JPH11297678A - Manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely avoid re-depositing unwanted products, without wastefully complicating the process when a Ti-contg. barrier metal film or W film through it is etched, thereby greatly improving the yield and reliability of the semiconductor device. SOLUTION: On the occasion of etching a Ti-contg. barrier metal film 5 or W film 2 through it, an inert gas such as Ar or He is fed in an etcher to expose an Si semiconductor substrate 4 to a plasma in the continuous plasma discharge condition after etching the W film 2 and barrier metal film 5. This avoids re-depositing unwanted products on the W film 2 or layer insulation film 3 near it owing to the high-energy plasma of the inert gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method of manufacturing a semiconductor device having a tungsten-based wiring or plug formed thereon via a titanium-based barrier metal film.

[0002]

2. Description of the Related Art Generally, in semiconductor devices such as ICs and LSIs, aluminum and its alloys are widely used as materials for various wirings. However, in recent years, as the integration of semiconductor devices further increases, when aluminum or an alloy thereof is used as a wiring material, stress migration and electromigration cannot be ignored, and the reliability thereof has become a problem.

Therefore, instead of the wiring made of aluminum or its alloy, a chemical vapor deposition (CV) method is performed via a barrier metal film containing titanium such as TiN, Ti, TiW or the like.
D)) has been proposed a technique for forming a tungsten film. This tungsten film is a wiring that is superior in stepability as compared with wiring made of aluminum or an alloy thereof, and is expected to be able to cope with higher integration of a semiconductor device.

When anisotropically etching a tungsten film and a barrier metal film when forming the above-described wiring, for example, a mixed gas of SF ₆ / Cl ₂ / Ar is used as an etching gas to apply an RF bias to be applied. Etching of various stages is performed, and first, a tungsten film is processed into a predetermined shape. Subsequently, the barrier metal film is etched according to the shape of the processed tungsten film by changing the etching gas to Cl ₂ .

[0005]

However, when the tungsten film and the underlying barrier metal film are etched into a wiring shape or a plug shape, the following problems occur.

When etching the barrier metal film, a chemical reaction occurs between the material of the barrier metal film and an etching gas component, and furthermore, a chemical reaction occurs between the etching gas component remaining on the surface of the tungsten film when the tungsten film is etched. , TiF and TiCl are generated, and such products are attached again to the side walls of the barrier metal film and the tungsten film. Although cleaning using an organic solvent is performed to remove the resist mask used for the etching in a subsequent step, the cleaning cannot remove the product. If such a product is left as it is, inconveniences such as a short circuit between wirings occur, and as a result, the yield of the semiconductor device is reduced.

One method for addressing this problem is disclosed in Japanese Patent Laid-Open No.
It is disclosed in Japanese Patent No. 21224. This method masks the peak of the metallic substance in order to remove the metallic substance left in the discontinuous portion of the upper layer of the semiconductor substrate, and removes the residual metallic substance existing on the unmasked surface. This is a method of over-etching for removal. However, in this case, since a step of forming a mask accurately at the peak is added, it is inevitable that the steps become complicated and the manufacturing time and the manufacturing cost increase.

Accordingly, the present invention provides an easy and reliable method of re-adhering unnecessary products without complicating the process when etching a barrier metal film containing titanium and a tungsten film formed through the barrier metal film. It is an object of the present invention to provide a method of manufacturing a semiconductor device which prevents the semiconductor device and significantly improves the yield and reliability of the semiconductor device.

[0009]

A method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device in which a film containing a refractory metal is formed on a semiconductor substrate via a film containing titanium. A first step of etching the film containing the refractory metal in the plasma in which the etching gas containing fluorine is excited, and in the plasma in which the etching gas containing chlorine is excited after the first step, A second step of etching the film containing titanium, and a third step of exposing the semiconductor substrate to plasma in which an inert gas is excited while continuing plasma discharge after the second step. And a process.

In one embodiment of the method of manufacturing a semiconductor device according to the present invention, in the third step, the inert gas is He or Ar.

