DE7216763U - OHMSCHER CONTACT CONNECTION - Google Patents

Description

Ohmic contact connection

The invention relates to an ohmic contact terminal for semiconductor compounds of III.-V. as well as IV-IV. Groups.

So far, there have been considerable difficulties in attaching electrical contacts to semiconductor carrier materials, the from compounds of III.-V. or IV.-IV. Groups exist. The reason for this is the relatively large band gap in such connections. This is particularly true to when the lead carrier material is lightly doped. Versatile attempts have also been made around the semiconductor substrate with a eutectic mixture of gold and germanium for contact purposes to provide. The main difficulty with using a eutectic for contacts arises from

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the alloy deterioration for the semiconductor substrate if the structure is above a critical one Temp, rature is heated beyond. The use of strange, eutectic mixtures is necessary

HEgEII UCl fli I. UCl lialUlCl ICl «Cl UlIlUUIIgCII, UXC a XO carrier use. Enrichment zones are used in most semiconductor materials ^{to facilitate the establishment of a good ohm-1} contact connection. The use of enrichment zones with eutectic material require such a material that is in some respects adapted to the material used for the enrichment. Unfortunately, with III.-V. or IV.-IV. Groups to achieve such an adjustment. This prevents the use of strange, eutectic mixtures in semiconductor arrangements made of gallium arsenide,

r _n iK, ... A ....; j_ni .. UiJ J ci-iz-i ν -uzj c τ - -

VIaXXXUIU ^- I-IISCIIXU ^- CIiUSJJiIXU. uiiu οχχχέ xuiii ~~ HcLi uxu dux iciiipcia ~ ture areas limited '- in which alloy deterioration cannot occur.

The invention is based on the object to ^{see an Ohm 1} contact connection to a semiconductor material made of compounds of III.-V. and IV.-IV. To create groups with the best possible properties, without impairing the semiconductor arrangement. In particular, it should be avoided that metallization layers applied for the contact connection trigger contamination of the semiconductor material. Such a contact connection should also withstand relatively high temperatures.

According to the invention, this object is achieved in that a layer of highly doped and amorphous silicon on that part of the surface of the undoped semiconductor material the semiconductor compound is attached,

- 2 - where

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with no enrichment zone for the contact connection necessary is. A special embodiment of the invention consists in that above the highly doped, amorphous Silicon layer, a metallization layer is arranged and the amorphous silicon layer is an electrical transition layer represents, which prevents contamination of the semiconductor material by the Metalli ^ ationsschicht.

With the help of the invention it is advantageously possible to have ohmic contact connections from a high temperature stable amorphous and highly doped silicon on semiconductor materials from the compounds of III.-V. or IV.-IV. Create groups without the need for an enrichment zone. The doping material of the amorphous silicon layer does not cause any Dotisrunp of the semiconductor carrier

- ³ - view

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With regard to the electrical properties, or if such doping takes place, the scope is, however insignificant. The quality of the contact connection is increased by the fact that the doping and the

Deposition of the amorphous silicon layer on the 'semiconductor body vorgencüünen virri- For further wi-

The gaseous doping agent can improve the contact quality

■ material first in a vertical reaction chamber of the

recently introduced that the atoms of the doping

! precipitate material on the surface of the semiconductor body. Immediately thereafter, the reaction products. introduced into the chamber to the highly doped, amorphous

Silicon layer on the surface of the semiconductor body with simultaneous deposition of the doping material build up. The presence of atoms of the doping material on the surface of the semiconductor body contributes for good contact formation and for doping the amorphous material to be deposited. This amorphous layer can extend over the entire calf conductor surface are formed, whereupon the pattern required for contacting is formed by etching in a conventional manner will. Any etchant can be used for etching; with which silicon can be etched.

