JP2781219B2 - Deposition film formation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a deposited film, and more particularly to a method for forming an Al—Si deposited film that is preferably applicable to wiring of a semiconductor integrated circuit device or the like.

[Prior Art] Conventionally, in an electronic device or an integrated circuit using a semiconductor, electrodes (Al) or Al
-Si and the like have been used. Here, Al-Si is inexpensive and has high electrical conductivity, and a dense oxide film is formed on the surface, so that the inside is chemically protected and stabilized, and the adhesion with Si is good. It has many advantages, including being there.

By the way, the integration degree of integrated circuits such as LSIs has increased, and fine wiring and multilayer wiring have become particularly necessary in recent years. Not tough demands are being made. Along with miniaturization due to an increase in the degree of integration, the surface of an LSI or the like has become increasingly uneven due to oxidation, diffusion, thin film deposition, etching, and the like. For example, an electrode or a wiring metal must be deposited on a stepped surface without disconnection or deposited in a via hole having a small diameter and a large diameter. 4Mbit and 16M
In a bit DRAM (dynamic RAM) or the like, the aspect ratio (via hole depth / via hole diameter) of a via hole on which a metal such as Al-Si must be deposited is 1.0 or more, and the via hole diameter itself is 1 μm or less. Therefore,
A technique that can deposit an Al-Si compound even in a via hole having a large aspect ratio is required.

In particular, in order to reliably connect to a device under an insulating film such as SiO ₂ , it is necessary to deposit Al—Si not to form a film but to fill only a via hole of the device. For this purpose, a method is required in which an Al alloy is deposited only on the surface of Si or a metal, but not on an insulating film such as SiO ₂ .

Such selective deposition or selective growth cannot be realized by the conventionally used sputtering method. Since the sputtering method is a physical deposition method based on the arrival of particles sputtered from the target in a vacuum, the film thickness at the steps and the side walls of the insulating film becomes extremely thin, and in severe cases, disconnection occurs. . In addition, the unevenness of the film thickness or the disconnection significantly lowers the reliability of the LSI.

Apply a bias to the substrate and use only the sputter etching and deposition effects on the substrate surface to
A bias sputtering method for performing deposition so as to bury Al or an Al-Si compound has been developed. However, since a bias voltage of several hundred volts or more is applied to the substrate, adverse effects such as a change in the threshold value of the MOS-FET due to damage of the charged particles occur. In addition, there is a problem that the deposition rate is not essentially improved because the etching action and the deposition action are mixed.

To solve the above problems, various types of
A CVD (Chemical Vapor Deposition) method has been proposed. In these methods, a chemical reaction of a source gas is used in some way during the film formation process. In plasma CVD and optical CVD, the decomposition of the source gas occurs in the gas phase, and the activated species formed there further react on the substrate to form a film. In these CVD methods, the surface covering property against unevenness of the substrate surface is good. However, carbon atoms contained in the source gas molecules are taken into the film. In particular, plasma CVD has a problem such as damage by charged particles (so-called plasma damage) as in the case of the sputtering method.

In the thermal CVD method, the film grows mainly by the surface reaction on the surface of the substrate, and therefore, has good surface coverage with irregularities such as steps on the surface. Also, it can be expected that deposition in the via hole is likely to occur. In addition, disconnection at the step can be avoided. Also, there is no charged particle damage as in plasma CVD or sputtering. An example of this type of method is the Journal of Elect
Some are described in the rochemical Society, vol. 131, p. 2175 (1984). In this method, triisobutyl aluminum (TIBA) is used as the organic aluminum gas.
After forming an Al film using {(i-C ₄ H ₉ ) ₃ Al} at a film forming temperature of 260 ° C. and a pressure in the reaction tube of 0.5 Torr, the substrate temperature was maintained at about 450 ° C., and SiH ₄ was introduced. An Al—Si film is obtained by diffusing Si into the Al film.

In the case of using TIBA, a continuous film cannot be obtained unless pretreatment such as flowing TiCl ₄ to activate the substrate surface and form nuclei before film formation is performed. In addition, when TIBA is used, including the case where TiCl ₄ is used, there is a problem that the surface flatness is generally inferior. In this method, selective growth such as Al—Si deposition only in the via hole cannot be caused.

Another method is the Japanese Journal of Applie
d Physics, Vol. 27, No. 11, page L2134 (1988). In this method, TIBA and Si ₂ H ₆ are dispersed and supplied in Ar gas, and the gas is heated before TIBA reaches the substrate. By this method, a low-resistance A
An l-Si film can be epitaxially grown. Although the film obtained by this method is of very good quality, there are problems such as difficulty in control due to the necessity of heating the gas and complicated equipment.

JP The 63-33569 discloses without using TiCl _4, a method of film formation is described by heating the organoaluminum instead in the vicinity of the substrate. According to this method, Al can be selectively deposited only on the metal or semiconductor surface from which the natural oxide film on the surface has been removed.

In this case, it is specified that a step of removing a natural oxide film on the substrate surface is necessary before introducing TIBA. Also, TI
Since BA can be used alone, it is not necessary to use a carrier gas other than TIBA, but it is described that Ar gas may be used as a carrier gas. However, no reaction between TIBA and another gas (for example, H ₂ ) is assumed at all, and there is no mention of using H ₂ as a carrier gas. In addition, other than TIBA, trimethylaluminum (TMA) and triethylaluminum (TEA) are mentioned, but there is no specific description of the other organic metals. This is because the chemical properties of organometallics generally change greatly when the organic substituent attached to the metal element changes slightly, and it is necessary to individually consider what kind of organometallic should be used. This method not only has the disadvantage that the natural oxide film must be removed, but also has the disadvantage that surface smoothness cannot be obtained. In addition, it is necessary to heat the gas, and there is a restriction that heating must be performed near the substrate, and it is necessary to experimentally determine how close the substrate must be heated. There is another problem that the place where the heater is placed cannot be freely selected.

