DE1285639B - Method for doping a monocrystalline semiconductor body from a combination of elements from the ó¾. and ó§. or from the ó�. and ó ÷. Group of the periodic table - Google Patents

Description

The invention relates to a method for doping a monocrystalline Semiconductor body made from a compound of elements from III. and V. or off the IL and VI. Group of the periodic table, which is generated by charge carrier injection enables direct recombination via the pn junction to generate coherent radiation, using the diffusion method, in which in a closed reaction vessel Doping substance evaporates and doping substances from the gas phase into the surface diffuse into the semiconductor body.

Semiconductor compounds are known to have for semiconductor components certain advantages that have not yet been found with monatomic semiconductor materials could determine. For example, certain semiconductor compounds of the III-V group of the periodic table, e.g. B. _Gallium arsenide, coherent light generate if certain manufacturing regulations when manufacturing the semiconductor component be respected.

The semiconductor device is thus capable of functioning as an optical transmitter (Laser) to act in the conversion of electrical energy into optical light energy. On the output side, a very limited wavelength spectrum is created.

The semiconducting compounds, including gallium arsenide, as well like the other III-V group semiconductor compounds and some semiconductor compounds of the II-VI group are also useful as semiconductor materials for other, more conventional Purposes become known.

The usual known method of manufacturing semiconductor devices used when introducing the impurities for the purpose of forming the pn junction in the semiconductor body the vapor diffusion. However, if you want vapor diffusion in the manufacture of semiconductor components, whose semiconductor bodies consist of semiconductor compounds apply, then the Diffusion can be carried out at an elevated temperature. But this has the disadvantage that at the elevated temperatures a decomposition of the semiconducting compound existing substrate occurs. At these elevated temperatures, however, one does not have to only reckon with a decomposition, but that which is composed of various elements Substrate can also still with the impurity elements, which are in very small Quantities are in the steam reaction vessel, connect.

So there is that of R. J. Keyes and T. M. Quist in the proceedings of the IRE, Vol. 50, No. 8, August 1962, on pages 1822 and 1823, known gallium arsenide diode used to emit recombination radiation of an n-type gallium arsenide single crystal and a p-type layer which in a closed, evacuated quartz tube by diffusion of zinc from a dilute solution of zinc in gallium is made.

Furthermore, there is a method for homogenizing and activating Semiconductor crystals and semiconductor layers such as cadmium sulfide or indium selenide or lead telluride, in which the semiconductor to be treated in a Powder is embedded that is made of the same or a related base material consists. The substances are added or added to this powder in a pretreatment. given the material properties which are desired in the semiconductor to be treated will. The powder with the embedded semiconductor is then applied to such. temperature brought that a material balance between the semiconductor and the powder as a result Thermal diffusion takes place.

The semiconductors embedded in the powder are heated at this known process in a neutral atmosphere or in a closed Container, the specific, determined by the total mass to be treated contains one or more gases or vapors by which the activation or the stoichiometric ratio of the basic substances of the semiconductor is influenced.

Furthermore, there is a method of making one from gallium phosphide existing semiconductor body of a semiconductor component, e.g. B. a diode, became known, in which a reaction product of gallium and phosphorus, in which the phosphorus content at most that corresponds to the compound gallium phosphide, for doping in one closed vessel with zinc and / or cadmium in the presence of at least one of these Substances is heated to such a high temperature that zinc and / or cadmium are in the reaction product diffuses in and at which the temperature of the coldest point of the vessel at least about 550 ° C for zinc and at least about 500 ° C for cadmium is, and that in at least a part of the semiconductor body p-conductivity type is produced.

It is also known that the manufactured by this method and a semiconductor body provided with at least one pn junction as a pn recombination radiation source to use.

Another important problem is with vapor diffusion for substrates from semiconductor compounds in that it is very difficult to completely clean one Substance and a highly purified diffusing sand material in a carefully measured one Amount to produce exactly the results you want.

For example, if metallic zinc for a gallium arsenide substrate Used as a diffusing sand material, it is very difficult to get the pure zinc metal without obtaining a zinc oxide layer on the metal. Furthermore, the metal is so hard that it is difficult to divide a pure metal sample into smaller pieces with it the exact amount for the diffusion process is obtained exactly.

The zinc oxide is on the surface of the metallic zinc diffuse sand material disadvantageous for many reasons. Oxygen is not wanted in the vapor diffusion process, and the zinc oxide tends to form a protective layer over the zinc, causing the Formation of the desired zinc metal vapor required for the diffusion process is disabled.

The difficulties and disadvantages mentioned of the known doping processes to remedy, is the underlying object of the invention.

