DD159386A1 - METHOD FOR STRUCTURING MOLYBDAEN LAYERS - Google Patents

Abstract

The method of patterning molybdenum layers is applicable in semiconductor technology. The object and the object of the invention are the development of a technologically favorable etching process, which guarantees high imaging accuracy and good selectivity. According to the invention, molybdenum and then an adhesive mask are applied to a substrate which may be covered with an insulator layer. The adhesive mask is patterned and the exposed molybdenum areas are preferably passivated in an oxygen, nitrogen or air plasma with appropriate plasma performance. After removal of the adhesive mask in a further plasma process, the removal of the molybdenum layer at the locations that were previously covered with the adhesive mask, which corresponds to the "Reversal Etching".

Description

Method for structuring molybdenum layers

Field of application of the invention j

The invention relates to a method for structuring molybdenum layers by means of gas plasma etching, the main fields of application being in semiconductor technology.

'' Characteristics of the known, technical solutions

The processes of plasma-chemical etching used for dry etching have, in addition to insufficient selectivity, the disadvantage and undercutting of a photoresist applied as an adhesive mask. This also occurs in the method of A. Jacob (U.S. Patent 3,995,170), where a molybdenum layer provided with a photoresist mask is exposed to a halogen / gas plasma. The edge quality of the etched structures is not sufficient if the photoresist used to make the adhesive mask changes its shape even slightly. To overcome this problem, T .. "Yamazaki et al ..- (J .. Electrpchem., Soc: Solid State Science and Technology 126/1979, No. 10, 1794-1798), a reverse etching method is given, in which the. After the lacquer has been removed, the surface is subjected to etching attack.This process, referred to as "reversal etching", etches non-reflective Cr stencils in a CCl, / Op / Np plasma.The advantage of this process is that sharp structural edges are achieved and conversion from negative to positive etching is possible, but disadvantageous is the limited applicability to Cr and CrO 2 layers.

The same reverse structuring specifically of SiC ^ layers on Si substrates is first reported by Bersin and Reichelderfer (Solid State Technology 20/1977) Ho 4, 78-80). In this case, the etching is carried out by dry hydrogen fluoride in the gas phase, whereby the use of plasma processes to passivate the photoresist uncovered areas to protect against etching attack is required. Another disadvantage is the limitation of this method on the layer sequence SiOp-Si.

Object of the invention

The object of the invention is the development of a technologically favorable etching process for structuring molybdenum layers.

Explanation of the essence of the invention

The object of the invention is to etch molybdenum structures with high imaging accuracy and good selectivity with respect to the underlying layers.

According to the invention the object is achieved by molybdenum and then an adhesive mask are applied to a substrate that may be covered with an insulator layer. The adhesive mask, which consists for example of photoresist, is patterned, and the exposed molybdenum areas are preferably passivated in an oxygen, nitrogen or air plasma with suitable performances of the plasma. Each subsequent removal of the adhesive mask, which is preferably carried out in an oxygen or air plasma or suitable solvent, is carried out in a further plasma process, the removal of the molybdenum layer at the areas that were previously covered with the adhesive mask. Polglich is a "Reversal Etching" to observe. When etching the molybdenum layer, a chlorine-oxygen mixture is used with a chlorine content of 5 to 80 % , laughing after etching, the passivated molybdenum areas can be "repassivated" again by immersion in a suitable etching solution, ie returned to the initial state , ,

It is expedient and cost-effective to carry out the plasma passivation, the subsequent removal of the adhesive mask and the etching of the IVIolybdenum layer successively in the same reactor,

wherein designed for plasma processes pipe and Pianarreaktoren be used. ,

Advantageous is the use of insulator layers under the molybdenum, as ßie find use in semiconductor technology, for. SiO ₂ , SiJJ. or AIpO, then high selectivities can be achieved during etching.

embodiment

In the following, the invention will be explained by way of example. Bs is shown in Figure 1 das'Schema the etching process according to the invention.

In the illustration of the principle of the etching process is _s which is covered with a aigo ..- layer 2 and a molybdenum layer 3 of a Si substrate l, assumed. The molybdenum layer 3 is provided with a structured adhesive mask 4, z. B. Photo resist AZ 1350 H, provided (Fig. La).

This layer sequence is exposed to passivation of the free molybdenum areas 6 a nitrogen plasma 5 , wherein the temperature in this ÜTiederdruckplasma to ensure a high imaging accuracy must not exceed 500 ⁰ K (Fig. Ib).

After passivation of the molybdenum regions 6, an oxygen plasma is generated in the same reactor, which serves to remove the adhesive mask 4. The power converted in the oxygen plasma must be such that no passivation effect occurs on the molybdenum layer 3 released under the paint (FIG. 1c). Removal of the resist mask may also occur in acetone.

Subsequently, a plasma etching process of the molybdenum layer is performed at the locations previously covered with the resist mask 4 using a chlorine-oxygen mixture having a chlorine content of 50 % (FIG. Id).

The passivation of the molybdenum areas 6 can be reversed if necessary v / ground by the surface z. B. is briefly over-etched in buffered hydrofluoric acid solution.

Claims (7)

invention claim 1. A method for patterning molybdenum layers, characterized Characterized in that a molybdenum layer (3) ·. an adhesive mask (4) is applied and patterned, then a passivation of the free molybdenum areas (6) in a plasma (5) and after removing the adhesive mask (4) the molybdenum layer (3), the before covered with the adhesive mask (4) fer, in a plasma, preferably in a chlorine-oxygen plasma with a chlorine content of 5-80 % _{f is} removed. ,. 2. The method according to item 1, characterized in that between the substrate (l) and molybdenum layer (3) an insulator layer (2)   is applied · «. · 3. The method according to item 1 and 2, characterized in that a photoresist layer is preferably used as the adhesive mask (4). , 4. The method according to item 1 Ms 3 *, characterized in that the passivation of not with the adhesive mask (4) covered molybdenum areas (6) preferably in an oxygen, nitrogen or air plasma (5). 5 «method according to item 1 to 4», characterized in that the removal of the adhesive mask (4) preferably in an oxygen or air plasma or in suitable solvent "follows. 6. The method according to item 1 to 5, characterized in that all process steps are carried out successively without interruption in a reactor. > 7. The method according to item 1 to 6, characterized in that the passivated molybdenum areas (6) repassivated by a chemical surface treatment, preferably by means of a suitable Xtzlösungj ^{n ?} become" - See 1 page drawings -