JPH0555569A - Manufacture of mos structure element using p-type cubic crystalline silicon carbide - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a MOS structure element using a p-type cubic crystalline silicon carbide which can form an ohmic electrode made of a thin Ti film on a thin low concentration silicon carbide film without influence to the state of a boundary of the thin oxide film-the film. CONSTITUTION:When a MOS structure element is manufactured by forming an ohmic electrode 14 made of an oxide film 12 and a thin Ti film on the surface of a thin p-type cubic crystalline silicon carbide film 11 and forming a gate electrode 13 on the surface of the film 12, the thin Ti film 14 formed on the surface of the film 11 is annealed at about 300 to about 700 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a MOS structure element using a p-type cubic silicon carbide (SiC) semiconductor.

[0002]

2. Description of the Related Art Single crystal silicon carbide is a material that is extremely mechanically and chemically stable and has a very high melting point (2000 ° C. or higher).
In addition, since it has a wide band gap (2.2 to 3.3 eV), it is a semiconductor that retains the p-type or n-type conductivity up to a higher temperature than silicon (Si) or gallium arsenide (GaAs).
Therefore, single crystal silicon carbide is expected as a semiconductor material for heat resistant semiconductor elements and semiconductor elements for high power.

For single crystal silicon carbide, cubic β-SiC is used.
There are other crystalline α-SiC, but β-SiC is more promising as a semiconductor device because it has a higher electron mobility at room temperature or higher. Since this β-SiC can be grown with good reproducibility as a single crystal thin film on the Si substrate whose surface is carbonized, a field effect transistor (MOSFET) using this β-SiC single crystal thin film is manufactured, The operation at high temperature has been verified, and the characteristics have been improved for practical use.

In order to improve the characteristics of the MOSFET using β-SiC, it is important to understand the MOS structure, especially the state of the interface between the gate oxide film and the β-SiC single crystal thin film. As a method for grasping the state of the interface between the gate oxide film and the β-SiC single crystal thin film, M including them is included.
Many methods are adopted in which an OS structure element is manufactured and the capacitance of the MOS structure element is measured to evaluate various physical properties. In particular, since an n-channel enhancement mode MOSFET, which is advantageous for high-speed operation, is manufactured on a p-type semiconductor, a MOS structure element is manufactured on a p-type β-SiC single crystal thin film, and this MOS structure element is evaluated. It is important to do.

FIG. 4 is a diagram showing an example of a MOS structure element formed on a p-type β-SiC single crystal thin film. In FIG. 5, 1 is a silicon single crystal substrate, 2 is a p-type β-SiC single crystal thin film grown and formed on this substrate 1, and 3 is a p-type β-.
Silicon oxide film formed on the SiC single crystal thin film 2, 4
Is a gate electrode formed on the silicon oxide film 3, 5 is formed in the vicinity of the gate electrode 4, and is a p-type β-SiC single crystal thin film 2
The gate electrode 4, the β-SiC single crystal thin film 2, and the silicon oxide film 3 sandwiched between these are ohmic electrodes that are in ohmic contact with a capacitor (of variable capacitance). Then, the relationship between the voltage V applied between the gate electrode 4 and the ohmic electrode 5 and the capacitance C of the capacitor, that is, the C-V characteristic is measured and analyzed to measure, for example, the formation temperature of the silicon oxide film 3. It is possible to grasp the state of these interfaces such as the influence of the difference on the interface state between the silicon oxide film 3 and the β-SiC single crystal thin film 2.

In this MOS structure element, the gate electrode 4 and the ohmic electrode 5 are formed after the oxide film 3 is formed in order to prevent impurities from being mixed in when the oxide film 3 is formed. This ohmic electrode 5 is, for example, Journal of Applied Physics, Vol 41 (1970), pp.77.
As shown in 1 to 773, it was manufactured by forming an electrode made of an Al-Si alloy on a β-SiC single crystal thin film by a vapor deposition method and then annealing (annealing) it at a high temperature. In particular, in order to realize a high-performance MOSFET, the hole concentration of the β-SiC single crystal thin film 2 is preferably 1 × 10 ¹⁷ cm ^-3 or less, and such a low concentration of β-SiC is preferred.
In order to form an electrode in ohmic contact with the single crystal thin film 2 with good reproducibility, it was necessary to perform annealing treatment at a high temperature of about 1000 ° C.

