EUV photoresist and underlayer adhesion modulation

Abstract

The embodiments disclosed herein include a method for developing a patterned stack. In one embodiment, the method includes providing a patterned stack, wherein the patterned stack includes a substrate and a photoresist on the substrate, and wherein the substrate and the photoresist have a first adhesion strength. The method may further include exposing and developing the photoresist using electromagnetic radiation and a developer, wherein scum remains on the surface of the substrate. In one embodiment, the method further includes treating the substrate such that the substrate and the scum have a second adhesion strength, and removing the scum.

Description

EUV photoresist and bottom layer adhesion adjustment This application claims the benefit of U.S. Provisional Application No. 63 / 430,596, filed December 6, 2022, the entire contents of which are incorporated herein by reference. Embodiments of the present disclosure relate to the field of semiconductor processing, and more particularly, to methods of forming a photoresist having an underlayer for adhesion regulation. Lithography has been used in the semiconductor industry for decades to create 2D and 3D patterns in microelectronic components. The lithography process involves spin-coating the deposition of a base layer and a film (photoresist) overlying the base layer. These spin-coated films may include chemical additives (e.g., boosters) to reduce the amount of the film. The process continues by irradiating the film with an energy source in a selected pattern (exposing) and removing (etching) the exposed (positive-tone) or non-exposed (negative-tone) areas of the film by dissolving in a solvent. A bake is performed to drive off any remaining solvent. Spin-coating base layer solutions have some drawbacks, particularly for extreme ultraviolet (EUV) lithography operations with smaller pitch features. These drawbacks may include, for example, compound uniformity and poor adhesion to the photoresist. Photoresist is a radiation-sensitive material. When irradiated, the exposed portions of the film undergo a chemical transformation, resulting in a solubility change between the exposed and unexposed areas. This solubility change is exploited to remove (etch) the exposed or unexposed areas of the photoresist. The photoresist is then developed, and the pattern can be transferred to the underlying film or substrate by etching. After the pattern is transferred, the remaining photoresist is removed, and this process is repeated multiple times to create 2D and 3D structures for microelectronics. Several properties are important in lithography processes. These include sensitivity, resolution, low line-edge roughness (LER), line-width roughness (LWR), etch resistance, and the ability to form thinner layers. When sensitivity is high, less energy is required to change the solubility of the freshly deposited film. This results in greater efficiency in the lithography process. Resolution and LER determine the extent to which narrow features can be achieved in the lithography process. Pattern transfer requires higher etch-resist materials to form deep structures. Higher etch-resist materials also enable thinner films. Thinner films increase the efficiency of the lithography process. LER and LWR are stochastic effects in the lithography process. They can be at least partially related to UV-material interactions (such as UV absorption, secondary electron generation, and back exposure from the underlying layer) and / or photoresist-underlying layer interactions (such as adhesion). Embodiments disclosed herein include methods for developing a patterned stack. In one embodiment, the method includes providing a patterned stack, wherein the patterned stack includes a bottom layer and a photoresist on the bottom layer, and wherein the bottom layer and the photoresist have a first adhesion strength. The method may also include exposing and developing the photoresist using electromagnetic radiation and a developer, wherein scum remains on a surface of the bottom layer. In one embodiment, the method further includes treating the bottom layer such that the bottom layer and the scum have a second adhesion strength, and removing the scum. Embodiments disclosed herein may also include a method of patterning a substrate, comprising providing a patterned stack on the substrate. In one embodiment, the patterned stack comprises a first bottom layer, a second bottom layer on the first bottom layer, and a photoresist on the second bottom layer. In one embodiment, the method further comprises exposing the patterned stack to electromagnetic radiation and developing the photoresist in the patterned stack. In one embodiment, the method further comprises modifying the second bottom layer to reduce adhesion to the photoresist and removing any scum on the second bottom layer. Embodiments disclosed herein may include a patterned stack. In one embodiment, the patterned stack includes a first bottom layer and a second bottom layer on the first bottom layer, wherein the second bottom layer has a thickness of up to about 5 nm and wherein the second bottom layer has a hydrophobic surface. In one embodiment, the patterned stack may further include a photoresist on the second bottom layer, wherein the photoresist has a hydrophobic surface. This document describes a method for forming a photoresist having a bottom layer for adhesion regulation. In the following description, many specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure, such as the thermal vapor phase process and material schemes for developing the photoresist. It will be apparent to those skilled in the art that the embodiments of the present disclosure can be implemented without these specific details. In other cases, in order not to unnecessarily obscure the embodiments of the present disclosure, conventional aspects, such as integrated circuit manufacturing, are not described in detail. In addition, it should be understood that the various embodiments shown in the drawings are illustrative representations and are not necessarily drawn to scale. To provide context, photoresist systems used in extreme ultraviolet (EUV) lithography suffer from inefficiencies. That is, existing photoresist material systems used in EUV lithography require high doses to provide the solubility switch necessary to develop the photoresist material. One type of resist system used in EUV lithography is the chemically amplified resist (CAR) system. One drawback of CAR systems is the limited CAR-underlayer interface strength (adhesion). Specifically, the bond between the two layers is achieved via van der Waals forces. In many cases, high adhesion between the