JP2006112897A - Semiconductor evaluation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of reducing the effects of noise which has intruded from a drain voltage Vd in noise measurements of semiconductor elements. <P>SOLUTION: This semiconductor evaluation apparatus is provided with resistors 103 and 104 connected to a drain of a MOS transistor 116 for converting a current passing through the drain of the MOS transistor 116 into a voltage and operational amplifiers 101 and 102 for amplifying the voltage. Power of the operational amplifiers 101 and 102 is impressed according to a drain potential. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor evaluation apparatus, and more particularly to a technique effective when applied to measurement and evaluation of noise characteristics of a semiconductor element.

  For example, as a technique studied by the present inventor, in general, in the measurement of 1 / f noise (flicker noise) of a semiconductor element, an operational amplifier, a spectrum analyzer, etc. are connected to a prober compatible with low current measurement, and a system is constructed and measured. It is carried out.

General discussion of 1 / f noise is described in Non-Patent Documents 1 and 2, for example.
K. K. Hung., "IEEE Transaction Electron Devices", (USA), 1990, 37, p. 654 K. K. Hung., "IEEE Transaction Electron Devices", (USA), 1990, 37, p. 1323

  By the way, as a result of the study by the present inventor on the measurement technique of the noise characteristics of the semiconductor element as described above, the following has been clarified. In the following description, unless otherwise specified, a symbol representing a terminal name also serves as a wiring name and a signal name, and also serves as a voltage value in the case of a power supply.

  In a current-voltage (IV) conversion amplifier circuit that applies a constant voltage to an element to be measured such as a MOS transistor (field effect transistor) and amplifies a signal change of a current flowing through the element to be measured, this becomes a reference potential. Since noise entering from the input voltage (drain voltage Vd) is amplified, the S / N ratio of the output is greatly deteriorated.

  With reference to FIG. 13, the appearance of external noise in the case of inversion amplification with respect to the ground will be described. 13A and 13B are diagrams showing voltage waveforms of the input and output of the inverting amplifier circuit. FIG. 13A shows the input waveform of the inverting amplifier circuit, FIG. 13B shows the inverting amplifier circuit, and FIG. 13C shows the output waveform of the inverting amplifier circuit. . As shown in FIG. 13A, the first-stage output voltage (input voltage of the inverting amplifier circuit) of the device under test is a value obtained by adding the Vd fluctuation caused by the system and the noise (Vnoise) of the device under test. . The input voltage Vd is amplified by the inverting amplifier circuit of FIG. 13B, and the output voltage of the inverting amplifier circuit is − (R2 / R1) · (Vd + Vnoise). That is, as shown in FIG. 13C, the inverting amplifier circuit also amplifies the Vd fluctuation caused by the system together with the noise of the element under measurement.

  Further, the input potential of the operational amplifier (operational amplifier) is not at the center of the positive and negative power supply voltages. Therefore, since the operation cannot be performed at the optimum operating point, problems such as a decrease in the maximum supply current and an increase in distortion occur.

  In addition, it is necessary to perform DC (direct current) measurement of the MOS device before noise measurement. However, since the current cannot be monitored in the conventional circuit, the circuit is rearranged and the DC characteristics are measured. Again, the noise measurement circuit was reassembled to measure the noise. As a result, noise measurement could not be automated.

  A method for monitoring DC characteristics will be described with reference to FIG. FIG. 14 shows a noise measuring circuit and a DC measuring device. As shown in FIG. 14, the noise measurement circuit includes an operational amplifier 1401, a positioner 1402, a probe needle 1403, and the like, and the DC measurement instrument includes an ammeter 1404 and a power source 1405. At the time of noise measurement, the probe needle 1403 is applied to the drain of the MOS transistor (device under test) 1406 and the operational amplifier 1401 amplifies the noise for measurement. However, at the time of DC measurement, the DC current must be removed unless the operational amplifier 1401 is removed. Could not be monitored.

  In addition, by connecting an operational amplifier having a constant gain (amplification factor) to the output terminal of a device under test such as a MOS transistor (drain in the case of a MOS transistor), 1 / f noise is measured while supplying a drain current. In this case, since the width of the spectrum intensity of the noise reaches 50 dB or more, measurement with low noise cannot be performed because it is buried in the noise floor. Therefore, when the gain is increased, the spectrum analyzer is saturated in the measurement under a high noise condition. Further, when the gain is increased, there is a problem that the current supply capability of the IV conversion circuit decreases.

