JP2011158753A - Electrooptical device and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily perform film thickness control of a capacitance insulating film in an electrooptical device such as a liquid crystal device. <P>SOLUTION: The electrooptical device includes: transistors (30) provided for respective pixels; pixel electrodes (9) provided corresponding to the transistors; and a storage capacitance (70) electrically connected to the pixel electrodes and made of a first capacitance electrode (2), a second capacitance electrode (5) disposed opposite to the first capacitance electrode from an upper layer side and the capacitance insulating film (7) formed between the first and second capacitance electrodes. The capacitance insulating film has: a first layer (7a) containing hafnium oxide; a second layer (7b) formed in an upper layer of the first layer and containing alumina; a third layer (7c) formed in a lower layer of the first layer and containing alumina; and a fourth layer (7d) formed in an upper layer of the second layer and containing hafnium oxide. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technical field of an electro-optical device such as a liquid crystal device and an electronic apparatus such as a liquid crystal projector including the electro-optical device.

  Some electro-optical devices of this type have a storage capacitor electrically connected to the pixel electrode. The storage capacitor is formed, for example, by disposing a dielectric film (in other words, a capacitor insulating film) between the capacitor electrodes (see, for example, Patent Document 1).

  The capacitor insulating film constituting the storage capacitor may have a structure in which a plurality of layers are stacked in order to improve the performance. For example, in Patent Document 2, the first ferroelectric film is crystallized, and the second ferroelectric film is formed thereon, thereby reducing the leakage current while maintaining a high polarization inversion amount, and also insulating There has been proposed a technique for realizing a storage capacity that is excellent in fracture resistance and imprint resistance.

Special Table 2000-514243 JP 2008-124274 A

  However, as described above, when a capacitive insulating film in which a plurality of layers are stacked is used, the number of layers constituting the capacitive insulating film is increased, so that the film thickness control of the dielectric film constituting each layer is highly accurate. Is required. If the film thickness control is not performed accurately, the function as a capacitive insulating film cannot be fully exhibited, and other parts constituting the device may be adversely affected.

  Here, in particular, the thickness of the capacitive insulating film may change relatively easily due to, for example, the patterning of the capacitive electrode located on the upper side of the capacitive insulating film or the chemical reaction with the capacitive electrode. It is extremely difficult to control the film thickness with high accuracy without applying it.

  As described above, even if a beneficial effect is obtained by using a laminated structure of the capacitive insulating film, the above-described technique has a highly complicated manufacturing process because the film thickness must be controlled with extremely high accuracy. There is a technical problem that there is a possibility of becoming.

  SUMMARY An advantage of some aspects of the invention is that it provides an electro-optical device and an electronic apparatus that can easily control the film thickness of a capacitive insulating film.

  In order to solve the above problems, a first electro-optical device of the present invention includes a transistor provided for each pixel, a pixel electrode provided corresponding to the transistor, and a pixel electrode electrically connected to the pixel electrode. And a storage capacitor comprising a first capacitor electrode, a second capacitor electrode disposed opposite to the first capacitor electrode from the upper layer side, and a capacitor insulating film formed between the first capacitor electrode and the second capacitor electrode; The capacitor insulating film is formed in a first layer containing hafnium oxide, a second layer containing alumina, a second layer containing alumina, and a lower layer of the first layer; A third layer containing alumina and a fourth layer formed on the second layer and containing hafnium oxide are included.

  The first electro-optical device of the present invention includes, for example, an element substrate provided with a pixel electrode and a transistor such as a pixel switching TFT (Thin Film Transistor) electrically connected to the pixel electrode, and a pixel electrode. An electro-optical material such as liquid crystal is sandwiched between a counter substrate provided with counter electrodes facing each other. During the operation of the electro-optical device, an image signal is selectively supplied to the pixel electrode, whereby image display is performed in a pixel region (or image display region) in which a plurality of pixel electrodes are arranged. The image signal is supplied from the data line to the pixel electrode at a predetermined timing, for example, when a transistor electrically connected between the data line and the pixel electrode is turned on / off.

  According to the first electro-optical device of the present invention, the storage capacitor is electrically connected to the pixel electrode. The storage capacitor is composed of a first capacitor electrode, a second capacitor electrode disposed opposite to the first capacitor electrode from the upper layer side, and a capacitor insulating film formed between the first capacitor electrode and the second capacitor electrode. For example, the first capacitor electrode is configured as an electrode electrically connected between the pixel electrode and the transistor, and the second capacitor electrode is fixed at a fixed potential by being electrically connected to a constant potential source. It is configured as a potential side capacitive electrode.

Here, in the present invention, in particular, the capacitor insulating film constituting the above-described storage capacitor is formed in a first layer containing hafnium oxide (HfO ₂ ) and an upper layer of the first layer, and alumina (Al ₂ O ₃ ). And a third layer including alumina, a third layer including alumina, and a fourth layer including hafnium oxide. Has been. That is, the capacitive insulating film according to the present invention is a four-layer structure in which a third layer containing alumina, a first layer containing hafnium oxide, a second layer containing alumina, and a fourth layer containing hafnium oxide are stacked in order from the lower layer side. It has a structure.

  Here, if the case where the capacitor insulating film has a three-layer structure of the first layer, the second layer, and the third layer (that is, the case where the fourth layer is not formed), among the layers constituting the capacitor insulating film, The uppermost second layer is in contact with the second capacitor electrode (that is, the upper capacitor electrode). Since the second layer contains alumina, which is relatively susceptible to reaction, there is a risk that it will react with the second capacitor electrode to form a different layer film. Further, when the second capacitor electrode is made of aluminum or the like, when the second capacitor electrode is patterned by etching or the like, even the second layer that does not need to be patterned may be cut together.

