Argon addition to remote plasma oxidation.

Abstract

To provide a method for conformal radical oxidation of structure such as high aspect ratio structure.SOLUTION: A method comprises the steps of: placing a substrate in a thermal processing chamber; flowing hydrogen into the thermal processing chamber at a first flow rate; flowing oxygen into a precursor activation device at a second flow rate; flowing argon into the precursor activation device at a third flow rate; generating plasma in the precursor activation device from oxygen and argon; flowing the plasma into the thermal processing chamber and mixing the plasma with a hydrogen gas to produce an activated processing gas; exposing a substrate to the activated gas to form an oxide film on the substrate; and controlling a growth rate of the oxide film by adjusting the third flow rate.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to semiconductor device fabrication, and more particularly to methods for conformal radical oxidation of structures, such as high aspect ratio structures. [Background technology]

[0002] The production of silicon integrated circuits places challenging demands on fabrication processes to reduce the minimum feature size on a chip while increasing the number of elements. These demands extend to fabrication processes that involve depositing layers of different materials in challenging topologies and etching additional features within these layers. The manufacturing process for next-generation NAND flash memory involves particularly challenging element geometries and scales. NAND is a type of non-volatile storage technology that does not require power to retain data. To increase memory capacity within the same physical space, three-dimensional NAND (3D NAND) designs are being developed. Such designs typically introduce alternating oxide and nitride layers into a substrate. The alternating oxide and nitride layers are then etched to create structures with one or more surfaces that extend substantially perpendicular to the substrate. Such design considerations have shifted the field from oxidizing relatively low aspect ratio structures, e.g., 10:1 aspect ratios, to high aspect ratio (HAR) structures, e.g., greater than 40:1 aspect ratios. Previous fabrication processes have included methods to fill gaps and trenches in HAR structures.

[0003] 3D NAND flash structures often require silicon nitride (SiN) to be conformally oxidized in HAR structures. x N y) layer, such as Si3N4. 3D NAND flash structures can have high or ultra-high aspect ratios, such as a 40:1 aspect ratio, between a 40:1 and a 100:1 aspect ratio, a 100:1 aspect ratio, or even greater than a 100:1 aspect ratio. New fabrication processes are expected to conformally deposit layers on the surface of HAR structures rather than simply filling gaps and trenches. For example, conformally forming on the surface of a HAR structure may involve slower deposition rates. The term "conformally" generally refers to a uniform and / or constant layer thickness on the surface of the structure. In the context of HAR structures, the term "conformally" is most relevant when discussing oxide thickness on the surface of the structure that is substantially perpendicular to the substrate. More conformal deposition can reduce material buildup at the top of features, which can result in premature sealing of the tops of trenches between adjacent features and the formation of voids within the trenches. Unfortunately, slowing the deposition rate also means increasing the deposition time, which reduces processing efficiency and production rates.

[0004] Therefore, there is a need for improved processes for the conformal oxidation of high aspect ratio structures. Summary of the Invention

[0005] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to semiconductor device fabrication, and in particular to methods for conformal radical oxidation of structures, such as high aspect ratio structures. In one embodiment, a method for oxidation is provided. The method includes flowing hydrogen gas at a first flow rate to a processing region of a processing chamber, with a substrate disposed in the processing region. The method further includes flowing oxygen gas at a second flow rate to a precursor activation apparatus. The method further includes flowing argon gas at a third flow rate to the precursor activation apparatus. The method further includes generating a plasma from the oxygen gas and the argon gas in the precursor activation apparatus. The method further includes flowing the plasma to the processing region, where the plasma mixes with the hydrogen gas to generate an activated processing gas. The method further includes exposing the substrate to the activated gas to form an oxide film on the substrate, where a growth rate of the oxide film is controlled by adjusting the third flow rate.

[0006] In another embodiment, a method for oxidation is provided. The method includes placing a substrate in a processing region of a processing chamber. The method further includes flowing hydrogen gas at a first flow rate to a precursor activation apparatus, the precursor activation apparatus being fluidly coupled to the processing region. The method further includes flowing oxygen gas at a second flow rate to the precursor activation apparatus. The method further includes flowing argon gas at a third flow rate to the precursor activation apparatus. The method further includes generating a plasma in the precursor activation apparatus from the hydrogen gas, oxygen gas, and argon gas. The method further includes flowing the plasma into the processing region. The method further includes exposing the substrate to the plasma to form an oxide film on the substrate, and the growth rate of the oxide film is controlled by adjusting the third flow rate.

[0007] In yet another embodiment, a method for oxidation is provided. The method includes placing a substrate in a processing region of a processing chamber. The method further includes flowing hydrogen gas at a first flow rate to a precursor activation apparatus, the precursor activation apparatus being fluidly coupled to the processing region. The method further includes flowing oxygen gas at a second flow rate to the precursor activation apparatus and the processing region. The method further includes flowing argon gas at a third flow rate to the precursor activation apparatus and the processing region. The method further includes generating a plasma in the precursor activation apparatus from the hydrogen gas, oxygen gas, and argon gas. The method further includes flowing the plasma into the processing region. The method further includes exposing the substrate to the plasma to form an oxide film on the substrate, and the growth rate of the oxide film is controlled by adjusting the third flow rate.

