WO2026015403A1

WO2026015403A1 - Nitride layer formation by cyclic deposition and treatment

Info

Publication number: WO2026015403A1
Application number: PCT/US2025/036516
Authority: WO
Inventors: Jonathan CHURCH
Original assignee: Lam Research Corp
Current assignee: Lam Research Corp
Priority date: 2024-07-08
Filing date: 2025-07-03
Publication date: 2026-01-15
Anticipated expiration: 2027-01-08

Abstract

A method for generating a mold stack on a substrate is presented. The mold stack comprises alternating layers of silicon nitride and silicon oxide. The method comprises forming a plurality of layers of alternating silicon nitride and silicon oxide. At least one silicon nitride layer is deposited using a plurality of cycles. Each cycle comprises depositing a sublayer of silicon nitride and performing a plasma treatment without silicon nitride deposition on the sublayer of silicon nitride.

Description

NITRIDE LAYER FORMATION BY CYCLIC DEPOSITION AND

TREATMENT

BACKGROUND

[0001] In semiconductor manufacturing, layers of different films with different interatomic spacings and different coefficients of thermal expansion (CTE) are commonly formed in stacks on a substrate. The internal stresses of the materials, as well as extrinsic stresses at interfaces between films, can lead to deformation of a substrate in the form of bow. Additional stress can be induced when a substrate is heated, such as in an annealing process. This can lead to additional bow. One example of substrate bowing is frequently found in alternating stacks of material layers formed on a substrate called “mold stacks.”

SUMMARY

[0002] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

[0003] Examples are disclosed that relate to forming a mold stack on a substrate. One example provides a method comprising forming a plurality of layers of alternating silicon nitride and silicon oxide. At least one silicon nitride layer is deposited using a plurality of cycles. Each cycle of the plurality of cycles comprises depositing a sublayer of silicon nitride, and performing a plasma treatment without silicon nitride deposition on the sublayer of silicon nitride.

[0004] In some such examples, depositing a sublayer of silicon nitride comprises forming a plasma using a gas mixture comprising a silicon-containing precursor and a nitrogen-containing precursor.

[0005] Alternatively or additionally, in some such examples, the plurality of cycles comprises between 2 and 10 cycles. [0006] Alternatively or additionally, in some such examples, performing the plasma treatment without silicon nitride deposition comprises forming a plasma using a gas mixture comprising ammonia.

[0007] Alternatively or additionally, in some such examples, performing the plasma treatment without silicon nitride deposition comprises using a high frequency (HF) energy component of 3 MHz to 300 MHz having a radiofrequency power of at least 1000 W to form a plasma for the plasma treatment.

[0008] Alternatively or additionally, in some such examples, performing the plasma treatment without silicon nitride deposition further comprises using a low frequency (LF) energy component of less than 3 MHz having a radiofrequency power of at least 500W to form the plasma for the plasma treatment.

[0009] Alternatively or additionally, in some such examples, the method further comprises annealing the mold stack at an annealing temperature that is greater than a deposition temperature.

[0010] Alternatively or additionally, in some such examples, the mold stack bows less than a threshold amount at the annealing temperature.

[0011] Alternatively or additionally, in some such examples, depositing a sublayer of silicon nitride and performing a plasma treatment without silicon nitride deposition are performed at a same temperature within a processing chamber.

[0012] Alternatively or additionally, in some such examples, each sublayer of silicon nitride is between 1 Angstrom (A) and 100 A in thickness.

[0013] Another example provides a plasma enhanced chemical vapor deposition (PECVD) tool, comprising a processing chamber, a substrate support disposed in the processing chamber, a radiofrequency power source configured to supply radiofrequency power to form a plasma in the processing chamber, flow control hardware configured to fluidly connect one or more processing chemical sources to the processing chamber, and a controller. The controller is configured to control the PECVD tool to deposit a silicon oxide film on a substrate, and after depositing the silicon oxide film, deposit a silicon nitride film using a plurality of cycles. Each cycle of the plurality of cycles comprising depositing a silicon nitride film sublayer, and then forming a plasma comprising a treatment gas under conditions configured not to deposit film onto the sublayer of silicon nitride film.

[0014] In some such examples, the controller is further configured to control the PECVD tool to deposit a next silicon oxide film onto the silicon nitride layer. [0015] Alternatively or additionally, in some such examples, the silicon nitride film is deposited using silicon-containing precursor and ammonia.

[0016] Alternatively or additionally, in some such examples, the treatment gas comprises ammonia.

[0017] Alternatively or additionally, in some such examples, the plurality of cycles comprises between 2 and 10 cycles.

[0018] Alternatively or additionally, in some such examples, the controller is configured control the PECVD tool to deposit the sublayer of the silicon nitride film using a high frequency (HF) energy component of 3 MHz to 300 MHz having a radiofrequency power of at least 1000 W to form a plasma and omits a low frequency (LF) component having a frequency less than 3 MHz.

[0019] Alternatively or additionally, in some such examples, the controller is configured to control the PECVD tool to form the plasma comprising the treatment gas using a multi -frequency plasma comprising a high frequency (HF) energy component of 3 MHz to 300 MHz and a low frequency (LF) energy component of less than 3 MHz. [0020] Alternatively or additionally, in some such examples, silicon nitride film sublayers are between 1 A and 100 A in thickness.

[0021] In yet another example, a method for controlling a stress of a silicon nitride film deposited on a substrate is provided. The method comprising iteratively depositing a sublayer of silicon nitride, and performing a plasma treatment by directing ions generated in a plasma comprising ammonia onto the sublayer of silicon nitride without silicon nitride deposition.

