DUAL PRESSURE OXIDATION METHOD FOR FORMING AN OXIDE LAYER IN A FEATURE

A method and apparatus for growing an oxide layer within a feature of a substrate is described herein. The method is suitable for use in semiconductor manufacturing. The oxide layer is formed by exposing a substrate to both a high pressure oxidant exposure and a lower pressure oxygen containing plasma exposure. The high pressure oxidant exposure is performed at a pressure of greater than 10 Torr, while the lower pressure oxygen containing plasma exposure is performed at a pressure of less than about 10 Torr. The features are high-aspect ratio trenches or holes within a stack of silicon oxide and silicon nitride layers.

BACKGROUND

Field

Embodiments of the present disclosure generally relate to apparatus for semiconductor device fabrication, and in particular to methods of oxidizing a feature formed in a three dimensional device structure.

Description of the Related Art

The production of silicon integrated circuits has placed difficult demands on fabrication operations to increase the number of devices while decreasing the minimum feature sizes on a chip. These demands have extended to fabrication steps including depositing layers of different materials onto difficult topologies and etching further features within those layers. Manufacturing processes for next generation NAND flash memory involve especially 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, a three-dimensional NAND (3D NAND) design has been developed. Such a design typically introduces alternating oxide layers and nitride layers which are deposited on a substrate and then etched to produce a structure having one or more surfaces extending substantially perpendicular to the substrate. One structure may have over 100 such layers. Such designs can include high aspect ratio (HAR) structures with aspect ratios of 30:1 or more.

HAR structures are often coated with silicon nitride (SiNx), amorphous silicon, or poly-silicon layers. Conformal oxidation of such structures to produce a  uniformly thick oxide layer is challenging. Uniform oxidation of each structure is increasingly difficult with increased aspect radios, such as HAR structures with an aspect ratio of greater than 50:1 or greater than 70:1.

Therefore, an improved method and apparatus for forming oxide layers within HAR structures is needed.

SUMMARY

The present disclosure generally relates to methods and apparatus for growing a layer on a substrate. In one embodiments, a method of processing a substrate is described. The method is suitable for use in semiconductor manufacturing. The method includes exposing a substrate to an oxidant at a first pressure of greater than about 20 Torr. After exposing the substrate to the oxidant at the first pressure, a pressure around the substrate is reduced from the first pressure to a second pressure of 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 around the substrate is at the second pressure.

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 a nitride wall surface on a substrate to an oxidant at a first pressure of greater than about 50 Torr to form an oxide layer on the nitride wall surface. After exposing the plurality of features to the oxidant at the first pressure, a pressure around the substrate is reduced from the first pressure to a second pressure of 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 around the substrate is at the second pressure to increase a thickness of the oxide layer.

In yet another embodiment, a non-transitory computer-readable medium is described. The non-transitory computer-readable medium stores instructions  suitable for use in semiconductor manufacturing. When the instructions are executed by a processor, the computer system performs several operations. The operations include exposing a substrate to an oxidant at a first pressure of greater than about 20 Torr. After exposing the substrate to the oxidant, a pressure around the substrate is reduced from the first pressure to a second pressure of 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 around the substrate is at the second pressure.

DETAILED DESCRIPTION

The present disclosure generally relates to methods and apparatus for conformal oxidation of high aspect ratio structures within a device stack. The method includes the utilization of a high-pressure exposure of a substrate to an oxidant. The high-pressure exposure of the substrate to the oxidant forms an oxide layer on a silicon nitride, amorphous silicon, or poly-silicon layer within the high aspect ratio trenches. The oxide layer is a conformal oxide layer with a conformality of 95% or greater. The oxide layer is grown to a thickness of about 2 nm to about 3 nm during the high-pressure exposure of the substrate. The oxide layer is grown from the silicon nitride, amorphous silicon, or poly-silicon layer, such that a portion of the silicon nitride, amorphous silicon, or poly-silicon layer is oxidized.

