JP2976931B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a MOSFET (metal-oxide-silicon field-effect transistor).
In particular, the present invention relates to a method for reducing damage caused by a plasma process by annealing.

[0002]

2. Description of the Related Art Conventionally, in the process of patterning a metal wiring material in a fine MOS / LSI manufacturing process,
Reactive ion etching is usually used because of its excellent vertical workability. In addition, a high-density plasma oxide film is used for forming an insulating film between wiring layers because of its excellent embedding property. However, the semiconductor substrate is exposed to a plasma atmosphere during the reactive ion etching process or the plasma oxide film forming process. At this time, the wiring connected to the gate electrode acts as a kind of antenna for the plasma, and charges are accumulated in the MOSFET, thereby deteriorating the gate insulating film or increasing the interface state of the gate insulating film (hereinafter, referred to as plasma). Damage). Therefore, in order to alleviate the damage applied to the gate insulating film, conventionally, after the formation of the wiring layer, a hydrogen annealing process for heating the semiconductor substrate in a hydrogen gas atmosphere is performed in a final manufacturing process of the semiconductor device. ing.

However, a barrier layer such as titanium, which is usually used as a lower layer or an upper layer of a wiring layer, has a property of absorbing hydrogen. Therefore, when a barrier layer exists so as to cover a MOSFET, plasma damage is removed by hydrogen annealing. However, there arises a problem that the effect obtained is not sufficiently obtained.
For example, S. Hirade et al.
(Processed P376)
It has been reported that when a large-area wiring material is present immediately above a gate electrode of a FET, a titanium film existing as a barrier metal below the wiring material absorbs hydrogen and cannot sufficiently remove plasma damage.

[0004] For example, in an input / output buffer circuit provided in a normal semiconductor device, a wiring having a line width wider than other parts is usually used for a power supply line. In this case, in the conventional method, hydrogen may not diffuse to the vicinity of the gate insulating film of the MOSFET located immediately below the power supply line, and the plasma damage may not be sufficiently removed, and a MOSFET having desired characteristics may be obtained. become unable.

In recent years, an attempt has been made to apply a low dielectric constant film to an interlayer insulating film for the purpose of suppressing the circuit delay time by reducing the capacitance between wirings. However, since this low dielectric constant film is generally a film synthesized from organic molecules, it has poor heat resistance, and it is impossible to perform hydrogen annealing at a conventional processing temperature of 400 to 500 ° C. For example, it has been reported by Endo and others that when fluorinated amorphous carbon is applied to an interlayer insulating film, the amorphous carbon film is decomposed and vaporized into a carbon fluoride-based gas when heated to 300 ° C. or more (Appl.Ph).
ys ・ Lett ・ 68 (20) 、 13May199
6). Therefore, when such an interlayer insulating film having poor heat resistance is used, a method of sufficiently removing plasma damage at a lower temperature than in the past has been required.

Japanese Patent Application Laid-Open No. 57-118635 describes a method of annealing using hydrogen ions generated by a plasma generator instead of a conventional hydrogen gas. According to this publication, even if the substrate temperature is set to a relatively low temperature, the hydrogen annealing effect is exhibited. However, in this method, since hydrogen ions generated by high-frequency power are used, plasma damage may be newly generated in this step, and as a result, there has been a problem that sufficient damage cannot be removed.

On the other hand, Japanese Patent Application Laid-Open No. Hei 2-177542 describes a method for improving the breakdown voltage characteristics of an oxide film formed on the surface of a silicon wafer by annealing the silicon wafer under pressure in a hydrogen atmosphere. . However, in this method, pressurized hydrogen annealing is performed before forming an oxide film for the purpose of reducing thermally induced crystal defects at the time of forming an oxide film. Therefore, a method of reducing plasma damage after forming a gate oxide film and forming an interlayer insulating film and wiring has not been known at all.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. In a semiconductor device such as a MOSFET, hydrogen such as a titanium film or a titanium nitride film is formed under a metal wiring layer. Even if a barrier layer is provided with a substance to be absorbed and exists in a large area immediately above the insulating film, the plasma damage is sufficiently removed and the MOSFET is removed.
It is an object of the present invention to provide a method of manufacturing a semiconductor device which improves characteristics and reliability of the semiconductor device.

