Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
1999-03-29
2001-11-27
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S315000, C430S324000, C430S326000, C438S697000
Reexamination Certificate
active
06322953
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains in general to a semiconductor manufacturing process and, more particularly, to a method for obtaining uniform photoresist coatings.
2. Description of the Related Art
Photoresist is a light-sensitive coating used during semiconductor device manufacturing processes, and is applied in liquid form. Typically, a small quantity of photoresist is applied to a wafer surface spun at high speed to spread the photoresist over the wafer surface. A pattern of light is then projected onto the photoresist. For a positive-type photoresist, regions exposed to the projected light may be removed by etchants, whereas regions not exposed to light are hardened and become resistant to etchants. In contrast, regions of a negative-type photoresist exposed to light become resistant to etchants. The steps of applying, exposing, and hardening of photoresist are essential in delineating patterns on the surface of a wafer in a semiconductor device manufacturing process.
During the manufacturing process, the wafer surface may acquire a complicated topography that include ridges and deep trenches. Trenches are often formed to isolate adjacent devices, prevent latch-ups in CMOS circuits, and provide capacitor components in high-density dynamic random-access memory cells (“DRAMs”). Because photoresist fills the trenches when it is applied over the wafer surface, the planarity of the coating referred to herein as uniformity, is difficult to obtain and, in some cases, leads to a dip in the photoresist layer above the trenches. For a DRAM manufacturing process, in particular, such a dip may lead to unacceptable variations in the formation of the device.
One method to minimize photoresist coating nonuniformity adds a second coating of photoresist over the first layer. Although the addition of a second layer may improve the uniformity of the coating surface, such an additional coating is insufficient when device size continues to shrink and the vertical features such as the trenches become comparable in size to horizontal features such as wiring.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a method for obtaining uniform photoresist coatings that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structures and methods particularly pointed out in the written description and claims thereof, as well as the appended drawings.
To achieve these and other advantages, and in accordance with the purpose of the invention as embodied and broadly described, there is provided a method for manufacturing a semiconductor device. The method includes providing a first layer of photoresist wherein the layer of photoresist has a thickness and is a positive type photoresist, exposing the first layer to light having a predetermined energy, developing the exposed first layer wherein a portion of the first layer remains, and providing a second layer of photoresist over the developed first layer.
In one aspect of the invention, providing a first layer of photoresist comprises providing an i-line photoresist layer having a thickness of approximately 3 um.
In another aspect of the invention, exposing the first layer to light having a predetermined energy comprises exposing the first layer to light having an energy of approximately 250 milli-Joules.
Also in accordance with the invention, there is provided a method of planarizing a photoresist coating for a semiconductor device having a surface including a trench. The method includes providing a first layer of photoresist over the surface including the trench wherein the layer has a thickness and the photoresist is a positive-type photoresist, exposing the first layer to light having a predetermined energy, developing the exposed first layer wherein a portion of the first layer remains within the trench, and providing a second layer of photoresist over the developed first layer.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
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Chang Wen-Pin
Lu Wen-Wha
Barreca Nicole
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Huff Mark F.
Winbond Electronics Corporation
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