  However, in the present invention, in particular, the fourth layer is formed on the second layer. Therefore, the fourth layer containing hafnium oxide is in contact with the second capacitor electrode. Compared with alumina, hafnium oxide is less likely to cause a reaction that forms a different layer film, and is less likely to be removed when the second capacitor electrode is etched. Therefore, it is possible to prevent the film thickness of the capacitive insulating film from changing due to the above-described formation of the different layer film, etching, or the like. That is, since the second layer whose thickness is likely to change is protected by the fourth layer whose thickness is difficult to change, the thickness of the capacitor insulating film can be controlled suitably. Thereby, it is possible to set the capacity value of the storage capacitor with high accuracy.

  In addition, according to the research of the present inventor, with the capacitive insulating film having a four-layer structure, the withstand voltage performance is improved as compared with the case of the three-layer structure (that is, when the fourth layer is not formed). It turns out. Therefore, in the present invention, the reliability of the apparatus can be improved.

  As described above, according to the first electro-optical device of the present invention, the capacitance value can be set with high accuracy and the reliability of the device can be improved.

  In one aspect of the first electro-optical device of the present invention, the capacitive insulating film is formed in a lower layer of the third layer, and has a fifth layer containing hafnium oxide.

  According to this aspect, the fifth layer containing hafnium oxide is formed below the third layer containing alumina. That is, the capacitive insulating film according to this aspect includes, in order from the lower layer side, the fifth layer containing hafnium oxide, the third layer containing alumina, the first layer containing hafnium oxide, the second layer containing alumina, and the second layer containing hafnium oxide. It has a five-layer structure in which four layers are laminated.

  According to the five-layer structure, the first capacitor electrode (that is, the capacitor electrode on the lower layer side) is in contact with the fifth layer containing hafnium oxide, not the third layer containing alumina. As described above, hafnium oxide is less likely to cause a reaction that forms a heterogeneous film than alumina, and is less likely to be removed during etching of the second capacitor electrode. Therefore, it is possible to prevent the film thickness of the capacitive insulating film from changing due to the formation of the different layer film or the etching described above.

  In this embodiment, the fourth layer protects the second layer on the upper layer side, and the fifth layer on which the film thickness hardly changes on the lower layer side is the fifth layer on which the film thickness is less likely to change. Since it is configured to protect, the film thickness of the capacitive insulating film can be suitably controlled. As a result, the capacity value of the storage capacitor can be set with higher accuracy. In addition, according to the research of the present inventor, it has been found that the withstand voltage performance is improved by making the capacitive insulating film have a five-layer structure as compared with the case of the four-layer structure (that is, when the fifth layer is not formed). ing. Therefore, in this aspect, the reliability of the apparatus can be further improved.

  In another aspect of the first electro-optical device of the present invention, the second capacitor electrode includes titanium nitride.

  According to this aspect, the second capacitor electrode is preferably formed of the material containing titanium nitride. Here, titanium nitride has a property that a different layer film is easily formed by reacting with alumina. On the other hand, in this aspect, the fourth layer is formed on the second layer. Therefore, the fourth layer containing hafnium oxide is in contact with the second capacitor electrode containing titanium nitride. Therefore, it is possible to reliably prevent the thickness of the capacitive insulating film from changing due to the formation of the different layer film.

  In another aspect of the first electro-optical device of the present invention, the second capacitor electrode contains aluminum.

  According to this aspect, the second capacitor electrode is preferably formed of the material containing aluminum. Here, aluminum may be etched using, for example, fluorine (F). In this case, alumina is likely to be etched as well. That is, when patterning the second capacitor electrode containing aluminum, there is a possibility that even the layer containing alumina that does not require patterning may be removed. On the other hand, in this aspect, the fourth layer is formed on the second layer. Therefore, the fourth layer containing hafnium oxide is in contact with the second capacitor electrode containing aluminum. Therefore, it is possible to reliably prevent the thickness of the capacitor insulating film from being changed by patterning such as etching.

  In order to solve the above problems, a second electro-optical device according to the present invention includes a transistor provided for each pixel, a pixel electrode corresponding to the transistor, and a pixel electrode electrically connected to the pixel electrode. And a storage capacitor comprising a first capacitor electrode, a second capacitor electrode disposed opposite to the first capacitor electrode from the upper layer side, and a capacitor insulating film formed between the first capacitor electrode and the second capacitor electrode; The capacitor insulating film is formed in a first layer containing hafnium oxide, a second layer containing alumina, a second layer containing alumina, and a lower layer of the first layer; A third layer containing alumina and a fourth layer formed under the third layer and containing hafnium oxide are included.

  The second electro-optical device according to the present invention includes, for example, an element substrate provided with a pixel electrode and a transistor such as a pixel switching TFT electrically connected to the pixel electrode, and a counter electrode facing the pixel electrode. An electro-optical material such as liquid crystal is sandwiched between the counter substrate provided. During the operation of the electro-optical device, an image signal is selectively supplied to the pixel electrode, whereby image display is performed in a pixel region (or image display region) in which a plurality of pixel electrodes are arranged. The image signal is supplied from the data line to the pixel electrode at a predetermined timing, for example, when a transistor electrically connected between the data line and the pixel electrode is turned on / off.

