phase transition described above, but may also be a composition change. x , MoO x , V.O. x are oxides whose valence can change. Thus, any of these, e.g. MoO 3 As a photosensitive hard mask, for example, a layer having a reducing effect is provided adjacent to the hard mask, and the MoO in the exposed area is converted to MoO by a reaction with the adjacent reducing layer due to heat generated when the hard mask is exposed to EUV light. 3 is reduced, which can result in a composition change.

[0035] <Advantages of patterning by EUV exposure using a photosensitive hard mask> Next, the advantages of patterning a transition metal oxide film by EUV exposure will be described in detail.

[0036] The first advantage is that the exposure time can be shortened. The exposure time when exposing a transition metal oxide film to EUV light can be easily calculated from the physical properties of the material. EUV light incident on a transition metal oxide film, which is an inorganic thin film, locally heats a volume determined by the extinction length in the film. HfO 2 , ZrO 2 , WO 3 , MoO 3 is 1.2 to 2.4 × 10 6 J / m 3 The heat capacity is about 100 K. The heat load on the substrate (wafer) during EUV exposure is 3 W / cm 2 (Laser Focus World August 29, 2019 "EUV As described above, when patterning is performed using thermal phase transition, the temperature of the exposed area is raised to the temperature required for the phase transition. However, since the temperature rise in the exposed area is determined by the power, the dose can be small and therefore the exposure time can be short. A simple adiabatic calculation using the above parameters shows that it is possible to heat the transition metal oxide film to about 1000°C, which is the temperature required to crystallize the amorphous phase, with an exposure time of EUV light of several milliseconds. According to calculations, the dose when the exposure time of EUV light is 1 millisecond is 3 mJ / cm. 2 However, this value is 70 mJ / cm, which is the dose when exposing a conventional chemically amplified resist to EUV light. 2 In other words, by using a patterning method in which a photosensitive hard mask made of a transition metal oxide film is exposed to EUV light to cause a phase transition, the exposure time can be reduced to 1 / 20 of that required when using a conventional chemically amplified resist, greatly improving throughput.

[0037] The second advantage is that the pattern edges can be smoothed by thermal diffusion, thereby reducing line edge roughness (LER). When an inorganic thin film of a transition metal oxide is exposed to EUV light and locally heated, the high temperature area expands outside the exposed area due to thermal diffusion caused by thermal conduction. However, the transition metal oxide HfO 2 , ZrO 2 The thermal diffusivity of such materials is 1×10 -6 m 2 / sec, and the high-temperature region that extends outside the exposed area is below the phase transition temperature and does not affect the patterned shape. On the other hand, thermal diffusion occurs quickly enough for the formation of nanometer-scale fine patterns, and as a result, the temperature of the exposed area and the high-temperature region outside it becomes uniform. This is expected to have the effect of smoothing out the line edge error (LER) that originates from the inhomogeneous structure of the transition metal oxide film when it is formed.

[0038] <Patterning of the film to be etched> Next, a method for forming a pattern on a film to be processed using the above-described photosensitive hard mask will be described.

[0039] FIG. 10 is a flow chart for explaining a pattern forming method for forming a pattern on a film to be processed using a photosensitive hard mask, and FIG. 11 is a process cross-sectional view illustrating the pattern forming method.

[0040] First, a photosensitive hard mask 304 made of a transition metal oxide film is formed on a substrate 300 having a film to be processed (step ST11, FIG. 11(a)). An example of the substrate 300 is a substrate having a film to be processed 302 formed on a semiconductor base (Si base) 301, and a hard mask 303 formed thereon. An insulating film or a metal film can be used as the film to be processed 302. A material that can ensure an etching selectivity to the film to be processed 302 is selected for the hard mask 303, and for example, SiO 2 , SiN, TiN, amorphous carbon, etc. Depending on the etching selectivity, a plurality of hard masks may be used to ensure a processing margin.

[0041] Next, in accordance with the above-mentioned steps ST2 to ST4, the photosensitive hard mask 304 is subjected to UVE exposure and development to form a pattern (step ST12, FIG. 11(b)).

[0042] Next, the hard mask 303 is etched using the patterned photosensitive hard mask 304 as a mask, and the pattern of the photosensitive hard mask 304 is transferred to the hard mask 303 (step ST13, FIG. 11(c)).

[0043] Next, the film to be processed 302 is etched using the hard mask 303 to which the pattern has been transferred as a mask, thereby forming a pattern in the film to be processed 302 (step ST14, FIG. 11(d)).

[0044] In this manner, by using a photosensitive hard mask made of a transition metal oxide film for patterning a film to be processed, it is possible to obtain the effects such as shortening the exposure time when forming an exposure pattern as described above, and also to obtain the effect of reducing the number of masks when patterning the film to be processed.

[0045] In the case of organic materials such as conventional chemically amplified resists, the etching resistance is low when the processing target film is patterned by etching. For this reason, for example, as shown in Figures 12(a) to (e), a processing target film 402 and a hard mask 403 are formed on a base 401, and a substrate 400 on which an amorphous carbon film 404 is further formed is used, and a chemically amplified resist film 405 is formed thereon and patterned. That is, after forming a pattern by performing UVE exposure and development on the chemically amplified resist film 405, the pattern is transferred to the amorphous carbon film 404, and then the transferred pattern is further transferred to the hard mask 403, and then the processing target film 402 is patterned.

