Selective oxidation of the substrate

Abstract

Described herein is a method for selectively oxidizing a substrate. The method includes forming a non-conformal layer on at least one sidewall of a trench or hole in the substrate. After forming the non-conformal layer, the at least one trench or at least one hole may be selectively oxidized, resulting in oxidation of the non-conformal layer and an exposed portion of the at least one sidewall not covered by the non-conformal layer to form an oxide layer. The oxide layer is tapered such that it is thicker at a bottom of the at least one sidewall than at an upper portion of the at least one sidewall.

Description

[Technical Field]

[0001] TECHNICAL FIELD

[0001] Embodiments of the present disclosure generally relate to methods for oxidizing a substrate, where the methods for oxidation use a non-conformal layer to enable selective oxidation between different regions of the substrate. [Background technology]

[0002]

[0002] In the semiconductor industry, devices are produced by numerous manufacturing processes that produce structures of ever decreasing size. Some of these devices contain high aspect ratio structures, which include multiple holes or trenches within the device.

[0003]

[0003] Oxidation steps are performed to fabricate some devices. However, it has been found that when high-aspect-ratio structures are oxidized, the oxide layer primarily forms on the top of the structure, with the oxide layer becoming thinner the deeper into the structure. This phenomenon is believed to occur because, when an oxidizing agent is applied to the structure, it first interacts with the top of the high-aspect-ratio structure, depleting the chemistry that causes oxidation. As the oxidizing agent interacts with the top region, it is consumed, and an oxide layer begins to form in the top region. This oxide layer prevents or inhibits the oxidizing agent from reaching the bottom of the high-aspect-ratio structure. This therefore results in the top or top of the high-aspect-ratio feature having a thicker oxide layer than the bottom or bottom of the aspect-ratio feature, resulting in a thinner or even absent oxide layer at the bottom or bottom of the aspect-ratio feature, resulting in the formation of a non-conformal oxide layer. Summary of the Invention

[0004] Some embodiments of the present disclosure provide a method for oxidizing a substrate. The method may include forming a non-conformal layer on at least one sidewall of a trench formed on a substrate, the non-conformal layer being formed on an upper portion of the at least one sidewall and decreasing in thickness with increasing trench depth. The non-conformal layer may include nitrogen or carbon. In some embodiments, the method may include selectively oxidizing the at least one trench containing the non-conformal layer. Oxidation of the non-conformal layer and an exposed portion of the at least one sidewall not covered by the non-conformal layer occurs to form an oxide layer. The oxide layer may be thicker at a lower portion of the at least one sidewall than at an upper portion of the at least one sidewall.

[0005]

[0005] In another embodiment of the present disclosure, an article is provided that includes a substrate. The substrate may have at least one trench formed therein. The at least one trench has a top surface, a bottom surface, and at least one sidewall. The article may further include an oxide layer on at least one sidewall of the at least one trench. The oxide layer has a greater thickness at a bottom of the at least one sidewall than at a top of the at least one sidewall.

[0006]

[0006] In another embodiment of the present disclosure, another method is provided. The other method includes receiving a substrate having at least one trench formed therein. The at least one trench has at least one sidewall, and the at least one sidewall of the trench includes a non-conformal layer coating an upper portion of the at least one sidewall without coating a lower portion of the at least one sidewall. The method may further include selectively oxidizing the substrate to form an oxide layer on the at least one sidewall, the non-conformal layer being converted to a gas and removed from the at least one sidewall as the oxide layer is formed. The oxide layer may have a greater thickness at a lower portion of the at least one sidewall of the at least one trench than at a top portion of the at least one sidewall.

[0007]

[0007] The present disclosure is illustrated by way of example, and not by way of limitation, in the accompanying drawings, in which like reference numerals indicate like elements. It should be noted that various references to "an" or "one" embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. [Brief explanation of the drawings]

[0008] [Figure 1] 1 shows a cross-sectional view of a remote plasma system. [Figure 2] FIG. 1 is a flow diagram illustrating a method for selectively oxidizing a substrate according to one embodiment of the present disclosure. [Figure 3A] 1 illustrates a trench in a substrate according to one embodiment of the present disclosure. [Figure 3B] 3B illustrates the trench of FIG. 3A after depositing a non-conformal layer on the sidewalls of the trench, according to an embodiment of the present disclosure. [Figure 3C] 3C illustrates the trench of FIG. 3B before completion of an oxidation step, according to an embodiment of the present disclosure. [Figure 3D] 3C illustrates the trench of FIG. 3B after completion of an oxidation step, according to an embodiment of the present disclosure. [Figure 4] 1 illustrates an exemplary chemical vapor deposition (CVD) system. [Figure 5] 1 shows a schematic top view of an electronic device manufacturing system. DETAILED DESCRIPTION OF THE INVENTION

[0009]

[0016] Many devices (e.g., semiconductor devices) fabricated using nanofabrication and microfabrication processes are oxidized during device fabrication to form an oxide layer over the device's structure. The oxide layer can serve multiple purposes, depending on the nature of the device on which it is formed and / or other variables. The thickness of the oxide layer can be controlled to minimize variability in device performance and / or to enable adequate yield. The oxide layer formed on the substrate of embodiments of the present disclosure is a tapered layer, such that the oxide layer is thicker at the bottom than at the top.

[0010]

[0017] Embodiments disclosed herein describe a method for selectively oxidizing a substrate. The method for selectively oxidizing a substrate can include forming a non-conformal layer on at least one sidewall of a trench or other high-aspect-ratio feature (e.g., hole) formed on the substrate. The non-conformal layer is formed on an upper portion of the at least one sidewall and decreases in thickness as the depth of the trench or other high-aspect-ratio feature increases. In embodiments, the non-conformal layer can include nitrogen or carbon. The method can further include oxidizing the at least one trench or other high-aspect-ratio feature including the non-conformal layer. Oxidation of the non-conformal layer and the exposed portion of the at least one sidewall not covered by the non-conformal layer occurs to form an oxide layer. Due to the presence of the non-conformal layer on the sidewall, the oxide layer can be thicker at the bottom of the at least one sidewall than at the top of the at least one sidewall.

[0011]

[0018] In some embodiments of the method, the oxidation may include an initial oxidation process having a first selectivity and at least one additional oxidation process having a second selectivity. In some embodiments, the initial oxidation process may be performed to achieve a target taper of the oxide layer, and at least one additional oxidation process may be performed to achieve a target thickness of the oxide layer. In some embodiments, the initial oxidation process may be performed to achieve about 5% to about 50% of the oxide layer thickness, and at least one additional oxidation process may be performed to produce the remaining oxide layer.

