JP2018135603A - Low-temperature deposition method of ceramic thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-temperature deposition method of a ceramic thin film having a mixed phase such as a carbide, nitride, and carbonitride by atomic layer deposition (ALD), nano-layer deposition (NLD), and chemical vapor deposition (CVD).SOLUTION: There is used a combination of deposition precursors that affects deposition temperature of a thin film of a carbide, nitride, and carbonitride of silicon (Si), carbon (C), germanium (Ge), phosphorus (P), arsenic (As), sulfur (S), boron (B), or selenium (Se) on a substrate. There is provided low-temperature deposition of various thin films containing components selected from the group of B, C, Si, Ge, N, P, As, O, S, and Se by atomic layer deposition (ALD), nano-layer deposition (NLD), and chemical vapor deposition (CVD). The combination of reactive precursors is selected based on reactivity to each other that is determined by the variation of Gibb's free energy (ΔG) relating to deposition temperature.SELECTED DRAWING: Figure 5

Description

[Cross-reference of related applications]
This application claims priority to US Provisional Patent Application No. 61 / 745,523, filed Dec. 21, 2012, the contents of which are incorporated herein by reference.

  The present invention generally relates to the deposition of thin films, particularly mixed phases such as carbides, nitrides, and carbonitrides by atomic layer deposition (ALD), nanolayer deposition (NLD), and chemical vapor deposition (CVD). The present invention relates to a method for low-temperature deposition of a ceramic thin film.

  Silicon, germanium, and boron carbide, nitride, and carbonitride, and their mixed phase thin films are used in high temperature and high power electronic devices, sensors that operate in harsh environments, corrosion and wear resistant coatings, and It has important and wide-ranging applications, such as in the manufacture of light emitting diodes (LEDs). Commonly practiced methods for depositing thin films of these materials include sputtering, physical vapor deposition (PVD), chemical vapor deposition (CVD), and atomic layer deposition (ALD), and plasma. Various other deposition methods are included. In these thin film deposition methods, however, CVD and ALD are both widely practiced because of the various advantages expressed with respect to film quality, composition, uniformity, adhesion, and a wide range of coatings. .

  The CVD process widely adopted in industry is a process that depends on flux. Under kinetically limited conditions, the CVD process is also sensitive to the temperature of the substrate. However, CVD processes can operate at high deposition rates ranging from a few microns / hour to 100 microns / hour and are quite useful for industrial manufacturing. On the other hand, ALD processes have several significant advantages over corresponding CVD processes in that the uniformity of the thin film and the substrate does not depend on flow and therefore does not depend on the size and shape of the substrate. In addition, ALD processing is also characterized by a coating on submicron scale substrates, and in some cases lower deposition processing temperatures that indicate surface catalytic interaction of the substrate with chemical precursors. However, ALD suffers from lower film deposition rates (which can be an order of magnitude or even lower) compared to corresponding CVD processes.

  Furthermore, in a typical CVD process, two or more reactive gases (chemical precursors) are mixed and passed through a heated substrate that is useful to achieve a wide range of deposition. Such a procedure is only suitable if the chemical precursor does not show a tendency to react in advance upon mixing. However, in some cases, if the chemical precursors are highly reactive with each other, the gases must be separated before reaching the substrate surface, but at the same time must be evenly distributed on the substrate. Such a requirement rather complicates the maintenance and operation of the dual injector CVD reactor.

  In the case of ALD processing, chemical precursors are sequentially sent to a processing vessel, and the chemical precursors are dispersed by a purge gas. The purge gas is practically any gas that does not actively participate in the chemical reaction of film deposition. Because it does not depend on flow, in ALD processing, uniform reactant distribution is typically not required. Therefore, a simple separation of the reactant injectors is sufficient to perform the ALD process. These advantages allow the selection of fairly active chemical precursors for the ALD process that can complicate the implementation of the CVD process. Indeed, precursors that are highly reactive with one another are particularly in demand and are highly desirable for efficient ALD thin film processing.

  In a typical ALD method, two or more reactant gases are sequentially pulsed onto a heated substrate placed in a processing chamber. The reactant gas pulse flow is sent separately from the purge gas pulse flow, or the two reactant gas pulse flows are dispersed in a constant flow of purge gas. On the other hand, in a CVD process, a heated substrate placed in a process chamber is simultaneously provided to a reactant stream along with an optional purge gas stream as a carrier gas.

