JPH04290481A - Plastic substrate for thin film laminated device and thin film laminated device using the same - Google Patents

Abstract

PURPOSE:To prevent moisture or the like from entering plastic by forming a thin insulating film on at least one of surfaces, forming two or more kinds of application films of the thin insulating film with spin-on application of a coating formation material comprising metallic organic compound and then making two or more layers of application films which have been subjected to plasma treatment. CONSTITUTION:Surfaces of a plastic plate or a plastic film substrate are uneven due to filler and drawing. Therefore, first coating forming agent is first applied on a plastic substrate 11 by a spinner and a roll coater, and it is heated in the air for the purpose of vaporizing reflow and solvent to form a first layer of an application film 12-1. Then second coating forming agent is applied and dried to form a second application film 13-1. Then the application films are treated in inert gas or plasma of inert gas containing a very small amount of oxygen. This treatment allows the two layers of the application films 12-1, 13-1 to change into first and second insulating films 12-2,13-2.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD The present invention relates to a plastic substrate for thin film laminated devices, an active matrix, and a plastic substrate for thin film laminated liquid crystal display devices. The present invention also relates to a thin film laminated device using the same, and a liquid crystal display device suitable for use in flat panel displays for OA equipment, TVs, etc.

0002

[Prior Art] There is a strong demand for the use of large-area liquid crystal panels in office automation equipment terminals and liquid crystal TVs. Therefore, in the active matrix method, a switch is provided for each pixel to maintain the voltage. Showa 62-62333
, No. 61-260219). Further, in recent years, there have been active efforts to reduce the weight and cost of liquid crystal panels, and the use of plastics for the substrates of switching elements is being considered (Japanese Unexamined Patent Publication No. 1-47769). However, when forming a thin film stacked device on a plastic substrate, the following problems occur. ■During the process, the substrate is immersed in solutions such as acids, alkalis, and water, and these components remain in the plastic, causing deterioration of device characteristics. It also causes expansion and contraction of the board. (2) The substrate curls and expands and contracts due to internal stress in the thin film for device fabrication deposited on the substrate. ■Generally, plastic film substrates have unevenness due to filler or stretching treatment, which can cause device defects (short circuits, disconnections). In order to avoid these problems, it is conceivable to form an insulating thin film on at least one side (the side on which the thin film laminated device is formed) of the plastic substrate, preferably on both sides. When forming such a thin film, in order to solve the above-mentioned problems (1) to (3), it must be formed as thick as possible for the following reasons. a) The above problem (2) occurs due to the diffusion (penetration) of acid, alkali, water, etc. in the insulating thin film, but considering the equation of diffusion, it can be prevented by increasing the thickness of the film. b) The part of the substrate that curls and expands/contracts in the above case (2) is the plastic substrate part, and if the insulating thin film is formed thickly, the composite Young's modulus of the substrate (plastic + insulating thin film) will be high and deformation can be reduced. c) In order to increase the leveling of the surface, it is more effective to make the film thicker and to use the coating method as the film formation method (in the vapor phase method, once unevenness is formed, it is more effective to make the film thicker). However, reflow is possible with the coating method.) Methods for forming insulating thin films can be roughly divided into vapor phase methods and coating methods, but vapor phase methods have a slow deposition rate and high internal stress in the film, so it is not practical to form a film with a thickness of several micrometers. isn't it. Further, in the coating method, the baking temperature after coating is as high as 450° C. or higher, and the coating method is limited to heat-resistant substrates. Therefore, neither method is satisfactory.

0003

An object of the present invention is to solve the above problems and provide a plastic substrate on which a thin film laminated device with good characteristics and less deterioration can be formed. That is, the purpose of the present invention is to prevent moisture etc. from entering plastics, and
It is an object of the present invention to provide a plastic substrate that can prevent moisture contained in plastics from entering an element, and that does not cause curling or expansion/contraction of the substrate. Another object of the present invention is to provide a thin film laminated device, particularly a thin film two-terminal device, using the improved plastic substrate.

