JPH04330418A - Thin-film two-terminal element - Google Patents

Abstract

PURPOSE:To prevent the peeling of thin films by forming an SiOx layer having a specific distribution in a film thickness direction on a high-polymer film, thin producing the thin-film two-terminal element. CONSTITUTION:The compsn. of the SiOx of the thin-film two-terminal element constituted by laminating a high-polymer film substrate 1, the SiOx, layer 2, a 1st conductor layer 4, an insulating film 5, and a 2nd conductor layer bin this order is constituted by distributing (x) in a 1.1 to 2.0 range in such a manner that the (x) is small on the high-polymer film substrate 1 side and increases on the 1st conductor layer 4 side. The film is colored and the resistivity decreases if the (x) is smaller than 1.1 relating to the ratio of the oxygen of the SiOx film 2 and, therefore, such substrate is not usable as the substrate for the thin-film two-terminal element, On the other hand, the resistance of the SiOx film 2 increases and the film becomes stable to environment if the (x) in the SiOx film 2 increases. Further, the film stress increases and the high- polymer film is liable to peel with an increase in the (x) in the relation between the high-polymer film and the SiOx.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD The present invention relates to a thin film two-terminal device, and more specifically, a thin film two-terminal device useful as a switching device suitably used in flat panel displays for office automation equipment, TVs, etc., and particularly useful as a switching device in liquid crystal display devices. Regarding elements.

0002

2. Description of the Related Art There is a strong demand for the use of large-area liquid crystal panels in office automation equipment terminals and liquid crystal TVs, and for this reason, in the active matrix system, a switch is provided for each pixel to maintain the voltage.

By the way, as one of the above-mentioned switches, MI
M (Metal Insulator Metal) elements and MSM elements (metal-semiconductor-metal) are often used. This is because the thin film two-terminal element exhibits nonlinear current-voltage characteristics that are good for switching. Conventional thin film two-terminal devices have a metal electrode such as Ta, Al, Ti, etc. as a lower electrode on an insulating substrate such as a glass plate, and an oxide of the metal, SiOx, SiNx, etc.
It is known that an insulating film or a semiconductor film made of a material such as the like is provided, and a metal electrode made of Al, Cr, etc. is provided thereon as an upper electrode.

By using such active elements, it is possible to significantly increase the number of scanning lines and achieve high contrast. However, since the substrate is made of thick glass, there are drawbacks such as absorption and scattering caused by the glass, making the display dark and floating. Furthermore, for similar reasons, it has been contrary to the trends toward larger capacity, lighter weight, thinner layers, and lower costs. From this point of view, by using a polymer film as a substrate, we aim to provide a liquid crystal display device that provides high contrast and clear display, and is lightweight, thin, and inexpensive despite its large capacity. A technique has been proposed.

However, it has been found that when producing an active element on a polymer film substrate, a problem arises in that the thin film forming the active element may peel off from the substrate. A possible countermeasure to this problem is to form a buffer layer on the polymer film. Although the objective of the countermeasure is different, an example in which a polymer film is coated with SiO2 is disclosed in Japanese Patent Publication No. 1-47769. However, according to our experiments, simply S
It has become clear that in a polymer film coated with iO2, peeling of SiO2 occurs when producing a thin film two terminal.

[0006]

OBJECTS OF THE INVENTION It is an object of the present invention to overcome the above-mentioned drawbacks of the prior art and to provide a new structure of a thin film two-terminal element used in active matrix LCDs and the like, which is inexpensive and has a high yield.

[0007]

[Structure] The present invention provides a polymer film substrate, SiOx(x
In a thin film two-terminal device having a laminated structure in the order of 1.1 to 2.0), a first conductor layer, an insulating film, and a second conductor layer, Si
The composition of Ox is smaller on the polymer film substrate side, and the first
The present invention relates to a thin film two-terminal device characterized by having a distribution such that x is large on the conductor side.