In general SiC CVD processing, this method is mainly followed. For example, Journal of Crystal Growth, vol. 255, pp. 136 (2003). Fujihira et al. Demonstrated a high-speed CVD process for 4H-SiC thin films performed at 1300 ° C. employing silane (SiH ₄ ) and propane (C ₃ H ₈ ). Sensors and Actuators A, vol. 97-98, pp. 410 (2002), Stoldt et al. Describe a single precursor, low temperature (800) of SiC thin film employing 1,3-disilabutane (SiH ₃ —CH ₂ —SiH ₂ —CH ₃ ). (~ 1000 ° C) CVD process was developed. On the other hand, Journal of Crystal Growth, vol. 219, pp. Sone et al. Describe a single precursor CVD SiC process employing methyltrichlorosilane (MTS: CH ₃ —SiCl ₃ ), performed at 1300 ° C., as published in H.245 (2000). Yes. In general, it is clear here that the deposition reaction of SiC thin films is carried out at temperatures in excess of 1000 ° C. It is well known that the deposition reactions of BN, B ₄ C, and Si ₃ N ₄ ceramic thin films are also carried out in a similar temperature range.

US Patent Application No. 2012/01222302 describes a plasma assisted low temperature SiC deposition process using 1,3,5-trisilacyclohexane (C ₃ Si ₃ Hi ₂ ) as a precursor, performed at 200 ° C. . However, during deposition, the SiC thin film needs to be further densified at 600 ° C. In U.S. Patent Application No. 2012/0177841, either plasma or heat treatment at temperatures below 600 ° C. to reduce H content in thin film products having the composition Si _x CyH ₂ (0 <z <16). Subsequent treatment by has described a repetitive deposition process employing silicon tetrachloride SiCl ₄ as the silicon source, reduced to trimethylaluminum [(CH ₃ ) ₃ AI]. In US Patent Application No. 2012/0214318 (A1), the inventors employed dichlorotetramethyldisilane [Si ₂ Cl ₂ (CH ₃ ) ₄ ] and H ₂ gas at a temperature in the range of 100-400 ° C. A plasma assisted ALD process has been described. A film product having the composition SiC was obtained, but the Si: C ratio was not confirmed. In the process described in US Reissue Pat. No. 42,887, we employ dichlorosilane (Si ₂ Cl ₂ ) and acetylene (C ₂ H ₂ ) in hydrogen at a temperature of about 900 ° C. Thus, an SiC thin film was obtained.

In US Pat. No. 7,901,508, mainly in a hydrogen stream, combined with silane (SiH ₄ ) as a silicon source and propane (C ₃ H ₈ ) as a carbon source at a substrate temperature of 1600 ° C. The use of halogenated hydrocarbons as a chlorine source is described. The use of halogenated hydrocarbons is known to increase the SiC deposition rate by inhibiting silicon nucleation at higher temperatures, and the HCl (hydrochloric acid) gas in the Si—H—C—Cl system. It is intended that a practical advantage is obtained from the addition. Silicon nucleation is known to be quite detrimental to the quality of SiC films in terms of defect density.

In the case of depositing a BN thin film, a process generally employed is to perform BCl ₃ in combination with NH ₃ gas at a temperature exceeding 1000 ° C. A somewhat new process for the deposition of BN layers has been developed, which is carried out employing the chemical precursor s-triazoborane (B ₃ H ₃ N ₃ ) bonded cyclically at a temperature of 1000 ° C. On the other hand, carbon nitride (C ₃ N ₄ ), which is said to be a superhard material, has recently been radio frequency (RF) or microwave (MW) plasma using methane (CH ₄ ) and N ₂ as a nitrogen source. Has been deposited.

  Because high processing temperatures are required, the choice of substrate for these thin films is rather limited to ceramic, silicon, and quartz, taking into account commercial and technical values. In addition, higher processing temperatures always result in some serious practical disadvantages that limit commercial applications. In terms of end product, high practical temperatures result in high film loading, very high defect density, which significantly reduces device performance. Furthermore, interdiffusion of layers, substrate warpage, difficulty in integrating with other thin films, and the inclusion of impurities are serious problems at high processing temperatures. From the standpoint of equipment operation, wastewater treatment in addition to high power consumption issues, the choice of materials that make up the treatment chamber and limitations on its durability, gas flow stability, chemical precursor consumption, and cost and complexity. is there.

Therefore, there is a need to develop low temperature CVD and ALD processes for various compositions of ceramic thin films that employ elements from the group including B, N, C, Si, and Ge elements. The thin film containing these elements is not limited to these, but SiC, BN, B ₄ C, SiCXN _y , Si ₃ N ₄ , Si _x Ge _(1-x) , Si _x Ge _(1-x) C, GeC, among others. including.

A method for low temperature deposition of carbide, nitride, and mixed phase ceramic thin film coatings, the method comprising:
Determining deposition chemistry that employs a combination of reactive precursors that affect the temperature required to deposit a thin film on the surface of the substrate;
A step of placing the substrate in the processing chamber;
Adjusting one or more process parameters including substrate temperature, process chamber pressure, and process chamber temperature;
Starting a deposition cycle; and determining whether the thin film coating has reached a predetermined thickness and repeating the deposition cycle until the predetermined thickness is reached;
The deposition is by atomic layer deposition (ALD), nanolayer deposition (NLD), or chemical vapor deposition (CVD);
A combination of reactive precursors is selected based on the reactivity between each of the reactive precursors as determined by the Gibbs free energy change (ΔG) with respect to the deposition temperature in the process chamber.

