DE1087425B - Method and device for producing doped semiconductor single crystals by vapor deposition and diffusion annealing - Google Patents

Description

GERMAN

The invention relates to a method for producing doped semiconductor single crystals, the dopants being vapor-deposited onto a single crystal made of semiconductor base material and distributed therein by diffusion annealing.

Required for flat diodes, flat transistors and the like one single crystals of the semiconductor materials concerned. So far, these single crystals have generally been used generated by careful recrystallization from a melt. It is also with tip transistors known to use vapor-deposited semiconductor layers, suitable for junction transistors and diodes However, the known vapor deposition layers do not, since they are polycrystalline.

It is also known to dope semiconductor single crystals by having the desired donor or Acceptor impurities evaporated onto the single crystal surface and diffused by heating brings. It is also known to vaporize only limited areas of the semiconductor surface by the area to be steamed is covered with a perforated mask.

For many purposes it is desirable to work with the thinnest possible semiconductor bodies. The thickness of the The base zone of a planar transistor, for example, largely determines its high-frequency properties. The previous methods, such as etching, electrolytic removal and the like, result in a lot of rejects and deliver results that are difficult to reproduce.

The invention is now intended to provide a method for the production of exceptionally thin doped Semiconductor single crystals are given, which does not have the disadvantages of the known methods. the Doping can be done in a known manner by vapor deposition of a dopant, which then is brought to diffusion under elevated temperature.

A method for producing doped semiconductor single crystals, based on a single crystal from semiconductor base material the dopants are vapor-deposited and distributed therein by diffusion annealing according to the invention characterized in that the base material single crystal by vapor deposition on a Monocrystalline base made of a different material, but with the crystal orientation required by the semiconductor single crystal and thus a comparable lattice constant is produced. The base crystal becomes during vapor deposition kept at such a temperature that the condensation of the vapor-deposited semiconductor material takes place in monocrystalline form. An alloy composed of the semiconductor material can advantageously be used for doping the base crystal and the dopant are vapor-deposited.

The invention avoids that the method and device

for producing doped

Semiconductor single crystals by vapor deposition

and diffusion annealing

Applicant:

Motorola Inc.,

Chicago, 111. (V. St. A.)

Representative: Dr.-Ing. E. Sommerfeld, patent attorney,
Munich 23, D.unantstr. 6th

Claimed priority:
V. St. v. America March 5, 1956

Jean Jules Achille Robillard, Stockholm-Valingby,
has been named as the inventor

Semiconductor material as in the usual vapor deposition process as an amorphous or polycrystalline layer precipitates with many small crystallites. Rather, it is in the method according to the invention possible to produce a single crystal of considerable size by condensation from the vapor phase. The single crystal is thus produced by condensation of the

Metal vapor grown on the surface of a suitable support; this document exists from a single crystal, which in turn has the same crystal class, such as germanium or Silicon, and which has a lattice constant very close to that of the crystal to be formed lies. For example, the base crystal consists of normally used for germanium, made from sodium chloride. This underlay crystal will now on a plane parallel to one of the main planes of the lattice, for example parallel in the case of sodium chloride to the .100 level, very carefully polished (optical polishing). This polished surface is prior to vapor deposition ion bombardment of the metal under suitable pressure and atmospheric conditions subject. . ,

The temperature of the substrate becomes essentially constant during the condensation of the metal kept at a very specific "temperature, the level of which depends on the metal to be evaporated. This temperature is very critical to its fluctuations

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should be kept within 1 to 10 ° C. Each area is present in which the speed of the

Metal has its own critical temperature for vapor atoms in the plane of the substrate surface

For germanium, for example, it is 480 ° C. This has just the right value for these atoms

The condensation temperature is thereby maintained - come into a mutual arrangement that one

obtained that one corresponds to the underlying crystal in close 5 single crystal.

thermal contact with a metal sheet (tantalum) The explanation given above concerned the arrangement

brings, which through an external high-frequency coil of the vapor-deposited atoms in a single crystal lattice

is heated. The metal sheet is also provided with a directly on the surface of the backing crystal; it

Thermocouple connected to the approximate tem- perature is clear that this first single crystal layer continued

temperature of the base crystal to be measured and continuously trained if further

equips. Steam atoms on the already crystallized surface of the

The invention is of course not to hit a special single crystal, provided that the previous theory to explain the phenomena occurring at the critical temperature mentioned instead of limited; the occurrence of this critical temperature takes place.

