JP2994056B2 - Thin-film two-terminal element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin-film two-terminal element, and more particularly, to a thin-film two-terminal element which can be suitably used for a flat panel display for OA equipment or TV, and particularly useful as a switching element for a liquid crystal display. Related to the element.

[0002]

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

By the way, one of the switches is 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 a good nonlinear current-voltage characteristic for switching. The conventional thin-film two-terminal element is formed by forming a lower electrode on an insulating substrate such as a glass plate.
a, a metal electrode such as Al, Ti, etc., an oxide film of the metal or an insulating film or semiconductor film made of SiOx, SiNx or the like is provided thereon.
One provided with a metal electrode such as l, Cr or the like is known.

If such an active element is used, it is possible to greatly increase the number of scanning lines and to obtain high contrast. However, since thick glass is used for the substrate, there are drawbacks such as absorption and scattering by the glass, dark display, and floating display. For the same reason, the tendency to increase the capacity, reduce the weight, reduce the thickness, and reduce the cost was contrary to the tendency. From such a point of view, by using a polymer film for the substrate, it is possible to obtain a high-contrast and clear display, and to provide a lightweight, thin, and inexpensive liquid crystal display device despite its large capacity. Technology has been proposed.

However, it has been found that when an active element is manufactured on a polymer film substrate, a thin film forming the active element may be peeled off from the substrate, causing a problem. As a countermeasure, a method of forming a buffer layer on a polymer film can be considered. Although the purpose of the countermeasure is different, an example in which a polymer film is coated with SiO ₂ is disclosed in Japanese Patent Publication No. 47767/94. However, according to our experiments, simply S
It has been clarified that the polymer film coated with iO ₂ peels off SiO ₂ when a thin film two-terminal is produced.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks in the prior art and to provide a new structure of a thin-film two-terminal element used for an active matrix LCD or the like at a low cost and a high yield.

[0007]

The present invention relates to a polymer film substrate, SiOx (x
Are 1.1 to 2.0) layers, a first conductor layer, an insulating film, and a second conductor layer.
When the composition of Ox is small on the polymer film substrate side,
The present invention relates to a thin-film two-terminal element having a distribution such that x is large on the conductor side.

When the oxygen ratio of the SiOx film is less than 1.1, the film is colored and the resistivity is low, so that 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 resistance of the SiOx film increases and the SiOx film becomes stable to the environment. Also,
Looking at the relationship between the polymer film and x of SiOx, the film stress increases as x increases, and the polymer film is easily peeled off. Therefore, in order to simultaneously satisfy the adhesion of SiOx to the polymer film and the insulating property and stability of SiOx, x of SiOx is smaller on the polymer film and x of SiOx is larger under the first conductor. This is solved by providing such a SiOx distribution.

As shown in FIG. 1, first, a polymer such as polyethylene terephthalate, polycarbonate, polyarylate, polyether sulfone, polyimide, polyethylene, polymethyl methacrylate, etc. is prepared to produce the thin film two-terminal element of the present invention. SiOx (1.1 <x <2.0) having a distribution in the film thickness direction is formed on the film surface 1 by a sputtering method, an evaporation method, a plasma CVD method, or the like. S
The composition distribution of iOx can be easily achieved by changing the oxygen flow rate and / or the oxygen partial pressure during film formation. Also,
The composition distribution of SiOx can be changed by other parameters such as a film forming speed.

FIG. 2 shows an example of the distribution of the composition of SiOx.
The distribution of the composition of SiOx includes the thickness of SiOx, the adhesion between the polymer film and SiOx, the first conductor (first electrode) and Si.
Various forms such as those shown in FIGS. 2A, 2B, 2C, and 2D can be adopted depending on the adhesion to Ox, the controllability of the x value of the film formation parameter, and the like. If the film forming parameters are continuously changed, the result will be (a), but in order to secure the adhesion at each interface, it is necessary to adopt shapes such as (b), (c), and (d). In particular, SiOx on the polymer surface and the first
When the adhesion to SiOx under the electrode is insufficient, types such as (b) and (d) are preferable. The thickness of SiOx is 5
00 ° or more and 2 μm or less, preferably 1000 ° or more,
1.5 μm or less.

