Research On Broadcast-scan-based Low-power Test Compression

With the development of semiconductor technology,the structure of circuit is increasingly complex and the scale is larger and larger.Thus,test is necessary to guarantee the yield and reliability of circuit.Testing a large-scale circuit requires a vast number of test data.What's more,the power dissipation during test is much higher than normal function power and excessive power will cause irreversible structural damage of the circuit under test.Therefore,circuit test is a challenge of semiconductor industry.Aimed at this problem,this thesis makes research on reducing both test power and test data volume simultaneously.A test data compression method which is based-on tri-state-controlled low-power intermittent broadcast scan is proposed.Scan slices are classified into three types in the proposed method.X-filling for capture power reduction is conducted first on sparse scan slice,then X-filling for shift power reduction on reference scan slice.Each scan slice is flagged by a bit of tri-state data according to its type.Only reference chain is stored in the proposed method,while the remaining scan slices are replaced by their flag bits.As experiments show,the proposed method achieves an average of 70.83% compression ratio which implies an effective reduction of test storage.The capture-power is reduced at least 20% while the shift power is effectively optimized simultaneously.A low-power BIST scheme which is based-on randomly-group broadcast scan is proposed.The proposed scheme groups multiple scan chains randomly.Each group contains a reference chain and several shared chains,both of which are divided into segments of the same length.Shared chains are loaded with constant value in most shift cycles except for shift cycles for the last scan segments.The hardware implementation of randomly-group broadcast scan is simple,because only some 2-1 multiplexers are needed.What's more,the grouped signal is generated by a register and a XOR network and only one additional test channel is needed.As the experiments show,the proposed scheme can optimize shift-power without the loss of fault coverage.