Predicting LED parameters from electroluminescent semiconductor wafer testing
OwnerDong Cheninventor
Life of this patent
Estimating the term…
Abstract
A diode model and conductive-probe measurements taken at the wafer lever are used to predict the characterization parameters of a semiconductor device manufactured from the wafer. A current-voltage curve (I-V) model that expresses a current-voltage relationship as a function of resistance, ideality factor, and reverse saturation current is fitted to a number of conductive-probe measurement data. The current-voltage curve (I-Vd) for the device is then estimated by subtracting from the (I-V) model the product of current times the resistance produced by fitting the (I-V) model.
Claims21
A method of characterizing a semiconductor device from conductive-probe measurements performed on a semiconductor wafer from which the device is manufactured, said wafer including a p-type semiconductor layer and an n-type semiconductor layer defining a p-n junction, the method comprising the following steps:
- applying electrical stimuli to the wafer through a probe in direct contact with one of said semiconductor layers to produce conductive-probe measurement data;
- fitting a current-voltage curve (I-V) model to said conductive-probe measurement data, said model expressing a current-voltage relationship as a function of resistance;
- and
- estimating a current-voltage curve (I-Vd) for the device by removing from the (I-V) model resistance effects calculated from data generated by the fitting step;
- wherein the resistance is assumed variable with current and the resistance is calculated from measurement data points from the equation:
- R
- =
- Δ
-
-
- V
- Δ
-
-
- I
- where R is resistance, V is voltage, and I is current;
- wherein the device's forward voltage, ideality factor, resistance and reverse saturation current are calculated from the following set of equations:
- R
- i
- =
- α
- I
- i
- β
- +
- C
- I
-
- (
- i
- )
- =
- I
- 0
-
- exp
-
- (
- q
-
- (
- V
- i
- -
- I
- i
-
- R
- i
- )
- nkT
- )
- V
- d
-
- (
- i
- )
- =
- I
- i
-
- R
- i
- +
- kT
- q
-
- n
-
-
- ln
-
- (
- I
- i
- I
- 0
- +
- 1
- )
- where Vd is the device's forward voltage, I0 is reverse saturation current, n is ideality factor, and α, β, and C are constant parameters estimated by fitting N current-voltage measurement data points, (Ii,Vi), i=1K N, with a multi-parameter minimization calculation;
- and
- wherein said multi-parameter minimization calculation is carried out with the following estimator:
- Σ
-
- (
- α
- ,
- β
- ,
- C
- ,
- n
- ,
- I
- 0
- )
- =
- ∑
- i
- =
- 1
- N
-
- [
- w
- i
-
- (
- I
- i
- -
- I
- Mi
- )
- 2
- +
- 1
- w
- i
-
- (
- V
- i
- -
- V
- Mi
- )
- 2
- ]
- where Mi refers to said measurement data points, and wi is an empirical weight factor that accounts for the increased sensitivity of the current-voltage curve for the device to current at high current values and to voltage at low current values.