photoresist and the underlayer is a desirable property. Strong adhesion allows for the formation of high-aspect-ratio features without the risk of pattern collapse, pattern lift-off, or other pattern defects. High adhesion can be achieved by tuning the underlayer to form a strong bond with the overlying photoresist. CAR photoresists are typically hydrophobic materials. Therefore, the underlayer is also formed to be hydrophobic to improve the bond between the two layers. However, strong adhesion can have negative drawbacks. For example, when the adhesion between layers is very strong, it can be difficult to completely remove the exposed photoresist with a developer solution. This unwanted residual photoresist material is sometimes referred to as scum. The presence of scum on the bottom layer can lead to patterning defects that are ultimately transferred to the bottom layer and substrate. Consequently, high-quality pattern transfer is impossible. Thus, embodiments disclosed herein include a modifiable bottom layer. As used herein, a modifiable layer can be a layer whose chemical composition can be changed or the chemical nature of the dangling bonds can be changed. For example, a treatment disclosed herein can convert a hydrophobic material into a hydrophilic material. When the bottom layer is hydrophilic, the bond strength between the bottom layer and the overlying hydrophobic photoresist is reduced. This makes the scum easier to remove. In one embodiment, the treatment can include exposing the bottom layer to an alkaline solution. An alkaline solution (e.g., approximately 3% tetramethylammonium hydroxide (TMAH) and 97% water) is used during the lithography development process. Since the alkaline solution already has water, the bottom layer does not need to undergo additional treatment to react with the water to form OH bonds. Thus, the method described herein can be easily added to an existing lithography process. It is understood that a balance needs to be struck between high adhesion strength for patterning and low adhesion strength for scum development and removal. Therefore, some embodiments described herein include a dual-layer bottom layer structure. The first bottom layer on the substrate may include a material combination that is highly responsive to processing, and the second bottom layer on the first bottom layer may be tuned for adhesion. More specifically, the second bottom layer may be thin (e.g., approximately 5 nm or less) and porous. This allows chemical changes in the first bottom layer to propagate through the second bottom layer, thereby modifying the interface between the second bottom layer and the photoresist. In other embodiments, a single bottom layer is used. The bottom layer may comprise a doped amorphous SiC:H material. For example, the dopant may comprise Si, Ge, B, or P. In one particular embodiment, the boron dopant may have a B co-flown with the SiC:H precursor (e.g., trimethylsilane). 2H 6. Doping elements easily react with water in alkaline solutions to form OH bonds, thereby converting the surface into a hydrophilic surface. The hydrophilic surface reduces adhesion strength and makes scum easier to remove. In yet another embodiment, an adhesion layer (e.g., comprising SiCH, SiOC, etc.) may be provided on the low absorption layer. The adhesion layer described herein is formed by a CVD / ALD process, which can be easily adjusted to control the overall composition to improve surface bonding. For example, the adhesion layer can be adjusted between silicon-rich and carbon-rich, which is difficult to achieve with a coating solution. However, in some embodiments, adjusting the overall composition may not be sufficient to affect surface bonding. Therefore, additional surface treatment may be required to enhance surface termination (e.g., -CH 3 capping). In one embodiment, the low absorption layer is also a CVD / ALD film that can be tuned from silicon-rich to carbon-rich in a similar manner. However, the low absorption layer serves a different purpose and can have a different composition than the adhesion layer in order to provide an optimal coupling and / or combination of layers. The adhesion layer provides improved coupling to the overlying photoresist layer, while the low absorption layer improves pattern development. The embodiments disclosed herein can be used in conjunction with a dual-layer bottom layer approach. For example, the bottom layer below the thin adhesion layer can react with water to form -OH bonds to tune the adhesion between the CAR and the adhesion-promoting layer, and / or be a low UV absorption layer, which can also reduce the random effects of line roughness (such as LER and LWR) and local CD uniformity (LCDU) degradation. In the embodiments disclosed herein, a photoresist layer is generally described. The photoresist layer may include an EUV resist material, such as a metal oxide photoresist system. In other embodiments, the photoresist layer may generally include a chemically amplified resist (CAR). The photoresist layer may be suitable for patterning in various electromagnetic radiations, including EUV, deep ultraviolet (DUV), ultraviolet (UV), etc. More generally, the photoresist layer described herein includes an electromagnetic radiation sensitive material. The photoresist layer may have a structure composed of chemical bonds (e.g., CH 3, etc.) provide a hydrophobic surface. Referring now to FIG. 1A , a cross-sectional view of an apparatus 100 according to one embodiment is shown. Apparatus 100 may include a substrate 101. Substrate 101 may include layers to be patterned using a lithography process. Substrate 101 may comprise a material typically patterned to form structures in a semiconductor device. For example, substrate 101 may include a semiconductor material (e.g., silicon), a metal layer, a dielectric layer, or an insulating layer. In some embodiments, substrate 101 may further include layers that facilitate the transfer of patterns into substrate 101. For example, additional layers may include a hard mask layer, an antireflective coating (ARC), and the like. In one embodiment, the device 100 may further include an adhesion promoting layer 110. The adhesion promoting layer 110 may be a material that can achieve good adhesion strength between the substrate 101 and the covering photoresist 120. The adhesion promoting layer 110 may have a surface that matches the hydrophobicity of the photoresist 120. Typically, the photoresist 120 is a CH Thus, the adhesion promoting layer 110 may also include a hydrophobic material having CH 3-terminated hydrophobic surface. One example of such a material is hexamethyldisilazane (HMDS), while another CVD-based example is SiC:H or the like. In some embodiments, adhesion-promoting