EUV photoresist and underlayer adhesion tuning

Abstract

Embodiments disclosed herein include a method of developing a patterned stack. In one embodiment, the method includes providing a patterned stack, the patterned stack including an underlayer and a photoresist over the underlayer, the underlayer having a first adhesion strength with the photoresist. The method can further include developing the photoresist by exposing it to electromagnetic radiation and a developer, whereby scum remains on a surface of the underlayer. In one embodiment, the method further includes treating the underlayer such that the underlayer has a second adhesion strength with the scum and removing the scum.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application No. 18 / 379,106, filed October 11, 2023, which claims the benefit of U.S. Provisional Patent Application No. 63 / 430,596, filed December 6, 2022, the entire contents of which are hereby incorporated by reference.

[0002] Field FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to the field of semiconductor processing, and more particularly to a method for forming a photoresist having an underlayer for adjusting adhesion. [Background technology]

[0003] Lithography has been used for decades in the semiconductor industry to create 2D and 3D patterns in microelectronic devices. The lithography process involves the spin-on deposition of an underlayer and a film (photoresist) over the underlayer. Such spin-on films may contain several chemical additives (e.g., adjuvants) for dose reduction. The process may be followed by irradiation (exposure) of the film with a selected pattern by an energy source and removal (etching) of the exposed (positive tone) or unexposed (negative tone) areas of the film by dissolution in a solvent. A bake is then performed to remove any remaining solvent. Spin-on underlayer solutions have several drawbacks, especially in extreme ultraviolet (EUV) lithography processes for smaller pitch features. For example, drawbacks may include composition uniformity and poor adhesion to the photoresist.

[0004] Photoresists must be radiation-sensitive materials, and upon irradiation, a chemical change occurs in the exposed areas of the film, which allows for a change in solubility between the exposed and unexposed areas. Using this change in solubility, the exposed or unexposed areas of the photoresist are removed (etched). The photoresist is then developed, and the pattern can be transferred by etching into the underlying thin film or substrate. After the pattern is transferred, the remaining photoresist is removed, and this process can be repeated multiple times to obtain 2D and 3D structures used in microelectronic devices.

[0005] Several properties are important in lithography processes. These properties include sensitivity, resolution, lower line-edge roughness (LER), linewidth roughness (LWR), etch resistance, and the ability to form thinner layers. Higher sensitivity requires less energy to change the solubility of the film during deposition, which can increase the efficiency of the lithography process. Resolution and LER determine how narrow features can be achieved by the lithography process. Pattern transfer to form deep structures requires materials with higher etch resistance. Also, the higher the etch resistance of a material, the thinner the film can be obtained. Thinner films increase the efficiency of the lithography process. LER and LWR are stochastic effects during photolithography. They may be related, at least in part, to UV light-material interaction processes (e.g., UV absorption, secondary electron generation, and backside exposure from the underlayer) and / or photoresist-underlayer interactions (e.g., adhesion). Summary of the Invention

[0006] Embodiments disclosed herein include a method of developing a patterned stack. In one embodiment, the method includes providing a patterned stack, the patterned stack including an underlayer and a photoresist over the underlayer, the underlayer having a first adhesion strength with the photoresist. The method can further include developing the photoresist by exposing it to electromagnetic radiation and a developer, whereby scum remains on a surface of the underlayer. In one embodiment, the method further includes treating the underlayer such that the underlayer has a second adhesion strength with the scum and removing the scum.

[0007]

[0010] Embodiments disclosed herein may also include a method of patterning a substrate, the method comprising providing a patterning stack over the substrate. In one embodiment, the patterning stack comprises a first underlayer, a second underlayer over the first underlayer, and a photoresist over the second underlayer. In one embodiment, the method further comprises exposing the patterning stack to electromagnetic radiation and developing the photoresist in the patterning stack. In one embodiment, the method further comprises modifying the second underlayer to reduce its adhesive strength to the photoresist and removing any scum that may be present on the second underlayer.

[0008]

