Source: http://www.docstoc.com/docs/55656339/Semiconductor-Device---Patent-7202497
Timestamp: 2013-12-20 17:17:41
Document Index: 630530084

Matched Legal Cases: ['Application No. 0010', 'art 106', 'art 206', 'Application No. 8', 'Application No. 7', 'Application No. 8', 'Application No. 7', 'art 2002', 'art 2003', 'art 2103', 'art 2106', 'art 2202', 'art 2203', 'art 2303']

Semiconductor Device - Patent 7202497
United States Patent: 7202497
7,202,497
A semiconductor device and a process for producing the same, the
semiconductor device comprising two conductive layers provided as
separate layers, and an insulating layer sandwiched by the two conductive
layers, in which the two conductive layers are electrically connected to
each other with an embedded conductive layer or an oxide conductive layer
provided as filling an opening formed in the insulating layer, and the
embedded conductive layer comprises an organic resin film containing a
conductive material dispersed therein or an inorganic film containing a
conductive material dispersed therein.
Ohtani; Hisashi (Kanagawa, JP), Nakazawa; Misako (Kanagawa, JP), Murakami; Satoshi (Kanagawa, JP)
09/197,767
9-344350
10-018050
257/59  ; 257/72; 257/E27.111
H01L 29/04&amp;nbsp(20060101); H01L 31/036&amp;nbsp(20060101); H01L 31/0376&amp;nbsp(20060101); H01L 31/20&amp;nbsp(20060101)
257/347,59,72 349/5,43
4796979
4911958
Mochizaki et al.
5084130
5148259
5176789
5270846
Xobayashi et al.
5412494
5473449
5473450
5541747
5638194
5652667
5658806
5706067
5757054
5757444
5905555
5946059
6008876
6043149
6049132
Katsuya et al.
6097453
6242343
0 404 575
0 733 931
0 738 012
57-020778
62-7022
63-198024
64-55527
01-120532
2-137819
2-503360
4-136814
04-220625
4-243228
4-362918
5-045636
5-297364
05-335424
6-40931
6-160812
6-160824
6-186533
6-214218
6-242409
6-289372
6-301015
6-301039
6-331948
6-337405
6-337418
6-347807
7-13143
07-098452
07-130848
07-135318
08-015686
08-101385
09-080464
9-211462
09-230806
WO 88/08552
AD.L. Chandani, et al., &quot;Antiferroelectric Chiral Smectic Phases Responsible for the Tristable Switching in MHPOBC,&quot; Tokyo Inst. Of Tech.,
Jun. 12, 1989, pp. 34-37. cited by other
Michio Shimizu, et al., &quot;Characteristic of a Novel Liquid Crystal Cell With Mixtue of FLC and U.V. Curable Resin,&quot; Mol. Cryst. Liq. Cryst. , Overseas Publishers Association, vol. 263, 1995, pp. 585-587. cited by other
Inventors: Higuchi et al., Specification and Drawings of U.S. Appl. No. 09/198,751, (with Filing Receipt), filed Nov. 24, 1998, &quot;Electrooptical Device, Method of Manufacturing the Same, and Electronic Equipment&quot;. cited by other
Notice of Rejection dated Oct. 17, 2006 for JP Application No. 0010-018050. cited by other.
1.  A semiconductor device comprising: at least one transistor;  at least one interlayer insulating film formed over said transistor, said interlayer insulating film having at
least one contact hole;  an embedded conductive layer provided to fill said contact hole wherein a top surface of said embedded conductive layer is flush with a top surface of said interlayer insulating film;  and a reflective pixel electrode having a
flat upper surface thereon, formed on said interlayer insulating film wherein said reflective, pixel electrode is electrically connected to said transistor through said embedded conductive layer, wherein the embedded conductive layer comprises a
conductive material dispersed in a medium, the conductive material being selected from the group consisting of carbon, zinc oxide, aluminum, and nickel.
2.  A device according to claim 1, wherein said medium is an organic material.
3.  A device according to claim 1, wherein said medium is an inorganic material.
4.  A device according to claim 1, wherein said interlayer insulating film comprises an organic material.
5.  A device according to claim 1, wherein said interlayer insulating film comprises an inorganic material.
6.  A semiconductor device comprising: at least one transistor;  at least one interlayer insulating film comprising an organic resin formed over said transistor, said interlayer insulating film having at least one contact hole;  an embedded
conductive layer provided to fill said contact hole wherein a top surface of said embedded conductive layer is flush with a top surface of said interlayer insulating film;  and a reflective pixel electrode having a flat upper surface thereon, formed on
said interlayer insulating film wherein said reflective pixel electrode is electrically connected to said transistor through said embedded conductive layer, wherein the embedded conductive layer comprises a conductive material dispersed in a medium, the
conductive material being selected from the group consisting of carbon, zinc oxide, aluminum, and nickel.
7.  A device according to claim 6, wherein said medium is an organic material.
8.  A device according to claim 6, wherein said medium is an inorganic material.
9.  A semiconductor device comprising: at least one transistor;  a first interlayer insulating film formed over said transistor;  a drain electrode formed on said first interlayer insulating film and electrically connected to a drain of said
transistor through an opening of said first interlayer insulating film;  a second interlayer insulating film formed over said drain electrode and said first interlayer insulating film;  a capacitor forming electrode formed on said second interlayer
insulating film to form a capacitor between said drain electrode and said capacitor forming electrode;  a third interlayer insulating film formed over said capacitor forming electrode and said second interlayer insulating film;  a contact hole opened
through said third and second interlayer insulating films to reach said drain electrode;  an embedded conductive layer filled in said contact hole;  and a reflective pixel electrode formed on said third interlayer insulating film, wherein said reflective
pixel electrode is electrically connected to said drain electrode through said embedded conductive layer, wherein a cross sectional shape of the contact hole is tapered, and wherein the embedded conductive layer comprises a conductive material dispersed
in a medium, the conductive material being selected from the group consisting of carbon, zinc oxide, aluminum, and nickel.
