JPH04109676A - Mimim element - Google Patents

Abstract

PURPOSE:To obtain excellent transistor characteristics with high reliability by reducing the thickness of a second insulating layer formed on a second electrode smaller than that of a first insulating layer. CONSTITUTION:A first electrode 2' is formed on a substrate 1, and a first insulating layer 3' is so formed on the electrode 2' as to cover the electrode 2'. A second electrode 4' is formed, an insulating layer 5' is formed on the electrode 4', and a third electrode 6' is further formed on the layer 5'. The thickness of the layer 5' is reduced smaller than that of the layer 3'. That is, even if the step coverage of the layer 5' is wrong at a position A where a largest step is generated in a laminated structure, an electrode material layer is not formed thereon, and hence it is not short-circuited. Thus, the short-circuit at the step scarcely occurs, and high reliability for operating stably for a long time is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to MIMIM type devices, which are metal-based transistors.

[Prior art]

The MIMIM type element, which is a metal-based transistor,
MIM is the probability of electrons tunneling through the insulating layer of the MIM structure.
This is an element that performs transistor operation by controlling an electrode inserted in the middle of the structure. The MIMIM type element has a metal base, has low resistance, and uses tunneling electrons, so it is attracting attention as an element capable of high power and high speed operation. However, although the basic concept of this MIMIM type element was established in 1961, it has not yet been put into practical use. One of the reasons for this is that it is not possible to form a high-quality insulating film uniformly and with good reproducibility.

For this insulating film, for example, M, Heiblum
[Solid State Electronics
ate Electronics) Vol, 24, p.
, 343-366, 1981) is known. Since this proposal uses natural oxidation of metal to form the insulating layer, it is difficult to strictly control the film thickness during fabrication, and many defects occur in the film, so it is difficult to put it into practical use. It was not possible to obtain sufficient characteristics suitable for Another proposal is to grow an insulating film in an oxidizing atmosphere or in an electric field directed plasma (Japanese Patent Application Laid-open No. 145880/1983). but,
These proposals do not contain specific descriptions, and the manufacturing methods based on these proposals are difficult to control film thickness or film quality, and there are also problems with reproducibility, so it is difficult to put them into practical use. It didn't work out.

In addition, thermal oxidation and anodic oxidation are used as methods for forming high-quality oxide films on metal surfaces. but,
The thermal oxidation method requires a high substrate temperature of about 400 DEG to 500 DEG C., and is therefore limited in substrate materials that can withstand high temperatures, and it is difficult to obtain thin films. Since the anodic oxidation method involves a chemical reaction in a solution, it is difficult to optimize the solution composition and reaction conditions, and annealing at about 150°C is required after oxidation.
It was unsuitable for manufacturing devices such as MIM type devices.

Other methods include depositing an oxide film by vapor deposition, plasma oxidation, and implantation of oxide ions, but in all of these methods, defects in the oxide film,
Non-uniformity or non-uniformity of the interfacial state between the metal and the oxide film has been a problem.

As described above, conventional MIMIM type devices are difficult to manufacture, and furthermore, the characteristics between devices vary due to the non-uniformity of the oxide film quality and the state of the metal-oxide film interface. However, it was not possible to obtain a device with good transistor characteristics.

In order to solve this problem, it has been proposed to use a hard carbon film for the insulating layer (Japanese Patent Application Laid-open No. 7577/1983). A hard carbon film can be formed at a relatively low temperature such as room temperature, and a high-quality film can be obtained uniformly and with good reproducibility8. FIG. 3 shows a cross-sectional view of a MIMIM-type device using the MIMIM type device.

A first electrode 2 is formed on a substrate 1, and a first insulation M3 made of a hard carbon film is formed on the first electrode 2.
It is formed to cover. A second electrode 4 is formed on the first insulating layer 3, a second insulating layer 5 is formed on the second electrode 4, and a second insulating layer 5 is formed on the second insulating layer 5. Three electrodes 6 are formed.

In the MIMIM type device having the above structure, the thickness of the first insulating layer 3 is sufficiently thin, for example, from several angstroms to several hundred angstroms, so that electrons from the first electrode 2 are transferred to the passes through the insulating layer 3 and flows into the second electrode 4, which is the base. These electrons are hot electrons with a high energy state, and some of them pass through the second insulating layer 5 and pass through the third insulating layer 5, which is the collector.
reaches the electrode 6. The probability that electrons tunnel through the first insulating layer 3 varies greatly depending on the potential difference between the first electrode 2, which is the emitter, and the second electrode 4, which is the base, so that the transistor can operate. However, in such a structure, MJI/! 3 is an extremely thin film that exhibits a tunneling effect, so coverage is insufficient particularly at the side or edge portions of the electrode material 2, making it easy to cause short circuits with the electrode material 4, resulting in a lack of reliability. .

