Patent ID: 12261049

DETAILED DESCRIPTION

Polymer films may be used in semiconductor device manufacturing for a number of structures and processes, including as a mask material, an etch resistant material, and a trench fill material, among other applications. More specific examples of applications for polymer films include the formation of hot implant hardmasks, metal gate (MG)-cut hardmasks, MG fabrication, and reverse tone patterning, among others. The present disclosure includes the formation of the polymer films on semiconductor substrates using molecular layer deposition (MLD).

Embodiments disclosed herein describe a method for selectively cleaning and/or selectively etching a substrate. The method for cleaning/etching a substrate may include placing a substrate into a chamber, where the substrate may include a layer including at least one trench formed therein, the at least one trench having a top surface, a bottom surface and at least one side wall. The method for etching may include depositing a polymer film on the bottom surface of the at least one trench without depositing the polymer film on the at least one side wall of the at least trench. The method may further include selectively forming a blocking film on the layer without forming the blocking film on the polymer film. The blocking film may be formed, for example, using a self-assembled monolayer (SAM) deposition technique. The method may further include removing the polymer film from the bottom surface of the at least one trench and etching the bottom surface of the trench using an etch chemistry, wherein the blocking film protects the at least one side wall from the etch chemistry.

By using different films to selectively coat one or more portions of the substrate, the profile of the substrate may be improved and blowouts of critical dimension of the trench may be improved. It has been found that using a self-assembled monolayer (SAM) blocks and/or protects a surface from being etched. By selectively protecting a surface from being etched, this allows for removal of material (e.g., such as any oxidized surfaces) in selective regions of the trench while avoiding a blowout of a critical dimension (e.g., such as a trench width or cross-sectional profile). The inventors have found that the bottom surfaces of trenches in a substrate often are oxidized, which is generally detrimental to performance in the final product. To remove oxidized surfaces, an etching process step may be performed. However, at this stage, not every surface needs to be etched, as it could affect a profile of the substrate (e.g., of trenches formed in or on the substrate).

Therefore, the SAM may be formed on a top surface, a side surface, or a combination thereof to protect these surfaces from etching. The inventors have found that depositing a polymer film on the bottom surface of the trench prevents the SAM from forming on the bottom surface, such that SAM is formed on the top surface, a side wall surface, or combination thereof. The SAM consists of an ordered arrangement of spontaneously assembled organic molecules adsorbed on a surface in embodiments. These molecules typically comprise of one or more moieties with an affinity for the substrate (head group) and a relatively long, inert, linear

In embodiments, a flowable polymer is deposited on the substrate, where the flowable polymer does not adhere to sidewalls of trenches, and instead pools at bottoms of the trenches. The flowable polymer may set or harden on the bottom of the surface of the trenches without forming on the sidewalls of the trenches. The SAM may then not adhere to the polymer that has been selectively deposited in the bottom of the trenches. Therefore after the SAM is selectively formed (e.g., everywhere except for on the polymer at the bottom of the trenches), the polymer film at the bottom of the trenches may be removed. An etch chemistry may then selectively etch an oxide on the bottom surface of the trench and/or etch the bottom surface of the trench at a much higher rate than the etch chemistry etches the SAM. Accordingly, the SAM protects the sidewalls and/or tops of the trenches from etching and the etching may be selectively performed on the bottom surfaces of the trenches.

By selectively etching or cleaning the surfaces of the trenches of the substrate without etching other surfaces of the trenches, it was found to produce lower variability in trench width across a depth of trenches in etched samples (i.e., substrates) when compared to traditional plasma etch processes. Thus, the inventors have found a method to selectively clean or etch the bottom surface of a trench without or with little etching of tops and/or sidewalls of the trenches.

In embodiments, the SAM may be selectively formed on the surfaces other than on the polymer film because the SAM and polymer film have different chemical reactivity. Therefore, the SAM may react with the surfaces that do not have a polymer film on them according to aspects of the present disclosure.

Disclosed herein are embodiments of a method for selectively cleaning or etching a substrate including depositing a polymer film and selectively forming a second film on the substrate. The polymer film is then removed and the substrate is etched until a target amount of the substrate has been etched. The polymer film may be deposited on a bottom surface of at least one trench of a substrate such that when the second film is formed on the substrate it does not form on the bottom surface because of the polymer film. It has been found that the polymer film and second film may have different chemical reactivity to control the selectivity on which the films are deposited and/or formed.