  According to the second electro-optical device of the present invention, the storage capacitor is electrically connected to the pixel electrode. The storage capacitor is composed of a first capacitor electrode, a second capacitor electrode disposed opposite to the first capacitor electrode from the upper layer side, and a capacitor insulating film formed between the first capacitor electrode and the second capacitor electrode. For example, the first capacitor electrode is configured as an electrode electrically connected between the pixel electrode and the transistor, and the second capacitor electrode is fixed at a fixed potential by being electrically connected to a constant potential source. It is configured as a potential side capacitive electrode.

Here, in the present invention, in particular, the capacitor insulating film constituting the above-described storage capacitor is formed in a first layer containing hafnium oxide (HfO ₂ ) and an upper layer of the first layer, and alumina (Al ₂ O ₃ ). And a second layer including alumina, a third layer including alumina, and a fourth layer including hafnium oxide formed under the first layer. Has been. That is, the capacitive insulating film according to the present invention is a four-layer structure in which a fourth layer containing hafnium oxide, a third layer containing alumina, a first layer containing hafnium oxide, and a second layer containing alumina are stacked in order from the lower layer side. It has a structure.

  Here, if the case where the capacitor insulating film has a three-layer structure of the first layer, the second layer, and the third layer (that is, the case where the fourth layer is not formed), among the layers constituting the capacitor insulating film, The lowermost first layer is in contact with the first capacitor electrode (that is, the lower layer capacitor electrode). Since the first layer contains alumina that is relatively susceptible to reaction, there is a risk that it will react with the first capacitor electrode to form a heterogeneous film.

  However, in the present invention, in particular, the fourth layer is formed below the first layer. Therefore, the fourth layer containing hafnium oxide is in contact with the first capacitor electrode. Hafnium oxide is less likely to cause a reaction that forms a heterogeneous film than alumina. Therefore, it is possible to prevent the thickness of the capacitor insulating film from changing due to the formation of the above-described different layer film. That is, since the first layer whose film thickness is likely to change is protected by the fourth layer whose film thickness is difficult to change, the film thickness of the capacitive insulating film can be controlled suitably. Thereby, it is possible to set the capacity value of the storage capacitor with high accuracy.

  In addition, according to the research of the present inventor, with the capacitive insulating film having a four-layer structure, the withstand voltage performance is improved as compared with the case of the three-layer structure (that is, when the fourth layer is not formed). It turns out. Therefore, in the present invention, the reliability of the apparatus can be improved.

  As described above, according to the second electro-optical device of the present invention, the capacitance value can be set with high accuracy and the reliability of the device can be improved.

  In one aspect of the second electro-optical device of the present invention, the first capacitor electrode contains titanium nitride.

  According to this aspect, the first capacitor electrode is preferably formed of the material containing titanium nitride. Here, titanium nitride has a property that a different layer film is easily formed by reacting with alumina. On the other hand, in this aspect, the fourth layer is formed below the first layer. Therefore, the fourth layer containing hafnium oxide is in contact with the first capacitor electrode containing titanium nitride. Therefore, it is possible to reliably prevent the thickness of the capacitive insulating film from changing due to the formation of the different layer film.

  In another aspect of the first and second electro-optical devices of the present invention, the first layer is formed thinner than the second layer and the third layer.

  According to this aspect, among the layers constituting the capacitive insulating film, the first layer containing hafnium oxide is located in the upper layer and the lower layer of the first layer, respectively, than the second layer and the third layer containing alumina. Thinly formed. According to the research of the present inventor, it has been found that the withstand voltage performance is dramatically improved by making the first layer the second layer and the third layer thin. Therefore, according to this aspect, it is possible to effectively improve the breakdown voltage performance of the storage capacitor. More preferably, if each layer of the capacitive insulating film is formed so that the ratio of hafnium oxide and alumina is 1: 2, the pressure resistance performance can be further effectively improved.

  In order to solve the above problems, an electronic apparatus according to the present invention includes the above-described electro-optical device according to the present invention (including various aspects thereof).

  According to the electronic apparatus of the present invention, since the electro-optical device according to the present invention described above is provided, a projection display device, a television set, and a mobile phone that can display with high reliability and high quality. Various electronic devices such as electronic notebooks, word processors, viewfinder type or monitor direct view type video tape recorders, workstations, videophones, POS terminals and touch panels can be realized. In addition, as an electronic apparatus of the present invention, for example, an electrophoretic device such as electronic paper can be realized.

  The effect | action and other gain of this invention are clarified from the form for implementing invention demonstrated below.

1 is a plan view showing an overall configuration of an electro-optical device according to a first embodiment. It is the HH 'sectional view taken on the line of FIG. FIG. 3 is an equivalent circuit diagram of various elements, wirings, and the like in a plurality of pixels constituting an image display region of the electro-optical device according to the first embodiment. It is a top view of a plurality of pixel parts which adjoin mutually. FIG. 5 is a cross-sectional view taken along line A-A ′ of FIG. 4. FIG. 3 is an enlarged cross-sectional view illustrating a configuration of a capacitive insulating film of the electro-optical device according to the first embodiment. FIG. 6 is an enlarged cross-sectional view illustrating a configuration of a capacitive insulating film of an electro-optical device according to a comparative example. It is a table | surface (the 1) which shows the pixel count destroyed in the pressure | voltage resistant test. It is a table | surface (the 2) which shows the pixel count destroyed in the pressure | voltage resistant test. FIG. 6 is an enlarged cross-sectional view illustrating a configuration of a capacitive insulating film of an electro-optical device according to a second embodiment. FIG. 10 is an enlarged cross-sectional view illustrating a configuration of a capacitive insulating film of an electro-optical device according to a third embodiment. It is a top view which shows the structure of the projector which is an example of the electronic device to which the electro-optical apparatus is applied.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Electro-optical device>
The electro-optical device according to this embodiment will be described with reference to FIGS. In the following embodiments, a TFT active matrix driving type liquid crystal device with a built-in driving circuit will be described as an example of the electro-optical device of the present invention.

