Selective deposition of silicon nitride

Abstract

To provide a method for selectively depositing silicon nitride on a microelectronic device substrate including a plurality of surfaces having different compositions.SOLUTION: A method for selectively depositing silicon nitride on a microelectronic device substrate including a plurality of surfaces having different compositions comprises: forming a silicon and nitrogen containing material (for example, silicon nitride) using a low temperature atomic layer deposition method and using silicon tetra-iodide (SiI4) or di-silicon hexa-iodide (Si2I6) as one precursor and a nitrogen containing material, such as ammonia as another precursor; and at first subjecting the surface of a substrate to ammonia plasma in the situation that selective deposition for depositing silicon nitride to silica dioxide is desired.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a methodology for the selective deposition of silicon nitride on microelectronic devices. [Background technology]

[0002] Silicon nitride is commonly used in the fabrication of integrated circuits. For example, silicon nitride is often used as an insulating material in the fabrication of various microelectronic devices, such as memory cells, logic devices, and memory arrays. Traditionally, silicon nitride films are deposited over the entire substrate surface, although deposition may only be required in specific areas. As a result, additional lithography and etching steps are utilized to remove any unwanted regions. As a means to reduce the overall cost of fabrication, it is highly desirable to reduce the number of lithography and etching steps involved. Furthermore, if silicon nitride is selectively deposited only where needed, lithography errors will not affect the definition of the coating area. Summary of the Invention

[0003] The use of selective silicon nitride deposition can eliminate traditional patterning steps by allowing silicon nitride to be deposited only in selected, desired areas. The use of silicon iodide precursors alternating with a thermal nitrogen source in an ALD or pulsed CVD mode allows silicon nitride to be preferentially deposited onto existing nitride surfaces (e.g., silicon nitride or aluminum nitride) and metal oxide surfaces (e.g., aluminum oxide or zirconium oxide), with very limited deposition on exposed silicon dioxide surfaces. Furthermore, the inventors have found that by pretreating different oxide surfaces with ammonia plasma, silicon nitride of several nanometers can be selectively deposited onto silicon dioxide surfaces via nitrogen compounds such as silicon tetraiodide and ammonia, while no or only limited deposition is achieved on some "adjacent" metal oxide surfaces (e.g., Al2O3 and ZrO2). This pretreatment step is therefore the basis for "selective" nitride growth. [Brief explanation of the drawings]

[0004] [Figure 1] Figure 1 is a diagram of silicon nitride (SiI4 / NH3) deposition at 200°C on various oxide substrates as shown. Thickness in Angstroms is plotted against cycle number. [Figure 2] Figure 2 shows the deposition of silicon nitride (SiI / NH) at 200°C onto various oxide surfaces, as shown, each of which was pretreated with ammonium plasma. Thickness in angstroms is plotted against cycle number. DETAILED DESCRIPTION OF THE INVENTION

[0005] The present invention provides a process for the selective atomic layer deposition (ALD) of silicon nitride layers onto various microelectronic device substrates. For purposes of this invention, we define ALD as a mode of chemical vapor deposition in which various reactants and co-reactants are separated in space or time, such that the substrate is alternately exposed to one reactant separately from the co-reactant. In a first embodiment, the present invention provides a process for selectively depositing silicon nitride on a microelectronic device substrate having multiple surfaces of different compositions, the process comprising contacting the substrate with sequentially pulsed silicon tetraiodide or disilicon 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 of less than 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 deposits at a manufacturable rate on some exposed surfaces, while other surfaces receive negligible or easily removed amounts of silicon nitride.

[0006] In certain embodiments, one of the microelectronic device surfaces comprises a nitride surface, such as titanium nitride, aluminum nitride, or silicon nitride. In other embodiments, one of the microelectronic device surfaces comprises a dielectric surface, such as silicon dioxide, silicon oxynitride, germanium dioxide, SiCO, or a low-k surface. In some embodiments, the dielectric comprises silicon dioxide. In some embodiments, the dielectric is a porous material. In some embodiments, the porous dielectric contains interconnected pores, while in other embodiments, the pores are not interconnected. In some embodiments, the dielectric comprises a low-k material, which is defined as an insulator having a dielectric value less than about 4.0. In some embodiments, the low-k material has a dielectric value less than about 3.5, less than about 3.0, less than about 2.5, or less than about 2.3. In some embodiments, the second surface comprises Si—O bonds. In some embodiments, the second surface is passivated, for example, by plasma treatment. In some embodiments, the second surface is a non-conductive surface. In certain embodiments, the substrate comprises a first surface, a portion of which is a dielectric and a portion of which is a metallic phase. In some embodiments, one of the surfaces is a dielectric having a higher dielectric constant than silicon dioxide, such as aluminum oxide, hafnium oxide, zirconium oxide, titanium oxide, lanthanide oxide, or a mixture of any or all of these oxides.