Subsequent the high-pressure exposure of the substrate to the oxidant, the pressure around the substrate is reduced. The reduced pressure enables the  formation of an oxygen-radical containing plasma. The oxygen-radical containing plasma also grows the oxide layer on the silicon nitride layer. The oxide layer formed during the high-pressure exposure serves as a base layer and the oxide layer is grown during exposure to the oxygen-radical containing plasma. The oxide layer grows uniformly due to the previously formed oxide layer reducing oxidant flux rate into the shallower portions of each high aspect ratio structure. The thickness of the oxide layer is grown to greater than about 5 nm, such as greater than about 6 nm, such as about 6 nm to about 8 nm during the exposure to the oxygen-radical containing plasma. The conformality of the oxide layer after completion of the exposure to the oxygen-radical containing plasma is still greater than about 95%.

The high-pressure oxidant exposure enables a greater number of species to arrive at a bottom of a high-aspect ratio feature of a substrate to form a conformal layer. However, the high-pressure oxidant has a low growth rate on amorphous silicon, poly-silicon and silicon nitride. Therefore, the second oxidant exposure of the oxygen-radical containing plasma is utilized to increase the growth rate of the oxide layer to achieve a target thickness with a reduced oxidation time. The oxygen-radical containing plasma exposure may be repeated or lengthened to increase the thickness of the oxide layer.

Each one of the high pressure oxide exposure and the oxygen-radical containing plasma exposure may be performed either in the same process system or in different process systems. Performing both process operations within one process system may enable for increased throughput and reduces overall cost. However, performing both a high pressure process and a plasma containing process within the same process system may be difficult with some process chamber architectures. An improved process system is described herein, which enables both the high pressure process and the plasma containing process to be formed within a same process volume.

In other embodiments, a substrate is moved between two or more process systems, such that a first process system performs the high pressure process and a second process system performs the plasma containing process. Multiple process system types may be utilized as described herein. The processes described herein may be performed during the manufacturing of a 3D NAND structure.

FIG.1Ais a cross-sectional view of a first process system100according to embodiments described herein. The first process system100includes a process chamber102and a remote plasma source104. The process chamber102may be a rapid thermal processing (RTP) chamber. The remote plasma source104may be any suitable remote plasma source, such as microwave coupled plasma source, that can operate at a power, for example, of about 6 kW. The remote plasma source104is coupled to the process chamber102to flow plasma formed in the remote plasma source104toward the process chamber102. The remote plasma source104is coupled to the process chamber102via a connector106. Radicals formed in the remote plasma source104flow through the connector106into the process chamber102during processing of a substrate.

The remote plasma source104includes a body108surrounding a tube110in which plasma is generated. The tube110may be fabricated from quartz or sapphire. The body108includes a first end114coupled to an inlet112, and one or more gas sources118may be coupled to the inlet112for introducing one or more gases into the remote plasma source104. In one embodiment, the one or more gas sources118include an oxygen containing gas source, and the one or more gases include an oxygen containing gas. The body108includes a second end116opposite the first end114, and the second end116is coupled to the connector106. A coupling liner (not shown) may be disposed within the body108at the second end116. A power source120(e.g., an RF power source) may be coupled to the remote plasma source104via a match network122to provide  power to the remote plasma source104to facilitate the forming of the plasma. The radicals in the plasma are flowed to the process chamber102via the connector106.

The process chamber102includes a chamber body125, a substrate support portion128, and a window assembly130. The chamber body125includes a first side124and a second side126opposite the first side124. In some embodiments, a lamp assembly132enclosed by an upper side wall134is positioned over and coupled to the window assembly130. The lamp assembly132may include a plurality of lamps136and a plurality of tubes138, and each lamp136may be disposed in a corresponding tube138. The window assembly130may include a plurality of light pipes140, and each light pipe140may be aligned with a corresponding tube138so the thermal energy produced by the plurality of lamps136can reach a substrate disposed in the process chamber102. In some embodiments, a vacuum condition can be produced in the plurality of light pipes140by applying a vacuum to an exhaust144fluidly coupled to the plurality of light pipes140. The window assembly130may have a conduit143formed therein for circulating a cooling fluid through the window assembly130.

A processing region146may be defined by the chamber body125, the substrate support portion128, and the window assembly130. A substrate142is disposed in the processing region146and is supported by a support ring148above a reflector plate150. The support ring148may be mounted on a rotatable cylinder152to facilitate rotating of the substrate142. The cylinder152may be levitated and rotated by a magnetic levitation system (not shown). The reflector plate150reflects energy to a backside of the substrate142to facilitate uniform heating of the substrate142and promote energy efficiency of the first process system100. A plurality of fiber optic probes154may be disposed through the substrate support portion128and the reflector plate150to facilitate monitoring a temperature of the substrate142.