Another object of the present invention is to provide a method of manufacturing a semiconductor device which can sufficiently remove plasma damage even when an annealing temperature lower than that of the related art is used.

[0010]

According to the present invention, a semiconductor substrate on which a gate insulating film, an electrode, a metal wiring, and an interlayer insulating film are formed by a manufacturing process including at least one process using plasma during the manufacturing process is provided. The present invention relates to a method for manufacturing a semiconductor device, characterized by heating in a pressurized hydrogen atmosphere.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a semiconductor substrate has
After forming a gate insulating film, an electrode, a metal wiring, and an interlayer insulating film, hydrogen annealing is performed in a pressurized hydrogen atmosphere in order to remove plasma damage received during these steps. Therefore, the step of heating in a pressurized hydrogen atmosphere is preferably performed as close as possible to the final step of semiconductor manufacturing. Further, on the semiconductor substrate, other layers may be formed as necessary in addition to the gate insulating film, the electrodes, the metal wirings, and the interlayer insulating films.

In the present invention, a larger amount of hydrogen is supplied into the interlayer insulating film and to the semiconductor substrate than in the prior art by performing hydrogen annealing in a pressurized hydrogen atmosphere, preferably in a pressurized hydrogen atmosphere of 0.5 MPa or more. As a result, plasma damage can be removed even in the case where the MOSFET is present immediately below a wiring having a wide line width and having a hydrogen absorbing material such as titanium in the lower layer and / or the upper layer. However, if the hydrogen partial pressure is too high, there is a danger of explosion, etc.
Usually, for example, it is preferable to carry out at about 5 MPa or less.
Hydrogen gas may be diluted with a suitable inert gas.

The metal wiring may be provided with a film made of a high melting point metal or a nitride of a high melting point metal as a lower layer and / or an upper layer as necessary. Such a material is generally hydrogen-absorbing, but the present invention can exert a particularly great effect when such a material is provided in a lower layer and / or an upper layer of a metal wiring. Examples of the high melting point metal or the nitride of the high melting point metal include titanium and titanium nitride.

Further, when the processing temperature of the normal hydrogen annealing is lowered, the diffusion coefficient of hydrogen in the interlayer film decreases, and it becomes difficult to diffuse hydrogen to the vicinity of the gate insulating film. However, in the present invention, since the hydrogen partial pressure near the interlayer film surface is increased,
By increasing the diffusion rate even at low temperatures, hydrogen can be sufficiently diffused. Therefore, even if the processing temperature is lowered, plasma damage can be removed.

In the present invention, since the hydrogen annealing treatment is performed in an atmosphere in which no plasma exists, a sufficient plasma damage removing effect can be obtained without adding new damage.

[0016]

【Example】

Embodiment 1 Next, an embodiment of the present invention will be described with reference to the drawings.

1 to 4 are views for explaining a method of manufacturing a semiconductor device according to the present embodiment. In the present embodiment, the second-layer metal wiring 11 is used for supplying power to the input / output buffer circuit, and is arranged so as to be wider than a normal line width and to cover the MOSFET. FIG. 1 is a plan view thereof,
FIG. 2 is a cross-sectional view taken along a line AB in FIG.

As shown in FIG. 2, an element isolation film 2, a source electrode 14, a drain electrode 15, a gate insulating film 30, and a gate electrode 16 are provided on a silicon substrate 1.
Further, a film 7 was formed thereon by a plasma CVD method.
A plasma silicon oxide film 3 having a thickness of 00 nm is formed as an interlayer insulating film.