10.  A device according to claim 9, wherein said medium is an organic material.
11.  A device according to claim 9, wherein said medium is an inorganic material.
12.  A device according to claim 9, wherein said interlayer insulating film comprises an organic material.
13.  A device according to claim 9, wherein said interlayer insulating film comprises an inorganic material.
14.  A semiconductor device comprising: at least one transistor;  a first interlayer insulating film formed over said transistor;  a drain electrode formed on said first interlayer insulating film and electrically connected to a drain of said
insulating film to form a capacitor between said drain electrode and said capacitor forming electrode;  a third interlayer insulating film comprising an organic resin formed over said capacitor forming electrode and said second interlayer insulating
film;  a contact hole opened through said third and second interlayer insulating films to reach said drain electrode;  an embedded conductive layer filled in said contact hole;  and a reflective pixel electrode formed on said third interlayer insulating
film, wherein said reflective pixel electrode is electrically connected to said drain electrode through said embedded conductive layer, wherein a cross sectional shape of the contact hole is tapered, and wherein the embedded conductive layer comprises a
15.  A device according to claim 14, wherein said medium is an organic material.
16.  A device according to claim 14, wherein said medium is an inorganic material.
17.  A semiconductor device comprising: at least one transistor;  a first interlayer insulating film comprising an organic resin formed over said transistor, said interlayer insulating film having at least one contact hole;  an embedded
said interlayer insulating film wherein said reflective pixel electrode is electrically connected to said transistor through said embedded conductive layer, wherein said embedded conductive layer comprises a same resin as said resin of the interlayer
18.  The semiconductor device according to claim 17 wherein said third interlayer insulating film and said embedded conductive layer both comprise an acrylic resin.
19.  A semiconductor device comprising: at least one transistor;  at least one interlayer insulating film formed over said transistor, said interlayer insulating film having at least one contact hole;  an embedded conductive layer provided to
fill said contact hole wherein a top surface of said embedded conductive layer is flush with a top surface of said interlayer insulating film;  and a reflective pixel electrode having a flat upper surface thereon, formed on said interlayer insulating
film wherein said reflective pixel electrode is electrically connected to said transistor through said embedded conductive layer, wherein said embedded conductive layer comprises an indium tin oxide.
20.  A device according to claim 19, wherein said interlayer insulating film comprises an organic material.
21.  A device according to claim 19, wherein said interlayer insulating film comprises an inorganic material.
22.  A device according to claim 19, wherein said interlayer insulating film comprises an inorganic material.
23.  A device according to claim 19, wherein said interlayer insulating film comprises an organic material.
24.  A semiconductor device comprising: at least one transistor;  at least one interlayer insulating film comprising an organic resin formed over said transistor, said interlayer insulating film having at least one contact hole;  an embedded
said interlayer insulating film wherein said reflective pixel electrode is electrically connected to said transistor through said embedded conductive layer, wherein said embedded conductive layer comprises an indium tin oxide.
25.  A device according to claim 24, wherein said interlayer insulating film comprises an organic material.
26.  A device according to claim 24, wherein said interlayer insulating film comprises an inorganic material.
27.  A semiconductor device comprising: at least one transistor;  a first interlayer insulating film formed over said transistor;  a drain electrode formed on said first interlayer insulating film and electrically connected to a drain of said
pixel electrode is electrically connected to said drain electrode through said embedded conductive layer, wherein a cross sectional shape of the contact hole is tapered, and wherein said embedded conductive layer comprises an indium tin oxide.
28.  A device according to claim 27, wherein at least one of said second and third interlayer insulating films comprises an organic material.
29.  A device according to claim 27, wherein said first interlayer insulating film comprises an inorganic material.
30.  A device according to claim 27, wherein said interlayer insulating film comprises an inorganic material.
31.  A device according to claim 27, wherein said interlayer insulating film comprises an organic material.
32.  A semiconductor device comprising: at least one transistor;  a first interlayer insulating film formed over said transistor;  a drain electrode formed on said first interlayer insulating film and electrically connected to a drain of said
film, wherein said reflective pixel electrode is electrically connected to said drain electrode through said embedded conductive layer, wherein a cross sectional shape of the contact hole is tapered, and wherein said embedded conductive layer comprises
an indium tin oxide.
33.  A device according to claim 32, wherein at least one of said second and third interlayer insulating films comprises an organic material.
34.  A device according to claim 32 wherein said first interlayer insulating film comprises an inorganic material.
35.  A semiconductor device according to any one of claims 1, 19, 24, 27, and 32, further comprising an alignment film.
36.  A semiconductor device according to claim 1, 6, 9, 14, 17, 19, 24, 27, or 32, wherein said device is a display device of a cellular phone.
37.  A semiconductor device according to claim 1, 6, 9, 14, 17, 19, 24, 27, or 32, wherein said device is a display device of a camcorder.
38.  A semiconductor device according to claim 1, 6, 9, 14, 17, 19, 24, 27, or 32, wherein said device is a display device of a portable computer.
39.  A semiconductor device according to claim 1, 6, 9, 14, 17, 19, 24, 27, or 32, wherein said device is a display device of a head mounting display.
40.  A semiconductor device according to claim 1, 6, 9, 14, 17, 19, 24, 27, or 32, wherein said device is a display device of a rear type projector.
41.  A semiconductor device according to claim 1, 6, 9, 14, 17, 19, 24, 27, and 32, wherein said device is a display device of a front type projector.
42.  A semiconductor device according to any one of claim 1, 19, 24, 27, and 32, wherein said device is an EL display device.  Description
The present invention relates to, in a semiconductor device using a thin film, a connection wiring ensuring electric connection between conductive thin films.  Particularly, it relates to, in a pixel region of an active matrix liquid crystal
display (AMLCD), a connection wiring ensuring electric connection between a switching element and a pixel electrode.
The semiconductor device used herein involves all devices functioning by utilizing semiconductor properties, and an electro-optical device such as an AMLCD and a semiconductor circuit such as a microprocessor are included.  Furthermore, an
electronic apparatus containing such an electro-optical device and a semiconductor circuit is also included in the semiconductor device.
Recently, the technique of providing a TFT on an inexpensive glass substrate is being rapidly developed.  This is because the demand of an AMLCD is increased.