  The method includes boron carbide (B), nitrogen (N), nitride, silicon (Si) carbonitride, carbon (C), germanium (Ge), phosphorus (P), arsenic (As), oxygen (O ), Sulfur (S), and selenium (Se) thin film deposition. A larger negative value of Gibbs free energy in the reaction is a criterion for selecting a combination of reactive precursors.

FIG. 1A shows that other molecules such as CO and CO ₂ do not bind firmly to the surface of the substrate and are only physically adsorbed, while —OH groups formed by chemical adsorption of moisture from the surroundings. A substrate having a surface is illustrated. FIG. 1B illustrates surface H and Cl exchange and O—Ti bonds from TiCl ₄ chemisorption. FIG. 1C shows the reaction of chemisorbed —TiCl ₃ with water (H ₂ O) molecules to form TiO ₂ during ALD processing. FIG. 2A shows a typical ALD cycle with a pulse flow of two purge gases and a pulse flow of two reactive precursors dispersed. FIG. 2B represents a variation of the ALD cycle having a pulse flow of two reactive precursors spaced at a constant flow rate of purge gas in the process chamber. FIG. 2C illustrates a variation of various process gas flow parameters in a typical CVD process. 2 is a flowchart of an exemplary ALD process sequence for forming a thin film of a desired thickness. 6 is a flow diagram illustrating a variation of deposition system parameters in a typical CVD process. FIG. 5A illustrates a substrate for deposition comprising a surface that adsorbs —OH groups, according to one embodiment of the present invention. FIG. 5B illustrates the formation of bonds with chemisorption of CCl ₄ molecules in the gas phase and release of HCl molecules into the gas phase on the —OH group surface, according to one embodiment of the present invention. FIG. 5C shows the reaction of silane (SiH ₄ ) molecules on the surface with pre-chemisorbed —CCl ₃ species, Si—C bond formation and HCl release, according to one embodiment of the present invention. And the surface terminated with H atoms. FIG. 5D shows the next ALD cycle starting with chemisorption of CCl ₄ on a surface terminated with H and having a bond formed between Si and C, according to one embodiment of the invention. The first stage is illustrated. FIG. 6A is a graph of Gibbs free energy change (ΔG) versus substrate temperature for the formation reaction of SiC with SiH ₄ and CCl ₄ as precursors of Si and C, respectively, according to one embodiment of the present invention. . 6B is a graph of Gibbs free energy change (ΔG) versus substrate temperature for a BN formation reaction with B ₂ H ₆ and NF ₃ as precursors of B and N, respectively, according to one embodiment of the present invention. is there.

  The method of the present invention provides low temperature deposition of mixed phase ceramic thin films such as carbides, nitrides and carbonitrides by atomic layer deposition (ALD), nanolayer deposition (NLD), and chemical vapor deposition (CVD). To do. The deposition chemistries include boron (B), carbide, nitrogen (N), nitride, silicon (Si) carbonitride, carbon on various substrates at substantially lower temperatures than conventional thin film deposition methods. Substantially lower temperature than recent deposition processes for thin film deposition of (C), germanium (Ge), phosphorus (P), arsenic (As), oxygen (O), sulfur (S), and selenium (Se) A combination of precursors that affect thin film processing is employed. The deposition temperature in the method embodiments of the present invention is preferably less than 600 ° C., while conventional deposition processes are performed at higher temperatures. Embodiments of ALD and corresponding NLD and CVD processes or methods of the present invention include various thin film containing elements from the group of B, C, Si, Ge, N, P, As and O, S, and Se. Provides low temperature deposition of deposition.

  The combination of reactive precursors in the deposition method embodiments of the present invention is selected based on their reactivity to each other as determined by the Gibbs free energy change (ΔG) with respect to the deposition temperature. Larger negative values of Gibbs free energy in the reaction are the basis for selection of preferred reactive precursor combinations.

For ALD and CVD processes, the various components, reactive precursors, are usually classified into one form, for example, either hydride or halide. On the other hand, compounds containing hydrogen and halogen bonded to C and Si form another class. Thin film deposition processes of various materials react with a second component halide that affects the intensive reaction of the deposition such that the substantial Gibbs free energy (ΔG) in the reaction is negative. It is embodied on the form of a gas, for example a hydride consisting of one component. In addition, in the case of thin films of three or four elements, one or more component hydrides are combined with other desired component halides. According to the ALD process of the present invention, one or more hydrides of the group consisting of B, C, N, Si, Ge, P, O, S, and Se are selected as the first reactive precursor. And one or more halides of F, Cl, Br, or I are selected as the second reactive precursor. For example, nitrogen trifluoride (NF ₃ ) is employed as a nitrogen source in combination with B ₂ H ₆ as a boron precursor. On the other hand, for ALD treatment of silicon carbide, the silicon source is from Si ₂ H ₆ , SiH ₄ , SiH ₃ X, SiH ₂ X ₂ , and SiHX _{3 where} X = F, Cl, Br, and I. Selected, the carbon source is selected from CX ₄ , CX ₃ H, CX ₂ H ₂ , and CX ₃ H, where X = F, Cl, Br, and I.