0004

[Structure] The first aspect of the present invention is a plastic substrate for a thin film laminated device having an insulating thin film formed on at least one side, in which the insulating thin film is made of two or more layers of a film-forming material made of a metal-organic compound by spin-on coating. The present invention relates to a plastic substrate for a thin film laminated device, characterized in that the plastic substrate is made up of two or more layers of coating film which are subjected to plasma treatment after forming the coating film. A second aspect of the present invention relates to the plastic substrate for a thin film laminated device, wherein the insulating thin film is composed of two or more layers having different properties. A third aspect of the present invention relates to a thin film laminated device formed by laminating thin film two-terminal elements on the substrate. A fourth aspect of the present invention relates to the thin film laminated device according to claim 3, wherein the insulating film in the thin film two-terminal element is a hard carbon film. In the present invention, the method for forming an insulating thin film on a substrate is shown in FIG.
Shown as a), (b), (c), and (d). (a) is a cross-sectional view of the plastic substrate before spin-on coating, (b)
is a cross-sectional view after the first spin-on coating and drying, (c) is a cross-sectional view after the second spin-on coating and drying, and (d) is a cross-sectional view after the second spin-on coating and drying. FIG. 3 is a cross-sectional view showing how the coating film has changed into an insulating thin film. A detailed explanation will be given below with reference to the drawings. The plastic plate or plastic film substrate 1 has irregularities on its surface due to the filler 5 and stretching treatment, as shown in FIG. 1(a). Therefore, first, the first film forming agent was coated on the plastic substrate 11 using a spinner or a roll coater, and the coating was applied for ~10 min to reflow and evaporate the solvent.
The first coating film 1 is heated at 0°C for about 1 hour in the air.
2-1 (FIG. 1(b)). Then, a second film-forming agent is applied thereon by the same means and dried to form a second film-forming agent.
A coating film 13-1 is formed (FIG. 1(c)). Next, it is processed in an inert gas or an inert gas plasma containing a trace amount of oxygen. Through this treatment, the two layers of the coating films 12-1 and 13-1 become the first and second insulating thin films 12-2 and 13-2.
(Fig. 1(d)). The temperature at this time is room temperature ~ 25
The temperature was 0°C, preferably 50°C to 150°C. Further, the inert gas includes Ar, N2, He, etc., but is not particularly limited to these. Processing pressure is 1/10
The pressure was 2 to several torr, preferably 0.05 to 1 torr. As shown in FIG. 8, the plasma processing apparatus is of a commonly used parallel plate type, and 101 is a ground electrode;
102 is an RF electrode, 103 is a processed material, 104 is an RF power source, and 105 is a bias power source. The RF power was several to several hundred W (electrode diameter φ100 cm), preferably 10 to 200 W. The main component of the film forming agent used is a metal organic compound (metal alkoxide, metal organic complex, metal alcoholate, etc.), and specifically, Si (
OR) x (OH) y (x = 0 to 4, y is 4-x)
R-COO-Si, Al(OR)x(OH)y(x=0
~4, y=3-x), but is not particularly limited to these. Alcohols, esters, ketones, etc. can be used as the solvent for applying the film forming agent. The effect of plasma treatment is that inert gas ions and oxygen ions in the plasma physically peen (infiltrate quite deeply) into the film forming agent (after application), resulting in residual -OR, -OH according to our IR measurements. It is clear from the analysis results that (it is effective up to a film thickness of several μm), it promotes the desorption of R and H from the film. When plasma treatment is not performed, a firing temperature of 450 to 500°C is required, but with the above method, the firing temperature is between room temperature and 500°C.
The objective can be achieved at 250°C, preferably from 50 to 150°C. The film obtained by plasma treatment is 100
% It is not a completely inorganic film, and some groups such as -OH, -R, -OR, which are components of the film forming agent, remain in the film, but the remaining amount is estimated from the IR spectrum. It is 15 wt% or less. In FIG. 1, the insulating thin film is formed only on one side, but considering the above-mentioned problems (1) and (2), it is easily understood that the effect is higher if it is formed on both sides of the substrate. The film thickness is several hundred Å to several μm,
Preferably it is about 1000 Å to 3 μm. Furthermore, in order to more completely eliminate the above-mentioned problems ① and ②, it is possible to form a second coat film made of an inorganic material with high adhesion and a high passivation effect on the upper or lower layer of the insulating thin film, which significantly improves the effect. It is something that enhances. Specifically, the inorganic substances include SiO2, Si3N4, Si
ON, Al2O3, AlN, hard carbon, etc., and these can be formed by sputtering, P-CVD, ECR-CVD, etc. The substrate of the present invention having the above-mentioned features can be used in various thin film laminated devices, such as switching elements for flat panel displays, sensors for reading documents,
Although it can be used as a light source for optical printers, it is particularly suitable for use as an active matrix substrate for liquid crystal displays. The thin film laminated device of the present invention includes an MIM type element having a metal-insulator-metal layer structure, JP-A-61-275
MSI element (Metal-
Semi-Insulator), SIS element with semiconductor-insulator-semiconductor layer structure, MIMI of metal-insulator-metal-insulator-metal described in JP-A-64-7577
There are M elements, etc. In an active matrix substrate, a switching element is provided for each pixel, and a thin film two-terminal element with an insulating film interposed between a first conductor and a second conductor is preferable as the switching element in terms of cost, aperture ratio, etc. It is particularly advantageous. Furthermore, by using a hard carbon film as the insulating film, it is possible to design a device over a wide range, and to obtain a thin film two-terminal device with little variation in device characteristics, excellent threshold voltage and breakdown voltage, and high yield. .