[0010] Embodiments disclosed herein may include a patterned stack. In one embodiment, the patterned stack includes a first underlayer and a second underlayer over the first underlayer, the second underlayer having a thickness of at most approximately 5 nm, and the second underlayer having a hydrophobic surface. In one embodiment, the patterned stack may further include a photoresist over the second underlayer, the photoresist having a hydrophobic surface. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are cross-sectional views of a device including a photoresist layer provided on an adhesion-promoting underlayer and a pair of adhesion-promoting underlayers, respectively, according to one embodiment. [Figure 2A] 1 is a schematic diagram of a device having a photoresist and an underlayer, showing chemical bonding between the layers, according to one embodiment. [Figure 2B] 2 is a schematic diagram of a device after the photoresist has been exposed to electromagnetic radiation, according to one embodiment. [Figure 2C] 1 is a schematic diagram of a device after the photoresist has been developed, leaving scum on the top underlayer, according to one embodiment. [Figure 2D] FIG. 1 is a schematic diagram of a device after the underlayer has been exposed to a treatment that converts the chemical bonds from hydrophobic to hydrophilic, according to one embodiment. [Figure 2E] FIG. 10 is a cross-sectional view of a device after scum has been removed, according to one embodiment. [Figure 3] FIG. 1 is a process flow diagram of a process for patterning a photoresist layer including a pair of underlayers, according to one embodiment. [Figure 4] Figure 4A is a schematic diagram of a device including a substrate, an underlayer, and photoresist, according to one embodiment, and Figure 4B is a schematic diagram of the device after the photoresist has been patterned and the underlayer has been processed, according to one embodiment. [Figure 5] 5A and 5B are cross-sectional views of a device having an adhesion layer between the photoresist and the low absorption layer, respectively, and a cross-sectional view of a device having a low absorption layer below the photoresist, according to one embodiment. [Figure 6] 6A and 6B are cross-sectional views of a device having a multi-layer patterning stack and a device having a multi-layer patterning stack including an anti-reflective coating (ARC), according to one embodiment. [Figure 7] FIG. 1 is a block diagram of an exemplary computer system according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Described herein is a method for forming a photoresist having an underlayer for adjusting adhesion. In the following description, numerous specific details are set forth, such as a thermal vapor phase process and material regimes for developing the photoresist, in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known aspects, such as integrated circuit fabrication, are not described in detail in order to avoid unnecessarily obscuring embodiments of the present disclosure. Furthermore, it should be understood that the various embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.

[0011] To provide background, photoresist systems used in extreme ultraviolet (EUV) lithography suffer from low efficiency. Existing photoresist material systems for EUV lithography require high doses to provide the solubility switching required to enable development of the photoresist material. One type of resist system for EUV lithography is the chemically amplified resist (CAR) system. One drawback of CAR systems is limited CAR-underlayer interfacial strength (adhesion). In particular, the bond between the two layers is due to van der Waals forces. High adhesion strength between the photoresist and the underlayer is often a desirable characteristic. Strong adhesion allows for the formation of high aspect ratio features without risk of pattern collapse, pattern delamination, or other patterning defects. High adhesion strength can be achieved by conditioning the underlayer to form a strong bond with the overlying photoresist. CAR photoresists are typically hydrophobic materials. Therefore, the underlayer is also formulated as a hydrophobic material to improve the bond between the two layers.

[0012] However, strong adhesive properties can also have drawbacks. For example, strong adhesive strength between layers can make it difficult to completely remove exposed photoresist using a developer solution. Unwanted residual photoresist material is sometimes referred to as scum. The presence of scum on an underlying layer can cause defects in the patterning that is ultimately transferred to the underlying layer and substrate. Therefore, high-quality pattern transfer is impossible.

[0013] Thus, embodiments disclosed herein include a modifiable underlayer. As used herein, a modifiable layer can be a layer whose chemical composition can be changed or whose dangling bond chemistry can be changed. For example, one treatment disclosed herein can convert a hydrophobic material to a hydrophilic material. When the underlayer is hydrophilic, the bond strength between the underlayer and the overlying hydrophobic photoresist is reduced. This can make scum removal easier. In one embodiment, the treatment can include exposing the underlayer to an alkaline solution. An alkaline solution (e.g., approximately 3% tetramethylammonium hydroxide (TMAH) and 97% water) is used during the lithography development process. Because the alkaline solution already contains water, the underlayer does not need to undergo an extra treatment to react with water to form O-H bonds. Therefore, the techniques described herein can be easily added to existing lithography processes.

[0014] As will be appreciated, a balance must be struck between high adhesive strength for patterning and low adhesive strength for development and scum removal. Accordingly, some embodiments described herein include a dual-layer underlayer structure. A first underlayer on the substrate can include a material composition that is highly reactive to processing, and a second underlayer on the first underlayer can be tailored for adhesion. More specifically, the second underlayer is thin (e.g., approximately 5 nm or less) and porous. This allows chemical changes to the first underlayer to propagate to the second underlayer to modify the interface between the second underlayer and the photoresist.

[0015] In other embodiments, a single underlayer is used. This underlayer can include a doped amorphous SiC:H material. For example, the dopant can include Si, Ge, B, or P. In one particular embodiment, a boron dopant can be provided with B2H6 flowed along with the SiC:H precursor (e.g., trimethylsilane). The doping element readily reacts with water in the alkaline solution to form OH bonds, which converts the surface to a hydrophilic surface. A hydrophilic surface can reduce adhesion strength and make scum removal easier.

