JPH0577290B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a method of manufacturing a semiconductor device, and particularly relates to a method of manufacturing a semiconductor device in which interconnection connections are embedded with a metal film such as tungsten. .

(Prior Art) Conventionally, in semiconductor devices, a method has been adopted in which, for example, a through hole is formed in a connection portion connecting upper and lower wiring layers, and the through hole is filled with a conductive material such as tungsten. This method will be explained with reference to FIG. That is, for example, a SiO 2 film 22 is formed as an insulating film on an N ⁺ or P ⁺ silicon wiring layer ₂₁ formed on a substrate 20, and an opening is formed in the SiO ₂ film 22 using ordinary photolithography and reactive ion etching. A hole 23, that is, a through hole is formed (FIG. 4a). After that, the pressure was reduced
Tungsten hexafluoride (WF ₆ ) in CVD equipment
A tungsten film 24 is formed on the silicon layer 21 using
(Figure 4b).

After silicon reacts with tungsten hexafluoride and the tungsten film 24 reaches a certain thickness, no reaction with silicon occurs, so by adding hydrogen (H ₂ ) gas to tungsten hexafluoride, the tungsten film 24 Tungsten is further grown on 24 to form a tungsten layer 24a as shown in FIG. 4c.

According to this method, the tungsten layer 24a is selectively applied to the silicon wiring 24a up to a thickness of about 0.5 μm.
Although it is possible to deposit the tungsten on the SiO ₂ film 22 above that point, there is a problem that nucleation and subsequent growth of tungsten tends to occur on the SiO 2 film 22, making it impossible to maintain selectivity.

There is a method shown in FIG. 5 to overcome the above problems. That is, as shown in FIG. 5a, after an oxide film 31 is deposited on a substrate 30, a desired opening 35 is provided to expose a portion of the substrate 30. Next, after forming a tungsten film 32 by the LPCVD method as shown in FIG. 5b, a photoresist 34 is applied as a planarizing material as shown in FIG. 5c, and after drying, the photoresist 34 and the tungsten film 32 are A method has been considered in which reactive ion etching is performed under conditions that provide a similar etching rate, and the tungsten film 32a is buried only in desired openings 35, as shown in FIG. 5d. According to this method, selective filling can be performed, but in order to fill the opening 35, it is necessary to deposit the tungsten film 32 with a thickness that is more than half the size of the opening 35. However, the opening 35 with a diameter of 1 μm or more, that is, the thickness of the tungsten film 32 is 0.5 μm.
In the above, the cavity 33 is clearly visible as shown in FIG. 5c.
, and the film becomes more likely to peel off. The peeling of the film causes non-uniformity in the thickness of the resist when the resist 34 is applied, so that the surface of the oxide film 31 becomes uneven as shown in FIG. 5d and cannot be flattened. In addition, if the adhesion between the oxide film 31 and the tungsten film 32a is poor in the opening 35, a layer may form between them, resulting in poor electrical contact or being exposed to moisture or acid, resulting in reliability problems. Furthermore, if the film peels off severely, the tungsten film 32a embedded in the openings 35 will also peel off at the same time, resulting in a large number of openings 35 formed on one chip.
It becomes impossible to embed tungsten in the

(Problems to be Solved by the Invention) The present invention has been made in consideration of the above-mentioned problems. An object of the present invention is to provide a method for manufacturing a semiconductor device in which peeling of the metal film and oxide film does not occur in a method of embedding the metal film.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention forms an insulating film on the surface of a semiconductor or metal, and opens a hole in the insulating film so that a part of the semiconductor or metal is exposed. Next, a step of depositing a semiconductor film on the insulating film and the surface of the opening and leaving the semiconductor film on at least the side wall of the opening by reactive ion etching, a step of reacting with a fluoride gas to deposit this metal on at least the side walls of the opening, and then depositing a first metal film having good adhesion to the insulating film over the opening and the insulating film. followed by a step of forming a second metal film on the first metal film to fill the opening, and then filling the first and second metal films existing outside the opening. The present invention provides a method for manufacturing a semiconductor device including a step of removing a metal film.

