RU2101720C1 - Method and device for measuring voltage drop across semiconductor in misim structure - Google Patents

Abstract

FIELD: instrumentation engineering and electronic engineering. SUBSTANCE: method involves measurement of voltage drop across insulation by integrating current flowing through MISIM structure with respect to insulation capacitance; then integral obtained is subtracted from total voltage applied to MISIM structure. Device implementing this method has supply voltage output from pulse voltage source for MISIM structure, MISIM structure, voltage divider, integrating and amplifying unit, instrument capacitor, differentiating amplifier, display unit for voltage across semiconductor and insulation, and their time dependences. EFFECT: enlarged functional capabilities. 2 cl, 3 dwg

Description

 The invention relates to the field of measurement technology and may find application in electronic technology for measuring voltages on a dielectric and a semiconductor, as well as their temporary changes in MDPM structures. The invention can also be used in optoelectronics to determine the basic parameters of optical information carriers based on MDPDM structures and their temporary changes (for example, the contrast of the recorded image and its temporary change).

Metal dielectric semiconductor dielectric metal structures (MISDM structures) based on a high-resistance photosensitive semiconductor with an electric effect are used to process optical information as information carriers operating in a dynamic mode. The total voltage U ₀ applied to the MPDDM structure is distributed on the high-resistance semiconductor and dielectric inversely to the capacitances of these layers:
U ₀ U _p (t) + U _d (t).

где Ф₀ интенсивность падающего на полупроводник света, Uλ/2 - - полуволновое напряжение электрооптического кристалла.One of the main values that determine the parameters of the recorded image (contrast, resolution) is the voltage on the semiconductor and its time dependence. In electro-optical crystals, the voltage on the semiconductor U _p (t) modulates the intensity Φ (t) of the transmitted polarized light transmitted in crossed polaroids [1]

where Ф _{0 is the} intensity of the light incident on the semiconductor, Uλ / 2 - is the half-wave voltage of the electro-optical crystal.

где Ф(t)_max и Ф(t)_min максимальная и минимальная интенсивность считывающего света на выходе электрооптического кристалла.In the case when an image is recorded in the MDPM structure, the voltage across the semiconductor at different points on its surface is different in magnitude. The difference in voltages at different points on the surface of the semiconductor, in accordance with expression (1), leads to different intensities of polarized neutral readout light passing through the semiconductor at these points, forming the image contrast K (t) that varies with time, defined as:

where Ф (t) _max and Ф (t) _{min is the} maximum and minimum intensity of the reading light at the output of the electro-optical crystal.

To determine the contrast of the image in this way, it is necessary to measure the voltage across the semiconductor and its change in time U _p (t), which determines the intensity of light F (t) passing through the MDPM structure.

 A known method for measuring the parameters of MIS structures and a device for its implementation [2] The basis for measuring the parameters of complex conductivity is a method of compensating for one of the components of the conductivity and measuring the other component when the current flows through the MIS structure.

 This method and device for its implementation cannot be used to measure the parameters of the complex conductivity of the MISPM structure, since a semiconductor in this structure, in contrast to the MIS structure, is highly resistive. It is not possible to measure voltage across a semiconductor using this method and device.

There is also a known method of recording the capacitance-voltage characteristics of an MIS structure [3] and a device for its implementation, which is based on a refined diagram of an MIS structure, when the equivalent capacitance of an MIS structure (C _equiv. MIS) is replaced by series-connected semiconductor capacitances C _p and dielectric C _d Due to the MIS structure in the strong enrichment output mode current measured value C _d and C in a deep depletion mode _n.

This method is not applicable for the case of the MISPM structure, since when using a high-resistance semiconductor insulated with dielectric layers, it is impossible to bring it into enrichment and depletion modes. Because of this, it is impossible to obtain the capacitance-voltage characteristic characteristic for an MIS structure and measure the voltage drop across the semiconductor and dielectric, as well as the capacitance C _d and C _p .

 The technical problem to which the invention is directed is to provide the ability to accurately measure voltage drops on both the dielectric and the semiconductor.

а затем проводят вычитание полученного интеграла, равного падению напряжения на диэлектрике, из полного напряжения, приложенного к МДПДМ-структуре:
U_п(t) U₀ U_д(t).The solution to this problem is achieved by determining the voltage drop across the dielectric by integrating the current J (t) flowing through the MDPM structure onto the capacitance of the dielectric:

and then subtract the obtained integral, equal to the voltage drop across the dielectric, from the total voltage applied to the MDPM structure:
U _p (t) U ₀ U _d (t).

