JP2000114369A - Formation of metal film and manufacture of electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a metal film which makes it possible to reduce film the formation temperature and further attain practical film formation speed, by adding carbonic gas to material gas containing metal halide gas and reducing gas. SOLUTION: A lower-layer interlayer insulating film 1 is formed on a semiconductor substrate, and lower-layer wiring 2 of Al alloy or the like is formed on the lower-layer interlayer insulating film 1. The lower-layer wiring 2 is subjected to spin coating, and subsequently to curing in an N2 atmosphere to form an organic polymeric material film 3 of polyarylether. An oxide film 4 is deposited thereon to form an interlayer insulating film 5. Connecting holes 6 facing on the lower-layer wiring is formed in the interlayer insulating film 5, and a barrier metal 7 film is formed on this structure. Thereafter, carbonic gas, such as CO and CH4, is added to reducing gas, such as metal halide and hydrogen, using a low-pressure CVD system to form a metal film 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a metal film and a method for manufacturing an electronic device, and more particularly, to a method for forming a metal film characterized by lowering a film forming temperature and a film forming rate, and using the same. And a method of manufacturing an electronic device such as a highly integrated semiconductor device.

[0002]

2. Description of the Related Art ULSI (Ultra Large Scale Integrate)
As the degree of integration of semiconductor devices such as d circuits increases, the wiring width and the wiring pitch need to be finer. At the same time, in order to meet the demands for lower power consumption and higher operating speed of semiconductor devices, especially semiconductor devices of high-speed logic type, the capacitance between wirings, which increases with the finer wiring spacing, is required. Suppression is essential, and selection of a low dielectric constant interlayer insulating film material is gaining importance as one of the elemental technologies. This is also an important problem in various high-frequency fine electronic devices other than semiconductor devices.

[0003] Insulating film materials conventionally used for interlayer insulating films of semiconductor devices and the like include SiO ₂ (dielectric constant 4), S
iON (relative permittivity 4 to 6) or Si ₃ N ₄ (relative permittivity 6)
And other inorganic materials. As a method of reducing the capacitance between wirings of a highly integrated semiconductor device or the like, it is effective to use an interlayer insulating film made of a material having a lower dielectric constant than these general inorganic materials. Representative examples of the low dielectric constant material include an inorganic insulating film material such as a silicon oxide insulating film containing fluorine atoms (hereinafter, referred to as SiOF) and an organic insulating film material containing carbon atoms.

[0004] SiOF is Si-O constituting SiO _2.
By terminating the F atoms to -Si bonds, that the density decreases, and the Si-F bonds and that O-F bond polarizability is small or the like, a low dielectric constant can be achieved than SiO _2. Since this SiOF is similar in film formation and etching process to conventional SiO ₂ , it can be easily adopted even in a current production apparatus. Also, since it is an inorganic material, it has excellent heat resistance. However, SiOF containing a high concentration of fluorine generates a Si = F ₂ bond in addition to a Si—F bond and an OF bond, which causes a problem of increased hygroscopicity. When the amount of water in the SiOF increases, inconveniences such as a decrease in the embedding characteristics of the metal layer and an increase in the contact resistance occur in the step of forming the contact plug and the like. Therefore, it is reported that the relative dielectric constant of SiOF formed by this method is limited to about 3.8 from the viewpoint of hygroscopicity.

Therefore, for example, 0.18 μm to 0.13 μm
An organic polymer material has been proposed as an interlayer insulating film material having a relative dielectric constant of 3 or less required for a semiconductor device to which a design rule of m or less is applied. These organic polymer materials include hydrocarbon-based polymers and fluorinated hydrocarbon-based polymers, all of which include a CH bond or a CF bond,
This is to realize a low dielectric constant by lowering the density and polarizability of the material itself.

The organic polymer material having a low dielectric constant is used as an interlayer insulating film, and low-resistance Cu is applied to a connection hole such as a via hole or a contact hole formed in the interlayer insulating film by CMP (Chem.
An inter-layer connection (Interconnection) method of burying flat by an ical mechanical polishing method has been proposed. Cu
In order to use Cu as a contact plug material, it is important to use a barrier metal together in order to prevent diffusion and oxidation of Cu into an interlayer insulating film of an organic polymer material.

