DD285119A5 - METHOD FOR PRODUCING AN ELECTROTHERMICALLY HIGHLY DURABLE DENSITY RESISTANT ELEMENT - Google Patents

Abstract

The invention relates to a method for producing an electrothermally highly resilient Duennschichtwiderstandselementes z. B. can be used for thermal printer. According to the invention, a double layer is sputtered onto the substrate for the production of the resistance layer. It is assumed that a CrSiW target and a NiCr target with a defined composition. The sputtering processes are carried out in an argon-nitrogen-oxygen mixture. In this case, the sputtering power, the partial pressures and the sputtering time are adjusted so that the ratio of the condensation rates of target material and reaction components for CrSiW and for NiCr is at nitrogen or at oxygen at certain values. The ratio of the surface resistances of the partial layers is also set in a defined manner. During structuring, the double layer must be retained at least in the area of the contacts. Finally, the layer system is subjected to a heat treatment at a temperature which is below the crystallization temperature for CrSiWN (O). {Duennschichtwiderstandselement heavy duty; Sustrat; Double layer; CrSiW target; NiCr target; Condensation rates; Argon-nitrogen-oxygen-mixture; Sub-layers; Flaechenwiderstaende}

Description

Characteristic of the known state of the art

There are a variety of thermal solutions for the heat-generating resistors in thermal print heads, IR radiation transmitters u. Ä. The general state of development goes to thermally higher resilient resistance layers. For favorable operating properties, a small temperature coefficient, a high oxidation resistance of the layers and a positive aging drift are additionally necessary. In the art is generally estimated that conventional resistance layer materials such. B. CrSiO and TaN ₂ not sufficient high temperature stability, as it is necessary for operation with very short heating pulses or for very high service life requirements, (see, for example, K. Nunomura et al., JEEE Trans. CHMT-6 [1983) 377). Therefore, alternative variants have been developed: Ta-SiC ₁ Ta-Si, ZrN and BaRuO ₁ . With regard to thermal resistance and electrical parameters of the resistive layer, the deficiency of these known solutions lies in the fact that only special requirements, and these in most cases also inadequate, have been met. Ta-SiC has a maximum temperature resistance of 500 ⁰ C (K. Nunomura, inter alia, IEEE Trans. CHMT-6 [1983] 377). Ta-Si and ZrN have a low oxidation resistance and thus high demands are made on the topcoat quality (S. Sato et al., Proc.33 ^th Electronic Components Conf., 1983, pp. 169ff., And T. Nozewa et al., Proc.35 ^lh Electronic Components Conf. 1985, p. 304 ff.). As with all other variants mentioned, the temperature coefficient of BaRuO ₃ is very high at 500 to 900 ppm / K (O.Takikawa et al., Proz, 36 ^lh Electronic Components Conf. 1986, p.214ff.). For the production of light reactive sputtering processes are also common in the reaction gas mixture argon and nitrogen.

Known thermal printheads according to US-PS 4 343 886 with CrSi as a resistor material, due to the use of non-reactive CrSi only up to 500 ⁰ C can be loaded. When oxygen is used as the reactive gas, there is a very large fluctuation range of the temperature coefficient of resistance in the range of -310 to +500 ppm / K. These layers can be loaded only up to 500 ⁰ C, as the resistance change is otherwise prohibitively large (EP0079585). As a bonding layer to the Al wiring layer, a Cr layer is used in both known thermal printing heads based on CrSI. The protective layer system must in both cases due to the poor stability of a complex combination layer SiO ₂ ATa ₂ O ₅ exist.

For the reproducible control of the contact with the conductive line layer is CrSi Al jointly heat-treated (for. Example, at 400 ° C to 500 ⁰ C in air in EP0079585). Without a conductive track CrSi oxidizes superficially so strongly that considerable and also strongly fluctuating contact resistance contributions occur. The negative influences are exacerbated by the fact that in the direct current transition between CrSi and contact layer, the zone of the current breakthrough is unfavorably small and thus also electrothermally unfavorable.

The limit of the heat treatment temperature of a layer system with Al is reached because of the low melting point of Al at about 550 ⁰ C, so that any for heat resistive advantageous higher heat treatments can not be carried out so.

Object of the invention

The aim of the invention is to find a method for the production of thin-film resistor elements for thermal applications, in which they achieve a long service life even with short heating pulses, the contact while avoiding high current densities in the current transition from the resistance to the contact layer is reproducible and the need one

Cover layer does not exist or have to be made in handling or wearing layers only low tightness requirements.

Explanation of the essence of the invention The invention has for its object to find a method in which the resistance layers among the Contact layers with and without cover layer can be thermally highly loaded, a small temperature coefficient

and the resistance change in aging are positive and in the contact area, the zone of

Stromdurchbruch is expanded as possible. According to the invention the object is achieved in that for the preparation of the resistive layer on the substrate a

special double layer is sputtered. In this case, a CrSiW target in which the Si content is between 70 and 80 at.% And the W content is between 0.5 and 5 at.%, And a NiCr target in which the Ni Content 50 at.% Is to be assumed. The

Sputtering processes are to be carried out in an argon-nitrogen-oxygen mixture. Essential is the correct adjustment of the Kondonsationsraten of the target material and the Reaktivgaskomponerv ¹ en, by

appropriate choice of the sputtering power and the partial pressure has to be made. The ratio of Kondonsationsraten of

Target material and reactive gas component must be for CrSiW at nitrogen between 1.5 and 2.5 and at oxygen above 10

lie. This gives a layer containing about 30 at.% Nitrogen and less than 9% oxygen.