As used herein, the term “substrate” refers to a surface, or portion of a surface, upon which a process acts. It will also be understood by those skilled in the art that reference to a substrate can also refer to only a portion of the substrate, unless the context clearly indicates otherwise. Additionally, reference to depositing on a substrate can mean both a bare substrate and a substrate with one or more films or features deposited or formed thereon.

A substrate as used herein may also refer to any substrate or material surface formed on a substrate upon which film processing is performed during a fabrication process. For example, a substrate surface on which processing can be performed include materials such as silicon, silicon oxide, strained silicon, silicon on insulator (SOI), carbon doped silicon oxides, silicon nitride, doped silicon, silicon germanium, and any other materials such as metals, metal nitrides, metal alloys, and other conductive materials, depending on the application. Substrates include, without limitation, semiconductor wafers.

Substrates may be exposed to a pretreatment process to polish, etch, reduce, oxidize, hydroxylate (or otherwise generate or graft target chemical moieties to impart chemical functionality), anneal and/or bake the substrate surface. In addition to film processing directly on the surface of the substrate itself, in the present disclosure, any of the film processing steps disclosed may also be performed on an underlayer formed on the substrate as disclosed in more detail below, and the term “substrate surface” is intended to include such underlayer as the context indicates. Thus for example, where a film/layer or partial film/layer has been deposited onto a substrate surface, the exposed surface of the newly deposited film/layer becomes the substrate surface. What a given substrate surface comprises will depend on what films are to be deposited, as well as the particular chemistry used. In one or more embodiments, the first substrate surface may comprise a metal, metal oxide, or H-terminated SixGe1-x, and the second substrate surface may comprise a Si-containing dielectric, or vice versa. In some embodiments, a substrate surface may comprise certain functionality (e.g., —OH, —NH, etc.).

Referring now to the figures,FIG.1is a sectional view of a processing chamber100(e.g., a semiconductor processing chamber) having one or more chamber components in accordance with embodiments of the present disclosure. The processing chamber100may be used for processes in which a corrosive plasma environment and/or corrosive chemistry is provided. For example, the processing chamber100may be a chamber for a plasma etch reactor (also known as a plasma etcher). Examples of chamber components that may be exposed to plasma in the processing chamber100are a substrate support assembly148, an electrostatic chuck (ESC), a ring (e.g., a process kit ring or single ring), a chamber wall, a base, a showerhead130, a gas distribution plate, a liner, a liner kit, a shield, a plasma screen, a flow equalizer, a cooling base, a chamber viewport, a chamber lid, a nozzle, process kit rings, and so on. In embodiments, processing chamber100is used to perform an etch process on a patterned substrate that includes a plurality of trenches formed thereon.

In one embodiment, the processing chamber100includes a chamber body102and a showerhead130that enclose an interior volume106. The showerhead130may or may not include a gas distribution plate. For example, the showerhead may be a multi-piece showerhead that includes a showerhead base and a showerhead gas distribution plate bonded to the showerhead base. Alternatively, the showerhead130may be replaced by a lid and a nozzle in some embodiments, or by multiple pie shaped showerhead compartments and plasma generation units in other embodiments. The chamber body102may be fabricated from aluminum, stainless steel or other suitable material. The chamber body102generally includes sidewalls108and a bottom110. Any of the showerhead130(or lid and/or nozzle), sidewalls108and/or bottom110may include the multi-layer plasma resistant coating.

An outer liner116may be disposed adjacent the sidewalls108to protect the chamber body102. The outer liner116may be a halogen-containing gas resist material such as Al2O3or Y2O3. The outer liner116may be coated with the multi-layer plasma resistant ceramic coating in some embodiments.

An exhaust port126may be defined in the chamber body102, and may couple the interior volume106to a pump system128. The pump system128may include one or more pumps and throttle valves utilized to evacuate and regulate the pressure of the interior volume106of the processing chamber100.