For a method for doping a monocrystalline semiconductor body from a combination of elements from III. and V. or from the Il. and VI. Group of the periodic system, which is generated by charge carrier injection via the pn junction allows direct recombination to generate coherent radiation using the vapor diffusion method, in which a dopant is placed in a closed reaction vessel evaporates and doping substances from the gas phase into the surface of the semiconductor body diffuse, then the invention is that in the reaction vessel chemical compound of the activator-cation element with an anion element from the same group of the periodic table as the anion element of the to be doped Semiconductor body is introduced and is evaporated there and that from this vapor Activator substance obtained as a decay product and used to diffuse into the surface of the semiconductor body also introduced into the reaction vessel at another point arrives, with another decomposition product from the vapor dissociating the semiconductor body with special needs.

The concentration of the acceptor cation element diffusand in the vapor is maintained at a low value so that no substantial alloying or plating can occur.

The invention is below with reference to the drawings for an example Embodiment explained in more detail.

F i g. 1 contains a schedule with details of the materials and the Process stages involved in the implementation of a special form of the process be used according to the invention; F i g. Fig. 2 shows an apparatus in use when performing preliminary procedural steps in practicing a preferred form of the Method according to the invention is used; F i g. 3 shows an apparatus that in the diffusion process in practicing a preferred form of the method according to the invention is used.

According to the detailed information in FIG. 1 becomes the compound semiconductor crystal, which serves as a substrate, preferably lapped, polished and chemically polished. then is carefully measured in the presence of the compound semiconductor crystal Charge introduced an acceptor diffusing sand that contains an anion which is the same is like the crystal anion or at least comes from the same periodic group.

The two materials are then placed in a vessel, which is evacuated and then heated for a measured length of time so that the desired Vapor diffusion can occur. The diffused crystal is then preferably cube-shaped, so that you can divide it into a number of separate systems and then those parts can attach appropriate electrodes. The electrodes are attached by alloying attached to the surfaces of the semiconductor components or by other known methods. It should be noted that the invention does not have the simplifications given by way of example is limited, but can also be used for modifications of the method. For example, certain process steps can be combined with others or eliminated. Furthermore, for example, the diffusion can be up to one Penetrate depth, which the depth of individual surface imperfections one lapped surface. Polishing can be omitted if the lapped Surface is sufficiently smooth.

According to FIG. 1 becomes a disk of n-type gallium arsenide crystal lapped, buffed and then chemically polished to give a very smooth surface for the To form diffusion. The crystal plate can be cube-shaped and have a diameter of about 10 mm and a thickness of about 0.5 mm.

According to FIG. 2, the substrate 10 is placed in a quartz tube 12. This has an inside diameter of about 11 mm. It contains a batch 14 of zinc arsenide (ZnAs2). This zinc arsenide batch weighs approximately 0.6 mg. The amount of the charge can, however, be in a wide range from 0.01 up to 10 mg, depending on the extent of the doping desired.

The quartz tube 12 is pressurized to less than 10-s Torr evacuated by a vacuum pump, the pump is shown in FIG. 2 denoted by 16. That Vessel is then, as indicated at 18, melted off so that there is a length of pipe of about 75 mm results. The remaining tightly closed tube then has a volume of about 6 m3.

The vessel 12 is then placed in a fireclay furnace 20 which has a cylindrical outer shape and a central opening 22 which is slightly longer than the vessel 12. After the capsule has been inserted, the end of the opening is sealed with a cotton ball made of fibrous aluminum silicate 24 and the furnace 20 , together with a protective cylinder 26, is then placed in a furnace tube and heated at a temperature of about 850 ° C. The jacket 26 is positioned over the opening 22 as indicated at 28. The furnace 20, together with the casing 26, essentially completely fills the interior of the tube furnace.

In the present process, temperatures in the range used from 750 to 950 ° C. The diffusion time required is a function of the desired diffusion depth and also the diffusion temperature to be maintained. The size of the diffusing sand compound batch is another related variable.

With the specific conditions given for this example the diffusion can be carried out over a period of 16 hours to a diffusion depth of 50 #tm. Under similar circumstances, cadmium arsenide (Cd3As2) as a diffusand source 80 hours are required to allow the cadmium to diffuse up to reach a depth of 50 #tm. According to the method according to the invention are in the case of semiconductor devices with pn junctions, diffusion depths of 5 to 125 .mu.m has been achieved.

The isothermal heating described above is preferably used at used to carry out the method according to the invention. However, others can Forms of heating can be used successfully.

The semiconductor substrate material used when practicing the method usable according to the invention may include any semiconductor compounds, which are useful in the production of electrical semiconductor components.

For example, it can be included, but not necessarily on it limited, the following III-V compounds as an additive to gallium arsenide: indium antimonide, Gallium phosphide, gallium antimonide and indium arsenide. The method according to the invention can also be exercised when using semiconductor substrates made from semiconductor compounds The elements are composed of other groups in the periodic table are selected.

For example, II-VI semiconductor compounds, such as cadmium sulphide or cadmium selenide can be used. The so-called mixed crystals, which more as a type of ion from one of the combined groups can also in carrying out the idea of the invention Find use. For example, in the III-V group, the gallium arsenide phosphide Ga (AsxP (l _x » be used. In the case where a Diffusand connection is used, has this has a dissociation pressure which is higher than that of the substrate compound. The anion of the diffusand compound always comes from the same group of the periodic System chosen as the anion of the substrate compound. In addition, the cation the diffusand compound always from a lower group of the periodic table chosen so that this can be effective as an acceptor.