(Function) According to the present invention, after a metal fluoride gas is applied to the semiconductor film formed on the side wall of the opening to deposit a metal, a first metal film having good adhesion to the insulating film is formed. In order to embed a second metal film such as dungsten into the opening through the opening, the first
Peeling of the metal film and the second metal film does not occur, and the metal film can be quickly filled into the opening, which reduces the contact resistance between the metal film embedded in the opening and the upper and lower wiring layers. is reduced, showing good ohmic properties.

Furthermore, in the present invention, the thickness of the first metal film and the second metal film can be made thinner by the thickness of the semiconductor film on which metal is deposited, so that etching during patterning can be easily performed. I can do it.

(Example) Hereinafter, an example of the method for manufacturing a semiconductor device according to the present invention will be described.

First, a first embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1a, a layer of about 1.2 μm as an insulating film is formed on a highly doped arsenic (As) layer 10 formed on a P-type (100) silicon substrate 16 of 5 Ωcm.
After forming the SiO ₂ film 11 by atmospheric pressure CVD method, it is etched at a desired location by reactive ion etching or the like with a diameter of 0.4 μm.
An opening 15 of m is provided. Next, as shown in Figure 1 b
Introducing hydrogen (H ₂ ) at a partial pressure of 0.15 Torr and Ticl ₄ at a partial pressure of 0.05 Torr in a reduced pressure CVD apparatus at 650 °C,
Titanium (Ti) film 1 which is the first metal film with a thickness of about 200 Å
2, and after evacuating the inside of the device, hydrogen (H ₂ ) was applied at a substrate temperature of 400°C and a partial pressure of 0.2 Torr.
Tungsten hexafluoride (WF ₆ ) is introduced at 0.03 Torr to form the tungsten film 13, which is the second metal film.
It was deposited to a thickness of 0.3 μm to fill the opening 15. After that, as shown in Figure 1c, a 0.5 μm photoresist 14 is applied.
After coating and baking at 200℃, Fig. 1 d
The dungsten film 13a formed outside the opening 15 is removed by reactive ion etching using CF ₄ and _{N 2} as shown in FIG. A shape is obtained in which only the opening 15 is filled with the tungsten film 13b and the titanium film 12b. In this example, no peeling of the tungsten film 13 was observed, and when the contact resistance with the silicon substrate was measured when Al-Si wiring (not shown) was formed on the upper layer, the current-voltage characteristic was 1×10 ^-6 Ωcm ² . It showed good ohmic properties.

In the above embodiment, the titanium film 12 was formed as the first metal film, but a tungsten-silicon alloy film may be formed instead. In the above example, after forming the openings 15 at desired locations in the SiO ₂ film 11 as shown in FIG. partial pressure to
Hydrogen (H ₂ ) at 0.06 Torr, SiH ₄ at 0.12 Torr,
It is formed by introducing 6ft tungsten (WF ₆ ) at 0.001 Torr and depositing a 500 Å thick tungsten-silicon alloy film with excess silicon content.
After this, as in the first embodiment, hydrogen (H ₂ ) is introduced at a partial pressure of 0.2 Torr, and tungsten hexafluoride (WF ₆ ) is introduced at a partial pressure of 0.03 Torr to form the tungsten film 13 as the second metal film. Deposit 0.3μm. After that, a photoresist 14 was applied as shown in Fig. 1c, and after baking at 200°C for 20 minutes, the photoresist 14 was applied as shown in Fig. 1d.
As shown in FIG.
a and the tungsten-silicon alloy film 12a are removed by reactive ion etching to obtain a shape in which the tungsten film 13b and the tungsten-silicon alloy film 12b are embedded only in the opening 15. Even in this process, no peeling of the tungsten film 13 was observed, and Al-Si (not shown) was formed in the upper layer.
When the contact resistance with the silicon substrate after wiring was measured, it was 2 to 3 x 10 ^-6 Ωcm ² , indicating good ohmic properties.

