JP3029064B2 - Method of manufacturing semiconductor device having Schottky barrier - Google Patents

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 semiconductor device having a Schottky barrier.

[0002]

2. Description of the Related Art A Schottky barrier (Schottky barrier) generated by a combination of a semiconductor region and a barrier electrode.
Is mainly based on the height of the barrier (barrier height) Φ
Determined by B. That is, generally, when the barrier height ΦB is increased, the reverse leakage current decreases, but the forward voltage drop increases. Conversely, when the barrier height ΦB is reduced, the forward voltage drop decreases, but the reverse leakage current increases. Therefore, it is ideal that the height of the barrier height ΦB can be selected according to the required electrical characteristics.

[0003]

However, the barrier height .PHI.B of the Schottky barrier is necessarily determined by the type of barrier metal used. In addition, since the height of the barrier height ΦB is easily changed by the heat treatment, the barrier height ΦB is changed.
It is difficult to control B over a wide range and stably.

SUMMARY OF THE INVENTION It is an object of the present invention to manufacture a semiconductor device having a Schottky barrier having a barrier height ΦB having a desired height and capable of controlling the height of the barrier height ΦB in a wide range and stably.

[0005]

According to the method of manufacturing a semiconductor device having a Schottky barrier according to the present invention, a metal capable of generating a Schottky barrier in combination with the semiconductor region (3) is formed at a vacuum of 1 × 10 ⁻⁶ torr or less. A step of forming a first electrode layer (4) by vacuum deposition on the main surface of the semiconductor region (3) in an atmosphere, and a step of 1 × 10 ⁻⁶ torr × 1 × containing residual gas.
Exposing the first electrode layer (4) to an atmosphere having a degree of vacuum of 10 torr to adsorb residual gas to the surface of the first electrode layer (4) to form an extremely thin adsorbed layer; The second electrode layer (5) made of a metal capable of generating a Schottky barrier in combination with the region (3) is formed at 1 × 10 ⁻⁶ torr.
Forming on the first electrode layer (4) in an atmosphere of the following degree of vacuum, and combining the semiconductor region (3), the first electrode layer (4), and the second electrode layer (5). Creates a Schottky barrier, and by controlling the degree of vacuum of the atmosphere for exposing the first electrode layer (4) in the range of 1 × 10 ⁻⁶ torr to 1 × 10 torr, the barrier height of the Schottky barrier is adjusted to a desired height. Set.

[0006]

[Function] 1 × 10 ^-6 torr including residual gas to 1 × 10 torr
By exposing the first electrode layer (4) in an atmosphere having a degree of vacuum, the residual gas is adsorbed on the surface of the first electrode layer (4) to form an extremely thin adsorption layer. This ultra-thin adsorption layer
The reaction between the second electrode layer (5) and the first electrode layers (4) and (3) during the subsequent heat treatment is suppressed. For this reason, if the degree of vacuum of the atmosphere to which the first electrode layer (4) is exposed is relatively reduced, the amount of adsorbed residual gas increases, and the reaction suppression effect is promoted, and the barrier height of the Schottky barrier is relatively reduced. Can be stabilized to a high level. Conversely, if the degree of vacuum of the atmosphere to which the first electrode layer (4) is exposed is relatively increased, the amount of residual gas adsorbed is reduced, so that the effect of suppressing the reaction is reduced and the barrier height of the Schottky barrier is relatively reduced. Can be stabilized at a low level. Therefore, the first electrode layer (4)
The barrier height of the Schottky barrier can be stably set to a desired height by the ultra-thin adsorption layer formed on the surface. In this specification, “extremely thin” refers to a thickness at which a quantum mechanical tunnel effect is possible.

[0007]

Next, a method of manufacturing a Schottky barrier diode according to an embodiment of the present invention will be described with reference to FIGS.

