Low hydrogen and uniform silicon nitride film for waveguides

Abstract

Embodiments of the present disclosure generally relate to a method of depositing a silicon nitride film on a substrate. In one or more embodiments, a method includes placing a substrate on a substrate support within a processing chamber. A first gas mixture is flowed into the processing chamber. The first gas mixture includes a silane (SiH4) precursor at a first flow rate, a nitrogen (N2) precursor at a second flow rate, and a hydrogen (H2) precursor at a third flow rate. A radio frequency (RF) power is applied to the first gas mixture at a first frequency and first power to deposit a silicon-nitride film on a surface of the substrate. The silicon-nitride film has a hydrogen content between about 3% and about 10% and a refractive index (Rl) uniformity between about 0.1% and about 0.7% across the surface of the substrate.

Description

PATENTAttorney Docket No.: 44025668WO01LOW HYDROGEN AND UNIFORM SILICON NITRIDE FILM FOR WAVEGUIDESBACKGROUNDField

[0001] Embodiments of the present disclosure generally relate to a method of depositing a silicon nitride film on a substrate.Description of the Related Art

[0002] In the processing of substrates, including semiconducting substrates used in integrated circuit and photonic device manufacturing, plasma-enhanced chemical vapor deposition (PECVD) processes are used to deposit thin films onto the substrate surface. Silicon nitride is one such material of thin films deposition.

[0003] During PECVD deposition of silicon nitride, however, hydrogen may become incorporated into the film and may be introduced onto the underlying substrate. Excess hydrogen within the deposited film or at the film-substrate interface can interact with device structures in undesirable ways, potentially leading to increased optical absorption, instability in material properties, or degradation of device performance.

[0004] Accordingly, there is a need for improved PECVD techniques capable of reducing hydrogen incorporation during silicon nitride deposition.SUMMARY

[0005] In one embodiment, a method of forming a film stack is disclosed. The method includes placing a substrate on a substrate support within a processing chamber. A first gas mixture is flowed into the processing chamber. The first gas mixture includes a silane (SiH4) precursor at a first flow rate, a nitrogen (N2) precursor at a second flow rate, and a hydrogen (H2) precursor at a third flow rate. A radio frequency (RF) power is applied to thePATENTAttorney Docket No.: 44025668WO01first gas mixture at a first frequency and first power to deposit a silicon-nitride film on a surface of the substrate. The silicon-nitride film has a hydrogen content between about 3% and about 10% and a refractive index (Rl) uniformity between about 0.1% and about 0.7% across the surface of the substrate.

[0006] In another embodiment, a method of forming a film stack is disclosed. The method includes placing a substrate on a substrate support within a processing chamber. A first gas mixture is flowed into the processing chamber. The the first gas mixture includes a silane (SiF ) precursor at a first flow rate, a nitrogen (N2) precursor at a second flow rate, and an ammonia (NH3) precursor at a third flow rate. A layer of a silicon-nitride film is deposited onto a surface of the substrate using the first gas mixture. A second gas mixture is flowed into the processing chamber to treat the layer of the silicon-nitride film. The second gas mixture includes an N2 precursor at a fourth flow rate. A radio frequency (RF) power is applied to the second gas mixture at a first frequency and a first power.

[0007] In another embodiment, a method of forming a film stack is disclosed. The method includes placing a substrate on a substrate support within a processing chamber. A deposition operation is performed to deposit a layer of a silicon-nitride film onto a surface of the substrate. The deposition operation includes flowing a first gas mixture into the processing chamber. The first gas mixture includes a silane (SiF ) precursor at a first flow rate, a nitrogen (N2) precursor at a second flow rate, and an ammonia (NH3) precursor at a third flow rate. The method further includes performing a plasma treatment operation on the layer. The plasma treatment operation includes flowing a second gas mixture into the processing chamber. The second gas mixture includes an N2 precursor at a fourth flow rate. A radio frequency (RF) power is applied to the second gas mixture at a first frequency and a first power. The deposition operation and the plasma treatmentPATENTAttorney Docket No.: 44025668WO01operation are repeated between about 200 times and about 400 times to form the silicon-nitride film.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of the disclosure and are therefore not to be considered limiting of its scope, as the disclosure may admit to other equally effective embodiments.

[0009] Figure 1 is a schematic, cross-sectional view of a processing system, according to one or more embodiments.