layer 110 may be further doped. For example, dopants such as silicon and boron may be provided in adhesion-promoting layer 110. Adhesion-promoting layer 110 can be made of a material with a modifiable attraction to water. For example, during exposure and development of the overlying photoresist 120, adhesion-promoting layer 110 exhibits a strong bond with the photoresist through hydrophobic interactions. After development, any remaining scum is removed. As the adhesion between adhesion-promoting layer 110 and photoresist 120 decreases, scum removal becomes easier. In this way, the adhesion-promoting layer 110's attraction to water can be transformed into a hydrophilic property. A hydrophobic first material (e.g., photoresist 120) will tend to repel a hydrophilic second material (e.g., the modified adhesion-promoting layer 110). Adhesion-promoting layer 110 can be converted to a hydrophilic surface by applying an alkaline solution. Water can react with the surface to form OH chemical bonds. Consequently, scum can be more easily removed from the surface of adhesion-promoting layer 110, providing improved pattern transfer. Referring now to FIG. 1B , a cross-sectional view of an apparatus 100 according to an additional embodiment is shown. In one embodiment, apparatus 100 may include a substrate 101. Substrate 101 in FIG. 1B may be substantially similar to substrate 101 in FIG. 1A . That is, substrate 101 may include a layer to be patterned (e.g., silicon, metal, dielectric, insulator, etc.) and a pattern transfer layer (e.g., hard mask, ARC, etc.). The device 100 in FIG. 1B can include a dual-layer bottom layer solution, rather than a single adhesion-promoting layer 110. A first bottom layer 115 can be disposed on the substrate 101, and a second bottom layer 110 can be disposed on the first bottom layer 115. The dual-layer bottom layer structure 115 / 110 can include a material suitable for switching the surface between hydrophobic and hydrophilic conditions. In addition to providing a switch between attraction and repulsion of water, the dual-layer bottom layer structure 115 / 110 allows for improved adhesion to the photoresist 120. This is because the second bottom layer 110 can be tuned to have high adhesion strength, while the first bottom layer 115 can be tuned to easily switch to a hydrophilic structure. In one embodiment, the second bottom layer 110 may be a relatively thin layer. For example, the second bottom layer 110 may have a thickness of about 10 nm or less, or about 5 nm or less. In addition, the second bottom layer 110 may be a porous material. Due to the small thickness and porosity of the second bottom layer 110, the change from hydrophobic to hydrophilic in the first bottom layer 115 easily propagates through the second bottom layer 110. In one embodiment, the first bottom layer 115 may include Si-H bonds, Si-CH bonds, and Si-CH bonds. The material of the first underlayer 115 may be easily converted into an OH termination when exposed to an alkaline solution including water or the like. In one embodiment, the first bottom layer 115 can have a thickness greater than that of the second bottom layer 110. For example, the first bottom layer 115 can have a thickness of up to about 20 nm, up to about 30 nm, or up to about 50 nm. The combined thickness of the first bottom layer 115 and the second bottom layer 110 can be greater than the thickness of the photoresist 120. However, in other embodiments, the photoresist 120 can be thicker than one or both of the first bottom layer 115 and the second bottom layer 110. In one embodiment, the photoresist 120 can be any suitable photoresist material. In one embodiment, the photoresist 120 is any suitable CAR material. The photoresist 120 can be sensitive to EUV radiation, DUV radiation, or UV radiation. Referring now to Figures 2A-2E , a series of cross-sectional views depicting a process for patterning photoresist 220 are shown, according to one embodiment. In the illustrated embodiment, the layers are separated from one another to more clearly illustrate the chemical bonding between the layers (e.g., dangling bonds on the surfaces of each layer). It should be understood that, in reality, the different layers are in contact with one another through adhesion strength provided by chemical bonds. Referring now to FIG. 2A , a cross-sectional view of an apparatus 200 according to one embodiment is shown. In one embodiment, the apparatus 200 may include a substrate 201 . The substrate 201 may be a material to be patterned (e.g., a semiconductor, metal, dielectric, insulator, etc.). The substrate 201 may also include some pattern transfer layer (e.g., a hard mask, ARC, etc.). In one embodiment, the first bottom layer 215 may cover the substrate 201. The first bottom layer 215 may include a material having a hydrophobic surface. For example, the dangling bond 214 may include H, etc. Although only the dangling bond of H is shown in FIG. 2A, in some embodiments, CH Si-H bonds may also exist on the surface of the first bottom layer 215. In one embodiment, the first bottom layer 215 may also include Si-H bonds, Si-CH 3 bonds, BH bonds, etc. These bonds may be hydrophobic in character. In one embodiment, the second bottom layer 210 may be disposed on the first bottom layer 215. The second bottom layer 210 may have a bond 211 between the first bottom layer 215 and the second bottom layer 210. As shown, the bond 211 may include an H bond and a CH bond. 3 bonds. Bond 211 can have the same polarity as bond 214 on the first bottom layer. For example, in some embodiments, bond 211 can be hydrophobic. Due to the matching hydrophobicity of bond 211 and bond 214, first bottom layer 215 and second bottom layer 210 have strong adhesion to each other, as indicated by the check mark between bond 211 and bond 214. In one embodiment, the second bottom layer 210 can be a relatively thin layer. For example, the second bottom layer 210 can have a thickness of up to approximately 10 nm, up to approximately 5 nm, or up to approximately 2 nm. The second bottom layer 210 can also be a porous material. Due to the thin and porous nature of the second bottom layer 210, the surface conditions of the first bottom layer 215 can be transmitted through the second bottom layer 210. That is, when the first bottom layer 210 has bonds 214 that are inherently hydrophobic, the second bottom layer 215 will also have bonds 212 that are also inherently hydrophobic. Similarly, when bonds 214 become hydrophilic, bonds 212 will also become hydrophilic. In this manner, a combination of a first bottom layer 215 and a second bottom layer 210 can be used to provide a patterned stack that enables higher adhesion to the photoresist 220 at one point in time