[0016] In yet another embodiment, an adhesion layer (e.g., comprising SiCH, SiOC, etc.) can be provided on the low-absorption layer. The adhesion layers described herein are formed by a CVD / ALD process that can be easily adjusted to control the bulk composition to improve surface bonding. For example, the adhesion layer can be modified between Si-rich and C-rich, which is difficult to achieve using a spin-on solution. However, modifying the bulk composition alone may not be sufficient to affect surface bonding in some embodiments. Therefore, additional surface treatment may be required to enhance surface termination (e.g., —CH termination). In one embodiment, the low-absorption layer is a CVD / ALD film that can also be modified from Si-rich to C-rich. However, the low-absorption layer serves a different purpose and may have a different composition from the adhesion layer to provide optimal coupling and / or combination of layers. The adhesion layer improves coupling with the overlying photoresist layer, and the low-absorption layer improves pattern development. The embodiments disclosed herein can be used in conjunction with a dual-underlayer approach. For example, the underlayer beneath the thin adhesive layer is a low UV absorbing layer that can react with water to form -OH bonds to adjust the adhesion between the CAR and the adhesion-promoting layer and / or reduce the stochastic impact on line roughness (e.g., LER and LWR) and degradation of local CD uniformity (LCDU).

[0017] The embodiments disclosed herein generally describe a photoresist layer. The photoresist layer may include an EUV resist material, such as a metal-oxo photoresist system. In other embodiments, the photoresist layer may generally include a chemically amplified resist (CAR). The photoresist layer is suitable for patterning with various electromagnetic radiations, including EUV, deep ultraviolet (DUV), and ultraviolet (UV). More generally, the photoresist layer described herein includes an electromagnetic radiation-sensitive material. The photoresist layer may have a hydrophobic surface provided by chemical bonds, such as CH3.

[0018] 1A illustrates a cross-sectional view of a device 100 according to one embodiment. The device 100 may include a substrate 101. The substrate 101 may include a layer that is patterned using a lithographic process. The substrate 101 may include a material that is typically patterned to form structures in a semiconductor device; for example, the substrate 101 may include a semiconductor material (e.g., silicon), a metal layer, a dielectric layer, or an insulating layer. In some embodiments, the substrate 101 may also include layers that aid in the transfer of a pattern to the substrate 101. For example, the additional layers may include a hard mask layer, an anti-reflective coating (ARC), etc.

[0019] In one embodiment, the device 100 may further include an adhesion promotion layer 110. The adhesion promotion layer 110 may be a material that enables good adhesion strength between the substrate 101 and the overlying photoresist 120. The adhesion promotion layer 110 may have a surface that matches the hydrophobicity of the photoresist 120. Typically, the photoresist 120 is a hydrophobic material with CH dangling bonds. Therefore, the adhesion promotion layer 110 may also include a hydrophobic surface with CH termination. One example of such a material is hexamethyldisilazane (HMDS), and another CVD-based example is SiC:H. In some embodiments, the adhesion promotion layer 110 may be further doped. For example, dopants such as silicon and boron may be provided in the adhesion promotion layer 110.

[0020] The adhesion-promoting layer 110 can be a material with a tunable affinity for water. For example, during exposure and development of the overlying photoresist 120, the adhesion-promoting layer 110 exhibits strong bonding to the photoresist through hydrophobic interactions. After development, any remaining scum is removed. Scum removal becomes easier when the adhesion between the adhesion-promoting layer 110 and the photoresist 120 is reduced. Thus, the water affinity of the adhesion-promoting layer 110 can be switched to hydrophilic. A hydrophobic first material (e.g., photoresist 120) tends to repel a hydrophilic second material (e.g., modified adhesion-promoting layer 110). The adhesion-promoting layer 110 can be converted to a hydrophilic surface through the application of an alkaline solution. Water can react with this surface to form OH chemical bonds. Thus, scum can be more easily removed from the surface of the adhesion-promoting layer 110, which provides better pattern transfer.

[0021] 1B illustrates a cross-sectional view of a device 100 according to a further embodiment. In one embodiment, device 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.).

[0022] Instead of having a single adhesion-promoting layer 110, the device 100 of FIG. 1B can include a dual-underlayer solution. A first underlayer 115 can be provided on the substrate 101, and a second underlayer 110 can be provided on the first underlayer 115. The dual-underlayer architecture 115 / 110 can include materials suitable for converting the surface between a hydrophobic and a hydrophilic state. In addition to providing a switch between an affinity and repulsion for water, the dual-underlayer structure 115 / 110 can also enable improved adhesion to the photoresist 120 because the second underlayer 110 can be tailored to have high adhesion strength and the first underlayer 115 can be tailored to be easily convertible to a hydrophilic structure.