A method of manufacturing an MIM element using a substrate, which is a feature of the present invention, will be explained with reference to FIG. first,
As described above, a transparent electrode material for a pixel electrode is deposited by a method such as vapor deposition or sputtering on the plastic substrate 1 for a thin film laminated device of the present invention having an insulating thin film layer, and is patterned into a predetermined pattern to form a pixel electrode 4. do. Next, a conductor thin film for the lower electrode is formed by a method such as vapor deposition or sputtering, and patterned into a predetermined pattern by wet or dry etching to form the first conductor 7 that will become the lower electrode. After coating the hard carbon film 2 by a method such as a dry etching method, it is patterned into a predetermined pattern by dry etching, wet etching, or a lift-off method using a resist to form an insulating film, and then a bus line conductor is formed on the insulating film by a method such as vapor deposition or sputtering. A thin film is coated and patterned into a predetermined pattern to form a second conductor (upper electrode) 6 that will become a bus line, and finally an unnecessary portion of the lower electrode is removed to expose the pixel electrode 4. In this case, the configuration of the MIM element is not limited to this, and after the MIM element is created, a transparent electrode is provided on the top layer, a transparent electrode also serves as an upper or lower electrode, and a side surface of the lower electrode. such as those with MIM elements formed on the
Various modifications are possible. Here, the thickness of the lower electrode, the upper electrode, and the transparent electrode is usually in the range of several hundred to several thousand Å, several hundred to several thousand Å, and several hundred to several thousand Å, respectively. The thickness of the hard carbon film is 100 to 8000 Å, preferably 200 to 6000 Å.
, more preferably in the range of 300 to 4000 Å. Furthermore, in the case of plastic substrates, it has been extremely difficult to fabricate active matrix devices using active elements due to their heat resistance. However, a hard carbon film can be produced at a substrate temperature of about room temperature, and can also be produced on a plastic substrate, making it a very effective means for improving image quality. Next, the material of the MIM element used in the present invention will be explained in more detail. First conductor 7 serving as the lower electrode
The materials include Al, Ta, Cr, W, Mo, Pt,
Ni, Ti, Cu, Au, W, ITO, ZnO:Al,
Various conductors such as In2O3 and SnO2 are used. Next, the material of the second conductor 9, which will become the bus line, is Al,
Cr, Ni, Mo, Pt, Ag, Ti, Cu, Au, W
, Ta, ITO, ZnO:Al, In2O3, SnO2
Although various conductors can be used, Ni, Pt, and Ag are preferred because they have particularly excellent stability and reliability of IV characteristics. In the MIM element using the hard carbon film 8 as an insulating film, the symmetry does not change even if the type of electrode is changed, and it can be seen from the relationship lnI∝√v that Poole-Frenkel type conduction is performed. Further, from this fact, it can be seen that in the case of this type of MIM element, the upper electrode and the lower electrode may be combined in any manner. However, the device characteristics (IV characteristics) deteriorate and change depending on the adhesion between the hard carbon film and the upper electrode and the state of the interface. Considering these, it was found that Ni, Pt, and Ag are good. The current-voltage characteristics of the MIM element of the present invention are shown in FIG. 4, and are approximately expressed by the conduction equation shown below.

