JP5125140B2 - Reflective liquid crystal device and electronic apparatus - Google Patents

Description

  The present invention relates to a reflective liquid crystal device and an electronic apparatus.

In a liquid crystal device, liquid crystal is held between an element substrate and a counter substrate that are arranged to face each other. In the case of a reflective liquid crystal device among the liquid crystal devices, a pixel switching element is formed on each of a plurality of pixels on the element substrate, and light reflection made of aluminum or an aluminum alloy is formed on the upper layer side of the switching element. A conductive conductive layer is formed. In this case, the light reflective conductive layer is often formed on the uppermost layer side of the element substrate. Accordingly, a configuration has been proposed in which a light-reflective conductive layer made of aluminum or an aluminum alloy is used as a mounting pad when forming a mounting pad on an element substrate (see, for example, Patent Document 1).
JP 2002-244151 A

  However, when mounting pads are formed of aluminum, aluminum alloy, etc., if the mounting pads are narrowed, the mounting pads become smaller, so migration is achieved when COF (Chip On Film) mounting or COG (Chip On Glass) mounting is performed. There is a problem that occurs. However, when the light-reflective conductive layer formed on the upper layer side of the element substrate is not used for forming the mounting pad, the gate electrode and the source of the pixel switching element are connected via the contact hole having a very large aspect ratio. It is necessary to make an electrical connection to the conductive film formed simultaneously with the electrode, which reduces productivity and reliability.

  In view of the above problems, an object of the present invention is to provide a reflective type in which, even when a light-reflective conductive layer is used for forming a mounting pad on which a flexible substrate or IC is mounted, a problem such as migration does not occur on the mounting pad. An object is to provide a liquid crystal device and an electronic apparatus using the same.

In order to solve the above problems, in the present invention, a pixel switching element formed in each of a plurality of pixels, an element substrate including a light-reflective conductive layer formed on an upper layer side of the pixel switching element, A counter substrate disposed opposite to the element substrate; and a liquid crystal held between the counter substrate and the element substrate, wherein the element substrate has a mounting pad on which a flexible substrate or an IC is mounted. in the reflection type liquid crystal device, the light reflective conductive layer is made of an aluminum film or an aluminum alloy film, the mounting pad to the underlying side conductive layer made of the light reflective conductive layer, the lower layer-side conductive layer The upper conductive layer is electrically connected through a contact hole formed in the insulating film to be covered.

  In the present invention, even when a light-reflective conductive layer made of aluminum or an aluminum alloy is formed on the uppermost layer, such a light-reflective conductive layer can be used only as a lower conductive layer for relaying to a mounting pad. Another upper conductive layer formed above the lower conductive layer is used as a mounting pad. For this reason, even when the mounting pad becomes smaller as the mounting pad becomes narrower, no migration occurs in the mounting pad unlike the mounting pad made of aluminum or aluminum alloy.

The present invention is applied, for example, when the pixel electrode is formed of the light-reflective conductive layer on the element substrate.

  In the present invention, the upper conductive layer is preferably composed of a titanium film, a titanium nitride film, or a laminated film thereof.

  In the present invention, in the mounting pad formation region, it is preferable that at least one of the surface of the lower conductive layer and the surface of the upper conductive layer is roughened by plasma treatment. With this configuration, the connection resistance can be reduced.

  A reflective liquid crystal device to which the present invention is applied is used in an electronic device such as a projection display device or a mobile device such as a mobile phone.

  Embodiments of the present invention will be described below. In the drawings to be referred to in the following description, the scales of the layers and the members are different from each other in order to make the layers and the members large enough to be recognized on the drawings.

(overall structure)
1A and 1B are a plan view of a reflective liquid crystal device to which the present invention is applied, as viewed from the side of the counter substrate, together with the components formed thereon, and a cross-sectional view taken along line HH ′ thereof. It is. FIG. 2 is an equivalent circuit diagram showing an electrical configuration of an image display area and the like of a reflective liquid crystal device to which the present invention is applied.

