JPH05183034A - Measurement of characteristics of semiconductor - Google Patents

Abstract

PURPOSE:To detemine a life time, etc., within a short period of time and accurately conduct the analysis through reduction of noise by generating a particular Zerbst curve by measuring change of capacitance value for voltage change of MOS structure and change of capacitance value for time and then calculating a gradient of this curve. CONSTITUTION:A capacitance COX of an oxide film 3 of a MOS structure 1 is measured, a characteristic curve indicating change of a capacitance C for change of a voltage V is obtained and a saturated capacitance value Cmin in the minimum value side on the characteristic curve is measured. Next, while change of the capacitance value C for time is being measured by applying a constant voltage to the MOS structure 1, a Zerbst curve is generated by plotting ((Cmin/C) -1) on the horizontal axis and the converted values derived from code with time t. When the values indicated by the Zerbst curve show almost constant change within the predetermined range of change, minority carrier generation life time etc., can be determined by calculating a gradient of the Zerbst curve of the range of change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of measuring a minority carrier generation lifetime and its surface recombination rate used for semiconductor crystal evaluation.

[0002]

Conventionally, from measuring the C-t characteristics of MOS structure, occurrence lifetime tau _g and the surface recombination velocity S _O of minority carriers it was determined. These measured onset lifetimes τ _g and surface recombination rates S
_O is used for controlling manufacturing processes in the semiconductor industry.

This measurement method is, for example, as shown in FIG. 5, a silicon dioxide film 13 on an n-type silicon wafer 12.
A polysilicon electrode 14 is formed through the above, and the MOS capacitor 11 thus formed is placed at a predetermined position in a dark box 15. The MOS capacitor 11 is connected to the high frequency capacitance meter 16. The high frequency capacitance meter 16 superimposes a high frequency signal on a direct current bias obtained from a direct current power source 18 to generate a test signal (measurement frequency 1 MHz). This test signal is applied to the n-type silicon wafer 12 and the polysilicon electrode 14 of the MOS capacitor 11.

In the test signal thus applied to the MOS capacitor 11, the bias voltage of the DC power supply 18 is once changed from -5V to + 5V, as shown in FIG. After such a change, the test signal is
The bias voltage of +5 V is maintained, the thickness of the depletion layer is set to zero, and the capacitance C _OX of the silicon dioxide film 13 is obtained. next,
The bias voltage of the DC power supply 18 is lowered to -5V again, and
As shown in, the change in the capacitance C of the MOS capacitor 11 with respect to the elapsed time t after the voltage is lowered to -5V is measured. As a result of this measurement, the final value C _fin of the capacitance C of the MOS capacitor 11 (marked by □ in FIG. 7) is the elapsed time t = 1500.
It became 19.3 pF in seconds.

Next, the analysis of the Ct curve of FIG.
As shown in, the analysis is performed on the Zerbst plot. Based on the capacitance C _OX and the final value C _fin , each measured value of this _Ct curve is plotted along the vertical axis with {-d.
(C _OX / C) ² / dt}, the horizontal axis is {(C _fin / C) -1}
Then, a Zelpst curve ZP is obtained by plotting. Then, the slope m is calculated for a portion of the Zerbst curve ZP that forms a substantially straight line (for example, a straight line k passing through the Δ mark and the □ mark in FIG. 8), and the generated lifetime τ _g Is the intercept Δ between this straight line k and the vertical axis.
The surface recombination velocity S _O is obtained from each.

[0006]

However, in such a conventional semiconductor characteristic measuring method, the elapsed time t until the final value C _fin of the capacitance of the MOS structure is measured is very long, and the final value t _fin is very long. Since the Zelpst analysis is performed after the measurement of the value C _fin is completed, there is a problem that it takes a long time to determine the lifetime and the like. Further, as shown in FIG. 8, in the Zelpst curve ZP by Zelpst plot, since the vertical axis is the differential value of {− (C _OX / C) ² }, there is a problem that a lot of noise is included.