As described above, if the method according to the present invention is used, there will be no film peeling or unevenness of the SiO ₂ film 11 due to film peeling, and there will be no irregularities in the openings 15 such as through holes or contact holes, and the openings 15 can be reliably formed. was able to be embedded.

Next, as a second embodiment of the present invention, a manufacturing method including a step of forming an opening in a SiO ₂ film and then forming a metal layer reacted with fluoride gas in the opening is shown in FIG. I will explain using

First, as shown in Figure 2a, arsenic (As) is applied to a 5Ωcm P-type (100) silicon substrate 1 at 30KeV in a 30×10 ¹⁵
After implanting cm ^-2 and performing heat treatment at 900°C for 40 minutes to form the N ⁺ diffusion layer 2, the substrate temperature was increased to 400°C using tungsten hexafluoride (WF ₆ ) and argon (Ar).
A tungsten wiring layer 3 of ~500 Å is formed by chemical vapor deposition at a temperature of 0.2 Torr.
Then use SiH ₄ and N ₂ O under a pressure of 0.35 Torr to approx.
A SiO ₂ film 11 is deposited as an insulating film with a thickness of 1.2 μm, and then an opening 15 with a diameter of 0.4 μm is formed by reactive ion etching or the like. After that, the temperature of the substrate 1 is
A polycrystalline silicon film 4 with a thickness of 0.1 μm is deposited on the openings 15 and 4 using low pressure chemical vapor deposition (CVD) at 600°C.
It is deposited on the SiO ₂ film 11. After that, Figure 2b
The polycrystalline silicon 4 is anisotropically etched by reactive ion etching using a chlorine-based gas such as BBr ₃ -cl ₂ as shown in FIG.
Leave a. Next, the pressure is 0.2 Torr, and the temperature of substrate 1 is
Tungsten hexafluoride (WF ₆ ), which is a tungsten fluoride gas, and argon (Ar) are flowed at 400°C to reduce the tungsten hexafluoride (WF ₆ ) in the silicon film 4a, and completely remove the sidewall silicon film 4a. It is replaced with a tungsten film 5 as shown in FIG. 2c. When all of the 0.1 μm silicon film 4a reacts with tungsten hexafluoride (WF ₆ ), a tungsten film 5 of about 500 Å is formed.

After that, reduced pressure CVD is performed as shown in Figure 2d.
Temperature of the substrate is 400℃ inside the device and partial pressure is applied.
Hydrogen (H ₂ ) at 0.06 Torr, SiH ₄ at 0.12 Torr,
Tungsten hexafluoride (WF ₆ ) was introduced at a pressure of 0.001 Torr, and a 500 Å tungsten-silicon alloy film 12 with an excess of silicon, which is the first metal film, was introduced, and then hydrogen (H ₂ ) was introduced at a partial pressure of 0.03 Torr. Tungsten hexafluoride (WF ₆ ) is introduced at Torr to deposit a 0.3 μm second metal film, here the tungsten film 13. After that, photoresist 14 is applied for planarization.
After baking at 200℃ for 20 minutes, apply CF ₄ and
The tungsten film 13a and tungsten-silicon alloy film 12a other than the opening 15 are removed by reactive ion etching using _N2 , and the tungsten film 13b and tungsten-silicon alloy film 12b are removed only in the opening 15 as shown in FIG. 2d. Obtain the embedded shape.

According to this embodiment, the thickness of the tungsten-silicon alloy film 12, which is the first metal film, and the tungsten film 13, which is the second metal film, can be made thinner by the thickness of the metal film 5. The etching process is easy, and no peeling of the film or unevenness of the SiO ₂ film 11 due to the peeling of the film is observed.
No cracks were observed in the aperture 15, and the aperture 15 could be reliably filled. Furthermore, when measuring the contact resistance when an Al-Si wiring (not shown) is formed on the upper layer, the contact resistance between the Al-Si wiring and the tungsten film 13b is 3 to 4 × 10 -9 Ωcm 2 , and the contact resistance between the tungsten film 13b and the lower tungsten wiring layer is 3 to 4 × 10 ^-9 Ωcm ^{2 .} The contact ^resistance between the tungsten wiring layer ³ and the highly concentrated arsenic (As) doped silicon layer 2 was 5×10 ^-7 Ωcm ² , showing good ohmic characteristics.