  With reference to FIG. 15, the above-described problem of the operational amplifier with a fixed amplification factor will be described. 15A and 15B are diagrams showing the frequency characteristics of the noise level measured by the spectrum analyzer. FIG. 15A shows a case where the noise level is low, and FIG. 15B shows a case where the noise level is high. As shown in FIG. 15A, with a low noise device to be measured, the high frequency region is buried in the noise floor and cannot be measured. Further, as shown in FIG. 15B, the spectrum analyzer is saturated with the high noise device to be measured, and the low frequency region cannot be measured.

  Therefore, an object of the present invention is to provide a technique capable of reducing the influence of noise entering from the drain voltage Vd in the noise measurement of a semiconductor element.

  Another object of the present invention is to provide a technique capable of improving the current supply capability to the drain in the noise measurement of a semiconductor element.

  Another object of the present invention is to provide a technique capable of automating measurement work in measuring noise of a semiconductor element.

  Another object of the present invention is to provide a technique capable of dealing with semiconductor elements having different characteristics in noise measurement of semiconductor elements.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  That is, a semiconductor evaluation apparatus according to the present invention includes an operational amplifier circuit that is connected to a drain of a field effect transistor, converts a current flowing through the drain of the field effect transistor into a voltage, and amplifies the voltage. The power supply is applied with the drain potential as a reference.

  The semiconductor evaluation apparatus according to the present invention is connected to the drain of a field effect transistor, converts an electric current flowing through the drain of the field effect transistor into a voltage, amplifies the voltage, and a direct current of the field effect transistor. When measuring, an external measuring device is connected to the operational amplifier circuit, and when measuring the noise of the field effect transistor, a means for separating the external measuring device from the operational amplifier circuit is provided.

  The semiconductor evaluation apparatus according to the present invention includes an operational amplifier circuit that is connected to a drain of the field effect transistor, converts a current flowing through the drain of the field effect transistor into a voltage, and amplifies the voltage. The device is characterized by comprising means for switching the amplification factor according to the noise level of the field effect transistor.

  Of the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  (1) By setting the reference potential of the operational amplifier as the drain potential, it becomes possible to make the amplification factor of noise entering from the drain voltage almost 0 dB, that is, not amplify the noise when measuring noise.

  (2) By making the reference potential of the operational amplifier the drain potential, the current supply capability to the drain can be improved.

  (3) By adding a DC current monitor circuit and switching the internal circuit, a series of measurements can be performed automatically and continuously, and a continuous automatic measurement of a plurality of devices becomes possible.

  (4) Since the optimum amplification factor can be selected according to the semiconductor element by switching the amplification factor of the operational amplifier according to the noise level, it is possible to measure semiconductor elements having different characteristics without saturating the measuring device. It becomes possible to carry out continuously.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  FIG. 1 is a circuit diagram showing a configuration of a semiconductor evaluation apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing a current-voltage conversion circuit in the semiconductor evaluation apparatus of the present embodiment, and FIG. FIG. 4 is a diagram showing the effect of reducing external noise.

  First, an example of the configuration of the semiconductor evaluation apparatus according to the present embodiment will be described with reference to FIG. The semiconductor evaluation apparatus according to the present embodiment is, for example, an apparatus that measures frequency characteristics of 1 / f noise generated in the drain current of a MOS transistor (field effect transistor), and includes operational amplifiers (operational amplifiers) 101 and 102 and a resistor 103. To 108, capacitors 109 to 113, switches 114 and 115, and the like.

