Method for forming high dielectric constant metal oxides

Abstract

To provide a method for forming a high dielectric constant (high-k) metal-oxide capable of reducing a cost and simplifying a process because a conventional ISSG process is not required, and capable of excellently forming a substrate interface layer (barrier layer) with high performance by generating SiH3 using a small amount of trisilylamine (TSA, chemical formula: N (SiO2) 3) and combining it with an organometallic compound precursor.SOLUTION: The method uses TSA to form a trace amount of SiO2 and combines with an organometallic precursor, such as TEMAH or TDMAH, to or deposit the SiO2 in the metal-oxide. By high-temperature annealing performed after deposition, Si / O atoms doped in the film move to the interface with the substrate to form a high-quality side SiO2 interface layer. Thereby, leakage is suppressed, and a high dielectric constant, a low leakage current, a high breakdown voltage, and high reliability are realized.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention belongs to the field of semiconductor manufacturing, and particularly relates to a technique for forming a high dielectric constant (high-k) metal oxide thin film used as a gate oxide film of a transistor. [Background technology]

[0002] In recent years, as semiconductor manufacturing advances to the nanometer scale, the formation of high-quality gate oxide films with high dielectric constants has become an important technology. Conventional silicon dioxide (SiO2) and silicon nitride (Si3N4) films have limitations as gate dielectric films in nanometer-scale CMOS (complementary metal-oxide-semiconductor) processes due to their insufficient dielectric constants. Therefore, metal oxide films with higher dielectric constants have become the natural choice for use as gate dielectric films.

[0003] Currently, the most common high-k material is hafnium oxide (HfO2), and its typical formation method involves depositing an alkylamide-based organometallic precursor (e.g., tetra(ethylmethylamino)hafnium (TEMAH) or tetra(dimethylamido)hafnium (TDMAH)) as a monolayer on a standard-cleaned silicon substrate using atomic layer deposition (ALD) technology, followed by heating to a specific temperature in an oxygen source (H2O, O3, or oxygen plasma) atmosphere to form a thin HfO2 film on the silicon wafer surface. However, during the subsequent high-temperature annealing process, oxygen in HfO2 diffuses into the silicon substrate (if the substrate is silicon), resulting in an uneven coating of SiO2 or silicate (M) at the Si / HfO2 interface. x Si y O z This interfacial layer is of poor quality and causes leakage, affects the crystallization behavior of HfO2, and significantly reduces the effective dielectric constant (k value). Summary of the Invention [Problem to be solved by the invention]

[0004] To address this issue, the conventional method involves using in-situ steam generation (ISSG) technology to first form a dense, ultrathin, uniform, high-quality SiO2 layer on the silicon wafer surface using ozone or steam, followed by deposition of HfO2. This dense SiO2 layer effectively blocks the diffusion of HfO2 into the substrate silicon, improving the effective dielectric constant. However, the ISSG process technology and equipment are expensive, and an additional high-temperature combustion step is required, increasing production costs. Therefore, there is a strong demand for a method to form high-k metal gate oxide films that simplifies the manufacturing process and reduces production costs. [Means for solving the problem]

[0005] This invention provides a technology for generating SiO2 using a small amount of trisilylamine (TSA, chemical formula N(SiH3)3), which is then combined with organometallic precursors such as TEMAH or TDMAH to add to high-k metal oxides (HfO2 is the primary example in the examples below). Using TSA as a precursor, SiO2 and HfO2 are mixed or layered using an oxygen source (e.g., H2O, O3, or oxygen plasma) in an ALD (atomic layer deposition) or CVD (chemical vapor deposition) process, ultimately yielding silicon-doped HfO2. A subsequent high-temperature annealing step diffuses the silicon and oxygen atoms doped in the film to the interface between the silicon substrate and HfO2, forming a high-quality SiO2 interfacial layer. This eliminates the need for the conventional ISSG process, which involves forming an SiO2 barrier layer before depositing HfO2, simplifying the process and achieving a high effective dielectric constant.

[0006] Alternatively, TSA alone can be used as a precursor for ALD to deposit high-quality SiO2 on a standard-cleaned silicon substrate surface, followed by subsequent deposition of a high-k metal oxide in the same equipment, simplifying the manufacturing flow without the need to switch to a different equipment such as ISSG to produce an ultra-thin SiO2 layer.