[0022] In some such examples, the silicon nitride film is deposited on a first side of the substrate, and wherein a second film is deposited on a second side of the substrate, opposite the first side of the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 schematically shows an example mold stack comprising alternating layers of silicon oxide and silicon nitride.

[0024] FIGS. 2A-2C schematically show example substrate bowing as a function of increasing temperature.

[0025] FIG. 3 shows a flow diagram of an example method for forming a mold stack on a substrate. [0026] FIG. 4A schematically shows an example mold stack comprising alternating layers of silicon oxide and silicon nitride, the silicon nitride layers comprising a plurality of sublayers.

[0027] FIG. 4B schematically shows an example of a silicon nitride layer deposited on a substrate, the silicon nitride layer comprising a plurality of sublayers. [0028] FIG. 5 schematically shows an example PECVD tool.

[0029] FIG. 6 shows a block diagram of an example computing device.

DETAILED DESCRIPTION

[0030] The term “anneal” generally represents a heat treatment applied to a substrate comprising a film or a stack of films (e.g. a mold stack) after deposition of the film or the stack of films.

[0031] The term “bow” generally represents a deviation of the center point of the median surface of a mold stack from a reference plane.

[0032] The term “chemical vapor deposition (CVD)” generally represents a process in which a solid phase film is formed on a substrate by directing a continuous flow of one or more precursor gases over the substrate surface under conditions configured to cause the film formation. Plasma enhanced chemical vapor deposition (PECVD) utilizes a plasma to facilitate the film formation.

[0033] The term “deposition” generally represents growth of a film on a substrate.

[0034] The term “flow control hardware” generally represents components that fluidly connect one or more chemical sources with a processing chamber. Flow control hardware can comprise conduits, mass flow controllers, and/or valves, for example.

[0035] The term “mold stack” generally represents a stack of alternating layers of materials formed on a substrate in the fabrication of three-dimensional (3D) integrated circuits. Example mold stacks include an “ONON stack” comprising alternating layers of silicon oxide and silicon nitride.

[0036] The term “nitrogen-containing precursor” generally represents any material that can be introduced into a processing chamber in a gas phase to react with a silicon-containing precursor to form a silicon nitride film on a substrate. Example nitrogen-containing precursors for forming silicon nitride films can include ammonia (NH3), molecular nitrogen (N2), hydrazine (N2H2), and amino silanes. Examples of amino silanes include those listed above. [0037] The term “oxygen-containing precursor” generally represents any material that can be introduced into a processing chamber in a gas phase to react with a silicon-containing precursor to form a silicon oxide film on a substrate. Example oxygen-containing precursors include molecular oxygen (O2), nitrous oxide (N2O), other nitrogen oxides, water vapor (H2O), ozone (O3), and hydrogen peroxide (H2O2).

[0038] The term “plasma” generally represents a gaseous phase of matter comprising cations and free electrons.

[0039] The term “plasma treatment” generally represents providing a plasma to a substrate surface without depositing a film on the substrate surface.

[0040] The term “processing chamber” generally represents an enclosure in which chemical and/or physical processes are performed on substrates. The pressure, temperature and atmospheric composition within a processing chamber are controllable to perform chemical and/or physical processes.

[0041] The term “processing tool” generally represents a machine comprising a processing chamber and other hardware configured to perform substrate processing.

[0042] The term “radiofrequency (RF) power source” generally represents a power source configured to provide RF power to electrodes to form a capacitively coupled plasma, or to a coil to form an inductively coupled plasma.

[0043] The term “silicon-containing precursor” generally represents any material that can be introduced into a processing chamber in a gas phase to form a silicon-containing film on a substrate. Example film precursors for forming silicon- containing films using CVD can comprise materials having the general structure: where Ri, R2 and R3 can be the same or different substituents. In various examples, Ri, R2, and R3 can include silanes, amines, halides, hydrogen, or organic groups such as alkylamines, alkyl, alkenyl, alkynyl, and cyclic groups (such as aromatic groups).

[0044] In some examples, the silicon-containing precursor is an alkoxysilane. Alkoxysilanes that can be used include compounds having a general formula of H_x-Si- (OR)_y, where x = 0 to 3, x + y = 4 and each R is a substituted or unsubstituted aliphatic or aromatic group; and H_x(RO)y-Si-Si-(OR)yH_x, where each R is a substituted or unsubstituted aliphatic or aromatic group. Example alkoxysilanes include tetramethoxysilane (TMOS), tetraethylorthosilicate (TEOS) diethoxymethylsilane (DEMS), di ethoxy silane (DES), dimethoxymethylsilane, dimethoxysilane (DMOS), methyl-diethoxysilane (MDES), methyl-dimethoxysilane (MDMS), t-butoxydisilane, triethoxysilane (TES), and trimethoxysilane (TMS or TriMOS).

[0045] In some examples, the silicon-containing precursor is a siloxane. Siloxanes include materials having Si-O-Si linkages. Example siloxanes include octamethylcyclotetrasiloxane (OMCTS), octamethoxydodecasiloxane (OMODDS), and tetramethylcyclotetrasiloxane (TMCTS).

[0046] In some examples, the silicon-containing precursor is an aminosilane. Aminosilanes include materials having a general formula H_x-Si-(NR)_y, where x = 1-3, x + y = 4, and R is a substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aromatic group, or hydride group. Example aminosilanes include bisdiethylaminosilane, diisopropylaminosilane, bis(t-butylamino) silane (BTBAS), di-sec-butylaminosilane, and tris(dimethylamino)silane (3DMAS).

[0047] In some examples, the silicon-containing precursor is a halogencontaining silane. A halogen-containing silane can be referred to as a halosilane. In some examples, a halosilane can comprise at least one hydrogen atom. Such a silane can have a general formula of SiXaHy where y > 1. Example halosilanes include dichlorosilane (EhSiCh), hexachlorodisilane (Si2Cle), and diiodosilane (H2SH2).

