JP2001077107A - Thermal oxide film formation, manufacture of semiconductor device using the same and manufacture device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain re-diffusion of impurities by forming a metallic film comprising oxygen on a semiconductor substrate surface, and forming a thermal oxide film on a semiconductor substrate surface through solid phase diffusion of oxygen incorporated in the metallic film through heat treatment. SOLUTION: A silicon wafer 2 is introduced into a sputter device 5, a target 1 of ruthenium metal is sputtered in atmospheric gas 3, and ruthenium atom 4 is deposited on the surface of a silicon wafer 2. In the process, oxygen in atmosphere takes the ruthenium atom 4 and a ruthenium film 6 is formed. A patterned ruthenium film 7 is formed by patterning by using photolithography, the silicon wafer 2 wherein the ruthenium film 7 is formed is subjected to a heat treatment, the oxygen in the ruthenium film 7 is subjected to solid phase diffusion, and a silicon heat oxide film 8 is formed in a lower part of the ruthenium film 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of forming a thermal oxide film of a semiconductor, a method of manufacturing a semiconductor device using the thermal oxide film, and a semiconductor device.

[0002]

2. Description of the Related Art FIG. 4 is a process chart for explaining a conventional thermal oxide film forming method. As shown in FIG. 4, first, a silicon nitride film 15 is formed on a silicon wafer 2 in an atmosphere 14 of silane and ammonia (FIG. 4A,
(B)) The silicon nitride film 15 is left in a region where a thermal oxide film is not desired to be formed by patterning using photolithography, and a patterned silicon nitride film 16 is formed and used as a mask (FIG. 4).
(C)).

Next, a thermal oxide film 8 is formed by heating the semiconductor wafer 2 in a steam atmosphere 17 (FIG. 4).
(D)).

Further, after the thermal oxide film 8 is formed, a gate electrode film (polysilicon) 18 is formed (FIG. 4E), and the silicon oxide film 16 and the extra gate electrode film 18 are removed. M having a gate electrode formed on film 8
OS (Metal-Oxide-Semiconductor)
(tor) structure is obtained (FIG. 4F).

[0005]

However, in the conventional method for forming a thermal oxide film, an oxidizing source is supplied by vapor phase diffusion from water vapor, so that a thermal oxidation heating temperature of about 750.degree. Re-diffusion of the impurities implanted into the semiconductor device may occur, and the impurity distribution may be changed from a desired distribution shape, particularly in a device having a fine pattern with shallow diffusion.

Further, the formation of the MOS structure requires a step of forming a gate electrode after thermal oxidation and removing a silicon nitride film and an extra gate electrode.

[0007] In addition to controlling the temperature, time, and atmospheric pressure, the control of the film thickness requires many control items such as the temperature of insertion into the oxidation furnace and the time from the insertion to the start of oxidation.

It is an object of the present invention to provide a method for forming a semiconductor thermal oxide film at a temperature low enough to suppress re-diffusion of impurities.

It is another object of the present invention to reduce the number of steps for forming a MOS structure and to improve the controllability of film thickness.

[0010]

The invention according to claim 1 is
A thermal oxide film forming method for forming a metal film containing oxygen on the surface of a semiconductor substrate, and solid-phase diffusing oxygen contained in the metal film by heat treatment to form a thermal oxide film on the surface of the semiconductor substrate. .

According to a second aspect of the present invention, in the thermal oxide film forming method according to the first aspect, the metal film is made of a platinum group metal or a noble metal.

According to a third aspect of the present invention, in the method for forming a thermal oxide film according to the first aspect, the metal film is formed in an atmosphere containing oxygen so that oxygen is contained in the metal film.

According to a fourth aspect of the present invention, in the method of forming a thermal oxide film according to the first aspect, after the metal film is formed, oxygen is contained in the metal film by oxygen ion implantation.

According to a fifth aspect of the present invention, a metal film containing oxygen is formed on a surface of a semiconductor substrate, and oxygen contained in the metal film is solid-phase-diffused by a heat treatment to form a gate insulating film on the surface of the semiconductor substrate. A method for manufacturing a semiconductor device in which a film and a gate electrode made of the metal film are formed.

