Pattern for evaluating electric characteristics, method for evaluating electric characteristics, method for manufacturing semiconductor device and method for providing reliability assurance
An increased area of an element transistor to be evaluated causes an increased leakage current due to a tunnel effect, leading to a reduced accuracy in predicting a TDDB lifetime. A test element group (TEG) 1 is a pattern for evaluating electric characteristics, comprising a plurality of unit transistors T 11 , T 12 , T 13 , T 21 , T 22 , T 23 , T 31 , T 32 , T 33 , which are arranged so as to form a lattice-shaped pattern. Each of the unit transistors comprises a gate dielectric serving as an object to be evaluated, and source region and drain region, which are a short-circuited.
1 . A pattern for evaluating electric characteristics of a transistor, comprising a plurality of unit transistors including a gate dielectric and a source and drain region arranged to form a lattice-shaped arrangement, wherein said source and drain region is mutually short-circuited.
2 . The pattern for evaluating electric characteristics of a transistor as set forth in claim 1 , wherein said source and drain region of each of said unit transistor is separated from said source and drain region of others of said unit transistors.
3 . A method for evaluating electrical characteristics utilizing the pattern for evaluating electric characteristics as set forth in claim 1 , comprising:
applying a first voltage to said gate dielectric of said plurality of unit transistors;
measuring a gate current for each of said a plurality of unit transistors when a second voltage is applied to said gate dielectric, after applying said first voltage;
determining a magnitude relation between a level of said gate current and a predetermined reference value; and
deciding that a breakdown is caused, if the level of said gate current exceeds said reference value according to a result in said determining the magnitude relation.
4 . The method for evaluating electrical characteristics as set forth in claim 3 , wherein, in said applying the first voltage and in said measuring the gate current, said first and said second voltages are applied so as to form an inversion layer in the semiconductor surface under said gate dielectric.
5 . The method for evaluating electrical characteristics as set forth in claim 4 , wherein each of said unit transistors is an n-channel, and wherein, in said applying the first voltage and in said measuring the gate current, said first and said second voltages are applied so as to provide a potential at the gate electrode that is higher than the potentials at said source and drain region.
6 . The method for evaluating electrical characteristics as set forth in claim 4 , wherein each of said unit transistors is a p-channel, and wherein, in said applying the first voltage and in said measuring the gate current, said first and said second voltages are applied so as to provide a potential at the gate electrode that is lower than the potentials at said source and drain region.
7 . The method for evaluating electrical characteristics as set forth in claim 3 , wherein said applying the first voltage, said measuring the gate current, said determining the magnitude relation and said deciding that a breakdown is caused are repeated until it is decided that a breakdown is caused in said deciding that a breakdown is caused.
8 . A method for manufacturing a semiconductor device, comprising:
forming a plurality of unit transistors so as to be arranged to form a lattice-shaped pattern, each of said unit transistors having a gate dielectric; and
forming an interconnect so as to short-circuit between a source and drain region of each of said unit transistors.
9 . The method for manufacturing the semiconductor device as set forth in claim 8 , wherein said plurality of unit transistors are formed on a scribe line of a semiconductor wafer.
10 . The method for manufacturing the semiconductor device as set forth in claim 9 , further comprising
dicing said semiconductor wafer having said plurality of unit transistors formed therein,
wherein said plurality of unit transistors formed on said scribe line of said semiconductor wafer disappears in said dicing the semiconductor wafer.
11 . A method for providing a reliability assurance, comprising:
acquiring a breaking time of said gate dielectric in said pattern for evaluating electric characteristics for said different first voltages according to the method for evaluating electrical characteristics as set forth in claim 3 ; and
acquiring a TDDB lifetime of said gate dielectric based on said breaking time obtained for said the first voltages,
wherein a reliability assurance of a semiconductor device is provided if said TDDB lifetime is not shorter than a standardized value.