The showerhead130may be supported on the sidewalls108of the chamber body102and/or on a top portion of the chamber body. The showerhead130(or lid) may be opened to allow access to the interior volume106of the processing chamber100, and may provide a seal for the processing chamber100while closed. A gas panel158may be coupled to the processing chamber100to provide process and/or carrier gases to the interior volume106through the showerhead130or lid and nozzle. Examples of process gas that may be delivered by the gas panel158and used to process substrates/samples in the processing chamber100include a silicon containing gas, halogen-containing gases, such as C2F6, SF6, HBr, NF3, CF4, CHF3, CH2F3, F, NF3, Cl2, CCl4, BCl3and SiF4, among others, and other gases such as O2or N2O. Examples of carrier gases (also referred to herein as a diluent) include N2, He, Ar, and other gases inert to process gases (e.g., non-reactive gases). The showerhead130includes multiple gas delivery holes132throughout the showerhead130. The showerhead130may be or may include aluminum, anodized aluminum, an aluminum alloy (e.g., Al 6061), or an anodized aluminum alloy. In some embodiments, the showerhead includes a gas distribution plate (GDP) bonded to the showerhead. The GDP may be, for example, Si or SiC. The GDP may additionally include multiple holes that line up with the holes in the showerhead.

A substrate support assembly148is disposed in the interior volume106of the processing chamber100below the showerhead130. The substrate support assembly148holds a substrate144(e.g., a wafer) during processing. The substrate support assembly148may include an electrostatic chuck that secures the substrate144during processing, a metal cooling plate bonded to the electrostatic chuck, and/or one or more additional components. An inner liner may cover a periphery of the substrate support assembly148. The inner liner may be a halogen-containing gas resist material such as Al2O3or Y2O3. The substrate support assembly, portions of the substrate support assembly, and/or the inner liner may be coated with the metal layer and barrier layer in some embodiments.

The processing chamber100may be an etch chamber. In embodiments, the etch process is performed to selectively etch films disposed on surfaces of the substrate144. For example, the substrate144may be a semiconductor wafer, a glass plate, a SiGe wafer, or another type of substrate. In one embodiment, the films disposed on the substrate144include a polymer film and a self-assembled monolayer. The substrate144may further include silicon (Si).

FIG.2Adisplays a sectional view of an article200including a substrate206. In some embodiments, the article200may have a stack of layers (e.g., alternating layers of two or more materials). The stack of layers may include a stack of silicon (Si) layers, silicon germanium (SiGe) layers, silicon nitride (SiN) layers, silicon dioxide (SiO2) layers, and so on. In embodiments, the stacks include stacks of alternating layers of two or more of the aforementioned materials (e.g., alternating stacks of Si and SiGe, alternating stacks of Si and SiO2, and so on). In one embodiment, article200corresponds to substrate144ofFIG.1. The substrate206includes Si layers260a-fdisposed thereon in a stack290. The Si layers260a-fmay be in the form of nanosheets (e.g., layers having thicknesses on the scale of nm) in some embodiments. In one embodiment, all of the Si layers260a-fhave approximately the same thickness. Alternatively, different Si layers260a-fmay have different thicknesses.

A pattern mask280(also referred to as an etch mask) may cover a top layer260ain the stack290. The pattern mask280may be a soft mask or a hard mask. Some hard masks that may be used include a polysilicon hard mask and a metal hard mask such as a tungsten hard mask or a titanium nitride hard mask. Pattern mask280includes open areas270which expose underlying layers to etch chemicals during etching processes. The pattern mask280additionally includes covered regions that protect underlying layers from etch chemicals. Regions of the stack290under the open areas270that are not protected by the pattern mask280may undergo an etching process.

The article200can be etched through the pattern mask280to create cavities or trenches having approximately the shape of the openings in the pattern mask280. Etchants will typically also etch the pattern mask280at some etch rate.

FIG.2Bshows a sectional view of an article204including the substrate206having the stack of layers260a-fthat has undergone an etch process. The etch process may be any etching process used in the art, including chemical etching. The chemical etching may include forming ammonium fluoride salt using ammonia and hydrofluoric acid. Other chemical etching may include, but are not limited to, using ammonia and water, NHF, NH4F, hydrogen fluoride, or hydrogen chloride. The process has etched a cavity400(e.g., a trench) in the layers260a-f. In one embodiment, the cavity400has a tapered cross sectional shape in which a bottom of the cavity is slightly narrower than a top of the cavity, having a U-profile. Notably, the sidewalls of trenches or holes formed from the etching process set forth in embodiments herein are nearly vertical, as opposed to sidewalls produced by prior etching processes.

