JPH0666286B2 - Method for forming silicon-containing metal film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to selective formation of a silicon-containing metal film on a silicon substrate or an exposed surface of aluminum or aluminum alloy wiring by a vapor phase growth method. On the exposed surface of the silicon substrate or only on the wiring so that
The purpose of the present invention is to provide a method for selectively forming a conductor film mainly composed of a refractory metal such as W or M ₀ , which is exposed by using a metal halide compound gas and a silane-based gas as a reaction gas. In the method of forming a silicon-containing metal film on a silicon substrate or wiring by vapor phase growth, the flow ratio of the silane-based gas to the flow rate of the metal-halogen compound gas is 2 or less and the growth temperature is 200 ° C. or less, and the silicon It is configured so that the contained metal film is selectively formed.

[Industrial application field]

The present invention relates to a method for forming a conductor film by vapor phase epitaxy, and more specifically, a silicon-containing metal film for filling or covering a contact hole to a wiring such as a silicon substrate or aluminum in a semiconductor device. The present invention relates to a selective forming method.

[Conventional technology]

2. Description of the Related Art In recent years, semiconductor devices such as LSI have been highly integrated and miniaturized, and improvements have been demanded in terms of filling contact holes, reliability of wiring, low resistance contact with a silicon substrate, and barrier metal. For example, as the wiring pattern becomes finer, the shape of the contact hole also becomes smaller. It is difficult to form a wiring connected to a silicon substrate through such a contact hole because of poor step coverage. Therefore, a refractory metal such as tungsten (W) is selectively vapor-deposited and filled in the contact hole, and then a wiring is formed to electrically connect with the silicon substrate through the filling material (refractory metal). Connect to. The selective growth of tungsten is performed at a temperature of 400 ° C. or higher, which is a practical growth rate, using WF ₆ gas and H ₂ gas as reaction gases. Further, it has been proposed to selectively grow tungsten silicide by using silane (SiH ₄ ) gas instead of H ₂ gas (Japanese Patent Laid-Open No. 59-72132). In the example of Japanese Patent Laid-Open No. 59-72132, WF ₆ gas is supplied at a flow rate of 1 cc / min, and silane gas is supplied at a flow rate of 3 cc / min in a low pressure CVD apparatus.
The substrate temperature is set to 45 by using argon gas at a flow rate of 1 per minute.
The contact hole is filled with a tungsten layer at 0 ° C. and a pressure of 0.2 Torr.

Furthermore, a low-pressure vapor phase growth method for metal silicides such as molybdenum and tungsten (MSi _x : M is metal, 1.7 × 2.3) is disclosed in Japanese Patent Laid-Open No. 267472/1987 (published on November 20, 1987, the first of the subject case). (Later than the date of domestic priority claim). In this case, for example, the amount of silane-based gas is large such that the flow rate of the SiH ₄ gas is 5 to 27 times higher than the flow rate of the M ₀ F ₆ gas in Example 1, and further, the growth is not the selective growth but the entire surface growth. . WF ₆ gas and high-order silane gas (Si _n H _{2 + n} , n = 2,3
...) and tungsten silicide (WSi
It is disclosed in US Pat. No. 4,684,542 that the vapor phase growth of _x : 2.2 _× 3.4, FIG. ₅ ) is performed. Also in this case, the flow rate of the high-order silane gas is higher than the flow rate of the WF ₆ gas, and the growth is not the selective growth but the entire surface growth.

[Problems to be Solved by the Invention]

In selective growth of tungsten using WF ₆ gas and H ₂ gas, encroachment of silicon substrate or wormhole (worm hole, elongated hole formed in silicon substrate) occurs, which increases junction leakage in semiconductor devices. There is.

Although selective growth occurs when silane (SiH ₄ ) gas is used instead of H ₂ gas, the growth temperature is still high, and a selective growth method at a lower temperature is required.

With the miniaturization and high density of semiconductor devices, the width and thickness of aluminum or aluminum alloy wiring are narrowed to submicron units. For this reason, the occurrence of voids and hillocks causes an increase in defects in which wirings are broken due to stress migration due to thermal stress, interlayer stress (strain), or electromigration due to increased current density. Therefore, in order to reduce defects, copper (Cu) should be added to the wiring aluminum or aluminum alloy.
And / or titanium (Ti) is added, the stress of the laminated film is reduced, or the tungsten (W) film is selectively formed only on the wiring.
Selective formation of tungsten is vapor phase growth by a chemical reaction between WF ₆ gas and SiH ₄ gas, and there is a problem that the growth temperature is high. That is, selective growth or overall growth of tungsten or tungsten silicide is usually performed at a temperature of 300 ° C. or higher, and the influence of thermal stress (for example, increase in stress migration) due to the formation process due to miniaturization is neglected. There is a demand for a lower temperature process (if possible, a room temperature forming process).

The main object of the present invention is to provide W, Mo, etc. on the exposed surface of the silicon substrate so as to fill the through holes at a lower growth temperature or only on the wiring so as to enhance the reliability of the wiring of a conductor such as aluminum. Another object of the present invention is to provide a method for selectively forming a conductor film containing the high melting point metal as a main component.

Another object of the present invention is to provide a method for further increasing the adhesion strength to a silicon substrate or wiring in the selective formation of the conductor film at the above-mentioned lower growth temperature.