Therefore, according to the present invention, since the final value C _fin of the capacitance of the MOS structure is equal to the saturation value C _min , the final value C _fin
To provide a semiconductor measuring method capable of determining lifetimes and the like in a short time by determining _fin from C _min of C-V characteristics and performing Zelpst analysis simultaneously with C-t measurement. That is the purpose. Another object of the present invention is to provide a semiconductor characteristic measuring method capable of removing noise in the Zelpst plot and performing accurate analysis.

[0008]

According to a first aspect of the present invention, there is provided a semiconductor characteristic measuring method, wherein a MOS structure is formed by interposing an oxide film between a semiconductor and a conductor, and the oxide film of the MOS structure is formed. By measuring the capacitance C _OX and measuring the capacitance value C of the MOS structure with respect to the change of the voltage V, a characteristic curve showing the change of the capacitance value with respect to the voltage change is obtained, and the saturation capacitance on the minimum value side on this characteristic curve is obtained. The value C _min is measured, a constant voltage is applied to the MOS structure, and the M
The change in the capacitance value C of the OS structure is measured, and while measuring the change in the capacitance value C, ((C _min / C) -1) is plotted on the horizontal axis,
(C _OX / C) ² is differentiated with respect to time t, and the conversion value obtained by sign conversion is plotted on the vertical axis to plot a change in the capacitance value C by a Zelpst plot to create a Zelpst curve. When there is a substantially constant change in a predetermined fluctuation range, the slope of the Zerbst curve in this fluctuation range is calculated to determine the lifetime of occurrence of minority carriers and the like.

Further, in the semiconductor characteristic measuring method according to the second aspect of the present invention, the plotted values by the Zelpst plot are averaged when the Zelpst curve is created.

[0010]

In the semiconductor characteristic measuring method according to the first aspect of the present invention, the saturation capacitance value C _min on the minimum value side on the characteristic curve showing the variation of the capacitance value C of the MOS structure with respect to the variation of the voltage V is obtained. _Is estimated as the final value C _fin of the capacitance of the MOS structure,
Perform a Zelpst plot analysis. This Zelpst analysis is performed at the same time as the Ct measurement, and the lifetime and the like are calculated and determined when the rate of change becomes constant according to the Zelpst curve. Therefore, the lifetime of the semiconductor or the like can be determined in a short time.

Further, in the semiconductor characteristic measuring method according to the second aspect of the present invention, the plotted values are subjected to, for example, averaging processing in the Zelpst plot. As a result,
The Zelpst curve can be smoothed and its noise can be removed. Therefore, the lifetime etc. can be determined more accurately.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a semiconductor characteristic measuring method according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a semiconductor characteristic measuring apparatus according to an embodiment of the present invention. This device includes a dark box 5 for installing the MOS capacitor 1, a high-frequency capacitance meter 6 for measuring the capacitance of the MOS capacitor 1, a DC power supply 8 for a test signal of the high-frequency capacitance meter 6, a voltmeter 7 for the DC power supply 8, and a dark box. 5, a fluorescent lamp 9 for illuminating the surface of the MOS capacitor 1 and the like.

In the semiconductor property measuring method of the present invention, first, an n-type silicon wafer 2 having a mirror surface is prepared. The surface of the n-type silicon wafer 2 is heat-treated in a high temperature oxidizing atmosphere. When heat-treated, a silicon dioxide layer 3 is formed on the surface of the n-type silicon wafer 2.
It is formed to a thickness of 2.5 nm. This silicon dioxide layer 3
A polysilicon electrode 4 is formed on the upper surface of the substrate in an area of 1.96 × 10 ⁻³ cm ² . In this way, the MOS capacitor 1
To manufacture.