A liner assembly156is disposed in the first side124of the chamber body125for radicals to flow from the remote plasma source104to the processing region146of the process chamber102. The liner assembly156may be fabricated from a material that is oxidation resistant, such as quartz, in order to reduce interaction with process gases, such as oxygen radicals. The liner assembly156is designed to reduce flow constriction of radical flowing to the process chamber102. The liner assembly156is described in detail below. The process chamber102further includes a distributed pumping structure133formed in the substrate support portion128adjacent to the second side126of the chamber body125to tune the flow of radicals from the liner assembly156to the pumping ports. The distributed pumping structure133is located adjacent to the second side126of the chamber body125.

An opening158is disposed through the second side126of the chamber body125. The opening158is configured to have a substrate passed therethrough. The opening158may be disposed adjacent to a transfer chamber or another process system.

A controller180may be coupled to various components of the first process system100, such as the process chamber102and/or the remote plasma source104to control the operation thereof. The controller180generally includes a central processing unit (CPU)182, a memory186, and support circuits184for the CPU182. The controller180may control the first process system100directly, or via other computers or controllers (not shown) associated with particular support system components. The controller180may be one of any form of general-purpose computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The memory186, or computer-readable medium, may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, flash drive, or any other form of digital storage, local or remote. The support circuits184are coupled to the CPU182for supporting the processor in a conventional manner.  The support circuits184include cache, power supplies, clock circuits, input/output circuitry and subsystems, and the like. Processing operations may be stored in the memory186as a software routine188that may be executed or invoked to turn the controller180into a specific purpose controller to control the operations of the first process system100. The controller180may be configured to perform any methods described herein.

FIG.1Bis a cross-sectional schematic plan view of the first process system100ofFIG.1A. The first process system100includes both the remote plasma source104and a gas injector192. The liner assembly156of the remote plasma source104and the gas injector192are disposed at different points along the circumference of the processing region146. Including both of the remote plasma source104and the gas injector192disposed through the same chamber body125and in communication with the same processing region146enables both of a high pressure oxidation operation and a low pressure plasma operation to be performed within the same processing region146.

One or more exhaust passages196a,196bare disposed adjacent to and/or within the opening158. The one or more exhaust passages196a,196bare exhaust outlets and are configured to exhaust gas and/or plasma from the processing region146. The one or more exhaust passages196a,196bare coupled to one or more exhaust pumps (not shown) to remove the exhaust gases and/or plasmas within the processing region146. The one or more exhaust passages196a,196binclude at least a first exhaust passage196aand a second exhaust passage196b. The first exhaust passage196ais disposed on a first side of the opening158, while the second exhaust passage196bis disposed on the opposite side of the opening158. Utilizing two exhaust passages196a,196bon opposite sides of the opening158enables more even evacuation of process gases and plasmas during processing.

The gas injector192is disposed through a wall of the chamber body125. The gas injector192includes a plurality of gas passages194therethrough  and in fluid communication with the processing region146. The gas injector192is configured to inject process gases into the processing region146and across a top surface of the substrate142. The gas injector192and each of the gas passages194disposed therein are coupled to a process gas source178. The process gas source178is configured to supply one or more oxidants. The one or more oxidants include one or a mixture of hydrogen (H2), oxygen (O2), ozone (O3), nitrous oxide (N2O), water/water vapor (H2O), hydrogen peroxide (H2O2), or hydroxide (OH−).

The center of the gas injector192may be disposed at a first angle θ1with respect to the center of the liner assembly156of the remote plasma source104. The first angle θ1is 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 θ1is about 90 degrees, such that the gas injector192and the liner assembly156of the remote plasma source104are perpendicular to one another along the circumference of the processing region146. Positioning each of the gas injector192and the liner assembly156at separate circumferential positions of the processing region enables both components to be utilized independently within the first process system100.

