Highly conductive lead adjoining MR stripe and extending beyond stripe height at junction
View Patent ↗Magnetoresistive (MR) sensors are disclosed that have leads with reduced resistance, improving the signal-to-noise ratio of the sensors. The leads have broad layers of highly conductive material for connection to MR structures, as opposed to thin wires of highly conductive material or broad layers of resistive material, lowering the resistance of the leads. The low-resistance leads can be formed without increasing the shield-to-shield spacing, providing highly sensitive and focused MR sensors.
1. A device comprising:
a solid body having a surface;
a magnetoresistive structure disposed in said body adjacent to said surface, said magnetoresistive structure extending a first amount in a first direction that is substantially parallel to said surface, extending a second amount in a second direction that is substantially perpendicular to said surface, and extending a third amount in a third direction that is perpendicular to said first and second directions, with said third amount being less than each of said first and second amounts;
a first lead layer disposed in said body adjacent to said surface and made of material having a resistivity of less than 6×10 −8 Ωm at room temperature, said first lead layer having a first edge extending in said second direction so that a first portion of said first edge adjoins said magnetoresistive structure and a second portion of said first edge is removed from said magnetoresistive structure and adjacent to the first portion, said first portion of said first edge having a first length, said second portion having a second length, the first length and the second length having a combined first and second length greater than the second amount; and
a second lead layer disposed in said body adjacent to said surface, separated from said first lead layer in said first direction and made of material having a resistivity of less than 6×10 −8 Ωm at room temperature, said second lead layer having a second edge extending in said second direction so that a first part of said second edge adjoins said magnetoresistive structure and a second part of said second edge is removed from said magnetoresistive structure and adjacent to the first part, the first part and the second part of the second edge having a combined length greater than the second amount; and
first and second metal layers each adjoining the first lead layer, extending along the first portion and having an electrical resistivity greater than 6×10 −8 Ωm at room temperature, the first metal layer having a thickness in the third direction that is at least about as large as a lead thickness of the first lead layer;
wherein said first portion is separated from said first part by a distance that is substantially identical to that separating said second portion from said second part.
2. The device of claim 1 , further comprising first and second ferromagnetic layers disposed adjacent to said magnetoresistive structure, with said magnetoresistive structure and said lead layers disposed between and electrically insulated from said first and second ferromagnetic layers.
3. The device of claim 1 , wherein said second portion is substantially parallel to said second part.
4. The device of claim 1 , wherein said first and second edges are formed by ion beam etching.
5. A device comprising:
a solid body having a surface;
a magnetoresistive structure disposed in said body adjacent to said surface, said magnetoresistive structure extending a first amount in a first direction that is substantially parallel to said surface, extending a second amount in a second direction that is substantially perpendicular to said surface, and extending a third amount in a third direction that is perpendicular to said first and second directions, with said first amount and said second amount each being greater than said third amount;
a first lead layer disposed in said body adjacent to said surface and having a first edge adjoining said magnetoresistive structure, said first edge extending a fourth amount in the first direction, said first lead layer including at least one of gold, copper, silver, aluminum, beryllium, magnesium, molybdenum and tungsten;
a second lead layer disposed in said body adjacent to said surface and having a second edge adjoining the magnetoresistive structure and extending a fifth amount in the second direction, the second lead layer including at least one of gold, copper, silver, aluminum, beryllium, magnesium, molybdenum and tungsten; and
a pair of metal layers, each of the pair of metal layers adjoining the first lead layer, having an electrical resistivity greater than 6×10 −8 Ωm at room temperature, and extending along the first edge by approximately the fourth amount, at least one of the pair of metal layers having a thickness in the third direction that is at least about as large as a lead thickness of the first lead layer;
wherein said fourth amount and the fifth amount are each greater than said second amount.
6. The device of claim 5 , wherein said first lead height is greater than said first amount.
7. The device of claim 5 , wherein said magnetoresistive structure and said first lead layer are disposed between and electrically insulated from a pair of ferromagnetic layers.
8. The device of claim 5 , wherein the first lead layer has a lead cross section and the magnetoresistive structure has a magnetoresistive structure cross section, and wherein the first lead layer cross section is at least two orders of magnitude greater than the magnetoresistive structure cross section.
9. A device comprising:
a solid body having a surface;
a magnetoresistive structure disposed in said body adjacent to said surface and having a magnetoresistive structure cross section, said magnetoresistive structure extending a first amount in a first direction that is substantially parallel to said surface, extending a second amount in a second direction that is substantially perpendicular to said surface, and extending a third amount in a third direction that is perpendicular to said first and second directions, with said first amount and said second amount each being greater than said third amount;
a first lead layer disposed in said body adjacent to said surface and having a first edge adjoining said magnetoresistive structure, the first edge extending a fourth amount in the second direction, the fourth amount being greater than the second amount, the first lead layer being made of material having an electrical resistivity of less than 6×10 −8 Ωm at room temperature and having a lead layer cross section;
a second lead having a second lead layer disposed in said body adjacent to said surface and having a second edge adjoining said magnetoresistive structure, the second edge extending a a fifth amount in the second direction, the fifth amount being greater than the second amount, the second lead layer being made of material having an electrical resistivity of less than 6×10 −8 Ωm at room temperature; and
a pair metal layers, each of the pair of metal layers adjoining said first lead layer, having an electrical resistivity greater than 6×10 −8 Ωm at room temperature, and extending along the first edge by approximately the fourth amount, at least one of the metal layers having a thickness in the third direction that is at least about as large as a lead thickness of the first lead layer;
wherein said lead cross section is at least two orders of magnitude greater than the magnetoresistive structure cross section.
10. The device of claim 9 , wherein said magnetoresistive structure and said first lead layer are disposed between and electrically insulated from a pair of ferromagnetic layers.