Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
1998-12-03
2001-01-16
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C118S7230ER, C118S7230IR
Reexamination Certificate
active
06174407
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to an apparatus and method for detecting an endpoint of an etching process, and more particularly to an apparatus and method for detecting an endpoint of an etching process by transmitting infrared light signals through a semiconductor wafer.
BACKGROUND OF THE INVENTION
The manufacture of semiconductor wafers to create semiconductor integrated circuit devices typically involves a sequence of processing steps which fabricate the multi-layer structure generally associated with the integrated circuit devices. Such processing steps may include (1) the deposition of metals, dielectrics, and semiconductor films, (2) the creation of masks by lithography techniques, (3) the doping of semiconductor layers by diffusion or implantation, (4) the polishing of outer layers (e.g. chemical-mechanical polishing), and (5) the etching of layers for selective or blanket material removal.
There is a continuing trend in the semiconductor industry to increase the functionality and performance of integrated circuit devices by increasing the number of circuit components within a given integrated circuit device. While in certain cases this may be accomplished by increasing the size of the integrated circuit device, in most cases this is accomplished by reducing the size and increasing the density of the circuit components.
Numerous manufacturing techniques have heretofore been developed in an effort to accomplish such component size reductions and density increases. For example, dry etch processes have been developed which do not require the immersion of the semiconductor wafer into an etching liquid. The most common dry etch process, generally referred to as “plasma etching”, utilizes plasma to etch films on the semiconductor wafer. Another type of dry etching, generally referred to as “dry developing”, utilizes a reactant gas to etch resist films from the semiconductor wafer.
In such dry etch processes, it is generally desirable to predict or detect when the desired layer of material associated with the semiconductor wafer has been etched away. In particular, it is desirable to detect when the semiconductor wafer has been etched to a desired level or “endpoint”. For example, systems have heretofore been designed which monitor the emission spectra of the plasma during plasma etching. However, such systems are typically complex and require expensive analysis equipment for operation thereof.
Thus, a continuing need exists for an apparatus and method which accurately and efficiently detects when an etching system etches a semiconductor wafer down to a desired level.
SUMMARY OF THE INVENTION
In accordance with a first embodiment of the present invention, there is provided a method of etching a first side of a semiconductor wafer down to a desired level. The method includes the step of etching the first side of the wafer in order to remove material from the wafer. The method also includes the step of transmitting a light signal through the first side of the wafer during the etching step such that the light signal propagates through the wafer and causes an attenuated signal to be emanated out of a second side of the wafer. The method further includes the step of refracting the attenuated signal if an intensity level of the attenuated signal has a predetermined relationship with an intensity threshold level. Moreover, the method includes the step of stopping the etching step in response to the attenuated signal being refracted in the refracting step.
Pursuant to a second embodiment of the present invention, there is provided an apparatus for etching a first side of a semiconductor wafer down to a desired level. The apparatus includes an etching chamber. The apparatus also includes a wafer chuck configured to engage the wafer by a second side of the wafer, and position the wafer in the etching chamber. The apparatus also includes a light source unit positioned such that light signals generated by the light source unit are directed toward the wafer. Moreover, the apparatus includes a light receiving unit positioned such that the light signals generated by the light source unit emanate from the wafer and are received with the light receiving unit, wherein the light signals are refracted by the light receiving unit when the wafer has been etched down to the desired level.
Pursuant to a third embodiment of the present invention, there is provided an apparatus for etching a first side of a semiconductor wafer down to a desired level. The apparatus includes an etching chamber. The apparatus also includes a wafer chuck configured to engage the wafer by a second side of the wafer, and position the wafer in the etching chamber. The apparatus also includes a light source unit positioned such that light signals generated by the light source unit are directed into the wafer. Moreover, the apparatus includes a light receiving unit positioned such that the light signals generated by the light source unit emanate out of the wafer and are received with the light receiving unit. The light receiving unit includes a first optical material and a second optical material having an interface therebetween. The first optical material has a linear index of refraction, whereas the second optical material has a nonlinear index of refraction which is dependent on an intensity level of the light signals received with the light receiving unit. The light signals are refracted at the interface if the linear index of refraction of the first optical material does not match the nonlinear index of refraction of the second optical material.
It is an object of the present invention to provide a new and useful apparatus and method for determining an endpoint of an etching process.
It is an object of the present invention to provide an improved apparatus and method for determining an endpoint of an etching process.
It is a further object of the present invention to provide an apparatus and method for determining that an etching system has etched a wafer down to a desired level without removing the wafer from the etching system.
The above and other objects, features, and advantages of the present invention will become apparent from the following description and the attached drawings.
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Johnson Gregory A.
Taravade Kunal N.
Goudreau George
LSI Logic Corporation
Mills Gregory
LandOfFree
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