Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-10-21
2003-05-06
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S093000, C345S097000, C345S100000, C345S103000, C345S098000, C257S204000, C257S369000
Reexamination Certificate
active
06559821
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates a matrix substrate and a liquid crystal display apparatus and, more particularly, it relates to a matrix substrate and a liquid crystal display apparatus featured by horizontal and vertical shift registers to be used for scanning liquid crystal devices for display operations as well as to a projector using the same.
2. Related Background Art
In recent years, display apparatus have been playing ever-increasing important roles as means of multi-media communication using images, sounds and written texts. Of them, liquid crystal display apparatus have the advantage of being very thin and consuming little power and the industry of manufacturing liquid crystal display apparatus has grown to a major industry that is comparable with the semiconductor manufacturing industry. It is expected that liquid crystal display apparatus are used in the future not only for personal computers but also for work stations and home television sets having a large display screen. However, a large liquid crystal display apparatus having a large screen is accompanied by high manufacturing cost and electric requirements to be met to drive its large screen. Normally, the manufacturing cost of a liquid crystal display apparatus increases as a function of the square to the cube of the size of the display screen.
In an attempt to bypass this problem, projection systems adapted to optically enlarge the image formed on a relatively small liquid crystal display screen for viewing have been attracting attention. Such a system has become feasible due to the recent technological development that has made it possible to manufacture micro-semiconductor devices on a mass production basis to exploit the scale merit. Then, in the liquid crystal display panel is of the TFT type, TFTs that are small and have a sufficient drive effect have to be used. Additionally, for technological reasons, TFTs using amorphous Si are being replaced by those using polycrystalline Si. On the other hand, video signals for the level of resolution required to meet the NTSC standards or other ordinary television standards do not necessarily have to be processed at high speed.
Thus, it is now possible to produce a liquid crystal display apparatus, wherein not only the TFTs but also the peripheral drive circuits such as shift registers and decoders are made of polycrystalline Si so that the display region and the peripheral drive circuits may be formed integrally. However, polycrystalline Si is not as good as single crystalline Si and, for producing a liquid crystal display apparatus of the XGA (extended Graphic Array) class or the SXGA (Super extended Graphics Array) class, as expressed in terms of the standards for the resolution of computer-generated graphic images, shift registers and other devices may have to be divided and arranged at a plurality of locations. Then, the junctions of adjacent devices can generate noises referred to as ghosts, which provide a problem to be dissolved in this field of technology.
On the other hand, display apparatus comprising a single crystalline Si substrate that shows a much higher drive force that display apparatus having an integral structure of polycrystalline Si has been attracting attention. Since the transistors of the peripheral drive circuits of such display apparatus show a satisfactory drive force and hence do not have to be divided, they are free from the problem of noises.
Regardless of polycrystalline Si or single crystalline Si, it is possible to provide a reflection type liquid crystal display apparatus comprising liquid crystal devices and realized by connecting the drains of TFTs to respective reflection electrodes and arranging pieces of liquid crystal respectively pinched by the reflection electrodes and a corresponding transparent common electrode to form reflection type liquid crystal devices, which liquid crystal devices are then scanned by means of horizontal and vertical shift registers arranged on a same semiconductor substrate.
The applicant of the present patent application has disclosed in Japanese Patent Application Laid-Open No. 9-73103 a reflection type liquid crystal display apparatus realized by using polycrystalline Si and single crystalline Si. A liquid crystal display apparatus as disclosed in the above patent document is proposed to solve some of the problems of known liquid crystal display apparatus of the type under consideration including that light entering the pixel electrodes are scattered in various directions by the undulations on the surface thereof to remarkably reduce the reflection efficiency of light and that such undulations on the surface of the pixel electrodes can give rise to a defective orientation in the process of rubbing the oriented film conducted in the course of mounting the liquid crystal to consequently produce a defective orientation in the liquid crystal that can degrade the quality of the displayed image due to a poor contrast.
According to the above cited Japanese Patent Application Laid-Open No. 9-73103, the surface of the pixel electrodes is polished by means of a technique of chemical mechanical polishing (referred to as CMP hereinafter). Then, all the surfaces of the pixel electrodes are made mirror plane and flush with each other.
Now, an active matrix substrate and a method of manufacturing the same will be summarily described by referring to
FIGS. 23A
to
23
E and
24
F to
24
H of the accompanying drawings. Note that, while
FIGS. 23A
to
23
E and
24
F to
24
H show only part of the pixel section of an active matrix substrate, peripheral drive circuits including shift registers for driving the switching transistors of the pixel section may also be formed on the same substrate.
Firstly, an n-type silicon semiconductor substrate
201
showing an impurity concentration level of not greater than 10
15
cm
−3
is partly and thermally oxidized to produce a LOCOS
202
for each pixel and then boron ions are implanted to a dosage level of 10
12
cm
−2
, using the LOCOS
202
as mask, to produce a PWL
203
which is a p-type impurity region showing an impurity concentration level of about 10
16
cm
−3
The substrate
201
is then thermally oxidized once again to produce a gate oxide film
204
having a film thickness of not greater than 1,000 angstroms (FIG.
23
A).
After forming a gate electrode
205
of n-type polysilicon doped with phosphor to a concentration level of about 10
20
cm
−3
, phosphor ions are implanted into the entire surface of the substrate
201
to a dosage level of about 10
12
cm
−2
to produce an NLD
206
which is an n-type impurity region showing an impurity concentration level of about 10
16
cm
−3
and subsequently phosphor ions are implanted to a dosage level of about 10
15
cm
−2
, using a patterned photoresist layer as mask, to produce source/drain regions
207
,
207
′ showing an impurity concentration level of about 10
19
cm
−3
(FIG.
23
B).
Then, a PSG layer
208
is formed on the entire surface of the substrate
201
as interlayer film. The PSG
208
may be replaced by NSG (Non-doped Silicate Glass)/BPSG (Boro-Phospho-Silicate Glass) or TEOS (Tetraethoxy-Silane). Thereafter, a contact hole is formed by patterning in the PSG
208
at a position right above the source/drain regions
207
,
207
′ and then an Al layer is deposited by evaporation, using a sputtering technique, and then patterned to produce an Al electrode
209
(FIG.
23
C). Desirably, a barrier metal layer such as a Ti/TiN layer is formed between the Al electrode
209
and the source/drain regions
207
,
207
′.
Thereafter, a plasma SiN layer
210
and then a PSG layer
211
are formed on the entire surface of the substrate
201
to respective thicknesses of about 3,000 angstroms and 10,000 angstroms (FIG.
23
D).
Then, The PSG layer
211
is patterned, using the plasma SiN layer
210
as dry etching stopper layer, until it is left only on the pixel separating regions and subsequently a through hole
Ichikawa Takeshi
Koyama Osamu
Kurematsu Katsumi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Hjerpe Richard
Lesperance Jean
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