CS240038B1 - Method of semidonductor system's homogenous end to end joint production with dilatation electrode - Google Patents

Abstract

The present invention relates to a process for producing a homogeneous one planar joint of a semiconductor system with an expansion electrode. Semiconductor system is one-sided coated with silver thickness max. 10 nm, followed by fusion molybdenum or tungsten dilatation aluminum-silicon-based film 25 to 70 µm at a temperature of 450 to 700 ° C; vacuum or protective atmosphere. Alternatively between the silver layer and the semiconductor surface nickel layer or titanium of a thickness of 3 nm or less; \ t a combination of both. Wolframová or a molybdenum dilatation electrode is coated in advance with a layer of silicide the respective metal electrode thickness a maximum of 20 jum or alternatively a layer aluminum of a maximum thickness of 20 nm.

Description

The invention relates to a method for producing a homogeneous planar joint of a semiconductor system with an electrolyte of molybdenum or tungsten.

In power semiconductor manufacturing technology, such as diodes, thyristors and transistors, a so-called alloy joint is usually used to connect a silicon wafer containing PN junction to a diode electrode using an aluminum foil or an aluminum-silicon foil, with the entire process takes place at a temperature higher than the eutectic point of the aluminum-silicon alloy / ie »above 570 ° C, usually at a temperature of about 700 ° C in a vacuum or protective atmosphere ·

In the process, during the cooling of the melt, a recrystallized layer, i.e. a layer of silicon containing dissolved aluminum, is formed. Since aluminum forms an acceptor dopant in silicon, if the fused region of the semiconductor system is of p-type conductivity (e.g., diodes and thyristors), it is enriched with dissolved aluminum, its conductivity is increased, the electrical parameters of the component are improved. The opposite situation occurs when the fused part of the semiconductor system is of the n / conductivity type. for power transistors. Then, due to dissolved aluminum, conductivity or even parasitic PN, transition and degradation of electrical properties occur. Some components, such as back-pass thyristors, need to be con- nected

240 038 by means of an alloy joint to clock the surface of the semiconductor system in which the conductivity type p i n is next to each other.

Another disadvantage of said alloy process is a certain inhomogeneity of the melt caused by uneven wetting of the silicon surface by the melt, stress formation in the silicon, and thus a significant percentage of failure rates and degradation of the component parameters.

The aforementioned disadvantages are eliminated by the method for producing a homogeneous planar joint of the semiconductor system with an expansion electrode according to the invention, which consists in that the semiconductor system is unilaterally metallized with a silver layer of maximum 10 µm, followed by fluxing of molybdenum or tungsten diode using aluminum alloy and a silicon thickness of 25 to 70 (dunes at a temperature of 450 to 700 ° C under vacuum or a protective atmosphere. A nickel or titanium layer with a thickness of at most 3-4 µm or a combination of both layers is formed between the silver layer and the surface of the semiconductor system.

The coating of the surface of the semiconductor system with suitable metal layers partially prevents the formation of a recrystallized layer of aluminum-doped silicon, improves the wettability of the contact surfaces during melt cooling, and allows the temperature of the alloy process to be reduced somewhat, thus reducing the recrystallized layer. Covering the surface of the diode with a layer of silicide of the metal and yet another layer of aluminum improves the wettability of the expansion electrode and reduces the dissolution of silicon in the melt, which again leads to a decrease in the thickness of the recrystallized layer.

The result is a structurally homogeneous bond that can be used to contact semiconductor structures with any type of conductivity of the contacted silicon surface.

The invention is suitable for use with special components of power switching transistors, back-pass thyristors, or it can be extended to the conventional production of power diodes and thyristors.

Example 1

On the N ⁺ side of the N ⁺ PNN ⁺ power transistor structure, a 3.5 µm silver layer is vaporized, and a 2 µm aluminum layer is bonded to the molybdenum electrode surface to be bonded, followed by an aluminum-silicon foil bonding under vacuum.

A · 30 µm thickness at 610 ° C and 10 ° C.

240 038

Example 2

A titanium layer of 0.3 µm / 1110 thickness is first vapor deposited onto the contact surface of the back-thyristor structure, then a nickel layer of 0.1 µm is galvanically deposited, followed by a vapor deposition of 3.5 µm silver, followed by an alloy bond. structures with molybdenum diode electrode as in example 1 ·

Claims (4)

Object of the invention 240 038 A method for producing a homogeneous planar joint of a semiconductor system with an expansion electrode, characterized in that the semiconductor system is unilaterally metallized with a silver layer of maximum 10 µm thickness, followed by fusing a molybdenum or tungsten diode electrode with aluminum-silicon foil at a temperature of 450 to 700 ° C under vacuum or a protective atmosphere. 2. A method according to claim 1, wherein a layer of nickel or titanium is formed between a silver layer and the surface of a semiconductor system with a thickness of at most 3 < 4 [mu] m or a combination of both. O 3. The process according to claim 1 or 2, characterized in that the molybdenum or tungsten electrode expansion is pre-coated on the side of the joint layer of the respective metal silicide electrode thickness of at most 20 _<Xim. O 4. Method according to claim 1 or 2, c h e / N ¹ characterized in that the molybdenum or tungsten electrode dilated beforehand unilaterally metallized on the side of the joint with an aluminum layer of thickness up to 10 _(4im.