Proceedings of the 2nd Symposium of the Electrochemical Society Japan Chapter (July 7, 1989), page 75, contain a description of Al film formation by double-wall CVD. In this method, a device is designed using TIBA so that the gas temperature becomes higher than the substrate temperature. This method is described in the above-mentioned JP-A-63-3356.
It can also be considered a variant of No. 9. In this method, Al can be selectively grown only on a metal or a semiconductor, but it is difficult to control the difference between the gas temperature and the substrate surface temperature, and the cylinder and the pipe must be heated. There is a disadvantage that. In addition, this method has problems that a uniform continuous film cannot be obtained unless the film is thickened to some extent, the flatness of the film is poor, and the selectivity for selective growth of Al cannot be maintained for a long time. Moreover, in the above two examples, there is an example of Al film formation, but Al-
There is no example of forming Si.

As described above, the conventional method does not always cause the selective growth of Al-Si, and even if it can, Al has problems in flatness, resistance, purity, and the like. Is difficult.

[Problems to be Solved by the Invention] As described above, in order to provide a highly integrated and high performance semiconductor device at a low cost in the semiconductor technical field where higher integration is desired in recent years. Had much room for improvement.

The present invention has been made in view of the above technical problems, and has as its object to provide a deposition film forming method capable of forming a high-quality Al-Si film as a conductor at a desired position with good controllability. .

[Means for Solving the Problems] To achieve the above object, the method of forming a deposited film according to the present invention comprises the steps of (a) forming tungsten, molybdenum, tantalum,
A material selected from the group consisting of aluminum, titanium aluminum, titanium hydride, copper, aluminum palladium, and titanium, or a substrate having an electron-donating surface and a non-electron-donating surface repelled from silicide of the material is deposited on a space for forming a film. (B) introducing an alkylaluminum hydride gas selected from dimethylaluminum hydride and monomethylaluminum hydride, a gas containing silicon atoms, and a hydrogen gas into the space for forming the deposited film; and (c) A) maintaining the temperature of the electron donating surface within a range of not less than the decomposition temperature of the alkyl aluminum hydride and not more than 450 ° C., and selectively forming an aluminum film containing silicon on the electron donating surface. It is characterized by having.

[Operation] First, a method of forming a deposited film using an organic metal will be outlined.

The decomposition reaction of organometallics and, consequently, the deposition reaction of thin films depend on the type of metal atom, the type of alkyl bonded to the metal atom,
It changes greatly depending on the conditions such as the means for causing the decomposition reaction and the atmospheric gas.

For example, in the case of M—R ₃ (M: Group III metal, R: alkyl group), trimethylgallium Is the thermal decomposition is radical cleavage to be decisions Ga-CH ₃ bond, triethyl gallium Is due to β-elimination in thermal decomposition And C ₂ H ₄ . Also, triethyl aluminum with the same ethyl group Is a radical decomposition in which the Al—C ₂ H ₅ bond is broken in the thermal decomposition. But iC ₄ H ₉ bound isotributyl aluminum Leaves β.

Trimethylaluminum comprising a CH ₃ group and Al (TMA)
Has a dimeric structure at room temperature The thermal decomposition is a radical decomposition in which the Al—CH ₃ group is cleaved, and reacts with the atmosphere H ₂ at a low temperature of 150 ° C. or lower to generate CH ₄ , and finally generates Al. But almost 300 ℃
At the above high temperature, even if H ₂ is present in the atmosphere, the CH ₃ group extracts H from the TMA molecule, and finally an Al—C compound is generated.

In the case of TMA, light or H ₂ atmosphere high frequency (approximately 1
In restricted areas of power at 3.56MHz) plasma, C ₂ H ₆ are generated by the coupling of the crosslinking CH ₃ between two Al.

The point is that even the simplest alkyl group, CH ₃ group, C ₂ H ₅ group or iC ₄ H ₉ group, and organic metal consisting of Al or Ga, the reaction form depends on the type of alkyl group, type of metal atom, excitation Since it depends on the decomposition means, in order to deposit metal atoms from an organometallic on a desired substrate, the decomposition reaction must be very strictly controlled. For example, triisobutylaluminum When depositing Al from
In the CVD method, irregularities on the order of μm are generated on the surface, and the surface morphology is inferior. In addition, hillocks are generated by heat treatment, Si surface roughness is caused by Si diffusion at the interface between Al and Si, and migration resistance is inferior, so that it is difficult to use the VLSI process.

Therefore, a method of precisely controlling the gas temperature and the substrate temperature has been attempted. However, the apparatus is complicated, and is a single-wafer processing type in which deposition can be performed on only one wafer in one deposition process. Moreover, the deposition rate is at most 500Å
/ Min, it is not possible to achieve the throughput required for mass production.

Similarly, when TMA is used, Al deposition by using plasma or light has been attempted.However, since plasma and light are used, the apparatus is complicated, and the throughput is sufficiently improved because the apparatus is a single wafer type. There is still room for improvement to make it happen.

Dimethyl aluminum hydride DM in the present invention
AH is a substance known as an alkyl metal.However, what kind of reaction forms what Al thin film is deposited,
The formation of a deposited film under all conditions was unexpected. For example, in the case of depositing Al by DMAH using photo-CVD, the surface morphology was poor, the resistance was several μΩ to 10 μΩ · cm, which was larger than the bulk value (2.7 μΩ · cm), and the film thickness was poor.

EXAMPLES Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

In the present invention, a high-quality Al-Si
The CVD method is used for selectively depositing a film on a substrate.

