DE1160105B - Diffusion process for the production of one or more transition surfaces in a semiconductor body of a semiconductor component - Google Patents

Description

GERMAN

PATENT OFFICE

117389 Vfflc / 21g

REGISTRATION DATE: DECEMBER 17, 1959

NOTICE
THE REGISTRATION
AND ISSUE OF
EDITORIAL: DECEMBER 27, 1963

The invention relates to a method for producing single or multiple planar Transitions in semiconductor bodies using the diffusion of foreign matter from the Surface of a semiconductor body on the inside and on semiconductor components produced by this method are made.

In semiconductor technology, the term “transition” denotes the separating layer between two zones of opposite conductivity type. Such transitions have to be made especially with diodes or transistors. Various methods are already known for producing such junctions. In some of these known methods, foreign substances are diffused from the surface into a semiconductor body. In this method, as is known, from a plate or a disk made of semiconductor material with a very low content, for example 10 ¹⁶ atoms per square centimeter, of a substance that acts as a doping impurity and gives the semiconductor a certain conductivity type, for example η conductivity, assumed. A foreign substance is deposited on the surface of the semiconductor body, which imparts conductivity of the opposite conductivity type to the semiconductor, and the entire arrangement is subjected to a heat treatment. The distribution of the impurity density depends on the temperature and duration of the heat treatment. This creates a zone in which the effect of the two foreign substances is canceled out. The semiconductor has η conductivity on one side of this zone and p conductivity on the other. The zone forms the transition.

It is already known to mix the foreign substances with an inert gas. The semiconductor wafers are in a closed container, which is filled with the mixture of foreign matter and inert gas is heated.

When the semiconductor wafers are placed in a tube in the furnace through which an inert gas flows, which carries the foreign matter with it, this process is called »carrier diffusion in the open Pipe «. All of these processes, especially those that use a carrier gas, to bring foreign matter into contact with the semiconductor wafer, have the disadvantage that the Results are not reproducible.

It is also known to sinter two semiconductor bodies of different conductivity types to one another, to one another to crystallize or to fuse together, so that a single semiconductor body with Diffusion process for producing one or more transition surfaces

in a semiconductor body
of a semiconductor component

Applicant:
International Standard Electric Corporation, New York, NY (V. St. A.)

Representative: Dipl.-Ing. H. Ciaessen, patent attorney,
Stuttgart W, Rotebühlstr. 70

Claimed priority:
France of December 18, 1958 (No. 781 989)

Albert Paul Bobenrieth, Montrouge (France),
has been named as the inventor

a sheet-like pn junction is obtained. For example, two semiconductor bodies are used here different melting point used. These known methods can also be applied to the surface of the one semiconductor body that is connected to the second semiconductor body, previously one Layer of foreign substances are applied, which in the unification of the two semiconductor bodies in a small amount Dimensions diffused into the semiconductor material.

It is also known to put two foreign substances of different diffusion speeds into one at the same time Diffuse semiconductor body.

In all of these cases, precise control of the concentration of foreign matter on the surface is not possible possible.

The invention relates to a diffusion method for diffusing foreign substances into a semiconductor body which avoids the disadvantages of the known method.

The invention also relates to semiconductor elements which are produced by this method.

The invention thus relates to a diffusion method for producing one or more Transition areas in a semiconductor body of a semiconductor component. This diffusion process is carried out according to the invention in such a way that

309 770/312

that on the semiconductor body at least a second The invention is based on the drawings

Semiconductor bodies made of the same semiconductor material are described in more detail.

