Dry Development of Metal-Free Photoresist

Abstract

A method of patterning an underlying layer, comprising depositing a metal-free polymer film over the underlying layer, exposing the film to EUV to form an exposed region and a mask region of the film, the exposed region being formed to be photoreactive to EUV, selectively dry etching a first portion of the film to form a feature including the remaining second portion of the film, the etching rate of the first portion being greater than the etching rate of the second portion of the film, the first portion being one of the exposed region and the mask region, the second portion being the other of the exposed region and the mask region that is not the first portion, the pitch of the feature being less than the feature size achievable with a 193 nm immersion lithography tool in a single patterning process, and using the second portion as an etching mask to pattern the underlying layer.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 335,525, filed Apr. 27, 2022, and U.S. Non - Provisional Patent Application No. 18 / 193,324, filed Mar. 30, 2023, which are hereby incorporated by reference herein.

[0002] The present invention generally relates to a method of processing a substrate, and in certain embodiments, to dry development of a metal - free photoresist.

Background Art

[0003] Generally, semiconductor devices such as integrated circuits (ICs) are manufactured by continuously depositing and patterning layers of dielectric, conductor, and semiconductor materials across a semiconductor substrate to form a network that integrates electronic components and interconnect elements (e.g., transistors, resistors, capacitors, metal wires, contacts, and vias) in a monolithic structure. At each successive technology node, the minimum feature size is reduced and the component packing density is approximately doubled to reduce costs.

[0004] Photolithography is a common patterning method in semiconductor manufacturing. The photolithography process can be initiated by exposing a coating of photoresist containing a radiation-sensitive material to a pattern of actinic radiation to define a relief pattern. For example, in the case of a positive photoresist, the irradiated portion of the photoresist can be dissolved and removed by a developing process using a developing solvent to form a relief pattern of the photoresist. Development refers to selectively removing the reacted or unreacted regions of the photoresist material. The relief pattern can then be transferred to a target layer under the photoresist or to a hard mask layer of an underlying layer formed over the target layer. Innovations in patterning, such as immersion lithography, multiple patterning, and extreme ultraviolet (EUV) optical systems with a wavelength of 13.5 nm, have reduced the critical feature size down to near 10 nanometers. At the same time, for these advanced photolithography technologies and systems, the development of new materials and process flows is required to meet the cost and quality requirements of patterning at the nanoscale features. Summary of the Invention Means for Solving the Problems

[0005] A method of patterning an underlying layer according to an embodiment of the present invention, comprising: providing a substrate including the underlying layer; depositing a metal-free polymer film over the underlying layer; exposing the metal-free polymer film to extreme ultraviolet (EUV) radiation through a photomask to form an exposed region and a masked region of the metal-free polymer film, wherein the exposed region photoreacts in response to EUV radiation; loading the substrate into a processing chamber; selectively dry etching a first portion of the metal-free polymer film using an etching gas in the processing chamber to form a plurality of features including a remaining second portion of the metal-free polymer film, wherein the etching rate of the first portion is greater than the etching rate of the second portion of the metal-free polymer film, the first portion is one of the exposed region and the masked region, the second portion is the other of the exposed region and the masked region that is not the first portion, and the pitch of the plurality of features is less than the feature size achievable with a 193 nm immersion lithography tool in a single patterning process; and using the second portion as an etch mask to pattern the underlying layer disposed under the metal-free polymer film.

[0006] According to an embodiment of the present invention, a method for patterning an underlying layer, comprising depositing a metal-free polymer film across a substrate by a spin-on process, wherein the metal-free polymer film contains carboxyl groups and the substrate contains the underlying layer; exposing the substrate to extreme ultraviolet (EUV) irradiation through a photomask to decarboxylate a portion of the metal-free polymer film, wherein the portion of the metal-free polymer film is the region exposed to the EUV irradiation and the decarboxylation includes a photoreaction in response to the EUV irradiation; loading the substrate into a processing chamber; exposing the substrate to a plasma to selectively remove the regions masked by the photomask and not exposed to the EUV irradiation, wherein the plasma is generated in the processing chamber and the etching rate of the masked region is at least twice as large as the etching rate of the exposed region; and using the exposed region as an etching mask to pattern the underlying layer disposed under the metal-free polymer film.

[0007] According to an embodiment of the present invention, a method for patterning an underlying layer, comprising depositing a metal-free polymer film across a substrate containing the underlying layer by a spin-on process; exposing the substrate to extreme ultraviolet (EUV) irradiation through a photomask to oxidize a portion of the metal-free polymer film, wherein the oxidation includes a photoreaction in response to the EUV irradiation; loading the substrate into a processing chamber; exposing the substrate to a plasma to selectively remove the exposed region, wherein the plasma is generated in the processing chamber and the etching rate of the exposed region is at least twice as large as the etching rate of the region masked by the photomask and not exposed to the EUV irradiation; and using the masked region as an etching mask to pattern the underlying layer disposed under the metal-free polymer film.

[0008] For a more detailed understanding of the present invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0009]

Fig. 1A-1F

Fig. 2A

Fig. 2B

Fig. 3

Fig. 4A-4E

Fig. 5

Fig. 6

Fig. 7

Fig. 8

Fig. 9A-9C

Fig. 10

DETAILED DESCRIPTION OF THE INVENTION

[0010] This application relates to a method of processing a substrate, and more specifically, to dry development of a metal-free polymer film. The common development technique for photoresist widely used in the industry is wet development, where the substrate is treated with a developer solution to dissolve only the reacted or unreacted regions of the photoresist. Wet development is very effective for conventional UV lithography optical systems and techniques, but as feature sizes continue to shrink, at least partially satisfactory development by wet development becomes impossible due to pattern collapse during wet development. In particular, in extreme ultraviolet (EUV) optical systems introduced at technology nodes below 10 nm, such problems specific to photoresist and development methods become more important than the optical resolution limit. To date, new types of photoresists based on metals and / or metal oxides for EUV patterning have been disclosed, for example, by Inpria (e.g., U.S. Patent Application Publication No. 2020 / 0064733A1, Meyers et al., U.S. Patent Application Publication No. 2019 / 0308998A1, Cardineau et al.) and Lam Research (U.S. Patent Application Publication No. 2021 / 0265163A1, Yu et al., U.S. Patent Application Publication No. 2017 / 0146909A1, Smith et al.). In certain manufacturing processes such as the front end of line (FEOL), metal contamination must be strictly avoided. Therefore, new EUV photoresist materials and their development techniques may be desired. Embodiments of this application disclose an EUV patterning method that uses a metal-free polymer film as a photoresist and dry development of the metal-free polymer film to obtain features that can be obtained by EUV lithography.