Further, in variations of ALD, NLD, and CVD processes, a chloro-- represented by the general formula C _n X _a Z _b (where n, a, b are integers, and X and Z are halogens) Mixed halogenated carbons such as fluoro-carbon are equally suitable as a carbon source. Another subclass of reactive precursors is the general formula M _n H _a X _b , where M = C and Si, X = F, Cl, Br, I, and n, a, b are integers. C and Si mixed halides represented. In the preferred embodiment, various combinations of reactive precursors employed to develop various thin film processes are described.

  However, for the development of ALD thin film processing, the first reactive precursor may be either halide or hydride, and then the corresponding second reactive precursor is hydride or halide. It is known. For the corresponding CVD processes of various materials such as carbides, nitrides, silicides, sulfides, selenides, phosphides, arsenides, and their mixed phases, the reactants as used in the ALD process A combination is employed to obtain the desired thin film structure.

  To carry out the method embodiments of the present invention, a variety of CVD reactors, commonly known in the industry, that individually and uniformly inject the two reactive reactants are used. One such ALD / CVD reactor and one of its various configurations is described in US Pat. No. 6,812,157, which is hereby incorporated by reference in its entirety.

  In order to perform the deposition process of the present invention, a process chamber is needed that can change and control process variables for performing the desired chemical reaction. In the processing chamber, a heated platen is supplied that can be adjusted and kept constant according to the requirements of the particular deposition process. The substrate on which the desired thin film is deposited is placed in thermal contact with the heating platen to heat the substrate to a preset temperature that affects the desired chemical reaction. The processing chamber further provides a gas inlet that is connected to the precursor gas supply through appropriate fluid metering and control valves. The processing chamber is also connected to a vacuum pump through a downstream throttle valve to adjust the processing chamber pressure during the deposition process. The processing chamber pressure can be kept constant by always adjusting the downstream throttle valve according to the incoming gas pulse flow, or can be dynamically changed by the gas pulse flow with the throttle valve position fixed. It can also be made.

  The thin film deposition process described in the present invention is in fact mainly divided into atomic layer deposition (ALD) and chemical vapor deposition (CVD). Since a typical ALD process includes repeated ALD cycles to form the desired film thickness, the precursor is a reaction that is dispersed by a purge gas that flows continuously in the background, or a pulsed stream of two purge gases. Along with any of the sex precursors, it is sequentially introduced into the processing chamber. The principle of ALD processing and its implementation are as described in US Pat. No. 4,058,430. In the case of a chemical vapor deposition (CVD) process, all reactive precursor gases, with a purge gas (primarily used as a dilution gas or ballast gas), simultaneously pass over the heated substrate at a constant rate. To do. In this case, the processing chamber pressure and / or the substrate temperature may be adjusted as necessary.

  With respect to an intermediate form of thin film deposition called nanolayer deposition (NLD), it has recently become common practice to omit one or both pulsed purge gas pulses from the continuous mode of processing. In the NLD process, the reactive gas is usually flowed in a pulsed manner or continuously. As a result, the reactive precursor molecule forms a chemical bond with the substance on the substrate. However, excess reactive precursor molecules are not wiped from near the substrate surface, and as a result, a film larger than a single layer is formed in a pulsed flow of a pair of gases. It should be understood that NLD processing is also within the scope of the present invention, that is, the deposition chemistry of the film is based on the appropriate selection and combination of reactive precursors disclosed herein.

  Furthermore, the processing (ALD, CVD, or NLD) described in the present specification can be effectively performed even at atmospheric pressure (760 Torr) or a processing chamber pressure as low as several milliTorr (mT). Also, the processing temperature can vary from ALD or CVD processing to other processing to be highly dependent on various factors such as the combination of reactive precursors, substrate type, and the like. Therefore, it should be noted that the applicable processing temperature conditions are quite wide ranging from room temperature to 1,000 ° C.