[0048] Further examples of silicon-containing precursors include silane (SiEU) and polysilanes ((SinH2n+2, where n >1, such as disilane, trisilane, and tetrasilane), trisilylamine, methylsilane, trimethylsilane (3MS), ethylsilane, butasilanes, pentasilanes, octasilanes, heptasilanes, hexasilanes, cyclobutasilane, cycloheptasilane, cyclohexasilane, cyclooctasilane, cyclopentasilane, 1, 4-dioxa-2, 3,5,6- tetrasilacyclohexane, triethoxysiloxane (TRIES), and tetraoxymethylcyclotetrasiloxane (TOMCTS).

[0049] The term “substrate” generally represents any object on which a film can be deposited.

[0050] The term “substrate support” generally represents any structure for supporting a substrate in a processing chamber during substrate processing. An example substrate support is a pedestal. [0051] The term “treatment gas” generally represents a gas or a mixture of gases used to perform a plasma treatment on a surface.

[0052] Alternating stacks of material layers formed on a substrate can be used to form 3-dimensional (3D) integrated circuits. Such alternating stacks of materials layers are sometimes referred to as mold stacks. A mold stack comprises a potentially large number of layers (e.g., in the 100s) of a first material and a second material arranged in alternating fashion. Some mold stacks can comprise layers of silicon oxide (SiCh) alternating with layers of silicon nitride (SiN). Such stacks can be referred to as ONON stacks, where “O” represents the “oxide” or SiCh layer and “N” represents the “nitride” or SiN layer. Example 3D integrated circuits that can be fabricated using ONON stacks include 3D NOT AND (NAND) memory devices.

[0053] FIG. 1 shows an example mold stack 100. Mold stack 100 is formed on a substrate, such as a silicon wafer 102. Mold stack 100 comprises alternating layers of silicon oxide 104 and silicon nitride 106. Mold stack 100 can be referred to as an ONON mold stack (oxide-nitride-oxide-nitride). While sixteen layers are shown, this is merely illustrative, and a mold stack can have many more layers. An ONON mold stack may have a total thickness on the order of 4-6 microns in some examples.

[0054] In a typical mold stack deposition process, silicon nitride layers and silicon oxide layers are deposited in an alternating fashion using plasma enhanced chemical vapor deposition (PECVD) at substrate temperatures up to 650° C . Silicon oxide can deposited using, for example, TEOS (tetraethyl orthosilicate) and oxygen, or silane and nitrous oxide. Silicon nitride can be deposited, for example, using silane and ammonia. A total processing chamber pressure can be within a range of 0.5 - 20 torr.

[0055] Stresses from the layers of the mold stack can contribute a significant amount of bow to the substrate, due at least in part to the thickness and number of material layers of the mold stack. This bowing can be on the orders of hundreds to thousands of microns. Deposition of the mold stack occurs at elevated temperatures (e.g., 500° C or greater), further bowing the substrate. Bowing can induce a number of failure modes in semiconductor manufacturing. For example, bowing can lead to lithographic misalignment, patterned structure bending, and crack and defect formation. [0056] FIGS. 2A-2C illustrate example bowing. At 200, FIG. 2A shows an example substrate 202 prior to mold stack film deposition. Substrate 202 is effectively flat. At 210, FIG. 2B shows substrate 202 at room temperature following PECVD deposition of a mold stack comprising alternating layers of silicon oxide and silicon nitride. Some substrate bowing occurs due to the internal and extrinsic stresses of the deposited films. In this example, a bowl-shaped substrate is defined as having a positive bow (by convention). At 220, FIG. 2C shows substrate 202 following deposition of a mold stack, and upon heating to an elevated (> 600° C) temperature, such as in an annealing process. As both the deposited material and substrate expand, the amount of bowing changes. In this example, the substrate becomes more tensile upon heating, generating additional positive bowing. In other examples, stresses can cause domeshaped bowing, saddle-shaped bowing, or other substrate profiles.

[0057] As a counter to this bowing, electrostatic clamping can be used to keep the substrate flat during processing at elevated temperatures. However, the clamping force is limited. As the stress on the substrate increases due to film deposition, the forces bowing the substrate can possibly overcome the maximum clamping force provided by an electrostatic chuck. One possible solution is to continue increasing the available power to increase the clamping force. This, however, can lead to other problems. For example, the backside of the substrate may be damaged, scratched, or the substrate can be cracked.

[0058] An alternative solution is to restrict a number of layers in a mold stack so that the substrate does not exceed a maximum bow. However, this can limit continued node scaling in 3D integrated circuit manufacturing, as increased scaling can be facilitated by depositing more layers vertically.

[0059] Another alternative solution is to deposit a film on the backside of the substrate, thereby compensating for bowing on the frontside. However, as a number of layers in a mold stack grows, the amount of compensation required increases, thus increasing the thickness of the backside deposition. The additional time and steps used for backside deposition can impact manufacturing throughput.

[0060] Accordingly, examples are disclosed that relate to reducing substrate bowing caused by a mold stack while at elevated temperatures. In particular, the disclosed examples relate to methods of depositing a silicon nitride layer to modify an internal stress of the silicon nitride layer compared to silicon nitride layers formed by other deposition methods. The disclosed methods increase the compressive stress of the silicon nitride layers, offsetting tensile stress of both the silicon nitride layers and the silicon oxide layers. The disclosed methods can be used, for example, to deposit silicon nitride layers in a mold stack during 3D memory manufacturing. The disclosed example processes help to reduce substrate bow while the substrate is at elevated temperatures during ONON deposition, and during any following higher temperature steps (e.g., annealing).