[0011] The methods described in this disclosure can advantageously improve process performance by preventing pattern collapse during development and improving throughput. Other advantages can include the elimination of the need for developers. Dry development in various embodiments can be enabled by changing the Ohnishi parameter of the metal-free polymer film, and thus its dry etch rate, as opposed to the solubility changes in the case of conventional wet development. Accordingly, based on the embodiments, a metal-free EUV photoresist based on a new polymer can be developed. The methods in various embodiments can also include area selective deposition (ASD) as part of the dry development process, which improves the etch selectivity between regions of the metal-free polymer film, thereby improving its tone as a metal-free EUV photoresist. The description of this disclosure refers primarily to EUV as the photoresist irradiation source, although other forms of irradiation (e.g., deep ultraviolet, X-rays, or electron beams) can also be contemplated in other embodiments.

[0012] First, an example of a negative photoresist will be used to describe a method of EUV patterning using a metal-free polymer film with reference to FIGS. 1A-1D according to various embodiments. In particular, the dry development process is illustrated in FIG. 1D along with FIGS. 2-3. Embodiments that include ASD during the dry development process to enhance tone are described with reference to FIGS. 2A and 2B. In FIG. 3, for comparison, the problem of pattern collapse with a conventional wet development process is described. Exemplary subsequent processes after dry development are shown in FIGS. 1E and 1F. Subsequently, patterning in the case of a positive photoresist is described with reference to FIGS. 4A-4E. In FIG. 5, the Ohnishi parameter is introduced as a parameter for empirically predicting the dry etch rate of a metal-free polymer film. Next, examples of possible structural changes in the metal-free polymer film that affect the dry etch rate are shown in FIGS. 6-8. Exemplary process flow diagrams are shown in FIGS. 9A-9C. FIG. 10 shows an exemplary system for dry development of a metal-free polymer film. All figures in this disclosure are drawn for illustrative purposes only and are not to scale, including the aspect ratios of the features.

[0013] Figures 1A - 1F show schematic views of an exemplary substrate 100 at various stages during an exemplary process of manufacturing a metal - free polymer film as a negative - type photoresist, including the step of dry - developing the polymer film, according to various embodiments. Figure 1A shows a cross - sectional view of a novel substrate 100.

[0014] In various embodiments, the substrate 100 can be part of a semiconductor device or can include a semiconductor device and, for example, can undergo several processing steps following a conventional process. Thus, the substrate 100 can include layers of semiconductors useful in various microelectronics. For example, a semiconductor structure can include a substrate 100 in which various device regions are formed.

[0015] In one or more embodiments, the substrate 100 can be a silicon wafer or a silicon - on - insulator (SOI) wafer. In certain embodiments, the substrate 100 can include a silicon - germanium wafer, a silicon - carbide wafer, a gallium - arsenide wafer, a gallium - nitride wafer, or other compound semiconductors. In other embodiments, the substrate 100 can include hetero - layers such as silicon - germanium - on - silicon, gallium - nitride - on - silicon, silicon - carbon - on - silicon, similar to a silicon - on - silicon layer or an SOI substrate. In various embodiments, the substrate 100 is patterned or embedded in other components of the semiconductor device.

[0016] In Figure 1A, the substrate 100 includes an underlayer 110 and a hard - mask (HM) layer 120. The structure shown in Figure 1A is an example, and in other embodiments, other suitable structures are also conceivable. In various embodiments, the underlayer 110 can be a layer that is patterned by an EUV lithography process. The underlayer 110 can include an oxide, amorphous silicon, polysilicon, or other dielectric materials useful in semiconductor manufacturing. In various embodiments, the oxide can include carbon, hydrogen, and nitrogen. In some embodiments, the underlayer 110 can include a silicon oxide that can be prepared, for example, by plasma - enhanced CVD or flowable CVD using tetraethyl orthosilicate (TEOS) as a precursor.

[0017] The hard mask (HM) layer 120 may include a metal hard mask layer such as titanium nitride, titanium oxide, and hafnium oxide in particular. HM 120 can be deposited using deposition techniques including chemical vapor deposition (CVD), physical vapor deposition (PVD), and atomic layer deposition (ALD), as well as other plasma processes such as plasma CVD (PECVD), sputtering, and other processes.

[0018] FIG. 1B shows a cross-sectional view of the substrate 100 after depositing the metal-free polymer film 130.

[0019] In various embodiments, the metal-free polymer film 130 can be deposited over the HM layer 120 using a dry process or a wet process, such as spin coating technology. In one or more embodiments using spin coating technology, the metal-free polymer film 130 or its precursor can be dissolved in a solvent to prepare a photoresist solution, which is then dispensed from a nozzle to the central portion of the substrate 100. The photoresist solution on the wafer can be dispensed while the wafer is rotating (i.e., dynamic dispensing) or without rotation (i.e., static dispensing). The wafer is rotated, for example, at a speed of 500 rpm to 4000 rpm to exert centrifugal force, causing the photoresist solution to spread outside the edge of the substrate 100 and towards the edge of the substrate 100. When the solvent evaporates from the photoresist solution, a photoresist film can be formed over the substrate 100, uniformly coating the surface of the substrate 100. In one embodiment, the thickness of the metal-free polymer film 130 is 10 nm to 100 nm.

[0020] The process conditions of the spin coating technology can particularly include spin speed, spin time, solvent system, and temperature. In certain embodiments, after spin coating, non-uniform features of the metal-free polymer film 130 may be formed in the edge portion (e.g., edge bead) of the substrate 100. These non-uniform features can be removed by a conventional edge bead removal (EBR) process that can dispense the solvent to the edge portion while rotating the substrate 100.

[0021] In certain embodiments, optionally, a soft bake can be performed to heat treat the substrate 100 and remove residual solvents from the metal-free polymer film 130. The soft bake process can include heating the metal-free polymer film 130 within a temperature range of, for example, 75° C. to 100° C.

[0022] In a further embodiment, an optional chemical treatment step can also be inserted after deposition of the metal-free polymer film 130 and before EUV exposure. The optional chemical treatment can introduce functional groups (e.g., carboxyl groups) that can enable or enhance the reactivity of the metal-free polymer film 130 in response to EUV exposure.