and lower adhesion to the photoresist at a second point in time. Specifically, the bonds 212 shown in FIG. 2A are hydrophobic in nature (e.g., CH 3 and H), and the hydrophobic bond 221 (e.g., CH 3) Strong bond. The dual-layer bottom layer structure is particularly beneficial because it allows the patterned stack to be tuned for adhesion and scum removal. The second bottom layer 210, which directly contacts the photoresist 220, can be specifically tuned for adhesion strength, while the first bottom layer 215 can be made of a material that can be easily switched between hydrophobic and hydrophilic properties. Because the second bottom layer 210 is relatively thin and porous, variations in the first bottom layer 215 can easily modify the surface condition of the overlying second bottom layer 210. This reduces adhesion to residual scum after developing the photoresist, and facilitates scum removal. It should be understood that the dual-layer bottom layer architecture can be formed using a dry deposition process. For example, both the first bottom layer 215 and the second bottom layer 210 can be formed using a chemical vapor deposition (CVD) process, an atomic layer deposition (ALD) process, or a similar process. In one embodiment, the photoresist 220 can also be formed using a dry deposition process. In some embodiments, the first bottom layer 215, the second bottom layer 210, and the photoresist 220 can be formed in a single deposition chamber. In one embodiment, photoresist 220 can be any suitable photosensitive material used in semiconductor manufacturing. For example, photoresist 220 can be any other suitable CAR material. Photoresist 220 can be sensitive to EUV, DUV, or UV electromagnetic radiation. In some embodiments, electromagnetic radiation can alter the chemical properties of photoresist 220. In some cases, exposure to electromagnetic radiation can also alter the chemical properties of one or both of first bottom layer 215 and second bottom layer 210. Referring now to FIG. 2B , a cross-sectional view of apparatus 200 is shown, according to one embodiment. As shown, electromagnetic radiation 251 passes through mask 250 to expose a portion of photoresist 220. As indicated by the different shading, exposed regions 222 may have a different chemical composition than the unexposed regions of photoresist 220. For example, exposed regions 222 may be more highly cross-linked than unexposed regions. In the illustrated embodiment, mask 250 having openings is used to selectively expose regions of photoresist 220. However, it should be understood that electromagnetic radiation may alternatively be reflected toward selected regions of photoresist 220. In one embodiment, the first bottom layer 215 and the second bottom layer 210 can also be altered by exposure to electromagnetic radiation 251. For example, the exposed area 213 can be provided in the second bottom layer 210, and the exposed area 217 can be provided in the first bottom layer 215. Although shown as being responsive to the electromagnetic radiation 251, it should be understood that one or both of the first bottom layer 215 and the second bottom layer 210 may not be responsive to the electromagnetic radiation 251. In one embodiment, exposure to electromagnetic radiation can modify the bond layers 214, 211, and 212. As shown in FIG2B , the exposed portions of the bonds are modified with *. * indicates that the bond has increased energy. This further improves subsequent reactions to convert hydrophobic bonds into hydrophilic bonds, as described in more detail below. Referring now to FIG. 2C , a cross-sectional view of apparatus 200 after a development process according to one embodiment is shown. In one embodiment, the development process may result in the removal of substantially all exposed areas 222 of photoresist 220. However, scum 223 or other residual portions of photoresist 220 may remain in opening 240. As indicated by the check mark between key 221 and key 212, scum 223 remains firmly attached to second bottom layer 210. Due to the strong adhesion between scum 223 and second bottom layer 210, removal of scum 223 is difficult. Consequently, pattern transfer to the bottom layer may be suboptimal. The development process may be a dry development process or a development process using liquid development chemistry. Referring now to FIG. 2D , a cross-sectional view of the device 200 during processing is shown according to one embodiment. The processing may be exposed to an alkaline solution 255. The alkaline solution 255 may contain H 2O or other oxygen-containing chemicals. Alkaline solution 255 can react with first bottom layer 215. First bottom layer 215 can be easily converted, causing exposed areas 217 of bonding layer 216 to be converted into OH bonds. Similarly, bonding layer 218 can be converted into OH bonds. Because bonding layers 216 and 218 have the same bond type (i.e., hydrophilic), a strong bond exists between first bottom layer 215 and second bottom layer 210, as indicated by the check mark. Similarly, the bond layer 219 on the second bottom layer 210 can be converted to a hydrophilic bond type. The bond layer 219 can be converted by exposure to the alkaline solution 255 and / or by changing into the bond layers 216 and 218. Due to the small thickness of the second bottom layer 210 and the porosity of the second bottom layer 210, the propagation of the hydrophilic type bond through the second bottom layer 210 is possible. As shown in the figure, the bond layer 219 no longer has a strong bond with the bond layer 221 of the scum 223, as indicated by the X mark between the two. 3 bond), while the second bottom layer 210 has hydrophilicity (e.g., OH bond), thus forming a weak bond. Since the adhesion between the two layers is reduced, the scum 223 can now be removed more easily. Referring now to FIG. 2E , a cross-sectional view of device 200 is shown after scum 223 has been removed, according to one embodiment. In the illustrated embodiment, the layers are now shown in direct contact with one another, without the bonding layer. However, it should be understood that the bonding layer, as shown in FIG. 2D , still exists but has been omitted for simplicity. As shown, photoresist 220 now has clear openings 240 exposing regions 217 and 213 of first and second bottom layers 215 and 210, respectively. After scum 223 has been removed, the pattern of openings 240 can be transferred to bottom layers 210 and 215 and substrate 201. 