Binning for semi-custom ASICs
View Patent ↗A binning method is disclosed for measuring semiconductor devices for certain parameters and placing specific devices into different categories or “bins” according to the measured parameters. Measurable parameters include performance/speed-grading, power consumption, current leakage, and the ability to operate at certain temperature extremes. A method for speed grading semi-custom ASIC devices is specifically described that does not require removing partially completed wafers from the fab line for testing. To speed-grade a new boat of partially completed un-customized wafers, a small number of wafers (1 or 2) are processed to completion while being customized specifically for a customer design requiring only the slowest bin. These wafer(s) are then performance tested and the remaining wafers in the boat are certified according to these results for their performance level and placed in a wafer bank for later use.
1. A method for binning semi-custom ASIC devices including the steps of:
fabricating a boat of partially completed generic base wafers lacking customizing masking layers applied during fabrication process to customize said wafers for a particular application, wherein processing steps are applied in the same timeframe to the generic base wafers in said boat; and
taking at least one wafer from said boat of partially completed generic base wafers; and
completing the fabrication process for said at least one wafer taken from said boat of partially completed generic base wafers where the customizing masking layers implement a design requiring the least restrictive bin relative to a parameter being considered; and
testing said at least one wafer after completion of the fabrication process to determine which bin it corresponds to relative to the parameter being considered, wherein the testing of said wafer taken from the boat is done prior to completion of the fabrication process for the remaining partially completed wafers in said boat; and
assigning the remaining un-customized and un-tested wafers in said boat of partially completed generic base wafers to a specific wafer bin according to the test results for said at least one wafer; and
saving the remaining wafers in said boat of partially completed generic base wafers for use at a later time with designs that require parameters supported by the remaining wafers in said boat of partially completed generic base wafers.
2. The method of claim 1 further including the steps of:
simulating a new design compared to the rated parameter ranges for the available wafer bins to determine which bins are characterized with rated parameters that meet the requirements of the new design; and
completing the processing for at least one previously assigned, un-customized wafer to customize the wafer for said new design, said un-customized wafer taken from a wafer bin whose rated parameters support the requirements of said new design.
3. The method of claim 2 where the rated parameter ranges for wafers in a particular bin are different than the parameter ranges measured during the testing step of claim 1 , such that a guard band is provided.
4. The method of claim 1 , where the parameter being considered is operational speed.
5. The method of claim 1 , where the parameter being considered is power consumption.
6. A method for binning semi-custom ASIC devices including the steps of:
fabricating a boat of partially completed generic base wafers lacking customizing masking layers applied during fabrication process to customize said wafers for a particular application, wherein processing steps are applied in the same timeframe to the generic base wafers in said boat; and
taking at least one wafer from said boat of partially completed generic base wafers; and
completing the fabrication process for said at least one wafer taken from said boat of partially completed generic base wafers where the customizing masking layers implement a design requiring the least restrictive bin relative to a parameter being considered; and
testing said at least one wafer after completion of the fabrication process to determine which bin it corresponds to relative to the parameter being considered, wherein the testing of said wafer taken from the boat is done prior to completion of the fabrication process for the remaining partially completed wafers in said boat; and
assigning the remaining un-customized and un-tested wafers in said boat of partially completed generic base wafers to a specific wafer bin according to the test results for said at least one wafer; and
saving the remaining wafers in said boat of partially completed generic base wafers for use at a later time with designs that require parameters supported by the remaining wafers in said boat of partially completed generic base wafers; and
simulating a new design compared to the rated parameter ranges for the available wafer bins to determine which wafer bins are characterized with rated parameters that meet the requirements of the new design; and
completing the processing for at least one previously assigned, un-customized wafer to customize the wafer for said new design, said un-customized wafer taken from a bin whose rated parameters support the requirements of said new design.
7. The method of claim 6 , wherein the rated parameter ranges for wafers in a particular bin are different than the parameter ranges measured during the testing step such that a guard band is provided, and wherein the parameter being tested is operational speed.
8. A method for binning semi-custom ASIC devices, said method comprising:
fabricating a boat of partially completed generic base wafers lacking customizing masking layers applied during fabrication process to customize said wafers for a particular application, wherein processing steps are applied in the same timeframe to the generic base wafers in said boat; and
taking at least two wafers from said boat of partially completed generic base wafers; and
completing the fabrication process for said at least two wafers taken from said boat of partially completed generic base wafers where the customizing masking layers implement a design requiring the least restrictive bin relative to a parameter being considered; and
testing each of said at least two wafers after completion of the fabrication process to determine which bin said at least two wafers correspond to relative to the parameter being considered, wherein the testing of each wafer taken from the boat is done prior to completion of the fabrication process for the remaining partially completed wafers in said boat; and
determining a degree of deviation and a lowest performance level between said at least two wafers according to test results of testing each of said at least two wafers; and
assigning the remaining un-customized and un-tested wafers in said boat of partially completed generic base wafers to a specific wafer bin associated with the lowest performance level determined from said test results; and
saving the remaining wafers in said boat of partially completed generic base wafers for use at a later time with designs that require parameters supported by the lowest performance level.
9. The method of claim 8 further comprising:
simulating a new design compared to the rated parameter ranges for the available wafer bins to determine which bins are characterized with rated parameters that meet the requirements of the new design; and
completing the processing for at least one previously assigned, un-customized wafer to customize the wafer for said new design, said un-customized wafer taken from a wafer bin whose rated parameters support the requirements of said new design.