That is, dimethyl aluminum hydride (DMAH) which is an organic metal is used as a source gas containing at least one atom serving as a constituent element of a deposited film. Or monomethyl aluminum hydride (MMAH ₂ ) And a gas containing Si atoms as a raw material gas and H ₂ as a reaction gas, and an Al—Si film is selectively formed on the substrate by vapor-phase growth using a mixed gas thereof.

A substrate applicable to the present invention has a first substrate surface material for forming a surface on which Al-Si is deposited, and a second substrate surface material for forming a surface on which Al-Si is not deposited. Things. And as the first substrate surface material,
A material having an electron donating property is used.

 This electron donating property will be described in detail below.

An electron donating material is a material in which free electrons are present in a substrate or whether free electrons are intentionally generated. For example, a chemical reaction occurs when electrons are exchanged with a source gas molecule attached to a substrate surface. A material having a surface that is promoted. For example, metals and semiconductors generally correspond to this. Also included are those in which a thin oxide film exists on a metal or semiconductor surface. This is because a chemical reaction occurs between the substrate and the attached raw material molecules by electron transfer.

Specifically, semiconductors such as single crystal silicon, polycrystalline silicon, and amorphous silicon, and binary systems composed of a combination of Ga, In, Al as a group III element and P, As, N as a group V element Or a ternary or quaternary III-V compound semiconductor, tungsten, molybdenum, tantalum, tungsten silicide, titanium silicide, aluminum, aluminum silicon, titanium aluminum, titanium nitride,
Includes metals such as copper, aluminum silicon copper, aluminum palladium, titanium, molybdenum silicide, tantalum silicide, alloys and silicides thereof.

On the other hand, a material forming a surface on which Al-Si is not selectively deposited, that is, as a non-electron donating material, silicon oxide by thermal oxidation, CVD, etc., glass or oxide film such as BSG, PSG, BPSG, etc. Thermal nitride film, plasma CVD, low pressure CVD, ECR-C
It is a silicon nitride film or the like by a VD method or the like.

For a substrate having such a configuration, Al-Si is used as a raw material gas.
In a reaction system with H _2, it is deposited only by a simple thermal reaction. For example the thermal reaction in the reaction system between DMAH and H ₂ are essentially it is conceivable that. DMAH has a dimeric structure at room temperature.
The formation of the Al-Si compound by the addition of Si ₂ H ₆ or the like is due to the fact that Si ₂ H ₆ arriving at the substrate surface is decomposed by a surface chemical reaction and Si is taken into the film. As also shown in the Examples below by MMAH _2, high-quality Al by thermal reaction
-Si could be deposited.

MMAH ₂ has a vapor pressure as low as 0.01 to 0.1 Torr at room temperature, so it is difficult to transport a large amount of raw material. The upper limit of the deposition rate in the present invention is several hundred m / min, and preferably, the vapor pressure at room temperature is 1 Torr.
It is most desirable to use DMAH, which is r.

FIG. 1 is a schematic diagram showing a deposited film forming apparatus to which the present invention can be applied.

Here, 1 is a substrate for forming an Al-Si film.
The substrate 1 is placed on a substrate holder 3 provided inside a reaction tube 2 for forming a space for forming a deposited film which is substantially closed with respect to FIG. Quartz is preferred as a material constituting the reaction tube 2, but it may be made of metal. In this case, it is desirable to cool the reaction tube. The base holder 3 is made of metal, and is provided with a heater 4 so as to heat the mounted base. The temperature of the substrate can be controlled by controlling the heat generation temperature of the heater 4.

 The gas supply system is configured as follows.

Reference numeral 5 denotes a gas mixer, which mixes the first source gas, the second source gas, and the reaction gas and supplies them to the reaction tube 2. Reference numeral 6 denotes a source gas vaporizer provided for vaporizing an organic metal as a first source gas.

Since the organic metal used in the present invention is in a liquid state at room temperature, the carrier gas passes through the organic metal liquid into saturated vapor in the vaporizer 6 and is introduced into the mixer 5.

 The exhaust system is configured as follows.

Reference numeral 7 denotes a gate valve which is opened when exhausting a large amount of gas, such as when exhausting the inside of the reaction tube 2 before forming a deposited film.
Reference numeral 8 denotes a slow leak valve, which is used when a small volume of gas is exhausted, for example, when adjusting the pressure inside the reaction tube 2 when forming a deposited film. Reference numeral 9 denotes an exhaust unit, which includes an exhaust pump such as a turbo molecular pump.

 The transport system for the base 1 is configured as follows.

Reference numeral 10 denotes a substrate transfer chamber capable of housing a substrate before and after forming a deposited film, and is evacuated by opening a valve 11.
Reference numeral 12 denotes an exhaust unit for exhausting the transfer chamber, which is constituted by an exhaust pump such as a turbo molecular pump.

The valve 13 is opened only when the substrate 1 is transferred between the reaction chamber and the transfer space.

As shown in FIG. 1, in a gas generation chamber 6 for generating a source gas, a liquid DM maintained at room temperature is provided.
AH is bubbled with H ₂ or Ar (or another inert gas) as a carrier gas to produce a substrate-like DMAH, which is transported to the mixer 5. H ₂ as reaction gas
Is transported to the mixer 5 from another route. The flow rate of each gas is adjusted so that its partial pressure becomes a desired value.

MMAH ₂ may be used as the first source gas, but DMAH sufficient for the vapor pressure to be 1 Torr at room temperature is most preferable.
It may also be used by mixing DMAH and MMAH _2.