[0008] In yet another embodiment, a method for oxidation is provided. The method includes flowing hydrogen gas at a first flow rate to a processing region of a processing chamber, with a substrate disposed in the processing region. The method further includes flowing hydrogen gas at a second flow rate to a precursor activation device, the precursor activation device being fluidly coupled to the processing region. The method further includes flowing oxygen gas at a third flow rate to the precursor activation device and the processing region. The method further includes flowing argon gas at a fourth flow rate to the precursor activation device and the processing region. The method further includes generating a plasma in the precursor activation device from hydrogen gas, oxygen gas, and argon gas. The method further includes flowing the plasma into the processing region, where the plasma mixes with the hydrogen gas to generate an activated processing gas. The method further includes flowing the plasma into the processing region.

[0009] In order that the above-mentioned features of the present disclosure may be understood in detail, a more detailed description of the present embodiments briefly summarized above may be had by reference to the following embodiments. Some embodiments are illustrated in the accompanying drawings. It should be noted, however, that the present disclosure may admit of other equally effective embodiments, and therefore, the accompanying drawings illustrate only typical embodiments of the present disclosure and should not be considered as limiting the scope of the present disclosure. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of a remote plasma system in accordance with one or more embodiments of the present disclosure. [Figure 2] FIG. 1 is a process flow diagram of a selective oxidation method according to one or more embodiments of the present disclosure. [Figure 3A] 1 illustrates a cross-sectional view of a membrane structure having high aspect ratio features that may be processed in accordance with one or more embodiments of the present disclosure. [Figure 3B] 3B illustrates a cross-sectional view of the film structure of FIG. 3A having a conformal oxide film formed in accordance with one or more embodiments of the present disclosure. [Figure 4] 4 is a graph illustrating the growth rate and center-to-edge uniformity of an oxide film formed in accordance with embodiments described herein. [Figure 5] 1 is a graph showing oxide conformality based on hydrogen gas percentage and the presence or absence of argon. [Figure 6] 1 is a graph showing oxide quality based on the ratio of hydrogen gas to argon gas. DETAILED DESCRIPTION OF THE INVENTION

[0011] For ease of understanding, wherever possible, identical reference numerals have been used to designate identical elements common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0012] The following disclosure describes methods for oxidizing silicon films. Specific details are presented in the following specification and in Figures 1-6 to provide a thorough understanding of various embodiments of the present disclosure. Other details describing known structures and systems often associated with remote plasma oxidation are not provided in the following disclosure to avoid unnecessarily obscuring the description of the various embodiments.

[0013] Many of the details, dimensions, angles, and other features shown in the drawings are merely illustrative of specific embodiments. Thus, other embodiments may have other details, components, dimensions, angles, and features without departing from the spirit and scope of the present disclosure. In addition, further embodiments of the present disclosure may be practiced without some of the details described below.

[0014] The embodiments described herein are described below with respect to a remote plasma oxidation process. The apparatus descriptions described herein are exemplary and should not be understood or interpreted as limiting the scope of the implementations described herein. Other tools capable of performing remote plasma oxidation may also be adapted to benefit from the implementations described herein.

[0015] As the aspect ratio of HAR structures continues to increase, it becomes increasingly difficult to grow conformal films on these HAR structures. For example, oxide films formed on HAR structures by currently available remote plasma oxidation processes exhibit poor conformality and high pattern loading (e.g., non-uniformity on patterned wafers compared to bare silicon wafers). The inventors have discovered that adding argon gas between remote plasma oxidation runs can improve conformal oxide growth while improving pattern loading. Without being bound by theory, it is believed that the addition of argon gas reduces oxygen radical recombination, thereby increasing the concentration of oxygen radicals available for the plasma oxidation process. Therefore, argon gas can be used to control the oxide growth rate. For example, increasing the argon gas flow rate typically results in an increased oxide growth rate, while decreasing the argon gas flow rate typically results in a decreased oxide growth rate. Furthermore, the addition of argon improves strike reliability because argon has a lower ionization energy and therefore easier plasma formation.

[0016] The methods described herein can be performed using a plasma source, such as a remote plasma source (RPS), and a process chamber designed for atomic oxygen radical (O) growth (e.g., conformal radical oxidation) in high aspect ratio (HAR) structures, such as trench capacitor dielectrics, gate dielectrics, and 3D NAND flash structures. In some embodiments, the plasma source utilizes a gas mixture of argon, oxygen, and optionally hydrogen to grow silicon nitride (Si). x N y In some implementations, the plasma initiates radical oxidation of silicon-containing materials such as silica (S)N. In some embodiments, the argon, oxygen, and optionally hydrogen gas mixture has an argon concentration in the range of about 5% to about 80%, e.g., about 10% to about 50%. In some implementations, the plasma initiates radical oxidation of silicon-containing materials such as silica (S). i Silicon oxynitrides (SiO), such as SiNO, are formed as intermediates in the formation of x N y ) to initiate a reaction to form

[0017] In some embodiments, a combination of argon, hydrogen, and oxygen in a precursor activator, and in some cases hydrogen injection after the activator, during high temperature processing (e.g., 500-1100 degrees Celsius) results in highly conformal oxide growth of films (e.g., amorphous silicon, polysilicon, or silicon nitride) on very high aspect ratio structures (e.g., 40:1 aspect ratio, between 40:1 and 100:1 aspect ratio, 100:1 aspect ratio, or even greater than 100:1 aspect ratio).

