Dual pressure oxidation method for forming an oxide layer on a feature - Patents.com

Abstract

A method and apparatus for growing an oxide layer in a feature of a substrate is described herein. The method is suitable for use in semiconductor manufacturing. The oxide layer is formed by exposing the substrate to both a high pressure oxidizer exposure and a low pressure oxygen-containing plasma exposure. The high pressure oxidizer exposure is performed at a pressure above 10 Torr, and the low pressure oxygen-containing plasma exposure is performed at a pressure below about 10 Torr. The feature is a high aspect ratio trench or hole in a stack of silicon oxide and silicon nitride layers.

Description

[Technical field]

[0001] TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate generally to apparatus for semiconductor device manufacturing, and more particularly to a method for oxidizing features formed in three-dimensional device structures. [Background technology]

[0002]

[0002] The manufacture of silicon integrated circuits has placed challenging demands on the manufacturing process to increase the number of devices while shrinking the minimum feature size on a chip. These demands extend to manufacturing steps that include depositing layers of different materials over challenging topologies and etching further features within those layers. The manufacturing process for next-generation NAND flash memory involves particularly challenging device 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 have been developed. Such designs typically introduce alternating oxide and nitride layers that are deposited on a substrate and then etched to form structures with one or more surfaces that extend substantially perpendicular to the substrate. A single structure may have more than 100 such layers. Such designs may also include high aspect ratio (HAR) structures with aspect ratios of 30:1 or greater.

[0003]

[0003] HAR structures are often coated with a silicon nitride (SiNx), amorphous silicon, or polysilicon layer. It is difficult to conformally oxidize such structures to form an oxide layer of uniform thickness. Uniform oxidation of each structure becomes increasingly difficult as the aspect ratio increases, such as HAR structures with aspect ratios greater than 50:1 or even greater than 70:1.

[0004] Therefore, there is a need for an improved method and apparatus for forming an oxide layer in a HAR structure. Summary of the Invention

[0005]

[0005] The present disclosure generally relates to methods and apparatus for growing a layer on a substrate. In one embodiment, a method for processing a substrate is described. The method is suitable for use in semiconductor manufacturing. The method includes exposing the substrate to an oxidizing agent at a first pressure greater than about 20 Torr. After exposing the substrate to the oxidizing agent at the first pressure, the pressure surrounding the substrate is reduced from the first pressure to a second pressure less than about 10 Torr. After reducing the pressure to the second pressure, the substrate is exposed to an oxygen-containing plasma while the pressure surrounding the substrate is at the second pressure.

[0006] In another embodiment, another method of processing a substrate suitable for use in semiconductor manufacturing is described. The method includes exposing a plurality of features having nitride wall surfaces to an oxidizing agent at a first pressure greater than about 50 Torr to form an oxide layer on the nitride wall surfaces on the substrate. After exposing the plurality of features to the oxidizing agent at the first pressure, a pressure surrounding the substrate is reduced from the first pressure to a second pressure less than about 5 Torr. After reducing the pressure to the second pressure, the substrate is exposed to an oxygen-containing plasma while the pressure surrounding the substrate is at the second pressure to increase a thickness of the oxide layer.

[0007] In yet another embodiment, a non-transitory computer readable medium is described. The non-transitory computer readable medium has stored thereon instructions suitable for use in semiconductor manufacturing. When the instructions are executed by a processor, the computer system performs several steps. The steps include exposing a substrate to an oxidizing agent at a first pressure greater than about 20 Torr. After exposing the substrate to the oxidizing agent, a pressure surrounding the substrate is reduced from the first pressure to a second pressure less than about 10 Torr. After reducing the pressure to the second pressure, the substrate is exposed to an oxygen-containing plasma while the pressure surrounding the substrate is at the second pressure.

[0008]

[0008] In order that the above-mentioned features of the present disclosure may be understood in detail, the present disclosure summarized above will now be more particularly described with reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings depict only exemplary embodiments and therefore should not be considered limiting in scope, as the present disclosure may admit of other equally effective embodiments. [Brief description of the drawings]

[0009] [Figure 1A] 1 is a cross-sectional schematic side view of a first processing system according to embodiments described herein. [Figure 1B] FIG. 1B is a cross-sectional schematic plan view of a first processing system of FIG. 1A according to embodiments described herein. [Figure 2A] FIG. 2 is a cross-sectional schematic plan view of a second processing system according to embodiments described herein. [Figure 2B] FIG. 13 is a cross-sectional schematic plan view of a third processing system according to embodiments described herein. [Diagram 3] FIG. 13 is a cross-sectional schematic side view of a fourth processing system according to embodiments described herein. [Figure 4] FIG. 13 is a cross-sectional schematic side view of a fifth processing system according to embodiments described herein. [Diagram 5] 1A-C are cross-sectional schematic side views of a device stack during a method of formation according to embodiments described herein. [Figure 6] FIG. 5B is a flow diagram of a method for forming FIGS. 5A-5C according to embodiments described herein. [Figure 7] 1 is a graph showing oxide growth rate on a device stack at various pressures and gas mixtures. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010]

[0018] To facilitate understanding, wherever possible, the same 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.

[0011]

[0019] The present disclosure generally relates to a method and apparatus for conformal oxidation of high aspect ratio structures in a device stack. The method includes utilizing high pressure exposure of a substrate to an oxidizing agent. The high pressure exposure of the substrate to an oxidizing agent forms an oxide layer on a silicon nitride, amorphous silicon, or polysilicon layer in the high aspect ratio trench. The oxide layer is a conformal oxide layer having a conformality of 95% or greater. The oxide layer grows to a thickness of about 2 nm to about 3 nm during the high pressure exposure of the substrate. As the oxide layer grows from the silicon nitride, amorphous silicon, and polysilicon layers, a portion of the silicon nitride, amorphous silicon, and polysilicon layers oxidize.

