KR19990050454A - Chemical vapor deposition of copper thin film by organometallic compound precursor - Google Patents

Abstract

The present invention is to solve the problems caused when forming a copper wiring thin film (CVD: chemical vapor deposition) excellent in the resistivity and electromigration (EM) characteristics compared to the conventional aluminum-based semiconductor wiring.

The present invention improves thin film deposition rate by increasing the vapor pressure by weakly bonding copper-ligand (Cu-L) using 1-pentene (C ₅ H ₁₀ ) as ligand L in β-diketonate-based (hfac) CuL copper compound as a copper precursor. Newly synthesized (hfac) Cu (1-pentene) [1,1,1,5,5,5-hexafluoro-2,4-pentanedionato (1-pentene) copper (I): C ₁₀ H ₁₁ CuF ₆ O ₂ ] compound was used. At this time, by using a mixed solution of 1-pentene added to (hfac) Cu (1-pentene) as a precursor of the copper deposition reaction, the thermal stability problem of the Cu (I) -based liquid precursors was solved. In this way, (hfac) Cu (1-pentene) or (hfac) Cu (1-pentene) + (1-pentene) mixed solution is evaporated as a copper source and introduced into a chemical vapor deposition reactor maintained at a constant temperature and pressure. By means of the copper source-substrate deposition reaction, a high-purity copper thin film having low electrical resistivity and crystal orientation close to a bulk value can be formed on the conductor, insulator and semiconductor substrate with high deposition rate. Therefore, by using the copper chemical vapor deposition method according to the present invention it is possible to form a copper thin film suitable for the semiconductor wiring process having excellent physical and chemical properties.

Description

Chemical vapor deposition of copper thin film by organometallic compound precursor

SUMMARY OF THE INVENTION The present invention is to solve various problems in the manufacture of a copper thin film for semiconductor wiring by the conventional copper chemical vapor deposition method, and improves the thermal stability of the copper precursor, excellent electrical resistivity and close to the bulk value at low deposition temperature and <111. It is to provide a copper chemical vapor deposition method capable of reproducibly forming a copper thin film having crystal orientation.

It is a material that will replace the existing aluminum-based semiconductor wiring to solve the signal transmission delay and the electromigration (EM) caused by the reduction of the wiring width and the increase of the wiring length due to the miniaturization of the semiconductor. In particular, the application of copper chemical vapor deposition (CVD: chemical vapor deposition) is under consideration in order to obtain a thin film having excellent physical properties. Where (hfac) Cu (VTMS) [1,1,1,5,5,5-hexafluoro-2,4-pentanedionato (vinyltrimethylsilane) copper (I): C ₁₀ H ₁₃ O ₂ CuF ₆ Si] Β-diketonate Cu represented by Cu (hfac) ₂ [ bis (1,1,1,5,5,5-hexafluoro-2,4-pentanedionato) copper (II): C ₁₀ H ₂ O ₄ CuF ₁₂ ] (I) and Cu (II) organometallic compounds are used. However, the thin film deposited by Cu (hfac) _{2, which} is a stable solid precursor, exhibits low deposition rate and high resistivity, whereas liquid (hfac) Cu (VTMS) has better deposition characteristics than Cu (hfac) ₂ but is thermally unstable. During the normal temperature storage of the precursor or during the evaporation process is gradually deteriorated. In addition, since the supply of the copper source to the reactor is usually performed by a bubbler method of directly heating the vessel containing the copper source, the supply flow rate during the deposition process is changed by the copper source temperature and the vapor pressure fluctuation, so that the precise flow rate It is difficult to supply and therefore extremely poor in deposition reproducibility and deposition uniformity. Therefore, there has been a need for the synthesis of new copper sources with fundamental thermal stability, high vapor pressure, and the establishment of chemical vapor deposition conditions to obtain excellent deposition properties when used as precursors thereof.

In order to apply the copper chemical vapor deposition method to the semiconductor wiring structure manufacturing, a deposition method must be developed that can secure a good deposition characteristics such as high deposition rate and basic thin film properties such as electrical resistivity and crystal orientation. However, in the conventional chemical vapor deposition method, it is possible to deposit thin films in the range of about 130 to 450 ^° C., but it is very difficult to obtain a low electrical resistivity copper thin film with a high deposition rate. In other words, at a high deposition rate, the connectivity between the thin films due to grain growth is poor and the specific resistance is increased.However, at low deposition temperatures, the microstructure having a low specific resistance is possible due to the dense microstructure, but the deposition rate is low, so the application to the actual manufacturing process is limited. There is a disadvantage. In the case of copper thin film, the EM resistance of the wiring is largely dependent on the crystal orientation of Cu (111) / Cu (200), and it is known that the higher this ratio is, the higher the ratio is. It is not easy to obtain a thin film.

