JPH02168236A - Manufacture of active matrix substrate - Google Patents

Abstract

PURPOSE:To contrive the improvement of the yield by forming a connecting film by extending it onto a composite film continuously from a picture element electrode at the time of forming the picture element electrode from a conductive film by second photoetching. CONSTITUTION:By sticking a transparent conductive film to the whole surface, and thereafter, bringing it to photoetching, a picture element electrode 10 is formed on an insulating substrate 1, and also, it is allowed to pass through a second photoetching process for forming a connecting film 11 continued from this picture element electrode 10 on a composite film, and a metal, an insulator and a metallic element 30 are integrated for driving a display of its picture element so as to be annexed to the picture element electrodes 10 arranged like a matrix, respectively. In this case, the number of times of photoetching required for the manufacture is decreased to two times from conventional three times. In such a way, the manufacture yield is improved.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an active matrix substrate in which a display driving element is incorporated in a pair of substrates constituting a display panel using liquid crystal or the like as a display medium. MIM (metal/insulator/metal/insulator/
The present invention relates to a method of manufacturing an active matrix substrate incorporating metal (metal) elements.

[Conventional technology]

Display panels, which are so-called flat displays that use liquid crystals as a display medium, have been used for large lids as display devices for small electronic devices such as watches and calculators for quite some time, but recently they have been used for displaying fixed images. Applications are increasing for the display of large variable or movable images such as those for televisions, and such large display panels have at least tens of thousands of pixels arranged in a matrix within the panel surface, and the pixels are arranged in a matrix according to the video signal. The display state of pixels can be switched at high speed. In such a matrix display panel, in order to switch the display, it is of course necessary to scan a large number of pixels within the screen at high speed in both vertical and horizontal directions, and it is necessary to keep the display state stable during one scanning period after each pixel is scanned. In order to maintain and obtain a clear image, the side where 1 tpl of pixels is provided)
Advantageously, i, +i is an active matrix substrate incorporating an active element associated with each of its pixels.

The active elements incorporated in this active matrix substrate drive each pixel by switching according to the display voltage, and can be incorporated into a very narrow gap of several microns between a pair of substrates of a display panel. It is necessary to have a Wi film structure, and 3-terminal elements such as thin film transistors and F
ill19 diode.

Two-element elements such as varistors and MIM elements are known, but the latter have a simpler structure and are advantageous in terms of manufacturing costs.In particular, MIM elements have the simplest structure and require less space to incorporate. It has the advantage of requiring less
The present invention relates to an active matrix substrate incorporating this MIM element, and the conventional jRiXi is
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araff at al, I[! l! E Trans,
, HD-28, pp. 736° June 1981.

In FIG. 3, a pixel type (jlo has an approximately rectangular outline as shown in the figure, and in the figure, a plurality of pixel electrodes 10 arranged in the horizontal direction A scanning center J) 20 for commonly carrying a display voltage or a scanning voltage is provided in an elongated shape. This running electric current I]20 is a metal such as tantalum2
and an insulating film 3 whose surface is positively oxidized)
1 structure, the protrusion 21 is
A recess 10a is provided in the pixel electrode 1O corresponding to the above. In this example, the Ml~1 element 30 is provided on the protruding part 21 of the scanning type 1, and the upper metal film 4 has its center part in contact with the insulating layer 3 of the protruding part 21, and both ends thereof are connected to the pixel electrodes. With lO! X-electrocontact class 1■ Provided in an I-shaped pattern.

metal! 1u edge M sandwiched between I22 and upper metal film 4
! J, 3 is a very thin tantalum pentoxide with a thickness of about several hundred, and when a voltage is applied between the two metal films 2 and 4, its conductivity is proportional to the square root of the voltage.
It exhibits Prenkel-type conductance characteristics, and by utilizing the nonlinear voltage and current characteristics of this insulating film 3, the MIM element can perform a switching function similar to a bidirectional varistor or an anti-parallel connected diode, and the thickness of the insulating film 3 By making it sufficiently thin, it can have this nonlinear characteristic necessary for driving pixels.

