Selective deposition of silicon nitride

Abstract

This application relates to the selective deposition of silicon nitride. Certain embodiments of the invention utilize a low-temperature atomic layer deposition method to form materials containing silicon and nitrogen (e.g., silicon nitride). The atomic layer deposition uses silicon tetraiodide (SiI4) or silicon hexaiodide (Si2I6) as a precursor and a nitrogen-containing material, such as ammonia, as another precursor. In cases where selective deposition of silicon nitride over silicon dioxide is required, the substrate surface is first treated with ammonia plasma.

Description

[0001] This application is a divisional application of the invention patent application filed on February 12, 2020, with application number 202080013812.3 and invention title "Selective Deposition of Silicon Nitride". Technical Field

[0002] This invention relates to a method for selectively depositing silicon nitride onto microelectronic devices. Background Technology

[0003] Silicon nitride is commonly used in the manufacture of integrated circuits. For example, it is frequently used as an insulating material in the manufacture of various microelectronic devices such as memory cells, logic devices, and memory arrays. Traditionally, silicon nitride films are deposited over the entire surface of a substrate, although this deposition may only be needed in certain areas. Therefore, additional photolithography and etching steps are used to remove any unwanted areas. There is a strong need to reduce the number of photolithography and etching steps involved as a means of reducing overall manufacturing costs. Furthermore, if silicon nitride is selectively deposited only where it is needed, errors in photolithography do not affect the clarity of the coated areas. Summary of the Invention

[0004] Selective deposition using silicon nitride eliminates the need for conventional patterning steps by allowing silicon nitride to deposit only in selected and desired regions. By alternating silicon iodide precursors with alternating thermal nitrogen sources in ALD or pulsed CVD modes, we can preferentially deposit silicon nitride on existing nitride surfaces (e.g., silicon nitride or aluminum nitride) and metal oxide surfaces (e.g., alumina or zirconium oxide), while depositing very limitedly on exposed silica surfaces. Furthermore, we have found that by pretreating different oxide surfaces with ammonia plasma, several nanometers of silicon nitride via tetraiodide and nitrogen compounds such as ammonia can be selectively deposited onto silica surfaces, while achieving no or limited deposition on some “neighboring” metal oxide surfaces (e.g., Al₂O₃ and ZrO₂). Therefore, this pretreatment step forms the basis for “selective” nitride growth. Attached Figure Description

[0005] Figure 1 Illustrations of silicon nitride (SiI4 / NH3) deposition on various oxide substrates as depicted, at 200°C. Thicknesses are plotted in angstroms relative to the number of cycles.

[0006] Figure 2 This illustration shows the deposition of silicon nitride (SiI4 / NH3) on various oxide surfaces as depicted, at 200°C, where each oxide surface has been pretreated with ammonium plasma. Thicknesses are plotted in angstroms relative to the number of cycles. Detailed Implementation

[0007] This invention provides a method for selective atomic layer deposition (ALD) of silicon nitride onto various microelectronic device substrates. For the purposes of this invention, we define ALD as a chemical vapor deposition mode that spatially or temporally separates various reactants and co-reactants, such that the substrate is alternatively exposed to a reactant separate from the co-reactants. In a first embodiment, the invention provides a method for selectively depositing silicon nitride onto a microelectronic device substrate having multiple surfaces with different compositions, the method comprising contacting the substrate with sequentially pulsed silicon tetraiodide or silicon hexaiodide and a nitrogen-containing co-reactant under atomic layer deposition conditions at a temperature of about 150°C to about 400°C and a pressure below about 15 Torr. In other embodiments, the temperature is about 175°C to about 350°C, or about 200°C to about 250°C. Selective deposition is achieved when a silicon nitride film is deposited at a manufacturable rate on some exposed surfaces and other surfaces receive a negligible or easily removable amount of silicon nitride.

[0008] In some embodiments, one of the surfaces of the microelectronic device will comprise a nitride surface, such as titanium nitride, aluminum nitride, or silicon nitride. In other embodiments, one of the surfaces of the microelectronic device will comprise a dielectric surface or a low-k surface, such as silicon dioxide, silicon oxynitride, germanium dioxide, or SiCO. In some embodiments, the dielectric comprises silicon dioxide. In some embodiments, the dielectric is a porous material. In some embodiments, the porous dielectric contains pores interconnected with each other, while in other embodiments, the pores are not interconnected with each other. In some embodiments, the dielectric comprises a low-k material, which is defined as an insulator having a dielectric value below about 4.0. In some embodiments, the dielectric value of the low-k material is below about 3.5, below about 3.0, below about 2.5, or below about 2.3. In some embodiments, the second surface comprises Si-O bonds. In some embodiments, the second surface is deactivated, for example, by plasma treatment. In some embodiments, the second surface is a non-conductive surface. In some embodiments, the substrate includes a first surface, some of which are dielectric and some of which are metallic phases. In some embodiments, one of the surfaces is a dielectric material having a higher k than silicon dioxide, such as aluminum oxide, hafnium oxide, zirconium oxide, titanium oxide, lanthanide oxides, or any or all of these oxides.