The process of making the ohmic contact ! The conclusion according to the invention offers a multitude

of advantages. First, a .olcher shear according to the invention produced Ohm ^one terminal contact stable up to temperatures of about 1000 ⁰ C. Thus the contact terminals may before further diffusion on! Semiconductor carriers are attached, if this is desired. Another benefit due to the use; of a highly doped, amorphous silicon contact

■ from the fact that the amorphous layer between

] the semiconductor carrier and the contact metallization as

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conductive layer is, imschicht wherein both between the semiconductor substrate and the amorphous Silizi than ¹ consists shear contact between the amorphous silicon layer and the metallization layer a real ohms.

Another advantage results from the use of an amorphous silicon layer, when using eutectic mixtures find that the amorphous silicon layer is useful as an alloy barrier, if such at high temperatures Alloying phenomena can occur and the semiconductor body could be damaged if the alloy is in the Semiconductor material can penetrate. This makes it possible to use alxe types of metallization as contact on amorphous silicon layers to be used because this: acts as a buffer and a deterioration in the crystal structure of the semiconductor substrate, as well as stoichiometry in a high temperature environment.

Finally, the advantage of using a doped, amorphous silicon layer is that the contact can be made at relatively low temperatures. This is particularly useful for semiconductor connections which III.-V. Belong to group, since these semiconductor ^{compounds are temperature-sensitive above temperatures of 700 0} C and can experience a stoichiometric as well as crystalline deterioration. Since the contact can be applied at temperatures below this value, this has a very advantageous effect on the crystal structure of the semiconductor body. In particular, if the amorphous silicon, as already proposed earlier, is applied first and then doped by diffusion, the temperatures required for diffusion lead to deterioration in the semiconductor material during this diffusion process. The present

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Process should therefore not involve doping processes for semiconductor carriers through an amorphous silicon boundary layer be confused because very little or no diffusion between contact material and cum the semiconductor carrier takes place during the practice of the invention. In other words, the conventional III.-V. Group for Siliz um in Krista _iner or amorphous form do not cause any electrical doping of semiconductor compounds of III. - V. Groups. In terms of The term "amorphous silicon" gives sj-h a definition difficulty, since this term refers to a silicon layer refers, in which there are no crystallite structures. However, there is a form of polycrystalline Silicon in which the crystallite structures are so small that they cannot be detected by normal means can be. The formation of amorphous silicon is largely due to the temperature at which it is formed of silicon from the gas phase. The higher the temperature, the larger the crystallites that are in the Silicon layer occur. So there is a type of policrystalline silicon that works at such low temperatures is built up so that it approximates amorphous silicon in terms of its characteristics and qualities. This type of pdicrystalline silicon is to be regarded as amorphous silicon in the context of the invention.

Due to the invention finds a heavily doped, .imorphes Use of silicon as a contact for semiconductor carriers, the doping level being sufficient to remove the amorphous silicon, the normally to be viewed as an insulator, to act as a conductor. By the manufacturing method according to the invention this amorphous silicon becomes in the surface of the semiconductor body before the deposition of the amorphous silicon the doping material introduced. Dad rch will not only

- 6 - Ohmic

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Ohmic contact with the semiconductor body is improved, but the amorphous silicon is more heavily doped. Although the Invention essentially on semiconductor compounds of III. - V. groups, as well as IV. - IV. Groups is directed Such a doped, amorphous silicon can also be used for contacting other semiconductor materials.

Although it is known to use amorphous silicon as a contact material and this up to one To heat degree that it recrystallizes and forms a conductor, just this is to recrystallize, amorphous semiconductor material can be avoided according to the invention, since the doping in the amorphous silicon is the desired Conductivity results. Such a recrystallized, amorphous one Silicon as a contact material is described in US Pat. No. 3,506,545.

A well-known problem with the use of eutectic churches is the formation of drops or Ball formations when the eutectic mixture on the surface of a semiconductor body from a composite semiconductor material is deposited. There are several known proposals for such Avoid drop or ball structures. However, the invention offers the advantage of use of amorphous silicon, so that the problem of the formation of drop or spherical structures no longer exists, since the eutectic mixture never contacts the surface of the semiconductor body of the composite semiconductor material comes into contact. When a eutectic mixture is required for contacting a semiconductor device it is attached directly to the amorphous silicon. However, this does not result in the aforementioned Drop or spherical structures.

