DE4438202A1 - Cobalt@-platinum@-chromium@ alloy magnetron sputtering target - Google Patents

Abstract

A magnetron sputtering target consists of a Co alloy contg. 6-20 at.% (exclusive) Pt and 10-22 at.% (exclusive) Cr, has a mainly cubic phase structure and has a magnetisation curve M(H) exhibiting an inversion point in the region H = O to 5 kA/m. with dM/dH (H=O) being less than dM/dH (inversion point) and an initial slope dM/muodH (H=O) of max. 30. Also claimed is prodn. of the above target by casting and then mechanical deformation at temps. of max. 0.8 Tsolidus.

Description

The invention relates to a target for a Magnetron sputtering device from one Co-based alloy with additions of Pt and Cr, with predominantly cubic phase components and one low initial permeability.

When magnetron sputtering are for optimization of the sputtering process permanent magnets behind the Target (cathode) arranged through which the Discharge plasma is localized. The area of Target surface over which the plasma is localized  is preferably atomized, which causes a Erosion ditch forms.

This occurs with ferromagnetic targets mainly two problems:

• - First, the magnetic flux of the permanent magnets is bundled in the target, so that a small flux can penetrate into the discharge space.
  This problem therefore requires the use of very thin ferromagnetic targets.
• - Second, the local one Cross-sectional decrease of the target during the Sputtering (erosion trench) ferromagnetic targets an increasing Magnetic flux directly over the erosion trench. As a result, a higher one occurs locally Ionization probability with which Consequence that the erosion trench becomes very narrow, associated with a very small Material yield of the target.

These problems can be mitigated by so-called roof targets are used in which no closed magnetic path exists. The target then essentially consists of three Parts, namely two roof parts and one racetrack part.

Simulation calculations show that the target exists from both roof parts and the racetrack part in this Roof target arrangement despite high fields in the  Discharge room operated at field strengths H 5 kA / m becomes. The magnetization curve of the target material in this area therefore has a significant impact the stray field entering the discharge space.

It is therefore an object of the present invention Target material based on CoPtCr alloys create that as high a stray field as possible the lowest possible magnetization in the area has lower H field strengths.

This object is achieved by a targetma material solved that the magnetization curve M (H) points with a turning point in the range 0 H 5 kA / m and for that too

The target composition preferably receives 6-20 at% Pt and 10-22% Cr. At lower Pt levels the permeability of the material is so low that no special treatment is required. At higher Pt contents are the writing and Reading properties of the layers unfavorable. this applies also for lower and higher Cr contents.

It has been shown that from about 5-10 at% Pt content the cubic fcc modification even at room temperature of the co-mixed crystal dominates and at most still small hexagonal hcp components are present. The Setting a predominantly hexagonal Target structure, such as. B. described in EP 252 478, is not possible because the martensitic  Conversion through the Pt installation either entirely has been suppressed, or only at such low levels Temperatures occur that it is of no importance (T <20 ° C).

For the same reasons, that in DE 38 19 906 described texture rolling using the hexagonal (0001) fiber texture not possible.

Different thermomechanical treatment processes were examined. Surprisingly, it was found that rolling treatment at temperatures in the range from 0.5 to 0.9 T _{solidus brought} about a marked increase in the penetration of the magnetic field over the target in accordance with FIG . X-ray phase examinations even showed a better expression of the magnetically softer and comparatively isotropic fcc phase than in the as-cast state. The magnetic characterization of the materials shows that the rolling treatment in the area of very low magnetic field strengths leads to a reduction in the magnetization generated.

At higher field strengths (H <1 to 5 kA / m) they are Magnetization curves for the as-cast state and the Rolling condition almost the same.

The reduction in magnetization at the beginning of the M (H) curve as a result of the rolling treatment leads to the S-shaped course shown schematically in FIG. 2.

In some cases the magnetization in the rolled state is slightly higher than in the cast state due to the better formation of the fcc phase even above H = 1-5 kA / m. That the magnetic field penetration is still better in the rolled state is due to the lower initial increase ΔM / ΔH compared to the cast state. For example, an alloy of the composition CoPt (11) Cr (20) was formed into a plate by melting and casting and then hot-rolled at temperatures in the range of 0.5-0.8 T _solidus .

The S-shaped curve shown in FIG. 2 resulted with an inflection point at H ≅ 1 kA / m and an initial increase (H = 0) <30.

The table below shows other examples listed:

Reference list

1 , 2 roof part
3 racetrack part
4 Fe spacer
5 magnet ↑
6 magnet ↓
7 iodine plate, Fe

Claims (2)

1. Target for a magnetron sputtering device made of a Co-based alloy with additions of Pt and Cr, characterized by a platinum content greater than 6% and less than 20 at% and a chromium content greater than 10% and less than 22 at% and predominantly cubic Phase components, the magnetization curve M (H) having an inflection point in the range 0 H 5 kA / m with and an initial slope of 30 or less. 2. A method for producing sputtering targets according to claim 1, characterized in that the targets are subjected to a mechanical deformation at temperatures of at most 0.8 T _solidus after casting.