Process for forming a magnetoresistive sensor for a reading head

DETAILED DESCRIPTION OF THE INVENTION With reference now to FIG.
1, the reading head 10, including the active element 12 that serves as the magnetic sensor, is shown positioned over a portion of the magnetic medium 14 of a disk in whose tracks is stored the information to be read.
The information is read by sensing the external vertical magnetic field H created above the transition regions 15 between directional changes of the aligned magnetic moments 16A, 16B that extend along the track of the magnetic medium 14.
The active element 12 is formed by a Corbino disk-like structure that includes a layer of semiconductive material that exhibits a strong magnetoresistive effect.
The active element further includes a first inner electrode 18A that is surrounded by the semiconductive material and a second outer electrode 18B that surrounds the inner electrode, in the manner characteristic of a Corbino disk.
Typically, the outer electrode 18B, which is shown rectangular in shape, has a long dimension of about 5 microns to match approximately the width of a track of the magnetic medium and a narrow dimension of about 500 to 1,000 Angstroms.
Typical dimensions of the inner electrode 18A are a length of about 1 micron and a width of about 200-400 Angstroms.
In accordance with the present invention, the active element positioned on the reading head is prepared as follows.
On the surface corresponding to the vertical edge of a reading head, such as surface 19 shown in FIG.
1, there is deposited a first conductive layer, typically of a metal, to a thickness sufficient to ensure high conductivity, and typically at least several hundred Angstroms thick, as depicted by layer 21 in FIG.
2A.
Next, a second layer of a semiconductor with a strong magnetoresistive effect is deposited, advantageously, to a thickness of at least 100 Angstroms, over the left edge portion of the layer 21 to form layer 22, as depicted in FIG.
2B.
Next, an insulating third layer, advantageously at least several hundred Angstroms thick to function well as a high resistance barrier, is deposited, as depicted by layer 23 in FIG