[Equation 1] I: Current V: Applied voltage κ: Conductivity coefficient β: Poole-Frenkel coefficient n: Carrier density μ: Carrier mobility q:
Electron charge Φ: Trap depth ρ: Specific resistance d: Hard carbon film thickness (Å) k: Boltzmann constant T: Ambient temperature ε
1: Dielectric constant of hard carbon ε2: Vacuum dielectric constant

Next, a method for manufacturing a liquid crystal display device will be described with reference to FIG. First, a transparent material for the common electrode 4', such as ITO, ZnO:Al, ZnO:Si, SnO, is placed on the insulating substrate 1'.
2. In2O3 etc. are sputtered or evaporated to a thickness of several hundred Å.
The common electrode 4' is deposited to a thickness of several μm and patterned into stripes. An alignment material 8 such as polyimide is applied to the surface of each of the substrate 1' on which the common electrode 4' is provided and the substrate 1 on which the MIM elements 5 are provided in a matrix, a rubbing process is performed, and a sealing material is applied. , gap material 9
is inserted to keep the gap constant, and the liquid crystal 3 is sealed to form a liquid crystal display device. In this way, a liquid crystal display device is obtained.

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. Regarding the hydrocarbon gas as the raw material gas, for example, paraffinic hydrocarbons such as CH4, C2H6, C3H8, C4H10, acetylenic hydrocarbons such as C2H4,
Gases containing at least all hydrocarbons such as olefinic hydrocarbons, diolefinic hydrocarbons, and even aromatic hydrocarbons can be used. Furthermore, other than hydrocarbons, compounds containing at least the carbon element can be used, such as alcohols, ketones, ethers, esters, CO, and CO2.

[0008] 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 the plasma CVD method. RF output: 0.1 to 50 W/cm2 Pressure: 1/103 to 10 Torr Deposition temperature: Room temperature to 950°C Due to this plasma state, the raw material gas is decomposed into radicals and ions and reacts, thereby forming carbon atoms C on the substrate.
A hard carbon film containing at least one of amorphous (amorphous) and microcrystalline (crystal size is several tens of angstroms to several μm) is deposited. Further, Table 1 shows various properties of the hard carbon film.

[0009]

[Table 1] Note) Measurement method; Specific resistance (ρ): Determined from IV characteristics using a coplanar cell. Optical bandgap (Egopt): Obtain the absorption coefficient (α) from the spectral characteristics and determine from the relationship shown in Equation 4.

[Equation 2] Amount of hydrogen in the film [C(H)]: 29 from the infrared absorption spectrum
It is determined by integrating the peak near 00/cm and multiplying it by the absorption cross section A. That is, [C(H)]=A・∫α(v)/v・dvSP3/SP
2 ratio: The infrared absorption spectrum is decomposed into Gaussian functions assigned to SP3 and SP2, respectively, and determined from the area ratio. Vickers hardness (H): Based on a micro Vickers meter. Refractive index (n): By ellipsometer. Defect density: Based on ESR.