[0012]

[0020] After the high pressure exposure of the substrate to the oxidizing agent, the pressure around the substrate is reduced. The reduced pressure allows for the formation of an oxygen radical-containing plasma. The oxygen radical-containing plasma also grows an oxide layer on the silicon nitride layer. The oxide layer formed during the high pressure exposure acts as an underlayer, and the oxide layer grows during the exposure to the oxygen radical-containing plasma. The oxide layer grows uniformly because the previously formed oxide layer reduces the flux rate of the oxidizing agent into the shallow portions of each high aspect ratio structure. The oxide layer grows to a thickness of greater than about 5 nm, e.g., greater than about 6 nm, e.g., from about 6 nm to about 8 nm, during the exposure to the oxygen radical-containing plasma. The conformality of the oxide layer after the exposure to the oxygen radical-containing plasma is completed remains greater than about 95%.

[0013]

[0021] The high pressure oxidizer exposure allows more species to reach the bottom of the high aspect ratio features of the substrate and form a conformal layer. However, high pressure oxidizers have slow growth rates on amorphous silicon, polysilicon, and silicon nitride. Therefore, a second oxidizer exposure of an oxygen radical-containing plasma is utilized to increase the growth rate of the oxide layer and reduce the oxidation time to achieve the target thickness. To increase the thickness of the oxide layer, the exposure to the oxygen radical-containing plasma can be repeated or lengthened.

[0014]

[0022] Each of the high pressure oxide exposure and the oxygen radical containing plasma exposure can be performed either in the same process system or in different process systems. Performing both process steps in one process system can allow for increased throughput and reduced overall costs. However, performing both high pressure and plasma containing processes in the same process system can be difficult depending on some process chamber architectures. Described herein is an improved process system that allows for both high pressure and plasma containing processes to be performed in the same process region.

[0015]

[0023] In other embodiments, the substrate is moved between two or more process systems, such that a first process system performs a high pressure process and a second process system performs a plasma-containing process. As described herein, multiple process system types can be utilized. The processes described herein can be performed during the manufacture of 3D NAND structures.

[0016]

[0024] FIG. 1A is a cross-sectional view of a first processing system 100 according to an embodiment described herein. The first processing system 100 includes a process chamber 102 and a remote plasma source 104. The process chamber 102 may be a rapid thermal processing (RTP) chamber. The remote plasma source 104 may be any suitable remote plasma source, such as a microwave coupled plasma source operable at a power of about 6 kW. The remote plasma source 104 is coupled to the process chamber 102 to flow plasma formed in the remote plasma source 104 toward the process chamber 102. The remote plasma source 104 is coupled to the process chamber 102 via a connector 106. Radicals formed in the remote plasma source 104 flow through the connector 106 into the process chamber 102 during processing of a substrate.

[0017]

[0025] The remote plasma source 104 includes a body 108 that surrounds a tube 110 in which the plasma is generated. The tube 110 may be made of quartz or sapphire. The body 108 includes a first end 114 coupled to an inlet 112 to which one or more gas sources 118 may be coupled to introduce one or more gases into the remote plasma source 104. In one embodiment, the one or more gas sources 118 include an oxygen-containing gas source, and the one or more gases include an oxygen-containing gas. The body 108 includes a second end 116 opposite the first end 114, the second end 116 being coupled to the connector 106. A coupling liner (not shown) may be disposed within the body 108 at the second end 116. A power source 120 (e.g., an RF power source) that provides power to the remote plasma source 104 to facilitate formation of the plasma may be coupled to the remote plasma source 104 via a matching network 122. The radicals in the plasma are flowed into the process chamber 102 through a connector 106 .

[0018]

[0026] The process chamber 102 includes a chamber body 125, a substrate support 128, and a window assembly 130. The chamber body 125 includes a first side 124 and a second side 126 opposite the first side 124. In some embodiments, a lamp assembly 132 surrounded by a top sidewall 134 is positioned above and coupled to the window assembly 130. The lamp assembly 132 may include a plurality of lamps 136 and a plurality of tubes 138, where each lamp 136 may be disposed in a corresponding tube 138. The window assembly 130 may include a plurality of light pipes 140, where each light pipe 140 may be aligned with a corresponding tube 138 such that thermal energy generated by the plurality of lamps 136 can reach a substrate disposed in the process chamber 102. In some embodiments, a vacuum may be created in the plurality of light pipes 140 by applying a vacuum to an exhaust 144 fluidly coupled to the plurality of light pipes 140. The window assembly 130 may have conduits 143 formed therein for circulating a cooling fluid through the window assembly 130 .

[0019]

[0027] The processing region 146 may be defined by the chamber body 125, the substrate support 128, and the window assembly 130. The substrate 142 is disposed within the processing region 146 and is supported by a support ring 148 above a reflector plate 150. The support ring 148 may be attached to a rotatable cylinder 152 to facilitate rotation of the substrate 142. The cylinder 152 may be levitated and rotated by a magnetic levitation system (not shown). The reflector plate 150 reflects energy to the backside of the substrate 142 to promote uniform heating of the substrate 142 and improve the energy efficiency of the first process system 100. A plurality of fiber optic probes 154 may be disposed through the substrate support 128 and the reflector plate 150 to facilitate monitoring the temperature of the substrate 142.