〔the purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to eliminate such drawbacks of the prior art and provide a MIMIM type device with high reliability and good transistor characteristics.

[Structure] The present invention includes a substrate, a first electrode formed on the substrate, a first insulating layer formed on the first electrode, and a first electrode formed on the substrate.
Awesome! MIMIM consisting of a second electrode formed on the # layer, a second insulating layer formed on the second electrode, and a third electrode formed on the second insulating layer. The present invention relates to a MIMIM type device, characterized in that the thickness of at least the second insulating layer is thinner than the thickness of the first insulating layer.

FIG. 1 shows a cross-sectional view for explaining a MIMIM type device according to the present invention. (b) is a side view of (a) [(a) is 9
05 rotation].

A first electrode 2' is formed on the substrate], and a first insulator M3' is formed on the electrode 2' so as to cover the electrode 2'. Subsequently, a second electrode 4' is formed, an insulating layer 5' is formed on the electrode 4', and a third electrode 6' is further formed on the insulating layer 5'. In the present invention, at least the thickness of the second insulating layer 5' is equal to that of the first #@edge layer 3'.
It is characterized by being thinner than the thickness of .

At this time, it is preferable that the first, second and third electrodes function as a collector and a base 5 emitter, respectively.

In other words, the electrons from the third electrode 6' are $1! due to the tunnel effect. It passes through the edge layer 5' and flows into the base, the second electrode 4'. Some of these electrons are transferred to the first absolute aFf
13' and reaches the collector, the first electrode 2'. In order for the above operation to be possible, ■insulating layer 5
' is required to be an extremely thin film that exhibits a tunnel effect, and (2) the base electrode 4' is required to be an extremely thin film so that electrons do not lose energy due to scattering.

There are no such strict restrictions on other material layers, so
In the laminated structure, the largest step differences occur at the locations indicated by A and A' in FIG. As can be seen from the figure, even if the step coverage of '41M5' is poor at the part A, no short circuit will occur because no electrode material layer is formed thereon.

In addition, since the thickness of the electrode material layer 4' is thin at the portion A', the level difference is small, and the coverage of the absolute 8N5' is relatively good, so that short circuits are unlikely to occur. On the other hand, in the conventional configuration shown in FIG. 3, the extremely thin insulating layer 3 is formed on the relatively thick first electrode 2, so the step coverage at the part A is insufficient. , a short circuit with the second electrode 4 is likely to occur.

Note that the electrodes 2', 4' and 6' are made of AQ, Cr, Ni, NiCr, PerTa, Ti, Mo, etc., as in the conventional case.
, W, Cu, Au, Ag and other metals and ITO, In2O
A transparent conductor such as .

There are no particular restrictions on the material that can be used for the insulating layer of the present invention, and hard carbon films, SiOx, SiNx, etc. can be used, but hard carbon films are particularly preferred.

An organic compound gas, especially a hydrocarbon gas, is used to form a hard carbon film. The phase state of these raw materials does not necessarily have to be a gas phase at room temperature and pressure; they can be used in either a liquid or solid phase as long as they can be vaporized through melting, evaporation, sublimation, etc. by heating or reduced pressure. be.

Regarding hydrocarbon gas as a raw material gas, for example, CH
4. A gas containing at least all hydrocarbons such as paraffinic hydrocarbons such as C2HIl, C4H, etc., olefinic hydrocarbons such as C, H4, diolefinic hydrocarbons, acetylenic hydrocarbons, and even aromatic hydrocarbons. is available.

In addition, compounds other than hydrocarbons, such as alcohols, ketones, ethers, esters, etc., can be used as long as they contain at least a carbon element.

In the present invention, a method for forming a hard carbon film from a raw material gas is preferably a method in which the film-forming active species is formed through a plasma state generated by a plasma method using direct current, low frequency, high frequency, microwave, etc. However, in order to perform deposition under low pressure for the purpose of increasing the area, improving uniformity, and/or forming a film at a low temperature, a method using a magnetic field effect is more preferable. Active species can also be formed by thermal decomposition at high temperatures.

In addition, it may be formed through an ion state generated by an ionization vapor deposition method or an ion beam vapor deposition method, or it may be formed from neutral particles generated by a vacuum vapor deposition method, a sputtering method, etc. Furthermore, it may be formed by a combination of these.

An example of the deposition conditions for the hard carbon film produced in this manner is approximately as follows in the case of plasma CVD method.

RF high power 20.1~50 W/cd Pressure: 10-'~10 Torr deposition temperature
: Room temperature to 950°C, preferably room temperature to 300°C This plasma state causes the source gas to decompose into radicals and ions and react.