The gas containing Si as the second source gas includes Si ₂ H ₆ , SiH ₄ , Si ₃ H ₈ , Si (CH ₃ ) ₄ , SiCl ₄ , SiH ₂ Cl ₂ , SiH ₃
Cl can be used. In particular, Si ₂ H _{6 which} is easily decomposed at a low temperature of 200 to 300 ° C. is most desirable. A gas such as Si ₂ H ₆ diluted with H ₂ or Ar is transported to the mixer 5 from a separate system from the DMAH and supplied to the reaction tube 2.

2 (a) to 2 (e) show the state of selective growth of the Al-Si film according to the present invention.

FIG. 2 (a) is a diagram schematically showing a cross section of a substrate before forming an Al—Si deposited film according to the present invention. 90 is a substrate made of an electron donating material, and 91 is a thin film made of a non-electron donating material.

DMAH, Si ₂ H ₆ as raw material gas and reactive gas
When the mixed gas containing H ₂ is supplied onto the substrate 1 heated within a temperature range not lower than the decomposition temperature of DMAH and not higher than 450 ° C.,
Al-Si precipitates on the substrate 90, as shown in FIG.
An Al-Si continuous film is formed. Here, the pressure in the reaction tube 2 is desirably 10 ^{−3 to} 760 Torr, and the partial pressure of DMAH is preferably 1.5 × 10 ^{−5 to} 1.3 × 10 ⁻³ times the pressure in the upper reaction tube. The partial pressure of Si ₂ H ₆ is desirably 1 × 10 ⁻⁷ to 1 × 10 ⁻⁴ times the pressure in the reaction tube 2.

When the deposition of Al-Si is continued under the upward condition, the Al-Si film grows to the uppermost level of the thin film 91 through the state of FIG. 2C, as shown in FIG. 2D. I do. Further, when grown under the same conditions, as shown in FIG. 2 (e), the Al—Si film can be grown up to 5000 ° with almost no lateral growth. This is the most characteristic point of the deposited film according to the present invention, and it can be understood how a good quality film can be formed with good selectivity.

As a result of analysis by Auger electron spectroscopy or photoelectron spectroscopy, contamination of impurities such as carbon and oxygen is not recognized in this film.

The resistivity of the deposited film thus formed has a thickness of 40
At 0 °, the resistivity is 2.7 to 3.0 μΩ · cm at room temperature, which is almost equal to the resistivity of the Al bulk, and is a continuous and flat film. In addition, film thickness 1μ
m, the resistivity is still approximately 2.7 to 3.0 at room temperature.
μΩ · cm, and a sufficiently dense film can be formed even with a thick film. The reflectance in the visible light wavelength region is also approximately 80%,
A thin film having excellent surface flatness can be deposited.

As described above, the substrate temperature is preferably not lower than the decomposition temperature of the raw material gas containing Al and not higher than 450 ° C., but specifically, the substrate temperature is preferably 200 to 450 ° C., and the deposition was performed under these conditions. In this case, when the DMAH partial pressure is 10 ^-4 to 10 ^-3 Torr, the deposition rate is as large as 100Å / min to 800Å / min,
A sufficiently high deposition rate can be obtained as Al-Si deposition technology for VLSI.

More preferably, the substrate temperature is 270 ° C. to 350 ° C., and the Al—Si film deposited under these conditions has a strong orientation and 450 ° C., 1 h
Even if our heat treatment is performed, the Al-Si film on the Si single crystal or Si polycrystal substrate becomes a high quality Al-Si film without generation of hillocks and spikes. In addition, such an Al-Si film has excellent electromigration resistance.

In the apparatus shown in FIG. 1, Al-Si can be deposited on only one substrate in one deposition. Approximately 800Å
Although a minute deposition rate can be obtained, it is not enough to deposit a large number of sheets in a short time.

As a deposited film forming apparatus for improving this point, there is a reduced pressure CVD apparatus capable of simultaneously loading a large number of wafers and depositing Al-Si. Since the Al-Si deposition according to the present invention uses a surface reaction on the heated electron donative substrate surface, if the hot wall type low pressure CVD in which only the substrate is heated DMAH and H ₂ and Si ₂ H ₆ By adding a Si source gas such as that described above, an Al-Si compound containing 0.5 to 2.0% of Si can be deposited.

Reaction tube pressure is 0.05-760 Torr, preferably 0.1-0.8 Torr
r, substrate temperature is 160 ° C to 450 ° C, preferably 200 ° C to 400 ° C
℃, DMAH partial pressure is 1 × 10 ^-5 times to 1.3 × 10 ^-3 times the pressure in the reaction tube.
And the partial pressure of Si ₂ H ₆ is 1 × 10 ⁻⁷ times to 1 times the pressure in the reaction tube.
The range is × 10 ⁻⁴ times, and Al—Si is deposited only on the electron donating substrate.

FIG. 3 is a schematic view showing a deposited film forming apparatus to which the present invention can be applied.

57 is a substrate for forming an Al-Si film. 50 is an outer reaction tube made of quartz which forms a space for forming a deposited film which is substantially closed with respect to the surroundings, and 51 is a quartz outer tube which is installed to separate a gas flow in the outer reaction tube 50. Inner reaction tube 54
Is a metal flange for opening and closing the opening of the outer reaction tube 50, and the substrate 57 is installed in a substrate holder 56 provided inside the inner reaction tube 51. Note that the base holder 56 is desirably made of quartz.

In addition, the present apparatus can control the substrate temperature by the heater unit 59. The pressure inside the reaction tube 50 can be controlled by an exhaust system connected via a gas exhaust port 53.

The source gas is the same as that of the apparatus shown in FIG.
A gas system, a second gas system, a third gas system, and a mixer (all are not shown).
It is introduced into the reaction tube 50 from 52. As shown by an arrow 58 in FIG. 3, the raw material gas reacts on the surface of the substrate 57 when passing through the inside of the inner reaction tube 51, and deposits Al—Si on the surface of the substrate. The gas after the reaction is supplied to the inner reaction tube 51 and the outer reaction tube.
The gas is exhausted from the gas exhaust port 53 through the gap formed by the gas exhaust port 50.