First, as shown in FIG. 1, an n + type region (2)
(Gallium arsenide) including an n + -type region (3) formed on the upper surface of the n + -type region (2) by epitaxial growth
A semiconductor substrate (1) comprising: Next, as shown in FIG. 2, a thin Ti layer (first electrode layer) (4) is formed as a metal capable of generating a Schottky barrier in combination with the n-type region (3). The Ti thin layer (4) is formed in a deposition chamber (chamber) in which the semiconductor substrate (1) is arranged at 1 × 10 ⁻⁶ torr.
r Keep in a high vacuum atmosphere of less than
i is formed by vacuum evaporation over the entire main surface of the semiconductor substrate (1) to a thickness of about 50 angstroms. Ti
After the formation of the thin layer (4), the degree of vacuum in the vapor deposition tank in which the semiconductor substrate (1) is arranged is once set to 1 × 10 ⁻⁶ torr to 1 × 10 torr, and the Ti thin layer (4) is placed in a low vacuum atmosphere. For a period of time. As a result, residual gas molecules such as oxygen contained in the vapor deposition tank are adsorbed on the Ti thin layer (4), and an extremely thin adsorbed layer is formed on the Ti thin layer (4).
It is formed on the surface of the i-thin layer (4). Subsequently, Al is vacuum-deposited on the entire surface of the thin Ti layer (4) via the extremely thin adsorption layer to form an Al layer (second electrode layer) (5) having a thickness of about 2 micrometers. . When vacuum depositing Al, the inside of the deposition tank in which the semiconductor substrate (1) is arranged is again 1 × 10 ⁻⁶ torr.
Keep in a high vacuum atmosphere of r or less. On the lower surface of the n + -type region (2), an ohmic contact electrode (6) made of an Au (gold) -Ge (germanium) alloy or the like is formed by vacuum evaporation.

Subsequently, as shown in FIG. 3, the element peripheral side of the Al layer (5) is removed by photo-etching to leave the Al layer (5a). The remaining Al layer (5
a) corresponds to a region that becomes a main path of a forward current and forms a Schottky barrier. Further, the Ti thin layer (4) is removed from the element peripheral region by photoetching, and A
The Ti thin layer (4a) under the l-layer (5a) and the Ti thin layer (4b) surrounding and adjacent to the Ti layer (4a) remain. Next, a thermal oxidation treatment is performed in air at 380 ° C. for about 5 to 30 minutes.
Thereby, as shown in FIG. 4, the Ti thin layer (4b) not covered with the Al layer (5a) is oxidized to a titanium oxide thin layer (Ti oxide thin layer) (7). , Al layer (5
The Ti thin layer (4a) under a) is not oxidized because it is masked by the Al layer (5a). Since Al and Ti are both metals capable of generating a Schottky barrier for an n-type GaAs semiconductor, a combination of both the Ti thin layer (4a) and the Al layer (5a) is referred to as a barrier electrode (8). Thereafter, as shown in FIG. 5, the upper surface of the thin Ti oxide layer (7) is covered with an insulating film (9) made of a silicon oxide film formed by a plasma CVD method. Further, a connection electrode (10) made of Al is formed on the upper surface of the Al layer (5a) and the insulating film (9). Through the above steps, a power Schottky barrier diode chip is completed.

In the above-described Schottky barrier diode chip, the first Schottky barrier is generated by the combination of the barrier electrode (8) and the n-type region (3), and the thin Ti oxide layer (7) and the n-type region (3) are formed. ) Produces a second Schottky barrier. In plan view, the second Schottky barrier is formed in an annular shape so as to surround the first Schottky barrier adjacently. The Ti oxide thin layer (7) functions as a resistive Schottky barrier field plate, and has an effect of improving the peripheral breakdown voltage of the first Schottky barrier. This resistive Schottky barrier field plate is disclosed by the present applicant in Japanese Patent Application No. 63-28504.
No. 9 (JP-A-1-251656) and others.

FIG. 6 conceptually shows a change in the barrier height Φ B of the first Schottky barrier with respect to the heat treatment time when the heat treatment is performed on the Schottky barrier diode chip manufactured according to the present embodiment. The first Schottky barrier is a Schottky barrier generated based on a composite electrode including the first electrode layer (4) and the second electrode layer (5). The solid lines A, B, and C shown are thin Ti layers (4) by vacuum evaporation.
, The pressure in the atmosphere for exposing the Ti thin layer (4) to 1 × 10 ⁻⁶ torr and 1 × 10 ⁻⁶ torr, respectively.
× shows the change in the barrier height ΦB for each heat treatment time in the case of setting to ^{10 -5 torr, 1 × 10 -4} torr.

FIG. 6 shows that the barrier height of the first Schottky barrier can be stabilized to a high level by lowering the degree of vacuum in the vapor deposition tank to which the Ti thin layer (4) is exposed. It is shown that the barrier height of the first Schottky barrier can be stabilized at a low level by increasing the degree of vacuum in the vapor deposition tank to which is exposed. Note that the initial value of the barrier height ΦB of the first Shokki barrier (the height of the barrier height before the heat treatment) is the Schottky barrier generated when the Al layer (5) is directly adjacent to the n-type region (3). Very close to the initial value of the barrier height. The Schottky barrier diodes having various barrier heights ΦB manufactured by these methods all have an ideal coefficient of n value in the range of 1.01 to 1.05, which means that the diode is excellent without any problem in characteristics. Has been confirmed.