In one embodiment of the method of manufacturing a semiconductor device according to the present invention, the high melting point metal is tungsten.

In one embodiment of the method of manufacturing a semiconductor device according to the present invention, in the first step, the film containing the high melting point metal is processed into a wiring shape, and in the second step, the film contains the titanium. The film is processed into a barrier metal film having a shape following the film containing the high melting point metal in the wiring shape.

In one embodiment of the method for manufacturing a semiconductor device according to the present invention, a connection hole is formed in the semiconductor substrate, the hole being formed in the interlayer insulating film, and the entire surface of the interlayer insulating film including the inner wall surface of the connection hole is formed. A film containing the high melting point metal is formed on the entire surface of the film containing titanium so that the film containing titanium fills the connection hole, and the film containing the high melting point metal is formed in the first step. Is processed into a plug shape that embeds only the inside of the connection hole, and in the second step,
The film containing titanium existing on the upper surface other than the inner wall surface of the connection hole is removed.

In this case, in one embodiment of the method of manufacturing a semiconductor device according to the present invention, after the third step, the first barrier metal film, the metal film, and the second barrier metal film are sequentially covered so as to cover the entire surface. The method further includes a fourth step of forming, and a fifth step of processing the first barrier metal film, the metal film, and the second barrier metal film into a wiring shape.

[0015]

In the method of manufacturing a semiconductor device according to the present invention, in etching a barrier metal film containing titanium and a refractory metal film formed through the barrier metal film, after the barrier metal film is etched following the refractory metal film, a discharge is performed. Is continued, the semiconductor substrate is exposed to plasma in which an inert gas such as Ar or He is excited. The inert gas in the high-energy plasma state cuts a chemical bond between the main material (Ti) of the barrier metal film and the main material (F) of the etching gas or the main material (W) of the high-melting-point metal film. Reattachment of the product due to binding is suppressed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some preferred embodiments of the method of manufacturing a semiconductor device according to the present invention will be described below with reference to the drawings. In these embodiments, a case where a thin film containing titanium such as TiN, Ti, TiW or the like is formed as a barrier metal film and a tungsten (W) film is formed as a high melting point metal film will be described.

First, an etching apparatus used in the following embodiments will be described. FIG. 1 is a schematic diagram showing a magnetic field ECR which is a plasma etching apparatus. This etching apparatus includes a sample stage 11 on which a material to be etched (a silicon semiconductor substrate 12) is placed in a reaction chamber 24. The reaction chamber 24 has a vacuum exhaust port 17 and an etching gas introduction port 18. In addition, a quartz bell jar 23 is attached to the upper part. Further, an RF (high frequency) power supply 13, a blocking capacitor 14, and a DC power supply 15 for electrostatic attraction are connected to the sample stage 11. Further, the sample stage cooling pipe 1 provided with a refrigerant inlet 16a and a refrigerant outlet 16b at both ends of the sample stage 11 is provided.
6 and a substrate cooling He gas pipe 20 provided with a He gas inlet 20a. A waveguide 22 connected to a magnetron 21 is arranged above the quartz bell jar 23, and an annular electromagnetic coil 19 is arranged on a side of the quartz bell jar 23.

The temperature of the sample stage 11 can be kept constant in the range of -60.degree. C. to 40.degree. C. by circulating a refrigerant such as Florinart (trade name, manufactured by 3M) inside the sample stage cooling pipe 16. . In this etching apparatus, as described above, the sample stage 11 is provided with the electrostatic suction mechanism,
The cooling efficiency is increased by filling He gas between the silicon semiconductor substrate 12 electrostatically adsorbed and the sample table 11.

(First Embodiment) First, a first embodiment will be described. Here, a case where the upper wiring of a MOS transistor is formed from a tungsten (W) film via a barrier metal film will be described. FIG.
It is a schematic sectional view explaining the main process of this embodiment.