[0018] In some embodiments, the combination of argon, hydrogen, and oxygen in the precursor activator, and in some cases hydrogen injection after the activator, during high temperature processing (e.g., 500-1100 degrees Celsius) results in improved oxide quality and / or prevents quality degradation.

[0019] 1 illustrates a substrate processing system 100 that may be used to perform the methods described herein. Other deposition chambers may also benefit from the present disclosure, and the parameters disclosed herein may 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 that require greater or lesser gas flow rates than those described for deposition chambers available from Applied Materials, Inc.

[0020] The substrate processing system 100 includes a thermal treatment chamber 102 and a precursor activation device 180 connected to the thermal treatment chamber 102 and used to remotely deliver plasma radicals to a processing region 113 of the thermal treatment chamber 102. The precursor activation device 180 can also be used to deliver a non-plasma activated gas mixture, for example, by adding energy to the gas that does not significantly ionize the gas. The thermal treatment chamber 102 includes 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 can 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 in 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 that surrounds the window assembly 117 around its periphery. The window assembly 117 also includes a first window 120 that covers first ends of the plurality of light pipes 141 and a second window 122 that covers 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, including the plurality of light pipes 141. In such cases, when light pipes are used, a vacuum can be created within the plurality of light pipes 141 by applying a vacuum to one of the plurality of light pipes 141 through a conduit 153 that passes through the outer wall 116, the one of the plurality of light pipes 141 being itself fluidly connected to the remaining pipes.

[0021] 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 also positioned through the separate reflector for optical access to electromagnetic radiation coming from the substrate 101.

[0022] 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 bore 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 bore 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.

[0023] 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, in this case a screwdriver. Operating the linear actuator 169 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.

[0024] Process gases are supplied to the thermal processing chamber 102 through a chamber inlet 175 and exhausted through a chamber outlet (not shown in FIG. 1 ) that is directed out of the plane of the paper and generally along the same plane as the chamber inlet 175 and the support ring 162. 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.

[0025] 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 a potential gradient that can 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 a 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 within 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.

[0026] To supply gas for plasma processing, a first gas source 192 is coupled 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 can 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 valve 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.

[0027] The precursor activator 180 may be coupled to an energy source (not shown) for providing excitation energy, such as energy having microwave or RF frequencies, to the precursor activator 180 and activating the process gas passing from the first gas source 192 into a plasma 183. When a nitrogen-containing gas, such as N, is used, plasma activation in the precursor activator 180 generates N * Radical, N + and N2 + Positively charged ions, such as radicals, and electrons are generated within the interior space 184. By positioning the precursor activator 180 away from the processing region 113 of the thermal processing chamber 102, exposure of the substrate to the 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. Use of an activated 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.

[0028] In some embodiments, a second hydrogen gas source (not shown) is fluidly coupled to the thermal treatment chamber 102. The second hydrogen gas source supplies hydrogen gas to the processing region 113, where the hydrogen gas is activated by a remote plasma comprising oxygen and argon that is transferred from the precursor activation device 180 to the processing region 113. In some embodiments 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.

[0029] In some implementations, a second argon gas source (not shown) is coupled to the thermal treatment chamber 102. A second hydrogen gas source supplies argon gas to the processing region 113, where the argon gas is activated by a remote plasma transferred from the precursor activation device 180 to the processing region 113. In some embodiments where a high percentage of argon gas is targeted, argon gas may be supplied to the processing region 113 through both the second gas source 198 and the second argon gas source.

[0030] FIG. 2 is a process flow diagram of an oxidation method 200 according to one or more embodiments of the present disclosure. Method 200 may be used to oxidize films such as amorphous silicon films, polysilicon films, silicon nitride films, alumina films, and silicon oxide films. FIG. 3A illustrates a cross-sectional view of a film structure having high aspect ratio features that may be processed according to method 200. FIG. 3B illustrates a cross-sectional view of the film structure of FIG. 3A with a conformal oxide layer formed according to method 200. Method 200 is described below with reference to high aspect ratio structures that may be formed on film stacks used to fabricate stair-like structures in film stacks for three-dimensional semiconductor devices, although method 200 may also be used to advantage in other device manufacturing applications. For example, method 200 may also be used to advantage for DRAMs (e.g., recessed channel array transistors (RCATs)). It should also be understood that the steps depicted in Figure 2 may be performed simultaneously and / or in a different order than that depicted in Figure 2. Additionally, method 200 may be used to advantage for selective and non-selective oxidation of films.