As the barrier metal material, a high melting point metal nitride such as TaN or WN is promising. However, these refractory metal nitrides having excellent barrier properties have extremely high hardness, and in particular, TaN has a low CMP polishing rate and requires a long time. In addition, these barrier metals are formed by CVD (Chemical
Although film formation by the vapor deposition method is desirable from the viewpoint of step coverage and the like, the problem for practical use remains, for example, the CVD method has not been established in WN.

[0008]

Therefore, instead of Cu, W
It has been studied to form a high-melting point metal such as the above by a CVD method and fill the connection hole formed in the low dielectric constant interlayer insulating film made of an organic polymer material. A high melting point metal such as W is a material that has been conventionally used as a contact plug for a connection hole formed in an inorganic interlayer insulating film. Cu
Although it has a slightly higher specific resistance than that, it is still an excellent conductive material in terms of oxidation resistance and stability. The CVD method of W as an example of the refractory metal is as follows: WF ₆ + 3H ₂ → W + 6HF Standard heat of formation 122 kJ
/ Mol and the rate of the hydrogen dissociation reaction (H ₂ → 2H) on the substrate to be treated is determined. Since this hydrogen dissociation reaction is temperature-controlled, C of W by hydrogen reduction
The VD method was also temperature-controlled. For this reason, in order to obtain a practical film forming speed, a film forming temperature of about 420 to 470 ° C. is conventionally used.

However, in this temperature range, the low dielectric constant interlayer insulating film made of an ordinary organic polymer material is thermally decomposed, so that the film forming temperature is set to 400 ° C. or less, for example, 350 to 380 ° C.
Attempts have been made to lower this. However, such a low-temperature film formation is not practical because the film formation speed is extremely reduced.
This is shown in FIG. FIG. 2 is an Arrhenius plot of the film formation rate of WF _{6 by} the H ₂ reduction method.

The present invention has been made in view of such problems of the background art. That is, the present invention provides a method for forming a metal film capable of achieving both a reduction in film forming temperature and a practical film forming rate, and a method for forming a metal film without thermally decomposing a low dielectric constant organic polymer material. It is an object of the present invention to provide a method for manufacturing an electronic device such as a highly integrated semiconductor device which can form a wiring material such as a contact plug.

[0011]

In order to achieve the above-mentioned object, a method for forming a metal film according to the present invention comprises a chemical vapor deposition method using a source gas containing a metal halide gas and a reducing gas. A method for forming a metal film on a substrate to be processed, wherein a carbon-based gas is further added to the source gas.

As the carbon-based gas, a CO-based gas, C
H-based gas or CHO-based gas is preferably used.
Specifically, CO, CO ₂ , C ₃ O ₂ , CH ₄ , C ₂ H
_{6, C 3 H 8, C} 2 H 4, C 2 H 2, HCHO, HCO
OH, CH ₃ OH, C ₂ H ₅ OH, CH ₃ OCH ₃ , C
H ₃ COCH ₃ , CH ₃ OC ₂ H ₅ or CH ₃ CO
Those having a relatively high vapor pressure and a low molecular weight such as OC ₂ H ₅ are desirable.

The method for forming a metal film according to the present invention is preferably applied when the substrate to be treated contains an organic polymer material. In other words, it is suitable for a case where a low dielectric constant interlayer insulating film or the like made of an organic polymer material is included in the substrate to be processed and the film is formed at a temperature lower than the thermal decomposition temperature of the organic polymer material.

The method of manufacturing an electronic device according to the present invention is formed by including the above-described method of forming a metal film during the manufacturing process.

The metal film applied in the present invention is W, Mo,
It is a high melting point metal such as Ta or Ti. Therefore,
Metal halides include WF ₆ , WCl ₆ , MoF
₆ , MoCl _{5 and the} like are selected from fluorides and chlorides having relatively high vapor pressure and being easily vaporized.

The reducing gas used in the present invention is H ₂ ,
Examples include SiH _{4 and} Si ₂ H ₆ .