with a doping impurity content of min- Fig. 1 shows an apparatus for carrying out the

at least 10 ²⁰ atoms per square centimeter is placed on the method according to the invention for the production that both semiconductor bodies so long on 5 of diodes;

a temperature below the melting point of the in Fig. 2, 3 and 4 are shown cross sections, the Semiconductor material are heated that the foreign- relate to the manufacture of transistors; material from the second semiconductor body in the first FIGS. 5 and 6 schematically show a section Semiconductor body up to such a depth through a semiconductor body as it diffuses in the hearth is, on which a transition surface is formed io position of a pnpn diode according to Fig. 7 is obtained, is to be, and that then the second semiconductor. As already stated, the diffusion body is removed from the first semiconductor body according to the invention as a source of foreign matter will. a semiconductor alloy with the same semiconductor

It is therefore used in the method according to the invention, which is subject to the diffusion method, as the source of foreign matter from which the diffusion 15 is intended. This alloy contains one or more leads, an alloy of the semiconductor material with rere foreign substances, namely in relatively large one or more doping foreign substances in larger quantities compared to the concentrations used in semiconductors, namely in another hybrid technique. The Störstoffverhältnis than is usual in the semiconductor technology, content can be about 10 ²⁰ atoms per square centimeter, for example in the ratio of amount to some or 20. The content of foreign matter determines the number of atoms of the foreign matter per 1000 atoms of impurity density on the surface of the semiconductor of the semiconductor material. This alloy can be an example of a body in which the diffusion takes place. The consensus to be polycrystalline. To produce an over-concentration on the surface of the semi-conductor, a semiconductor wafer is of a conductivity type that is as large as the concentration in the foreign matter, for example of an n-conductivity source. According to the method, junctions for capability can be produced in diodes or transistors with a plate of this alloy. The brought into contact, which serves as a source or store of various modifications of the process according to foreign matter. This alloy platelet according to the invention is described below, holds in the above-specified ratio foreign- First, with reference to FIG. 1, the production materials are described, which are described in the semiconductor as the opposite 30 of a diode. For this purpose, one-conduction type, in the above-mentioned case p-conductivity, sometimes silicon platelets with p-conductivity are used. The two flakes brought into contact with one another by sawing up a single-crystal semiconductor will now be obtained by a heat treatment rod to which boron as an impurity is exposed. The impurities diffuse from an amount of 10 ¹⁶ atoms per square centimeter of the alloy wafer into the semiconductor wafer ₃₅ meters and has a resistance of about η-type, and the diffusion depth is known to be 2 ohm · cm. These platelets are produced in two ways by the temperature and the duration of the flat, parallel surfaces, so that the thickness determines the heat treatment. of the plate is a few hundred microns. At-

The heat treatment can either be done in one of the similar platelets by sawing

neutral atmosphere at atmospheric pressure or made of a silicon rod with η conductivity,

reduced pressure, or in a vacuum, the phosphorus carried out as a contaminant in one concentration

will. The process can also contain an oxy- of 10 and ²⁰ atoms per square centimeter

atmosphere if its resistance is of the order of

The semiconductor oxide layer that forms for the contaminants is 0.001 Ohm · cm. These tiles will be

from the alloy is permeable. In particular, this also produces two parallel flat surfaces. the

this is the case when phosphorus diffuses into silicon. Thickness of these platelets is about 1 mm. You put-

is dated. The formed oxide layer prevents the source of foreign matter. In a tube

that the platelets stick together. (Fig. 1) made of quartz, with a preferably flat

In some cases it is necessary to ground at the same time, alternating a tile 2 des

with the diffusion, the η-type semiconductor and two silicon wafers 3 used as a source of foreign matter

applied wafer to the semiconductor wafer and 4 p-type, a silicon wafer 5 from

weld. In this case, according to the Er-η type, two silicon wafers 6 and 7 become p-type

finding, on the two platelets a print, etc. stacked on top of one another. The whole arrangement

practiced. The surfaces of the two platelets will be in an oven in a vacuum or a neutral one

very well polished beforehand. The procedure is carried out on 1200 to 55 atmosphere for a few hours