In embodiments, a native oxide may form on a bottom of the trenches. In order to remove the native oxide, one or more etch or clean processes may be performed. However, these etch or clean processes may also etch sidewalls of the trench, which may change a profile of the trench. Additionally, or alternatively, after the trenches are formed, further processes may be performed to etch the substrate206that may be exposed at a bottom of the trenches. However, etching the trench bottom (e.g., the substrate206) may also cause etching of the sidewalls of the trenches, again changing the profile of the trench walls. This may affect a critical dimension of manufactured devices. Embodiments described herein enable the bottom of the trench to be cleaned or etched without negatively impacting the profile or critical dimensions of devices (e.g., of the trenches).

In embodiments, the bottom of the trench is cleaned and/or etched using a process that includes depositing a flowable film on a bottom of the trench without depositing the flowable film on sidewalls of the trench. The flowable film may be, for example, a liquid flowable chemical vapor deposition (CVD) film. A liquid flowable CVD film may be used to fill or partially fill trenches with up to 30:1 aspect ratios. In embodiments, the flowable film lacks carbon in the film, which hampers transistor isolation and causes voltage shifts and leakage. The flowable film may be formed by depositing a liquid precursor that flows to low points, and then reacting the liquid precursor with one or more other materials to form a film.

In other embodiments, the flowable film may be formed by introducing a reactant and a precursor into a chamber, such that the reactants are present in the chamber in the vapor phase and form a flowable film. Thus, the flowable film by flowed into the trenches and deposited at the bottom of the trenches.

Subsequent to formation of the flowable film, a self-assembled monolayer (SAM) is formed. The SAM may not form on the flowable film, but may form on other exposed surfaces. Accordingly, in embodiments the SAM may form everywhere except on the flowable film at the bottom of the trenches. After the SAM is formed, the flowable film may be removed from the bottom of the trenches. An etch process may then be performed, where the etch process may have a high selectivity of a material at a bottom of the trenches (e.g., Si or a native oxide such as SiO2) over the SAM.

FIG.3illustrates a process for forming a self-assembled monolayer (SAM) on a surface305of a substrate310. Substrate310may represent, for example, a semiconductor wafer with one or more trenches formed thereon (e.g., trenches formed from stacks of alternating materials such as Si and SiO2). As understood in the art, SAM may be organic molecules, where the molecules are formed spontaneously on surfaces by adsorption and are organized into more or less large ordered domains. In some embodiments, the molecules that form the SAM do not interact strongly with the substrate. In other embodiments, the molecules may possess a head group that has a strong affinity to the substrate and anchors the molecule to it. The article310and surface305may be made from, for example, Si, SiO2, SiG, SiN, or any other material or combination of materials.

Each individual chemical reaction between a precursor and the surface is known as a “half-reaction.” During each half reaction, a precursor is pulsed onto the surface for a period of time sufficient to allow the precursor to fully react with the surface. The reaction is self-limiting as the precursor will only react with a finite number of available reactive sites on the surface, forming a uniform continuous adsorption layer on the surface. Any sites that have already reacted with a precursor will become unavailable for further reaction with the same precursor unless and/or until the reacted sites are subjected to a treatment that will form new reactive sites on the uniform continuous coating. Exemplary treatments may be plasma treatment, treatment by exposing the uniform continuous adsorption layer to radicals, or introduction of a different precursor able to react with the most recent uniform continuous film layer adsorbed to the surface.

InFIG.3, substrate310having surface305may be introduced to a first precursor360for a first duration until a first half reaction of the first precursor360with surface305partially forms layer315by forming an adsorption layer314. In embodiments, the adsorption layer314does not form on a flowable film that may have been deposited on one or more portions of the surface305(e.g., at a bottom of trenches formed on the surface305). Subsequently, article310may be introduced to a second precursor365(also referred to as a reactant) to cause a second half reaction to react with the adsorption layer314and fully form the layer315. Layer315may be uniform, continuous and conformal. The substrate310may alternately be exposed to the first precursor360and second precursor365up to x number of times to achieve a target thickness for the layer315. X may be an integer from1to100, for example.

The surface reactions (e.g., half-reactions) are done sequentially. Prior to introduction of a new precursor, the chamber in which the ALD or MLD process takes place may be purged with an inert carrier gas (such as nitrogen or air) to remove any unreacted precursor and/or surface-precursor reaction byproducts. At least two precursors may be used in embodiments. In some embodiments, more than two precursors may be used to grow film layers having the same composition (e.g., to grow multiple layers of SAM on top of each other). In other embodiments, different precursors may be used to grow different film layers having different compositions.