  In ALD processing, the selection of precursors that are highly reactive with each other is preferred for effective implementation. However, due consideration is given to the effective separation and uniform distribution of both precursor streams until the substrate surface is prevented from unwanted pre-reaction and particulate formation by appropriate process chamber design. If so, it should be noted that the same combination of reactive precursors is employed to proceed the corresponding CVD process with the same combination of reactive precursors. The interaction between the substrate surface and the reactive precursor is extremely important in ALD processing. Therefore, the nature of the reactive precursor molecule in terms of its geometry, size, and the stereospecificity of the surrounding reactive groups is attributed to good film coverage, high film density, and overall film quality. Is a fairly important measure for realizing an efficient ALD process comprising

Typically, ALD processing is so high that on a substrate in the gas phase, chemical precursor molecules sent into the processing chamber react with pre-adsorbed surface species (in the surrounding environment). It is surface sensitivity (surface sensitive). These surface species are typically moisture (H ₂ O), and CO and CO ₂ and N ₂ gases. However, among these four gas species present in the surrounding environment, H ₂ O molecules show a strong tendency to react with surface atoms (metal or non-metal), and therefore, as shown in FIG. It is noted that the terminated surface is easily present. Thus, by treating the surface with a suitable gas plasma, high temperature or high vacuum, or a combination thereof, this surface performance and thus its reactivity can be changed.

Therefore, inflowing gas precursor molecules, for example, TiCl ₄ having high reactivity with the surface —OH group, chemisorbs by substitution with Cl atoms on the surface, and the surface O species and —TiCl 4 A chemical bond with ₃ is formed. During the chemisorption process, HCl molecules are released as shown in FIG. 1B. In the next step, H ₂ O molecules flowing into the gas phase are chemisorbed to Cl groups of —TiCl ₃ groups to form Ti—O bonds as shown in FIG. 1C. At this stage, the surface terminates with —OH groups that accept the next pulse stream of the gas precursor. The order of the gas pulse flow does not describe the purge gas pulse flow in which both the TiCl ₄ and H ₂ O pulse flows flow as described above. The main purpose of the purge gas pulse flow is to wipe off excess TiCl ₄ and / or H ₂ O molecules that are physisorbed or loosely attached to the substrate. From the foregoing discussion, it is sufficiently clear that for efficient ALD processing, it is essential to select chemical precursors that are highly reactive with each other. Flow-independent chemisorption based on ALD processes is advantageous because it greatly simplifies process chamber design and process chamber operation. However, considerable emphasis and importance are placed on the chemical properties of the substrate surface to accept (retain) the first reactive chemical precursor molecule and initiate the ALD cycle to obtain the desired product.

  The processing sequence of FIGS. 1A-1C is one ALD with four separate pulse streams (first reactive gas, purge gas, second reactive gas, and last purge gas), as shown in FIG. 2A. The cycle is described and repeated until the thin film is formed to the desired thickness. Alternatively, the purge gas flow is kept constant in the process chamber, and the reactive gas pulse flow is dispersed at the time as shown in FIG. 2B in the ALD cycle and then until it is formed to the desired film thickness. Repeated. Thus, the formation of bonds with surface species requires chemical precursors that are highly reactive with each other while a pulsed flow of reactive precursors flows over the substrate in an ALD process. However, for chemical vapor deposition (CVD) processing, all precursor gases with a purge gas (primarily used as a dilution or ballast gas) are simultaneously passed at a constant rate over the heated substrate. . At that time, the processing chamber pressure and / or the substrate temperature may be adjusted. The variation of the reactive precursor and inert gas / purge gas flow sequence over time (at a constant temperature and pressure) in a typical CVD process is as shown in FIG. 2C.

  FIG. 3 illustrates a logical flow diagram of a typical ALD process sequence (10) using four distinct pulse streams. The processing starts with a step (12) of placing the substrate in the processing chamber and a step (14) of adjusting processing parameters including the substrate temperature, the processing chamber pressure, and the like. Thereafter, the ALD cycle starts the step (16) of introducing a pulse flow of the first reactive precursor gas into the processing chamber, and then the step of introducing the pulse flow of the purge gas (18), the second reaction The step (20) of introducing a pulse flow of the oxidative precursor gas, and then the step (22) of introducing a pulse flow of the purge gas are performed. It is then determined whether the deposited coating on the substrate has reached a predetermined thickness (24). If the coating has reached a predetermined thickness, the process ends (26). However, if the coating on the substrate has not reached the predetermined thickness, the ALD cycle of the pulsed flow of gas in sequence (16)-(22) is repeated until the predetermined thickness is reached.

  FIG. 4 illustrates a theoretical flow diagram of a typical CVD process (30). The processing starts with a step (32) of placing the substrate in the processing chamber and a step (44) of adjusting processing parameters including the substrate temperature, the processing chamber pressure, and the like. Thereafter, the CVD cycle starts the step (36) of introducing the inert gas into the processing chamber, then introduces the first reactive precursor gas flow (38) into the processing chamber, and then the first The step (40) of introducing the second precursor gas flow is started while maintaining the precursor gas flow. It is then determined whether the deposited coating on the substrate has reached a predetermined thickness (42). If the coating has reached a predetermined thickness, the process ends (44). However, if the thickness of the coating on the substrate has not reached the predetermined thickness, the CVD cycle of the pulsed flow of gas in sequence (36)-(40) is repeated until the predetermined thickness is reached.

