System and apparatus for electrically testing lead-to-lead shorting during magnetoresistive sensor fabrication
View Patent ↗Built-in electrical test structures are measured for lead-to-lead shorting during the fabrication of MR elements on a wafer. The test structures are fabricated in the same fashion as the MR elements, however, the active sensor region or track width is omitted from the test structures. Thus, the left and right leads for each test structure are electrically isolated from each other in their “track width” region. If there is lead-to-lead shorting on a test structure, then the left and right leads are electrically connected in the track width region. A simple resistance measurement between the left and right leads determines the extent of any lead shorting by giving a quantitative resistance value.
1. A system for detecting electrical shorts formed during the fabrication of MR heads on semiconductor wafers, the system comprising:
a semiconductor wafer;
a plurality of MR heads formed on the semiconductor wafer, each MR head having a pair of electrical leads that defines a track width therebetween, and a sensor that spans the track width between the electrical leads so that the electrical leads are electrically connected to each other;
at least one test structure formed on the semiconductor wafer with the plurality of MR heads, the test structure having a pair of test structure electrical leads that define a test structure track width therebetween, the test structure being void of a sensor that spans the test structure track width between the test structure electrical leads so that the test structure electrical leads are electrically isolated from each other in the test structure track width; and
means for electrically detecting and quantitatively measuring an electrical short formed between the test structure electrical leads.
2. The system of claim 1 , wherein said at least one test structure comprises a plurality of test structures, and the plurality of test structures is interspersed among the MR heads on the semiconductor wafer.
3. The system of claim 2 , wherein the plurality of test structures comprises less than 100 of a number of the MR heads.
4. The system of claim 1 , wherein the semiconductor wafer is rejected if the electrical short has a relatively low electrical resistance, and the semiconductor wafer is accepted if the electrical short has a relatively high electrical resistance.
5. An apparatus for detecting electrical shorts formed during the fabrication of a product on a wafer, the apparatus comprising:
a wafer;
a plurality of products formed on the wafer, each product having electrical leads that define a space therebetween, and a device that spans the space between the electrical leads that electrically connects the electrical leads;
a test structure formed on the wafer with the plurality of products, the test structure having test structure electrical leads that define a test structure space therebetween, the test structure being void of a device that spans the test structure space between the test structure electrical leads so that the test structure electrical leads are electrically isolated, such that an electrical short formed between the test structure electrical leads is electrically detectable and quantitatively measurable; and wherein
the wafer comprises a semiconductor wafer, the products comprise MR heads, the space comprises a track width, the device comprises a sensor, and the test structure space comprises a test structure track width.
6. The apparatus of claim 5 , wherein the test structure comprises a plurality of test structures, and the plurality of test structures are interspersed among the MR heads on the semiconductor wafer.
7. The apparatus of claim 6 , wherein the plurality of test structures comprises less than 1% of a number of the MR heads.
8. The apparatus of claim 5 , wherein the semiconductor wafer is rejected if the electrical short has a relatively low electrical resistance, and the semiconductor wafer is accepted if the electrical short has a relatively high electrical resistance.