KR20030027392A - Method for forming a titanium silicide thin film - Google Patents

Abstract

PURPOSE: A method for fabricating a titanium silicide thin film is provided to easily form a titanium silicide layer having low resistivity at a relatively low temperature by cyclically supplying reaction gas and purge gas as inert gas, and to shorten a time interval for depositing a layer by forming the layer composed of a single atom layer or several atom layers. CONSTITUTION: TiCl4 gas as a reaction material with a substrate is introduced. A part of the reaction material is chemically absorbed to the substrate. The reaction material not absorbed to the substrate is eliminated. SiH4 gas or Si2H6 gas is introduced to the substrate to form a solid material containing TiSi2 on the substrate by exchanging a ligand with the absorbed reaction material. A reaction byproduct generated by the exchange of the ligand is eliminated. The abovementioned processes are repeated at least once to transform the solid material into a TiSi2 thin film.

Description

Method for forming a titanium silicide thin film}

The present invention relates to a method for forming a titanium silicide thin film, and more particularly, to a method of forming a titanium silicide thin film by alternately supplying a TiCl ₄ gas and a silicon source gas as a reaction material.

BACKGROUND With the rapid spread of information media such as computers, semiconductor devices are also rapidly developing. In terms of its function, the semiconductor device is required to operate at a high speed and to have a large storage capacity. In response to these demands, manufacturing techniques have been developed in the direction of improving the degree of integration, reliability, response speed, and the like of the semiconductor device.

In the semiconductor device, the line width of the gate electrode of the transistor is reduced because each device is highly integrated, thereby increasing the resistance of the gate electrode. In addition, the junctions of the impurity regions of the transistor, that is, the source and the drain, are becoming shallower. Such shallow junctions increase the resistance of the source and the drain. Therefore, in order to reduce the resistance, a self-aligned silicide (SALICIDE) process is performed by depositing a refractory metal on the gate electrode, the source, and the drain, and then silicideing it. The silicide film should be formed to have a low specific resistance. The silicide film that satisfies these conditions is, for example, a titanium silicide film (hereinafter, TiSi ₂ film). Since the titanium silicide film also has a low contact resistance, it is widely used as a metal film for forming an ohmic contact.

The TiSi ₂ film doped with a desired impurity on a silicon substrate, and performing the chemical vapor deposition method on the top after the formation of a film of titanium (Ti) by the (CVD) heat treatment step it can be formed by a TiSi ₂ film. However, according to the method, defects such as a decrease in the dopant of the lower layer or a current leakage at the junction located under the contact may occur during the heat treatment. In order to prevent such defects, the TiSi ₂ film itself may be deposited by a chemical vapor deposition method. In this case, however, since the deposition temperature for depositing the TiSi ₂ film is about 650 ° C. to 800 ° C., there is a problem that the dopant profile of the lower film is changed and a recess of Si occurs.

Therefore, recently, an atomic layer deposition (ALD) method or a cyclic chemical vapor deposition method has been proposed as a technique to replace the chemical vapor deposition.

Here, referring to Table 1 below, let's consider thermodynamically the formation reaction of the TiSi ₂ film. The pressure at this time represents a reaction state under 1 atmosphere (760 Torr).

Temperature (℃) Pressure (ATM) Reactant TiCl ₄ + SiH ₄ 326 One 0.72Si + 0.99TiCl3 526 One 0.42TiSi + 0.47TiCl3 TiCl ₄ + Si2H ₆ 326 One 1.72Si + 0.99TiCl3 426 One 1.35Si + 0.21TiSi + 0.78TiCl3 526 One 0.96 TiSi 626 One 0.04Si + 0.94TiSi TiCl ₄ + 2Si ₂ H ₆ + 100H ₂ 326 One 1.73Si + 0.07TiSi + 0.32TiCl3 426 One 0.92 TiSi

According to Table 1, in order to obtain TiSi without precipitation of the chloride of TiCl _3, a TiSi film may be deposited at a temperature of about 430 ° C. or higher in a three-way reaction of TiCl _4, Si ₂ H _{6, and} H ₂ . However, the reaction is carried out at 1 atm (760 Torr), and when the process is carried out by the CVD method at 0.3 to 10 Torr, which is the pressure that actually proceeds to the process, the process may be performed at a temperature of about 650 ° C. or more.