Next, this MOS capacitor 1 has a dark box 5
It is installed in a predetermined position. This MOS capacitor 1
A high-frequency capacitance meter 6 is connected to. The high frequency capacitance meter 6 generates a high frequency signal of 1 MHz as a test signal. A DC bias obtained from the DC power supply 8 is superimposed on this high frequency signal. The test signal is MOS
It is applied to the lower surface of the n-type silicon wafer 2 and the upper surface of the polysilicon electrode 4 of the capacitor 1.

Next, a bias voltage of -5 V is superposed on the test signal applied to the MOS capacitor 1 from the DC power supply 8. Then, the polysilicon electrode 4 has a negative voltage. Simultaneously with the application of this bias voltage, the fluorescent lamp 9 in the dark box 5 is turned on. The light of this fluorescent lamp 9 illuminates the surface of the MOS capacitor 1. After 30 seconds, the fluorescent lamp 9 is turned off. During the irradiation of the fluorescent lamp 9, the DC power source 8 is
A bias voltage of -5V is continuously applied to the S capacitor 1.

Next, the bias voltage of the DC power supply 8 is set to -5V.
To + 5V with constant change. The capacitance C of the MOS capacitor 1 with respect to this change in bias voltage is measured by the high frequency capacitance meter 6. The measured value C of the capacitance of the MOS capacitor 1 and the measured value V of the voltmeter 7 are input to a computer (not shown). These input values are
It is converted into a CV curve (FIG. 2) showing the CV characteristic of the MOS capacitor 1. The above measurement is performed at 300K. And the total time required for the C-V measurement is 150 seconds (30 seconds + 120 seconds). Furthermore, this C-
Data processing of V-curve. As a result of this data processing, the following is determined. That is, the capacitance value C _OX of the silicon dioxide layer 3 is 295 pF. Further, the saturation capacitance value C _min on the minimum value side of the MOS capacitor 1 of the CV curve is 19.3 pF.
Is.

Next, the bias voltage of the DC power supply 18 is lowered to -5V again. As shown in FIG. 3, the change in the capacitance C of the MOS capacitor 1 with respect to the elapsed time t after the voltage is lowered to −5V is measured. At the same time, this Ct curve is analyzed. This C-t curve is analyzed using the Zelpst plot analysis, as shown in FIG. In this Zelpst plot, using the capacitance value C _OX of the silicon dioxide layer 3 and the saturation capacitance value C _min on the minimum value side of the MOS capacitor 1 of the CV curve, the vertical axis represents {−d (C _OX. / C) ² / d
t} and the horizontal axis are {(C _min / C) -1} and the above measured values are plotted to obtain a Zelpst curve. Further, in this case, data fitting is performed for the differential value shown on the vertical axis. For more information,
The data of each differential value is averaged in the short range of the elapsed time t. As a result of this averaging, noise is removed from the Zelpst curve. It is possible to smooth the Zerbst curve. In the smoothed Zelpst curve, a straight line is created when the rate of change becomes constant or when the rate of change shows the minimum value, but this straight line can be created accurately. For example, this straight line can be created when the elapsed time from the start of the measurement of the Ct characteristic reaches 500 seconds. Simultaneously with the creation of this straight line, the measurement of the change in the capacitance C of the MOS capacitor 1 is completed. The slope m of the portion (broken line passing through the Δ mark and the □ mark in FIG. 4) where the Zerbst curve becomes a substantially straight line (broken line in FIG. 4)
The generation lifetime τ _g of minority carriers in the n-type silicon wafer 2 can be calculated, and the recombination velocity S _O can be obtained from the intercept Δ of the straight line with respect to the vertical axis. If you cannot create a straight line from a Zelpst curve in Zelpst analysis,
Refit the data.

