Salsa clean process

Details Salsa clean process Salsa clean process

2000-03-16

2002-01-22

Carrillo, Sharidan (Department: 1746)

Cleaning and liquid contact with solids

Processes

For metallic, siliceous, or calcareous basework, including...

C134S003000, C134S022170, C134S023000, C134S025100, C134S025400, C134S025500, C134S026000, C134S028000, C134S029000, C134S032000, C134S033000, C134S034000, C134S036000, C134S902000, C216S108000, C438S906000, C510S175000, C510S176000, C510S367000, C510S372000, C510S435000, C252S186280

Reexamination Certificate

active

06340395

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to integrated circuit manufacturing processes, and in particular to cleaning processes for photoresist coated silicon wafers.
BACKGROUND OF THE INVENTION
During the integrated circuit manufacturing process, lithography is employed repeatedly to form imaging masks on the surface of the wafer, from organic materials called photoresists (PR). Surface cleaning of the semiconductor wafer is required at different points in the process in order to remove or strip organic materials such as the photoresist from the surface, or in order to remove particulate contaminants which are on the surface. Various wet processes for such cleaning have been known in the art. Wet processes are generally simpler and more cost and time effective than dry plasma cleaning and stripping methods. A description of wafer cleaning procedures is found in
Silicon Processing for the VLSI Era
, S. Wolf and R. Tauber, Lattice Press, 1986, pp 516-520.
One of the best known of such wet cleaning methods is called the RCA clean. The RCA cleaning method is generally used just prior to a diffusion step to remove surface contaminants, where the wafers are in a nearly clean state, and any photoresist on the wafer had been previously stripped. This cleaning method comprises the steps of:
a) immersing the wafers in a sulfuric acid/hydrogen peroxide mixture (hereinafter referred to as Sulfuric Peroxide Mixture, or SPM),
b) rinsing in De-Ionized (DI) water,
c) then immersing the wafers in an ammonium hydroxide/hydrogen peroxide mixture (hereinafter referred to as Ammonium Peroxide Mixture, or APM) to remove residual organic contaminants,
d) DI water rinse,
e) immersing the wafers in hydrofluoric acid/water to remove the hydrous oxide film formed by the APM step,
f) immersing the wafers in hydrochloric acid/hydrogen peroxide/water to remove metallic or other contaminants,
g) DI water rinse,
h) nitrogen dry.
Removing or stripping thick organic layers, particularly photoresist which has been hardened or polymerized, is a difficult task. Some previous methods for stripping PR use acids to chemically degrade the organic material. Immersion of wafers in SPM to strip photoresist layers is described in U.S. Pat. No. 3,900,337 by Beck et al. Use of spray processor equipment to provide multiple cycles of SPM exposure and DI water rinse is described in U.S. Pat. No. 5,861,064 by Oikari et al. The use of spray processors is advantageous over immersion of wafers into cleaning baths, due to lowered contamination of the cleaning fluid.
None of the aforementioned cleaning methods has been consistently effective under a variety of conditions in removing thick photoresist layers (1.8 to 3.0 microns thick, e.g. for implant layer masking), because of high residual contaminant particle count.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide an improved integrated circuit manufacturing wet method for removing organic layers from the surface of semiconductor wafers.
It is a further object of this invention to provide an integrated circuit manufacturing wet method for removing organic layers from the surface of semiconductor wafers that leaves a low residual contaminant particle count and contributes to reduced defect densities.
It is a further object of this invention to provide an integrated circuit manufacturing wet method for removing organic layers from the surface of semiconductor wafers that leaves a low residual contaminant particle count for organic layer thicknesses up to 3.0 microns and higher.
It is a further object of this invention to provide an integrated circuit manufacturing wet method for removing organic layers from the surface of semiconductor wafers that utilizes spray processing apparatus and methods.
It is a further object of this invention to provide an integrated circuit manufacturing wet method for removing photoresist organic layers from the surface of semiconductor wafers that simultaneously strips thick hardened photoresist layers, and additionally provides low residual contaminant particle count on those portions of the wafer having photoresist thereon, and those having no photoresist thereon.
These objects are met by utilizing a novel cleaning sequence hereinafter known as SALSA which utilizes multiple cycles of SPM and APM treatments without drying between cycles, thereby preventing the redeposition of material removed during previous cycles and resulting in significantly reduced defect densities.


REFERENCES:
patent: 3900337 (1975-08-01), Beck et al.
patent: 3990462 (1976-11-01), Elftmann et al.
patent: 4609575 (1986-09-01), Burkman
patent: 4682615 (1987-07-01), Burkman et al.
patent: 5637151 (1997-06-01), Schulz
patent: 5679171 (1997-10-01), Sage et al.
patent: 5853491 (1998-12-01), Schulz
patent: 5861064 (1999-01-01), Oikari et al.
patent: 5896875 (1999-04-01), Yoneda
patent: 04142741 (1992-05-01), None

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