JPH0786395A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a work surface treating method through which a work or the like can be prevented from being charged up with static electricity and damaged, and a surface layer can be removed from the work. CONSTITUTION:The surface of a tungsten film 13, a tungsten-containing film, a molybdenum film, or a molybdenum-containing film formed on a silicon oxide film 12 provided onto the surface of a substrate 11 is treated in an nitrogen trifluoride-containing atmosphere keeping the substrate 11 and the silicon oxide film 12 heated, and a surface layer is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device including a surface treatment for removing a native oxide film on the surface of a lower wiring layer or the like.

[0002]

2. Description of the Related Art In recent years, with the high integration of semiconductor devices, there has been a demand for multi-layer wiring and miniaturization of wiring layers. In order to realize the miniaturization of the wiring layer, a tungsten film or the like may be formed on the Al film as a measure against migration of the Al film. Then, in order to obtain good contact between the lower wiring layer and the upper wiring layer, before forming the upper wiring layer,
A surface treatment is performed to remove a metal oxide that naturally forms on the surface of the lower wiring layer and an altered layer on the surface to expose a clean surface of the lower wiring layer.

Conventionally, dry etching using a plasma gas such as argon ions has been performed as such surface treatment. When applied to the via hole 6 on the gate electrode 4 of the MOS transistor, as shown in FIG. 3A, after the surface layer of the gate electrode 4 at the bottom of the via hole 6 is removed by irradiation with argon ions, the structure shown in FIG. ), The upper wiring layer 7 is formed in connection with the gate electrode 4. As a result, a clean surface of the gate electrode 4 appears at the bottom of the via hole 6, so that the gate electrode 4 and the upper wiring layer 7 are formed.
A good ohmic contact can be obtained with.

[0004]

However, in the surface treatment of the above-mentioned conventional example, the gate electrode 4 is charged by the argon ions and a high electric field is applied between the gate electrode 4 and the silicon substrate 1. Therefore, there is a problem that the gate insulating film 3 causes electrostatic breakdown. Also, the insulating films 5b and 5c exposed to argon ions
There is also a problem that the gate electrode 4 and the like are damaged by the impact of argon ions.

The present invention has been made in view of the problems of the conventional example, and prevents charge-up of the object to be processed and prevents damage to the object to be processed.
An object of the present invention is to provide a method for manufacturing a semiconductor device including a surface treatment capable of removing a surface layer of an object to be processed or the like.

[0006]

The above-mentioned problems are as follows. First, the surface of the tungsten film or the tungsten-containing film, or the molybdenum film or the molybdenum-containing film formed on the substrate is exposed in a gas containing nitrogen trifluoride. And a method for manufacturing a semiconductor device, which comprises treating the substrate in a heated state and removing the surface layer. Secondly, a tungsten film or a tungsten-containing film, or a molybdenum film or a molybdenum-containing film is formed on the substrate. A step of forming a lower wiring layer formed of a film, a step of forming an interlayer insulating film by covering the lower wiring layer, a step of forming an opening in the interlayer insulating film on the lower wiring layer, and the opening A step of treating the surface of the lower wiring layer at the bottom of the substrate in a gas containing nitrogen trifluoride and heating the substrate to remove the surface layer; And a step of forming an upper wiring layer by connecting to a line layer. Thirdly, the surface layer is formed of a tungsten film or an oxide of a tungsten-containing film, or a molybdenum film or a molybdenum-containing film. First or second characterized by being an oxide
The method for manufacturing a semiconductor device according to any one of the first to third inventions, wherein the substrate temperature is 200 ° C. or higher. Achieved by

[0007]

[Operation] In a method of manufacturing a semiconductor device according to the present invention
Is NF with the substrate heated. ₃Tangs by gas
A surface treatment such as a ten film is performed. For example, Tungsute
Oxide of tungsten film and NF of tungsten film itself₃Against gas
The reaction formula to do is as follows. WO₃+ 2NF₃-WOF_Four＋ 2NOF W ＋ 2NF₃-WF₆＋ N₂ Due to the above reaction, oxide and tungsten of the tungsten film
Ten film itself is NF₃Reacts with gas, gaseous WOF_FourAnd NOF
Or WF₆And N₂Oxide on the surface tungsten film
And the tungsten film is removed. This allows the upper
Tongue for obtaining good contact with the wire layer
The clean surface of the film is exposed.

