JPH07109904B2 - Heterojunction diode manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a heterojunction diode used for detecting light, radiation and the like.

2. Description of the Related Art Conventionally, a junction element using a semiconductor has been widely used as a device for converting visible light, infrared light, radiation, etc. into an electric signal. A depletion layer generated when a reverse bias voltage is applied to a pn (pin) junction diode manufactured by the injection method is used as a sensitive layer. However, these manufacturing processes require high-temperature treatment of 900 ° C. or higher, which causes thermally-induced defects, and in the case of the ion implantation method, the substrate damage due to implantation generated during implantation is also caused by the annealing treatment. Often cannot be removed. As a result, the dark current due to recombination increases and S / N
It was hard to get the ratio.

Therefore, recently, a non-natural silicon carbide film was deposited on a silicon single crystal substrate by a high frequency or direct current plasma CVD method at a relatively low temperature process of 200 ° C to 300 ° C to form a heterojunction, and then ohmic electrodes were formed on both surfaces. Attempts have been made to reduce the induction of defects and reduce dark current by the hetero effect, for example by forming aluminum electrodes and adopting a hetero-coupled diode configuration.

However, in the heterojunction diode by the above method,
In the present situation, the dark current at the time of applying a reverse bias voltage becomes large due to the recombination current through the defect level at the interface caused by plasma damage on the surface of the crystalline semiconductor substrate.

Therefore, an object of the present invention is to provide a method for manufacturing a heterojunction diode that can solve the above problems.

Means for Solving the Problems In order to solve the above problems, a method for manufacturing a heterojunction diode according to the present invention includes an annealing treatment in a manufacturing process for depositing an amorphous silicon carbide film containing hydrogen on a silicon single crystal substrate. This is a method of adding.

Effect According to the manufacturing method of the present invention, by annealing the heterojunction diode in which the amorphous silicon carbide film containing hydrogen is deposited on the silicon single crystal substrate,
The isolated hydrogen contained in the amorphous silicon carbide film, which is not in a bound state, fills the defects due to plasma damage of the silicon substrate, and the recombination current through the interface defect level is reduced, so that the dark current can be reduced.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a manufacturing process of a heterojunction diode manufactured by the manufacturing method of the present invention.

First, an amorphous silicon carbide film 2 forming a heterojunction with the substrate 1 is formed on the entire upper surface of a silicon single crystal substrate (P type, 10 kΩcm) 1 using a parallel plate plasma CVD apparatus under the following conditions. (FIG. 1 (a)).

Substrate temperature 200 ℃ Gas used Monosilane (100%), Methane (100%) Gas flow rate Monosilane 70SCCM Methane 30SCCM Gas pressure 0.6Torr Film thickness 100-200nm RF power 30W (42mW / cm ² ) Next, amorphous silicon carbide An aluminum electrode 4 having a thickness of about 300 nm is formed on the deposition surface of the film through a metal mask 3 by a resistance heating vapor deposition device (FIG. 1 (b)).

Further, an aluminum electrode 5 is formed on the entire back surface by a resistance heating vapor deposition device to a thickness of about 300 nm (FIG. 1 (c)).

Finally, an annealing process is performed using an electric furnace under the following conditions (Fig. 1 (d)).

Atmosphere Nitrogen temperature 230 ° C Time 30 to 90 minutes Annealing temperature was determined from the annealing temperature dependence data of dark current under the reverse bias application condition of the heterojunction diode manufactured by the above method shown in FIG. This is for an annealing time of 1 hour, but from now on 20
It can be seen that the dark current can be minimized by annealing at a temperature of 0 ° C to 250 ° C. The annealing temperature is 100 ℃
If it is above, the effect is exhibited.

FIG. 3 shows the IV characteristics of the heterojunction diode manufactured by the above method, in which the dark current is 6 in the case where the annealing treatment is performed as compared with the case 7 in which the annealing treatment is not performed.
~ 2 digits decrease.

The annealing treatment of the present invention may be performed after forming the amorphous silicon carbide film and before forming the electrodes.

In order to investigate the reason why the dark current is decreased by the annealing treatment, the thermal desorption of hydrogen from the amorphous silicon carbide film of the heterojunction diode manufactured by the above method was measured. Figure 4 shows the measurement results at a heating rate of 20 ° C / min.
It can be seen that the release curve is composed of three peaks. Among them, the lowest temperature peak (about 180 ° C) is the release peak of free hydrogen in the bonded silicon contained in the amorphous silicon carbide film, and the other two peaks (about 450 ° C,
Approximately 750 ° C) is considered to be the release peak of hydrogen in the bound state. From this, the effect of annealing treatment will be explained with reference to FIG. 2. Up to 200 ° C., the amount of isolated hydrogen contained in the amorphous silicon carbide film that is not in a bonded state is about 1 hour in a short annealing treatment. The dark current is unchanged from that before annealing because it does not fill the defects due to the plasma damage of the silicon substrate, but at 200 ℃ ~ 300 ℃ the isolated hydrogen which is not in the bonded state causes the defects due to the plasma damage of the silicon substrate. By fully filling the interface, the recombination current through the defect level at the interface is reduced and the dark current is reduced.
It is considered that at 0 ° C., hydrogen in a bonded state is released and dangling bonds (unbonded hands) are generated in the film, so that the dark current is increased.

Effects of the Invention According to the manufacturing method of the present invention, an annealing treatment is performed,
By mitigating plasma damage on the substrate surface,
The dark current can be reduced, and it is extremely effective in practice for realizing a high-performance heterojunction diode using an amorphous silicon carbide film.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a process of an embodiment of the present invention, FIG. 2 is a view showing an annealing temperature dependency of dark current in a reverse bias applied state, and FIG. 3 is an I-of a heterojunction diode of the embodiment.
FIG. 4 is a diagram showing V characteristics, and FIG. 4 is a diagram in which the thermal desorption of hydrogen in the amorphous silicon carbide film was measured. 1 ... Silicon crystal substrate, 2 ... Amorphous silicon carbide film, 3 ... Metal mask, 4,5 ... Aluminum electrode, 6 ... Annealing treatment, 7 ... No annealing treatment.

Front Page Continuation (72) Inventor Takashi Hirao 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References Japanese Journal of Applied Physics, Part 1, Vol. 23, No. 5, P. 515-524 (1984)

Claims (2)

[Claims] 1. In manufacturing a diode in which ohmic electrodes are formed on both surfaces of a heterojunction in which an amorphous silicon carbide film containing hydrogen is deposited on a silicon single crystal substrate by a plasma CVD method, an annealing treatment is performed. A method for manufacturing a heterojunction diode, characterized in that free hydrogen contained in an amorphous silicon carbide film which is not in a bound state is activated to fill a defect due to plasma damage generated in a silicon substrate. 2. The method for manufacturing a heterojunction diode according to claim 1, wherein the annealing treatment is performed in a temperature range of 100 ° C. to 300 ° C.