3, a process flow diagram of a process 380 for scum removal according to one embodiment is shown. The process 380 shown in FIG3 can be substantially similar to the process described above with respect to FIG2A-2E. In one embodiment, process 380 may begin with operation 381, which includes forming a photoresist layer on a first bottom layer and a second bottom layer. In one embodiment, the second bottom layer is tuned to promote adhesion to the photoresist layer. For example, both the photoresist layer and the second bottom layer may have hydrophobic dangling bonds. In one embodiment, the second bottom layer may have a small thickness (e.g., up to about 10 nm, up to about 5 nm, or up to about 2 nm). The second bottom layer may also be porous. In this way, the surface properties of the underlying first bottom layer can be transmitted through the second bottom layer. In one embodiment, process 380 may continue with operation 381, which includes patterning the photoresist layer by exposure to electromagnetic radiation and a developer. In one embodiment, the electromagnetic radiation may be EUV radiation, DUV radiation, UV radiation, or the like. The development process may be a liquid development process or a dry development process. In one embodiment, the development process may result in residual scum at the bottom of the opening through the photoresist layer. In one embodiment, process 380 may continue with operation 383, which includes modifying the second bottom layer to reduce adhesion to residual scum on the second bottom layer. In one embodiment, the modification may be a treatment. The treatment may involve exposing the first and second bottom layers to an alkaline solution. The first bottom layer readily reacts with the alkaline solution to form OH bonds. Due to the thin and porous nature of the second bottom layer, the surface chemistry of the first bottom layer can propagate through the second bottom layer. In other embodiments, the alkaline solution may directly alter the bond chemistry of the second bottom layer. This modification causes the surface chemistry of the second bottom layer to shift from hydrophobic to hydrophilic. As a result, the (hydrophobic) scum now has a weaker bond to the second bottom layer. In one embodiment, process 380 may continue with operation 384, which includes removing scum from the second bottom layer. Since adhesion between the scum and the second bottom layer is reduced, the scum can be removed more easily. For example, a rinse process or similar process may be used to remove the scum. After the scum is removed, the pattern in the photoresist layer can be transferred to the bottom layer and the underlying substrate. Referring now to Figures 4A and 4B, a pair of schematic cross-sectional views of an apparatus 400 for treating a substrate to remove scum is shown, according to one embodiment. Referring now to FIG. 4A , a cross-sectional view of a device 400 is shown. Device 400 may include a substrate 401. Substrate 401 may be similar to any of the substrate structures described in more detail above. In one embodiment, a bottom layer 410 may be disposed on substrate 401. A photoresist 420 may be disposed on bottom layer 410. Although shown as spaced apart from bottom layer 410, it should be understood that photoresist 420 may be directly disposed on bottom layer 410. The spaced apart relationship is shown to illustrate the presence of bonding chemistry 418. In one embodiment, the bottom layer 410 may have a bonding chemistry 418 comprising an amorphous SiC:H composition. The SiC:H composition may be doped with one or more dopant atoms. The dopant atoms may include Si, Ge, B, P, or the like. The dopant elements are selected to readily react with water in an alkaline solution to form OH bonds. In FIG. 4A , the dopant atoms are represented by X in the bonding chemistry 418. As shown, the bonding chemistry includes H bonds and CH bonds that provide a hydrophobic surface for the bottom layer 410. 3. The bonding chemical 425 of the photoresist can be an organic compound, which also leads to the formation of a hydrophobic surface. The matching hydrophobic surface allows for strong adhesion between the bottom layer 410 and the photoresist 420. Referring now to FIG. 4B , a cross-sectional view of device 400 after exposure, development, and processing is shown according to one embodiment. Exposure and development result in the formation of openings 440 through photoresist 420. Residual scum can be removed from openings 440 by using a process that converts the exposed portion of the underlying layer into a hydrophilic surface. Specifically, by applying an alkaline solution, water readily reacts with the dopant, forming OH bonds on the underlying layer surface. Due to the hydrophilic conversion of the surface, underlying layer 410 no longer adheres strongly to the scum. This makes the scum easier to remove (e.g., using a rinse process). Referring now to FIG. 5A and FIG. 5B , a pair of cross-sectional views depicting a patterned stack for device 500 are shown, according to a pair of embodiments. In the embodiment shown in FIG. 5A , device 500 includes substrate 501 having stacks 561 and 562 . Substrate 501 can be similar to any of the substrates described in greater detail above. In one embodiment, stacks 561 and 562 can comprise any suitable material. In particular, layer 562 can be a low-absorbing layer. Low-absorbing layer 562 can comprise SiCH and have C(H) bonds. The chemistry of low-absorbing layer 562 can be selected to minimize absorption of EUV radiation. In one embodiment, an adhesion layer 510 may be provided on the low absorption layer 562. The adhesion layer 510 may have a thickness of up to about 10 nm, up to about 5 nm, or up to about 2 nm. In one embodiment, the adhesion layer 510 is a hydrophobic material that preferentially bonds to the overlying photoresist layer 520. The adhesion layer 510 may include SiCH, HMDS, SiOC, carbon, and the like. The surface of the adhesion layer 510 may include H bonds or CH The photoresist layer 520 may have an opening 540 . The photoresist layer 520 may also have a hydrophobic surface to facilitate bonding with the adhesive layer 510 . 