DE2525482A1 - MATERIAL COMPOSITIONS SUITABLE FOR SEMICONDUCTOR COMPONENTS - Google Patents

Description

Dipl.-Ing. H. Sauerland · Dr.-ing. R. König · Dipl.-Ing. K. Bengen Patent Attorneys ■ 4odd Düsseldorf 3O ■ Cecilienallee 7B · Telephone 433732

June 6, 1975 30 039 B

RCA Corporation, 30 Rockefeiler Plaza, New York , NY 10020 (V.St.A ₀ )

"Material compositions suitable for semiconductor components"

The invention relates to semiconductor components, in particular to material compositions suitable for such components.

Various semiconductor components include one or more metal layers. A problem associated with the production of such components problem is that it is necessary in the preparation, in general, to carry out process steps at high temperatures, for example during different impurity diffusion processes, thereby vaporize or metals commonly used, for example, _o aluminum, either high in these Temperatures are subject to various undesirable interactions. It has therefore hitherto been fundamentally necessary to apply the metal layers to the components only after the high-temperature treatments mentioned had already been carried out. As a result, the possible applications for which these metal layers could be used are limited and, in addition, restrictions are brought about with regard to the structure, design and manufacture of the semiconductor components.

fu 509881/0781

The object of the present invention is to provide heat-resistant Metal additions to propose the are compatible with known manufacturing processes for semiconductors, thereby increasing flexibility to achieve with regard to the design and manufacture of such components. According to the invention This object is achieved by a material that is the oxidation product of a silicon and a heat-resistant Metal that reacts with silicon to form a silicide, contain existing composition

In the context of the invention are suitable as heat-resistant or difficult to melt metals that with silicon react to a silicide, for example. Platinum, molybdenum, tungsten, rhodium and rhenium.

The following is a method which is preferably to be used for the preparation of the compositions according to the invention described.

First, a target that is a refractory metal silicide contains, bombarded with electrical charges, e.g. with argon ions, with a spray or Atomization effect occurs. Small particles of the target material, at least approximately stoichiometric Ratio, are deposited on a substrate, from what is to be specified below Base preferably on a substrate containing silicon. Either AC or DC voltages can can be used. However, for some inexplicable reason, when AC voltages are used, something achieved better results in terms of the adherence of the deposited layer to the substrate.

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The exact composition of the small target particles, which are sprayed onto the substrate is not known. It is believed that the sprayed material Includes particles of the metal itself, particles of silicon and / or particles of the metal silicide. Preferably a target is used that contains the compound of the metal with silicon, and it is to be expected that the deposited layer is at least approximately, if not exactly, over its entire area Range contains a stoichiometric ratio of the metal silicide. It is also to be expected that, even if the metal silicide compound of the target is separated during the spraying process, at least to some extent Part of the substrate recombination to the silicide compound occurs, either during the deposition process or during later high-temperature treatment of the substrate »

It is believed to be extremely likely that the use of a target comprising a metal and silicon contains in a non-stoichiometric ratio, too leads to metal silicide layers containing the excess metal or silicon.

Although the metal-silicon layer can be applied to substrates made of a large number of materials, it adheres particularly well to substrates containing silicon, for example silicon itself, glass, silicon dioxide and silicon nitride. The deposited layer is heat-resistant and can be produced with different degrees of electrical conductivity, depending on the parameters used in the spraying process. For example, at a substrate temperature of approximately 200 ^° C., the specific resistance is

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a deposited layer containing tungsten and silicon in an approximately stoichiometric ratio, approximately 450 to 600 fJ £? cm. At a final temperature of about 300 to 400 ⁰ C, the specific resistance of the tungsten-silicon layer is, however, at about 100 / cm WJL.

A further reduction in the specific resistance of the deposited layer by about 25% _t can be achieved by a subsequent heat treatment step, for example by placing the coated substrate in an oxygen-free atmosphere, e.g. in an argon atmosphere, for about 30 minutes at a temperature of about 900 ⁰ C is held.

Provided that the surface of the substrate on which the layer is deposited is sufficiently clean is what can be achieved, for example, by known "back spray" techniques, and furthermore that Substrate is sufficiently conductive, good ohmic connections can also be made between the deposited Layers and the substrates can be achieved.