In embodiments of the deposition process of the present invention, component halides including B, C, Si, Ge, N, P, As, S, and Se can be obtained by employing ALD, NLD, and CVD processes. Selected as the first group of reactive precursors to obtain a thin film. The second reactive precursor for ALD, NLD, and CVD processes is selected from component hydrides including B, C, Si, Ge, N, P, As, O, S, and Se. For example, representative compounds of these components include, but are not limited to, B ₂ H ₆ , CH ₄ , SiH ₄ , Si ₂ H ₆ , NH ₃ , N ₂ H ₄ , PH ₃ , AsH ₃ , H ₂ Selected from the group comprising O, H ₂ S, and H ₂ Se. In addition, another subclass of reactive precursors containing C and Si are represented by the general formula C _n X ′ _a X ″ _b , where X = F, Cl, Br, and I, and n, a, b are each Further subclasses of reactive precursors are represented by the general formula M _n H _a X _b , where M = C and Si, X = F , Cl, Br, I, and n, a, and b are integers). The preferred embodiments are employed to achieve various thin film processes. Various combinations of reactive precursors are described.

  Embodiments of the present invention are further illustrated by the following examples and associated drawings.

[Example 1]
(Deposition of silicon carbide (SiC) films by ALD, NLD, and CVD processes)
As explained in the background art, SiC is an important industrial ceramic with various applications. However, the thin film deposition process commonly performed for SiC is performed at temperatures exceeding 1000 ° C. Therefore, low temperature ALD and CVD SiC thin film processing are also highly desirable. Referring to FIG. 5A, the surface of the substrate is terminated with —OH groups that are highly receptive and reactive to Cl atoms. Then, in FIG. 5B, the chemisorption of carbon tetrachloride (CCl ₄ ) molecules on —OH terminated at the substrate surface with the formation of HCl as the product released into the gas phase is completed. At the end of the CCl ₄ chemisorption stage, the substrate is terminated with a Cl group by the formation of M-O-CCl ₃ (M: substrate surface atoms represented by squares in FIGS. 5A, B, C, and D) bonds. Is done. A pulse stream of purge gas (not shown) is then introduced for the process of wiping away excess CCl ₄ molecules near the substrate. Thereafter, a pulse flow of silane (SiH ₄ ) gas is introduced into the processing chamber. As shown in FIG. 5C, silane gas molecules react vigorously with the chemisorbed —O—CCl ₃ group under the treatment conditions, and form Si—C bonds with the elimination of HCl molecules. A purge gas pulse flow is employed to remove excess SiH ₄ molecules (not shown). The surface is terminated with H atoms and therefore accepts the next incoming pulsed flow of CCl ₄ as shown in FIG. 5D. The overall reaction of SiC deposition is as follows.
CCl ₄ + SiH ₄ → SiC + 4HCl Formula (1)

  FIG. 6A illustrates the change in Gibbs free energy with respect to temperature (ΔG) for the reaction as shown in equation (1) and a comparison with a conventional SiC CVD process. With respect to process temperature (even at room temperature), the high negative value of ΔG in FIG. 6A indicates that the feasibility of a low temperature SiC deposition process (ALD or CVD) as described in equation (1) is potentially quite high. Is shown.

  It is understood that the ALD process for SiC is not limited by process chamber pressure so that it can be performed over a wide range of process chamber pressure values, ranging from a few mT to over 760 Torr (1 atm) as described above. The Furthermore, the ALD treatment of SiC can be performed over a wide temperature range from room temperature to 1000 ° C., for example. Furthermore, the deposition chemistry as described in equation (1) is equally applicable to the corresponding CVD and NLD processes.

[Example 2]
Another thin film with industrial value is boron nitride (BN). BN thin films are currently deposited using BCl ₃ and ammonia (NH ₃ ) at high temperatures ranging from 700 to 1000 ° C. and beyond. FIG. 6B shows the change in Gibbs free energy (ΔG) versus temperature for the following chemical reaction.
B ₂ H ₆ + 2NF ₃ → 2BN + 6HF Formula (2)

  Compared to conventional BN processes (ALD or CVD), the fairly high value of ΔG for the temperature of the reaction in equation (2) indicates a high value for developing a low temperature BN thin layer deposition process. The BN deposition process can be performed at a pressure ranging from a few mT to 760 Torr and a temperature range of 20 ° C to 1000 ° C.