5B, a cross-sectional view of the device 500 according to one embodiment is shown without the adhesive layer 510. In one embodiment, when the low absorption layer 562 provides sufficient adhesion strength to the overlying photoresist layer 520, the adhesive layer 510 can be removed. Referring now to Figures 6A and 6B, a pair of cross-sectional views depicting a patterned stack are shown according to an alternative embodiment. The embodiments shown in Figures 6A and 6B can utilize any of the adhesion and release properties or systems described in more detail herein. That is, embodiments can allow for initial strong adhesion between photoresist layers, followed by a reduction in adhesion strength to allow for improved scum removal. Referring now to FIG. 6A , a cross-sectional view of an apparatus 600 according to one embodiment is shown. In one embodiment, apparatus 600 may include a substrate 601. Substrate 601 may include layers to be patterned using a lithography process. Substrate 601 may include a material typically patterned to form structures in semiconductor devices. For example, substrate 601 may include a semiconductor material (e.g., silicon), a metal layer, a dielectric layer, or an insulating layer. In some embodiments, substrate 601 may further include layers that facilitate the transfer of patterns into substrate 601. For example, additional layers may include a hard mask layer, an ARC layer, and the like. In one embodiment, a patterned stack may be provided on a substrate 601. The patterned stack may include a plurality of different layers. For example, the patterned stack may include a first layer 671, a second layer 672, and a third layer 673. In one embodiment, the first layer 671 may include one or more of silicon, oxygen, hydrogen, nitrogen, and carbon. In one embodiment, the second layer 672 may include one or more of silicon, amorphous silicon, oxygen, hydrogen, and nitrogen. In one embodiment, the third layer 673 may include at least carbon. For example, the carbon may be a CVD carbon layer, an ALD carbon layer, or the like. In some embodiments, implanted substances (e.g., silicon, germanium, boron, phosphorus, iodine, and / or hydrogen) may be implanted into one or more of layers 671-673 to modify various properties, such as adhesion strength, chemical reactivity, etc. A photoresist layer 620 may be disposed on the patterned stack. The photoresist layer 620 may be a metal oxide resist (MOR) or a chemically enhanced resist (CAR). In a particular embodiment, the device 600 may include a stack of the following material layers. In one embodiment, the first layer 671 may include an oxide, such as silicon oxide. The first layer 671 may have a thickness of up to approximately 100 nm. For example, the first layer 671 may have a thickness of approximately 50 nm or less. In one embodiment, the second layer 672 may include an amorphous silicon layer. The amorphous silicon layer may be formed using any suitable deposition process, such as plasma-enhanced CVD (PECVD). In some embodiments, the second layer 672 may have a thickness of up to approximately 50 nm. In a particular embodiment, the second layer 672 may have a thickness of approximately 20 nm or less. In one embodiment, the third layer 673 may include a carbon layer, such as a CVD carbon layer. The third layer 673 may have a thickness of up to approximately 50 nm. For example, the third layer 673 may have a thickness of approximately 30 nm or less. In yet another embodiment, the patterned stack may have the following material layers. In one embodiment, the first layer 671 may include silicon, oxygen, and nitrogen. For example, in some embodiments, the first layer 671 may include SiON. The second layer 672 may include silicon, oxygen, and hydrogen. In one embodiment, the third layer 673 may include the same elements as the first layer 671. In the specific embodiments described herein, the third layer 673 may include silicon, oxygen, and nitrogen (e.g., SiON). The first layer 671, the second layer 672, and the third layer 673 may have a thickness of less than approximately 1,000 Å. For example, the first layer 671 may have a thickness of up to approximately 350 Å, the second layer 672 may have a thickness of up to approximately 450 Å, and the third layer 673 may have a thickness of up to approximately 250 Å. In yet another embodiment, the patterned stack may be constructed as follows. The first layer 671 may include an oxide, such as an oxide including silicon and oxygen (eg, SiO 2). The second layer 672 may include silicon. For example, the second layer 672 may include an amorphous silicon layer. In one embodiment, the third layer 673 may be any suitable underlying material. For example, the third layer may include silicon, carbon, and hydrogen (e.g., SiCH), HMDS, silicon, oxygen, and carbon (SiOC), etc. The first layer 671, the second layer 672, and the third layer 673 may each have a thickness of up to approximately 500 nm. In yet another embodiment, the patterned stack may include an additional interface layer (not shown) between the substrate 601 and the first layer 671. For example, the interface layer may be considered an adhesion layer, a hard mask layer, or the like. In some embodiments, the interface layer may include titanium and nitrogen. For example, in some embodiments, the interface layer may include TiN. Referring now to FIG. 6B , a cross-sectional view of a device 600 according to an additional embodiment is shown. The device 600 in FIG. 6B can be substantially similar to the device 600 in FIG. 6A , except that an antireflective coating (ARC) 675 is added to the third layer 673 . The ARC 675 can be any suitable ARC material. For example, the ARC can include one or both of a dielectric ARC (DARC) or a bottom ARC (BARC). That is, in some embodiments, the ARC 675 can include at least two different layers. In some embodiments, the ARC 675 can have a thickness of up to approximately 40 nm. In a particular embodiment, the ARC 675 can have a thickness of up to approximately 20 nm. FIG7 illustrates a schematic diagram of a machine in the exemplary form of a computer system 700 within which a set of instructions for causing the machine to perform any one or more of the methodologies described herein may be executed. In alternative embodiments, the machine may be connected (e.g., networked) to other machines in a local area network (LAN), an intranet, an extranet, or the Internet. The machine may operate as a server or a client in a client-server network environment, or as a peer in a peer-to-peer (or distributed) network environment. The machine may be a personal computer (PC), a tablet, a set-top box (STB), a personal digital assistant (PDA), a cellular phone, a network appliance, a server, a network router, a switch or bridge, or any machine capable of executing a set of instructions (sequential or otherwise) specifying actions to be taken by the machine. Furthermore, while a single machine is illustrated, the term "machine" shall be construed to include any collection of machines (e.g., computers) that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies described herein. The exemplary computer system 700 includes a processor 702, a main memory 704 (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM) or Rambus DRAM (RDRAM)), a static memory 706 (e.g., flash memory, static random access memory (SRAM), MRAM, etc.), and an auxiliary memory 718 (e.g., a data storage element), which communicate with each other via a bus 730. Processor 702 represents one or more general-purpose processing devices, such as