[0007] Furthermore, the method of the present invention can also be applied to the fabrication of dielectric layers in DRAM capacitors, improving the dielectric constant while suppressing leakage current. Currently, high-k metal oxides (HfO2, ZrO2, La2O3, Al2O3, etc.) or metal-doped ternary oxides (Al, Zr, Si, lanthanides) are used for the dielectric layers of DRAM capacitors and the gate oxides of transistors. For example, doping HfO2 with Al promotes phase transition to a higher-k phase (orthorhombic) or suppresses leakage due to grain boundaries. However, during high-temperature annealing, Al diffusion into the silicon substrate causes spikes, increasing leakage and reducing effective capacitance. Therefore, the conventional method involves first forming a high-quality SiO2 barrier layer on the silicon wafer surface and then layering a high-performance metal oxide layer on it. Using the method of the present invention, even in the high-k metal oxide process for DRAM capacitors, a high-quality SiO2 interfacial layer is naturally formed during annealing, suppressing leakage and improving the capacitor's charge retention performance and overall effective dielectric constant.

[0008] In order to clarify the above features and advantages, preferred embodiments will be illustrated and described in detail below with reference to the drawings. [Brief explanation of the drawings]

[0009] [Figure 1A] 1 is a schematic diagram of an atomic layer deposition (ALD) system and process. [Figure 1B] 1 is a schematic diagram of an atomic layer deposition (ALD) system and process. [Figure 2A] 1A to 1C are cross-sectional views showing steps in a conventional method for forming a metal oxide dielectric layer. [Figure 2B]1A to 1C are cross-sectional views showing steps in a conventional method for forming a metal oxide dielectric layer. [Figure 2C] 1A to 1C are cross-sectional views showing steps in a conventional method for forming a metal oxide dielectric layer. [Figure 2D] 1A to 1C are cross-sectional views showing steps in a conventional method for forming a metal oxide dielectric layer. [Figure 2E] 1A to 1C are cross-sectional views showing steps in a conventional method for forming a metal oxide dielectric layer. [Figure 3A] 1A to 1C are cross-sectional views showing steps in a method for forming a high-dielectric metal oxide according to the present invention. [Figure 3B] 1A to 1C are cross-sectional views showing steps in a method for forming a high-dielectric metal oxide according to the present invention. [Figure 3C] 1A to 1C are cross-sectional views showing steps in a method for forming a high-dielectric metal oxide according to the present invention. [Figure 3D] 1A to 1C are cross-sectional views showing steps in a method for forming a high-dielectric metal oxide according to the present invention. [Figure 4] 1 is a graph showing X-ray photoelectron spectroscopy (XPS) compositional analysis results of a HfO 2 thin film containing 4% TSA-based precursor after deposition and annealing in accordance with the present invention. [Figure 5] FIG. 1 illustrates a process flow according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes the differences between the embodiments of the present invention and the prior art with reference to the drawings. The drawings are merely schematic examples for ease of explanation and do not limit the scope of the present invention. The same reference numerals denote similar elements.

[0011] 1A and 1B, Fig. 1A shows a schematic diagram of an ALD system 100. The ALD system 100 includes a reaction chamber 101, into which a precursor 103 supplied via a precursor introduction line 102 is introduced at a predetermined timing and flow rate pattern 104, and adsorbs on the surface of a substrate 105 maintained at a specific temperature to form a desired thin film.

[0012] Figure 1B is a schematic diagram of the ALD process using HfO2 deposition as an example. In step A, TEMAH (Tetrakis(ethylmethylamino)hafnium) is introduced for approximately 1000 ms and saturated adsorbed onto the substrate 105 surface. In step B, N2 is purged for approximately 1500 ms to remove excess TEMAH, leaving only a monolayer of TEMAH on the substrate surface. In step C, H2O is introduced for approximately 1000 ms while the substrate temperature is maintained at approximately 150-300°C, allowing the reaction between H2O and TEMAH to proceed and form HfO2 on the substrate 105 surface. In step D, N2 is purged again for approximately 1500 ms to remove excess H2O and by-products.

[0013] ALD is characterized by the fact that it introduces only one type of precursor at a time, and after the reaction, excess precursor and by-products are purged with an inert gas (such as Ar or N2), resulting in self-regulating film formation. These steps A to D constitute one cycle, and by repeating them until the desired film thickness is reached, a high-quality metal oxide dielectric layer can be formed.

[0014] 2A to 2E are process diagrams that schematically show a conventional method for forming a metal oxide dielectric layer. As shown in FIG. 2A, a substrate 201 is first prepared. In nanometer-scale semiconductor processes, in addition to flat silicon wafers, wafers with fin structures and wafers with columnar structures for capacitors are also targeted. First, the native oxide film on the substrate surface is removed.