Regarding the oxygen ratio of the SiOx film, x is 1
．． If it is less than 1, the film will be colored and the resistivity will be low, so it cannot be used as a substrate for a thin film two-terminal device. On the other hand, when x in the SiOx film increases, the SiOx film becomes high in resistance and stable against the environment. Also, looking at the relationship between x of the polymer film and SiOx, x
As the amount increases, the stress on the membrane increases, making it easier to peel off from the polymer film. Therefore, in order to simultaneously satisfy the adhesion of SiOx to the polymer film and the insulation and stability of SiOx, it is necessary to use SiOx on the polymer film.
This can be solved by providing an SiOx distribution in which x of x is smaller and x of SiOx is larger under the first conductor.

In order to produce the thin film two-terminal device of the present invention, as shown in FIG. SiOx (1.1<x<2.0) having a distribution in the film thickness direction is formed on the film surface 1 by sputtering, vapor deposition, plasma CVD, or the like. S
The iOx composition distribution can be easily achieved by changing the oxygen flow rate and/or oxygen partial pressure during film formation. Also,
It is also possible to change the composition distribution of SiOx by changing other parameters such as the film forming rate.

FIG. 2 shows an example of the distribution of SiOx composition. The distribution of the composition of SiOx depends on the thickness of the SiOx film, the adhesion between the polymer film and SiOx, the first conductor (first electrode) and the SiOx
Various shapes such as those shown in FIGS. 2(a), (b), (c), and (d) can be adopted depending on the adhesion strength with Ox, controllability of x value of film forming parameters, etc. If the film forming parameters are continuously changed, the result will be (a), but in order to ensure the adhesion of each interface, the shapes shown in (b), (c), and (d) should be adopted. In particular, SiOx on the polymer surface and the first
If the adhesion to the SiOx under the electrode is insufficient, types such as (b) and (d) are preferable. The film thickness of SiOx is 5
00 Å or more and 2 μm or less, preferably 1000 Å or more, 1
．． It is 5 μm or less.

Next, a transparent electrode material for a pixel electrode is deposited on the SiOx film 2 by a method such as vapor deposition or sputtering, and patterned into a predetermined pattern to form a pixel electrode 3. Furthermore, a conductor thin film for the lower electrode is deposited by a method such as vapor deposition or sputtering, and patterned into a predetermined pattern to form a first conductor layer (lower electrode) 4. After that, an insulating film made of a hard carbon film or the like is deposited using a plasma CVD method. The insulating layer 5 is formed by depositing it by an ion beam method or the like and patterning it into a predetermined pattern. Next, a conductor thin film for the bus line is deposited thereon by a method such as vapor deposition or sputtering, and patterned into a predetermined pattern to form the second conductor layer (upper electrode) 6. Finally, unnecessary portions of the lower electrode 4 are removed. Then, the transparent electrode pattern is exposed and used as the pixel electrode 3. The configuration of the MIM element is not limited to this, and after the MIM element is manufactured, a transparent electrode is provided on the top layer, the transparent electrode also serves as the upper or lower electrode, and the MIM element is formed on the side of the lower electrode. Various modifications are possible.

Electrodes 3, 4 and 6 in the present invention include:
For example, Al, Cr, Ni, NiCr, Pt, Ta, Ti
, Mo, W, Cu, Au and other metals and ITO, In2O
3. A transparent conductor such as SnO2 or ZnO is used, and is formed by a vapor deposition method, a sputtering method, or the like.

[0013] The materials constituting the insulating layer in the present invention are:
Examples include hard carbon films, SiNx, SiOx, etc., but hard carbon films (i-C films) are used as insulating films for MIM elements.
is preferred. This hard carbon film is a film containing carbon atoms and hydrogen atoms as main structure-forming elements and at least one of amorphous and microcrystalline materials, and is also called a diamond-like carbon film, an amorphous diamond film, or a diamond thin film.