However, door can be simplified by the following. According to an important feature of the invention clarification to be understood. The atoms of the underlay is the temperature of the surface of the underlay crystal are arranged in a crystal lattice crystals are not determined by direct measurement, and have electrical charges. As a result of this, but rather because one with the help of optical there is a method that tracks the growth of the single crystal just above the surface described, of the backing crystal one in both directions of the 20 This is achieved by having an elliptically polar surface periodic electric field. In others ized light at a small angle on the Words would make a graph of a growing crystal stand out. That reflected Cross-section through the field in a first Rieh- light is made by a dynamic device that tion of the plane a curve with alternating maxima from a quarter-wave plate and a and minima result, with a cross section in a Nicoischen rotated by a synchronous motor second direction within this plane, but there is a lower prism, analyzed. The light falls right to the first direction, the same curve would result. finally to a photocell, its output signal

The atoms of the condensing vapor are also electrically charged after a suitable amplification on the screen and interact with a cathode ray oscillograph, which is observed with the periodic field that the vapor atoms strive for. The time deflection of the oscilloscope is the locations of the lowest potential energy with the motor that rotates the Nicol prism, syn in the field. These places of lowest energy are chronized by. Under these test conditions, the crystal lattice of the base crystal determines the growth of a single crystal and shows two maxima for one. As required, rotation by 180 ° corresponds to the two main axes of this grid arrangement of the base as far as possible 35 ellipse. A polycrystalline layer of the arrangement of the atoms of the condensing results in more than two maxima and sometimes also substance, if this substance is none at all in the monocrystalline (depolarization). An amorphous layer is located in the state. The steam atoms are no longer there either. You have to make sure that they hit the potential wells of the field reversals in order to avoid incorrect measurements, which decrease from a division on the surface of the base crystal 40 confusing the reflection on the base with a mutual position that results in a reflection on the layer originate too closely to avoid the true monocrystalline form of the. This error can be prevented by approximating steamed material. This initial opposition to working at very small angles of incidence,
lateral arrangement is such a good approximation mutual kept small. A fine regulation of the heating can be brought about, which corresponds to the true single crystal of the on-surface, by the use of two vaporized materials. High-frequency heating coils with oppositely

The ability of the vapor atoms to be reached in one of the established fields. The subtractive Influence of these two fields allows a temperature range and to remain there, obviously depends on regulation with less thermal inertia than on the speed component of the atoms in if one were to use only a single coil, the level of the surface of the support. How- The last adjustment of the temperature can also knows, this speed component is a 55 achieved with the help of an infrared radiation source Function of temperature. When this temperature will be.

is too low, the steam speed is too low Atoms in this plane are so small that the vapor atoms have two maxima, corresponding to the optical measuring device settle before they indicate the locations of lowest reflection on the base single crystal. To reach potential energy and thus begin these two maxima by the 60 a few minutes periodic field on the surface disappear in a sufficiently ordered manner, since the first, monoatomic layer is on later on in the desired single crystal shape of the surface. By making slow changes to be able to pass over. On the other hand, if the temperature is equal to the temperature by means of one of the above-mentioned precautions If it is high, the atoms in the plane of the directions can then be stabilized again Underlay such large velocity components, 65 reach a state where two other maxima existed they seem to jump over the potential minima that can escape the growth of the new crystal and speak in a contrast to the mono. These maxima are initially weak, they crystalline arrangement, which is striven for, but begins to become more and more prominent over time Location to come to rest. However, it was kicked. A small change in temperature of the Krifest that a small critical temperature stalls is immediately at the effect on both of them

IUO /

Maxima recognizable in the oscilloscope. The correct temperature can be achieved by controlling the heating of the crystal holder according to the display on the oscilloscope.

It is important that the vaporized metal is as pure as possible. To achieve a high degree of purity, a type of molecular distillation is performed prior to evaporation. The metal will melted in a suitable crucible (graphite for germanium) and placed on a first tantalum sheet vaporized. This sheet is the first of four similar sheets that are related to each other are arranged in cascade form. Each of these sheets can by means of the Joule effect by means of electrical connections be heated at both sheet metal ends. If you heat while the crucible is also heated, the first sheet, in order to sublimate the metal that has been deposited on it, is struck Part of the metal is deposited on the second sheet. If you now heat this second sheet so that it is on it The deposited metal in turn sublimates, while the crucible and the first sheet are still are hot, some of the metal from the second sheet is deposited on the third sheet, and so on The process is continued up to the fourth sheet. The metal, for example germanium, found on the fourth sheet is condensed, has a much greater degree of purity than the metal from the Melting pot.

Another advantage of this staged evaporation process is that there is an evaporation of the metal from the fourth plate at a much lower temperature, than is needed for the evaporation of the metal from the crucible. The evaporating metal comes from a large surface and a relatively thin layer and can therefore get through Sublimation can be obtained. By creating the metal vapor in this way, it is possible to reduce the Precise control of the condensation rate of the metal on the substrate, and one achieved at the same time a high purity of the steam. The condensation rate should be kept low, to allow control of the temperature on the base crystal, the temperature keeps within the critical range. The crystal produced in this way can be especially doped be made suitable for use as semiconductors for electrical applications.

This doping can be achieved by evaporating an alloy, which is made up of the main substance of the crystal and a dopant, whose condensation on the surface of the crystal and finally through The last vapor-deposited layer is allowed to diffuse into the crystal by the action of heat. In this context, a dopant is to be understood as meaning an impurity which, in introduced a pure germanium single crystal, which gives it improved semiconductor properties. procedure for the introduction of dopants in single crystals and the most varied of them suitable for this purpose Substances are well known.