Further, since plasma gas is not used as an etchant, the substrate or the like is not damaged by ion bombardment and is not charged. On the other hand, the surrounding silicon oxide film is hardly etched by the NF ₃ gas.
Therefore, when this surface treatment method is used for removing a lower wiring layer at the bottom of a via hole formed in a silicon oxide film or the like, or a surface layer such as a gate electrode, for example, a natural oxide film or an altered layer, This prevents damage to the gate insulating film due to charge-up, or prevents damage to the lower wiring layer and the like.

Based on the substrate temperature dependence of the etching rate confirmed by experiments, the substrate temperature is practically 2
It is preferably 00 ° C or higher.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. (1) Description of Investigation Experiment of Substrate Temperature Dependence of Etching Rate of Tungsten Film According to Example of the Present Invention FIG. 1A shows substrate temperature dependency of etching rate of tungsten film according to an example of the present invention. 2B is a cross-sectional view for explaining the results of the investigation experiment, and FIG. 1B is a cross-sectional view for explaining the sample used in the investigation experiment.

As shown in FIG. 1B, a silicon substrate 1
An experimental sample in which a tungsten film 13 was formed on the silicon oxide film 12 on 1 was placed on the heater 14 and pressure 10
The etching rate was measured by changing the temperature of the silicon substrate 11 variously in NF ₃ gas of Pa or less. Figure 1 (a)
The results are shown in. According to the results, the substrate temperature is 200 ℃
It is 0.5 nm / min, and the etching rate increases as the substrate temperature rises to 3 nm / min at a substrate temperature of 600 ° C.

In the experiment, the etching rate of the tungsten film 13 was investigated, but the oxide rate of the tungsten film 13 has a similar etching rate. The natural oxide film formed on the surface altered layer or on the surface is considered to have a film thickness of usually several tens to hundreds of nm. Therefore, in order to remove the surface layer of the tungsten film 13 and expose a clean surface, it is practically preferable to perform the surface treatment while maintaining the substrate temperature at 200 ° C. or higher.

The tungsten-containing film, the molybdenum film, and the molybdenum-containing film are not so different from this etching rate, and the above results can be applied to these films. Further, although the heater 14 is used for heating the substrate in the above experiment, an infrared lamp or other heating means may be used.

(2) Description of Surface Treatment Method Before Formation of Upper Wiring Layer According to the Embodiment of the Present Invention FIGS. 2A to 2D are views before formation of the upper wiring layer according to the embodiment of the present invention. It is sectional drawing explaining the surface treatment method of a lower wiring layer. First, as shown in FIG. 2A, a silicon oxide film 22 is formed on a silicon substrate 21 by thermal oxidation. Then, a film thickness of about 3000 is formed on the silicon oxide film 22.
After the tungsten film of Å is formed by the sputtering method, it is patterned to form the lower wiring layer 23.

Next, as shown in FIG. 2B, the lower wiring layer 23 is covered and a silicon oxide film 24 having a film thickness of about 4000 Å to be an interlayer insulating film is formed by the plasma CVD method. Subsequently, SOG is applied to fill the recesses and planarize the surface, and the SOG film 25 is formed. Next, using the resist film (not shown) as a mask, the SOG film 25 and the silicon oxide film 2
4 is etched by dry etching and removed to form a via hole 26 on the lower wiring layer 23. After this,
It is assumed that tungsten oxide is naturally formed on the lower wiring layer 23 at the bottom of the via hole 26.