[Example 3]
(Deposition of C ₃ N ₄ thin film)
The deposition process and various applications of C ₃ N ₄ as a thin film material have not yet been fully explored. It is expected to be known as one of the supercured materials. Formation of a C ₃ N ₄ film by ALD, NLD, or CVD treatment can be performed using a halogenated carbon (for example, CF ₄ , CF ₄ , CF ₂ Cl ₂ or CCl ₄ ) and NH ₃ as the nitrogen source. The overall deposition chemistry (using CCl ₄ as the C source) is as follows.
3CF ₄ + 4NH ₃ → C ₃ N ₄ + 12HF Formula (3)

[Example 4]
(Deposition of Si ₃ N ₄ film)
Silicon nitride is an important industrial ceramic with anti-corrosion and wear-resistant materials with excellent optical properties. Silicon nitride is utilized in ball bearing coatings, electrical insulators, antireflection coatings, and the like. Formation of a thin film of Si ₃ N ₄ is performed in an ALD, NLD, or CVD process by employing silane (SiH ₄ ) as the silicon source and NF ₃ as the nitrogen source. The overall chemical reaction of Si ₃ N ₄ deposition is as follows.
3SiH ₄ + 4NF ₃ → Si ₃ N ₄ + 12HF Formula (4)

[Example 5]
(Deposition of SiXGe (1_X) film)
A thin film of SiXGe (1_X) can be deposited by ALD, NLD, or CVD methods by employing a Si hydride source and a Ge halide source. The pulsed flow of the first reactive gas comprises a mixture of SiCl ₄ and GeCl ₄ at a fixed ratio of a: b, forming a first monolayer comprising Si and Ge atoms terminated with Cl groups. The pulsed flow of the second reactive gas contains a mixture of GeH ₄ and SiH ₄ in the ratio a: b and a fixed value x is obtained. The overall reaction of the SiXGe (1_X) deposition process is described as follows (without balancing the equations):
(SiCl ₄ + GeCl ₄ ) + (SiH ₄ + GeH ₄ )
→ SiXGe (1_X) + HCl Formula (5)

The parentheses represent a group of pulse flows. An alternative method for adjusting the Si: Ge ratio is by employing either silane or germane gas as the second reactive precursor. The ALD treatment reaction is as follows.
(SiCl ₄ + GeCl ₄ ) + (SiH ₄ ) → SiXGe (1_X) + HCl Formula (6)

The treatment described in equation (6) leads to a silicon rich (X is greater value) phase. On the other hand, the adoption of GeH ₄ as the second reactive precursor leads to a Ge-rich phase as described in equation (7).
(SiCl ₄ + GeCl ₄ ) + (GeH ₄ ) → SiXGe (1_X) + HCl Formula (7)

  Furthermore, the Si: Ge ratio in the film SiXGe (1_X) (X value) can be changed by changing processing conditions such as the substrate temperature and pulse width.

[Example 6]
A three-element deposition of various materials such as SiCXN _y in an ALD, NLD, or CVD process produces SiH ₄ as the first reactive gas pulse flow and CCl in the second reactive gas pulse flow. ₄ (or CF ₄ is equally effective) and in combination with an NF ₃ mixture.
(SiH ₄ ) + (CCl ₄ + NF ₃ ) → SiCXN _y + HCl Formula (8)

Example 7
A four-element thin film can be deposited in an ALD, NLD, or CVD process by employing a mixture of hydrides in the first pulse stream and a mixture of halides in the second pulse stream. For example, a thin film of SiCXB _y NZ has a first reactive precursor gas mixture comprising silane (SiH ₄ ) and diborane (B ₂ H ₆ ) in the overall chemical reaction represented by formula (9), and four It can be deposited by using a second reactive precursor gas mixture comprising carbon chloride (CCl ₄ ) and nitrogen trifluoride (NF ₃ ).
(SiH ₄ + B ₂ H ₆ ) + (CCl ₄ + NF ₃ ) → SiCXB _y NZ + HCl + HF Formula (9)

[Example 8]
(Carbon thin film)
ALD, NLD, or CVD processing of thin films containing carbon is performed by employing a combination of various reactive precursors. The main reactive precursor combination is a di-chloro-halogen pulse stream represented by the general formula (CH ₂ X ₂ , X═F, Cl, Br, and I) shown in Formula (10). .
CH ₂ X ₂ + CH ₂ X ₂ → C + 2HX Formula (10)

Alternatively, CX ₄ (where X = F, Cl, Br, and I) as the first reactive precursor and CH ₄ as the second reactive precursor are It is equally suitable for depositing carbon thin films by chemical reaction.
CX ₄ + CH ₄ → C + 4HX Formula (11)

[Example 9]
(Reduction of halogenated carbon using hydro-silane and borane to form a single layer of carbon)
Silane (SiH ₄ ) and disilane (Si ₂ H ₆ ) are used as reducing agents in ALD processes for the deposition of metals such as tungsten in the temperature range of 200-400 ° C. by the following reactions: It has been known.
WF ₆ + SiH ₄ → W + SiF ₄ + 2HF + H ₂ formula (12)
WF ₆ + Si ₂ H ₆ → W + 2 SiHF ₃ + 2H ₂ formula (13)
References:
(A) J.A. W. Elam, C.I. E. Nelson, R.A. K. Grubbs and S.M. M.M. George: Thin Solid Films, volume 386, pp. 41 (2001)
(B) Journal of Vacuum Science & Technology (B), Volume 22, 4, pp. 181 1-1821 July 2004

