KR100280102B1 - Method of forming single crystal cobalt disulfide contact using cobalt-carbon alloy thin film - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a single crystal cobalt disilicide using a cobalt-carbon alloy thin film in forming a contact in a MOS transistor for use in a highly integrated circuit semiconductor device. Cobalt-carbon alloy in forming single crystal CoSi ₂ layer using silicide process to reduce contact resistance and specific resistance of source / drain and poly-silicon gate electrode of semiconductor device The thin film is deposited at a substrate temperature of 350 ° C. or lower by a co-sputtering method, or a cobalt-carbon alloy thin film is deposited at a substrate temperature of about 350 ° C. by chemical vapor deposition, and then without using a protective layer. Combination of Cobalt and Silicon on Silicon Surface with (100) Orientation by Subsequent Rapid Thermal Treatment The CoSi to a method of forming a _second layer directly.

According to the present invention, the intermediate layer deposition and the protection layer deposition processes used in the conventional method can be omitted, thereby simplifying the silicide formation process and growing the CoSi ₂ layer of the epitaxial layer closer to the single crystal or the single crystal than the conventional method. It has excellent step coverage and can be used to manufacture ultra-semiconductor integrated circuits of more than giga DRAM grade.

Description

Method of forming single crystal cobalt disilicide contact using cobalt-carbon alloy thin film

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to contact formation of ultra-fine semiconductor devices for ultra large scale integration (ULSI) of Giga DRAM or higher grade. The present invention relates to a method for forming single crystal cobalt silicide in a salicide process, which is a method of forming a contact silicide formed by reaction of a polycide with a high melting point metal and silicon in a source / drain.

It is known that the method of forming a contact in the memory device of the conventional giga DRAM class or more has many technical difficulties, and the source, in the microstructure of the highly integrated semiconductor device according to the contents of Korean Patent Application Nos. A salicide process is shown to reduce the resistance of the drain and gate electrodes. Another prior art is the use of an intermediate layer between cobalt and silicon substrates (see M. L.A. Dass, Applied Physics Letter 1991, Vol. 58, 1308). In the salicide process performed to reduce the resistance of the source / drain and the polysilicon gate electrode, a single crystal cobalt disilicide formation method of the source / drain is shown in FIG. 6, which is briefly summarized as follows.

The temperature of the silicon substrate 1 is maintained at room temperature, and the source / drain and the gate are formed. Then, the titanium 6 is deposited to a thickness of 20 kPa, and the cobalt 4 is sputtered to a thickness of 150 kPa using a sputtering and vacuum evaporator. after the sputtering deposition, and reactive of TiN (5) with a protective layer to prevent the oxidation and aggregation of the heat treatment after vacuum evaporation deposited at 200~400 ℃ by (reactive evaporation) method by heat treatment at more than 700 ℃ of the single crystal CoSi ₂ Form layer 7.

As a subsequent process, unreacted cobalt (4), titanium (6) and TiN (5) are etched and then secondary heat treated at a high temperature of 800 ° C. or higher to finally form silicides having low contact resistance and specific resistance.

On the other hand, in addition to titanium (6), a method such as tongue using a chemical oxide film having a composition of SiOx such as a so-called 'Shiraki oxide film' formed on a silicon wafer during chemical cleaning of sulfuric acid and hydrochloric acid (RT Tung, Applied Physics Letter 1996, Vol. 68 (See page 3461) and by Ogino using germanium (see T. Ogino, Applied Surface Science, 1997, Vol 117/118, 280), but this also requires multi-step deposition and a thickness of 500Å. It is reported that it is very difficult to form a single crystal CoSi ₂ layer 7 to a degree. And Dormans et al. (See J. Crystal Growth, 1991, Vol. 114, 364) describe the possibility of cobalt deposition at 300-600 ° C by chemical vapor deposition, but did not suggest a new salicide process. .

The sheet resistance of the silicide thin film obtained by the conventional salicide process method mentioned above is about 5-10 ohms / square. However, these conventional methods require complicated apparatuses and expensive equipment, such as the deposition and heat treatment of the intermediate layer and the protective layer in one reactor by sputtering and vacuum evaporation at room temperature to 400 ° C., and the oxidation and agglomeration of metals. It is difficult to obtain a uniform thin film because it is not only necessary to have a protective layer to prevent), but also has a poor coating property in ultra-fine devices, and a method of using titanium (6), which is most widely used as an intermediate layer, is an oxide film (field oxide and space). oxide) (2) During the heat treatment of the edge (pin) is formed a pin-hole (pin-hole), causing a leakage current resulting in the deterioration of the characteristics of the device and has the disadvantage of poor reproducibility.