Next, as shown in FIG. 2C, the silicon substrate 21 is placed on the heater of the pretreatment chamber (not shown) to reduce the pressure inside the chamber. Further, the silicon substrate 21 is heated by a heater (not shown) to maintain the temperature of the silicon substrate 21 at about 450 ° C. When the chamber reaches a predetermined pressure and the substrate temperature reaches a predetermined level, NF ₃ gas is introduced into the chamber to set the pressure to 1.33.
Hold at Pa. At this time, the etching rate of the tungsten film or the tungsten oxide is about 2 nm / min, and normally, the tungsten oxide can be removed in about several minutes. This completes the surface treatment of the lower wiring layer 23.

Subsequently, without exposing the silicon substrate 21 to the atmosphere, the silicon substrate 21 was moved to the CVD apparatus connected to this pretreatment chamber to first form a titanium nitride (TiN) film having a film thickness of about 500 Å to be a barrier metal. After that, an Al film having a film thickness of about 1 μm to be an upper wiring layer is continuously formed. After that, when the Al film and the TiN film are patterned to form the upper wiring layer 27b and the barrier metal layer 27a, the connection between the upper wiring layer 27b and the lower wiring layer 23 is completed as shown in FIG.

As described above, according to the embodiment of the present invention,
Since the surface treatment does not use plasma, the lower wiring layer 2
The surface treatment can be performed while preventing the charge-up of No. 3 and the introduction of damage to the lower wiring layer 23. When the surface treatment described above is used for removing the surface layer of the gate electrode at the bottom of the via hole, dielectric breakdown of the gate insulating film due to charge-up of the gate electrode can be prevented.

Further, in the embodiment, N is used as the surface treatment gas.
Although only F ₃ gas is used, for example, NF ₃ gas and
A mixed gas with an inert gas or another gas may be used.

[0020]

As described above, according to the method of manufacturing a semiconductor device of the present invention, since NF ₃ gas is used for the surface treatment of the lower wiring layer, the gate electrode, etc., and plasma is not used, charge-up is caused. It is possible to prevent dielectric breakdown of the lower wiring layer and the insulating film underlying the gate electrode. Further, it is possible to prevent the introduction of damage to the lower wiring layer and the gate electrode due to ion bombardment.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the substrate temperature dependence of an etching rate of a tungsten film in a surface treatment method according to an example of the present invention.

FIG. 2 is a cross-sectional view illustrating a method of surface-treating a lower wiring layer before forming an upper wiring layer according to an example of the present invention.

FIG. 3 is a cross-sectional view illustrating a problem of a conventional example.

[Explanation of symbols]

 11, 21 Silicon substrate, 12, 22, 24 Silicon oxide film, 13 Tungsten film, 14 Heater, 23 Lower wiring layer, 25 SOG film, 26 Via hole, 27a Barrier metal film, 27b Upper wiring layer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/88 M

Claims (4)

[Claims] 1. A surface of a tungsten film, a tungsten-containing film, a molybdenum film, or a molybdenum-containing film formed on a substrate is treated in a gas containing nitrogen trifluoride and in a state where the substrate is heated, A method for manufacturing a semiconductor device, which comprises removing a surface layer. 2. A step of forming a lower wiring layer made of a tungsten film, a tungsten-containing film, a molybdenum film, or a molybdenum-containing film on a substrate, and a step of forming an interlayer insulating film by covering the lower wiring layer, Forming an opening in the interlayer insulating film on the lower wiring layer, and treating the surface of the lower wiring layer at the bottom of the opening in a gas containing nitrogen trifluoride and while heating the substrate. ,
A method of manufacturing a semiconductor device, comprising: a step of removing a surface layer; and a step of forming an upper wiring layer by connecting to a lower wiring layer at a bottom of the opening. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the surface layer is an oxide of a tungsten film or a tungsten-containing film, or a molybdenum film or an oxide of a molybdenum-containing film. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the substrate temperature is 200 ° C. or higher.