In an AMLCD, each of several tens to several millions of pixels arranged in a matrix form is equipped with a thin film transistor (TFT) as a switching element, and input/output of an electric charge on each of pixel electrodes is controlled by
the switching function of the TFT.
A liquid crystal is sandwiched between the pixel electrode and a counter electrode to form a kind of capacitor.  Therefore, the electro-optical characteristics of the liquid crystal can be changed by controlling input/output of an electric charge
on the capacitor, and thus an image can be displayed by controlling light passing through the liquid crystal panel.
As a characteristic phenomenon in such a display device using a liquid crystal, there is a phenomenon called disclination.  While the liquid crystal sandwiched between the pixel electrode and the counter electrode is arranged with orientation
having regularity, the orientation may be disturbed by rubbing failure due to unevenness on the surface of the electrodes.  The function of light shutter is lost in the location at which disclination occurs, and display failure such as leakage of light
In order to prevent disclination, measures have been conducted such as covering the TFT with a flattened film, but such cannot become drastic countermeasures because flattening of the contact part of the pixel electrode finally produced is
impossible even if a flattened film is utilized.
Particularly, the invention intends to prevent generation of disclination due to a step of a contact part by completely flattening a pixel electrode of an AMLCD, whereby an effective pixel area is enlarged by reducing an area of a black mask, so
as to realize an AMLCD of high precision and high contrast.
Examples of the inorganic film include a silicon dioxide film of a solution coating type called SOG (spin on glass).  Specifically, OCD (Ohka Coating Diffusion source) produced by Tokyo Ohka Kogyo Co., Ltd.  and general silicate glass (PSG, BSG
and BPSG) can be exemplified.
As the material providing conductivity, a carbon material (such as graphite), zinc oxide, aluminum flakes and nickel flakes can be used.  Particularly, graphite is preferred since it is good in general-purpose properties and handling properties.
Those having a shape or a particle diameter that cannot fall into the opening provided in the insulating layer cannot be used.
Therefore, the material providing conductivity is preferably in the form of fine particles having a particle diameter of 1/2 or less (more preferably 1/10 or less, particularly preferably 1/100 or less) of the opening width of the opening
provided in the insulating layer.  For example, in the case where the opening has a diameter of 1 .mu.m (contact hole) to connect the wiring (conductive layers), the material dispersed in the embedded conductive layer preferably has a diameter of 0.5
.mu.m or less (more preferably 0.1 .mu.m or less, particularly preferably 0.01 .mu.m or less).
The inventors have selected a solution coating type conductive layer as a material that is preferred for filling in the fine contact hole, and have given attention to an ITO (indium tin oxide) film of a solution coating type as a representative
material thereof.
Examples of the ITO film include a thin film produced by using ADEKA ITO coating solution produced by Asahi Denka Kogyo K. K. While an indium tin organic compound is dissolved in a xylene solvent to form this ITO coating solution, other oxide
conductive layers can be formed by changing the solvent and the solute.
Since the oxide conductive layer is formed as concentrated at the uneven part, it is suitable for effectively filling and flattening the unevenness.  The number of coating is not limited to once, and it is effective to coat twice or more to
enhance the flatness.
One embodiment of the invention is described with reference to FIGS. 1A to 1C.  In FIG. 1A, numeral 100 denotes an underlayer, which may be any of an insulating layer, a semiconductor layer or a conductive layer, and a first conductive layer 101
having a pattern is formed thereon.
The first conductive layer 101 is covered with an insulating layer (interlayer insulating layer) 102.  As the insulating layer 102, an insulating film containing silicon such as silicon oxide, silicon nitride and silicon oxide nitride, or an
organic resin layer is used as a single layer or as having a multilayer structure.  The case where an organic resin layer is provided as a single layer is described herein, for example.
After forming the insulating layer 102, an opening (contact hole) 103 is formed by etching.  The method for etching may be a wet etching method or a dry etching method.  It is effective that the cross sectional shape of the opening 103 is tapered
to improve the coverage of a thin film subsequently formed.
After forming the opening 103, an embedded conductive layer 104 is formed.  As the embedded conductive layer 104, an organic resin film containing a carbon material dispersed therein or an inorganic resin film containing a carbon material
dispersed therein is used.  A solution containing the carbon material dispersed therein is coated on the insulating layer 102, and an excess of the solution is removed by spin drying, to form the thin film.  This technique is called a spin coating
After forming the embedded conductive layer 104 by the spin coating method, an excess of the solvent is removed by a baking (curing) step to improve the film quality depending on necessity.  The conditions for the curing step are not limited, and
baking (heat treatment) at 300.degree.  C. for 30 minutes is generally required.
The advantages of the thin film formed by coating a solution are that the film formation is extremely easy, and the film thickness can be easily increased.  Furthermore, since the film is in the form of solution in the stage of film forming, it
exhibits excellent covering properties of minute unevenness and is extremely suitable for filling a minute opening such as the contact hole.  The invention has been attained with making attention to such excellent covering properties of a material of
solution coating type.
Another advantage of the material of solution coating type is easiness of coloring.  For example, a black colored organic resin film by dispersing a carbon series material is utilized as a black mask.
The inventor have made attention to the fact that among the organic resin films containing carbon material dispersed therein, an organic resin film using graphite as the carbon material becomes a film having a low resistance, and have found that
it is used as the conductive layer for filling a contact hole, with combining the excellent covering properties of the material of solution coating type.
The state of FIG. 1A can be obtained after forming the embedded conductive layer 104.  After that, the embedded conductive layer 104 is subjected to an etch back process by a dry etching method, to obtain a state in which the embedded conductive
layer 104 fills only the opening 103, as shown in FIG. 1B.
In the etch back process, the etching selectivity of the insulating layer 102 and the embedded conductive layer should be noted.  Since an organic resin film is used as the insulating film 102 in FIG. 1A, it is etched to the extent similar to the
embedded conductive layer 104 in the etch back process, and no step is formed therebetween.
However, in the case where the insulating layer 102 is a silicon oxide film, the etch back process must be terminated at the time when the silicon oxide film is exposed, otherwise only the embedded conductive layer 104 is etched in the opening to
form a step at the opening.