  A reflective liquid crystal device 100 shown in FIGS. 1A and 1B includes an element substrate 10 and a counter substrate 20 facing the element substrate 10. The element substrate 10 and the counter substrate 20 are sealed. The materials 52 are bonded together to face each other. A liquid crystal layer 50 made of TN (Twisted Nematic) liquid crystal or the like is held in an inner region of the sealing material 52. A liquid crystal injection port 52 a is formed in the sealing material 52, and the liquid crystal injection port 52 a is sealed by the sealing material 25 after liquid crystal is injected. A light shielding film 53 as a frame is formed on the counter substrate 20 in parallel with the inner side of the sealing material 52, and the inner region is used as the image display device 10a. A common electrode 21 is formed on substantially the entire inner surface (the liquid crystal layer 50 side) of the counter substrate 20.

  In the element substrate 10, the data line driving circuit 101 and the mounting pad 102 are formed along one side of the element substrate 10 in a region outside the sealing material 52, and along two sides adjacent to the one side, A scanning line driving circuit 104 is formed. A plurality of wirings 109 extend from the mounting pad 102 toward the data line driving circuit 101 and the scanning line driving circuit 104. Further, a flexible substrate 108 on which an IC 107 is mounted is connected to the element substrate 10 using a mounting pad 102. On the remaining side of the element substrate 10, a plurality of wirings 105 are formed for connecting the scanning line driving circuits 104 provided on both sides of the image display region 10a. At the four corners of the counter substrate 20, vertical conduction members 106 are formed for electrical conduction between the element substrate 10 and the counter substrate 20. In the element substrate 10, a plurality of pixel electrodes 9a are formed in a matrix in the pixel display region 10a.

  As shown in FIG. 2, in the element substrate 10 of the reflective liquid crystal device 100, the pixel electrode 9 a and the pixel electrode 9 a for switching control are respectively applied to a plurality of matrix-like pixels 100 a constituting the image display region 10 a. A MOS field effect transistor 30 as a pixel switching element is formed. In the image display area 10a, a plurality of data lines 6a for supplying image signals and a plurality of scanning lines 3a for supplying scanning signals extend in directions intersecting with each other. Connected to the data line driving circuit 101, the scanning line 3 a is connected to the scanning line driving circuit 104. The data line 6 a is connected to the source of the field effect transistor 30, and the scanning line 3 a is connected to the gate of the field effect transistor 30. The pixel electrode 9a is electrically connected to the drain of the field effect transistor 30. By turning on the field effect transistor 30 for a certain period, a data signal supplied from the data line 6a is supplied to each pixel. Write to 100a at a predetermined timing. Then, a pixel signal of a predetermined level written in the liquid crystal capacitor 50a formed by the pixel electrode 9a, the liquid crystal layer 50, and the common electrode 21 shown in FIG.

Here, a storage capacitor 70 is formed in parallel with the liquid crystal capacitor 50a, and the voltage of the pixel electrode 9a is held by the storage capacitor 70 for a time that is, for example, three orders of magnitude longer than the time when the source voltage is applied. . As a result, the charge retention characteristic is improved, and the reflective liquid crystal device 100 capable of displaying with a high contrast ratio can be realized. In this embodiment, in order to configure the storage capacitor 70, the capacitor line 5b is formed in parallel with the scanning line 3a.
b is connected to a common potential line (COM) and is held at a predetermined potential. The storage capacitor 70 may be formed between the previous scanning line 3a.

  The reflective liquid crystal device 100 includes a power supply circuit 201, an image processing circuit 202, and a timing generation circuit 203. These circuits are configured in the IC 107 shown in FIGS. 1A and 1B. . In the timing generation circuit 203, a dot clock for driving each pixel 100a is generated, and based on this dot clock, clock signals VCK, HCK, inverted clock signals VCKB, HCKB, transfer start pulses HSP, VSP are generated, It is supplied to the element substrate 10. When input image data is input from the outside, the image processing circuit 202 generates an image signal based on the input image data and supplies the image signal to the element substrate 10. The power supply circuit 201 generates a plurality of power supplies VDD, VSS, VHH, and VLL and supplies them to the element substrate 10.