[0023] The metal-free polymer film 130 can be used as a photoresist for forming a relief pattern by EUV lithography, as further described below with reference to FIGS. 1C-1F. In various embodiments, the "metal-free" property of the metal-free polymer film 130 indicates the absence of metal in the polymer repeating unit. The absence of metal can be beneficial for the application of the metal-free polymer film 130 as an EUV photoresist in manufacturing processes where metal contamination is severely prohibited.

[0024] In various embodiments, the metal-free polymer film 130 may contain metals below the detection limit in the polymer film. The detection limit of the metal may be based on conventional analytical techniques for determining the metal content, such as inductively coupled plasma optical emission spectrometry (ICP-OES). In one or more embodiments, the metal-free polymer film 130 may contain less than 100 ppm of metal, and in some embodiments may contain metal at a concentration of less than 1 ppm. In one or more embodiments, the content of critical metals such as calcium, cobalt, chromium, copper, iron, potassium, iron, manganese, molybdenum, sodium, and nickel in the metal-free polymer film 130 may be less than that of smaller amounts of critical metals such as tungsten, hafnium, aluminum, and titanium. In one or more embodiments, the metal-free polymer film 130 may contain silicon.

[0025] In various embodiments, the metal-free polymer film 130 may contain a photo-responsive polymer that changes the dry etching rate during EUV exposure. The metal-free polymer film 130 may be a chemically amplified resist (CAR), and additional polymeric or non-polymeric photo-responsive components (e.g., photoacid generators) may be included to amplify the structural changes in the metal-free polymer film. Possible photo-induced chemicals of the metal-free polymer film 130 that enable EUV lithography in various embodiments are further described with reference to FIGS. 5-8.

[0026] FIG. 1C shows a cross-sectional view of the substrate 100 after extreme ultraviolet (EUV) exposure through the photomask 145.

[0027] In FIG. 1C, the EUV lithography process is performed by exposing the substrate 100 to EUV irradiation 140 through the photomask 145. Only the unmasked areas of the substrate 100 are irradiated with the UV irradiation 140 by the photomask 145. In the example shown, a metal-free polymer film functions as a negative photoresist. Thus, in response to EUV exposure, directly or indirectly, the exposed areas of the metal-free polymer film 130 are converted into the reacted polymer film 150. On the other hand, the masked areas of the metal-free polymer film 130 remain unreacted. The reacted polymer film 150 may have undergone a structural change that results in a change in the dry etching rate, which can be utilized in a subsequent dry development process. In various embodiments, such a structural change from the metal-free polymer film 130 to the reacted polymer film 150 may include, for example, decarboxylation, cyclization, or crosslinking.

[0028] In certain embodiments, after EUV exposure, the substrate 100 can be thermally processed to optionally perform a post-exposure bake (PEB). The PEB can be beneficial to ensure the removal of residual solvents and / or to further differentiate the material properties of the reacted polymer film 150 from those of the metal-free polymer film 130. In one or more embodiments, the PEB can be performed at 80 - 220 °C.

[0029] FIG. 1D shows a cross-sectional view of the substrate 100 after dry-developing the metal-free polymer film 130 to remove the reacted polymer film 150.

[0030] Dry development in the present disclosure refers to any development process in which the selective removal of the photoresist is driven by exposure to a reactive gas and / or plasma without the intervention of a solvent (i.e., wet development) (i.e., dry etching). The dry development process can include, for example, a selective plasma etching process, a purely chemical process, or a thermal process, and advantageously excludes the use of a developer solution. In certain embodiments, the dry development process can be reactive ion etching (RIE) or atomic layer etching (ALE). In one or more embodiments, the etching gas for the dry development process is H 2may contain a mixture of and CO. In other embodiments, the etching gas is a halogen (e.g., HBr, HCl, or HI), oxygen (e.g., O 2 ), and / or sulfur (e.g., SO 2 or SF 6 ). In certain embodiments, for example, when ALE is used in a dry development process, a circulation process can be performed. The etching gas composition and process conditions of the dry development process can be selected, for example, in the shown example of a negative photoresist, to maximize the dry etching selectivity for the metal-free polymer film 130. As a result, in FIG. 1D, the reacted polymer film 150 remains after the dry development process, and the unreacted regions of the metal-free polymer film 130 are removed. In one embodiment, the etching rate of the reacted polymer film 150 is at least twice greater than the etching rate of the masked (unreacted) regions of the metal-free polymer film 130. In certain embodiments, area-selective deposition (ASD) can be performed in connection with the etching of the dry development process. ASD can be utilized because EUV exposure as described above in FIG. 1C results in two regions of polymers having different compositions (i.e., the metal-free polymer film 130 and the reacted polymer film 150). The ASD across the metal-free polymer film 130 can advantageously enhance or reverse the inherent tonality of the metal-free polymer film 130.

[0031] FIG. 2A shows a cross-sectional view of a substrate 100 during a dry development process of a metal-free polymer film 130 including area-selective deposition (ASD) according to various embodiments.

[0032] FIG. 2B shows a cross-sectional view of the substrate 100 after completion of the dry development process of the metal-free polymer film 130 according to the embodiment of FIG. 2A.

[0033] By enhancing the dry etching selectivity, the performance of the dry developing photoresist can be improved. According to one embodiment, one way to enhance the dry etching selectivity is to utilize ASD during the etching of the metal-free polymer film. As shown in FIG. 2A, for example, a material 250 containing a carbonaceous material can be selectively deposited over the reacted polymer film 150 while dry etching the metal-free polymer film 130 using an etching gas containing carbon. The inventors of the present application have identified that such ASD can be enabled by controlling the C / O and / or H / C ratio of the etching gas. In one embodiment, the material 250 containing carbon can be selectively deposited over a carbon-rich polymer (e.g., polystyrene-based) while etching a carbon-deficient polymer (e.g., polymethyl methacrylate-based). Such ASD is enabled and can be enhanced by reducing the H / C ratio of the etching gas. As shown in FIG. 2B, after the selective removal of the metal-free polymer film 130 is completed, the reacted polymer film 150 is reinforced by the addition of the material 250. The material 250 on the polymer film 150 can function as an additional layer of the etching mask during subsequent pattern transfer etching.

