JPS5965262A - Apparatus for measuring channel potential - Google Patents

Abstract

PURPOSE:To enable the measurement of source potential, by a method wherein a DC voltage form is connected between a source electrode and a reference potential supply source and it is utilized that the potential of a channel becomes equal to that of a source when voltage equal to or less than channel potential and voltage equal to or more than said potential are applied in this order to a drain electrode. CONSTITUTION:Because channel potential phiCH is lower than source and drain potentials phiS, phiD at time t1 as shown by (a), charge is not moved. At time t2, because drain applied voltage VD comes to OV, charge is supplied from a drain region 14 as shown by (b) and the potentials phiS, phiD are equal and come to a value lower than the channel potential phiCH. At time t3, when the drain applied voltage VD comes to high positive voltage, phiD becomes high while charge is moved to the drain region 14 from a low source region 13 and phiS is also raised but, when phiS becomes equal to phiCH, the charge movement is stopped by phiCH as barrier to form potential distribution as shown by (c) and phiCH to gate applied voltage VG is displayed by a DC voltmeter 21 connected to the source electrode 13. As the result, the channel potential phiD can be known by the DC voltmeter 21.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a channel potential measuring device for measuring the channel potential of, for example, a buried channel type MOS transistor.

[Technical background of the invention]

Conventionally, when measuring the channel potential of a buried channel type MOS transistor, a channel potential measuring device as shown in FIG. 1 has been used.

In the figure, 1 is a MOS transistor to be measured, which includes n+ type source and drain regions 13 and 14 formed on a p type semiconductor substrate 12, and source and drain regions 13 and 14 formed on a p type semiconductor substrate 12.
3. An n-type buried channel 15 formed between . The dirt electrode 17 is formed between the drain regions 14.

18 is the source region 1 of the MO8) run raster 1 for measurement.
3 is a variable DC power supply that applies a predetermined voltage; 19 is a DC ammeter for detecting the channel current generated by the movement of charge from the source region 13 to the drain region 14; 20 is a DC ammeter that applies a high positive voltage to the drain region 14; It is a DC power source that cannot be applied.

In the above configuration, when measuring the channel potential, first set the output 11I voltage vs of the variable DC power supply 18 to a high voltage, and then gradually lower the 15 voltage vs while watching the DC ammeter 19. The value of the voltage v8 of the variable DC power supply 18 when the current starts to flow through the DC ammeter 19 is read and taken as the channel potential. Note that FIG. 1 shows the case where the channel potential is measured when the applied pressure to the r-t is Ov.

FIGS. 2(a) to 2(c) are potential diagrams when measuring the channel potential of the MOS transistor shown in FIG. 1 above. In the figure, φ8 indicates a source potential, φCH a channel potential, and φ0 a drain potential. Source applied voltage v8
If is higher than the channel potential φCH, the potential distribution as shown in the figure (a) will occur, and the channel potential φ. acts as a barrier, so charge does not move from the source region to the drain region, and no channel current flows. The source applied voltage v8 is gradually lowered, and the source potential φ8 becomes the channel potential φ
When CH becomes lower, the potential distribution becomes as shown in Figure (c), the charge moves from the source region to the drain region, and a channel current ICH is generated. Therefore, channel current engineering CH
The channel potential can be set to the source potential φ8, which is the threshold value when the current begins to flow. That is, since the channel potential φcH at this time is equal to the source potential φ8, the channel potential φcH is determined by measuring the source potential φ6. , can be detected. Figure (b) shows the potential distribution in this state.

[Problems with background technology]

However, in the above configuration, it is necessary to detect a minute channel current), and delicate adjustment of the source applied voltage (8) is also necessary. Therefore, single-point measurement is not possible, the measurement time becomes long, and measurement errors tend to be large.

[Purpose of the invention]

This invention was made in view of the above circumstances,
The objective is to provide an excellent channel potential measuring device that can easily measure channel potential in a short time and with small measurement errors.

[Summary of the invention]

That is, in this invention, a pressure gauge is connected to the DC 7 between the source electrode and the reference potential supply source, and a voltage lower than the channel potential is first applied to the drain electrode, and then a potential higher than the channel potential is applied. By taking advantage of the fact that the channel potential and source potential at this time are equal, the nine channel potential is detected by measuring the source potential with the 14-pressure gauge described above.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

Figure 3 shows its configuration, including the device under test (MOS).
) shows the case where the channel potential is measured when the dart applied voltage of transistor) is Ov. In the figure, reference numeral 1 denotes a MOS transistor to be measured. A DC voltmeter 21 is connected between the ground region 13 of the transistor 11 and a reference potential supply source (ground point) as a voltage measuring means.

