In-situ calibration structures and methods of use in semiconductor processing

Abstract

Systems and methods of in-situ calibration of semiconductor material layer deposition and removal processes are disclosed. Sets of test structures including one or more calibration vias or posts are used to precisely monitor processes such as plating and polishing, respectively. Known (e.g., empirically determined) relationships between the test structure features and product feature enable monitoring of wafer processing progress. Optical inspection of the calibration feature(s) during processing cycles permits dynamic operating condition adjustments and precise cessation of processing when desired product feature characteristics have been achieved.

1 . A method of in-situ calibrating a material deposition process, comprising the steps of:
 depositing a material within each of a product feature and at least a first calibration via formed in a photoresist layer on a substrate, under approximately the same depositing conditions, wherein the first calibration via has a cross-sectional dimension such that, when the material is deposited within both the product feature and the first calibration via under approximately identical depositing conditions, a height of the material within the first calibration via exceeds the height of the photoresist layer at approximately the same deposition time that the height of the material within the product feature reaches a selected height;   determining whether the height of the material deposited into the first calibration via exceeds the height of the photoresist layer; and   halting the depositing process if the height of the material deposited into the first calibration has exceeded the height of the photoresist layer, otherwise repeating the depositing and height determination steps.   
     
     
         2 . The method of  claim 1 , wherein determining whether the height of the material deposited further comprises optically identifying when the height of the material deposited in the first calibration via exceeds the thickness of the photoresist layer. 
     
     
         3 . The method of  claim 2 , wherein optically identifying the height of the material deposited in the first calibration via comprises observing at least one of an unsmoothed effect in the deposited material at the height of the photoresist layer and a dimensional increase of a feature formed thereby. 
     
     
         4 . The method of  claim 1 , further comprising the steps of:
 determining additional cross-sectional dimensions for additional calibration vias having dimensions different from the first calibration via and each other and such that a height of the material in each of the respective calibration vias is greater than the height of the material within the product feature at a given deposition time and depositing conditions, and when material that is deposited into the respective calibration via under approximately the same depositing conditions exceeds the height of the photoresist, a known height for the material deposited in the product feature is indicated;   forming, within the test region of the photoresist layer, the additional calibration vias having the additionally determined cross-sectional dimensions; and   monitoring the height of the metal deposited in the product feature through observation of the material depositing in the additional calibration vias and exceeding the height of the photoresist.   
     
     
         5 . The method of  claim 4 , wherein the first and additional calibration vias are spaced sufficiently apart to be optically distinguishable. 
     
     
         6 . The method of  claim 4 , wherein the first calibration via is flanked by the additional calibration vias. 
     
     
         7 . The method of  claim 1 , wherein the material depositing comprises a metal plating process. 
     
     
         8 . The method of  claim 1 , wherein the test region is spaced sufficiently apart from the product region so as to reduce depositing rate varying field effects. 
     
     
         9 . The method of  claim 1 , further comprising, in response to determining that the height of the material deposited into the first calibration via has not exceeded the height of the photoresist layer, adjusting operating conditions of the depositing process. 
     
     
         10 . The method of  claim 1 , further comprising:
 providing a substrate;   depositing a photoresist layer upon the substrate;   forming, within a product region of the photoresist layer, the product feature extending through a height of the photoresist layer;   determining the cross-sectional dimension of the first calibration via; and   forming, within a test region of the photoresist layer that is different than the product region, the first calibration via possessing the determined cross-sectional dimension.   
     
     
         11 . A test structure for in-situ monitoring of the height of a deposited material on a semiconductor wafer, comprising:
 a product region in the deposited material including a product feature extending through the thickness of the deposited material;   a calibration region in the deposited material distinct from the product region; and   at least one calibration via extending through the thickness of the deposited material, the at least one calibration via having a cross-sectional dimension such that when a metal is deposited within the product feature and the at least one calibration via under approximately the same depositing conditions, the height of the metal within the at least one calibration via exceeds the height of the photoresist layer at approximately the same deposition time that a desired height for metal deposited in the product feature is attained.   
     
     
         12 - 17 . (canceled) 
     
     
         18 . A test structure for in-situ monitoring of wafer polishing, comprising:
 a material layer having a height and including a product region and a test region, the product region for patterning a product feature therein;   a plurality of test features of different known heights formed in the test region, and embedded below the height of the material layer, the test features optically observable through the material of the material layer, such that exposure of a top surface of a particular test feature is observable as a change from rough to smooth and indicates a corresponding reduction of the material layer height in response to polishing to the known height of said particular test feature, thereby exposing the top of the particular test feature.