[0046] In contrast, a photosensitive hard mask made of a transition metal oxide film has higher etching resistance than organic materials such as conventional chemically amplified resists, and therefore, as described above, the pattern of the photosensitive hard mask can be directly transferred to a hard mask, and the film to be processed can be patterned using the transferred pattern of the hard mask.

[0047] <Other applications> Although the embodiments have been described above, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims.

[0048] For example, in the above embodiment, the transition metal oxide constituting the photosensitive hard mask is HfO 2 , ZrO 2 , WO x , MoO x , V.O. xHowever, the present invention is not limited to this, and other transition metal oxides can also be used. [Explanation of symbols]

[0049] 100,300;Substrate 101,303;Photosensitive hard mask 102,202,212,222;EUV light 103, 203, 213, 223; Exposure area 104; State change area 105; Non-state change area 201;a-HfO 2 film 204, 214, 224; Phase transition region 211;a-MoO 3 film 221;c-MoO 3 film 302; Film to be processed 303;Hard Mask

Claims

1. forming a photosensitive hard mask made of a transition metal oxide film on a surface of a substrate; exposing the photosensitive hard mask to EUV light in a desired pattern; causing a state change in the exposed region by heat during exposure; Selectively removing either the region in which the state change has occurred or the region in which the state change has not occurred; having The pattern forming method, wherein a thickness t of the transition metal oxide film constituting the photosensitive hard mask is in a range of λ≦t≦3λ, where λ is the extinction length of EUV light used for exposure.

2. The pattern formation method according to claim 1 , wherein the state change is a phase transition or a composition change.

3. 3. The pattern formation method according to claim 2, wherein the transition metal oxide constituting the transition metal oxide film is a tetravalent transition metal oxide.

4. The tetravalent transition metal oxide is HfO ２ Or ZrO ２ The pattern forming method according to claim 3 ,

5. The transition metal oxide film is an amorphous phase HfO ２ 5. The pattern formation method according to claim 4, wherein the exposed region is a film, and is heated to a crystallization temperature or higher to undergo a phase transition to a crystalline phase.

6. 3. The pattern formation method according to claim 2, wherein the transition metal oxide constituting the transition metal oxide film is a low melting point polyvalent oxide.

7. The low melting point polyvalent oxide is WO ｘ , MoO ｘ , V.O. ｘ 7. The pattern forming method according to claim 6, wherein the pattern forming method is any one of the above.

8. The transition metal oxide film is an amorphous phase MoO ｘ MoO in film or crystalline phase ｘ A film of MoO in an amorphous phase. ｘ In the case of a film, the exposed area is heated above the crystallization temperature to undergo a phase transition to a crystalline phase, and the MoO ｘ 8. The pattern forming method according to claim 7, wherein in the case of a film, the exposed region undergoes a phase transition to an amorphous phase by being heated to a temperature equal to or higher than the melting point and then rapidly cooled.

9. The pattern formation method according to claim 1 , wherein the selective removal is performed by dry etching or wet etching.

10. forming a photosensitive hard mask made of a transition metal oxide film on a surface of a substrate on which a film to be processed and a hard mask are formed; exposing the photosensitive hard mask to EUV light in a desired pattern; causing a state change in the exposed region by heat during exposure; selectively removing either the region where the state change has occurred or the region where the state change has not occurred to form a pattern on the photosensitive hard mask; transferring the pattern of the photosensitive hard mask to the hard mask; Etching the film to be processed using the hard mask to which the pattern has been transferred as a mask, thereby forming a pattern in the film to be processed; having The pattern forming method, wherein a thickness t of the transition metal oxide film constituting the photosensitive hard mask is in a range of λ≦t≦3λ, where λ is the extinction length of EUV light used for exposure.

11. A photosensitive hard mask that is exposed to EUV light in a desired pattern and developed to form a pattern, a transition metal oxide film, wherein when exposed to EUV light, a state change occurs in an exposed region due to heat generated during exposure, and the pattern is formed by selectively removing either the region where the state change occurs or the region where the state change does not occur; A photosensitive hard mask, wherein a thickness t of the transition metal oxide film constituting the photosensitive hard mask is in a range of λ≦t≦3λ, where λ is the extinction length of EUV light used for exposure.

12. 12. The photosensitive hardmask of claim 11, wherein the change in state is a phase transition or a composition change.

13. 13. The photosensitive hard mask according to claim 12, wherein the transition metal oxide constituting the transition metal oxide film is a tetravalent transition metal oxide.

14. The tetravalent transition metal oxide is HfO ２ Or ZrO ２ 14. The photosensitive hard mask of claim 13, wherein

15. The transition metal oxide film is an amorphous phase HfO ２ 15. The photosensitive hard mask of claim 14, wherein the exposed areas undergo a phase transition to a crystalline phase upon heating above a crystallization temperature.

16. 13. The photosensitive hard mask according to claim 12, wherein the transition metal oxide constituting the transition metal oxide film is a low melting point polyvalent oxide.

17. The low melting point polyvalent oxide is WO ｘ , MoO ｘ , V.O. ｘ 17. The photosensitive hard mask of claim 16, wherein

18. The transition metal oxide film is an amorphous phase MoO ｘ MoO in film or crystalline phase ｘ A film of MoO in an amorphous phase. ｘ In the case of a film, the exposed area is heated above the crystallization temperature to undergo a phase transition to a crystalline phase, and the MoO ｘ 20. The photosensitive hard mask of claim 17, wherein, in the case of a film, the exposed areas undergo a phase transition to an amorphous phase by heating above their melting point and quenching.

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