A special crucible that holds the metal alloyed with the dopant, for example germanium with indium is brought in front of the crystal. The alloy is evaporated then while the crystal is at room temperature. The deposited layer is amorphous, and the curve produced by the optical system on the oscilloscope is irregular and has no pronounced maxima. The amount of dopant evaporated is carefully chosen established that the metal is weighed prior to evaporation to the desired percentage of dopant after evaporation and diffusion in the crystal to obtain.

The diffusion of the doping layer into the crystal is achieved by heating the crystal to a temperature which is much lower than the evaporation temperature. The progress of diffusion is indicated by the optical device. The end of the diffusion process can be recognized by that on the oscilloscope screen after the amorphous doping layer has disappeared as a result of complete Diffusing into the crystal, the two maxima characteristic of the single crystal reappear.

The method described above results in a monocrystalline layer of semiconductor material with p- or η conductivity according to the dopant used.

Multiple layers, such as n-p, n-p-n, or p-n-p, can be created by repeating the above Process and by changing the dopant are produced. One uses for this purpose, several crucibles with different types of dopants.

The monocrystalline layer, when it has grown to the desired thickness, becomes the underlying crystal removed. This can be done quite generally by the fact that the base crystal in one dissolves suitable solvent. The layer is then washed and metallized on both sides, to get connection contacts for the shift.

A special embodiment of a device for performing the method according to the invention is shown in FIG shown in the drawings, which, however, are only schematic.

Fig. 1 is a side view of a vacuum system used for carrying out the method according to the invention suitable is;

Fig. 2 is a schematic illustration of an optical system and display device which to be used in conjunction with the vacuum system according to FIG. 1;

Figures 3A, 3B, 3C and 3D are schematic representations to explain the production of a plurality of p- or η-layers or both in one Single crystal made according to the invention.

The following description will first describe the plant described in the drawings, then a process for the production of a monocrystalline layer of η-germanium and finally the production of Germanium single crystals with n-, p- and n-layers will be explained.

Vapor deposition

In Fig. 1, a vacuum system is shown which contains a base plate 1 and a dome 2, which is located above the base plate and by means of a seal 3 on the circumference of the base plate encloses a space 7 α hermetically sealed from the atmosphere. The base plate 1 is carried by a hollow foot 3 α , which encloses an inner channel 3 b , which on the one hand opens into the chamber Ta and on the other hand is connected to a pump device (not shown) in connection, for example (in the order from the vacuum chamber ge

calculates) can consist of a cold trap with liquid air, a standard mercury diffusion pump and a rotating pump. The pumping device should be · preferably be able to reduce the pressure in the container la to 10 ^"7 mm Hg. Through an inlet 3 c can, if desired, a certain amount of a gas such. As water vapor, are introduced into the recipient. the inlet 3 c opens on one hand in the channel 3b, while standing on the other hand with the gas supply in connection. in order to regulate the gas supply better is the inlet 3 c with the two valves 3 d and 3 are provided e, between which a reservoir 3 / is located.

Within the recipient la , a round plate 4 is attached above the base plate 1 by means of a foot 4a, which can be rotated around the foot 4a. The plate 4 is electrically connected to the outside space by a plurality of electrical lines 6 which lead through the bushings 7 in the base plate 1. The individual conductors 6 each have enough play in their length so that the plate 4 can be rotated through 180 ° in one direction.

The rotatable plate 4 carries on its upper side a plurality of crucibles, which are shown, for example, ^a 5 as the crucibles 8 α and 8 b , which are respectively surrounded by the tungsten spirals 8c and Sd . Each of these spirals can be heated by an electric current by means of a suitable conductor 6 and thus acts as a heating device for the crucibles 8 a and 8 b. The rotatable plate 4 also carries a plurality of tantalum sheets 9, 10, 11 and 12 for condensation and sublimation, which are each held on the plate 4 by a pair of electrically conductive rods, of which the rods 9 a, 10 a, 11 a and 12 a are shown, the other rods of each pair lying behind the corresponding rods 9 a to 11 a in FIG. The bars of each pair are connected to opposite ends of the tantalum sheet supported by these bars. Each rod is connected at its lower end to a conductor 6 in such a way that an electric current can be passed through a desired tantalum sheet. If an electric current is sent through a given sheet of tantalum, the electrical resistance of this sheet causes it to be heated to a temperature of, for example, 1200 ° C.

The cleaning of the germanium from the 'crucible 8 a through the metal sheets 9 to 12 is accomplished as follows. By heating the crucible 8 a, the germanium contained therein is liquefied. In this state, some atoms on the surface of the liquid have enough energy to overcome the forces which they strive to hold back in the surface, and therefore there is a constant leakage of atoms into the vacuum above the crucible. The middle one Because of the high vacuum prevailing in the recipient la , the free path of the emerging atoms is so great that the evaporated atoms form molecular beams which behave quite similarly to optical beams. For this reason, the atoms escaping from the crucible 8 a describe straight paths, and a substantial fraction of the totality of these evaporating atoms is condensed on the sheet metal arranged above the crucible.