[Action] Taking the method of forming W by the H ₂ reduction method of WF ₆ as an example, this reaction system is, as described above, WF ₆ + 3H ₂ → W + 6HF standard heat of formation 122 kJ
/ Mol endothermic reaction. When CO is added to this reaction system, an exothermic reaction represented by WF ₆ + 6H ₂ + CO → W + 6HF + CH ₄ + H ₂ O standard heat of formation −899.65 kJ / mol is obtained. Therefore, the reaction proceeds easily, and even if the film forming temperature is lowered to, for example, 400 ° C. or lower, a film forming rate equal to or higher than that of the conventional hydrogen reduction method can be obtained.

When CO ₂ is added, WF ₆ + 7H ₂ + CO ₂ → W + 6HF + CH ₄ + 2H ₂
O Standard heat of formation Exothermic reaction expressed by -857.29 kJ / mol, and a film formation temperature can be reduced and a practical film formation rate can be obtained by the same principle as that of CO.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor device will be described below as an example of an electronic device, and a method of forming a contact plug in which a connection hole opened in an interlayer insulating film made of an organic polymer material having a low dielectric constant is filled with W will be described as an example. This will be described with reference to FIG. As electronic devices, in addition to semiconductor devices, various electronic devices such as thin-film magnetic heads, magnetoresistive heads, thin-film inductors, thin-film coils, micromachines, etc. The present invention can be applied to a device employing an insulating film made of a material.

Embodiment 1 FIG. 1A is a schematic sectional view showing a main part of a semiconductor device to which the present invention is applied. That is, a predetermined element (not shown) such as a MOS transistor is formed on a semiconductor substrate, and the lower interlayer insulating film 1 is formed.
On this lower interlayer insulating film 1, a lower wiring 2 made of an Al alloy, Cu or the like is formed. In this embodiment, Al-1% Cu
TiN was formed on the alloy by sputtering, and this was patterned by RIE (Reactive Ion Etching) to form a lower wiring 2.

The structure on which the lower wiring 2 is formed is set on a spin coater, and 3 to 5 cc of an organic solvent solution of a polyaryl ether as an organic polymer material is added dropwise to the structure.
Spin coating at a rotation speed of 0-3000 rpm. Subsequently, after baking at 150 ° C. for 1 minute and at 250 ° C. for 1 minute, it is further carried into a curing oven and cured at 425 ° C. for 1 hour in an N ₂ atmosphere. The thickness of the organic polymer material film 3 made of polyaryl ether is 500 nm.

On the organic polymer material film 3, a plasma C
An oxide film 4 made of SiO ₂ is formed to a thickness of 600 nm by the VD method. Plasma CVD of oxide film 4 SiH ₄ 50 sccm N ₂ O 1000 sccm Pressure 10 Torr RF power 0.5 kW (13.56 MHz) Temperature 350 ° C. Interlayer insulation consisting of a laminated structure of organic polymer material film 3 and oxide film 4 The film 5 is formed.

A photoresist is coated on the oxide film 4 and is patterned into an opening shape of a via hole to form a resist mask (not shown). The substrate to be etched is carried into a magnetron RIE apparatus, and the oxide film 4 is etched. Oxide film etching conditions C ₄ F ₈ 14 sccm CO 250 sccm Ar 100 sccm O ₂ 2 sccm Pressure 5.3 Pa RF power 1.6 kW Temperature 20 ° C.

Thereafter, the substrate to be etched is placed in an ECR (Elec
(tron Cyclotron Resonance) The organic polymer material film 3 is transported to a plasma etching apparatus and etched. Etching conditions for organic polymer material film N ₂ 40 sccm He 165 sccm Pressure 0.8 Pa μ wave power 0.5 kW Base bias 0.1 kW Temperature −50 ° C. The resist mask is peeled off, and the lower wiring is formed on interlayer insulating film 5. A connection hole (via hole) 6 facing the semiconductor device 2 is completed. FIG. 1A shows this state.

FIG. 1B: The structure shown in FIG. 1A is carried into a sputtering apparatus, and a barrier metal 7 is formed. This sputtering apparatus is a long throw sputtering apparatus in which a distance between a target and a substrate to be processed is widened and a vertical incident component of sputtered particles is increased.
By employing such an apparatus, the bottom coverage at the bottom of the connection hole 6 having a high aspect ratio can be improved. The barrier metal 7 has a thickness of 30 nm for Ti and 70 n for TiN from the lower layer.
m to form a film.