[0009] In some embodiments, the device substrate comprises at least one silicon dioxide surface and at least one aluminum oxide surface, thereby selectively depositing the silicon nitride on the aluminum oxide surface.

[0010] In some embodiments, the device substrate comprises at least one silicon dioxide surface and at least one zirconium dioxide surface, thereby selectively depositing the silicon nitride on the at least one zirconium dioxide surface.

[0011] In some embodiments, the device substrate comprises at least one silicon dioxide surface and at least one aluminum oxide surface, the device surfaces being pretreated with ammonia plasma, thereby selectively depositing the silicon nitride onto the at least one silicon dioxide surface.

[0012] In some embodiments, the device substrate comprises at least one silicon dioxide surface and at least one hafnium oxide surface, the device surfaces being pretreated with ammonia plasma, thereby selectively depositing silicon nitride on the at least one silicon dioxide surface.

[0013] In some embodiments, the device substrate comprises at least one silicon dioxide surface and at least one zirconium dioxide surface, the device surfaces being pretreated with ammonia plasma, thereby selectively depositing the silicon nitride onto the at least one silicon dioxide surface.

[0014] In such embodiments, the terms "selective deposition" or "selectivity" are intended to reflect the preference for silicon nitride deposition on one surface over another. The numerical value given by Gladfelter [Chem. Mater. 5, 1372 (1993)] is defined as the difference in coverage between two surfaces, normalized to the sum of coverage on the same two surfaces. In practice, the selectivity of the process generally depends on the film thickness. This invention enables... The selectivity can be greater than 90%. In other embodiments, silicon nitride is preferentially deposited on one surface over the other surface for more than [a certain period of time]. It occurs in more than 95% of cases.

[0015] This ALD method utilizes silicon tetraiodide (SiI4) or silicon hexaiodide (Si2I6) as a “silicon” precursor and uses a nitrogen-containing material as a co-reactant or as another precursor. The nitrogen-containing material can be organic (e.g., tert-butylhydrazine) or inorganic (e.g., NH3). In some embodiments, a mixture of nitrogen-containing materials can be used as an ALD precursor, and in other embodiments, only one nitrogen-containing material can be used as an ALD precursor (e.g., only NH3 or only tert-butylhydrazine). As used herein, the term “nitrogen-containing material” can be used to refer to a pure (e.g., entirely NH3 or entirely tert-butylhydrazine) precursor material, or to a precursor containing “nitrogen-containing material” as part of a mixture of nitrogen-containing materials. In some embodiments, ALD can be used to form a material comprising silicon and nitrogen. Such materials may comprise silicon nitride, consist substantially of silicon nitride, or consist of silicon nitride, and / or may have other compositions.

[0016] We have discovered that by pretreating different oxide surfaces with ammonia plasma, silicon nitride of several nanometers via silicon tetraiodide and nitrogen compounds such as ammonia can be selectively deposited onto silica surfaces, while achieving no or limited deposition on some metal oxide surfaces (e.g., Al₂O₃ and ZrO₂). In cases where silicon nitride deposition is required to occur preferentially on existing silicon nitride, aluminum nitride, or metal oxide surfaces (but not on silica surfaces), the pretreatment step with ammonia plasma can be omitted.

[0017] In atomic layer deposition (ALD), sequential processing steps are often referred to as “pulses” or cycles. Therefore, the ALD method is based on controlled, self-limiting surface reactions of precursor chemicals. This invention can be practiced with fully saturated reactions or (if more manufacturable) individual pulses of only precursors and co-reactants. Gas-phase reactions are largely avoided by alternating and sequentially contacting the substrate with the precursors. This can be done by moving the substrate from regions of different reactants and co-reactants or by alternating gas flows over a stationary substrate. In both cases, gas-phase reactants are temporally and on the substrate surface separated from each other, for example, by removing excess reactants and / or reactant byproducts from the reaction chamber between reactant pulses. In some embodiments, one or more substrate surfaces are alternately and sequentially contacted with two or more gas-phase precursors or reactants. Contacting the substrate surface with gas-phase reactants means that the reactant vapors are in contact with the substrate surface for a limited period of time. In other words, it can be understood as exposing the substrate surface to each gas-phase reactant for a limited period of time.

