DE2257897A1 - PROCESS FOR THE PRODUCTION OF CROSSINGS IN INTEGRATED CIRCUITS - Google Patents

Description

Western Electric Company, Inc. Cheney 3-2 -New York NvY. V.St.A.

Process for making crossovers in integrated circuits

The invention relates to the production of crossovers in integrated circuits as well as the products _{E produced by such production processes}

The production of complete electronic circuits on a single Siilsiumsefoeibchen by the application of a limited number of procedural steps _& such as dopant = diffusion, thermal growth of iron silicon dioxide and metallization _s all by means of photolithographic. Masks are precisely controlled, »is a cornerstone of today

electronic industry * The success of integrated circuits in Siliziura is due to their low cost per unit ₉ which is due to the limited view! of Ye? - driving steps are possible _p which can be repeated in different Κθει · = »binations o A problem that frequently occurs in the design of such circuits is the formation of line crossings, so" the zone in which two conductors intersect "remain isolated have to" ,

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An obvious method of forming crossovers is simply by depositing insulating Material on a lower conductor and the subsequent formation of the upper conductor on top of the applied Insulator. However, the application of insulating material increases the cost of manufacturing integrated ones

Circuits, as this creates a further procedure -

to be led. For this reason, the lower conductor is usually cut through, the ends facing each other are diffused into the silicon wafer with a Zone connected and then thermally silicon dioxide over the diffused zone generated by this at increased Temperatures exposed to oxygen · The top conductor is then formed on the silicon dioxide isolating it from the lower conductor. During operation, the diffused from the Zone formed with the disc transition biased in the reverse direction, so that the lower conductor is independent can transmit currents from other currents in the disc.

With this procedure, the necessity will indeed be met with success the application of an insulating material on a metallic conductor is avoided, but it has certain disadvantages, since the specific resistance of the diffused zone bridging the lower conductor is inevitably quite high is. For structural reasons, this diffused zone must be comparatively long, as a result of which considerable resistance losses can occur. However, it is even more important that the diffused zone capacitively with the silicon chip

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is coupled, and therefore forms a lossy, distributed transmission line section, "whichever the speed, the access time and the high frequency properties of the integrated circuit can degrade considerably.

In contrast, the invention is based on the object of creating an effective crossover structure that is simple and can be produced without great expense ".

According to the invention, a method for production is provided for this purpose of crossovers in integrated circuits on silicon wafers, in which a conductive layer is applied from a metal silicide to a portion of the disc in such a way that the layer and the disc are substantially isolated from one another during operation, the metal being selected from a palladium, platinum, and rhodium Iridium is chosen as the conductive layer of an oxygen-containing atmosphere at such temperature is exposed to an insulating layer on one section Forms from silicon dioxide and in which a conductive Material is applied to the insulating layer »

Platinum silicide is advantageously used as a metal silicide

In an advantageous further development, in the with metal silicide occupied section of the disc · a pn junction formed with the main portion of the disc. Alternatively

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the metal silicide layer can be a Schottky barrier layer with the metal silicide-coated section of the disc.

The invention is in the following description of an exemplary embodiment explained in more detail in connection with the drawing, namely shows

Fig. 1 is a sectional view of a portion of an integrated manufactured in accordance with the invention Circuit; and

2 shows a sectional view of another in the invention

appropriately provided integrated circuit.

In the following, reference is made to FIG. 1, in which a semiconductor wafer 11 is shown, on which an integrated circuit is produced by means of known methods, the major part of which is not shown. The circuit has two conductors 13 and 14 which intersect at right angles. The problem according to the invention consists in making it possible to cross one conductor with the other, with mutual insulation being ensured. This is achieved by bridging a gap between segments 13a and 13b of conductor 13 with a diffused zone 15 and a layer 16 of platinum silicide, which transmits current between segments 13a and 13b, but through an insulating layer 17 of Sni ₂ iumdioxyd is separated from the conductor 14. In operation, the between the

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diffused zone 15 and the pn junction 11 formed biased by the voltage source 18 in the reverse direction, so that current flowing in layer 16 is isolated from other currents occurring in disk 11 is.

As mentioned above, it is known to bridge conductor segments, such as segments 13a and 13b, by a diffused zone ₅ , such as the diffused zone 15, for conducting currents between them. The advantage of using such a diffused bridging zone is that there is always one Siliziu'rodioxydschicht can be generated on a diffused Siiisiurazone, whereby an economical production of an insulator against the crisscrossing .Lleiter. 14 is possible.

A platinum silicide layer 16 is provided on the diffused zone 15 for the transmission of currents between the conductor segments 13a and 13b. It has been found ₉ that platinum silicide offers the most advantageous properties of both metal and silicon as a bridging conductor? its specific resistance is almost as low as that of good metallic conductors and - in contrast to other metals - an insulating layer of silicon dioxide can be produced thermally on it. Therefore, the purpose of the diffused zone 15 is not to transmit currents _s but only to form a pn junction which can be stressed in the reverse direction

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is, so that the platinum silicide conductor 16 from the wafer can be isolated.

All individual process steps for production of the structure according to FIG. 1 are known and do not lead to additional expenditure, which increases the manufacturing costs considerably would increase. It is essential that it is not necessary to apply the insulator 17 as it normally would this is the case when a metallic lower conductor is used in a crossover.