  A gate voltage Vg is applied to the gate terminal of the MOS transistor 116 which is a device to be measured, the source terminal is connected to the ground (ground) GND, the drain is input to the inverting input terminal of the operational amplifier 101, and the switch 114 is connected. Is connected to a voltmeter. Further, between the input and output terminals of the operational amplifier 101, the resistor 103 and the capacitor 109 connected in parallel, and the resistor 104 and the capacitor 110 are switched and connected to either one via the switch 115. The output of the operational amplifier 101 is connected to a voltmeter via the switch 114, and the voltage between the input and output of the operational amplifier 101 can be measured by the voltmeter. The non-inverting input terminal of the operational amplifier 101 is connected to the power supply (drain potential) Vd. The output of the operational amplifier 101 is input to the non-inverting input terminal of the operational amplifier 102 via the capacitor 111 and is connected to the power supply Vd via the resistor 105. The inverting input terminal of the operational amplifier 102 is connected to the power supply Vd via the resistor 106. A resistor 107 and a capacitor 112 are connected in parallel between the inverting input terminal of the operational amplifier 102 and the output. The output of the operational amplifier 102 is externally output via a capacitor 113, and the external output is connected to the ground GND via a resistor 108.

  The power source (drain potential) Vd is supplied using a battery or the like, and is electrically independent from the ground GND. Voltages are applied to the power supplies Vcc and Vee supplied to the operational amplifiers 101 and 102 using a battery or the like with reference to the power supply Vd. For example, Vcc = Vd + 9 (V) and Vee = Vd-9 (V).

  As described above, this semiconductor evaluation apparatus has the first stage amplifier having the basic configuration of the current-voltage (IV) conversion circuit and the amplifier circuit. The drain current of the MOS transistor 116 is converted from current to voltage by the resistors 103 and 104, and the voltage is amplified by the operational amplifiers 101 and 102 and output.

  Next, the principle of noise reduction in the current-voltage conversion circuit and the voltage amplification circuit will be described with reference to FIGS.

  Many outputs of active elements such as MOS transistors apply a constant voltage Vd and detect changes in the drain current Id. In general, the outputs of these active elements have high constant current characteristics, and current fluctuation due to fluctuations in the externally applied voltage Vd is slight. Therefore, if the negative feedback resistance R2 of the first stage amplifier circuit is sufficiently smaller than the output resistance Rd of the device under test (MOS transistor 116), it is output as it is regardless of the amplification factor of the circuit. In other words, in FIG. 2, the output voltage Vo of the operational amplifier 101 can be expressed by Expression (1).

Vo = Id × R2 + Vnoise (1 + R2 / Rd) (1)
Here, Rd is the equivalent resistance of the drain. Usually, the drain of the MOS transistor has a strong constant current characteristic, so it is considered that Rd >> R2. Therefore, Equation (1) can be approximated as Equation (2), and noise entering from Vd is not amplified.

Vo≈Id × R2 + Vnoise (2)
Therefore, as shown in FIG. 3, by making the second stage amplifier a differential amplification of the power source Vd and the output Vin of the first stage amplifier, the signal from the Vd is not amplified (amplification factor≈1). Only can be amplified. That is, in FIG. 3, Vd including system-induced Vd variation is input to the inverting input terminal of the operational amplifier 102, and Vin including system-induced Vd variation and noise of the element under test is input to the non-inverting input terminal. By amplifying, only the noise is amplified, the fluctuation of Vd (noise caused by the system) is not amplified, and the output voltage Vo of the operational amplifier 102 is as shown in Expression (3).

Vo = Vd + (R1 / R2) · Vnoise (3)
However, R1 / R2 = R3 / R4
In the circuit configuration described above, the input operating point of the first stage IV conversion circuit and the second stage voltage amplifier circuit is Vd, so that the optimal operating point (the central potential of the positive and negative power supply potentials) is not achieved. For this reason, adverse effects such as a decrease in current supply capability to the device under measurement and an increase in waveform distortion appear. In order to solve this problem, the power supply circuit floating from the external ground potential such as a battery is used for the entire circuit, and ± Vs (Vs: power supply voltage) is applied to Vd, so that the operating point of the operational amplifier is set to the optimum potential. Makes it possible to

  By taking this potential, it is possible to improve the current supply capability to the device under test up to the rated maximum current of the first stage amplifier.

  In other words, the operational amplifier of the circuit according to the present embodiment is driven by a power supply independent of the ground level of the measurement system, so the potential of the terminal to be measured is always at the operational point of the operational amplifier, so regardless of the operational range of the operational amplifier. The potential can be set freely. As a result, even a voltage exceeding the operational range of the operational amplifier can be measured.

  FIG. 4 shows an amplification factor (circuit simulation result) with respect to Vd power supply noise by the circuit of this embodiment. In this circuit, the amplification factor of the second stage voltage amplifier circuit is 40 dB.