[0018] In short, a substrate comprising at least a first surface and a second distinct surface is typically heated to a suitable deposition temperature in the range of 150°C to 400°C under a reduced pressure of approximately 0.5 Torr to 15 Torr. In other embodiments, the temperature is approximately 175°C to 350°C or 200°C to 250°C. The deposition temperature is typically maintained below the thermal decomposition temperature of the reactants, but should be maintained at a sufficiently high temperature to avoid condensation of the reactants and to provide activation energy for the desired “selective” surface reactions. Exemplary surfaces include nitrides such as silicon nitride, titanium nitride, and aluminum nitride, and oxides such as silicon dioxide, aluminum oxide, hafnium oxide, and zirconium oxide.

[0019] The substrate surface is brought into contact with the gaseous first reactant. In some embodiments, a pulse of the gaseous first reactant is provided to the reaction space containing the substrate. In other embodiments, the substrate is moved into the reaction space containing the gaseous first reactant. Conditions are typically selected such that no more than about a monolayer of the first reactant is adsorbed onto the substrate surface in a self-limiting manner. Those skilled in the art can readily determine the appropriate contact time based on the specific conditions, substrate, and reactor configuration. Excess first reactant and reaction byproducts, if present, are removed from the substrate surface, for example, by rinsing with an inert gas or by removing the first reactant present on the substrate.

[0020] Rinsing means, for example, removing gaseous precursors and / or gaseous byproducts from the substrate surface by evacuating the chamber with a vacuum pump and / or by replacing the gas inside the reactor with an inert gas, such as argon or nitrogen. In some embodiments, the rinsing time is from about 0.05 seconds to 20 seconds, between about 1 second and 10 seconds, or between about 1 second and 2 seconds. However, other rinsing times may be used where necessary, such as in cases requiring highly conformal stepped coverage across structures with extremely high aspect ratios or other structures with complex surface morphologies.

[0021] The substrate surface is brought into contact with a gaseous second gaseous reactant. In some embodiments, a pulse of the second gaseous reactant is provided to a reaction space containing the substrate. In other embodiments, the substrate is moved to a reaction space containing the gaseous second reactant. Excess second reactant and gaseous byproducts of the surface reaction are removed (if present) from the substrate surface. The contacting and removing steps are repeated until a film of the desired thickness has been selectively formed on a first surface of the substrate, wherein each cycle leaves no more than about one molecular monolayer. Additional stages may be included, comprising alternating and sequential contacting of the substrate surface with other reactants, to form more complex materials, such as ternary materials.

[0022] Each stage of each cycle is generally self-limiting. An excess of reactant precursor is supplied in each stage to saturate the susceptible structural surfaces. Surface saturation ensures that the reactant occupies all available reactive sites (limited by, for example, physical size or "steric hindrance"), thus ensuring excellent ladder coverage. Typically, less than one molecular layer of material is deposited per cycle; however, in some embodiments, more than one molecular layer is deposited during cycling.

[0023] Removing excess reactants may include evacuating some contents from the reaction space and / or rinsing the reaction space with helium, nitrogen, or another inert gas. In some embodiments, rinsing may involve cutting off the flow of the reactant gases while allowing the inert carrier gas to continue flowing into the reaction space. In another embodiment, the rinsing step may employ a vacuum step to remove excess reactants from the surface.

[0024] Reactors capable of growing thin films can be used for the deposition described herein. Such reactors include ALD reactors and CVD reactors equipped with suitable devices and components for providing precursors in a “pulsated” manner. According to some embodiments, nozzle reactors may be used.

[0025] Examples of suitable reactors that can be used include commercially available equipment as well as homemade reactors, and will be known to those skilled in the art of CVD and / or ALD.

[0026] The invention can be further illustrated by the following examples of certain embodiments thereof, but unless otherwise specifically indicated, it should be understood that these examples are included for illustrative purposes only and are not intended to limit the scope of the invention.

[0027] Experimental Section

[0028] Example 1

[0029] In this example, SiN is selectively deposited on the first and second surfaces of the substrate relative to a third different surface. In this example, the first surface of the substrate contains Al2O3 deposited by ALD and the second surface of the substrate contains ZrO2 deposited by ALD, and the third different surface contains natural silicon oxide (grown on a polished single-crystal silicon surface under ambient conditions).

