Eddy-optic sensor for object inspection

#1. Field of the Invention

#The present invention relates to a sensor for the efficient inspection and measurement of objects such as semiconductor wafers upon which dielectric and conducting films are deposited.

#2. Description of the Related Art

#These and other features and benefits of the invention will be readily appreciated in light of the following detailed description of the preferred embodiments thereof, given by way of example only with reference to the accompanying drawings wherein:

#FIG. 1 shows a first embodiment of the inventive sensor;

#FIG. 2 shows a cross section of the inventive sensor;

#Preferred embodiments of the present invention will now be described with reference to the attached drawings, wherein identical elements are designated with like numerals.

#The eddy-optic sensor offers clear and distinct advantages over other sensors to measure conducting film thickness. In a typical installation, referring to FIG. 1, a sensor 100 is positioned from a few microns to a few hundreds of microns over an object 150, such as a semiconductor wafer, upon which a conducting film 151 has been deposited. An eddy current inspection coil 103 as shown in FIG. 2 is energized by a radio frequency generator 110 using conductor 107. The eddy current inspection coil 103 induces eddy currents 152 in the conducting film 151 which are then detected by an eddy current detector 120. Measurements taken by the eddy current detector 120 are representative of the resistance of the conducting film 151, and in the case of constant resistance also of the thickness of the film.

#The sensor also illuminates the film using a light source 130 which emits light is conducted by a first fiber 101 to a location at which film measurement is to be made. The light source 130 will be either a broadband light source or a laser having a wavelength in the range of 200 to 1100 nanometers (ultraviolet to near infrared). Light reflected by the conducting film 151 then is conducted by a second fiber 102 to a light detector 140. The light detector 140 may be a device such as a charge coupled device or a photodiode array, though any detector suitable for this purpose may be used. Measurements taken by the light detector 140 may be used to determine the thickness, the index of refraction and the index of extinction of transparent or semi-transparent films 151.