According to a sixth aspect of the present invention, there is provided a semiconductor substrate, a gate electrode made of a metal film formed on the semiconductor substrate, and oxygen between the gate electrode and the semiconductor substrate. And a gate insulating film formed by solid-phase diffusion.

According to a seventh aspect of the present invention, in the semiconductor device according to the sixth aspect, the metal film is made of a platinum group metal or a noble metal.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a process chart showing a thermal oxide film forming method according to the first embodiment of the present invention. First, the silicon wafer 2 is introduced into the sputtering apparatus 5, and the atmosphere gas 3 is set to argon + oxygen. Ruthenium atoms 4 are deposited on the surface of the silicon wafer 2 maintained at room temperature by sputtering the ruthenium metal target 1 in the atmosphere gas 3 (FIG. 1A). At this time, oxygen in the atmosphere is also taken into the ruthenium film, and a ruthenium film 6 containing a large amount of oxygen is formed on the surface of the silicon wafer 2 (FIG. 1B).

A patterned ruthenium film 7 is formed by patterning using photolithography (FIG. 1C).

Next, the silicon wafer 2 on which the ruthenium film 7 is formed is subjected to a heat treatment at 500 ° C. in a vacuum atmosphere 9 of 10 ⁻⁵ Pa or less, so that oxygen in the ruthenium film 7 is solid-phase diffused. A silicon thermal oxide film 8 is formed below (FIG. 1D).

FIG. 2 is a transmission electron micrograph of the ruthenium / silicon interface before (a) and after (b) vacuum heat treatment at 500 ° C. for 30 minutes. Before the vacuum heat treatment, there is a natural oxide film on the silicon wafer surface.
After 0 minute vacuum heat treatment, the oxide film thickness has increased to 2.2 nm. From this, it can be seen that a thermal oxide film of 0.7 nm is grown by the heat treatment at 500 ° C., which is said to hardly grow an oxide film by the conventional oxidation method in an oxygen atmosphere containing water vapor.

In the first embodiment, a silicon wafer is used as the semiconductor substrate 2, but the semiconductor substrate may be silicon carbide, gallium arsenide, or the like.

Although the ruthenium metal film is used in the first embodiment, a metal film which does not easily form an oxide may be used as the film containing oxygen, and a platinum group such as platinum or palladium, gold, silver, etc. Noble metal film may be used. Further, the vacuum heat treatment temperature may be changed to a temperature higher than 500 ° C. or lower as necessary.

FIG. 1D shows a MOS structure in which ruthenium metal is used as a gate electrode.

In the first embodiment, oxygen as an oxidation source is supplied to the semiconductor substrate by solid-phase diffusion, so that the oxygen source becomes a high-density oxygen source as compared with the conventional case of vapor-phase diffusion, and the oxidation temperature is reduced. It has the effect of lowering the temperature.

By using ruthenium metal for the gate electrode, the number of steps for forming the MOS structure can be reduced as compared with the conventional number of steps.

Further, since the thickness of the thermal oxide film is determined only by the amount of oxygen contained in the metal film and the heat treatment temperature, the thickness can be easily controlled and the accuracy of the thickness can be improved.

Embodiment 2 FIG. FIG. 3 is a process chart showing a thermal oxide film forming method according to the second embodiment of the present invention. First, the silicon wafer 2 is introduced into the sputtering apparatus 5 and the atmosphere gas is argon (Ar) 10. Ruthenium 4 is deposited on the surface of the silicon wafer 2 held at room temperature by sputtering the ruthenium metal target 1 in this atmosphere (FIG. 3A). At this time, since oxygen is not contained in the atmosphere, the formed ruthenium film 11 does not contain oxygen (FIG. 3B).

Next, oxygen ions 12 are ion-implanted so that a predetermined concentration of oxygen 13 is contained in a specific depth position of the ruthenium film 6 (FIG. 3C).

Next, a patterned ruthenium film 7 is formed by patterning using photolithography, leaving the ruthenium film 6 containing oxygen only at a specific depth position in a region where an oxide film is to be formed (FIG. 3). (D)).

