Preparation of lanthanide-containing precursors and deposition of lanthanide-containing films

Abstract

The disclosed lanthanide precursor compounds include cyclopentadienyl ligands having at least one aliphatic group as a substituent and at least one bidentate ligand. These precursors are suitable for depositing lanthanide-containing films.

Description

[Technical Field]

[0001] The field of this disclosure relates to chemicals for vapor deposition of materials for semiconductor manufacturing.

[0002] The present invention is at least industrially applicable to depositing lanthanide materials for the manufacture of semiconductors. [Background technology]

[0003] One of the significant challenges facing the semiconductor industry is developing new gate dielectric materials for dynamic random access memory (DRAM) and capacitors. For decades, silicon dioxide (SiO2) has been a reliable dielectric. However, as transistors continue to shrink and technology transitions from "full silicon" to "metal gate / high-k" transistors, the reliability of SiO2-based gate dielectrics is reaching its physical limits. As current technologies shrink in size, the need for new high-k materials and processes is growing and becoming increasingly important. A new generation of oxides, particularly those based on lanthanide-containing materials (those with atomic numbers 57-17, primarily lanthanum), is expected to offer significant capacitance advantages compared to conventional dielectric materials.

[0004] Nevertheless, the deposition of lanthanide-containing layers is challenging, and new materials and processes are increasingly needed. For example, atomic layer deposition (ALD) has been identified as an important thin film growth technique for microelectronics manufacturing, and is often performed with an inert gas purge. alternating ALD relies on a series of saturated surface reactions of precursors applied to the lanthanide layer. The surface-controlled nature of ALD allows for the growth of thin films with high conformality and uniformity through precise thickness control. There is a clear need to develop new ALD processes for lanthanide materials.

[0005] Unfortunately, successful incorporation of these compounds into deposition processes has proven challenging. Three types of molecules are typically proposed: β-diketonates, bis(trimethylsilyl)amides, and cyclopentadienyls. While the first two families of compounds are stable, their melting points can exceed 90 °C, making them impractical. For example, the melting point of lanthanum 2,2-6,6-tetramethylheptanedionate [La(thd)3] is as high as 230 °C, and that of lanthanum tris(bis(trimethylsilyl)amide) [La(tmsa)3] is 150 °C. Furthermore, the delivery efficiency of these precursors is very difficult to control. Unsubstituted cyclopentadienyl compounds also exhibit high melting points and low volatility. Molecular design can help both improve volatility and lower melting points. However, process conditions have proven limiting the use of these types of materials. For example, La(iPrCp)3 does not tolerate the ALD regime above 225 °C. Summary of the Invention [Problem to be solved by the invention]

[0006] As discussed above, most of the currently available lanthanide-containing precursors exhibit numerous drawbacks when used in deposition processes. Therefore, there is a need for alternative precursors for depositing lanthanide-containing films. [Means for solving the problem]

[0007] For a further understanding of the nature and objects of the present invention, reference should now be made to the following detailed description taken in conjunction with the accompanying drawings, in which like elements are given the same or similar reference numerals, and in which: [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a TGA graph showing the percentage of weight as the temperature increases. [Figure 2] FIG. 2 shows the onset temperatures of melting (77° C.) and decomposition (410° C.) of the product measured by differential scanning calorimetry (DSC). DETAILED DESCRIPTION OF THE INVENTION

[0009] The disclosed precursor compounds include a cyclopentadienyl ligand having at least one aliphatic group as a substituent and a bidentate ligand. The precursor has one of these three general formulas: 1.Ln(R1Cp)m(O-CR2=CH-CR2=O)n 2.Ln(R1Cp)m(R3N-CR2=CH-CR2=O)n 3.Ln(R1Cp)m(R3N-CR2=CH-CR2=NR3)n

[0010] In the above formulas 1 to 3, Ln is a lanthanide element, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu. R1, R2, and R3 are each independently H or a C1-C5 alkyl (linear or branched). m is 1 or 2, and n is 1 or 2.