In view of the above, it is preferred that the insulating layer 102 and the embedded conductive layer 104 are in the conditions in that they have the same etching selectivity as possible.  In order to accomplish such conditions, the etching
conditions may be optimized or the same material is used in both the insulating layer 102 and the embedded conductive layer 104.
It is an important factor in the invention that the film thickness can be easily increased.  In FIG. 1A, the thickness of the embedded conductive layer 104 must be the same as or thicker than the thickness of the insulating layer 102.  Therefore,
a CVD method and a sputtering method are not practical since the throughput is rather deteriorated by using these methods.
After thus obtaining the state shown in FIG. 1B, a second conductive layer 105 is formed to have a pattern.  As a result, the two conductive layers (the first conductive layer 101 and the second conductive layer 105) insulatedly separated by the
insulating layer 102 are electrically connected through the embedded conductive layer 104, as shown in FIG. 1C.  The second conductive layer 105 can maintain complete flatness even at a contact part 106.
In this example, ITO is used as the embedded plug (conductive layer).  In FIG. 2A, numeral 200 denotes an underlayer, which may be any of an insulating layer, a semiconductor layer or a conductive layer, and a first conductive layer 201 having a
pattern is formed thereon.
The first conductive layer 201 is covered with an insulating layer (interlayer insulating layer) 202.  As the insulating layer 202, an insulating film containing silicon such as silicon oxide, silicon nitride and silicon oxide-nitride, or an
organic resin layer is used as a single layer or as having a multilayer structure.
After forming the insulating layer 202, an opening (contact hole) 203 is formed by etching.  The method for etching may be a wet etching method or a dry etching method.  It is effective that the cross sectional shape of the opening 203 is tapered
After forming the opening 203, an oxide conductive layer 204 is formed.  As the oxide conductive layer 204, an ITO film of solution coating type is used.  A solution containing an indium tin organic compound dissolved in an organic solvent such
as xylene is coated on the insulating layer 202, and an excess of the solution is removed by spin drying, to form the thin film.  This technique is called a spin coating method.
After forming the oxide conductive layer 204, a drying step at a temperature of from 150 to 170.degree.  C. and a baking step at 300.degree.  C. or higher are conducted, and further an annealing step is conducted depending on necessity, to
improve the film quality.  The conditions of the curing step are not limited to the above, and the optimum conditions may be determined through experiments.
The advantages of the thin film formed by coating a solution are that the film formation is extremely easy, and the covering properties are excellent.  That is, since the film is in the form of solution in the stage of film forming, it exhibits
excellent covering properties of minute unevenness and is extremely suitable for filling a minute opening such as the contact hole.  The invention has been attained with making attention to such excellent covering properties of a material of solution
coating type.
In some cases, the ITO film of solution coating type can be colored black by adding a carbon series material or a pigment to the solution for coating the ITO film, and as a result, the light shielding property in the contact hole can be
The state of FIG. 2A can be obtained after forming the oxide conductive layer 204.  After that, the oxide conductive layer 204 is subjected to an etch back process by a dry etching method, to obtain a state in which the oxide conductive layer 204
fills only the opening 203, as shown in FIG. 2B.
In the case where the wet etching method is employed, a commercially available etchant for ITO can be used.  In the case where the dry etching method is employed, HBr (hydrogen bromide), HI (hydrogen iodide) and CH.sub.4 (methane) can be used as
an etching gas.  Among these, HBr is preferred from the standpoint of workability and general-purpose properties.
After thus obtaining the state shown in FIG. 2B, a second conductive layer 205 is formed to have a pattern.  As a result, the two conductive layers (the first conductive layer 201 and the second conductive layer 205) insulatedly separated by the
insulating layer 202 are electrically connected through the oxide conductive layer 204, as shown in FIG. 2C.  The second conductive layer 205 can maintain complete flatness even at a contact part 206.
In this example, a production process of a unit pixel (unit picture element) constituting a pixel matrix circuit of an active matrix liquid crystal display device (AMLCD) driven in a reflection mode is described with reference to FIGS. 3A through
A quartz substrate 301 having an insulating surface is prepared.  In this example, because a heat treatment at a temperature of from 900 to 1,1000.degree.  C. is conducted, a material having high heat resistance must be used.  A crystalline glass
(glass ceramics) substrate provided with an underlayer film and a silicon substrate provided with a thermal oxidized film may be used.
An amorphous silicon film 302 having a thickness of 65 nm is formed thereon, and the amorphous silicon film 302 is crystallized by using the technique described in Unexamined Published Japanese Patent Application No. 8-78329.  The technique
described in this publication is to conduct selective crystallization by using a catalytic element accelerating crystallization.
A mask insulating film 303 is formed to selectively add a catalytic element (nickel in this example) to the amorphous silicon film 302.  An opening 304 is formed in the mask insulating film 303.
After thus obtaining the state of FIG. 3A, removal of hydrogen is conducted at 450.degree.  C. for 1 hour, and a heat treatment is conducted at 570.degree.  C. for 14 hours, to obtain a lateral growing region 306.  After thus finishing the
crystallization step, an addition step of phosphorus is conducted by using the mask insulating film 303 itself as a mask, through which a phosphorus-added region 307 is formed.
After thus obtaining the state of FIG. 3B, a heat treatment at 600.degree.  C. for 12 hours is conducted, so that nickel remaining in the lateral growing region 306 is subjected to gettering into the phosphorous-added region 307.  As a result, a
region in which the nickel concentration is lowered to 5.times.10.sup.17 atoms/cm.sup.3 (called a gettered region) 308 is obtained as shown in FIG. 3C.
Active layers 309 and 310 composed only of the gettered region 308 are formed by patterning, and then a gate insulating film 311 having a thickness of 120 nm is formed.  The gate insulating film 311 is composed of a silicon oxide film, a silicon
nitride film, a silicon oxide-nitride film, or a laminated film thereof.