After a layer of refractory metal and silicon is made in the manner described above is, this is oxidized, i.e. either the entire thickness of the layer or only the outer part of the layer oxidized, with the result that in the last-mentioned case a metal-silicon layer is formed, which is a covering "Skin" or layer of the oxidized product or a Having "oxide" of the underlying material.

A simple way of carrying out the oxidation is that the metal-silicon layer

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is heated in an oxidizing atmosphere, for example by placing the workpiece having the layer in an oven and heating the workpiece in the presence of air, the thickness of the oxide coating being a function of the time and temperature used in the process. As will be described below, it is important that the oxidation ^{temperature can be relatively low, for example approximately 400 °} C., the oxidation rate at such a temperature and with air as the oxidizing environment initially being approximately 200 Å / min, up to one Thickness of about 1000 Å, and then drops to about 40 & / min.

The exact composition of the oxide of the metal-silicon material is not known, especially for this reason not because, as already mentioned, the exact composition of the refractory metal-silicon material is also not known. The electrical resistance of the oxidized material, however, is very high, which indicates suggests that each of the components of the metal-silicon layer is likely to be at least partially oxidized is, and the resulting oxide layer is therefore in all probability oxides of silicon, Refractory metal oxides and refractory metal silicide oxides.

Certain physical properties of the oxidized metal-silicon material are carried out by the Oxidation process impaired. For example, it has been found that at higher oxidation temperatures The more strongly adherent oxide layers resulted, the lower the proportion of oxygen in the oxidizing Atmosphere was. At an oxidation temperature

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of about 400 ° C, for example, showed cohesive, adhesive layers, when the oxidation was carried out in air atmosphere containing "However, that is, in an approximately 20% oxygen at temperatures of about 600 ⁰ C led Oxydationsatmosphären that more than 1% oxygen ( radical, for example, nitrogen or other non-oxidizing gases) contained to oxidized layers or non-adhesive were _o non-contiguous.

With "adherent; ¹¹ or" continuous "is meant a relatively dense layer with a smooth surface, free of hairline cracks or corresponding holes, homogeneous, well adhering to the underlying substrate and etchable at a constant rate. By "non-adherent" or "non-contiguous" is meant a layer which has an "inflated" or rough surface which is generally poorly adhered to the underlying pad and is prone to rapid and uneven etch rates the various materials used for this are adhesive, as such materials provide greater uniformity in characteristics from part to part.

As already mentioned, the electrical resistance of the oxidized metal-silicon layer is very high. Even the materials have a high dielectric field strength and can be etched with etchants that various materials commonly used in semiconductor components, e.g. Silicon dioxide, silicon nitride, Germanium, gallium arsenide and silicon either not or only

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attack very little, while they are not attacked by certain caustic agents, which in turn attack the last-mentioned materials. The oxidized materials are therefore suitable for semiconductor components as insulators, dielectrics and masking layers on the HalTDleiterchips such components in very similar Way like "known substances, such as silicon dioxide and silicon nitride.

Based on, for example, a 10,000 & thick layer of tungsten and silicon which was deposited on a silicon body by spraying or bombarding a tungsten disilicide target and from which the surface was ^{oxidized to a depth of approximately 4000 S at 440 °} C. in air , the dielectric strength of the oxidized part, measured as the voltage that the oxidized layer withstood without breakdown, was more than 600 V.

The resistance of the layer was measured using an aluminum lead with a diameter of 0.75 mm applied to the surface of the oxidized layer, a voltage between the terminal and the conductive, layer of non-oxidized tungsten-silicon material underneath and the layer in between flowing current has been determined. At a voltage of 500 V, the measured current is less than 20 Nanoampere for a 4000 Å thick oxidized layer.

The oxidized tungsten-silicon material can be etched with etchants such as potassium hydroxide (KOH) and various mixtures of hydrofluoric acid (HF) and nitric acid (HNO,), e.g. 97% nitric acid and 3% hydrofluoric acid. The oxidized material is treated with hydrofluoric acid or salt

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pitric acid alone is not etched, nor is it attacked by sulfuric acids (H ₂ SO ^) or hydrochloric acids (HC ₁ ) or by buffered etchant (HF-NH-F).