ALD or MLD processes may be conducted at various temperatures depending on the type of ALD or MLD process. The optimal temperature range for a particular ALD or MLD process is referred to as the “ALD temperature window” or “MLD temperature window.” Temperatures below the temperature window may result in poor growth rates and non-ALD type deposition. Temperatures above the temperature window may result in thermal decomposition of the article or rapid desorption of the precursor. The temperature window may range from about 20° C. to about 400° C. In some embodiments, the MLD temperature window is between about 200-350° C.

The ALD/MLD process allows for conformal film layers having uniform film thickness on articles and surfaces having complex geometric shapes, holes with large aspect ratios, and three-dimensional structures. Sufficient exposure time of the precursor to the surface enables the precursor to disperse and fully react with the surface in its entirety, including all of its three-dimensional complex features. The exposure time utilized to obtain conformal ALD in high aspect ratio structures is proportionate to the square of the aspect ratio and can be predicted using modeling techniques. Additionally, the ALD technique is advantageous over other commonly used coating techniques because it allows in-situ on demand material synthesis of a particular composition or formulation without the need for a lengthy and difficult fabrication of source materials (such as powder feedstock and sintered targets).

With the ALD/MLD technique, films such as self-assembled monolayers (SAMs) may be grown, for example, by proper sequencing of the precursors.

In previous embodiments, chemical passivation or directional etching was used to selectively etch the bottom surface of a trench and not etch the side walls.

FIG.4is a flow chart representing a method400of selectively etching or cleaning a substrate according to an embodiment of the present disclosure. In the method400, at block401, a substrate is received that has already been patterned. The substrate may be patterned to have at least one trench. The at least one trench may have a top surface, at least one side wall surface and a bottom surface. For example, the substrate may have a trench as show inFIG.5. InFIG.5, a substrate507is formed having a trench508in block501. The substrate507may include silicon. The trench508has a top surface511, at least one side wall509and a bottom surface510. The bottom surface510may have an epitaxial silicon oxide (epi) layer510athat formed during formation of the trench508or afterwards. The at least one side wall509in some embodiments has a layer509a, that is different from the epi layer510a, formed on the side wall509. The layer509amay include silicon nitride (SiN) in one embodiment. In other embodiments, the layer509amay be silicon, damaged silicon nitride, silicon oxide, or low κ material. As understood herein, the term “low κ material” refers to a material with a small relative dielectric constant (κ, kappa) relative to silicon dioxide. The method400of the present disclosure allows for the epi layer or another layer at the bottom of the trench508to be removed without etching the sidewall509.

Referring back toFIG.4, after receiving the patterned substrate, a polymer film is deposited to the bottom surface of the at least one trench of the substrate. This can be seen in502ofFIG.5. In block502, a polymer film512is deposited onto the bottom surface. The polymer film512may be deposited using capillary action. By using capillary action, low vapor pressure and low reactivity is beneficial. Further, to use capillary action, the chamber should be below the boiling point of the polymer film512so that the polymer film512may condense in the bottom of the trench. The polymer film312may be deposited to a target height of the trench308. The target height may be about 1 nm to about 100 nm, about 10 nm to about 90 nm, about 20 nm to about 80 nm, about 30 nm to about 70 nm, about 40 to about 60 nm, or about 45 nm to about 55 nm. The polymer film512may be deposited by flowing the film to the bottom surface510of the trench.

In embodiments, the polymer film512is formed via a flowable film deposition process, such as flowable CVD. In such a process, a liquid precursor may be deposited on the substrate, which may flow to low points (e.g., bottoms of trenches) in the substrate.

In some embodiments, the polymer film512may include a carbon-based compound. The carbon-based compound may include a material, or may be formed from a precursor, selected from Formula A.

wherein, Formula A includes two reactive groups “—Y” arranged in the para position around a central aromatic ring. In one embodiment, —Y groups may include a hydroxide group, an aldehyde group, a ketone group, an acid group, an amino group, an isocyanate group, a thiocyanate group, or an acyl chloride group, among other reactive groups. In other embodiments, there may be two or more —Y groups, three or more —Y groups, four or more —Y groups, five or more —Y groups etc. that are arranged around the aromatic ring. Additional embodiments may also include each —Y group being the same reactive group, at least two —Y groups being different reactive groups, and all —Y groups being different reactive groups, among other combinations of —Y groups in the carbon-based compound and/or a precursor. Specific examples of the carbon-based compound or precursor include hydroquinone, terephthalaldehyde, terephthaloyl chloride, and p-phenylenediamine, among others.