FIG. 4 shows a conventional manufacturing process of an active matrix substrate incorporating such an MIM element, and corresponds to a cross section taken along the line X--X in FIG. 3. The insulating substrates vj, l for the active matrix substrate shown in FIG. 4(a) are normally flat glass plates, and first, a metal 2a such as tantalum is deposited on the upper surface of the substrate for forming a metal film.

In the step shown in FIG. 3, this metal 2a is photo-etched for the first time to form a metal film 2 having a scanning pattern of the poles 20 and their protrusions 21 as shown in FIG. The same figure (C
1 is an oxidation step in which the surface of the tank of metal film 2 is
For example, the insulating film 3 is made of tantalum pentoxide or the like by positive oxidation in a citric acid solution.

By making the thickness of this insulating film extremely thin, on the order of several hundred layers, as described above, nonlinear voltage/current characteristics unique to MIM elements can be obtained.

In the process shown in FIG. 4(d), a metal such as chromium is completely bonded for the upper gold film 4 so as to cover the composite film of the metal film 2 and the insulating film 3, and then it is removed by the second photo-etching process. An upper metal shell 4 with a strip-like pattern as shown in the figure is formed. In the final step (e) in the same figure, the transparent conductive film 5 is completely ruptured, and the third photo-etching process is performed to form a pixel shape).
The MIO is formed into a rectangular pattern with recesses 10a as shown in FIG. Note that the steps in FIG. 4(d) and (el) may be performed in reverse order.

[Problems to be Solved by the Invention] In the above conventional active matrix substrate 1, the structure can be simplified by carefully controlling the conditions when the surface of the metal film 2 is oxidized and covered with the insulating film 3. It is possible to incorporate MIM elements with well-matched characteristics, but as you can see from the above explanation, three photoetching steps are required to fabricate it, so as explained next, every seven photoetching steps are required. There is a problem in that errors in photomask alignment accumulate and defects are likely to occur, resulting in lower yields and higher costs for display panels.

As can be seen from FIG. 3, the protrusions 31 of the scanning electrodes 30 and the upper metal film 4 are both made of metal and do not transmit display light. Since light unrelated to the brightness and darkness of the pixel display leaks from the gap between the pixel electrode 10 and the pixel electrode 10, the contrast of the image becomes unclear. Therefore, to improve image quality,
It is necessary to make the size of the MIM element 30 and its surroundings as small as possible to reduce the area that does not contribute to display, and to improve the so-called aperture ratio of the display panel to brighten the display and increase the contrast of the display. For this reason, the above 3
A photomask with a fine pattern is used in each of the photo-etching steps of j5. Therefore, high precision is required for mask alignment.

However, the dimensions of the insulators, plates, and photomasks used in the production of active matrix substrates are much larger than semiconductor wafers and are easily affected by temperature and other factors, and even with careful mask alignment, there is always some Since errors are unavoidable, the errors tend to accumulate as the photoetching process is repeated and cause defects. Furthermore, unlike in the case of semiconductor chips, it is not possible to throw away defective chips and make use of only good chips; all active matrix substrates with defects have no choice but to be discarded as defective products. In addition, as mentioned above, if the photo-etching process is performed three times, of course mask alignment is required two times.
In order to improve the yield, it is desirable to reduce the number of photoetching steps to one.3 From this perspective, the present invention provides a method for manufacturing active matrix 4J& that can reduce the number of photoetching steps (
)The porpose is to do.

[Failure to solve the problem]

According to the present invention, a gold film is entirely deposited on an insulating substrate, and the surface is oxidized to form a continuous moat film, thereby making it completely insulated from the metal film. (a step of forming a composite 1i2 including a film) a first photo-etching step of photoetching the composite j pattern to form a predetermined pattern, and a step of forming a composite j pattern into a predetermined pattern; A side oxidation step is performed to form an insulating layer by oxidizing the layer 11, and then a transparent conductive film is deposited on the entire surface and then photoetched to form a pixel type (I) layer on the insulating substrate. )
This is achieved by a method of manufacturing an active matrix substrate including a second photo-etching step for forming a continuous connection pattern on top of the first pattern.