[0010] As a result of analysis by Raman spectroscopy and IR absorption method, the hard carbon film thus formed shows that the carbon atoms have SP3 hybrid orbitals and SP2 hybrid orbitals, as shown in FIGS. 6 and 7, 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. 2800-3150/cm for IR spectrum
Although the spectra of many modes overlap and are measured,
The attribution of peaks corresponding to each wave number is clear, and if we perform peak separation using a Gaussian distribution as shown in Figure 5, calculate the area of each peak, and find the ratio, we can obtain SP.
3/SP2 can be known. Moreover, according to X-ray and electron diffraction analysis, it has been found that it is in an amorphous state (a-C:H) and/or an amorphous state containing microcrystalline grains of about 50 Å to 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 specific resistance and hardness of the film, and the lower the pressure, the longer the life of active species, so lowering the substrate temperature and increasing the The area can be made uniform, 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 optimal for lowering the temperature of the MIM 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. Furthermore, as shown in Table 1, the structure and physical properties of the hard carbon film can be controlled over a wide range, so there is an advantage that device characteristics can be designed freely. Furthermore, the dielectric constant of the film is also 2.
~6 and Ta2O5 used in conventional MIM elements,
Since it is smaller than Al2O3 and SiNx, when making an element with the same capacitance, the element size only needs to be larger, so there is no need for much fine processing and the yield is improved (due to the driving conditions, LCD and MIM The capacitance ratio of the element needs to be about C(LCD)/C(MIM)=10:1). Also, since the element steepness is β∝1/√ε・√d, the smaller the dielectric constant ε, the greater the steepness, and the on-current I
The ratio between the on current and the off current Ioff can be increased. Therefore, it becomes possible to drive the LCD at a lower duty ratio, and a high-density LCD can be realized. Furthermore, since the film has high hardness, there is less damage caused by the rubbing process during encapsulation of the liquid crystal material, which also improves the yield. Considering the above points, by using a hard carbon film, it is possible to achieve low cost and gradation (
Colorization) and high-density LCDs can be realized. Furthermore, this hard carbon film contains carbon atoms, hydrogen atoms, and
It may contain a group II element, a group IV element, a group V element, an alkali metal element, an alkaline earth metal element, a nitrogen atom, an oxygen element, a chalcogen element, or a halogen atom as a constituent element. Periodic table III as one of the constituent elements
Group elements, also Group V elements, alkali metal elements, alkaline earth metal elements, nitrogen atoms, or oxygen atoms introduced, have a hard carbon film thickness of about 2 to 30% compared to non-doped ones.
It is possible to increase the thickness by three times, thereby preventing the occurrence of pinholes during device fabrication, and dramatically improving 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, periodic table I
When group V elements, chalcogen elements, or halogen elements are introduced, the stability of the hard carbon film is dramatically improved, and the hardness of the film is also improved, making it possible to produce highly reliable elements. 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) abstraction for hydrogen The reaction promotes the decomposition of the raw material gas and reduces dangling bonds in the film, and 2) during the film formation process, the halogen element X pulls out hydrogen in the C-H bond and replaces it, forming a C-X bond. enters the film and increases the bond energy (C-H and C-
This is because the bond energy between X is larger between C and X). In order to use these elements as constituent elements of the film, in addition to hydrocarbon gas and hydrogen as raw material gases, elements from group III, group IV, and group V of the periodic table must be added as dopants to the film. 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. Here, as a compound containing a group III element of the periodic table, for example, B
(OC2H5)3,B2H6,BCl3,BBr3,B
F3, Al(O-i-C3H7)3, (CH3)3Al
, (C2H5)3Al, (i-C4H9)3Al, Al
Cl3, Ga(O-i-C3H7)3, (CH3)3G
a, (C2H5)3Ga, GaCl3, GaBr3, (
Examples include O-i-C3H7)3In and (C2H5)3In. Examples of compounds containing Group IV elements of the periodic table include Si3H8, (C2H5)3SiH, SiF4, Si
H2Cl2, SiCl4, Si(OCH3)4, Si(
OC2H5)4, Si(OC3H7)4, GeCl4,
GeH4, Ge(OC2H5)4, Ge(C2H5)4
, (CH3)4Sn, (C2H5)4Sn, SnCl4
etc. Compounds containing Group V elements of the periodic table include:
For example, PH3, PF3, PF5, PCl2F3, PCl
3, PCl2F, PBr3, PO(OCH3)3, P(
C2H5)3, POCl3, AsH3, AsCl3, A
sBr3, AsF3, AsF5, AsCl3, SbH3
, SbF3, SbCl3, Sb(OC2H5)3, etc. As a compound containing an alkali metal atom, for example, L
iO-i-C3H7, NaO-i-C3H7, KO-i
-C3H7 etc. Examples of compounds containing alkaline earth metal atoms include Ca(OC2H5)3, Mg(OC
2H5)2, (C2H5)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 monoxide, carbon dioxide, suboxide, nitrogen monoxide, nitrogen dioxide, dinitrogen trioxide, and dinitrogen pentoxide. , inorganic compounds such as nitrogen trioxide, hydroxyl groups, aldehyde groups, acyl groups, ketone groups, nitro groups, nitroso groups, sulfone groups, ether bonds, ester bonds, peptide bonds,
Examples include organic compounds having a functional group or bond such as a heterocycle containing oxygen, and metal alkoxides. Examples of compounds containing chalcogen elements include H2S, (C
H3)(CH2)4S(CH2)4CH3,CH2=C
HCH2SCH2CH=CH2, C2H5SC2H5,
C2H5SCH3, thiophene, H2Se, (C2H5
)2Se, H2Te, etc. Examples of compounds containing halogen elements include fluorine, chlorine, bromine, iodine, hydrogen fluoride, carbon fluoride, chlorine fluoride, bromine fluoride, iodine fluoride, hydrogen chloride, bromine chloride, iodine chloride, and hydrogen bromide. , inorganic compounds such as iodine bromide and hydrogen iodide, and organic compounds such as alkyl halides, aryl halides, halogenated styrene, halogenated polymethylene, and haloform. A hard carbon film suitable as a liquid crystal driving MIM element has a film thickness of 100 to 8000 Å and a specific resistance of 106 to 1013 Ω depending on the driving conditions.
Advantageously in the cm range. In addition, considering the margin between drive voltage and withstand voltage (dielectric breakdown voltage), it is desirable that the film thickness be 200 Å or more, and color unevenness due to the step difference (cell gap difference) between the pixel part and the thin film two-terminal element part should be avoided. In order to prevent this from becoming a practical problem, the film thickness should be 6.
Since it is desirable that the thickness is 000 Å or less, the thickness of the hard carbon film is 200 to 6000 Å, and the specific resistance is 5 × 10 6 to
More preferably, it is 1013 Ω·cm. The number of device defects due to pinholes in hard carbon films increases as the film thickness decreases, and becomes especially noticeable below 300 Å (
The defect rate exceeds 1%), and the uniformity of the in-plane distribution of film thickness (and thus the uniformity of device characteristics) cannot be ensured (
The accuracy of film thickness control is limited to about 30 Å, and the variation in film thickness exceeds 10%), so it is more desirable that the film thickness is 300 Å or more. Further, in order to prevent the hard carbon film from peeling off due to stress and to drive at a lower duty ratio (preferably 1/1000 or less), the film thickness is more preferably 4000 Å or less. Taking all of these into account, the thickness of the hard carbon film is 30
0~4000Å, specific resistivity 107~1011Ω・cm
It is more preferable that

