High throughput dual ion beam deposition apparatus

Details High throughput dual ion beam deposition apparatus High throughput dual ion beam deposition apparatus

2002-10-31

2004-08-31

McDonald, Rodney G. (Department: 1753)

Chemistry: electrical and wave energy

Processes and products

Coating, forming or etching by sputtering

C204S298040, C250S42300F, C250S42300F, C315S111510, C315S111810

Reexamination Certificate

active

06783637

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to an apparatus for the deposition of thin films, and, more particularly, the present invention relates to an apparatus for depositing a multilayered material from a sputtering target.
BACKGROUND OF THE INVENTION
Memory devices are an extremely important component in electronic systems. The three most important commercial high-density memory technologies are SRAM, DRAM, and FLASH. Each of these memory devices uses an electronic charge to store information and each has its own advantages. SRAM has fast read and write speeds, but it is volatile and requires large cell area. DRAM has high density, but it is also volatile and requires a refresh of the storage capacitor every few milliseconds. This requirement increases the complexity of the control electronics.
FLASH is the major nonvolatile memory device in use today. Typical non-volatile memory devices use charges trapped in a floating oxide layer to store information. Drawbacks to FLASH include high voltage requirements and slow program and erase times. Also, FLASH memory has a poor write endurance of 10
4
-10
6
cycles before memory failure. In addition, to maintain reasonable data retention, the thickness of the gate oxide has to stay above the threshold that allows electron tunneling, thus restricting FLASH's scaling trends.
To overcome these shortcomings, magnetic memory devices are being evaluated. One such device is magnetoresistive random access memory (hereinafter referred to as “MRAM”). MRAM has the potential to have speed performance similar to DRAM. To be commercially viable, however, MRAM must have comparable memory density to current memory technologies, be scalable for future generations, operate at low voltages, have low power consumption, and have competitive read/write speeds.
MRAM devices are typically fabricated using sputtering deposition systems, such as physical vapor deposition (hereinafter referred to as “PVD”) systems or ion beam deposition (hereinafter referred to as “IBD”) systems. Such sputter-deposition systems create electromagnetic fields in an evacuated chamber into which an inert, ionizable gas, such as argon, is introduced.
Turn now to
FIG. 1
which illustrates a prior art ion beam deposition apparatus
203
. Ion beam deposition apparatus
203
includes a vacuum chamber
210
. A substrate stage
212
is positioned therein vacuum chamber
210
and a substrate
214
is positioned on substrate stage
212
. Substrate
214
can include, for example, a silicon wafer or a similar supporting substrate.
A target holder
250
is positioned within vacuum chamber
210
. Target holder
250
is capable of holding at least one holding member, such as a sputtering target. In this example, target holder
250
holds a target
258
with a surface
233
, a target
262
, a target
294
, a target
295
, and a target
296
, wherein target
258
is initially positioned in a desired sputtering position
259
facing an ion beam source
238
. Further, target holder
250
is rotatable about an individual axis
221
, as will be discussed presently. Ion beam deposition apparatus
203
typically includes an assist ion beam source
297
to clean substrate
214
and subsequent layers grown thereon.
Ion beam source
238
directs a flux of ions
241
at target holder
250
. It is well known by those skilled in the art that when a flux of ions strike a sputtering target, material from the sputtering target is sputtered through a continuous range of angles relative to the sputtering target. Atoms from the ion beam are also scattered from the target into a continuous range of angles. For example, when flux of ions
241
strikes the target in position
259
, material from the target in position
259
is substantially sputtered in a direction
222
, a direction
234
, a direction
216
, and a direction
219
. Ions and atoms from the beam are also scattered with significant energy into those angles. Further, a stray beam from ion flux
241
is substantially directed in a direction
281
. The material generally sputtered in direction
216
will be incident on substrate
214
, as desired, to grow a material film thereon. Further, the atoms generally sputtered and scattered in directions
222
,
219
, and
234
and the stray beam in direction
281
can cause significant contamination within chamber
210
and on substrate
214
by resputtering material from the chamber walls or fixtures. Thus, it is desirable to shield the chamber walls and other regions where contamination may be generated to prevent this resputtered material from reaching substrate
214
.
For example, the material sputtered and scattered in direction
219
typically sputters chamber
210
in a region
255
and causes a contamination flux
256
. The material sputtered and scattered in direction
219
is generally sputtered at an angle, &thgr;′, relative to a reference line
268
oriented parallel to surface
233
of desired sputtering position
259
. It will be understood that angle, &thgr;′, is typically within a range from 30° to 45°. In the prior art, a baffle
227
is sometimes positioned near region
255
on chamber
210
to shield contamination flux
256
. Contamination flux
256
is generally sputtered along a reference line
270
which is not incident to substrate
214
and causes minimal contamination problems.
However, material sputtered in direction
222
typically sputters chamber
210
in a region
224
and causes a contamination flux
226
which is sputtered toward substrate
214
along a reference line
269
. The material sputtered and scattered in direction
222
is generally called a forward scattered flux and is sputtered at a shallow angle, &thgr;, relative to reference line
268
. It will be understood that shallow angle, &thgr;, is typically within a range given approximately from 0° to 20°. This forward scattered flux is of particular concern since it typically contains most energetic atoms. Contamination flux
226
is typically sputtered such that baffle
227
is insufficient to shield substrate
214
.
The stray beam in direction
281
from ion flux
241
typically sputters chamber
210
in a region
284
and causes a contamination flux
282
which is sputtered toward substrate
214
along a reference line
283
. The stray beam in direction
281
is generally a small flux of ions in a tail of the ion beam that misses the target and hits chamber
210
behind the targets in region
284
. This stray beam will sputter material from the wall, some of which will deposit with the growing film and result in contamination.
To illustrate a method of operation for apparatus
203
, consider the following example. Assume that it is desired to deposit a material layer
211
on substrate
214
, a material layer
213
on material layer
211
, a material layer
215
on material layer
213
, and a material layer
217
on material layer
215
as illustrated in FIG.
1
. Further assume that material layer
211
includes material sputtered from target
258
, material layer
213
includes material sputtered from target
262
, material layer
215
includes material sputtered from target
295
, and material layer
217
includes material sputtered from target
296
.
Initially, target
258
is positioned in desired sputtering position
259
. To deposit material layer
211
, ion beam source
238
is turned on. After material layer
211
is deposited, ion beam source
238
is turned off and target
262
is rotated into desired sputtering position
259
. Ion source
238
is turned on to deposit material layer
213
. After layer
213
is deposited, ion beam source
238
is turned off and target
295
is rotated to desired sputtering position
259
.
Ion source
238
is turned on to deposit material layer
215
. After layer
215
is deposited, ion beam source
238
is turned off and target
296
is rotated to desired sputtering position
259
to deposit material layer
217
. It is well know by those skilled in the art that a time for rotation for target holder
250
is approximately 5 seconds to 10 seconds per targe

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