Vacuum or in a neutral atmosphere from- 1300 ° C heated so that in each silicon wafer

guided. diffused in by p-type phosphorus. The diffusion

With this diffusion process, the depth of the disturbance depends on the one hand on the temperature and on the other hand on the density of locations on the surface very well controlled by the duration of the heat treatment. That to lean. It corresponds to half the density of the foreign process is conducted in such a way that the phosphorus is about substance diffused into the Le- 20 μ deep used as a source of foreign matter and the surface concentration. concentration of phosphorus equal to half the concentration

Due to the diffusion process according to the erosion of the phosphor in the source of impurities, that is, simple and reproducible half-conductor components such as diodes and transistors ^{can be produced at 5 · 10 19 atoms per square centimeter} is to be adjusted, in particular it is possible not to weld the individual platelets together, fan-like complicated semiconductor components. B. pnpn diodes. can be excluded, the procedure according to the

Finding can be carried out in an oxidizing atmosphere so that it is on the surface of the platelet forms a silicon dioxide layer. Such a layer is permeable to phosphorus. The so obtained Platelets contain a pn junction and can be used for production in a known manner after cutting used by diodes. In performing this procedure you can without difficulty in a small oven for each batch

The same process can be used to make diodes with high reverse voltage, if as Starting material silicon platelets with intrinsic conductivity and a resistance of about 100 ohms cm are used, which are arranged between two plates, one of which is contaminants p-type and which contains other n-type impurities.

selects that a thin unchanged layer of i-silicon between the two by diffusion obtained p-type and n-type layers remain.

2 and 3 show cross sections through the semiconductor wafer, which according to a modified Process according to the invention can be obtained. This method is particularly suitable for

the bores are about 5 mm apart if there are round plates with a 2 mm diameter be used. The whole arrangement is made in a vacuum oven or an inert one 5 atmosphere heated for 10 hours at a temperature of 1200 to 1300 ° C, so that the phosphorus diffused about 40 μ deep.

In Fig. 3 is a section through the plate 10 is shown after diffusion. This tile has

4000 elements of 1 mm ² cross section from round io a zone 13, in which phosphorus from the plate 9 small plates of 20 mm diameter are obtained. has diffused in and therefore has n-conductivity.

The boundary of this zone forms the transition 14. On the other side of the plate 10 is the phosphorus diffused from the plate 12 (Fig. 2) and 15 reaches the area 16 along the surface. the Points at which the platelets 12 have been located have the deeper diffusion zone 15. The surface diffusion at the places where no platelets 12 have been located, it is no greater than some in depth In this case the temperature and duration will be 20 microns. If the plate on this side up to one The heat treatment is ground in a known manner to a greater depth than that of the surface diffusion is, for example up to line 17, the p-zone 18 is exposed. The plate will then be in cut up small square plates, as indicated by the lines 19 and 20.

The semiconductor component shown in FIG. 4, which has two n-zones 21 and 22, is thus obtained contains, which serve as emitter or collector zone and an intermediate p-zone 23,

Manufacture of high performance transistors. It 30 which forms the base zone. The following starting material is used from these platelets: Type high-power transistors can be produced a) silicon platelets of the p-type, which are made by crushing. In the method described above, sawing a single crystal rod is obtained through the diffusion of a single semiconductor plate with which, for example, boron is obtained as a foreign substance in various zones. If, however, on the stack shown at a concentration of 5 x 10 ¹⁵ atoms per 35 in FIG. 2 a platelet of square centimeter is contained and a reverse P-type is placed which corresponds to the platelet 10, on top of it an n-type platelet as a source of foreign matter , which corresponds to the plate 9, etc., several plates, as shown in Fig. 3, can be obtained in a single heat treatment.

On the other hand, the quartz plate 11 and the plate 12 can be replaced by small pieces of rectangular or square cross-section,

Has a resistance of about 0.001 ohm · cm. «Which alternately consist of quartz and silicon from these platelets, which are a source of phosphorus in ⁿ - ^T ? P f ^s source of foreign matter. In the same

Way can the pieces of quartz through a Foreign matter source can be replaced with a p-type foreign matter, increasing the resistance of the base layer exposed by grinding or etching is reduced. In this case only the Plate 10 can be cut differently.