[0012]

[0019] Embodiments are described herein in the context of forming a non-conformal layer and ultimately an oxide layer on the sidewalls of a trench in a substrate. However, it should be understood that a trench is one example of a high aspect ratio (HAR) feature to which the techniques described herein can be applied. Furthermore, it should be understood that the techniques described herein with respect to a trench will work equally well for any other type of high aspect ratio feature. A high aspect ratio feature can be a feature (e.g., a trench, hole, channel) whose length / depth to width / diameter ratio is greater than a threshold length / depth to width / diameter ratio. The threshold length / depth to width / diameter ratio can be, for example, 5:1, 10:1, 20:1, 50:1, 100:1, 200:1, 300:1, or other threshold. It should be further understood that embodiments also apply to the selective oxidation of features on a substrate that are not high aspect ratio features.

[0013]

[0020] In some embodiments, the formation of the non-conformal layer is achieved by a chemical vapor deposition (CVD) process, an atomic layer deposition (ALD) process, a radical plasma process (e.g., a radical plasma deposition or growth process), or a thermal process. In embodiments using a chemical vapor deposition (CVD) process or an atomic layer deposition (ALD) process, the process can be adjusted to deposit more on the top of the substrate compared to the bottom of the substrate. In some embodiments of CVD and / or ALD processes, this can be achieved by a combination or continuous cycle of ammonia and a precursor for non-conformal deposition, which can be performed at temperatures between about 250°C and about 750°C. The precursor can be dichlorosilane (DCS), hexachlorodisilane (HCDS), or a combination thereof. In embodiments using a radical plasma process, a remote plasma process can be used that includes nitrogen, ammonia, hydrogen, argon (Ar), helium (He), or a combination thereof. In embodiments using a thermal process, ammonia can be used. Whether radical plasma or thermal, the process may be carried out for a time period of from about 5 seconds to about 4 hours at a temperature of from about 250° C. to about 1250° C. The pressure may be selected to ensure better deposition or growth of non-conformal layers on the top of the substrate compared to the bottom of the substrate.

[0014]

[0021] In some embodiments, oxidation can be performed through thermal oxidation. Thermal oxidation is known in the art. During thermal oxidation, an oxygen source is introduced into a chamber containing the substrate, the substrate is heated to an elevated temperature, and a layer of oxide is grown on the surface of the substrate. In some embodiments, thermal oxidation can be performed using an oxidizing plasma. In other embodiments, thermal oxidation can be performed without an oxidizing plasma.

[0015]

[0022] In some embodiments of the method, the oxide layer formed on at least one sidewall may be silicon dioxide. For example, if the sidewall is formed from silicon or polysilicon, the oxide may react with the silicon or polysilicon to form silicon dioxide.

[0016]

[0023] In certain embodiments of the method, selectively oxidizing the at least one trench may include reacting the non-conformal layer with an oxidizing agent to grow an oxide layer on the non-conformal layer while simultaneously converting the non-conformal layer to a gas and removing it from the at least one sidewall. Alternatively or additionally, the oxidizing agent may react with the oxide layer to form a gas and dissipate a portion of the non-conformal layer.

[0017]

[0024] In some embodiments of the method, the non-conformal layer may have a thickness of about 5 Å to about 50 Å, about 10 Å to about 45 Å, about 15 Å to about 40 Å, about 20 Å to about 35 Å, or about 25 Å to about 30 Å, or any subrange within that range. In some embodiments, the non-conformal layer may have a thickness of about 5 Å, about 10 Å, about 15 Å, about 20 Å, about 25 Å, about 30 Å, about 35 Å, about 40 Å, about 45 Å, or about 50 Å, or any value within that range.

[0018]

[0025] In some embodiments of the method, the non-conformal layer is not formed on a bottom of the at least one sidewall, resulting in the bottom of the at least one sidewall being an exposed portion of the at least one sidewall. In embodiments, the non-conformal layer is a tapered layer that is thickest at the top or entrance of the trench and gradually becomes thinner as the trench depth increases.

[0019]

[0026] In some embodiments, the non-conformal layer is formed from about 25% of at least one sidewall, about 50% of at least one sidewall, about 75% of at least one sidewall, or about 80% of at least one sidewall.

[0020]

[0027] In some embodiments of the method, the selective oxidation can be performed using an oxidizing agent including peroxide, steam (HO), or H:O, where the ratio of H to O is from 5.5:1 to about 9:1. In some embodiments of the method, the substrate can be or include silicon, polysilicon, and / or silicon nitride.

[0021]

[0028] In another embodiment of the present disclosure, an article is provided. The article may include a substrate. At least one trench may be formed in the substrate, the at least one trench having a top surface, a bottom surface, and at least one sidewall. The article may further include an oxide layer on at least one sidewall of the at least one trench. The oxide layer has a greater thickness at a bottom of the at least one sidewall than at a top of the at least one sidewall. The oxide layer on the sidewall of the at least one trench of the article may be formed according to a method described herein.

[0022]

[0029] In certain embodiments of the article, the oxide layer on the bottom of at least one sidewall may have a thickness of about 50 Å to about 100 Å, about 55 Å to about 95 Å, about 60 Å to about 90 Å, about 65 Å to about 85 Å, or about 70 Å to about 80 Å, or any value or subrange within that range. The oxide layer may be a tapered oxide layer that is thicker at or near the bottom of the trench and thinner at or near the top of the trench. In certain embodiments of the article, the oxide layer on the top of at least one sidewall may have a thickness of about 25 Å to about 50 Å, or may be about 25 Å, about 30 Å, about 35 Å, about 40 Å, about 45 Å, or about 50 Å, or any subrange or value within that range.

[0023]

[0030] Previously, nanofabrication and microfabrication processes have not been able to form tapered layers in high aspect ratio features. The layers were thickest in the deepest regions of the high aspect ratio feature (e.g., the portions of the feature furthest from the top region). The embodiments described herein enable the formation of tapered oxide layers on high aspect ratio features, which can be beneficial for certain types of devices (e.g., certain types and / or structures of semiconductor devices).

[0024]

[0031] In yet another embodiment, a method is provided. The method includes receiving a substrate having at least one trench formed therein, the at least one trench having at least one sidewall. The at least one sidewall of the trench includes a non-conformal layer coating an upper portion of the at least one sidewall without coating a lower portion of the at least one sidewall. The method further includes selectively oxidizing the substrate to form an oxide layer on the at least one sidewall, the non-conformal layer being converted to a gas and removed from the at least one sidewall as the oxide layer forms. The oxide layer has a greater thickness at the lower portion of the at least one sidewall of the at least one trench than at the upper portion of the at least one sidewall.

[0025]

[0032] As used herein, the term "substrate" refers to a surface or portion of a surface on which a process acts. Examples of substrates include semiconductor wafers (optionally with one or more features, layers, etc. formed thereon), displays (optionally with one or more features, layers, etc. formed thereon), etc. Those skilled in the art will also understand that when reference is made to a substrate, it may refer to only a portion of the substrate unless the context clearly indicates otherwise. Furthermore, when reference is made to deposition on a substrate, it may refer to both a bare substrate and a substrate with one or more films or features deposited or formed thereon.

