JPH0248141B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention relates to a semiconductor capture center measurement method for measuring the carrier capture center of a semiconductor material constituting a semiconductor diode based on the observation of current transient response characteristics and capacitance transient response characteristics of the semiconductor diode. Method,
In particular, the present invention relates to an adaptive semiconductor capture center measurement method that enables efficient measurement by changing observation conditions in accordance with the results of real-time processing of observation data.

Prior Art The conventional method for measuring this type of semiconductor capture center is to observe the light emission phenomenon and electrical conduction phenomenon that occur in a semiconductor diode when the semiconductor diode is regularly irradiated with light or a high frequency voltage is applied. In addition to the method of measuring the carrier capture center using a semiconductor diode, it is also possible to observe the current transient phenomenon and capacitance transient phenomenon that occur in a semiconductor diode when a light pulse is irradiated or a voltage pulse is applied to the semiconductor diode. The method used was to measure the center of carrier capture.

However, in such conventional measurement methods, not only the former method but also the latter method can measure the capture cross section, capture center density distribution, and capture energy level as parameters of the carrier capture center with high sensitivity. On the other hand, the measurable range and measurement sensitivity of the capture center parameters described above are strong against the observation conditions of the irradiation pulse light intensity, the applied pulse voltage value, the sampling time of the transient response signal, and the sweep speed of the measurement environment temperature. Because of this dependence, a high degree of skill was required to effectively and appropriately set observation conditions.

On the other hand, in order to be able to measure the semiconductor capture center using the latter method without requiring such a high degree of skill, the intensity of the irradiated pulsed light and the value of the applied pulse voltage are varied over a wide range based on so-called computer processing. By changing the temperature in multiple stages and performing multi-point sampling by moving the sampling point of the transient response signal forward, this measurement aims to set all the necessary observation conditions and ensure complete measurement centered on semiconductor capture. Methods are also conventionally known, but in such conventional methods, it is necessary to measure and once store a large amount of data that is unnecessary for determining the capture center parameter, and then perform a huge amount of arithmetic processing. This method has disadvantages in that it requires a lot of time for measurement and calculation processing, and also requires a storage device with a huge storage capacity to temporarily store the measurement data, resulting in a large amount of waste.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks of the prior art, without requiring a high level of skill, without requiring a large amount of time for data measurement and processing, and without requiring the use of large-capacity storage devices. To provide a semiconductor trap center measuring method that can quickly and accurately determine the trap center parameters and efficiently measure the carrier trap center of a semiconductor material, and in particular, to provide a self-adaptive semiconductor trap center measuring method. be.

That is, the adaptive semiconductor capture center measuring method of the present invention measures the carrier capture center of the semiconductor material constituting the semiconductor diode based on observation of at least one of the current transient response characteristics and capacitance transient response characteristics of the semiconductor diode. Hits the,
Among the observation conditions for performing the observation, the speed of the temperature sweep as the observation condition and the voltage applied to the semiconductor diode are adjusted based on the results of processing the data from the observation at a speed that is almost as fast as the temperature sweep that takes time to set. The method is characterized in that at least one observation condition among the voltage value, the intensity of the irradiated light pulse, and the time point of sampling the transient response signal is changed so that the result of applying convolution and integration to the data obtained from the observation becomes an extreme value. It is something.

EXAMPLES The present invention will be explained in detail below using examples with reference to the drawings.

First, FIG. 1 shows an example of the configuration of a semiconductor trap center measuring device constructed as a voltage application/capacitance transient response measurement type according to the method of the present invention. The semiconductor capture center measuring device with the illustrated configuration controls measurement data regarding a semiconductor diode sample 12 installed in a cryostat 11 by a main control section 1, a precontrol section 4, and an analog signal measurement control section 6, and also performs arithmetic processing. It was designed to do so. That is,
Analog signal measurement control section 6 in the illustrated configuration
operates the internal analog-to-digital converter 7 in accordance with the control signal from the precontrol unit 4 to generate a voltage pulse signal to be applied to the semiconductor diode sample 12 fixedly installed in the cryostat 11. At the same time, a temperature control signal is generated to be supplied to the heater 13 for controlling the measured environmental temperature inside the cryostat 11. Also, according to the control signal from the front control section 4, the analog
The digital converter 8 is operated to sample the capacitance transient response signal from the semiconductor diode sample 12 via the well-known capacitance measuring device 10, and the measurement environment temperature inside the cryostat 11 is measured using a temperature sensor. The temperature is measured via a well-known thermocouple thermometer 9 introduced into the cryostat 11. Furthermore, the applied pulse voltage value, the temperature control signal strength, and the end point of transient response sampling are also determined by the control signal from the precontrol unit 4, and the capacitance measurement data and temperature measurement data are sent to the precontrol unit 4. supply