[0034] In an alternative embodiment, the area selective deposition (ASD) of the material 250 can be achieved stepwise by performing a deposition process separated from the selective etching shown in FIG. 1D. In other words, the dry developing process can include a series of process steps. For example, after EUV exposure (e.g., FIG. 1C), a deposition gas can be introduced into the processing chamber to selectively deposit the material 250 over the reacted polymer film 150 without substantially affecting the metal-free polymer film 130. When a sufficient amount of the material 250 is deposited, an etching gas can be introduced into the processing chamber to selectively etch the metal-free polymer film 130. In certain embodiments, the deposition gas and the etching gas are similar gas mixtures (e.g., H 2and CO), and the switching from the ASD to the selective etching can be achieved by changing the mixing ratio of the gas mixture or other process conditions such as bias power, temperature, and pressure.

[0035] FIG. 3 shows a cross-sectional view of another exemplary substrate 100 after a conventional wet development process with pattern collapse problems.

[0036] Compared with the dry development process described above, the wet development process is a solution-based process that uses a developer to selectively dissolve either the reacted or unreacted regions of the photoresist. Although wet development is mainly used in the industry, as the pitch of the features patterned by lithography becomes smaller and the aspect ratio becomes higher, problems such as pattern collapse as shown in FIG. 3 occur. Pattern collapse can be caused by the surface tension of the developer and / or peeling during the wet development process. In general, EUV lithography can be used to form small features that are not easily achievable with other lithography techniques such as 193nm immersion lithography. For example, the minimum pitch of a resist line and space pattern formed using 193nm immersion lithography is about 75nm, while the shorter 13.5nm EUV lithography enables the minimum pitch to be reduced to about 20nm to about 40nm.

[0037] The dry development of the metal-free polymer film 130 enabled in various embodiments can advantageously overcome the problem of pattern collapse at such scales of features patterned by EUV lithography. The dry development process can be achieved by selectively dry etching a portion of the metal-free polymer film 130 using an etching gas in a processing chamber to form features including the remaining portions of the metal-free polymer film 130. In certain embodiments, the pitch of the features after dry development is close to or less than the feature size achievable with a 193nm immersion lithography tool in a single patterning process. For example, using an EUV lithography tool with 13.5nm EUV at a numerical aperture (NA) of 0.33, the resolution limit can be as small as 22.5nm corresponding to a k 1 factor of 0.5. The resolution limit can be, in various embodiments, half the pitch size of the features. Further, the dry development method of the present disclosure can be particularly advantageous in high-NA (e.g., 0.5) systems that improve the resolution limit. In one or more embodiments, the pitch of the features achievable without pattern collapse can be from 10nm to 80nm. Avoiding solution-based processes also has the advantage of improving process efficiency by reducing chemical waste and enabling development to be performed in the same processing chamber as subsequent pattern transfer etching.

[0038] FIG. 1E shows a cross-sectional view of the substrate 100 after the first pattern transfer etching.

[0039] FIG. 1F shows a cross-sectional view of the substrate 100 after the second pattern transfer etching.

[0040] Referring back to FIGS. 1E and 1F, after the dry development process (e.g., FIGS. 1D or 2B), subsequent processes of EUV patterning can be performed. In various embodiments, the subsequent processes are part of the manufacturing process of semiconductor devices such as the front end of line (FEOL). In certain embodiments, this stage of manufacturing may require strict elimination of metal contamination. Since conventionally known dry development techniques are designed for photoresists based on metal oxides and may be difficult to implement in such a manufacturing process with strict limitations, it may be advantageous to apply a method for dry development of a metal-free polymer film.

[0041] In FIG. 1E, the pattern of the reacted polymer film 150 can be first transferred to the hard mask (HM) layer 120, for example, by selective etching using reactive ion etching (RIE). During this first pattern transfer etching, the reacted polymer film 150 functions as an etching mask. After the first pattern transfer etching, the reacted polymer film 150 can be partially or completely consumed. Similarly, in certain embodiments, a second pattern transfer etching can follow, and the pattern of the HM layer 120 is further transferred to the underlying layer 110, for example, using reactive ion etching (RIE). In various embodiments, the dry development process, the first pattern transfer etching, and the second pattern transfer etching can advantageously be performed in the same processing chamber. Area selective deposition (ASD) for enhancing the selectivity of dry etching can be incorporated into any of these three processes and / or inserted separately therebetween.

[0042] Figures 4A - 4E show schematic views of an alternative exemplary substrate 100 at various stages in an exemplary process of manufacture including a dry development process of a metal - free polymer film 430 as a positive photoresist, according to other embodiments. The details of the structure of the substrate 100 and the process of manufacture including optional processes such as area - selective deposition (ASD), soft - bake, and post - exposure bake (PEB) are the same as the previous embodiments (negative photoresist embodiments) illustrated in FIGS. 1A - 1F, except for the conditioning of the metal - free polymer film 430, and thus will not be repeated.

[0043] Figure 4A shows a cross - sectional view of the substrate 100 after depositing a metal - free polymer film 430.

[0044] Figure 4B is a cross - sectional view of the substrate 100 after performing extreme ultraviolet (EUV) exposure through a photomask 145.

[0045] In FIG. 4A, the metal - free polymer film 430 can be deposited, for example, by spin - coating technology. In FIG. 4B, an EUV lithography process is performed by exposing the substrate 100 to EUV irradiation 140 through the photomask 145. In the shown example of the positive photoresist, in response to EUV exposure, the exposed region of the metal - free polymer film 430 is directly or indirectly converted into a reacted polymer film 450. In various embodiments, the structural change from the metal - free polymer film 130 to the reacted polymer film 450 can include, for example, addition of oxygen (oxidation), ring - opening, or chain - scission.

[0046] Figure 4C shows a cross - sectional view of the substrate 100 after dry - developing the metal - free polymer film 430 to remove the masked regions of the metal - free polymer film 430.

[0047] In certain embodiments, the dry development process can be reactive ion etching (RIE) or atomic layer etching (ALE). The etching gas composition and process conditions of the dry development process can be selected, for example, to maximize the dry etching selectivity for the reacted polymer film 450 in the shown example of a positive photoresist. As a result, in FIG. 4C, the unreacted regions of the metal-free polymer film 430 remain after the dry development process, and the reacted polymer film 450 is removed. In one embodiment, the etching rate of the reacted polymer film 450 is at least two times lower than the etching rate of the masked (unreacted) regions of the metal-free polymer film 430.

[0048] FIG. 4D shows a cross-sectional view of the substrate 100 after the first pattern transfer etching.

[0049] FIG. 4E shows a cross-sectional view of the substrate 100 after the second pattern transfer etching.