[0061] As described in more detail below, the disclose examples utilize a cyclic method to deposit a silicon nitride layer by PECVD. The cyclic method involves, for each cycle, a deposition step and a treatment step. The deposition step involves the deposition of a sublayer of silicon nitride. The term “sublayer” refers to a portion of an overall thickness of a silicon nitride layer that is deposited in a single deposition and treatment cycle. The treatment step involves exposure of the sublayer to a plasma treatment that causes plasma exposure without silicon nitride deposition. In the treatment step, the sublayer is bombarded by ions from the plasma during the treatment step. The treatment step is configured to make the silicon nitride layer exert more compressive stress, rather than tensile stress, when heated. The silicon nitride deposition can be configured to cause, at room temperature, a substrate bow that can match that of silicon nitride deposited without using a cyclic deposition and treatment process. However, when heated, the resulting substrate and mold stack can experience less stress and mechanical deformation than a substrate with a mold stack comprising silicon nitride layers deposited without the cyclic deposition and treatment process.

[0062] The cyclic deposition and treatment steps can be performed at any suitable interval. In some examples, the treatment step is performed after approximately 10-100 A of silicon nitride. The cyclic deposition and treatment process can be implemented without significant tool upgrades or new chemistry delivery systems. By reducing substrate bowing during heating, the failure modes during manufacturing while at elevated temperatures can be reduced. This may facilitate the vertical scaling of future technology nodes by allowing the use of thicker mold stacks with more material layers.

[0063] FIG. 3 shows a flowchart depicting an example method 300 for depositing a mold stack on a substrate. The mold stack comprises alternating layers of silicon nitride and silicon oxide. Method 300 can be implemented using plasma- enhanced chemical vapor deposition tool, for example. Example processing tools are discussed below with regard to FIG. 5. At 310, method 300 comprises forming a plurality of layers of alternating silicon nitride and silicon oxide. FIG. 4A shows an example mold stack 400 having a substrate 402, and alternating layers of silicon oxide 404 and silicon nitride 406. In some examples, the silicon nitride layers may be on the order of 200-600 A in thickness. The silicon oxide layers can have similar thicknesses. [0064] Any suitable silicon-containing precursor can be used to deposit the layer of silicon oxide 404. In some examples, the silicon-containing precursor is an alkoxysilane. Alkoxysilanes that can be used include those having a composition of H_x- Si-(OR)_y, where x = 0-3, x+y = 4 and each R is a substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, or substituted or unsubstituted aromatic group; and H_x(RO)y,-Si-Si-(OR)yH_x, where each R is a substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, or substituted or unsubstituted aromatic group. Example alkoxysilanes include tetramethoxysilane (TMOS), diethoxymethylsilane (DEMS), diethoxysilane (DES), dimethoxymethylsilane, dimethoxysilane (DMOS), methyldiethoxysilane (MDES), methyl-dimethoxysilane (MDMS), tetraethylorthosilicate (TEOS), t-butoxydisilane, triethoxysilane (TES), and trimethoxysilane (TMS or TriMOS).

[0065] In some examples, the silicon-containing precursor is a siloxane. Siloxanes include materials having Si-O-Si linkages. Example siloxanes include octamethylcyclotetrasiloxane (OMCTS), octamethoxydodecasiloxane (OMODDS), and tetramethylcyclotetrasiloxane (TMCTS).

[0066] In some examples, the silicon-containing precursor is an aminosilane. Aminosilanes include materials having the general formula H_x-Si-(NR)_y, where x = 1- 3, x+y = 4, and R is a substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aromatic group, or hydride group. Example aminosilanes include bisdiethylaminosilane, diisopropylaminosilane, bis(t-butylamino) silane (BTBAS), di-sec-butylaminosilane, and tris(dimethylamino)silane (3DMAS).

[0067] In some examples, the silicon-containing precursor can be a halosilane. In some examples, a halosilane can comprise at least one hydrogen atom. Such a silane can have a chemical formula of SiXaHy where y = 1-3, a+y = 4. Examples of halosilanes can include dichlorosilane (EESiCh), hexachlorodi silane (Si2Cle), and diiodosilane (H2SH2).

[0068] Further examples of silicon-containing precursors include silanes (Si _n H211+2, where n >1), such as silane, disilane, trisilane, and tetrasilane). Additional examples include trisilylamine, methylsilane, trimethylsilane (3MS), ethylsilane, butasilanes, pentasilanes, octasilanes, heptasilane, hexasilane, cyclobutasilane, cycloheptasilane, cyclohexasilane, cyclooctasilane, cyclopentasilane, 1,4-dioxa- 2,3,5,6-tetrasilacyclohexane, triethoxysiloxane (TRIES), and tetraoxymethylcyclotetrasiloxane (TOMCTS).

[0069] An oxygen-containing precursor also is introduced into the processing chamber to react with the silicon-containing precursor to form the layer of silicon oxide. The oxygen-containing precursor can comprise any suitable oxygen-containing substance that can react with a silicon-containing precursor to form a film of silicon oxide. Examples of oxygen-containing precursors include oxygen, ozone, water vapor, hydrogen peroxide, nitrous oxide, and other nitrogen oxides.

[0070] At 320, method 300 comprises depositing at least one silicon nitride layer using a plurality of cycles of a cyclic deposition and treatment process. At 410 of FIG. 4A, a single layer of silicon nitride 406 is expanded to show a plurality of sublayers 412. In some examples, each sublayer can be between 1 and 100 A in thickness.