[0031] Method 200 begins in step 210 by placing a substrate in a processing chamber, such as thermal processing chamber 102 shown in FIG. 1 . The substrate may be a substrate 302 having a membrane structure 300 formed thereon, or any subset of membrane structure 300. A substrate 302 without a membrane structure (i.e., only substrate 302) may also be processed according to method 200. High aspect ratio features 340 are formed in membrane structure 300. Here, the surfaces defining high aspect ratio features 340 are substantially perpendicular to substrate 302; however, other types of features having tapered, angled, sloped, or curved surfaces may be processed using method 200. Note that high aspect ratio features 340 provide access to the surfaces of the HAR structure, for example, for gas transfer and / or reactant removal. As the aspect ratio increases, the surface area of ​​the HAR structure and the depth of the feature likewise increase. As the aspect ratio increases, conformal radical oxidation of the surface of the HAR structure is increasingly hindered by a depletion of oxygen radicals, especially near the bottom of the high aspect ratio feature 340. This depletion of oxygen radicals results in an increase in incubation time and a corresponding decrease in the conformal oxide growth rate. As disclosed herein, the addition of argon to the radical plasma oxidation process reduces oxygen recombination near the bottom of the high aspect ratio feature 340, thereby improving the availability of oxygen radicals for conformal radical oxidation and increasing the conformal oxide growth rate. While activated argon may be passivated by reaction with other species within the high aspect ratio feature 340, the activated argon is not further consumed by deposition on the surface of the high aspect ratio feature 340. As a result, more activated argon can penetrate to the bottom of the high aspect ratio feature 340 and react with and reactivate other species, such as gas phase oxygen and hydrogen, that may have been deactivated during their journey into the high aspect ratio feature 340.Thus, the activated argon adds chemical potential energy to the gas mixture within the high aspect ratio feature 340, increasing the overall reactivity, especially at the bottom of the high aspect ratio feature 340.

[0032] 3, only one high aspect ratio feature 340 is shown, it is understood that method 200 may be utilized with a substrate having multiple high aspect ratio features formed in film structure 300. In some embodiments, film structure 300 may comprise a gate structure or precursor structure for a three-dimensional NAND semiconductor application. In the fabrication of three-dimensional NAND semiconductor applications, stepped oxide-nitride pair structures are often utilized to form high aspect ratio gate stack NAND cells to increase circuit density.

[0033] A membrane structure 300 may be formed on a substrate 302. The membrane structure 300 may include a plurality of material layer stacks 3061, 3062, 3063, 3064...306 n (collectively 306) are sequentially formed on the substrate 302. Each material layer stack of the plurality of material layer stacks 306 includes a first film layer 3081, 3082, 3083, 3084...308 n (collectively 308), and second film layers 3101, 3102, 3103, 3104...310 formed thereon. n (collectively 310), such that the film structure 300 includes a plurality of alternating first and second film layers 308 and 310. In some embodiments, the plurality of first film layers 308 are silicon oxide layers and the plurality of second film layers 310 are silicon nitride layers. The plurality of material layer stacks 306 may be formed by PECVD deposition techniques in a plasma processing chamber.

[0034] In further embodiments, the first material layer stack / second material layer stack can be oxide / silicon, silicon / doped silicon, or silicon / nitride. All of these material combinations can be used in Bit-Cost Scalable (BiCS), Terabit Cell Array Transistor (TCAT), DRAM, and other 3D memory structures. In other embodiments, the first material layer stack and second material layer stack can be other material combinations. The deposition order of the first film layer 308 and the second film layer 310 on the substrate 302 can also be reversed.

[0035] The number of layers can depend on the memory device being fabricated. In some embodiments, the number of stacks can be 8x, or 16x, or 24x, or greater, where each stack of 8, 16, 24, 32, 64, 128, or more layers corresponds to one memory device. Two layers of different materials form each stack, so for an 8x stack number, the corresponding number of layers is 16, a 16x stack number has 32 layers, a 24x stack number has 48 layers, and so on, with each larger stack number having a higher number of layers.

[0036] In some embodiments, the substrate 302 can have a substantially planar surface, a non-planar surface, or a structured substantially planar surface. The substrate 302 can be crystalline silicon (e.g., Si <100> or Si <111> The substrate 302 can be made of materials such as silicon dioxide, strained silicon, silicon germanium, doped or undoped polysilicon, silicon-on-insulator (SOI) wafers (doped or undoped) and patterned or unpatterned wafers, carbon-doped silicon dioxide, silicon nitride, doped silicon, germanium, gallium arsenide, glass, or sapphire. The substrate 302 can have a variety of shapes and sizes, such as 200- or 300-mm diameter wafers and rectangular or square panels. Unless otherwise specified, the embodiments and examples described herein refer to a 300-mm diameter substrate. In some embodiments, the substrate 302 can be a crystalline silicon substrate (e.g., monocrystalline silicon or polycrystalline silicon).