microprocessors, central processing units, and the like. More specifically, processor 702 may be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a processor implementing another instruction set, or a processor implementing a combination of instruction sets. Processor 702 may also be one or more special-purpose processing devices, such as an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), a network processor, and the like. Processor 702 is configured to execute processing logic 726 for performing the operations described herein. The computer system 700 may further include a network interface device 708. The computer system 700 may further include a video display unit 710 (e.g., a liquid crystal display (LCD), a light emitting diode display (LED), or a cathode ray tube (CRT)), an alphanumeric input device 712 (e.g., a keyboard), a cursor control device 714 (e.g., a mouse), and a signal generating device 716 (e.g., a speaker). Secondary memory 718 may include machine-accessible storage media (or, more specifically, computer-readable storage media) 732 on which one or more sets of instructions (e.g., software 722) are stored, embodying any one or more of the methods or functions described herein. During execution of software 722 by computer system 700, software 722 may also reside, completely or at least partially, within main memory 704 and / or within processor 702, with main memory 704 and processor 702 also constituting machine-readable storage media. Software 722 may also be transmitted or received over network 720 via network interface device 708. Although the machine-accessible storage medium 732 is shown as a single medium in the exemplary embodiment, the term "machine-readable storage medium" should be understood to include a single medium or multiple media (e.g., a centralized or distributed database, and / or associated caches and servers) that store one or more sets of instructions. The term "machine-readable storage medium" should also be understood to include any medium that can store or encode a set of instructions for execution by a machine and cause the machine to perform any one or more of the methods disclosed herein. Thus, the term "machine-readable storage medium" should include, but is not limited to, solid-state memory, optical, and magnetic media. According to an embodiment of the present disclosure, a machine-accessible storage medium has instructions stored thereon that cause a data processing system to execute a method for providing a photoresist stack having a first bottom layer and a second bottom layer. In one embodiment, the second bottom layer is less than 5 nm thick and is tuned to have high adhesion to an overlying photoresist layer. After patterning, the first and second bottom layers are treated with an aqueous alkaline solution. This solution converts the hydrophobic surfaces of the first and second bottom layers into hydrophilic surfaces with reduced bond strength to the photoresist layer. Any scum can be easily rinsed from the stack. Thus, a method for forming a photoresist stack having high adhesion and improved descum has been disclosed. 100: Device 101: Substrate 110: Second Bottom Layer 115: First Bottom Layer 120: Photoresist 200: Device 201: Substrate 210: Bottom Layer 211: Key 212: Key 213: Region 214: Key 215: Bottom Layer 216: Key Layer 217: Region 218: Key Layer 219: Key Layer 220: Photoresist 221: Key 222: Exposure Area 223: Scum 240: Opening 250: Mask 251: Electromagnetic Radiation 255: Alkaline Solution 380: Process 3 81: Operation 382: Operation 383: Operation 384: Operation 400: Device 401: Substrate 410: Bottom Layer 418: Bonding Chemistry 420: Photoresist 425: Bonding Chemistry 440: Opening 500: Device 501: Substrate 510: Adhesion Layer 520: Photoresist Layer 540: Opening 561: Stack 562: Stack 600: Device 601: Substrate 620: Photoresist Layer 671: First Layer 672: Second Layer 673: Third Layer 675: ARC 700: Computer system 702: Processor 704: Main memory 706: Static memory 708: Network interface device 710: Video display unit 712: Alphanumeric input device 714: Cursor control device 716: Signal generating device 718: Auxiliary memory 722: Software 726: Processing logic 730: Bus 731: Machine accessible storage medium C: Carbon CH 3: Methyl H: Hydrogen O: Oxygen OH: Hydrogen and Oxygen PG: Programmable Gate Si: Silicon FIG. 1A is a cross-sectional view of a device including a photoresist layer disposed over an adhesion-promoting underlayer according to one embodiment. 1B is a cross-sectional view of a device including a photoresist layer disposed over a pair of adhesion-promoting underlayers according to one embodiment. FIG. 2A is a schematic diagram of a device having a photoresist and an underlying layer, showing the chemical bonds between the layers, according to one embodiment. FIG. 2B is a schematic diagram of the device after exposure of the photoresist to electromagnetic radiation according to one embodiment. FIG. 2C is a schematic diagram of the apparatus after developing the photoresist and scum remaining on the topmost bottom layer according to one embodiment. FIG. 2D is a schematic diagram of the device after the bottom layer has been exposed to a treatment that converts chemical bonds from hydrophobic to hydrophilic, according to one embodiment. FIG. 2E is a cross-sectional view of the apparatus after scum removal according to one embodiment. FIG. 3 is a process flow diagram of a process for patterning a photoresist layer including a pair of bottom layers according to one embodiment. FIG. 4A is a schematic diagram of a device including a substrate, an underlayer, and a photoresist according to one embodiment. FIG. 4B is a schematic diagram of the device after the photoresist is patterned and the bottom layer is processed according to one embodiment. FIG. 5A is a cross-sectional view of a device having an adhesion layer between a photoresist and a low-absorbing layer according to one embodiment. FIG. 5B is a cross-sectional view of a device having a low-absorbing layer under the photoresist according to one embodiment. FIG. 6A is a cross-sectional view of a device having a multi-layer patterned stack according to one embodiment. FIG. 6B is a cross-sectional view of a device having a multi-layer patterned stack with an anti-reflective coating (ARC) according to one embodiment. FIG. 7 shows a block diagram of an exemplary computer system according to one embodiment of the present disclosure. Domestic deposit information (please note in the order of deposit organization, date, and number) None Foreign deposit information (please note in the order of deposit country, organization, date, and number) None 201:Substrate 210: Bottom 211:Key 212:Key 214:Key 220: Photoresist 221:Key CH 3: Methyl H: Hydrogen