In the second embodiment described above, even when the tungsten wiring layer 3 is not formed, that is, even when the SiO ₂ film 11 is formed directly on the N ⁺ diffusion layer 2,
A similar effect can be obtained. In this case, the final structure obtained is shown in FIG. Here, the same parts as in FIG. 2 are indicated by the same symbols.

In each of the above examples, titanium or a tungsten-silicon alloy was used as the first metal, and tungsten was used as the second metal, but the present invention is not limited to these, and titanium (Ti) was used as the first metal. , zirconium (Zr), hafnium (Hf), niobium (Nb), tantalum (Ta), and their silicides (alloys with silicon), nitrides,
Alternatively, it may be a silicide of molybdenum (Mo) or tungsten (W), and the same effect can be obtained by using molybdenum (Mo) or silicides thereof in addition to tungsten (W) as the second metal. It will be done.
Further, in the embodiment shown in FIGS. 2 and 3, tungsten is used as the metal formed on the side wall of the opening 15, but molybdenum may also be used.

Furthermore, the lower layer of the SiO ₂ film 11 is a N ⁺ or P ⁺ silicon substrate, titanium, zirconium, hafnium, niobium, tantalum, chromium, molybrine, etc.
Any of tungsten and silicides or nitrides thereof, nickel, palladium, platinum and silicides thereof, or a metal film mainly composed of aluminum or copper may be used.

〔Effect of the invention〕

As described above, according to the present invention, when filling an opening such as a contact hole or a through hole formed in an insulating film with a metal film such as dungsten, an insulating film is formed between the metal film and the insulating film. Since the first metal film having good adhesion to the film is interposed, the metal film does not peel off and the surface of the insulating film remains flat even after etching. Further, since no curvature occurs in the openings, electrical contact is also good.

[Brief explanation of the drawing]

FIG. 1 is a process sectional view showing an embodiment of the present invention;
2 and 3 are process sectional views showing another embodiment of the present invention, and FIGS. 4 and 5 are process sectional views showing a conventional example. 1,16...Silicon substrate, 2,10...N ⁺
Diffusion layer, 3...Tungsten film, 4, 4a...Silicon film, 5...Tungsten film, 12, 12
a, 12b...first metal film, 13, 13a, 1
3b...Second metal film, 14...Photoresist.

Claims (1)

[Claims] 1. A step of forming an insulating film on the surface of a semiconductor or metal, and providing an opening in the insulating film so that a part of the semiconductor or metal is exposed; A step of depositing a semiconductor film on the surface of the hole and leaving the semiconductor film on at least the side wall of the hole by reactive ion etching, and reacting the remaining semiconductor film with a metal fluoride gas to remove the metal from the opening. a step of depositing it on at least the side wall in the hole, and then a step of depositing a first metal film having good adhesion to the insulating film on the aperture and the insulating film;
Subsequently, forming a second metal film on the first metal film to fill the opening, and then removing the first and second metal films existing outside the opening. A method for manufacturing a semiconductor device, comprising the step of: 2 The first metal is titanium, zirconium, hafnium, niobium, tantalum, and silicides thereof,
2. The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is made of nitride, tungsten, or molybdenum silicide. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the second metal is tungsten, molybdenum, or a silicide thereof. 4 The metal forming the metal surface is titanium, zirconium, hafnium, niobium, tantalum, chromium,
The metal according to claim 1, which is any of molybdenum, tungsten, and their silicides or nitrides, or nickel, palladium, platinum, and their silicides, or a metal whose main component is aluminum or copper. A method for manufacturing a semiconductor device. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the first and second metals are deposited by chemical vapor deposition. 6. The method of manufacturing a semiconductor device according to claim 1, wherein the metal constituting the fluoride gas is tungsten or molybdenum.