First, a pair of impurity diffusion layers functioning as a gate electrode and a source / drain are formed on a silicon semiconductor substrate 4, and an interlayer insulating film 3 made of a silicon oxide film covering these is formed to a thickness of about 600 nm. . In FIG. 2, for convenience, the gate electrode and the source / drain are not shown and the interlayer insulating film 3 is formed directly on the silicon semiconductor substrate 4.

Subsequently, a titanium (Ti) film is formed to a thickness of about 200 ° and a titanium nitride (TiN) is formed to a thickness of about 1000 ° in order on the interlayer insulating film 3 by sputtering.
The barrier metal film 5 has a layer structure.

Subsequently, the barrier metal film 5 is formed by the CVD method.
A tungsten film 2 is formed thereon to a thickness of about 4000 °. Thereafter, a photoresist is applied on the tungsten film 2 and a resist mask 1 having a predetermined wiring shape is formed by photolithography. The situation at this time is shown in FIG.

Next, the silicon semiconductor substrate 4 is loaded and installed in the etching apparatus shown in FIG. 1, and the tungsten film 2 and the barrier metal film 5 are anisotropically etched while being cooled to -30.degree. This etching process includes the following four steps.

First, as a step 1, anisotropic etching according to the shape of the resist mask 1 is partially applied to the tungsten film 2 under the following conditions. Etching gas used and its flow rate: SF ₆ / Cl ₂
/ Ar = 55/25/135 sccm Degree of vacuum: 10 mTorr Microwave current: 300 mA Applied RF bias: 40 W (2.0 MHz) In this case, the etching rate is about 600 nm / min.
The state at this time is shown in FIG.

Subsequently, in step 2, in order to completely remove the tungsten film 2, R applied under the following conditions is applied.
Overetching is performed by lowering the F bias. Etching gas used and its flow rate: SF ₆ / Cl ₂
/ Ar = 55/25/135 sccm Degree of vacuum: 10 mTorr Microwave current: 400 mA Applied RF bias: 5 W (2.0 MHz) The etching rate at this time is about 450 nm / min.
In order to achieve the vertical shape of the tungsten film 2, overetching equivalent to 200 nm in terms of the thickness of the tungsten film 2 is performed. In this over-etching, the barrier metal film 5
Is almost zero. Figure 2 shows the situation at this time.
It is shown in (c).

Subsequently, the discharge is temporarily stopped to replace the etching gas, and the gas is exhausted.
The barrier metal film 5 is completely anisotropically etched under the following conditions. Etching gas used and its flow rate: Cl ₂ = 120
sccm Degree of vacuum: 5 mTorr Microwave current: 200 mA Applied RF bias: 40 W (2.0 MHz) In order to achieve the vertical shape of the barrier metal film 5, the barrier metal film 5 is overetched by a thickness equivalent to 300 nm.

Subsequently, in a state where the discharge is continued, Ar gas which is an inert gas is flowed into the etching apparatus. As a step 4, the silicon semiconductor substrate 4 is placed in the plasma in which Ar is excited under the following conditions. Expose for about 10 seconds. Gas used and its flow rate: Ar = 150 sccm Degree of vacuum: 10 mTorr Microwave current: 200 mA Applied RF bias: 5 W (2.0 MHz) The etching amount of the barrier metal film 5 in steps 3 and 4 is about 20 nm. The state at this time is shown in FIG. In this step 4, the chemical bond between the main material (Ti) of the barrier metal film 5 and the main material (F) of the etching gas and the material of the tungsten film 2 is cut by the inert gas (Ar) in a high energy plasma state. As a result, as shown in the figure, the re-adhesion of the product due to the chemical bond to the side wall of the etched tungsten film 2 is suppressed.

Thereafter, the resist mask 1 is removed by washing using an organic solvent, and a wiring 10 having a desired shape without the product as shown in FIG. 2E is obtained.

As described above, according to the first embodiment, when forming the wiring 10 by etching the barrier metal film 5 and the tungsten film 2 formed through the barrier metal film 5, the process is complicated. Unnecessary re-adhesion of products can be easily and surely prevented without causing the semiconductor device to be manufactured with high yield and high reliability.