[0010] Figure 2 is a schematic, cross-sectional view of a film stack, according to one or more embodiments.

[0011] Figure 3 is a flow diagram of a method for forming a film stack, according to one or more embodiments.

[0012] Figure 4 is a flow diagram of a method for forming a film stack, according to one or more embodiments.

[0013] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.DETAILED DESCRIPTION

[0014] The embodiments described herein generally relate to a method of depositing a silicon nitride film on a substrate. The silicon nitride film includes low-hydrogen content, has both high thickness and refractive-index uniformity,PATENTAttorney Docket No.: 44025668WO01and exhibits low optical loss in the O-band and C-band wavelengths. The film may be deposited in a PECVD deposition process using nitrogen (N2), rather than ammonia (NH3), as a nitrogen precursor, reducing the amount of hydrogen introduced during deposition. Further, co-flow of hydrogen (H2) scavenges hydrogen from Si— H dangling bonds, enabling the formation of a silicon nitride film with reduced hydrogen incorporation while maintaining thickness and refractive-index uniformity. Additionally, the film may be deposited in a cyclic deposition and plasma treatment approach to incrementally remove hydrogen from each deposited layer, achieving low hydrogen content for applications requiring low optical loss.

[0015] Figure 1 is a schematic illustration of a processing system 132, such as a plasma enhanced chemical vapor deposition (PECVD) chamber, according to one or more embodiments.

[0016] The processing system 132 includes a process chamber 100 coupled to a gas panel 130 and a controller 110. The process chamber 100 generally includes a top 124, a side 101 and a bottom wall 122 that define an interior processing volume 126. A substrate support pedestal 150 is provided in the interior processing volume 126 of the process chamber 100. The substrate support pedestal 150 is supported by a stem 160 and may be typically fabricated from aluminum, ceramic, and other suitable materials. The substrate support pedestal 150 may be moved in a vertical direction inside the process chamber 100 using a displacement mechanism (not shown).

[0017] The substrate support pedestal 150 may include an embedded heater element 170 suitable for controlling the temperature of a substrate 190 supported on a surface 192 of the substrate support pedestal 150. The substrate support pedestal 150 may be resistively heated by applying an electric current from a power supply 106 to the heater element 170. The electric current supplied from the power supply 106 is regulated by the controller 110 to control the heat generated by the heater element 170, thereby maintaining the substrate 190 and the substrate support pedestal 150PATENTAttorney Docket No.: 44025668WO01at a substantially constant temperature during film deposition. The supplied electric current may be adjusted to selectively control the temperature of the substrate support pedestal 150.

[0018] A temperature sensor 172, such as a thermocouple, may be embedded in the substrate support pedestal 150 to monitor the temperature of the substrate support pedestal 150 in a conventional manner. The measured temperature is used by the controller 110 to control the power supplied to the heater element 170 to maintain the substrate at a desired temperature.

[0019] A vacuum pump 102 is coupled to a port formed in the bottom of the process chamber 100. The vacuum pump 102 is used to maintain a desired gas pressure in the process chamber 100. The vacuum pump 102 also evacuates post-processing gases and by-products of the process from the process chamber 100. Although not shown, the processing system 132 may further include additional equipment for controlling the chamber pressure, for example, valves (e.g., throttle valves and isolation valves) positioned between the process chamber 100 and the vacuum pump 102 to control the chamber pressure.

[0020] A showerhead 120 having a plurality of apertures 128 is disposed on the top of the process chamber 100 above the substrate support pedestal 150. The apertures 128 of the showerhead 120 are utilized to introduce deposition gases into the process chamber 100. The apertures 128 may have different sizes, number, distributions, shape, design, and diameters to facilitate the flow of the various deposition gases for different process requirements. The showerhead 120 is connected to the gas panel 130 that allows various gases to be supplied to the interior processing volume 126 during processing.

[0021] A plurality of gas sources 180 are fluidly coupled to the gas panel 130. The plurality of gas sources 180 includes a first gas source 180A, a second gas source 180B, a third gas source 180C, a fourth gas source 180D,PATENTAttorney Docket No.: 44025668WO01and a fifth gas source 180E. Each gas source of the plurality of gas sources 180 is configured to provide a process gas to the gas panel 130 and through the showerhead 120. According to one or more embodiments, which can be combined with other embodiments described herein, the process gas includes at least one or more of silane (SiH4) precursors, nitrogen (N2) precursors, hydrogen (H2) precursors, ammonia (NH3) precursors, and argon (Ar) precursors.