[0007] In a particular embodiment, the device substrate is comprised of at least one silicon dioxide surface and at least one aluminum oxide surface, whereby the silicon nitride is selectively deposited onto the aluminum oxide surface.

[0008] In certain embodiments, the device substrate is comprised of at least one silicon dioxide surface and at least one zirconium dioxide surface, whereby the silicon nitride is selectively deposited on the at least one zirconium dioxide surface.

[0009] In a specific embodiment, the device substrate is comprised of at least one silicon dioxide surface and at least one aluminum oxide surface, and the device surfaces are pretreated with an ammonia plasma, whereby the silicon nitride is selectively deposited on the at least one silicon dioxide surface.

[0010] In a specific embodiment, the device substrate is comprised of at least one silicon dioxide surface and at least one hafnium oxide surface, and the device surface is pretreated with an ammonia plasma, whereby the silicon nitride is selectively deposited on the at least one silicon dioxide surface.

[0011] In a specific embodiment, the device substrate is comprised of at least one silicon dioxide surface and at least one zirconium dioxide surface, and the device surface is pretreated with an ammonia plasma, whereby the silicon nitride is selectively deposited on the at least one silicon dioxide surface.

[0012] In such embodiments, the term "selectively deposit" or "selectivity" is intended to reflect the preferential deposition of silicon nitride on one surface relative to another. A numerical definition is given by Gladfelter [Chem. Mater. 5, 1372 (1993)] as the difference in coverage between two surfaces normalized to the sum of the coverages of the two surfaces. In practice, the selectivity of the process generally depends on the film thickness. The present invention allows for selectivity of greater than 90% at 18 Å. In other embodiments, preferential deposition of silicon nitride on one surface over another occurs with an incidence of greater than 95% at greater than 100 Å.

[0013] This ALD methodology uses silicon tetraiodide (SiI4) or disilicon hexaiodide (Si2I6) as one "silicon" precursor and a nitrogen-containing material as a co-reactant or separate precursor. The nitrogen-containing material can be organic (e.g., t-butylhydrazine) or inorganic (e.g., NH3). In some embodiments, a mixture of nitrogen-containing materials may be utilized as an ALD precursor, while in other embodiments, only one nitrogen-containing material (e.g., only NH3 or only t-butylhydrazine) may be utilized as an ALD precursor. As used herein, the term "nitrogen-containing material" may be utilized to refer to a pure (e.g., all NH3 or all t-butylhydrazine) precursor material or to a precursor containing a "nitrogen-containing material" as part of a mixture of nitrogen-containing materials. In certain embodiments, ALD can be used to form materials containing silicon and nitrogen. Such materials may include, consist essentially of, or consist of silicon nitride, and / or may have other compositions.

[0014] The inventors have found that by pretreating different oxide surfaces with ammonia plasma, silicon nitride of several nanometers can be selectively deposited on silicon dioxide surfaces via nitrogen compounds such as silicon tetraiodide and ammonia, while no or only limited deposition is achieved on some metal oxide surfaces (e.g., Al2O3 and ZrO2).When it is desired that silicon nitride deposition occur preferentially on existing silicon nitride, aluminum nitride, or metal oxide surfaces (and not on silicon dioxide surfaces), the ammonia plasma pretreatment step is omitted.

[0015] In atomic layer deposition, successive processing steps are commonly referred to as "pulses" or cycles. Thus, ALD processes are based on controlled, self-limiting surface reactions of precursor chemicals. The present invention can be implemented with fully saturated reactions or, more manufacturable, simply separate pulses of precursor and co-reactant. Gas-phase reactions are substantially avoided by alternately and sequentially exposing the substrate to precursors. This can be achieved by moving the substrate from different reactant and co-reactant regions or by alternating gas flows over a stationary substrate. In both cases, the gas-phase reactants are separated from each other in time and on the substrate surface, for example, by removing excess reactant and / or reactant by-products 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 a substrate surface with a gas-phase reactant means that the reactant vapor is in contact with the substrate surface for a limited time. In other words, the substrate surface can be understood to be exposed to each gas-phase reactant for a limited time.