Amorphous (non-crystalline) consisting of carbon atoms C and hydrogen atoms H and microcrystalline quality (crystal size is from several dozen to
A hard carbon film containing at least one of several microns+) is deposited. Table 1 shows the properties of the hard carbon film.

Note) Measurement method: Specific resistance (ρ): Determined from the IV characteristics using a coplanar cell.

Vickers hardness (H): Based on micro Vickers meter.

Refractive index (n): by ellipsometer.

Defect density: Based on ESR.

As a result of analysis by IR absorption method and Raman spectroscopy, the hard carbon film thus formed was found to have interatomic bonds that formed a hybrid orbital of BF3 and a hybrid orbital of BF2 in carbon atoms, as shown in Figures 4 and 5. It is clear that there is a mixture of

The ratio of BF3 bonds to BF2 bonds can be roughly estimated by peak-separating the IR spectrum.

In the IR spectrum, the spectra of many motes overlap between 2800 and 3I50■-1, but the attribution of the peak corresponding to each wave number has been clarified, and as shown in Figure 6, it has a Gaussian distribution. If you perform peak separation by , calculate the area of each peak, and find the ratio, S
P'/SP2 can be known.

Furthermore, according to X-ray and electron diffraction analysis, the hard carbon film is in an amorphous state (a-C:H) and/or about 50 to
It is known that it is in an amorphous state containing microcrystalline grains of about several μm.

In the case of the plasma CVD method, which is generally suitable for mass production of hard carbon films, the lower the RF output power, the higher the specific resistance value and hardness of the film, and the lower the pressure, the longer the life of active species, so the substrate temperature will decrease. It tends to lower the temperature, achieve uniformity over a large area, and increase specific resistance and hardness. Furthermore, since the plasma density decreases at low pressures, methods using magnetic field confinement effects are particularly effective in increasing resistivity. Furthermore, this method has the characteristic that a high quality hard carbon film can be formed even under relatively low temperature conditions of about room temperature to 150° C., so it is optimal for lowering the temperature of the MIMIM element manufacturing process. Therefore, the degree of freedom in selecting the substrate material to be used is increased, and the substrate temperature can be easily controlled, so that a uniform film can be obtained over a large area.

The hard carbon film of the present invention can contain a dopant.

Group ■, group ■, group ■ elements of the periodic table, alkali metal elements, alkaline earth metal elements, nitrogen elements, oxygen atoms, or halogen elements as dopants are included in the raw material gas for forming a hard carbon film. Mix and use. The mixed form of the dopant can be used not only in its single form, but also as a gas in a compound (or molecule) containing it (hereinafter, these may be referred to as "other compounds").

Examples of compounds containing Group I elements of the periodic table include B (OC2Hs)3p B2 H5y BCQ,
1 rBBr, lBF3, AQ(0-4-Cs
Ht)s + (C)+3)3Aβ, (C,H5)□
Affl.

(1-C4H,), AQ, AQCQ3. Ga(0-
i-(:, Fl,)3. (CI(,), Ga1(C,H
), Ga, GaCQ,, GaBr3. (0-i
-C,H7)3In.

(C2H5)3In, etc.

As a compound containing an element of group Ⅰ of the periodic table.

For example, Si, H,, (CzHs)aslHy 5IF4
15IHzCQzySiCR4,5i (ocH3)4.
5dOC,11,)4.5x(QC3H7)4°GaC
Q4. GeH4,Ge(OCzH5)*-Ge(Cz
H5)*, (CH3)4Sn-(C2H,)4Sn,
There are 5nCQ4 etc.

Examples of compounds containing Group Ⅰ elements of the periodic table include PH
,,PF,, PF,, PCQ2F,, P(4,,
PCI22F.

PBr3. PO(OCH3)37 P(C2HE)3
1 POCQ3. ASH3゜, AsCQ, 3+ A
SB'3+ AsF3+ AsF5+ AsCQ
3+ sbH,, 5bFitSbCQ,, 5b(O
There are C2H, )3, etc.

Examples of compounds containing alkali metal atoms include Li0-
i-C, H,, Na0-i-C, H7, KO-i-C,
There is 87 mag.

Examples of compounds containing alkaline earth metal atoms include Ca
(OC2H5)! r Mg(OCzt(s)z t
(CzHs)2Mg, etc.

Examples of compounds containing nitrogen atoms include nitrogen gas, inorganic compounds such as ammonia, organic compounds having functional groups such as amino groups and cyano groups, and nitrogen-containing heterocycles.

Examples of compounds containing oxygen atoms include oxygen gas, ozone, water (steam), hydrogen peroxide, -carbon oxide, carbon dioxide, carbon suboxide, -nitrogen oxide, nitrogen dioxide, dinitrogen trioxide, dinitrogen pentoxide, Inorganic compounds such as nitrogen trioxide, hydroxyl groups,
Examples include organic compounds having functional groups or bonds such as aldehyde groups, acyl groups, ketone groups, nitro groups, nitroso groups, sulfone groups, ether bonds, ester bonds, peptide bonds, and oxygen-containing heterocycles, as well as metal alkoxides. It will be done.