The present invention solves the problems of deposition reproducibility and uniformity in the deposition process due to deterioration and decomposition of copper precursors and fluctuations in the supply flow in copper chemical vapor deposition, and the electrical resistivity and crystal orientation close to the bulk at low deposition temperature. It is intended to ensure a highly reliable copper thin film formation method capable of forming a copper thin film having a high deposition rate.

In the present invention, 1-pentene (C ₅ H ₁₀ ) is used as ligand L in β-diketonate-based (hfac) CuL copper compound to weakly bond copper-ligand (Cu-L) to increase vapor pressure to increase the thin film deposition rate. Newly synthesized (hfac) Cu (1-pentene) [1,1,1,5,5,5-hexafluoro-2,4-pentanedionato (1-pentene) copper (I): C ₁₀ H ₁₁ CuF ₆ O ₂ ] compound was used.

At this time, by using a mixed solution of 1-pentene added to (hfac) Cu (1-pentene) as a precursor for copper deposition reaction, the thermal stability problem of the Cu (I) -based liquid precursors was solved.

In this way, (hfac) Cu (1-pentene) or (hfac) Cu (1-pentene) + (1-pentene) mixed solution is evaporated as a copper source and introduced into a chemical vapor deposition reactor maintained at a constant temperature and pressure. By means of the copper source-substrate deposition reaction, a high-purity copper thin film can be formed on the conductor, insulator, and semiconductor substrate with high deposition rate.

1 is a schematic diagram of a copper chemical vapor deposition apparatus used in the present invention.

2 is a structural formula of (hfac) Cu (1-pentene): C ₁₀ H ₁₁ CuF ₆ O ₂ copper precursor used in the present invention.

Figure 3 is a characteristic change of the deposition rate and electrical resistivity according to the deposition temperature of the copper thin film formed by the chemical vapor deposition method of the present invention.

Figure 4 is an exemplary view showing an electron microscope (SEM) picture of the surface and cross-sectional microstructure according to the deposition temperature of the copper thin film formed by the chemical vapor deposition method of the present invention.

<Description of the code | symbol about the principal part of drawing>

1: quartz reactor 2: copper source container

3: copper source 4: shutoff valve

5 carrier gas 6 flange

7,8: electric furnace 1, 2 9: ball joint

10: vacuum gauge 11: vacuum valve

12 substrate 13 graphite susceptor

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a pilot type copper chemical vapor deposition apparatus used to apply a method for manufacturing a copper thin film in the present invention. A copper source container 2 is provided on one side wall of the inlet of the quartz reactor 1 via a shutoff valve 4, and a carrier gas (2) is provided in the copper source container 2 and the quartz reactor 1. An inlet for injecting Ar, H ₂ , He, N ₂ ) 5 is provided, and an electric furnace 1 (T / C) is provided on the outer circumferential surface of the quartz reactor 1 in which the inlet is opened and closed by the flange 6. 1) 7 and an electric furnace 2 (T / C2) 8 are installed, and a substrate 12 supported by a graphite susceptor 13 is placed in the quartz reactor 1. The substrate 12 has a thermocouple T / C 3 connected to the outside of the flange 6, and the other end of the reactor 1 has a ball joint 9, a vacuum gauge 10 and a vacuum valve. It is configured to control the vacuum exhaust through (11).

The quartz reactor 1 has a hot-wall horizontal type structure having an inner diameter of 45 mm, a thickness of 2.5 mm, and a length of 500 mm. The front end of the reactor 1 is sealed with a flange 6 made of stainless steel through which a carrier gas 5 such as Ar, H ₂ , He, N _2, etc. is supplied, and a thermocouple T for measuring the temperature of the substrate 12. / C 3) The connector is mounted. The liquid copper source 3 is filled in a stainless steel container 2, which is connected to the quartz reactor 1 via a shutoff valve 4. Furnace 1 (7) is for preventing condensation of the copper source (3) evaporated from the copper source vessel (2) at room temperature and for preheating of the carrier gas (5) and is heated in the range of 30 to 35 ^° C. 2 x 2 cm ² flakes are used as the substrate 12, which is placed on the graphite susceptor 13 and heated by an electric furnace 2 (8). The reactor 1 is maintained at a basic vacuum of 10 ^-2 Torr by a rotary vane vacuum pump in the process atmosphere, and in the actual deposition process, the conduction pressure of the vacuum valve is controlled to maintain the reactor pressure. The process gas introduced into the reactor 1 is excited by thermal energy to precipitate a copper thin film on the surface of the substrate 12 and then evacuated while forming a laminar flow.

