JPS6399580A - Tunnel injection control semiconductor device - Google Patents

Abstract

PURPOSE:To eliminate the carrier storing effect almost completely and to obtain a semiconductor device operating at an extremely high speed, by tunnel implanting an impurity from at least part of a source and a channel to provide a gate region in contact with the channel, so that control is performed by the gate region. CONSTITUTION:A p<++> region 11 serves as a source region and an n<+> region 14 as a drain region. Reference marks 15 and 15' indicate gate electrodes. Potential distribution of an n-type region 13 is regulated at that of the n<+> region providing a current path through an insulation film 16. The impurity concentrations of the n<+>-type region 12 and the n-type region 13 are made higher, the shorter the distance between gates is or the shorter the distance between gate and drain is. A gate voltage is applied to the n<+> region more effectively, the thinner the insulation film 16 contacted with the n<+> 12 is. In order to supply more tunnel current, it is better that the n<+> region 12 has a higher concentration of impurity and a smaller thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a device that is at the ultimate limit of miniaturization and speeding up of semiconductor devices, and is a semiconductor device that controls the potential distribution in front of the source by the electrostatic induction effect of the control electrode and controls the tunnel injection current. Regarding.

Conventionally, bipolar 1-transistors (hereinafter referred to as B P
) and electrostatic dielectric II +- transistor (hereinafter referred to as SI)
(referred to as T). In Bl)T, the potential of the base is controlled by the voltage of the base electrode, which is a control electrode, via the base resistor, and the amount of minority carriers flowing from the emitter is controlled. On the other hand, in SIT, the channel region through which current flows is almost or completely depleted, and the channel region is controlled by capacitive coupling to the control electrode Goo 1 using the electrode voltage.
The amount of carrier injection from the source region is controlled. In any transistor, the current flowing across the potential barrier is controlled by thermal energy. Therefore, although not so much, there is a carrier accumulation effect between the potential barrier and the source or emitter, which is one of the factors that limits the speed during ultra-high-speed operation.

An object of the present invention is to provide a semiconductor device that almost completely eliminates such carrier accumulation effects and operates at extremely high speed.

The following is a detailed explanation of the present invention with reference to the drawings. 3. First, regarding the tunnel current when reverse bias is applied to a p + n junction diode (direct) transfer type tunnel current The formula for the density is given by the following formula.

However, 2: unit charge, nlx: right effect suspension, 1) = 2
π-blank constant, ε: band cap, ■oL:
The applied voltage and F are given at the maximum of the ll"l'l junction. Here, ND: impurity density m of the n region, ε5: dielectric constant of the semiconductor, Vb;: diffusion potential of the p"n junction. Figure 1 shows the dependence of the reverse channel current density of the p''n junction on the reverse applied voltage given by equations 1) and (2).

FIG. 1 shows the results obtained by using GaAs as the semiconductor material. Therefore, ε,=1.43eV, ε,=10.9ε
. It is. ε. is the dielectric constant of vacuum.

m * −(t, −± 1., −s me, rne+h, and III b” = 0, 068 m OX
III ah" = 0.121110. mo is the mass of free electrons. In Figure 1, the current density is shown as a solid line and the electric field strength is shown as a dotted line. N is the impurity density in the n region. As N becomes larger, the depletion layer width becomes narrower and the electric field becomes larger, so the current density becomes larger.For example, when N=3X1Q18Ql-3, at a voltage of 1V, 3 ) current density is obtained.

As calculated here, semiconductor materials in which tunnel injection occurs through direct transition can cause tunnel injection more efficiently at a lower voltage than those with indirect transition.

The semiconductor device of the present invention has a structure in which the tunnel current 157 as shown in FIG. 1 is controlled by the control electrode G1- and the drain voltage.

FIG. 2 shows a cross-sectional structure for explaining the operation of the one-herald transistor of the present invention. The p1+ region 11 is a source region, and the n+
A region 14 is a drain region, and 15 and 15' are gate electrodes, which control the potential distribution of the n+ region and the n region 13, which serve as current paths, via an insulating film 16. The impurity density of each region is J, depending on the gate spacing, but the p++ region 11: 5 x 10 -1
5xlO-1xl0 cm, n13:lX10
~ lX10 Cm, n1
4:1×10'8 to 5×1020 clTl-3.