An example of a method of forming the titanium silicide film using the atomic layer stacking is disclosed in Korean Patent No. 97-30215. According to the disclosed method, the titanium silicide film can be formed by atomic layer deposition using the TiCl ₄ gas and SiH ₄ gas. However, the SiH ₄ gas is self decomposed and deposited on a silicon (Si) film when the substrate temperature is about 500 ° C. or more. Therefore, in order to perform complete ligand exchange with the reaction material adsorbed by TiCl ₄ gas, an atomic layer deposition process should be performed at a temperature of 500 ° C. or lower. However, since the reaction of titanium (Ti) and silicon (Si) hardly occurs at a temperature below 500 ° C., since deposition of the TiSi ₂ film is hardly performed, it is difficult to form a film substantially. In addition, when the film is formed by the atomic layer stacking method formed of monoatomic layers, the deposition rate of the film is slow.

Therefore, there is a need for a new method of forming a titanium silicide film that can be carried out at a low temperature, has a low specific resistance, and is easy to implement excellent step coverage.

Accordingly, an object of the present invention is to provide a method of forming a titanium silicide thin film at a low temperature.

1A and 1D are cross-sectional views illustrating a method of forming a titanium silicide thin film according to the method of the present invention.

FIG. 2 is a timing diagram in which gases flow when a titanium silicide thin film is formed in a first embodiment of the present invention.

3 is a timing diagram in which gases flow when a titanium silicide thin film is formed according to a second embodiment of the present invention.

4 is a graph showing the results of confirming the thin film formed by the method of the present invention by XRD.

5 is a graph showing the results of confirming the components of the thin film formed according to the method of the present invention.

6A through 6B are cross-sectional views illustrating a method of forming a titanium silicide film in a contact hole.

7A to 7C show that a titanium silicide film is formed in a transistor.

In order to achieve the above object, the present invention comprises the steps of a) introducing a TiCl ₄ gas as a reaction material with the substrate and adsorbing on the substrate, and b) chemically adsorbing a portion of the reaction material on the substrate. C) removing non-adsorbed reactant from the reactant on the substrate, and d) introducing one of SiH ₄ and Si ₂ H ₆ gas onto the substrate to exchange ligand with the adsorbed reactant. Forming a solid material containing TiSi ₂ on the substrate, e) removing the reaction by-products generated by the ligand exchange, and f) repeating the a) to e) at least once. And forming the material into a TiSi ₂ thin film.

In order to achieve the above object, the present invention provides a method for preparing a substrate comprising: a) supplying hydrogen gas and an inert gas onto a substrate, b) introducing TiCl ₄ gas as a reaction material with the substrate, c) a part of the reaction material. Chemically adsorbing on the substrate, d) stopping supply of the TiCl ₄ gas to remove reactants that do not adsorb on the substrate from the reactants, e) SiH _4, Si ₂ H on the substrate Introducing one of _six gases to form a solid material containing TiSi ₂ on the substrate by ligand exchange with the adsorbed reactant, f) a SiH ₄ or Si ₂ H ₆ gas introduced on the substrate steps to stop the supply of the to remove the reaction by-products generated by the ligand exchange, and g) formed with a step of forming the solid material by the a) - f) repeating at least once the TiSi ₂ films May.

According to the method of the present invention, TiSi ₂ can be formed by monoatomic layers or several atomic layers by sequentially supplying the reaction gas and an inert gas, which is a purge gas, cyclically. Therefore, it is possible to easily form a thin film having a low specific resistance at a relatively low temperature at a high deposition rate. In particular, since the gas can be activated by a remote plasma method, process variables due to plasma formation can be excluded.

Hereinafter, a method of forming a titanium silicide thin film of the present invention will be described in detail with reference to the accompanying drawings.

1A to 1D are cross-sectional views illustrating a method of forming a titanium silicide thin film according to the method of the present invention.