<First Embodiment>
First, the overall configuration of the electro-optical device according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a plan view showing the overall configuration of the electro-optical device according to this embodiment, and FIG. 2 is a cross-sectional view taken along the line HH ′ of FIG.

  1 and 2, in the electro-optical device according to the present embodiment, a TFT array substrate 10 and a counter substrate 20 are disposed to face each other. The TFT array substrate 10 is an example of the “substrate” in the present invention, and is, for example, a transparent substrate such as a quartz substrate or a glass substrate, a silicon substrate, or the like. The counter substrate 20 is a transparent substrate such as a quartz substrate or a glass substrate. A liquid crystal layer 50 is sealed between the TFT array substrate 10 and the counter substrate 20. The liquid crystal layer 50 is made of, for example, a liquid crystal in which one or several types of nematic liquid crystals are mixed, and takes a predetermined alignment state between a pair of alignment films.

  The TFT array substrate 10 and the counter substrate 20 are bonded to each other by a sealing material 52 provided in a sealing region located around the image display region 10a provided with a plurality of pixel electrodes.

  The sealing material 52 is made of, for example, an ultraviolet curable resin, a thermosetting resin, or the like for bonding the two substrates, and is applied on the TFT array substrate 10 in the manufacturing process and then cured by ultraviolet irradiation, heating, or the like. It is. In the sealing material 52, a gap material such as glass fiber or glass beads for dispersing the distance between the TFT array substrate 10 and the counter substrate 20 (that is, the inter-substrate gap) to a predetermined value is dispersed. Note that the gap material may be arranged in the image display region 10a or a peripheral region located around the image display region 10a in addition to or instead of the material mixed in the seal material 52.

  A light-shielding frame light-shielding film 53 that defines the frame area of the image display area 10a is provided on the counter substrate 20 side in parallel with the inside of the seal area where the sealing material 52 is disposed. A part or all of the frame light shielding film 53 may be provided as a built-in light shielding film on the TFT array substrate 10 side.

  A data line driving circuit 101 and an external circuit connection terminal 102 are provided along one side of the TFT array substrate 10 in a region located outside the sealing region in which the sealing material 52 is disposed in the peripheral region. The scanning line driving circuit 104 is provided along two sides adjacent to the one side so as to be covered with the frame light shielding film 53. Further, in order to connect the two scanning line driving circuits 104 provided on both sides of the image display region 10 a in this way, a plurality of the pixel lines are covered along the remaining side of the TFT array substrate 10 and covered with the frame light shielding film 53. Wiring 105 is provided.

  In a region facing the four corners of the counter substrate 20 on the TFT array substrate 10, vertical conduction terminals 106 for connecting the two substrates with a vertical conduction material are arranged. Thus, electrical conduction can be established between the TFT array substrate 10 and the counter substrate 20.

  In FIG. 2, on the TFT array substrate 10, a layered structure is formed in which pixel switching TFTs as drive elements, wiring lines such as scanning lines and data lines are formed. Although the detailed structure of this laminated structure is not shown in FIG. 2, pixel electrodes 9 made of a transparent material such as ITO (Indium Tin Oxide) are provided on the laminated structure with a predetermined pattern for each pixel. It is formed in an island shape.

  The pixel electrode 9 is formed in the image display area 10 a on the TFT array substrate 10 so as to face the counter electrode 21. On the surface of the TFT array substrate 10 facing the liquid crystal layer 50, that is, on the pixel electrode 9, an alignment film 16 is formed so as to cover the pixel electrode 9.

  A light shielding film 23 is formed on the surface of the counter substrate 20 facing the TFT array substrate 10. For example, the light shielding film 23 is formed in a lattice shape when viewed in plan on the facing surface of the facing substrate 20. In the counter substrate 20, a non-opening area is defined by the light shielding film 23, and an area partitioned by the light shielding film 23 is an opening area through which light emitted from, for example, a projector lamp or a direct viewing backlight is transmitted. The light shielding film 23 may be formed in a stripe shape, and the non-opening region may be defined by the light shielding film 23 and various components such as data lines provided on the TFT array substrate 10 side.

  On the light shielding film 23, a counter electrode 21 made of a transparent material such as ITO is formed so as to face the plurality of pixel electrodes 9. Further, in order to perform color display in the image display area 10a, a color filter (not shown in FIG. 2) may be formed on the light shielding film 23 in an area including a part of the opening area and the non-opening area. Good. An alignment film 22 is formed on the counter electrode 21 on the counter surface of the counter substrate 20.

  In addition to the above-described drive circuits such as the data line drive circuit 101 and the scanning line drive circuit 104, the image signal on the image signal line is sampled on the TFT array substrate 10 shown in FIGS. Sampling circuit that supplies lines, precharge circuit that supplies pre-charge signals of a predetermined voltage level to multiple data lines in advance of image signals, inspection of quality, defects, etc. of the electro-optical device during production or shipment An inspection circuit or the like may be formed.

  Next, an electrical configuration of the pixel portion of the electro-optical device according to the present embodiment will be described with reference to FIG. FIG. 3 is an equivalent circuit diagram of various elements, wirings, and the like in a plurality of pixels formed in a matrix forming the image display area of the electro-optical device according to this embodiment.