After forming the gate insulating film 311, a heat treatment at 950.degree.  C. for 30 minutes in an oxygen atmosphere is conducted to form a thermal oxidized film at the interface between the active layer and the gate insulating film, by which
the interface properties can be largely improved.  The active layer 309 and 310 are oxidized to be thinned through the thermal oxidation step.  In this example, the thickness of the active layers is finally adjusted to 50 nm.  That is, the thickness of
the initial film (amorphous silicon film) is 65 nm, and oxidation is conducted for 15 nm, to result in a thermal oxidized film having a thickness of 30 nm.  The gate insulating film 311 has a total thickness of 150 nm.  The state until this step is shown
in FIG. 3D.  An aluminum film containing 0.2% by weight of scandium (not shown in figure) is formed, and an island pattern as a base of a gate electrode is formed by patterning.  After forming the island pattern, the technique described in Unexamined
Published Japanese Patent Application No. 7-135318 is applied, the details of which can be referred to the publication.
While a resist mask used for patterning remains on the island pattern, anodic oxidation is conducted in a 3% aqueous oxalic acid solution.  A formation current of from 2 to 3 mV is applied using a platinum electrode as a cathode to a carry-over
voltage of 8V.  As a result, porous anodic oxidized films 312 and 313 are formed.
After removing the resist mask, anodic oxidation is conducted in a 3% ethylene glycol solution of tartaric acid neutralized with aqueous ammonia, at which the formation current is from 5 to 6 mV, and the carry-over voltage is 100V.  As a result,
dense non-porous anodic oxidized films 314 and 315 are formed.
Gate electrodes 316 and 317 are thus finished through the above-described procedures.  In the pixel matrix circuit, gate lines connecting the gate electrodes per one line are formed simultaneously with the formation of the gate electrodes.  The
state until this step is shown in FIG. 4A.
The gate insulating film 311 is etched by using the gate electrodes 316 and 317 and the porous anodic oxidized films 312 and 313 as a mask.  The etching is conducted by the dry etching method using CF.sub.3 gas.  As a result, the gate insulating
films 318 and 319 having the shape shown in FIG. 4B are formed.
The porous anodic oxidized films 312 and 313 are removed by the wet etching method.  The etching is conducted by using a mixed solution of phosphoric acid, acetic acid and nitric acid, the concentrations of which are 72.3% by weight .+-.0.1, 9.5%
by weight .+-.1.0 and 2.0% by weight .+-.0.4, respectively, with water as a solvent.
An impurity ion endowing one conductivity is added by an ion injecting method or a plasma doping method.  In the case where the pixel matrix circuit is constituted by an N-type TFT, P (phosphorus) ion is added, and in the case where it is
constituted by a P-type TFT, B (boron) ion is added.
The addition of the impurity ion is conducted as separated into two steps.  The first step is conducted at a high accelerating voltage of about 80 keV, with the peak of the impurity ion being focused at the lower part of the edge (protruding
part) of the gate insulating films 318 and 319.  The second step is conducted at a low accelerating voltage of about 5 keV in such a manner that the impurity ion is not added to the lower part of the edge (protruding part) of the gate insulating films
318 and 319.
The addition of the impurity ion is preferably conducted so that the sheet resistance of the source/drain region becomes from 300 to 500 .OMEGA.  per square.  The low concentration impurity regions must be optimized according to the performance
of the TFT.  After completing the addition step of the impurity ion, a heat treatment is conducted to activate the impurity ion.
A silicon oxide film having a thickness of 400 nm is formed as a first interlayer insulating film 328, and contact holes are formed to produce source electrodes 329 and 330 and drain electrodes 331 and 332.  In this example, the drain electrodes
331 and 332 are formed as spread within the pixel.
This is a measure of obtaining a capacitance as large as possible, as the drain electrode is used as a lower electrode of an auxiliary capacitance.  Because what is produced in this example is a reflection type liquid crystal display device, the
lower part of the region at which the pixel electrode is formed later can be freely used without considering the aperture ratio.
After thus obtaining the state shown in FIG. 4C, a silicon nitride film 333 having a thickness of 50 nm is formed as covering the source/drain electrodes, and a first metallic film (titanium in this example) 334 is formed thereon.  In this
example, an auxiliary capacitance is formed between the drain electrode 331 and the first metallic film 334 with using the silicon nitride film 333 as a dielectric material.
An acrylic resin film having a thickness of 1 .mu.m is formed as a second interlayer insulating film 335.  Other organic resin films, such as a polyimide resin film, may be used instead of the acrylic resin film.  A second metallic film 336 is
formed on the second interlayer insulating film 335.
While the second metallic film 336 has a function of a black mask, it mainly functions as an electric field shielding film, i.e., it has a function of protecting the pixel electrode formed later from influence of an electric field generated by
the source/drain wiring.
After thus obtaining the state shown in FIG. 4D, an acrylic resin film having a thickness of 1 .mu.m is formed as a third interlayer insulating film 337, and openings 338 and 339 are formed therein.  An embedded conductive layer 340 is formed as
covering the third interlayer insulating layer 337 and the openings 338 and 339, as shown in FIG. 5A.
In this example, an acrylic resin film containing graphite dispersed therein is used as the embedded conductive layer 340.  Since the graphite dispersed in the embedded conductive layer 340 is in the form of flakes, it is sufficiently filled in
the interior of the openings 338 and 339.
Pixel electrodes 343 and 344 composed of a material mainly comprising aluminum are formed on the third interlayer insulating film 337 that has been completely flattened by the embedded conductive layers 341 and 342.  Because the interior of the
contact holes (openings) is filled with the embedded conductive layers 341 and 342, electric connection to the drain electrodes can be realized without forming any step, as shown in FIG. 5C.
After that, an alignment film (not shown in figure) is formed on the pixel electrodes 343 and 344 to finish an active matrix substrate, which is one substrate of a liquid crystal display device.  The active matrix substrate and a counter
substrate prepared according to the conventional manner are fabricated into a cell to finish an active matrix liquid crystal display device.
In this example, a production process of a unit pixel constituting a pixel matrix circuit of an active matrix liquid crystal display device (AMLCD) driven in a reflection mode using ITO as an embedded plug (conductive layer) is described with
reference to FIGS. 6A through 8C.