[0023] In one embodiment, the second underlayer 110 may be a relatively thin layer. For example, the second underlayer 110 may have a thickness of approximately 10 nm or less, or approximately 5 nm or less. In addition, the second underlayer 110 may be a porous material. Due to the small thickness and porosity of the second underlayer 110, the change from hydrophobic to hydrophilic properties of the first underlayer 115 may easily propagate to the second underlayer 110. In one embodiment, the first underlayer 115 may include a material having Si-H bonds, Si-CH bonds, B-H bonds, and the like. The bonds of the first underlayer 115 may easily convert to OH terminations when exposed to an alkaline solution containing water, for example.

[0024] In one embodiment, the first underlayer 115 can have a thickness greater than the thickness of the second underlayer 110. For example, the first underlayer 115 can have a thickness of up to approximately 20 nm, up to approximately 30 nm, or up to approximately 50 nm. The combined thickness of the first underlayer 115 and the second underlayer 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 underlayer 115 and the second underlayer 110.

[0025] In one embodiment, photoresist 120 can be any suitable photoresist material. In one example, photoresist 120 is any suitable CAR material. Photoresist 120 can be sensitive to EUV radiation, DUV radiation, or UV radiation.

[0026] 2A-2E show a series of cross-sectional views illustrating a process for patterning photoresist 220, according to one embodiment. In the illustrated embodiment, the layers are spaced apart to more clearly show the bonding chemistry between the layers (e.g., dangling bonds at the surfaces of the various layers). It should be understood that the various layers are actually in contact with each other with adhesive strength provided by chemical bonds.

[0027] 2A illustrates a cross-sectional view of a device 200 according to one embodiment. In one embodiment, the device 200 may include a substrate 201. The substrate 201 may be a material to be patterned (e.g., a semiconductor, a metal, a dielectric, an insulator, etc.). The substrate 201 may include several pattern transfer layers (e.g., a hard mask, an ARC, etc.).

[0028] In one embodiment, the substrate 201 may be covered by a first underlayer 215. The first underlayer 215 may include a material having a hydrophobic surface. For example, the dangling bonds 214 may include H, etc. While only H dangling bonds are shown in FIG. 2A, in some embodiments, CH bonds may also be present on the surface of the first underlayer 215. In one embodiment, the first underlayer 215 may also include Si—H bonds, Si—CH bonds, B—H bonds, etc. The bonds may be characterized as hydrophobic.

[0029] In one embodiment, a second sublayer 210 may be provided on top of a first sublayer 215. The second sublayer 210 may have a bond 211 between the first sublayer 215 and the second sublayer 210. As shown, the bond 211 may include an H bond and a CH bond. The bond 211 may have the same polarity as the bond 214 on the first sublayer. For example, the bond 211 may be hydrophobic in some embodiments. The hydrophobic matching between the bond 211 and the bond 214 allows the first sublayer 215 and the second sublayer 210 to have strong adhesion to each other, as indicated by the check mark between the bond 211 and the bond 214.

[0030] In one embodiment, the second sublayer 210 can be a relatively thin layer. For example, the second sublayer 210 can have a thickness of at most approximately 10 nm, at most approximately 5 nm, or at most approximately 2 nm. The second sublayer 210 can be a porous material. Due to the thin and porous nature of the second sublayer 210, the surface state of the first sublayer 215 can be transferred to the second sublayer 210. That is, when the first sublayer 210 has hydrophobic bonds 214, the second sublayer 215 will also have hydrophobic bonds 212. Similarly, when bonds 214 change to hydrophilic, bonds 212 will also change to hydrophilic.

[0031] In this manner, a combination of first underlayer 215 and second underlayer 210 can be used to provide a patterned stack that allows high adhesion to photoresist 220 at one time and low adhesion to photoresist 220 at a second time. In particular, bonds 212 shown in Figure 2A are hydrophobic (e.g., CH3 and H) and bond strongly to hydrophobic bonds 221 (e.g., CH3) of photoresist 220.

[0032] The dual-underlayer structure is particularly beneficial because it allows the patterning stack to be tailored for both adhesion and scum removal. The second underlayer 210, which directly contacts the photoresist 220, can be precisely tailored for adhesion strength, while the first underlayer 215 can be made of a material that can be easily switched between hydrophobic and hydrophilic properties. Because the second underlayer 210 is relatively thin and porous, changes in the first underlayer 215 easily modify the surface condition of the overlying second underlayer 210. In this way, adhesion to residual scum after photoresist development can be reduced, allowing the scum to be easily removed.