[0050] In FIG. 4D, the pattern of the unreacted metal-free polymer film 430 can first be transferred to the hard mask (HM) layer 120 by selective etching, for example, using reactive ion etching (RIE). Similarly, in certain embodiments, a second pattern transfer etching can follow, and the pattern of the HM layer 120 is further transferred to the underlying layer 110, for example, using reactive ion etching (RIE).

[0051] FIG. 5 shows a schematic diagram of the relationship between the Ohnishi parameter (OP) of a polymer and its dry etching rate.

[0052] The effectiveness of a metal-free polymer film as a photoresist mainly depends on the change in dry etching rate caused by lithographic exposure. Therefore, when designing a metal-free polymer film, it is useful to know how the photoinduced structural change of the polymer can correlate with the dry etching rate. The Ohnishi parameter (OP) or Ohnishi number is a useful parameter in this regard. The OP of a polymer is defined as the number of atoms in the polymer repeating unit (i.e., monomer unit) divided by the number obtained by subtracting the number of oxygen atoms from the number of carbon atoms. Therefore, the higher the carbon content of the polymer, the lower the corresponding OP. Polymers with high aromaticity and a ring structure also have a smaller OP than aromatic polymers with low aromaticity and no ring structure. As shown in Figure 5, it is empirically known that the etching rate of a polymer by reactive ion etching (RIE) is linearly proportional to the OP of the polymer. By calculating the OP of different polymer compositions, the dry etching rate can be generally predicted from the chemical structure of the polymer repeating unit. For example, in Figure 5, two polymer compositions A (with a high carbon content) and B (with a low carbon content) can be considered. Since composition A has a lower OP than composition B, it should exhibit a slower dry etching rate. If this difference can be utilized to induce a structural change from composition A to composition B or vice versa by lithographic exposure, the modulation of the polymer as a photoresist can be achieved. Therefore, the metal-free polymer films in various embodiments can include polymers whose OP can change in response to EUV exposure. In certain embodiments, the change in OP of the metal-free polymer film caused by EUV exposure can be at least twofold. Although OP is derived from the chemical structure of the polymer repeating unit, this does not limit the polymer of the metal-free polymer film to having only one type of monomer. In various embodiments, the polymer of the metal-free polymer film can be formed from multiple types of monomers (e.g., copolymers from two types of monomers and terpolymers from three types of monomers). In certain embodiments, the average OP of such a polymer system can be assumed, and a similar design approach can be applied.

[0053] In various embodiments, the metal-free polymer film may contain oxygen, and a portion of the oxygen in the metal-free polymer film may be removed in response to EUV exposure. As a result, the OP of the reacted polymer film decreases from the initial OP. Thereby, the metal-free polymer film becomes a negative photoresist. In certain embodiments, when the metal-free polymer film contains carboxyl groups, the removal of oxygen can be achieved by decarboxylation. In one embodiment, each of the polymer repeating units may contain a carboxyl group. In other embodiments, the metal-free polymer film may contain carbohydrates, and oxygen removal may proceed by deoxygenation. On the other hand, for example, when oxygen atoms are added to the metal-free polymer film by oxidation, the OP increases, enabling a positive photoresist.

[0054] In further embodiments, the metal-free polymer film can be cyclized in response to EVU exposure, for example, via a Diels-Alder reaction to form a ring structure. Cyclization can also lower the OP, which is advantageous for negative tone. Conversely, ring opening of the metal-free polymer film containing a ring structure can enable a positive photoresist by increasing the OP.

[0055] FIG. 6 shows an exemplary mechanism of decarboxylation that can lower the Ohnishi parameter (OP) of a metal-free polymer film containing carboxyl groups in response to UV exposure.

[0056] In FIG. 6, only the polymer repeating units of the metal-free polymer film are shown for illustrative purposes. In various embodiments, a catalyst for this reaction may or may not be required for the decarboxylation of the metal-free polymer film. In this shown example of decarboxylation catalyzed by a photooxidant, the carboxyl group of the polymer repeating unit forms a carboxylate anion (ROO - ) under basic conditions, and this can donate an electron to a photooxidant (e.g., phenanthrenium cation) excited by the catalyst and UV irradiation to form a reactive carboxyl radical (RCOO·). This radical then dissociates to form CO 2Release to form R·. In other embodiments, decarboxylation may proceed by a different mechanism.

[0057] In further embodiments, chemical reactions that do not necessarily involve a change in the Ohnishi parameter (OP) (i.e., do not change the polymer repeating unit) can also be utilized to condition the metal-free polymer film as a photoresist. Examples of such reactions include crosslinking and chain scission. In various embodiments, it may be advantageous for the change in OP to involve other mechanisms such as crosslinking / chain scission, which can further enhance the conditioning of the metal-free polymer film. The formation or removal of cage functional groups can also be utilized. Such mechanisms may further include reacting functional groups containing silicon, phosphorus, fluorine, or sulfur, which can result in high dry etching resistance. In one embodiment, the sulfur functional group is SO 2 Can be removed by releasing. In addition, the formation of micro / mesopores and / or the increase in free volume in the metal-free polymer film as a result of the photoreaction can also be another factor that affects the overall etch rate through a change in the etch rate.

[0058] Furthermore, a change in the glass transition temperature (T g ) can also be utilized to affect the dry etching selectivity. Without being bound by any theory, generally, the dry etching rate of a polymer can increase with an increase in the process temperature, and the effect of the process temperature on the etching rate can become significant near or above the T g of the polymer material. Therefore, any reaction that has the potential to lower the T g of the metal-free polymer film can increase its etching rate. On the other hand, increasing the T g of the metal-free polymer film may result in a decrease in the etching rate. One example of a reaction that lowers T g is, for example, the formation of carboxylic acid performed as a deprotection step. On the other hand, decarboxylation is an example of a reaction that raises T g .

[0059] FIG. 7 shows a schematic diagram of a metal-free polymer film that undergoes a structural change by crosslinking in response to EUV exposure.

[0060] In FIG. 7, the polymer chains containing the metal-free polymer film are crosslinked by bond formation induced by EUV exposure. In certain embodiments, the crosslinking may include, in particular, C-C bond formation or S-S bond formation. Such bond formation may be catalyzed by the photoacid generated by EUV exposure. In one embodiment, the metal-free polymer film may include hydroxystyrene that can be crosslinked by EUV exposure. Although the Ohnishi parameter (OP) does not substantially change due to crosslinking, the crosslinked polymer exhibits improved dry etching resistance and may provide the advantage of negative tone modulation.