[0014] A hard carbon film can be produced at a substrate temperature (film formation temperature) of about 150°C from room temperature, and has good current-voltage (I)
-V) characteristics. Therefore, it is possible to manufacture a good MIM element, and since the film properties can be changed greatly depending on the film forming conditions, it is possible to select a substrate from a wide range, and the control of the element properties can be expanded.From these points of view, LCD design Furthermore, MI with less variation in characteristics
It is possible to manufacture an M element, and since this film is a hard film, there is less damage caused by the rubbing process during liquid crystal encapsulation.Furthermore, since the dielectric constant is low, the area of the MIM element can be made larger than that of the LCD, so microfabrication is not necessary. Therefore, the yield can be improved. Regarding the film-forming temperature, 3.
For TFTs, a-Si and Poly-Si require temperatures of 300°C and 900°C, respectively, and these materials are not suitable for polymer film substrates. do not have.

The hard carbon film in the present invention will be explained in detail. 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 normal 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.

[0016] Regarding the hydrocarbon gas as the raw material gas, for example, paraffin hydrocarbons such as CH4, C2H6, C3H8, C4H10, olefin hydrocarbons such as C2H4, acetylene hydrocarbons, diolefin hydrocarbons, and even aromatic hydrocarbons. Gases containing at least all hydrocarbons, such as group hydrocarbons, can be used.

Furthermore, in addition to hydrocarbons, for example, alcohols, ketones, ethers, esters, CO,
Any compound containing at least carbon element, such as CO2, can be used.

In the method of forming a hard carbon film from a raw material gas in the present invention, active species for film formation are formed through a plasma state generated by a plasma method using direct current, low frequency, high frequency, microwave, etc. However, since the deposition is performed under low pressure for the purpose of increasing the area, improving uniformity, and 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 ionic state generated by ionization vapor deposition, ion beam vapor deposition, etc., or may be formed from neutral particles generated by vacuum vapor deposition, sputtering, etc. However, it may also be formed by a combination of these.

An example of the deposition conditions for the hard carbon film produced in this manner is as follows in the case of plasma CVD method. RF output: 0.1 to 50 W/cm2 Pressure: 1/103 to 10 Torr Deposition temperature: Room temperature to 250°C

In this plasma state, the raw material gas is decomposed into radicals and ions and reacts, resulting in amorphous (amorphous) and microcrystalline (crystal size) consisting of carbon atoms C and hydrogen atoms H on the substrate. is several 10 Å to several μm
) is deposited. The properties of the hard carbon film are shown in Table 1.

[0021]

[Table 1]

Note) Measuring method: Specific resistance (ρ): Obtained from the IV characteristics using a coplanar cell. Vickers hardness (H): Based on a micro Vickers meter. Refractive index (n): By ellipsometer. Defect density: Based on ESR. Note that the dielectric constant is as low as 5 or less.

As a result of analysis by Raman spectroscopy and IR absorption method, the hard carbon film thus formed shows that carbon atoms have SP3 hybrid orbitals and SP2 hybrid orbitals, as shown in FIGS. 3 and 4, respectively.
It has become clear that there are interatomic bonds that form a hybrid orbital. The ratio of SP3 bonds to SP2 bonds can be approximately estimated by peak-separating the IR spectrum. IR spectrum includes 2800-3150/c
Although the spectra of many modes overlap in the measurement, the attribution of the peak corresponding to each wavenumber is clear, and the peak area is calculated by separating the peaks using a Gaussian distribution as shown in Figure 5. However, by finding the ratio, SP3/SP2 can be found.

[0024] Also, according to X-ray and electron diffraction analysis, it is in an amorphous state (a-C:H) and/or about 50 Å~
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, the lower the RF output, the higher the resistivity and hardness of the film, and the lower the pressure, the longer the life of the active species. It is possible to achieve uniformity over a large area, and the specific resistance and hardness tend to increase. 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 it can form a hard carbon film of good quality even under relatively low temperature conditions of about room temperature to 150°C, so it is ideal for lowering the temperature of the MIM element manufacturing process. be. 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.

