Cleaning and liquid contact with solids – Processes – Hollow work – internal surface treatment
Reexamination Certificate
2003-09-02
2004-11-30
Carrillo, Sharidan (Department: 1746)
Cleaning and liquid contact with solids
Processes
Hollow work, internal surface treatment
C134S022120, C134S022180, C134S023000, C134S032000, C134S033000, C134S034000, C134S036000, C134S042000, C134S061000, C134S094100, C134S099100, C134S149000, C134S153000, C134S158000, C134S902000
Reexamination Certificate
active
06823876
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to a method of cleaning and maintenance used for a rotational etching tool, and more particularly to a method combining a PM (preventive maintenance) computer program to clean the rotational etching tool automatically and rapidly.
2. Description of the Related Art
The machines of manufacturing the semiconductors, in the form of so-called wafer (disk-shaped article based on silicon) require preventive maintenance (PM). For example, the maintenance of rotational etching tool, for treating one wafer in each case with at least two media and with a carrier to hold the wafer, has been performed with the hands by ejecting deionized (DI) water from a DI gun. However, the steps of PM, such as mechanical disassembly before DI water ejection, are usually complicated and time-consuming.
Recently, the most commercial successful rotational etching tools are provided by SEZ Semiconductor-Equipment Zubehor furdie Habbleiterfertigung (Villach, AT). The related mechanical structure and function in details have been disclosed in U.S. patents, such as U.S. Pat. No. 4,903,717, U.S. Pat. No. 6,536,454 and U.S. Pat. No. 6,383,331. The etching may be of a dry type (etched by gases) or wet type (etched by chemical liquids).
FIG. 1
illustrates a sectional view of a rotational etching tool. There are several etching chambers, a cleaning chamber
104
, and a wafer supporting means such as chuck
112
in the process room
102
. Those etching chambers situated below the cleaning chamber
104
are the first etching chamber
106
, the second etching chamber
108
and the third etching chamber
109
(from the top down). The chuck
112
is used for holding the wafer
116
by the lateral guiding elements (often also called pins)
114
, projected from the top surface
112
a
of the chuck
112
. The lateral guiding elements
114
are guided excentrically and grip the wafer
116
along its periphery in the operational position. The wafer
116
is held aligned parallel to the top surface
112
a
of the chuck
112
. Here holding wafer can be done using a vacuum or the wafer
116
floats on an air cushion and is prevented from sliding off sideways by lateral guiding elements
114
. The lack of physical contact between the rest of the wafer
116
with the top surface
112
a
of the chuck
112
helps to prevent damage to the wafer during treatment.
The chuck
112
may further has a gas supply channel (not shown). A gas, supplied through the channel and existing between the wafer
116
and chuck
112
, is jetted against the guiding elements
114
and the adjacent portion of the lower surface of the wafer
116
. In this way, the passage of etching fluid to the underside of the wafer
116
can be prevented, especially the undesirable etched potions in the region of the guiding elements
114
(so-called pin mark). Also, the chuck
112
is connected to a shaft
118
within an elevated part
120
, so that the chuck
112
can be rotated on the shaft
118
, and moved back and forth between the cleaning chamber
104
and the etching chambers (
106
,
108
and
109
) in the direction of the arrow F.
In wet-etching process, the treatment liquid (such as etching liquid and rinse water) and gas (such as N
2
and isopropyl alcohol (IPA)) are stored in the liquid tanks and gas tanks, respectively. The treatment fluid (liquid and gas) can be transported via the medium conduit to the conduit terminate, such as medium nozzle. The medium nozzles positioned at a distance from the wafer will discharge the media according to the stage requirement of etching process. Also, each etching chamber is connected to the associated etching liquid tank via a conduit, for recycle of etching liquid. The cleaning chamber is connected to a discharge conduit to drain the deionized water after rinse.