Next, a transparent electrode material for a pixel electrode is deposited on the SiOx film 2 by a method such as evaporation or sputtering, and is patterned into a predetermined pattern to form a pixel electrode 3. Further, a conductor thin film for a lower electrode is deposited by a method such as evaporation or sputtering, and is 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 formed by a plasma CVD method. The insulating layer 5 is formed by applying an ion beam method or the like and patterning this into a predetermined pattern. Next, a conductor thin film for a bus line is deposited thereon by a method such as vapor deposition or sputtering, and is patterned into a predetermined pattern to form a second conductor layer (upper electrode) 6. Finally, an unnecessary portion of the lower electrode 4 is removed. Then, the transparent electrode pattern is exposed to form a pixel electrode 3. The configuration of the MIM element is not limited to this. After the MIM element is manufactured, the transparent electrode is provided on the uppermost layer, the transparent electrode also serves as the upper or lower electrode, and the MIM element is provided on the side surface of the lower electrode.
Various modifications, such as those in which an element is formed, are possible.

The electrodes 3, 4 and 6 in the present invention include:
For example, Al, Cr, Ni, NiCr, Pt, Ta, T
Metals such as i, Mo, W, Cu, Au and ITO, In ₂
A transparent conductor such as O ₃ , SnO ₂ , or ZnO is used, and is formed by a vapor deposition method, a sputtering method, or the like.

The material constituting the insulating layer in the present invention is as follows:
Hard carbon film, SiNx, SiOx, etc. can be mentioned, but a hard carbon film (i-C film) is used as an insulating film of the MIM element.
Is preferred. This hard carbon film is a film containing at least one of amorphous and microcrystalline materials using carbon atoms and hydrogen atoms as main structure forming elements, and is also called a diamond-like carbon film, an amorphous diamond film, and a diamond thin film.

The hard carbon film can be formed at a substrate temperature (film formation temperature) of about room temperature to about 150 ° C. and has a good current-voltage (I
-V) characteristics. Therefore, a good MIM element can be manufactured, and the film characteristics can be largely changed depending on the film forming conditions, so that the substrate can be selected in a wide range, and the control of the element characteristics can be expanded. M
An IM device can be manufactured, and since this film is a hard film, there is little damage due to the rubbing process at the time of enclosing the liquid crystal, and since the dielectric constant is low, the area of the MIM device can be increased with respect to the LCD. Therefore, the yield can be improved. As for the film forming temperature, a temperature of about 300 ° C. is necessary for other materials, and even in the case of a TFT, a-Si and Poly-Si are 300 ° C. and 900 ° C., respectively.
, And none of these materials are suitable for polymer film substrates.

The hard carbon film of the present invention will be described 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 need to be a gaseous phase at normal temperature and normal pressure, but may be used in a liquid phase or a solid phase as long as it can be vaporized through melting, evaporation, sublimation, etc. by heating or decompression. is there.

The hydrocarbon gas as a raw material gas includes, for example, paraffinic hydrocarbons such as CH ₄ , C ₂ H ₆ , C ₃ H ₈ , C ₄ H ₁₀ , olefinic hydrocarbons such as C ₂ H ₄ , and acetylene. Gases containing at least all hydrocarbons such as hydrocarbons, diolefinic hydrocarbons, and aromatic hydrocarbons can be used.

Furthermore, other than hydrocarbons, for example, alcohols, ketones, ethers, esters, CO,
Any compound containing at least a carbon element such as CO ₂ can be used.

In the method of forming a hard carbon film from a raw material gas in the present invention, a film-forming active species is formed through a plasma state generated by a plasma method using a direct current, a low frequency, a high frequency, or a microwave. However, a method using a magnetic field effect is more preferable because deposition is performed at a low pressure for the purpose of increasing the area, improving uniformity, and forming a film at a low temperature. 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 evaporation method, an ion beam evaporation method, or the like, or may be formed from neutral particles generated by a vacuum evaporation method, a sputtering method, or the like. Alternatively, it may be formed by a combination of these.

