Apparatus and method for pulsed plasma processing of a semiconductor substrate
First Claim
1. A plasma processing system for processing a semiconductor substrate, the a system comprising:
- a processing chamber for producing the plasma;
an induction coil surrounding at least a portion of the processing chamber;
a first pulse power source coupled to the induction coil such that the induction coil couple power into the plasma using both high power cycles and low power cycles;
a substrate support for supporting the substrate the substrate support being positioned adjacent to the plasma; and
a second pulse power source coupled to the substrate support for applying a bias to the substrate;
wherein the second pulse power source is configured to alternate between high and low power cycles with a frequency ranging from about 500 kHz to 60 MHz.
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Abstract
Apparatus and method for an improved etch process. A power source alternates between high and low power cycles to produce and sustain a plasma discharge. Preferably, the high power cycles couple sufficient power into the plasma to produce a high density of ions (≳1011cm−3) for etching. Preferably, the low power cycles allow electrons to cool off to reduce the average random (thermal) electron velocity in the plasma. Preferably, the low power cycle is limited in duration as necessary to prevent excessive plasma loss to the walls or due to recombination of negative and positive ions. It is an advantage of these and other aspects of the present invention that average electron thermal velocity is reduced, so fewer electrons overcome the plasma sheath and accumulate on substrate or mask layer surfaces. A separate power source alternates between high and low power cycles to accelerate ions toward the substrate being etched. In one embodiment, a strong bias is applied to the substrate in short bursts. Preferably, multiple burst occur during the average transit time for an ion to cross the plasma sheath and reach the substrate surface. Ions are pulsed toward the surface for etching. These ions are not deflected into sidewalls as readily as ions in conventional low energy etch processes due to reduced charge buildup and the relatively low duty cycle of power used to pulse ions toward the substrate surface.
84 Citations
26 Claims
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1. A plasma processing system for processing a semiconductor substrate, the a system comprising:
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a processing chamber for producing the plasma;
an induction coil surrounding at least a portion of the processing chamber;
a first pulse power source coupled to the induction coil such that the induction coil couple power into the plasma using both high power cycles and low power cycles;
a substrate support for supporting the substrate the substrate support being positioned adjacent to the plasma; and
a second pulse power source coupled to the substrate support for applying a bias to the substrate;
wherein the second pulse power source is configured to alternate between high and low power cycles with a frequency ranging from about 500 kHz to 60 MHz. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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Specification