  In FIG. 3, a pixel electrode 9 and a TFT 30 are formed in each of a plurality of pixels formed in a matrix that forms the image display region 10a. The TFT 30 is electrically connected to the pixel electrode 9, and performs switching control of the pixel electrode 9 during operation of the electro-optical device according to the present embodiment. The data line 6 to which the image signal is supplied is electrically connected to the source of the TFT 30. The image signals S1, S2,..., Sn to be written to the data lines 6 may be supplied line-sequentially in this order, or may be supplied to each of a plurality of adjacent data lines 6 for each group. May be.

  The scanning line 11 is electrically connected to the gate of the TFT 30, and the electro-optical device according to the present embodiment pulses the scanning signals G 1, G 2,. Gm is applied in this order in a line sequential manner. The pixel electrode 9 is electrically connected to the drain of the TFT 30, and the image signal S1, S2,... Supplied from the data line 6 is closed by closing the switch of the TFT 30 serving as a switching element for a certain period. Sn is written at a predetermined timing. A predetermined level of image signals S1, S2,..., Sn written in a liquid crystal as an example of an electro-optic material via the pixel electrode 9 is held for a certain period with the counter electrode formed on the counter substrate. The

  The liquid crystal constituting the liquid crystal layer 50 (see FIG. 2) modulates light and enables gradation display by changing the orientation and order of the molecular assembly depending on the applied voltage level. For example, in the normally white mode, the transmittance for incident light is reduced according to the voltage applied in units of each pixel. In the normally black mode, the transmittance is applied in units of each pixel. As a result, the transmittance for incident light is increased, and light having a contrast corresponding to an image signal is emitted from the electro-optical device as a whole.

  In order to prevent the image signal held here from leaking, a storage capacitor 70 is added in parallel with the liquid crystal capacitor formed between the pixel electrode 9 and the counter electrode 21 (see FIG. 2). The storage capacitor 70 is a capacitive element that functions as a storage capacitor that temporarily holds the potential of each pixel electrode 9 in response to supply of an image signal. A specific configuration of the storage capacitor 70 will be described in detail later.

  Next, a specific configuration of the pixel portion that realizes the above-described operation will be described with reference to FIGS. FIG. 4 is a plan view of a plurality of adjacent pixel portions. FIG. 5 is a cross-sectional view taken along the line A-A ′ of FIG. 4. In FIGS. 4 and 5, the scale of each layer / member is different for each layer / member to have a size that can be recognized on the drawing. 4 and 5, for convenience of explanation, illustration of a portion located above the pixel electrode 9 is omitted.

  In FIG. 4, on the TFT array substrate 10, scanning lines 11 and data lines 6 are arranged along the X direction and the Y direction, respectively. A pixel switching TFT 30 is provided at each of the locations where the scanning line 11 and the data line 6 intersect each other. Although not shown in FIG. 4, a plurality of pixel electrodes 9 are provided in a matrix so as to cover the opening area excluding the non-opening area defined by the scanning lines 11, the data lines 6, and the like.

  4 and 5, the TFT 30 is configured to include a semiconductor layer 30a and a gate electrode 30b that are disposed to face each other.

  The semiconductor layer 30a is made of, for example, polysilicon, and includes a source region 30a1, a channel region 30a2, and a drain region 30a3. An LDD (Lightly Doped Drain) region may be formed at the interface between the channel region 30a2 and the source region 30a1, or the channel region 30a2 and the drain region 30a3.

  The gate electrode 30b is made of, for example, conductive polysilicon, and is electrically connected to the scanning line 11 through a contact hole (not shown). The gate electrode 30b and the semiconductor layer 30a are insulated by the gate insulating film 13.

  In FIG. 5, the scanning line 11 is provided on the lower layer side of the TFT 30 on the TFT array substrate 10 through the base insulating film 12. The scanning line 11 includes, for example, at least one of refractory metals such as Ti (titanium), Cr (chromium), W (tungsten), Ta (tantalum), Mo (molybdenum), and Pd (palladium). It is made of a light shielding material such as a simple metal, an alloy, a metal silicide, a polysilicide, or a laminate of these. The scanning line 11 is incident on the TFT array substrate 10 from the TFT array substrate 10 side, which is back-surface reflection on the TFT array substrate 10 or light that is emitted from another liquid crystal device by a multi-plate projector or the like and penetrates the composite optical system. It also functions as a lower light-shielding film that shields the channel region 30a2 of the TFT 30 and its periphery from light.

  In addition to the function of insulating the TFT 30 from the scanning line 11 between layers, the base insulating film 12 is formed on the entire surface of the TFT array substrate 10 so that the surface of the TFT array substrate 10 is roughened when it is polished, or remains after cleaning. Thus, the pixel switching TFT 30 has a function of preventing deterioration of characteristics.

  In FIG. 5, the data line 6 and the relay layer 1 are provided on the upper layer side of the TFT 30 on the TFT array substrate 10 via the first interlayer insulating film 14.

  The data line 6 is electrically connected to the source region 30a1 of the semiconductor layer 30a through a contact hole 31 penetrating the first interlayer insulating film 14 and the gate insulating film 13. The data line 6 and the inside of the contact hole 31 are made of, for example, an Al (aluminum) -containing material such as Al—Si—Cu or Al—Cu, Al alone, or a multilayer film including an Al layer and a TiN layer. The data line 6 also has a function of shielding the TFT 30 from light.