[0020]

[0028] A liner assembly 156 is disposed on the first side 124 of the chamber body 125 to allow radicals to flow from the remote plasma source 104 to the processing region 146 of the process chamber 102. The liner assembly 156 may be made of an oxidation-resistant material, such as quartz, to reduce interaction with process gases, such as oxygen radicals. The liner assembly 156 is designed to reduce constriction of the flow of radicals into the process chamber 102. The liner assembly 156 is described in more detail below. The process chamber 102 further includes a distributed pumping structure 133 formed in the substrate support 128 adjacent the second side 126 of the chamber body 125 to regulate the flow of radicals from the liner assembly 156 to a pumping port. The distributed pumping structure 133 is located adjacent the second side 126 of the chamber body 125.

[0021]

[0029] An opening 158 is disposed through the second side 126 of the chamber body 125. The opening 158 is configured to allow a substrate to pass therethrough. The opening 158 may be disposed adjacent to a transfer chamber or other process system.

[0022]

[0030] The controller 180 may be coupled to and control the operation of various components of the first process system 100, such as the process chamber 102 and / or the remote plasma source 104. The controller 180 generally includes a central processing unit (CPU) 182, a memory 186, and support circuits 184 for the CPU 182. The controller 180 may directly control the first process system 100 or may control it through other computers or controllers (not shown) associated with certain support system components. The controller 180 may be one of any form of general-purpose computer processor that may be used in an industrial environment to control various chambers and sub-processors. The memory 186, or computer readable medium, may be one or more of readily available memories such as random access memory (RAM), read only memory (ROM), floppy disks, hard disks, flash drives, or any other form of digital storage, local or remote. The support circuits 184 are coupled to the CPU 182 for supporting the processor in a conventional manner. The support circuits 184 may include cache, power supplies, clock circuits, input / output circuits and subsystems, and the like. The processing operations may be stored in memory 186 as software routines 188 that may be executed or invoked to turn the controller 180 into a special purpose controller that controls the operation of the first processing system 100. The controller 180 may be configured to perform any of the methods described herein.

[0023]

[0031] 1B is a cross-sectional schematic plan view of the first processing system 100 of FIG. 1A. The first processing system 100 includes both a remote plasma source 104 and a gas injector 192. The liner assemblies 156 of the remote plasma source 104 and the gas injector 192 are disposed at different points along the periphery of the processing region 146. The inclusion of both the remote plasma source 104 and the gas injector 192 disposed through the same chamber body 125 and coupled to the same processing region 146 allows both high pressure oxidation and low pressure plasma processes to be performed within the same processing region 146.

[0024]

[0032] One or more exhaust passages 196a, 196b are disposed adjacent to and / or within the opening 158. The one or more exhaust passages 196a, 196b are exhaust ports and are configured to exhaust gas and / or plasma from the processing region 146. The one or more exhaust passages 196a, 196b are coupled to one or more exhaust pumps (not shown) to remove exhaust gas and / or plasma in the processing region 146. The one or more exhaust passages 196a, 196b include at least a first exhaust passage 196a and a second exhaust passage 196b. The first exhaust passage 196a is disposed on a first side of the opening 158, and the second exhaust passage 196b is disposed on the opposite side of the opening 158. Utilizing two exhaust passages 196a, 196b on opposite sides of the opening 158 allows for more even exhaust of process gas and plasma during processing.

[0025]

[0033] A gas injector 192 is disposed through a wall of the chamber body 125. The gas injector 192 includes a plurality of gas passages 194 disposed therethrough and fluidly connected to the processing region 146. The gas injector 192 is configured to inject process gas into the processing region 146 and across an upper surface of the substrate 142. The gas injector 192 and each of the gas passages 194 disposed therein are coupled to a process gas source 178. The process gas source 178 is configured to supply one or more oxidizers. The one or more oxidizers may be hydrogen (H2), oxygen (O2), ozone (O3), nitrous oxide (N2O), water / water vapor (H2O), hydrogen peroxide (H2O2), or hydroxide (OH). - ) or a mixture thereof.

[0026]

[0034] The center of the gas injector 192 may be disposed at a first angle θ1 relative to the center of the liner assembly 156 of the remote plasma source 104. The first angle θ1 is about 45 degrees to about 135 degrees, such as about 60 degrees to about 120 degrees, such as about 75 degrees to about 105 degrees. In some embodiments, the first angle θ1 is about 90 degrees such that the gas injector 192 and the liner assembly 156 of the remote plasma source 104 are perpendicular to each other along the periphery of the processing region 146. Positioning each of the gas injector 192 and the liner assembly 156 at separate locations around the processing region allows both components to be independently utilized in the first processing system 100.

[0027]

[0035] The center of the liner assembly 156 of the remote plasma source 104 is disposed at a second angle θ2 relative to the center of the opening 158 configured to deliver the substrate 142 into and out of the processing region 146. The second angle θ2 is about 150 degrees to about 210 degrees, such as about 175 degrees to about 195 degrees, such as about 190 degrees. In some embodiments, the liner assembly 156 and the opening 158 are aligned along a similar axis. Aligning the liner assembly 156 and the opening 158 allows the plasma to flow uniformly across the substrate 142 and be exhausted through one or more exhaust passages 196a, 196b on either side of the opening 158. Positioning each of the gas injectors 192 and the opening 158 at an angle relative to one another allows a helical gas flow across the surface of the substrate 142. The helical gas flow has been shown to allow for a more uniform oxide formation.

[0028]

[0036] The second process system 100a and the third process system 100b of FIGS. 2A and 2B can be used in place of the first process system 100 of FIGS. 1A-1B. The second process system 100a and the third process system 100b are separate process systems, but can be used together to perform the processes described herein. Each of the second process system 100a and the third process system 100b is vacuum coupled such that a substrate, such as the substrate 142, passing between the second process system 100a and the third process system 100b is kept in a vacuum environment and is not exposed to the atmosphere. FIG. 2A is a cross-sectional schematic plan view of the second process system 100a. FIG. 2B is a cross-sectional schematic plan view of the third process system 100b. The second process system 100a and the third process system 100b are similar to the first process system 100, except that the second process system 100a does not include a remote plasma source 104 and the third process system 100b does not include a gas injector 192.

