Low temperature via fill using liquid phase transport

Details Low temperature via fill using liquid phase transport Low temperature via fill using liquid phase transport

1998-01-20

2001-01-23

Bowers, Charles (Department: 2813)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S660000, C438S926000

Reexamination Certificate

active

06177348

ABSTRACT:

FIELD OF THE INVENTION
This invention is directed toward semiconductor device manufacturing in general, and more specifically to structures and methods of filling vias such that the vias are substantially free of non-conformities.
BACKGROUND
Advanced integrated circuit technology continues to create new challenges as components and architecture are reduced in size. Communication between different levels deposited on a substrate has become more complex since the size of the features, typically vias, connecting the different levels has changed in size and shape, especially the aspect ratio. By via it is meant an area created by either etching away a portion of a layer so that a ‘hole’ is created or an area created by the deposition of raised portions that define the walls of the area. For the remainder of the discussion, a feature will be referred to as a via.
The aspect ratio of a via is a measure of the height (H) compared to the width (W). If a via is wide and shallow, the aspect ratio is less than 1, H/W<1. If a via is narrow and deep then the aspect ratio will be greater than 1, H/W>1.
After a via is created it usually is filled with a material. Filling a via with an H/W<1 is well understood in the art and can be efficiently done with known techniques. However, filling a via with an H/W>1 still presents a challenge. As shown in
FIG. 1
, when the aspect ratio is greater than 1, the via,
1
, has the shape of a rectangle with the length of the bottom of the rectangle (W),
2
, at most equal to the length of the sidewalls (H),
3
. Current via filling techniques must be followed with precision to fill vias with an aspect ratio approaching 1. There is little margin for error when filling high aspect ratio vias where the ratio is greater than 1. As the value of H/W increases even the most precise methods might not produce reliably filled vias. As shown in
FIG. 2
, the shape of void portion,
5
, of a via,
1
, may, for example, be tear-shaped. The two side portions covering the walls of the via,
5
a
and
5
b
, may, for example, be in the shape of the tear, where one side of the void area,
5
, is open at the surface,
5
c
. The two side portion covering the walls of the via,
5
a
and
5
b
, may or may not be perpendicular to the bottom of the via and also may or may not be in contact with each other. When the tops of the two side portions,
5
a
and
5
b
are in contact with each other “pinchoff” is said to have occurred.
Current methods of filling high aspect ratio vias involve deposition techniques like high temperature sputtering, chemical vapor deposition (CVD) and forceful. Most, if not all, of these techniques fill vias in such a way that it is requires either a high temperature or expensive methods.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a low temperature method of filling voids.
It is also an object of the present invention to provide a method of reliably filling high aspect ratio features.
It is a further object of the present invention to provide a low temperature method of filling voids in vias where a sacrificial layer of a second metal is deposited.
In accordance with the above listed and other objects, we disclose and claim a method for depositing materials on a surface, comprising:
a) obtaining a surface having at least feature thereon, the surface and the feature having a layer of first material deposited thereon, the first material not filling substantially all of the feature;
b) depositing a layer of a second material on the first material, wherein the melting point of the second material is less than that of the first material, and wherein the first material is soluble in the second material at a temperature less than the melting point of the first material;
c) heating the surface to a first temperature of at least equal to the melting point of the second material and at most equal to the melting point of the first material, wherein substantially all of the feature is filled with the first material.


REFERENCES:
patent: 5308794 (1994-05-01), Tu
patent: 5843842 (1998-12-01), Lee

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