JPH08288507A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

PURPOSE: To suppress the deterioration in the withstand voltage characteristics of a thin gate oxide film by forming an Al oxide thin film on the surface of a silicon oxide film by wet processing step after the formation of the silicon oxide film. CONSTITUTION: A field oxide film as an element separating region 12 is selectively formed by selective oxidizing step on a silicon substrate 10 so as to form a gate silicon oxide film 13 on the main surface of the element separating region 12 sectioned by this region 12. Next, this silicon substrate 10 is immersed in alkalic solution containing Al of 0.1-10000ppb. Thus, an Al side thin film 14 is formed on the surface of the silicon oxide film 13. Next, an electrode 15 is formed on this Al oxide thin film 14. Through these procedures, the stabilization and the reliability upon the device characteristics can be enhanced by making the gate oxide film dual structured of the silicon oxide film 13 and the oxide thin film 14.

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 a semiconductor device, and more particularly to a method of manufacturing a semiconductor device having a highly reliable gate oxide film and a semiconductor device having the gate oxide film.

[0002]

2. Description of the Related Art In a conventional semiconductor device having a gate oxide film, as shown in FIG. 5, an element isolation region 22 is selectively formed on a silicon substrate 20 by a selective oxidation method and partitioned by the element isolation region 22. On the main surface of the element region 21,
The gate oxide film 23 is formed by a thermal oxidation method, a rapid thermal oxidation method, a chemical vapor deposition method, or the like (FIG. 5A), and after the wafer cleaning (for example, RCA cleaning; SC1 → SC2) step, the gate oxidation is performed. The electrode 25 was formed on the film 23 by aluminum, polycrystalline silicon, or metal silicide by a sputtering method, a vapor deposition method, a chemical vapor deposition method, or the like (FIG. 5B).

[0003]

The gate oxide film having the above-mentioned conventional structure has a problem that reliability is deteriorated as the gate oxide film is made thinner. That is, as the degree of integration of semiconductor devices is improved, the required film thickness of the gate oxide film is becoming thinner and closer to its physical limit. In particular, when the oxide film thickness is in the region of 10 nm or less, the influence of the tunnel current becomes large, and the original characteristics of the oxide film cannot be obtained. Further, the conventional oxide film single layer structure has a problem that the presence of weak spots in the oxide film significantly deteriorates the characteristics of the oxide film. That is, there is a problem that the withstand voltage characteristic is significantly deteriorated, initial defects frequently occur, and long-term reliability is significantly impaired.

Therefore, an object of the present invention is to provide a method of manufacturing a semiconductor device in which the breakdown voltage characteristics of a silicon oxide film, especially a thin gate oxide film, are suppressed, and a semiconductor device therefor.

[0005]

A feature of the present invention is that after forming a silicon oxide film, particularly a silicon oxide film to be a gate insulating film, a wet treatment is performed, preferably 0.1 to 1000.
It is a method of manufacturing a semiconductor device in which a thin film of aluminum oxide is formed on the surface of the silicon oxide film by a treatment of immersing in an alkaline solution containing 0 ppb of aluminum.

Another feature of the present invention is a silicon oxide film formed on the main surface of a silicon substrate, and an aluminum oxide thin film deposited on the surface of the silicon oxide film and thinner than the silicon oxide film. A semiconductor device having an electrode deposited on the upper surface of the aluminum oxide thin film.

[0007]

As described above, according to the present invention, since the thin film of aluminum oxide is formed on the surface of the gate silicon oxide film by the wet treatment, the deterioration of the withstand voltage characteristic is suppressed and the semiconductor device has improved reliability.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1A to 1D are sectional views showing a method of manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps.

A field oxide film is selectively formed as an element isolation region 12 on a silicon substrate 10 by a selective oxidation method, and the element region 1 partitioned by the element isolation region 12 is formed.
A gate silicon oxide film 13 having a film thickness of 10 nm is formed on the main surface of No. 1 by a thermal oxidation method, a rapid thermal oxidation method, a chemical vapor deposition method or the like (FIG. 1A).

Next, this silicon substrate is treated, for example, with 100
It is immersed in an alkaline solution containing ppb of aluminum (for example, ammonium hydroxide, TMAH, etc.) and treated for about 10 minutes. As a result, a thin film 14 of aluminum oxide having a film thickness of 1 nm is formed on the surface of the silicon oxide film 13 (FIG. 1 (B)).

Next, on the aluminum oxide thin film 14,
An electrode 15 made of aluminum, polycrystalline silicon, or metal silicide is formed by a sputtering method, a vapor deposition method, a chemical vapor deposition method, or the like (FIG. 1C).

In the step of FIG. 1B, aluminum becomes hydroxide or oxide in the alkaline solution and is adsorbed on the surface of the silicon wafer. At this time, if the alkaline solution contains an oxidizing agent such as hydrogen peroxide, an oxide is more likely to be formed. Further, since aluminum hydroxide can be easily converted into oxide by thermal decomposition, the wafer surface is covered with a thin film of aluminum oxide. Further, by dipping the silicon wafer in an alkaline solution, a more uniform thin film formation of aluminum oxide can be achieved.

In the present invention, the aluminum concentration in the alkaline solution is defined as 0.1 to 10000 ppb for the following reason.