[0061] FIG. 8 shows a schematic diagram of a metal-free polymer film that undergoes a structural change by chain scission in response to EUV exposure.

[0062] In FIG. 8, the polymer chains containing the metal-free polymer film are fragmented by chain scission induced by EUV exposure. In certain embodiments, the metal-free polymer film may include a polymer from one type of monomer (upper part of FIG. 8), while in other embodiments, it may include a copolymer from two types of monomers (lower part of FIG. 8). Such chain scission may be catalyzed by the photoacid generated by EUV exposure. Similar to crosslinking, chain scission may not substantially change the Ohnishi parameter (OP). However, the decrease in the degree of polymerization may reduce the dry etching resistance and may provide benefits for positive tone modulation. Exemplary structures that undergo chain scission by EUV exposure can include methacrylates (e.g., polymethyl methacrylate, PMMA).

[0063] FIGS. 9A - 9C show an exemplary process flow diagram of a manufacturing process including dry development of a metal-free polymer film. Since the process flow can follow the figures described above (FIGS. 1A - 1F and FIGS. 4A - 4E), it will not be described again.

[0064] In FIG. 9A, process flow 90 begins with providing a substrate including an underlying layer (block 900, FIG. 1A), followed by depositing a metal-free polymer film over the underlying layer (block 910, FIG. 1B or FIG. 4A). In certain embodiments, an optional soft bake can be performed prior to lithographic exposure (block 915). Next, the metal-free polymer film can be exposed to extreme ultraviolet (EUV) radiation through a photomask (block 920, FIG. 1C or FIG. 4B). The exposed regions of the metal-free polymer film photoreact in response to the EUV radiation. The substrate can then be loaded into a processing chamber (block 930). In certain embodiments, an optional post-exposure bake (PEB) can be performed (block 935). Next, an etching gas can be used in the processing chamber to selectively etch a portion of the metal-free polymer film (block 940). This process of selective etching is part of the dry development of the metal-free polymer film, and the portion of the metal-free polymer film that is etched can be the mask region (FIG. 1D) or the exposed region (FIG. 4C), depending on the tonality of the metal-free polymer film. After dry development, the underlying layer disposed under the metal-free polymer film can be patterned using the remaining portion of the metal-free polymer film as an etch mask (block 950, FIGS. 1E-1F or FIGS. 4D-4E). In certain embodiments, the process of selective etching can further include area selective deposition (ASD) to enhance the selectivity of the dry etching.

[0065] FIG. 9B shows an example of a negative photoresist, and process flow 92 begins by depositing a metal-free polymer film containing carboxyl groups over the underlying layer of the substrate by a spin-on process (block 912, FIG. 1B). In certain embodiments, an optional soft base can be functionalized prior to lithographic exposure (block 915). Next, by exposing the substrate through a photomask to EUV irradiation, a portion of the metal-free polymer film can be decarboxylated (block 922, FIG. 1C). The substrate can then be loaded into a processing chamber (block 930). In certain embodiments, an optional post-exposure bake (PEB) can be performed (block 935). Next, the mask region of the metal-free polymer film can be selectively removed by the plasma generated in the processing chamber (block 942, FIG. 1D). After this dry development, the underlying layer disposed under the metal-free polymer film can be patterned using the remaining portion of the metal-free polymer film (the reacted decarboxylated region) as an etch mask (block 952, FIGS. 1E - 1F).

[0066] In FIG. 9C, an example of a positive photoresist is shown, and process flow 94 begins by depositing a metal-free polymer film over the underlying layer of the substrate by a spin-on process (block 912, FIG. 4A). In certain embodiments, an optional soft base can be activated prior to lithographic exposure (block 915). Next, by exposing the substrate to EUV irradiation through a photomask, a portion of the metal-free polymer film can be oxidized (block 924, FIG. 4B). The substrate can then be loaded into a processing chamber (block 930). In certain embodiments, an optional post-exposure bake (PEB) can be performed (block 935). Next, the exposed and oxidized regions of the metal-free polymer film can be selectively removed by a plasma generated in the processing chamber (block 944, FIG. 4C). After this dry development, the remaining portion of the metal-free polymer film (the masked unreacted regions) can be used as an etch mask to pattern the underlying layer disposed under the metal-free polymer film (block 954, FIGS. 4D - 4E).

[0067] FIG. 10 shows an exemplary plasma processing tool for dry development according to an embodiment of the present disclosure.

[0068] In FIG. 10, plasma processing system 1000 includes a plasma processing chamber 1050 configured to maintain a plasma directly over substrate 1002 loaded in substrate holder 1010, enabling selective plasma etching for the dry development of a metal-free polymer film. Process gas can be introduced into plasma processing chamber 1050 through gas inlet 1022 and pumped out of plasma processing chamber 1050 through gas outlet 1024. As the process gas, a gas mixture (e.g., CO and H 2) is used to enable dynamic control of the gas mixture composition during dry development. To this end, the gas inlet 1022 and the gas outlet 1024 may each include a plurality of series-connected gas inlets and gas outlets. The gas flow rate and the chamber pressure can be controlled by a gas flow control system 1020 coupled to the gas inlet 1022 and the gas outlet 1024. The gas flow control system 1020 may include various components such as a high-pressure gas cylinder, valves (e.g., throttle valves), pressure sensors, gas flow sensors, vacuum pumps, pipes, and electronically programmable controllers. The RF bias power supply 1034 and the RF source power supply 1030 may be coupled to respective electrodes of the plasma processing chamber 1050. The substrate holder 1010 may also be an electrode coupled to the RF bias power supply 1034. The RF source power supply 1030 is shown coupled to a helical electrode 1032 wound around the dielectric sidewall 1016. In FIG. 10, the gas inlet 1022 is an opening in the upper plate 1012, and the gas outlet 1024 is an opening in the bottom plate 1014. The upper plate 1012 and the bottom plate 1014 may be conductive and may be electrically connected to a system ground (reference potential).

[0069] By selectively etching a portion of the metal-free polymer film, dry development generates gaseous products within the plasma processing chamber 1050. In certain embodiments, these gaseous products can be analyzed using a gas analyzer 1040. The gas analyzer 1040 can identify and quantify the gas species generated during dry development and then pump them out of the plasma processing chamber 1050 via the gas outlet 1024. Based on the data obtained by the gas analyzer 1040, process conditions such as the gas flow rate, the process temperature, and the RF power of the plasma can be adjusted to optimize the selectivity of the dry etching.

