DE4307182C2 - Passivation layers to protect functional layers of components and processes for their production - Google Patents

Description

The invention relates to a passivation layer and a method for its Manufacture to protect functional layers of components, in particular microelectronic components and preferably those based on high-temperature superconductor (HTSL), against contamination and / or chemical or physical changes in these layers.

It is known to use oxide and nitride layers for passivation to use a wide variety of application areas (cf. e.g. DE-OS 16 14 872, DE-OS 38 03 014 or US-PS 3,663,279). Still is it is known that thin layers, in particular HTSL layers of REBaCuO systems (RE = rare earth) a strong one Corrosion susceptibility to air, especially its water, CO₂- or have carbon dioxide content. To maintain the HTSL properties such layers it is necessary to decompose them Layers due to external influences and the diffusion of To avoid oxygen from these layers. To protect such Layers against the above-mentioned effects are therefore passivated with suitable cover layers are required. It is known to consist of layers To use oxides and nitrides (e.g. U.S. Patent 5,124,311). These have been found to have the disadvantage that they are not sufficient diffusion barriers to the above represent atmospheric components or a harmful Effects on superconductor properties due to interdiffusion processes to have.

From IBM Techn. Discl. Bulletin Vol. 30, No. 8 (Jan. 1988) pp. 436-437 is known to reactively sputter intermediate layers of RuO₂ or IrO₂ in the case of Al contacts of Si components in order to avoid the interfering interdiffusion processes of Al and Si occurring at higher process temperatures prevent. It is unknown whether such layers can also protect against contamination from the atmosphere or against oxygen loss from functional layers. A disadvantage of these oxides is their high electrical conductivity (resistivity on the order of 10 ^-5 Ωcm), which is why they would constitute impermissible auxiliary connections outside of contact areas.

Some metal layers such as Pd or Cu can form thin reaction layers on the border to oxidic materials such as REBaCuO, which reduce oxygen loss (Phys. Rev. B Vol. 38 (1988) pp. 232-239). However, such a barrier to the metal layer is not sufficiently electrically insulating. Likewise, specially applied thicker CuO _x or PdO _x layers would be unsuitable in most cases due to their conductivity for passivating electrically conductive functional layers, although a passivating effect of CuO _x on YBCO layers was found (J. Less Common Metals, Vol. 164 and 165 (1990) pp. 1261-1268).

There are also attempts to use polyimide layers (hutchings, C .; Grunze, M. "Passivation of YBCO-HTSL surface layers with Polyimide ", VDI-TZ-Proceedings, 3rd Status Seminar" Superconductivity and Low temperature technology ", Potsdam 1992). When using such  Layers, e.g. B. for the hermeticization of HTSL thin layers, has shown how found was that these do not offer a sufficient guarantee that Component properties (such as the transition temperature) constant to hold when the functional layers after its manufacture before coating with polyimide layers exposed to air even for a short time.

Metallic passivation layers that can be produced with sufficient density, prohibit for most applications through their i. a. intolerable electrical shunt.

Another disadvantage when using conventional passivation layers is that to contact the functional layers, especially if it is these are HTSL layers, a free etching of Contact windows required by means of photolithographic processes is, the backup being lower and more reproducible Contact resistances with a considerable effort connected is.

The invention is therefore based on the object of passivation layers and a process for their manufacture and for the production of contact and / or interconnect areas to indicate that the deficiencies of the prior art do not have and which can be produced uncritically.

The task is accomplished through the distinctive means of Claims resolved. The essence of the invention consists of the use of high-impedance Noble metal oxide or noble metal alloy oxide layers, those by plasma activated methods, in particular Atomization produced in an oxygen-containing atmosphere  be, and by local heating, e.g. B. means Laser, electron or ion beams to be conductive Metal layers are reducible. The production the oxide layers mentioned can be used without additional substrate heating and especially in the separation of HTSL layers are process compatible with these in situ done without intermediate ventilation. This will cause contamination of the functional layers with the layer properties influencing atmospheric components avoided, so that the layers also compared to thermal Load of commonly used ion beam structuring processes are effectively protected. Especially in Case of HTSL layers as functional layers, whose crystal structure has a strongly anisotropic layer-like Has structure with high diffusion constants, can in the case of layer-like stratification parallel to the substrate plane the inventive method and the after manufactured passivation layer effective for secondary passivation, should mean for coating the after Structuring exposed side areas of the functional layer can be used without harmful intermediate ventilation of the coating apparatus is required. The advantages of the invention Contact and / or interconnect area production also remain received with a secondary passivation.

A particular advantage of the invention is that the invention Conversion of the passivation layer into Contact and / or interconnect areas can take place in air and does not have to be carried out under vacuum conditions, which in turn is particularly useful when using HTSL layers functional layers, based on their stability, to be emphasized as particularly favorable.

To illustrate the invention in more detail, the following Serve non-limiting embodiment of the invention, that of the passivation and contact production of thin-film HTSL components going out. It shows

Fig. 1 shows a characteristic example of the change in the transition temperature of a high-Tc superconductor sample without inventive passivation layer after a heat treatment.

FIG. 2 shows the same measurement of the magnetic susceptibility as in FIG. 1, but with a HTSL sample and passivated according to the invention

Fig. 3 for a characteristic curve of the drag reduction Passivierungsschichtbereiche selected for manufacture. B. of contacting areas in the passivation layer itself.

