US-12628579-B2 - Ligand selection for ternary oxide thin films

Abstract

Embodiments of the present invention are directed to forming a ternary compound using a modified atomic layer deposition (ALD) process. In a non-limiting embodiment of the invention, a first precursor and a second precursor are selected. The first precursor includes a first metal and a first ligand. The second precursor includes a second metal and a second ligand. The second ligand is selected based on the first ligand to target a second metal uptake. A substrate is exposed to the first precursor during a first pulse of an ALD cycle and the substrate is exposed to the second precursor during a second pulse of the ALD cycle, the second pulse occurring after the first pulse. The substrate is exposed to a third precursor (e.g., an oxidant) during a third pulse of the ALD cycle. The ternary compound can include a ternary oxide film.

Inventors

• Martin Michael Frank
• John Rozen
• Yohei Ogawa

Assignees

• INTERNATIONAL BUSINESS MACHINES CORPORATION

Dates

Publication Date

20260512

Application Date

20220628

Claims (10)

1. 1 . A method of depositing a compound, the method comprising: selecting a first precursor comprising a first metal and a first ligand; selecting a second precursor comprising a second metal and a second ligand, the second metal different than the first metal, the second ligand selected based on the first ligand to target a second metal uptake on a substrate, wherein the target second metal uptake comprises a final second metal concentration in the compound, wherein the second ligand is selected to have a molecule size that is larger than a molecule size of the first ligand, wherein a difference in relative size between the first ligand and the second ligand is selected based on the targeted second metal uptake; forming a sub-stoichiometric atomic layer deposition (ALD) layer, the sub-stoichiometric ALD layer formed by: exposing the substrate to the first precursor during a first pulse of an atomic layer deposition (ALD) cycle; and exposing the substrate to the second precursor during a second pulse of the ALD cycle, the second pulse occurring after the first pulse without an intervening oxidant pulse; and exposing the substrate to a third precursor during a third pulse of the ALD cycle.
2. 2 . The method of claim 1 further comprising selecting a precursor partial pressure, gas flow, and pulse time for at least one of the first pulse and the second pulse based on the target second metal uptake.
3. 3 . The method of claim 1 , wherein the compound comprises a ternary oxide and the third precursor is an oxidant.
4. 4 . The method of claim 1 , wherein during the first pulse the first metal of the first precursor adsorbs onto a surface of the substrate.
5. 5 . The method of claim 4 , wherein one or more adsorption sites remain open after the first pulse; and wherein during the second pulse the second metal of the second precursor chemisorbs onto the one or more open adsorption sites.
6. 6 . The method of claim 1 , wherein the first ligand and the second ligand react during the second pulse to form one or more byproducts; and wherein at least a portion of the one or more byproducts are removed via off-gassing.
7. 7 . The method of claim 1 , wherein the second pulse occurs directly after the first pulse without an intervening pulse.
8. 8 . The method of claim 1 , wherein the second pulse occurs after the first pulse such that any intervening pulse is a non-reactive purge pulse.
9. 9 . The method of claim 1 , wherein the first metal comprises one or more of Hf, Ta, Zr, Al, La, and Si, the second metal comprises one or more of Hf, Ta, Zr, Al, La, and Si, the first ligand comprises a halide, and the second ligand comprises a metalorganic.
10. 10 . The method of claim 1 , wherein the first metal comprises one or more of Hf, Ta, Zr, Al, La, and Si, the second metal comprises one or more of Hf, Ta, Zr, Al, La, and Si, the first ligand comprises a metalorganic, and the second ligand comprises a halide.

Description

BACKGROUND The present invention generally relates to film deposition techniques. More specifically, the present invention relates to the selection of ligands when depositing ternary oxide (mixed metal-oxide) thin films. The semiconductor industry is characterized by a trend toward fabricating larger and more complex circuits on a given semiconductor chip. The larger and more complex circuits are achieved by reducing the size of individual devices within the circuits and spacing the devices closer together. In recent years, high dielectric constant (high-k) materials have gradually replaced silicon dioxide as the insulating layer used in state-of-the-art CMOS fabrication technologies, including, for example, the CMOS fabrication technologies used to fabricate memory cells in a semiconductor memory device. Zirconium oxide (ZrO), for example, has a dielectric constant from about 24 to 40. To meet the scaling requirements for smaller and smaller devices, these high-k films must be deposited to increasingly lower thickness levels. Atomic layer deposition (ALD) is a deposition technique uniquely suited for thin-film deposition. During ALD a film is grown on a substrate layer by layer by exposing the substrate surface to alternating gaseous species, typically referred to as precursors. The precursors are deposited during a series of sequential, non-overlapping pulses. In each of these pulses the precursor molecules react with the surface in a self-limiting way so that the reaction terminates once all the reactive sites on the surface are consumed. Consequently, the maximum amount of material deposited on the surface after a single exposure to all of the precursors (a so-called ALD cycle) is determined by the nature of the precursor-surface interaction. By varying the number of cycles, it is possible to grow materials uniformly and with high precision on arbitrarily complex and large substrates. SUMMARY Embodiments of the invention are directed to a method for forming a compound (e.g., a ternary oxide film) using a modified atomic layer deposition (ALD) process. A non-limiting example of the method includes selecting a first precursor and a second precursor. The first precursor can include a first metal and a first ligand. The second precursor can include a second metal and a second ligand. The second ligand is selected based on the first ligand to target a second metal uptake. A substrate can be exposed to the first precursor during a first pulse of an ALD cycle. The substrate can be exposed to the second precursor during a second pulse of the ALD cycle. The second pulse can occur directly after the first pulse without an intervening oxidant pulse. The substrate can be exposed to a third precursor during a third pulse of the ALD cycle. In some embodiments of the invention, the third precursor is an oxidant. In some embodiments of the invention, the metal of the first precursor chemisorbs onto a surface of the substrate during the first pulse. In some embodiments of the invention, one or more adsorption sites remain open after the first pulse. In some embodiments of the invention, the metal of the second precursor chemisorbs onto the one or more open adsorption sites during the second pulse. In some embodiments of the invention, the first ligand and the second ligand react during the second pulse to form one or more byproducts. In some embodiments of the invention, at least a portion of the one or more byproducts are removing using off-gassing. In some embodiments of the invention, the second pulse occurs directly after the first pulse without an intervening pulse. In some embodiments of the invention, the second pulse occurs after the first pulse such that any intervening pulse is a non-reactive purge pulse. In some embodiments of the invention, a precursor partial pressure, gas flow, and pulse time are selected for at least one of the first pulse and the second pulse based on the target second metal uptake. Embodiments of the invention are directed to a method for depositing a ternary oxide film. A non-limiting example of the method includes selecting a first metal and a second metal for the ternary oxide. A target second metal uptake (final second metal concentration in the film) is also selected for the ternary oxide. The method includes determining, based on the first metal and the second metal, one or more ligand pairs with known second metal uptakes. The method includes selecting, based on the target second metal uptake and the known second metal uptakes, a first ligand pair of the one or more ligand pairs. The first ligand pair includes a first ligand and a second ligand. The method includes exposing a substrate to an ALD cycle having a first precursor pulse, a second precursor pulse, and an oxidant pulse. The first precursor includes the first metal and the first ligand, and the second precursor includes the second metal and the second ligand. In some embodiments of the invention, the method includes sele