On the other hand, the biggest disadvantage of using the conventional method is that the cobalt (4) easily diffuses into the silicon substrate (1) through the grain boundary of the polycrystalline CoSi ₂ layer (7), so that the CoSi ₂ layer (7) and silicon In the case where the interface of the substrate 1 is not uniform and severe, a silicide layer is formed inside the junction layer of the source / drain, thereby degrading the characteristics of the device. Next-generation MOS transistors with small device size must form a single crystal CoSi ₂ layer 7 having a uniform interface, which is also essential in the process of forming source / drain regions of very shallow junctions.

In general, it is known that the silicon substrate 1 and the CoSi ₂ layer 7 in the (100) orientation have the same surface as the (110) and (221) in addition to the matching surface of the (100) orientation. because the interface energy is higher than the other side is very difficult to form a uniform interface with the single crystal CoSi ₂ layer 7. In order to have a uniform interface, it is preferable to form a single crystal CoSi ₂ layer 7 having a matching surface of the silicon substrate 1 and the (100) orientation as much as possible. In order to form the single crystal CoSi ₂ layer 7 The surface of the silicon substrate 1 should be in a very clean state, and it is an important parameter that cobalt suppresses diffusion into the silicon substrate 1. In the case of fast diffusion of cobalt, phases having compositions such as Co ₂ Si, CoSi, and CoSi ₂ are continuously formed during the heat treatment process, and finally polycrystals are formed, and the interfacial energy is lower than that of the interface having a high (100) interface. It is difficult to form the CoSi ₂ layer 7 having a uniform interface because an interface having another matching surface having a structure is easily formed. Therefore, in order to suppress the diffusion of cobalt, it has conventionally been a main method to form an intermediate layer between the cobalt 4 and the silicon substrate 1 so that the diffusion of cobalt is suppressed by the intermediate layer. However, the method of using the intermediate layer has various problems as mentioned above.

The present invention uses a cobalt-carbon alloy thin film (8) without depositing cobalt (4) on a silicon substrate (1) to form a CoSi ₂ layer (7), without using an intermediate layer such as TiN (5). It was. Donaton (see RA Donaton, Applied Physics Letter, pp. 70 (1997), 1266) reports that trace amounts of carbon inhibit the diffusion of cobalt. The present invention uses the cobalt-carbon alloy thin film (8) by chemical vapor deposition, vacuum evaporator and sputtering to suppress the diffusion of cobalt (4) to the silicon substrate (1) to form a single crystal CoSi ₂ layer (7) It was.

The present invention is to deposit a cobalt-carbon alloy thin film (8) on the (100) orientation silicon substrate (1) by the method mentioned above, and then to heat-treat the single crystal having a silicon-like (100) orientation by reaction with the silicon of the substrate. By forming a CoSi ₂ layer 7 of an epitaxial layer close to a single crystal or a single crystal, only the cobalt-carbon alloy thin film 8 is carried out in a reaction chamber without performing multi-step deposition using a metal and an intermediate layer. By depositing and performing heat treatment process, the contact forming process can be simplified and low resistance can be realized.

1 is a cobalt-carbon alloy thin film deposited on a silicon substrate by using a cyclopentadienyl cobalt dicarbonyl [C ₅ H ₅ Co (CO) ₂ ], which is a cobalt metal organic compound, at a silicon substrate temperature of 350 ° C. Is an X-ray diffraction pattern graph showing an amorphous state of.

FIG. 2 is a spectral graph of an Auger electrom spectroscopy (AES) showing the compositional distribution of the cobalt-carbon alloy thin film of FIG.

3 is a X-ray diffraction pattern graph of the silicon surface after depositing cobalt on a silicon substrate and then depositing Ti as a protective layer and heat-treating at 800 ° C.

4 is an X-ray diffraction pattern graph of a single crystal silicon substrate surface source / drain after cobalt is deposited on a silicon substrate and then heat treated at 600 ° C. to 800 ° C. without using a protective layer.

FIG. 5 is a graph showing a composition distribution of a silicon surface after heat treatment at 800 ° C. without using a protective layer on a silicon substrate using an Ohze electron spectrometer.

FIG. 6 is a cross-sectional structural view of a MOS transistor schematically showing a method of forming a single crystal cobalt disilicide by sputtering or evaporator between silicon and a metal in a source / drain and a polysilicon gate; FIG.

(a) shows a spacer in which a source / drain and a polysilicon gate of an MOS transistor are formed of an oxide film or a nitride film.