n+12.1]13 The impurity density in each region is
The culm has a short culm interval, and the culm has a short source-drain interval. Gate-to-gate spacing is, for example, 2μm
From the above, the source-drain distance is approximately 1000A, and the distance between the source and drain is 1.
It is about 2 to 3 μm from 000A. The thinner the insulating film 16 in contact with n4'12, the more effectively the gate voltage is applied to the n+12 region. is the potential distribution when a positive voltage is also applied to the gate to make it conductive, and (b) is the potential distribution when the gate is at zero potential (the source is also at the same potential) when it is cut off. (a) ), then
Since a positive voltage is applied to the gate, the potential gradient in front of the source becomes steeper, whereas in (b) it becomes more gradual due to the gate voltage. Since the electric field E determined by this gradient is large in (a), a tunnel current flows,
In (b), since E is small, no tunnel current flows. As shown in FIG. 3, the potential distribution of the channel serving as a current path is controlled by capacitive coupling, that is, the electrostatic induction effect, and the tunnel current from the source is controlled. Therefore, the transistor of the present invention is an electrostatic induction tunnel transistor. (5t
atic induced tunnel
Transist.

r:5ITT). If a large amount of tunnel current is to flow, the higher the impurity density in the n+12 region, the better, and the thinner the thickness.

For example, the thickness is from 0.2 μm to 0.03 μm. When the thickness of the n+12 region becomes thinner,
It is also necessary to narrow the gate-to-gate spacing. This is to more effectively control the entire surface of the channel to allow current to flow. For example, from 1 μm to 0.1 μm.

The insulating layer 16 is made of SiO2, Si3N4, A
See 20. , /IN etc. or a composite film thereof, GaAS
If so, GaO engineering Ny-8i, N4, A, 1203
, AiN, etc.

So far, we have explained a transistor with a structure in which the source region and drain region are composed of high impurity density regions of opposite conductivity types, but it can also be , a transistor that takes advantage of the spirit of the present invention can be formed. An example thereof is shown in FIG. The n48 region 31 is a source region, the n+ region 34 is a drain region, 35.35) is a gate electrode, and 36 is an insulating layer. The p+ region 32 is a region that forms a potential barrier to the source, and serves as a so-called true gate region. n area 3
3 becomes almost depleted, and the impurity density is determined. The thickness and impurity density of the p+ region 32 are set so that the entire region is depleted by the diffusion potential with the source n++ region, the diffusion potential with the n+ drain region, and the voltage applied to the train. The impurity density of the n+1 source region is 10'
9~1X10"Cl11-3, p+ region 32 and drain n'? region 34 are respectively 5x10~1Qcm, n
The area 33 is about 10 to 1 Qcm. FIG. 5 shows the potential distribution in the source-drain direction when a positive voltage is applied to the train. Depleted p+ region 32 forms a barrier to the source. Electron injection from the source is
blocked by this barrier. If the barrier is wide, even if the gate voltage lowers the barrier height, tunnel injection will not occur, and current will flow due to carriers crossing the barrier. That is, it is a conventional STT. However, when the width of the barrier is set to 1000 A or less, preferably 500 A or less, tunnel injection becomes noticeable. P region 32 is adapted to be depleted during operation. Thickness WP
and impurity density N, approximately 9X10 cm <NaW2<5x10'cm-'
Select as follows. For example, if W=500A, 3.6X1017cm-3<Na<2x10"cm
-3W=200A then 2.25X10'8c+++-'<Na <1.25X
1o +9 cm -3 and so on.

With this configuration, if a positive voltage is applied to the gates 1 to 1, the potential barrier is lowered and a tunnel current flows. Of course, if the barrier is lowered to a certain extent, carrier injection over the barrier will also occur at the same time.

So far, we have basically explained one gate electrode that controls tunnel injection. Of course, divided gates are included, but by providing a plurality of tunnel injection control gate electrodes and selecting the gate to which a control voltage is applied, a functional operation can be performed. 1. For example, in Figure C) ([shown 1゜11+''4
1: Source region, n 44 Ni drain region, 45.45
', 46.46' are the goo 1 ~ electrodes, 41', 44' are the source electrodes, and doshi twin electrodes 5. In this example, 4G
, 46' 4qt floating electrode, Goo 1-
The voltage is applied to the drain 45, 45', and when a positive voltage is applied to the drain 1-45 with a large positive voltage 1111'u applied, electrons flow near the lower surface.