An opening reaching the source electrode 14 and the drain electrode 15 is provided at a predetermined position in the plasma silicon oxide film 3, and a tungsten plug 4 for making contact with the source electrode 14 and the drain electrode 15 is provided through the opening. The first layer metal wiring 31 is connected to the tungsten plug. The first layer metal wiring is composed of a laminated film of titanium film 5 / titanium nitride film 6 / aluminum / copper alloy film 7 / titanium nitride film 8, and their thickness is 60 nm / 100 nm / 500 nm / 100 nm. The contact surface between the source electrode 14 and the drain electrode 15 is silicidized to form a titanium silicide film 17.
Are formed.

A 500 nm-thick plasma silicon oxide film 13 formed by a plasma CVD method is formed as an interlayer insulating film over the first layer metal wiring, and a second layer metal wiring 32 is provided thereon. ing. Similarly, the second-layer metal wiring is also composed of a laminated film of titanium film 9 / titanium nitride film 10 / aluminum / copper alloy film 11 / titanium nitride film 12, each having a thickness of 60 nm / 100 nm / 500 n.
m / 100 nm. The line width of the second-layer metal wiring 32 is 1
It is as wide as 0 μm, and largely covers the MOSFET as shown in FIG.

The annealing of the substrate thus formed is performed as follows.

As shown in FIG. 3, a 400 nm-thick plasma silicon oxide film 18 is formed on the substrate on which the metal wiring up to the second layer in FIG. 2 is formed, and then introduced into a 1 MPa pressurized hydrogen gas atmosphere. Then, it was annealed by heating at 400 ° C. for 20 minutes.

Next, as shown in FIG. 4, a plasma silicon nitride oxide film 19 having a thickness of 300 nm is formed. In the step of forming the plasma silicon oxynitride film 19, the entire wiring layer is covered with the insulating film, and the MOSFET is not damaged by plasma existing in the film formation atmosphere.

After this step, a desired semiconductor device was obtained by forming a cover film, opening bonding pads, and assembling.

In this embodiment, since the line width of the second-layer metal wiring is wide and a layer of titanium and titanium nitride is provided below the metal wiring, the conventional hydrogen anneal occurs during the formation of an interlayer insulating film. Although plasma damage could not be sufficiently removed, in the present example, a large amount of hydrogen could be diffused into the interlayer film and plasma damage could be removed.

[Embodiment 2] In this embodiment, first, FIG.
As shown in FIG. 1A, an element isolation film 2 is formed on a silicon substrate 1.
Source electrode 14, drain electrode 15, gate insulating film 30
Then, a gate electrode 16 was formed, and then a plasma silicon oxide film 3 was formed as an interlayer insulating film, and subsequently a contact hole was formed by using lithographic and etching techniques. Next, after sputtering titanium and titanium nitride as shown in FIG.
Was embedded in the contact hole opening, and subsequently, a metal wiring material was sputtered, and a first layer metal wiring 31 was formed by patterning using photolithography and etching techniques. The first-layer metal wiring has the same four-layer structure as in the first embodiment, but is not shown.

Next, a silicon oxide film 35 is deposited by a CVD method as shown in FIG.
A fluorinated amorphous carbon film 36 was deposited by the method. Then, the silicon oxide film 37 is again formed by the CVD method.
Then, the silicon oxide film was polished by chemical mechanical polishing (CMP) to flatten the surface.

Next, as shown in FIG. 6A, the first and second interlayer insulating films including the silicon oxide film 35, the fluorinated amorphous carbon film 36 and the silicon oxide film 37 are formed.
The through holes for connecting the metal wiring layers are opened, and the first
In the same manner as the formation of the layer metal wiring, the tungsten plug 2
0 and the second layer metal wiring 32 were formed. The second-layer metal wiring also has the same four-layer structure as in the first embodiment, but is not shown.