The center of the liner assembly156of the remote plasma source104is disposed at a second angle θ2with respect to a center of the opening158through which the substrate142is configured to pass into and out of the processing region146. The second angle θ2is 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 assembly156and the opening158are aligned along a similar axis. Aligning the liner assembly156and the opening158enables plasma to be flowed evenly across the substrate142and evacuated through one or more exhaust passages196a,196bon either side of the opening158. Positioning each of the gas injector192and the opening158at angles to  one another enables a spiral gas flow across the surface of the substrate142. The spiral gas flow has been shown to enable more even oxide formation.

The second process system100aand the third process system100bofFIGS.2A and2Bmay be utilized in place of the first process system100ofFIGS.1A-1B. The second process system100aand the third process system100bare separate process systems, but may be utilized together to perform the processes described herein. Each of the second process system100aand the third process system100bare vacuum coupled, such that a substrate, such as the substrate142, passing between the second process system100aand the third process system100bis kept in a vacuum environment and not exposed to atmosphere.FIG.2Ais a cross-sectional schematic plan view of the second process system100a.FIG.2Bis a cross-sectional schematic plan view of the third process system100b. The second process system100aand the third process system100bare similar to the first process system100, but the second process system100adoes not include a remote plasma source104and the third process system100bdoes not include the gas injector192.

Separating the remote plasma source104and the gas injector192into two separate process systems100a,100benables the high pressure oxidation operation to be performed in a separate processing region146than the a low pressure plasma operation. Separating the process systems100a,100bmay enable increased process flexibility and increase efficiency of maintenance performed on either of the process systems100a,100b.

As shown inFIG.2A, the second process system100aincludes a passage157opposite the opening158. The passage157may be configured to include one or more sensors, exhaust liners, or process gas injectors disposed therein. As shown inFIG.2B, the third process system100bincludes a passage191perpendicular to the opening158and the liner assembly156. The passage191may be configured to include one or more sensors or exhaust liners.

FIG.3is a cross-sectional schematic side view of a fourth process system300. The fourth process system300includes a chamber body302, a showerhead308disposed within the chamber body302, a substrate support304, and an inductive coil306disposed around the chamber body302. The fourth process system300may be used in place of any one of the first process system100, the second process system100a, or the third process system100b. The fourth process system300is configured to enable a high-pressure oxidation operation as well as a low-pressure plasma operation.

The showerhead308is disposed within the chamber body302and above the substrate support304. The showerhead308is configured to distribute one or a combination of process gases and plasmas into a processing region315of the fourth process system300. The showerhead308includes a plurality of gas passage312formed therethrough. The plurality of gas passages312may be in fluid communication with a plenum310disposed above the showerhead308as well as the processing region315. A gas source316is in fluid communication with the plenum310through a passage314formed within the chamber body302. The gas source316is configured to supply one or more process gases, such as one or more oxidants. The one or more oxidants include one or a mixture of hydrogen (H2), oxygen (O2), ozone (O3), nitrous oxide (N2O),water/water vapor (H2O), hydrogen peroxide (H2O2), or hydroxide (OH−). Mixtures of water (H2O), ozone (O3) and/or hydrogen peroxide (H2O2) may be delivered by the gas source316during a high pressure operation, such as an operation with a pressure of greater than about 50 Torr. A mixture of hydrogen (H2) and oxygen (O2) is introduced during a low pressure operation, such as an operation at a pressure of about 0.5 Torr to about 5 Torr. The hydrogen and oxygen mixture during the low pressure operation improves oxygen radical (O*) species lifetimes.

One or more exhaust passages318are formed through the chamber body302. The one or more exhaust passages318are formed below the substrate support304and the inductive coil306. The one or more exhaust passages318are coupled to an exhaust pump (not shown) and configured to remove gases and/or plasmas from the processing region315. The substrate support304is disposed within the processing region315and is configured to support a substrate, such as the substrate142. The substrate support304is configured to rotate around a central axis and actuate in one or more directions.

The inductive coil306is disposed around the circumference of the chamber body302. The inductive coil306is configured to generate a plasma within the processing region315. The inductive coil306is coupled to a power source320. The power source320is a radio frequency (RF) power source. The power source320is configured to apply power to the inductive coil306and generate the plasma within the processing region315during a plasma operation.