Deposition conditions for the hard carbon film thus produced
Is as follows in the case of the plasma CVD method. RF output: 0.1-50W / cm^Two  Pressure: 1/10^Three~ 10 Torr Deposition temperature: room temperature ~ 250 ℃

The raw material gas is decomposed into radicals and ions by the plasma state and reacts with each other, thereby forming an amorphous (amorphous) and microcrystalline (crystal size) comprising carbon atoms C and hydrogen atoms H on the substrate. Is several tens to several μm)
A hard carbon film containing at least one of these is deposited. Table 1 shows various properties of the hard carbon film.

[0021]

[Table 1]

Note) Measuring method; Specific resistance (ρ): Determined from the IV characteristics of a coplanar cell. Pecker hardness (H): Measured by Micro Vickers meter. Refractive index (n): Based on ellipsometer. Defect density: by ESR. The dielectric constant is as low as 5 or less.

The hard carbon film thus formed was analyzed by Raman spectroscopy and IR absorption. As a result, as shown in FIG. 3 and FIG. 4, the carbon atom has a hybrid orbital of SP ^{3 and} a hybrid orbital of SP ² , respectively. It is clear that the formed interatomic bonds are mixed. The ratio between the SP ³ bond and the SP ² bond can be roughly estimated by separating the peak of the IR spectrum. In the IR spectrum, spectrums of many modes are overlapped and measured at 2800 to 3150 / cm. The assignment of peaks corresponding to each wave number is clear, and peak separation is performed by Gaussian distribution as shown in FIG. And calculate the respective peak areas, and calculate the ratio to obtain SP ³ / SP ²
You can know.

According to X-ray and electron diffraction analysis, it is known that the film is in an amorphous state (aC: H) and / or an amorphous state containing fine crystal grains of about 50 ° to several μm.

In general, in the case of the plasma CVD method suitable for mass production, the smaller the RF output, the higher the specific resistance and hardness of the film, and the lower the pressure, the longer the life of the active species. And uniformity over a large area can be achieved, and the specific resistance and hardness tend to increase. Furthermore, since the plasma density decreases at low pressure, the method utilizing the magnetic field confinement effect is particularly effective for increasing the specific resistance.

Further, this method has a feature that a high-quality hard carbon film can be similarly formed even at a relatively low temperature condition of about room temperature to about 150 ° C., and is therefore most suitable for lowering the temperature of the MIM element manufacturing process. is there. Therefore, there is a feature that a degree of freedom in selecting a substrate material to be used is widened and a uniform film can be obtained over a large area because the substrate temperature can be easily controlled.

Further, this hard carbon film has a group III element of the periodic table as a dopant in addition to carbon atoms and hydrogen atoms.
It may contain a group IV element, a group V element, an alkali metal element, an alkaline earth metal element, a nitrogen atom, an oxygen atom, a chalcogen element or a halogen atom as constituent elements.
Group III element of the periodic table as one of the constituent elements, also V
The group in which a group element, an alkali metal element, an alkaline earth metal element, a nitrogen atom or an oxygen atom is introduced can increase the thickness of the hard carbon film to about two to three times as compared with the non-doped one. Accordingly, it is possible to prevent the occurrence of pinholes at the time of fabricating the device, and to 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 is obtained.

In the same manner, the one in which a Group IV element of the periodic table, a chalcogen-based element or a halogen element is introduced significantly improves the stability of the hard carbon film and also improves the hardness of the film, which is highly reliable. A device having a characteristic can be manufactured. These effects are obtained because the group IV element and the chalcogen element reduce the active double bond existing in the hard carbon film, and in the case of the halogen element, 1) abstraction with respect to hydrogen. The reaction promotes the decomposition of the source gas and reduces dangling bonds in the film. 2) During the film formation process, the halogen element X extracts hydrogen in the C—H bond and replaces it, forming a C—X bond. After entering the film, the binding energy increases (the binding energy between CH and CX is C-
X is larger).