A quartz substrate 601 having an insulating surface is prepared.  In this example, because a heat treatment at a temperature of from 900 to 1,100.degree.  C. is conducted, a material having high heat resistance must be used.  A crystalline glass
An amorphous silicon film 602 having a thickness of 65 nm is formed thereon, and the amorphous silicon film 602 is crystallized by using the technique described in Unexamined Published Japanese Patent Application No. 8-78329.  The technique
A mask insulating film 603 is formed to selectively add a catalytic element (nickel in this example) to the amorphous silicon film 602.  An opening 604 is formed in the mask insulating film 603.
After thus obtaining the state of FIG. 6A, removal of hydrogen is conducted at 450.degree.  C. for 1 hour, and a heat treatment is conducted at 570.degree.  C. for 14 hours, to obtain a lateral growing region 606.  After thus finishing the
crystallization step, an addition step of phosphorus is conducted by using the mask insulating film 603 itself as a mask, through which a phosphorus-added region 607 is formed.
After thus obtaining the state of FIG. 6B, a heat treatment at 600.degree.  C. for 12 hours is conducted, so that nickel remaining in the lateral growing region 606 is subjected to gettering into the phosphorus-added region 607.  As a result, a
region in which the nickel concentration is lowered to 5.times.10.sup.17 atoms/cm.sup.3 (called a gettered region) 608 is obtained as shown in FIG. 6C.
Active layers 609 and 610 composed only of the gettered region 608 are formed by patterning, and then a gate insulating film 611 having a thickness of 120 nm is formed, as shown in FIG. 6D.  The gate insulating film 611 is composed of a silicon
oxide film, a silicon nitride film, a silicon oxide nitride film, or a laminated film thereof.
After forming the gate insulating film 611, a heat treatment at 950.degree.  C. for 30 minutes in an oxygen atmosphere is conducted to form a thermal oxidized film at the interface between the active layer and the gate insulating film, by which
the interface properties can be largely improved.
The active layer 609 and 610 are oxidized to be thinned through the thermal oxidation step.  In this example, the thickness of the active layers is finally adjusted to 50 nm.  That is, the thickness of the initial film (amorphous silicon film) is
65 nm, and oxidation is conducted for 15 nm, to result in a thermal oxidized film having a thickness of 30 nm.  The gate insulating film 611 has a total thickness of 150 nm.  An aluminum film containing 0.2% by weight of scandium (not shown in figure) is
formed, and an island pattern as a base of a gate electrode is formed by patterning.  After forming the island pattern, the technique described in Unexamined Published Japanese Patent Application No. 7-135318 is applied, the details of which can be
referred to the publication.
voltage of 8V.  As a result, porous anodic oxidized films 612 and 613 are formed.
After removing the resist mask, anodic oxidation is conducted in a 3% ethylene glycol solution of tartaric acid neutralized with aqueous ammonia, at which the formation current is from 5 to 6 mV, and the carry-over voltage is 100 V. As a result,
dense non-porous anodic oxidized films 614 and 615 are formed.
Gate electrodes 616 and 617 are thus finished through the above-described procedures.  In the pixel matrix circuit, gate lines connecting the gate electrodes per one line are formed simultaneously with the formation of the gate electrodes.  The
state until this step is shown in FIG. 7A.
The gate insulating film 611 is etched by using the gate electrodes 616 and 617 and the porous anodic oxidized films 612 and 613 as a mask.  The etching is conducted by the dry etching method using CF.sub.3 gas.  As a result, the gate insulating
films 618 and 619 having the shape shown in FIG. 7B are formed.
The porous anodic oxidized films 612 and 613 are removed by the wet etching method.  The etching is conducted by using a mixed solution of phosphoric acid, acetic acid and nitric acid, the concentrations of which are 72.3% by weight .+-.0.1, 9.5%
An impurity ion endowing one conductivity is added by an ion injecting method or a plasma doping method.  In the case where the pixel matrix circuit is constituted by an N-type TFT, P (phosphorous) ion is added, and in the case where it is
part) of the gate insulating films 618 and 619.  The second step is conducted at a low accelerating voltage of about 5 keV in such a manner that the impurity ion is not added to the lower part of the edge (protruding part) of the gate insulating films
618 and 619.
A silicon oxide film having a thickness of 400 nm is formed as a first interlayer insulating film 628, and contact holes are formed to produce source electrodes 629 and 630 and drain electrodes 631 and 632.  In this example, the drain electrodes
631 and 632 are formed as spread within the pixel.
After thus obtaining the state shown in FIG. 7C, a silicon nitride film 633 having a thickness of 50 nm is formed as covering the source/drain electrodes, and a first metallic film (titanium in this example) 634 is formed thereon.  In this
example, an auxiliary capacitance is formed between the drain electrode 631 and the first metallic film 634 with using the silicon nitride film 633 as a dielectric material.
A polyimide resin film having a thickness of 1 .mu.m is formed as a second interlayer insulating film 635.  Other organic resin films, such as an acrylic resin film, may be used instead of the polyimide resin film.  A second metallic film 636 is
formed on the second interlayer insulating film 635.
While the second metallic film 636 has a function of a black mask, it mainly functions as an electric field shielding film, i.e., it has a function of protecting the pixel electrode formed later from influence of an electric field generated by
After thus obtaining the state shown in FIG. 7D, a polyimide resin film having a thickness of 1 .mu.m is formed as a third interlayer insulating film 637, and openings 638 and 639 are formed therein.  An oxide conductive layer 640 is formed as
covering the third interlayer insulating layer 637 and the openings 638 and 639, as shown in FIG. 8A.
In this example, a coating type ITO film having a viscosity of from 10 to 30 cps (produced by Asahi Denka Kogyo K. K.) is used as the oxide conductive layer 640.  After coating the solution by the spin coating method, it is subjected to a drying
step at a temperature of from 150 to 200.degree.  C. for from 5 to 10 minutes and a baking step at a temperature of from 300 to 400.degree.  C. for from 1 to 2 hours, to improve the film quality.  The treatments for improving the film quality is not
limited to those conducted in this example.
