Failure analysis vehicle for yield enhancement with self test at speed burnin capability for reliability testing
View Patent ↗A test vehicle for evaluating a manufacturing process for integrated circuits that uses a more space efficient layout of library driving cells arranged to produce circuits that exercise many interconnections that may be designed at the minimum design parameters of a manufacturing process. The cells can be configured to operate as ring oscillators increasing the effective circuit frequency of the test module allowing higher frequency circuit testing, and shortening the time it takes to perform life cycle testing. Visibly marking cells, combined with electrically isolating error prone circuit segments makes, identifying defects much more efficient. The accessibility of many testing methods allows quick location of root cause failures, which allows improvements to be made to the manufacturing process.
1. A test vehicle for an integrated circuit comprising: a plurality of unit delay cells wherein each said unit delay cell comprises a unit cell input, a unit cell output, a library driving cell, and an interconnect module wherein said unit cell input is connected to said library driving cell, said library driving cell is further connected to said interconnect module, said interconnect module is further connected to said unit cell output, said plurality of unit delay cells are connected in series to each other from said unit delay cell output to said unit delay cell input creating a chain of said unit delay cells; an input signal trace that is connected to the lead unit delay cell unit cell input of said chain of said unit delay cells; and an output signal trace that is connected to the last unit delay cell unit cell output of said chain of said unit delay cells.
2. The test vehicle of claim 1 wherein said library driving cells comprise at least one of the group comprising: a NAND gate, a NOR gate, a buffer, and an inverter.
3. The test vehicle of claim 1 wherein said interconnect modules comprise at least one of the group comprising: a capacitor, a metal comb, a serpentine, a contact chain, and a via chain.
4. The test vehicle of claim 1 wherein said input signal trace is connected to an external clock signal and said output signal trace writes a clock output signal logically correlating to said external clock.
5. The test vehicle of claim 4 further comprising: an inverting select cell wherein said inverting select cell has a ring oscillator enable input, two select cell data inputs, and a select cell data output; said select cell data output is connected to said input signal trace; one of said two select cell data inputs is connected to said external clock signal; the other of said two select cell data inputs is connected to said unit delay cell chain output signal trace; the state of said ring oscillator enable input determines which of said two select cell data inputs is inverted and sent to said select cell data output; and said output signal trace of said chain of said unit delay cells is delivered externally as said clock output signal.
6. The test vehicle of claim 5 wherein said clock output signal is further connected to one of said two select cell inputs as said external clock signal.
7. A test vehicle for an integrated circuit comprising: a plurality of unit delay cells wherein each unit delay cell comprises a plurality of unit delay cell inputs, a plurality of unit delay cell outputs, a plurality of library driving cells arranged side-by-side, and a plurality of interconnect modules arranged on overlapping layers, wherein a single unit delay cell input of said plurality of unit delay cell inputs is connected to a single library driving cell of said plurality of library driving cells, said single library driving cell being connected to a single interconnect module of said plurality of interconnect modules, said single interconnect module being connected to a single unit delay cell output of said plurality of unit delay cell outputs; said plurality of unit delay cells being connected in series to each other from said plurality of unit delay cell outputs to said plurality of unit delay cell inputs creating a chain of said unit delay cells; a plurality of input signal traces that are connected to the lead unit delay cell plurality of unit cell inputs of said chain of said unit delay cells; and a plurality of output signal traces that are connected to the last unit delay cell plurality of unit cell outputs of said chain of said unit delay cells.
8. The test vehicle of claim 7 wherein said library driving cells comprise at least one of the group comprising: a NAND gate, a NOR gate, a buffer, and an inverter.
9. The test vehicle of claim 7 wherein said interconnect modules comprise at least one of the group comprising: a capacitor, a metal comb, a serpentine, a contact chain, and a via chain.