On the other hand, in accordance with the control signal from the main control section 1, the precontrol section 4 in the illustrated configuration sends a control signal and instructions for generating an applied pulse voltage corresponding to the instructed voltage value to the analog signal measurement control section 6. Temperature control signals corresponding to the temperature control heater currents are sequentially sent out. Furthermore, the capacitance measurement data and temperature measurement data supplied from the analog signal measurement control section 6 are averaged for each specified voltage value and each sampling time, and then temporarily stored in the internal storage device 5. Note that the number of times the applied voltage is repeated and the number of times the sampled data is averaged is given by a control signal from the main controller 1, and at the end of the specified repeated measurement,
The average results of the capacitance measurement data and temperature measurement data are sent to the main control unit 1.

In contrast, the main control unit 1 in the illustrated configuration
sends control signals to the precontrol unit 4 instructing the applied voltage series to the semiconductor diode sample 12, the temperature control heater current, the end point of transient response signal sampling, the number of times the applied voltage is repeated, and the number of times the sampling data is averaged. From the precontrol unit 4, capacitance measurement data and temperature measurement data are transmitted and averaged for each applied pulse and each sampling time point. Each of the received data is stored in the storage device 3 in the main control unit 1, and then processed by the internal processing/judgment mechanism 2 for data measurement in order to generate a measurement control signal for the front control unit 4. speed of setting observation conditions,
In particular, so-called real-time processing is performed at a speed that does not lag behind the speed of the measurement environment temperature sweep, which requires the most time to set. Its real-time data processing/judgment mechanism 2
The question is whether it is necessary to set more types of measurement conditions and perform more precise measurements based on the measurement data sent sequentially through the analog signal measurement control section 6 and pre-control section 4. If it is determined that it is necessary, reduce the sweep speed of the measured environmental temperature, increase the type of applied pulse voltage,
Furthermore, control is performed so that the end point of transient response signal sampling is postponed to minutely change the measurement conditions. On the other hand, if it is determined that there is no need to perform precise measurements, the sweep speed of the measurement environment temperature is increased, the types of applied pulse voltages are reduced to only one type, and the transient response signal sampling is performed. The measurement conditions are controlled to be roughly changed by moving the end point of the measurement forward. Therefore, by simply sweeping the measurement environment temperature once, desired data measurement can be completed with all necessary observation conditions set.

Therefore, the above-mentioned determination of whether precision measurement is necessary or not in the real-time data processing/judgment mechanism 2 is based on the fact that the result of applying convolution to the measurement data is an extreme value, that is, within a region where the maximum value or the minimum value is present. It is preferable to use the presence or absence as a criterion for determination. The weighting coefficient A _i in the convolution integral is
The typical transient response signal amplitude is automatically generated as a result of arithmetic processing performed within the main control unit 1, for example, according to the following formulas using the data series S _i for the measured environmental temperature and the measured environmental temperature T. . _+N 〓 ^i=-N A _i (b _i +c)=0 (b, c: arbitrary numbers) _+N 〓 ^i=-N A _i d/dTS _i =0 _+N 〓 ^i=-N A _i ² →Minimum _+N 〓 ^i=-N A _i・S _i = 1 Environment near the temperature where the result of applying convolution to the measured data using the weighting coefficient A _i given by each formula above is an extreme value It is known, for example from research documents written by the inventors, that useful data regarding carrier capture centers in semiconductor materials can be determined at temperature.

In the semiconductor capture center measurement device configured as described above according to the method of the present invention, the temperature of the measurement environment in which the semiconductor diode sample is installed is swept from a certain temperature setting value to another temperature measurement value, and the static When measuring the capacitance transient response, a limited range of potentially useful data on the capture center density distribution, capture cross section, and capture energy level can be measured as measured data on the carrier capture center. Only at the measurement environment temperature, the temperature sweep speed is reduced, the types of applied pulse voltages are increased, and the end point of transient response signal sampling is postponed to minutely change the measurement conditions, making highly sensitive and precise measurements more efficient. can do well.

