Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
1999-10-06
2001-09-18
Powell, William A. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C156S345420, C216S037000, C216S067000, C216S079000, C438S719000, C438S734000, C438S735000
Reexamination Certificate
active
06291357
ABSTRACT:
BACKGROUND
The present invention relates to etching of a substrate in a plasma of process gas.
Electronic devices, such as integrated circuits, are formed by deposition, growth (such as by oxidation, nitridation, etc.) and etching of material on a substrate. In a typical etching process, a patterned etch-resistant mask is formed on the substrate by a conventional photolithographic process, and thereafter, exposed portions of the substrate are etched away with energized gases. In the etching process, a reactive gas is introduced into a chamber and is supplied with electromagnetic energy, such as microwave or radio frequency energy, to form an energized gas, such as a plasma, to etch the substrate. In addition, a biasing voltage may be applied to the plasma to energize charged plasma species to provide more anisotropic etching.
In the etching process, it is desirable to control the dimensions of the features being etched, and it also desirable to etch features, such as openings or trenches, with smooth vertical sidewalls. However, conventional etching processes often result in non-uniform etching rates and microloading effects across the substrate. Microloading is a general term used to describe undesirable variations in etch rates, feature shapes, or other etching attributes, from one etched feature to another and across the substrate. For example, the etching rates of the etched holes may vary between small diameter holes which have a high aspect ratio and large diameter holes or open spaces. As another example, the shape or etching rates of the etched features may vary from regions of the substrate having a high density of features (dense feature regions) to regions having relatively few and isolated features (isolated feature regions). Critical dimension microloading may also arise from the variations in critical dimensions of the etched features, the critical dimensions (CD) being those dimensions that are used to calculate the electrical properties of the etched features in the design of integrated circuits. For example, the cross-sectional area of an interconnect line or contact is a critical dimension that should be close to predetermined dimensions to provide the desired electrical resistance.
Accordingly, it is desirable to etch features, such as holes and interconnect lines, across the substrate at uniform and reproducible etch rates. It is further desirable to reduce variations in the etching rate of the high aspect ratio holes relative to open spaces on the substrate. It is also desirable to obtain etched features having uniform and predictable shapes.
SUMMARY
The present invention satisfies these needs. In one aspect, the present invention comprises a method of processing a substrate having a surface. In the method, the substrate is placed in the process zone and gas is introduced in the process zone and energized. First process conditions are set to form etch-passivating deposits on the surface of the substrate. Second process conditions are set to etch the surface of the substrate.
In another aspect, a method for etching a substrate comprises (i) in a plasma ignition stage, providing a gas to a process zone and capacitively coupling electromagnetic energy to the gas at an initial bias power level to form a plasma from the gas; (ii) in a plasma stabilization stage, reducing the initial bias power level to a first bias power level and inductively coupling electromagnetic energy to the plasma at a first source power level capable of stabilizing the plasma; (iii) in an etch-passivating deposit formation stage, reducing the first source power level to a second source power level and maintaining a second bias power level, thereby forming etch-passivating deposits on the substrate; and (iv) in an etching stage, increasing the second bias power level to a third bias power level, thereby etching the substrate.
In another aspect, a method of etching a substrate in a process zone comprises the steps of placing a substrate in a process zone and providing a non-reactive gas in the process zone. A plasma of the gas is formed by applying a bias power level to process electrodes in the process zone. The bias power level applied to the process electrodes is reduced while providing an etchant gas, thereby forming etch-passivating deposits on the substrate. Thereafter, the bias power level is increased to etch the substrate.
In another aspect, a method of processing a substrate comprises the steps of placing the substrate in a process zone. A gas is introduced in the process zone and energized to form a plasma. First conditions of the plasma are set to form etch-passivating deposits on the surface of the substrate. Second conditions of the plasma are set to etch the surface of the substrate.
In yet another aspect, the present invention comprises a substrate processing apparatus comprising a chamber having a support capable of receiving a substrate, a gas supply capable of introducing gas into the chamber, and a gas energizer to form a plasma of the gas. The apparatus also comprises a controller adapted to set first process conditions to form etch-passivating deposits onto a surface of the substrate, and to set second process conditions to etch the surface of the substrate.
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Adisaputro Ida Ariani
Kim Kwang-Soo
Wang Ruiping
Zhang Luke
Applied Materials Inc.
Janah and Associates
Powell William A.
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