With reference to Fig. 5 is a manufacturing method for a pnpn diode with three junctions be-The starting material forms a a transition 25, the

for example was produced in the manner as described with reference to FIG. 1 or according to a similar process, with the formation of a

a

stood at about 5 ohm cm. These plates are ground so that they have two parallel, have flat surfaces and a thickness of about 100 μ.

b) platelets obtained by sawing a silicon rod of the p-type, which contains phosphorus as an impurity, for example 10 ²⁰ atoms per square centimeter, and one

serve for diffusion, are also sanded so that they have two flat, parallel surfaces have a thickness of about 1 mm. c) Small platelets made by cutting a Rod of η conductivity, the properties of which correspond to the platelets, which serve as a source of phosphorus. This plat-

chen are square or round and are _{werüen L}

as large as the emitter area of the _silicon plate to be produced 24 transistor. The thickness is about 1 mm. u ": ™: _a ," L _; , ":" ,, "

amounts to

On the plate 8 shown in Fig. 2 made of pure

Quartz is first a plate 9 made of η-silicon, g

applied with phosphorus as an impurity, which is avoided as a Phos 60 layer with i-conductivity. It who-

phosphor source is used, on it a plate 10 of p-silides, two plates 26 and 27, which are used as

zium of 100 μ thickness. A plate 11 sources of foreign matter for foreign matter from the p or

laid from pure quartz or made from another n-type serving. The plate 24, which

Material that does not constitute a diode with the elements present, with an n-type zone 28

reacted. The thickness of the quartz plate is equal to or 65 and a zone 29 of the p-type, is between the

smaller than that of the platelets 12, which as phosphorus platelets 26 with an impurity of the p-type and the

serve source and which are placed in the bores of the plate 27 with an n-type disruptive substance,

Quartz plate 11 are inserted. The center points as shown in FIG.

The whole arrangement is then heated to a suitable temperature for a certain time, to diffusion of the p-type and η-type impurities into the n- and p-type layers reach. The diffusion is directed so that two new junctions 30 and 31 are on both sides of the plate 24 form. After the heat treatment, a plate with the layer sequence pnpn obtain. This plate is cut up and attached to the outer layers of the parts obtained Electrodes attached.

In the examples described, an attempt was made to avoid welding the different platelets together, in particular welding the interfering substance platelets to the semiconductor platelets into which the interfering substances are diffused. According to the further development of the concept of the invention, welding can be brought about during diffusion in that a certain pressure is exerted on the stack and the surface of the platelets has previously been polished as well as possible. The diffusion is carried out in a vacuum of, for example, 10 ~ ⁶ mm Hg or in a reducing atmosphere.

This method will be described with reference to FIGS. 6 and 7 for the production of a pnpn diode. It is z. B. the arrangement shown and described in Fig. 5 is used. The surfaces of the platelets 24, 26 and 27 which are in contact with one another are polished very well and the diffusion is then carried out in a reducing atmosphere or in a high vacuum by simultaneously exerting pressure on the stack. The three platelets weld together and after cutting one receives rods which, as shown in Fig. 6, successively a layer 32 of the n-type and great thickness, for example 1 to 2 mm, with heavy doping and a resistance of about 0.001 ohms · Cm, which is followed by a further zone 33 of the η type, which was created by the diffusion of foreign substances from the plate 32. The following zone 34 of the p-type and the subsequent zone 35 of the η-type with the transition in between were already present in the plate 24 before the diffusion. The p-type zone 36 was created by the inward diffusion of foreign matter from the zone 37, which served as a source of foreign matter for η-type foreign matter. The thickness of zone 37 is approximately 1 to 2 mm and its resistance is approximately 0.001 ohm · cm. The temperatures and the duration of the diffusion as well as the thickness of the plate 24 at the beginning of the process are chosen so that the zones 34 and 35 are approximately 10 to 20 μm thick. In some cases, especially in the case of pnpn diodes, the area of the junctions must be reduced. The semiconductor rods obtained can be fastened in a simple manner between two leads 40 and 41, as is shown in FIG. The two supply lines are fastened in an insulating foot 42 or in a bead made of insulating material. The zones 32 and 37 with low resistance and a corresponding cross-section enable low-resistance contact with the power supply lines 40 and 41. The insulating base in which the supply lines are attached enables the semiconductor component to be cleaned chemically or electrolytically in a simple manner, and it is used for handling. The action of an etching solution can be continued until the zones 33 to 36 according to FIG. 6 have been reduced to the desired cross section.