[0022] The plurality of gas sources 180 have a respective plurality of flow controllers 182. A first flow controller 182A is disposed between the first gas source 180A and the gas panel 130. The first flow controller 182A may control the flow of an SiH4 precursor, for example, at a flow rate of about 10 standard cubic centimeters per minute (seem) to about 300 seem. A second flow controller 182B is disposed between the second gas source 180B and the gas panel 130. The second flow controller 182B may control the flow of a N2 precursor, for example, at a flow rate of about 500 seem to about 11,000 seem. A third flow controller 182C is disposed between the third gas source 180C and the gas panel 130. The third flow controller 182C may control the flow of a H2 precursor, for example, at a flow rate of about 500 seem to about 3,000 seem. A fourth flow controller 182D is disposed between the fourth gas source 180D and the gas panel 130. The fourth flow controller 182D may control the flow of a NH3 precursor, for example, at a flow rate of about 2 seem to about 50 seem. A fifth flow controller 182E is disposed between the fifth gas source 180E and the gas panel 130. The fifth flow controller 182E may control the flow of an Ar precursor, for example, at a flow rate of about 1,000 seem to about 8,000 seem. Each flow controller of the plurality of flow controllers 182 may be operated independently from each other. Each flow controller of the plurality of flow controllers 182 may be operated simultaneously.

[0023] A plasma is formed from the various process gases exiting the showerhead 120 to enhance thermal decomposition of the process gases resulting in the deposition of material on a surface 191 of the substrate 190.PATENTAttorney Docket No.: 44025668WO01The showerhead 120 and the substrate support pedestal 150 may form a pair of spaced apart electrodes in the interior processing volume 126. One or more radio frequency (RF) power sources 140 provide a bias potential through a matching network 138 to the showerhead 120 to facilitate generation of plasma between the showerhead 120 and the substrate support pedestal 150. Alternatively, the RF power sources 140 and matching network 138 may be coupled to the showerhead 120, substrate support pedestal 150, or coupled to both the showerhead 120 and the substrate support pedestal 150, or coupled to an antenna (not shown) disposed exterior to the process chamber 100. The RF Power may be provided at a fixed or tunable frequency in a range from about 50 kilohertz (kHz) to about 62 megahertz (MHz), although other frequencies and powers may be provided as desired for particular applications. In one or more embodiments, the RF frequency may be a high frequency RF of about 26 megahertz (MHz) to about 28 MHz, such as about 27 MHz, that is capable of producing either continuous or pulsed power, although other higher or lower frequencies and powers may be provided as desired for particular applications. The RF power sources 140 are operated at an RF power of about 100 Watts to about 1,500 Watts, such as from about 140 Watts to about 700 Watts.

[0024] The controller 110 includes a central processing unit (CPU) 112, a memory 116, and a support circuit 114 utilized to control the process sequence and regulate the gas flows from the gas panel 130. The CPU 112 may be of any form of a general purpose computer processor that may be used in an industrial setting. The software routines can be stored in the memory 116, such as random access memory, read only memory, floppy, or hard disk drive, or other form of digital storage. The support circuit 114 is conventionally coupled to the CPU 112 and may include cache, clock circuits, input / output systems, power supplies, and the like. Bi-directional communications between the controller 110 and the various components of the processing system 132 are handled through numerous signal cables collectively referred to as signal buses 118, some of which are illustrated in Figure 1.PATENTAttorney Docket No.: 44025668WO01

[0025] Figure 2 is a schematic, cross-sectional view of a film stack 200. The substrate 202 of the film stack 200 of Figure 2 may correspond to the substrate 190 as shown in Figure 1 and explained above.

