Multi air-knife box and method of use

Details Multi air-knife box and method of use Multi air-knife box and method of use

1999-12-20

2001-09-04

Wilson, Pamela (Department: 3749)

Drying and gas or vapor contact with solids

Process

Gas or vapor contact with treated material

C034S508000, C034S207000, C034S210000, C034S216000, C034S217000, C034S232000, C034S236000, C034S241000, C228S223000, C228S020100

Reexamination Certificate

active

06282812

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to an apparatus for drying semiconductor components as part of their processing sequence.
2. Description of the Prior Art
In the field of high density interconnect technology, it is necessary to fabricate a multilayer structure on the substrate to connect integrated circuits to one another. To achieve a high wiring and packing density, many integrated circuit chips are physically and electrically connected to a single substrate commonly referred to as a multi-chip module (MCM). Typically, layers of a dielectric such as a polyimide separate metal power and ground planes in the substrate. Embedded in other dielectric layers are metal conductor lines with vias (holes) providing electrical connections between signal lines or to the metal power and ground planes. Adjacent layers are ordinarily formed so that the primary signal propagation directions are orthogonal to each other. Since the conductor features are typically narrow in width and thick in a vertical direction (in the range of 5 to 10 microns thick) and must be patterned with microlithography, it is important to produce patterned layers that are substantially flat and smooth (i.e., planar) to serve as the base for the next layer.
Surface mounted, high pin count integrated circuit packages have in the past been configured using Quad Flat Packs (QFP's) with various pin configurations. These packages have closely spaced leads for making electrical connections distributed along the four edges of the flat package. These packages have become limited by being confined to the edges of the flat package even though the pin to pin spacing is small. To address this limitation, a new package, a Ball Grid Array (BGA) is not so confined because the electrical contact points are distributed over the entire bottom surface of the package. More contact points can thus be located with greater spacing between the contact points than with the QFP's. These contacts are solder balls that facilitate flow soldering of the package onto a printed circuit board.
A Ball Grid Array (BGA) is an array of solderable balls placed on a chip carrier. The balls contact a printed circuit board in an array configuration where, after reflow, the balls connect the chip to the printed circuit board.
Interconnecting lines and vias are planarized by multiple coatings of a dielectric material such as polyimide which are used to achieve an acceptable degree of planarization. Application of multiple coatings of thick polyimide is time-consuming and creates high stress on the substrate.
Chemical solutions have been used extensively for the manufacture of semiconductor devices. Wet chemical processing baths have been used for cleaning semiconductor wafers, as well as for etching deposited films on these wafers. For example, the use of hydrogen peroxide (H
2
O
2
), containing solutions for cleaning silicon semiconductor wafers, is well known. In addition to wafer cleaning, hydrogen peroxide is utilized in combination with sulfuric acid for photoresist removal and in combination with phosphoric acid, sulfuric acid or ammonium hydroxide for selective titanium etching.
At most semiconductor fabrication facilities, liquid processing baths are used for a certain time period and then discarded. This practice not only results in high chemical costs, but it also leads to the generation of more waste than would be required. Environmentally, it is preferred to reduce such waste.
In more advanced manufacturing facilities, automated controllers are utilized to achieve some degree of chemical composition control. These controllers spike the bath with certain chemicals at predefined intervals and can also add one or more chemicals to the bath to make up for a drop in the bath liquid level. With the exception of liquid level sensors, no analytical instrumentation is employed to provide feedback for guiding the chemical composition adjustment process. Thus, departure from “normal” operating conditions is not detected, nor are appropriate corrective actions taken.
After semiconductor devices have been attached to a substrate, the substrate is cleaned to remove any remaining residue from the surface of the board. This process typically involves washing of the substrate in a solvent that is selected such that residue on the surface of the board is dissolved in the solvent after which the solvent is removed from the cleaning apparatus. This however results in a solvent that may contain chemicals that are harmful to the environment, which requires special treatment of the solvent solution. One of the methods that is used to prevent impurities in a solvent is to apply solid carbon dioxide (CO
2
) particles to the surface that needs to be cleaned. These particles, upon striking the surface that needs to be cleaned, sublimate in the process of which residue on the surface of the board is absorbed and removed from that surface. The use of CO
2
however does result in the build-up of an electrostatic charge on the surface of the board that is being cleaned. This electrostatic charge must either be prevented from building up or must be removed before the board is passed on to further processing steps. The former can be accomplished by grounding the board while it is being treated by the CO
2
, the latter can at least partially be accomplished by mixing the CO
2
with another substance, such as a water mist, that prevents or alleviates the accumulation of the electrostatic charge during the cleaning process.
Solvents that are used to clean semiconductor device packages must meet a number of requirements that relate to both the effectiveness of the cleaning operation and to the toxicity of the waste products that are produced during the cleaning operation. The by-products of the cleaning operation must not result in products that are contaminating, difficult to degrade, have a long retention period and have in any other way an undesirable impact on the environment in which they are deposited. For these reasons, chlorinated hydrocarbon and chlorofluorinated solvents have largely been abandoned even though these substances have excellent qualities as solvents of rosin flux and other by-products of solder operations. In recent years, terpene compounds appeared to offer an attractive alternative to the previous generation of solvents, this because terpene compounds offer significant advantages for the cleaning operation. It is for instance known that terpene compounds are widely available and are safe enough that they have seen use as a food additive. Terpene compounds are also readily biodegradable and can readily be handled be regular waste disposal facilities. Terpene compounds can be applied under room temperature; they are not volatile and have a boiling point that is considerably higher than halogenated solvents. Furthermore, terpene compounds can penetrate between densely mounted components and can therefore provide excellent cleaning of surfaces of high density. While the indicated advantages of terpene compounds are considerable, terpene compounds however have the disadvantage that they are flammable under relatively low temperatures (100 to 200 degrees F.) and that they readily solidify when brought into contact with water. Terpene compounds further have a profoundly objectionable odor while terpene compounds, because they are not volatile, must be rinsed away after application. This process of rinsing however can readily result in the gelling of the terpene compounds, which makes the process of removal of the terpene compounds cumbersome.
One of the more frequently used type of apparatus for cleaning printed circuit board using terpene compounds is manufactured by the Vitronics Corporation of Newmarket, N.H. U.S. Pat. Nos. 5,103,846 and 5,240,018 detail such an apparatus as marketed by the Vitronics Corporation. The apparatus of invention U.S. Pat. Nos. 5,103,846 and 5,240,018 includes three different components, a first housing that co

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