[0037] The high aspect ratio feature 340 has an opening 350. The high aspect ratio is defined by a bottom surface 360 ​​and sidewalls 370. In some embodiments, the bottom surface 360 ​​is an exposed silicon surface or a silicon-containing surface (such as a monocrystalline silicon surface). In some embodiments, the bottom surface 360 ​​is an exposed germanium surface or a germanium-containing surface. In some embodiments, the bottom surface 360 ​​is defined by an exposed surface of the substrate 302. In some embodiments where the high aspect ratio feature 340 does not extend to the surface of the substrate 302, the bottom surface 360 ​​may be defined by the material layer stack 306 or the base layer, if present. The sidewalls 370 are defined by multiple material layer stacks 306.

[0038] The methods described herein improve the conformality of layers formed in aspect ratio features 340 with aspect ratios (hole height divided by hole width) of at least about 5:1 or greater (e.g., 6:1 or greater, 7:1 or greater, 8:1 or greater, 9:1 or greater, 10:1 or greater, 11:1 or greater, 12:1 or greater, 20:1 or greater, 50:1 or greater, 100:1 or greater, 16:7 or greater, or between about 10:1 and about 20:1, or between about 30:1 and about 50:1, or between about 40:1 and about 100:1, or between about 70:1 and about 100:1). Exemplary feature definitions include channels, vias, trenches, gaps, lines, contact holes, through-holes, or other feature definitions utilized in semiconductor devices, solar devices, or other electronic devices such as high-ratio contact plugs.

[0039] In some embodiments, the substrate 302 is placed in the processing region 113 under a non-reactive atmosphere and subjected to a temperature and pressure ramp-up process. Gases considered non-reactive include, but are not limited to, nitrogen gas (N), helium (He), argon (Ar), neon (Ne), and xenon (Xe). Gases containing hydrogen, argon, and / or oxygen may be supplied to the processing region 113 before and / or during the temperature and pressure ramp-up. Gases containing hydrogen, argon, and / or oxygen may be introduced directly into the processing region 113. In some embodiments, gases containing hydrogen, argon, and / or oxygen may be introduced into the processing region 113 via the precursor activation system 180. In some embodiments, a non-reactive atmosphere may be maintained during the ramp-up by flowing non-reactive gases into and out of the process chamber. The temperature and pressure may be ramped simultaneously or sequentially in any pattern to the desired predetermined process conditions.

[0040] In some embodiments, the methods described herein are performed by maintaining a pressure in the processing region 113 below 20 Torr, e.g., between about 1 Torr and about 10 Torr (e.g., between about 2 Torr and about 8 Torr, between about 2 Torr and about 3 Torr, or between about 2.5 Torr and about 3 Torr). In some embodiments, the methods described herein are performed by maintaining a substrate temperature between about 500 and about 1100 degrees Celsius, e.g., between about 600 and about 1100 degrees Celsius, between about 700 and about 800 degrees Celsius, or between about 750 and about 800 degrees Celsius.

[0041] In some embodiments, during processing, the chamber, the substrate, or both are maintained at a temperature between about 700 and about 800 degrees Celsius, and a chamber pressure between about 2 and about 3 Torr.

[0042] In step 220, the method 200 can further include flowing hydrogen gas into the processing region 113. In some embodiments, hydrogen gas is introduced directly into the substrate processing region 113. In some embodiments, hydrogen gas is introduced into the processing region 113 via the precursor activation system 180. In some embodiments, hydrogen gas is introduced into the processing region 113 both directly and via the precursor activation system 180. The hydrogen gas may be supplied to the processing chamber during the temperature and pressure ramp-up, or may be flowed after a set temperature is reached for better process control. In some embodiments, the set temperature includes the substrate temperature described above. Hydrogen (H) gas is used, although other gases, such as ammonia (NH), may be used.

[0043] For a 300 mm substrate in an appropriately sized chamber, the flow rate of H can be about 0.01 slm to about 20 slm (e.g., about 1 slm to about 10 slm) for a 300 mm substrate. Hydrogen can be flowed into the chamber to maintain a total chamber pressure of about 0.01 Torr to about 10 Torr (e.g., between about 0.5 Torr and about 8 Torr, between about 0.5 Torr and about 5 Torr, between about 2 Torr and about 3 Torr, or between about 2.5 Torr and about 3 Torr). In some embodiments, the temperature of the substrate can be raised to between about 500 degrees Celsius and about 1100 degrees Celsius, such as about 800 degrees Celsius.

[0044] In some embodiments, at least one of oxygen and argon is introduced into the processing region 113 before the plasma is generated from the plasma precursor gas mixture in step 230. The oxygen and / or argon can be introduced directly into the processing region 113. Alternatively, the oxygen and / or argon can be introduced into the processing region 113 via the precursor activation system 180. In some embodiments, the oxygen and / or argon is introduced into the processing region 113 for a period between about 5 seconds and about 30 seconds, e.g., about 15 seconds for a 300 mm substrate. It is believed that flowing the oxygen and / or argon gas mixture before the introduction of the plasma species provides continuous thermal and pressure stabilization of the processing region 113. The stabilization process may be performed before or overlap with step 230.