  The relay layer 1 is formed in the same layer as the data line 6 on the first interlayer insulating film 14 and is electrically connected to the drain region 30a3 of the semiconductor layer 30a through the contact hole 32. The data line 6 and the relay layer 1 are formed by, for example, forming a thin film made of a conductive material such as a metal film on the first interlayer insulating film 14 using a thin film forming method, and removing the thin film partially. It forms in the state mutually spaced apart by patterning. Therefore, since the data line 6 and the relay layer 1 can be formed in the same process, the manufacturing process of the apparatus can be simplified.

  A shield layer 4 is provided on the upper layer side of the data line 6 and the relay layer 1 on the TFT array substrate 10 via the second interlayer insulating film 15. The shield layer 4 is supplied with a common potential (i.e., a constant voltage or a rectangular potential that is inverted at a predetermined period), thereby generating an electric field generated due to a potential difference between a first capacitor electrode 2 and a data line 6 described later. Cut off.

  A storage capacitor 70 is provided above the shield layer 4 on the TFT array substrate 10 via the third interlayer insulating film 16. The storage capacitor 70 is formed by arranging the first capacitor electrode 2 and the second capacitor electrode 5 to face each other with the capacitor insulating film 7 interposed therebetween.

  The first capacitor electrode 2 includes, for example, titanium nitride and is a pixel potential side capacitor electrode that is electrically connected to the drain region 30a3 of the TFT 30 and the pixel electrode 9. More specifically, the first capacitor electrode 2 is electrically connected to the drain region 30a3 via the contact hole 33, the relay layer 1, and the contact hole 32 on the lower layer side, and via the contact hole 34 on the upper layer side. The pixel electrode 9 is electrically connected. The first capacitor electrode 2 has a function as a light shielding film in addition to a function as a pixel potential side capacitor electrode.

  The second capacitor electrode 5 is a fixed potential side capacitor electrode that is electrically connected to a constant potential source via a capacitor line 300 (see FIG. 3) and maintained at a fixed potential. The second capacitor electrode 5 is formed of a non-transparent metal film containing, for example, a metal such as aluminum or an alloy, and also functions as a light shielding film that shields the TFT 30.

  The capacitor insulating film 7 has a multilayer structure in which, for example, hafnium oxide and alumina layers are stacked. A specific configuration of the capacitive insulating film 7 will be described in detail later.

  According to the storage capacitor 70 described above, the potential holding characteristic of the pixel electrode 9 is improved, and display characteristics such as contrast improvement and flicker reduction can be improved.

  In FIG. 5, the pixel electrode 9 is formed on the upper layer side of the storage capacitor 70 via the interlayer insulating films 17, 18 and 19. On the upper surface of the pixel electrode 9, an alignment film that has been subjected to a predetermined alignment process such as a rubbing process is provided.

  The configuration of the pixel portion described above is common to each pixel portion as shown in FIG. Such pixel portions are periodically formed in the image display area 10a (see FIG. 1).

  Next, a specific configuration and effect of the capacitor insulating film 7 in the above-described storage capacitor 70 will be described with reference to FIGS. FIG. 6 is an enlarged cross-sectional view showing the configuration of the capacitive insulating film of the electro-optical device according to the first embodiment, and FIG. 7 is an enlarged cross-sectional view showing the configuration of the capacitive insulating film of the electro-optical device according to the comparative example. FIG. 8 and 9 are tables showing the number of pixels destroyed in the withstand voltage test, respectively. In FIGS. 6 and 7, the scales of the layers and members are different from each other in order to make the layers and members recognizable on the drawings.

  6, in the storage capacitor 70 provided in the electro-optical device according to the present embodiment, the capacitor insulating film 7 includes a first layer 7a containing hafnium oxide, a second layer 7b containing alumina, and a first layer containing alumina. The third layer 7c includes a fourth layer 7d containing hafnium oxide and a fifth layer 7e containing hafnium oxide. Specifically, a five-layer structure in which a fifth layer 7e, a third layer 7c, a first layer 7a, a second layer 7b, and a fourth layer 7d are stacked in this order from the lower layer side.

  Here, as shown in FIG. 7, a comparative example in which the capacitive insulating film 7 has a three-layer structure of the first layer 7a, the second layer 7b, and the third layer 7c (that is, the fourth layer 7d and the fifth layer 7e are formed). Think if not).

  In the capacitor insulating film 7 shown in FIG. 7, the third layer 7 c that is the lowest layer is in contact with the first capacitor electrode 2. As described above, the first capacitor electrode 2 is configured to include titanium nitride, but this titanium nitride reacts with alumina included in the third layer 7c, and the different layer film 200 as shown in the figure. May be formed.

  On the other hand, in the capacitive insulating film 7 according to this embodiment shown in FIG. 6, the fifth layer 7e containing hafnium oxide is formed in the lower layer of the third layer 7c. Formation can be prevented. That is, the formation of the different layer film 200 can prevent the film thickness of the capacitive insulating film 7 from changing.

  Further, the capacitor insulating film shown in FIG. 7 has a configuration in which the second layer 7 b that is the uppermost layer is in contact with the second capacitor electrode 5. As described above, the second capacitor electrode 5 includes aluminum. However, the fluorine used when etching the aluminum also scrapes the alumina contained in the second layer 7b. That is, when the second capacitor electrode 5 is patterned by etching, even the second layer 7b that does not need to be etched may be removed together.