It should be noted that the MIM element can be constituted by a metal film, an insulating film, and a connection layer in the composite structure described above, and in this case, the connection layer, which is electrically conductive, is a conventional upper metal layer. It will also play a role in the desert.

However, in some cases, it may be desirable to construct a composite layer by overlaying the upper metal layer 1 on top of the metal layer and the insulation layer. In addition to serving as a connection to the electrode, it can also serve as a mask when removing the unnecessary upper metal film on the insulation crotch by etching.

In addition, the insulation BH2 formed by the side oxidation process in the above configuration is MIM! in the composite II! 1: It is preferable that the running edge be j'1 more than the insulating film for the child, or 1@edge 1 for the element (a type of running edge II that is suitable for 1).

[Function] As can be seen from FIG. 3, in the conventional structure, the upper metal film for the M1~1 element connects the element to the pixel electrode at t11.
The river is flowing. The present invention connects the MIM element and the pixel electrode to the point formed by the conductivity for the picture electrode, and as described in the above structure, the connection is made by the second photoetching. When forming the pixel electrode from the conductive layer 11, it is necessary to extend the connecting film continuously from the pixel 1 layer to the top of the composite layer 1i. I made it S so that I only had to do it once. As mentioned in the previous section, this connection film can serve as a conductive film or a conventional upper metal film for the MIM element.

For this reason, in the method of the present invention, a metal film is first deposited on the entire surface of an insulating substrate and the surface is oxidized to form an insulating film, and includes at least the metal film and the insulating film, and if necessary, an upper metal film as well. After forming a composite film, the patterning of this composite film is completed by the first photoetching. Next, the conductive film is connected to the pixel electrode by the second photoetching described above. II! However, if left as is, the metal film exposed on the side surface of the composite film after the first photoetching would be short-circuited with the connecting film, so the first and second photoetching steps would be In between, the exposed surface of the metal film is oxidized to form an insulating film by sandwiching the side oxidation step described in the above structure.In this step, the exposed surface of the metal film is simply oxidized, and photo-etching is of course unnecessary. However, if the upper metal film is included in the composite film, it is necessary to use the connecting film as a mask to remove the portions other than those under the connecting film by etching after the second photoetching.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings. 1st
The figure illustrates an active matrix substrate manufactured by the method of the present invention at each stage of the process, and the completed state is shown in a plan view in FIG. 2, and the left column of FIG. This corresponds to the XX cross section in FIG. 2, and the right column in FIG. 1 corresponds to the YY cross section in FIG. In addition,
In these figures, parts common to those in FIGS. 3 and 4 described above are given the same reference numerals. Hereinafter, before going into the description of FIG. 1, in order to facilitate understanding, the structure of the active matrix substrate will first be briefly described with reference to FIG. 2.

As shown in FIG.
It is the same as the conventional case shown in FIG. 3 that each of the electrodes j20 is formed in an elongated manner, but in this embodiment, the protruding portion 2■ of the scanning electrode 20 is located at a position where the gap 1ii between the pixel-type PilOs can be utilized. The MIM element 30 is built into this protrusion 21 . Furthermore, in this embodiment, the scanning electrode 20 and its protrusion 21 are formed of the same composite film, and the composite film contains gold! i! Isolated from l desert 2! ! It is assumed that an upper metal film is included in addition to l3.

The connection film 11 is formed as an extension that is continuous with the pixel type IMIO and protrudes from it, and its tip is provided so as to cover the protrusion 21 of the scanning electrode, and in this example, the composite film forming the protrusion is provided. The upper stand! Conductive contact is made with the membrane.

As can be seen from the figure, the scanning electrode is made of metal IQ 2
and an insulating film 3, instead of providing the protrusion 21 thereon, the connection film 1 is formed from the pixel electrode lO.
It is also possible to extend the MIM element 1 downward in the figure and build the MIM element 30 on the scanning ttffi 20. Conversely, when the MIM element 2o is built into the protrusion 21 as in this example, it is not necessary to form the scanning electrode 2o with a composite film.