Examples of compounds containing halogen elements include fluorine, chlorine, bromine, iodine, hydrogen fluoride, chlorine fluoride, bromine fluoride, iodine fluoride, hydrogen chloride, bromine chloride, iodine chloride, hydrogen bromide, iodine bromide, Inorganic compounds such as hydrogen iodide, alkyl halides,
Organic compounds such as halogenated aryl, halogenated styrene, halogenated polymethylene, and haloform are used (Japanese Patent Application No. 93352.2-114867.2-12
(See No. 4469).

The substrate used in the present invention is glass, plastic,
Examples include a wide variety of substrates such as plastic films and the above-mentioned substrates whose surfaces are coated with inorganic and/or organic materials. In terms of weight reduction and cost reduction, it is advantageous to use plastics or plastic film substrates.

The MIMIM type device according to the present invention is a high-speed transistor such as a metal base transistor.

It can be applied to high-speed operation circuits using high-speed transistors.

〔Example〕

Examples of the present invention are shown below, but the present invention is not limited thereto.

Example 1 The MIMIM type device shown in FIG. 1 was manufactured as follows.

Pyrex glass is used as the substrate 1, and AQ
was formed into a film by a vapor deposition method and patterned to form a first electrode layer 2'. Next, a hard carbon film was formed by plasma CVD to form the first insulating layer 3'. Furthermore, AQ is formed into a film by a vapor deposition method and patterned to form a second electrode layer 4'.
was formed. On top of this, a hard carbon film is formed by plasma CVD to form a second insulating layer 5'.

Further, AQ was deposited thereon by vapor deposition and patterned to form a third electrode layer 6'.

According to this example, no defects due to short circuits at the step portion occurred, and the device operated stably for a long period of time.

Example 2 A MIMIM type device shown in FIG. 2 was manufactured as follows. The major difference from Embodiment 1 is the insulating layer 7 for limiting the active part.
By doing so, the probability of characteristic defects due to minute defects such as pinholes is reduced,
A more reliable device can be manufactured. First electrode layer 2'
The method of forming the first insulating layer 3', the second electrode layer 4', and the second insulating layer 5' was the same as in Example 1. On top of this, an insulating layer 7 for limiting active parts is applied with a spinner using a polyimide photosensitive resin "Photonice" (manufactured by Toshi), patterned through exposure, development, and rinsing, followed by heat treatment. Formed by doing. Further, AQ was deposited thereon by vapor deposition and patterned to form a third electrode layer 6'. Note that this does not preclude the use of other materials, such as a hard carbon film, as the insulating layer 7.

According to this embodiment, in addition to the effects of Embodiment 1, the active part of the element is limited by the patterned third insulating layer 7 for limiting the active part. The probability that minute defects such as pinholes will be introduced into the insulating layer is reduced. As a result, the transistor operation of the device becomes more stable and reliable. Furthermore, since the third insulating layer is present in the parts other than the active part of the element, reliable glabellar insulation between the emitter and the base can be achieved.

〔effect〕

By adopting the structure of the present invention, short circuits at the step portion are less likely to occur, and as a result, a highly reliable MIMIM type element that operates stably for a long time can be provided.

[Brief explanation of drawings]

FIG. 1(a) is a cross-sectional view of one specific example of the MIMIM device of the present invention, FIG. 1(b) is a side view of FIG. 1(a), and FIG. 2 is a cross-sectional view showing another example of the MIMIM device of the present invention. , FIG. 3 is a cross-sectional view of a conventional MIMIM device, and FIG. 4 is a cross-sectional view of a MIMI device of the present invention.
Figures 5 and 6 are spectral diagrams showing the results of Raman spectroscopy analysis of the hard carbon film used as the insulating layer of the M-type element. FIG. 2 is a spectrum diagram showing the results of analysis using an IR absorption method. 1...Substrate 2, 2'...First electrode 3.3'...First insulating layer 4,4'...Second electrode 5.5'...Second insulation N 6,6'・
...Third electrode 7...Insulating layer for limiting active part

Claims (1)

[Claims] 1. A substrate, a first electrode formed on the substrate, a first insulating layer formed on the first electrode, and a first insulating layer formed on the first insulating layer. In a MIMIM type element comprising a second electrode formed, a second insulating layer formed on the second electrode, and a third electrode formed on the second insulating layer, A MIMIM type device characterized in that the thickness of the second insulating layer is thinner than the thickness of the first insulating layer. 2. The MIMIM type device according to claim 1, wherein at least one of the insulating layers is a hard carbon film.