Next, as shown in FIG.
A plasma silicon oxide film 21 having a thickness of 3 nm is formed, and the semiconductor substrate is introduced into a pressurized hydrogen gas atmosphere of 2 MPa.
Annealing was performed at 00 ° C. for 20 minutes. Subsequently, a plasma silicon nitride oxide film and a polyimide film are formed,
Subsequently, a bonding pad was opened, and further assembly was performed to obtain a desired semiconductor device.

Also in this case, as in the first embodiment, in the step of forming the plasma silicon oxynitride film, the metal wiring layer is entirely covered with the insulating film, and
T is not damaged by plasma existing in the film formation atmosphere.

As described above, in this embodiment, although the amorphous carbon fluoride film, which is a low dielectric constant film, is used as the interlayer insulating film for the purpose of reducing the capacitance between wirings, hydrogen annealing can be performed at a lower temperature than in the prior art. The plasma damage was sufficiently reduced without damaging the fluorinated amorphous carbon film.

[0032]

According to the present invention, in a semiconductor device such as a MOSFET, a material that absorbs hydrogen, such as a titanium film or a titanium nitride film, is used as a barrier layer above and / or below a metal wiring layer. Even in the case where a large area exists immediately above the film, plasma damage can be sufficiently removed, and a semiconductor device with improved MOSFET characteristics and reliability can be manufactured.

Further, according to the present invention, it is possible to manufacture a semiconductor device from which plasma damage has been sufficiently removed even if an annealing temperature lower than that of the related art is used.

[Brief description of the drawings]

FIG. 1 is a plan view showing a structure of a semiconductor substrate to be annealed in a pressurized hydrogen atmosphere.

FIG. 2 is a cross-sectional view taken along a line AB in FIG.

FIG. 3 is a view showing a semiconductor substrate to be annealed in a pressurized hydrogen atmosphere.

FIG. 4 is a diagram showing a semiconductor device manufacturing process following an annealing process in a pressurized hydrogen atmosphere.

FIG. 5 is a view showing a manufacturing process shown in Example 2.

FIG. 6 is a view showing a manufacturing step shown in Example 2 following FIG. 5;

[Explanation of symbols]

 Reference Signs List 1 silicon substrate 2 element isolation film 3 plasma silicon oxide film 4 tungsten plug 5 titanium film 6 titanium nitride film 7 aluminum / copper alloy film 8 titanium nitride film 9 titanium film 10 titanium nitride film 11 aluminum / copper alloy film 12 titanium nitride film 13 Plasma silicon oxide film 14 Source electrode 15 Drain electrode 16 Gate electrode 17 Titanium silicide film 18 Plasma silicon oxide film 19 Plasma silicon nitride oxide film 20 Tungsten plug 21 Plasma silicon oxide film 30 Gate insulating film 31 First layer metal wiring 32 Second layer Metal wiring 35 silicon oxide film 36 fluorinated amorphous carbon film 37 silicon oxide film

Claims (6)

(57) [Claims] In a manufacturing process including a process using plasma at least once during the manufacturing process, a gate insulating film,
A method for manufacturing a semiconductor device, comprising: heating a semiconductor substrate on which an electrode, a metal wiring, and an interlayer insulating film are formed, in a pressurized hydrogen atmosphere. 2. The method for manufacturing a semiconductor device according to claim 1, wherein said metal wiring has a laminated structure having a layer made of a high melting point metal or a nitride of a high melting point metal in a lower layer and / or an upper layer. . 3. The semiconductor device according to claim 1, wherein at least one of said interlayer insulating films is a plasma silicon oxide film.
Or a method for manufacturing a semiconductor device according to item 2. 4. The method according to claim 1, wherein at least one of the interlayer insulating films is an interlayer insulating film including a fluorinated amorphous carbon layer. 5. The temperature of the pressurized hydrogen atmosphere is 300 to
The method according to claim 4, wherein the temperature is 400 ° C. 6. The hydrogen partial pressure of the pressurized hydrogen atmosphere is 0.5
The method for manufacturing a semiconductor device according to claim 1, wherein the pressure is at least MPa.