  In a conventional circuit (a circuit ground connected to a measurement system ground, which is expressed as “conventional circuit” in the figure), noise entering from Vd is also amplified by approximately 40 dB. On the other hand, in the simulation result (denoted as “Vd-GND circuit” in the figure) by the circuit configuration of the present embodiment, it can be seen that the amplification factor is almost 0 dB, that is, not amplified.

  FIG. 5 is a diagram illustrating another example of a method of supplying power to the amplifier.

  In the IV conversion circuit as in the above embodiment, the power supply is used in a state of floating from the apparatus ground. For this purpose, a power source such as a battery is used. However, in the case of a battery, since the discharge capacity is limited, the measurement time is limited. In addition, it is possible to float the power supply circuit using a transformer or the like, but since this circuit uses alternating current, the influence of the power supply peak may appear in the spectrum.

  For this purpose, as shown in FIG. 5, a solar battery 502 is used as a driving power source of the operational amplifier 501, and energy is supplied to the solar battery by light 505 from a light source (light bulb) 503. As a result, the power source 504 and the operational amplifier 501 can be electrically completely insulated. Further, if the light source 503 and the solar cell 502 are configured to transmit light using an optical fiber, the influence of electrical noise can be further reduced.

  Next, a circuit that enables direct current monitoring will be described with reference to FIG.

  The drain current of the MOS transistor can be obtained from the potential difference Vf between both ends of the negative feedback resistor 103 or 104 of the first stage IV conversion circuit by the following equation.

Drain current Id = potential difference Vf / negative feedback resistance value Rf (4)
Therefore, if a voltmeter is connected to both terminals of the negative feedback resistor 103 or 104 and the potential difference is obtained, the direct current can be obtained from the value.

  However, the negative feedback resistor 103 or 104 is also an element that simultaneously converts a current signal into a voltage. When an external device is connected, there is a possibility of adversely affecting the conversion of small signals such as noise of the element under measurement. Therefore, it is preferable to disconnect an external device such as a voltmeter at the time of small signal conversion (amplification).

  For this purpose, a switching element (switch 114) is connected to both terminals of the negative feedback circuit so that an external device can be disconnected. That is, when monitoring the direct current, the switch 114 such as a relay is turned on and connected to an external voltmeter. At the time of noise measurement, the switch 114 is turned off.

  In addition, in the measurement of the noise level where the influence of the voltmeter can be ignored, the measurement can be performed while the direct current is monitored while the voltmeter is connected.

  In the present embodiment, a low noise element such as a mechanical relay is used so that noise generated by the switch 114 itself does not affect small signal measurement such as noise of the element under measurement. The circuit is switched by an external control signal.

  As an alternative, as shown in FIG. 8, a circuit that directly switches the operational amplifier 801 and the ammeter 802 with a relay 803 or the like is also possible. However, in this case, measurement of small signals such as noise and monitoring of DC characteristics cannot be performed simultaneously. In FIG. 8, 804 is a positioner, 805 is a drain terminal of a MOS transistor, and 806 is a probe needle.

  When the device under test is not a MOS transistor but a noise of a bipolar transistor is measured, the output of the device is a collector.

As described above, since no current flows into the inverting input terminal side of the first stage IV conversion circuit, the drain current Id of the device under test flows through the negative feedback resistor Rf (corresponding to R2 in FIG. 2). It will be. Therefore, if the potential difference between both ends of the negative feedback resistor is Vf, the resistance value of the negative feedback resistor is Rf, and the drain current is Id, Vf = Rf · Id (5)
Therefore, the drain current Id can be obtained by measuring Vf.

  However, in general, when measuring the direct current characteristics of a MOS transistor, it is common to measure by sweeping the gate voltage or the like in order to measure the gate voltage-drain current characteristic. However, in the 1 / f noise measurement, the gate voltage cannot be swept because a low pass filter having a large time constant is added to the gate side in order to cancel the external noise entering from the gate. Therefore, the gate voltage can be swept by adding the following time constant switching circuit and time constant variable filter.

  FIG. 6 is a circuit diagram showing a schematic configuration of a time constant variable filter connected to the gate of the MOS transistor, and FIG. 7 is a circuit diagram showing an example of a specific configuration of the time constant variable filter.