[0071] In the cyclic silicon nitride deposition process, at 330, method 300 comprises depositing a sublayer of silicon nitride. In some examples, the deposition can be performed by using PECVD. As such, at 340, method 300 can comprise forming a plasma using a gas mixture comprising one or more silicon-containing precursors and one or more nitrogen-containing precursors. In some examples, the silicon nitride film precursors comprise a silicon-containing precursor (e.g. silane) and ammonia. Other examples of silicon-containing precursors and nitrogen-containing precursors include those listed above. One or more other gases can be added to the silicon nitride film precursor mixture. Examples include inert gases such as argon, and/or nitrogencontaining gases, such as molecular nitrogen (N2).

[0072] In some examples, the PECVD deposition of a sublayer of silicon nitride can be performed using a capacitively coupled plasma having a single-frequency of RF energy. The RF energy can have a frequency within a range of 3 MHz to 300 MHz. Such frequences can be referred to as “relatively higher frequency” (HF) RF energy, or high frequency RF energy. This is in contrast with “relatively lower frequency” (LF) RF energy, also referred to as low frequency RF energy, with frequencies below 3MHz. The use of lower power HF RF may generate additional compressive stress in the mold stack. HF RF may be provided on the order of 1000 W and higher per processing chamber (e.g., 4000 W and higher in a quad chamber processing tool). When LF RF is present, it may be provided on the order of 250 W or less per processing chamber.

[0073] In some examples, a pressure in the processing chamber may be maintained between 0.5 and 20 Torr during the PECVD deposition of a silicon nitride sublayer. Further, in some examples, a gap between the substrate and the showerhead providing the plasma may be between 0.1 and 1 inches. A wider gap may generate additional compressive stress in the mold stack. Similar pressures and gap distances can be used for the deposition of the silicon oxide layers of the mold stack.

[0074] Continuing with FIG. 3, after depositing a silicon nitride sublayer, a treatment step is performed. Thus, at 350, method 300 comprises performing a plasma treatment without silicon nitride deposition on the sublayer of silicon nitride. At 420 of FIG. 4A a subset of silicon nitride sublayers 412 is shown, with a plasma treatment performed in between depositing consecutive sublayers.

[0075] In some examples, performing the plasma treatment without silicon nitride deposition comprises forming a plasma using a gas mixture comprising ammonia. In some such examples, the gas mixture may comprise one or more other gases, such as N2, helium, argon, krypton, neon, or xenon. In other examples, a nitrogen-containing gas other than ammonia can be used. The plasma treatment causes ion bombardment of the silicon nitride layer. The ion bombardment densifies the silicon nitride sublayer. This helps to move the silicon nitride sublayer toward compressive stress at elevated temperatures, such as annealing temperatures. At room temperature, the tensile stress of mold stacks featuring the sublayered/treated silicon nitride layers may approach the tensile stress at room temperature in mold stacks featuring a singlelayer of silicon nitride (e.g., not deposited through cyclical deposit! on/treatm ent) but may have much greater compressive stress upon heating. The tensile stress at room temperature may thus be selected to meet specifications for substrates comprising mold stacks featuring a single-layer of silicon nitride. For example, the specifications may indicate any of the following at room temperature: a compressive bow, a neutral bow, or a tensile bow.,

[0076] In some examples, a multifrequency plasma can be used to perform the treatment step of the cyclic silicon nitride deposition/treatment process. In some such examples, performing the plasma treatment without silicon nitride deposition comprises using a HF RF energy component of 3 MHz to 300 MHz, and a LF RF component having a frequency of less than 3 MHz, to perform the treatment. In some such examples, the HF RF energy component can have an RF power within a range of 500 to 8000 W. Further, the LF RF energy component can have an RF power within a range of 50 to 3000 W. In other examples, performing the plasma treatment without silicon nitride deposition comprises using a single frequency HF RF energy to form a plasma. The deposition and treatment steps of the cyclic deposition/treatment silicon nitride deposition process can be performed at a same pressure within a processing chamber in some examples. The HF RF energy component may be presented at a same or similar RF power as to that used during silicon nitride deposition.

[0077] The deposition and treatment steps of a cyclic deposition/treatment silicon nitride deposition process can be repeated for any suitable number of cycles to form a desired silicon nitride film. In some examples, the cyclic deposition/treatment silicon nitride deposition process can be performed for 2 to 20 cycles. In other examples, a number of cycles outside of this range can be used. Further, in some examples, all silicon nitride layers of a mold stack can be deposited using a cyclic deposition/treatment process as disclosed. In other examples, a subset of silicon nitride layers (e.g. from 1 to n-1 silicon nitride layers, where a mold stack has n silicon nitride layers) can be deposited using a cyclic deposition/treatment process.

[0078] Optionally, at 360, after depositing the mold stack, the method 300 comprises annealing the mold stack at an annealing temperature that is greater than a deposition temperature. For example, an annealing temperature may be between 650° C and 1000° C in the presence of molecular nitrogen or an inert gas. Annealing the mold stack may be performed in a different processing chamber from the deposition steps. The mold stack may exhibit less than a threshold amount of bow at the annealing temperature. In comparison, a mold stack comprising no silicon nitride layers formed using a cyclic deposition/treatment process as disclosed may exhibit bow at or above the threshold amount.

