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Two-Step Quartz Etchback Process

IP.com Disclosure Number: IPCOM000038716D
Original Publication Date: 1987-Feb-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Chen, L: AUTHOR [+4]

Abstract

An improved quartz etchback process has been developed which reduces cycle time by etching the semiconductor structure with two different gas mixtures. The structure to be planarized in the process consists of a thick layer of planar resist 1 (Fig. 1), a planar quartz layer 2 and the metal line or stud 3 to be exposed by etching. In the previous method, etchback of the wafer took place in a single wafer reactive plasma reactor with essentially 100% tetrafluoromethane CF4, used to achieve the desired etch rate ratio of 1.2 between quartz and resist necessary for planarity. The method described required approximately 4.5 minutes to complete with much of the etching time due to the relatively low initial etch rate of the planar resist in a CF4 discharge.

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Two-Step Quartz Etchback Process

An improved quartz etchback process has been developed which reduces cycle time by etching the semiconductor structure with two different gas mixtures. The structure to be planarized in the process consists of a thick layer of planar resist 1 (Fig. 1), a planar quartz layer 2 and the metal line or stud 3 to be exposed by etching. In the previous method, etchback of the wafer took place in a single wafer reactive plasma reactor with essentially 100% tetrafluoromethane CF4, used to achieve the desired etch rate ratio of 1.2 between quartz and resist necessary for planarity. The method described required approximately 4.5 minutes to complete with much of the etching time due to the relatively low initial etch rate of the planar resist in a CF4 discharge. The addition of a small amount of O2, while greatly increasing the etch rate, also tends to upset the etch rate ratio, resulting in large quartz peaks and insulator thinning.

(Image Omitted)

In the proposed two-step method, the high etch rate of O2 is exploited by using a high percentage of O2 along with a low percentage of CF4 to initially thin the resist 1 (Fig. 2) until quartz peaks in the quartz layer 2 are just revealed. In the second step, pure CF4 plasma is used to achieve the desired etch rate ratio to complete the planarization (Fig. 3). The two-step method reduces the quartz etchback process time to approximately two minutes, in effect doubling the throughput and reducing t...