US-12618152-B2 - Method of depositing a transition metal dichalcogenide

Abstract

In one aspect, a method of depositing a transition metal dichalcogenide is provided. The method includes depositing a layer of the transition metal dichalcogenide on a substrate by a metalorganic chemical vapor deposition process including exposing the substrate to a mixture of reactant gases including a transition metal precursor and a chalcogen precursor. The mixture further includes a gas-phase halogen-based reactant to volatilize transition metal adatoms deposited on the substrate.

Inventors

• Benjamin Groven
• Vladislav Voronenkov
• Dries VRANCKX

Assignees

• IMEC VZW
• KATHOLIEKE UNIVERSITEIT LEUVEN

Dates

Publication Date

20260505

Application Date

20231009

Priority Date

20221012

Claims (17)

1. 1 . A method of depositing a transition metal dichalcogenide, the method comprising: depositing a layer of the transition metal dichalcogenide on a substrate by a metalorganic chemical vapor deposition process comprising exposing the substrate to a mixture of reactant gases comprising a transition metal precursor and a chalcogen precursor, wherein the mixture further comprises a gas-phase halogen-based reactant to volatilize transition metal adatoms deposited on the substrate, and wherein in the metalorganic chemical vapor deposition process, a deposition temperature and a gas-phase halogen-based reactant concentration of the mixture are such that a desorption flux from the substrate exceeds a net condensation flux to the substrate.
2. 2 . The method according to claim 1 , wherein a deposition temperature of the metalorganic chemical vapor deposition process is 750° C. or lower.
3. 3 . The method according to claim 1 , wherein the substrate is arranged in a reactor and wherein the gas-phase halogen-based reactant is introduced into the reactor simultaneous to the transition metal precursor and chalcogen precursor.
4. 4 . The method according to claim 3 , wherein the gas-phase halogen-based reactant is introduced into the reactor in an amount exceeding an amount of the transition metal precursor introduced into the reactor.
5. 5 . The method according to claim 1 , wherein the gas-phase halogen-based reactant is HCl or Cl 2 .
6. 6 . The method according to claim 1 , wherein the transition metal precursor comprises W, Mo, Zr, or Hf.
7. 7 . The method according to claim 1 , wherein the transition metal precursor is a carbonyl (M-(CO) x ), an alkyl (M-R x ), or an alkoxide (M-(OR) x ).
8. 8 . The method according to claim 1 , wherein the chalcogen precursor comprises S, Se, or Te.
9. 9 . The method according to claim 1 , wherein the chalcogen precursor is H 2 S, H 2 Se, or H 2 Te.
10. 10 . The method according to claim 1 , wherein the layer of the transition metal dichalcogenide is deposited on an amorphous or crystalline surface of the substrate.
11. 11 . The method according to claim 10 , wherein the surface of the substrate is a sapphire surface.
12. 12 . The method according to claim 10 , wherein the surface of the substrate is a surface of a scaled dielectric layer of the substrate.
13. 13 . The method according to claim 12 , wherein the dielectric layer is a layer of SiO 2 , Al 2 O 3 , HfO 2 , ZrO 2 , Si 3 N 4 , or SiCO.
14. 14 . The method according to claim 1 , wherein the transition metal precursor comprises W, the chalcogen precursor comprises S, and the gas-phase halogen-based reactant is HCl.
15. 15 . The method according to claim 14 , wherein the transition metal precursor is W(CO) 6 and the chalcogen precursor is H 2 S.
16. 16 . The method according to claim 1 , wherein a nucleation density is less than 1 μm −2 .
17. 17 . The method according to claim 16 , wherein micrometer size transition metal dichalcogenide crystals without grain boundaries are grown.