[0033] It should be appreciated that the formation of a dual underlayer architecture is enabled through the use of a dry deposition process. For example, first underlayer 215 and second underlayer 210 may both be formed by a chemical vapor deposition (CVD) process, an atomic layer deposition (ALD) process, or the like. In one embodiment, photoresist 220 may also be formed by a dry deposition process. First underlayer 215, second underlayer 210, and photoresist 220 may be formed in a single deposition chamber in some embodiments.

[0034] 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, the electromagnetic radiation can alter the chemistry of photoresist 220. In some cases, exposure to electromagnetic radiation can also alter the chemistry of one or both of first underlayer 215 and second underlayer 210.

[0035] 2B illustrates a cross-sectional view of device 200, 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 the unexposed regions. In the illustrated embodiment, mask 250 with openings is used to selectively expose regions of photoresist 220. However, it should be understood that electromagnetic radiation may be reflected differently toward selected regions of photoresist 220.

[0036] In one embodiment, first underlayer 215 and second underlayer 210 may also be modified by exposure to electromagnetic radiation 251. For example, exposed region 213 may be provided in second underlayer 210 and exposed region 217 may be provided in first underlayer 215. Although illustrated as being reactive to electromagnetic radiation 251, it should be understood that one or both of first underlayer 215 and second underlayer 210 need not be reactive to electromagnetic radiation 251.

[0037] In one embodiment, exposure to electromagnetic radiation can alter bond layers 214, 211, and 212. As shown in Figure 2B, the exposed portions of the bond are modified with a *. The * indicates that the energy of the bond has increased. This further improves the subsequent reaction to convert the hydrophobic bond to a hydrophilic bond, as described in more detail below.

[0038] FIG. 2C illustrates a cross-sectional view of device 200 after a development process, according to one embodiment. In one embodiment, the development process may remove substantially all of exposed region 222 of photoresist 220. However, scum 223 or other residual portions of photoresist 220 may remain within opening 240. As indicated by the check mark between bond 221 and bond 212, scum 223 remains strongly adhered to second underlayer 210. Due to the strong adhesion between scum 223 and second underlayer 210, removal of scum 223 is difficult. Therefore, pattern transfer to the underlayer may be suboptimal. The development process may be a dry development process or a development process using liquid development chemistry.

[0039] 2D shows a cross-sectional view of device 200 during processing, according to one embodiment. The processing can be exposure to alkaline solution 255. Alkaline solution 255 can be HO or other oxygen-containing chemical. Alkaline solution 255 can react with first underlayer 215. First underlayer 215 can be readily convertible such that exposed regions 217 of bonding layer 216 are converted to OH bonds. Similarly, bonding layer 218 can be converted to OH bonds. Because bonding layers 216 and 218 have the same bond type (i.e., hydrophilic), a strong bond exists between first underlayer 215 and second underlayer 210, as indicated by the check marks.

[0040] Similarly, the bonding layer 219 on the second underlayer 210 can be converted to a hydrophilic bonding type. The bonding layer 219 can be converted by exposure to an alkaline solution 255 and / or by conversion to bonding layers 216 and 218. The propagation of the hydrophilic type bonding through the second underlayer 210 is made possible by the small thickness and porosity of the second underlayer 210. As shown, bonding layer 219 no longer has a strong bond with bonding layer 221 of scum 223, as indicated by the X between the two. This weak bond is formed because scum 223 has a hydrophobic nature (e.g., CH bonds) and second sublayer 210 has a hydrophilic nature (e.g., OH bonds). Scum 223 can now be more easily removed because the adhesion between the two layers is reduced.

[0041] FIG. 2E illustrates a cross-sectional view of device 200 after scum 223 has been removed, according to one embodiment. In the illustrated embodiment, the various layers are in direct contact with one another, and no bonding layers are shown. However, it should be understood that the bonding layers shown in FIG. 2D are still present; they have been omitted for simplicity. As shown, photoresist 220 has clear openings 240 to expose regions 217 and 213 of first underlayer 215 and second underlayer 210, respectively. After scum 223 has been removed, the pattern of openings 240 can be transferred into underlayers 210 and 215, as well as into substrate 201.

[0042] Figure 3 shows a process flow diagram of a process 380 for scum removal, according to one embodiment. The process 380 shown in Figure 3 can be substantially similar to the process described above with reference to Figures 2A-2E.

[0043] In one embodiment, process 380 begins at step 381 with forming a photoresist layer over the first and second underlayers. In one embodiment, the second underlayer is tailored to promote adhesion with the photoresist layer. For example, the photoresist layer and the second underlayer may both have hydrophobic dangling bonds. In one embodiment, the second underlayer may have a small thickness (e.g., at most approximately 10 nm, at most approximately 5 nm, or at most approximately 2 nm). The second underlayer may be porous. Thus, the surface properties of the underlying first underlayer may be propagated to the second underlayer.