[0016] Briefly, a substrate comprising at least a first surface and a second, different surface is heated to a suitable deposition temperature, typically in the range of 150°C to 400°C, at a low pressure of about 0.5 to 15 Torr. In other embodiments, the temperature is about 175°C to 350°C or 200°C to 250°C. The deposition temperature is generally maintained below the thermal decomposition temperature of the reactants, but high enough to avoid condensation of the reactants and to provide activation energy for the desired "selective" surface reactions. Exemplary surfaces include nitrides, such as nitrides of silicon, titanium, and aluminum, and oxides, such as silicon dioxide, aluminum oxide, hafnium oxide, and zirconium oxide.

[0017] The surface of the substrate is contacted with the vapor-phase first reactant. In certain embodiments, a pulse of the vapor-phase first reactant is supplied to the reaction space containing the substrate. In other embodiments, the substrate is moved into the reaction space containing the vapor-phase first reactant. Conditions are generally selected so that no more than about one monolayer of the first reactant is self-limitingly adsorbed onto the substrate surface. An appropriate contact time can be readily determined by one skilled in the art based on the specific conditions, substrate, and reactor configuration. Excess first reactant and reaction by-products, if present, are removed from the substrate surface, for example, by purging with an inert gas or by removing any present first reactant from the substrate.

[0018] Purging refers to removing vapor-phase precursors and / or vapor-phase by-products from the substrate surface, for example, by evacuating the chamber with a vacuum pump and / or by replacing the gas in the reactor with an inert gas such as argon or nitrogen. In certain embodiments, the purge time is about 0.05-20 seconds, about 1-10 seconds, or about 1-2 seconds. However, other purge times may be utilized as needed, such as when a highly conformal step is required to coat very high aspect ratio structures or other structures with complex surface morphology.

[0019] The surface of the substrate is contacted with a second gaseous reactant in the vapor phase. In certain embodiments, pulses of the second gaseous reactant are supplied to the reaction space containing the substrate. In other embodiments, the substrate is moved into the reaction space containing the second reactant in the vapor phase. Excess second reactant and gaseous byproducts of the surface reaction, if present, are removed from the substrate surface. The contacting and removing steps are repeated until a thin film of the desired thickness is selectively formed on the first surface of the substrate, leaving about one monolayer or less in each cycle. To form more complex materials, such as ternary materials, additional steps may be included, including alternating sequential contact of the surface of the substrate with other reactants.

[0020] Each step in each cycle is generally self-limiting. Excess reactant precursor is supplied at each step to saturate susceptible structure surfaces. Surface saturation ensures reactant occupation of all available reaction sites (e.g., subject to physical size or "steric" limitations), thus ensuring excellent step coverage. Typically, less than one molecular layer of material is deposited in each cycle, although in some embodiments, more than one molecular layer is deposited during a cycle.

[0021] Removing excess reactants can include evacuating a portion of the contents of the reaction space and / or purging the reaction space with helium, nitrogen, or another inert gas. In certain embodiments, purging can include turning off the flow of reactive gas while continuing to flow an inert carrier gas through the reaction space. In another embodiment, the purging step can utilize a vacuum step to remove excess reactants from the surface.

[0022] The deposition described herein can use a reactor that can be used to grow thin films. Such reactors include ALD reactors and CVD reactors equipped with appropriate devices and means for supplying precursors in a "pulsed" manner. According to certain embodiments, showerhead reactors can be used.

[0023] Examples of suitable reactors that can be used include commercially available equipment and home-built reactors and are known to those skilled in the art of CVD and / or ALD.

[0024] The present invention can be further illustrated by the following examples of specific embodiments thereof, although it will be understood that these examples are included for illustrative purposes only and are not intended to limit the scope of the invention unless otherwise specified. [Example]

[0025] experiment Example 1 In this example, SiN was selectively deposited on a first and second surface of a substrate relative to a third, different surface of the substrate, where the first surface of the substrate comprised Al2O3 deposited by ALD, the second surface of the substrate comprised ALD-deposited ZrO2, and the third, different surface comprised native silicon oxide (grown under ambient conditions on a polished single crystal silicon surface).