[0045] In step 230, the method 200 further includes generating a remote plasma from a plasma precursor gas mixture containing at least oxygen gas, argon gas, and optionally hydrogen gas. While oxygen (O) gas is used, other gases, such as nitrous oxide (NO), may be used. In some embodiments, the flow rates of oxygen gas, argon gas, and optionally hydrogen gas are increased to set points so that temperature, pressure, and flow control are responsive to initiation of the reaction. Without being bound by theory, it is believed that including hydrogen in the plasma precursor gas mixture further improves the conformality of the oxide in the HAR structure and increases the growth rate of the oxide film. In some embodiments, the remote plasma is generated in the precursor activation system 180. Oxygen is supplied to the precursor activation system 180 by a first gas source 192, argon gas is supplied to the precursor activation system 180 by a second gas source 198, and hydrogen gas is supplied to the precursor activation system 180 by a third gas source 199.

[0046] In step 230, oxygen gas is flowed into the precursor activator 180 at about 0.01 slm to about 15 slm per 300 millimeter substrate (e.g., about 1 slm to about 10 slm per 300 millimeter substrate). The oxygen gas can be mixed with argon gas and hydrogen gas to form a plasma precursor gas mixture. In some embodiments, argon gas is flowed into the precursor activator 180 at about 0.01 slm to about 15 slm per 300 millimeter substrate (e.g., about 1 slm to about 10 slm per 300 millimeter substrate). In some embodiments, hydrogen gas is flowed into the precursor activator 180 at about 0.01 slm to about 20 slm (e.g., about 1 slm to about 10 slm per 300 millimeter substrate). In some embodiments, the plasma precursor gas mixture includes an additional inert gas. The additional inert gas can include gases such as helium or krypton. The plasma precursor gas mixture can then be converted into a plasma using an energy source, which can be an RPS, a magnetron type plasma source, a modified magnetron type (MMT) plasma source, a remote plasma oxidation (RPO) source, a capacitively coupled plasma (CCP) source, an inductively coupled plasma (ICP) source, a microwave source, an ultraviolet source, or a toroidal plasma source.

[0047] In some embodiments where hydrogen is not included in the plasma and is supplied directly to the processing region 113, the plasma precursor gas mixture includes oxygen (O) and argon (Ar), and an argon concentration of up to about 55 percent provides beneficial effects on film growth rate and conformality. Above about 55 percent, the beneficial effects may be realized to a lesser extent. The argon concentration relative to the total amount of oxygen and argon is at least 0.5 to 55 percent, e.g., 20 to 50 percent, or 30 to 40 percent, e.g., 35 percent. In such cases, the oxygen concentration in the plasma precursor gas is at least 19.5 to 95.5 percent, e.g., 45 to 95.5 percent, e.g., 50 to 80 percent, or 60 to 70 percent, e.g., 65 percent.

[0048] In some embodiments, when the plasma precursor gas mixture includes oxygen (O), argon (Ar), and hydrogen (H), the argon concentration relative to the total amount of oxygen, argon, and hydrogen is at least 0.5 to 80 percent, e.g., 20 to 50 percent, or 30 to 40 percent, e.g., 35 percent. In such cases, the oxygen concentration in the plasma precursor gas is at least 20 to 95.5 percent, e.g., 45.5 to 90 percent, or 50 to 80 percent, or 60 to 70 percent, e.g., 60 percent. Furthermore, in such cases, the hydrogen concentration relative to the total amount of oxygen, argon, and hydrogen is at least 0.5 to 80 percent, e.g., 5 to 50 percent, or 10 to 40 percent, or 20 to 30 percent, e.g., 5 percent.

[0049] In some embodiments, the oxygen concentration (O2 / (H2+O2)%) is about 20 percent or greater.

[0050] The plasma precursor gas mixture is supplied at a total flow rate of between about 1,000 sccm and about 50,000 sccm (e.g., between about 6,000 sccm and about 15,000 sccm, or between about 10,000 sccm and about 35,000 sccm, or between about 25,000 sccm and about 35,000 sccm) within the above percentage ranges. For example, when both oxygen (O) and argon (Ar) are supplied, the oxygen (O) and argon (Ar) are supplied at a total flow rate of between about 10,000 sccm and about 50,000 sccm, particularly between about 25,000 sccm and about 35,000 sccm, or about 30,000 sccm, within the above percentage ranges. When the plasma-forming gas includes oxygen (O), argon (Ar), and hydrogen (H), the oxygen (O), argon (Ar), and hydrogen (H) are supplied at a total flow rate of between about 10,000 sccm and about 50,000 sccm (e.g., between about 10,000 sccm and about 35,000 sccm, or between about 25,000 sccm and about 35,000 sccm) within the above percentage ranges.

[0051] Gas flows for the processes described herein can be controlled by ratio. The ratio of oxygen to argon in the gas mixture affects the conformality and growth rate of the layers formed in the processes described herein, and different ratios can provide the most beneficial results for different processes. For the processes described herein, the gas flow ratio of oxygen gas to argon gas (O2:Ar) is between 1:4 and 50:1 (e.g., between 1:1 and 20:1, between 1:1 and 5:1, or between 5:1 and 10:1).

