Fill material for dual damascene processes

Details Fill material for dual damascene processes Fill material for dual damascene processes

2001-08-16

2002-05-21

Jones, Deborah (Department: 1775)

Stock material or miscellaneous articles

All metal or with adjacent metals

Composite; i.e., plural, adjacent, spatially distinct metal...

Reexamination Certificate

active

06391472

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is broadly concerned with fill compositions and methods useful for protecting the surfaces forming the contact and via holes during dual damascene processes for the production of integrated circuits. More particularly, the compositions of the invention comprise a quantity of solid cross-linkable components including a polymer binder, and a solvent system for the solid components. The boiling point of the solvent system is preferably sufficiently lower than the cross-linking temperature of the composition so that essentially all of the solvent system is evaporated during the first stage bake without the fill composition being cross-linked to any appreciable degree. In use, the fill compositions are applied to a substrate previously patterned with contact or via hole according to conventional methods followed by heating the composition to its reflow temperature in order to evaporate the solvent system and cause the composition to flow into the hole for uniform coverage. The composition is then cured and the remainder of the dual damascene process carried out in the usual fashion.
2. Description of the Prior Art
The damascene process, or the process of forming inlaid metal patterning in preformed grooves, is generally a preferred method of fabricating interconnections for integrated circuits. In its simplest form, the dual damascene process starts with an insulating layer which is first formed on a substrate and then planarized. Horizontal trenches and vertical holes (i.e., the contact and via holes) are then etched into the insulating layer corresponding to the required metal line pattern and hole locations, respectively, that will descend down through the insulating layer to the device regions (if through the first insulating layer, i.e., a contact hole) or to the next metal layer down (if through an upper insulating layer in the substrate structure, i.e., a via hole). Metal is next deposited over the substrate thereby filling the trenches and the holes, and thus forming the metal lines and the interconnect holes simultaneously. As a final step, the resulting surface is planarized using the known chemical-mechanical polish (CMP) technique, and readied to accept another dual damascene structure.
During the dual damascene process, the contact and via holes are typically etched to completion prior to the trench etching. Thus, the step of trench etching exposes the bottom and sidewalls (which are formed of the insulating or dielectric layer) of the contact or via holes to over-etch which can deteriorate the contact with the base layer. An organic material is therefore used to partially or completely fill the via or contact holes and to protect the bottom and sidewalls from further etch attack. These organic fill materials can also serve as a bottom anti-reflective coating (BARC) to reduce or eliminate pattern degradation and linewidth variation in the patterning of the trench layer, provided the fill material covers the surface of the dielectric layer.
Fill materials have been used for the past several years which have high optical density at the typical exposure wavelengths. However, these prior art materials have limited fill properties. For example, when the prior art compositions are applied to the via or contact holes formed within the substrate and to the substrate surface, the films formed by the compositions tend to be quite thin on the substrate surface immediately adjacent the holes, thus leading to undesirable light reflection during subsequent exposure steps. Also, because the prior art compositions etch more slowly than the dielectric layer, the unetched fill compositions provide a wall on which the etch polymer will deposit. This etch polymer build-up then creates undesirable resistance within the metal interconnects of the final circuit. These problems are explained in more detail below.
There is a need in the art for contact or via hole fill materials which provide complete coverage at the top of via and contact holes. Furthermore, this material should provide adequate protection to the base of the via and contact holes during etching to prevent degradation of the barrier layer and damage to the underlying metal conductors. In order to prevent sidewall polymer buildup, the etch rate of the material should be equal to or greater than the etch rate of the dielectric material, or the contact or via holes should be filled partially so that the fill material in the holes does not extend above the base of the trench following trench etch.
SUMMARY OF THE INVENTION
The instant invention overcomes the problems in the art by providing a fill material or composition which can be applied to via and/or contact holes during damascene processing to provide complete surface coverage while avoiding undue buildup of the etch polymer around the top edge of the holes at the base of the trench of the damascene structure.
In more detail, the compositions (fill material and fill composition are used interchangeably herein) of the invention comprise a quantity of solid components including a polymer binder or resin, and a solvent system (either single or multiple solvents) for the solid components. The inventive compositions are superior to prior art compositions in that they are formulated to achieve two requirements: the inventive composition will freely and evenly flow into the contact or via holes with minimal or no cross-linking of the composition during the pre-bake stage (i.e., first stage bake); and during the pre-bake stage essentially all of the solvent is evaporated so that the composition incurs very little shrinkage during the final bake stage. These two requirements are quantified by subjecting the composition to the “pre-bake thermal stability test” and the “film shrinkage test” set forth in detail below.
There are numerous factors which affect the ability of the fill composition to meet the foregoing requirements. For example, the polymer binder or resin preferably comprises an aliphatic backbone and has a molecular weight of less than about 80,000, preferably less than about 25,000, and more preferably from about 2000-7500. Suitable polymer binders include polyesters, polyacrylates, polyheterocyclics, polyetherketones, polyhydroxystyrene, polycarbonates, polyepichlorohydrin, polyvinyl alcohol, oligomeric resins (such as crown ethers, cyclodextrins, epoxy resins), and mixtures of the foregoing. The solvent systems utilized in the composition of the invention preferably have a boiling point of less than about 160° C., more preferably less than about 140° C., and most preferably less than about 120° C. The solvent system should also have a flash point of greater than about 85° C., and more preferably greater than about 100° C. When more than one solvent is utilized in the solvent system, the boiling point or flash point of the solvent system refers to the boiling point or flash point of the highest boiling or lowest flashing solvent. It is also important that the solvent system be compatible with the resist system chosen for the particular damascene process. That is to say, an air-dried film of the fill composition should redissolve in the chosen resist solvent system within 30 seconds with essentially no undissolved residue being visible in the solution.
The concentrations of the solvent system and other volatile species present in the composition is not critical, so long as the total concentration of the solvent system and volatile species in the film just prior to cross-linking of the film (i.e., just prior to the second stage bake) is less than about 5% by weight, and preferably less than about 2% by weight, based upon the total weight of the fill composition taken as 100% by weight. This solvent system and volatile weight percent in combination with the above solvent system boiling and flash points is important to ensure that minimal shrinking of the composition occurs during the second stage bake. Preferred solvents for use in the solvent system include alcohols, ethers, glycol ethers, amides,

Affiliated with

Also associated with

Rating

Fill material for dual damascene processes does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Fill material for dual damascene processes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fill material for dual damascene processes will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2915101