First embodiment

FIG. 2 is a timing diagram in which gases flow when a titanium silicide thin film is formed according to a first embodiment described below.

First, the substrate 10 made of a silicon material is placed in the chamber. The pressure in the chamber is carried out at a constant pressure in the range of 0.3 to 10 Torr. The temperature of the substrate is maintained at a temperature of 650 ℃ or less. Preferably, the process is carried out under a pressure of 0.3 Torr to 5 Torr and a temperature of 580 to 600 ° C.

Subsequently, hydrogen gas (H ₂ ) is introduced into the chamber as an atmospheric gas. The hydrogen gas is continuously supplied into the chamber until the process for forming the thin film is completed. (S10) The hydrogen gas is inhibited from disintegrating SiH ₄ or Si ₂ H ₆ into a Si film to form TiSi. Promote the reaction formed by ₂ . Therefore, the titanium silicide layer (TiSi ₂ layer) may be formed at a low temperature.

Referring to FIG. 1A, TiCl ₄ gas is introduced as a reaction material 12 onto a substrate lying in the chamber. (S12) Accordingly, a portion of the reaction material 12 is chemically adsorbed onto the substrate 10. do.

Referring to FIG. 1B, reactants that are not chemically adsorbed among the reactants 12 are removed from the substrate 10. Removal of the reactive material 12 is performed by introducing an inert gas into the chamber (S14). The inert gas includes argon (Ar) or nitrogen (N ₂ ).

Referring to FIG. 1C, SiH ₄ or Si ₂ H ₆ gas is introduced as a silicon source gas onto the substrate 10. (S16) The SiH ₄ or Si ₂ H ₆ gas is a reactant adsorbed on the substrate. By performing ligand exchange in reaction with, a solid material 14 containing TiSi ₂ is formed on the substrate. In this case, the SiH ₄ or Si ₂ H ₆ gas may be activated by using a remote plasma method. When the activated SiH ₄ or Si ₂ H ₆ gas is used, the reaction with the reactant is further promoted so that TiSi ₂ is contained even at a temperature at which silicon does not self-decompose from the gas (eg, 580 ° C. or lower). Material 14 may be formed. The solid material formed at this time is formed of TiSi ₂ of several atomic layers as well as monoatomic layers.

Referring to FIG. 1D, the reaction by-products 16 generated by the ligand exchange are removed. (S18) The reaction by-products 18 are pumped out by the inert gas introduced into the chamber. The inert gas includes argon (Ar) or nitrogen (N ₂ ).

By repeatedly performing the above-described series of processes, a TiSi ₂ film having a desired thickness can be formed.

Second embodiment

It will be described a method of forming the titanium silicide thin film by a method different from the above-described method.

FIG. 3 is a timing diagram in which gases flow in forming a titanium silicide thin film according to a second embodiment described below.

First, as described above, a substrate made of a silicon material is placed in a chamber. The pressure in the chamber is carried out at a constant pressure in the range of 0.3 to 10 Torr. The temperature of the substrate is maintained at a temperature of 650 ℃ or less. Subsequently, hydrogen gas (H ₂ ) is introduced into the chamber as an atmospheric gas. At the same time, an inert gas is introduced. The inert gas may be argon or nitrogen. (S30) The hydrogen gas and the inert gas are continuously supplied into the chamber until the process for depositing the TiSi ₂ film is completed.

TiCl ₄ gas is introduced as a reactant on the substrate 10 (S32). Thus, a part of the reactant 12 is chemically adsorbed on the substrate. At this time, the inert gas supplied on the substrate serves as a carrier gas for smoothly transporting the TiCl ₄ gas.

Subsequently, the reaction material 12 which is not chemically adsorbed in the reaction material is removed from the substrate. Removal of the reactant material 12 may be performed by introducing an inert gas into the chamber. (S34) Thus, by stopping the supply of the TiCl ₄ gas, only the inert gas and the hydrogen gas are supplied into the chamber. Excess TiCl ₄ gas that is not adsorbed on the substrate 10 may be purged.