[0070] The configuration of the plasma processing system 1000 described above is merely exemplary. In alternative embodiments, various alternative configurations of the plasma processing system 1000 can be used. For example, inductively coupled plasma (ICP) can be used with capacitively coupled plasma (CCP) generated using RF source power coupled to a planar coil on an upper dielectric cover or a disk-shaped upper electrode within the plasma processing chamber 1050, and the gas inlet and / or gas outlet can be coupled to the sidewall, etc. In some embodiments, pulsed RF power sources and pulsed DC power sources (as opposed to continuous wave RF power sources) can also be used. Additionally, microwave plasma (MW) or other suitable systems can be used. In various embodiments, RF power, chamber pressure, substrate temperature, gas flow rate, and other plasma processing parameters can be selected according to their respective processing recipes. In some embodiments, the plasma processing system 1000 can be a resonator such as a helical resonator.

[0071] In addition, embodiments of the present invention can also be applied to remote plasma systems, similar to batch systems. For example, the substrate holder can be capable of supporting multiple wafers that are rotated around a central axis as they pass through different plasma zones.

[0072] Here, exemplary embodiments are summarized. Other embodiments can also be understood from the entire specification and the claims filed herein.

[0073] Example 1. A method of patterning an underlying layer, comprising: providing a substrate including the underlying layer; depositing a metal-free polymer film over the underlying layer; exposing the metal-free polymer film to extreme ultraviolet (EUV) radiation through a photomask to form an exposed region and a masked region of the metal-free polymer film, wherein the exposed region is photoreactive in response to EUV radiation; loading the substrate into a processing chamber; selectively dry etching a first portion of the metal-free polymer film using an etching gas in the processing chamber to form a plurality of features including a remaining second portion of the metal-free polymer film, wherein an etching rate of the first portion is greater than an etching rate of the second portion of the metal-free polymer film, the first portion is one of the exposed region and the masked region, the second portion is the other of the exposed region and the masked region that is not the first portion, and a pitch of the plurality of features is less than a feature size achievable with a 193 nm immersion lithography tool in a single patterning process; and using the second portion as an etching mask to pattern the underlying layer disposed under the metal-free polymer film.

[0074] Example 2. The method of Example 1, wherein the etching of the metal-free polymer film is performed using a plasma from the etching gas.

[0075] Example 3. The method according to any one of Examples 1 or 2, wherein the etching gas contains H2 and CO.

[0076] Example 4. The method according to any one of Examples 1 to 3, wherein the composition of the etching gas is changed while etching the metal-free polymer film.

[0077] Example 5. The method according to any one of Examples 1 to 4, wherein a material is selectively deposited from the etching gas over the second portion while etching the metal-free polymer film.

[0078] Example 6. The method according to any one of Examples 1 to 5, wherein the first part is a mask region and the second part is an exposure region.

[0079] Example 7. The method according to any one of Examples 1 to 6, wherein the photoreaction of the metal-free polymer film in response to EUV irradiation includes reducing the Ohnishi parameter of the metal-free polymer film to 1 / 2 or less.

[0080] Example 8. The metal-free polymer film contains a carboxyl group, and the photoreaction of the metal-free polymer film in response to EUV irradiation includes decarboxylating the exposed metal-free polymer film. The method according to any one of Examples 1 to 7.

[0081] Example 9. The method according to any one of Examples 1 to 8, wherein the photoreaction of the metal-free polymer film in response to UV irradiation includes cyclizing the exposed metal-free polymer film.

[0082] Example 10. The method according to any one of Examples 1 to 5, wherein the first part is an exposure region and the second part is a mask region.

[0083] Example 11. The method according to Example 10, wherein the photoreaction of the metal-free polymer film in response to EUV irradiation includes increasing the Ohnishi parameter of the metal-free polymer film by at least 2 times.

[0084] Example 12. The method according to any one of Examples 10 to 11, wherein the photoreaction of the metal-free polymer film in response to UV irradiation includes adding oxygen atoms to the metal-free polymer film.

[0085] Example 13. The method according to any one of Examples 10 to 12, wherein the photoreaction of the metal-free polymer film in response to UV irradiation includes opening the ring structure of the metal-free polymer film.

[0086] Example 14. The method according to any one of Examples 1 to 13, wherein the patterning is performed in a processing chamber.

[0087] Example 15. The deposition is carried out by a spin-on process and is any one of the methods of Examples 1 to 14.

[0088] Example 16. A method of patterning an underlying layer, comprising depositing a metal-free polymer film across a substrate by a spin-on process, the metal-free polymer film containing carboxyl groups, the substrate containing the underlying layer; exposing the substrate to extreme ultraviolet (EUV) radiation through a photomask to decarboxylate a part of the metal-free polymer film, wherein the part of the metal-free polymer film is the region exposed to the EUV radiation, and the decarboxylation includes a photoreaction in response to the EUV radiation; loading the substrate into a processing chamber; exposing the substrate to a plasma to selectively remove the region masked by the photomask and not exposed to the EUV radiation, wherein the plasma is generated in the processing chamber and the etching rate of the masked region is at least twice greater than the etching rate of the exposed region; and using the exposed region as an etching mask to pattern the underlying layer disposed under the metal-free polymer film.

[0089] Example 17. The method of Example 16, further comprising cyclizing a part of the metal-free polymer film, wherein the cyclization includes a photoreaction in response to the EUV radiation.

[0090] Example 18. The photoreaction of the metal-free polymer film in response to the EUV radiation raises the glass transition temperature of the metal-free polymer film, and is any one of the methods of Example 16 or 17.

[0091] Example 19. A method of patterning an underlying layer, comprising depositing a metal-free polymer film over a substrate including the underlying layer by a spin-on process; oxidizing a portion of the metal-free polymer film by exposing the substrate to extreme ultraviolet (EUV) radiation through a photomask, the oxidizing including a photoreaction responsive to the EUV radiation; loading the substrate into a processing chamber; exposing the substrate to a plasma to selectively remove the exposed regions, the plasma being generated in the processing chamber and the etch rate of the exposed regions being at least two times greater than the etch rate of regions masked by the photomask and not exposed to the EUV radiation; and using the masked regions as an etch mask to pattern the underlying layer disposed under the metal-free polymer film.

[0092] Example 20. The method of Example 19, further comprising opening a ring structure of a portion of the metal-free polymer film, the opening of the ring including a photoreaction responsive to the EUV radiation.

[0093] Example 21. The method according to any one of Examples 1 to 15, wherein the metal-free polymer film comprises silane.

