Cleaning and liquid contact with solids – Processes – For metallic – siliceous – or calcareous basework – including...
Reexamination Certificate
1999-12-20
2002-03-19
El-Arini, Zeinab (Department: 1746)
Cleaning and liquid contact with solids
Processes
For metallic, siliceous, or calcareous basework, including...
C134S003000, C134S006000, C134S026000, C134S030000, C134S032000, C134S902000, C015S077000
Reexamination Certificate
active
06358325
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to an apparatus and methods for using the same in the fabrication of an integrated circuit, and particularly an apparatus for performing both a cleaning process and a scrubbing process upon a semiconductor substrate utilizing one machine that integrates the cleaning and scrubbing processes in the fabrication of an integrated circuit situated on a semiconductor substrate.
2. The Relevant Technology
In the context of this document, the term “semiconductor substrate” is defined to mean any construction comprising semiconductive material, including but not limited to bulk semiconductive material such as a semiconductive wafer, either alone or in assemblies comprising other materials thereon, and semiconductive material layers, either alone or in assemblies comprising other materials. The term “substrate” refers to any supporting structure including but not limited to the semiconductor substrates described above.
Producing a substantially impurity free semiconductor substrate is an ongoing challenge during fabrication of operable integrated circuits and other microelectronic devices. During fabrication, several operations are completed with that require a thorough cleaning of the semiconductor substrate prior to any further processing.
Processes used to remove impurities from a semiconductor substrate include etching, cleaning, and scrubbing. A scrubber can be used after an abrasive operation such as a polishing process. Such abrasive operations can be mechanical or chemical mechanical. For example, after a chemical mechanical planarization (CMP) process has been completed, one or more contaminates can remain on a surface of a semiconductor substrate that was subjected to the CMP process. In this situation the contaminate is typically not completely removed with a wet-cleaning process alone. The extra cleaning power of a physical cleaner is needed. Scrubbers such as brush scrubbers are used to provide the needed physical cleaning action. The brush scrubber is not, however, used immediately after every CMP process. There are times when an intermediate cleaning step is utilized. One cleaning process that is regularly done prior to the scrubber cleaning process is some type of a cleaning process such as a wet-cleaning process.
A wet-cleaning process is particularly useful after semiconductor substrates have been processed on a polishing tool. A wet-cleaning process is needed between the CMP process and the scrubber because if the semiconductor substrates go from the polishers to the scrubbers, the scrubber tends to get loaded with polishing residuals. The polishing residuals are typically in the form of a slurry or abrasive media combined with particles from the portion of the semiconductor substrate that was removed by the polisher. A cleaning process such as a wet-clean process can remove a large portion of the polishing residue.
Current technology requires two separated work stations and machines for the cleaning process and the scrubber process. A semiconductor substrate must currently be loaded and unloaded for each of the two separated machines and be transferred therebetween. With each transfer of the semiconductor substrate between various machines used during fabrication, the possibility of contamination increases and with that, also the likelihood of lower process yield. As such, it would be advantageous to control the surface chemistry, the ambient humidity, the temperature, and the ambient particle contamination between the cleaning process and the scrubber process.
By way of example, a semiconductor substrate may have situated thereon a mixed interface of hydrophobic and hydrophilic material on a surface thereof. A batch of the semiconductor substrates is to be first processed in a wet cleaning machine and then processed in a scrubber machine that is proximally close yet separated from the wet cleaning machine. The separation of machines may, during transportation of the semiconductor substrates therebetween, cause some oxidizing or localized air drying of regions of hydrophobicity on the semiconductor substrates that can cause problems later on. Also, if the semiconductor substrates have a polishing residue thereon that, once dried will not scrub off, a nucleation site can develop that may later reduce fabrication yields and increase device failures. Extra precautionary measures are desirable in the fabrication process to try to reduce the potential contamination caused by the transfer of the semiconductor substrate between various separated machines. Such measures tend to reduce throughput.
Fabrication processes performed upon semiconductor substrates must be done in a tightly controlled environment, typically referred to as a clean room. Because of the closely controlled environment of a clean room and the expense and equipment required to maintain the conditions of the clean room, floor space is very valuable. At the same time, however, the increasing number of processes and innovations that require new or additional machines are competing for valuable space in the clean room.
As seen in
FIG. 5
, an exposed interface of silicon dioxide
54
and polysilicon
56
on a semiconductor substrate
50
was formed using a CMP machine. The CMP machine would leave slurry particles
55
as seen in
FIG. 5
upon the exposed interface. Semiconductor substrate
50
would then be moved to a different machine that would perform a scrubbing process upon semiconductor substrate
50
. The scrubbing process would remove slurry particles
55
as seen in
FIG. 5
, but would leave a cleaning solution droplets
62
,
64
as seen in
FIG. 7
upon the exposed interface. While cleaning solution droplets
64
are upon the hydrophobic polysilicon
60
and tend to bead up due to high surface tension, cleaning solution droplets
62
are upon the hydrophilic silicon dioxide
58
and tend to spread out due to the lower surface tension.
After the scrubbing machine, semiconductor substrate
50
would again be moved to a spin-dry machine, separate from the scrubbing machine, that would perform a drying process. The drying machine spins whiling drying semiconductor substrate
50
. This process typically leaves water spots on the hydrophobic exposed surface of polysilicon
58
. These water spots result in an oxidation of the polysilicon, leaving oxide
61
. Oxide
61
causes problems in later processing, where an electrically conductive material is deposited over polysilicon
58
upon oxide
61
. The oxidized portion
61
of polysilicon
58
causes an increase in resistivity between polysilicon
58
and the electrically conductive material thereover, leading to improper device performance and other defect-related reduction in performance characteristics.
Alternately, prior art processes have also oxidized an exposed surface of polysilicon of an exposed interface of silicon dioxide and polysilicon before the semiconductor substrate was dry or otherwise subjected to a drying process. The oxidation of the exposed polysilicon occurred either during the brush scrubbing process or could also occur even before the brush scrubbing process. Thereafter, the oxidized portion of the exposed polysilicon surface would be removed in a high-pH solution, such a solution of ammonium hydroxide and peroxide. This oxide removal process tended to also etch the polysilicon while still leaving a thin oxide on the polysilicon. Next, the wafer was dried in a spin rinse and dry process in which the oxide layer still remained and had not yet been removed. Consequently, a still further hydrofluoric acid etchant would be needed to remove the oxidation from the polysilicon.
As noted above, prior art processes moved the semiconductor wafer across distanced between multiple tools. Tools that integrated various processes have been suggested nor taught the combined tools of brush scrubbing with spin rinse drying. This present state of the art in such an integrated tool is known to cause water spots on hydrophobic surfaces such as polysilicon, and thus
El-Arini Zeinab
Micro)n Technology, Inc.
Workman & Nydegger & Seeley
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