In order to expel the condensed germanium atoms from the sheet 9, this is brought to a temperature heated below the melting temperature of germanium, but the temperature is high enough an evaporation of the germanium atoms from the deposited layer in an acceptable Guarantee percentage. This evaporation occurs through sublimation, i.e. H. by a change of the state of aggregation of the germanium atoms from the solid phase (in the condensed layer) to the Vapor phase without taking on the liquid phase in between. The advantages of sublimation are twofold. First, the rate at which the germanium sublimates into the vapor state is transferred, calculated and therefore controlled much more precisely than if the atoms were removed from the liquid Evaporate phase; this more precise control is desirable in order to be monocrystalline and not to obtain a polycrystalline formation of the condensing germanium on the substrate. Secondly sublimation reduces the undesirable effects that often occur with evaporation from the liquid phase, such as the entrainment of impurities by the evaporating Germanium atoms.

When the germanium atoms evaporate from the sheet 9, they migrate in the form of molecular beams in such a way that a significant percentage of all atoms evaporating from the sheet 9 on the Condense sheet 10. During this process (as explained in more detail under "Procedure") is) the crucible 8 a is kept at an elevated temperature, while the germanium atoms from Sheet 9 are evaporated, so that the next cold surface in the vicinity of the sheet 9, on which the Germanium atoms can condense, is given by the sheet 10.

In an analogous manner, the germanium atoms are then transferred from the sheet 10 to the sheet 11 and from there to the sheet 12. Although part of the germanium is lost between the crucible 8 α and the sheet 12, a considerable percentage of the germanium is condensed on the sheet 12 and is there for later evaporation from this sheet (by sublimation), which leads to the formation of the monocrystalline layer directly precedes the base crystal.

The high vacuum in the recipient la is useful because it allows the formation of the molecular beams described. The high vacuum also has the advantage that the base crystal is free of a gas layer which would be absorbed there under poor vacuum conditions and which could interfere with the formation of the monocrystalline layer.

Although in the foregoing description, the substance condensed on the underlying crystal is one had gone through multiple evaporation process, it remains of course within the scope of the inventive idea if one on the base crystal one Can condense substance that only a single evaporation process from a source, such as a crucible.

The recipient 7 α is above the rotatable plate 4 by a horizontal partition 13 made of tantalum, which extends from one side of the boiler 2 to the other, into an upper and a lower vacuum space divided. The partition 13 is on the boiler 2 by means of an annular holder 16 of square Cross-section attached. The intermediate wall 13 has an opening 15, the axis 15 a of which is perpendicular to the plane of the partition and the sheet 12 intersects.

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The axis 15α is eccentric with respect to the foot 4a which carries the plate 4. If the crucible 8 ei has the same distance from the foot 4 a as the axis 15 a, it is possible by rotating the plate 4 by a corresponding angle to move the sheet 12 away from its position below the axis 15 a and the crucible Bb to this Place to bring. Other crucibles can be brought to the location below the axis 15 α in the same way.

The opening 15 allows the passage of vaporized germanium atoms in the form of molecular beams in the upper part of the recipient Ta from a source which is located just below the axis 15 α. These molecular beams can through a shutter 14, which is through one of the intermediate wall

13 hanging down support 14 a is held, released or interrupted. The closure

14 can be actuated by a magnet, not shown, so that you can open the opening as desired 15 α can close or release.

The intermediate wall 13 also carries a circular, perforated disc 17 which is rotatably mounted on the foot 17a. The disk 17 has a plurality of openings 17b, 17c, YId (Fig. 3b, 3c, 3d). The purpose of these openings will be explained later.

The kettle 2 has a closed, tubular extension 17 /, which is the recipient of a shaft above the disk 17th Inside this shaft is a flat heating and support plate 20 made of tantalum, which is held by a support 20a extending downward from the top surface of the boiler 2. The upwardly facing surface of the plate 20 is in contact with a thermocouple 21, which is electrically connected to the exterior of the recipient via the feedthroughs 21 α, 21 b. On the underside of the plate 20, as shown, a base crystal 19 is attached, on which the single crystal according to the invention is to be formed. During operation, the tantalum plate 20 and thus the base crystal 19 are heated by conducting high-frequency electrical currents through two separate coils 23, 24 which surround the attachment 17 /.