  On the other hand, in the capacitive insulating film 7 according to the present embodiment shown in FIG. 6, the fourth layer 7d containing hafnium oxide is formed in the upper layer of the second layer 7b. Can be suppressed. That is, since the fourth layer 7d functions as an etch stopper, even the second layer 7b can be prevented from being etched and the thickness of the capacitive insulating film 7 being changed.

  In addition, according to the inventor's research, it has been found that with the capacitor insulating film 7 having a five-layer structure, the withstand voltage performance is improved as compared with the case of a three-layer structure as shown in FIG. .

  In FIG. 8, according to the withstand voltage test conducted by the inventor of the present invention, the five-layer structure (that is, the structure according to this embodiment shown in FIG. 6) increases the voltage applied to each pixel from 13V to 20V. In this case, the pixel that has been destroyed is “0”. That is, no problem occurred.

  On the other hand, in the case of the three-layer structure (that is, the structure according to the comparative example shown in FIG. 7), one pixel is destroyed when the voltage applied to each pixel becomes 17V, and two pixels further at 19V. Was destroyed, and 3866 pixels were destroyed at 20V. That is, an extremely large number of pixels have been destroyed as compared with the five-layer structure.

  From the above results, it can be seen that the capacitive insulating film 7 having a five-layer structure according to the present embodiment has extremely high breakdown voltage performance. Therefore, it is possible to improve the reliability of the apparatus.

  Further, according to the research of the present inventor, the thickness of the layer containing hafnium oxide (that is, the first layer 7a) in the capacitor insulating film 7 is set to the layer containing alumina (that is, the second layer 7b and the third layer 7c). It has been found that the withstand pressure performance is further improved by making the thickness less than the thickness of.

  In FIG. 9, according to the pressure resistance test conducted by the present inventor, in the apparatus having the capacitive insulating film 7 in which the ratio of the thickness of the layer containing hafnium oxide to the thickness of the layer containing alumina is 1: 2, When the voltage applied to the pixel was increased from 13 V to 20 V, the pixel that was destroyed was “0”. That is, no problem occurred.

  On the other hand, in the device having the capacitive insulating film 7 in which the ratio of the thickness of the layer containing hafnium oxide to the thickness of the layer containing alumina is 2: 1, the voltage applied to each pixel becomes 1V. The pixels were destroyed, 91 pixels were destroyed at 18V, 4455 pixels were destroyed at 19V, and 7330 pixels were destroyed at 20V. That is, an extremely large number of pixels were destroyed as compared with the case where the layer containing hafnium oxide was thinner.

  From the above results, it can be seen that the pressure resistance performance is further improved by making the thickness of the layer containing hafnium oxide thinner than the thickness of the layer containing alumina.

  As described above, according to the electro-optical device according to the present embodiment, a change in film thickness of the capacitive insulating film 7 can be prevented, so that the capacitance value can be set with high accuracy. In addition, since the pressure resistance performance can be improved, the reliability of the device can be improved.

Second Embodiment
Next, an electro-optical device according to a second embodiment will be described with reference to FIG. FIG. 10 is an enlarged cross-sectional view showing the configuration of the capacitive insulating film of the electro-optical device according to the second embodiment. The second embodiment differs from the first embodiment described above in a part of the configuration of the capacitive insulating film 7, and the other configurations are substantially the same. Therefore, in the second embodiment, portions different from the first embodiment will be described in detail, and descriptions of other overlapping portions will be omitted as appropriate.

  10, in the storage capacitor 70 of the electro-optical device according to the second embodiment, the capacitor insulating film 7 includes a first layer 7a containing hafnium oxide, a second layer 7b containing alumina, and a third layer 7c containing alumina. And a fourth layer 7d containing hafnium oxide. That is, a four-layer structure in which the fifth layer 7e formed in the first embodiment does not exist is employed.

  According to the capacitive insulating film 7 having the four-layer structure described above, the second layer 7b reacts with the second capacitive electrode 5 due to the presence of the fourth layer 7d, as in the first embodiment, so that the different layer film 200 is formed. (See FIG. 7) or the second layer 7 b can be prevented from being scraped together during the patterning of the second capacitor electrode 5. Therefore, it is possible to prevent the thickness of the capacitive insulating film 7 from changing on the upper layer side.

  Further, since the fifth layer 7e does not exist on the lower layer side, the third layer 7c and the first capacitor electrode 2 are in contact with each other. However, for example, if the first capacitor electrode 2 is not made of a material that easily reacts with alumina such as titanium nitride but is made of a material that does not easily react, no problem occurs. Therefore, depending on the material constituting the first capacitor electrode 2, even if the capacitor insulating film 7 has a four-layer structure as shown in FIG. 10, it is possible to obtain the same effect as in the first embodiment.

<Third Embodiment>
Next, an electro-optical device according to a third embodiment will be described with reference to FIG. FIG. 11 is an enlarged cross-sectional view showing the configuration of the capacitive insulating film of the electro-optical device according to the third embodiment. Note that the third embodiment differs from the first and second embodiments described above in a part of the configuration of the capacitive insulating film 7, and the other configurations are substantially the same. Therefore, in the third embodiment, portions different from those in the first and second embodiments will be described in detail, and description of other overlapping portions will be omitted as appropriate.

  11, in the storage capacitor 70 of the electro-optical device according to the third embodiment, the capacitor insulating film 7 includes a first layer 7a containing hafnium oxide, a second layer 7b containing alumina, and a third layer 7c containing alumina. And a fifth layer 7e containing hafnium oxide. That is, a four-layer structure in which the fourth layer 7d formed in the first embodiment does not exist is provided.