Complex II in Figure 1(a)! In the forming process, first, a metal 2a such as tantalum for the metal film 2 is deposited on the entire surface of the insulating substrate 1 for the active matrix substrate, which is usually made of glass, by sputtering or the like to a thickness of about 4,000, as described above. to adhere to. Then, for example, 0.05% of citric acid
The surface of the metal 2a is anodized by applying a voltage of about 40 V in an aqueous solution of the metal to form an insulating film 3a of tantalum pentoxide or the like with a thickness of, for example, about 400 volts. Furthermore, in this embodiment, a metal 4a such as chromium for the upper metal film 4 is deposited on the entire surface of the film by sputtering or the like, for example, on the order of 1,000 layers.

FIG. 1(b) shows the state after the first photoetching step. It is recommended to use dry etching for this purpose (at that time, the reaction gas is a metal 2 such as chromium for the upper metal film 2).
For a, a mixed gas of carbon tetrachloride and oxygen is applied to 1 insulating film 3
For tantalum pentoxide 3a for gold [1112] and tantalum 2a for gold [1112], a mixed gas of carbon tetrafluoride and oxygen was used, and these three-layer films were coated simultaneously using a photoresist film as a mask while switching the reaction gas. Dry etching Etching is performed in one step inside the gastric cavity. Through this first photoetching process, the metal film 2. In this example, a three-layer composite membrane consisting of the insulation M 3 and the upper metal III 4 is formed with the pattern of the scanning electrode 20 and its protrusion 21 in FIG. Note that the width of this composite membrane is, for example, 5 to 10
He is said to be II years old.

In the step shown in FIG. 1C, the surface of the metal film 2 exposed on the side surface of the composite film etched in the previous step is oxidized to form the side surface insulation g3b. For this purpose, for example, the positive oxidation method in a citric acid aqueous solution may be used as before, but the voltage is increased to, for example, about 80 V, and the side insulating film 3b is made to be thicker than the insulating M3 by less than 1,000 volts. The degree is 0. During this oxidation process, the insulating film 3 on the upper surface of the metal 1122 is removed by the upper metal l!
4, so its thickness does not change, of course.
Even if the upper gold layer 1711124 is not provided, the thickness of the insulating film 3 can be maintained as it was by oxidizing the side surface while leaving the photoresist film for the previous first photoetching process on the insulating film 3. can be kept.

In the second photoetching process shown in FIG. 1(d), ITO (indium tin oxide) or the like is etched by 3,000 people by sputtering, for example, as a transparent conductive material for the pixel electric current and contact layer. After the entire surface has been bonded to approximately 0 thickness, the pixel electrode f! is chemically etched using a C3 solution of ferric chloride and hydrochloric acid. ilO and connecting film 11
is formed in the pattern shown in FIG.

As described above, the connecting film 11 is an extension of the pixel electrode and is in conductive contact with the upper metal film 4 of the composite I11 in this example. Insulation It! 3 and an upper metal film 4 is connected to the pixel electrode IO. If the upper metal film 4 is not present, the MIM element 30 is configured with the metal film 2. Consisting of an insulating film 3 and a contact film 11,
II! It is connected to the pixel electrode 10 by I 1 t. In both cases, the contact Vt film 11 covers the sides of the composite film, but the metal 1! 2 is insulated from the connection film II by the side insulating film 3b.

If there is no upper metal film 4, this completes the entire process, but if there is an upper metal film 4, the I# continuous protective film is Since the upper metal film 4 remains on the surface of composite III other than the lower part of 11,
In the step of FIG. 1(e), the excess portion of the upper metal 1rff4 is removed by dry etching using the connection film 11 as a mask, and the entire process is completed.