[0044] In one embodiment, process 380 may continue with step 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 openings through the photoresist layer.

[0045] In one embodiment, process 380 can continue with step 383, which involves modifying the second underlayer to reduce adhesion to residual scum on the second underlayer. In one embodiment, the modification can be a treatment. This treatment can be exposure of the first and second underlayers to an alkaline solution. The first underlayer can readily react with the alkaline solution to form O-H bonds. The surface chemistry of the first underlayer can be propagated to the second underlayer through the thin and porous second underlayer. In another embodiment, the alkaline solution can directly alter the chemistry of the bonds on the second underlayer. As a result of the modification, the surface chemistry of the second underlayer is converted from hydrophobic to hydrophilic. Therefore, the scum (which is hydrophobic) now has a weaker bond to the second underlayer.

[0046] In one embodiment, process 380 may continue at step 384, which includes removing the scum from the second underlayer. Because the adhesion between the scum and the second underlayer is reduced, the scum may be more easily removed. For example, a rinsing process or the like may be used to remove the scum. After the scum is removed, the pattern in the photoresist layer may be transferred into the underlayer and the underlying substrate.

[0047] 4A and 4B show a pair of cross-sectional schematic views of a device 400 including treatment of the underlying layers to remove scum, according to one embodiment.

[0048] 4A shows a cross-sectional view of device 400. Device 400 may include a substrate 401. Substrate 401 may be similar to any of the substrate architectures described in more detail above. In one embodiment, an underlayer 410 may be provided on substrate 401. Photoresist 420 may be provided on underlayer 410. While shown spaced apart from underlayer 410, it should be understood that photoresist 420 may reside directly on underlayer 410. The spaced apart location is intended to illustrate the presence of binding chemistry 418.

[0049] In one embodiment, underlayer 410 can include bonding chemistry 418 including an amorphous SiC:H composition. The SiC:H composition can be doped with one or more doping atoms. The doping atoms can include Si, Ge, B, or P, among others. The doping elements are selected to readily react with water in alkaline solutions to form O-H bonds. In FIG. 4A , the doping atoms are represented by X in bonding chemistry 418. As shown, the bonding chemistry includes H and C-H bonds, which provide a hydrophobic surface for underlayer 410. Photoresist bonding chemistry 425 can be an organic compound, which also provides a hydrophobic surface. The matching hydrophobic surfaces result in strong adhesion between underlayer 410 and photoresist 420.

[0050] 4B shows a cross-sectional view of device 400 after exposure, development, and processing, according to one embodiment. Exposure and development can form openings 440 through photoresist 420. Residual scum can be removed from openings 440 by using a process that converts the exposed portions of the underlying layer to a hydrophilic surface. In particular, an alkaline solution is applied, and water readily reacts with the dopants to form O-H bonds on the surface of the underlying layer. Because this surface is converted to a hydrophilic surface, the underlying layer 410 no longer adheres strongly to the scum. This allows the scum to be easily removed (e.g., by a rinsing process).

[0051] 5A-5B show a pair of cross-sectional views illustrating the patterned stacks of device 500, according to one embodiment. In the embodiment shown in FIG. 5A, device 500 includes substrate 501 having stacks 561 and 562. Substrate 501 may be similar to any of the substrates described in more detail above. In one embodiment, stacks 561 and 562 may include any suitable material. In particular, layer 562 may be a low absorption layer. Low absorption layer 562 may include SiCH and have C(H) bonds. The chemistry of low absorption layer 562 may be selected to minimize absorption of EUV radiation.

[0052] 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 at most approximately 10 nm, at most approximately 5 nm, or at most approximately 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-bonds. The photoresist layer 520 may have an opening 540. The photoresist layer 520 may also have a hydrophobic surface that promotes bonding to the adhesion layer 510.

[0053] 5B shows a cross-sectional view of device 500 without adhesion layer 510, according to one embodiment. In one embodiment, adhesion layer 510 can be removed when low absorption layer 562 has sufficient adhesion strength with the overlying photoresist layer 520.

[0054] 6A-6B show a pair of cross-sectional views illustrating a patterned stack according to an alternative embodiment. The embodiment shown in Figures 6A and 6B can utilize any of the adhesion and release properties or systems described in more detail herein. That is, the embodiment allows for strong initial adhesion between the photoresist layer and subsequently allows for reduced adhesion strength to allow for improved scum removal.