FIG. 1C: The substrate to be processed is carried into a single-wafer type low-pressure CVD apparatus, and a metal film 8 made of W is formed so as to fill the connection hole 6. At this time, the film forming temperature is set to 375 ° C. to 400 ° C. or lower, which is lower than the substantial heat-resistant temperature of the organic polymer material film 3 made of polyaryl ether in the substrate to be processed. That is, when the film formation temperature exceeds 400 ° C., the embedded shape of the metal film 8 deteriorates due to outgas containing carbon and oxygen due to thermal decomposition of the polyaryl ether,
This is because the oxidation may increase the contact resistance.

In this embodiment, a CO gas is added to the chemical vapor deposition reaction system of the metal film 8 in order to prevent a decrease in the deposition rate due to a low film forming temperature.
Metal film CVD conditions WF ₆ 80 sccm H ₂ 2000 sccm CO 3 to 10
sccm N ₂ 100 sccm Ar 1900 sccm pressure 350 Torr temperature 350-375 ° C.

The standard heat of formation of W under the film formation conditions by the addition of the CO gas is an exothermic reaction of -899.65 kJ / mol. Therefore, the reaction easily proceeds regardless of the film formation temperature of 350 to 375 ° C., and the film formation rate is 3
Values between 00 and 500 nm / min are obtained. On the other hand, the standard heat of formation of W by the conventional hydrogen reduction method is 122 kJ / m
Since the reaction is an endothermic reaction of
When the temperature is lowered to 75 ° C., the film forming speed is 150 to 230 nm.
/ Min. In addition, the deposition rate is 400 nm.
In order to achieve this, a film formation temperature of 420 ° C. is required (see FIG. 2). Therefore, even if the film formation temperature is reduced below the heat-resistant temperature of the organic polymer material, the film formation rate can be made equal to or higher than that of the conventional hydrogen reduction method under high temperature conditions.

FIG. 1D: After that, the metal film 8 and the barrier metal 7 on the interlayer insulating film 5 are removed by CMP (Chemical Mec.).
The upper wiring 9 is formed on the buried contact plug by removing and flattening by a hanical polishing method or an entire etch-back method. In the subsequent steps, the process returns to FIG. 1A to form an upper layer wiring structure.
The steps of (a) to FIG. 1 (d) may be repeated. Finally, a semiconductor device is completed through formation of a final passivation film, formation of a pad electrode, and the like.

Embodiment 2 This embodiment is an example in which CO ₂ gas is added in place of CO in the process of forming the metal film 8. Since the steps other than the step of forming the metal film are the same as those of the first embodiment, the description will be limited to the CVD method of the metal film 8 shown in FIG.

[0031] CVD conditions _{WF 6 80 sccm H 2 2000 sccm} CO 2 3~10 sccm N 2 100 sccm Ar 1900 sccm Pressure 350 Torr temperature three hundred and fifty to three hundred and seventy-five ° C. of the metal film

The standard heat of formation of W under the film formation conditions due to the addition of CO ₂ gas is an exothermic reaction of −857.29 kJ / mol. Therefore, the reaction easily proceeds regardless of the film formation temperature of 350 to 375 ° C., and a film formation rate of 300 to 500 nm / min is obtained as in the first embodiment.

[Embodiment 3] In this embodiment, in the step of forming the metal film 8, H ₂ and S
This is an example in which iH ₄ is adopted and CO gas is added thereto.
The steps other than the step of forming the metal film are the same as those of the first embodiment. Therefore, FIG.
Only the description of the CVD method for the metal film 8 shown in FIG.

Metal film CVD conditions WF ₆ 80 sccm H ₂ 2000 sccm CO 3 to 10 sccm SiH ₄ 3 to 10 sccm N ₂ 100 sccm Ar 1900 sccm Pressure 350 Torr Temperature 350 to 375 ° C.

This reaction system is represented by the following reaction formula. WF ₆ + 2H ₂ + CO + SiH ₄ → W + SiF ₄ + CH
₄ + H ₂ O + 2HF Standard heat of formation −1464.55 kJ / mol

On the other hand, the reduction reaction using only H ₂ and SiH ₄ without adding CO is as follows. WF ₆ + SiH ₄ → W + SiF ₄ + 2HF + H ₂ Standard heat of formation -442.9 kJ / mol

Therefore, even in the case of the silane reduction method, the reaction proceeds easily by the addition of CO. In this embodiment, the film formation rate is the same as that of Embodiment 1 regardless of the film formation temperature of 350 to 375 ° C. 300-500 nm / m
The value of in is obtained.

