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Method for scribing ceramic MEMS lids to relieve stress during wafer-level bonding

IP.com Disclosure Number: IPCOM000130136D
Publication Date: 2005-Oct-12
Document File: 2 page(s) / 590K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for scribing ceramic micro electro-mechanical systems (MEMS) lids to relieve stress during wafer-level bonding. Benefits include improved yield and improved throughput.

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Method for scribing ceramic MEMS lids to relieve stress during wafer-level bonding

Disclosed is a method for scribing ceramic micro electro-mechanical systems (MEMS) lids to relieve stress during wafer-level bonding. Benefits include improved yield and improved throughput.

Background

              Ceramic lids are used to hermetically seal fragile MEMS devices by bonding the ceramic wafer lid to a silicon MEMS wafer before packaging. However, the difference between the coefficients of thermal expansion (CTEs) of the ceramic and silicon materials can cause severe substrate cracking during cooling (see Figure 1).

      Cracking problems are conventionally reduced by using an extremely slow rate of cooling, such as 1-2°C/min. The cool down process can require long dwell times of 3+ hours at intermediate temperatures. The result is that wafer stress can be relieved gradually so the materials do not crack. However, the process is costly due to the length of time required and the unacceptable throughput rate.

 

Description

      The disclosed method pre-scribes ceramic lids to relieve stress during wafer-level bonding. The scores are placed in the streets of the wafer. A saw cuts scribe lines into the substrate to a depth of ~40% of the total substrate thickness. As a result, a much faster cool down rate can be used. Cracking can still occur, but it is contained within the scribe lines, protecting all other dice from cracking.

The disclosed method can be implemented using...