[0026]

[0033] As used herein, a substrate may also refer to any substrate or material surface formed on a substrate upon which film processing is performed during a manufacturing process. For example, substrate surfaces upon which processing may be performed include silicon, polysilicon, silicon oxide, strained silicon, silicon-on-insulator (SOI), carbon-doped silicon oxide, silicon nitride, doped silicon, silicon germanium, and any other material such as metals, metal nitrides, metal alloys, and other conductive materials, depending on the application. Substrates include, but are not limited to, semiconductor wafers.

[0027]

[0034] The substrate may be exposed to a pretreatment process that polishes, etches, reduces, oxidizes, hydroxylates (or otherwise generates or grafts target chemical moieties to impart chemical functionality), anneals, and / or bakes the substrate surface. In addition to film treatment directly on the surface of the substrate itself, the present disclosure also contemplates that any of the disclosed film treatment steps may be performed on an underlying layer formed on the substrate, as disclosed in more detail below. The term "substrate surface" is intended to include such underlying layers, as the context indicates. Thus, for example, when a film / layer or partial film / layer is deposited on a substrate surface, the exposed surface of the newly deposited film / layer is the substrate surface. What a given substrate surface comprises will depend on what film is being deposited as well as the particular chemistry used. In one or more embodiments, the first substrate surface may be a metal, metal oxide, H-terminated Si, or other suitable substrate. x Ge 1-x and the second substrate surface may be composed of a Si-containing dielectric, or vice versa. In some embodiments, the substrate surface may include specific functionality (e.g., —OH, —NH, etc.).

[0028]

[0035] Referring now to the drawings, Figure 1 illustrates a substrate processing system 100 that can be used to perform the selective oxidation methods described herein. Other deposition chambers can also benefit from the present disclosure, and the parameters disclosed herein can vary depending on the particular deposition chamber used to form the HAR structures described herein. For example, other deposition chambers may have larger or smaller volumes and use gas flow rates that are greater or less than those disclosed herein.

[0029]

[0036] The substrate processing system 100 includes a thermal treatment chamber 102 and a precursor activator 180. The precursor activator 180 is coupled to the thermal treatment chamber 102 and is used to remotely deliver plasma radicals to a processing region 113 of the thermal treatment chamber 102. The precursor activator 180 can also be used to deliver an activated gas mixture that is not a plasma, for example, by adding energy to the gas that does not significantly ionize the gas. The thermal treatment chamber 102 has a processing region 113 surrounded by one or more sidewalls 114 (e.g., four sidewalls) and a base 115. The top of the sidewalls 114 can be sealed to a window assembly 117 (e.g., using an "O" ring). A radiant energy assembly 118 is disposed above and coupled to the window assembly 117. The radiant energy assembly 118 includes a plurality of lamps 119, which may be tungsten halogen lamps, each mounted in a receptacle 121 and positioned to emit electromagnetic radiation into the processing region 113. Although the window assembly 117 of FIG. 1 includes a plurality of light pipes 141, the window assembly 117 may simply include a flat, solid window without any light pipes. The window assembly 117 includes an outer wall 116 (e.g., a cylindrical outer wall) that forms a rim surrounding the window assembly 117 around its periphery. The window assembly 117 further includes a first window 120 covering first ends of the plurality of light pipes 141 and a second window 122 covering second ends of the plurality of light pipes 141 opposite the first ends. The first window 120 and the second window 122 extend to and engage the outer wall 116 of the window assembly 117 to enclose and seal the interior of the window assembly 117, which includes a plurality of light pipes 141. In such a case, when light pipes are used, a vacuum can be created within the plurality of light pipes 141 by applying a vacuum through a conduit 153 that passes through the outer wall 116 to one of the plurality of light pipes 141, which is fluidly connected to the remaining pipes.

[0030]

[0037] The substrate 101 is supported in the thermal treatment chamber 102 within the processing region 113 by a support ring 162. The support ring 162 is mounted on a rotatable cylinder 163. By rotating the rotatable cylinder 163, the support ring 162 and the substrate 101 are rotated during processing. The base 115 of the thermal treatment chamber 102 has a reflective surface 111 for reflecting energy to the backside of the substrate 101 during processing. Alternatively, a separate reflector (not shown) can be positioned between the base 115 of the thermal treatment chamber 102 and the support ring 162. The thermal treatment chamber 102 can include multiple temperature probes 171 positioned through the base 115 of the thermal treatment chamber 102 to detect the temperature of the substrate 101. As mentioned above, if a separate reflector is used, the temperature probes 171 are further positioned through the separate reflector for optical access to electromagnetic radiation coming from the substrate 101.

[0031]

[0038] The rotatable cylinder 163 is supported by a magnetic rotor 164, which is a cylindrical member having a ledge 165 on which the rotatable cylinder 163 rests when both members are installed in the thermal treatment chamber 102. The magnetic rotor 164 has a plurality of magnets in a magnet region 166 below the ledge 165. The magnetic rotor 164 is disposed in an annular well 160 located at the periphery of the thermal treatment chamber 102 along the base 115. A cover 173 rests on the periphery of the base 115 and extends above the annular well 160 toward the rotatable cylinder 163 and the support ring 162, leaving a tolerance gap between the cover 173 and the rotatable cylinder 163 and / or the support ring 162. The cover 173 generally protects the magnetic rotor 164 from exposure to processing conditions in the processing region 113.

[0032]

[0039] The magnetic rotor 164 is rotated by magnetic energy from a magnetic stator 167 disposed about the base 115. The magnetic stator 167 has a plurality of electromagnets 168 that are energized in a rotational pattern during processing of the substrate 101 to create a rotating magnetic field that provides the magnetic energy to rotate the magnetic rotor 164. The magnetic stator 167 is coupled by a support 170 to a linear actuator 169. Operating the linear actuator 169, in this case a screwdriver, moves the magnetic stator 167 along an axis 172 of the thermal processing chamber 102, which in turn moves the magnetic rotor 164, rotatable cylinder 163, support ring 162, and substrate 101 along axis 172.

[0033]

[0040] Process gases are supplied to the thermal processing chamber 102 through a chamber inlet 175 and exhausted through a chamber outlet, which faces out of the plane of the paper and generally along the same plane as the chamber inlet 175 and the support ring 162 (not shown in FIG. 1). Substrates enter and exit the thermal processing chamber 102 through an access port 174 formed in the sidewall 114, which is shown at the rear in FIG. 1. The substrate transfer process will not be described herein.