[0026] SiN films were selectively deposited by an ALD process using silicon tetraiodide (SiI4) as the first precursor and NH3 as the second precursor. The SiI4 was contained in a ProE-Vap ampoule and heated to 100 °C. N2 carrier gas was flowed over the surface of the solid SiI4, delivering SiI4 vapor to the heated chamber containing the substrate. Each deposition cycle was performed with the substrate at a temperature of 200 °C and a reaction chamber pressure of 1.5 Torr. Each deposition cycle included a 10-second SiI4 vapor pulse, a 10-second inert N2 purge, a 10-second NH3 pulse, and a 10-second inert N2 purge. Referring to Figure 1, in an ALD process consisting of 100 deposition cycles, the selectivity of SiN deposited on Al2O3 and ZrO2 (both deposited by ALD) relative to native silicon oxide was 90% when 18 Å of SiI4 was deposited on the high-k film.

[0027] Example 2 In this example, SiN was selectively deposited on a first surface of a substrate relative to a second and third different surface of the substrate. The first surface of the substrate comprised native silicon oxide. The second surface of the substrate comprised Al2O3 deposited by ALD. The third surface comprised ZrO2 deposited by ALD. Prior to SiN deposition, the substrate was subjected to an NH3 plasma treatment process.

[0028] Using the same process as described in Example 1, SiN films were selectively deposited by 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. As shown in Figure 2, the thickness of the material deposited on the first, plasma-treated native silicon oxide surface was measured and compared to the thickness of the material deposited on the second and third surfaces, i.e., plasma-treated Al2O3 and ZrO2. Figure 2 shows that SiN deposition on the first surface, comprising plasma-treated native silicon oxide, was highly selective relative to both the plasma-treated Al2O3 and ZrO2 surfaces (selectivity greater than 95%).

Claims

1. 1. A method for selectively depositing silicon nitride on a microelectronic device substrate having multiple surfaces of different composition, comprising contacting the microelectronic device substrate with sequentially pulsed silicon tetraiodide or disilicon 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 of less than about 15 Torr, further comprising pretreating the microelectronic device substrate with an ammonia plasma; the microelectronic device substrate comprises at least one silicon dioxide surface and at least one aluminum oxide surface, whereby the silicon nitride is selectively deposited on the at least one silicon dioxide surface compared to the at least one aluminum oxide surface; method.

2. 1. A method for selectively depositing silicon nitride on a microelectronic device substrate having multiple surfaces of different composition, comprising contacting the microelectronic device substrate with sequentially pulsed silicon tetraiodide or disilicon 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 of less than about 15 Torr, further comprising pretreating the microelectronic device substrate with an ammonia plasma; the microelectronic device substrate comprises at least one silicon dioxide surface and at least one zirconium dioxide surface, whereby the silicon nitride is selectively deposited on the at least one silicon dioxide surface relative to the at least one zirconium dioxide surface; method.

3. 1. A method for selectively depositing silicon nitride on a microelectronic device substrate having multiple surfaces of different composition, comprising contacting the microelectronic device substrate with sequentially pulsed silicon tetraiodide or disilicon 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 of less than about 15 Torr, further comprising pretreating the microelectronic device substrate with an ammonia plasma; the microelectronic device substrate comprises at least one silicon dioxide surface and at least one hafnium dioxide surface, whereby the silicon nitride is selectively deposited on the at least one silicon dioxide surface compared to the at least one hafnium dioxide surface; method.

4. A method for selectively depositing silicon nitride on a microelectronic device substrate having a plurality of surfaces of different composition, comprising contacting the microelectronic device substrate with sequentially pulsed silicon tetraiodide or disilicon 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 of less than about 15 Torr; the microelectronic device substrate comprises at least one silicon dioxide surface and at least one aluminum oxide surface, whereby the silicon nitride is selectively deposited on the at least one silicon dioxide surface compared to the at least one aluminum oxide surface; method.

5. 1. A method for selectively depositing silicon nitride on a microelectronic device substrate having multiple surfaces of different composition, comprising contacting the microelectronic device substrate with sequentially pulsed silicon tetraiodide or disilicon 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 of less than about 15 Torr; the microelectronic device substrate comprises at least one silicon dioxide surface and at least one zirconium dioxide surface, whereby the silicon nitride is selectively deposited on the at least one silicon dioxide surface relative to the at least one zirconium dioxide surface; method.

6. A method for selectively depositing silicon nitride on a microelectronic device substrate having a plurality of surfaces of differing composition, comprising contacting the microelectronic device substrate with sequentially pulsed silicon tetraiodide or disilicon 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 of less than about 15 Torr; the microelectronic device substrate comprises at least one silicon dioxide surface and at least one hafnium dioxide surface, whereby the silicon nitride is selectively deposited on the at least one silicon dioxide surface compared to the at least one hafnium dioxide surface; method.

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