Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
325 words
An apparatus for detecting a thickness (t) of at least one layer (12a) disposed over a surface of a wafer (13) having one or more first regions provided with circuit and other features, and one or more second regions showing an absence of circuit and other features, comprising: - an optical system (14) for collecting light reflecting from said at least one layer (12a) and said surface of said wafer (13), said optical system (14) having an optical axis (OA; 14a) and a cone of acceptance angles disposed about said optical axis (OA; 14a); - a camera (16) coupled to said optical system (14) for obtaining an image from the collected light; - a first light source (22; LS1) for illuminating said layer (12a) with light; and - a data processor (28a) having an input coupled to an output of said camera (16), characterized by - said first light source (22; LS1) emitting light that is directed along said optical axis (OA; 14a) and within said cone of acceptance angles; - at least one second light source (18; LS2, LS3) for illuminating said layer (12a) with light that is directed off said optical axis (OA; 14a) and outside of said cone of acceptance angles; and - said data processor (28a) obtaining from said camera (16) first pixel data corresponding to at least one first image obtained with light from said first light source (22; LS1), and obtaining second pixel data corresponding to at least one second image obtained with light from said at least one second light source (18; LS2, LS3), said data processor (28a) including means (28b, 28c) for generating an image mask from said second pixel data for distinguishing said first wafer regions from said second wafer regions, and further including means for detecting a thickness (t) of said at least one layer (12a) within said second regions in accordance with said first pixel data and in accordance with predetermined reference pixel data.
Claim 2
Dependent Claim
19 words
The apparatus of claim 1, characterized in that said optical system (14) is comprised of a telecentric optical system.
Claim 3
Dependent Claim
96 words
The apparatus of claim 1 or 2, characterized in that said first light source (22; LS1) provides illumination with a first incidence angle on said layer (12a), the first incidence angle being an angle that causes specularly reflected light to enter said cone of acceptance angles of said optical system (14), and that said second light source (18; LS2, LS3) provides illumination with a second incidence angle on said layer (12a), the second incidence angle being an angle that causes specularly reflected light to not enter said cone of acceptance angles of said optical system (14).
Claim 4
Independent Claim
154 words
The apparatus of any of claims 1 - 3, characterized in that said first light source (22; LS1) includes means (24) for sequentially illuminating said layer (12a) with light having different predetermined wavelengths, that said camera (16) obtains a plurality of first images, individual ones of the plurality of first images being obtained with light having one of the predetermined wavelengths, that said data processor (28a) includes means (28c), responsive to each of said plurality of first images, for comparing associated first pixel data values corresponding to one or more of said second regions with individual ones of a plurality of sets of predetermined image pixel values, each of the plurality of sets corresponding to a different layer thickness (t), and that said data processor (28a) further includes means for selecting as a layer thickness value (t) a thickness associated with a set that gives a best match with the first pixel data values.
Claim 5
Independent Claim
41 words
The apparatus of any of claims 1 - 4, characterized in that said at least one second light source is comprised of first and second second light sources (LS2, LS3) that are disposed for illuminating said layer (12a) from different directions.
Claim 6
Independent Claim
24 words
The apparatus of any of claims 1 - 5, characterized by means (19) for varying a polarization state of said second light source (18).
Claim 7
Dependent Claim
103 words
The apparatus of claim 1, characterized by a reference surface (RS; 30) that is disposed within a field of view of said camera (16), said reference surface (RS; 30) being oriented with respect to said surface of said wafer (13) for specularly reflecting light from said second light source (18; LS2, LS3), and wherein said image mask generating means is responsive to second pixel data corresponding to an image of said reference surface (RS; 30) for thresholding said second pixel data into first image mask regions corresponding to said first wafer regions and second image mask regions corresponding to said second wafer regions.
Claim 8
Independent Claim
195 words
A method for determining a thickness (t) of a layer (12a) disposed over a surface of a substrate (13), comprising the steps of: - illuminating the layer (12a) with light having a first incidence angle; - obtaining at least one first image of the layer (12a) with light reflecting from the layer (12a) and the substrate (13); - illuminating the layer (12a) with light having a second incidence angle; - obtaining at least one second image of the layer (12a) with light reflecting from the layer (12a) and the substrate (13), the reflected light being primarily due to a presence of features within the layer (12a) or substrate (13) that scatters and/or diffracts the light having the second incidence angle; - determining from the at least one second image a location of one or more regions of the layer (12a) or substrate (13) having the features and a location of one or more regions of the layer (12a) or substrate (13) not having the features; and - determining, in accordance with the at least one first image, a thickness (t) of the layer (12a) only within the one or more regions not having the features.
Claim 9
Dependent Claim
67 words
The method of claim 8, characterized in that the first incidence angle is an angle that causes specularly reflected light to enter an acceptance cone of an optical system (14) used to obtain the first image, and that the second incidence angle is an angle that causes specularly reflected light to not enter the acceptance cone of the optical system (14) used to obtain the second image.
Claim 10
Dependent Claim
165 words
The method of claim 8, characterized in that - the step of illuminating the layer (12a) with light having a first incidence angle includes the sub-step of sequentially illuminating the layer (12a) with light having different predetermined wavelengths; - that the step of obtaining at least one first image of the layer includes the sub-step of obtaining a plurality of first images, individual ones of the plurality of first images being obtained with light having one of the predetermined wavelengths; and - that the step of determining includes the substeps of: -- for each of the plurality of first images, comparing image pixel values corresponding to the one or more regions not having the features with individual ones of a plurality of sets of predetermined image pixel values, each of the plurality of sets corresponding to a different layer thickness; and -- selecting as a layer thickness value (t) a thickness associated with a set that gives a best match with the image pixel values.