[0034]

[0041] The precursor activation device 180 has a body 182 that encloses an interior space 184 in which a plasma 183 of ions, radicals, and electrons can be formed. A liner 185 made of quartz or sapphire protects the body 182 from chemical attack by the plasma. The interior space 184 is preferably free of any potential gradient that could attract charged particles (e.g., ions). A gas inlet 186 is located at a first end 187 of the body 182, opposite a gas outlet 188 located at a second end 189 of the body 182. When the precursor activation device 180 is coupled to the thermal treatment chamber 102, the gas outlet 188 is fluidly connected to the thermal treatment chamber 102 through a delivery line 190 to the chamber inlet 175, thereby supplying radicals from the plasma 183 generated in the interior space 184 to the processing region 113 of the thermal treatment chamber 102. The gas outlet 188 can have a larger diameter than the gas inlet 186, allowing the excited radicals to be efficiently released at a targeted flow rate and minimizing contact between the radicals and the liner 185. If targeted, a separate orifice can be inserted into the liner 185 of the gas outlet 188 to reduce the internal dimension of the interior space 184 at the gas outlet 188. The diameter of the gas outlet 188 (or orifice, if used) can be selected to provide a pressure differential between the processing region 113 and the precursor activator 180. The pressure differential can be selected so that the composition of ions, radicals, and molecules entering the thermal treatment chamber 102 is appropriate for the process being performed therein.

[0035]

[0042] To supply gas for plasma processing, a first gas source 192 is connected to the gas inlet 186 via a first input of a four-way valve 194 and a valve 197 used to control the flow rate of gas released from the first gas source 192. A second input of the four-way valve 194 can be connected to a second gas source 198. A third input of the four-way valve can be connected to a third gas source 199. Each of the first gas source 192, the second gas source 198, and the third gas source 199 can be or include one or more of a nitrogen-containing gas, an oxygen-containing gas, a silicon-containing gas, a hydrogen-containing gas, or a plasma-forming gas such as argon or helium. A flow controller 196 is connected to the four-way valve 194 and switches the four-way valve 194 between its different positions depending on which process is being performed. The flow controller 196 also controls the switching of the four-way valve 194.

[0036]

[0043] The precursor activator 180 may be coupled to an energy source (not shown). The energy source supplies excitation energy, such as energy having microwave or RF frequencies, to the precursor activator 180 to activate the process gas traveling from the first gas source 192 into a plasma 183. When a nitrogen-containing gas (e.g., N) is used, plasma activation within the precursor activator 180 generates positively charged ions, such as N* radicals, N+, and N2+, and electrons within the interior space 184. By locating the precursor activator 180 remotely from the processing region 113 of the thermal processing chamber 102, exposure of the substrate to ions is minimized. While ions can damage sensitive structures on the semiconductor substrate, radicals are reactive and can be used to carry out beneficial chemical reactions. The use of an activation gas source such as the precursor activator 180 promotes exposure of the substrate 101 to radicals and minimizes exposure of the substrate 101 to ions.

[0037]

[0044] In some implementations, a second hydrogen gas source (not shown) is fluidly connected to the thermal treatment chamber 102. The second hydrogen gas source supplies hydrogen gas to the processing region 113, where the hydrogen gas may be activated by a remote plasma supplied to the processing region 113 from the precursor activation device 180. In some implementations where a high percentage of hydrogen gas is targeted, hydrogen gas may be supplied to the processing region 113 through both the third gas source 199 and the second hydrogen gas source.

[0038]

[0045] 2 is a flow diagram illustrating a method 200 of selectively oxidizing a substrate according to one embodiment of the present disclosure. In method 200, at block 205, a previously patterned substrate is received. The substrate may be patterned to have at least one trench and / or other features. Although the substrate is described with reference to a trench, the trench may be replaced with other types of features, which may be high aspect ratio features.

[0039]

[0046] The at least one trench can have a top surface, at least one sidewall surface, and a bottom surface. For example, a substrate can have a trench as shown in Figure 3A. Figure 3A shows a trench 306 in a substrate 303, according to one embodiment of the present disclosure.

[0040]

[0047] In FIG. 3A , substrate 303 is shown having trench 306. Substrate 303 may comprise silicon or silicon nitride. Trench 306 has at least one sidewall 302. The trench may be etched into a substrate (e.g., a silicon wafer) and / or may be etched or otherwise formed in one or more layers formed on the surface of the substrate. In embodiments, trench walls 302 are formed from the same material as the bottom of the trench. In other embodiments, trench walls 302 are formed from a different material than the bottom of the trench (e.g., when one or more silicon nitride layers are formed on a silicon wafer and the silicon nitride layer(s) are etched to expose the silicon wafer at the bottom of the trench). At least one sidewall 302 in some embodiments may have a layer (not shown) formed thereon. In one embodiment, the layer may comprise silicon nitride (SiN). In other embodiments, the layer may be silicon, damaged silicon nitride, silicon oxide, or a low-κ material. As understood herein, the term "low-κ material" refers to a material that has a low dielectric constant (κ) relative to silicon dioxide. The method 200 of the present disclosure enables the formation of an oxide layer that is thicker on the lower portion 302b of the at least one sidewall 302 than on the upper portion 302a of the at least one sidewall 302 due to the selective oxidation of the at least one trench 306.

[0041]

[0048] Returning to Figure 2, after receiving the patterned substrate, in block 210, a non-conformal layer may be formed on at least one sidewall of a trench formed on the substrate. This can be seen in Figure 3B, which shows the trench 306 of Figure 3A after depositing a non-conformal layer 304 on the sidewall 302 of the trench 306, in accordance with an embodiment of the present disclosure.

[0042]

[0049] 3B, a non-conformal layer 304 is formed on an upper portion 302a of at least one sidewall 302. In some embodiments, the non-conformal layer 304 may also be known as a "poison layer" or a "retard layer." Such a non-conformal layer 304 acts as a barrier to control the oxidation rate of the trench in the substrate.

[0043]

[0050] The non-conformal layer 304 is a tapered layer that decreases in thickness with increasing depth into the trench 306. The non-conformal layer has a thickness of about 5 Å to about 50 Å on the top of the at least one sidewall 302. In some embodiments, the non-conformal layer 304 has a thickness of about 5 Å, about 10 Å, about 15 Å, about 20 Å, about 25 Å, about 30 Å, about 35 Å, about 40 Å, about 45 Å, or about 50 Å on the top of the at least one sidewall 302a. As shown in FIG. 3B , the non-conformal layer 304 may not form on the lower portion 302b of the at least one sidewall 302, resulting in the lower portion 302b of the at least one sidewall 302 being an exposed portion of the at least one sidewall 302. In some embodiments, the non-conformal layer 304 is formed on about 50% of at least one sidewall 302, about 55% of at least one sidewall 302, about 60% of at least one sidewall 302, about 65% of at least one sidewall 302, about 70% of at least one sidewall 302, about 75% of at least one sidewall 302, about 80% of at least one sidewall 302, about 85% of at least one sidewall 302, or about 90% of at least one sidewall 302.

[0044]

[0051] In some embodiments, the non-conformal layer 304 is a nitrogen-containing layer. In some embodiments, the non-conformal layer 304 is a nitride layer, such as silicon nitride. In some embodiments, the non-conformal layer 304 includes carbon. In some embodiments, the non-conformal layer 304 is a carbide layer, such as a silicon carbide layer.