[Means and Actions for Solving the Problems]

The above-mentioned object is a method for forming a silicon-containing metal film by vapor phase growth on a substrate having a conductor or semiconductor surface and an insulator surface, using a metal halogen compound gas and a silane-based gas as reaction gases. In the method, the ratio of the flow rate of the silane-based gas to the flow rate of the metal halide compound gas is set to 2 or less and the growth temperature is set to a temperature of less than 200 ° C., whereby the silicon-containing material on the conductor or semiconductor of the substrate. This is achieved by a method for forming a silicon-containing metal layer, which comprises the step of selectively forming a metal film.

The metal of the silicon-containing metal film is W, Mo, Ti, Ta, Pt or Pd, and if the silicon-containing metal formed by the method of the present invention is represented by the chemical formula, MSi _x (M is the metal mentioned above). , And the molar ratio x is 0.6 or less, preferably 0.01 to 0.1).
However, silicon is contained in an amount smaller than that of general metal silicide (it can be interpreted that the metal contains an impurity called silicon).

Metal halide compounds are fluoride gas and chloride gas that have been used conventionally, and include WF ₆ , MoF ₆ , TaF ₆ and Ti.
F ₄ , WCl ₆ , MoCl ₆ , TaCl ₅ , TiCl _{4 and the} like are preferable.

Silane-based gas when represented by the chemical formula _{Si n H 2n + 2 (n} = 1,2,
It is 3 ...), and it is particularly preferable to use disilane and trisilane because the higher the silane is, the lower the selective growth temperature becomes.

The preferred conditions for the selective formation of the silicon-containing tungsten film are that when silane (SiH ₄ ) gas is used, the gas flow rate ratio (SiH ₄ / WF ₆ ) is 2 or less, the growth temperature is 200 to 180 ° C., and disilane (SiH ₄ ) is used. ₂ H ₆ ) gas is used, the gas flow rate ratio (Si ₂ H ₆ / WF ₆ ) is set to 1 or less and the growth temperature is set to 200 to 80.
C., and when trisilane (Si ₃ H ₈ ) gas is used, the gas flow rate ratio (Si ₃ H ₈ / WF ₆ ) is 0.7 or less, and the growth temperature is 100 ° C. to room temperature.

Immediately before the selective growth of the silicon-containing metal film as described above, it is desirable to etch the exposed surface (the surface of the silicon substrate and the wiring) to clean the surface. A SiO ₂ thin film easily forms on the surface of the silicon substrate and an A ₂ O ₃ thin film (so-called natural oxide film) easily forms on the wiring surface of aluminum or aluminum alloy. If these remain, it may hinder the growth of the silicon-containing metal film. As a result, not only the adhesion strength of the film is lowered but also the contact resistance is increased. Therefore, by removing such a natural oxide film, favorable selective growth of the silicon-containing metal film becomes possible for the first time.

In general, when the growth temperature is lowered, the adhesion strength of the silicon-containing metal film selectively vapor-grown tends to be low. Therefore, although the thermal stress can be reduced by the low temperature growth, the decrease in the adhesion strength accompanying this can reduce the reliability of the semiconductor device. In order to increase the adhesion strength and realize a low temperature process, the silicon substrate or wiring is heated to a high temperature of 400 to 500 ° C for a short time of 10 to 30 seconds before the selective formation of the silicon-containing metal film described above. It is desirable to form a thin film of a refractory metal or a silicon-containing refractory metal that thinly covers the exposed surface. Such a thin film enhances the adhesion strength and, at the same time, serves as a growth nucleus of a silicon-containing metal film to be formed thereafter and contributes to the uniform formation of the silicon-containing metal film over the entire semiconductor wafer.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings by experiments including preferred embodiments of the present invention and comparative examples.

First, a case will be described in which a contact hole formed in an insulating film for connecting a silicon substrate and a wiring is selectively grown and embedded in a silicon-containing metal film by the forming method according to the present invention.

As shown in FIG. 1A, an insulating film (SiO ₂ film) 3 is formed on a p-type silicon (Si) substrate 2 having an n-type impurity doped region 1 by a known method such as a thermal oxidation method or a CVD method. To do. As the insulating film, in addition to SiO ₂ , PSG, BSG, BPSG, S
i ₃ N ₄ or polyimide can be used. The contact hole 4 exposing the impurity-doped region 1 is formed by selectively etching the SiO ₂ film 3. While proceeding to the next process,
The exposed silicon is oxidized by oxygen in the atmosphere to form a thin SiO ₂ film 5 on the exposed surface of the impurity-doped region 1.

As shown in FIG. 1B, a thin SiO ₂ film 5 is used as an etching gas 6
Remove by. After this dry etching process,
H ₂ gas or an inert gas such as Ar, He or N ₂ is excited into a plasma state by high frequency power (13.56MHz, 100W) under vacuum pressure, and SiO _{2 is} removed by sputtering. Alternatively, SiO ₂ can be removed by using a halogen compound gas such as NF ₃ , CCl ₄ , SF ₆ , BCl ₃ and activating the gas with energy such as microwaves, high frequency waves or ultraviolet rays. In this etching, not only the thin SiO ₂ film 5 but also the insulating film (SiO ₂ film) 3 is etched at the same time.
Since the insulating film 3 is thick, it remains almost as it is.