Furthermore, in addition to carbon atoms and hydrogen atoms, this hard carbon film contains elements of group III of the periodic table, elements of group IV, elements of group V of the periodic table, alkali metal elements,
It may also contain an alkaline earth metal element, a nitrogen atom, an oxygen atom, a chalcogen element, or a halogen atom as a constituent element. If a group III element of the periodic table, a group V element, an alkali metal element, an alkaline earth metal element, nitrogen atom, or oxygen atom is introduced as one of the constituent elements, the thickness of the hard carbon film is non-doped. It can be made about 2 to 3 times thicker than that of 100%, and this can prevent the occurrence of pinholes during device fabrication and dramatically improve the mechanical strength of the device. Further, in the case of a nitrogen atom or an oxygen atom, the same effect as in the case of a group IV element of the periodic table as described below can be obtained.

Similarly, in the case of introducing Group IV elements of the periodic table, chalcogen elements, or halogen elements, the stability of the hard carbon film is dramatically improved, and the hardness of the film is also improved, resulting in high reliability. It is possible to create a sexual element. These effects can be obtained because Group IV elements and chalcogen elements reduce the active double bonds present in the hard carbon film, and in the case of halogen elements, 1)
The abstraction reaction for hydrogen promotes the decomposition of the source gas and reduces dangling bonds in the film, and 2) during the film formation process, the halogen element X extracts hydrogen from the C-H bond and replaces it, This is because it enters the film as an X bond and the bond energy increases (the bond energy between C-H and between C-X is larger for C-X).

In order to use these elements as constituent elements of the film, in addition to hydrocarbon gas and hydrogen, elements from group III, group IV, and group V of the periodic table should be added to the film as raw material gases. In order to contain elements, alkali metal elements, alkaline earth metal elements, nitrogen atoms, oxygen atoms, chalcogen elements, or halogen elements, compounds (or molecules) containing these elements or atoms (hereinafter referred to as "other gases (sometimes referred to as "compounds") are used.

Examples of compounds containing Group III elements of the periodic table include B(OC2H5)3, B2H6, B2H6,
Cl3, BBr3, BF3, Al(O-i-C3H7)
3, (CH3)3Al, (C2H5)3Al, (i-C
4H9)3Al,AlCl3,Ga(O-i-C3H7
)3, (CH3)3Ga, (C2H5)3Ga, GaC
l3, GaBr3, (O-i-C3H7)3In, (C
2H5)3In etc.

Examples of compounds containing Group IV elements of the periodic table include Si2H6, (C2H5)3SiH, and SiF.
4, SiH2Cl2, SiCl4, Si(OCH3)4
,Si(OC2H5)4,Si(OC3H7)4,Ge
Cl4, GeH4, Ge(OC2H5)4, Ge(C2
H5)4, (CH3)4Sn, (C2H5)4Sn,S
There are nCl4, etc.

Compounds containing Group V elements of the periodic table include, for example, PH3, PF3, PF5, PCl2F3, PC
l3, PCl2F, PBr3, PO(OCH3)3, P
(C2H5)3, POCl3, AsH3, AsCl3,
AsBr3, AsF3, AsF5, AsCl3, SbH
3, SbF3, SbCl3, Sb(OC2H5)3, etc.

Compounds containing alkali metal atoms include:
For example, LiO-i-C3H7, NaO-i-C3H7,
There are KO-i-C3H7 and the like.

Examples of compounds containing alkaline earth metal atoms include Ca(OC2H5)3, Mg(OC2H5)
2, (C2H5)2Mg, etc.

Compounds containing nitrogen atoms include, for example, 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 monoxide, carbon dioxide, carbon suboxide, nitrogen monoxide, nitrogen dioxide, dinitrogen trioxide, and Inorganic compounds such as dinitrogen oxide and nitrogen trioxide; functional groups such as hydroxyl groups, aldehyde groups, acyl groups, ketone groups, nitro groups, nitroso groups, sulfone groups, ether bonds, ester bonds, peptide bonds, and heterocycles containing oxygen; Alternatively, organic compounds having bonds, metal alkoxides, etc. may be mentioned.

Compounds containing chalcogen elements include:
For example, H2S, (CH3) (CH2)4S (CH2)4
CH3,CH2=CHCH2SCH2CH=CH2,C
2H5SC2H5, C2H5SCH3, thiophene, H
There are 2Se, (C2H5)2Se, H2Te, etc.