[0007]

However, in the above-described conventional method for manufacturing a MOS structure element, the annealing treatment is performed at a high temperature of 1000 ° C. which is close to the formation temperature of the silicon oxide film 3. The treatment changes the state of the interface between the oxide film 3 and the β-SiC single crystal thin film 2 and changes the CV characteristics, which makes it difficult to accurately grasp the original state of the interface. It was

If Ti (titanium) is used for the electrodes,
An ohmic electrode can be formed on a high-concentration p-type β-SiC single crystal thin film having a hole concentration of 8 × 10 ¹⁷ cm ^-3 or more without annealing (Japanese Patent Laid-Open No. 62-71271). In this method, an ohmic electrode cannot be formed on the low concentration β-SiC single crystal thin film 2 having a hole concentration of 1 × 10 ¹⁷ cm ^-3 or less.

It is an object of the present invention to form an ohmic electrode composed of a Ti thin film on a low-concentration silicon carbide thin film without affecting the state of the oxide film-thin film interface. MO using p-type cubic silicon carbide
It is to provide a method for manufacturing an S structure element.

[0010]

To explain the present invention with reference to FIG. 1 showing an embodiment, the present invention provides an ohmic electrode 14 composed of an oxide film 12 and a Ti thin film on the surface of a p-type cubic silicon carbide thin film 11. It is applied to a method of forming a gate electrode 13 on the surface of the oxide film 12 to manufacture a MOS structure element. The above-described object is achieved by providing a step of forming a Ti thin film 14 on the surface of the silicon carbide thin film 11 and then annealing the Ti thin film 14 at a temperature of about 300 ° C. or higher and about 700 ° C. or lower. To be done.

[0011]

The temperature of the annealing treatment applied to the Ti thin film 14 is much lower than the temperature at which the oxide film 12 is formed.
The state of the interface of No. 1 is not adversely affected.

Incidentally, in the section of means and action for solving the above problems for explaining the constitution of the present invention, the drawings of the embodiments are used for making the present invention easy to understand. It is not limited to.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a process chart for explaining one embodiment of a method for manufacturing a MOS structure element using p-type cubic silicon carbide according to the present invention.

First, as shown in FIG. 1A, a single crystal silicon substrate 10 is prepared, the surface of the substrate 10 is carbonized, and then the surface of the substrate 10 is processed as shown in FIG. 1B. To p
The type β-SiC single crystal thin film 11 is grown by an epitaxial method. Then, as shown in FIG. 1 (c), p-type β-Si
A silicon oxide film 12 is formed on the surface of the C single crystal 11 by a thermal oxidation method (1000 ° C. or higher).

Further, as shown in FIG. 1D, a gate electrode 13 made of Au (gold), Al (aluminum), a polycrystalline silicon film (polysilicon), or the like is vacuumed in a predetermined region on the surface of the silicon oxide film 12. It is formed by a vapor deposition method, a sputtering method, or the like. Then, as shown in FIG.
The exposed surface of the p-type β-SiC single crystal thin film 11 is not oxidized or contaminated after a part of the silicon oxide film 12 near 3 is removed by etching with plasma of HF (hydrofluoric acid) or CF _4. Promptly transfer to the vacuum device,
As shown in FIG. 1F, a Ti thin film electrode 14 is formed on this exposed portion by using a vacuum evaporation method, a sputtering method or the like.

Then, the Ti thin film electrode 14 is annealed at a temperature of about 300 ° C. or higher and about 700 ° C. or lower in a vacuum or in a gas atmosphere such as argon that does not react with Ti to form an ohmic electrode. MOS structure elements can be manufactured.

Next, the effect of this embodiment will be demonstrated by the results of experiments conducted by the present inventors. FIG. 2 shows a current-voltage between the Ti thin film electrode 14 and the p-type β-SiC single crystal thin film 11 before being annealed by vapor deposition / forming in a high vacuum atmosphere of 3 × 10 ⁻⁸ Torr or less. It is a figure which shows a characteristic. As shown in FIG. 2, there is no proportional relationship between the current and the voltage, and it can be understood that ohmic contact is not formed.