(b) is a state in which a titanium layer is deposited on a silicon substrate as an intermediate layer by sputtering and vacuum evaporator.

(c) deposits cobalt (Co) on an intermediate layer on which titanium (Ti) is deposited on a silicon substrate by sputtering or vacuum evaporator, and then deposits TiN, a protective layer for preventing oxidation and agglomeration of cobalt. It is a state.

(d) is a state in which a single crystal CoSi ₂ layer is formed by heat treatment at 700 ° C. or higher.

(e) is the state which etched unreacted titanium (Ti), cobalt (Co), and TiN.

7 is a schematic view of a CoSi ₂ layer formation process by the cobalt-carbon alloy thin film of the present invention.

(a) shows a state where the source / drain and the polysilicon gate of the MOS transistor are formed.

(b) is a state in which a cobalt-carbon alloy thin film is deposited on a silicon substrate in the (100) orientation at about 350 ° C. by chemical vapor deposition.

(c) is a state in which a single crystal CoSi ₂ layer is formed on a source / drain by a cobalt and silicide formation reaction in a silicon substrate and a cobalt-carbon alloy thin film by a heat treatment of 700 ° C. or higher.

(d) is a state which etched the unreacted cobalt-carbon alloy thin film.

<Description of reference numerals for the main parts of the drawings>

1: silicon substrate 2: oxide film

3: polysilicon gate 4: cobalt (Co)

5: TiN 6: Titanium (Ti)

7: CoSi ₂ layer 8: Cobalt-carbon alloy thin film

The present invention can simplify the CoSi _two- layer contact process, which can be directly contacted at the source / drain and gate of the MOS transistor using the cobalt-carbon alloy thin film 8, compared to the conventional process shown in FIG. 7 is shown. As shown in FIG. 7, when the MOS transistor is fabricated using the cobalt-carbon alloy thin film 8 used in the present invention, a process of depositing an intermediate layer is omitted compared to the conventional process so that the contact process can be performed more simply. do.

The process of the present invention is as follows. First, a silicon substrate 1 composed of a source / drain of n + and p + and a polysilicon gate 3 is maintained at a temperature of 300 ° C. to 400 ° C., and then cyclopentadienyl cobalt dicarbonyl [Co (C ₅ H ₅ ) Cobalt-metal organic sources, such as (CO) ₂ ] or biscyclopentadienyl cobalt [Co (C ₅ H ₅ ) ₂ ], are stored in a gaseous state from the storage vessel to the reactor stored at a temperature of -10 ° C to 50 ° C. Transfer the cobalt-metal organic source to the reactor using hydrogen, nitrogen, and argon gas or the like and deposit by chemical vapor deposition to deposit the cobalt-carbon alloy thin film (8) on the source / drain silicon, and then 700 ° C. or more. CoSi ₂ layer 7 of the epitaxy layer in the (100) orientation in the same orientation as the (100) orientation of the silicon substrate 1 by reaction of cobalt 4 and silicon in the cobalt-carbon alloy thin film 8 by heat treatment. ) Is formed, and on the polysilicon gate 3 Forming a polycrystalline CoSi ₂ layer 7 is directly and it is possible the cobalt (4) formed on the oxide film (2) remains without reacting with the oxide film (2).

In the case of depositing the cobalt-carbon alloy thin film 8 using a vacuum evaporator, carbon and cobalt 4 may be deposited at room temperature by a co-evaporation method. In the vacuum evaporator, cobalt (4) and carbon are charged in two tungsten and molybdenum boats or effusion cells, and the temperature is maintained at 1,000 to 1,500 ° C and the standard vacuum is 10 ^-7 Torr. If kept below, it is possible to deposit on the substrate.

When the cobalt-carbon alloy thin film 8 is deposited by sputtering, the temperature of the silicon substrate 1 is increased by using an alloy target in which cobalt-to-carbon has a composition ratio of 1 to 1 or a composition ratio of 2 to 1. When argon gas is flowed to a 1-10 sccm sputtering machine at room temperature, the pressure is maintained at about 1-10 mTorr, and the substrate is kept at room temperature or 350 ° C. or less, and is deposited on the silicon substrate 1. In addition to the cobalt-carbon alloy thin film (8) target, the cobalt (4) and carbon targets were sputtered in a similar manner to the co-sputtering method, respectively. Carbon alloy thin film 8 is deposited. Subsequently, in the same orientation as the (100) orientation of the silicon substrate 1 by the reaction between the cobalt 4 and the silicon in the cobalt-carbon alloy thin film 8 by the heat treatment of 700 ° C. or the like, as in the chemical vapor deposition method, the (100) orientation CoSi ₂ layer 7 of epitaxial layer of is formed, polycrystalline CoSi ₂ layer 7 is formed directly on polysilicon gate 3 and cobalt 4 does not react with oxide film 2 on oxide film 2. Will remain.