Then, the exposed surface of the silicon substrate 2 is kept so that the SiO ₂ film is not formed again, that is, the state where it is not exposed to the atmosphere, and as shown in FIG. 1C, WF _{6 is} formed according to the forming method according to the present invention. A silicon-containing tungsten film 7 is selectively formed on the exposed silicon surface of the impurity-doped region 1 using a gas and a silane-based gas to fill the contact hole up to the height of the insulating film (SiO ₂ film) 3.

And aluminum (Al) or aluminum alloy (Al
A conductive metal film such as an alloy) is deposited on the entire surface by a sputtering method or a vacuum evaporation method, and selective etching is performed in a predetermined pattern to form a wiring 8 as shown in FIG. 1D. In this manner, the wiring 8 is connected to the impurity region 1 through the silicon-containing tungsten film 7 with which the wiring 8 is embedded.

The growth of the above-described silicon-containing tungsten film will be described with reference to the results (FIGS. 2 to 5) obtained by the experiment conducted by the present inventor as follows.

For the growth, a cold wall parallel plate type load lock type reactor was used, and WF ₆ was used as a reaction gas and SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ (4% / Ar) and H ₂ Comparative Example) used He or Ar as a carrier gas. The flow rate of each reaction gas is 1 to 20 SCCM, the flow rate of H ₂ and carrier gas is 0.5 to ₂ SLM, the growth temperature (substrate heating temperature) is from room temperature to 460, and the growth pressure is 0.2 to 0.3 Torr. SiH ₄ / WF ₆ = 1.0, Si ₂ H ₆ / WF ₆ = 0.
5, Si ₃ H ₈ / WF ₆ = 0.3 was set. FIG. 2 shows the relationship between the growth rate and the growth temperature of the grown silicon-containing tungsten films A, B and C (and the tungsten film D). As it can be seen from Figure 2, the reduction reaction of tungsten growth D in WF ₆ + H ₂ is the surface reaction rate, according to the present invention WF ₆ + Si _n
The reduction reaction of the silicon-containing tungsten growth A, B, C at H _{2n + 2} (n = 1,2,3) is rate-controlled. Si _n H _{2n + 2}
In the reduction reaction, the growth start temperature (lower limit temperature) becomes lower as n increases, and in the Si ₃ H ₈ reduction reaction at room temperature (25 ° C)
Growth also occurs in the vicinity. In the present invention, the growth rate indicates the growth film thickness per unit time in the portion of the substrate which is not covered with the insulating film.

In any of the silicon-containing tungsten growths A, B, and C according to the present invention, the growth rate decreases as the growth temperature increases. This is dominated by exposed surface reaction and selective growth due to surface reaction of previously grown silicon-containing tungsten at an appropriate temperature. This is because they are also deposited (grown) on the insulating film (SiO ₂ film), and the amount of deposition is relatively small in the portion where only selective growth has occurred so far. It will be full-scale growth instead of selective growth.

Silicon-containing tungsten film growth A, B and C described above
In FIG. 3, the relationship between the X-ray diffraction intensity and the growth temperature of the formed film is shown in FIG. In the case of growth A (SiH ₄ / WF ₆ = 1.0), the W (110) intensity decreases as the growth temperature increases, while the diffraction of W ₅ Si ₃ (002) appears from the growth temperature of about 360 ° C. Increase with. Growth similar to this B
(Si ₂ H ₆ / WF ₆ = 0.5) and growth C (Si ₃ H ₈ / WF ₆ = 0.3)
There is also about.

Furthermore, FIG. 4 shows the X-ray diffraction pattern of the silicon-containing tungsten film grown at growth temperature 320 ° C. (SiH ₄ / WF ₆ = 1).
And the case of 380 ° C and the case of growth in which the reaction gas flow rate ratio is SiH ₄ / WF ₆ = 4 and the silane flow rate is increased at the growth temperature of 320 ° C. As can be seen from FIG. 4, even when the reaction gas flow rate ratio is constant at 1, the structure shows a tungsten (W) structure at a growth temperature of 320 ° C. and a W ₅ Si ₃ structure at a growth temperature of 380 ° C.
The structure appears as shown in FIG. Even if the growth temperature is constant at 320 ° C, the flow rate of silane gas is increased to increase the SiH
_{When 4} / WF ₆ = 4, β-w is contained in the silicon-containing tungsten film in addition to α-w. This β-w is 70
It is a metastable phase that changes to α-w by heat treatment at 0 to 900 ° C. and has high resistance. Further, as in FIG. 4, an X-ray diffraction pattern of the silicon-containing tungsten film is shown in FIG.
The case of growth B (Si ₂ H ₆ / WF ₆ = 0.5) at a growth temperature of 150 ° C. and the case of Si ₂ H ₆ / WF ₆ = 0.5 at a growth temperature of 220 ° C. are shown. As can be seen from Fig. 5, the growth temperature at Si ₂ H ₆ / WF ₆ = 5
At 220 ° C, W ₅ Si ₃ structure appears in addition to α-w (110) structure.

The present inventor further conducted an experiment and conducted a reaction gas flow rate ratio (Si _n
The results shown in FIG. 6 are obtained for the relationship between H _{2n + 2} / WF ₆ ) and the growth rate. WF ₆ gas flow rate is constant (5SCCM / mi
n) as the gas flow rate of SiH ₄ , Si ₂ H ₆ and Si ₃ H ₈ is changed,
WF ₆ -SiH ₄ (△): 280 ℃, WF ₆ -Si ₂ H ₆ (○): 183 ℃
And WF ₆ -Si ₃ H ₈ (□): Selective growth rate of silicon-containing tungsten film at 25 ° C. Flow ratio is shifted from the selective growth exceeding 2 in the case of SiH ₄ / WF ₆ to confluence, Si ₂ H
_In the case of ₆ / WF ₆ , if it exceeds 1, it is easy to shift from selective growth to full-scale growth. Further, when the flow rate ratio of Si ₃ H ₈ / WF ₆ exceeds 0.7, the selective growth proceeds to the full-scale growth.