  As shown in FIG. 6, the variable time constant filter according to the present embodiment includes resistors 601, 602, a capacitor 603, a switch 604, an operational amplifier 605, and the like. The resistors 601 and 602 are connected in parallel, and the resistors 601 and 604 are connected. Are connected in series. One ends of the resistors 601 and 602 are connected to a capacitor 603 and an operational amplifier 605, and the output of the operational amplifier 605 is input to the gate of the MOS transistor 116 which is a device under test. In this filter circuit, a circuit switching element (switch 604) such as a relay is added to a time constant circuit composed of resistors 601 and 602 and a capacitor 603, and the time constant can be switched to a value having no practical problem by the switch 604. It is what I did. A resistor having a small resistance value is used as the resistor 601, and a resistor having a large resistance value is used as the resistor 602.

  When measuring the DC characteristics of the MOS transistor 116 or the like and requiring a voltage sweep, the switch 604 is turned on and the time constant is set to be short so that the voltage can be followed. In general, in the weak signal measurement, the voltage sweep is rarely performed. Conversely, in the measurement requiring the voltage sweep, the external noise is not often a problem.

  When this function is used, the internal time can be stabilized with a short time constant in a short time when using the filter, and then the waiting time for voltage stabilization can be shortened by switching the time constant for a long time. can do.

  FIG. 7 shows an actual circuit example of this time constant variable filter. The time constant variable filter includes, for example, resistors 601a, 601b, 602a, 602b, 606a, 606b, capacitors 603a, 603b, 607a, 706b, switches 604a, 604b, operational amplifiers 605a, 605b, and the like. 602a and 602b are connected in parallel, and resistors 601a and 601b and switches 604a and 604b are connected in series, respectively. In addition, one ends of the resistors 601a, 601b, 602a, and 602b are connected to capacitors 603a and 603b and the non-inverting input terminals of the operational amplifiers 605a and 605b, respectively, and the output of the operational amplifier 605a is connected to the resistor 602b and the switch 604b. Is input to the gate of the MOS transistor 116 which is a device under test.

  Next, referring to FIG. 1, a circuit for changing the gain (gain) of the semiconductor evaluation apparatus of the present embodiment will be described.

  In the circuit shown in FIG. 1, IV conversion is performed by an operational amplifier 101 at the first stage. A switching element (switch 115) such as a relay is attached to the negative feedback resistors 103 and 104 of the IV conversion circuit. Since the first-stage gain is determined by the resistors 103 and 104 of the negative feedback circuit of this circuit, the first-stage gain can be switched by switching the resistance value. Moreover, a constant frequency characteristic can be ensured by simultaneously switching the phase advance capacitors 109 and 110 that match the resistance value of the switching circuit. Since the first stage IV conversion circuit is also a current supply circuit to the drain at the same time, if the resistance is reduced to reduce the amplification factor, the current supply capability to the drain is improved as a result.

  FIG. 9 shows simulation results and actual measurement values of the frequency characteristics of the circuit of FIG.

  In general, since the noise level of a MOS transistor increases when the drain current is large, if a low resistance value (resistor 103 in FIG. 1) is selected, a large current can be supplied at the same time as the gain decreases. Conversely, since the noise level is low in the low current region, a high gain can be obtained by selecting a high resistance value (resistor 104 in FIG. 1). Note that the maximum supply current value is given by the following equation.

Maximum supply current value = operational amplifier output voltage / feedback resistance value Rf (6)
IV converter gain (Vout / Iin) = feedback resistance value Rf (7)
In order to suppress the noise generated by the element itself and the conduction resistance to be low, the circuit switching element is controlled by a direct current from the outside using a mechanical relay.

  In the measurement of the bipolar transistor, the device output is the collector.

  Further, instead of switching the gain with a switch as described above, a method of automatically switching with software is also conceivable. For example, at the time of measurement, a noise level of a specific frequency (eg, 1 kHz) is first measured with a small gain, and the gain is switched when it is determined that the gain needs to be increased.

  Next, a circuit for directly measuring input conversion noise will be described with reference to FIGS.