SiH ₄ or Si ₂ H ₆ gas is introduced as a silicon source gas onto the substrate on which the reactant 12 is adsorbed. (S36) The SiH ₄ or Si ₂ H ₆ gas is adsorbed onto the substrate 10. By performing ligand exchange by reacting with the reaction material 12, a solid material 14 containing TiSi ₂ is formed on the substrate 10. The solid material formed at this time is formed of TiSi ₂ of several atomic layers as well as monoatomic layers. The SiH ₄ or Si ₂ H ₆ gas may be activated by using a remote plasma method. At this time, the inert gas continuously supplied serves as a carrier gas for smoothly transporting the SiH ₄ or Si ₂ H ₆ gas.

Then, the supply of the SiH ₄ or Si ₂ H ₆ gas is stopped, and only the inert gas and the hydrogen gas are supplied into the chamber to remove the reaction by-products generated by the ligand exchange. (S38)

By repeatedly performing the above-described series of processes, a TiSi ₂ film having a desired thickness can be formed.

Figure 4 is a graph showing the result of confirming the thin film formed by the method of the present invention by XRD. Specifically, the TiSi ₂ film was formed by the method according to the second embodiment, wherein the temperature of the substrate proceeded to 585 ° C.

As a result of crystallinity analysis of the film formed by the above method, most of the C54-TiSi ₂ component was detected. The film having C54-TiSi ₂ is a film obtained when the process is performed at about 800 ° C. by a conventional deposition process. However, by using the method of sequentially supplying the reaction gas and the inert gas, which is a purge gas, by cyclically, the TiSi ₂ film can be formed even at a lower temperature than the conventional deposition process. In addition, the film formed at this time was confirmed that the C54-TiSi ₂ (311 direction) appears as a peak (peak).

5 is a graph showing the results of confirming the components of the thin film formed according to the method of the present invention.

Specifically, FIG. 5 shows a structure in which a silicon oxide film is formed on a silicon substrate, and a TiSix film is formed on the silicon oxide film by the method according to the second embodiment, and is sputtered downward from an upper surface of the structure. It is a graph showing the component analysis of the membrane while etching in a manner (sputter etch). The temperature of the substrate at the time of forming the TiSix film proceeded to 585 ° C.

The X axis of the graph is sputter time, corresponding to the film shown below the X axis. The graph shows the atomic distribution in each film, where A represents a silicon (Si) component, B represents a titanium (Ti) component, and C represents an oxygen (O) component.

At this time, as a result of component analysis of the TiSix film, Ti: Si = 1: 2.09 shows that the desired TiSi2 film was obtained successfully. It can also be seen that Cl component is not detected.

Hereinafter, a method of forming a titanium silicide thin film in a semiconductor device will be described in detail.

6A to 6B are cross-sectional views illustrating a method of forming a titanium silicide film on a bottom of a contact hole.

Referring to FIG. 6A, an insulating layer 34 is formed on the silicon substrate 30, and then a contact hole 36 is formed in a predetermined portion of the insulating layer 34 to expose the surface of the substrate. A junction 32 is formed under the substrate exposed on the bottom of the contact hole 36.

Referring to FIG. 6B, the titanium silicide thin film 38 is formed on the silicon substrate exposed to the bottom surface of the contact hole 36 by the above-described method.

That is, hydrogen gas is supplied onto the substrate. The hydrogen gas is continuously introduced during the process. At this time, the temperature of the substrate is maintained at 580 to 630 ° C. Next, TiCl ₄ gas is introduced as a reaction material to chemically adsorb a portion of the reaction material on the silicon substrate exposed on the bottom of the contact hole. An inert gas is then introduced to remove reactants that do not adsorb in the reactants. A gas of any one of SiH _{4 and} Si ₂ H ₆ is introduced to form a solid material containing TiSi ₂ on the silicon substrate exposed to the bottom of the contact hole by ligand exchange with the adsorbed reactant. An inert gas is then introduced to remove reaction byproducts. By repeating the above series of processes, a titanium silicide film having a desired thickness is formed on the silicon substrate exposed on the bottom of the contact hole. At this time, the inert gas may be continuously introduced during the process to be used as a carrier gas and a purge gas of the reaction gas.