Therefore, CCl ₄ is reduced to deposit thin films of carbon in various forms, such as amorphous and / or graphene, in the temperature range of 200-800 ° C. The overall reaction can be summarized as follows.
CCl ₄ + SiH ₄ → C + SiCl ₄ + 2H ₂ formula (14)
CCl ₄ + SiH ₄ → C + SiH ₂ Cl ₂ + 2HCl Formula (15)
CCl ₄ + Si ₂ H ₆ → C + Si ₂ H ₂ Cl ₄ + 3H ₂ formula (16)

The entire deposition reaction of carbon or graphene films can also be accelerated by using diborane (B ₂ H ₆ ) as a reducing agent instead of disilane.

  The foregoing description describes specific embodiments of the present invention but is not meant to be limited to those implementations. The claims that follow are intended to define the scope of the invention, including all equivalents thereof.

Claims (14)

A method for low temperature deposition of carbide, nitride, and mixed phase ceramic thin film coatings, comprising:
Determining a deposition chemistry that employs a combination of reactive precursors that affect the temperature required to deposit the thin film on the surface of the substrate;
Placing the substrate in a processing chamber;
Adjusting one or more process parameters including substrate temperature, process chamber pressure, and process chamber temperature;
Starting a deposition cycle; and determining whether the thin film coating has reached a predetermined thickness and repeating the deposition cycle until the predetermined thickness is reached;
The deposition is by atomic layer deposition (ALD), nanolayer deposition (NLD), or chemical vapor deposition (CVD);
The method wherein the combination of reactive precursors is selected based on the reactivity between each of the reactive precursors determined by a Gibbs free energy change (ΔG) with respect to the deposition temperature in the process chamber.   The thin film comprises boron carbide (B), nitrogen (N), nitride, silicon (Si) carbonitride, carbon (C), germanium (Ge), phosphorus (P), arsenic (As), oxygen (O ), Sulfur (S), and selenium (Se).   The method of claim 1, wherein a greater than negative value of Gibbs free energy in the reaction is a criterion for selection of the combination of reactive precursors.   The method of claim 1, wherein for the ALD and CVD processes, the reactive precursor comprising various components is usually classified by either hydride or halide.   The first component from the hydride reacts with the second component from the halide that affects the intensive deposition reaction such that the substantial Gibbs free energy (ΔG) in the reaction is negative. The method according to claim 4. The first component is selected from the group of hydrides comprising B, C, N, Si, Ge, P, O, As, S, and Se;
6. The method of claim 5, wherein the second component is selected from the group of halides comprising F, Cl, Br, or I. The method of claim 6, wherein nitrogen trifluoride (NF ₃ ) is employed as a nitrogen source in combination with B ₂ H ₆ as a boron precursor. The ALD treatment is selected from Si ₂ H ₆ , SiH ₄ , SiH ₃ X, SiH ₂ X ₂ , and SiHX ₃ (wherein X is independently F, Cl, Br, or I). Silicon chloride based on treatment with a silicon source,
Carbon _{source, CX 4, CX 3 H,} CX 2 H 2, and _CX 3 H (wherein, F X are each independently, Cl, Br, or a is I) is selected from, in claim 6 The method described.   The method of claim 6 wherein the mixed carbon halide is a carbon source. The mixture halocarbon is represented by the general formula C _n X _a Z _b chloro - fluoro - is carbon, A method according to claim 9.
(In the formula, n, a, and b are integers, and X and Z are halogens.) The method of claim 6, wherein the halide further comprises a mixed halide subclass of C and Si represented by the general formula M _n H _a X _b .
(Wherein M is C and Si, X is independently F, Cl, Br, or I, and n, a, and b are integers.)   The method of claim 1, wherein the process chamber pressure ranges from atmospheric pressure (760 Torr) to as low as 1 milliTorr (mT). Depositing a silicon carbide film by terminating the surface of the substrate with —OH groups that are highly receptive and reactive to Cl atoms;
Introducing carbon tetrachloride (CCl ₄ ) molecules to form —O—CCl ₃ groups for chemisorption onto the surface of the substrate terminated with —OH groups;
Sending a purge gas into the processing chamber to wipe off excess CCl ₄ molecules near the substrate;
A process in which silane (SiH ₄ ) gas to be fed is introduced into the processing chamber and reacts with the chemisorbed —O—CCl ₃ groups to form Si—C bonds;
Further comprising removing excess SiH ₄ molecules leaving the surface of the substrate having hydrogen (H) terminations that receive the purge gas flow and receive a pulsed flow of CCl ₄ being pumped;
The method of claim 1, wherein the overall reaction of the SiC deposition is CCl ₄ + SiH ₄ → SiC + 4HCl.   The film | membrane manufactured by the method of any one of Claims 1-13.

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