In addition, the drain region 14 is set to a ground potential (first potential) or a DC power source 22 by switching the switch SW.
(second potential) is selectively supplied, and the dirt electrode 17 is grounded.

In the above configuration, FIGS. 4 and 5(a)
, (b), the operation will be explained.

Figure 5 (=) is the potential diagram at timing t1 in Figure 4, and Figure 5 (b) is the potential diagram at timing t2. When the movable contact of switch SW is connected to the terminal I side, the drain applied voltage becomes O■. The potential distribution at this time is shown in Figure 5 (a
) as shown in the drain potential φ. and the source potential φ8 become equal. Next, when the movable contact of the switch SW is connected to the terminal ■ side, the drain applied voltage (DC power supply 22
Since the drain potential φ0 is a high positive voltage, the drain potential φ0 becomes high. At this time, the charge in the source region 130 is attracted to the drain region 14 and moves, and the source potential φ8 also rises.
Source potential φ8 is at channel 7, φ. When it becomes equal to □, the channel potential φcH is the pupil! 1. There is no movement of different stains, resulting in a potential distribution as shown in FIG. 5(b). Therefore, in this state kE2, the source potential φ6 is fixed to a value equal to the channel potential φCH, so the source potential φ
.

The channel potential can be determined by measuring the upstream [α current] with the pressure gauge 21.

By the way, when a DC voltmeter is used to measure the source potential φ8, a leakage current is generated depending on the input impedance of the DC voltmeter, and the source potential φ8 slightly decreases, but this value is measured in advance and the source potential φ8 is measured. Just correct the value.

According to such a +1 toso configuration, there is no need to adjust the voltage applied to the drain while detecting the channel current as in the conventional case, and the channel potential φ can be adjusted by simply switching the switch. 8
can be displayed on the DC voltmeter 21, so the channel potential φ.

□ can be easily measured and the measurement time can be shortened. still,
Since the channel potential φC□ can be displayed on the voltmeter 21, there is little reading error.

Fig. 6 shows a circuit for measuring the channel potential of a buried channel type MO8) transistor with respect to a dart applied voltage. Fig. 7 shows a timing chart of each applied voltage, and Figs. 8 (a) to (C) 2 shows the potential distribution of each state. This circuit is provided with a drain potential supply circuit 23 for supplying a voltage VD in the form of a voltage fluctuating between QV and 15V as shown in FIG. , dart electrode 17
■Voltage that changes level stepwise.

An r-) potential supply circuit 24 is provided.

The operation will be described with reference to the potential diagrams in FIGS. 8(a)'; (b) and (e) corresponding to the timing of tllt2+t3 shown in FIG. 7.

First, at timing t1, as shown in FIG. 8(a),
Channel potential φC1 is source, drain potential φ8. φo
Since the J density is also low, there is no charge movement.

Next, at timing t2, the drain applied voltage VD is 0■
Therefore, as shown in FIG. 8(b), charges are supplied from the drain/f drain region 14 and the source.

Drain potential φ8. φ0 are equal and channel potential φ9
．． ．． Yoshi also has a low value. Next, at timing t3, when the drain applied voltage VD becomes a high positive voltage, the drain potential φ. becomes high and the charge is in the source region 13 with a low potential.
The source potential φ8 moves from the source to the drain region 14 with a high potential, and the source potential φ8 also rises, but the source potential φ8 is lower than the channel potential φc.
When the channel potential φCH becomes equal to H, the channel potential φCH acts as a barrier and the movement of charges is stopped, resulting in a potential distribution as shown in FIG. 8(c). Therefore, the channel potential φCH and the source potential φ8 are approximately the same potential, which is the dart applied voltage V. (6
The channel potential φCH with respect to V) is displayed on the DC voltmeter 21 connected to the source electrode 13. Here, f-
) Applied voltage■. As mentioned above, the voltage changes stepwise, so the above operation is repeated for each dart applied voltage level, and the channel potential φCH with respect to the dart applied voltage VG is determined.
is obtained.

FIG. 9 shows the dart applied voltage V determined by the channel potential measuring device shown in FIG. 6 above. An example of the channel potential φ and H for each channel is shown below.