As described above, the titanium silicide thin film has selective deposition characteristics. Specifically, the thin titanium silicide thin film has a characteristic that a film is well formed by reaction on a silicon (Si) surface, but a film is not formed on the surface of a silicon oxide film (SiO ₂ ) or a silicon nitride film (SiN). Accordingly, the titanium silicide thin film is selectively formed only on the bottom surface of the contact hole exposing the silicon substrate.

According to the above-described method, since the titanium silicide film is formed at a relatively low temperature (650 ° C. or less), defects such as junction leakage and dopant reduction can be reduced. In addition, an ohmic contact may be realized by forming a low-resistance titanium silicide layer on the bottom of the contact hole.

7A to 7C show that a titanium silicide film is formed in a transistor.

Referring to FIG. 7A, a gate oxide layer pattern 52 and a polysilicon layer pattern 54 are formed on the silicon substrate 50. Subsequently, the source and drain regions 58 are formed by implanting impurities under the surface of the substrate using the polysilicon layer pattern 54 as an ion implantation mask.

Referring to FIG. 7B, a thin silicon film 60 is selectively formed only on the upper surface of the polysilicon film pattern 54. This is used as a base film for selectively forming a titanium silicide film only on the polysilicon film pattern 54 provided as a gate electrode of the transistor by a subsequent process.

Referring to FIG. 7C, an upper surface of the source and drain regions 58 formed under the surface of the silicon substrate 50 may be selectively formed on the polysilicon layer pattern 54 by performing the method described above in the result. The titanium silicide thin film 60 is formed. When the process is performed by the above method, the alternatingly supplied reactant gas (TiCl ₄ ) and silicon source gas (SiH ₄ or Si ₂ H ₆ ) are provided under the silicon substrate surface, and the upper surface of the source and drain regions; It selectively adsorbs on the polysilicon pattern on which the silicon film is formed and reacts by ligand exchange. Therefore, the titanium silicide thin film is selectively formed only on the top surface of the source, drain region, and the polysilicon pattern provided below the silicon substrate surface. The titanium silicide thin film formed on the upper surfaces of the source and drain regions may have a thickness smaller than that of the gate oxide layer so that a short with the gate electrode does not occur. Therefore, in general, the formed titanium silicide thin film is formed to have a thin thickness of about 100 to 300Å. The thickness of the film is controlled by controlling the number of alternation of the reaction gas (TiCl ₄ ) and the silicon source gas (SiH ₄ or Si ₂ H ₆ ).

In addition to the above-described method, a thin titanium silicide thin film may be primarily formed on the upper surface of the source and drain regions, and secondly, the titanium silicide thin film may be thickly formed on the gate electrode.

Therefore, the titanium silicide film has an effect of reducing the resistance in the gate electrode and the source drain region, thereby improving the characteristics of the transistor. In addition, according to the above-described method, since the titanium silicide film is formed at a relatively low temperature (650 ° C. or less), thermal defects that may occur during deposition of the film can be minimized.

As described above, according to the present invention, a titanium silicide film having a low specific resistance can be easily formed at a relatively low temperature by cyclically supplying a reactive gas and an inert gas that is a purge gas. In addition, since the film is formed of a monoatomic layer or several atomic layers, the deposition time of the film is shortened. In addition, by supplying the silicon source gas by activating the remote plasma method, the titanium silicide thin film may be formed even at a temperature at which the silicon source does not decompose itself.

As described above, although described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified without departing from the spirit and scope of the invention described in the claims below. And can be changed.