 The essential distinguishing features of the proposed method for determining the voltage drop across the semiconductor is the integration of the current flowing through the MDPM structure on the dielectric capacitance, the numerical determination of the integral corresponding to the voltage drop across the dielectric, and then the subtraction of this integral from the total voltage applied to the MDPM structure.

 These distinguishing features are new because they were not used in the known methods for determining the voltage drop across the semiconductor in the MDPM structure, and significant because they provide a solution to the problem.

 The method is implemented using a device for measuring voltage on a semiconductor and dielectric and their temporary measurement. The measurement device comprises a pulse voltage source, a measurement object (MDPM structure), a voltage divider, a differentiating device, an integrating device, a measuring capacitance, an indicator device, while the output of the pulse voltage source is connected to the input of the measurement object and the voltage divider, the first input of the differentiating device is connected with the output of the voltage divider, the second input with the output of the integrating device, and through the measuring capacitance with the first input of the integrating device and with the output of the measurement object, the output of the differentiating device is connected to the input of the indicator device, the second input of which, together with the second input of the integrating device, are grounded.

 The block diagram of the device is shown in FIG. 1. In FIG. 2 is an equivalent diagram of an MDPDM structure. In FIG. Figure 3 shows the time dependence of the voltage (a) applied to the structure, the voltage drop across the dielectric (b) and the semiconductor (c).

The device (Fig. 1) contains the output of the supply voltage U (t) from the source of the pulse voltage for the MDPDM structure 1, the MDPDM structure 2, a voltage divider 3, an integrating amplifier unit 4, a measuring capacitance C meas _. 5, a differentiating amplifier 6, a unit for indicating voltages on a semiconductor and a dielectric and their time dependences 7. In FIG. 2 shows: C _{d the} capacitance of the layers of dielectrics in the MDPDM structure 2, R _p and C _{p the} resistance and capacitance of the semiconductor in the MDPDM structure 2. In FIG. 3 denotes: U _{of the} amplitude of the pulse applied to the voltage MDPDM-structure (a), the voltage U _to drop-on-insulator (B) and semiconductor (a) U _at the feed point _{of the} U (tt _on).

Тогда, в силу соотношения (3), напряжение на полупроводнике U_п(t) равно:

Временные изменения напряжений на диэлектрике U_д(t) и полупроводнике U_п(t) при подаче через вход (фиг. 1) схемы измерения на МДПДМ-структуру 2 ступеньки напряжения с амплитудой U_о от источника 1 показаны на фиг. 3. При C_д/C_п 1 в начальный момент времени t t_о приложенное к МДПДМ-структуре напряжение делится пополам: U_до U_по U_о/2. В дальнейшем происходит заряд через сопротивление полупроводника R_п с постоянной времени τ R_п(C_д + C_п), и напряжение на емкости полупроводника будет падать (режим заряда).On the equivalent circuit of the MDPM structure (Fig. 2), the semiconductor is represented by a geometric capacitance C _p and a resistance R _p , depending on the intensity and wavelength of the incident light. The dielectric layers are represented by the total geometric capacity C _d . The dielectric resistance was neglected, since for a workable optical information carrier it should be significantly greater than R _p . In this equivalent circuit, the voltage U (t) applied to the MDPM structure is distributed over voltage drops across the dielectric layers U _d (t) and the semiconductor U _p (t) inversely to the capacitances C _d and C _p :
U (t) U _d (t) + U _p (t) (3)
The voltage drop across the dielectric layer U _d (t) is an integral of the current J (t) flowing through the MDPM structure:

Then, by virtue of relation (3), the voltage on the semiconductor U _p (t) is equal to:

Temporary changes in the voltage across the dielectric U _d (t) and the semiconductor U _p (t) when a measurement circuit is applied to the MDPDM structure 2 of a voltage step with amplitude U _о from source 1 through the input (Fig. 1) is shown in FIG. 3. At C _d / C _p 1 at the initial time tt _{о, the} voltage applied to the MDPDM structure is divided in half: U _to U _by U _о / 2. Subsequently, a charge occurs through the semiconductor resistance R _p with a time constant τ R _p (C _d + C _p ), and the voltage across the semiconductor capacitance will fall (charge mode).

