CS229976B1 - Alloy for soldering, especially the back of silicon semiconductor wafers - Google Patents

Abstract

The purpose of the invention is to reduce the consumption of gold in the production of rectifying semiconductor elements by alloying technology without increasing investment costs and labor. The stated purpose is achieved by using a three-component soldering alloy of semiconductor purity, the working soldering temperature of which is identical to the working temperature of forming a rectifying P-N junction based on aluminum-silicon. The essence of the invention is that the alloy contains 75 weight percent gold, 24 weight percent silver and 1 weight percent antimony. Due to its good mechanical and soldering properties, the alloy can also be used in other fields, e.g. mechanical engineering, where the most perfect connection of materials is required.

Description

The invention relates to an alloy for soldering, in particular the back of silicon semiconductor wafers, and to a suitable composition thereof,

In the manufacture of rectifying semiconductor elements by alloy technology, where the rectifying P-N transition is formed on the front side of the silicon wafer by means of an aluminum pin, it is necessary to dope the rear side of the wafer. This enrichment of the silicon structure is carried out during soldering of the silicon wafer to the substrate by the doping metal contained in the solder alloy. Of the known filler materials known to date, the most widely used is composed of gold and antimony, e.g. solder B-Au99Sb. The disadvantage of this material is that the gold content is high and, after the metallurgical reaction, a large amount of this precious metal is used for the bulk gap filler to eliminate surface unevenness of the bonded materials. Another known additive material comprises silver, tin and antimony, e.g. solder B-Ag91Sn8, 6Sb. The disadvantage of this add-on material is the high precision soldering temperature, so that soldering and doping of the backside of the silicon wafer cannot be accomplished in a single thermal cycle and creating a rectifying P-N transition on the front of the silicon wafer. This increases production costs. The previously known filler materials do not contain precious metals. These are tin-antimony-based materials, e.g. B-Sn90Sb and lead-antimony, e.g. B-Pb89Sb. The disadvantage of these alloys is that they do not form a sufficiently satisfactory metallurgy with the silicon bond. Therefore it is necessary to pre-coat the silicon wafer or the substrate with a layer of gold or silver. In order to carry out these technological operations, special equipment such as metallization lines, vacuum steamers and the like is required, which also adversely affects production costs.

These drawbacks are overcome by a solder alloy, in particular the back of silicon semiconductor pads, while providing a rectilinear P-N transition through the aluminum peg on the front of the invention, comprising:

229,976 weight percent gold, 24 weight percent silver and 1 weight percent antimony.

The main advantage of the alloy according to the invention is its low gold content, which after soldering remains as a fill of the joint gap, while the working soldering temperature of the alloy allows simultaneous doping and the formation of a guiding FH transition in one soldering cycle. apply coatings of precious metals. The solder alloy of the present invention exhibits good mechanical properties, so that very thin films can be rolled out therefrom at the intermediate annealing to recover the material. The excellent soldering properties of the alloy allow small amounts of filler material to be used for the brazing metallurgical reaction.

As a practical example of the use of the cobob according to the invention, the production of zener diodes of the 1-3HZ 70 series alloyed by the technology of curved silicon wafers 0 2.9 mm, etched in a mixture of acids to a depth of about 56C / µm. The solder alloy was made by placing the appropriate amounts of semiconductor-pure metals in a crucible. The batch was degassed under vacuum in a solid state and melted under argon protective atmosphere. The quadratic cross-section cast was gradually rolled into a 0.06 mm thick film by rolling. Between each of the rolling has been placed on the recovery of the alloy intermediate annealing at a temperature of about 33C ^c C. The film produced from pain using the solder-cut roll of 0 2.9 mm. Aluminum pins 0,9 0.9 x 30 mm, silicon wafers, solder discs and blacksmith expansion pads 2 2.9 x 0.5mm were successively placed in the solder mold. The mold is sealed and placed dc continuous soldering furnace with a hydrogen atmosphere, wherein at operating temperature, ^c C 6l0 carried brazed silicon wafers with dilatation pads with simultaneous doping of the silicon, and antimony to the other side of the semiconductor wafers are formed guiding FR gradients. The quality of the solder joints was satisfactory and the semiconductor systems encapsulated in metal shells met the prescribed thermal and electrical parameters. * Life tests have shown that the performance of the diodes produced in this way is also satisfactory. 3 satisfactory results! the alloy rolling on a 0.03 mm thick film was also verified and the experimentally produced diodes using 0.03 mm thick solder discs do not differ from those of conventional series production.

Claims (1)

OBJECT OF THE INVENTION 229 979 Alloy for soldering, in particular the back of silicon semi-conductor pads, while forming a directional PN transition through an aluminum pin on the front of the silicon wafers in the manufacture of diodes characterized by containing 75 weight percent gold, 24 weight percent silver and 1 weight percent antimony.