Claims (18)

a) introducing TiCl ₄ gas as a reactant with the substrate; b) chemically adsorbing a portion of said reactant on a substrate; c) removing reactants that do not adsorb onto the substrate among the reactants; d) introducing one of SiH ₄ and Si ₂ H ₆ gas onto the substrate to form a solid material containing TiSi ₂ on the substrate by ligand exchange with the adsorbed reactant; e) removing the reaction byproducts produced by the ligand exchange; And f) repeating the steps a) to e) at least once to form the solid material into a TiSi ₂ thin film. The method of claim 1, wherein the H ₂ gas is continuously introduced during the steps a) to e). The method of claim 1, wherein the steps a) to e) are performed under a temperature of 650 ° C. or less. The method of claim 1, wherein the steps a) to e) are performed under a pressure of 0.3 to 10 Torr. The method of claim 1, wherein the chemically non-adsorbed reactant is removed using an inert gas. The method of claim 1, wherein the reaction by-products generated by the ligand exchange are removed using an inert gas. The method of claim 4, wherein the inert gas is Ar or N ₂ . The method of claim 8, wherein the SiH ₄ or Si ₂ H ₆ gas is activated by a remote plasma method. a) supplying hydrogen gas and inert gas onto the substrate; b) introducing TiCl ₄ gas as a reactant with the substrate; c) chemically adsorbing a portion of said reactant on a substrate; d) stopping supply of the TiCl ₄ gas to remove reactants that do not adsorb on the substrate among the reactants; e) introducing a gas of any one of SiH _{4 and} Si ₂ H ₆ onto the substrate to form a solid material containing TiSi ₂ on the substrate by ligand exchange with the adsorbed reactant; f) stopping supply of SiH ₄ or Si ₂ H ₆ gas introduced on the substrate to remove reaction byproducts generated by ligand exchange; And g) repeating steps a) to f) at least once to form the solid material into a TiSi ₂ thin film. 10. The method of claim 9, wherein a) to g) is performed at a temperature of 650 ° C. or less. 10. The method of claim 9, wherein the inert gas is Ar or N ₂ . The method of claim 9, wherein the SiH ₄ or Si ₂ H ₆ gas is activated by a remote plasma method. a) forming an insulating layer on the silicon substrate; b) etching a predetermined portion of the insulating layer to form a contact hole exposing a surface of the silicon substrate on a bottom surface thereof; c) introducing TiCl ₄ gas as a reactant into the insulating layer and the contact hole; d) chemically adsorbing a portion of the reactant material on a silicon substrate exposed at the bottom of the contact hole; e) supplying an inert gas to the resultant to remove reactants that are not chemically adsorbed in the reactants; f) selectively introducing TiSi ₂ on the silicon substrate exposed to the bottom of the contact hole by ligand exchange by introducing a gas of any one of SiH _{4 and} Si ₂ H ₆ into the insulating layer and the contact hole; Forming a solid material containing; g) feeding the resultant inert gas to remove reaction by-products generated by ligand exchange; And h) repeating the steps a) to g) at least once to selectively form a TiSi ₂ thin film on the bottom of the contact hole. The method of claim 13, wherein the H ₂ gas and the inert gas are continuously introduced during the steps a) to g). The method of claim 13, wherein the a) to g) step is carried out at a temperature of less than 650 ℃. a) forming a gate structure on which a silicon oxide pattern and a polysilicon pattern are stacked on a silicon substrate; b) forming source and drain regions below the silicon substrate surface using the gate structure as a mask; c) selectively forming a silicon film on an upper surface of the gate structure; d) introducing TiCl ₄ gas as a reactant material onto a substrate having the gate structure, source and drain regions; e) chemically adsorbing a portion of the reactant material on the silicon film, source and drain regions; f) supplying an inert gas to the resultant to remove reactants that are not chemically adsorbed in the reactants; g) introducing a gas of any one of SiH _{4 and} Si ₂ H ₆ onto a substrate on which the reactant is adsorbed, thereby selectively exchanging the adsorbed reactant with the adsorbent reactant to the upper surface of the gate structure, source and drain regions; Forming a solid material containing TiSi ₂ ; h) feeding the resultant inert gas to remove reaction by-products generated by ligand exchange; And i) repeating steps a) to h) at least once to selectively form a TiSi ₂ thin film on top surfaces of the gate structure, source and drain regions. The method of claim 16, wherein the H ₂ gas and the inert gas are continuously introduced during the steps a) to g). The method of claim 16, wherein the steps a) to g) are performed under a temperature of 650 ° C. or less.