Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2001-09-19
2002-12-24
Dang, Trung (Department: 2823)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S637000, C438S735000, C438S740000, C257S774000, C257S775000
Reexamination Certificate
active
06498089
ABSTRACT:
This application is based on Japanese Patent Application 2001-067165, filed on Mar. 9, 2001, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a semiconductor device and its manufacture method, and more particularly to a semiconductor integrated circuit device having a moisture-proof ring formed in a peripheral area of a chip and its manufacture method.
b) Description of the Related Art
A semiconductor integrated circuit device is formed by fabricating a number of elements in a semiconductor chip and forming a multi-layer wiring structure on the semiconductor chip. The multi-layer wiring structure is made of a plurality of wiring layers and a plurality of interlevel insulating films for insulating wiring layers. In order to have electrical connection between different wiring layers, via holes are formed through an interlevel insulating film before an upper level wiring layer is formed on this interlevel insulating film. When the upper level wiring layer is formed, this layer also fills the via holes.
A resist mask is formed on the wiring layer formed on the interlevel insulating film, and by using the resist mask as an etching mask, the wiring layer is etched to form a wiring pattern. Deposits and the like on the side walls of a wiring pattern are removed by chemicals such as alkali. Thereafter, in order to provide electrical insulation between the wiring patterns of the same level wiring layer and between upper and lower wiring patterns, an interlevel insulating film of silicon oxide or the like is formed by plasma CVD.
As the material of a wiring layer, aluminum (Al), tungsten (W) and the like capable of being etched have been used conventionally. In order to prevent the surface of a wiring pattern from being oxidized during an ashing process of removing the resist mask after the wiring pattern is formed, an anti-oxidation layer of TiN or the like is formed on the main wiring layer of Al or W.
An interlevel insulating film of silicon oxide or the like has the nature of transmitting moisture in the ambient air therethrough. If moisture in the air reaches a semiconductor element, the semiconductor element characteristics are deteriorated. In order to prevent invasion of moisture in the ambient air, a passivation film of SiN or the like having a moisture-proof ability is formed on the uppermost insulating layer and in addition an electrically conductive moisture-proof ring is formed in the chip peripheral area.
The moisture-proof ring is formed by forming a ring trench surrounding a circuit area in a loop shape through etching at the same time when via holes are formed through an interlevel insulating film, and then filling a wiring layer in the ring trench and patterning the wiring layer in a wiring pattern forming process.
An integration degree of semiconductor integrated circuit devices is continually required to be raised. In order to raise the integration degree, semiconductor elements are made finer or smaller to form a more number of semiconductor elements in a unit area. As semiconductor elements are made finer, the density of wiring patterns formed above the semiconductor elements increases more. As the wiring density increases, the width of each wiring pattern becomes narrower and the distance between adjacent wiring patterns becomes shorter.
Assuming the same thickness of a wiring layer, as the wiring pattern width is made narrower, the wiring resistance increases. As the distance between adjacent wiring patterns is made shorter, the capacitance between wiring patterns increases. In order to suppress an increase in the wiring resistance, it is required to thicken the wiring layer. In order to maintain the cross section of a wiring pattern constant, a reduction in the wiring pattern width is required to be compensated by an increase in the wiring pattern thickness.
However, as a wiring layer is made thick, the opposing area between adjacent wiring patterns increases so that the capacitance between the wiring patterns increases further. Increases in the wiring resistance and capacitance between wiring patterns lower the signal transmission speed. Since higher integration and lower power consumption are main issues of memory devices, wiring material such as Al has been used as conventional.
A main issue of logic circuits is an arithmetic operation speed so that a reduction in a signal transmission speed is required to be suppressed as much as possible. It is therefore desired to lower a wiring resistance and a parasitic wiring capacitance. In order to lower a wiring resistance, it has been proposed to use refractory metal such as Cu as the wiring material having a resistivity lower than that of Al. In order to lower a parasitic wiring capacitance, it has been proposed to lower a dielectric constant of an insulating film which provides electric insulation between wiring patterns. For example, as an insulating film having a low dielectric constant, a fluorine-containing silicon oxide film (FSG: fluorine-containing silicate glass) or the like is used.
A Cu wiring layer is difficult to be patterned through etching. From this reason, a damascene process is used to form a Cu wiring pattern. In the damascene process, a trench is formed in an insulating film, a Cu layer is formed filling the trench, and an unnecessary Cu layer on the insulating film is removed by chemical mechanical polishing (CMP) or the like. It is known that the damascene process includes a single damascene process and a dual damascene process.
In the single damascene process, a photoresist pattern for forming via holes is formed on the underlying insulating film and via holes are formed through etching. After the photoresist pattern is removed, a Cu layer is deposited and an unnecessary Cu layer is removed by CMP. Another insulating layer is formed and a photoresist pattern for forming wiring patterns is formed on the insulating layer. Wiring pattern trenches are formed in the overlying insulating layer. After the photoresist pattern is removed, a Cu layer is deposited and an unnecessary Cu layer is removed by CMP.
In the dual damascene process, a via hole forming photoresist pattern is formed on an insulating layer to form via holes through etching. A wiring pattern forming photoresist pattern is formed on the same insulating layer to form wiring pattern trenches in the insulating layer. Thereafter, a Cu layer is deposited, completely filling the via holes and wiring pattern grooves by the same process, and an unnecessary Cu layer is removed by CMP.
If an underlying Cu wiring layer is exposed, while the photoresist pattern is removed by ashing after via holes are formed, the exposed surface of the Cu wiring layer is oxidized. In order to prevent oxidation of the Cu wiring layer surface, an anti-oxidation film having an etching stopper function is formed covering the surface of the Cu wiring pattern. This anti-oxidation film serving also as an etching stopper is made of, for example, SiN.
If the etching stopper/anti-oxidation film is formed under an insulating film, a via hole passing through the insulating film and exposing the etching stopper/anti-oxidation film is formed through etching. At this stage, the photoresist pattern is removed by ashing. Thereafter, the etching stopper/anti-oxidation film exposed at the bottom of the via hole is removed. In the following, the etching stopper/ant-oxidation film is simply called an etching stopper film (layer).
Cu has the nature of diffusing into an insulating film of silicon oxide or the like and degrading the dielectric characteristics and insulating characteristics of the insulating layer. In order to prevent diffusion of Cu, a barrier layer of TiN, TaN or the like is formed prior to forming a Cu wiring layer, and then the Cu wiring layer is formed on the barrier layer.
In forming a moisture-proof ring when Cu wiring is adopted, the insulating film in the chip peripheral area is etched in a loop trench shape at the same time when the insulating film is etch
Armstrong Westerman & Hattori, LLP
Dang Trung
Fujitsu Limited
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