Further features and advantages of the invention result

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from the following description of an exemplary embodiment in conjunction with the claims and the Drawing. Show it:

1 shows a partial sectional view of a semiconductor carrier material on its surface as an introductory measure doping material immediately before the application of a doped, amorphous silicon layer is attached;

FIG. 2 shows a sectional partial view of the structure according to FIG. 1, after the amorphous Silicon layer;

3 shows the structure according to FIG. 2 after an etching treatment to create an amorphous silicon pattern suitable for contact terminals;

Fig. 4 the use of an alloy metal or another material for metallizing the surface of the amorphous silicon layer;

Fig. 5 is a graph showing the linearity and lack of offset between an represents the applied voltage and the current flowing through the amorphous layer and which shows that there is a pure ohmic contact connection with the semiconductor carrier consists.

The following description is based on the use of a highly doped, amorphous silicon layer as a contact material for a semiconductor carrier with compounds of III. - V. Groups and IV. - IV. Groups from, whereby for

the

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the contact connection does not require an enrichment zone. The highly doped, amorphous silicon contact can, because of its high temperature stability, be used directly for attaching the contact or as an intermediate transition layer between the surface of the semiconductor carrier from the group of compounds mentioned and the contact metallization. The amorphous silicon is doped and deposited in one process step, a dopant being used which only insignificantly dopes the semiconductor carrier on which the amorphous silicon layer is applied. In the context of the invention, instead of an amorphous silicon layer, an amorphous layer made of another semiconductor material can also be used, provided this is highly dopable. Although it may be possible that a certain enrichment diffusion occurs because the special, amorphous substance is doped, this doping material does not primarily have the purpose of building up an enrichment zone in the semiconductor carrier. The initial application of an atomic layer of the doping material to the surface of the semiconductor carrier serves on the one hand to form a uniform doping distribution in the amorphous layer and on the other hand to improve the contact between the amorphous layer and the semiconductor body. Although such an improvement in contact is clearly evident, no theoretical justification can be given for this. The doping material which is normally used for doping the amorphous material, as a rule, does not have a doping effect on the semiconductor material of the carrier used.

For the carrier find semiconductor compounds from III. - V. Use of groups. Such semiconductor devices

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Bonds are, for example, gallium arsenide, gallium arsenide phosphide, but also silicon carbide, which is a compound from IV. - IV. groups. In known methods for producing contact connections, the Haiuicitertidgci are provided with a cxiici ftfiicxCiiciüugä- zone in such a way that the area immediately below the contact connection is heavily doped. In this method, a doping material is used which is suitable for doping the semiconductor carrier and which is compatible with it. In the present invention, however, a doping material is used which is suitable for doping the amorphous silicon layer, but which cannot necessarily also be used as a doping material for the semiconductor carrier from the given semiconductor compound. The most practical structure of an ohm * see contact connection according to the invention

Liici Ticxoc cxiic ΐΐυν-ιινιυ (, xc J. wc , aiiiuipac oxx Xi. Χ ums L ii χ v. Ii L

as an intermediate layer between the metallization applied to the amorphous silicon layer and the semiconductor substrate use. This amorphous silicon layer represents a barrier for the already mentioned disadvantageous alloy due to excessively high temperatures to which the semiconductor structure may have to be exposed.

In Fig. 1, a lightly doped semiconductor carrier is shown. It should be noted that attaching a Contact on such a semiconductor carrier is more difficult, the less this semiconductor carrier is doped. With a light doping in this context is a doping of the order of magnitude of about 10 to 10 Atoms / cm. As a method for applying a doped, amorphous contact, the known, chemical Used by vapor deposition. For an example description it is assumed that the semiconductor carrier 10 is made of