(Specific pixel configuration)
3A and 3B are respectively a plan view of adjacent pixels on the element substrate of the reflective liquid crystal device to which the present invention is applied, and a position corresponding to the line AA ′ in FIG. FIG. 6 is a cross-sectional view when the reflective liquid crystal device 100 is cut. In FIG. 3A, the semiconductor layer is indicated by a thin and short dotted line, the scanning line 3a is indicated by a thick solid line, the data line 6a and the thin film formed simultaneously with it are indicated by a one-dot chain line, and the capacitance line 5b is indicated by two dots The pixel electrode 9a and the thin film formed simultaneously with the pixel electrode 9a are indicated by a thick and long dotted line, and the relay electrode is indicated by a thin solid line.

  As shown in FIG. 3A, a rectangular pixel electrode 9a is formed on each of the plurality of pixels 100a on the element substrate 10, and a data line is formed along the vertical and horizontal boundaries of each pixel electrode 9a. 6a and scanning line 3a are formed. A capacitor line 5b is formed in parallel with the scanning line 3a, and a field effect transistor 30 is formed in a region where the data line 6a and the scanning line 3a intersect.

  As shown in FIG. 3B, the element substrate 10 includes a substrate body 10d made of a translucent material such as a quartz substrate or a glass substrate, a pixel electrode 9a formed on the surface of the liquid crystal layer 50, and pixel switching. The counter substrate 20 is mainly composed of the substrate body 20d, the common electrode 21 formed on the surface of the liquid crystal layer 50, and the alignment film 22. Has been.

  In the element substrate 10, a field effect transistor 30 is formed at a position adjacent to the pixel electrode 9a. The field effect transistor 30 has, for example, an LDD (Lightly Doped Drain) structure. The semiconductor layer 1 a has a channel region 1 a ′ facing the scanning line 3 a through the gate insulating layer 2, a low concentration. A source region 1b, a low concentration drain region 1c, a high concentration source region 1d, and a high concentration drain region 1e are formed.

  The semiconductor layer 1a is composed of, for example, a single crystal silicon layer formed on a substrate body 10d made of a quartz substrate via a base insulating film 12, and the element substrate 10 having such a configuration includes a quartz substrate and a single crystal silicon. This can be realized by using an SOI (Silicon On Insulator) substrate in which the substrate is bonded through an insulating layer. Such an SOI substrate is formed by, for example, a method in which a silicon oxide film is formed on a single crystal silicon substrate and bonded to a quartz substrate, or a silicon oxide film is formed on both a quartz substrate and a single crystal silicon substrate and then silicon. A method in which oxide films are brought into contact with each other and bonded can be employed. In this case, the gate insulating layer 2 can be formed by a thermal oxide film for the semiconductor layer 1a. For the scanning line 3a, a silicon film such as polysilicon, amorphous silicon, or a single crystal silicon film, a polycide or a silicide thereof, or a metal film is used.

  On the upper layer side of the scanning line 3a, a first interlayer insulating film 41 made of a silicon oxide film or the like having a contact hole 82 leading to the high concentration source region 1d and a contact hole 83 leading to the high concentration drain region 1e is formed. Yes. Relay electrodes 4 a and 4 b are formed on the first interlayer insulating film 41. The relay electrode 4a is formed in a substantially L shape extending along the scan line 3a and the data line 6a with the position where the scan line 3a and the data line 6a intersect as a base point. The relay electrode 4b It is formed along the data line 6a at a position separated from 4b. The relay electrode 4a is electrically connected to the high-concentration drain region 1e through the contact hole 83, and the relay electrode 4b is electrically connected to the high-concentration source region 1d through the contact hole 82.

  A dielectric film 42 made of a silicon nitride film or the like is formed on the upper layer side of the relay electrodes 4a and 4b, and a capacitor line 5b is formed through the dielectric film 42 so as to face the relay electrode 4a. A storage capacitor 70 is formed. The relay electrodes 4a and 4b are made of a conductive polysilicon film, a metal film, or the like, and the capacitor line 5b is made of a conductive polysilicon film, a metal silicide film containing a refractory metal, a laminated film thereof, or a metal film.

