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Interlayer for Endpointing MOL Poly CMP

IP.com Disclosure Number: IPCOM000022713D
Original Publication Date: 2004-Apr-25
Included in the Prior Art Database: 2004-Apr-25
Document File: 1 page(s) / 55K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

The Mid-Of-Line Polysilicon Chemical Mechanical Polishing (MOL Poly CMP) step of a semiconductor production line has a small process window, which is mostly consumed by unpredictable removal rate fluctuations as well as removal profile changes. In addition, the removal rate is affected by factors like the pad age and also depends on the history of the production process, i.e. the wafer previously polished. Usually, the approach to balance these variations is to calculate the polish time by taking into account as many factors as possible that can help to predict the removal rate of the wafer to be polished. The effort to provide those factors is large and includes extensive measurements after and before the process, operator inputs, decision paths and frequent tool monitoring. Another method is to use optical in-situ methods to monitor the thickness change of the layer to be polished. Unfortunately, both methods are not very reliable and don't yield satisfactory results.

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Interlayer for Endpointing MOL Poly CMP

Idea: Peter Lahnor, DE-Dresden

The Mid-Of-Line Polysilicon Chemical Mechanical Polishing (MOL Poly CMP) step of a semiconductor production line has a small process window, which is mostly consumed by unpredictable removal rate fluctuations as well as removal profile changes. In addition, the removal rate is affected by factors like the pad age and also depends on the history of the production process, i.e. the wafer previously polished. Usually, the approach to balance these variations is to calculate the polish time by taking into account as many factors as possible that can help to predict the removal rate of the wafer to be polished. The effort to provide those factors is large and includes extensive measurements after and before the process, operator inputs, decision paths and frequent tool monitoring. Another method is to use optical in-situ methods to monitor the thickness change of the layer to be polished. Unfortunately, both methods are not very reliable and don't yield satisfactory results.

The more reliable chemical endpoint methods are only applicable when the composition of the layer to be polished changes at or close to the level of the target remaining thickness. Therefore it is proposed to modify the deposition process of the layer to be polished so that an interlayer is formed at or close to the level where the polishing process is targeted to stop (Figure 1). The interlayer has a modified composition wit...