It is also effective to conduct annealing at a high temperature after the baking step.  On conducting annealing, the heat resistance of the material of the electrodes must be considered.  In order to avoid the whole of the device subjected to
annealing at a high temperature, lamp annealing or the like measure are preferably employed.
The resistance of the oxide conductive layer 640 becomes 1 k.OMEGA.  per square or less by conducting such a treatment for improving the film quality.  It is considered this order of the resistance is enough to ensure electric connection of a
submicron distance.
The thickness of the oxide conductive layer 640 can be controlled by the viscosity of the solution, and the rotation number and the rotation speed on spin coating.  The thickness must be changed depending on the diameter of the contact holes
(opening area), and it is enough to adjust the thickness within the range of from 100 to 500 nm (typically from 150 to 300 nm) to sufficiently fill up the interior of the contact holes.
An etch back process is conducted by the dry etching method using an etching gas selected from HBr, HI and CH.sub.4 diluted with Ar (argon).  In this example, HBr is employed.  As a result, the state in that the openings 638 and 639 are filled
with oxide conductive layers 641 and 642 is realized, as shown in FIG. 8B.
Pixel electrodes 643 and 644 composed of a material mainly comprising aluminum are formed on the third interlayer insulating film 637 that has been completely flattened by the oxide conductive layers 641 and 642.  Because the interior of the
contact holes (openings) is filled with the oxide conductive layers 641 and 642, electric connection to the drain electrodes can be realized without forming any step, as shown in FIG. 8C.
After that, an alignment film (not shown in figure) is formed on the pixel electrodes 643 and 644 to finish an active matrix substrate, which is one substrate of a liquid crystal display device.  The active matrix substrate and a counter
While the etch back treatment is applied to the embedded conductive electrode or the oxide conductive electrode in Examples 1 to 3, a polishing treatment can be employed instead of the etch back treatment.  A technique called CMP (chemical
mechanical polishing) can be typically employed.
In the case where this technique is employed, dusts generated during the treatment should be carefully managed.  By using this technique, excellent flatness can be ensured even when the third interlayer insulating film and the embedded conductive
layer are formed of different materials.
In Example 2, an acrylic resin layer is employed as the third interlayer insulating film 337, and the main component of the embedded conductive layer is an acrylic resin.  Other organic resins, such as a polyimide resin, may be used as the main
component of the embedded conductive layer.
In the case where a silicon oxide film is used as the third interlayer insulating film, it is effective to use a silicon oxide film of solution coating type called SOG as the main component of the embedded conductive layer.  In this case, a
carbon material, such as graphite, is dispersed in the solution, and the film formation can be conducted by the spin coating method.
The third interlayer insulating film and the embedded conductive layer may be formed of different materials.  In such a case, measures should be taken not to form a step at the opening after the etch back treatment.
Since an organic resin film, such as the polyimide film, only has low heat resistance, the baking temperature of the oxide conductive layer and the subsequent annealing temperature are limited.  However, by constituting the interlayer insulating
film with a silicon oxide film, etc., annealing at a higher temperature can be realized to obtain a film having further improved film quality.
Since a material mainly composed of aluminum is used as the gate electrode and the source/drain electrode in Example 3, the heat resistance of that material should be considered.  However, when a material having high heat resistance is used as
the material for the electrodes, an annealing treatment at a high temperature exceeding 500.degree.  C. can be conducted.
The state shown in FIG. 9A is obtained according to the procedures of Example 2.  In FIG. 9A, numeral 337 denotes the third interlayer insulating film, and 340 denotes the embedded conductive layer.
Pixel electrodes 901 and 902 composed of a material mainly comprising aluminum are formed on the embedded conductive layer 340.  The pixel electrodes 901 and 902 are physically insulated from each other by openings 903 and 904, as shown in FIG.
The embedded conductive layer 340 is etched by using the pixel electrodes 901 and 902 as a mask, to form embedded conductive layers 905 and 906 patterned into the same shape as the pixel electrodes.  The embedded conductive layers 905 and 906 are
also physically insulated from each other and thus function as a part of the pixel electrodes, as shown in FIG. 9C.
According to the constitution of this example, while the openings (corresponding to 903 and 904) separating the pixel electrodes 901 and 902 have a depth of 1 .mu.m or more, this does not bring about any problem since this part positions above
the source electrode (source wiring) and is shielded from light.  Furthermore, disclination is concentrated at this part, and thus an effect of preventing disclination spreading to the necessary region in the pixel (pinning effect) can also be expected.
The state shown in FIG. 10A is obtained according to the procedures of Example 3.  In FIG. 10A, numeral 637 denotes the third interlayer insulating film, and 640 denotes the oxide conductive layer.
Pixel electrodes 1001 and 1002 composed of a material mainly comprising aluminum are formed on the oxide conductive layer 640.  The pixel electrodes 1001 and 1002 are physically insulated from each other by openings 1003 and 1004, as shown in
The oxide conductive layer 640 is etched by using the pixel electrodes 1001 and 1002 as a mask, to form oxide conductive layers 1005 and 1006 patterned into the same shape as the pixel electrodes.  The oxide conductive layers 1005 and 1006 are
also physically insulated from each other and thus function as a part of the pixel electrodes, as shown in FIG. 10C.
According to the constitution of this example, while the openings (corresponding to 1003 and 1004) separating the pixel electrodes 1001 and 1002 have a depth of 1 .mu.m or more, this does not bring about any problem since this part positions
above the source electrode (source wiring) and is shielded from light.  Furthermore, disclination is concentrated at this part, and thus an effect of preventing disclination spreading to the necessary region in the pixel (pinning effect) can also be
While an AMLCD driven in a reflection mode is exemplified in Examples 1 to 9, the invention can be applied to an AMLCD driven in a transmission mode.  In this case, the constitutions shown in Examples 7 and 8 cannot be applied since the whole of
the pixel is shielded from light, but the constitutions shown in Examples 2 and 3 (constitutions in which the embedded conductive layer is filled only in the opening) can sufficiently applied.
In the case where a transmission type LCD is produced, when the pixel electrode (transparent conductive film) and the active layer is directly connected to each other, there arises a problem of leakage of light from the contact part.  Even in
such a case, the opening is filled with the embedded conductive layer to shield the opening from light, and thus the leakage of light can be prevented.