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims foreign priority to European Patent Application No. EP 22201093.6, filed Oct. 12, 2022, the content of which is incorporated by reference herein in its entirety. BACKGROUND Technical Field The disclosed technology relates to a method of depositing a transition metal dichalcogenide by a metalorganic chemical vapor deposition process. Description of the Related Technology Transition metal dichalcogenides (abbreviated MX2) have appeared as an interesting channel material candidate in scaled electronic devices, for instance, for devices with sub-nanometer channel thickness and channel lengths below 10 nm. An MX2 material is formed by a monolayer or a stack of monolayers, wherein each monolayer is formed by a single layer of transition metal atoms M (for example, group-IV or group-VI transition metals such as molybdenum (Mo) or tungsten (W)) sandwiched between two layers of chalcogen atoms X (for example, sulfur (S), selenium (Se), or tellurium (Te)). In current research, particular attention is given to the integration of molybdenum and tungsten disulfide (MoS2, WS2) in advanced complementary metal-oxide semiconductor (CMOS) and memory systems. Realizing the theoretically predicted MX2 electrical performance relies partly on the manufacturable deposition of such materials with desired control over crystallinity, structure, and material properties. The research community considers chemical vapor deposition (CVD) as the most promising deposition technique for MX2 materials in view of its superior control over crystallinity, structure, and layer thickness at reduced cost and relevant wafer throughput. Historically, CVD is a widely established deposition technique in the semiconductor industry. Yet, for the semiconductor foundries to adopt MX2, one key challenge lies in identifying the CVD reaction chemistry that provides desired control over crystallinity and structure through the MX2 growth behavior, while being compatible with industry standards. Such industry-compatible deposition chemistries are denoted hereafter as Fab-compatible. Fab-compatible CVD precursors typically need to fulfill a few requirements in terms of (i) ease of use, purity, impurity, and contamination levels, in addition to (ii) more fundamental aspects related to reaction chemistry, such as metal and chalcogen precursor thermal stability, reactivity, volatility and diffusivity, and the resulting MX2 deposition efficiency and deposition rate. For various instances, it is desired that the precursors exhibit sufficient volatility at room temperature to ease delivery of a carefully controlled concentration of vapor into the reaction chamber through dedicated precursor delivery systems (for example, bubbler or sublimator). Although metal-oxide based CVD has received most attention in the MX2 CVD literature, metal-oxide precursors (for example, MoO3) are employed in laboratory set-ups, where the poor sublimation rate of the metal-oxide precursor is overcome by placing the metal-oxide precursor inside the furnace. This, however, hinders careful control over the metal-oxide precursor dose and flow profile inside the furnace. Metal-oxide based CVD is hence not Fab-compatible. SUMMARY OF CERTAIN INVENTIVE ASPECTS Transition metal-organic precursors suitable for metalorganic CVD (MOCVD) such as molybdenum hexacarbonyl (Mo(CO)6) do, in contrast to metal-oxide precursors, exhibit sufficient volatility at room temperature (for example, ˜0.1 Torr). However, transition metal-organic precursors (hereinafter for conciseness referred to as transition metal precursor) suffer from negligible precursor desorption rate. As a result, transition metal precursor adsorption is substantially irreversible. Consequently, adsorbed surface species (for example, transition metal adatoms) are incorporated in growing MX2 crystals predominantly or exclusively through surface diffusion. Surface diffusion proceeds rather slowly and occurs at comparatively short length scales (for example, <1 μm) at Fab-compatible deposition temperatures (for example, ≤750° C.). The general lack of diffusional transport results in a high MX2 nucleation density and the deposited MX2 monolayer develops a nanocrystalline grain structure (for example, 10 nm to a few hundred of nm). Thus, MOCVD of MX2 generally suffer from poor control over crystallinity and crystal grain size, hindering their electrical performance in semiconductor devices. In light of the above, it is an objective to provide a method enabling Fab-compatible MOCVD of a transition metal dichalcogenide/MX2 material with improved control over crystallinity and grain size. Further and alternative objectives may be understood from the following. According to an aspect, there is provided a method of depositing a transition metal dichalcogenide, the method including: depositing a layer of the transition metal dichalcogenide on a substrate by a metalorganic chemical vapor deposi