Direct detection of dielectric etch system magnet driver and...

Details Direct detection of dielectric etch system magnet driver and... Direct detection of dielectric etch system magnet driver and...

2001-07-11

2004-05-11

Hassanzadeh, Parviz (Department: 1763)

Adhesive bonding and miscellaneous chemical manufacture

Differential fluid etching apparatus

With measuring, sensing, detection or process control means

C156S345460, C156S345490, C118S7230MR, C118S7230MA

Reexamination Certificate

active

06733617

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to magnet drivers, such as magnet drivers for dielectric etch systems, and particularly to the detection of malfunctions within such drivers.
BACKGROUND OF THE INVENTION
There are four basic operations in semiconductor processing, layering, patterning, doping, and heat treatments. Layering is the operation used to add thin layers to the surface of a semiconductor wafer. Patterning is the series of steps that results in the removal of selected portions of the layers added in layering. Doping is the process that puts specific amounts of dopants in the wafer surface through openings in the surface layers. Finally, heat treatments are the operations in which the wafer is heated and cooled to achieve specific results, where no additional material is added or removed from the wafer.
Of these four basic operations, patterning is typically the most critical. The patterning operation creates the surface parts of the devices that make up a circuit on the semiconductor wafer. The operation sets the critical dimensions of these devices. Errors during patterning can cause distorted or misplaced defects that result in changes in the electrical function of the device, as well as device defects.
The patterning process is also known by the terms photomasking, masking, photolithography, and microlithography. The process is a multi-step process similar to photography or stenciling. The required pattern is first formed in photomasks and transferred into the surface layers of the semiconductor wafer. This is shown by reference to
FIGS. 1A and 1B
. In
FIG. 1A
, the wafer
100
has an oxide layer
102
and a photoresist layer
104
. The wafer
100
itself may be referred to as the silicon or semiconductor substrate. The oxide layer
102
is a dielectric, which is a material that conducts no current when it has a voltage across it. Oxide, or more specifically silicon dioxide, is one type of dielectric, whereas another type is silicon nitride.
A mask
106
is precisely aligned over the wafer
100
, and the photoresist
104
is exposed, as indicated by the arrows
108
. This causes the exposure of the photoresist layer
104
, except for the part
110
that was masked by the part
112
of the mask
106
. In
FIG. 1B
, the unexposed part
110
of the photoresist layer
104
is removed, creating a hole
114
in the photoresist layer
104
.
Next, a second transfer takes place from the photoresist layer
104
into the oxide layer
102
. This is shown in
FIG. 1C
, where the hole
114
extends through both the photoresist layer
104
and the oxide layer
102
. The transfer occurs when etchants remove the portion of the wafer's top layer that is not covered by photoresist. The chemistry of photoresists is such that they do not dissolve, or dissolve very slowly, in the chemical etching solutions. Finally, the photoresist layer
104
is removed, as shown in
FIG. 1D
, such that only the wafer
100
and the oxide layer
102
with the hole
114
remains.
The removal of the photoresist layer can be accomplished by either wet or dry etching. Wet etching refers to the use of wet chemical processing to remove the photoresist. The chemicals are placed on the surface of the wafer, or the wafer itself is submerged in the chemicals. Dry etching refers to the use of plasma stripping, using a gas such as oxygen (O
2
), C
2
F
6
and O
2
, or another gas. Whereas wet etching is a low-temperature process, dry etching is typically a high-temperature process.
In one type of dry etching process, the wafer is placed within a chamber and is exposed to plasma. The plasma has its temperature modified by being subjected to electromagnetic fields. Precise control of the fields allows for proper stripping, or etching, of the dielectric from the semiconductor wafer. More specifically, plasma etching is performed by applying electrical and/or magnetic fields to a gas containing some chemically reactive element, like fluorine or chlorine. The plasma releases chemically reactive ions that can remove, or etch, materials very rapidly. It also gives the chemicals an electrical charge that directs them toward the wafer vertically.
FIG. 2
shows an example of a dielectric etch system
200
. The system
200
includes a chamber
202
surrounded by electromagnetic coils
204
,
206
,
208
, and
210
. Applying different currents at different times to various of the coils
204
,
206
,
208
, and
210
produces varying magnetic fields within the chamber
202
, providing for proper electric etching of the wafer placed inside the chamber
202
. The coils
204
,
206
,
208
, and
210
are also referred to as channels. Examples of dielectric etch systems include the eMxP+, the eMax, and others available from Applied Materials Taiwan (AMT), of Taiwan.
If the dielectric etch system fails, semiconductor wafers placed in the system chamber can be damaged. For example, too much or not enough dielectric may be removed, or some of the silicon substrate may also be removed. Typically, the edges of the wafer are damaged, as compared to other parts of the wafer. This reduces the number of semiconductor devices that can be delivered from the wafer. That is, the yield of the wafer may be reduced if the dielectric etch system fails.
As a result, most dielectric etch systems include a detector to detect when a malfunction or failure, where these terms are used synonymously herein, occurs. For example,
FIG. 3
shows driver circuitry
300
for the etch system
200
of
FIG. 2
which includes a current sensor
308
to detect malfunctions. A three-phase power supply
302
powers both drivers
304
and
306
, which are configured to send the correct amount of power to the coils
204
,
206
,
208
, and
210
, so that proper etching occurs within the chamber (not shown in FIG.
3
). The current sensor
308
measures the current being input directly into the drivers
304
and
306
, and therefore ideally detects indirectly whether one or more of the drivers
304
and
306
and the coils
204
,
206
,
208
, and
210
are malfunctioning.
The current sensor
308
detects malfunctions in the drivers
304
and
306
and/or the coils
204
,
206
,
208
, and
210
by, for a minimum magnetic field and a minimum current rise being generated. This means, however, that the sensor
308
is detecting failure in an indirect manner. Rather than the drivers
304
and
306
or the coils
204
,
206
,
208
, and
210
being directly monitored, they are indirectly monitored by measuring the current fed into the drivers
304
and
306
. As a result, the sensor
308
may detect catastrophic failure, where, for instance, all the coils
204
,
206
,
208
, and
210
fail, but may not detect less major failures, such as where only one of the coils
204
,
206
,
208
, and
210
malfunctioning. However, even one of the coils
204
,
206
,
208
, and
210
failing can damage semiconductor wafers in the manner that has been described.
The following table shows an example of the lack of failure detection of current detection technology, such as the current sensor
308
of FIG.
3
.
Minimum
Driver
One channel
Driver
Minimum
current
failure
failure
decay
field
rise
detected?
detected?
detected?
Setting
10 gauss
0.01 A
No
No
No
1
Setting
10 gauss
0.05 A
Yes
No
No
2
Setting
10 gauss
 0.1 A
Yes
Yes
No
3
The three rows of the table correspond to three different settings. Each setting has a minimum magnetic field of 10 gauss. The settings as to minimum current rise vary, where settings one, two, and three are set to 0.01 amps, 0.05 amps, and 0.1 amps, respectively. The driver failure detected column indicates whether, for a given setting, driver failure is detected by the current sensor
308
. The one channel failure detected column indicates whether, for a given setting, the failure of just one coil is detected by the sensor
308
. Finally, the driver decay detected column indicates whether, for a given setting, driver decay is detected by the sensor
308
. Driver decay can be, for instance, when the current out

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