[0038] Compounds containing halogen elements include:
For example, fluorine, chlorine, bromine, iodine, hydrogen fluoride, chlorine fluoride,
Bromine fluoride, iodine fluoride, hydrogen chloride, bromine chloride, iodine chloride,
Inorganic compounds such as hydrogen bromide, iodine bromide, and hydrogen iodide, and organic compounds such as alkyl halides, aryl halides, halogenated styrene, halogenated polymethylene, and haloform are used.

[0039]

EXAMPLES The present invention will be explained below by way of examples. Example 1 Using a Si target on a polyarylate film, A
A SiOx film with a thickness of 4000 Å was fabricated by sputtering with a mixed gas of r and O2. SiOx was produced with the distribution shown in FIG. 2(a) by controlling the flow rate ratio of Ar and O2. Next, I.T.
O was deposited to a thickness of 1000 Å by sputtering and patterned to form a pixel electrode. Next, MIM as an active element
The device was provided as follows. First, Al was deposited to a thickness of 1000 Å by vapor deposition, and then patterned to form a lower electrode. On top of that, an i-C film is deposited as an insulating film by plasma CVD.
After depositing Ni to a thickness of 850 Å using the EB deposition method, Ni was deposited to a thickness of 1000 Å using the EB evaporation method and patterned to form an upper electrode. Next, the i-C film was patterned by dry etching, and unnecessary Al films on the pixel electrodes were further etched to complete the MIM element. According to this method, an MIM element exhibiting good characteristics was obtained, and problems such as film peeling were eliminated during the manufacturing process.

Example 2 A SiOx film of 4000 Å was formed on a polyether sulfone film by reactive vapor deposition of SiO using O2 gas. SiOx was produced with the distribution shown in FIG. 2(b) by controlling the O2 partial pressure. Next, ITO was applied by sputtering method.
000 Å was deposited and patterned to form a pixel electrode. Next, an MIM element as an active element was provided as follows. First, Al was deposited to a thickness of 1000 Å by vapor deposition, and then patterned to form a lower electrode. On top of that, as an insulating film,
After depositing a C film to a thickness of 850 Å by plasma CVD, N
i was deposited to a thickness of 1000 Å by EB evaporation and patterned to form an upper electrode. Next, the i-C film was patterned by dry etching, and unnecessary Al films on the pixel electrodes were further etched to complete the MIM element. According to this method, an MIM element exhibiting good characteristics was obtained, and problems such as film peeling were eliminated during the manufacturing process.

[0041]

[Effect] According to the present invention, after forming SiOx (x is 1.1 to 2.0) with distribution in the film thickness direction on a polymer film, in order to fabricate a thin film two-terminal device, There is no peeling of the thin film, which occurs when devices are made directly on the film. Furthermore, since x in SiOx has a distribution, the adhesion between the polymer film and SiOx was good, and the insulation and environmental resistance of SiOx were also ensured. Therefore, it was possible to provide thin film two-terminal devices at low cost and with a high yield.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a thin film two-terminal element of the present invention.

FIG. 2 shows four aspects of the composition distribution of the SiOx layer (a),
Shown in (b), (c), and (d). In both cases, the left end of the horizontal axis is the polymer film surface, the right end is the first conductor surface, and the space between the left end and the right end is the SiOx layer. The vertical axis indicates the x value of SiOx.

[Explanation of symbols]

1 Polymer film substrate 2 SiOx layer (film) 3 Pixel electrode 4 First conductor layer (lower electrode) 5 Insulating layer 6 Second conductor layer (upper electrode)

Claims (2)

[Claims] Claim 1: A thin film two-terminal device comprising a polymer film substrate, a SiOx (x is 1.1 to 2.0) layer, a first conductor layer, an insulating film, and a second conductor layer in this order:
A thin film two-terminal element characterized in that the composition of x has a distribution such that x is small on the polymer film substrate side and x is large on the first conductor side. 2. The thin film two-terminal device according to claim 1, wherein the insulating film is a hard carbon film.