In some embodiments, the polymer film512may include a material, or may be formed from a precursor, selected from Formula 1 and 2, which may be alternatively pulsed to a chamber using a MLD process as described inFIG.3. The MLD temperature window may be less than 150° C.

In embodiments, Formula 1 may be:

wherein R may be H, an alkyl group, or an aryl group and R′ may be Cl, Br, I OR, OH, H NR2, Si(NCO)4, Si(NCS)4, or

wherein R may be H, an alkyl group, or an aryl group and R′ may be Cl, Br, I OR, OH, H NR2.

In embodiments, Formula 2 may be

wherein, R, R′, and R″ may each independently may be H, an alkyl group or an aryl group; or

wherein, R, R′, and R″ may each independently may be H, an alkyl group or an aryl group.

In some embodiments, the polymer film512may be terephthalaldehyde. It has been found that terephthalaldehyde may be effective by itself, without an amine, by tuning the pulse process, such as by tuning the temperature of the pulse process.

In some embodiments, the polymer film512may be a flowable film that flows to the bottom surface510of the trench508during depositing of the polymer film512in block502. The depositing of the polymer film512may occur at a temperature in a target temperature range. The target temperature range may be about 0° C. to about 400° C., about 25° C. to about 300° C., about 50° C. to about 250° C., or about 75° C. to about 200° C., or about 200° C. to about 400° C., about 100° C. to about 300° C., or any value or sub range not disclosed herein. The polymer film512flows to the bottom surface510of the trench508without sticking to the side walls509.

During depositing of the polymer film512, a purge gas may also be applied. The purge gas may be any inert gas, such as nitrogen, argon or helium. The depositing of the polymer film may be performed using a molecular layer deposition (MLD) or chemical vapor deposition (CVD) process in embodiments.

Referring back toFIG.4, after the polymer film is deposited to the bottom surface of the trench, a second film is selectively formed on a layer of the substrate. The second film may be a blocking film. The second film is selectively formed on a layer of the substrate without forming the second film on the polymer film in block403. That is, the second film may be formed on the top surface of the at least one trench, on at least one side wall of the at least one trench, or a combination of both. This can be seen in block503ofFIG.5. As can be seen inFIG.5, a second film513, i.e. a blocking film, is formed on layer509aof the substrate. The second film513may include a self-assembled monolayer (SAM) that does not form on the polymer film512. In embodiments, the second film513is formed using an ALD or MLD process, such as is described with reference toFIG.3. In other embodiments, the second film513may be formed using chemical passivation.

The second film513may include at least one of a silyl amide, a silyl halide, a silyl alkoxide or a cyclic silylamide in embodiments. The silyl amide is a compound according to Formula III, the silyl halide is a compound according to Formula IV, the silyl alkoxide is a compound according to Formula V, and the cyclic silylamide is a compound having a C3-C8ring.
RnSi(NR′2)(4-n)Formula IIIwherein in Formula III, R is each independently a C1-C18alkyl group, a C1-C18alkene group, a C1-C18alkyne group, a C1-C18aliphatic group, or a C1-C18aromatic and n=1-3;
RnSiX(4-n)Formula IVwherein in Formula IV, R is each independently a C1-C18alkyl group, a C1-C18alkene group, a C1-C18alkyne group, a C1-C18aliphatic group, a C1-C18aromatic,X is Cl, F, Br or I and n=1-3; and
RnSi(OR′)(4-n)Formula Vwherein in Formula V, R is each independently a C1-C18alkyl group, a C1-C18alkene group, a C1-C18alkyne group, a C1-C18aliphatic group, or a C1-C18aromatic and n=1-3.

In some embodiments, a silyl amide may be used for SiO functionalization of a surface. In other embodiments, an aldehyde may be used as the second film if SiN functionalization may be used. In yet another embodiment, silylchlorides may be used for functionalization of both SiN and SiO.