[0015] Next, as shown in Fig. 2B, an ISSG (in-situ steam generation) process is used to form an ultra-thin and high-density SiO2 layer 202 on the substrate 201. In this process, oxygen or hydrogen is used as the reactive gas, and the O2 flow rate is 10 to 30 slm, the H2 flow rate is 5 to 15 slm, and the ratio of O2:H2 is about 2:1. The operating pressure is generally 20 Torr or less, and the substrate temperature is high-temperature conditions of over 1000°C.

[0016] Next, as shown in FIG. 2C, a high-dielectric-constant metal oxide film 203 is deposited using ALD. Examples of high-dielectric-constant metal oxide films include HfO2, ZrO2, La2O3, Al2O3, and ternary oxides doped with Al, Zr, Si, lanthanides, etc. For example, in the case of HfO2, TEMAH or TDMAH is used as the precursor, the pulse time is about 0.5 to 2 seconds, and the substrate temperature is about 25 to 150°C. H2O, O3, O2 plasma, etc. is used as the oxygen source, with a flow rate of 50 to 100 sccm, a substrate temperature of 150 to 300°C, and an operating pressure of 10 -2 ~10 2 Torr, and the pulse time can be set to about 0.5 to 2 seconds.

[0017] In the process shown in Figure 2D, rapid thermal annealing (RTA) is performed to optimize the crystal structure and leakage current characteristics of the metal oxide dielectric film. The process is performed under an inert atmosphere such as Ar or N2 with a gas flow rate of 0.5 to 10 slm and a pressure of 10 -2 ~10 2 Torr, temperature 400 to 900°C, and time 60 seconds or less are typical.

[0018] Finally, as shown in FIG. 2E, a gate electrode material 204 (for example, TiN, TaN, etc.) is deposited on the high dielectric constant metal oxide film 203.

[0019] 3A to 3D are process diagrams that schematically show the method for depositing a metal oxide dielectric layer according to the present invention. Fig. 3A shows the state after the native oxide film on substrate 301 has been removed, as in the conventional example.

[0020] Next, as shown in Figure 3B, while conventionally a high-quality SiO2 layer is formed first, in the present invention, a metal oxide precursor containing trisilylamine (TSA) is introduced in the ALD process, and silicon (or SiO2) is doped into the metal oxide 303 at a certain ratio before deposition. This results in silicon being mixed into the metal oxide during the deposition stage.

[0021] Next, as shown in Figure 3C, RTA is performed to re-optimize the metal oxide 303. It was confirmed that this process diffuses the silicon atoms doped in the metal oxide to the interface between the substrate 301 and the metal oxide 303, forming a dense SiO2 interface layer 302. In other words, this invention eliminates the need for SiO2 deposition by ISSG, thereby simplifying the process and reducing costs.

[0022] Specifically, in the case of HfO2, the present invention uses a TSA doping concentration of approximately 0.1 to 10% and a HfO2 precursor such as TEMAH or TDMAH mixed with TSA for CVD or ALD. The deposition is repeated until the desired film thickness is reached, followed by annealing. Another method involves repeating the following steps: (1) ALD of SiO2 using TSA (1 cycle) → (2) ALD of HfO2 using TEMAH (24 cycles). In either case, RTA is performed to finally obtain the layered structure shown in Figure 3C, optimizing the HfO2 crystal structure (higher dielectric constants are expected in the orthorhombic or tetragonal phases).

[0023] An example of HfO2 deposition conditions is a TSA precursor temperature of 25 to 150°C, a pulse time of 0.5 to 2 seconds, a substrate temperature of 150 to 450°C, an oxygen source (H2O, O3, O2 plasma, etc.) flow rate of 30 to 200 sccm, and an operating pressure of 10 -2 ~10 2 The RTA process is carried out at 300 to 1100°C for 60 seconds or less, using Ar or N2 as the atmosphere, with a flow rate of 0.5 to 10 slm and a pressure of 10 2 ~10 -2 This can be done at about Torr.

[0024] Figure 4 shows a graph 400 of XPS compositional depth profile analysis of a HfO thin film containing approximately 4% silicon deposited on a silicon substrate in accordance with the present invention, followed by RTA. Curve 401 represents the hafnium (Hf) concentration, 402 represents the oxygen (O) concentration, and 403 represents the silicon (Si) concentration. In the region indicated by the oval 404 in the figure, the Hf signal weakens and the Si signal strengthens, while the O signal remains stable, suggesting the presence of an SiO interfacial layer there. This indicates that, according to the present invention, a high-quality SiO interfacial layer (302) is naturally formed between the HfO (303) and the silicon substrate (301).