[0029]

[0037] Separating the remote plasma source 104 and gas injector 192 into two separate process systems 100a, 100b allows the high pressure oxidation step to be performed in a separate processing region 146 from the low pressure plasma step. Separating the process systems 100a, 100b allows for greater process flexibility and improved efficiency in maintenance performed on either of the process systems 100a, 100b.

[0030]

[0038] As shown in Figure 2A, the second process system 100a includes a passageway 157 opposite the opening 158. The passageway 157 may be configured to include one or more sensors, exhaust liners, or process gas injectors disposed therein. As shown in Figure 2B, the third process system 100b includes a passageway 191 perpendicular to the opening 158 and the liner assembly 156. The passageway 191 may be configured to include one or more sensors or exhaust liners.

[0031]

[0039] 3 is a cross-sectional schematic side view of a fourth process system 300. The fourth process system 300 includes a chamber body 302, a showerhead 308 disposed within the chamber body 302, a substrate support 304, and an inductive coil 306 disposed around the chamber body 302. The fourth process system 300 can be used in place of any one of the first process system 100, the second process system 100a, or the third process system 100b. The fourth process system 300 is configured to enable high pressure oxidation and low pressure plasma processes.

[0032]

[0040] A showerhead 308 is disposed above the substrate support 304 in the chamber body 302. The showerhead 308 is configured to distribute one or a combination of process gases and plasma into a processing region 315 of the fourth process system 300. The showerhead 308 includes a number of gas passages 312 formed therethrough. The number of gas passages 312 may be fluidly coupled to a plenum 310 disposed above the showerhead 308 as well as the processing region 315. A gas source 316 is fluidly coupled to the plenum 310 through passages 314 formed in the chamber body 302. The gas source 316 is configured to supply one or more process gases, such as one or more oxidizers. The one or more oxidizers may be hydrogen (H2), oxygen (O2), ozone (O3), nitrous oxide (N2O), water / water vapor (H2O), hydrogen peroxide (H2O2), or hydroxide (OH). - ). A mixture of water (H2O), ozone (O3) and / or hydrogen peroxide (H2O2) may be delivered by the gas source 316 during a high pressure process, such as a process using a pressure greater than about 50 Torr. A mixture of hydrogen (H2) and oxygen (O2) is introduced during a low pressure process, such as a process at a pressure of about 0.5 Torr to about 5 Torr. The mixture of hydrogen and oxygen during the low pressure process produces oxygen radicals (O * ) improve the longevity of the species.

[0033]

[0041] One or more exhaust passages 318 are formed through the chamber body 302. The one or more exhaust passages 318 are formed below the substrate support 304 and the inductive coil 306. The one or more exhaust passages 318 are coupled to an exhaust pump (not shown) and configured to remove gas and / or plasma from the processing region 315. The substrate support 304 is disposed within the processing region 315 and configured to support a substrate, such as substrate 142. The substrate support 304 is configured to rotate about a central axis and move in one or more directions.

[0034]

[0042] The inductive coil 306 is disposed about the chamber body 302. The inductive coil 306 is configured to generate a plasma in the processing region 315. The inductive coil 306 is coupled to a power source 320. The power source 320 is a radio frequency (RF) power source. The power source 320 is configured to apply power to the inductive coil 306 to generate a plasma in the processing region 315 during a plasma process.

[0035]

[0043] FIG. 4 is a cross-sectional schematic side view of a fifth processing system 400. The fifth processing system 400 is a batch processing system such that multiple substrates 142 may be processed simultaneously. The fifth processing system 400 may be configured to perform a high pressure oxidation step. An oxidant is supplied to a processing region 415 of the fifth processing system 400 from a plurality of gas inlets 406. The plurality of gas inlets 406 may be nozzles or injectors and are coupled to a gas distribution tower 404. The plurality of gas inlets 406 are disposed along the gas distribution tower 404 and configured to supply process gases to various locations within the processing region 415. A gas supply 418 is fluidly coupled to the gas distribution tower 404 and the plurality of gas inlets 406. The gas supply 418 may be any of hydrogen (H2), oxygen (O2), ozone (O3), nitrous oxide (N2O), water / water vapor (H2O), hydrogen peroxide (H2O2), or hydroxide (OH). -), or a mixture thereof. A mixture of water (H2O), ozone (O3) and / or hydrogen peroxide (H2O2) may be delivered by the gas supply 418 during a high pressure process, such as a process using a pressure greater than about 50 Torr. A mixture of hydrogen (H2) and oxygen (O2) may then be introduced into the fifth process system 400 during a low pressure process, such as a process at a pressure less than about 1 Torr, to perform a batch low pressure process. The mixture of hydrogen and oxygen combusts during the low pressure process to form atomic oxygen.

[0036]

[0044] A plurality of substrates 142 are disposed on a carrier assembly 408. The carrier assembly 408 includes a plurality of substrate support shelves 412. Each support shelf 412 has a substrate support surface. The substrate support surface may include a single support ring or may include a plurality of discreet substrate support ledges. Each pair of support shelves 412 forms a slot therebetween for the substrate 142 to be inserted therein. Each of the support shelves 412 is associated with at least one gas inlet 406 such that the at least one gas inlet 406 is disposed parallel to or above each support shelf 412. Each of the support shelves 412 are parallel to one another, forming a row of support shelves 412. Both the carrier assembly 408 and the gas distribution tower 404 are disposed within a processing region 415 of the chamber body 402.