[0011] The disclosed precursor compounds of Formulas 1-3 above offer unique physical and chemical properties when compared to their corresponding homoleptic counterparts, including the tris-substituted cyclopentadienyl lanthanide compound Ln(RCp)3 and the tris-substituted β-diketonate compound Ln(O-CR=CH-CR=O)3 (or Ln(R'N-CR=CH-CR=O)3, Ln(R'N-CR=CH-CR=NR')3). These properties include better control of steric crowding around the metal center, thereby controlling surface reactions on the substrate and reactions with a second reactant (such as an oxygen source). Independently, tailoring the substituents on the ligands improves volatility and thermal stability, lowering the melting point to produce either a liquid or a low-melting solid (having a melting point below about 105°C, preferably below about 80°C).

[0012] The properties of certain exemplary molecules and comparative molecules are summarized in Table 1.

[0013] [Table 1] [Example]

[0014] Example 1 - Lanthanum isopropylcyclopentadienyl tetramethylheptanedionate = La(iPrCp)2(thd) A solution of 2,2,6,6-tetramethyl-3,5-heptanedione (2 g, 10.8 mmol) in 30 mL of toluene was added dropwise to a solution of La(iPrCp)3 (5 g, 10.8 mmol) in 15 mL of toluene at -78 °C. The reaction mixture was allowed to slowly warm to room temperature with stirring overnight. After filtration, the solvent was removed under reduced pressure to give a brown solid. This brown solid was sublimed at approximately 180 °C under 35 mTorr to give a yellow solid in approximately 44% yield (2.54 g).

[0015] During open-cup TGA analysis, run at atmospheric pressure with a nitrogen flow of 200 mL / min and a heating rate of 10°C / min, the purified product retained 5.4% residual mass. These results are shown in Figure 1, a TGA graph showing the percentage of weight as the temperature increases. The onset temperatures of melting (77°C) and decomposition (410°C) of the product were measured by differential scanning calorimetry (DSC) and are shown in Figure 2.

[0016] Abbreviations and Terminology While the present invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist of, or consist essentially of the elements disclosed, or may be practiced in the absence of elements not disclosed. Furthermore, where there is language referring to an order, such as first and second, this language is intended to be illustrative and not limiting. For example, this language may indicate that certain steps can be combined into a single step by one skilled in the art.

[0017] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0018] "Comprising" in the claims is an open transitional term, meaning that the claim elements identified thereafter are a non-exclusive list (i.e., other things may additionally be included and remain within the scope of "comprising"). As used herein, "comprising" may be substituted with the more restrictive transitional terms "consisting essentially of" and "consisting of," unless otherwise indicated herein.

[0019] In the claims, "providing" is defined to mean to equip, supply, make available, or prepare something. Unless the claim expresses language to the contrary, steps may be performed by any actor.

[0020] Optional or optionally means that the subsequently described event or circumstance may or may not occur. The present specification includes instances where the event or circumstance occurs and instances where it does not occur.

[0021] Ranges may be expressed herein as from about one particular value and / or to about another particular value. When such a range is expressed, it will be understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within that range.

[0022] All references identified herein are each incorporated herein by reference in their entirety into this application, as are the specific information for which each is cited.

[0023] It will be understood that many additional changes in the details, materials, steps and arrangements of parts described herein to explain the principles of the invention may be made by those skilled in the art within the principles and scope of the invention as expressed in the appended claims. Accordingly, it is not intended that the invention be limited to the particular embodiments of the examples set forth above.

Claims

1. La(isopropylcyclopentadienyl) ２ (O-C(tBu)=CH-C(tBu)=O), Er(methylcyclopentadienyl) ２ ((Et)N-C(Me)=CH-C(Me)=O), or Er(methylcyclopentadienyl) ２ ((nPr)N-C(Me)=CH-C(Me)=O).

2. Chemical vapor deposition and / or atomic layer deposition for manufacturing semiconductors comprising the chemical substance of claim 1. A composition suitable for use in deposition.

3. 3. The composition of claim 2, wherein the chemical is 99% or more by weight of the composition.

4. 10. The vapor phase chemical of claim 1 is provided in a chemical vapor deposition process or an atomic layer deposition process.

1. A method for depositing a lanthanide-containing film, comprising the steps of:

5. The chemical vapor deposition process or the atomic layer deposition process produces a lanthanide-containing film on a substrate. The method of claim 4, comprising:

6. The method of claim 5 , wherein the substrate is a semiconductor substrate.

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