Figure 2 shows the chemical structure of (hfac) Cu (1-pentene): C ₁₀ H ₁₁ CuF ₆ O ₂ copper precursor of 99.99% purity used in the present invention. It is a light green β-diketonate-based copper compound, in which copper-ligand bonds of (hfac) CuL (where L is Lewis base ligand) are weakly bound by 1-pentene, resulting in high vapor pressure even at room temperature (10 ^-2 Torr, 25-27 ^{o Because of} C), it is possible to increase the deposition rate of the copper thin film because a large amount of copper source can be supplied to the reactor during the organic metal chemical vapor deposition.

In general, a Cu (I) precursor of (hfac) CuL proceeds by a disproportionation of 2 (hfac) CuL → Cu (s) + Cu (hfac) ₂ + 2L. However, Cu (I) -based liquid precursors are mostly thermally unstable, so that disproportionation reactions occur in the container by heating the storage container during normal temperature storage or deposition process of the copper source. Therefore, the copper source temperature and vapor pressure change in the vessel along with the deterioration and decomposition of the copper source, condensation / deposition and supply of particles on the supply line, resulting in problems such as thin film deposition reproducibility and uniformity caused by fluctuations in the supply flow during the deposition process.

In the present invention, in order to enhance the thermal stability of the (hfac) Cu (1-pentene) copper source, that is, to prevent disproportionation reaction in the container during normal temperature storage or for long time heating, the (hfac) Cu (1-pentene) copper source In addition 1-pentene ligand of 99.99% purity was added.

First, in order to obtain the optimal copper source mixing ratio, the addition ratio of 1-pentene in Table 1 is changed to a range of 0 to 50 vol% (value for the amount of pure copper source), so that the bubbler method and the vaporizer method The thermal stability of the mixed solution was investigated in two copper source transport methods. As the mixing ratio was increased from 0% to 10% at 30 ^o C heating conditions, the amount of decomposition of precipitates in the mixed solution was observed to decrease gradually, and at 20 to 50% mixing ratio, thermal stability over 8 hours in both modes of transport was observed. Is showing.

Therefore, by using a (hfac) Cu (1-pentene) + (1-pentene) solution containing 20 vol% or more of 1-pentene ligand as a copper source, thermal stability can be maintained while maintaining high vapor pressure.

Therefore, in the chemical vapor deposition apparatus of FIG. 1, a mixed solution of (hfac) Cu (1-pentene) or (hfac) Cu (1-pentene) + (1-pentene) is used as the copper source or Ar, H ₂ , A copper thin film can be formed by simultaneously introducing a carrier gas such as He or N ₂ into a chemical vapor deposition reactor. In particular, the deposition reproducibility and deposition of the chemical vapor deposition process are eliminated by using the precursor mixture solution, excluding the problems caused by the deterioration of the copper source itself and fluctuations in the supply flow during the deposition process, which appear in the β-diketonate Cu (I) liquid copper precursor. Uniformity can be secured.

Table 2 shows typical deposition conditions of the copper chemical vapor deposition method devised in the present invention. As a substrate, a multilayer thin film specimen in which SiO ₂ 2000 Pa and reactive sputter TiN 900 Pa was sequentially coated on a p- type Si flake was used. The thickness, microstructure, crystal orientation, and electrical resistivity of the deposited film were measured by SEM, x-ray diffractometer (XRD), and 4-point probe, respectively. First, the correlation between the deposition rate, the change in electrical resistivity value and the deposition temperature of the copper thin film formed by the chemical vapor deposition method of the present invention was analyzed.