[0030] SiN films were selectively deposited using silicon tetraiodide (SiI4) as the first precursor and NH3 as the second precursor via an ALD process. SiI4 was contained in a ProE-Vap ampoule and heated to 100°C. An N2 carrier gas flowed above the surface of the solid SiI4, carrying the SiI4 vapor into a heated chamber containing the substrate. Deposition cycles were performed on the substrate at a temperature of 200°C and a reaction chamber pressure of 1.5 Torr. Each deposition cycle consisted of a 10-second SiI4 vapor pulse, a 10-second inert N2 purge, a 10-second NH3 pulse, and a 10-second inert N2 purge. (Reference) Figure 1 For an ALD process consisting of 100 deposition cycles, in the case of When deposited on high-k films, the selectivity of SiN deposited on Al2O3 and ZrO2 (both deposited via ALD) relative to natural silicon oxide is 90%.

[0031] Example 2

[0032] In this example, SiN is selectively deposited on a first surface of the substrate relative to second and third different surfaces of the substrate. The first surface of the substrate comprises natural silicon oxide. The second surface of the substrate comprises Al₂O₃ deposited via ALD. The third surface comprises ZrO₂ deposited via ALD. Prior to SiN deposition, the substrate is subjected to an NH₃ plasma treatment process.

[0033] Using the same process as described in Example 1, SiN films were selectively deposited via an ALD process using silicon tetraiodide (SiI4) as the first precursor and NH3 as the second precursor. Samples were deposited using an ALD process consisting of 100 to 200 deposition cycles. Figure 2As described, the thickness of the material deposited on the first plasma-treated natural silica surface was measured and compared with the thickness of the material deposited on the second and third plasma-treated Al2O3 and ZrO2 surfaces. Figure 2 The deposition of SiN on a first surface comprising plasma-treated natural silica demonstrates extremely high selectivity relative to plasma-treated Al2O3 and ZrO2 surfaces (selectivity exceeding 95%).

Claims

1. A method for selectively depositing silicon nitride on a microelectronic device substrate having multiple surfaces with different compositions, the method comprising contacting the substrate with sequentially pulsed silicon tetraiodide or silicon hexaiodide and a nitrogen-containing co-reactant under atomic layer deposition conditions, at a temperature of 175°C to 350°C and a pressure below 15 Torr, wherein the device substrate comprises a number of surfaces selected from silicon nitride, titanium nitride, tantalum nitride, aluminum nitride, hafnium oxide, zirconium oxide, aluminum oxide, and combinations thereof, the surfaces having enhanced silicon nitride deposition compared to other surfaces on the same substrate selected from silicon dioxide, germanium dioxide, SiCO, and low-k substrates with suppressed silicon nitride deposition, wherein the method further comprises a step of pretreating the substrate with ammonia plasma.

2. The method according to claim 1, wherein the temperature is 200°C to 250°C.

3. A method for selectively depositing silicon nitride on a microelectronic device substrate having multiple surfaces with different compositions, the method comprising contacting the substrate with sequentially pulsed silicon tetraiodide or silicon hexaiodide and a nitrogen-containing co-reactant under atomic layer deposition conditions, at a temperature of 150°C to 400°C and a pressure below 15 Torr, wherein a Si source is heated above its melting point and vaporized together with a carrier gas, wherein the method further comprises a step of pretreating the substrate with ammonia plasma.

4. The method according to claim 1 or 3, wherein the nitrogen-containing co-reactant is selected from ammonia, dimethylhydrazine, tert-butylhydrazine, methylhydrazine, or mixtures thereof.

5. A method for selectively depositing silicon nitride on a microelectronic device substrate having multiple surfaces with different compositions, the method comprising contacting the substrate with sequentially pulsed silicon tetraiodide or silicon hexaiodide and a nitrogen-containing co-reactant under atomic layer deposition conditions, at a temperature of 175°C to 350°C and a pressure of less than 15 Torr, and further comprising a step of pretreating the substrate with ammonia plasma, wherein the surfaces to be deposited are selected from silicon dioxide, germanium dioxide, SiCO and low-k substrates.

6. The method of claim 5, wherein the device substrate comprises at least one silicon dioxide surface and at least one aluminum oxide surface, thereby selectively depositing the silicon nitride on the at least one silicon dioxide surface.

7. The method of claim 5, wherein the device substrate comprises at least one silicon dioxide surface and at least one zirconium dioxide surface, thereby selectively depositing the silicon nitride on the at least one silicon dioxide surface.

8. The method of claim 5, wherein the device substrate comprises at least one silicon dioxide surface and at least one hafnium oxide surface, thereby selectively depositing the silicon nitride on the at least one silicon dioxide surface.

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