[0094] Example 22. The method according to any one of Examples 1 to 15 and 21, wherein the metal-free polymer film comprises phosphorus.

[0095] Example 23. The photoreaction of the metal-free polymer film responsive to the EUV radiation generates an acid, and the acid can induce further reactions of the metal-free polymer film. The method according to any one of Examples 1 to 15 and 21 to 22.

[0096] Example 24. The photoreaction of the metal-free polymer film changes the free volume of the polymer. The method according to any one of Examples 1 to 15 and 21 to 23.

[0097] Example 25. The method according to any one of Examples 1 to 15 and 21 to 24, wherein the metal-free polymer film comprises poly(methyl methacrylate) (PMMA).

[0098] Example 26. A metal-free polymer film is prepared by any one of the methods of Examples 1 to 15 and 21 to 25, which contains a polysaccharide.

[0099] Example 27. A method according to any one of Examples 1 to 15 and 21 to 26, further comprising performing a chemical modification to introduce carboxyl groups into the metal-free polymer film before exposing the metal-free polymer film to EUV irradiation.

[0100] Although the invention has been described with reference to exemplary embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the exemplary embodiments, as well as other embodiments of the invention, should be apparent to those skilled in the art upon reading the above description. Accordingly, the appended claims are intended to embrace any such modifications or embodiments.

Claims

Claim 1 A method of patterning an underlying layer, comprising: providing a substrate including the underlying layer; depositing a metal-free polymer film over the underlying layer; exposing the metal-free polymer film to extreme ultraviolet (EUV) radiation through a photomask to form an exposed region and a masked region of the metal-free polymer film, wherein the exposed region is photoreactive in response to the EUV radiation; loading the substrate into a processing chamber; selectively dry etching a first portion of the metal-free polymer film using an etching gas in the processing chamber to form a plurality of features including a remaining second portion of the metal-free polymer film, wherein an etching rate of the first portion of the metal-free polymer film is greater than an etching rate of the second portion, the first portion is one of the exposed region and the masked region, the second portion is the other of the exposed region and the masked region that is not the first portion, and a pitch of the plurality of features is smaller than a feature size achievable by a 193 nm immersion lithography tool in a single patterning process; using the second portion as an etching mask to pattern the underlying layer disposed under the metal-free polymer film; A method having the above steps. Claim 2 The method according to claim 1, wherein the step of etching the metal-free polymer film is performed using plasma from the etching gas. Claim 3 The etching gas contains H ２ and CO, and the method according to claim 1. Claim 4 The method according to claim 1, wherein a composition of the etching gas changes while the metal-free polymer film is being etched. Claim 5 The method according to claim 1, wherein the photoreaction of the metal-free polymer film in response to the EUV radiation generates an acid that can induce another reaction of the metal-free polymer film. Claim 6 The method according to claim 1, wherein the first portion is the masked region and the second portion is the exposed region. Claim 7 The step in which the metal-free polymer film undergoes a photoreaction in response to the EUV irradiation includes the step of reducing the Ohnishi parameter of the metal-free polymer film by at least a factor of 2, the method according to claim 6.

8. The metal-free polymer film contains carboxyl groups, The step in which the metal-free polymer film undergoes a photoreaction in response to the EUV irradiation includes the step of decarboxylating the exposed metal-free polymer film, the method according to claim 6.

9. The step in which the metal-free polymer film undergoes a photoreaction in response to the UV irradiation includes the step of cyclizing the exposed metal-free polymer film, the method according to claim 6.

10. The first portion is the exposed area, and the second portion is the mask area, the method according to claim 1.

11. The step in which the metal-free polymer film undergoes a photoreaction in response to the EUV irradiation includes the step of increasing the Ohnishi parameter of the metal-free polymer film by at least a factor of 2, the method according to claim 10.

12. The step in which the metal-free polymer film undergoes a photoreaction in response to the UV irradiation includes the step of adding oxygen atoms to the metal-free polymer film, the method according to claim 10.

13. The step in which the metal-free polymer film undergoes a photoreaction in response to the UV irradiation includes the step of opening the ring structure of the metal-free polymer film, the method according to claim 10.

14. The step of patterning is performed within the processing chamber, the method according to claim 1.

15. The step of depositing is performed by a spin-on process, the method according to claim 1.

16. A method for patterning an underlayer, A step of depositing a metal-free polymer film over a substrate by a spin-on process, wherein the metal-free polymer film contains carboxyl groups and the substrate includes the underlayer, A step of exposing the substrate to extreme ultraviolet (EUV) irradiation through a photomask to decarboxylate a portion of the metal-free polymer film, wherein the portion of the metal-free polymer film is the area exposed to the EUV irradiation, and the step of decarboxylating includes a photoreaction in response to the EUV irradiation, Loading the substrate into a processing chamber; Exposing the substrate to a plasma to selectively remove areas masked by the photomask and not exposed to EUV irradiation, wherein the plasma is generated within the processing chamber and the etching rate of the masked area is at least twice greater than the etching rate of the exposed area; Using the exposed area as an etching mask to pattern the underlying layer disposed beneath the metal-free polymer film; A method comprising the steps of. **Claim 17** Further comprising the step of cyclizing a portion of the metal-free polymer film; The method according to claim 16, wherein the cyclizing step comprises a photoreaction in response to the EUV irradiation. **Claim 18** The method according to claim 16, wherein the photoreaction in response to the EUV irradiation generates a photooxidizing agent that catalyzes the decarboxylation of the portion of the metal-free polymer film. **Claim 19** A method of patterning an underlying layer, comprising: Depositing a metal-free polymer film over a substrate including the underlying layer by a spin-on process; Oxidizing a portion of the metal-free polymer film by exposing the substrate to extreme ultraviolet (EUV) irradiation through a photomask, the oxidizing step including a photoreaction in response to the EUV irradiation; Loading the substrate into a processing chamber; Exposing the substrate to a plasma to selectively remove the exposed area, wherein the plasma is generated within the processing chamber and the etching rate of the exposed area is at least twice greater than the etching rate of the area masked by the photomask and not exposed to the EUV irradiation; Using the masked area as an etching mask to pattern the underlying layer disposed beneath the metal-free polymer film; A method comprising the steps of. **Claim 20** Further comprising the step of opening the ring structure of a portion of the metal-free polymer film; The method according to claim 19, wherein the step of opening the ring comprises a photoreaction in response to the EUV irradiation.

Images