As can be seen from the above embodiments, in the method of the present invention, the photo-etching process when manufacturing an active matrix substrate can be completed only twice as shown in FIGS. 1(a) and 1(d). Both steps (C) and (e) can be performed using the portion patterned in the previous step as a mask. M I M element 3 incorporated into an active matrix substrate by the method of the present invention
0, it is desirable that the nonlinear characteristics are determined by the insulating film 3, and even if the side insulating film 3b is formed by anodic oxidation like the insulating film 3, its film quality is poor, so it is better not to use it. These insulation films 3 and side insulation! The thickness and characteristics of il 3 b can be controlled as appropriate by changing conditions such as the vacancy of the citric acid aqueous solution during positive oxidation, the voltage used, and the oxidation time.

The present invention is not limited to the embodiments described above, but can be implemented in various embodiments8.For example, titanium, aluminum, etc. may be used for the gold layer 4, and molybdenum, tantalum, titanium, aluminum, etc. may be used for the upper metal film 4. 1 pixel 1! Second tin oxide or the like can be used for the transparent conductive films for iLo and the connection film 11, respectively. Further, in addition to the above-mentioned sputtering method, a vacuum evaporation method can be used to deposit these films.

[Effects of the Invention] As can be seen from the above description, in the uninvented method, a metal 1 pattern is entirely deposited on the active matrix f temporary board, and then the surface is oxidized to form an insulating film. a first photoetching step of photoetching the composite film to form a predetermined pattern; A side oxidation step in which the metal film exposed on the side is oxidized to form an insulating interlock, and a transparent conductive film is completely ruptured and then photoetched to form a pixel electrode of 1 m on the insulating substrate. and a second photo-etching process to form a continuous connection film on the composite film, resulting in images arranged in a matrix! By manufacturing an active matrix substrate that incorporates an MIM element for display driving the pixel associated with each g electrode, the number of photoetching steps required for manufacturing can be reduced from the conventional three times to two times, and the manufacturing process can be simplified. In addition to streamlining, the number of masks and alignments has been changed from the conventional two to one, based on the mask alignment error (significantly reducing the defect rate, increasing the manufacturing yield of active matrix substrates, and improving its economic efficiency. can be significantly increased.

In recent years, there has been a demand for larger display panels and an increase in the number of built-in pixels, and the practicality of these panels tends to be limited by the defect rate during the manufacturing of active matrix substrates. This problem can be overcome and the practical application of large display panels can be promoted.

[Brief explanation of the drawing]

Figures 1 and 2 relate to the present invention; Figure 1 is an enlarged cross-sectional view of the main parts of an active matrix substrate showing an embodiment of the manufacturing method according to the present invention in each main manufacturing process, and Figure 2 is a completed view of the active matrix substrate. It is a partially enlarged plan view of the state. Figure 3 and subsequent figures relate to the prior art. Figure 3 is a plan view of one pixel of an active matrix substrate, and Figure 4 is an enlarged sectional view of the main parts of an active matrix substrate showing the conventional manufacturing method at each main step. In Figure 0, 1: insulating substrate for near active matrix substrate, 2: metal film, 2a: metal or tantalum, 3: insulating film, 3a: insulating film before patterning, 3b: side insulating film, 4: Upper metal film, 4a: metal, 5: transparent conductive film, lO: pixel!
Pole, 10a: recess, 11: connection film, 20: scanning electrode, 2
1: protrusion of scanning electrode; 30: MIM element. kΔ” Target 1 1a3 Figure 2 Figure 4

Claims (1)

[Claims] A method for manufacturing an active matrix substrate in which MIM elements are incorporated in pixel electrodes arranged in a matrix for display driving of the pixels, the method comprising:
A step of forming a composite film containing a metal film and an insulating film by depositing a metal film on the entire surface of an insulating substrate for an active matrix substrate and then oxidizing the surface to form an insulating film; a first photo-etching step in which a predetermined pattern is formed by photo-etching; a side oxidation step in which an insulating film is formed by oxidizing the metal film exposed on the etched side surface of the composite film; and a transparent conductive film. manufacturing an active matrix substrate, including depositing on the entire surface and photo-etching to form a pixel electrode on an insulating substrate, and a second photo-etching step of forming a connection film continuous with the pixel electrode on the composite film. Method.