In the first embodiment, the temperature of the test stand 11 is set to -30 ° C., but the above-described good results can be obtained even within a temperature range of 60 ° C. to ± 0 ° C.

(Second Embodiment) Next, a second embodiment will be described. Here, a case will be described in which, for example, a tungsten plug is formed in which only a contact hole of a MOS transistor is filled with a tungsten (W) film via a barrier metal film. FIG. 3 is a schematic cross-sectional view illustrating main steps of the present embodiment.

First, a pair of impurity diffusion layers functioning as a gate electrode and a source / drain are formed on a semiconductor substrate 44, and an interlayer insulating film 43 made of a silicon oxide film covering them is formed to a thickness of about 600 nm. In FIG. 3, for convenience, the gate electrode and the source / drain are not illustrated, and the interlayer insulating film 43 is formed directly on the semiconductor substrate 44.

Subsequently, the interlayer insulating film 43 is patterned to form a contact hole 41 exposing a part of the source / drain surface, for example.

Subsequently, the contact holes 4 are formed by sputtering.
A two-layer barrier metal film 45 is formed by sequentially forming a titanium (Ti) film to a thickness of about 200 Å and titanium nitride (TiN) to a thickness of about 1000 Å on the interlayer insulating film 3 including the inner wall surface 1.

Subsequently, the contact hole 41 is formed by the CVD method.
And a tungsten film 42 is formed on the barrier metal film 45 to a thickness of about 6000 °. The state at this time is shown in FIG.

Next, the silicon semiconductor substrate 44 is loaded and installed in the etching apparatus shown in FIG. 1, and the tungsten film 2 and the barrier metal film 4 are cooled to −10 ° C.
5 is subjected to anisotropic etching. This etching process
It consists of the following four steps.

First, as a step 1, anisotropic etching is performed on the entire surface of the tungsten film 42 halfway under the following conditions so that the barrier metal film 45 is not exposed. Etching gas used and its flow rate: SF ₆ / Cl ₂
/ Ar = 55/25/135 sccm Degree of vacuum: 10 mTorr Microwave current: 300 mA Applied RF bias: 40 W (2.0 MHz) In this case, the etching rate is about 600 nm / min.
The situation at this time is shown in FIG.

Subsequently, as step 2, in order to completely remove the tungsten film 42, the RF bias applied under the following conditions is reduced to perform over-etching. Etching gas used and its flow rate: SF ₆ / Cl ₂
/ Ar = 55/25/135 sccm Degree of vacuum: 10 mTorr Microwave current: 400 mA Applied RF bias: 5 W (2.0 MHz) The etching rate at this time is about 450 nm / min.
The tungsten film 4 is removed so that the remaining tungsten film 42 on the upper surface of the barrier metal 45 is completely removed and a predetermined amount of the tungsten film 42 remains in the contact hole 41.
Overetching equivalent to 100 nm in film thickness conversion of 2.
In this over-etching, the etching amount of the barrier metal film 45 is almost zero. Figure 3 shows the situation at this time.
It is shown in (c).

Subsequently, the discharge is temporarily stopped to replace the etching gas, and the gas is exhausted.
The barrier metal film 45 is completely anisotropically etched under the following conditions. Etching gas used and its flow rate: Cl ₂ = 120
sccm Degree of vacuum: 5 mTorr Microwave current: 200 mA Applied RF bias: 40 W (2.0 MHz) To completely remove the remaining barrier metal 45 on the upper surface,
The barrier metal film 45 is overetched by a thickness equivalent to 50 nm.