[0079] ONON mold stacks formed using method 300 may thus demonstrate less bowing than those with silicon nitride layers formed without using cyclic deposition/treatment processes, both at room temperature and when heated. In one example, such a film matched the bowing of a single-layer silicon nitride ONON film within 10% at room temperature but demonstrated 48% less bowing at annealing temperature. Substrate bow was evaluated in two indirect ways. In an experiment, plasma probes were monitored at 570° C (e.g., near deposition temperature). During this experiment, substrates were held with no electrostatic clamping, allowing the substrates to bow within the chamber. The plasma probe signal, which becomes more negative for a more heavily bowed substrate, was less negative for the substrate with silicon nitride layers formed using a cyclic deposition/treatment process. In another experiment, the substrates were electrostatically clamped and monitored with plasma probes. The plasma probe signal changes as a substrate shape changes. Flattening of this signal indicated that substrates are clamped flat. It was found that films generated through method 300 clamped at lower voltages, as they were not as heavily bowed. The films also declamped later when the clamping voltage was lowered, for the same reason. [0080] Film density and film refractive index were slightly lower for the ONON mold stack with the cyclic deposition/treatment silicon nitride layers (2.4 to 2.6 g/cc and 1.826 vs 1.907 RI). Films formed using method 300 demonstrate a significantly different stress shift after an 850° C/30min anneal in nitrogen ambient in the negative (compressive direction). When analyzed through Fourier transform infrared spectroscopy (FTIR), films generated through method 300 had fewer Si-N bonds. In other words, the Si-N bond density was lower. Si-H bonds were also reduced. The overall film was denser.

[0081] In some examples, the sublayering and cyclic deposition of silicon nitride may be performed directly onto a substrate or other deposited film that does not comprise alternating layers of silicon oxide. For example, a sublayer of silicon nitride may be deposited on to a substrate. A plasma treatment may be performed by directing ions generated in a plasma comprising ammonia onto the sublayer of silicon nitride without silicon nitride deposition. The cycles of silicon nitride deposition and plasma treatment may be performed iteratively as described.

[0082] FIG. 4B schematically shows a structure 450 having a substrate 452 and a silicon nitride layer 454. In some examples, the silicon nitride layer may be on the order of 200-600 A in thickness. At 460 of FIG. 4B, a single layer of silicon nitride 454 is expanded to show a plurality of sublayers 412. In some examples, each sublayer can be between 1 and 100 A in thickness. At 470 of FIG. 4B a subset of silicon nitride sublayers 462 is shown, with a plasma treatment performed in between depositing consecutive sublayers.

[0083] In some examples, the silicon nitride film is deposited on a first side of the substrate, and wherein a second film is deposited on a second side of the substrate, opposite the first side of the substrate. For example, the layered silicon nitride film can be deposited on the backside of a substrate to compensate for bowing on the front side [0084] FIG. 5 schematically shows an example processing tool 500 that can implement the method described with reference to FIG. 3. Processing tool 500 comprises a processing chamber 502 and a substrate support 504 within the processing chamber. The substrate support 504 is configured to support a substrate 506 disposed within the processing chamber 502. The substrate support 504 can comprise an electrostatic chuck (ESC) pedestal in some examples. The substrate support 504 comprises a substrate heater 508. In other examples, a heater can be omitted, or can be located elsewhere within processing chamber 502.

[0085] The processing tool 500 further comprises a showerhead 510. In other examples, a processing tool can comprise a nozzle or other apparatus for introducing gas into processing chamber 502, as opposed to or in addition to a showerhead. The showerhead 510 and the substrate support 504 form a processing station for processing substrate 506. While a single processing station is shown in FIG. 5, in some examples, a processing tool can have two, three, four or more processing stations in a processing chamber.

[0086] The processing tool 500 further comprises flow control hardware 512. The flow control hardware 512 connects processing gas source(s) to the processing chamber. In the depicted example, the flow control hardware 512 connects a silicon- containing precursor source 516, an oxygen-containing precursor source 517, a nitrogen-containing precursor source 518, a treatment gas source 520, and an inert gas source 522.

[0087] The silicon-containing precursor source 516 comprises any suitable silicon-containing chemical(s) for forming a silicon oxide film. Examples of silicon- containing precursors include those listed above. While a single silicon-containing precursor source 516 is shown in FIG. 5, in other examples, two or more different silicon-containing precursor sources can be included. For example, different silicon- containing precursors from different silicon-containing precursor sources can be used to deposit silicon oxide films and silicon nitride films.

[0088] The processing tool 500 further comprises an oxygen-containing precursor source 517. The oxygen-containing precursor source provides an oxygencontaining precursor for forming silicon oxide. Examples of oxygen-containing precursors can include molecular oxygen, water, hydrogen peroxide, ozone, and nitrogen oxides.

[0089] The nitrogen-containing precursor source 518 comprises any suitable nitrogen-containing precursors chemical(s) for reacting with a silicon-containing precursor to form a silicon nitride film. Example nitrogen-containing precursors include ammonia, molecular nitrogen, and hydrazine. [0090] Treatment gas source 520 comprises any suitable precursor gas or mixture of gases to treat a silicon nitride sublayer in a treatment step according to the disclosed examples. Example treatment gases include ammonia and inert gases, as described above. The inert gas source 522 can comprise any suitable inert gas. Examples include argon, helium, neon, krypton, and xenon.

[0091] The flow control hardware 512 can include any suitable components for controlling a flow of processing chemicals to the processing chamber 502. Examples include mass flow controllers, valves, and conduits. For example, the flow control hardware 512 can comprise one or more valves controllable to place a selected processing chemical source or selected processing chemical sources in fluid connection with showerhead 510. The flow control hardware 512 also can comprise one or more mass flow controllers or other controllers for controlling a mass flow rate of processing chemical.

[0092] The processing tool 500 further comprises an exhaust system 532. The exhaust system 532 is configured to exhaust gases from the processing chamber 502. The exhaust system 532 can comprise any suitable hardware, including one or more low vacuum pumps and one or more high vacuum pumps. Together, flow control hardware 512 and exhaust system 532 can be operated to achieve a selected pressure in processing chamber 502 during substrate processing.

[0093] The processing tool 500 further comprises a radiofrequency power source 534 that is electrically connected to showerhead 510. Radiofrequency power source 534 is configured to form a plasma using a gas mixture. For example, during a deposition step, radiofrequency power source 534 can be operated to form a plasma using a gas mixture comprising one or more film precursors to deposit a silicon- containing film. Additionally, during a treatment step, radiofrequency power source 534 can be operated to form a plasma using a gas mixture comprising a treatment gas (e.g. ammonia and/or an inert gas) to treat a silicon nitride sublayer.