  According to the capacitor insulating film 7 having the four-layer structure described above, the third layer 7c reacts with the first capacitor electrode 2 due to the presence of the fifth layer 7e, as in the first embodiment, and thus the different layer film 200. (See FIG. 7) can be prevented from being formed. Therefore, it is possible to prevent the thickness of the capacitive insulating film 7 from changing on the lower layer side.

  On the upper layer side, since the fourth layer 7d does not exist, the second layer 7b and the second capacitor electrode 5 are in contact with each other. However, for example, if the second capacitor electrode 5 is not a material that can be etched in the same manner as alumina such as aluminum, or a material that easily reacts with alumina such as titanium nitride, no problem occurs. Absent. Therefore, depending on the material constituting the second capacitor electrode 5, even if the capacitor insulating film 7 has a four-layer structure as shown in FIG. 11, it is possible to obtain the same effect as in the first embodiment.

<Electronic equipment>
Next, the case where the liquid crystal device which is the above-described electro-optical device is applied to various electronic devices will be described. FIG. 12 is a plan view showing a configuration example of the projector. Hereinafter, a projector using the liquid crystal device as a light valve will be described.

  As shown in FIG. 12, a lamp unit 1102 including a white light source such as a halogen lamp is provided inside the projector 1100. The projection light emitted from the lamp unit 1102 is separated into three primary colors of RGB by four mirrors 1106 and two dichroic mirrors 1108 arranged in the light guide 1104, and serves as a light valve corresponding to each primary color. The light enters the liquid crystal panels 1110R, 1110B, and 1110G.

  The configurations of the liquid crystal panels 1110R, 1110B, and 1110G are the same as those of the liquid crystal device described above, and are driven by R, G, and B primary color signals supplied from the image signal processing circuit. The light modulated by these liquid crystal panels enters the dichroic prism 1112 from three directions. In the dichroic prism 1112, R and B light is refracted at 90 degrees, while G light travels straight. Therefore, as a result of the synthesis of the images of the respective colors, a color image is projected onto the screen or the like via the projection lens 1114.

  Here, paying attention to the display images by the liquid crystal panels 1110R, 1110B, and 1110G, the display image by the liquid crystal panel 1110G needs to be horizontally reversed with respect to the display images by the liquid crystal panels 1110R and 1110B.

  Since light corresponding to the primary colors R, G, and B is incident on the liquid crystal panels 1110R, 1110B, and 1110G by the dichroic mirror 1108, it is not necessary to provide a color filter.

  In addition to the electronic device described with reference to FIG. 12, a mobile personal computer, a mobile phone, a liquid crystal television, a viewfinder type, a monitor direct-view type video tape recorder, a car navigation device, a pager, an electronic device Examples include notebooks, calculators, word processors, workstations, videophones, POS terminals, and devices with touch panels. Needless to say, the present invention can be applied to these various electronic devices.

  In addition to the liquid crystal devices described in the above embodiments, the present invention includes a reflective liquid crystal device (LCOS), a plasma display (PDP), a field emission display (FED, SED), an organic EL display, and a digital micromirror device. (DMD), electrophoresis apparatus and the like are also applicable.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and an electro-optical device with such a change. In addition, an electronic apparatus including the electro-optical device is also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 2 ... 1st capacity electrode, 5 ... 2nd capacity electrode, 6 ... Data line, 7 ... Capacity insulating film, 7a ... 1st layer, 7b ... 2nd layer, 7c ... 3rd layer, 7d ... 4th layer, 7e 5th layer, 9 ... Pixel electrode, 10 ... TFT array substrate, 10a ... Image display area, 11 ... Scanning line, 20 ... Counter substrate, 30 ... TFT, 50 ... Liquid crystal layer, 200 ... Different layer film

Claims (8)

A transistor provided for each pixel;
A pixel electrode provided corresponding to the transistor;
Electrically connected to the pixel electrode, formed between a first capacitor electrode, a second capacitor electrode opposed to the first capacitor electrode from the upper layer side, and between the first capacitor electrode and the second capacitor electrode A storage capacitor made of a capacitive insulating film,
The capacitive insulating film is
A first layer comprising hafnium oxide;
A second layer formed on the first layer and containing alumina;
A third layer formed under the first layer, comprising alumina;
An electro-optical device comprising: a fourth layer formed on an upper layer of the second layer and containing hafnium oxide.   2. The electro-optical device according to claim 1, wherein the capacitive insulating film is formed in a lower layer of the third layer and includes a fifth layer containing hafnium oxide.   The electro-optical device according to claim 1, wherein the second capacitor electrode includes titanium nitride.   4. The electro-optical device according to claim 1, wherein the second capacitor electrode contains aluminum. 5. A transistor provided for each pixel;
A pixel electrode provided corresponding to the transistor;
Electrically connected to the pixel electrode, formed between a first capacitor electrode, a second capacitor electrode opposed to the first capacitor electrode from the upper layer side, and between the first capacitor electrode and the second capacitor electrode And a storage capacitor made of a capacitive insulating film,
The capacitive insulating film is
A first layer comprising hafnium oxide;
A second layer formed on the first layer and containing alumina;
A third layer formed under the first layer, comprising alumina;
An electro-optical device comprising: a fourth layer formed under the third layer and containing hafnium oxide.   56. The electro-optical device according to claim 55, wherein the first capacitor electrode includes titanium nitride.   The electro-optical device according to claim 1, wherein the first layer is formed thinner than the second layer and the third layer.   An electronic apparatus comprising the electro-optical device according to claim 1.

Images