The method according to the invention has been described in terms of the diffusion of a single one Foreign matter from a foreign matter source.

However, if you have two foreign substances with different diffusion speeds at the same time the concentration specified above is alloyed with the semiconductor, but the concentration of both foreign substances is different and z. B. the foreign substance with the lower diffusion rate is used in a larger concentration, a foreign matter source can be produced with which two transitions can be produced in a single process step. For example, if silicon is alloyed with arsenic and boron, one obtains a source of foreign matter with the diffusion in one Η-type silicon wafers with a resistance of the order of a few ohm · cm at a time the base and emitter regions of a transistor can be produced. In this procedure more than two foreign substances can also be used at the same time.

Claims (7)

PATENT CLAIMS: 1. Diffusion method for producing one and more transition surfaces in a semiconductor body of a semiconductor component, characterized in that at least one second semiconductor body made of the same semiconductor material with a doping impurity content of at least 10 ²⁰ atoms per square centimeter is placed on the semiconductor body for so long be heated to a temperature below the melting point of the semiconductor material so that the foreign substance has diffused from the second semiconductor body into the first semiconductor body to a depth at which a transition surface is to be formed, and that the second semiconductor body is then removed from the first semiconductor body . 2. The method according to claim 1, characterized in that to avoid welding of the two semiconductor bodies an oxidizing atmosphere is used, so that on an oxide layer is formed on the surface of the semiconductor body. 3. The method according to claim 1 or 2, characterized in that for the second semiconductor body a single crystal is used. 4. The method according to any one of claims 1 to 3, characterized in that the second semiconductor body with several foreign substances, preferably with different diffusion speeds, is endowed. 5. The method according to any one of claims 1 to 4, characterized in that on the first semiconductor body a doping second and a third made of an intrinsically conductive semiconductor material Semiconductor bodies made of the same semiconductor material are applied, one of which P-type foreign matter and the other η-type foreign matter contains that the foreign matter of the doping second and third semiconductor body only so far into the intrinsic first Semiconductor body are diffused in that a thin intrinsic zone in the first semiconductor body remains and that the two doping semiconductor bodies are then removed. 6. The method according to any one of claims 1 to 5, characterized in that on the first semiconductor body with two zones of opposite conductivity type, a doping second and a third Semiconductor bodies made of the same semiconductor material are applied, both of which are foreign substances contain the opposite conductivity type of the adjacent zone of the first semiconductor body, that by heating the impurities from the doping second and third semiconductor bodies be diffused so far into the first inner semiconductor body that in the first semiconductor body four zones alternately Set conductivity type are obtained and that finally the two outer doping semiconductor bodies be removed from the first semiconductor body. 7. The method according to claim 6, characterized in that the middle of the four zones of the semiconductor body partially removed by chemical or electrochemical etching will. Considered publications: German Auslegeschriften No. 1036 393, S 32505 VIIIc / 21g (published on January 12, 1956),
S 32506 VHIc / 21 g (published January 12, 1956); Swiss Patent No. 293 271; Austrian Patent No. 185 893; U.S. Patent No. 2743,201. 1 sheet of drawings © 309 770/312 12.63