[0037]

[0045] One or more exhaust passages 410 are formed through the chamber body 402. The one or more exhaust passages 410 are formed below a substrate support shelf 412. The one or more exhaust passages 410 are coupled to an exhaust pump (not shown) and configured to remove gas and / or plasma from a processing region 415.

[0038]

[0046] 5A-5C are cross-sectional schematic side views of a device stack 500 during a formation method 600. The device stack 500 includes multiple layers, such as multiple oxide layers 502 and multiple nitride layers 504. The oxide layers 502 are silicon oxide materials. The nitride layers 504 are silicon nitride materials. Each pair of oxide layers 502 is separated by a nitride layer 504, and the oxide layers 502 and nitride layers 504 are arranged in an alternating stack. Each of the oxide layers 502 and nitride layers 504 has a thickness of about 10 nm to about 30 nm, such as about 15 nm to about 25 nm, such as about 20 nm. A single nitride layer 504 in contact with a single oxide layer 502 is bonded to each other to form a pair 505. There are more than 100 pairs 505 of oxide layers 502 and nitride layers 504, such that there are at least 100 oxide layers 502 and at least 100 nitride layers 504. In some embodiments, there are more than 125 pairs 505 of oxide layers 502 and nitride layers 504, such that there are at least 125 oxide layers 502 and at least 125 nitride layers 504. In some embodiments, there are more than 140 pairs 505 of oxide layers 502 and nitride layers 504, such that there are at least 140 oxide layers 502 and at least 140 nitride layers 504.

[0039]

[0047] The device stack 500 includes a plurality of features 520 formed therein. The features 520 may be trenches or holes formed in the device stack 500. The features 520 are formed through a plurality of pairs 505, such as at least 100 pairs 505, such as at least 125 pairs 505, such as at least 140 pairs 505. The features 520 are formed from a top surface 518 of the device stack 500 to a bottom surface 509 of each feature 520. Each feature 520 is formed from two portions 510, 512. The two portions 510, 512 are a first portion 510 and a second portion 512. The first portion 510 is disposed inwardly from the top surface 518, and the second portion 512 is adjacent to the first portion 510 and extends further inwardly away from the top surface 518 from the bottom of the first portion 510. The first portion 510 includes at least 50 pairs 505, such as at least 60 pairs 505, such as at least 70 pairs 505. Similarly, the second portion 512 includes at least 50 pairs 505, such as at least 60 pairs 505, such as at least 70 pairs 505. The first portion 510 and the second portion 512 are separated by a transition portion 514.

[0040]

[0048] As the depth of each portion 510, 512 of the feature 520 in the device stack 500 increases, the width of the feature 520 decreases, narrowing the feature 520. Thus, as the first portion 510 extends away from the top surface 518 toward the bottom surface 509, the feature 520 narrows. Similarly, as the second portion 512 extends away from the top surface 518 toward the bottom surface 509, the feature 520 narrows. At the transition 514, where the trench extends from the first portion 510 to the second portion 512, the feature 520 widens. The feature 520 widens as the transition 514 due to the use of two separate processes to form the feature 520. The second portion 512 may be formed prior to the formation of the first portion 510. This causes the transition 514 to include a change in width. The bottom surface 509 of each feature 520 may further include a base that is wider than the bottom of the second portion 512.

[0041]

[0049] The inner surface of each feature 520 is coated with a silicon layer 508 such that the silicon layer 508 forms on the walls of each feature 520. The silicon layer 508 acts as a liner of each feature 520 and covers both the first portion 510 and the second portion 512. The silicon layer 508 is deposited using an atomic layer deposition (ALD) process. The silicon layer 508 may be a silicon nitride layer, amorphous silicon, or polysilicon. In some embodiments, the silicon layer 508 is a silicon nitride layer.

[0042]

[0050] Each feature has an aspect ratio. The aspect ratio is the ratio of the depth of the feature 520 to the width of the feature 520 measured at the top opening that limits reactant transport. The width of the feature 520 is the width at the top opening of the first portion 510 or the top opening of the second portion 512, and the width of the feature 520 is measured as the width adjacent the top surface 518 of the device stack 500. The aspect ratio is greater than about 70:1, such as greater than about 75:1, such as greater than about 100:1, such as greater than about 120:1, such as greater than about 150:1, such as greater than about 170:1.

[0043]

[0051] A method 600 is performed on the device stack 500. The method 600 is illustrated in Figure 6 and includes positioning 602 a substrate in a first process chamber. The substrate includes the device stack 500 and may be a substrate similar to the substrate 142 of Figures 1A, 1B, 2, 3, and 4. The first process chamber may be any one of the first process system 100, the second process system 100a, the fourth process system 300, or the fifth process system 400. The substrate is disposed on a substrate support surface in the first process chamber.

[0044]

[0052] Once the substrate is positioned in the first process chamber, the substrate is exposed to an oxidizing agent 516 at a first pressure during another step 604. The oxidizing agent 516 may include oxygen, hydrogen (H2), oxygen (O2), ozone (O3), nitrous oxide (N2O), water / water vapor (H2O), hydrogen peroxide (H2O2), or hydroxide (OH - ), or a combination thereof. In one embodiment, the oxidizer 516 includes water vapor (H2O), ozone (O3), and / or hydrogen peroxide (H2O2). In another embodiment, the oxidizer 516 includes ozone (O3) and hydrogen (H2). The oxidizer 516 can be flowed with a carrier gas such that the oxidizer 516 is part of a mixed oxidizer including the oxidizer 516 and the carrier gas. The carrier gas can be any one or combination of helium (He), hydrogen (H2), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), or nitrogen (N2). The mixed oxidizer is composed almost entirely of the oxidizer 516 and the carrier gas, such that the mixed oxidizer is entirely one or more of the oxidizers 516 and the carrier gas. Water vapor, ozone, or hydrogen peroxide can be used alone or in combination. The oxidizing agent 516 induces the formation of an oxide layer 522 on the silicon layer 508, as shown in Figure 5B. When water vapor, ozone, and hydrogen peroxide are used alone, the growth rate of the oxide layer 522 is slower than when a combination of at least two of water vapor, ozone / hydrogen, and hydrogen peroxide is used.