FIG. 3 shows the reactor pressure and carrier gas after charging a mixture of 50 vol% of 1-pentene with respect to (hfac) Cu (1-pentene) in a copper source vessel in a hot wall pilot copper chemical vapor deposition apparatus. Substrate temperature (T /) of the copper thin film fixed at a flow rate and an electric furnace 1 at 0.1 Torr, 0 sccm, and 30 to 35 ^° C., respectively, and deposited for 5 to 10 minutes (copper consumption: 0.8 to 1.2 g) on the TiN substrate. C 3: shows the deposition rate and the specific resistance change according to 100 ~ 200 ^o C). The deposition rate of the copper thin film represented by the Arrhenius plot is rapidly increasing from 1450Å / min to 3500Å / min with the increase of substrate temperature from 100 ^o C to 200 ^o C. Therefore, it can be seen that thermal energy directly affects the copper nucleation density and surface deposition reaction of the initial deposition in the low temperature deposition region below 200 ^o C.

The apparent activation energy value according to the substrate temperature of the copper deposition reaction obtained from FIG. 3 is 3.07 kcal / mol, which is usually 5 to 13 kcal / mol obtained from the surface reaction dominant region using (hfac) Cu (VTMS) precursor. In comparison, the value is very low. This reduction in activation energy is due to the weak bonding between Cu (hfac)-(1-pentene) in the (hfac) Cu (1-pentene) precursor used in the present invention. This is because disproportionation of Cu (1-pentene) → Cu (s) + Cu (hfac) ₂ +2 (1-pentene) is easily generated even at low deposition temperature and shows high deposition rate.

3 shows the correlation between the electrical resistivity and the deposition temperature of the copper thin film manufactured by the chemical vapor deposition method of the present invention to a thickness of 1 ㎛ or more. The resistivity of the copper-deposited thin film on the TiN substrate was 2.17 μΩ-cm (1.45 μm thick) at 100 ^o C and 1.98 μΩ-cm (1.1 μm thick) at 150 ^o C and decreased with increasing substrate temperature, in particular 200 ^o C Shows good electrical properties of 1.80 μΩ-cm (thickness 2.0 μm). That is, in the high temperature deposition region, the growth rate is faster than the copper nucleation rate due to the activation of the surface deposition reaction, densely filling the grains and increasing the micropore density in the thin film, thereby improving the electrical resistivity characteristics.

Therefore, by using the (hfac) Cu (1-pentene) + (1-pentene) mixed solution as the copper source, it is possible to form a copper thin film having excellent resistivity characteristics close to the bulk even at a low substrate temperature of 200 ^° C. or less.

4 is a SEM photograph of the surface and cross-sectional microstructures of the copper thin film formed on the TiN substrate under the deposition conditions of FIG. 3 by the chemical vapor deposition method of the present invention. From the cross-sectional microstructure photograph, the copper thin film deposited at the substrate temperature of 100 to 200 ^° C. shows that the surface roughness is in a good state with a flat structure. On the other hand, the 100 ^o C deposited thin film has a dense microstructure with small grain size and small pore density. As the deposition temperature increases, only the grains grow and the macroscopic thin film structure is maintained. It is showing. Therefore, the thin film resistivity characteristic according to the deposition temperature in FIG. 3 is considered to be related to the microstructure change of the deposited layer.

Table 3 shows the correlation between the crystal orientation and deposition temperature of the copper thin film formed under the deposition conditions of FIG. 3 by the chemical vapor deposition method of the present invention. The <111> orientation was determined by the ratio of the intensity of the (111) peak to the (200) peak of copper in the XRD results, which is about 2.174 for the standard copper powder standard specimen.

First, as a result of the deposition temperature change, the deposited film on the TiN substrate had a Cu (111) face-centered cubic (FCC) -specific Cu (111) due to the influence of the TiN (111) orientation of the lower substrate due to the low deposition rate at 100 ^o C. ), The deposition rate is restored as the deposition temperature increases, and the <111> orientation is decreased. Therefore, it can be seen that low temperature deposition conditions of about 100 ^° C. are advantageous for improving the orientation of the copper thin film.

In addition, by controlling the amount of 1-pentene added or diluted in (hfac) Cu (1-pentene), the copper source-substrate deposition reaction on the substrate was controlled by thermal energy in the chemical vapor deposition reactor to improve the thin film characteristics of the copper deposited film. More precise adjustment It is known that resistance to EM, which is a phenomenon of mass transfer due to electron wind or stress, of a semiconductor wiring made of a FCC structure metal thin film is particularly influenced by <111> orientation, grain size distribution in the wiring, and the like.

Therefore, (hfac) Cu (1-pentene ) - copper films is form the grain size distribution uniformly dense thin film on the microstructures result in the previous Figure 4 obtained by the (1-pentene) system, and in Table 3 100 ^o Since the copper thin film exhibits a <111> orientation at low temperature deposition, a highly reliable copper thin film having a long wiring life can be formed thereby.