  On the upper layer side of the capacitor line 5b, a second interlayer insulating film 43 made of a silicon oxide film having a contact hole 87 leading to the relay electrode 4a and a contact hole 81 leading to the relay electrode 4b is formed. A data line 6 a and a drain electrode 6 b are formed on the second interlayer insulating film 43. The data line 6a is electrically connected to the relay electrode 4b through the contact hole 81, and is electrically connected to the high concentration source region 1d through the relay electrode 4b. The drain electrode 6b is electrically connected to the relay electrode 4a through the contact hole 87, and is electrically connected to the high concentration drain region 1e through the relay electrode 4a. The data line 6a and the drain electrode 6b are made of a conductive polysilicon film, a metal silicide film containing a refractory metal, a laminated film thereof, and a metal film.

  On the upper layer side of the data line 6a and the drain electrode 6b, a third interlayer insulating film 44 made of a silicon oxide film having a contact hole 86 leading to the drain electrode 6b is formed. A pixel electrode 9 a is formed in the upper layer of the third interlayer insulating film 44, and the pixel electrode 9 a is electrically connected to the drain electrode 6 b through the contact hole 86.

  Here, the pixel electrode 9a is formed of aluminum or aluminum alloy (light reflective conductive film) having a thickness of about 150 nm, and reflects light incident from the counter substrate 20 side toward the counter substrate 20 side. Functions as a light reflecting layer.

  A protective film 45 (insulating film) made of a silicon oxide film, a silicon nitride film, or a laminated film thereof having a thickness of about 150 nm is formed on the pixel electrode 9a. An alignment film 16 is formed on the surface of the protective film 45.

(Configuration of mounting pad)
4A and 4B are a plan view of the mounting pad 102 formed in the reflective liquid crystal device 100 of this embodiment and a cross-sectional view taken along the line CC ′, respectively.

  As described with reference to FIG. 3B, the element substrate 10 of this embodiment includes the base insulating film 12, the first interlayer insulating film 41, the gate insulating layer 2, the dielectric film 42, and the second interlayer insulating film. 43, a third interlayer insulating film 44, and a protective film 45 are laminated in this order, and between these insulating films, the semiconductor layer 1a, the scanning line 3a, the relay electrodes 4a and 4b, the capacitor line 5b, and the data line 6a (Drain electrode 6b) and pixel electrode 9a are formed.

  Therefore, as shown in FIGS. 4A and 4B, the wiring 109 is formed using the conductive film from the mounting pad 102 toward the data line driving circuit 101 and the scanning line driving circuit 104. it can. In this embodiment mode, a configuration in which the wiring 109 is formed using a conductive film formed simultaneously with the data line 6a (drain electrode 6b) is illustrated. Since the pixel electrode 9a is formed as the uppermost conductive film in the image display region 10a of the element substrate 10, the mounting pad 102 can be formed by using the pixel electrode 9a. However, in this embodiment, the pixel electrode 9a is formed of aluminum or an aluminum alloy (light-reflective conductive film), and using such a conductive film as the mounting pad 102 causes migration or the like.

  Therefore, in this embodiment, first, in the third interlayer insulating film 44, two contact holes 88 are formed at positions overlapping with the wiring 109, and the relay terminal 9b (lower side) is made of aluminum or aluminum alloy formed simultaneously with the pixel electrode 9a. A conductive layer) is formed. In this state, the relay terminal 9 b is electrically connected to the wiring 109 through the two contact holes 88.

  Further, in this embodiment, in the protective film 45, a contact hole 89 is formed in a region overlapping the relay terminal 9b, for example, in a region between two contact holes 88, and a titanium film having a thickness of about 100 nm, or A laminated film of a titanium nitride film having a thickness of about 2 nm and a titanium film having a thickness of about 100 nm is formed, and an upper conductive layer 13a that is electrically connected to the relay terminal 9b through the contact hole 89 is formed. . In this embodiment, a region of the upper conductive layer 13a that avoids the position overlapping the contact holes 88 and 89 is used as the mounting pad 102. That is, the terminal of the flexible substrate 108 is connected to the mounting pad 102 via an anisotropic conductive film.

