Browse Prior Art Database

Application of Chemically Cured Polyimides in the Fabrication of Multi-level Composite Semiconductor and Semiconductor Package Structures

IP.com Disclosure Number: IPCOM000050399D
Original Publication Date: 1982-Oct-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Acosta, RE: AUTHOR [+2]

Abstract

Polyimides are useful as the dielectric material for the fabrication of semiconductor devices and of semiconductor device packages due to the unique characteristics: low inherent defect density, low cost of application, and relatively high thermal stability.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 2

Application of Chemically Cured Polyimides in the Fabrication of Multi-level Composite Semiconductor and Semiconductor Package Structures

Polyimides are useful as the dielectric material for the fabrication of semiconductor devices and of semiconductor device packages due to the unique characteristics: low inherent defect density, low cost of application, and relatively high thermal stability.

As their use extends to more complex (e.g., muitilevel) structures, special precautions must be exercised in their processing to avoid cracking of the polyimide films. A cause of cracking of the polyimide film is the large mismatch between the coefficients of thermal expansion of the polyimide (on the order of 50 x 10/-6//degrees C) and the substrate over which the polyimide film is formed, silicon or ceramic (3--7 x 10/-6//degreesC). The method of curing the polyimide precursor normally involves heating the whole structure to high temperatures, in the 250 to 400 degrees C range. Because Because the polyimide film is fairly rigid after curing, upon cooling the structure to room temperature the polyimide film is left in a state of high stress, which makes it prone to cracking upon subsequent processing.

An additional problem exists with the high temperature cure. In a technical bulletin (1) it is explained that high temperature aging of polyimides degrades their mechanical properties fairly quickly, particularly at high temperatures. Because multilevel structures are fabricated in a sequential manner, the first polyimide layers to be formed are subjected to several aging cycles that deteriorate their properties and that can lead to failure of the final structure. By avoiding high temperature curing, this problem can also be solved.

The present method of fabricating structures with polyimide films takes advantage of the fact that a large number of polyimide films are obtained from polyamic acid precursors, and that these precursors may be cured (i.e., the polyamic acid converted to polyimide) by means of a chemical technique that does not require subjecting the structure to elevated temperatures. This technique utilizes dehydrating agents such as acid anhydrides (e.g., acetic anhydride) and a catalyst such as tertiary amines (e.g., pyridine). This chemical technique for imidization of polyamic acids is...