As a result, according to the measurement method of the present invention, the memory capacity required for arithmetic processing of measurement data can be significantly reduced. That is, in the conventional measurement method, for example, 1〓 in the temperature range from 80〓 to 380〓 for 30 kinds of applied pulse voltage values and 20 data sampling points.
A memory capacity of 30 x 20 x (380 - 80)/1 = 180K words was required to store the measurement data obtained at temperature intervals of . On the contrary,
In the measurement method of the present invention, usually, as a result of performing convolution integration on measurement data obtained by performing the same temperature sweep as described above only for one type of applied pulse voltage value and two data sampling points, Only in the temperature range near the temperature where useful measurement data can be obtained, the number of data sampling points is increased to 20 points, the applied pulse voltage value remains at one type, and temperature sweep is performed. The applied pulse voltage value is increased to 30 types by focusing on only one type of temperature, and the data sampling time point is only 2 points. As a result, the number of types of semiconductor carrier capture centers that can be detected by measurement is N types, and the temperature range in which the temperature sweep is performed is ±
20〓, then 1×2×(380-80)+N×(1×20
This means that the measurement data can be processed with a memory capacity of only 40+30×2×1) words. Therefore, the number N of semiconductor trapping-centered types is usually 1 to 5.
Therefore, the memory capacity required for arithmetic processing of measurement data in the measurement method of the present invention is
It will only be 1,460 to 4,900 words, which is a significant decrease compared to the previous version.

On the other hand, regarding the effect of improving the signal-to-noise ratio in high-sensitivity measurements centered on semiconductor capture using the method of the present invention, as mentioned above, the memory capacity required for arithmetic processing of measurement data is significantly reduced. This means that measurement data can be collected a large number of times for one applied pulse voltage value, one sampling time point, and one temperature within a period of time. In other words, although it is not necessarily limited to uniformly increasing the number of measurement data collections for each measurement point, by increasing the number of measurement data collections, approximately √1801460 ~
The signal-to-noise ratio of the measured value is improved by √1804900, that is, about 11 to 6 times.

In the above explanation, an example of the configuration of voltage application/capacitance transient response measurement type was described, but the capacitance measuring device 1 in the configuration example shown in the first figure
If 0 is replaced with a well-known and commonly used ammeter and the semiconductor diode sample 12 is modified to be irradiated with a light pulse through an optical modulator driven by a voltage pulse, measurements can be made using the configuration shown in Figure 1. The device can also be configured to perform light irradiation and current transient response measurement.

Effects As is clear from the above explanation, according to the present invention, when measuring the carrier capture center of a semiconductor by observing the current transient response characteristics and capacitance transient response characteristics of the semiconductor diode, A real-time data processing process is added to perform convolution and integration on the measured data, and the intensity of the irradiated light pulse or applied voltage pulse, the period of transient response signal sampling, and the measurement environment are adjusted based on the results of the data processing. By effectively and appropriately changing the temperature sweep speed, it is possible to complete the required measurement with a single measurement environment temperature sweep, and the measurement sensitivity can be improved, making it possible to perform extremely efficient and accurate measurements. Effects can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the configuration of an automatically adaptive semiconductor capture center measuring apparatus for implementing the method of the present invention. DESCRIPTION OF SYMBOLS 1... Main control unit, 2... Real-time data processing/judgment mechanism, 3... Measured data storage device, 4... Pre-control unit, 5... Storage device for averaging, 6... Analog signal measurement control Section 7... Digital-to-analog converter, 8... Analog-to-digital converter,
9...Thermocouple thermometer, 10...Capacitance measuring device,
11... Cryostat, 12... Semiconductor diode sample, 13... Heater.

Claims (1)

[Claims] 1. When measuring the carrier capture center of the semiconductor material constituting the semiconductor diode based on the observation of at least one of the current transient response characteristics and the capacitance transient response characteristics of the semiconductor diode, the observation conditions for the above observation are set. The speed of the temperature sweep, the value of the voltage applied to the semiconductor diode, the intensity of the irradiated light pulse, and 1. An adaptive semiconductor capture center measuring method, characterized in that at least one observation condition among transient response signal sampling points is changed so that the result of convolving and integrating the observation data becomes an extreme value.