The addition of tungsten reduces the necessary degree of reactivity of the layer. This will be a much better Guaranteed reproducibility of the resistivity of the CrSiWN layer. CrSiWN layers this Degree of reactivity and the W content are temperature stable up to 600 ⁰ C. If the Reaktmtätsgrad the layer is too low, achieved

not the demanded resistivity and required temperature stability. If the degree of reactivity is too high, the resistivity increases abruptly. The ratio of the condensation rates of target material and

Reactive gas component must be between 3 and 5 for NiCr at nitrogen and oxygen. These are sputtering power and Choose coating time so that the ratio of surface resistances of the layers of the CrSiW and the NiCr target as 5-10 to 1 behave. If these values are observed, the advantageous electrothermal properties, ie

high thermal capacity and a favorable current distribution through a wide zone of Stromdurchbruch in Kontakterreicht.

At the double layer then required structuring processes or other processes can be performed. there

The structuring must be carried out so that at least in the region of the contacts, the double layer is maintained. Finally, the bilayer is subjected to a heat treatment which is below the crystallization temperature of the CrSiWN. The

Application of contact layers and, where appropriate, of solder layers and of cover layers can then be carried out in general

usually done. Advantageous is a regulation of the reactive gas partial pressure by a gas inlet system.

The advantage is that resistance elements with and without cover z. B. with continuous current load of 5h in air and

a current intensity, which leads to a heating of the resistors to 600 ⁰ C, resistor} changes of less than 10% have, the magnitude of the temperature coefficient of resistance below 200ppm / K is and the resistance changes of the heating elements are positive in aging.

Thus, a long life of the resistive elements is achieved even with pulse heating with short pulse times. It

Low requirements can be placed on an action or wear protection layer.

It is achieved a long life of the thermal print heads at high printing speed. embodiment The invention will be explained in more detail below using an exemplary embodiment. A CrSiW target of composition 24 at.% Cr, 74 at.% Si and 2At.% W and a NiCr target of the composition are used Composition 50:50. Of these, a double layer is deposited on a substrate of glazed Al ₂ O ₃ ceramic. For the CrSiW is through

a sputtering power density of 2.2 W / cm ² and a reactive gas partial pressure of 1.2 10 " ³ mbar a ratio of

Condensation rates of CrSiN and nitrogen of 2.0 set and kept constant by a gas inlet system. oxygen

is not fed. When sputtering the CrNi target air is introduced as a reaction gas in the plasma chamber, whose

Partial pressure is about 2.67 mPa. The controlled partial inlet of the air through the plasmatron leads to an activation of the Nitrogen, so that the ratio of the condensation rates of the target material to that of the nitrogen and the oxygen 3.0

and the ratio of nitrogen to oxygen is 2: 1.

At a sputter power density of 1 W / cm ² and 22 min. Coating time (at a distance source / substrate of 10cm and

moved substrate with a ratio of coating time / dark cycle of 1: 7), a ratio of the surface resistances of the sub-layers of CrSiW to NiCr5: 1 (1000/0: 200/0) is achieved.

For structuring, the heater region of the layers is implemented using photolithography with positive photoresist Slit exposure free-blown and the CrNi topcoat removed. In the area of the contacts, the double layer is retained. Finally, the layer system is subjected to a heat treatment at 550 ° C. This temperature is below the Crystallization temperature for CrSiWN (O). The annealing leads to a desired segregation and recrystallization of the CrNi Layer. This results in a semiconducting CrNi oxide at the surface and a metallic, recrystallized NiCr phase at the surface Border to CrSiW.

Claims (1)

A method for producing a thin electrochemically heavy-strength sheet resistance element, which consists of a substrate with resistance and contact layers and optionally cover layers and in which the thermally highly stressed layer parts are prepared by a reactive sputtering process in a mixture of argon with the reactive gas components nitrogen and optionally oxygen and which are structured and annealed, characterized in that first in a reactive sputtering process, a double layer with two targets, consisting of a CrSiW alloy with 70-80 at .-% Si and 0.5-5 at .-% W and NiCr with 50 At .-% Ni, wherein the sputtering power, the partial pressures and the sputtering time are to be adjusted so that the ratio of condensation rates of target material and reactive gas components for CrSiW at nitrogen between 1.5 and 2.5 and at oxygen above 10 and for NiCr at nitrogen and oxygen is between 3 and 5 and that the ratio of the surface resistances of the sublayers CrSiW- and the NiCr target, such as 5-10 behaves to 1, that the double layer is structured so after the ^r eaktiven sputtering that the double layer is retained at least in the area of the contacts and this layer system then a heat treatment at a temperature below the crystallization temperature for CrSiWN (O) is exposed. Field of application of the invention The invention relates to a method for producing an electrothermally heavy-duty thin-film resistor element. It can be used for thermal printers in thin film resistive elements.