JP2579629B2 - Semiconductor electrode formation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming a semiconductor electrode.

[Conventional technology]

The conventional method of forming a semiconductor electrode is performed as shown in FIG. That is, first, as shown in FIG.
Semiconductor substrate 1 made of, for example, silicon whose surface is roughened
Prepare Next, as shown in FIG. 1B, a Ni film 2 is formed on both front and back surfaces of the semiconductor substrate 1 by vapor deposition or plating. Next, this is subjected to a heat treatment in a hydrogen atmosphere to form a Ni and Si oxide layer 3 and a Si—Ni silicide layer 4 immediately below the Ni film 2 as shown in FIG. Then
As shown in FIG. 3 (D), the mixed acid of nitric acid and hydrochloric acid
The Ni film 2 and the oxide layer 3 are removed. After that, the same figure (E)
As shown in FIG. 5, an electrode 5 made of Ni is formed on the Si-Ni silicide layers 4 on both surfaces by vapor deposition or plating again.

[Problems to be solved by the invention]

However, in the above-mentioned conventional method for forming a semiconductor electrode, the Si-Ni
To facilitate the formation of the silicide layer 4 and to increase the bonding area, both surfaces of the semiconductor substrate 1 are subjected to mechanical or chemical surface roughening. For this reason, there has been a problem that the yield strength is reduced due to cracking caused by deterioration of the breakdown voltage characteristics and damage of the semiconductor element. Further, since the Si-Ni silicide layer 4 is formed, a local cavity is generated at the interface, which causes a decrease in mechanical strength. Further, the N film 2 on the Si-Ni silicide layer 4
Since it is difficult to completely remove the oxide layer 3 with a mixed acid, the electrode 5 is formed with some of the oxide layers 3 interposed. As a result, the bonding strength of the electrode 5 was weak, and the electrode 5 was peeled off.

The present invention has been made in view of the above points, and has been developed to prevent the deterioration of the withstand voltage of the element, prevent the occurrence of cracks, improve the yield, and improve the adhesive strength of the electrodes to improve the reliability. An object of the present invention is to provide a method for forming a semiconductor electrode, which can easily obtain a semiconductor device.

[Means for solving the problem]

The present invention provides a step of immersing a semiconductor substrate whose surface is not roughened in a hydrofluoric acid bath containing nickel carbonate as a main component to form a Ni plating layer on the surface by electroplating, Forming a solder layer on the Ni plating layer by immersing in a solder solution at a temperature, and forming a Ni silicide layer immediately below the Ni plating layer. is there.

[Action]

According to the method of forming a semiconductor electrode according to the present invention, an electrode is formed without roughening a semiconductor substrate. For this reason, it is possible to prevent the deterioration of the breakdown voltage of the element and to prevent the occurrence of cracks, thereby improving the yield. The electrodes are formed by electrolytic treatment in a plating solution and heat treatment in a solder solution. For this reason, it is possible to easily provide a semiconductor device in which the electrodes are formed with high adhesive strength by preventing the generation of a cavity and an oxide layer and the reliability of the element is improved.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, as shown in FIG. 1, nickel carbonate 100 g, citric acid 30 g, hydrofluoric acid 75 cc, sodium laurate 40 mg, pure water 1000
A semiconductor substrate 12 made of, for example, silicon whose surface is not subjected to a surface roughening treatment is immersed in a plating solution 11 made of cc. Next, a metal plate 13 made of a Ni plate is immersed so as to face the semiconductor substrate 12. Next, the power supply unit 14 is interposed between the semiconductor substrate 12 so that a negative bias is applied thereto and the metal plate 13 is applied with a positive bias. Next, the power supply
A predetermined current is applied between the semiconductor substrate 12 and the metal plate 13 for a predetermined time. Here, the semiconductor substrate is
The thickness of the Ni plating layer 15 formed on the surface of the substrate 12 is desirably thin so that no void is generated between the Ni silicide layer and the Ni plating layer 15 during the subsequent heat treatment. However, when the solder electrode is formed after the Ni plating layer 15 is formed, if the thickness is too thin, the adaptation of the solder becomes extremely poor. Therefore, it is necessary to provide the Ni plating layer 15 with a necessary minimum thickness.
From this point of view, the diameter of the semiconductor substrate 12 is 76 mm and the surface concentration is
In the case of 10 ¹⁹ cm ^-3 , the conduction current is 0.5 A and the conduction time is 150
Desirably seconds. In this case, the thickness is 0.05 ~ 0.10μm
Ni plating layer 15 can be formed on semiconductor substrate 12.

Next, as shown in FIG. 2, the semiconductor substrate 12 on which the Ni plating layer 15 is formed is immersed in the solder liquid 16 at 365 to 370 ° C. for about 9 seconds.

Thereafter, when the semiconductor substrate 12 is pulled out of the solder liquid 16, a solder layer 17 is formed on the Ni plating layer 15, and a Ni silicide layer 18 is formed immediately below the Ni plating layer 15, as shown in FIG. Are formed.

In this way, it is possible to form both electrodes of the solder layer 17 and the Ni plating layer 15 simultaneously in a short time without generating any void between the Ni silicide layer 18 and the Ni plating layer 15. In addition, since the semiconductor substrate 12 is not subjected to a surface roughening treatment, it is possible to not only reduce the number of steps but also prevent the withstand voltage of the element from deteriorating and prevent the occurrence of cracks to improve the yield. Furthermore, since an oxide layer of Si, Ni, or the like cannot be formed, the electrodes of the solder layer 17 and the Ni plating layer 15 can be formed with high adhesive strength to improve reliability.

〔The invention's effect〕

As described above, according to the method of forming a semiconductor electrode according to the present invention, the yield is improved by preventing the breakdown voltage of the element and the occurrence of cracks, and the reliability is improved by increasing the adhesive strength of the electrode. The obtained semiconductor device can be easily obtained.

[Brief description of the drawings]

1 to 3 are explanatory views showing an embodiment of the present invention in the order of steps, and FIG. 4 is an explanatory view showing a conventional method for forming a semiconductor electrode in the order of steps. 11 ... Plating solution, 12 ... Semiconductor substrate, 13 ... Metal plate, 14
…… Power supply unit, 15… Ni plating layer, 16… Solder liquid, 17 ……
Solder layer, 18 ... Ni silicide layer.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-50-14275 (JP, A) JP-A-62-209824 (JP, A) JP-A-56-130911 (JP, A) JP-A 52-209 11766 (JP, A)

Claims (1)

(57) [Claims] A step of immersing a semiconductor substrate whose surface is not roughened in a hydrofluoric acid bath containing nickel carbonate as a main component to form a Ni plating layer on the surface by electroplating; Forming a solder layer on the Ni plating layer by dipping in a solder solution at a predetermined temperature, and forming a Ni silicide layer immediately below the Ni plating layer. .