[0025] As explained above, in the present invention, by adding a small amount of TSA when depositing a metal oxide dielectric layer, a high-quality SiO2 layer is formed at the interface with the substrate, and leakage due to diffusion of metal oxide into the silicon substrate can be suppressed.

[0026] FIG. 5 is a diagram showing a flow for forming a metal oxide dielectric layer according to the present invention. Step 501: A substrate (eg, silicon) is prepared, and a native oxide film is removed. Step 502: A substrate is loaded into a sealed chamber and the process conditions (precursor flow rate, inert gas flow rate, pressure, temperature, etc.) are made controllable. Step 503: Form a silicon-doped metal oxide dielectric layer using TSA. Step 504: RTA is used to optimize the crystal phase of the metal oxide and simultaneously form a SiO2 barrier layer at the substrate interface.

[0027] In particular, using TSA as a reactive precursor in step 503 allows for a high-quality SiO2 interfacial layer to be obtained after the annealing in step 504. Step 503 can be performed in any of several ways, including mixing TSA with a metalorganic precursor and performing CVD in an atmosphere containing an active oxygen source, or by ALD, alternating between SiO2 deposition cycles using TSA and metal oxide deposition cycles using, for example, TEMAH.

[0028] The RTA performed in step 504 has the effect of promoting the crystalline phase of the metal oxide dielectric to a high-dielectric-constant phase (orthorhombic or tetragonal in the case of HfO), further increasing the effective dielectric constant of the (SiO+HfO) structure.

[0029] As described above, the present invention has been disclosed based on the preferred embodiments, but these are not intended to limit the present invention. Those skilled in the art can make appropriate changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. providing a substrate; loading the substrate into a sealed chamber; forming a silicon-doped metal oxide dielectric layer on the substrate; and subjecting the substrate to a rapid thermal process to form a silicon dioxide interfacial layer between the substrate and the metal oxide dielectric layer; The silicon doping was performed using trisilylamine (chemical formula N(SiH) 3 ) 3 ) is used to form a metal oxide dielectric layer.

2. 2. The method for forming a metal oxide dielectric layer according to claim 1, wherein the silicon-doped metal oxide dielectric layer is formed by mixing the trisilylamine with an organometallic precursor and reacting the precursor in an environment containing an active oxygen source.

3. 10. The method of claim 1, wherein the silicon-doped metal oxide dielectric layer is formed by an atomic layer deposition process that alternates between depositing silicon dioxide using trisilylamine as a precursor and depositing metal oxide using an organometallic precursor.

4. 2. The method for forming a metal oxide dielectric layer according to claim 1, wherein the metal oxide dielectric layer is a metal oxide or a metal nitride.

5. 2. The method for forming a metal oxide dielectric layer according to claim 1, wherein the metal oxide dielectric layer is selected from the group consisting of hafnium oxide, zirconium oxide, lanthanum oxide, or aluminum oxide.

6. 3. The method of claim 2, wherein the organometallic precursor is tetra(ethylmethylamino)hafnium or tetra(dimethylamido)hafnium, and the metal oxide dielectric layer comprises hafnium oxide.

7. 2. The method for forming a metal oxide dielectric layer according to claim 1, wherein the doping concentration of the silicon is 0.1% to 10%.

8. 2. The method for forming a metal oxide dielectric layer according to claim 1, wherein the step of forming a silicon-doped metal oxide dielectric layer on the substrate is carried out by introducing an active oxygen source into a sealed chamber and maintaining the temperature of the substrate at 100° C. or higher and 450° C. or lower.

9. 2. The method for forming a metal oxide dielectric layer according to claim 1, wherein the rapid thermal treatment is performed at a temperature of 300° C. or more and 1100° C. or less.

10. 7. The method for forming a metal oxide dielectric layer according to claim 6, wherein the hafnium oxide formed has an orthorhombic or tetragonal phase.

11. 9. The method for forming a metal oxide dielectric layer according to claim 8, wherein the active oxygen source is selected from the group consisting of ozone, neutral oxygen atoms, or oxygen ions.

12. 2. The method for forming a metal oxide dielectric layer according to claim 1, wherein the substrate is selected from the group consisting of silicon, silicon carbide, or a compound semiconductor.

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