Using the circuit shown in FIG. 1, the voltage on the semiconductor U _p (t) is determined by integrating the current J (t) flowing through the MDPDM structure 2 at the dielectric capacitance C _d and subtracting the obtained integral equal to the dielectric voltage from the voltage U _о applied to the input of the MDPM structure using an integrating amplifier unit 4 based on the measuring capacitance C _rev. 5. The measuring capacity is selected so that its value satisfies the inequality: C _meas. ≥> C _d , C _p in order to avoid the influence of this capacitance on the redistribution of stresses between C _d and C _p . The input impedance of the integrating unit 4 is selected so that the leakage current is much less than the current flowing through the MDPM structure. At the output of the integrating amplifier unit 4, we obtain the voltage across the dielectric U _d (t) (Fig. 3, b), which is input to the differential amplifier 6.

 The device operates as follows.

When applying a rectangular voltage pulse with an amplitude U _о (Fig. 3, a) to the input of the MDPDM structure (“charge” mode) at the first time tt _{о, the} voltage U _о in accordance with the equivalent circuit of the MDPDM structure (Fig. 2) is divided on C _d and C _p inversely proportional to their values: U _d U _to , U _p U _to U _about U _to . In the charge circuit flows _edited QQ Q Q _{d p.} If the semiconductor is now illuminated with active light for it, then the resistance R _p will decrease sharply, which will lead to the shortening of C _p through R _p . In this case, the voltage on C _d increases with time to U _d U _o (Fig. 3, b), and on the semiconductor decreases to almost zero (Fig. 3, c).

The voltage divider 3 serves to set the magnitude of the desired scale factor for the voltage U _о supplied to the input of the differentiating amplifier unit 6, and should not distort its shape. Using block 6, the voltage drop across the dielectric U _d (t) is subtracted from the voltage drop U _and the voltage drop across the semiconductor U _p (t) is applied to the indicator device 7 at the output of the block.

The advantage of the proposed method and device for measuring the voltage drop across the semiconductor in the MDPM structure is as follows. It is possible to indirectly measure the absolute values of the voltage drop across the semiconductor and its temporary change, as well as their dependence on the intensity, duration and dose of illumination of the recording backlight when the MDPM structure is used as a carrier of optical information. Based on the dependence of U _n (t) recording the intensity of illumination or dose of illumination by the formula (2) can determine the contrast of the recorded image K. In addition, the ratio of the voltage drops on semiconductor and insulator _of U _to U at the time of the power supply voltage pulse U _of (tt _о ) at a known value of the capacitance of the MDPM structure C (measured by the usual method), we can calculate the capacitance of the layers of the dielectric C _d and the semiconductor C _p , given that:
C ^-1 = C $\genfrac{}{}{0ex}{}{\text{-1}}{\text{d}}$ + C $\genfrac{}{}{0ex}{}{\text{-1}}{\text{P}}$ (6) and
C _d / C _p U _to / U _to . (6)
In addition, the advantage of the method and device is visibility, since the dependences U _p (t) and U _d (t), their ratios and influence can be recorded on the screen of the indicator device, which is used as a storage oscilloscope, which is part of the device for implementing the method on them the intensity and duration of the recording backlight.

Claims (2)

 1. The method of measuring the voltage drop across the semiconductor in the MDPDM structure, namely, that a current is passed through the MDPDM structure, characterized in that the voltage drop across the dielectric is determined by integrating the capacitance of the dielectric flowing through the MDPDM structure, and then subtraction of the obtained integral from the total voltage applied to the MDPDM structure.  2. A device for measuring the voltage drop across a semiconductor in an MDPM structure containing a voltage source, a measurement object, a voltage divider and an indicator device, wherein the voltage source output is connected to the input of the measurement object, the first input of the indicator device is connected to the output of the voltage divider and the output of the measurement object characterized in that a differentiating amplifier, an integrating device and a measuring capacitance are introduced, wherein the output of the voltage source is connected to the input of the measurement and voltage amplifier, the first input of the differentiating amplifier is connected to the output of the voltage divider, the second input to the output of the integrating device, and through the measuring capacitance with the first input of the integrating device and the output of the measurement object, the output of the differentiating amplifier is connected to the input of the indicator device, the second input of which together with the second the input of the integrating device is grounded.

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