The unreacted cobalt-carbon alloy thin film 8 on the spacer or field oxide 2 is then removed by etching for the final salicide process.

Through the following examples will be described the present invention. However, this embodiment is provided only to facilitate the description of the present invention, the technical scope of the present invention is not limited by this embodiment.

<Example 1>

A silicon substrate composed of polysilicon gates and sources / drains of n + and p + was maintained in a reactor at a temperature of 350 ° C., and then biscyclopentadienylcobalt [Co (C ₅ H ₅ ) ₂ ] as a cobalt-metal organic source. 50 sccm of hydrogen as a transfer gas from the storage vessel at 35 ° C flows out through the storage vessel, transferred to the reactor, deposited by chemical vapor deposition, and then heat treated for 5 minutes by rapid thermal treatment at a temperature of 800 ° C. CoSi ₂ layer 7 was formed on (1). At this time, the deposition pressure is in the range of 10 to 500 mtorr, and the composition ratio of cobalt to carbon of the thin film deposited within this range is slightly different, but usually has a composition ratio of 50%: 50%.

On the other hand, the vapor pressure of the cobalt-metal organic source varies depending on the temperature of the storage container. When the temperature of the storage container is room temperature, the vapor pressure of the cobalt-metal organic source can be sufficiently transferred without using hydrogen or other transport gas. Likewise, in the case of using hydrogen as a transport gas, a cobalt-carbon alloy thin film having a thickness of 500 kPa or more can be formed on the silicon substrate 1 within 1 minute.

<Example 2>

After storing the cyclopentadienyl cobalt dicarbonyl [Co (C ₅ H ₅ ) (CO) ₂ ] as a cobalt-metal organic source at a substrate temperature of 350 ° C. in a 35 ° C. storage vessel, 50 sccm of hydrogen was flowed into the storage vessel. At this time, the amount of Co (C ₅ H ₅ ) (CO) ₂ converted was 5-15 sccm (Square per Cubic Centi Meter), and the deposition pressure was 400-500 mtorr. After the deposition was performed by heat treatment for 5 minutes at a temperature of 800 ℃ rapid thermal treatment to form a CoSi ₂ layer 7 on the silicon substrate (1). In this case, the deposited cobalt-carbon alloy thin film is composed of 50% cobalt and 50% carbon, and the result of performing the X-ray diffraction pattern is shown in FIG. 1.

Wide and gentle curves instead of the relatively sharp diffraction lines of FIG. 1 indicate that the cobalt-carbon alloy thin film is in an amorphous state. In addition, Oze spectrophotometer spectrum showing the composition ratio of cobalt-carbon is shown in FIG. It can be seen that the composition ratios of cobalt-carbon deposited at 350 ° C. in FIG. 2 are approximately similar compositions.

<Example 3>

After depositing cobalt (4) on the silicon substrate (1), the CoSi ₂ layer (7) is formed on the silicon substrate (1), which is deposited titanium (6) as a protective layer and rapidly heat treated at 800 ℃ in a nitrogen atmosphere for 5 minutes An X-ray diffraction pattern is shown in FIG. 3, in which a single crystal CoSi ₂ layer 7 of 700 ° C. or more is formed on a silicon substrate 1 that is heat-treated according to temperature without depositing cobalt 4 and then depositing a protective layer. An X-ray diffraction pattern indicating is shown in FIG. 4. In FIG. 3, (200) shows that the epitaxial layer CoSi ₂ layer 7 having the diffraction line showing the silicon substrate 1 and the (100) orientation as the silicon in the (100) orientation is formed in the silicon substrate 1 after heat treatment. It can be seen that only the diffraction lines of azimuth appear. In addition, in FIG. 4, when the protective layer is not used, the epitaxial layer CoSi ₂ layer 7 is formed at 700 ° C. or higher.

At this time, the cobalt (4) on the SiO ₂ which is the oxide film (2) does not react with SiO ₂ and the cobalt (4) is replaced by NH ₄ OH / H ₂ O ₂ or HNO ₃ / H ₂ O or H ₂ SO ₄ / H. ₂ O is etching the _second solution.