The structure according to FIG. 1 is produced by initially the zone 15, which can be p-conductive, in the disc 11, which, as shown, can be η-conductive, is diffused in. The platinum silicide layer 16 is then in a known manner, i.e. by vapor deposition or spraying of pure platinum in a thickness of, for example, 1000 8, applied this Layer is then used for a sufficiently long period of time to convert the entire layer to platinum silicide on one layer Heated to a temperature of about 450 ° C. Then the silicon dioxide layer 17 thermally formed over a major portion of the platinum silicide in-which there is an oxygen or H., 0 containing atmosphere is heated in a furnace to a temperature of, for example, 500 ° C.

It has been found that a layer of silicon dioxide is deposited in about 10 to 15 minutes a thickness \ m about 1000 X is generated if

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the silicide layer to a flow rate of one liter / minute is exposed to a gas containing 1% 0 ₂ or 1% HJJ · It was interestingly found that, when a predetermined OXYGEN-offangriff silica from platinum silicide faster than on pure silicon originated ,, what the The reason for the relatively low proportion of oxygen that can be used in the atmosphere is, apart from this difference in thermal growth rate, the silicon dioxide layer 17 can normally be produced simultaneously with the silicon dioxide layer 19, which is on most of the remaining surface of the silicon wafer is produced. In the manufacture of integrated circuits, differences in the thickness of silicon dioxide layers of up to 10,000 can normally be tolerated. After the thermal generation of the silicon dioxide layers 17 and 19, the conductors 13a and 13b and 14 are produced in a known manner, for example by vapor deposition.

Although layer 16 is preferably made of platinum silicide other platinum family metal silicides alternatively use findai · The platinum family consists of the well-known, palladium, rhodium, and iridium Metal group containing platinum. These metals are sufficient active to form a solid silicon alloy when heated as described above while they are on the other hand are sufficiently inert to not react with

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Enter oxygen or water vapor. The structural build-up of these metal ilias is not yet complete explainable, but it is clear that the silicon molecules in it form a connection with oxygen much more easily, than the silicon molecules of the crystal disc

In operation, the component is polarized in the reverse direction Spannarriam operated pn junction, which, as mentioned above, is supplied by a voltage source 18. The bias naturally leads to a depletion zone at the transition, which prevents current flow across the junction. However, there is a capacity and a capacity at this interlocking zone The property of each crossover is that the bridge between conductors 13a and 13b provides a distributed transmission

to
line forms, the losses of which can limit a transmitted signal frequency. The present invention can significantly increase the frequency transmission properties of the component because the conductive layer 16 has a desired low specific resistance.

It is known that a platinum silicide layer forms a Schottky boundary layer with a silicon disk if the disk has a sufficiently high specific resistance. A Schottky boundary layer is an electronic boundary layer the many properties of a pn junction? Has. A Schottky boundary layer contact can therefore be biased in the reverse direction to provide the required Verariaingszone for insulation

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of the lower crossover ladder

The following is on Pig * 2 reference genoraieUj, Ln of the various components ira essential to establishing and functioning of the components in Fig »1 _y are identical which is why they referred to the same Meise - are · The only difference is that in ,, Fig. 2 no one »

diffused zone 15 is provided ₉ and that the discs
Chen 11 has a sufficiently high specific resistance that it can form a Schottky barrier layer with the platinum silicide layer 16. If the silicon disc has a specific resistance of 10 −Ω, for example. cm , a platinum silicide layer produced in the above-mentioned manner forms a Schottlcy-Grenaschlcht «, Ia operation, therefore, a generally barren voltage source 18 forms a depletion layer at the interface of the wafer with the platinum silicide conductor ISo

A disadvantage of the device shown in FIG. 2 relative to that of FIG. 1 is the relatively greater tendency for Schottky interfaces to be "permeable" depletion zones can be formed at upstream ■ given voltage, somewhat lower than in devices according to Fig, 1 is expected · Further information regarding the preparation of Platinsilizidkontakten example, U.S. Patent No. ~ are taken ₀ 3,274,670.

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Although the method discussed above is only applicable to integrated circuits in silicon it is still a significant improvement as silicon is by far the most commonly used material for such Circuits is. However, modifications can always be made where silicon dioxide is thermally on a conductor should be grown up. For example, others can be used alternatively than the line types shown.

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Claims (4)

2257837 Claims SBSBBBXaaaBBBSCSBCSBBSSBBBBSB / Iy method of making crossovers in integrated Circuits on silicon cups, characterized in that that a conductive layer (16) of a metal silicide on a portion of the disc (11) is applied in such a way that the layer and the wafer are substantially isolated from one another during operation are, where the metal consists of a palladium, platinum> Rhodium and iridium is chosen that the conductive layer of an oxygen-containing atmosphere is exposed at such temperatures that an insulating layer (17) made of silicon dioxide is on one section forms, and that conductive material (14) is applied to the insulating layer. 2. The method according to claim 1, characterized in that platinum silicide is used as the metal silicide 3. The method according to claim 1 or 2, characterized in that in the covered with metal silicide portion of the disc -a-pn-junction - <at 15) with the main section of the Disc is formed. 4. The method according to claim 1 or 2, characterized in that that the metal silicide layer forms a Schottky boundary layer with the metal silicide-coated portion of the disc forms. ■ · · ■ 309824/080 6 Blank page