Measuring a property of a layer in multilayered structure
First Claim
1. A method for determining a property of a portion of a substrate, the method comprising:
- heating a region of a metal layer in the substrate using power modulated at a frequency that is predetermined to be sufficiently low to ensure that at least a majority of heat is transferred out of the region by diffusion rather than by a thermal wave;
measuring a change in reflectance of the metal layer at the frequency of modulation of the power of heating; and
using the change in reflectance in a programmed computer, to determine a measure of electrical conductance of a feature formed by patterning the metal layer.
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Abstract
An apparatus measures a property of a layer (such as the sheet resistance of a conductive layer or thermal conductivity of a dielectric layer that is located underneath the conductive layer) by performing the following method: (1) focusing the heating beam on the heated a region (also called “heated region”) of the conductive layer (2) modulating the power of the heating beam at a predetermined frequency that is selected to be sufficiently low to ensure that at least a majority (preferably all) of the generated heat transfers out of the heated region by diffusion, and (3) measuring the power of another beam that is (a) reflected by the heated region, and (b) modulated in phase with modulation of the heating beam. The measurement in act (3) can be used directly as a measure of the resistance (per unit length) of a conductive line formed by patterning the conductive layer. Acts (1)-(3) can be repeated during fabrication of a semiconductor wafer, at each of a number of regions on a conductive line, and any change in measurement indicates a corresponding change in resistance of the line. When the measurement changes by more than a predetermined amount (e.g. by 10%), a process parameter that controls the fabrication process is changed to return the measurement to normal in the next wafer. Moreover, the thermal conductivity of the dielectric layer can be measured, or monitored for changes beyond a predetermined limit during a scan across the wafer, if resistance is known.
90 Citations
17 Claims
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1. A method for determining a property of a portion of a substrate, the method comprising:
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heating a region of a metal layer in the substrate using power modulated at a frequency that is predetermined to be sufficiently low to ensure that at least a majority of heat is transferred out of the region by diffusion rather than by a thermal wave;
measuring a change in reflectance of the metal layer at the frequency of modulation of the power of heating; and
using the change in reflectance in a programmed computer, to determine a measure of electrical conductance of a feature formed by patterning the metal layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for determining a property of a portion of a substrate, the method comprising:
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heating a region of conductive material in the substrate using a continuous heat source whose power is modulated at a frequency that is predetermined to be sufficiently low to ensure that at least a majority of heat is transferred out of the region by diffusion rather than by a thermal wave;
measuring a change in reflectance of the region of conductive material at the frequency of modulation of the power of the continuous heat source; and
using the change in reflectance of the conductive material in a programmed computer, to determine an indication of thermal conductivity of a dielectric material underneath the conductive material. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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Specification