DE1419730A1 - Doping process - Google Patents

Description

Doping process

It is known to dope silicon in that on a Si rod is a boron-containing glass thread that is melted lengthwise and the rod prepared in this way is zone-melted. From the Boron-containing glass, boron got into the silicon and gives the rod p-conduction and, depending on the boron content, a corresponding one electrical resistivity.

This procedure has the disadvantage that with the dopant other parasitic substances can also get into the material to be doped, e.g. alkali metals and oxygen. aside from that there is a risk that the surface of the Si will become slagged and the crystal growth will be inhibited and disrupted as a result.

There has now been a method of doping elements, intermetallic Compounds and alloys by applying the dopant to the body to be doped in the form of the pure Doping substance or the predoped material to be doped, apart from the doping, and then the same Zone melting found, which is characterized in that the dopant is vapor-deposited onto the body to be doped will.

In this context, doping bodies are to be understood as meaning a body which contains the dopants and with which the dopants are attached to doping bodies are brought up.

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The process can be used for zone melting in a crucible or boat and for zone melting without a crucible. When working in the shuttle you place z. B. on a germanium blank as a doping body a germanium tab of equal length, which contains aluminum , boron or phosphorus, with a smaller diameter and melts it zone by zone together with the blank.

In the crucible zone melting z. B. a 20 mm thick and 300 mm long ailioium rod with a further 3 mm thick and equally long box or phosphorus-containing Si rod zoned, the SohmelKzone sioh extends over the cross section of the starting rod and the doping body. During the zone melting, the 3 mm thick doping tab lies parallel to the longitudinal axis of the starting bar and as close as possible to its surface. Both bars are zone melted together one or more times. A specific electrical resistance is obtained that is uniformly distributed over the length of the rod and deviates from the mean value by less than 1 #, for example. ^;;

Prerequisite for this consistent distribution of the specific electrical resistance is inter alia. a uniform dopant distribution in the doping body. For example, the doping body has a specific one v / resistance profile, this appears to be less pronounced in the body to be doped because it has a larger cross-section than the doping body. Ee succeeds in this way by specifying a certain Dopant distribution in the doping body a certain, predictable To generate distribution in the body to be doped.

The attachment of the doping bodies to the body to be doped before the Zone melting can be achieved by known measures. How to bind the doping rod z. B. at its upper end in the vertical Zone melting in a vacuum or protective gas with a Edelatahlodθr iTungsten wire tight. But also simultaneous clamping of both Body in the upper layer of the exit tube is possible. It also succeeds in passing through the doping body with the starting body

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Electron beams to be distributed punctiformly or over their entire length sohweissen. Parts of electron beams are also suitable Focused ion or heat rays “The same thing achieved” on with an electrical high-frequency heating that slightly melts the surface of the output tab and the surface of the doping tab. It is also possible to use the doping body in the form of a welding bead to apply »by placing a Lets the arc burn «Welding is also intiglioh with hot gases ·

The method offers the great advantage of simply pinning and Zone melting of one or more doping bodies on an output body, the electrical, mechanical, optical, magnetic or to adjust thermal properties to a specific degree · It is thus easily possible by attaching two identical doping bodies For example, to reduce the resistance by half. If three identical doping bodies are used, the resistance drops to 1/3.

The doping body does not always have to cover the entire lung of the starting table be distributed, Br can also only tiöor a part or several Parts of the starting body extend, if one wishes see B in the In the middle of a rod a certain distance with a certain property, then a corresponding to the desired length long doping body attached · The adjacent parts then remain undoped. By attaching dopants, the opposite contain effective dopants, ee is possible, üljer the length dee To obtain Auagangskörpers differently doped zones. One staples z. B. on half the length of a Bi-Aueßangsatabea a doping tab, that contains boron, and adjoining a rod that contains phosphorus, it is possible to produce a rod that is half p-conductive and the other half is η-conductive *

In most cases, the shape of the doping bodies is rod-shaped. Indeed If the process is not tied to defined shaped doping bodies

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The diameter is advantageously chosen to be smaller than that Output body. This is ever do oh no condition »Ss is also possible, several equally large rods eonensueohmelsen · As a suitable shape for The doping body is suitable for threads, rods, tubes, strips or a relatively small sticks, brooks, grains or defined large pods, balls or cubes.

The position of the doping bodies on the starting body can vary and depends on which fora and which mechanical Properties of the doping body possesses. In the simplest case it is parallel to the longitudinal axis of the input body there was a correspondingly elongated and equally long doping body »Ea let but auoh possible to wind the doping body in a spiral around the output body Relatively small doping bodies such as little balls Grains or brooks are advantageously placed in a row the surface of the doping body and tacking it with the above-mentioned method »With silicon β» Β »one can achieve very exact resistance values by using small values, about 2 on the round and about 1 ma thick doped Soheibohen on the Auaganga body in same spacing hangs up, tacking and eonenaehmilat · Instead of But you can also boo balls of the same size, cubes or eokies Tokens are used »

If you put the defined shaped small doping bodies in the same Distance and in a line on the outer bodies (tube or rod), bo one obtains a straight course of the desired property over the distance formed by the doping bodies «Every non-monotonous arrangement of the doping bodies provides a fluctuation, d. h ·, you can thereby at certain points of the starting body stronger or weaker, doping · The same can be achieved with differently heavily doped and equally large or uniformly doped and doping bodies of different sizes with a monotonic arrangement.

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It is also possible to apply the body to the doping body to be applied by vapor deposition · When the pressure is reduced, the outer bodies are exposed to a jet of vapor that contains the dopants contains. On the Auagango body, the dopants separate as solid layer from · This is to be explained using an example. · A gallium arsenide rod is placed horizontally in a recipient and de-eected from the underside by 2 metal sheets so that the zinc vapor rising from the bottom of the clay brushes an uncovered strip about 2 mm wide on the gallium arsenide tab, which is parallel to the longitudinal axis of the rod! lan receives a Galliujpareenid rod prepared with zinc, which is then melted by the sun. the actual doping and distribution of the dopant in Gallium arsenide takes place.

The zinc is evaporated from a secret molybdenum ship. Of the Pressure in the patient is about 1 <j * Torr · The temperature of the Gallium arsenide rod is oa. 150 ° C. Works on silicon one z. B. so, dad a piece of boron or a boron-Sllloium-Mlsohung is used as a steam source, the surface of which is high by means of electrical high frequencies, electron or ion bombardment Depending on the temperature of the doping body, more or less doping material is evaporated

Analogously, oioh have all the other substances mentioned above doped. The main advantage of this working environment is that during the The applied amount can be controlled, b »B, optically through the colors of thin plates or according to known control methods · The steaming method is preferred if there are many Output bodies are to be doped all at once · The individual bodies are then allowed to slide over the steam sources and thus obtained a very precisely dosed doping

Suitable as vapor-deposited doping material are elements, compounds; Alloys, mixtures or doped material »

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Only rods or similarly shaped bodies are not suitable as exit bodies Body · It is also iaöglioh, pipes, bundles, threads or similar to dope shaped bodies afterwards.

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Claims (2)

Claims 1. Process for doping elements, intermetallic compounds and alloys by applying the doping agent on the body to be doped in the form of the pure dopants or the predoped, the one to be doped, apart from the doping of the same material and subsequent zone melting, characterized in that that the dopant is evaporated onto the body to be doped. 2. The method according to claim], characterized that the doping body extends over the entire length or only partially over the starting body distributed. BATH ORIGINAL B096> 2/1 2F <2 documents {Ait.7§ 1 fbs.iu ι r ^ ·. * Am./■*&.>·.·■.·,w* \. * s v-ti)