Semiconductor device manufacturing: process – Including control responsive to sensed condition – Optical characteristic sensed
Reexamination Certificate
2000-07-06
2002-03-19
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Including control responsive to sensed condition
Optical characteristic sensed
C438S069000
Reexamination Certificate
active
06358759
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing an electro-optical device having a light transmissive substrate and a monocrystalline layer bonded to the substrate, the electro-optical device and electronic equipment. In particular, the present invention relates to a method for manufacturing an electro-optical device having a light shielding layer formed on a light transmissive substrate, the electro-optical device and electronic equipment.
2. Description of the Related Art
The SOI technology in which a seminconductor device is formed on a silicon thin film on top of an insulating substrate is appropriate for use in an electro-optical device such as a liquid-crystal display device, because the SOI technology offers high-speed, low-power consumption features and the high degree of integration in devices.
When the SOI technology is applied to the electro-optical device, a monocrystalline silicon substrate is bonded to a light transmissive substrate, and is polished to form a thin monocrystalline silicon layer. Then, a transistor element such as a MOSFET for driving a liquid crystal is formed from the monocrystalline silicon layer.
In a projection-type display apparatus such as a projector employing a liquid-crystal display device, light is typically incident on the surface of a light transmissive substrate. The projection-type display apparatus is thus typically provided with a light shielding layer on a MOSFET to prevent a leakage photocurrent from entering a channel region of the MOSFET formed on the substrate.
Even if the light shielding layer is arranged on top of the MOSFET, light incident on the front surface is reflected from the back surface of the substrate, returns to and enters the channel region of the MOSFET, when a support substrate is light transmissive. Although the returning light is a mere fraction of the light quantity of light incident on the surface of the substrate, it is strong enough to cause a leakage photocurrent in an apparatus, such as a projector, which handles a high-power light source. The returning light from the back surface adversely affects the switching characteristics of the element, thereby degrading the device characteristics. Here, the surface having the monocrystalline silicon layer formed thereon is referred to as the front surface of the substrate, and the opposite surface thereof is referred as the back surface.
Japanese Unexamined Patent Application Publication No. 10-293320 discloses a technique for forming a light shielding layer on the surface of a substrate in an area corresponding to a transistor element. In such a technique, the light shielding layer is patterned on the surface of the substrate, an insulating layer is deposited on the light shielding layer and is then planarized, and a monocrystalline silicon substrate is then bonded onto the planarized surface.
SUMMARY OF THE INVENTION
Since such a liquid-crystal display device includes, on the substrate thereof, an area where transistor elements are concentrated and an area where no transistor elements are present, the light shielding layers are accordingly distributed on the substrate. Similarly, protrusions of the insulating layer prior to a polishing process are densely distributed in one area while sparsely distributed in the other area on the substrate. In the polishing process for planarizing the insulating layer, variations take place in polishing performance between the area of densely distributed protrusions and the area of sparsely distributed protrusions. Specifically, the thickness of the insulating layer becomes thick in the area of the densely distributed protrusions, while the thickness of the insulating layer becomes thin in the area of the sparsely distributed protrusions. As a result, the insulating layer suffers from waviness in the surface thereof subsequent to the polishing process.
If the insulating layer suffers from the waviness on the surface thereof, the following problems arise. First, a void is caused in the interface with the insulating layer and the monocrystalline silicon layer, and the MOSFET formed in the void suffers from poor performance characteristics or suffers from a complete failure. Second, the bond between the insulating layer and the monocrystalline silicon layer is weakened. A weakened bond in the MOSFET forming process subsequent to the formation of the monocrystalline silicon layer, causes a failure such as a peel of the monocrystalline silicon layer thereby decreasing the production yield of the device.
To resolve the above problems, the present invention has been developed. It is an object of the present invention to provide a method for manufacturing an electro-optical device that planarizes an insulating layer to which a monocrystalline silicon layer is bonded, the electro-optical device and electronic equipment.
Means for Solving the Problem
To achieve the above object, a method for manufacturing an electro-optical device of the present invention includes the step of forming a light shielding layer on one side of a light transmissive substrate, patterning the light shielding layer, forming an insulating layer on the patterned light shielding layer, planarizing the insulating layer, bonding a monocrystalline silicon layer on the surface of the planarized insulating layer, and forming a transistor element from the monocrystalline silicon layer, wherein the patterned light shielding layer is arranged in an area facing the transistor element and in a peripheral area surrounding the transistor element.
In accordance with the manufacturing method of the present invention, the light shielding layer formed on one side of the light transmissive substrate is present not in either the formation area of the transistor element or in the peripheral area of the transistor element, and variations of protrusions of the substrate due to the light shielding layer are reduced. A uniformity in the polishing rate on the substrate is substantially improved when the insulating layer on the light shielding layer is planarized through the polishing process. Through the planarizing process of the insulating layer, the surface of the light transmissive substrate is thus planarized to be flat without introducing waviness therein. No void occurs in the interface between the insulating layer and the monocrystalline silicon layer, the bond between the insulating layer and the monocrystalline silicon layer increases, and the transistor element is thus free from variations in performance characteristics and failures.
In accordance with the present invention, the light transmissive substrate is bonded to a counter substrate by a sealing member, and the peripheral area area facing the sealing member. Since the light shielding layer is arranged facing the sealing member, the peripheral area is uniformly planarized, and the monocrystalline silicon layer is well bonded.
In the method of the present invention for manufacturing an electro-optical device, the step of planarizing the insulating layer formed on the light transmissive substrate uses a chemical mechanical polishing process.
An electro-optical device of the present invention includes a patterned light shielding layer formed on one side of a light transmissive substrate, a planarized insulating layer formed on the patterned light shielding layer, and a switching element formed on the planarized insulating layer, wherein the patterned light shielding layer is arranged in an area facing the transistor element and in a peripheral area surrounding the transistor element.
In accordance with the present invention, the surface of the insulating layer is thus planarized to be flat. No void occurs in the interface between the insulating layer and the monocrystalline silicon layer. An electro-optical device features a strong bond between the insulating layer and the monocrystalline silicon layer, with the transistor element free from variations in the performance characteristics and failures.
In the electro-optical device of the present invention, the
Dang Phuc T.
Nelms David
Oliff & Berridg,e PLC
Seiko Epson Corporation
LandOfFree
Method for manufacturing electro-optical device,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for manufacturing electro-optical device,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for manufacturing electro-optical device,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2889729