[0026] The film stack 200 includes the substrate 202. The substrate 202 includes, at least, a supporting layer 202A. The supporting layer 202A can be any substrate used in the art, and can be either opaque or transparent to a chosen wavelength of light, depending on the use of the supporting layer 202A as a substrate for a waveguide. Substrate selection may include substrates of any suitable material, including, but not limited to, amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, polymers, or combinations thereof. In one or more embodiments, the supporting layer 202A includes, but is not limited to, a silicon-containing material, a silicon and oxygen containing compound, a germanium-containing material, a indium and phosphide containing compound, a gallium and arsenic containing compound, a gallium and nitrogen containing compound, a carbon-containing material, a silicon and carbon containing compound, a silicon, carbon, and oxygen containing compound, a silicon and nitrogen containing compound, a silicon, oxygen, and nitrogen containing compound, a niobium and oxygen containing compound, and lithium, niobium, and oxygen containing compound, an aluminum and oxygen containing compound, a indium, tin, and oxygen containing compound, a titanium and oxygen containing compound, a lanthanum and oxygen containing compound, a gadolinium and oxygen containing compound, a zinc and oxygen containing compound, a yttrium and oxygen containing compound, a tungsten and oxygen containing compound, a potassium, and oxygen containing compound, a phosphorous and oxygen containing compound, a barium and oxygen containing compound, a sodium and oxygen containing compound, or combinations thereof. In other embodiments, which can be combined with other embodiments described herein, the supporting layer 202A includes an oxide including one or more of gadolinium, silicon, sodium, barium, potassium, tungsten, phosphorus, zinc, calcium, titanium, tantalum, niobium, lanthanum, zirconium, lithium, or yttrium containing-materials. Example materials of the supporting layer 202A includePATENTAttorney Docket No.: 44025668WO01silicon (Si), silicon monoxide (SiO), silicon dioxide (SiC>2), silicon carbide (SiC), fused silica, diamond, quartz germanium (Ge), silicon germanium (SiGe), indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), sapphire, sapphire (AI2O3), lithium niobate (LiNbOs), indium tin oxide (ITO), lanthanum oxide (La20s), gadolinium oxide (Gd20s), zinc oxide (ZnO), yttrium oxide (Y2O3), tungsten oxide (WO3), titanium oxide (TiO2), zirconium oxide (ZrOs), sodium oxide (Na2O), niobium oxide (Nb20s), barium oxide (BaO), potassium oxide (K2O), phosphorus pentoxide (P2O5), calcium oxide (CaO), or combinations thereof.

[0027] In one or more embodiments, the substrate 202 includes a cladding layer 202B disposed over the supporting layer 202A. The cladding layer 202B is made of a material having a refractive index that is relatively low, as compared to the refractive index of a film 204 disposed thereover. In one or more embodiments, the cladding layer 202B has a refractive index between 1.3 and 1.5. In one or more embodiments, the cladding layer 202B is formed from one or more low-index materials. In one or more embodiments, the low-index material may be silicon dioxide (SiC ).

[0028] A film 204 is disposed over the film stack 200. The film 204 is a silicon-nitride film having the chemical formula SiNx, where x is between about 1 and about 1.5.

[0029] The film 204 has a hydrogen content of about 2% to about 10%. For example, the hydrogen content may be about 3% to about 5%, about 5% to about 7%, or about 7% to about 10%. In one or more embodiments, the hydrogen content may be minimized from about 2.1% to about 2.2%.

[0030] The film 204 has a thickness of about 380 nanometers (nm) to about 440 nm. For example, the film 204 may have a thickness from about 380 nm to about 390 nm, about 390 nm to about 400 nm, about 400 nm to about 410 nm, about 410 nm to about 420 nm, about 420 nm to about 430 nm, or about 430 nm to about 440 nm. The film 204 may have a thickness uniformity of about 0.8% to about 2.0%. For example, the thickness uniformityPATENTAttorney Docket No.: 44025668WO01may be from about 0.8% to about 1.0%, about 1.0% to about 1.5%, or about 1.5% to about 2.0%

[0031] The film 204 has a tunable refractive index (Rl) of about 1.9 to about 2.2. For example, the film 204 may have an Rl from about 1.9 to 2.0, about 2.0 to 2.1, or about 2.1 to about 2.2 The film 204 has an Rl uniformity across the surface of the substrate 202 of about 0.1% to about 0.7%. For example, the Rl uniformity may be from about 0.1% to about 0.2%, about 0.2% to about 0.4%, or about 0.4% to about 0.7%.

