Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Including integrally formed optical element
Reexamination Certificate
2001-03-02
2004-02-24
Booth, Richard (Department: 2812)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Including integrally formed optical element
C438S158000
Reexamination Certificate
active
06696309
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods for making electrooptical devices and driving substrates for the electrooptical devices. In particular, the present invention relates to a method suitable for, for example, a liquid crystal display having an active region of a top-gate-type thin-film insulating-gate field-effect transistor (hereinafter referred to as top-gate-type MOSTFT) using a single-crystal silicon layer, grown by heteroepitaxy on an insulating substrate, and a passive region. Herein, the top-gate types include a stagger type and a coplanar type. Also, the present invention relates to a method suitable for, for example, a liquid crystal display having an active region of a bottom-gate-type thin-film insulating-gate field-effect transistor (hereinafter referred to as bottom-gate-type MOSTFT) using a single-crystal silicon layer, grown by heteroepitaxy on an insulating substrate, and a passive region. Herein, the bottom-gate types include an inverted-stagger NSI type and an inverted-stagger ISI type. Moreover, the present invention relates to a method suitable for, for example, a liquid crystal display having an active region of a dual-gate-type thin-film insulating-gate field-effect transistor (hereinafter referred to as dual-gate-type MOSTFT) using a single-crystal silicon layer, grown by heteroepitaxy on an insulating substrate, and a passive region. These configurations are suitable for liquid crystal displays etc.
2. Description of the Related Art
Various types of active-matrix liquid crystal displays are known. For example, a liquid crystal display has a display region using amorphous silicon for TFTs and an IC for an external driving circuit. Another type of liquid crystal display integrates a display section using solid phase deposition polycrystalline silicon TFTs and a driving circuit, as disclosed in Japanese Patent Application Laid-Open No. 6-242433. Integration of a display section using excimer laser annealing polycrystalline silicon TFTs and a driving circuit is also known in Japanese Patent Application Laid-Open No. 7-131030.
Although conventional amorphous silicon TFTs have high productivity, they are not suitable for production of p-channel MOSTFTs (hereinafter referred to as pMOSTFTs) due to a low electron mobility of 0.5 to 1.0 cm
2
/v.sec. Since a peripheral driving section using pMOSTFTs and a display section cannot be formed on the same substrate, the driver IC should be an external component, which is mounted by, for example, a tape automated bonding (TAB) method, which has high production costs. This configuration inhibits production of high-resolution devices. Furthermore, the small electron mobility, as described above, causes a small ON current; hence, the size of the transistors in the display section is inevitably large, resulting in a small aperture ratio of pixels.
Conventional polycrystalline silicon TFTs have an electron mobility of 70 to cm
2
/v.sec and can facilitate production of high-resolution devices. Thus, liquid crystal displays (LCDs) which use polycrystalline silicon and are integrated with driving circuits have attracted attention. The above electron mobility, however, is insufficient for driving a large LCD of 15 inches or more, and thus ICs for an external driving circuit are required.
TFTs using polycrystalline silicon formed by a solid-phase deposition process require annealing at a temperature of 600° C. or more for several tens of hours and thermal oxidation at approximately 1,000° C. to from a gate SiO
2
layer. Thus, the production of such TFTs requires using a semiconductor production apparatus. Thus, the wafer size is limited to 8 to 12 inches and the use of expensive heat-resistant quartz glass is inevitable, resulting in high production cost. Thus, the use of such TFTs is limited to EVF and audiovisual (AV) projectors.
Polycrystalline silicon TFTs produced by excimer laser annealing have many problems, including unstable output of the excimer lasers, low productivity, increasing price of the apparatus with increasing size, low yield and low quality. These problems are pronounced when large glass substrates having a side of, for example, 1 meter are used.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for uniformly depositing a single-crystal silicon thin-film having high electron/hole mobility at a relatively low temperature in a peripheral driving circuit to facilitate production of an electrooptical device such as a thin-film semiconductor display device using the single-crystal silicon thin-film, to form an integrated configuration of a display section including n-channel MOSTFTs (hereinafter referred to as nMOSTFTs) or pMOSTFTs having high switching characteristics and a lightly-doped drain (LDD) structure or complementary thin-film insulating gate electric field transistors (hereinafter referred to as cMOSTFTs) and a peripheral driving circuit including cMOSTFTs, nMOSTFTs, and/or pMOSTFTs, to facilitate production of a large display panel with high quality, high definition, a narrow frame, and high efficiency, to facilitate the use of a large glass substrate which has a low distortion point and does not require expensive facilities, to readily control the threshold voltage (Vth) of the device, and to facilitate operation of the device at a high rate due to reduced resistance.
The present invention is directed to a method for making an electrooptical device comprising a first substrate (a driving substrate) including a display section provided with pixel electrodes (arranged in a matrix) and a peripheral-driving-circuit section provided on a periphery of the display section, a second substrate (opposite substrate), and an optical material disposed between the first substrate and the second substrate, and to a method for making a driving substrate for the electrooptical device.
According to a first aspect of the present invention, the method for making an electrooptical device comprises the steps of: forming a material layer having a high degree of lattice matching with single-crystal silicon on one main face of the first substrate; forming a polycrystalline or amorphous silicon layer having a given thickness on the first substrate including the material layer and then forming a low-melting-point metal layer on or under the polycrystalline or amorphous silicon layer on the first substrate, or forming a low-melting-point metal layer containing silicon on the first substrate having the material layer; dissolving the polycrystalline or amorphous silicon layer or the silicon into the low-melting-point metal layer by a heat treatment; precipitating a single-crystal silicon layer from the silicon in the polycrystalline or amorphous silicon layer or the silicon in the low-melting-point metal layer by heteroepitaxy including a cooling treatment using the material layer as a seed; and treating the single-crystal silicon layer through a predetermined process to form at least an active device between the active device and a passive device.
According to a second aspect of the present invention, the method for making an electrooptical device comprises the steps of: forming a gate section comprising a gate electrode and a gate insulating film on one face of the first substrate; forming a material layer having a high degree of lattice matching with single-crystal silicon on the same face of the first substrate; forming a polycrystalline or amorphous silicon layer having a given thickness on the first substrate including the material layer and the gate section, and then forming a low-melting-point metal layer on or under the polycrystalline or amorphous silicon layer on the first substrate, or forming a low-melting-point metal layer containing silicon on the first substrate having the material layer; dissolving the polycrystalline or amorphous silicon layer or the silicon into the low-melting-point metal layer by a heat treatment; precipitating a single-crystal silicon layer from the silicon in the polycrystalline or amorphous silic
Sato Yuuichi
Yagi Hajime
Yamanaka Hideo
Yamoto Hisayoshi
Booth Richard
Depke Robert J.
Holland & Knight LLC
LandOfFree
Methods for making electrooptical device and driving... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods for making electrooptical device and driving..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods for making electrooptical device and driving... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3293390