[0045]

[0052] The formation of a non-conformal layer can be achieved through a chemical vapor deposition (CVD) process or a radical plasma process (e.g., a radical plasma deposition or growth process). During the radical plasma process, a remote plasma containing radicals can be generated. The remote plasma can include nitrogen plasma (e.g., having nitrogen radicals), ammonia plasma (e.g., having ammonia radicals), or a combination thereof. The radical plasma process is performed in a relatively high-pressure regime (e.g., 1 Torr or higher) to create excited states in the high-pressure regime. For example, when nitrogen plasma is used, N2* excited states can be generated. In another example, when ammonia plasma is used, NH2 or NH radical fragments are generated. The pressure should be controlled low enough to react with the substrate. For example, the pressure can be controlled to create a radical lifetime that focuses the radical plasma process near the top of the substrate. In addition, the process time should be set to a short time (e.g., from about 5 seconds to about 4 hours) to enable selective reaction to the target region of the substrate (e.g., the top portion 302a). In some embodiments, the pressure for performing the radical plasma process may be about 0.5 Torr (T) to about 5 T, or about 0.5 T, about 1 T, about 2 T, about 3 T, about 4 T, about 5 T, or any value or subrange therein. The time for performing the radical plasma process may be about 5 seconds to about 1 hour. By performing the radical plasma process to form the nonconformal layer 304, the energy of the radicals can be controlled so that the radicals cannot react along the entire sidewall 302 but can selectively react with the upper portion 302 a of the sidewall 302 of the substrate (e.g., without reaching or reacting with the lower portion 302 b of the sidewall 302). In other embodiments, the thermal process can be performed under similar conditions, except that the pressure may be about 0.5 T to about 500 T.

[0046]

[0053] In some embodiments, the non-conformal layer 304 is formed via CVD or ALD. There are a variety of CVD processes, and the specific type can be selected based on several factors, including the surface to be coated, the coating material, the chemical interaction between the surface and the coating material, the desired thickness, and the desired coating properties. Some example CVD processes include atmospheric pressure CVD (APCVD), low pressure CVD (LPCVD), plasma enhanced CVD (PECVD), and vapor phase epitaxy. Any of these CVD processes can be used in embodiments. For various CVD processes, the substrate is exposed to one or more volatile precursors, which react and / or decompose on the article surface to produce the desired coating. By-products may be generated, but these are removed by being vented from the deposition chamber in which the CVD process occurs.

[0047]

[0054] FIG. 4 illustrates an exemplary chemical vapor deposition (CVD) system that may be utilized to coat an article according to an embodiment.

[0048]

[0055] The system includes a chemical vapor precursor delivery system 405 and a CVD reactor 410. The role of the vapor precursor delivery system 405 is to generate a vapor precursor 420 (e.g., a vapor precursor for the non-conformal layer 304) from a starting material 415, which may be in solid, liquid, or gas form. The vapor is then transferred to the CVD reactor 410 and deposited as a thin film 445 on a substrate 430 (which may, for example, correspond to substrate 300A in FIG. 3A ), which may be positioned on a holder 435.

[0049]

[0056] The CVD reactor 410 uses a heater 440 to heat the substrate 430 to a deposition temperature. In some embodiments, the heater may heat the walls of the CVD reactor (also called a "hot-wall reactor"), which can transfer heat to the substrate 430. In other embodiments, the walls of the CVD reactor may be kept cool while only the substrate is heated (also called a "cold-wall reactor"). It should be understood that the configuration of the CVD system should not be construed as limiting. A variety of equipment is available for CVD systems, and the equipment is selected to provide optimal processing conditions that result in a coating of uniform thickness, surface morphology, structure, and composition.

[0050]

[0057] Various CVD processes consist of the following process steps: (1) generating activated gaseous reactive species (also known as "precursors") from starting materials, (2) transporting the precursors to a reaction chamber (also called a "reactor"), (3) absorbing the precursors onto a heated substrate (i.e., the top portion 302a of substrate 300A), (4) engaging in a chemical reaction between the precursors and the substrate at a gas-solid interface to form deposits and gaseous by-products, and (5) removing the gaseous by-products and unreacted gaseous precursors from the reaction chamber.

[0051]

[0058] Suitable CVD precursors may be stable at room temperature, may have a low evaporation temperature, may be capable of generating a stable vapor at low temperatures, may have a suitable deposition rate (low for thin film coatings and high for thick film coatings), and may have relatively low toxicity, be cost-effective, and may be relatively pure. For some CVD reactions, such as thermal decomposition reactions (also known as "pyrolysis") or disproportionation reactions, the chemical precursor alone may be sufficient to complete the deposition. For other CVD reactions, other reagents or reactants (e.g., oxygen- or fluorine-containing reactants) may be utilized in addition to the chemical precursor to complete the deposition and form a metal fluoride protective coating (e.g., a coating described herein).

[0052]

[0059] CVD offers many advantages, including the ability to deposit dense, highly pure coatings at reasonably high deposition rates with good reproducibility and adhesion. In embodiments, layers deposited using CVD may have porosity of less than 1%, and even less than 0.1% (e.g., about 0%). Thus, CVD can be used to coat components with complex shapes and deposit non-conformal films when sufficiently small amounts of precursor are used so that they do not (or only a small amount of) reach areas that are not intended to form the deposited layer.

[0053]

[0060] Referring again to FIG. 3B , in some embodiments, the non-conformal layer 304 can include nitrogen. In some embodiments, the non-conformal layer 304 can further include silicon. For example, the non-conformal layer 304 can include silicon nitride. In some embodiments, the non-conformal layer 304 including nitrogen is formed by performing nitridation of the substrate 303. The nitridation can be achieved by applying nitrogen (N ), ammonia (NH ), hydrogen (H ), argon (Ar), helium (He), or a combination thereof. In some embodiments, the nitridation can be achieved using a plasma. The plasma can include nitrogen (N ), ammonia (NH ), hydrogen (H ), argon (Ar), helium (He), or a combination thereof. In some embodiments, the nitridation can be achieved by applying ammonia to the substrate with or without a plasma. Nitriding can be carried out at a pressure of about 0.5 T to about 5 T, about 0.5 T, about 1 T, about 2 T, about 3 T, about 4 T, or about 5 T, or any value or subrange within that range. Nitriding can be carried out at a temperature of about 250°C to about 1250°C, about 350°C to about 1150°C, about 450°C to about 1050°C, about 550°C to about 950°C, about 650°C to about 850°C, or about 250°C, about 350°C, about 450°C, about 550°C, about 650°C, about 750°C, about 950°C, about 1050°C, about 1150°C, or about 1250°C, or any value or subrange within that range.

[0054]

[0061] In certain embodiments, a native oxide may form on the surface of substrate 303 (e.g., sidewalls 302 of substrate 303) prior to the formation of non-conformal layer 304. For example, native oxide may form when substrate 303 is exposed to oxygen and / or moisture. In embodiments, the native oxide may inhibit the formation of non-conformal layer 304. Therefore, in embodiments, a cleaning or etching process is performed to remove the native oxide prior to the formation of non-conformal layer 304.