FIG.4is a cross-sectional schematic side view of a fifth process system400. The fifth process system400is a batch process system, such that a plurality of substrates142may be processed simultaneously. The fifth process system400may be configured to perform a high-pressure oxidation operation. Oxidant is supplied to a processing region415of the fifth process system400from a plurality of gas inlets406. The plurality of gas inlets406may be nozzles or injectors and are coupled to a gas distribution tower404. The plurality of gas inlets406are disposed along the gas distribution tower404and configured to supply a process gas to a variety of positions within the processing region415. A gas supply418is fluidly coupled to the gas distribution tower404and the plurality of gas inlets406. The gas supply418is configured to supply one or a mixture of hydrogen (H2), oxygen (O2), ozone (O3), nitrous oxide (N2O), water/water vapor (H2O), hydrogen peroxide (H2O2), or hydroxide (OH−). Mixtures of water (H2O), ozone (O3) and/or hydrogen peroxide (H2O2) may be delivered by the gas supply418during a high pressure operation, such as an operation with a pressure of greater than about 50 Torr. A mixture of hydrogen (H2) and oxygen (O2) may then be introduced during a low pressure operation, such as an operation at a pressure of less than about 1 Torr to the fifth process system400to perform a batch low  pressure operation. The hydrogen and oxygen mixture combusts and forms atomic oxygen during the low pressure operation.

The plurality of substrates142are disposed on a carrier assembly408. The carrier assembly408includes a plurality of substrate support shelves412. Each support shelf412has a substrate support surface. The substrate support surface may include a single support ring, or a plurality of discreet substrate support ledges. Each pair of support shelves412forms a slot therebetween for a substrate142to be inserted. Each one of the support shelves412is associated with at least one gas inlet406, such that at least one gas inlet406is disposed parallel to or above each support shelf412. Each of the support shelves412are parallel to one another and form a column of support shelves412. Both of the carrier assembly408and the gas distribution tower404are disposed within the processing region415of a chamber body402.

One or more exhaust passages410are formed through the chamber body402. The one or more exhaust passages410are formed below the substrate support shelves412. The one or more exhaust passages410are coupled to an exhaust pump (not shown) and configured to remove gases and/or plasmas from the processing region415.

FIGS.5A-5Care cross-sectional schematic side views of a device stack500during a method600of formation. The device stack500includes a plurality of layers, such as a plurality of oxide layers502and a plurality of nitride layer504. The oxide layers502are a silicon oxide material. The nitride layers504are a silicon nitride material. Each pair of oxide layers502is separated by a nitride layer504, such that the oxide layers502and the nitride layers504are disposed in an alternating stack. Each of the oxide layers502and the nitride layers504have 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 oxide layer502and a contacting single nitride layer504coupled together form a pair505. There are over 100 pairs505of oxide layers502and nitride layers504, such that there are at least 100  oxide layers502and there are at least 100 nitride layers504. In some embodiments, there are over 125 pairs505of oxide layers502and nitride layers504, such that there are at least 125 oxide layers502and there are at least 125 nitride layers504. In some embodiments, there are over 140 pairs505of oxide layers502and nitride layers504, such that there are at least 140 oxide layers502and there are at least 140 nitride layers504.

The device stack500includes a plurality of features520formed therein. The features520may be a trench or a hole formed in the device stack500. The feature520is formed through a plurality of pairs505, such that the features520are formed through at least 100 pairs505, such as at least 125 pairs505, such as at least 140 pairs505. The features520are formed from a top surface518of the device stack500to a bottom surface509of each feature520. Each of the features520are formed of two portions510,512. The two portions510,512are a first portion510and a second portion512. The first portion510is disposed inward from the top surface518and the second portion512is adjacent to the first portion510and extends from a bottom of the first portion510further inward away from the top surface518. The first portion510includes at least 50 pairs505, such as at least 60 pairs505, such as at least 70 pairs505. Similarly, the second portion512includes at least 50 pairs505, such as at least 60 pairs505, such as at least 70 pairs505. The first portion510and the second portion512are separated by a transition514.

As each of the portions510,512of the features520increases in depth within the device stack500the feature520decreases in width, such that the feature520narrows. Therefore, as the first portion510extends away from the top surface518and towards the bottom surface509, the feature520narrows. Similarly, as the second portion512extends away from the top surface518and towards the bottom surface509, the feature520narrows. At the transition514, the width of the feature520expands as the trench extends from the first portion510to the second portion512. The feature520expands as the transition514due  to the use of two separate processes for forming the features520. The second portion512may be formed before the formation of the first portion510. This causes the transition514to include a change of width. The bottom surface509of each of the features520may further include a base, which is wider than the bottom of the second portion512.

