Test structure for detection of defect devices with lowered resistance

A test method, comprising the steps of:

• measuring a test quantity that is dependent on a total electrical resistance between a first and second test contact pads of a test structure;
• determining a number of devices under test, which have an electrical device resistance indicating a defect state, from a measured test-quantity value,
• wherein the test structure includes respective first test resistors and respective second test resistors connected in series between the respective devices under test and either the first or second test contact pad,
• wherein the measurement step further comprises measuring a current flow between the first and second test contact pads at a given voltage between the first and second test contact pads,
• wherein the determining step further comprises:
• finding a particular device under test, wherein a current flow corresponding to the particular device under test is the largest from a subset of devices under test of the test structure, and wherein the current flow corresponding to the particular device under test is smaller than the measured current flow, and storing or outputting an identifier of the respective device under test;
• generating a difference value by subtracting the current flow corresponding to the particular device under test from the measured current flow;
• and
• repeating the finding step using the difference value, until the generated difference value reaches zero.

A testing method for testing at least two devices, wherein both devices include a first electrical device resistance in a non-defect state and a second electrical device resistance in a defect state, the first electrical device resistance being higher than the second electrical device resistance, the method comprising:

• connecting the at least two devices under test in parallel and to a first test contact pad with a first conducting line;
• connecting the at least two devices in parallel to a second test contact pad with a second conducting line;
• connecting respective first test resistors in series between the respective devices under test and either the first or second conducting line, the first test resistors having known respective electrical test resistances such that a total electrical resistance between the first and second test contact pads is indicative of the number of devices under test;
• connecting respective second test resistors in series between the respective devices under test and the first or second conducting line;
• measuring a current flow between the first and second test contact pads at a given voltage between the first and second test contact pads;
• and
• determining a number of devices under test, which have an electrical device resistance indicating a defect state, from a measured test-quantity value, wherein the determining step further comprises:
• finding a particular device under test, wherein a current flow corresponding to the particular device under test is the largest from a subset of devices under test of the test structure, and wherein the current flow corresponding to the particular device under test is smaller than the measured current flow, and storing or outputting an identifier of the respective device under test;
• generating a difference value by subtracting the current flow corresponding to the particular device under test from the measured current flow;
• repeating the finding step using the difference value, until the generated difference value reaches zero.