FIG. 10 shows another embodiment of the invention, in which CC
A case is shown in which the dart voltage of the input dart of the D transfer register measures the channel potential at Ov. In the figure, 25 is a p-type half-core substrate, 26 is an n-type impurity region, 271.27□, 273 is an n+-type impurity region, 28 is a p--type impurity region, 29 is a transfer electrode, and 30 is a Silicon oxide film, 31 is the output circuit, IG is the input p-to, OG is the output dirt, IS is the input source, R8
is a reset dirt, and RD is a recent drain. When the movable contact of the switch SW connected to the reset drain terminal RD is connected to the terminal I side, the ground potential Ov is supplied to the reset drain region 271, and the switch SW
When the rTJ' dynamic contact is connected to the terminal ■ side, a high positive voltage (for example, 12 V) is supplied from the DC power supply 22 to the reset drain region 27.

A DC voltmeter 21, which is a high input impedance voltage measuring means, is connected between the input source terminal Is and the ground point, and the input terminal IG is grounded.

Other gate weight 4:F (!7 set dirt electrode,
A voltage of 15 V, for example, is applied from the power supply 32 to the output gate electrode and transfer electrode so as not to affect the measurement of the channel potential of the input IG.

The operation in the above-mentioned 4;T configuration will be explained with reference to the potential diagram in FIG.

First, connect the movable contact of the switch SW to the terminal Ifllll.
If you connect it to the terminal ■ side after a specified period of time,
input source) IC channel potential φIG and input source IS
The potentials φ18 of the two terminals become equal to each other. Therefore, if you measure the input source ISO potential with the DC voltmeter 21, the input source is
G channel potential can be sensed.

For example, when measuring the channel potential when the dart voltage of D to which the control signal φ is supplied to the transfer electrode 29 in FIG. 10 is Ov, the potential of the control signal φ is
and apply 15V to the input dart IG. Then, the movable contact of the switch SW is connected to the terminal I side, and after a predetermined time, is connected to the terminal ■ side. The πL potential diagram at this time is shown in FIG. As shown in the figure, the control (III) φ at the transfer electrode 29 is supplied by the switching operation of the switch SW, and the channel potential φ9 of 4IiD becomes equal to the input source xsc1 potential φ□8. By measuring the input source ISO voltage using the DC voltmeter 21, the channel potential φ9 can be detected.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain an excellent channel potential measuring device that can easily measure channel potential in a short time and has small measurement errors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional channel potential measuring device, FIGS. 2(a) to (C) are potential diagrams for explaining the operation of the channel potential measuring device shown in FIG. 1, and FIG. Embodiments of the Invention - Reasons for a channel potential measuring device according to an example, FIGS. 4 and 5 (a) and (b)
6 are a timing chart and a potential diagram for explaining the operation of the channel potential measuring device shown in FIG. 3 above, respectively.
The figure is a block diagram showing another embodiment of the present invention, and FIGS. 7 and 8 (a) to (c) are timing charts and potentials for explaining the operation of the channel potential measuring device shown in FIG. 6, respectively. Figure, 2! ! FIG. 9 is a characteristic diagram showing the yJ relationship between the dart applied voltage and the channel potential measured by the channel potential measurement JL f'i in FIG. This is a diagram for explanation. 11... Regular use C10S transistor, 13...
- Source region, 14... Drain region, 17... Dart electrode, 21... DC voltmeter (voltage measurement means), 2
3... Drain potential supply circuit, 24... Dart potential supply port F13° immediate representative Benko (± Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 5 (a) (b) 6th diagram A Jl1 diagram time re't(t) - s8 diagram (a) (b) Figure 9

Claims (5)

[Claims] (1) Attach the first to the drain of the device to be measured. drain potential supply means for supplying a second potential; high input impedance voltage measuring means connected between the source of the element and the reference potential; and a potential for controlling the channel potential between the source and drain of the element. and supplying a first potential to the drain of the element for a predetermined period of time, then supplying a second potential, and measuring the voltage between the source and the reference potential at this time with the voltage measuring means. A channel potential measuring device characterized in that the channel potential of the element to be measured is detected by the above measurement value. (2) The drain potential supply means switches the potentials of a first potential supply source that generates a low voltage, a second potential supply source that generates a high positive voltage, and the first and second potential supply sources to 2. The channel potential measuring device according to claim 1, further comprising a switch for supplying the voltage to the drain of the device to be measured. (3) The potential that controls the channel potential between the source and drain of the device under test is a potential whose level changes step by step, and while this potential is at a constant level, the drain potential supply means is used to 2. The channel potential measuring device according to claim 1, wherein the channel potential measuring device is configured to supply two potentials and measure the channel potential for each level. (4) The channel potential measuring device according to claim 1, wherein the device to be measured is an MDS transistor. (5) The channel potential measuring device according to claim 1, wherein the device to be measured is a CCD transfer register, and the channel potential under each electrode of the device is measured.