When the base is taken in and out, the metal flange 54 is lowered together with the base holder 56 and the base 57 by an elevator (not shown), and is moved to a predetermined position to mount and remove the base.

By using such an apparatus and forming a deposited film under the conditions described above, high-quality Al-
Si films can be formed simultaneously.

As described above, the film obtained by the Al-Si film forming method based on the present invention is dense, has a very low impurity content such as carbon, has a resistivity comparable to that of a bulk, and has high surface smoothness. The remarkable effects described in (1) are obtained.

Hillock reduction Hillock causes Al-Si to partially migrate when internal stress during film formation is released in the heat treatment process,
-A projection is formed on the Si surface. A similar phenomenon also occurs due to local migration due to energization. The Al-Si film formed according to the present invention has almost no internal stress and is in a state close to a single crystal. Therefore 450
1Hr heat treatment at 10 ⁴ to 10 ⁶ pieces / cm in conventional Al-Si film
According to the present invention, the number of hillocks was as large as 0 to 10 / cm ² , while ² hillocks were generated. Thus Al
-Since there are almost no convex parts on the Si surface, the thickness of the resist film and the interlayer insulating film can be reduced, which is advantageous for miniaturization and flattening.

Improvement of Electromigration Resistance Electromigration is a phenomenon in which wiring atoms move when a high-density current flows. Due to this phenomenon, voids are generated and grown along one grain boundary, and as a result, the wiring is heated and disconnected due to the reduction in cross-sectional area. Conventional Al-
Migration resistance has been improved by adding Cu, Ti, etc. to Si and alloying it. However, alloying raises the problem of complexity of the etching process and difficulty of miniaturization.

Generally, the migration resistance is evaluated based on the average wiring life.

Under the current test conditions of 250 ° C. and 1 × 10 ⁶ A / cm ² , the wiring according to the conventional method is 1 × 10 ² to 10 ³ (in the case of a wiring cross section of 1 μm ² ).
The average wiring life in hours is obtained. On the other hand, in the Al-Si film obtained by the Al-Si film forming method according to the present invention, an average wiring life of 10 ³ to 10 ⁴ hours was obtained with a wiring having a cross-sectional area of 1 μm ² by the above test. .

Therefore, according to the present invention, for example, when the wiring width is 0.8 μm
A wiring layer thickness of 0.3 μm can sufficiently withstand practical use. That is, since the thickness of the wiring layer can be reduced, the unevenness of the semiconductor surface after the wiring is installed can be reduced to a minimum, and high reliability can be obtained in flowing a normal current. It is also possible with a very simple process.

Reduction of alloy pits in the contact area Due to heat treatment during the wiring process, Al in the wiring material and Si in the base
However, a eutectic reaction occurs, and a eutectic of Al and Si, called an alloy pit, penetrates into the substrate on the spike, and as a result, a shallow junction may be broken.

As a countermeasure, when the joining depth is 0.3μm or more, pure Al
If the joining depth is 0.2μm or less, use Ti,
It is common to use W, Mo based barrier metal technology.

However, there are points to be improved, such as the complexity of etching and the increase in resistance of the contact. The Al-Si formed according to the present invention can suppress the generation of alloy pits in the contact portion with the base crystal even by the heat treatment in the wiring step, and can provide a wiring having good contact properties. In other words, even when the junction is made shallow to about 0.1 μm, Al-Si
Wiring can be performed using only the material without breaking the junction.

Improvement of Surface Smoothness (Improvement of Patternability of Wiring) Conventionally, the roughness of the surface of a metal thin film has caused disadvantages in an alignment step for a mask and a substrate and an etching step in a wiring patterning step.

In other words, the surface of the conventional AlCVD film has irregularities of several μm and has poor surface morphology. Therefore, 1) the alignment signal is irregularly reflected on the surface, so that the noise level becomes high and the original alignment signal cannot be identified.

2) To cover large surface irregularities, the resist film thickness must be made large, which is contrary to miniaturization.

3) If the surface morphology is poor, halation due to the internal reflection of the resist is extremely generated, and the resist remains.

4) If the surface morphology is poor, there is a drawback that the side walls are jagged in the wiring etching step according to the irregularities.

According to the present invention, the surface morphology of the formed Al-Si film is remarkably improved, and all the above-mentioned disadvantages are improved.

Improvement of contact hole and through-hole resistance and contact resistance.

When the size of the contact hole becomes as fine as 1 μm × 1 μm or less, Si in the wiring deposits on the base of the contact hole during the heat treatment in the wiring process and covers the substrate, and the resistance between the wiring and the element becomes extremely large. Become.

According to the present invention, since a dense film is formed by the surface reaction, it has been confirmed that Al-Si completely filled in the contact hole and the through hole has a resistivity of 2.7 to 3.3 μΩcm. The contact resistance is 0.6μm × 0.6μ
When the Si portion has an impurity of 10 ²⁰ cm ^-3 in the hole of m
× 10 ⁻⁶ Ω · cm ² can be achieved.

That is, according to the present invention, the wiring material can be completely embedded in the fine holes, and good contact with the base can be obtained. Therefore, the present invention can greatly contribute to the improvement of the in-hole resistance and the contact resistance, which are the biggest problems in a fine process of 1 μm or less.

That is, in the patterning process, an alignment accuracy of 3σ = 0.15 μm can be achieved at the line width of the limit of the resolution performance of the exposure machine, and a wiring having a smooth side surface without causing halation can be obtained.

It is possible to eliminate or eliminate the heat treatment during the wiring process at a low temperature.