For the production of HTSL components such as SQUIDs, Bolometers and a. become stripline structures from epitaxial REBaCuO layers on single-crystalline substrates like MgO, Si, SrTiO₃ needed. To make the epitaxial HTSL layers become reactive sputtering of ceramic REBaCuO targets using a dc magnetron used and a substrate temperature of 750 to 800 ° C selected. The layer is deposited using a Discharge power of 100 W in an O₂ / Ar mixture with a mixing ratio of 1:10 at a total pressure from 15 Pa. For layer thicknesses of 100 nm, the coating time is approx. 1 h needed. After switching off the magnetron sputter source the oxygen particle pressure becomes 50 kPa raised and the layers to room temperature within an hour cooled down.  

Subsequently, the substrate is pivoted by means of a rotary lead through a second magnetron with a platinum target. The platinum target is atomized with a power of 80 W in an O₂ / Ar mixture of 1: 1 at a total pressure of 1 Pa. In this case, a platinum oxide layer according to the invention is deposited on the HTSL layer with a specific resistance of 100 Ωcm, which can be increased or decreased with the aid of the O₂ / Ar mixing ratio as required, ie depending on the required electrical insulation values. A coating time of 10 minutes is required to deposit a platinum oxide layer 300 nm thick. After this coating, the HTSL layers are stable in relation to temperature treatments in air up to tempering temperatures T _t of 250 ° C. with regard to their superconductor properties (see FIG. 2), while they degrade strongly without a passivation layer, such as a comparison of the magnetic susceptibility measurements of (T) Show course before and after tempering for the passivated and non-passivated state (see FIGS. 1 and 2). In both figures, the curves with the reference numeral 1 denote the temperature dependence of the magnetic susceptibility of similar GdBa₂Cu₃O _y superconductor layers on SrTiO₃ substrates without aftertreatment and the curves 2 samples after one hour of heating in air at the tempering temperature T _t .

The contact and / or interconnect production according to the invention can take place before or after ion beam structuring. In the example described, the passivation layer is locally heated with a laser beam at four points for a resistance-temperature measurement of the superconductor layer, which causes an oxygen reduction in irradiated areas. As a result, areas for contacting are generated within the passivation layer itself without having to open the same and subsequent cleaning steps. In Fig. 3, the uncritical resistance setting depending on the laser energy used is shown as an example. The starting point for the curve profile shown is the electrical resistance between two contacts of a passivated GdBa₂Cu₃O _y superconductor layer on a SrTiO₃ substrate. The contacts were made by scanning the platinum oxide passivation layer with an argon laser beam of power N on the contact area of 0.3 mm × 2 mm. Suitable contacts were made for 0.15 <N <0.3W. Smaller capacities lead to incomplete reduction of PtO _x , larger ones to degradation of the superconductor layer underneath. The absolutely required performance depends on the passivation layer thickness, the type of noble metal oxide layer and the type of thermal radiation source used and can be easily adapted to the respective conditions in individual cases. The contact resistance between the superconductor and a platinum contact produced by reduction can also be found to be minimized by the conditions of the laser radiation.

The main advantages of the invention are that by a high-resistance cover of thin functional Layers (in the example HTSL layers) with precious metal oxide or precious metal alloy oxide layers both a good passivation as well as an easy way of contacting by reducing the oxide layer over a local warming is made possible. This is a process compatible Low temperature deposition of the oxide layers without intermediate ventilation, d. H. without contamination  the layer surface of the functional layer takes place, giving a contact and / or Production of interconnects possible in one process step is. The invention is of particular importance for the Increasing the long-term stability of HTSL thin-film components.

The invention is not based on the use of HTSL layers limited as functional layers. The Use on other functional layers wherever there is no extremely high insulation Passivation layers are required.

Claims (8)

1. Passivation layer for protection against contamination, chemical and / or physical changes in functional layers of components, characterized in that the passivation layer is consistently formed from a predominantly platinum and / or gold-containing noble metal oxide or noble metal alloy oxide. 2. Passivation layer according to claim 1, characterized in that Areas of the noble metal oxide or noble metal alloy oxide layer even as electrical contact and / or interconnect layers Conversion by means of local thermal oxygen deprivation are. 3. passivation layer for high-temperature superconductor (HTSL) components, characterized in that the passivation layer consistently of a predominantly platinum and / or gold containing noble metal oxide or noble metal alloy oxide is. 4. passivation layer according to claim 3, characterized in that Areas of the noble metal oxide or noble metal alloy oxide layer even as electrical contact and / or interconnect layers Transformation are formed. 5. Process for producing a passivation layer for protection against contamination, chemical and / or physical Changes in functional layers of components, characterized in that immediately after production of a Precious metal oxide or platinum and / or gold containing predominantly Precious metal alloy oxide layer by reactive magnetron sputtering a structuring of these and the functional layer is made.   6. The method according to claim 5, characterized in that a repeated coating after structuring exposed side Areas of the functional layer (s) with the noble metal oxide or noble metal alloy oxide layer is made. 7. The method according to any one of claims 5 or 6, characterized characterized in that the noble metal oxide or noble metal alloy oxide layer local thermal exposure for as long as and with subjected to such energy until electrical conductivities of the affected areas of the passivation layer can be reached, the their use as contact and / or interconnect layers enable. 8. Method for producing a passivation layer with areas different electrical conductivity on HTSL thin layers, characterized in that in situ after the production of the HTSL thin film on this one deposit at least one, Precious metal oxide or platinum and / or gold containing predominantly Precious metal alloy oxide layer by means of known plasma-activated Coating process is done, and local Areas of the layer produced in this way, if necessary with interposition usual masking and structuring steps, a temperature application as long and subject to such energy until electrical conductivities of the affected areas the passivation layer can be achieved, the use thereof as Enable contact and / or interconnect layers.