The high-frequency current for the coil 23 can be supplied by a high-frequency oscillator (not shown) originate, it being possible for an adjustable attenuator to be switched on between this and the coil. Of the High frequency power for coil 24 may come from the same oscillator, with a second, also attenuator, not shown, between the oscillator and the coil 24 can be switched on. The coils 23 and 24 are arranged and polarized with respect to one another so that the flowing in them High-frequency currents generate electric fields which counteract one another in the flap 20. By attitude of the two attenuators, the size of the field resulting in the plate 20 can be very large precisely adjusted so that a sensitive control of the temperature that this plate assumes is possible. A component 18, which represents an electrode, is drawn below the base crystal 19 which allows, the crystal 19 during a method step of the later to be more precise descriptive method to be subjected to ion bombardment. Although in Fig. 1 this electrode directly seems to lie next to the crystal 19, the drawing is to be understood, however, that this electrode is actually behind the plane of the drawing of FIG. 1, assuming that the Crystal 19 is located in this plane of the drawing. Another electrode 18, not shown, lies opposite of the drawn electrode 18 in front of the plane of the drawing in FIG. 1. These two electrodes 18 have a sufficient distance so that the entire polished upper surface of the crystal 19 from the Molecular beams that penetrate the opening 15 can be achieved. The electrodes 18 can over

ίο devices not shown to a high voltage source of for example 2000 volts can be connected.

The approach 17 / has two windows 22, 22 made of translucent at opposite points on its wall Material that allows light to be sent through the attachment 17 / to the Growth of the monocrystalline layer by means of the optical device described below monitor.

Fig. 2 shows the optical device that allows the growth of the on the base crystal monitor condensed layer. The optical device consists of a source 26 for monochromatic Light, a collimator 27, a Nicol prism 28 and a quarter wave plate 29, which lie one after the other in the beam path and by means of which a beam of elliptically polarized Light at a very small angle of incidence on the deposited layer, which is on the underlying crystal forms, can be thrown. This beam of light is from the deposited layer reflects and then successively passes through a quarter-wave plate 30, a Nicol prism 31 and finally falls into a photocell 33. The Nicol prism is driven by a synchronous motor 32 driven by an alternating current source 36 is fed, rotated about the beam axis. The AC power source 36 synchronizes at the same time the horizontal time axis of a cathode ray oscillograph.

The output of the photocell 33 is amplified by an amplifier 34 and then to the vertical Deflection plates of the cathode ray oscilloscope placed. The output of amplifier 34 can also serve to automatically control the currents in coils 23 and 24 to control the temperature of the Keep crystal 19 within the critical range.

The arrangement described above can be used for practicing the method according to the present invention can be used, some examples of which will be discussed below.

Method of manufacture
of single crystals of h-germanium

Preparation and activation of the base crystal:

The base crystal 19 is a polished and transparent single crystal of sodium chloride 1.5-1.5-0.5 cm in size. This crystal is attached to a tantalum plate 20 by placing a few drops of water on the top surface of the crystal and pressing it against the tantalum plate. The assembly is now ^{evacuated to about 10 -7} mm Hg.

During the evacuation, the tantalum plate becomes moderate by means of one or both coils 23 and 24 heated so that it assumes a temperature of about 100 ° C.

After 15 minutes, the connection with the diffusion pump is interrupted and the recipient only

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11 12

still connected to the rotating pump. The large axis of the ellipse parallel to the plane of the lower

c is the inlet 3 is somewhat water vapor is located in the position Rezi- crystal. The quarter wave plate

patient admitted so that the pressure on about 30 is in the same main directions as the platelet

10 " ¹ HImHg increases. The pressure is adjusted to about 29. The angle of incidence and reflection,

this value is maintained and, in the process, an electrical discharge of the polarized light beam with the crystal 19

charge of about 2000 volts alternating voltage between forms is set to a value of 2 to 5 °,

the electrodes 18 generated. The pressure is sufficient. The reflection on the base crystal now results in two

low, so that due to the electrical discharge inside various maxima that appear on the screen of the

the water vapor oscilloscopes appear half of a fairly wide range. The establishment is now

molecules are ionized. This makes the Oberio able to work.

surface of the sodium chloride crystal to a bombarde- ν ^, ν + ^ π- ,, „„ - u * + ,, ™
_TTr , -. ,, T ^ i TTT -Cvriaicinwcicnsium
ment of water vapor ions. Since water vapor is a solvent for sodium chloride and initially the shutter 14 is still closed, since the water vapor ions that hit the crystal surface are heated at considerable speeds at high speeds. sit, these ions etch away the amorphous layer (i.e. the temperature is measured by the thermocouple 21 Beilby layer), which is measured by the optical polish.

was formed on the crystal surface. The sheet metal 12 is now gradually etched to 900 ° C., the monocrystalline part underneath is heated and exposed to the order of the sodium chloride crystal during the entire evaporation process, and this temperature is maintained. At 900 ° the underlying crystal is activated so that germanium sublimes from sheet metal 12 slowly enough to keep its function, namely the arrangement of the condensation rate of condensation germanium atoms on the substrate small enough to form a single crystal. It lies in an area that can facilitate and fulfill. After 5 minutes of etching in the ated despite the delay of the temperature Rege If the inlet 3 c closed, and the recipient 25 lung of the base crystal with respect to the control is returned to a pressure of 10 ^-7 mm Hg evacua- the current in the RF coil, a correction . During the evacuation process, that of the growth of the monocrystalline layer, if the underlying crystal continues to have a temperature of this tendency to become polycrystalline, is kept below -100 ° C. Before depositing metal Hch is.