As described in detail above, by applying the present invention to the wiring forming method of the semiconductor integrated circuit, it is possible to significantly improve the yield and promote the cost reduction as compared with the conventional Al-Si wiring. Becomes

(Example 1) First, the procedure of Al-Si film formation is as follows. Using the apparatus shown in FIG. 1, the inside of the reaction tube 2 is evacuated to approximately 1 × 10 ⁻⁸ Torr by the exhaust equipment 9. However, even if the degree of vacuum in the reaction tube 2 is lower than 1 × 10 ⁻⁸ Torr, Al—Si is formed.

After cleaning the Si wafer, the transfer chamber 10 is released to the atmospheric pressure, and the Si wafer is loaded into the transfer chamber. The transfer chamber is evacuated to approximately 1 × 10 ⁻⁶ Torr, and then the gate valve 13 is opened to mount the wafer on the wafer holder 3.

After mounting the wafer on the wafer holder 3, the gate valve
13 is closed and the chamber 2 is evacuated until the degree of vacuum in the reaction chamber 2 becomes approximately 1 × 10 ⁻⁸ Torr.

In this embodiment, DMAH is supplied from the first gas line.
Carrier gas DMAH line with H _2. The second gas line is for H ₂ and the third gas line is for Si ₂ H ₆ .

Flow H ₂ from the second gas line and use the slow leak valve 8
The pressure inside the reaction tube 2 is adjusted to a predetermined value by adjusting the opening of the reaction tube 2.
The typical pressure in this embodiment is approximately 1.5 Torr. Thereafter, the heater 4 is energized to heat the wafer. After the wafer temperature reaches the specified temperature, the DMAH line and Si ₂ H ₆ line
DMAH and Si ₂ H ₆ are introduced into the reaction tube. Total pressure is approximately 1.5 Torr
And the DMAH partial pressure is approximately 1.5 × 10 ⁻⁴ Torr. The partial pressure of Si ₂ H ₆ is 2 × 10 ⁻⁶ Torr. When Si ₂ H ₆ and DMAH are introduced into the reaction tube 2, Al—Si is deposited. After a predetermined deposition time has elapsed, the supply of DMAH and Si ₂ H ₆ is stopped. Next, heater 4
Is stopped, and the wafer is cooled. After the supply of H ₂ gas is stopped and the inside of the reaction tube is evacuated, the wafer is transferred to a transfer chamber, and only the transfer chamber is brought to atmospheric pressure, and then the wafer is taken out. Above is Al
-It is an outline of a Si film formation procedure.

 Next, sample preparation in the present invention will be described.

Hydrogen combustion method (H ₂ : 4 /
M, 0 _2: was subjected to thermal oxidation at a temperature of 1000 ° C. The 2 / M).

The thickness was 7000 ± 500 ° and the refractive index was 1.46. A photoresist is applied to the entire surface of the Si substrate, and a desired pattern is baked by an exposure machine. The pattern is 0.25μm
Various kinds of holes of × 0.25 μm to 100 μm × 100 μm are formed. After the phenomenon of the photoresist, the reactive ion etching (RIE) etc. is used to mask the underlying S
The iO ₂ was etched to partially expose the substrate Si. In this way, samples were prepared 130 sheets having 0.25μm × 0.25μm~100μm × 100μm various sizes SiO ₂ pores of,
The substrate temperature is set in 13 ways, and the total pressure is 1.5 Torr, the DMAH partial pressure is 1.5 × 10 ^-4 Torr, the Si ₂ H ₆ partial pressure is 2 × 10 ^-6 Torr, for each of the ten samples at each substrate temperature according to the procedure described above. An Al-Si film was deposited under the conditions.

The Al-Si film deposited by changing the substrate temperature to 13 levels was evaluated using various evaluation methods. Table 1 shows the results.

Al-Si is formed on SiO ₂ in the temperature range of 160 ° C. to 450 ° C. In the sample without deposition, Al-Si was deposited only on the portion where SiO ₂ is opening and Si is exposed. It should be noted that the same selective deposition number was maintained when deposition was performed continuously for two hours in the above temperature range.

(Example 2) By the same procedure as in Example 1, the total pressure was set to 1.5 Torr, the DMAH partial pressure was set to 5 × 10 ^-4 Torr, the substrate temperature (Tsub) was set to 300 ° C., and the partial pressure of Si ₂ H ₆ was set to 1.5 × 10 ^-7 Torr. From 1 × 10 ^-4 Torr
The deposition was performed by changing to In the formed Al-Si film
The Si content (Wt%) changed from 0.005% to 5% almost in proportion to the Si ₂ H ₆ partial pressure. With respect to resistivity, carbon content, average wiring life, deposition rate, hillock density, and generation of spikes, the same results as in Example 1 were obtained. But more than 4%
In the sample having the Si content, a precipitate thought to be Si was formed in the film, the surface morphology was deteriorated, and the reflectance was 65% or less. The reflectance of the sample having a Si content of less than 4% was 80 to 95%, which was the same as in Example 1. Further, as in the case of Example 1, the selective deposition by the substrate surface material was confirmed in all regions.

(Example 3) First, the procedure of Al-Si film formation is as follows. Exhaust equipment 9
Evacuates the reaction tube 2 to approximately 1 × 10 ⁻⁸ Torr. Even if the degree of vacuum in the reaction tube 2 is lower than 1 × 10 ⁻⁸ Torr, Al—Si is formed.

After cleaning the Si wafer, the transfer chamber 10 is released to the atmospheric pressure, and the Si wafer is loaded into the transfer chamber. The transfer chamber is evacuated to approximately 1 × 10 ⁻⁶ Torr, and then the gate valve 13 is opened and the wafer is mounted on the wafer holder 3. After the wafer is mounted on the wafer holder 3, the gate valve is mounted.
13 is evacuated until the degree of vacuum in the reaction chamber 2 becomes approximately 1 × 10 ⁻⁸ Torr.