FIG. 3 shows the relationship between the aluminum concentration in the alkaline solution and the amount of aluminum adsorbed on the surface of the silicon wafer as aluminum oxide. When the aluminum concentration in the solution is in the range of 0.1 to 1000 ppb, the concentration in the solution and the adsorption amount on the wafer surface are in a proportional relationship, and when the concentration in the solution exceeds 10,000 ppb, the adsorption amount on the wafer is almost saturated. Further, when the concentration in the solution is less than 0.1 ppb, it becomes difficult to control the aluminum concentration in the solution, and at the same time, the adsorption amount on the wafer surface becomes unstable. Therefore, in order to control the adsorption amount of aluminum on the wafer surface and strictly control the film thickness of the aluminum oxide thin film, the aluminum concentration in the alkaline solution should be 0.1 to 10000 p.
must be pb, and within the proportional range 0.1-1
More preferably, it is 000 ppb.

FIG. 2 shows a sectional structure of a MOS diode according to an embodiment of the present invention. A field oxide film 12 is selectively formed on the silicon substrate 10 to form an element isolation region 12. A gate silicon oxide film 13 having a film thickness of 10 nm is formed on the element region 11 of the silicon substrate surrounded by the element isolation region by a thermal oxidation method. Then, from the upper surface of the gate silicon oxide film 13 to the upper surface of the field oxide film 12, a thin film 14 of aluminum oxide having a film thickness of 1 nm is deposited by the process of FIG. 1B, and the silicon oxide film 13 is formed on the element region 11. And aluminum oxide thin film 14 on it
Is a multi-layered gate oxide film. An electrode 15 is deposited on the upper surface of the aluminum oxide thin film 14 to form a MOS diode having the electrode 15 and the element region 11 of the silicon substrate as both electrodes.

Aluminum oxide is thermally and chemically stable and has a high relative dielectric constant of about 10. Therefore, by forming a gate oxide film by laminating a silicon oxide film and a thin film of aluminum oxide as in the present invention, a gate insulating film is formed as compared with a conventional gate oxide film of a single silicon oxide film. The stability and reliability of the thin film can be increased.

Although the MOS diode has been described as an embodiment with reference to FIG. 2 above, it is also possible to use a MOS capacitor element having a dielectric film of a multi-layer oxide film composed of a silicon oxide film 13 and a thin film 14 of aluminum oxide. Also, MOS
By using the present invention for forming a gate insulating film of a transistor,
A MOS transistor can be manufactured in exactly the same manner as the MOS diode of the embodiment. In the case of a MOS transistor, the electrode 15 serves as a gate electrode, the element region 11 below the electrode 15 serves as a channel region, and source and drain regions are formed on both sides of the channel region (both sides in the direction perpendicular to the plane of the drawing).

FIG. 4 shows the breakdown voltage characteristics of each gate oxide film in the MOS diode manufactured by the method according to the prior art and the method according to the present invention. The gate oxide film had a thickness of about 10 nm, and polycrystalline silicon was used for the electrodes.

In the case of the method according to the prior art shown in FIG. 1 (A), a so-called A-mode defect of 2 MV / cm or less frequently occurs, whereas in the case of the method according to the present invention shown in FIG. 1 (B). Shows that the withstand voltage characteristic is significantly improved and almost shows an intrinsic withstand voltage (original withstand voltage) of 8 MV / cm or more.

[0020]

As described above, according to the present invention, since the gate oxide film has a two-layer structure of a silicon oxide film and a thin film of aluminum oxide, stability of device characteristics,
The reliability can be dramatically improved, and the semiconductor device can be manufactured with high reliability and high yield.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a method of manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps.

FIG. 2 is a sectional view showing a semiconductor device according to an exemplary embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the aluminum concentration in an alkaline solution and the amount of aluminum adsorbed on the surface of a silicon wafer.

4A and 4B are diagrams respectively showing gate oxide film breakdown voltage characteristics in a MOS diode manufactured by using the method according to the related art and the method according to the present invention, where FIG. 4A is the method according to the related art and FIG. This is the case of the method according to.

FIG. 5 is a cross-sectional view showing a method of manufacturing a semiconductor device in the related art in the order of steps.

[Explanation of symbols]

 10, 20 Silicon substrate 11, 21 Element region 12, 22 Element isolation region (field oxide film) 13, 23 Gate oxide film 14 Aluminum oxide thin film 15, 25 Electrode

Claims (4)

[Claims] 1. A method of manufacturing a semiconductor device, comprising forming a thin film of aluminum oxide on the surface of the silicon oxide film by a wet process after the formation of the silicon oxide film. 2. The wet treatment is 0.1-10000.
The method of manufacturing a semiconductor device according to claim 1, wherein the step is a step of immersing in an alkaline solution containing ppb of aluminum. 3. A step of forming a gate oxide film on a main surface of a semiconductor substrate, and 0.1 to 10000 pp of the semiconductor substrate.
b) forming a thin film of aluminum oxide on the surface of the gate oxide film by immersing it in an alkaline solution containing aluminum; and forming an electrode on the thin film of aluminum oxide. A method for manufacturing a characteristic semiconductor device. 4. A silicon oxide film formed on a main surface of a silicon substrate, and an aluminum oxide thin film deposited on the surface of the silicon oxide film and thinner than the silicon oxide film.
A semiconductor device, comprising: an electrode deposited on the upper surface of the aluminum oxide thin film.