Next, a silicon thermal oxide film 8 is formed under the patterned ruthenium film 7 by heat-treating the silicon wafer 2 at 500 ° C. in a vacuum atmosphere 9 of 10 ⁻⁵ Pa or less (FIG. 3E). )).

In the second embodiment, the ruthenium metal film 1
Although 2 was used, the film into which oxygen ions are implanted may be a metal film that does not easily form an oxide, and may be a film of a platinum group such as platinum or palladium, or a noble metal such as gold or silver. Further, the vacuum heat treatment temperature may be changed to a temperature higher than 500 ° C. or a lower temperature as necessary.

In FIG. 3E, a MOS structure using ruthenium metal as a gate electrode is formed.

In the second embodiment, the same effects as in the first embodiment can be obtained.

[0034]

According to the first to seventh aspects of the present invention,
Forming a metal film containing oxygen on the surface of the semiconductor substrate, solid-phase diffusion of oxygen contained in the metal film by heat treatment, and forming a thermal oxide film on the surface of the semiconductor substrate,
The oxidation temperature can be reduced compared to the conventional thermal oxidation using the gas phase, and the re-diffusion of the impurities implanted into the wafer can be suppressed, so that a device having a fine pattern with shallow diffusion can be formed. . Further, since the thermal oxide film thickness is determined only by the amount of oxygen contained in the film and the heat treatment temperature, controllability of the film thickness can be improved.

According to the present invention, the metal film containing oxygen is formed on the surface of the semiconductor substrate, and the oxygen contained in the metal film is solid-phase-diffused by the heat treatment. Since the MOS structure is formed simultaneously with the formation of the thermal oxide film by forming the gate insulating film and the gate electrode made of the metal film on the surface, the number of steps can be reduced.

[Brief description of the drawings]

FIG. 1 is a process chart showing a thermal oxide film forming method according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional transmission electron microscope (TEM) photograph of a ruthenium film containing oxygen / silicon substrate interface showing a change in thermal oxide film thickness before and after heat treatment.

FIG. 3 is a process chart showing a thermal oxide film forming method according to a second embodiment of the present invention.

FIG. 4 is a process diagram showing a conventional thermal oxide film forming method.

[Explanation of symbols]

1 Ruthenium target, 2 silicon wafer, 3
Atmosphere gas of argon and oxygen, 4 ruthenium atoms adhering to silicon wafer surface, 5 sputtering equipment, 6, 1
1 ruthenium film, 7 patterned ruthenium film, 8 thermal oxide film, 9 vacuum atmosphere, 10 argon atmosphere gas, 12 oxygen ions implanted, 13
Oxygen implanted at a specific depth, 14 silane + ammonia atmosphere, 15 silicon nitride film,
16 Patterned silicon nitride film, 1
7 Water vapor atmosphere, 18 Gate electrode film (polysilicon), 19 Gate electrode

Claims (7)

[Claims] An object of the present invention is to form a metal film containing oxygen on the surface of a semiconductor substrate, and to solid-phase diffuse oxygen contained in the metal film by heat treatment to form a thermal oxide film on the surface of the semiconductor substrate. A method for forming a thermal oxide film. 2. The method according to claim 1, wherein the metal film is made of a platinum group metal or a noble metal. 3. The thermal oxide film forming method according to claim 1, wherein oxygen is contained in the metal film by forming the metal film in an atmosphere containing oxygen. 4. The method for forming a thermal oxide film according to claim 1, wherein after the metal film is formed, oxygen is contained in the metal film by oxygen ion implantation. 5. A metal film made of a platinum group or a noble metal containing oxygen is formed on a surface of a semiconductor substrate, and oxygen contained in the metal film is solid-phase diffused by heat treatment to form a gate insulating film on the surface of the semiconductor substrate. A method for manufacturing a semiconductor device, comprising forming a film and a gate electrode comprising the metal film. 6. A semiconductor substrate, a gate electrode made of a metal film formed on the semiconductor substrate, and solid phase diffusion of oxygen in the gate electrode between the gate electrode and the semiconductor substrate. And a gate insulating film. 7. The semiconductor device according to claim 6, wherein the metal film is made of a platinum group or a noble metal.