Apparatus for characterizing a semiconductor device from conductive-probe measurements performed on a semiconductor wafer from which the device is manufactured, said wafer including a p-type semiconductor layer and an n-type semiconductor layer defining a p-n junction, comprising:
- a conductive probe adapted to contact directly a surface of one of said semiconductor layers of the wafer for characterization measurements by electrical stimulation;
- an electrode adapted for electrical connection to another of said semiconductor layers of the wafer;
- a power source capable of applying electrical stimuli to said wafer through the probe and the electrode;
- and
- a processor that includes means for characterizing the wafer based on current-voltage measurement data produced by said electrical stimuli;
- wherein said characterizing means includes means for:
- fitting a current-voltage curve (I-V) model to said measurement data, said model expressing a current-voltage relationship as a function of resistance;
- and for
- estimating a current-voltage curve (I-Vd) for the device by removing from the (I-V) model resistance effects calculated from data generated by the fitting means;
- wherein the resistance is assumed variable with current and the resistance is calculated from measurement data points from the equation:
- R
- =
- Δ
-
-
- V
- Δ
-
-
- I
- where R is resistance, V is voltage, and I is current;
- wherein the device's forward voltage, ideality factor, resistance and reverse saturation current are calculated from the following set of equations:
- R
- i
- =
- α
- I
- i
- β
- +
- C
- I
-
- (
- i
- )
- =
- I
- 0
-
- exp
-
- (
- q
-
- (
- V
- i
- -
- I
- i
-
- R
- i
- )
- nkT
- )
- V
- d
-
- (
- i
- )
- =
- I
- i
-
- R
- i
- +
- kT
- q
-
- n
-
-
- ln
-
- (
- I
- i
- I
- 0
- +
- 1
- )
- where Vd is the device's forward voltage, I0 is reverse saturation current, n is ideality factor, and α, β, and C are constant parameters estimated by fitting N current-voltage measurement data points, (Ii,Vi), i=1K N, with a multi-parameter minimization calculation;
- and
- wherein said multi-parameter minimization calculation is carried out with the following estimator:
- Σ
-
- (
- α
- ,
- β
- ,
- C
- ,
- n
- ,
- I
- 0
- )
- =
- ∑
- i
- =
- 1
- N
-
- [
- w
- i
-
- (
- I
- i
- -
- I
- Mi
- )
- 2
- +
- 1
- w
- i
-
- (
- V
- i
- -
- V
- Mi
- )
- 2
- ]
- where Mi refers to said measurement data points, and wi is an empirical weight factor that accounts for the increased sensitivity of the current-voltage curve for the device to current at high current values and to voltage at low current values.
Non-transitory computer readable medium containing computer instructions stored therein for causing a computer processor to perform the steps of applying electrical stimuli to a semiconductor wafer, said wafer having a p-type semiconductor layer and an n-type semiconductor layer defining a p-n junction, through a probe in direct contact with one of said semiconductor layers to produce conductive-probe measurement data;
- fitting a current-voltage curve (I-V) model to said conductive-probe measurement data, said model expressing a current-voltage relationship as a function of resistance;
- and estimating a current-voltage curve (I-Vd) for a semiconductor device manufactured from the wafer by removing from the (I-V) model resistance effects calculated from data generated by fitting the current-voltage curve (I-V) model to the conductive-probe measurement data from the wafer;
- wherein the resistance is assumed variable with current and the resistance is calculated from measurement data points from the equation:
- R
- =
- Δ
-
-
- V
- Δ
-
-
- I
- where R is resistance, V is voltage, and I is current;
- wherein the device's forward voltage, ideality factor, resistance and reverse saturation current are calculated from the following set of equations:
- R
- i
- =
- α
- I
- i
- β
- +
- C
- I
-
- (
- i
- )
- =
- I
- 0
-
- exp
-
- (
- q
-
- (
- V
- i
- -
- I
- i
-
- R
- i
- )
- nkT
- )
- V
- d
-
- (
- i
- )
- =
- I
- i
-
- R
- i
- +
- kT
- q
-
- n
-
-
- ln
-
- (
- I
- i
- I
- 0
- +
- 1
- )
- where Vd is the device's forward voltage, I0 is reverse saturation current, n is ideality factor, and α, β, and C are constant parameters estimated by fitting N current-voltage measurement data points, (Ii,Vi), i=1K N, with a multi-parameter minimization calculation;
- and
- wherein said multi-parameter minimization calculation is carried out with the following estimator:
- Σ
-
- (
- α
- ,
- β
- ,
- C
- ,
- n
- ,
- I
- 0
- )
- =
- ∑
- i
- =
- 1
- N
-
- [
- w
- i
-
- (
- I
- i
- -
- I
- Mi
- )
- 2
- +
- 1
- w
- i
-
- (
- V
- i
- -
- V
- Mi
- )
- 2
- ]
- where M refers to said measurement data points, and wi is an empirical weight factor that accounts for the increased sensitivity of the current-voltage curve for the device to current at high current values and to voltage at low current values.
Dependencies are inferred from the claim text.