In order to make these elements the constituent elements of the film, in addition to the hydrocarbon gas and hydrogen as the raw material gas, a group III element, a group IV element, and a group V element of the periodic table are contained in the film. element,
Alkali metal elements, alkaline earth metal elements, nitrogen atoms,
In order to contain an oxygen atom, a chalcogen element or a halogen element, a gas of a compound (or molecule) containing these elements or atoms (hereinafter, these may be referred to as “other compounds”) is used.

The compound containing a Group III element of the periodic table includes, for example, B (OC ₂ H ₅ ) ₃ , B ₂ H ₆ , BCl ₃ , BBr ₃ , BF ₃ ,
Al (OiC ₃ H ₇ ) ₃ , (CH ₃ ) ₃ Al, (C ₂ H ₅ ) ₃ Al, (iC ₄ H ₉ ) ₃ Al, A
lCl ₃ , Ga (OiC ₃ H ₇ ) ₃ , (CH ₃ ) ₃ Ga, (C ₂ H ₅ ) ₃ Ga, GaCl ₃ , Ga
_{Br 3, (OiC 3 H 7} ) 3 In, there is a (C ₂ H _{5) 3} In like.

Examples of the compound containing a Group IV element of the periodic table include Si ₂ H ₆ , (C ₂ H ₅ ) ₃ SiH, SiF ₄ , SiH ₂ Cl ₂ and SiC
l ₄ , Si (OCH ₃ ) ₄ , Si (OC ₂ H ₅ ) ₄ , Si (OC ₃ H ₇ ) ₄ , GeCl ₄ , Ge
_{H 4, Ge (OC 2 H} 5) 4, Ge (C 2 H 5) 4, (CH 3) 4 Sn, (C 2 H 5) 4 Sn, SnCl
There are ₄ magnitudes.

Examples of the compound containing a Group V element of the periodic table include PH ₃ , PF ₃ , PF ₅ , PCl ₂ F ₃ , PCl ₃ , PCl ₂ F, PB
r ₃ , PO (OCH ₃ ) ₃ , P (C ₂ H ₅ ) ₃ , POCl ₃ , AsH ₃ , AsCl ₃ , AsB
_{r 3, AsF 3, AsF 5} , AsCl 3, SbH 3, SbF 3, SbCl 3, Sb (OC 2 H 5)
There are _three magnitudes.

As the compound containing an alkali metal atom,
For example, there are LiO-iC ₃ H ₇ , NaO-iC ₃ H ₇ , KO-iC ₃ H _{7 and the} like.

Examples of the compound containing an alkaline earth metal atom include Ca (OC ₂ H ₅ ) ₃ , Mg (OC ₂ H ₅ ) ₂ and (C ₂ H ₅ ) ₂ Mg.

Examples of the compound containing a nitrogen atom include nitrogen gas, inorganic compounds such as ammonia, organic compounds having a functional group such as an amino group and a cyano group, and heterocycles containing nitrogen.

Examples of the compound containing an oxygen atom include oxygen gas, ozone, water (steam), hydrogen peroxide, carbon monoxide, carbon dioxide, carbon suboxide, nitrogen monoxide, nitrogen dioxide, nitrous oxide, Inorganic compounds such as nitrous oxide and nitric oxide, hydroxyl group, aldehyde group, acyl group, ketone group,
An organic compound having a functional group or a bond such as a nitro group, a nitroso group, a sulfone group, an ether bond, an ester bond, a peptide bond, and a heterocyclic ring containing oxygen, and a metal alkoxide may be used.