Among these flowing electrons, electrons accelerated to high energy cross the barrier of the insulating layer 47, flow into the floating gate 4G, and are accumulated. When electrons are accumulated in the floating gate 46, the floating gate 46 becomes negatively charged and is therefore moved away from the vicinity of the lower surface. The same thing as IF5 can also be done with the upper gate electrode 45', 4G). When electrons are accumulated in the floating goo 1 by applying a large positive voltage to the drain or the goo 1 as described above, electrons no longer flow near the surface thereof. When the train voltage and gate voltage are returned to the normal operating voltage and the device is operated, the following operation occurs. 4G, 4G) Gai-4゛Remo) Electric 1 "Ha\ written in [1 and the same, 45.45
Electrons can be cured by applying +F goo 1 to ◇ to each surface. If lightning is being sent in and out of 4G and 46', electrons will concentrate near the center and flow with 45.45 1; voltage 4 applied. The electrons in the floating goo 1-1. ! Contains 41 goo 1- and electric loaf +lt1
In other words, electrons flow along the surface of A (1). If the drains are separated, or if the drain is placed in a Schottky junction as shown in step 1), the current flow will depend on the state of the electrons.
The inn will change.

For example, if electrons are occupied in 4G and 46', if a voltage is applied to either or both of 45 and 45', most of the current will flow to the drain inside. Assuming that 4G is written and 46 is not written, when voltage is applied to 45, the middle and upper drains are applied when voltage is applied to 45', and to the middle and upper drains when voltage is applied to both. It can be imagined that electric current flows.

There are cases in which electrons tunnel-injected from the source travel in the travel region up to the train by drifting, and cases in which they travel with almost no scattering (while being gradually accelerated).

The appearance of both is determined by the relationship between the mean free path of the electron and the distance in the traveling space. If the traveling space distance is sufficiently long compared to the free path, the vehicle will drift. Otherwise, the vehicle will be running gradually accelerated by the initial velocity and the electric field. It is said that the free path of Qa As is several times longer than that of Si. Therefore, the motion of electrons on the rear right is more likely to be flattened in GaAs.

When electrons travel with less scattering, their traveling speed increases, and the upper limit frequency determined from the traveling time becomes extremely high.

In the embodiments described above, it has been described that the impurity density in the source where tunnel injection occurs and the region directly adjacent to the source is spatially uniform; however, it is not necessarily necessary that the impurity density be uniform. It goes without saying that the semiconductor device of the present invention, which increases the tunnel injection efficiency by increasing the impurity density where tunnel injection is desired to occur most strongly, is not limited to the embodiments described here. Reverse the conductivity) 1,
: Of course it's good to have a good structure. In any case, the carrier fluid from the source is injected by tunnel injection,
Any semiconductor device may be used as long as it has a structure in which the amount of implantation is controlled by the electrostatic induction effect of the G1-voltage and the train voltage. j
・In order to cause channel implantation to occur efficiently, it is better to have a high impurity density. Moreover, the semiconductor device of the present invention is essentially a miniaturized device because this region is depleted and the potential distribution is controlled by capacitive coupling. It is ideal for not only individual devices but also ultra-high density and ultra-high speed integrated circuits. The smaller the dimensions of the device, the more effective it is. Moreover, since the chitria is directly implanted from the high impurity density region by channel, the effect of carrier accumulation near the source is extremely small, making it extremely suitable for high-speed operation.

Here, we have shown an example in which the source region is formed in a high impurity density region, but it is also possible to make the source a Schottky junction by using metal or silicide, and to cause tunnel injection by making the potential gradient in front of the Schottky junction steep. Of course.

The semiconductor device of the present invention can be manufactured using conventionally known manufacturing techniques.

[Brief explanation of the drawing]

Figure 1 shows the results of calculations using semiconductor materials as Qa AS.
Figures 2 and 3 are potential distributions in the source-drain direction, with (a) showing the conduction state and (b) the cut-off state;
6 through 6 are cross-sectional views showing embodiments of the present invention.

Claims (6)

[Claims] (1) A thin region where at least a portion of the source and drain regions of the first conductivity type with high impurity density and the channel region between the source and drain is in contact with the source is a conductivity type opposite to the first conductivity type with high impurity density. and a region with a low impurity density of the first conductivity type in contact with the drain, the tunnel is implanted through at least a portion of the source and the channel, and is controlled by a gate region provided in contact with the channel. Injection control semiconductor device. (2) A tunnel according to claim 1, characterized in that a high impurity density region of an opposite conductivity type is provided only in a portion substantially in contact with the high impurity density source region to determine the direction in which the tunnel effect occurs. Injection control semiconductor device. (3) The tunnel injection control semiconductor device according to claim 1 or 2, wherein the control electrode is an insulated gate. (4) The tunnel injection control semiconductor device according to claim 1 or 2, wherein the control electrode is a junction type gate. (5) The tunnel injection control semiconductor device according to claim 1 or 2, wherein the control electrode is a Schottky gate. (6) The tunnel injection control semiconductor device according to any one of claims 1 to 5, characterized in that a plurality of the control electrodes are provided.