[0032] The film 204 has an optical propagation loss of about 0.01 decibels per centimeter (dB / cm) to about 1.0 dB / cm in waveguide applications. For example, the propagation loss may be from about 0.01 dB / cm to about 0.2 dB / cm, about 0.2 dB / cm to about 0.5 dB / cm, or about 0.5 dB / cm to about 1.0 dB / cm. In the O-band (e.g., wavelengths around 1310 nm), optical loss may be influenced primarily by the thickness uniformity or Rl uniformity of the film 204, whereas in the C-band (e.g., wavelengths around 1550 nm), optical loss may be more strongly affected by the hydrogen content of the film 204. Accordingly, by adjusting process parameters described above, the optical propagation loss in either the O-band or C-band may be tailored to fall within the desired ranges for various applications, such as photonic, datacom, or telecom applications.

[0033] Figure 3 is a flow diagram illustrating operations of a method 300 for forming the film stack 200, according to one or more embodiments.

[0034] At operation 302, the substrate 202 is introduced to the processing system 132 and processing parameters are adjusted accordingly. The substrate 202 is positioned on the substrate support pedestal 150. The spacing (i.e., a distance between the showerhead and the substrate support) may be between about 400 mils to about 700 mils. For example, the spacing may be between about 400 mils to about 500 mils, about 500 mils to about 600 mils, or about 600 mils to about 700 mils.PATENTAttorney Docket No.: 44025668WO01

[0035] Generally, the processing system 132 may exhibit the following exemplary operation parameters during deposition operations on the substrate 202. The pressure within the processing system 132 may range from about 5 Torr to about 10 Torr. For example, the pressure within the process chamber may be from about 5 Torr to about 6 Torr, about 6 Torr to about 7 Torr, about 7 Torr to about 8 Torr, about 8 Torr to about 9 Torr, or about 9 Torr to about 10 Torr. The process parameters may range from a processing temperature of about 350° Celsius to about 500° Celsius. For example, the processing temperature may be from about 350° Celsius to about 375° Celsius, about 375° Celsius to about 400° Celsius, about 400° Celsius to about 425° Celsius, or about 425° Celsius to about 450° Celsius, about 450° Celsius to about 475° Celsius, or about 475° Celsius to about 500° Celsius. These exemplary operation parameters may be adjusted as processing conditions call for. Variations in these parameters directly influence the characteristics of the resulting film 204 of the film stack 200. For example, the pressure within the processing system 132 may particularly affect the refractive index of the film.

[0036] At operation 304, a first gas mixture is flowed into the processing chamber 100. The first gas mixture includes, at least, a silane (SiF ) precursor, a nitrogen (N2) precursor, and a hydrogen (H2) precursor. The SiH4 precursor is flowed into the gas panel 130 at a first flow rate. For example, the first flow rate is about 50 seem to about 300 seem. The N2 precursor is flowed into the gas panel 130 at a second flow rate. For example, the second flow rate is about 3,000 seem to about 11,000 seem. The H2 precursor is flowed into the gas panel 130 at a third flow rate. For example, the third flow rate is about 500 seem to about 3,000 seem. The first gas mixture, including the SiF precursor, the N2 precursor, and the H2 precursor is formed in the gas panel 130. The first gas mixture is then flowed from the gas panel 130 into the processing chamber 100. In one or more embodiments, the first gas mixture further includes an argon (Ar) precursor. The Ar precursor is flowed into the gas panel 130 at a fourth flow rate. For example, the fourth flow rate is about 3,000 seem to about 8,000 seem. InPATENTAttorney Docket No.: 44025668WO01such embodiments, the first gas mixture, including the SiH4 precursor, the N2 precursor, the H2 precursor, and the Ar precursor, is formed in the gas panel 130, and is then flowed from the gas panel 130 into the processing chamber 100.

[0037] The use of N2as the nitrogen-containing precursor, rather than NH3, may advantageously reduce the amount of hydrogen introduced into the reaction environment. Additionally, hydrogen gas H2is co-flowed with the other precursors (e.g., SiH4and N2) to facilitate hydrogen scavenging during film formation. In particular, the introduced hydrogen may react with and remove Si-H dangling bonds formed during deposition, thereby reducing the overall hydrogen content within the resulting silicon nitride film. Through the combined effects of employing N2in place of NH3and introducing H2as a scavenging agent, the hydrogen concentration in the film may be minimized.