- 10 - N-conductive

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N-type gallium arsenide is made, which is a doping of about 10 atoms / cm. Phosphorus is used as the doping material for the amorphous layer, The entire process takes place in a vertical reactor suitable for an epitaxial structure,

in which the silane is pyrolytically precipitated in a nitrogen atmosphere together with the doping gas of phosphine dissolved in hydrogen. At the beginning of the process, only the dopant in its carrier gas is introduced into the reactor for about 30 seconds, so that atoms of the dopant material are on the surface of the gallium arsenide carrier when the silicon is subsequently deposited. It was found that the quality of the Ohm ¹ contact connection is critically related to the presence of such doping atoms on the interface between the amorphous silicon and the semiconductor substrate. The more the amorphous silicon layer is doped, the better the ohmic contact is. It was found on the basis of experiments

that a doping concentration in the amorphous silicon

18 3

layer above about 10 atoms / cm leads to the desired results, this doping concentration being dependent on the Mixed crystal formation of the doping material in the amorphous material is limited.

For the following example, a gallium arsenide is assumed as the semiconductor carrier with a doping concentration of about 10 atoms / cm. This semiconductor substrate is arranged in a vertical epitaxial reactor, which is introduced into molecular nitrogen as a carrier stream and hydrogen dissolved phosphine at a temperature of about 55O ⁰ C to about 700 ⁰ C for a period of 30 seconds. Then, in addition to the phosphine dissolved in hydrogen, Sslan is introduced. Through the common

- 11 - same

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the same and simultaneous introduction of silane and phosphine results in a layer of amorphous silicon in the range from about 1000 Å to about 10 OCO R with a doping

18 Concentration in the order of magnitude of about 10 atoms / cm, the doping being carried out by the phosphorus atoms. It should be pointed out that phosphorus is not an electrical doping material for gallium arsenide and that the improvement of the Ohir ¹ contact connection does not start from any enrichment diffusion in the semiconductor carrier.

Of course, other doping materials, such as boron, arsenic and antimony, can also be used for doping the amorphous material. Furthermore, boron-hydrogen (E ₀ H _n -, when using boron, arsine ( ^ft sH _T ) when using arsenic and stibine (SbH,) when using antimony is used as the doping material doped, amorphous layer II according to FIG. 2 on the surface of the semiconductor carrier 10. This amorphous layer can then be partially etched away using suitable etching agents which are suitable for the etching of silicon, forming a suitable pattern. 3 create the contact area of amorphous silicon provided with 15. It is generally desirable to apply a metal layer to the amorphous semiconductor contact material either before or after the etching off for shaping Such a metal layer is shown in FIG chicht shown 15, -ur metallization may include aluminum in a thickness of about 5000 Å to about 10,000 S are used, which is applied at temperatures between about 25O ° C to about 300 ⁰ C. As already mentioned, this is for the semiconductor carrier

- 12 - used

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Galiium arsenide used is relatively sensitive and fragile at temperatures above about 700 C. It should be pointed out that, although temperatures above about 7OC ⁰ C are necessary for the formation of eutectic mixtures, the contact according to the invention can be applied at temperatures that are good ran below acceptable temperatures for gallium arsenide or gallium arsenide phosphide. According to FIG. 5, there is a linearity between the current and voltage characteristics for the contact, from which it can be ^{seen that this is a real Ohm 1} contact. This linearity can also be taken from the following table, whereby a doped, amorphous silicon on gallium arsenide was assumed for the determination of the values.

TARELLE

^Volts Passage Milliamps

passage

3.8 20 3.5

3.1 10 2.0

1.3 5 1.1

0.52 2 0.48

0.27 1 0.26

0.135 0.5 0.135

0.12 0.05 0.012

Although it is known to make acceptable contacts to semiconductor substrates made from III.-V. groups It is extremely difficult to attach such a contact connection in the form of a metal layer on a silicon carbide material by depositing the metal alone. The use of an amorphous silicon for contacting silicon carbide is therefore of the utmost importance

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Particular advantage because two separating layers are created. The first separating layer is between the amorphous silicon and the semiconductor carrier., whereas the second separating layer lies between the amorphous silicon and the metallization layer. This contact can be in very easy to carry out, since the doping and the deposition de amorphous during the entire process Silicon can take place simultaneously at temperatures that are considerably lower than those temperatures at which material damage occurs in the semiconductor carrier. Although it has already been suggested, amorphous silicon to be attached to a semiconductor carrier and to undertake the diffusion through the amorphous layer at the temperatures necessary for such a diffusion Deteriorations in many semiconductor compound materials from III. - V. Groups cannot be avoided.