[0055]

[0062] 2, after a non-conformal layer is formed on a portion of at least one sidewall of the trench, in block 215, an oxidizing agent is applied to the at least one sidewall having the non-conformal layer. The oxidizing agent may include peroxide, steam (HO), or H:O, where the H:O ratio is between 5.5:1 and about 9:1. In an embodiment, the oxidizing agent is applied while the substrate is heated.

[0056]

[0063] The oxidizing agent is selected based on its selectivity for oxidizing the substrate. In some embodiments, it is preferable to have a highly selective oxidizing agent that reacts quickly with materials within the substrate (i.e., silicon) while reacting more slowly with non-conformal layers (i.e., nitrogen- or carbon-containing layers). For example, a hydrogen (H)-rich oxidizing agent may be more selective during this step. In other examples, (H2O) and / or hydrogen peroxide (H2O2) may be selective oxidizing agents. In contrast, oxygen radicals (O*) and / or hydroxides (OH) may be less selective.

[0057]

[0064] In block 220, an oxidizing agent reacts with the non-conformal layer and the substrate to grow an oxide layer thereon over a period of time. As can be seen in Figure 3C, an oxide layer 305 grows along at least one sidewall 302 of the trench 306, while the non-conformal 304 layer shrinks on at least one sidewall 306. Figure 3C illustrates the trench of Figure 3B after the oxidation process has begun but before the oxidation process is completed, according to one embodiment of the present disclosure.

[0058]

[0065] The time for which the oxidizing agent is allowed to react can depend on the selectivity of the oxidizing agent, and in some embodiments, the time can be about 30 seconds, about 45 seconds, about 1 second, about 5 seconds, about 10 seconds, about 15 seconds, about 20 seconds, about 30 seconds, about 45 seconds, about 1 hour, about 2 hours, about 3 hours, about 4 hours, about 5 hours, or about 6 hours, or any value within that range.

[0059]

[0066] In some embodiments, multiple different oxidizing agent chemistries may be used. For example, a first oxidation step may be performed using a first oxidizing agent with a first selectivity (e.g., lower selectivity between bare portions of sidewall 302 and portions of the sidewall covered with a non-conformal layer), and a second oxidation step may be performed using a second oxidizing agent with a second selectivity (e.g., higher selectivity between bare portions of sidewall 302 and portions of the sidewall covered with a non-conformal layer). A first time for the first oxidation step and a second time for the second oxidation step may be selected to adjust the selectivity of the overall oxidation process to a target selectivity, which may be between the first selectivity of the first oxidation step and the second selectivity of the second oxidation step. Additional oxidation steps may be performed to control the selectivity of the oxidation.

[0060]

[0067] Returning to FIG. 2 , in block 225, the non-conformal layer is simultaneously removed from the trench while the oxide layer is being grown. In some embodiments, as the oxidizing agent reacts with the non-conformal layer, a portion of the non-conformal layer may be converted to a gas phase. The gas phase of the reacted portion of the non-conformal layer may then be removed from the process chamber where oxidation occurs (e.g., by pumping out reaction by-products). For example, if the non-conformal layer includes nitrogen, the oxidizing agent reacts with both the substrate and the nitrogen, thereby beginning to grow an oxide layer on the exposed portion of at least one sidewall of the trench on the substrate, while converting the nitrogen to a gas that eventually replaces it. In this way, the non-conformal layer is removed during the selective oxidation process, so that an oxide layer can grow only on the substrate.

[0061]

[0068] In block 230, an oxide layer is formed that is thicker at the bottom of at least one sidewall than at the top of the at least one sidewall. This is also shown in FIG. 3D , which illustrates the trench of FIG. 3B after completion of the oxidation process, according to an embodiment of the present disclosure. As seen in FIG. 3D , the oxide layer 205 is thicker at the bottom 302b of the trench and gradually thins out near the top 302a of the sidewall 302 of the trench 306. In some embodiments, the oxide layer grows to form a thicker layer on the exposed lower portion of at least one sidewall of the substrate trench. This is because non-conformal layers (e.g., nitride) oxidize more slowly than exposed portions of the sidewalls (e.g., more slowly than silicon). Thus, the oxidation rate and degree of taper are controlled to reach a target thickness and a target amount of taper (e.g., in embodiments, a target thickness profile across the surface of the trench sidewall).

[0062]

[0069] In certain embodiments of the article, the oxide layer underneath at least one sidewall may comprise a thickness of about 50 Å to about 100 Å, about 55 Å to about 95 Å, about 60 Å to about 90 Å, about 65 Å to about 85 Å, or about 70 Å to about 80 Å, or any value or subrange therein. In some embodiments, the oxide layer underneath at least one sidewall may have a thickness of about 50 Å, about 55 Å, about 60 Å, about 65 Å, about 70 Å, about 75 Å, about 80 Å, about 85 Å, about 90 Å, about 95 Å, or about 100 Å.

[0063]

[0070] In some embodiments, the oxide layer on top of at least one sidewall may have a thickness of about 25 Å to about 50 Å, or may be about 25 Å, about 30 Å, about 35 Å, about 40 Å, about 45 Å, or about 50 Å, or any subrange or value therein. In some embodiments, the oxide layer on top of at least one sidewall may have a thickness of about 25 Å, about 30 Å, about 35 Å, about 40 Å, about 45 Å, or about 50 Å.

[0064]

[0071] In some embodiments, the oxide layer on the at least one sidewall may gradually increase in thickness (e.g., may taper) from the top to the bottom of the at least one sidewall. The thicknesses of the bottom and top, and the amount of taper, may be controlled based on the non-conformal layer formed in the previous steps of the method, the selectivity of the oxidation process, and the time and / or temperature of the oxidation.

[0065]

[0072] In some embodiments, the selective oxidation method can be performed by a first oxidation step that grows a target profile on at least one sidewall of the substrate trench, followed by a second oxidation step (e.g., a radical oxidation step) that completes the oxidation of the substrate trench. The second oxidation step allows the substrate to be oxidized at a faster rate in embodiments. In embodiments, the first oxidation step has higher selectivity but a lower oxide growth rate, and the second oxidation step has lower selectivity but a higher growth rate. In some embodiments, the complete oxidation of the substrate trench (selective oxidation, then radical oxidation) can be performed in less than about 1 hour.

[0066]

[0073] As described above, in some embodiments, a native oxide may form on the sidewalls of the trench in the substrate before a non-conformal layer is formed on the sidewalls of the trench. In some embodiments, an electronic device manufacturing system including a cluster tool is used to process the substrate. After forming the trench in the substrate and before forming the non-conformal layer on the sidewalls of the trench, the substrate may be maintained in a vacuum. Moving the substrate between chambers without breaking vacuum can prevent the formation of a native oxide.