As the compound containing a chalcogen element,
For example, H ₂ S, (CH ₃ ) (CH ₂ ) ₄ S (CH ₂ ) ₄ CH ₃ , CH ₂ = CHCH ₂ SCH ₂ CH
_{= CH 2, C 2 H 5} SC 2 H 5, C 2 H 5 SCH 3, _{thiophene, H 2 Se, (C 2} H
₅ ) There are ₂ Se, H ₂ Te, etc.

As the compound containing a halogen element,
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 halide, aryl halide, styrene halide, polymethylene halide, and haloform are used.

[0039]

The present invention will be described below with reference to examples. Example 1 Using a Si target on a polyarylate film,
The SiOx film was produced 4000Å by sputtering r and O ₂ mixed gas. SiOx was produced with the distribution shown in FIG. 2A by controlling the flow ratio of Ar and O ₂ . Next, IT
O was deposited at a thickness of 1000 ° by sputtering and patterned to form a pixel electrode. Next, MIM is used as an active element.
The device was provided as follows. First, Al was deposited to a thickness of 1000 ° by a vapor deposition method, and then patterned to form a lower electrode. An iC film is formed thereon as an insulating film by plasma CVD.
After depositing 850 mm thick by the EB method, Ni was deposited to a thickness of 1000 mm by the EB vapor deposition method and patterned to form an upper electrode. Next, the iC film was patterned by dry etching, and unnecessary Al films on the pixel electrodes were etched to complete the MIM element. According to this method, an MIM element exhibiting good characteristics was obtained, and the problem of film peeling or the like was eliminated in the manufacturing process.

Example 2 An SiOx film was formed on a polyether sulfone film by reactive evaporation using O ₂ gas of 4000 ° to form an SiOx film at 4000 °. SiOx was produced with the distribution shown in FIG. 2B by controlling the partial pressure of O ₂ . Next, ITO was sputtered by sputtering.
A pixel electrode was formed by depositing and patterning 000 °. Next, an MIM element was provided as an active element as follows. First, Al was deposited to a thickness of 1000 ° by a vapor deposition method, and then patterned to form a lower electrode. On top of this, i-
After depositing a C film to a thickness of 850 ° by a plasma CVD method,
i was deposited to a thickness of 1000 ° by EB evaporation and patterned to form an upper electrode. Next, the iC film was patterned by dry etching, and unnecessary Al films on the pixel electrodes were etched to complete the MIM element. According to this method, an MIM element exhibiting good characteristics was obtained, and the problem of film peeling or the like was eliminated in the manufacturing process.

[0041]

According to the present invention, after forming SiOx (x is 1.1 to 2.0) having a distribution in the film thickness direction on a polymer film, a polymer thin film two-terminal element is manufactured. It does not peel off the thin film as observed when the device is directly formed on the film. In addition, since x of SiOx has a distribution, the adhesion between the polymer film and SiOx is improved, and the insulation and environmental resistance of SiOx are secured. For this reason, the thin-film two-terminal element could be provided at low cost and with good yield.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one 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),
(B), (c) and (d) show. In each case, the left end of the horizontal axis is the polymer film surface, the right end is the first conductor surface, and the portion between the left end and the right end means the SiOx layer. The vertical axis indicates the value of x of SiOx.

FIG. 3 is a spectrum diagram showing a result of analyzing a hard carbon film used for an insulating layer of the MIM element of the present invention by a Raman spectrum method.

FIG. 4 is a spectrum diagram showing an analysis result obtained by analyzing a hard carbon film used for an insulating layer of the MIM element of the present invention by an IR absorption method.

FIG. 5 shows a Gaussian distribution of an IR spectrum of a hard carbon film used for an insulating layer of the MIM element of the present invention.

[Explanation of symbols]

 Reference Signs List 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)

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuji Kimura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Masayoshi Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Kenji Kameyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (58) Field surveyed (Int.Cl. ⁶ , DB name) G02F 1/136 510 G02F 1/1333 505

Claims (2)

(57) [Claims] 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 laminated in this order.
A thin-film two-terminal element, wherein 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 method according to claim 1, wherein the insulating film is a hard carbon film.
The thin-film two-terminal element as described in the above.