[0045]

[0053] The first pressure is greater than about 10 Torr, e.g., greater than about 15 Torr, e.g., greater than about 20 Torr, e.g., greater than about 50 Torr, e.g., from about 50 Torr to about 760 Torr. The partial pressure of the oxidizer is greater than about 10 Torr partial pressure. In some embodiments, the partial pressure of the oxidizer is greater than about 50 Torr partial pressure, preferably greater than 100 Torr partial pressure.

[0046]

[0054] The temperature of the substrate and the processing region in which the substrate is disposed during step 604 may range from about 500°C to about 1500°C, such as from about 600°C to about 1200°C, such as from about 700°C to about 1000°C, such as about 900°C.

[0047]

[0055] As shown in FIG. 7, the growth rate of silicon oxide generally increases with increasing pressure and peaks when the partial pressure of ozone in the process gas mixture of O3 and H2O is about 20% to about 80%, e.g., about 30% to about 70%. The graph includes three data sets. The first data set is the growth rate at a first pressure P1. The second data set is the growth rate at a second pressure P2. The third data set is the growth rate at a third pressure P3. Each data set includes data points where the process gas mixture includes a different partial pressure % of ozone (O3) relative to the pressure of the total mixture. The mixture in FIG. 7 includes ozone (O3) and water vapor (H2O). The first pressure P1 is about 10 Torr to about 12 Torr. The second pressure P2 is about 20 Torr. The third pressure P3 is about 60 Torr. The data confirm that at pressures above 10 Torr, H2O and O3 react to form species that are more reactive than would be expected from a mixture of the non-reactive components.

[0048]

[0056] The transition 514 can act as a choke point during oxide formation. Increasing the pressure and partial pressure during exposure of the substrate to the oxidizer 516 helps drive the oxidizer 516 into the lower portions of the feature 520, such as the second portion 512 of the feature 520. The increased pressure also helps reduce the effect of the sticking coefficient on oxidation within the feature 520, complementing the high flow rate of the oxidizer into the high aspect ratio features caused by the increased surface area. Thus, a high oxidizer partial pressure has been shown to improve the conformality of the oxide layer in high aspect ratio features.

[0049]

[0057] As shown in FIG. 5B, the oxide layer 522 is allowed to grow to a desired thickness before exposure to the oxidizing agent is stopped during another step 606. Ceasing exposure of the substrate to the oxidizing agent stops the growth of the oxide layer 522 on the silicon layer 508. The desired thickness of the oxide layer 522 is a first thickness T1. The first thickness T1 is about 1 nm to about 3 nm. Thus, the first thickness T1 is about 1 nm to about 1.5 nm, about 1.5 nm to about 2 nm, or about 2 nm to about 3 nm. The first thickness T1 is large enough to improve the uniformity of oxide growth within the feature 520 during subsequent process steps, but small enough to improve the manufacturing rate of the device stack 500.

[0050]

[0058] The oxide layer 522 formed during step 604 has been found to be very uniform throughout the feature 520. Previous attempts to oxidize the interior surface of a feature 520 have been limited to features 520 having smaller depths D. The features 520 described herein have depths D greater than about 5 μm, such as greater than about 7 μm, such as greater than about 8 μm, such as greater than about 10 μm. The method 600 described herein allows for the formation of a uniform oxide layer 522 in features having large depths D, such as features 520 having depths D greater than 5 μm.

[0051]

[0059] Once the exposure of the substrate to the oxidizing agent is stopped during step 606, the substrate may optionally be moved to a second process chamber during another step 608. Moving the substrate to the second process chamber involves a reduction in the pressure surrounding the substrate. The pressure is reduced from a first pressure to a second pressure. The second pressure is less than about 10 Torr, such as less than about 7 Torr, such as less than about 5 Torr, such as about 0.1 Torr to about 5 Torr. The pressure is reduced in either the first process chamber or the second process chamber.

[0052]

[0060] In some embodiments, the pressure in the processing region of the first process chamber is reduced before the substrate is moved to the second process chamber, and the processing region of the second process chamber is brought to a second pressure. In other embodiments, the pressure in the processing region of the first process chamber remains the same while the substrate is moved to the second process chamber, and the processing region in the second process chamber is reduced to a second pressure once the substrate enters the second process chamber. In still other embodiments, the substrate remains in the first process chamber, and the processing region of the first process chamber is reduced from the first pressure to the second pressure. There may be an intermediate chamber, such as a transfer chamber (not shown), that couples each of the first and second process chambers. This allows the substrate to pass through the transfer chamber at an intermediate pressure between the first and second pressures while being transferred from the first process chamber to the second process chamber. In some embodiments, the pressure surrounding the substrate is generally described as being reduced from the first pressure to the second pressure.

[0053]

[0061] The second process chamber may be any one of the first process system 100, the third process system 100b, or the fourth process system 300. The second process chamber is equipped to plasma process a substrate.

[0054]

[0062] Once the substrate is positioned in the second process chamber, the substrate is exposed to an oxygen-containing plasma at a second pressure during another step 610. The oxygen-containing plasma is configured to perform radical oxidation of the substrate features 520. The oxygen-containing plasma is formed using a remote plasma source (RPS), an inductively coupled plasma (ICP) source, a capacitively coupled plasma (CCP) source, or thermal radical combustion.