[0067]

[0074] FIG. 5 illustrates a schematic top view of an electronic device manufacturing system 500 according to an embodiment of the present disclosure. The electronic device manufacturing system 500 is configured to process substrates and may include a main frame (also referred to as a transfer chamber) 504 having four sides 501A-D. While the four sides 501A-D are shown in a rectangular configuration, the main frame 504 may alternatively have other numbers of sides (e.g., five sides, six sides, seven sides, eight sides, etc.) and / or other shapes. In embodiments, the sides may have the same size (e.g., the same width) or different sizes. In one embodiment, the main frame 504 has a rectangular shape, with sides 501A and 501C being approximately parallel to one another, sides 501B and 501D being approximately parallel to one another, and sides 501A and 501C being approximately perpendicular to sides 501B and 501D. In one embodiment, the main frame 504 has a pentagonal shape. In one embodiment, the main frame includes a first surface having a first length, and a second surface and a third surface on either side of the first surface, each having a second length greater than the first length, and a fourth surface and a fifth surface connected to the second surface and the third surface, respectively, each having a third length greater than or equal to the first length and less than the second length.

[0068]

[0075] The main frame 504 may include an interior space 534, and the faces 501A-D may define sidewalls of the interior space 534. The main frame 504 may further include a base (not shown) and a lid (not shown). The faces 501A-D, the base, and the lid together may define the interior space 534. A robot arm (also referred to as a robot assembly) 536 may be disposed within the interior space 534 of the main frame 504. The interior space 534 may typically be under vacuum during operation of the main frame 504.

[0069]

[0076] Each side 501A-D may include one or more substrate access ports 532. Each substrate access port 532 may be configured to allow a horizontally oriented substrate 540 to pass therethrough. The substrate 540 may be a wafer (e.g., a semiconductor wafer or a non-semiconductor device substrate), a glass plate or panel, and / or other workpiece used to fabricate electronic devices or circuit components. Each substrate access port 532 may be, for example, an elongated slot or slit formed in a sidewall of the main frame 504. Each substrate access port 532 may include, for example, a slit valve or other suitable device for opening and closing the substrate access port 532, and / or a local center finder (LCF) suitable for determining the position of the substrate 540 being transported through the substrate access port 532. The slit valve may be of any suitable conventional structure, such as, for example, an L-motion slit valve. Other suitable devices may also be used to open and close the substrate access port 532. In embodiments, the substrate access port 532 may include a single gate or a dual gate (e.g., having a first gate internal to the interchangeable interface plate at the substrate access port and a second gate external to the interchangeable interface plate at the substrate access port).

[0070]

[0077] The processing chambers 506, 508, 510, 512, 514, 516 are mounted on various sides 501A-D of the main frame 504. Each processing chamber 506-116 has a chamber port that aligns with the substrate access port 532.

[0071]

[0078] Each of the load lock chambers 126 may be a batch-type or single-substrate-type load lock chamber. In some embodiments, the load lock chambers 526 may be stacked load lock chambers. For example, the load lock chambers 126 may be dual-stacked load lock chambers, triple-stacked load lock chambers, load lock chambers with four or more stacked load locks (e.g., quad load lock chambers), etc. Alternatively, the load lock chambers 126 may be single-space load lock chambers. Each load lock chamber 126 may have one or more chamber ports corresponding to the respective substrate access ports 532. For example, a stacked load lock chamber 126, which may have two separate substrate spaces, may have two vertically aligned chamber ports corresponding to the vertically aligned substrate access ports 532. A triple-stacked load lock chamber, which may have three separate substrate spaces, may have three vertically aligned chamber ports corresponding to the vertically aligned substrate access ports. A single-space load lock chamber may have a single chamber port corresponding to the single substrate access port 532. Any one or more of the load lock chambers 126 may be stacked load lock chambers, triple stacked load lock chambers, and / or single volume load lock chambers. Additionally, in some embodiments, any one or more of the load lock chambers 126 may be a chamber with processing capabilities. That is, any one or more of the load lock chambers 126, or any one of the volumes located therein, may be capable of performing pre-heating, mitigation, cool-down, and / or other processing steps on a substrate.

[0072]

[0079] The main frame 504, the processing chambers 506-516, and / or the load lock chamber 526 may each operate at vacuum pressure. The processing chambers 506-516 may perform the same or different processes (including, for example, deposition, oxidation, nitridation, etching, polishing, cleaning, lithography, inspection, etc.) on the substrate 540. Other processes may also be performed therein.

[0073]

[0080] The main frame 504 may further include a robot assembly 536 within the interior space 534. The robot assembly 536 may be configured to transfer one or more substrates 540 between each of the processing chambers 506-516 and the load lock chamber 526. The robot assembly 536 may be configured to transfer a substrate 540 from any one chamber directly to any other chamber attached to the main frame 504. In some embodiments, the substrates 540 may be transferred by the robot assembly 536 in any order or direction. In some embodiments, the robot assembly 536 may have dual transport blades (or more transport blades, also referred to as end effectors) that can independently extend from and retract into any chamber attached to the main frame 504, enabling simultaneous substrate transfers and increasing system throughput. In some embodiments, the robot assembly 536 may have a single transport blade and / or may be a SCARA (Selectively Adaptive Articulated Robot Arm) robot. Alternatively, the robot assembly 536 may be any suitable mechanism (eg, a linear robot or a non-linear robot) for transferring substrates between chambers mounted on the main frame 504 .

[0074]

[0081] The load lock chambers 126 may be coupled to a factory interface 502, which may be coupled to one or more FOUPs (Front Opening Unified Pods) 518. The one or more load lock chambers 126 may provide a first vacuum interface between the factory interface 502 and the transfer chamber 126. In some embodiments, each of the load lock chambers 526 may alternately communicate with the mainframe (transfer chamber) 504 and the factory interface 502 to increase substrate throughput. That is, one load lock chamber 526, or any one space of the stacked or triple stacked load lock chambers, may communicate with the transfer chamber 504, while another load lock chamber 126, or other space of the stacked or triple stacked load lock chambers, may communicate with the factory interface 502. Substrate transfer between the factory interface 502, the load lock chambers 126, and the transfer chamber 504 may be performed in any other suitable manner.

[0075]

[0082] The FOUPs 518 may each be a container with a stationary cassette therein for holding multiple substrates. The FOUPs 518 may each have a front-opening interface configured for use with the factory interface 502. The factory interface 502 may include a buffer chamber (not shown) and one or more robot assemblies 538 configured to transfer substrates 540 via linear, rotational, and / or vertical movement between the FOUPs 518 and the load lock chambers 126. Substrates may be transferred between the FOUPs 518 and the load lock chambers 126 in any order or direction. The load lock chambers 126 may be batch or single-substrate load lock chambers.

[0076]

[0083] Controller 571 may control the operation of robot assembly 538, robot assembly 536, and / or the electronic device manufacturing system. Controller 571 may control the processing and transfer of substrates 540 within and through the electronic device manufacturing system. Controller 571 may be, for example, a general-purpose computer and / or may include a microprocessor or other suitable CPU (central processing unit), memory for storing software routines that control the electronic device manufacturing system, input / output peripherals, and support circuitry (e.g., power supplies, clock circuits, circuitry to drive robot assemblies 538, 536, cache, and / or the like). Controller 571 may be programmed to process one or more substrates sequentially, for example, through each of the processing chambers mounted on mainframe 504. In other embodiments, controller 571 may be programmed to process substrates in any order through the processing chambers. In still other embodiments, controller 571 may be programmed to skip and / or repeat the processing of one or more substrates in one or more processing chambers. The controller 571 may alternatively be programmed to process one or more substrates in an electronic device manufacturing system in any suitable manner.