FIG. 3 is a diagram showing current-voltage characteristics after the Ti thin film electrode 14 was annealed at temperatures of 100 ° C. (two-dot chain line), 200 ° C. (one-dot chain line) and 300 ° C. (dashed line). Is. For reference, the solid line shows the current-voltage characteristics before the annealing treatment. As shown in FIG. 3, it can be understood that the ohmic characteristics can be obtained only when the annealing temperature reaches 300 ° C.

If the annealing temperature of the Ti thin film electrode 14 is about 300 ° C. or higher, the ohmic characteristics shown by the broken line in FIG. 3 can be obtained, but the annealing temperature is about 30 ° C.
When the temperature exceeds 800 ° C., a reaction occurs with the p-type β-SiC single crystal thin film 11 under the Ti thin film electrode 14 to cause this electrode 1
Silicide (a compound of silicon and Ti in this case) is formed in the electrode 4, and the surface shape of the electrode 14 becomes rough so that the lead wire bonded to the electrode 14 can be easily peeled off, or on the silicide on the surface of the electrode 14. There is a possibility that a silicon oxide film is further formed and it becomes difficult to establish electrical continuity with the lead wire. Therefore, it is desirable that the annealing temperature of the Ti thin film electrode 14 is about 300 ° C. or higher and about 700 ° C. or lower.

Therefore, according to this embodiment, the formation temperature (100 ° C. or higher and 700 ° C. or lower) of the silicon oxide film 12 (100
Since the Ti thin film electrode 14 is annealed at a temperature significantly lower than (0 ° C. or more), it does not affect the state of the interface between the p-type β-SiC single crystal thin film 11 and the silicon oxide film 12 A Ti thin film electrode (ohmic electrode) 14 having characteristics can be formed. Therefore, by measuring the CV characteristics and the like of the MOS structure element using the Ti thin film electrode 14, the original interface state can be grasped.

Further, in the conventional MOS structure element made of silicon, the element is annealed at a temperature of 350 ° C. to 500 ° C. in a hydrogen atmosphere after the electrodes are formed to improve the characteristics of the interface between the silicon oxide film and silicon. However, according to the present embodiment, the p-type β-Si is subjected to the annealing treatment at a temperature lower than the above temperature range (for example, 300 ° C.).
Since an ohmic electrode can be formed on the C single crystal thin film, M
The OS structure is not exposed to a temperature of 350 ° C to 500 ° C during electrode formation, and the same annealing treatment as in the case of the silicon MOS structure element is performed using a p-type β-SiC single crystal thin film MOS.
It is also possible to study the effect when applied to the structural element.

The details of the method of manufacturing a MOS structure element using p-type cubic silicon carbide of the present invention are not limited to the above-mentioned one embodiment, and various modifications are possible.

[0023]

As described above in detail, according to the present invention, the ohmic electrode is formed by annealing the Ti thin film at a temperature of about 300 ° C. or higher and about 700 ° C. or lower. An ohmic electrode made of a Ti thin film can be formed without affecting the state of the interface between the p-type cubic silicon carbide and the silicon oxide film. Therefore, if this ohmic electrode is used, it is possible to grasp the original state of the interface of the MOS structure element.

[Brief description of drawings]

FIG. 1 is a process drawing for explaining a method for manufacturing a MOS structure element using p-type cubic silicon carbide, which is an embodiment of the present invention.

FIG. 2 is a diagram showing measurement results of current-voltage characteristics of electrodes by the present inventors.

FIG. 3 is a view similar to FIG.

FIG. 4 is a diagram showing an example of a MOS structure element using p-type cubic silicon carbide.

[Explanation of symbols]

 10 Silicon Substrate 11 p-Type β-SiC Single Crystal Thin Film 12 Silicon Oxide Film 13 Gate Electrode 14 Ti Thin Film Electrode

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 27/12 8728-4M 29/40 A 7738-4M

Claims (1)

[Claims] 1. A method for manufacturing a MOS structural element by forming an ohmic electrode composed of an oxide film and a Ti thin film on the surface of a p-type cubic silicon carbide thin film, and forming a gate electrode on the surface of the oxide film. A p-type cubic silicon carbide is provided which comprises a step of forming a Ti thin film on the surface of the silicon carbide thin film and then annealing the Ti thin film at a temperature of about 300 ° C. or higher and about 700 ° C. or lower. And method for manufacturing a MOS structure element.