As already mentioned, the oxidized material can be used for essentially the same purposes: such as the well-known materials silicon dioxide and silicon nitride, and for these purposes the initial one Heat-resistant metal-silicon layer, preferably completely oxidized. But if the oxidizing doesn't takes place through the entire initial layer, the result is a core of non-oxidized material, the is surrounded by oxidized material on its otherwise exposed surfaces. Oxidizing the outer surfaces the initial layer affects the conductivity of the non-oxidized core, so that this combination can be used as an insulated conductor. For example, on the surface of an integrated circuit that contains several different circuit components has, with the help of these conductors, various electrical connections between the components are produced, the conductors consisting of the materials according to the invention can cross without short circuits occurring.

Another advantage of the materials according to the invention is that, as already mentioned, they are comparatively can be produced at low temperatures. So if, for example, the metal-silicon layer first in the spray process that does not require excessive heating of the substrate is, and the deposited layer is then oxidized at a relatively low temperature, that is Workpiece not exposed to high temperature processes.

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This can be extremely desirable, and indeed in those cases in which the workpiece is made of semiconductor material exists, which is to be subsequently subjected to diffusion. That means for example at Use of a silicon workpiece that does not allow heating to a temperature that is too high (i.e. a temperature below 600 ° C) only too little or no oxidation of the surfaces of the silicon body and thereby either a very simple cleaning of the silicon surfaces or no cleaning at all is required before the later diffusion processes are carried out. You can also avoid it high temperatures for the workpiece "movements" of previously formed diffusion areas can be avoided.

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Claims (13)

- ίο - RCA Corporation, 30 Rockefeller Plaza, New York , NY 10020 (V.St.A.) Claims; ο Kitz-resistant material, especially for semiconductor components, characterized by the oxidation product of a silicon and a heat-resistant metal that merges with silicon to form one Silicide reacts to existing composition. 2. Composition according to claim 1, characterized in that the heat-resistant Metal and silicon are present in an approximately stoichiometric ratio of the silicide of the metal. 3. Composition according to claim 1 or 2, characterized in that the heat-resistant Metal is tungsten. 4. The composition of claim 1 or 2, d a by ch characterized in that the refractory metal is platinum, molybdenum, rhodium or rhenium. 5. A method for producing a composition according to one or more of claims 1 to 4, characterized in that on a substrate in the spray process by bombarding a target made of silicon and heat-resistant metal a layer of silicon and the refractory metal is deposited, and that the layer then in an oxygen-containing atmosphere 50988 1/078 1 is warmed. 6. The method according to claim 5, characterized in that the layer is deposited on a silicon substrate and heated ^{to a temperature below 60O 0 C.} 7. The method according to claim 5 or 6, characterized in that the layer is ^{heated to a temperature between 400 and 600 0} C, wherein the percentage of oxygen in the atmosphere is in the range of 1% to 20% and in this range the lower it is chosen, the higher the temperatures are. 8. Object consisting of a heat-resistant material, characterized that the material consists of silicon and a refractory metal that is interlaced with silicon Formation of a silicide reacts and has a coating which is the oxidation product of a surface layer contains. 9. The article of claim 8, characterized in that the metal and silicon in an approximately stoichiometric ratio of the Silicide of the metal are present. 10. The article of claim 8 or 9, characterized in that the metal is platinum, Is molybdenum, tungsten, rhodium or rhenium. 11. A method for producing the article according to a or more of claims 8 to 10, characterized 509881/0781 characterized in that on a substrate in a spraying process, in which a target made of silicon and bombarding the refractory metal, a layer of silicon and the refractory metal is deposited, and that this layer is subsequently is heated in an oxygen-containing atmosphere to form a surface part of the layer of the coating to oxidize. 12. The method according to claim 11, characterized in that the layer on a Silicon substrate is deposited and heated to a temperature below 600 ° C. 13. The method according to claim 11 or 12, characterized in that the layer is ^{heated to a temperature in the range from 400 0} C to 600 ⁰ C and the oxygen content in the atmosphere is selected between 1% and 20%, the higher temperatures the lower Oxygen levels and vice versa can be assigned. 509881/0781