[0094] The substrate support 504 is configured as a powered electrode in this example. The showerhead 510 is configured as a grounded electrode. This allows the substrate support 504 electrode to be biased to accelerate ions from a plasma toward the substrate. In other examples, the radiofrequency power source 534 can supply radiofrequency power to showerhead 510, or to another suitable electrode structure. Thus, the radiofrequency power source 534 forms a capacitively coupled plasma (CCP) when operated. Further, the radiofrequency power source 534 can be operated to pulse the plasma, for example, using any suitable duty cycle. Alternatively, the radiofrequency power source 534 can form a continuous wave plasma.

[0095] The radiofrequency power source 534 can be configured to provide RF energy of any suitable frequency and power. In some examples, the radiofrequency power source 534 is configured to operate at a plurality of different frequencies and/or powers. As depicted, the radiofrequency power source 534 comprises a HF RF power source 535 and an LF RF power source 537. The HF RF power source 535 can provide RF power at one or more frequencies within a range of 3 MHz to 300 MHz. The LF RF power source 537 can provide RF power at one or more frequencies below 3 MHz. The processing tool 500 further includes include a matching network 536 for impedance matching of the RF power source 534. The RF power source can be configured to provide RF power of any suitable magnitude. In some examples, the RF power source can supply HF RF power between 0 and 2000W per processing station. Further, in some examples, the RF power source can supply LF RF power between 0 and 2000W per processing station.

[0096] The processing tool 500 further comprises a controller 550 configured to control operation of the processing tool. The controller 550 is operatively coupled to the substrate heater 508, the flow control hardware 512, the exhaust system 532, and the radiofrequency power source 534. The controller 550 is configured to control various functions of processing tool 500 to perform a deposition cycling including deposition steps and treatment steps without deposition. For example, the controller 550 is configured to operate the substrate heater 508 to heat a substrate to a desired temperature. The controller 550 also is configured to operate the flow control hardware 512 to flow a selected gas or mixture of gases at a selected rate into the processing chamber 502. The controller 550 is further configured to operate the exhaust system 532 to remove gases from processing chamber 502. The controller 550 is configured to operate the radiofrequency power source 534 to form a plasma, as well as to control any other suitable functions of processing tool 500.

[0097] The controller 550 can comprise any suitable computing system. FIG. 6 schematically shows an example of a computing system 600 that can enact one or more of the methods and processes described above. Computing system 600 is shown in simplified form. Computing system 600 may take the form of one or more personal computers, workstations, computers integrated with substrate processing tools, and/or network accessible server computers. [0098] Computing system 600 includes a logic machine 602 and a storage machine 604. Computing system 600 may optionally include a display subsystem 606, input subsystem 608, communication subsystem 610, and/or other components not shown in FIG. 6. Controller 550 is an example of computing system 600.

[0099] Logic machine 602 includes one or more physical devices configured to execute instructions. For example, the logic machine may be configured to execute instructions that are part of one or more applications, services, programs, routines, libraries, objects, components, data structures, or other logical constructs. Such instructions may be implemented to perform a task, implement a data type, transform the state of one or more components, achieve a technical effect, or otherwise arrive at a desired result.

[00100] The logic machine may include one or more processors configured to execute software instructions. Additionally or alternatively, the logic machine may include one or more hardware or firmware logic machines configured to execute hardware or firmware instructions. Processors of the logic machine may be single-core or multi-core, and the instructions executed thereon may be configured for sequential, parallel, and/or distributed processing. Individual components of the logic machine optionally may be distributed among two or more separate devices, which may be remotely located and/or configured for coordinated processing. Aspects of the logic machine may be virtualized and executed by remotely accessible, networked computing devices configured in a cloud-computing configuration.

[00101] Storage machine 604 includes one or more physical devices configured to hold instructions 612 executable by the logic machine to implement the methods and processes described herein. When such methods and processes are implemented, the state of storage machine 604 may be transformed — e.g., to hold different data.

[00102] Storage machine 604 may include removable and/or built-in devices. Storage machine 604 may include optical memory (e.g., CD, DVD, HD-DVD, Blu-Ray Disc, etc.), semiconductor memory (e.g., RAM, EPROM, EEPROM, etc.), and/or magnetic memory (e.g., hard-disk drive, floppy-disk drive, tape drive, MRAM, etc.), among others. Storage machine 604 may include volatile, nonvolatile, dynamic, static, read/write, read-only, random-access, sequential-access, location-addressable, file- addressable, and/or content-addressable devices.

[00103] It will be appreciated that storage machine 604 includes one or more physical devices. However, aspects of the instructions described herein alternatively may be propagated by a communication medium (e.g., an electromagnetic signal, an optical signal, etc.) that is not held by a physical device for a finite duration.

[00104] Aspects of logic machine 602 and storage machine 604 may be integrated together into one or more hardware-logic components. Such hardware-logic components may include field-programmable gate arrays (FPGAs), program- and application-specific integrated circuits (PASIC / ASICs), program- and applicationspecific standard products (PSSP / ASSPs), system-on-a-chip (SOC), and complex programmable logic devices (CPLDs), for example.

[00105] When included, display subsystem 606 may be used to present a visual representation of data held by storage machine 604. This visual representation may take the form of a graphical user interface (GUI). As the herein described methods and processes change the data held by the storage machine, and thus transform the state of the storage machine, the state of display subsystem 606 may likewise be transformed to visually represent changes in the underlying data. Display subsystem 606 may include one or more display devices utilizing virtually any type of technology. Such display devices may be combined with logic machine 602 and/or storage machine 604 in a shared enclosure, or such display devices may be peripheral display devices.