The present invention devised a copper chemical vapor deposition method using a new (hfac) Cu (1-pentene) copper source to form a semiconductor copper wiring thin film having physical and chemical properties such as electrical resistivity and EM resistance. In particular, in order to increase the thermal stability of the copper source, a mixed solution of (hfac) Cu (1-pentene) + (1-pentene), in which 1-pentene is added to (hfac) Cu (1-pentene), is evaporated as a raw material gas. The high-reliability copper chemical vapor deposition method was designed to control the deposition reaction on the substrate by thermal energy by introducing it into a chemical vapor deposition reactor. This method has the following advantages and effects compared to the conventional copper chemical vapor deposition method. Have

First, since a newly synthesized (hfac) Cu (1-pentene) compound is used to increase the vapor pressure by weakening the copper-ligand bond by 1-pentene in the copper precursor, it is possible to improve the deposition rate of the copper thin film even at low deposition temperature. Can be.

Second, the (hfac) Cu (1-pentene) can form a copper thin film having low electrical resistivity and crystal orientation close to a bulk value at a low deposition temperature.

Third, Cu (I), including (hfac) Cu (VTMS), was improved by improving the thermal stability by using a mixed solution of 1-pentene added to (hfac) Cu (1-pentene) as a precursor for copper deposition. It not only prevents the deterioration, decomposition, copper source condensation, deposition and particle generation of the copper source in the liquid precursor, but also eliminates the problems caused by fluctuations in the supply flow during the deposition process. In addition to ensuring uniformity, it is possible to reduce the maintenance time of the deposition apparatus.

Fourth, by changing the amount of 1-pentene added or diluted in (hfac) Cu (1-pentene), the deposition rate and thin film of the copper deposition film were controlled by controlling the copper source-substrate deposition reaction on the substrate by the thermal energy in the chemical vapor deposition reactor. You can adjust the characteristics.

Therefore, according to the present invention, which provides a highly reliable semiconductor copper wiring manufacturing method using a chemical vapor deposition method, it is possible to form a copper thin film having excellent physical and chemical properties.

Claims (8)

(Hfac) Cu (1-pentene) into a reactor consisting of a susceptor for mounting a substrate, a substrate heating source, a process gas inlet for a copper source and a carrier gas, a pressure and substrate temperature measurement unit, and a vacuum exhaust unit [1, 1,1,5,5,5-hexafluoro-2,4-pentanedionato (1-pentene) copper (I): C ₁₀ H ₁₁ CuF ₆ O ₂ ] on a conductor, semiconductor, or insulator substrate by introducing a copper precursor A method of chemical vapor deposition of a copper thin film by a copper precursor, characterized in that a copper thin film is formed on the copper precursor. The method of claim 1, A method of chemical vapor deposition of a copper thin film by a copper precursor, characterized by using a 1-pentene (C ₅ H ₁₀ ) compound together with (hfac) Cu (1-pentene) copper source to form a copper thin film. The method of claim 1, In order to form a copper thin film, a process gas mixed with (hfac) Cu (1-pentene) + carrier gas or a process gas mixed with (hfac) Cu (1-pentene) + (1-pentene) + carrier gas is used as a chemical vapor deposition system. Chemical vapor deposition method of a copper thin film by the copper precursor characterized by the above-mentioned. The method of claim 3, wherein As a carrier gas for the formation of a copper thin film, a copper thin film made of a copper precursor, characterized in that argon (Ar), helium (He), hydrogen (H ₂ ), nitrogen (N ₂ ) is used alone or in combination with each other. Chemical vapor deposition method. The method of claim 1, A method of chemical vapor deposition of a copper thin film by a copper precursor, characterized in that the substrate is heated using heat energy as a process gas excitation source for forming a copper thin film. The method of claim 1, A method of chemical vapor deposition of a copper thin film by a copper precursor, comprising using a thermal energy and a plasma source as a process gas excitation source for forming a copper thin film or applying a bias on a substrate. The method of claim 1, A method of chemical vapor deposition of a copper thin film by a copper precursor, characterized in that the substrate temperature in the reactor for the formation of a copper thin film using a deposition temperature in the range of 80 ~ 300 ^° C. The method of claim 1, A method of chemical vapor deposition of a copper thin film by a copper precursor, characterized in that the pressure in the reactor is used as a deposition pressure in the range of 0.01 to 100 Torr to form a copper thin film.