As described above, according to the method of manufacturing the Schottky barrier diode of the present embodiment, the size of the barrier height of the Schottky barrier diode of the same metal can be controlled over a wide range and stably. In the present embodiment, the reason why the barrier height of the first Schottky barrier can be stably controlled over a wide range is not necessarily clear,
When the Ti thin layer (4) is exposed to an atmosphere having a low degree of vacuum, a residual gas is present in the vapor deposition tank in accordance with the degree of vacuum. The residual gas molecules are adsorbed to form an ultra-thin adsorption layer (having a thickness capable of quantum mechanical tunneling), and this ultra-thin adsorption layer forms an Al layer (5) and T
It is considered that the cause is to suppress the reaction between the i-thin layer (4a) and the n-type region (3). Therefore, if the degree of vacuum of the atmosphere to which the Ti thin layer (4) is exposed is relatively reduced, the amount of adsorption of the residual gas molecules is increased, whereby the effect of suppressing the reaction is enhanced and the barrier height is increased to a relatively high level. Can be stabilized.

The embodiments of the present invention are not limited to the above embodiments, but can be modified. (1) InP (indium phosphide) instead of GaAs
And the like, and a method of manufacturing a Schottky barrier semiconductor device using silicon or a group III-V compound. (2) The thickness of the first electrode layer (4) is 10 Å to 100 Å, preferably 20 Å to 80 Å so that the effects of the present invention can be sufficiently obtained.
It is better to set it in the angstrom range. When the thickness of the first electrode layer (4) is increased, the barrier height of the Schottky barrier can be relatively reduced.
The barrier height can be relatively increased by reducing the thickness of the metal. Therefore, by combining the thickness control of the first electrode layer (4) with the present invention, the barrier height level can be controlled more stably over a wide range. (3) When the first electrode layer (4) is vacuum-deposited, the degree of vacuum in the evaporation tank is more than 1 × 10 ^-4 torr so that the first electrode layer (4) is formed well. It is preferable to carry out the treatment at a higher temperature.

[0015]

As described above, according to the present invention, it is possible to manufacture a semiconductor device having a Schottky barrier having a desired barrier height ΦB.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a semiconductor substrate used in a method for manufacturing a Schottky barrier diode according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state where a thin Ti layer and an Al layer are formed on the semiconductor substrate of FIG. 1;

FIG. 3 is a cross-sectional view showing a state in which the element peripheral side of the Ti thin layer and the Al layer in FIG. 2 is removed by etching;

FIG. 4 is a sectional view showing a state where the thin Ti layer in FIG. 3 is oxidized;

FIG. 5 is a sectional view showing a state in which an insulating film and a connection electrode are formed in FIG. 4;

FIG. 6 is a graph showing a change in barrier height with respect to a heat treatment time of a Schottky barrier diode manufactured according to an embodiment of the present invention.

[Explanation of symbols]

(3) ··· n-type region (semiconductor region), (4) ··· Ti thin layer (first electrode layer), (5) ··· Al layer (second electrode layer),

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-22475 (JP, A) JP-A-63-157466 (JP, A) JP-A-60-145672 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 29/872

Claims (1)

(57) [Claims] 1. A first electrode layer is formed by vacuum-depositing a metal capable of generating a Schottky barrier in combination with a semiconductor region on a main surface of the semiconductor region in an atmosphere having a degree of vacuum of 1 × 10 ⁻⁶ torr or less. And adsorbing the residual gas to the surface of the first electrode layer by exposing the first electrode layer to an atmosphere having a degree of vacuum of 1 × 10 ⁻⁶ torr to 1 × 10 torr containing the residual gas. Forming a very thin adsorption layer, and forming a second electrode layer made of a metal capable of generating a Schottky barrier in combination with the semiconductor region at 1 × 10 ⁻⁶ torr.
Forming on the first electrode layer in an atmosphere having the following degree of vacuum, wherein a combination of the semiconductor region, the first electrode layer, and the second electrode layer generates a Schottky barrier, The degree of vacuum of the atmosphere for exposing the first electrode layer is 1 × 10 ⁻⁶ to
A method of manufacturing a semiconductor device having a Schottky barrier, wherein the barrier height of the Schottky barrier is set to a desired height by controlling the range of rr to 1 × 10 torr.