[00106] When included, input subsystem 608 may comprise or interface with one or more user-input devices such as a keyboard, mouse, or touch screen. In some examples, the input subsystem may comprise or interface with selected natural user input (NUI) componentry. Such componentry may be integrated or peripheral, and the transduction and/or processing of input actions may be handled on- or off-board. Example NUI componentry may include a microphone for speech and/or voice recognition, and an infrared, color, stereoscopic, and/or depth camera for machine vision and/or gesture recognition.

[00107] When included, communication subsystem 610 may be configured to communicatively couple computing system 600 with one or more other computing devices. Communication subsystem 610 may include wired and/or wireless communication devices compatible with one or more different communication protocols. As non-limiting examples, the communication subsystem may be configured for communication via a wireless telephone network, or a wired or wireless local- or wide-area network. In some examples, the communication subsystem may allow computing system 600 to send and/or receive messages to and/or from other devices via a network such as the Internet. [00108] It will be understood that the configurations and/or approaches described herein are exemplary in nature, and that these specific examples or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. As such, various acts illustrated and/or described may be performed in the sequence illustrated and/or described, in other sequences, in parallel, or omitted. Likewise, the order of the above-described processes may be changed.

[00109] The subject matter of the present disclosure includes all novel and non- obvious combinations and sub-combinations of the various processes, systems and configurations, and other features, functions, acts, and/or properties disclosed herein, as well as any and all equivalents thereof.

Claims

CLAIMS:

1. A method for generating a mold stack on a substrate, the mold stack comprising alternating layers of silicon nitride and silicon oxide, the method comprising: forming a plurality of layers of alternating silicon nitride and silicon oxide, wherein at least one silicon nitride layer is deposited using a plurality of cycles, each cycle of the plurality of cycles comprising depositing a sublayer of silicon nitride, and performing a plasma treatment without silicon nitride deposition on the sublayer of silicon nitride.

2. The method of claim 1, wherein depositing the sublayer of silicon nitride comprises forming a plasma using a gas mixture comprising a silicon-containing precursor and a nitrogen-containing precursor.

3. The method of claim 1, wherein the plurality of cycles comprises between 2 and 10 cycles.

4. The method of claim 1, wherein performing the plasma treatment without silicon nitride deposition comprises forming a plasma using a gas mixture comprising ammonia.

5. The method of claim 1, wherein performing the plasma treatment without silicon nitride deposition comprises using a high frequency (HF) energy component of 3 MHz to 300 MHz having a radiofrequency power of at least 1000 W to form a plasma for the plasma treatment.

6. The method of claim 5, wherein performing the plasma treatment without silicon nitride deposition further comprises using a low frequency (LF) energy component of less than 3 MHz having a radiofrequency power of at least 500W to form the plasma for the plasma treatment.

7. The method of claim 1, further comprising annealing the mold stack at an annealing temperature that is greater than a deposition temperature.

8. The method of claim 7, wherein the mold stack bows less than a threshold amount at the annealing temperature.

9. The method of claim 1, wherein depositing the sublayer of silicon nitride and performing the plasma treatment without silicon nitride deposition are performed at a same temperature within a processing chamber.

10. The method of claim 1, wherein each sublayer of silicon nitride is between 1 A and 100 A in thickness.

11. A plasma enhanced chemical vapor deposition (PECVD) tool, comprising: a processing chamber; a substrate support disposed in the processing chamber; a radiofrequency power source configured to supply radiofrequency power to form a plasma in the processing chamber; flow control hardware configured to fluidly connect one or more processing chemical sources to the processing chamber; and a controller configured to control the PECVD tool to: deposit a silicon oxide film on a substrate positioned on the substrate support, and after depositing the silicon oxide film, deposit a silicon nitride film using a plurality of cycles, each cycle of the plurality of cycles comprising depositing a silicon nitride film sublayer, and forming a plasma comprising a treatment gas under conditions configured not to deposit film onto the sublayer of silicon nitride film.

12. The PECVD tool of claim 11, wherein the controller is further configured to control the PECVD tool to deposit a next silicon oxide film onto the silicon nitride layer.

13. The PECVD tool of claim 11, wherein the silicon nitride film is deposited using a silicon-containing precursor and ammonia.

14. The PECVD tool of claim 13, wherein the treatment gas comprises ammonia.

15. The PECVD tool of claim 11 , wherein the plurality of cycles comprises between

2 and 10 cycles.

16. The PECVD tool of claim 11, wherein the controller is configured control the PECVD tool to deposit the sublayer of the silicon nitride film using a high frequency (HF) energy component of 3 MHz to 300 MHz having a radiofrequency power of at least 1000 W to form a plasma and omits a low frequency (LF) energy component having a frequency of less than 3 MHz.

17. The PECVD tool of claim 16, wherein the controller is configured to control the PECVD tool to form the plasma comprising the treatment gas using a multi -frequency plasma comprising a high frequency (HF) energy component of 3 MHz to 300 MHz and a low frequency (LF) energy component of less than 3 MHz.

18. The PECVD tool of claim 11, wherein the silicon nitride film sublayers are between 1 A and 100 A in thickness.

19. A method for controlling a stress of a silicon nitride film deposited on a substrate, the method comprising iteratively: depositing a sublayer of silicon nitride, and performing a plasma treatment by directing ions generated in a plasma comprising ammonia onto the sublayer of silicon nitride without silicon nitride deposition.

20. The method of claim 19, wherein the silicon nitride film is deposited on a first side of the substrate, and wherein a second film is deposited on a second side of the substrate, opposite the first side of the substrate.