The inside surface of each of the features520is coated with a silicon layer508, such that a silicon layer508is formed over the walls of each of the features520. The silicon layer508serves as a liner of each of the features520and covers both the first portion510and the second portion512. The silicon layer508is deposited using an atomic layer deposition (ALD) process. The silicon layer508may be a silicon nitride layer, amorphous silicon, or poly-silicon. In some embodiments, the silicon layer508is a silicon nitride layer.

Each of the features has an aspect ratio. The aspect ratio is a ratio of the depth of the features520to the width of the features520measured at the top opening, which restricts reactant transport. The width of the features520is the width at the top opening of the first portion510or the top opening of the second portion512, such that the width of the features520is measured as the width adjacent to the top surface518of the device stack500. 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.

A method600is performed on the device stack500. The method600is illustrated inFIG.6and includes an operation602of positioning a substrate in a first process chamber. The substrate includes the device stack500and may be a substrate similar to the substrate142ofFIGS.1A,1B,2,3, and4. The first process chamber may be any one of the first process system100, the second process system100a, the fourth process system300, or the fifth process system400. The substrate is placed within the first process chamber on a substrate support surface.

Once the substrate is positioned in the first process chamber, the substrate is exposed to an oxidant516at a first pressure during another operation604. The oxidant516includes oxygen and may be one or a combination of one or a mixture of hydrogen (H2), oxygen (O2), nitrous oxide (N2O), ozone (O3), water/water vapor (H2O), hydrogen peroxide (H2O2), or hydroxide (OH−). In one embodiment, the oxidant516includes water vapor (H2O), ozone (O3), and/or hydrogen peroxide (H2O2). In another embodiment, the oxidant516includes ozone (O3) and hydrogen (H2). The oxidant516may be co-flowed with a carrier gas, such that the oxidant516is part of an oxidant mixture containing the oxidant516and the carrier gas. The carrier gas may be any one or a combination of helium (He), hydrogen (H2), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), or nitrogen (N2). The oxidant mixture consists almost entirely of the oxidant516and the carrier gas, such that the oxidant mixture is entirely one or more oxidants516and the carrier gas. Either of water vapor, ozone, or hydrogen peroxide may be utilized individually or in combination. The oxidant516induces the formation of an oxide layer522on the silicon layer508as shown inFIG.5B. When utilized by themselves, each of water vapor, ozone, and hydrogen peroxide induce a lower growth rate of the oxide layer522compared to when a combination of at least two of water vapor, ozone/hydrogen, and hydrogen peroxide is utilized.

The first pressure is greater than about 10 Torr, such as greater than about 15 Torr, such as greater than about 20 Torr, such as greater than about 50 Torr, such as about 50 Torr to about 760 Torr. The partial pressure of the oxidant is greater than about 10 Torr partial pressure. In some embodiments, the partial pressure of the oxidant is greater than or equal to about 50 Torr partial pressure, preferrably greater than or equal to 100 Torr partial pressure.

The temperature of the substrate and the processing region within which the substrate is disposed during the operation604is about 500° C. to about 1500° C., such as about 600° C. to about 1200° C., such as about 700° C. to about 1000° C., such as about 900° C.

As shown inFIG.7, the growth rate of silicon oxide generally increases with increased pressures and peaks when a partial pressure of ozone within the process gas mixture of O3and H2O is about 20% to about 80%, such as about 30% to about 70%. The graph includes three data sets. A first data set is the growth rate at a first pressure P1. A second data set is the growth rate at a second pressure P2. A third data set is the growth rate at a third pressure P3. Each of the data sets includes data points where the process gas mixture contains different partial pressure percentages of ozone (O3) relative to the total mixture pressure. The mixture ofFIG.7includes ozone (O3) and water vapor (H2O). The first pressure P1is about 10 Torr to about 12 Torr. The second pressure P2is about 20 Torr. The third pressure P3is about 60 Torr. This data confirms the reaction of H2O and O3to form a more reactive species than predicted from a mixture of non-reacting components in the high pressure regime >10 Torr.