[0055]

[0063] An oxygen-containing plasma includes radicalized oxygen atoms. The oxygen-containing plasma described herein includes both molecular hydrogen and molecular oxygen. An oxygen-containing plasma may include any of a variety of sources, including hydrogen (H2), oxygen (O2), nitrous oxide (N2O), ozone (O3), water / water vapor (H2O), hydrogen peroxide (H2O2), or hydroxide (OH- ), or a combination thereof. In one embodiment, the oxygen-containing plasma includes water vapor (H2O), ozone (O3), and / or hydrogen peroxide (H2O2). In another embodiment, the oxygen-containing plasma includes ozone (O3) and hydrogen (H2). The oxygen-containing plasma can be flowed with a carrier gas such that the oxygen-containing plasma is part of a mixed oxygen plasma that includes the oxygen-containing plasma and the carrier gas. The carrier gas can be any one or combination of helium (He), hydrogen (H2), neon (Ne), argon (Ar), krypton (Kr), or xenon (Xe). The mixed oxygen plasma is composed almost entirely of the oxygen-containing plasma and the carrier gas, and the mixed oxygen plasma is an oxygen and hydrogen plasma that is flowed entirely with the carrier gas.

[0056]

[0064] During the process 610 and exposure of the substrate to the oxygen-containing plasma, the process region is maintained at a second pressure of less than about 10 Torr, e.g., less than about 7 Torr, e.g., less than about 5 Torr, e.g., about 0.5 Torr to about 5 Torr. The pressure is reduced in either the first process chamber or the second process chamber. The partial pressure of the oxygen-containing plasma in the process region during the process 610 is about 0.1 Torr to about 8 Torr, e.g., about 0.5 Torr to about 6 Torr, e.g., about 0.5 Torr to about 4 Torr, e.g., about 1 Torr to about 3 Torr. Reducing the partial pressure of the oxygen-containing plasma during the process 610 increases the lifetime of the oxygen radicals. The inventors have surprisingly discovered that the peak lifetime of the oxygen radicals is achieved at a pressure of about 1 Torr to about 3 Torr. The oxidation rate is generally constant at reduced partial pressures, but changes (e.g., fluctuates) or decreases at pressures other than the reduced partial pressures mentioned above.

[0057]

[0065] The temperature of the substrate and the processing region in which the substrate is disposed during step 610 may range from about 500°C to about 1500°C, such as from about 600°C to about 1200°C, such as from about 700°C to about 1000°C, such as about 900°C.

[0058]

[0066] During step 610, the oxide layer 522 grows to a desired thickness before terminating the exposure to the oxygen-containing plasma. Ceasing exposure of the substrate to the oxygen-containing plasma stops the growth of the oxide layer 522 on the silicon layer 508. The desired thickness of the oxide layer 522 after step 610 is the second thickness T2. The second thickness T2 is about 2 nm to about 10 nm, such as about 2 nm to about 8 nm, such as about 3 nm to about 6 nm, such as about 4 nm to about 5 nm. In some embodiments, the second thickness T2 is about 6 nm to about 10 nm.

[0059]

[0067] The growth rate of the oxide layer 522 during the oxygen-containing plasma exposure of step 610 is higher than the growth rate of the oxide layer 522 during the high pressure oxide exposure of step 604. The plasma exposure of step 610 is utilized to increase the overall growth rate of the oxide layer 522. The growth rate of the oxide layer 522 during the high pressure oxide exposure of step 604 is a first growth rate, which is less than about 30 Angstroms / square root min, such as less than about 25 Angstroms / square root min, such as less than about 20 Angstroms / square root min. The growth rate of the oxide layer 522 during the oxygen-containing plasma exposure of step 610 is greater than about 20 Angstroms / square root min, such as about 30 Angstroms / square root min to about 40 Angstroms / square root min.

[0060]

[0068] As described herein, the high pressure oxide exposure of step 604 and the oxygen-containing plasma exposure of step 610 can each be performed in either the same process chamber or different process chambers. In one embodiment, the high pressure oxide exposure of step 604 and the oxygen-containing plasma exposure of step 610 are both performed in a first process system 100. In another embodiment, the high pressure oxide exposure of step 604 is performed in a second process system 100a and the oxygen-containing plasma exposure of step 610 is performed in a third process system 100b. In yet another embodiment, the high pressure oxide exposure of step 604 and the oxygen-containing plasma exposure of step 610 are both performed in a fourth process system 300. In yet another embodiment, the high pressure oxide exposure of step 604 is performed in a process system similar to the fourth process system 300 and the oxygen-containing plasma exposure of step 610 is performed in another process system similar to the fourth process system 300. In yet another embodiment, the high pressure oxide exposure of step 604 is performed in the fifth processing system 400 and the oxygen-containing plasma exposure of step 610 is performed in either the third processing system 100b or the fourth processing system 300.

[0061]

[0069] In yet another embodiment, the high pressure step is performed in a furnace, such as the fifth processing system 400, and the oxygen-containing plasma exposure of step 610 is replaced with a low pressure hydrogen (H2) and oxygen (O2) combustion process. The high pressure step is performed at a pressure greater than about 50 Torr. A mixture of hydrogen (H2) and oxygen (O2) can then be introduced into the fifth processing system 400 during a low pressure step, such as a step at a pressure less than about 1 Torr. The low pressure step is a batch low pressure step. During the batch low pressure step, the mixture of hydrogen and oxygen is combusted during the low pressure step to form atomic oxygen. During a batch system, such as the fifth processing system 400, combustion of the mixture of hydrogen and oxygen is utilized instead of the plasma exposure.

