Coating processes – Centrifugal force utilized
Reexamination Certificate
1996-05-22
2001-06-19
Edwards, Laura (Department: 1734)
Coating processes
Centrifugal force utilized
C427S294000, C427S377000, C427S425000, C118S050000, C118S052000, C118S056000, C118S603000, C118S610000, C118S319000, C118S320000, C118S500000
Reexamination Certificate
active
06248398
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor manufacturing process and, in particular, to a coater for dispensing an organic and/or inorganic material on a substrate in a controllable pressurized process chamber.
2. Description of the Related Art
In manufacturing a semiconductor device, a substrate, such as a wafer, is typically coated with an inorganic and/or organic material in a process step. Often, a wafer is coated with a photoresist. The wafer is first positioned in a coater, or specifically on a wafer chuck. A motor spins the wafer chuck and wafer while the photoresist is dispensed onto the center of the wafer. The spinning imparts an angular torque onto the photoresist, which forces the photoresist out in a radial direction, ultimately covering the wafer. This semiconductor manufacturing process step is generally known as “the spin-on photoresist step”. The photoresist coated wafer then may be removed from the coater and baked to form a photoresist layer on the wafer.
During the spin-on photoresist step, a solvent vapor is typically introduced into an area near the surface of the wafer in order to control the coating of the photoresist. As the photoresist moves radially from the center of the wafer, the photoresist tends to cure prematurely due to the evaporation of solvent in the photoresist. As the curing photoresist moves radially from the center of the wafer, a non-uniform surface is created. By introducing solvent vapor near the wafer during the spin-on step, this premature curing of the photoresist may be reduced. A flat plate may be positioned above the wafer forming a very small gap to trap the solvent fumes from the photoresist during the spinon step in order to minimize the rate at which the photoresist cures. However, the introduction of solvent vapors and a plate does not adequately solve the premature curing of photoresist and the resulting non-uniformly coated wafer surface.
Generally, the photoresist is deposited upon a preexisting varied wafer topology. The wafer may have undergone previous manufacturing process steps creating the varied wafer topology. A uniform planar photoresist region on a semiconductor device is important to offset the effects of varied wafer topology. Typically, semiconductor manufacturing process steps require a uniform planar region in order to have a uniform process. A uniform planarized photoresist surface or layer will reduce semiconductor device manufacturing defects and improve semiconductor reliability and cost.
The uniform planarization of a photoresist layer depends on many factors. One of these factors includes the pressure surrounding the formation of the photoresist layer on the wafer. The pressure surrounding the wafer substrate surface during the photoresist spin-on step affects the evaporation rate of the solvent in the photoresist and eventually the surface uniformity of the photoresist layer.
Another factor affecting photoresist planarization includes the chemical composition of the environment during the photoresist spin-on step. Ideally, a solvent vapor-rich and contaminant-free environment is desirable in the photoresist spin-on step. As discussed above, a solvent vapor-rich environment will reduce solvent evaporation from the photoresist. Also, contaminants from the surrounding air entering the coater should be eliminated. Chemical contaminants, such as n-butyl acetate fumes, from processes elsewhere in the manufacturing of a semiconductor reduce the adhesion of the photoresist to the wafer substrate and should be eliminated. Likewise, solid particles generated by operators or process equipment adjacent to the coater should not be allowed to enter the photoresist spin-on process step.
Coaters typically waste a large amount of photoresist during the photoresist spin-on step. As much as 97% of the photoresist may be spun off the surface of the wafer and eventually not directly used in forming the photoresist layer. The wasted photoresist may add significant costs to the production of a wafer containing semiconductor devices. In order to coat a wafer with photoresist, approximately $20 may be expended on only the photoresist. These costs are expected to rise as semiconductor device geometries are reduced in order to obtain faster operating speeds. Furthermore, there are added costs in properly disposing of the photoresist waste which may be considered hazardous waste.
Thus, it is desirable to provide a coater for dispensing organic and/or inorganic material, such as photoresist, onto a wafer substrate surface in a controlled environment. The controlled environment would enable forming uniformly planarized photoresist layers in a contaminant reduced environment, thereby reducing semiconductor manufacturing costs and defects while enhancing semiconductor reliability and performance. Further, it is desirable to have a coater which minimizes photoresist waste, thereby reducing costs in manufacturing semiconductor devices
SUMMARY OF THE INVENTION
In accordance with the present invention, a photoresist coater having a controllable process chamber is provided. The controllable process chamber enables the formation of a uniform planarized photoresist layer on a wafer in a predetermined pressure and chemical environment. The coater also includes a recycling apparatus for storing excess photoresist.
The photoresist coater includes a wafer chuck having a wafer chuck surface for positioning a wafer substrate to be coated with the photoresist. A spin motor is coupled to the wafer chuck and rotates the wafer chuck. A lower housing section having a first exhaust opening is coupled to the wafer chuck and an upper housing section is coupled to the lower housing section forming a process chamber surrounding the wafer chuck surface. A vacuum device is coupled to the lower housing section and creates back pressure in the process chamber through the first exhaust opening. A control device coupled to the lower housing controls the pressure in the process chamber.
According to another aspect of the present invention, the photoresist coater includes an upper housing section having a material dispensing opening and a lower housing section having an exhaust opening. The lower housing section is positionable to access the process chamber. The upper housing section also includes a cavity for containing solvent vapor and a plurality of cavity openings for introducing solvent vapor into the process chamber.
According to another aspect of the present invention, the lower housing section includes an opening for introducing nitrogen into the process chamber.
According to still another aspect of the present invention, the photoresist coater includes a photoresist recycling apparatus coupled to an exhaust tube for storing unused photoresist from the process chamber. The photoresist recycling apparatus includes a photoresist container coupled to a control device for sealing the photoresist container.
According to another aspect of the present invention, the photoresist recycling apparatus includes a collection tube having a baffle coupled to the exhaust tube. The collection tube is further coupled to a vacuum. Also, the collection tube is coupled to a reservoir for holding unused photoresist.
According to another aspect of the present invention, a process for forming a photoresist layer on a wafer substrate in a pressurized controllable process chamber is provided. The process comprises the steps of opening the process chamber and positioning the wafer substrate on a wafer chuck in the process chamber. The process chamber is then closed. The process chamber is then evacuated and the chamber value is set to a predetermined setting. The process chamber is pressurized with a solvent vapor. The photoresist is applied and the wafer chuck is spun, while nitrogen may be introduced. The chamber value is then opened.
REFERENCES:
patent: 5108792 (1992-04-01), Anderson et al.
patent: 5254367 (1993-10-01), Matsumura et al.
patent: 5362372 (1994-11-01), Tepman
patent: 5362526 (1994-11-01), Wang et al
Lurye Alex
Talieh Homayoun
Applied Materials Inc.
Edwards Laura
Stern Robert J.
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