Method and a system for characterising structures through a substrate
AssigneeUnity Semiconductor Corporation
InventorsWolfgang Alexander Iff, Alain Courteville
Life of this patent
Estimating the term…
Abstract
A method for characterizing structures etched in a substrate, such as a wafer is disclosed. The method includes the following steps: illuminating the bottom of at least one structure with an illumination beam issued from a light source emitting light with a wavelength adapted to be transmitted through the substrate, acquiring, with an imaging device positioned on the bottom side of said substrate, at least one image of a bottom of the at least one structure through the substrate, and measuring at least one data, called lateral data, relating to a lateral dimension of the bottom of the at least one HAR structure from the at least one acquired image. A system implementing such a method is also disclosed.
Claims13
A method for characterizing structures etched in a substrate, such as a wafer, the substrate having a top side on which the structures are etched and a bottom side opposite to the top side, the method comprising the following steps:
- illuminating at least one structure with an illumination beam issued from a light source emitting light with a wavelength adapted to be transmitted through the substrate;
- acquiring, with an imaging device positioned on the bottom side of said substrate, at least one image of a bottom of said at least one structure through the substrate, comprising scanning said at least one structure and/or the substrate below said at least one structure along a direction, z, corresponding to a depth direction of said structure, comprising:
- moving an object plane optically conjugate of an image plane of the imaging device along the z direction;
- acquiring an image or a sequence of images of the object plane at different positions of the object plane along the z direction;
- and
- identifying at least one image of a bottom of the at least one structure, acquired with the object plane positioned at a bottom of the at least one structure, comprising:
- detecting a transition in the sequence of images between the at least one structure and the substrate below the at least one structure;
- and
- measuring the sharpness or the spatial frequencies of the acquired images;
- and
- measuring at least one data, called lateral data, relating to a lateral dimension of the bottom of said at least one structure from the at least one acquired image.
A system for characterizing structures etched in a substrate, such as a wafer, the substrate having a top side on which the structures are etched and a bottom side opposite to the top side, the system comprising:
- at least one light source for illuminating a structure, the at least one light source emitting light of a wavelength adapted to be transmitted through the substrate;
- an imaging device positioned on the bottom side of said substrate for acquiring at least one image of the bottom of the structure through the substrate;
- focus controlling means configured to scan said at least one structure and/or the substrate below said at least one structure along a direction, z, corresponding to a depth direction of said structure, the focus controlling means being configured to:
- move an object plane optically conjugate of an image plane of the imaging device along the z direction;
- acquire an image of the object plane at different positions of the object plane along the z direction;
- and
- identify at least one image of a bottom of the at least one structure, acquired with the object plane positioned at a bottom of the at least one structure, the focus controlling means being further configured to:
- detect a transition in the sequence of images between the at least one structure and the substrate below the at least one structure;
- and
- measure the sharpness or the spatial frequencies of the acquired images;
- and
- an image processing hardware module for measuring at least one data, called lateral data, relating to a lateral dimension of the bottom of the structure from the at least one acquired image.
Dependencies are inferred from the claim text.