  In the semiconductor evaluation apparatus according to the above-described embodiment, 1 / f noise generated in the drain current is measured. However, in the design of the semiconductor apparatus or the like, input conversion noise may be necessary. In this case, the input conversion noise can be measured by a circuit in which the measurement circuit is partially changed and the device to be measured is connected to the negative feedback circuit of the first-stage current-voltage circuit.

  FIG. 10 is a diagram illustrating the principle of measuring input conversion noise, and FIG. 11 is a circuit diagram illustrating an example of a circuit for measuring input conversion noise.

  The source terminal of the MOS transistor 116 which is a device under test is connected to the inverting input of the operational amplifier 1001. The source terminal is also connected to the constant voltage source 1003 via the resistor 1002. The gate terminal of the MOS transistor 116 is connected to the output of the operational amplifier 1001, and the MOS transistor 116 forms a negative feedback circuit. The non-inverting input of the operational amplifier 1001 is connected to the ground GND. In this circuit, the input terminal of the operational amplifier 1001 becomes a virtual short, and the source terminal of the MOS transistor 116 always maintains the ground level. Since the source current Is entirely flows into the resistor 1002 connected to the negative feedback input, the source current Is = V / R. Since the voltage V of the constant voltage source 1003 is a constant voltage, the source current Is is kept constant. Here, when the noise current In is applied to the drain, the noise current In flows through the resistor 1002 and the source potential fluctuates. However, negative feedback is applied by the operational amplifier 1001 to cancel the fluctuation, and the source current Is is kept constant. At this time, the voltage variation fed back to the gate is the input conversion noise.

  FIG. 11 shows an actual circuit example. This circuit includes a first-stage negative feedback circuit and a second-stage voltage amplification circuit that amplifies the output, that is, input conversion noise, to an appropriate level. In an actual circuit, since an active element is inserted into the first stage negative feedback circuit, oscillation easily occurs, and an oscillation prevention circuit 1101 is added. In order to prevent oscillation, a resistance that does not affect the measurement (<< gate insulation resistance), a time constant circuit that cuts other than the necessary frequency band, and the like are combined in accordance with the characteristics of the MOS transistor 116.

  FIG. 12 shows an example measured for an actual MOS transistor. In FIG. 12, black circles indicate the input conversion noise measured by this apparatus, and the solid line indicates the input conversion noise obtained from the noise current measurement result. In this measurement result, the input conversion noise measured by the semiconductor evaluation apparatus according to the present embodiment is compared with the value obtained from the result of directly measuring the noise current. As a result of comparison, it was confirmed that the effect of the present invention was effective.

  Therefore, according to the semiconductor evaluation apparatus of the embodiment, the following effects can be obtained.

  (1) By setting the reference potential of the operational amplifier as the drain potential, the gain of noise entering from the drain voltage Vd at the time of 1 / f noise measurement can be set to approximately 0 dB, that is, the noise is not amplified. Since the influence of noise entering from the drain potential Vd can be reduced, it is not necessary to take noise countermeasures such as a low-pass filter on the Vd side, and the measurement system can be simplified. In addition, the current supply capability to the drain can be improved. Since the current supply capability to the drain is improved, it can be applied to measurement of a wider range of MOS transistors. Furthermore, since the applied voltage does not depend on the operating voltage of the operational amplifier, an arbitrary voltage can be specified.

  (2) Normally, in the noise measurement, first, the DC characteristics of the MOS transistor are measured, then the measurement bias condition is obtained, and the noise is measured. However, by adding a DC current monitor circuit, it becomes possible to monitor DC current by switching the internal circuit, so that a series of measurements can be performed automatically and continuously. It becomes possible.

  (3) Since the gain of the operational amplifier can be switched, the optimum gain can be selected according to the device (device to be measured). Therefore, measurement of devices with different characteristics can be performed continuously without saturating the measurement device. It becomes possible to do.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  For example, in the above-described embodiment, the MOS transistor has been described as the element to be measured. However, the present invention is not limited to this and can be applied to other semiconductor elements such as a bipolar transistor.

  In the above description, the case where the invention made mainly by the present inventor is applied to the measurement and evaluation technique for noise characteristics of a semiconductor element, which is the technical field to which the invention belongs, has been described. However, the present invention is not limited to this. It is also possible to apply to an IV conversion measurement system. That is, since the influence of external noise can be reduced, the noise floor level can be lowered and the influence on the weak signal can be reduced. Further, by applying the power supply of the measurement circuit with the measurement potential as a reference, the input potential of the operational amplifier is always in the middle of the positive and negative power supply circuits, so that the output voltage of the operational amplifier can be utilized to the maximum. Also, in principle, there is no limit to the voltage range for setting the voltage at the input end, and it can be applied to a wide voltage range.