Preferred conditions for selectively forming a silicon-containing tungsten film by using a _{WF 6 + Si n H 2n +} 2 of the reaction gas from these experiments, the growth temperature is 380 ° to 180 ° C. at a SiH ₄ / WF ₆ 2 at the SiH ₄ gas, Especially, in order to reduce the thermal stress on the wiring structure, the temperature is 200 ° to 180 ° C. With Si ₂ H ₆ gas, Si ₂ H ₆
1. The growth temperature is 200 ℃ ~ 80 ℃, Si ₃ H ₈ gas is Si ₃ H ₈
0.7, growth temperature 100 ℃ ~ room temperature. Trisilane (Si ₃ H ₈ ) gas is optimal because of its low growth temperature. The composition ratio (x) of the silicon-containing tungsten film expressed by WSi _x is 0.1 to 0.12 when SiH ₄ / WF ₆ = 2.
And when SiH ₄ / WF ₆ = 1 x is 0.01 to 0.1,
When Si ₂ H ₆ / WF ₆ = 0.5 and Si ₃ H ₈ / WF ₆ = 0.3, x is
Common tungsten silicide WS with 0.05 or less
Si concentration is much lower than i ₂ . The composition distribution in the depth direction of the silicon-containing tungsten film when SiH ₄ / WF ₆ = 1 is
The results of SIMS analysis are shown in FIG. As shown in the figure, a film having a substantially constant composition in the film thickness direction is obtained. The resistivity of the silicon-containing tungsten film grown at the growth temperature of 200 ° C. or less is 8 to 10 μΩ · cm, and the same characteristics as the resistivity of the tungsten film in the WF ₆ + H ₂ reaction are obtained. Was given. The specific resistance tends to increase as the ratio of the silane-based gas to WF ₆ increases and as the growth temperature increases. SiH ₄ / WF ₆
It was found that the specific resistance of the obtained silicon-containing tungsten film was as high as 35 μΩ · cm when the growth temperature was 380 ° C. = 2.

When the temperature is low, it is considered that the reaction between WF ₆ gas and Si _n H _{2n + 2} gas proceeds as follows, Therefore, the ratio of silane-based gas to WF ₆ is SiH ₄ : Si ₂ H ₆ : Si ₃ H ₈ = 1.5: 0.75: 0.5. Therefore, the ratio of silane-based gas to WF ₆ gas is
When standardized with 1 for ₄ / WF ₆ , silane-based / WF ₆ = 1: 0.5: 0.3. Therefore, the higher the silane gas, the lower the flow rate. The experimental results shown in FIG. 6 shown above are in good agreement with those described above.

In the above case, it is also possible to form a film containing silicon in a refractory metal (Mo, Ti, Ta, Pt, Pa, etc.) other than tungsten, which is a silicon-containing tungsten film,
In that case, halogen compounds of each metal are fluorides such as MoF ₆ , TiF ₆ and TaF ₅ , or chlorides such as WC.
l ₆ , FoCl ₆ , FiCl ₄ , TaCl ₅ or the like is used. Further, the silane-based gas may be used the above-mentioned Si _n H _2n-2 chlorine in these gases in addition to gas (Cl) or fluorine (F) is bound gas.

As described above, when using a silane-based gas according to the present invention, the growth rate is higher than when using a H ₂ gas,
Since the growth is at a low temperature, the reaction with the silicon substrate is small, and therefore the amount of erosion of the silicon substrate is small. Further, prior to vapor phase growth, the exposed surface is dry-etched beforehand to remove the natural oxide film of the SiO ₂ film or Al ₂ O ₃ film, so that a silicon-containing metal film with a stable and uniform film thickness can be obtained. It can be selectively formed.

FIG. 8 shows a case where the contact hole is filled with a silicon-containing tungsten film and a tungsten film as an application example of the forming method according to the present invention.

Selection of a silicon-containing tungsten film using the above-mentioned WF ₆ gas and Si _n H _{2n + 2} gas on the surface of the impurity introduced region 1 of the silicon substrate 2 exposed in the contact hole formed in the insulating film (SiO ₂ film) 3. By growth, a thin silicon-containing tungsten film 11 having a thickness of several tens nm is formed. next,
Tungsten selective growth using conventional WF ₆ gas and H ₂ gas is performed to form a tungsten film 12 on the silicon-containing tungsten film 11, and the contact hole is filled as shown in FIG.

As the selective growth condition of tungsten, the growth temperature (substrate heating temperature) is, for example, 400 to 600 ° C., and WF ₆ gas (2
～10SCCM) and using a H ₂ gas (1000~2000SCCM) as a reaction gas, a growth pressure 0.1~1Torr as, tungsten growth rate is 200- 300nm / min. The reaction at this time is as follows.