[0038] At operation 306, a plasma is generated in the processing system 132 using the first gas mixture. An RF power is applied to the first gas mixture within the processing system 132. The plasma treatment operation is a continuous plasma process, which includes maintaining the RF power on while continuing to expose the film stack 200 to the first gas mixture. The RF Power is provided at a fixed or tunable frequency in a range from about 26 MHz to about 28 MHz, such as about 27 MHz. In one or more embodiments, the RF power level applied in operation 306 for generating the plasma may be between about 600 Watts and about 1 ,500 Watts, such as between about 600 Watts and about 900 Watts, between about 900 Watts and about 1 ,200 Watts, or between about 1 ,200 Watts and about 1 ,500 Watts.

[0039] At operation 308, the film 204 is disposed over the substrate 202 using the generated plasma. In one or more embodiments, the film 204 is disposed directly over the supporting layer 202A. In one or more other embodiments, the film 204 is disposed directly over the cladding layer 202B. The deposition operation may occur until a film 204 of desired thickness is formed on the supporting layer 202A. The film 204 thickness may be betweenPATENTAttorney Docket No.: 44025668WO01about 380 nanometers (nm) to about 440 nm. For example, the film 204 may have a thickness between about 380 nm and about 390 nm, between about 390 nm and about 400 nm, between about 400 nm and about 410 nm, between about 410 nm and about 420 nm, between about 420 nm and about 430 nm, and about 430 nm and about 440 nm. In one or more embodiments, the film 204 may be deposited on the substrate 202 at a rate greater than 1 kiloangstrom (kA) per minute. In one or more embodiments, for a film thickness of about 420 nm, the operation may range from about 200 seconds to about 224 seconds, for example, from about 200 seconds to about 208 seconds, about 208 seconds to about 216 seconds, or about 216 seconds to about 224 seconds.

[0040] Figure 4 is a flow diagram illustrating operations of a method 400 for forming a film stack 200, according to one or more embodiments.

[0041] At operation 402, the substrate 202 is introduced to the processing system 132 and processing parameters are adjusted accordingly. The substrate 202 is positioned on the substrate support pedestal 150. The spacing (i.e., a distance between the showerhead and the substrate support) may be between about 400 mils to about 700 mils. For example, the spacing may be between about 400 mils to about 500 mils, about 500 mils to about 600 mils, or about 600 mils to about 700 mils.

[0042] Generally, the processing system 132 may exhibit the following exemplary operation parameters during deposition operations on the substrate 190. The pressure within the processing system 132 may range from about 1 Torr to about 5 Torr. For example, the pressure within the process chamber may be from about 1 Torr to about 2 Torr, about 2 Torr to about 3 Torr, about 3 Torr to about 4 Torr, or about 4 Torr to about 5 Torr. The process parameters may range from a processing temperature of about 400° Celsius to about 600° Celsius. For example, the processing temperature may be from about 400° Celsius to about 450° Celsius, about 450° Celsius to about 500° Celsius, about 500° Celsius to about 550° Celsius, or about 550°PATENTAttorney Docket No.: 44025668WO01Celsius to about 600° Celsius. These exemplary operation parameters may be adjusted as processing conditions call for.

[0043] At operation 404, a second gas mixture is flowed into the processing chamber 100. The second gas mixture includes, at least, a SiH4 precursor, an N2 precursor, and an NH3 precursor.. The SiH4 precursor is flowed into the gas panel 130 at a first flow rate. For example, the first flow rate is about 10 seem to about 30 seem. The N2 precursor is flowed into the gas panel 130 at a second flow rate. For example, the second flow rate is about 500 seem to about 1,500 seem. The NH3 precursor is flowed into the gas panel 130 at a third flow rate. For example, the third flow rate is about 2 seem to about 50 seem. The second gas mixture, including the SiFk precursor, the N2 precursor, and the NH3 precursor, is formed in the gas panel 130. The second gas mixture is then flowed from the gas panel 130 into the processing chamber 100. In one or more embodiments, the second gas mixture further includes an argon (Ar) precursor. The Ar precursor is flowed into the gas panel 130 at a fourth flow rate. For example, the fourth flow rate is about 3,000 seem to about 8,000 seem. In such embodiments, the first gas mixture, including the SiF precursor, the N2 precursor, the H2 precursor, and the Ar precursor, is formed in the gas panel 130, and is then flowed from the gas panel 130 into the processing chamber 100.

[0044] At operation 406, a layer of the film 204 is deposited onto the substrate 202, using the second gas mixture. The thickness of the layer may be about 5 nm to about 30 nm, such as about 10 nm to about 25 nm. In such approach, the film 204 is formed incrementally, with each layer of the film 204 deposited sequentially. After a layer of desired thickness is deposited onto the substrate, the second gas mixture may optionally be purged from the processing chamber 100.