Although the present invention has been described with reference to the three embodiments, the metal halide other than WF ₆ may be WC.
The l _6, MoF _6, MoCl relatively vapor pressure is vaporized high tends compounds such as ₅ can be adopted. In addition, SiH ₄ may be used as the reducing gas in addition to H ₂ . However, the specific resistance of the W film obtained by the silane reduction method is about 20 μΩ / cm, which is at least twice as high as the specific resistance of the W film obtained by the hydrogen reduction method of 8 to 10 μΩ / cm. Is preferably a hydrogen reduction method.

As the organic polymer material, a polyaryl ether is exemplified, but polyimide, organic SOG, benzocyclobutene, polynaphthalene, polyparaxylylene, Teflon (trade name), Cytop (trade name) and the like are used. be able to. These are all low dielectric constant materials that are desirable as insulating films for highly integrated electronic devices.

The method of forming a metal film according to the present invention is suitably used for a method of manufacturing a semiconductor device, particularly, a highly integrated semiconductor device using an organic polymer material having a low dielectric constant for an interlayer insulating film. The present invention is effective when applied to a method of manufacturing various electronic devices such as a thin film magnetic head, a magnetoresistive head, a thin film inductor, a thin film coil, and a micromachine, which require a lower process temperature and an increased deposition rate.

[0041]

As is clear from the above description, according to the metal film forming method of the present invention, the film forming temperature is set to 350 ° C. to 3 ° C.
Even if the temperature is reduced to 75 ° C., a film forming rate equal to or higher than the conventional film forming temperature of about 420 ° C. can be obtained. Therefore, by using this method of forming a metal film, it becomes possible to manufacture a wiring structure of a microelectronic device using an interlayer insulating film made of an organic polymer material having a low dielectric constant with low resistance and high reliability. .

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an example in which an electronic device manufacturing method of the present invention is applied to a semiconductor device manufacturing method.

FIG. 2 is an Arrhenius plot of a film formation rate of WF _{6 by} an H ₂ reduction method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lower interlayer insulation film, 2 ... Lower wiring, 3 ... Organic polymer material film, 4 ... Oxide film, 5 ... Interlayer insulation film, 6 ... Connection hole, 7 ...
Barrier metal, 8: Metal film, 9: Upper wiring

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 AA03 AA04 AA06 AA09 AA10 AA14 AA16 BA12 BA17 BA18 BA20 BA44 CA07 DA04 HA03 HA04 LA15 4M104 BB02 BB14 BB16 BB18 BB30 DD08 DD16 DD20 DD44 DD45 DD49 DD65 EE08 EE18 FF15 FF22 GG13 HH20 5F033 JJ18 JJ19 JJ20 JJ33 KK09 KK33 NN03 NN06 NN07 NN38 PP09 PP15 QQ08 QQ09 QQ10 QQ12 QQ13 QQ31 QQ37 QQ48 QQ74 QQ84 RR04 RR21 SS15 SS22 TT04 VV08 VVXXV

Claims (6)

[Claims] 1. A method for forming a metal film on a substrate to be processed by a chemical vapor deposition method using a source gas containing a metal halide gas and a reducing gas, the method comprising: A method of forming a metal film, further comprising adding a carbon-based gas. 2. The gas according to claim 1, wherein the carbon-based gas is at least one of a CO-based gas, a CH-based gas, and a CHO-based gas.
The method for forming a metal film according to the above. 3. The method according to claim 1, wherein the substrate to be processed contains an organic polymer material. 4. A method for manufacturing an electronic device, comprising: forming a metal film on a substrate to be processed by a chemical vapor deposition method using a source gas containing a metal halide gas and a reducing gas. A method for manufacturing an electronic device, further comprising adding a carbon-based gas to the source gas. 5. The gas according to claim 4, wherein the carbon-based gas is at least one of a CO-based gas, a CH-based gas, and a CHO-based gas.
A manufacturing method of the electronic device according to the above. 6. The method according to claim 4, wherein the substrate to be processed contains an organic polymer material.