WF ₆ + 3H ₂ → W + 6HF + H _{2 In} this tungsten growth, there is a silicon-containing tungsten film 11 already formed, and this acts as a barrier film, so that the silicon substrate 2 (that is, the impurity introduction region 1)
Will not be eroded. In this case, since the embedded material (filling material) is mainly tungsten, the resistance as the filling material is equivalent to that of tungsten.

In the above-described embodiment, the silicon-containing tungsten film is selectively grown on the exposed surface of the silicon substrate, but it can be similarly selectively grown on the surface of the wiring of aluminum or aluminum alloy as described below. .

First, FIG. 9A shows an aluminum alloy wiring 21 formed on an insulating film (not shown) which is a part of a semiconductor device. An interlayer insulating film (SiO ₂ film) 22 is formed on the entire surface including the wiring 21 by the CVD method. The insulating film 22 is selectively etched to form a contact hole 23 that exposes a part of the wiring 21. During the next step, oxygen in the atmosphere oxidizes the exposed aluminum alloy to form a thin Al ₂ O ₃ film (natural oxide film) 24 on the exposed surface.

As shown in FIG. 9B, the thin Al ₂ O ₃ film 24 is dry-etched, and, for example, the inert gas 25 is turned into plasma and removed by sputtering. This Al ₂ O ₃ film can be removed by using a halogen compound gas (CF ₄ , BCl ₃ , CCl _4, etc.) by activating the gas by ultraviolet light or by reactive sputter etching.

Next, so that the exposed aluminum alloy surface of the wiring 21 is not oxidized again, that is, kept in a state of not being exposed to the atmosphere, as shown in FIG. 9C, WF ₆ gas according to the forming method according to the present invention described above. And a silane-based gas are used to selectively form a silicon-containing tungsten film 26 on the exposed surface to fill the contact hole 23.

Then, a conductor metal film such as an aluminum alloy is deposited on the entire surface by a sputtering method, and selective etching is performed in a predetermined pattern to form a wiring 27 as shown in FIG. 9D. In this way, the upper wiring 27 and the lower wiring 21 are connected via the silicon-containing tungsten film 26 embedded in the contact hole.

WF ₆ on aluminum or aluminum alloy wiring
When gas and H ₂ gas or silane-based gas are used as reaction gas, WF ₆ gas reacts with aluminum (Al) as shown in the following formula, and WF ₆ → 2Al → W + 2AlF ₃ wiring (aluminum) and deposition It is considered that AlF ₃ precipitates at the interface with the tungsten (or silicon-containing tungsten) that forms the contact resistance. So Al
Although F ₃ can be reduced by sublimation in an environment under vacuum hot (about 400 ° C. or higher), the acting force as a reducing agent to _{WF 6 (H 2 <Al <} SiH 4 <Si 2 H 6 <Si It is possible to suppress AlF ₃ precipitation by using a silane-based gas in which ₃ H ₈ ) is larger than the WF ₆ —H ₂ system reaction. By the way, in the WF ₆ -SiH ₄ reaction system, the contact resistance between W / Al at the growth rate of 2 μm / min and at 0.25 μm / min is higher than that of Al / Al. It was 2-3 times that, and the latter was 20-30 times that. In the case of H ₂ / WF ₆ , W
The contact resistance between Al and Al is 10 to 10 times that of Al / Al.
It was 0 times. Therefore, the contact resistance at the aluminum interface is lower in the present invention than in the case of H ₂ gas.

With the miniaturization of the wiring of aluminum or aluminum alloy, the disconnection defect increases due to the generation of voids and hillocks, as well as thermal migration and electromigration, whereas on the wiring of the silicon-containing metal film according to the present invention. It will be described that selective formation on the substrate is an effective defect prevention method.

First, as a sample of the conventional example (Sample H), as shown in FIG. 10, a PSG insulating film 31 is formed on a silicon substrate (not shown).
, And an aluminum alloy (Al-Si alloy) film with a thickness of 1.2 μm is formed on the entire surface by sputtering, and with a width of 1.0 μm and a total length of 4 μm by selective etching.
A predetermined pattern wiring 32 of 0 m was formed. A PSG insulating film 33 is formed on the entire surface including the aluminum alloy wiring 32 by a CVD method, and a Si ₃ N ₄ film 34 is further formed on the PSG insulating film 33 by a CVD method.

According to the forming method of the present invention, as shown in FIG.
Samples (Samples I and J) are prepared in the same manner as the sample of FIG. 9 except that the selective formation of the silicon-containing tungsten film 35 (thickness: about 20 nm) on the alloy wiring 32 is added. Sample I
The silicon-containing tungsten film 35 in WF ₆ gas and SiH ₄
Gas and reaction gas as flow ratio (SiH ₄ / WF ₆ ) 1 at 350 ℃
It is formed at the growth temperature, also in Sample J WF ₆ gas and S
Flow rate ratio (Si ₃ H ₈ / WF ₆ ) 0.3 with i ₃ H ₈ gas as reaction gas
The silicon-containing tungsten film 35 is formed at a growth temperature of room temperature (25 ° C.).

