US 5,872,633 A · Methods and apparatus for detecting removal of thin film layers during planarization

Abstract

The present invention provides methods and apparatus which permit the in-process, in-situ, substantially real time measurement of the actual thickness of a surface layer of a work piece, e.g., a semiconductor wafer. A probe is disposed proximate to the outer perimeter of a polishing pad on a CMP table such that the probe establishes optical contact with the wafer surface as a portion of the wafer extends beyond the outer perimeter of the polishing pad. A nozzle may be provided to apply a stream of compressed air at the disk surface under inspection to thereby remove excess slurry from the local region of the workpiece being inspected. A broad band light source is employed in conjunction with a fiber optic cable to direct light at the wafer surface. A bifurcated probe is employed such that the light applied to the workpiece surface is reflected back to and captured by a corresponding optical sensor connected to a fiber optic cable. The captured reflected light received by the receptor sensor and fiber optic cable assembly is applied to a photospectrum meter which analyzes the reflected light. An output signal from the photospectrum meter is transmitted to a processor which includes a smart algorithm configured to calculate the thickness of the surface layer. Alternatively, the reflective characteristics of the semiconductor layers may affect the nature of the reflected signal; changes in the reflected signal can be detected to indicate when a metallic layer has been removed from an oxide layer.

Claims17

Dependent claims

In a planarization system configured to process a semiconductor wafer initially having at least a first material layer formed over a second material layer, a method for detecting the removal of said first material layer from said semiconductor wafer during operation of said planarization system, said method comprising the steps of:

directing a broadband input interrogation signal at a portion of said first material layer, said broadband input interrogation signal having a plurality of wavelength components;
detecting a reflected portion of said broadband input interrogation signal reflected directly from said first material layer;
analyzing characteristics of said reflected portion of said broadband input interrogation signal;
directing a second broadband input interrogation signal at a portion of said second material layer after removal of said first material layer, said second broadband input interrogation signal having a plurality of wavelength components;
detecting a reflected signal produced in response to said second broadband input interrogation signal;
analyzing characteristics of said reflected signal;
and
indicating removal of said first material layer from said semiconductor wafer in response to characteristics of said reflected signal, where characteristics of said reflected signal differ from characteristics of said reflected portion of said input interrogation signal.

5 more elements

An apparatus for detecting removal of a first material layer initially formed over a second material layer on a semiconductor wafer during a planarization procedure, said apparatus comprising:

means for generating input signal for establishing optical communication with a surface of said semiconductor wafer during said planarization procedure;
said broadband input interrogation signal having a plurality of wavelength components;
a receptor configured to receive a reflected signal produced in response to said input signal, said reflected directly from said first material layer, and said receptor being further configured to receive a reflected signal produced in response to a second broadband input interrogation signal directed at said material layer after removal of said first material layer, said second broadband input interrogation signal having a plurality of wavelength components;
and
a processor configured to process said reflected portion of said broadband input interrogation signal to thereby produce a first output signal having a first characteristic indicative of the presence of said first material layer and to process said reflected signal to thereby produce a second output signal having a second characteristic indicative of the exposure of said second material layer.

2 more elements

Dependencies are inferred from the claim text.

Methods and apparatus for detecting removal of thin film layers during planarization

Life of this patent

Methods and apparatus for detecting removal of thin film layers during planarization

Life of this patent

Abstract

Claims17