In this example, an AMLCD fabricated by using the active matrix substrate (substrate on which elements are formed) having the constitution shown in Examples 1 to 10 are exemplified.  The appearance of the AMLCD of this example is shown in FIGS.
In FIG. 11A, numeral 1101 denotes an active matrix substrate, on which a pixel matrix circuit 1102, a driver circuit on source side 1103 and a driver circuit on gate side 1104 are formed thereon.  The driver circuits preferably comprise a CMOS
circuit complementarily combining an N-type TFT and a P-type TFT.  Numeral 1105 denotes a counter substrate.
In the AMLCD shown in FIG. 11A, the active matrix substrate 1101 and the counter substrate 1105 are joined in such a manner that the edges thereof are arranged, provided that a part of the counter electrode 1105 is removed to expose the active
matrix substrate 1101, and an FPC (flexible printed circuit) 1106 is connected thereto.  Signals from outside are transferred to the inner circuit by the FPC 1106.
IC chips 1107 and 1108 are mounted utilizing the surface on which the FPC 1106 is attached.  These IC chips are constituted by forming various circuit, such as a video signal processing circuit, a timing pulse generating circuit, a gamma
compensation circuit, a memory circuit and an operation circuit, on a silicon substrate.  While two IC chips are mounted in FIG. 11A, one IC chip or three or more of them may be mounted.
An AMLCD may have the constitution shown in FIG. 11B.  In FIG. 11B, the same parts as in FIG. 11A are denoted by the same symbols, respectively.  In this constitution, the signal processing that is carried out by the IC chips in FIG. 11A is
conducted by a logic circuit 1109 composed of TFT formed on the same substrate 1101.  In this case, the logic circuit 1109 is formed based on a CMOS circuit as similar to the driver circuits 1103 and 1104.
The AMLCD shown in Example 11 can be utilized as a display of various electronic apparatuses.  The electronic apparatuses exemplified in this example are defined as a product equipped with an active matrix liquid crystal display device.
Examples of such an electronic apparatus include a camcorder, a still camera, a projection display, a projection television, a head-mounted display, a car navigation system, a personal computer (including a notebook computer) and a portable
information terminal (such as a portable computer and a cellular phone).  Specific examples thereof are shown in FIGS. 12A through 12F.
FIG. 12A shows a cellular phone, which is composed of a main body 2001, a sound output part 2002, a sound input part 2003, a display device 2004, an operation switch 2005 and an antenna 2006.  The invention can be applied to the display device
FIG. 12B shows a camcorder, which is composed of a main body 2101, a display device 2102, a sound input part 2103, an operation switch 2104, a battery 2105 and an image receiving part 2106.  The invention can be applied to the display device
FIG. 12C shows a portable computer, which is composed of a main body 2201, a camera part 2202, an image receiving part 2203, an operation switch 2204 and a display device 2205.  The invention can be applied to the display device 2205.
FIG. 12D shows a head mounting display, which is composed of a main body 2301, a display device 2302 and a belt part 2303.  The invention can be applied to the display device 2302.
FIG. 12E shows a rear type projector, which is composed of a main body 2401, a light source 2402, a display device 2403, a polarized beam splitter 2404, reflectors 2405 and 2406, and a screen 2406.  The invention can be applied to the display
device 2403.
FIG. 12F shows a front type projector, which is composed of a main body 2501, a light source 2502, a display device 2503, an optical system 2504 and a screen 2505.  The invention can be applied to the display device 2503.
As described in the foregoing, the field to which the invention can be applied is extremely broad, and the invention can be applied any electronic apparatus of any field.  Furthermore, the invention can be applied to an electric display board and
an advertisement display.
The invention relates to a technique for realizing a completely flat pixel electrode in each of pixels constituting a pixel matrix circuit of an AMLCD.  The constitution of the invention is particularly effective in a reflection type AMLCD in
which the whole surface of the pixel electrode becomes an effective display area.
The disclination generating on the pixel electrode can be effectively prevented, and the effective display area is widely enlarged by practicing the invention.  Therefore, high contrast can be realized even in an LCD device of higher precision.
Semiconductor device, Ohtani, et al., Hisashi Ohtani, Misako Nakazawa, Satoshi Murakami, Application number 09 197-767, Active Solid-State Devices (E.G. Transistors Solid-State Diodes), semiconductor device, semiconductor devices, semiconductor materials, free electrons, Semiconductor Device Fabrication, cat's whisker, Bipolar junction transistors, gate electrode, present invention relates, integrated circuit
The present invention relates to, in a semiconductor device using a thin film, a connection wiring ensuring electric connection between conductive thin films. Particularly, it relates to, in a pixel region of an active matrix liquid crystaldisplay (AMLCD), a connection wiring ensuring electric connection between a switching element and a pixel electrode.The semiconductor device used herein involves all devices functioning by utilizing semiconductor properties, and an electro-optical device such as an AMLCD and a semiconductor circuit such as a microprocessor are included. Furthermore, anelectronic apparatus containing such an electro-optical device and a semiconductor circuit is also included in the semiconductor device.BACKGROUND OF THE INVENTIONRecently, the technique of providing a TFT on an inexpensive glass substrate is being rapidly developed. This is because the demand of an AMLCD is increased.In an AMLCD, each of several tens to several millions of pixels arranged in a matrix form is equipped with a thin film transistor (TFT) as a switching element, and input/output of an electric charge on each of pixel electrodes is controlled bythe switching function of the TFT.A liquid crystal is sandwiched between the pixel electrode and a counter electrode to form a kind of capacitor. Therefore, the electro-optical characteristics of the liquid crystal can be changed by controlling input/output of an electric chargeon the capacitor, and thus an image can be displayed by controlling light passing through the liquid crystal panel.As a characteristic phenomenon in such a display device using a liquid crystal, there is a phenomenon called disclination. While the liquid crystal sandwiched between the pixel electrode and the counter electrode is arranged with orientationhaving regularity, the orientation may be disturbed by rubbing failure due to unevenness on the surface of the electrodes. The function of light shutter is lost in the location at which disclination occ