[0045] At operation 408, a plasma treatment operation is conducted. A third gas mixture is flowed into the processing chamber 100. The third gas mixture includes, at least, an N2 precursor. The N2 precursor is flowed intoPATENTAttorney Docket No.: 44025668WO01the gas panel 130 at a fifth flow rate. For example, the fifth flow rate is about 5,000 seem to about 8,000 seem. The third gas mixture, including the N2 precursor, is formed in the gas panel 130. The third gas mixture is then flowed into the processing chamber 100. In one or more embodiments, the third gas mixture further includes an argon (Ar) precursor. The Ar precursor is flowed into the gas panel 130 at a sixth flow rate. For example, the sixth flow rate is about 3,000 seem to about 7,000 seem. In such embodiments, the third gas mixture, including the N2 precursor, and the Ar precursor, is formed in the gas panel 130, and is then flowed from the gas panel 130 into the processing chamber 100. The pressure within the processing chamber 100 may be changed at operation 408. For example, operation 408 may be conducted at a pressure of between about 3 Torr and about 5 Torr, such as about 4 Torr.

[0046] Still at operation 408, an RF power is applied to the third gas mixture within the processing chamber 100. The RF Power is provided at a fixed or tunable frequency in a range from about 26 MHz to about 28 MHz, such as about 27 MHz. In one or more embodiments, the RF power level applied in operation 408 for generating the plasma may be about 100 Watts and about 750 Watts, such as about 100 Watts to about 300 Watts, about 300 Watts to about 500 Watts, or about 500 Watts to about 750 Watts.

[0047] Operations 404-408 may be optionally repeated as needed until a desired overall thickness of the film 204 is achieved. In one or more embodiments, the sequence of deposition and plasma treatment may be performed multiple times in succession to build the film 204 in a controlled, layer-by-layer manner. For example, operations 404-408 may be carried out between about 200 and about 400 times, such as about 300 times, depending on the targeted film thickness and processing objectives. By cycling deposition and plasma treatment operations, the process incrementally reduces the hydrogen content of the film at each layer. Repeating this deposition-and-treatment sequence over multiple cycles allows the silicon nitride film to be built up with progressively lower hydrogen concentration,PATENTAttorney Docket No.: 44025668WO01ultimately achieving reduced hydrogen levels and improved optical performance.

[0048] Benefits of the present disclosure include a low-hydrogen content, silicon-nitride film having both high thickness and refractive-index uniformity, and exhibiting low optical loss in the O-band and C-band wavelengths. The film may be deposited in a PECVD deposition operation using N2, rather than NH3, as a nitrogen precursor, reducing the amount of hydrogen introduced during deposition. Further, co-flow of hydrogen gas scavenges hydrogen from Si-H dangling bonds, enabling the formation of a silicon nitride film with reduced hydrogen incorporation while maintaining thickness and refractive-index uniformity. Additionally, the film may be deposited in a cyclic deposition and plasma treatment approach to incrementally remove hydrogen from each deposited layer, achieving low hydrogen content for applications requiring low optical loss.

[0049] The preceding discussion is directed to various embodiments. However, one of ordinary skill in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

[0050] The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

[0051] In the preceding discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through aPATENTAttorney Docket No.: 44025668WO01direct connection of the two devices, or through an indirect connection that is established via other devices, components, nodes, and connections. Further, when used herein (including in the claims), the words “about,” “generally,” “substantially,” “approximately,” and the like, when used to refer to a stated value, mean within a range of plus or minus 10% of the stated value.

[0052] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

PATENTAttorney Docket No.: 44025668WO01What is claimed is:

1. A method of forming a film stack, comprising:placing a substrate on a substrate support within a processing chamber;flowing a first gas mixture into the processing chamber, the first gas mixture including:a silane (SiH4) precursor at a first flow rate;a nitrogen (N2) precursor at a second flow rate; and a hydrogen (H2) precursor at a third flow rate;applying a radio frequency (RF) power to the first gas mixture at a first frequency and first power to deposit a silicon-nitride film on a surface of the substrate, wherein the silicon-nitride film has:a hydrogen content between about 3% and about 10%; anda refractive index (Rl) uniformity between about 0.1% and about 0.7% across the surface of the substrate.