The transition514may serve as a choke point during oxide formation. The increased pressure and partial pressure during exposure of the substrate to the oxidant516assists in driving the oxidant516down into the lower portions of the features520, such as the second portions512of the features520. The increased pressure also assists in reducing the impact of the sticking coefficient on oxidation within the features520and compensates for the large oxidant flux rate into high aspect ratio features caused by the increase in surface area. High oxidant partial pressure has therefore been shown to improve conformality of oxide layers within high aspect ratio features.

As shown inFIG.5B, the oxide layer522is grown to a desired thickness before exposure to the oxidant is ceased during another operation606. Ceasing the exposing of the substrate to the oxidant stops the growth of the oxide layer522on the silicon layer508. The desired thickness of the oxide layer522is a first thickness T1. The first thickness T1is about 1 nm to about 3 nm. The first thickness T1is therefore 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 T1is large enough to improve  uniformity of oxide growth within the feature520during later process operations, but small enough to improve the manufacturing rate of the device stack500.

It has been found the oxide layer522formed during the operation604is highly uniform throughout the feature520. Previous attempts at oxidizing the inner surface of the features520are limited to features520with smaller depths D. The depth D of the features520described herein is 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 method600described herein enables uniform oxide layer522formation within features, such as the features520, with large depths D, such as depths D greater than 5 μm.

Once exposure of the substrate to the oxidant is ceased during the operation606, the substrate may optionally be moved to a second process chamber during another operation608. Moving the substrate to the second process chamber is accompanied by a reduction in pressure around 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 either in the first process chamber or in the second process chamber.

In some embodiments, the pressure within the processing region of the first process chamber is reduced before moving the substrate to the second process chamber, where the processing region of the second process chamber is brought to the second pressure. In other embodiments, the pressure within the processing region of the first process chamber stays the same while the substrate is moved to the second process chamber and once the substrate is within the second process chamber, the processing region within the second process chamber is depressurized to the second pressure. In yet 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)  coupling each of the first process chamber and the second process chamber. The substrate may therefore pass through the transfer chamber at an intermediate pressure between the first pressure and the second pressure while being transferred from the first process chamber to the second process chamber. In some embodiments, the pressure around the substrate is generally described as being reduced from the first pressure to the second pressure.

The second process chamber may be any one of the first process system100, the third process system100b, or the fourth process system300. The second process chamber is equipped to plasma treat the substrate.

Once the substrate is positioned within the second process chamber, the substrate is exposed to an oxygen containing plasma at the second pressure during another operation610. The oxygen containing plasma is configured to perform a radical oxidation of the features520of the substrate. 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.

The oxygen containing plasma includes radicalized oxygen atoms. As described herein, the oxygen containing plasma includes both hydrogen and oxygen molecules. The oxygen containing plasma may further contain one or more additional oxygen containing molecules, such as one or a combination of hydrogen (H2), oxygen (O2), nitrous oxide (N2O), ozone (O3), water/water vapor (H2O), hydrogen peroxide (H2O2), or hydroxide (OH−). 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 may be co-flowed with a carrier gas, such that the oxygen containing plasma is part of an oxygen plasma mixture containing the oxygen containing plasma and the carrier gas. The carrier gas may be any one or a combination of helium (He), hydrogen (H2), neon (Ne), argon (Ar), krypton (Kr), or xenon (Xe). The oxygen plasma  mixture consists almost entirely of the oxygen containing plasma and the carrier gas, such that the oxygen plasma mixture is entirely oxygen and hydrogen plasma flowed with the carrier gas.

While performing the operation610and exposing the substrate to the oxygen containing plasma, the processing region is kept at a second pressure of less than about 10 Torr, such as less than about 7 Torr, such as less than about 5 Torr, such as about 0.5 Torr to about 5 Torr. The pressure is reduced either in the first process chamber or in the second process chamber. The partial pressure of the oxygen containing plasma within the processing region during the operation610is about 0.1 Torr to about 8 Torr, such as about 0.5 Torr to about 6 Torr, such as about 0.5 Torr to about 4 Torr, such as about 1 Torr to about 3 Torr. Reducing the partial pressure of the oxygen containing plasma during the operation610increases the lifetime of oxygen radicals. The inventors have surprisingly discovered peak lifetime for oxygen radicals is achieved at a pressure of about 1 Torr to about 3 Torr. The oxidation rate is generally constant at the reduced partial pressure, but varies (e.g., fluctuates) or is reduced outside of the reduced partial pressures described above.