[0011]

[Example] Example 1 Mainly Si-(OR)4 on polyarylate film
(R is an organic group such as methyl, ethyl, propyl, butyl) was spin-coated to a thickness of 2000 Å, dried at 80°C, and then spin-coated and dried once again, under the following conditions. plasma treatment was performed. Plasma generation means: RF capacitive coupling type, parallel plate internal electrode type Substrate position: Pressure above RF electrode
:0.1Torr gas
:Ar Power: 0.5w/cm2
Time: 60min Treatment temperature: 150℃ Comparing the FTIR spectra before and after plasma treatment,
Plasma treatment reduces absorption based on Si-OH around 950/cm, and Si-O- around 1050/cm
Absorption based on Si is clear. That is, it was possible to form an insulating thin film having a Si-O-Si network on a plastic substrate at a low temperature of 150° C. by plasma treatment. Next, an ITO thin film was deposited on this substrate to a thickness of about 1000 Å by sputtering, and then patterned to form a pixel electrode. Next, a thin film two-terminal element was provided as follows. First, Al was deposited to a thickness of about 1000 Å by vapor deposition, and then patterned to form a lower electrode, and a hard carbon film was placed on top of it as an insulating layer using plasma carbon.
After being deposited to a thickness of about 1000 Å by the VD method, it was patterned by dry etching. Furthermore, Ni was deposited on this layer to a thickness of about 1000 Å by EB evaporation, and then patterned to form an upper electrode. Example 2 An organosilicon compound containing Si-(CH4)4 was spin-coated onto a polyarylate film to a thickness of 4000 Å, and after drying at 80°C, an organic silicon compound containing mainly Si-(OR)4 was spin-coated onto a polyarylate film.
After spin-coating an organosilicon compound consisting of the following to a thickness of 2000 Å and drying at 80° C., plasma treatment was performed under the same conditions as in Example 1. Since the first layer of insulating thin film contains Si--CH3 bonds, the film has flexibility and stress in the film is small. Therefore, although a thick film can be formed at one time, the rigidity of the substrate cannot be increased. On the other hand, the second insulating layer is thin but has high rigidity. By combining these first and second layer insulating thin films, it has become possible to form a thick and highly rigid insulating thin film. Next, a thin film two-terminal element was formed in the same manner as in Example 1. In the thin film two-terminal devices according to Examples 1 and 2 described above, no film peeling, no deformation of the substrate, and no curling of the substrate were observed. Moreover, no deterioration of the element was observed even after continuous driving for 200 hours.