[0052] Using the substrate processing system 100 of FIG. 1 , a plasma precursor gas mixture is activated by exposure to RF power. The exposure to RF power ionizes at least a portion of the plasma precursor gas mixture, forming a plasma. RF power at a frequency between about 10 kHz and about 14 MHz is applied at a power level between about 1,000 W and about 5,000 W (e.g., between about 2,000 W and about 3,000 W, or about 2,500 W) to generate the plasma. In one example, a frequency of 13.56 MHz is used. In another example, a lower frequency of 400 kHz is used. Alternatively, a gas mixture of oxygen and argon can be activated by exposure to a microwave source, for example, a 2.45 GHz microwave source. The microwave source can be operated at a power level between approximately 1,000 W and 5,000 W, for example, 3,000 W, depending on the gas flow rate through the microwave source and the degree of activation.

[0053] In step 240, the method 200 further includes flowing a remote plasma into the processing chamber. In some embodiments in which hydrogen gas is present in the processing region 113, the remote plasma mixes with the hydrogen gas to generate an activated processing gas. The plasma mixes with the hydrogen above the substrate to generate H, O, and OH species. In some embodiments in which hydrogen is part of the plasma precursor gas, the remote plasma functions as an activated processing gas. When using a plasma, the residence time and degree of activation of the plasma in the interior space 184 and delivery line 190 before the plasma reaches the processing region 113 can be selected to provide a desired amount of quenching. As the gas residence time increases for a given activation level, more plasma quenching is achieved, and less activated gas is supplied to the processing region 113. Similarly, as the gas residence time decreases, less quenching is achieved.

[0054] In some embodiments, the chamber is flushed with an inert gas or hydrogen gas prior to forming the activated gas. This flushing can occur simultaneously with the formation of the oxygen and argon plasma. Similarly, hydrogen can be flowed into the chamber before the oxygen and argon plasma is flowed from a remote plasma source, or hydrogen can be flowed simultaneously and mixed with the oxygen and argon plasma above the substrate.

[0055] In operation 250, the method 200 further includes exposing the substrate to an activated gas to oxidize the substrate surface to form an oxide film, such as silicon oxide layer 380, as shown in Figure 3B. In some embodiments, the silicon oxide layer is a conformal silicon oxide layer.

[0056] In step 260, the argon flow rate is controlled to increase or decrease the oxide deposition rate. The inventors discovered that flowing argon into either the remote plasma source or the chamber slit valve generates energetic argon species that prevent oxygen radical recombination. Therefore, increasing the argon gas flow rate to the remote plasma source can increase the oxide growth rate, thereby reducing oxygen radical recombination and increasing the concentration of oxygen radicals available for oxide formation. Furthermore, in some embodiments where slowing the oxide growth rate is appropriate, decreasing the argon gas flow rate to the remote plasma source increases oxygen radical recombination, thereby decreasing the amount of oxygen radicals available for oxide growth and decreasing the growth rate, despite the increased concentration of oxygen species. Thus, argon provides an independent knob for increasing or decreasing the oxide growth rate for the remote plasma oxidation process. Furthermore, Ar addition can be adjusted independently of other parameters (pressure, flow rate, temperature, etc.) to achieve wafer-wide oxidation uniformity.

[0057] FIG. 4 is a graph 400 illustrating the growth rate and center-to-edge uniformity of oxide films formed according to embodiments described herein. As shown in FIG. 4, the growth rate begins to decrease when the argon content in the remote plasma exceeds 50%. FIG. 4 further illustrates that the oxide growth rate at approximately 15% argon is approximately 3% faster than oxide films grown without argon for a 10% H / (H+O) ratio, despite the significant dilution of reactive precursor gases in the process chamber when argon is used. Without being bound by theory, it appears that deactivation of reactive species increases faster than the overall concentration of reactive species (as opposed to non-reactive species such as argon) as the argon concentration decreases, resulting in an overall decrease in film growth rate as the argon concentration decreases. Thus, in the methods described herein, film growth rate is inversely related to the argon flow rate up to approximately 55 percent argon, based on the total amount of argon species plus oxygen species, all other conditions being equal. Above approximately 55 percent, lesser benefits are realized. Furthermore, the conformality of the deposited film is directly related to the argon flow rate, as more argon reduces the concentration gradient of activated species in HAR features, such as high aspect ratio feature 340.

[0058] 5 is a graph 500 showing oxide conformality based on the percentage of hydrogen gas and the presence or absence of argon. The portion of graph 500 labeled "No" was performed using only hydrogen and oxygen gases. The portion of graph 500 labeled "Yes" was performed using hydrogen, oxygen, and argon gases. As shown in graph 500, only a certain percentage of hydrogen gas with argon present results in improved conformality of the as-deposited oxide film.

[0059] 6 is a graph 600 illustrating oxide quality based on the percentage of hydrogen gas relative to the percentage of argon gas. Graph 600 demonstrates that, in the absence of argon, a certain percentage of hydrogen gas can degrade oxide quality. By adding sufficient argon gas, it is possible to eliminate or reduce the degradation of oxide quality without argon gas.