Keep these samples (samples: H, I, J) heated to 180 ℃ and
A heat deterioration test for up to 000 hours was conducted to examine open circuit defects, and the results are shown in FIG. The cumulative open circuit frequency includes the wiring resistance increased by 10% or more. As can be seen from FIG. 12, in the sample H of the conventional example, the open circuit defects increase with the elapsed time, but when the wiring is coated with the silicon-containing tungsten film of the sample J grown at room temperature, even 1000 hours can be reached. The open circuit frequency does not change (open circuit defects do not increase). Further, in the case of the silicon-containing tungsten coating of sample I grown at 350 ° C., open circuit defects start to increase from the time when it exceeds 700 hours. This is because the voids and cracks are generated in the Al-Si wiring 32, the cross-sectional area of the wiring is reduced and the resistance is increased, or the wiring body is cut, etc.
Compared to the conventional example, open circuit defects are greatly suppressed.

FIGS. 13A to 13D show a case where a method for forming a silicon-containing tungsten film according to the present invention is applied to form a multilayer wiring structure of aluminum or aluminum alloy wiring in a semiconductor device.

As shown in FIG. 13A, an insulating film (SiO 2
₂ film) 42 is formed by, for example, a thermosetting method. A film of Al or Al alloy is formed on the insulating film 42 by a sputtering method or the like, and is selectively etched to form a first wiring 43 having a predetermined pattern. Since Al (or Al alloy) of the wiring 43 is very easily oxidized and has an Al ₂ O ₃ thin film (not shown) on its surface, a pretreatment for removing this is performed. For example, BCl ₃ gas (10SCCM) is used as etching gas and the pressure is 0.7 Torr.
r, the frequency is 13.56 MHz, and the plasma reactive etching process is performed with high-frequency power of 100 W output.
Subsequently, plasma sputter etching processing is performed using H ₂ gas (500 SCCM) at a pressure of 0.3 Torr and the same high frequency power. Al ₂ O by reactive etching with BCl ₃
Wiring 4 by sputter etching with H ₂ after almost removing ₃
Clean the surface of 3. Then, WF ₆ gas and silane according forming method according to the present invention (Si _n H _{2n + 2)} selectively vapor phase growth form a silicon-containing tungsten film 44 on the wiring 43 by using the gas.

The selective growth conditions for the silicon-containing tungsten film 44 are the same as the above-described growth conditions on the exposed surface of the silicon substrate. In particular, Si ₃ H ₈ gas (1SCCM) was used, and WF ₆ gas was
SCCM, pressure 0.3 Torr, Ar carrier gas 500 SC
As the CM, it is preferable to form a silicon-containing tungsten film having a growth temperature of 25 ° C. (room temperature). In this case, it is not necessary to heat, and since Si ₃ H ⁸ has a strong reducing effect on WF ₆ , AlF ₃ is almost not present on the Al (or Al alloy) surface (that is, the interface between Al and deposited tungsten). Does not precipitate.

Next, as shown in FIG. 13B, an insulating film (interlayer insulating film) 45 such as PSG or SiO ₂ is formed on the entire surface by the CVD method, and a contact hole 46 is formed by selective etching.

On the silicon-containing tungsten film 44 exposed in the contact hole, a silicon-containing tungsten film 47 is selectively grown using WF ₆ gas and silane-based gas as described above, and as shown in FIG. 13C, Fill the contact hole.

Then, as shown in FIG. 13D, the second wiring 48 of Al (or Al alloy) is formed in the same manner as the formation of the first wiring 43. From the surface of this wiring 48, the Al ₂ O ₃ film is formed by the plasma described above. It is removed by etching pretreatment. A silicon-containing tungsten film 49 is formed on the surface of the wiring 48 by the same method as that on the surface of the first wiring 43.

In this way, a multilayer wiring structure having an Al (or Al alloy) wiring covered with a silicon-containing tungsten film and a contact hole filling material of the silicon-containing tungsten film can be obtained. In this way, it is possible to obtain a highly reliable multi-layer wiring structure that prevents open circuit defects and reduces contact interface resistance.

In the case of selectively forming a silicon-containing tungsten film according to the present invention using WF ₆ gas and silane-based gas,
When the exposed surface of the silicon substrate is the surface of the n-type region and the surface of the p-type region, a difference in the concentration of the doped impurities causes a difference in the growth start time (especially, the lower the growth temperature, the larger the difference). The film thickness varies. Also, Al
(Or Al alloy) The adhesion strength of the silicon-containing tungsten film changes depending on the surface condition of the wiring, the surface condition of the silicon substrate, the impurity conductivity type, and the impurity concentration, and if it is bad, it peels off the film, causing contact failure and peeling. The film becomes dust in the reactor and adversely affects growth. Therefore,
Prior to the formation of the silicon-containing tungsten film according to the present invention, it is preferable that the initial reaction until the deposited silicon-containing tungsten covers the exposed silicon or Al (Al alloy) is completed at a high temperature in a short time. Since the deposited thin film of this initial reaction serves as a growth nucleus for the subsequent vapor phase growth, the growth starts almost at the same time, and since the temperature is high, the bond between silicon or aluminum and the silicon-containing tungsten is improved and the adhesion strength becomes uniform. improves.

The initial reaction mainly proceeds by a self-controlled surface reaction between the substrate (or wiring) itself and the metal halide compound gas (WF ₆ gas).

In the case of silicon: MX _n + Si → M + SiX _n ↑ (M is a metal such as W, X is a halogen such as F) and the silicon surface is covered with M (metal). According to the results of experiments conducted by the inventor, it was confirmed that this reaction occurs in a short time of about 10 seconds. This initial reaction occurs more uniformly at higher temperatures, but if growth continues at high temperatures even after the completion of the initial reaction, the reaction between the silicon substrate and the metal such as tungsten progresses during this growth, and the silicon substrate is eroded. Therefore, a uniform and thick silicon-containing tungsten film should be formed in the shortest possible time (preferably 10 to 30 seconds), and then the growth rate with temperature does not change so much in accordance with the molding method of the present invention. Form.