0012

[Effects] Since the present invention is configured as described above, there is no deformation or curling of the substrate, and it is possible to achieve low cost and light weight. Further, when the thin film stacked device is made into an MIM element using a hard carbon film as an insulating layer, it has the following characteristics. 1) Since it is produced by a vapor phase synthesis method such as plasma CVD, the physical properties can be controlled over a wide range by changing the film forming conditions, and therefore there is a large degree of freedom in device design. 2) Since it is hard and can be made into a thick film, it is less susceptible to mechanical damage, and pinholes are reduced by making the film thicker. 3) Since high-quality films can be formed even at low temperatures near room temperature, there are no restrictions on the substrate material. 4) Excellent uniformity in film thickness and film quality, making it suitable for thin film devices. 5) Since the dielectric constant is low, advanced microfabrication technology is not required, which is advantageous for increasing the area of the device. Therefore,
The MIM element using the plastic substrate for thin film laminated devices of the present invention is suitable as a switching element for liquid crystal display.

[Brief explanation of the drawing]

FIG. 1 shows a method of forming an insulating thin film on a substrate in the order of steps in the present invention (a), (b), (c), and (d). (a) is a cross-sectional view of the plastic substrate before spin-on coating, (b) is a cross-sectional view after the first spin-on coating and drying, and (c) is a cross-sectional view of the plastic substrate after the second spin-on coating. A cross-sectional view after coating and drying, and (d) a cross-sectional view showing how the coating film is transformed into an insulating thin film by plasma treatment.

FIG. 2 is a cross-sectional view showing an example of an MIM element according to the third aspect of the present invention.

FIG. 3 is a schematic diagram of a liquid crystal display device using an MIM element using the plastic substrate for a thin film laminated device of the present invention as a switching element.

[Figure 4] a, b are the IV characteristic curves of the MIM device, lnI
−√v characteristic curves are shown respectively.

FIG. 5 shows the Gaussian distribution of the IR spectrum of the hard carbon film used as the insulating layer of the MIM device of the present invention.

FIG. 6 is a spectrum diagram showing the results of Raman spectroscopy analysis of the hard carbon film used as the insulating layer of the MIM element of the present invention.

FIG. 7 is a spectrum diagram showing the results of an IR absorption analysis of the hard carbon film used for the insulating layer of the MIM element of the present invention.

FIG. 8 is a schematic diagram showing an example of a plasma processing apparatus of the present invention.

[Explanation of symbols] 1 Plastic substrate 1' Plastic substrate 2 Hard carbon film 3 Liquid crystal 4 Pixel electrode 4' Common electrode 5 Active element (MIM element) 6
Second conductor (bus line) (upper electrode) 7 First conductor (lower electrode) 8 Alignment film 9 Gap material 11 Plastic substrate 12-1 First layer coating formed by first spin-on coating 12-2 First layer insulating thin film obtained by plasma treatment of the first layer coating 13-1 Second layer coating 13- formed by second spin-on coating 2 Second layer insulating thin film 14 obtained by plasma processing the second layer coating film Filler 101 Earth electrode 102 RF electrode 103 Processed material (processed substrate) 104
RF power supply 105 Bias power supply

Claims (4)

[Claims] 1. A plastic substrate for a thin film laminated device having an insulating thin film formed on at least one side, wherein the insulating thin film is formed by forming two or more layers of a film-forming material made of a metal-organic compound by a spin-on coating method. 1. A plastic substrate for a thin film laminated device, characterized in that it is made of two or more coating films that have been subjected to plasma treatment. 2. The insulating thin film has different properties.
The plastic substrate for a thin film laminated device according to claim 1, which is composed of more than one layer. 3. A thin film laminated device comprising a thin film two-terminal element laminated on the substrate according to claim 1 or 2. 4. The thin film laminated device according to claim 3, wherein the insulating film in the thin film two-terminal element is a hard carbon film.