is generally a pumping time of at least 30 When the germanium begins to evaporate, what

15 minutes are required to detect any traces of one on the underside of the closure 14

To remove water vapor. can, and if a temperature equilibrium on the

During all of these described process underlay crystal, what is most congruent is achieved the shutter 14 was closed. sees constant thermal current, the shutter 14

35 opened so that the germanium atoms are in the form of

Preparation of the metal to be evaporated, molecular beams enter through the opening 15 and

can hit the base crystal and there

The crucible 8 a will gradually condense to about. A few minutes after opening the

1500 ° C heated and held at this temperature, the two maxima on the shutter 14

until all germanium evaporates and some of it 40 oscilloscopes become weaker and seem to vanish.

is condensed on the first tantalum sheet 9. the. You can now by slowly changing the

As the next step, the sheet metal 9 gradually strengthens the two currents in the coils 23 and 24

heated to a temperature of 1200 ° C while finding a setting at which the two maxima

the crucible 8 c remain stable at a constant temperature. This state is during the

is held until all the germanium from this sheet 45 has retained all evaporation. The evaporation

has evaporated and part of it has to take place very slowly so that a distortion

Sheet metal 10 has knocked down. Subsequently the free crystal is created.

Plate 10 gradually to a temperature of 1200 ° C. After the end of the evaporation, the heating is carried out, while the crucible 8 a and the end 14 close again and the temperature of the plate 9 continues to be at the same temperature as before 50 base crystal gradually to room temperature until all germanium is lowered from sheet 10. Even at this point in time, the two can be steamed and partially deposited on the sheet metal 11 - maxima on the screen of the oscilloscope has still been reflected. Now the sheet 11 will gradually be observed.
1200 ° C while the crucible and

the sheets 9 and 10 are at their temperatures, 55 evaporation of the doping layer
until all the germanium has evaporated from the plate 11

and a part thereof is condensed on the sheet 12. For evaporation of the doping layer, the

The germanium on the metal sheet 12 is now ready, and the melting crucible 8 d containing the doping alloy has been vapor-deposited onto the base crystal 19 by rotating the plate 4 under the opening 15. 60 brought. The crucible 8 d is closed

During all of these operations, the closure closure 14 was gradually heated, the closure remains 14 closed. . closed during the degassing period of the crucible. When the evaporation of the doping adjustment of the optical device begins, the shutter is opened so that

65 the evaporated doping metal on the crystal

As already mentioned, the quarter-wave plate is surface that is still at room temperature,

29 with respect to the Nicol prism 28 so arranged, is reflected. During the formation of this new one

that its neutral axes make an angle of about slice either the two maxima disappear

Include 22.5 ° with the axis of the prism. Prism on the oscilloscope screen, there is a depolarization

28 and the wafer 29 are arranged so that the 70 occurs when the deposited layer is amorphous

13 14

is. On the other hand, many new maxima arise when they are established, on the other hand they can also be substantial the deposited layer is polycrystalline. After thicker layers are generated.

Termination of this second evaporation will be the

Shutter 14 closed again. , Electrical connections to the crystal

Diffusion of the dopant layer into the crystal ^D he electrical contact between the fine

Metal mesh and the germanium plate can through

The crystal is vapor-deposited on a thin metallic layer by means of coils 23 and 24 350 ° C heated. When the diffusion is finished, the openings of the network are improved. On the the two maxima, the other side of the germanium plate from the vapor deposition, appear to be equal of the doping layer were present, again if a metal layer was vapor-deposited to the second on the oscilloscope screen. To get the appearance of the electrode. This evaporation is due to two maxima indicates that the diffusion of the do- a special diaphragm made through it coating layer in the crystal satisfactorily completely - a short circuit with the other electrode is used is. * Avoid 5. Now you can with the help of a silver paste

Wires to both sides of the semiconductor assembly distance of the germanium crystal are connected by the support.

When the sodium chloride crystal is peeled off, processes for the production of n- and p-layers are required

one can take precaution that the thin germanium-20 _{in a} germanium single crystal
crystal layer not due to stress caused by the

at the interface between the germanium and n, p and η layers of germanium are dadem Sodium chloride occurs during the dissolution - produced by verdening as described above osmothic pressure is destroyed. Drive around these three times with different dopants

To reduce stresses on the crystal, 25 is exerted. For this purpose, there are three on the plate 4 the crystal is not dissolved in pure water, but different crucibles with dopants

in an almost completely saturated solution of (two of them to generate η-conductivity and

Sodium chloride in water. After removing the NaCl one of them to generate p-conductivity) and

Crystal, the thin germanium layer is attached with three different germanium sources 12,

a fine metal net and in pure 30 The sources 12 and those charged with alloy

washed in distilled water. Crucibles are each placed on the plate 4 in this way.