[0077]

[0084] The electronic device manufacturing system may have any other suitable number of FOUPs 518 and / or load lock chambers 526 other than those shown. In some embodiments, the number of load lock chambers coupled to face 501A may be independent of the number of processing chambers coupled to any one of faces 501B-D. For example, the number of load lock chambers may be different from the maximum number of processing chambers coupled to a face. Furthermore, in some embodiments, up to four processing chambers may be coupled to a single face, or more than four processing chambers may be coupled to a single face, depending on the size of mainframe 504 relative to the size of four processing chambers.

[0078]

[0085] In embodiments, a substrate may be moved to the mainframe 504 and may undergo multiple processes through various process chambers 506-516 without breaking vacuum. For example, process chamber 506 may form a trench in the substrate, process chamber 508 may form a non-conformal layer on the sidewalls of the trench, and process chamber 510 may perform oxidation to form an oxide layer on the sidewalls of the trench and remove the non-conformal layer. The substrate 540 may be passed between process chambers 506-516 under vacuum by robot 532. Thus, in some embodiments, native oxide may not grow on the substrate during the formation of the trench, the formation of the non-conformal layer on the trench, and the formation of the oxide layer on the trench.

[0079]

[0086] The methods of the present disclosure can be used to form tapered oxide layers in or on features with high aspect ratios. For example, high aspect ratio processes can benefit from thicker oxide layers at the bottom of trenches. Therefore, this can be achieved using methods such as those described above.

[0080]

[0087] The foregoing description sets forth numerous specific details, such as examples of specific systems, components, methods, etc., to provide a thorough understanding of some embodiments of the present invention. However, it will be apparent to those skilled in the art 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 form to avoid unnecessarily obscuring the present invention. Thus, the specific details shown are merely exemplary. Particular implementations may vary from these example details and still be contemplated as being within the scope of the present invention.

[0081]

[0088] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or." When the terms "about" or "approximately" are used herein, this is intended to mean that the nominal value presented is accurate to within ±10%.

[0082]

[0089] 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 changed, with certain operations being performed in reverse order, or certain operations being performed at least in part concurrently with other operations. In alternative embodiments, instructions of separate operations or sub-operations may be performed intermittently and / or interleaved.

[0083]

[0090] It is to be understood that the foregoing description is intended to be illustrative, and not limiting. Many other embodiments will become apparent to those skilled in the art upon reading and understanding the above description. The scope of the present invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. forming a non-conformal layer on at least one sidewall of a trench or hole formed on a substrate, the non-conformal layer being formed on a top of the at least one sidewall and decreasing in thickness with increasing depth of the trench or hole, the non-conformal layer comprising nitrogen; oxidizing the at least one sidewall of the trench or hole including the non-conformal layer, wherein oxidation of the non-conformal layer and exposed portions of the at least one sidewall not covered by the non-conformal layer occurs to form an oxide layer, the oxide layer having a greater thickness at a bottom of the at least one sidewall than at an top of the at least one sidewall; A method comprising:

2. 10. The method of claim 1, wherein the oxidizing comprises an initial oxidation process having a first selectivity and at least one additional oxidation process having a second selectivity.

3. 3. The method of claim 2, wherein the initial oxidation process is performed to achieve a target taper of the oxide layer, and the at least one additional oxidation process is performed to achieve a target thickness of the oxide layer.

4. The method of claim 2 , wherein the initial oxidation process is performed to achieve about 5% to about 50% of the thickness of the oxide layer.

5. The method of claim 1 , wherein forming the non-conformal layer is accomplished by a chemical vapor deposition process, a thermal process, or a radical plasma process.

6. The method of claim 1 , wherein forming the non-conformal layer comprising nitrogen is performed by nitriding the substrate.

7. The nitriding is performed by adding nitrogen (N ２ ), ammonia (NH ３ ), hydrogen (H ２ 7. The method of claim 6, wherein the method is achieved by applying argon (Ar), helium (He), or a combination thereof.

8. The method of claim 7, wherein the nitriding is carried out at a pressure of about 0.5 T to about 500 T.

9. The method of claim 7, wherein the nitriding is carried out at a temperature of about 250°C to about 1250°C.

10. The method of claim 1 , wherein the oxidizing is performed through thermal oxidation.

11. The method of claim 1 , wherein the oxide layer comprises silicon dioxide.

12. The method of claim 1 , wherein the non-conformal layer has a thickness of about 5 Å to about 50 Å at the top of the at least one sidewall.

13. 2. The method of claim 1, wherein the non-conformal layer is not formed on the lower portion of the at least one sidewall, such that the lower portion of the at least one sidewall becomes the exposed portion of the at least one sidewall.

14. The method of claim 1 , wherein the non-conformal layer forms approximately 25% of the at least one sidewall.

15. The oxidizing step may comprise the step of oxidizing a mixture of peroxides, steam (H ２ O), or H ２ :O ２ and is carried out using an oxidizing agent containing H ２ and O ２ 2. The method of claim 1, wherein the ratio of is from 5.5:1 to about 9:

1.

16. The method of claim 1 , wherein the substrate comprises silicon or silicon nitride.

17. a substrate having at least one trench or at least one hole formed therein, the at least one trench or the at least one hole having a top surface, a bottom surface, and at least one sidewall; and an oxide layer on the at least one sidewall of the at least one trench or the at least one hole, the oxide layer having a greater thickness at a bottom of the at least one sidewall than at an upper portion of the at least one sidewall; Items including.

18. 18. The article of claim 17, wherein the oxide layer on the lower portion of the at least one sidewall has a thickness of about 50 Å to about 100 Å.

19. 18. The article of claim 17, wherein the oxide layer on the top of the at least one sidewall has a thickness of about 25 Å to about 50 Å.

20. receiving a substrate having at least one trench or at least one hole formed therein, the at least one trench or the at least one hole having at least one sidewall, the at least one sidewall of the trench or the hole including a non-conformal layer coating an upper portion of the at least one sidewall without coating a lower portion of the at least one sidewall; selectively oxidizing the substrate to form an oxide layer on the at least one sidewall, wherein selectively oxidizing the at least one trench or the at least one hole comprises reacting the non-conformal layer with an oxidizing agent to grow the oxide layer while simultaneously removing the non-conformal layer from the at least one sidewall; wherein the rate at which the oxide layer grows is slowed by the non-conformal layer containing nitrogen, such that the oxide layer is thicker at the bottom of the at least one sidewall of the at least one trench or at least one hole than at the top of the at least one sidewall.

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