As shown in
FIG. 1
, the first etching liquid
136
, the second etching liquid
138
and the third etching liquid
139
are stored in the first etching liquid tank
126
, the second etching liquid tank
128
and the third etching liquid tank
129
, respectively; also, are transported via the first conduit
146
, the second conduit
148
and the third conduit
149
to the first medium nozzle
156
, the second medium nozzle
158
and third medium nozzle
159
, respectively. Preferably, those medium nozzles (
156
,
158
and
159
) are positioned in a joint aperture, such as a medium dispenser
160
, to maintain the relative distance between the chuck
112
and nozzles. The DI water nozzle and N
2
nozzle are also positioned above the wafer
116
to eject DI water and N
2
as required. Furthermore, the first etching chamber
106
, the second etching chamber
108
and the third etching chamber
109
are connected to the first etching liquid tank
126
, the second etching liquid tank
128
and the third etching liquid tank
129
, respectively. Each conduit leads to a three-way valve (not shown). By appropriate setting the valves, etching liquid withdrawn from the etching chamber can either be recycled into the etching liquid tank, or drained through the discharge conduit.
General steps of wet-etching process are described as follows:
(a) Wafer
116
over the chuck
112
is rotated around its axis at a certain speed, and the surface of the wafer
116
is then wetted with a liquid, for example, deionized water.
(b) The chuck
112
is moved to the position associated with the appropriate etching chamber. For example, the chuck
112
is moved downward to the first etching chamber
106
if the first etching liquid
126
is required to use. Then, the etching liquid is applied to the wetted surface of the wafer
116
.
(c) The surface of the wafer
116
is washed with a non-etching liquid (such as deionized water), and dried with a volatile gas (such as N
2
).
The etching liquid comprises at least one of following acids: hydrofluoric acid, nitric acid, phosphoric acid and sulfuric acid. In semiconductor manufacturing, it is known that a silicon dioxide layer can be etched with aqueous hydrofluoric acid, water-soluble hexafluorosilicic acid (H
2
SiF
6
) being formed. Addition of ammonium fluoride to hydrofluoric acid is also known, and this etching liquid is so-called as “BHF” (buffered hydrogen fluoride) or “BOE” (buffered oxide etch). After the etching process is conducted for several times, it is required to do the cleaning and maintenance job for the interior of etching tool, especially “BOE” being applied as one of etching liquids. When BOE is applied to the surface of the spinning wafer
116
, it is thrown off and adheres to the walls of the etching chamber, and turns into the form of crystal-powder after drying. Those BOE powders (numeral
170
) accumulated in etching chamber will contaminate the wafer; thus, it requires a regular cleaning and maintenance to remove those BOE powders.
FIG. 2
is a block diagram of a conventional PM (Preventive Maintenance) process for rotational etching tool. The conventional PM process comprises the steps of:
(1) Preparation for maintenance—the maintenance crew need to wear chemical splash goggles, a chemical resistant apron or garment, and chemical resistant gloves; also, cleanroom wipers, cotton wraps and IPA (isopropyl alcohol) should be ready to use.
(2) Disassembly of etching tool hardware—the medium dispenser
160
is detached first, and then the chuck
112
is removed from the process room
102
.
(3) Clean and wipe—the walls and edges of etching chambers are cleaned by DI water using DI gun (held by man), and then dried by cleanroom wipers.
(4) Reassembly of etching tool hardware and test—the chuck
112
and the medium dispenser
160
are put back, and then the chuck movement is checked to make sure it works well.
(5) Wipe with IPA—the chuck
112
, the medium dispenser
160
and the accessory around are wiped with IPA.
(6) flush conduits (pipes), comprising steps of:
(a) refilling DI water in etching liquid tank and flushing the conduits with DI water;
(b) refilling etching liquid in etching liquid tank and flushing the conduits with etc
Chang Ming-Hsien
Chang Yuan-Hsun
Lin Chung-Ping
Liu Tzu-Hao
Carrillo Sharidan
Macronix International Co. Ltd.
Thomas Kayden Horstemeyer & Risley
LandOfFree
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