  The invention disclosed in the present application can be applied to a 1 / f noise measurement system of a semiconductor element.

It is a circuit diagram which shows the structure of the semiconductor evaluation apparatus by one embodiment of this invention. In the semiconductor evaluation apparatus by one embodiment of the present invention, it is a figure showing a current-voltage conversion circuit. In the semiconductor evaluation apparatus by one embodiment of the present invention, it is a figure showing a voltage amplification circuit. It is a figure which shows the reduction effect of an external noise in the semiconductor evaluation apparatus by one embodiment of this invention. It is a figure which shows another example of the power supply method to amplifier in the semiconductor evaluation apparatus by one embodiment of this invention. 1 is a circuit diagram showing a schematic configuration of a time constant variable filter connected to a gate of a MOS transistor in a semiconductor evaluation device according to an embodiment of the present invention. FIG. It is a circuit diagram which shows an example of a specific structure of the time constant variable filter of FIG. It is a figure which shows the circuit which switches an operational amplifier and an ammeter directly in the semiconductor evaluation apparatus by one embodiment of this invention. It is a figure which shows the simulation result and measured value of the frequency characteristic of the circuit of FIG. It is a figure which shows the measurement principle of the input conversion noise in the semiconductor evaluation apparatus by one embodiment of this invention. FIG. 5 is a circuit diagram showing an example of an input conversion noise measurement circuit in the semiconductor evaluation device according to the embodiment of the present invention. It is a figure which shows the measurement result of the input conversion noise measured by the circuit of FIG. (A), (b), (c) is a figure which shows the voltage waveform of the input of an inverting amplifier circuit examined as a premise of this invention, and an output. It is a figure which shows the structure of the noise measuring circuit and DC measuring device which were examined as a premise of this invention. (A), (b) is a figure which shows the frequency characteristic of the noise level measured with the spectrum analyzer examined as a premise of this invention.

Explanation of symbols

101, 102, 501, 605, 605a, 605b, 801, 1001, 1401 operational amplifiers 103-108, 601, 601a, 601b, 602, 602a, 602b, 1002 resistors 109-113, 603, 603a, 603b capacitors 114, 115, 604, 604a, 604b Switch 116 MOS transistor 502 Solar cell 503 Light source 504, 1405 Power source 505 Light 802, 1404 Ammeter 803 Relay 804, 1402 Positioner 805 MOS transistor drain terminals 806, 1403 Probe needle 1003 Constant voltage source 1101 Oscillation prevention circuit

Claims (5)

A semiconductor evaluation apparatus for measuring and evaluating noise of a field effect transistor,
A circuit connected to the drain of the field effect transistor, converting a current flowing through the drain of the field effect transistor into a voltage, and amplifying the voltage;
A semiconductor evaluation apparatus, wherein a power source of the circuit is applied based on a drain potential. The semiconductor evaluation apparatus according to claim 1,
A semiconductor evaluation apparatus, wherein a power source of the circuit is electrically independent from a ground. A semiconductor evaluation apparatus for measuring and evaluating noise of a field effect transistor,
A circuit connected to the drain of the field effect transistor, converting a current flowing through the drain of the field effect transistor into a voltage, and amplifying the voltage;
And means for connecting an external measuring device to the circuit when measuring the direct current of the field effect transistor, and disconnecting the external measuring device from the circuit when measuring noise of the field effect transistor. Semiconductor evaluation equipment. The semiconductor evaluation apparatus according to claim 3,
A semiconductor evaluation apparatus comprising a filter circuit connected to a gate of the field effect transistor and provided with means for switching a time constant. A semiconductor evaluation apparatus for measuring and evaluating noise of a field effect transistor,
A circuit connected to the drain of the field effect transistor, converting a current flowing through the drain of the field effect transistor into a voltage, and amplifying the voltage;
The semiconductor evaluation apparatus, wherein the circuit includes means for switching an amplification factor according to a noise level of the field effect transistor.

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