US 5,617,340 A · Method and reference standards for measuring overlay in multilayer structures, and for calibrating imaging equipment as used in semiconductor manufacturing

Abstract

Imaging instruments for inspecting products, such as semiconductor chips, are calibrated by providing a reference test structure having features which can be located by electrical measurements not subject to tool-induced shift and wafer-induced shift experienced by the imaging instrument. The reference test structure is first qualified using electrical measurements, and is then used to calibrate the imaging instrument. The electrical measurements may be made by forcing a current between a plurality of spaced reference features and an underlying conductor, or may be made by capacitive, conductive, magnetic, or impedance-measuring techniques. Capacitive techniques may also be used to detect features not susceptible of resistance measurement, such as dielectric or insulative materials, or metallic structures not accessible for forcing a current therethrough. A series of test structure elements may be fabricated with one component of each being spaced at progressively greater distances from an arbitrary baseline, such that a null-overlay element may be identified.

Claims36

Dependent claims

A method for calibrating an imaging instrument with respect to measurements of distance between features of a structure formed in a sequence of steps on a substrate, measurements made by said imaging instrument being susceptible to one or both of tool-induced shift (TIS) and wafer-induced shift (WIS), comprising the steps of:

forming a structure comprising components formed in a sequence of steps on a substrate, said components of said structure each comprising first artifacts the spacing of which is measurable using said imaging instrument, and also comprising second artifacts the spacing of which is analyzable using electrical measurement techniques not susceptible to TIS or WIS, said first and second artifacts being in defined physical relation to one another;
measuring the spacing of said first artifacts employing said imaging instrument;
analyzing the spacing of said second artifacts employing said electrical measurement technique;
and
calibrating said imaging instrument responsive to comparison of said measurements and analyses.

2 more elements

A method for calibrating optical measurements of overlay exhibited with respect to successive steps in fabrication of a multiple-layer planar product, comprising the steps of:

providing a test structure comprising:
a substrate;
a first conductive layer, formed on said substrate in a first fabrication step, and patterned to define optically-detectable reference members, and to further define a number of test point locations in fixed spatial relation to said reference members;
and
a second layer of a second material formed overlying said first layer in a subsequent fabrication step, said second layer being patterned to define optically-detectable reference marks for optical measurement of the relation thereof to said reference members defined by said first layer, and to further define a series of features spaced successively greater distances from a baseline in fixed spatial relation to said reference marks;
said features being such that the positions of the features with respect to said test points are determinable employing an electrical technique;
optically measuring the spatial relation of the reference marks with respect to the reference members, to derive an optically-measured value for overlay of the first and second layers;
performing a series of electrical measurements with respect to each of said features, to derive a series of electrically-measured values for overlay, each responsive to the degree of alignment of the corresponding feature to an underlying test point;
comparing the series of electrically-measured values in order to identify a null-overlay feature most closely approaching a predetermined relation to the corresponding test point;
and
correcting the optically-measured value for the overlay accordingly.

8 more elements

A test structure enabling calibration of imaging instruments for measurement of overlay as experienced during fabrication of products formed in multiple-step processes, measurements of overlay as made by such imaging instruments being susceptible to one or both of tool-induced shift (TIS) and wafer-induced shift (WIS), said structure comprising a first component formed in a first step and at least a second component formed in a second step, said first and second components together defining a number of artifacts on said substrate, an electrical characteristic of each of said artifacts varying in accordance with the relative alignment of the first and second components thereof, such that the relative alignment of said first and second components comprised by each of said artifacts are measurable using said imaging instrument to be calibrated and using electrical measurement techniques not susceptible to TIS and WIS.

Dependencies are inferred from the claim text.

Method and reference standards for measuring overlay in multilayer structures, and for calibrating imaging equipment as used in semiconductor manufacturing

Life of this patent

Method and reference standards for measuring overlay in multilayer structures, and for calibrating imaging equipment as used in semiconductor manufacturing

Life of this patent

Abstract

Claims36