The thin layers adhere owing to the fact that they are arranged one behind the other and in the correct position

surface tension very good on the metallic network, order under the axis 15 α can be brought

that can be used as an electrode and can be

serves early to strengthen the germanium layer. 35 Let it be assumed that a monocrystalline

The linear body 40 (FIG. 3 a) to be produced by the process steps described, the product produced is a thin platelet made of an n _t -layer, on which lies a p-layer, germanium, which is completely single-crystal structure which is in turn of a n ₂ layer is covered, has. The front or back surface, ie the main To generate the n ₁ layer is, as in Fig. 3 b surfaces of the plate, are lattice planes, the 4 ° is shown, the disk 17 rotated so that the single crystal. It should be expressly mentioned that the opening 17 & comes to lie in the axis 15 α. Now that these main surfaces are activated surfaces in which the n ₁ -layer is produced according to the sense described that the single crystal lattice of the metal extends, with a germanium source 12 extending up to the surface of the platelet. That and a crucible with an alloy of a written germanium platelet differs 45 suitable dopant one after the other, which in this respect are basically brought by germanium axis 15 α .

disks made by a grinding process As already mentioned, the evaporated atoms fly

were and where the material is under the top of the germanium and the dopant in the form

surface of the plate as a result of the grinding process one of molecular beams through the recipient 7 a, where-

has adopted an amorphous structure. 50 straight paths, like rays of light, describe

When the germanium platelets verbs as a semiconductor. The result of this is that only such rays should find application, it must contain a small percentage of the underlay set of doping material during the formation of the ^ -layer, which can reach in the above crystal 19, the manner described in the solid angle in the Germanium platelets one that is delimited by the opening 17 b , lie and can be diffused. 55 which is considered the source of the evaporating atoms

The germanium platelet can have several p- or vertices. It follows from this that the ^ -layer contain η-layers or both at the same time, as will be described in more detail later on the base crystal only within one area. A mono- arises that represents an approximate image of the opening 17 & crystalline platelets of the type described has many. The limitation of this area is given by the interesting properties, the polycrystalline layers 41, 42, 43 and 44 in Fig. 3a,
th do not have and this monocrystalline After completion of the ^ layer, the broken-through plate 17, which is very suitable for many areas of application, is rotated so that the opening 17 c can be used in a wide variety of technological areas. (Fig. 3C) comes to lie below the axis 15 a. The platelets can, for example, be used as an optical interface. The p-layer is then used in a manner analogous to the reference filter; on the other hand, they are made of a 65 ^ layer. A comparison of FIG. 3 B and 3 C for the most varied of electrical applications shows that the openings 17 d and 17 c areas are suitable if the platelet is made of semiconductor material that borders on some parts that do not have in common. With the teaching given by the invention, while other parts of these surfaces overlap, it is possible to form layers with a thickness of the correspondingly. Layer,

which had previously been produced, overlapped, while another part was again separated from this layer is. The area of the p-layer is limited by the straight lines 42, 43, 45 and 46 in FIG. 3A.

In the same way as the two previously produced layers, the n ₂ layer is now also produced after the disk 17 had been rotated in such a way that the opening 17 d (FIG. 3 B) was switched on. The area bounded by this opening 17 b again partially overlaps the areas defined by the openings 17 d and 17 c , while it is partially separated from them. _{As a result, the n 2} layer formed in the single crystal 40 is also partially separated from the previously produced Ti ₁ and p layer, while on the other hand it overlaps. The area of the n ₂ layer is delimited by the straight lines 42, 47, 44 and 46 in FIG. 3A.

By constructing the single crystal body, as shown in FIG. 3A, so that the various Layers each have a part that does not overlap the other layers, it is possible to be independent Connections to the various layers with contacts 48, 49 and 50 to be attached.

The single crystal body 40 can be further treated in the same way after its completion, as already under the headings »Removing the crystal from the surface« and »Electrical connections to the crystal ”. The single crystal 40 can therefore be provided with a mesh base and a metallic layer vapor-deposited through the holes in the mesh can be the electrode layer form for the body 40.

The above-described exemplary embodiments for the device, the method and the product are intended only to explain the idea of the invention, but this also includes exemplary embodiments, which differ in form or details from the exemplary embodiments described. It is for example, it goes without saying that the evaporation and diffusion temperatures are not critical and that therefore other temperatures instead of those mentioned for the production of the germanium single crystal can be applied. It is also understood that the invention does not apply to the Production of germanium single crystals is limited, but also other single crystals from others Substances such as germanium, for example silicon, exist and include their production.

Another example of how the scope of the invention is to be understood is that, although the concept of the invention is described by an example for the production of a single single crystal several single crystal bodies can also be produced at the same time.

For example, the finished crystals with the base can also represent the finished product, that is a single crystal layer located on the surface of the underlying crystal and the semiconductor properties by their content of dopant, although the method described so far has the Including removal of the semiconductor layer from the underlying crystal by peeling. Such a product can be used, for example, as an interference filter or to determine the intensity depending on the wavelength in a luminous body. This determination can for example in the manner described in the related application USA. Number 549 337 of November 28, 1955 was described by making a distribution of standing Waves of different wavelengths are generated which are present in the luminous body that one in sections this distribution shifts in relation to the layer so that in the course of the shift different points of distribution fall on the layer at different times, and ultimately thereby, that one measures the resulting changes through the ohmic resistance of the layer.

