SU402836A1 - DEVICE FOR DETERMINATION OF PARAMETERS OF BARRIER CAPACITIES OF RR TRANSITIONS - Google Patents

Description

one

The invention relates to the field of electronics and can be applied to measure the parameters of semiconductor devices.

Devices are known for determining the parameters of the barrier capacitances of the i-7 transitions, comprising an oscillating excitation system, an oscillating circuit, and a frequency meter.

To determine the parameters of the barrier capacitances of pn junctions, it is necessary to obtain the dependence of the capacitance on the bias voltage, however, the known device does not allow to automate the installation of the required voltages at the measured / -n junction, therefore, the measurement takes a lot of time.

The purpose of the invention is to automate the measurement process.

This is achieved by the fact that the proposed device contains a reference oscillator, a controlled frequency divider, a phase detector, a low-pass filter, a frequency divider and a digital voltmeter, while the output of the reference oscillator is connected via a controlled frequency divider to the input of the phase detector, to another input the frequency divider is connected to the output of the excitation system, and the output of the phase detector is connected to a digital voltmeter and through a low-pass filter to one of the terminals for

connect the test / o-n-junction, the other terminal is connected to the inductance of the oscillating circuit and the input of the excitation system of the oscillations.

The drawing shows the block diagram of the described device.

The device contains a reference oscillator 1, the output signal of which is fed to the control input of its splitter 2 frequency with the control input (or switch) 3 of the frequency division factor. The output of the frequency divider 2 is connected to one of the inputs of the phase detector 4, the output of which is connected to the low-pass filter elements 5: a resistor

6 and capacitances 7 and 8. The alternating current / - / g-junction 9 is connected to the inductance through the capacitor 8, but to the output current of the phase detector 4 through the inductance 10 to the inductance 10. The studied rsl-junction 9 with the inductance 10 forms an oscillating circuit connected to the system 11 of small-scale excitations.

The output of the oscillation excitation system is connected to the input of the frequency divider 12, the output signal of which is fed to the input of the phase detector 4. The device also contains a digital voltmeter 13 and a device 14 for processing data. The device works as follows. The barrier capacitance with the p- / r-junction is described by the equation: C a (b + u) where a is constant; b - contact potential difference; and - reverse external voltage applied to the n-junction, n - exponent. The three parameters a, b, p are not directly measurable. They can be determined by solving, for example, a system of equations: C,: a (6-U,) - C, and (6 +,) - C, and (6 +,) where C, Cz, Cs - capacitance / 7-n-junction values measured at voltages Ui, U, Uz, respectively. The pn-junction 9 under study with inductance 10 forms an oscillatory circuit. (Capacity 8 is much greater than barrier capacity, it is blocking). In the circuit, with help, and the excitation system 11 is excited to oscillate at a small amplitude at the restarting frequency of the circuit. The phase detector 4, which compares the resonant frequency divided by the division factor of divider 12 with frequency at the output of controlled frequency divider 2, sets the voltage at which these frequencies are strictly equal at yO - j - transition 9. This means that the stationary states (after transients) of the device control system with the division factors of the controlled divider 2, the frequencies K, Kz Km correspond to the system equations: where S is the division factor of the divider 12; / o is the frequency of the reference oscillator; L is the inductance value 10 of the oscillating circuit. Each equation is obtained by substituting the expression for the pn junction barrier capacitance into the Thomson formula. When determining the sought parameters a, b, n according to this system of equations, only values 11 are transmitted to the data processing device 14 during measurement. Uz Urn is outputted from the digital voltmeter 13. The values of the coefficients Кь KzKm and frequency / о can be stored in the memory device data processing in advance. In cases where it is not necessary to determine the nominal capacitance or the parameter a /; - "- transition, the magnitude / o can be excluded. The frequency of the reference oscillator 1 is then only presented with the requirement of stability during the cycle of switching the coefficients KI, Do - Km. Thanks to the static nature of the phase-locked loop of the resonant frequency of the circuit with the pn junction under study, the accuracy of determining the parameters depends almost only on the digital voltmeter error 13. The 7-p-junction and switch division factors of the controlled divider (which can also be automated), the data processing device 14 provides the values of the desired pairs etrov. The capacitance 8 of the lowpass filter smoothes the pulsations at the output of the phase detector. The resistor 6 and the capacitance 7 form a chain ensuring the stability of the automatic control system. The subject of the invention is a device for determining the parameters of barrier capacitance-p-junctions, which contains an excitation system and an oscillatory oscillator, characterized in that, in order to automate the measurement process, it contains a reference oscillator, a controlled frequency divider, a phase detector, a low-pass filter, a divider frequency and digital voltmeter, while the output of the reference oscillator through a controlled frequency divider is connected to the input of the phase detector, to the other input of which through the frequency divider the output s is connected Topics oscillation drive, and the output of the phase detector to a digital voltmeter podklyuchep and through the low-pass filter to one of the terminals for connecting the test pn ierehoda, a second terminal connected to the oscillator circuit inductance and the input of the system oscillation drive.

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