[0055] 6A illustrates a cross-sectional view of a device 600 according to one embodiment. In one embodiment, the device 600 may include a substrate 601. The substrate 601 may include a layer that is patterned using a lithographic process. The substrate 601 may include a material that is typically patterned to form structures in a semiconductor device; for example, the substrate 601 may include a semiconductor material (e.g., silicon), a metal layer, a dielectric layer, or an insulating layer. In some embodiments, the substrate 601 may also include layers that aid in the transfer of a pattern to the substrate 601. For example, the additional layers may include a hard mask layer, an ARC, etc.

[0056] In one embodiment, a patterned stack may be provided over the substrate 601. The patterned stack may include multiple 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 species (e.g., silicon, germanium, boron, phosphorus, iodine, and / or hydrogen) may be implanted into one or more of the layers 671-673 to alter different properties, such as adhesion strength and chemical reactivity. A photoresist layer 620 may be provided over the patterned stack. Photoresist layer 620 can be a metal-oxide resist (MOR) or a chemically amplified resist (CAR).

[0057] In certain embodiments, device 600 may include a stack having the following material layers: In one embodiment, first layer 671 may include an oxide, such as silicon oxide. First layer 671 may have a thickness of up to approximately 100 nm. For example, first layer 671 may have a thickness of approximately 50 nm or less. In one embodiment, second layer 672 may include an amorphous silicon layer. The amorphous silicon layer may be formed by any suitable deposition process, such as plasma-enhanced chemical vapor deposition (PECVD). Second layer 672 may have a thickness of up to approximately 50 nm, in some embodiments. In certain embodiments, second layer 672 may have a thickness of approximately 20 nm or less. In one embodiment, third layer 673 may include a layer of carbon, such as a CVD carbon layer. Third layer 673 may have a thickness of up to approximately 50 nm. For example, third layer 673 may have a thickness of approximately 30 nm or less.

[0058] In yet another embodiment, the patterned stack can have the following material layers: In one embodiment, the first layer 671 can include silicon, oxygen, and nitrogen. For example, the first layer 671 can include SiON in some embodiments. The second layer 672 can include silicon, oxygen, and hydrogen. In one embodiment, the third layer 673 can include the same elements as the first layer 671. In certain embodiments described herein, the third layer 673 can include silicon, oxygen, and nitrogen (e.g., SiON). The first layer 671, the second layer 672, and the third layer 673 can have thicknesses of less than approximately 1,000 Å. For example, the first layer 671 can have a thickness of up to approximately 350 Å, the second layer 672 can have a thickness of up to approximately 450 Å, and the third layer 673 can have a thickness of up to approximately 250 Å.

[0059] In yet another embodiment, the patterned stack may be configured as follows: The first layer 671 may include an oxide, such as one containing silicon and oxygen (e.g., SiO2). 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 underlayer material. For example, the third layer may include silicon, carbon, and hydrogen (e.g., SiCH), HMDS, or 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.

[0060] In yet another embodiment, the patterning stack can include an additional interfacial layer (not shown) between the substrate 601 and the first layer 671. For example, the interfacial layer can be considered an adhesion layer, a hard mask layer, or the like. In some embodiments, the interfacial layer can include titanium and nitrogen. For example, the interfacial layer can include TiN in some embodiments.

[0061] FIG. 6B illustrates a cross-sectional view of a device 600 according to a further embodiment. The device 600 of FIG. 6B is substantially similar to the device 600 of FIG. 6A, with the addition of an antireflective coating (ARC) 675 on the third layer 673. The ARC 675 can be one or more suitable ARC materials. For example, the ARC can include one or both of a dielectric ARC (DARC) or a bottom layer ARC (BARC). That is, in some embodiments, the ARC 675 can include at least two separate layers. The ARC 675 can have a thickness of up to approximately 40 nm in some embodiments. In certain embodiments, the ARC 675 can have a thickness of up to approximately 20 nm.

[0062] 7 illustrates a schematic diagram of an exemplary form of a machine within 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 in the capacity of a server or client machine in a client-server network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. The machine may be a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile phone, a web appliance, a server, a network router, switch, or bridge, or any machine capable of executing a set of instructions (sequential or otherwise) that specify operations to be performed by the machine. Additionally, although a single machine is shown, the term "machine" should also be construed to include any collection of machines (e.g., computers) that individually or together execute a set of instructions (or multiple sets of instructions) to perform any one or more of the methodologies described herein.

[0063] 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 a secondary memory 718 (e.g., a data storage device), which communicate with each other via a bus 730.

[0064] Processor 702 represents one or more general-purpose processing devices, such as a microprocessor or central processing unit. 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 other instruction sets, 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), or a network processor. Processor 702 is configured to execute processing logic 726 for performing the operations described herein.