As mentioned previously, the terminal contact for an integrated circuit or a discrete semiconductor device before diffusion of the semiconductor body can be made with certain materials, since the amorphous silicon can withstand temperatures of up to more than 1 000 ⁰ C. Thus, the contact connection can be attached at the same time or before the formation of the active elements in the semiconductor carrier. This differs from the known practice of providing the contacts as the final step in the manufacture of semiconductor devices because of the fragility and temperature instability of the contacts as used heretofore. The present invention thus also enables significantly greater flexibility in the manufacture of semiconductor arrangements.

During the shipment of gallium arsenic and gallium arsenide phosphide elements in matrix fields the difficulty arises

- 14 - ness

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, Direction of the connection of the individual fields in XY 'around this to make addressable. If, in a structure shown in FIG. 4, a polycrystalline gallium arsenide is present on the surface Of the structure is attached, the amorphous silicon and the metal layer 20 constitutes one in the polycrystalline Gallium arsenide is a buried layer. The semiconductor substrate can then be lapped off to such an extent that an active Element can be formed in the lapped surface. Depending on the configuration of the pattern for the amorphous contact and / or the metallization layer can make the elements buried through depth diffusions Layer are connected, so that a field of gallium arsenide or gallium arsenide phosphide that is addressable in the X and Y directions can be easily manufactured. Since it's a little less of a hassle, add buried layers and contact terminals to apply them in silicon and germanium structures, The present invention provides an advantageous method of creating a Murter of buried layers so that these Layers can be connected to one another by deep diffusions up to the amorphous layer.

The invention thus offers a new type of contact that does not require an enrichment zone and with the help of a doped, Amorphous substance can be produced as a contact connection to a semiconductor material from a chemical Connection is usable. Although the amorphous silicon is the cheapest amorphous substance for this purpose, you can other amorphous semiconductor materials are also used, such as amorphous germanium, which is initially in crystalline Form is present but is precipitated in amorphous form. In doing so, these materials are used to such an extent doped so that they become conductive to about the same extent as conventional metallic conductors. The so doped, amorphous material can on the one hand itself represent the »contact, or as an intermediate element between a metallic one

- 15 - contact

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Find contact connection and the semiconductor carrier use. This layered design leads to reliable ohmic contact connections in materials that were previously available It was difficult to transmit metallic connection contacts to attach. Especially since alloy deterioration can hardly be avoided.

- 16 - Claims for protection

Claims (6)

M262P / G-78O / 1 protection claims 1. Ohm ¹ shear contact connection for semiconductor connections of III.-V. as well as IV.-IV. Groups, characterized in that a layer (15] of a highly doped and amorphous silicon is applied to that part of the surface of the undoped semiconductor material of the semiconductor compound which is ^{to be provided with the ohm 1} contact, with no enrichment zone being necessary for the contact connection. 2. Ohm ¹ shear contact connection according to claim 1, characterized in that the amorphous silicon is formed and doped at the same time. 3. Ohmic contact connection according to claim 2, characterized gekennz eichnet that the doping material is first applied to the semiconductor body and immediately the highly doped, amorphous silicon layer is formed thereon. 4. Ohmic contact connection according to claim 3, characterized characterized in that the doping material applied to the semiconductor body is the same as that of the amorphous silicon layer is. 5. Ohm ¹ shear contact connection according to claim 1, characterized in that the "albleitermaterial made of gallium - arsenide or Galiium-arsenide-phosphide or silicon carbide and that the amorphous M262P / G-7PO / 1 -.ο silicon with phosphorus in a concentration above 10 Atoms / cm is doped. 6. Ohm ¹ shear contact connection according to claim 1, characterized in that a metallization layer is arranged over the hech-doped, amorphous silicon layer and the amorphous silicon layer represents an electrical upper layer which prevents contamination of the semiconductor material by the metallization layer.