In this embodiment, the first gas line is used for DMAH. DMAH
Ar was used as the carrier gas for the line. The second gas line
It is for H _2. The third gas line is for Si ₂ H ₆ .

Flow H ₂ from the second gas line and use the slow leak valve 8
Is adjusted so that the pressure in the reaction tube 2 becomes a desired value.
The typical pressure in this embodiment is approximately 1.5 Torr. Thereafter, the heater 4 is energized to heat the wafer. After the wafer temperature reaches the desired temperature, DMAH line, Si ₂ H ₆ line
DMAH and Si ₂ H ₆ are introduced into the reaction tube. Total pressure is approximately 1.5 Torr
And the DMAH partial pressure is approximately 1.5 × 10 ⁻⁴ Torr. The partial pressure of Si ₂ H ₆ is 2 × 10 ⁻⁵ Torr. When Si ₂ H ₆ and DMAH are introduced into the reaction tube 2, Al—Si is deposited. After the desired deposition time has elapsed, the supply of DMAH and Si ₂ H ₆ is stopped. Next, heating of the heater 4 is stopped, and the wafer is cooled. After the supply of H ₂ gas is stopped and the inside of the reaction tube is evacuated, the wafer is transferred to the transfer chamber, and only the transfer chamber is set to the atmospheric pressure, and then the wafer is taken out. The above is the outline of the Al-Si film formation.

The deposited film thus formed obtained the same results as in Example 1 in terms of resistivity, carbon content, average wiring life, deposition rate, hillock density, spike generation and reflectance.

The selective deposition by the substrate was also the same as in Example 1.

(Example 4) The total pressure is set to 1.5 Torr DMAH partial pressure 5 × 10 ^-4 Torr The substrate temperature (Tsub) is set to 300 ° C., and the partial pressure of Si ₂ H ₆ is set to 1.5 × 10 ^-7 Torr in the same procedure as in Example 3. From 1 × 10 ^-4 Torr
The deposition was performed by changing to In the formed Al-Si film
The Si content (Wt%) changed from 0.005% to 5% almost in proportion to the Si ₂ H ₆ partial pressure. With respect to resistivity, carbon content, average wiring life, deposition rate, hillock density, and generation of spikes, the same results as in Example 1 were obtained. But more than 4%
Samples with a Si content have a reflectivity of 65% due to the formation of precipitates likely to be Si in the film and the deterioration of the surface morphology.
It was as follows. The reflectance of a sample with a Si content of less than 4% is 80 ~
95%, similar to Example 1. Further, as in the case of Example 1, the selective deposition by the substrate surface material was confirmed in all regions.

(Example 5) Al-Si was applied to a substrate (samples 5-1 to 5-179) having the following configuration by using the low pressure CVD apparatus shown in FIG.
A film was formed.

Preparation of Sample 5-1 A thermally oxidized SiO ₂ film as a non-electron-donating second substrate surface material was formed on a single-crystal silicon as an electron-donating first substrate surface material. Patterning was performed by a photolithography process as shown in Example 1 to partially expose the single crystal silicon surface.

At this time, the thickness of the thermally oxidized SiO ₂ film was 7000 °, and the size of the exposed portion of the single crystal silicon, that is, the size of the opening was 3 μm × 3 μm. Thus, Sample 5-1 was prepared (hereinafter, such a sample is referred to as “thermally oxidized SiO ₂ (hereinafter abbreviated as T-SiO ₂ ) / single-crystal silicon”).

Preparation of Samples 5-2 to 5-179 Sample 5-2 was an oxide film (hereinafter abbreviated as SiO ₂ ) formed by normal pressure CVD / single crystal silicon Sample 5-3 was boron doped by normal pressure CVD Oxide film (hereinafter abbreviated as BSG) / single-crystal silicon, Sample 5-4 is phosphorus-doped oxide film (hereinafter abbreviated as PSG) / single-crystal silicon formed by atmospheric pressure CVD, Sample 5-5 is an atmospheric pressure CVD Sample 5-6 is a phosphorous and boron doped oxide film (hereinafter abbreviated as BSPG) / single crystal silicon. Sample 5-6 is a nitride film (hereinafter abbreviated as PS: N) / single crystal silicon formed by plasma CVD. Sample 5 -7 is a thermal nitride film (hereinafter abbreviated as TS: N) /
Single crystal silicon, Sample 5-8 is a nitride film (hereinafter abbreviated as LP-S: N) formed by low-pressure CVD / single crystal silicon, Sample 5-9 is a nitride film formed by an ECR device (hereinafter ECR-SiN). Abbreviation) / single-crystal silicon. Further, Samples 5-11 to 5-179 shown in Table 2 were prepared by combining an electron-donating first substrate surface material and a non-electron-donating second substrate surface material. Single-crystal silicon (single-crystal Si), polycrystalline silicon (polycrystalline Si), amorphous silicon (amorphous Si), tungsten (W), molybdenum (Mo), tantalum (T
a), tungsten silicide (WSi), titanium silicide (TiSi), aluminum (Al), aluminum silicon (Al-Si), titanium aluminum (Al-Si), titanium nitride (Ti-N), copper (Cu), Aluminum silicon copper (Al-Si-Cu), aluminum palladium (Al-
Pd), titanium (Ti), molybdenum silicide (Mo-Si)
Tantalum silicide (Ta-Si) was used. These samples, the Al ₂ O ₃ substrate, and the SiO ₂ glass substrate were placed in the reduced pressure CVD apparatus shown in FIG. 3, and an Al—Si film was formed in the same batch. The deposition conditions were as follows: reaction tube pressure 0.3 Torr, DMAH partial pressure 3.0 × 10
^-5 Torr, Si ₂ H ₆ partial pressure 1.0 × 10 ⁻⁶ Torr, substrate temperature 300 ° C., and film formation time 10 minutes.