(Main effects of this form)
As described above, in this embodiment, the conductive film formed in the uppermost layer in the image display region 10a is the pixel electrode 9a, but the pixel electrode 9a is made of aluminum or an aluminum alloy. For this reason, if the mounting pad 102 is formed simultaneously with the pixel electrode 9a, problems such as migration occur. However, in this embodiment, aluminum or aluminum alloy formed simultaneously with the pixel electrode 9a is used as the relay terminal 9b. Thus, another upper conductive layer 13a is formed above the relay terminal 9b, and this upper conductive layer 13a is used as the mounting pad 102. For this reason, even when the mounting pad 102 becomes smaller as the mounting pad 102 becomes narrower in pitch, no migration or the like occurs. Therefore, the reliability of the reflective liquid crystal device 100 can be improved.

[Other embodiments]
In the above embodiment, the wiring 109 is formed by the conductive film formed simultaneously with the data line 6a (drain electrode 6b). However, the conductive film formed simultaneously with the scanning line 3a and the capacitor line 5b is used as the wiring. The present invention may be applied to.

  Further, in the above embodiment, the conductive film formed in the uppermost layer in the image display region 10a is the pixel electrode 9a made of aluminum or aluminum alloy. However, the conductive film is insulated on the upper layer of the solid light reflecting layer made of aluminum or aluminum alloy. When a pixel electrode made of ITO (Indium Tin Oxide) film is formed through the film, aluminum or aluminum alloy is used as the lower conductive layer, and when forming the pixel electrode made of ITO film, The mounting pad 102 may be formed by forming layers simultaneously.

  Further, in the formation region of the mounting pad 102, the surface of the relay terminal 9b (lower conductive layer) is preferably roughened by plasma treatment using an inert gas such as argon gas. If comprised in this way, the connection resistance of the relay terminal 9b (lower conductive layer) and the upper conductive layer 13a can be reduced. In the formation region of the mounting pad 102, the surface of the upper conductive layer 13a is preferably roughened by a plasma treatment using an inert gas such as an argon gas. With this configuration, the connection resistance between the upper conductive layer 13a and the flexible substrate 108 can be reduced.

  In the above embodiment, the present invention is applied to the mounting pad 102 for the flexible substrate 108 on which the IC 107 is mounted. However, the mounting pad, the data line driving circuit 101, and the scanning line driving circuit when the IC 107 is mounted on the element substrate 10 are used. In the case where 104 is configured not in the element substrate 10 but in the driving IC, the present invention may be applied to a mounting pad for mounting the driving IC on the element substrate 10.

  Furthermore, although the case where the semiconductor layer 1a is made of a single crystal silicon layer has been described as an example in the above embodiment, the semiconductor layer 1a is formed of polycrystalline silicon by laser annealing or lamp annealing after an amorphous silicon film is formed by a low temperature process. The present invention may also be applied to a reflection type liquid crystal device using a formed polysilicon film. In this case, an inexpensive glass substrate can be used as the substrate body 10d. In such a case, the gate insulating layer 2 is composed of a silicon oxide film, a silicon nitride film, or a stacked film thereof formed by a CVD method or the like.

[Example of mounting on electronic devices]
The reflective liquid crystal device 100 according to the present invention is used for a projection display device shown in FIG. 5A, a (liquid crystal projector / electronic device), and a portable electronic device shown in FIGS. 5B and 5C. Can do.