Claims (22)

Patent claims: 1. A method for producing doped semiconductor single crystals, wherein a single crystal from Semiconductor base material, the dopants are vapor-deposited and distributed in it by diffusion annealing are, characterized in that the base material single crystal by vapor deposition on a single crystal Base made of a different material, but with that required by the semiconductor single crystal Crystal orientation and thus comparable lattice constant is produced. 2. The method according to claim 1, characterized in that the second vapor-deposited substance consists of an alloy of the semiconductor material and a dopant. 3. The method of claim 1 or 2, characterized in that the \ described for the production of a doped semiconductor layer is repeated ^r out wherein η-conductive by an appropriate selection of dopants alternately p and layers are produced. 4. The method according to claim 3, characterized in that the respective area on steam Vapor deposition of the individual layers are covered in such a way that an arrangement of layers is created in which overlaps a part of all evaporated layers, while another part of each Single layer does not overlap with at least a part of another single layer. 5. The method according to any one of the preceding claims, characterized in that during the vapor deposition of the semiconductor material an elliptically polarized light beam under a Small angle is directed to the condensation surface that the ellipticity of the condensation surface reflected light is measured continuously by means of a rotating polarizer and a photocell and that the temperature of the base crystal is controlled so that a reflection on the surface of a Measurement display corresponding to the single crystal is retained. 6. The method according to claim 5, characterized in that the angle of incidence is 2 to 5 °. 7. The method according to claim 5 or 6, characterized in that the measurement signal by means of a Oscilloscope is reproduced. 8. The method according to claim 5, 6 or 7, characterized in that after the vapor deposition of the material containing a dopant, the underlying crystal is heated until the measurement signal again corresponds to a monocrystalline structure of the reflective layer. 9. The method according to any one of the preceding claims, characterized in that the Base single crystal is thermally coupled to a metal part, which in turn is inductive is heated by high frequency. 10. The method according to claim 9, characterized in that the control of the heating of the Base crystal takes place by adjusting the high-frequency magnetic field through which the metal part is heated. 11. The method according to claim 10, characterized in that a at the location of the metal part High frequency field is generated from the difference of the components of two opposite ones There is high frequency fields, and that the dynamic adjustment of the resulting field is done by adjusting the strength of one of the two subfields in relation to the other. 12. The method according to any one of the preceding claims, characterized in that the finished semiconductor film is separated from the underlying crystal in that both into one Liquid that is a solvent for the pad, but not for the Semiconductor film represents, the liquid initially almost completely with the material of the Pad is saturated and that the pad can slowly dissolve in the liquid. 13. The method according to claim 12, characterized in that after the separation of the semiconductor film and the base of the semiconductor film removed from the liquid and on both Sides is provided with a metallic coating, so that ohmic connections on the semiconductor film develop. 14. The method according to any one of the preceding claims, characterized in that the Semiconductor material cleaned by multiple sublimation in a high vacuum before vapor deposition will. 15. The method according to any one of the preceding claims, characterized in that the vapor deposition surface is produced on the single crystal prior to vapor deposition by having a corresponding polished surface on the single crystal a main crystal plane produces that one continues the single crystal in a vacuum +0 brings, which contains a trace of a solvent for the material of the single crystal, and that one in the vacuum in the vicinity of the polished surface creates an electrical discharge, so that the The surface is bombarded with ions of the solvent until the Beilby layer of this The surface is etched off and the monocrystalline internal structure of the single crystal is exposed. 16. The method according to any one of the preceding claims, characterized in that the temperature of the base crystal is about 430 ° C during vapor deposition. 17. The method according to any one of claims 1 to 15, characterized in that the temperature is about 350 ° C. during diffusion of the doping material. 18. The method according to any one of the preceding claims, characterized in that as much Semiconductor material is vapor-deposited that the thickness of the resulting layer is of the order of magnitude the wavelength of visible light. 19. The method according to any one of the preceding claims, characterized in that the semiconductor material Germanium or silicon is used. 20. The method according to any one of the preceding claims, characterized in that as Underlying crystal a sodium chloride crystal is used. 21. Device for performing the method according to one of claims 5 to 8, characterized in that that the device for generating the elliptically polarized light beam from a monochromatic light source, a Nicol prism and a quarter-wave plate and that the device for measuring the ellipticity of the reflected light beam consists of one second quarter-wave plate, a rotatable, second Nicol prism and a photocell consists. 22. Device according to claim 21, characterized by a second Nicol prism continuously rotating synchronous motor, for displaying the signal supplied by the photocell an oscilloscope is used and the electron beam of the oscilloscope in a Coordinate as a function of the changes in amplitude of the alternating current feeding the motor is distracted. Considered publications:
U.S. Patent No. 2,695,852. 1 sheet of drawings ®. 009 587/219 8.60