As a result of forming a film under such conditions, a sample subjected to patterning from samples 5-1 to 5-179 In all cases, the deposition of the Al-Si film occurred only on the surface of the first substrate which was electron donating, and completely filled the opening having a depth of 7000 °. The film quality of the Al-Si film was the same as that of Example 1 having the substrate temperature of 300 ° C., and was very good. On the other hand, a non-electron donating second substrate surface has Al
-Si film was not deposited at all and complete selectivity was obtained. Non-electron-donating Al ₂ O ₃ substrates and SiO ₂ glass substrates also have Al-S
No i film was deposited.

Example 6 An Al—Si film was formed on a substrate having the following configuration using the low-pressure CVD apparatus shown in FIG.

A polycrystalline Si as an electron-donating first substrate surface material is formed on a thermal oxide film as a non-electron-donating second substrate surface material, and is subjected to a photolithography process as shown in Example 1. Patterning was performed to partially expose the thermal oxide film surface. At this time, the thickness of the polycrystalline silicon is
2000mm, the size of the exposed part of the thermal oxide film, that is, the opening is 3μ
m × 3 μm. Such a sample is designated as 6-1. Non-electron donating second substrate surface material (T-Si
O ₂ , CVD-SiO ₂ , BSG, PSG, BPSG, P-SiN, T-SiN, N, LP-SiN,
ECR-SiN) and electron-donating first substrate surface material (polycrystalline Si, amorphous Si, Al, W, Mo, Ta, WSi, TiSi, TaSi, Al-Si, Al
-Ti, TiN, Cu, Al-Si-Cu, Al-Pd, Ti, Mo-Si) were prepared, and samples 6-1 to 6-169 shown in Table 3 were prepared. These samples were subjected to reduced pressure CVD shown in FIG.
The device was placed in an apparatus, and an Al-Si film was formed in the same badge. The film formation conditions were: reaction tube pressure 0.3 Torr, DMAH partial pressure 3.0 × 10 ^-5 Torr, Si ₂ H
_{The 6-} minute pressure is 1.0 × 10 ⁻⁶ Torr, the substrate temperature is 300 ° C., and the film formation time is 10 minutes. As a result of forming a film under such conditions, 6-1 to 6-16
Non-electron donating in all samples up to 9
No Al-Si film is deposited on the opening where the substrate surface is exposed, and only the electron-donating first substrate surface has an Al-Si film.
Al-Si of 7000Å was deposited, and complete selectivity was obtained. The quality of the deposited Al—Si film was the same as that of the substrate temperature of 300 ° C. shown in Example 1 and was very good.

(Example 7) MMAH ₂ was used as a source gas, and the total pressure was set to 1.5 Torr MMAH ₂ partial pressure 5 × 10 ^-4 Torr Si ₂ H ₆ partial pressure 1 × 10 ^-5 Torr When the deposition was performed according to the procedure, an Al-Si thin film having excellent flatness, compactness, and selectivity depending on the substrate surface material was obtained in the same manner as in Example 1 in the temperature range of the substrate temperature of 160 ° C. to 400 ° C., as in Example 1. Was deposited.

(Example 9) Total pressure 1.5 Torr DMAH partial pressure 5 × 10 ^-4 Torr SiH ₄ 1 × 10 ^-5 in the same procedure as in Example 1 except that SiH ₄ was used as a raw material containing Si instead of Si ₂ H _6. Torr was set and deposition was performed.
In the temperature range of ° C., an Al—Si thin film containing no carbon impurities and excellent in flatness, denseness and selectivity depending on the substrate surface material was deposited in the same manner as in Example 1.

[Effects of the Invention] As described above, according to the present invention, a low-resistance, dense, and flat Al-Si film can be selectively deposited on a substrate.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a deposited film forming apparatus to which the present invention can be applied, FIG. 2 is a schematic sectional view for explaining a deposited film forming method according to the present invention, and FIG. 3 is applicable to the present invention. It is a schematic diagram which shows another example of a deposited film forming apparatus. DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Reaction tube, 3 ... Substrate holder, 4 ... Heater, 5 ... Mixer, 6 ... Vaporizer, 7 ... Gate valve, 8 ... Slow leak valve, 9 ... Exhaust unit, 10… Transfer chamber, 11… Valve, 12… Exhaust unit, 50… Quartz outer reaction tube, 51… Quartz inner reaction tube, 52… Source gas inlet, 53… Gas Exhaust port, 54: Metal flange, 56: Base holder, 57: Gas, 58: Gas flow, 59: Heater.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-55-67135 (JP, A) JP-A-1-198475 (JP, A) JP-A-62-202079 (JP, A) JP-A-62-202079 20870 (JP, A) JP-A-63-248795 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C23C 16/00-16/56 H01L 21/88

Claims (1)

(57) [Claims] 1. An electron donating surface comprising a material selected from tungsten, molybdenum, tantalum, aluminum, titanium aluminum, titanium nitride, copper, aluminum palladium, titanium or a silicide of the material, and a non-electron donor. Disposing a substrate having a neutral surface in a space for forming a deposited film, and (b) disposing a gas of an alkyl aluminum hydride selected from dimethyl aluminum hydride and monomethyl aluminum hydride, a gas containing silicon atoms, and a hydrogen gas. And (c) maintaining the temperature of the electron-donating surface within the range of not less than the decomposition temperature of the alkyl aluminum hydride and not more than 450 ° C. to form an aluminum film containing silicon. Selectively on the electron donating surface The deposited film forming method characterized by comprising the step of forming.