As described above, in the measurement of the CV characteristics of the MOS capacitor 1 using light irradiation, the saturation capacitance value C _min on the minimum value side and the capacitance value C _OX of the silicon dioxide layer 3 should be determined in a short time. You can And this capacity value C _min is C
It is estimated to be the saturation value C _fin of the capacitance when the −t characteristic is measured. As a result, C _fin can be determined in a short time. Then, the above C _OX and C _min can be used for the analysis of the Zerbst plot of the Ct characteristic. In other words, it becomes possible to perform the Zerbst analysis in parallel with the measurement of the Ct characteristic, and when the straight line can be determined from the Zelpst curve of the Ct characteristic, the measurement of the Ct characteristic can be stopped. That is, it is not necessary to measure the Ct characteristic until the capacitance C of the MOS capacitor 1 is saturated. As a result, it is possible to extremely determined short time the surface recombination velocity S _O of the minority carriers in the n-type minority carrier generation lifetime tau _g and n-type silicon wafer 2 of silicon wafer 2.

By fitting the vertical axis data of the Zelpst plot, the slope m of the straight line and the intercept Δ with respect to the vertical axis can be accurately obtained.
As a result, the reliability of the generation lifetime τ _g of the minority carriers of the n-type silicon wafer 2 and the data of the surface recombination velocity S _O of the minority carriers of the n-type silicon wafer 2 can be improved.

[0020]

Since the present invention is configured as described above, the final value C _fin of the capacitance of the MOS structure is estimated from the saturation value C _min to determine the final value C _fin in a short time. can do. As a result, it is possible to extremely determined short time the surface recombination velocity S _O of minority carrier generation lifetime tau _g and semiconductors minority carriers in the semiconductor. In addition, as a result of being able to remove the noise in the Zelpst plot of the Ct characteristic of the MOS structure, the data of the generation lifetime τ _g of semiconductor minority carriers and the data of the surface recombination velocity S _O of semiconductor minority carriers are obtained. The reliability can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a semiconductor characteristic measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing CV characteristics of a MOS structure according to an embodiment of the present invention.

FIG. 3 is a graph showing a Ct characteristic of a MOS structure according to an embodiment of the present invention.

FIG. 4 is a graph showing a Zelpst plot of a MOS structure according to an embodiment of the present invention.

FIG. 5 is a block diagram showing a semiconductor characteristic measuring apparatus according to a conventional example.

FIG. 6 is a graph showing a change in bias applied voltage to a MOS structure according to a conventional example with respect to time.

FIG. 7 is a graph showing Ct characteristics of a MOS structure according to a conventional example.

FIG. 8 is a graph showing a Zelpst plot of a MOS structure according to a conventional example.

[Explanation of symbols]

 1 MOS Capacitor 2 n-type Silicon Wafer 3 Silicon Dioxide Layer 4 Polysilicon Electrode 6 High Frequency Capacitance Meter 7 Voltmeter 8 DC Power Supply

Claims (2)

[Claims] 1. A MOS structure is formed by interposing an oxide film between a semiconductor and a conductor, the capacitance C _OX of the oxide film of this MOS structure is measured, and the capacitance value of the MOS structure with respect to a change in voltage V is measured. A characteristic curve showing the change of the capacitance value with respect to the voltage change is obtained by measuring C, the saturation capacitance value C _min on the minimum value side on this characteristic curve is measured, and a constant voltage is applied to the MOS structure, The change in the capacitance value C of the MOS structure with respect to t is measured, and while measuring the change in the capacitance value C, ((C _min / C) −
1) on the abscissa, (C _OX / C) ² is differentiated by time t, and the converted value obtained by sign conversion is plotted on the ordinate, and the change in the capacitance value C is Zelpst plotted to create a Zelpst curve. When the value shown in this Zelpst curve has a substantially constant change in a predetermined fluctuation range, the generation lifetime of the decimal carrier is determined by calculating the slope of the Zelpst curve in this fluctuation range. Method for measuring semiconductor characteristics. 2. The method for measuring the characteristics of a semiconductor according to claim 1, wherein plot values obtained by a Zelvst plot are averaged when the Zerbst curve is created.