The sheet resistance of the cobalt silicide thin film obtained as described above is 5 to 10 Ω / □, and shows a similar sheet resistance value as compared with the sputtering method, and the specific resistance value is about 16 to 20 µΩ · cm. In addition, when the protective layer was used, a matching epitaxial layer cobalt disilicide layer having a thickness of about 450 시 was formed in the transmission electron microscope analysis indicating whether the epitaxial layer was formed and whether the epitaxial layer was matched with the silicon substrate. have.

<Example 4>

Cobalt-carbon using cyclopentadienylcobaltdicarbonyl [Co (C ₅ H ₅ ) (CO) ₂ ] as a cobalt metal organic source gas in the method of Example 2 on the silicon substrate 1 without using a protective layer. After depositing the alloy thin film (8) to form a CoSi ₂ layer (7) on the silicon substrate (1) by heat treatment for 5 minutes in a rapid heat treatment method under a nitrogen atmosphere of 800 ℃ and then using a Ohze electron spectrometer A graph showing the surface composition distribution of (1) is shown in FIG. 5.

FIG. 5 shows the amount of each element in units of atomic percent after sputtering from the silicon surface, showing that cobalt (4) diffused into the silicon substrate (1) from the cobalt-carbon alloy thin film (8) containing carbon. As can be seen, carbon inhibits excessive diffusion of cobalt 4 to form an epitaxial CoSi ₂ layer 7. In addition, it can be seen that the oxidation of cobalt (4), which is commonly seen in the heat treatment process, is also very small in the cobalt-carbon alloy thin film (8) formed by carbon inhibiting the diffusion of oxygen. That is, the cobalt-carbon alloy thin film 8 used in the present invention suppresses the diffusion of the cobalt 4 into the silicon substrate 1 to form the single crystal CoSi ₂ layer 7 during the heat treatment process, and the cobalt 4 It can be seen that it plays two roles to inhibit the oxidation of.

In the contact formation method of the present invention, in forming a single crystal CoSi ₂ layer, there is a problem of a conventional contact formation method that requires various processes such as a multi-stage intermediate layer deposition, a TiN deposition process as a protective layer, and a high temperature heat treatment performed after the process. The low resistivity and high reproducibility of the epitaxial CoSi ₂ layer can be formed by deposition and heat treatment of carbon-cobalt alloy thin film containing carbon without going through a multi-stage interlayer deposition process, greatly simplifying the contact wiring process. Can be.

In addition, by using the chemical vapor deposition method, it is excellent in coating property in the ultra-fine contact wiring process and can form a uniform interface, and also forms epitaxial layer silicide, so that the interface defect between silicide and silicon is small, The excellent bonding characteristics can be obtained, and thus it can be utilized for the manufacture of high-integrated circuit ultra-fine semiconductor devices of more than GDRAM level.

Claims (6)

Cobalt containing carbon was deposited on the silicon substrate (1), and then the epitaxial layer CoSi ₂ layer 7 was formed in the source / drain of the MOS transistor by rapid thermal treatment at high temperature, and the single crystal CoSi ₂ layer 7 was formed in the polysilicon gate. Forming a single crystal cobalt disilicide contact using a cobalt-carbon alloy thin film. The method of claim 1, wherein biscyclopentadienyl cobalt (C ₅ H ₅ ) ₂ Co) or cyclopentadienyl cobalt dicarbonyl, C, is deposited to deposit carbon-containing cobalt on a silicon substrate. ₅ H ₅ Co (CO) ₂ ) A method for forming a single crystal cobalt dissilicide contact using a cobalt-carbon alloy thin film. The method of claim 1, wherein the carbon-containing cobalt is deposited by using a cobalt-carbon alloy thin film 8 containing carbon by sputtering or evaporation in addition to chemical vapor deposition. A method of forming a single crystal cobalt disulfide contact using a cobalt-carbon alloy thin film. 3. The method of claim 1 or 2, wherein the composition ratio of cobalt to carbon is 1 to 1 or 2 to 1 of cobalt to carbon. 2. The single crystal cobalt using a cobalt-carbon alloy thin film according to claim 1, characterized in that a rapid heat treatment at a temperature of 700 to 800 DEG C to form a CoSi ₂ layer 7 having a specific resistance of 15 to 20 mu OMEGA -cm. Method of forming disilicide contact. The method according to claim 3, wherein, as an application thereof, instead of the cobalt-carbon alloy thin film 8, carbon is deposited on the silicon substrate 1 and cobalt is deposited thereon, followed by heat treatment to form a single crystal CoSi ₂ layer 7. A method of forming a single crystal cobalt dissilicide contact using a cobalt-carbon alloy thin film, characterized in that.