So is z. B. for a Galhum arsenide substrate the zinc arsenide or the cadmium arsenide is very effective as a source of diffusion sand. The arsenic component of Diffusanden is used to create a protective arsenic vapor atmosphere during the diffusion process to form, and the zinc or the cadmium serves as the acceptor material in the real Diffusion of the semiconductor surface.

For a II-VI substrate compound, e.g. B. zinc selenide, is a diffusing sand material made of copper selenide, the copper serving as an acceptor material.

The uses of a compound as a source of diffusion sand have a number of advantages. If z. B. Zinc arsenide instead of pure zinc metal as a source of diffusion sand is used, then the zinc arsenide is much easier to handle because it is chemical is more stable and because it is much more brittle and easier to subdivide, in order to extremely to achieve precise measurements of very small batches. Furthermore. provides the dissociation of the zinc arsenide creates an arsenic vapor inside during the diffusion process the closed diffusion capsule. This arsenic vapor serves to dissociate of gallium arsenide during the diffusion process. The one that has become free Zinc metal serves as the acceptor diffusion sand in the gallium arsenide crystal. Preferably the anion of the diffusand compound should consist of the same element as that Anion of the substrate-crystal compound. This combination is highly effective at preventing the crystal compound from dissociating. However, if the anion element is chosen from the same group of the periodic table, then the anion element is still quite effective in the vapor diffusion atmosphere to prevent dissociation, and acceptable results are obtained. For example, the zinc arsenide has been successful has been used as a diffusion sand source for gallium phosphide crystals.

The problems with which the invention has dealt have been extremely difficult and have resulted in many mistakes. Different older proposals for solving these problems have remained largely unsuccessful. For example, it has been proposed to use arsenide crystals in the diffusion of gallium Introduce amounts of crushed gallium arsenide into the vapor diffusion vessel according to the theory that the total degradation of gallium arsenide is due to the presence of additional Gallium arsenide would be reduced and that the degradation of the desired gallium arsenide crystal therefore would be kept within limits. However, this arrangement only reduces the problem of gallium arsenide degradation and does not solve the problem. It's also beautiful it has been proposed to use pure metallic acceptor material along with pure arsenic to be introduced as a protective steam atmosphere. However, these two materials combine easy with the oxygen and are completely free of oxygen in a completely pure form and other components difficult to obtain, so this proposal without Success has remained.

In contrast, the invention solves these multiple problems a single choice of diffuse sand bonding material. The cadmium arsenide and that Zinc arsenide are particularly favorable diffusion sand materials for gallium arsenide. These salts are easy to obtain and maintain in pure form because they oxidize much less easily than the metallic acceptor diffusing sand. Another The advantage of these salts is that they are fragile.

Claims (9)

Claims: 1. A method for doping a monocrystalline semiconductor body made from a compound of elements from III. and V. or from the Il. and VI. Group of the periodic system, which enables direct recombination to generate coherent radiation by charge carrier injection via the pn junction, using the vapor diffusion method in which doping substance evaporates in a closed reaction vessel and doping substances diffuse from the gas phase into the surface of the semiconductor body, characterized in that, that a chemical compound (14) of the activator cation element with an anion element from the same group of the periodic system as the anion element of the semiconductor body (10) to be doped is introduced into the reaction vessel (12) and is evaporated there and that from this steam activator substance obtained as a decomposition product and arrives to diffuse into the surface of the semiconductor body (10) , which has also been introduced into the reaction vessel (12) at another point, another decomposition product from the steam preventing dissociation of the semiconductor body (10) . 2. The method according to claim 1, characterized in that the substrate (10) gallium arsenide and the diffusing sand (14) zinc arsenide is used. 3. Procedure according to claim 2, characterized in that the amount of diffusing sand introduced is 0.01 up to 10 mg. 4. The method according to claims 2 and 3, characterized in that that the amount of gallium arsenide introduced into the reaction vessel is about 0.6 mg is. 5. The method according to claims 1 to 4, characterized in that before the beginning of the reaction process and after the introduction of the substrate (10) and the dopants (14) an internal pressure of less than 10-s Torr is produced. 6. The method according to claims 1 to 5, characterized in that that the diffusion process at a temperature in the range of 750 up to 950 ° C. 7. The method according to claims 1 and 3 to 6, characterized in that cadmium arsenide or indium antimonide or gallium phosphide or gallium antimonide or indium arsenide or zinc arsenide is used as diffusing sand (14). B. Process according to Claims 1, 3, 5 and 6, characterized in that zinc selenide is used as the substrate (10) and copper selenide is used as the diffusing sand (14). 9. The method according to claims 1, 3, 5 and 6, characterized in that the substrate (10) gallium phosphide and the diffusing sand (10) zinc arsenide is used.