In the case of aluminum: MX _n + Al → M + AlX _n ↓, not only the aluminum surface is covered with M (metal), but AlX _n (AlF ₃ ) is simultaneously deposited. This AlF ₃ is A
l-MX _n reaction system highly reactive than system _{(Al-Si n H 2n +} 2,
In particular, Al-Si ₃ H ₈ ) can be used to reduce the precipitation relatively, but the deposited AlF ₃ is decompressed and heated to a high temperature (400 ° C or higher).
Can be removed by sublimation. After the initial reaction, it is the same as in the case of silicon described above.

The initial reaction at high temperature for a short time and the subsequent silicon-containing tungsten film growth reaction can be performed as follows.

If a reactor 51 capable of reducing the pressure as shown in FIG. 14 is used, a silicon substrate 52 is placed on a transparent plate (quartz or the like) 53, and a heating lamp (infrared lamp) 54 is placed below the transparent plate 53. Have been installed. Above the reaction gas and carrier gas of the silicon substrate _{52 (WF 6 + Si n H} 2n + 2 + H 2 + He (or + A
A shower 55 for mixing and jetting r)) is provided. The heating lamp may be installed on the upper side or the side of the device 51. Although the back side of the silicon substrate 52 is adhered to the transparent plate 53 so that the reaction gas does not enter, a gas that does not affect the reaction may be blown onto the back surface of the substrate.

First, the inside of the reaction device 51 is brought into a predetermined vacuum pressure state by a vacuum pump (not shown), and as shown in FIG. 15, by rapid heating by the heating lamp 54, for example, is heated to a high temperature (400 ° C.), Maintain the initial reaction period I (about 10 seconds). WF ₆ gas (2SCCM), SiH ₄ gas (2SCCM), He
A gas (500 SCCM) is flown from the shower 55 toward the silicon substrate 52 to selectively form a silicon-containing tungsten thin film having a thickness of about 10 nm or more. The pressure at this time is 0.01
It is preferably set to 0.1 Torr. H ₂ instead of SiH ₄ gas
Gas may be used, or Ar gas may be used instead of He gas. Then, the temperature of the silicon substrate 52 is lowered to the temperature at which the silicon-containing tungsten film grows according to the forming method of the present invention by natural cooling or forced cooling. And
WF ₆ gas and Si _n H _{2n + 2} (n = 1,2,3,4) gas are passed through the shower 55 during the film forming period II to form a silicon-containing tungsten film having a predetermined thickness. For example, WF ₆ gas (2.5 SCCM) and Si ₂ H ₆ gas (1 SCCM) are flowed at a substrate temperature of about 120 ° C. for about 1 minute. If Si ₃ H ₈ gas is used as the silane-based gas, the film can be formed at room temperature, so that the silicon substrate can be heated only for a short time of about 10 seconds in the initial reaction period I.

〔The invention's effect〕

According to the present invention, it becomes possible to selectively grow a silicon-containing metal film at a much lower temperature and at a higher growth rate than in the conventional selective growth of tungsten using WF ₆ gas and H ₂ gas. When the present invention is applied to aluminum or aluminum alloy wiring, the reliability of the wiring can be increased, which contributes to the improvement of the reliability of the semiconductor device.

Further, it becomes possible to vapor-deposit a silicon-containing metal (high melting point metal) film at room temperature, in which case heating equipment and the like can be omitted and energy consumption (electric power etc.) can be saved.

[Brief description of drawings]

1A to 1D are schematic cross-sectional views of a silicon substrate for explaining the steps of the method for forming a silicon-containing metal film according to the present invention, and FIG. 2 shows the growth temperature of the metal film with a silane-based gas and H ₂ gas. Fig. 3 is a graph showing the relationship with the growth rate, Fig. 3 is a graph showing the relationship between the growth temperature of a metal film in a silane-based gas and the X-ray diffraction intensity, and Fig. 4 is a silicon-containing metal by WF ₆ gas and SiH ₄ gas. graph showing an X-ray diffraction pattern of the film, FIG. 5 is a graph showing the X-ray diffraction pattern of a silicon-containing metal layer by WF ₆ gas and the Si ₂ H ₆ gas, Figure 6 is _{Si n H 2n + 2 / WF} 6 flow rate ratio And FIG. 7 is a graph showing the compositional distribution in the film thickness direction of the silicon-containing tungsten film, and FIG. 8 is a schematic view of the silicon-containing metal film and the silicon substrate in which the contact holes are filled with the metal film. Sectional views, Figures 9A-9D Is a schematic sectional view of a wiring in which a contact hole in an aluminum or aluminum alloy wiring is filled with a silicon-containing metal, FIG. 10 is a schematic sectional view of a conventional aluminum alloy wiring and an insulating film, and FIG. 11 is a silicon-containing metal film. Schematic cross-sectional views of the coated aluminum alloy wiring and insulating film, FIG. 12 is a graph showing the open circuit cumulative frequency of the aluminum alloy wiring, and FIGS. 13A to 13D are multilayer wiring structure of aluminum alloy wiring coated with a silicon-containing metal. FIG. 14 is a schematic diagram of a reactor equipped with a rapid heating mechanism, and FIG. 15 is a graph of a temperature profile in the method for forming a silicon-containing metal film according to the present invention having a high temperature heating step in the initial reaction period. 2 ... Silicon substrate, 3 ... Insulating film, 7 ... Silicon-containing metal film, 8 ... Wiring, 32 ... Aluminum alloy wiring, 33 ... Insulating film, 35 ... Silicon-containing metal film, 51 ... Reaction Equipment, 52 …… Silicon substrate, 53 …… Transparent plate, 54 …… Heat lamp, 55 …… Shower.