[0060] In summary, some embodiments described herein enable conformal oxide (e.g., silicon oxide) growth in HAR structures. The inventors have found that adding argon during several remote plasma oxidation runs can improve conformal oxide growth while also improving pattern loading. Without being bound by theory, it is believed that the addition of argon gas reduces oxygen radical recombination, thereby increasing the concentration of oxygen radicals available for the plasma oxidation process. Therefore, argon gas can be used to control the oxide growth rate. For example, increasing the argon gas flow rate typically results in an increased oxide growth rate, while decreasing the argon gas flow rate typically results in a decreased oxide growth rate.

[0061] The articles "a," "an," "the," and "said" when introducing elements of the disclosure or exemplary aspects of embodiments of the disclosure are intended to mean that there is one or more than one of the element.

[0062] The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0063] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of which is defined by the claims that follow.

Claims

1. 1. A method for oxidation comprising: placing a substrate in a processing region of a processing chamber; flowing hydrogen gas at a first flow rate through a precursor activation device, the precursor activation device being fluidly coupled to the processing region; flowing oxygen gas at a second flow rate into the precursor activation device; flowing argon gas into the precursor activation device at a third flow rate; generating a plasma from the hydrogen gas, the oxygen gas, and the argon gas in the precursor activation device; flowing the plasma into the processing region; exposing the substrate to the plasma to form an oxide film on the substrate, wherein a growth rate of the oxide film is controlled by adjusting the third flow rate, and a ratio of the second flow rate to the third flow rate (O ２ exposing the substrate to the plasma to form an oxide film on the substrate, wherein the ratio of Ar to Ar is between 1:4 and 50:1; A method comprising:

2. 10. The method of claim 1, further comprising increasing the third flow rate to increase the growth rate of the oxide film.

3. 10. The method of claim 1, further comprising decreasing the third flow rate to decrease the growth rate of the oxide film.

4. 10. The method of claim 1, further comprising flowing the hydrogen gas through the precursor activation device and into the processing region before generating the plasma.

5. The method of claim 1 , further comprising flowing the oxygen gas and / or the argon gas into the processing region before flowing the plasma into the processing region.

6. 10. The method of claim 1, wherein the concentration of the argon gas in the precursor activation apparatus is between 0.5 percent and 80 percent based on the total amount of the argon gas, the oxygen gas, and the hydrogen gas.

7. 7. The method of claim 6, wherein the substrate is maintained at a temperature between 700 and 800 degrees Celsius and a chamber pressure between 2 and 3 Torr.

8. 10. The method of claim 1, wherein the substrate comprises at least one of an exposed silicon nitride surface, an exposed polysilicon surface, an exposed alumina surface, an exposed crystalline silicon surface, and an exposed silicon oxide surface.

9. The method of claim 1 , wherein the substrate is maintained at a temperature between 500 degrees Celsius and 1100 degrees Celsius.

10. 10. The method of claim 9, wherein the processing region is maintained at a pressure between 0.5 Torr and 5 Torr.

11. 10. The method of claim 1, wherein the substrate has a high aspect ratio feature thereon having an aspect ratio of 40:1 or greater, and the oxide film is formed on surfaces defining the high aspect ratio feature.

12. 12. The method of claim 11, wherein the high aspect ratio features are formed in a membrane structure formed on the substrate, the membrane structure including multiple material layers each having a silicon oxide layer and a silicon nitride layer.

13. 1. A method for oxidation comprising: placing a substrate in a processing region of a processing chamber; flowing hydrogen gas into a precursor activator at a first flow rate of 0.01 standard liters per minute (slm) to 20 slm, the precursor activator being fluidly coupled to the processing region; flowing oxygen gas into the precursor activation device at a second flow rate of 0.01 standard liters per minute (slm) to 15 slm; flowing argon gas into the precursor activation device at a third flow rate; generating a plasma from the hydrogen gas, the oxygen gas, and the argon gas in the precursor activation device; flowing the plasma into the processing region; exposing the substrate to the plasma to form an oxide film on the substrate, wherein a growth rate of the oxide film is controlled by adjusting the third flow rate between 0.01 slm and 15 slm, and a ratio of the second flow rate to the third flow rate (O ２ exposing the substrate to the plasma to form an oxide film on the substrate, wherein the ratio of H:Ar) is between 1:4 and 50:1, and the substrate is maintained at a temperature between 500 degrees Celsius and 1100 degrees Celsius and a chamber pressure between 1 Torr and 10 Torr; A method comprising:

14. 14. The method of claim 13, further comprising increasing the third flow rate to increase the growth rate of the oxide film.

15. 14. The method of claim 13, further comprising decreasing the third flow rate to decrease the growth rate of the oxide film.

16. 14. The method of claim 13, wherein the concentration of the argon gas in the precursor activation apparatus is between 0.5 percent and 80 percent based on the total amount of the argon gas, the oxygen gas, and the hydrogen gas.

17. 14. The method of claim 13, further comprising flowing the oxygen gas through the precursor activation device into the processing region before generating the plasma.

18. 18. The method of claim 17, further comprising flowing the argon gas through the precursor activation device into the processing region before generating the plasma.

19. 20. The method of claim 18, wherein the oxygen gas and the argon gas are flowed into the processing region for a period of between 5 and 30 seconds before generating the plasma.

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