Local etching apparatus

Details Local etching apparatus Local etching apparatus

1999-09-08

2001-10-16

Kunemund, Robert (Department: 1765)

Adhesive bonding and miscellaneous chemical manufacture

Differential fluid etching apparatus

With microwave gas energizing means

Reexamination Certificate

active

06302995

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a local etching apparatus and a local etching method for locally etching a protrusion on a surface of a wafer by radicals or locally etching a relatively thick portion of a wafer so as to make the distribution of thickness of the wafer uniform.
2. Description of the Related Art
FIG. 10
is a schematic sectional view of an example of a local etching apparatus of the related art.
This local etching apparatus is provided with a discharge tube
100
, a gas feed device
110
, a plasma generator
120
, and a stage
130
.
Due to this configuration, it is possible to feed gas from the gas feed device
110
to the discharge tube
100
, generate microwaves M from a microwave generator
121
of the plasma generator
120
to the inside of a waveguide
122
to cause plasma discharge of the gas in the discharge tube
100
, and spray the radicals G produced by the plasma discharge from a nozzle portion
101
of the discharge tube
100
on to a wafer W on the stage
130
.
By making the stage
130
move in the horizontal direction, a portion Wa relatively thicker than a defined thickness on the surface of the wafer W (hereinafter referred to as a “relatively thick portion”) is guided directly under the nozzle
101
where the radicals G are sprayed from the nozzle
101
to the relatively thick portion Wa to locally etch the relatively thick portion Wa. By locally etching the entire surface of the wafer W in this way, it is possible to make the distribution of the surface thickness of the wafer W uniform and flatten the surface of the wafer W as a whole.
The above local etching apparatus of the related art, however, had the following problems.
The depth of local etching of the wafer W by the radicals G depends on the temperature of the discharge tube
100
.
FIG. 11
is a graph depicting the correlation between the surface temperature of the discharge tube
100
and the etching depth.
As shown in
FIG. 11
, the etching depth by the radicals G increases with the rise of the surface temperature of the discharge tube
100
. When the surface temperature of the discharge tube
100
reaches a certain value T
0
, the etching depth at temperatures above the temperature T
0
becomes substantially constant.
At the time of ignition of the plasma discharge in the discharge tube
100
, the discharge tube
100
is cold. The temperature of the discharge tube
100
rises in time due to the heat of the plasma. Therefore, the etching depth of the wafer W by the radicals G will not stabilize until the surface temperature of the discharge tube
100
reaches temperature T
0
. Accordingly, if the etching work is commenced before the surface temperature of the discharge tube
100
reaches T
0
, the etching rate of the wafer W becomes unstable and it is not possible to flatten the wafer W to a high precision. In view of this, in the local etching apparatuses of the related art, it was necessary to allow for a long standby time for the surface temperature of the discharge tube
100
to reach T
0
. It was not possible to start the etching work during the standby period. As a result, the throughput of the flattening of the wafer W was low and the mass producibility was poor.
SUMMARY OF THE INVENTION
The present invention was made to solve the above problem and has as its object the provision of a local etching apparatus and local etching method improving the throughput of the local etching apparatus by preheating the discharge tube before ignition of the plasma discharge.
To achieve the above object, according to a first aspect of the present invention, there is provided a local etching apparatus comprising: a discharge tube with a spray port of a nozzle portion facing an object to be etched in a chamber; a plasma generator for causing plasma discharge of a predetermined gas in the discharge tube so as to produce radicals for locally etching a relatively thick portion present on a surface of the object to be etched; and a heater for heating the discharge tube to a predetermined temperature.
Due to this configuration, it is possible to use the heater to heat the discharge tube to a predetermined temperature, specifically to at least a temperature at which the etching depth of the object to be etched becomes substantially constant. Suitably thereafter, the plasma generator is used to cause plasma discharge of a predetermined gas in the discharge tube to produce radicals for locally etching a relatively thick portion present on the surface of the object to be etched. Further, by making the nozzle portion of the discharge tube move along the surface of the object to be etched, it is possible to locally etch a relatively thick portion present on the surface of the object to be etched by the radicals sprayed from the nozzle portion. In this way, since it is possible to preheat the discharge tube to at least a temperature at which the etching depth of the object to be etched becomes substantially constant, there is no need to wait to perform the local etching work until the discharge tube rises to a predetermined temperature by the heat due to the plasma discharge, such as with the local etching apparatus of the related art, and it is possible to immediately perform local etching at a stable etching depth by performing the local etching work.
Various heaters may be considered for heating the discharge tube, but giving a preferable example of a heater, according to an embodiment of the invention, the heater is provided with: a heating member surrounding the discharge tube and capable of raising the temperature in accordance with voltage applied thereto; and a voltage controller for controlling the voltage applied to the heating member. In particular, according to an embodiment of the invention, the heating member of the heater is a heating wire wound around the discharge tube. Further, as another preferable example of the heater, according to an embodiment of the invention, the heater is an optical heater which emits infrared rays or a laser beam to the discharge tube to heat the discharge tube. Further, as another example, according to an embodiment of the invention, the heater is provided with: a heating block arranged to surround the discharge tube in a state contacting the outer side of the discharge tube and has a fluid feed port and fluid exhaust port communicating with a fluid storage portion at the inside; and a fluid feeder for heating the fluid to a predetermined temperature and feeding it to the fluid storage portion of the heating block. In particular, according to an embodiment of the invention, the heating block of the heater is comprised of a thin tube wound around the discharge tube.
Note that it is possible to use various types of discharge tubes as the discharge tube for the local etching apparatus. Therefore, according to an embodiment of the invention, the discharge tube used is any one of an alumina discharge tube, an aluminum nitride discharge tube, a sapphire discharge tube, and a quartz discharge tube.
Note that the steps executed by the local etching apparatuses in their operation also stand as method inventions.
Therefore, according to a second aspect of the present invention, there is provided a local etching method comprising: a plasma generating step for causing plasma discharge of a predetermined gas in a discharge tube so as to produce radicals and spraying the radicals from a nozzle portion of the discharge tube; a local etching step for locally etching a relatively thick portion present on the surface of the object to be etched by the radicals sprayed from the nozzle portion while making the nozzle portion of the discharge tube move relatively along the surface of the object to be etched; and a heating step for heating the discharge tube at least to a time of start of plasma discharge of the plasma generating step to at least a temperature at which the etching depth of the object to be etched at the local etching step becomes substantially constant.
In the heating step, the discharge tube may be heated at least

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