The temperature of the substrate and the processing region within which the substrate is disposed during the operation610is about 500° C. to about 1500° C., such as about 600° C. to about 1200° C., such as about 700° C. to about 1000° C., such as about 900° C.

During the operation610, the oxide layer522is grown to a desired thickness before ceasing the exposure to the oxygen containing plasma. Ceasing the exposing of the substrate to the oxygen containing plasma halts the growth of the oxide layer522on the silicon layer508. The desired thickness of the oxide layer522after the operation610is a second thickness T2. The second thickness T2is 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 T2is about 6 nm to about 10 nm.

The growth rate of the oxide layer522during the oxygen containing plasma exposure of operation610is greater than the growth rate of the oxide layer522during the high pressure oxide exposure of operation604. The plasma exposure of operation610is utilized to increase the overall growth rate of the oxide layer522. The growth rate of the oxide layer522during the high pressure oxide exposure of operation604is a first growth rate and is less than about 30 Angstroms/(square root minute), such as less than about 25 Angstroms/(square root minute), such as less than about 20 Angstroms/(square root minute). The growth rate of the oxide layer522during the oxygen containing plasma exposure of operation610is greater than about 20 Angstroms/(square root minute), such as about 30 Angstroms/(square root minute) to about 40 Angstroms/(square root minute).

As described herein, each of the high pressure oxide exposure of operation604and the oxygen containing plasma exposure of operation610may be performed in either the same or different process chambers. In one embodiments, the high pressure oxide exposure of operation604and the oxygen containing plasma exposure of operation610are both performed in the first process system100. In another embodiment, the high pressure oxide exposure of operation604is performed in the second process system100aand the high of operation610is performed in the third process system100b. In yet another embodiment, the high pressure oxide exposure of operation604and the oxygen containing plasma exposure of operation610are both performed in the fourth process system300. In yet another embodiment, the high pressure oxide exposure of operation604is performed in a process system similar to the fourth process system300while the oxygen containing plasma exposure of operation610is performed in a separate process system similar to the fourth process system300. In yet another embodiment, the high pressure oxide exposure of operation604is performed in the fifth process system400and the oxygen containing plasma exposure of operation610is performed in one of the third process system100bor the fourth process system300.

In yet another embodiment, the high pressure operation is performed in a furnace, such as the fifth process system400and the oxygen containing plasma exposure of operation610is replaced by a low pressure hydrogen (H2) and oxygen (O2) combustion process. The high pressure operation is performed at a pressure of greater than about 50 Torr. A mixture of hydrogen (H2) and oxygen (O2) may then be introduced into the fifth process system400during a low pressure operation, such as an operation at a pressure of less than about 1 Torr. The low pressure operation is a batch low pressure operation. During the batch low pressure operation, the hydrogen and oxygen mixture combusts and forms atomic oxygen during the low pressure operation. The combustion of the hydrogen and oxygen mixture is utilized in place of the plasma exposure while in a batch system, such as the fifth process system400.

Due to the operations described herein, the oxide layer522has a uniform thickness throughout the depth of the feature520. The uniformity of the oxide layer522is measured by measuring the thickness of the oxide layer522at cross sections530,532through the first portion510and the second portion512of the feature520. A first cross-section530is taken about 250 nm to about 750 nm from the top surface518of the device stack500, such as about 300 nm to about 700 nm, such as about 400 nm to about 600 nm, such as about 500 nm. The second cross-section532is taken about 250 nm to about 750 nm from the bottom surface509of the feature520of the device stack500, such as about 300 nm to about 700 nm, such as about 400 nm to about 600 nm, such as about 500 nm. The thicknesses of the oxide layer522as measured at the first cross-section530and the second cross-section532has a high conformality. As described herein, conformality is measured as the thickness of the oxide layer522at the second cross-section532over the thickness of the oxide layer522at the first cross-section530. The conformality when utilizing methods described herein 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%.