Subsequently, with the discharge continued, Ar gas, which is an inert gas, is introduced into the etching apparatus.
Is exposed to Ar-excited plasma for about 10 seconds. Gas used and its flow rate: Ar = 150 sccm Degree of vacuum: 10 mTorr Microwave current: 200 mA Applied RF bias: 5 W (2.0 MHz) At this time, the etching amount of the barrier metal film 45 in steps 3 and 4 becomes about 10 nm, and the barrier metal film 4
The contact plug 50 filling the contact hole 41 is formed through the contact hole 5. The state at this time is shown in FIG. In this step 4, the barrier metal film 4 is formed by using an inert gas (Ar) in a high energy plasma state.
The chemical bond between the main material (Ti) of No. 5 and the main material (F) of the etching gas and the material of the tungsten film 42 is cut, and as shown in FIG. Will be suppressed.

Subsequently, TiN is formed on the entire surface by sputtering.
The barrier metal film 46 made of
The aluminum alloy film 47 is formed to a thickness of about 3000
A barrier metal film 48 made of N is sequentially formed to a thickness of about 300 °. The state at this time is shown in FIG.

Thereafter, the barrier metal film 48, the aluminum alloy film 47, and the barrier metal film 46 are patterned in a belt shape, and are connected to a lower source / drain or the like via a contact plug 50 and have a desired shape without the product. 49 is obtained. The situation at this time is shown in FIG.
Shown in

As described above, according to the second embodiment, when the contact plug 50 is formed by etching the barrier metal film 45 and the tungsten film 42 formed through the barrier metal film 45, the process is complicated. It is possible to easily and surely prevent the re-adhesion of unnecessary products without causing the semiconductor device to be manufactured, and to manufacture a semiconductor device with high yield and high reliability.

The present invention is not limited to the first and second embodiments. For example, good results can be obtained even when He gas is used as the inert gas used in step 4 described above.

[0045]

According to the present invention, when etching a barrier metal film containing titanium and a tungsten film formed through the barrier metal film, it is easy to re-attach unnecessary products without complicating the process. In addition, it is possible to provide a method of manufacturing a semiconductor device which reliably prevents the semiconductor device and significantly improves the yield and reliability of the semiconductor device.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an etching apparatus used in a method for manufacturing a semiconductor device according to each embodiment of the present invention.

FIG. 2 is a schematic sectional view showing main steps of a method for manufacturing a semiconductor device according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional view showing main steps of a method for manufacturing a semiconductor device according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Resist mask 2,42 Tungsten film 3,43 Interlayer insulating film 4,44 Silicon semiconductor substrate 5,45 Barrier metal film 41 Contact hole 46,48 Barrier metal film 49,10 Wiring 50 Contact plug

Claims (6)

[Claims] 1. A method of manufacturing a semiconductor device, comprising forming a film containing a refractory metal on a semiconductor substrate via a film containing titanium, wherein the etching gas containing fluorine is excited in a plasma. A first step of etching a film containing a refractory metal, and after the first step, a second step of etching the film containing titanium in a plasma in which an etching gas containing chlorine is excited, A third step of exposing the semiconductor substrate to plasma in which an inert gas is excited with the plasma discharge continued after the second step. . 2. The method according to claim 1, wherein the inert gas is He or Ar in the third step. 3. The method according to claim 1, wherein the refractory metal is tungsten. 4. In the first step, the film containing the high melting point metal is processed into a wiring shape, and in the second step, the film containing titanium is converted into a film containing the high melting point metal in the wiring shape. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is processed into a barrier metal film having a shape following the shape of the semiconductor device. 5. 5. A connection hole formed in the interlayer insulating film on the semiconductor substrate, wherein a film containing titanium fills the entire surface of the interlayer insulating film including an inner wall surface of the connection hole. A film containing the refractory metal is formed on the entire surface of the film containing titanium. In the first step, the film containing the refractory metal is processed into a plug shape that fills only the inside of the connection hole. 4. The method according to claim 1, wherein, in the second step, a film containing titanium existing on an upper surface other than an inner wall surface of the connection hole is removed. 5. . 6. A fourth step of sequentially forming a first barrier metal film, a metal film, and a second barrier metal film so as to cover the entire surface after the third step, and 6. The method for manufacturing a semiconductor device according to claim 5, further comprising: a fifth step of processing the metal film and the second barrier metal film into a wiring shape.