Claims (18)

[Claims] 1. A method for forming a silicon-containing metal film by vapor phase growth on a substrate having a conductor or semiconductor surface and an insulator surface, using a metal halide compound gas and a silane-based gas as reaction gases. In the above, by setting the flow rate ratio of the silane-based gas to the flow rate of the metal halogen compound gas to 2 or less and the growth temperature to 200 ° C. or less, the silicon-containing metal film is selectively formed on the surface of the conductor or semiconductor. A method for forming a silicon-containing metal film, comprising the step of forming. 2. The method according to claim 1, wherein the surface of the conductor or semiconductor is an exposed surface in a contact hole formed in an insulating film or an exposed surface of a wiring. 3. The metal of the silicon-containing metal film is W, Mo, Ti,
The method according to claim 1, wherein the metal is at least one of Ta, Pt and Pd. 4. The method of claim 3, wherein the metal is W. 5. The method according to claim 3, wherein the metal halide compound gas is a fluoride gas of the metal. 6. The fluoride of the refractory metal is WF ₆ , MoF ₆ Ta.
The method of claim 5, wherein the method is one of F ₅ and TiF ₄ . 7. The method of claim 3, wherein the metal halide gas is a chloride gas of the metal. 8. The chloride of the refractory metal is WCl ₆ , MoCl ₆ , TaC.
The method according to claim 7, wherein the method is any one of l ₅ and TiCl ₄ . 9. The silane-based gas is Si _n H _{2N + 2} (n = 1,
2. The method according to claim 1, wherein the gas is 2,3, ... 10. The silane-based gas is silane (SiH ₄ ) gas, the metal halogen compound gas is WF ₆ gas, and the gas flow rate ratio (SiH ₄ / WF ₆ ) is 2 or less,
The method according to claim 1, wherein the growth temperature is 200 to 180 ° C. 11. The silane-based gas is disilane (Si ₂ H ₆ ).
Gas, the metal halogen compound gas is WF ₆ gas, and the gas flow rate ratio (Si ₂ H ₆ / WF ₆ ) of these gases is 1 or less, and the growth temperature is 200 to 80 ° C. The method of claim 1, wherein 12. The silane-based gas is trisilane (SH
₃ H ₈ ) gas, the metal halide compound gas is WF ₆ gas, the gas flow rate ratio (Si ₃ H ₈ / WF ₆ ) is 0.7 or less, and the growth temperature is 100 ° C. to room temperature. The method according to claim 1, wherein: 13. The method according to claim 1, further comprising a step of etching the exposed surface to clean the exposed surface immediately before the vapor deposition. 14. The etching process comprises a step of dry etching using NF ₃ , carbon halide, SF ₆ , BCl ₃ , H ₂ and an inert gas as an etching gas. The method according to Item 13. 15. The method of claim 14, wherein in the dry etching, the etching gas is activated by at least one energy of microwave, high frequency and energy ray. 16. Prior to the vapor phase growth, the surface of the conductor or semiconductor of the substrate is heated to 400 to 500 ° C. for 10 to 30 seconds, and the metal halide compound gas and the reducing gas are heated during this heating. 2. The method according to claim 1, further comprising the step of selectively forming a thin film of a metal or a metal containing silicon on the surface of the conductor or semiconductor by using it as a reaction gas. 17. A WF ₆ gas and the reducing gas of H ₂ or SiH ₄ are used to form the thin film of tungsten or silicon-containing tungsten by heating at a high temperature for a short time at 400 to 500 ° C.
On the thin film, using WF ₆ gas and Si _n H _{2n + 2} (n = 2,3,4) gas, the flow rate ratio (Si _n H _{2n + 2} / WF ₆ ) was set to 1 or less and the growth temperature was set to 200 ° C. or less. 17. The method according to claim 16, wherein the silicon-containing tungsten film is grown to a predetermined thickness. 18. A method of manufacturing a semiconductor device having a multi-layered wiring structure of aluminum or aluminum alloy wiring comprises: (a) a step of forming the first wiring on an insulating film on a semiconductor substrate; A step of selectively forming a first silicon-containing metal film only on the first wiring; (c) a step of forming an interlayer insulating film on the entire surface; (d) a contact hole by selectively etching the interlayer insulating film. Forming and exposing a part of the first wiring; (e) selectively forming a second silicon-containing metal film only in the contact hole; (f) the second silicon-containing metal film and the interlayer. The step of forming the second wiring on the insulating film; (g) the step of selectively forming the third silicon-containing metal film only on the second wiring; and (a) and (e) above.
In the selective formation of the silicon-containing metal film in the step (g), a metal halide compound gas and a silane-based gas are used as reaction gases, and the flow ratio of the silane-based gas to the flow rate of the metal-halogen compound gas is 2 or less. And a growth temperature of 200 ° C. or lower.