The second film513may be selectively formed on the surfaces of the trench508without forming on the polymer film on the bottom of the trench. As illustrated in block503, the second film513is selectively formed on the top surface511and side wall509of the trench508without forming on the polymer film512. Alternatively, the second film513may be selectively formed on only the side walls509of the trench508.

In an alternative embodiment, forming the second film513may be repeated as there is a selectivity window of the second film material and to ensure that the side wall surface is fully or nearly fully covered with the SAM. That is, there may be gaps when applying the second film513, or SAM on the side walls, depending on the chemical used, so multiple cycles may be performed. Thus, the second film513or SAM has selectivity such that it only forms on the side wall.

Referring back to the flow chart ofFIG.4, after the second film is formed on the substrate, the polymer film is then removed from the bottom surface of the trench in block404. This is illustrate in block504ofFIG.5, which will be described herein. As can be seen inFIG.5, the polymer film512is removed from the bottom surface510of the trench after the second film is formed. The polymer film may be removed by heating the substrate in embodiments. The substrate may be heated within the boiling point range of the polymer film512. The boiling point range may be about 200° C. to about 400° C., or about 2500 to about 350° C. The substrate may be heated for about 5 minutes to about 30 minutes, about 10 minutes to about 25 minutes, or about 15 minutes to about 20 minutes. As a result of heating the substrate, the polymer film may transition to a gas, which may be pumped out of a chamber in which the substrate is processed.

In some embodiments, the polymer film may be removed using a plasma. For example, the substrate may be exposed to a plasma containing H2, NF3, Ar, He, N2, O2and/or a mixture thereof. The plasma may react with the polymer film to form a gas, which may be pumped from a chamber containing the substrate.

As can be seen inFIG.4, after the polymer film is removed in block404, an etch process is then performed on the substrate in block405. This is illustrated in block505ofFIG.5. The bottom surface510of the trench508may be etched using an etch chemistry. During etching of the bottom surface510of the trench508, the second film513protects the side walls from the etch chemistry, i.e., selectively etching the substrate. During the etching process, the epi oxide (e.g., epitaxial silicon dioxide) may be removed from the bottom surface. In some embodiments, the chemical etching process may be performed using ammonia and/or hydrofluoric acid. Other chemicals that may be used include, but are not limited to, are ammonia and water, NHF, NH4F, hydrogen fluoride, or hydrogen chloride. In embodiments, the etch process is a plasma etch process. In embodiments, the etch process is a wet etch process. The etching process may also be an isotropic etching or an anisotropic etching.

As can be seen inFIG.4, after the etch process is performed, the second film is then removed from the substrate in block406. This can also be seen in block506ofFIG.5, where the second film513is removed from the side wall of the trench. The second film513may be removed through an additional chemical etching process, using one of the chemicals described above. Thus, after undergoing the selective etching process, the trench508of the substrate does not have the epi layer and maintains the profile of the trench because it was protected by the SAM during the etching process.

The chemical etching process may be performed using ammonia and hydrofluoric acid or ammonium fluoride. Other chemicals that may be used include, but are not limited to, are ammonia and water, NHF, NH4F, hydrogen fluoride, or hydrogen chloride.

In one embodiment, the etching process may be performed using ammonium fluoride. When the SAM is formed on the side wall, the carbon-based groups prevent the ammonium fluoride from interacting with the side wall. Thus, this carbon-based group acts as the blocking agent during the chemical etching process of the trench.

The preceding description sets forth numerous specific details such as examples of specific systems, components, methods, and so forth, in order to provide a good understanding of several embodiments of the present invention. It will be apparent to one skilled in the art, however, that at least some embodiments of the present invention may be practiced without these specific details. In other instances, well-known components or methods are not described in detail or are presented in simple block diagram format in order to avoid unnecessarily obscuring the present invention. Thus, the specific details set forth are merely exemplary. Particular implementations may vary from these exemplary details and still be contemplated to be within the scope of the present invention.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. In addition, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” When the term “about” or “approximately” is used herein, this is intended to mean that the nominal value presented is precise within +10%.

Although the operations of the methods herein are shown and described in a particular order, the order of the operations of each method may be altered so that certain operations may be performed in an inverse order or so that certain operation may be performed, at least in part, concurrently with other operations. In another embodiment, instructions or sub-operations of distinct operations may be in an intermittent and/or alternating manner.

It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.