2. The method of claim 1, wherein the first flow rate is about 50 standard cubic centimeters per minute (seem) to about 300 seem.

3. The method of claim 1, wherein the second flow rate is about 3,000 standard cubic centimeters per minute (seem) to about 11 ,000 seem.

4. The method of claim 1, wherein the third flow rate is about 500 standard cubic centimeters per minute (seem) to about 3,000 seem.

5. The method of claim 1 , wherein the first gas mixture further includes: an argon (Ar) precursor at a fourth flow rate, wherein the fourth flow rate is about 3,000 standard cubic centimeters per minute (seem) to about 8,000 seem.PATENTAttorney Docket No.: 44025668WO016. The method of claim 1, wherein the first frequency is about 26 megahertz (MHz) to about 28 MHz, and wherein the first power is about 600 Watts to about 1500 Watts .

7. A method of forming a film stack, comprising:placing a substrate on a substrate support within a processing chamber;flowing a first gas mixture into the processing chamber, the first gas mixture including:a silane (SiH4) precursor at a first flow rate;a nitrogen (N2) precursor at a second flow rate; and an ammonia (NH3) precursor at a third flow rate;depositing a layer of a sil icon-nitride film onto a surface of the substrate using the first gas mixture;flowing a second gas mixture into the processing chamber to treat the layer of the sil icon-nitride film, the second gas mixture including:an N2 precursor at a fourth flow rate; andapplying a radio frequency (RF) power to the second gas mixture at a first frequency and a first power.

8. The method of claim 7, wherein the second gas mixture further includes an argon (Ar) precursor at a fifth flow rate.

9. The method of claim 8, wherein the fifth flow rate is about 3,000 standard cubic centimeters per minute (seem) to about 7,000 seem.

10. The method of claim 7, wherein the first flow rate is about 10 standard cubic centimeters per minute (seem) to about 30 seem.

11. The method of claim 10, wherein the second flow rate is about 500 standard cubic centimeters per minute (seem) to about 1 ,500 seem.PATENTAttorney Docket No.: 44025668WO0112. The method of claim 11, wherein the third flow rate is about 2 standard cubic centimeters per minute (seem) to about 50 seem.

13. The method of claim 7, wherein the first frequency is about 26 megahertz (MHz) to about 28 MHz, and the first power is about 100 Watts to about 750 Watts.

14. The method of claim 7, wherein the first gas mixture further includes:an argon (Ar) precursor at a sixth flow rate, wherein the sixth flow rate is about 1,000 standard cubic centimeters per minute (seem) to about 3,000 seem.

15. A method of forming a film stack, comprising:placing a substrate on a substrate support within a processing chamber;performing a deposition operation to deposit a layer of a silicon-nitride film onto a surface of the substrate, the deposition operation comprising:flowing a first gas mixture into the processing chamber, the first gas mixture including:a silane (SiH4) precursor at a first flow rate;a nitrogen (N2) precursor at a second flow rate; and an ammonia (NH3) precursor at a third flow rate; performing a plasma treatment operation on the layer, the plasma treatment operation comprising:flowing a second gas mixture into the processing chamber, the second gas mixture including:an N2 precursor at a fourth flow rate; andapplying a radio frequency (RF) power to the second gas mixture at a first frequency and a first power; andrepeating the deposition operation and the plasma treatment operation between about 200 times and about 400 times to form the silicon-nitride film.PATENTAttorney Docket No.: 44025668WO0116. The method of claim 15, wherein the second gas mixture further includes an argon (Ar) precursor at a fifth flow rate, and wherein the fifth flow rate is about 3,000 standard cubic centimeters per minute (seem) to about 7,000 seem.

17. The method of claim 15, wherein the first flow rate is about 10 standard cubic centimeters per minute (seem) to about 30 seem, the second flow rate is about 500 seem to about 1,500 seem, and the third flow rate is about 2 seem to about 50 seem.

18. The method of claim 15, wherein the silicon-nitride film has a hydrogen content between about 2% and about 3%.

19. The method of claim 15, wherein the silicon-nitride film has a refractive index (Rl) uniformity between about 0.1% and about 0.7% across the surface of the substrate.

20. The method of claim 15, wherein the first frequency is about 26 megahertz (MHz) to about 28 MHz, and wherein the first power is about 140 Watts to about 700 Watts.

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