[0062]

[0070] The process described herein results in the oxide layer 522 having a uniform thickness throughout the depth of the feature 520. The uniformity of the oxide layer 522 is measured by measuring the thickness of the oxide layer 522 at cross sections 530, 532 through the first and second portions 510, 512 of the feature 520. The first cross section 530 is measured at about 250 nm to about 750 nm, such as about 300 nm to about 700 nm, such as about 400 nm to about 600 nm, such as about 500 nm, from the top surface 518 of the device stack 500. The second cross section 532 is measured at about 250 nm to about 750 nm, such as about 300 nm to about 700 nm, such as about 400 nm to about 600 nm, such as about 500 nm, from the bottom surface 509 of the feature 520 of the device stack 500. The thickness of the oxide layer 522 measured at the first cross section 530 and the second cross section 532 has a high degree of conformality. As described herein, conformality is measured as the thickness of the oxide layer 522 at the second cross section 532 relative to the thickness of the oxide layer 522 at the first cross section 530. Using the methods described herein, conformality has been found to be greater than about 95%, such as greater than about 96%, such as greater than about 97%, such as greater than about 98%.

[0063]

[0071] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof, as determined by the following claims.

Claims

1. 1. An apparatus for processing a substrate suitable for use in semiconductor manufacturing, comprising:

1. A process system comprising: A chamber body; a process gas source coupled to the chamber body and configured to introduce a process gas into a processing region; a process system comprising: a substrate support configured to support a substrate within the processing region; A controller, exposing the substrate to an oxidizing agent from the process gas source at a first pressure greater than about 20 Torr; reducing the pressure surrounding the substrate from the first pressure to a second pressure less than about 10 Torr; exposing the substrate to an oxygen-containing plasma while the pressure surrounding the substrate is at the second pressure. With a controller configured like this: An apparatus comprising:

2. The apparatus of claim 1 , wherein the processing system further comprises a plasma source coupled to the chamber body and configured to introduce a plasma into the processing region.

3. 10. The apparatus of claim 1 , wherein the processing system is a first processing system, the apparatus further comprising a second processing system including a plasma source coupled to a second chamber body and configured to introduce a plasma into a second processing region.

4. The apparatus of claim 1 , wherein the processing system is configured to process multiple substrates simultaneously.

5. The apparatus of claim 4 , wherein the substrate support further comprises a plurality of substrate support shelves.

6. The apparatus of claim 1 , wherein an inductive coil is disposed about the chamber body.

7. A non-transitory computer readable medium having stored thereon instructions suitable for use in semiconductor manufacturing, the instructions, when executed by a processor, causing a computer system to: exposing the substrate to an oxidizing agent at a first pressure greater than about 20 Torr; reducing the pressure surrounding the substrate from the first pressure to a second pressure less than about 10 Torr; exposing the substrate to an oxygen-containing plasma while the pressure surrounding the substrate is at the second pressure. A non-transitory computer readable medium for causing steps to be performed.

8. The medium of claim 7 , wherein the oxygen-containing plasma is formed using a remote plasma source or an inductively coupled plasma source.

9. The medium of claim 7 , wherein the oxidizing agent comprises one or a mixture of ozone, nitrous oxide, water, hydrogen, and hydrogen peroxide, and the oxygen-containing plasma comprises radicalized oxygen atoms.

10. 8. The medium of claim 7, wherein the first pressure is greater than about 50 Torr and the second pressure is less than about 5 Torr, and the substrate is disposed on a substrate support at a temperature of about 600° C. to about 1200° C. during exposure of the substrate to the oxidizing agent and exposure of the substrate to the oxygen-containing plasma, respectively.

11. 1. A method for processing a substrate suitable for use in semiconductor manufacturing, comprising the steps of: exposing a plurality of features having silicon or nitride wall surfaces to an oxidizing agent at a first pressure greater than about 50 Torr to form an oxide layer on the silicon or nitride wall surfaces on a substrate; reducing a pressure surrounding the substrate from the first pressure to a second pressure less than about 5 Torr; exposing the substrate to an oxygen-containing plasma while the pressure surrounding the substrate is at the second pressure to increase a thickness of the oxide layer; The method includes:

12. 12. The method of claim 11 , wherein the oxide layer has a first thickness of about 2 nm to about 3 nm after exposing the plurality of features to the oxidizing agent and a second thickness of about 6 nm to about 10 nm after exposing the plurality of features to the oxygen-containing plasma.

13. 12. The method of claim 11, wherein exposing the features to the oxidizing agent is performed in a first chamber and exposing the features to the oxygen-containing plasma is performed in a second chamber.

14. 12. The method of claim 11, wherein the features have nitride walls, the nitride walls being silicon nitride surfaces, and the oxide layer being silicon oxide.

15. 12. The method of claim 11, wherein each of the plurality of features has a depth greater than about 5 μm and an aspect ratio greater than about 70:

1.

16. 12. The method of claim 11, wherein the substrate is disposed on a substrate support at a temperature of about 600° C. to about 1200° C. during each of exposing the substrate to the oxidizing agent and exposing the substrate to the oxygen-containing plasma.

17. The method of claim 11 , wherein the feature is formed in a stack including multiple silicon oxide layers and multiple silicon nitride layers.

18. 12. The method of claim 11, wherein the oxidizing agent comprises one or a mixture of ozone, nitrous oxide, water, hydrogen, and hydrogen peroxide.

19. The method of claim 11 , wherein the oxygen-containing plasma comprises radicalized oxygen atoms.

20. 20. The method of claim 19, wherein the oxygen-containing plasma further comprises hydrogen and molecular oxygen.

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