[0065] The computer system 700 may further include a network interface device 708. The computer system 700 may also 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).

[0066] The secondary memory 718 may include a machine-accessible storage medium (or specifically a computer-readable storage medium) 731 that stores one or more sets of instructions (e.g., software 722) that embody any one or more of the methods or functions described herein. The software 722 may reside, completely or at least partially, within the main memory 704 and processor 702, which also constitute machine-readable storage media, while being executed by the computer system 700. This software 722 may also be transmitted or received over a network 720 via the network interface device 708.

[0067] Although machine-accessible storage medium 732 is shown as a single medium in an exemplary embodiment, the term "machine-readable storage medium" should be interpreted to include single or multiple media (e.g., a centralized or distributed database, and / or its associated caches and servers) that store one or more sets of instructions. The term "machine-readable storage medium" should also be interpreted to include any medium that can store or encode a set of instructions that are executed by a machine, causing the machine to perform any one or more of the methodologies of the present disclosure. Accordingly, the term "machine-readable storage medium" should be interpreted to include, but is not limited to, solid-state memory, and optical and magnetic media.

[0068] According to an embodiment of the present disclosure, a machine-accessible storage medium stores instructions that cause a data processing system to perform a method of providing a photoresist stack having a first underlayer and a second underlayer. In one embodiment, the second underlayer is less than 5 nm thick and is tailored for high adhesion strength with the overlying photoresist layer. After patterning, the first and second underlayers are treated with an alkaline solution containing water. The solution converts the hydrophobic surfaces of the first and second underlayers to hydrophilic surfaces that have reduced bonding strength with the photoresist layer. Any scum can then be easily rinsed from the stack.

[0069] Thus, a method for forming a photoresist stack with high adhesion and improved scum removal has been disclosed.

Claims

1. 1. A method of developing a patterned stack, comprising: providing a patterned stack including an underlayer and a photoresist on the underlayer, the underlayer having a first adhesion strength with the photoresist; exposing the photoresist to electromagnetic radiation and developing it with a developer, wherein scum remains on the surface of the underlying layer; treating the underlayer so that the underlayer has a second adhesive strength with the scum; removing the scum; A method comprising:

2. The method of claim 1 , wherein the underlayer is hydrophobic before the treatment and hydrophilic after the treatment.

3. The underlayer may be H-terminated and CH-terminated prior to the treatment. ３ The method of claim 1 , including termination.

4. The method of claim 3 , wherein the underlayer comprises OH terminations after the treatment.

5. The method of claim 1 , wherein the treatment is exposure to an alkaline solution.

6. The method of claim 1 , wherein the underlayer has a thickness of at most approximately 5 nm.

7. The method of claim 6 further comprising a second underlayer below the underlayer.

8. The method of claim 6 , wherein the second underlayer is more reactive to the treatment than the underlayer.

9. The method of claim 1 , wherein the underlayer comprises an amorphous SiC:H material.

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

11. 11. The method of claim 10, wherein the one or more of Ge, B, and P react more readily with the treatment to form O-H bonds compared to the SiC:H.

12. 1. A method of patterning a substrate, comprising: providing a patterning stack over the substrate, the patterning stack comprising: A first lower layer, a second sublayer over the first sublayer; and a photoresist on the second underlayer providing a patterned stack comprising: exposing the patterned stack to electromagnetic radiation; developing the photoresist in the patterned stack; modifying the second underlayer to reduce its adhesive strength to the photoresist; removing any scum on said second sublayer; A method comprising:

13. The method of claim 12 , wherein the second underlayer has a thickness of at most approximately 5 nm.

14. The method of claim 13 , wherein the second underlayer is porous.

15. The method of claim 12 , wherein the second underlayer has a hydrophobic surface before modification and a hydrophilic surface after modification.

16. The method of claim 12 , wherein modifying the second sublayer comprises exposing the first sublayer and the second sublayer to an alkaline solution.

17. The method of claim 12 wherein the photoresist is a CAR.

18. A first lower layer, a second sublayer over the first sublayer, the second sublayer having a hydrophobic surface; and a photoresist on the second underlayer having a hydrophobic surface; A patterned stack comprising:

19. 20. The patterned stack of claim 18, wherein the second underlayer is converted to a hydrophilic surface after exposure to an alkaline solution.

20. a first layer comprising one or more of silicon, oxygen, hydrogen, nitrogen, and carbon; a second layer on the first layer comprising one or more of silicon, amorphous silicon, oxygen, hydrogen, and nitrogen; a third layer on the second layer comprising carbon; and a photoresist on the third layer that is a metal-oxide resist (MOR) or a chemically amplified resist (CAR); A patterned stack comprising:

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