United States Patent im
Avanzino et al.
 COMPOSITE INSULATION WITH A
DIELECTRIC CONSTANT OF LESS THAN 3
IN A NARROW SPACE SEPARATING
175] Inventors: Steven Avanzino, Cupertino; Darrell M. Erb. Los Altos; Robin Cheung, Cupertino; Rich Klein, Mountain View, all of Calif.
 Assignee: Advanced Micro Devices, Inc., Sunnyvale, Calif.
 Appl. No.: 481,030
 Filed: Jun. 7,1995
 Int CL6 H01L 23/485; H01L 23/52
 U.S. CI 257/758; 257/752; 257/642;
 Field of Search 257/758,642,
 References Cited
U.S. PATENT DOCUMENTS
5,004,704 4/1991 Maedaetal 432/195
5,124,014 6/1992 Fooetal 204/5
5^75,977 1/1994 Otsubo et al 437/235
5,278,103 1/1994 MallonetaJ 437/240
5,432,128 7/1995 Tsu 437/194
5,451,804 9/1995 Luretal 257/758
5,530,293 6/1996 Coheaetal 257/5
5,566,045 10/1996 Summerfelt et a] 437/52
US005691573A [ii] Patent Number: 5,691,573  Date of Patent: Nov. 25, 1997
Primary Examiner—Tom Thomas
Assistant Examiner—Alexander Oscar Williams
Attorney Agent, or Firm—Foley & Lardner
A method of forming low dielectric insulation between those pairs of conductive lines, of a level of interconnection for integrated circuits, having a gap of about 0.5 microns or less by depositing a nonconformal source with a poor step function for the insulating material, such as silane (SiH4) as the silicon (Si) source for silicon dioxide (SiO^), so as to create, in the gap, a large void whose dielectric constant is slightly greater than 1. After all of the conductive lines have received a deposit of conformal insulating material and a flowable insulating material, the composite insulating materials are removed, preferably by etching, from those pairs of conductive lines with a gap of about 0.5 microns or less. Now, a nonconformal insulating material with a poor step function is deposited and creates a large void in the open gaps of 0.5 microns or less. After creating the void, the deposition continues and is planarized at the desired composite thickness of insulation. Alternatively, a thin conformal insulating layer is first deposited as a liner on the conductive lines. The resulting structure of the interconnection level comprises a layer of insulation between and on the conductive lines with the dielectric constant of the insulation between the pairs of conductive lines with the gap of 0.5 or less being, in combination with the void, at least about 3 or lower, and all of the remaining gaps are filled with the flowable insulating material and are void free with a composite dielectric constant of greater than about 3.5.
14 Claims, 4 Drawing Sheets