A projection display apparatus 1000 shown in FIG. 5A includes a polarization illumination apparatus 800 including a light source unit 810, an integrator lens 820, and a polarization conversion element 830 arranged along the system optical axis L, and the polarization illumination apparatus 800. The polarization beam splitter 840 that reflects the emitted S-polarized light beam by the S-polarized light beam reflection surface 841 and the blue light (B) component of the light reflected from the S-polarized light beam reflection surface 841 of the polarization beam splitter 840 are separated. And a dichroic mirror 844 that reflects and separates the red light (R) component of the luminous flux after the blue light is separated. In addition, the projection display device 1000 includes three reflective liquid crystal devices 100 (reflective liquid crystal devices 100R, 100G, and 100B) on which each color light is incident. Further, the projection display apparatus 1000 combines the light modulated by the three reflective liquid crystal devices 100R, 100G, and 100B by the dichroic mirrors 844 and 843 and the polarization beam splitter 840, and then combines the combined light with a screen. The mobile phone 3000 shown in FIG. 5B includes a plurality of operation buttons 3001, scroll buttons 3002, and a reflective liquid crystal device 100 as a display unit. By operating the scroll button 3002, the screen displayed on the reflective liquid crystal device 100 is scrolled. A personal digital assistant (PDA) shown in FIG. 5C includes a plurality of operation buttons 4001, a power switch 4002, and a reflective liquid crystal device 100 as a display unit, and when the power switch 4002 is operated. Various information such as an address book and a schedule book are displayed on the reflective liquid crystal device 100.

  Further, if a color filter is formed on the counter substrate 20 or the like, the reflective liquid crystal device 100 capable of color display can be formed. In addition, when the reflective liquid crystal device 100 in which a color filter is formed is used, a single-plate projection display device can be configured.

(A), (b) is the top view which looked at the reflective liquid crystal device to which this invention is applied from the opposing substrate side with each component formed on it, and its HH 'sectional drawing, respectively. . FIG. 3 is an equivalent circuit diagram illustrating an electrical configuration of an image display area and the like of a reflective liquid crystal device to which the present invention is applied. (A), (b) is a plan view of adjacent pixels on the element substrate of a reflective liquid crystal device to which the present invention is applied, and a cross section when the liquid crystal device is cut at a position corresponding to the line AA ′. FIG. (A), (b) is the top view of the mounting pad formed in the reflective liquid crystal device to which this invention is applied, respectively, and its CC 'sectional drawing. (A), (b), (c) is each explanatory drawing of the electronic device using the reflection type liquid crystal device to which this invention is applied.

Explanation of symbols

1a..Semiconductor layer, 2..Gate insulating layer, 3a..Scan line (gate electrode), 4a, 4b..Relay electrode, 5b..Capacitor line, 6a..Data line, 6b..Drain electrode, 9a ..Pixel electrode, 9b..Relay terminal (lower conductive layer), 10..Element substrate, 13a..Upper conductive layer, 20..Counter substrate, 30..Field effect transistor (pixel switching element), 41 .. First interlayer insulating film 42.. Dielectric film 43.. Second interlayer insulating film 44.. Third interlayer insulating film 45.. Protective film (insulating film) 100. Equipment, 109 ... wiring

Claims (4)

A pixel switching element formed in each of a plurality of pixels; an element substrate including a light-reflective conductive layer formed on an upper layer side of the pixel switching element; a counter substrate disposed opposite to the element substrate; In a reflective liquid crystal device comprising a counter substrate and a liquid crystal held between the element substrate, the element substrate having a mounting pad on which a flexible substrate or IC is mounted,
The light reflective conductive layer is made of an aluminum film or an aluminum alloy film,
The mounting pad is constituted by an upper conductive layer that is electrically connected to a lower conductive layer made of the light-reflective conductive layer through a contact hole formed in an insulating film covering the lower conductive layer. Has been
At least one of the surface of the lower-layer side conductive layer and the surface of the upper-layer side conductive layer is roughened by plasma treatment .   2. The reflective liquid crystal device according to claim 1, wherein a pixel electrode is formed on the element substrate by the light reflective conductive layer.   The reflective liquid crystal device according to claim 1, wherein the upper conductive layer is made of a titanium film or a laminated film of a titanium nitride film and a titanium film. An electronic apparatus comprising the reflective liquid crystal device according to any one of claims 1 to 3 .

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