Claims

1. A method for developing a patterned stack, comprising: providing a patterned stack, wherein the patterned stack includes a substrate and a photoresist on the substrate, wherein the substrate and the photoresist have a first adhesion strength; exposing and developing the photoresist using electromagnetic radiation and a developer, wherein scum is retained on a surface of the substrate; processing the substrate such that the substrate and the scum have a second adhesion strength; and removing the scum.

2. The method as described in claim 1, wherein the underlying layer is hydrophobic before the treatment and hydrophilic after the treatment.

3. The method as described in claim 1, wherein the underlying layer includes an H end cap and a CH3 end cap before the processing.

4. The method as described in claim 3, wherein the underlying layer includes the processed OH end caps.

5. The method as described in claim 1, wherein the treatment involves exposure to an alkaline solution.

6. The method as described in claim 1, wherein the underlying layer has a thickness of up to approximately 5 nm.

7. The method as described in claim 6 further includes: The second layer is below the first layer.

8. The method as described in claim 6, wherein the second layer is more responsive to the processing than the first layer.

9. The method as described in claim 1, wherein the underlying layer comprises an amorphous SiC:H material.

10. The method as described in claim 9, wherein the SiC:H is doped with one or more of Ge, B and P.

11. The method as described in claim 10, wherein one or more of Ge, B, and P react more readily with the treatment to form an OH bond than with SiC:H.

12. A method of patterning a substrate, comprising: providing a patterned stack on the substrate, wherein the patterned stack includes: The first layer; A second layer above the first layer; And a photoresist on the second layer; The patterned stack is exposed to electromagnetic radiation; the photoresist in the patterned stack is developed; the second layer is modified to reduce the adhesion strength of the photoresist. And remove any scum from the bottom layer of the second layer.

13. The method as described in claim 12, wherein the second layer has a thickness of up to about 5 nm.

14. The method as described in claim 13, wherein the second bottom layer is porous.

15. The method as described in claim 12, wherein the second sublayer has a hydrophobic surface before modification and a hydrophilic surface after modification.

16. The method as described in claim 12, wherein the step of modifying the second substrate comprises: exposing the first substrate and the second substrate to an alkaline solution.

17. The method as described in claim 12, wherein the photoresist is a CAR.

18. A patterned stack comprising: a first substrate; a second substrate on the first substrate, wherein the second substrate has a hydrophobic surface; and a photoresist on the second substrate, wherein the photoresist has a hydrophobic surface, wherein the hydrophobic surface of the second substrate may be modified to a hydrophilic surface to reduce an adhesion strength between the second substrate and the photoresist.

19. The patterned stack as described in claim 18, wherein the second bottom layer transforms into a hydrophilic surface upon exposure to an alkaline solution.

20. A patterned stack, comprising: A first layer, wherein the first layer comprises one or more of silicon, oxygen, hydrogen, nitrogen, and carbon; a second layer on the first layer, wherein the second layer comprises one or more of silicon, amorphous silicon, oxygen, hydrogen, and nitrogen; a third layer on the second layer, wherein the third layer comprises carbon, wherein the third layer may be implanted to reduce an adhesion strength between the third layer and the photoresist; and a photoresist on the third layer, wherein the photoresist is a metal oxide resist (MOR) or a chemically enhanced resist (CAR).

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