The document discusses ion beam etching, which is a physical dry etching process. Ion beam etching works by ionizing an inert gas like argon to create a plasma of positive ions and electrons. The ions are accelerated towards the target material, physically removing atoms from the surface through sputtering. Ion beam etching is highly directional and provides precise etching with minimal damage to the substrate. It can etch all materials and is used for applications requiring long lifetimes and precise specifications, like microelectronics and sensors.

1. Ion-beam etching
B. OMKARESHWAR
MS16BTECH11004
DEPT. OF MSME
COURSE: THIN FILMS
INSTRUCTOR: DR. CHANDRASHEKAR M
1

2. Dry Etch Methods
 Dry Etching can be a physical or chemical process (or both)
 Ion Beam Etch - a physical etch process
 Gaseous chemical etch
 Plasma enhanced etch
 Reactive Ion Etch
 Deep Reactive Ion Etch
2

3. Physical Dry Etch
 Ion beam etching is similar to the ion beam milling process that is used for transmission
electron microscopy sample preparation. This is a physical process where ionized inert gas
ions (usually Ar) are used to remove material from the wafer. The process is not selective
but it is highly directional. The ion beam etching process.
 Sputtering (Ion Milling or Ion Beam Etch)
 Reduced pressure environment (<50 m Torr)
o Increases mean free path between molecules
 Fewer collisions between molecules
 Inert gas injected at low pressure is used as “milling” tool
 RF Plasma in chamber
 Energy transfer to gas molecules, creates a plasma of equal numbers of ions and molecules
 Positive ions bombard negatively charged target (wafer), removing molecules from the surface
3

4. Ion Milling
 Plasma etch has low selectivity
 Plasma etch tends to be anisotropic
 High RF levels can cause damage to the
wafer
4
Schematic of the ion beam etching process. Ar gas is introduced into the
vacuum chamber where they are ionized by bombarding with electrons. These
ions are then directed on to the wafer where they remove material by physical
bombardment. Adapted from Microchip fabrication - Peter vanZant.

5. Reactive Ion Etch
 In RIE, a combination of physical and
chemical etching occurs.
 In this case, both Ar and the chemical gas are
used
 Ar performs an ion milling physical etch and
the chemical etch proceeds as well.
 RIE has the advantages of the physical ion
milling etching and those of the dry chemical
etch.
 Anisotropic Profile
 Higher Etch Rate than either process
 Higher selectivity ratio than physical etch
 Smaller feature sizes possible
5

6. Dry Etch Parameters
 Factors Influencing Dry Etch Process
 Etch rate
- RF Power level
- Gas formula
- Etch Temperature
 Pressure
- Extremely high pressure results in an isotropic etch
- Low pressure with high energy can damage wafer
 Micro-loading
- Different etch rates across wafer surface
- Ashing can occur
 Post-etch corrosion
- Due to residual etchant left on wafer after final
rinse
- Using a non- chlorine based etchant such as
fluorine.eliminates the problem.
6

7. Ion Beam Source
 An Ion Source generates a broad Ion Beam directed at the substrate (or product to
be patterned). common broad beam source is the Kaufman (grid) type.
 Ions are generated in a discharge chamber where atoms of a gas (Argon).
 Electrons are emitted from a cathode filament and collected by the anode. A
magnetic field is used to contain the electrons and increase the probability of
ionization.
 The bombardment of electrons with gas atoms forms a plasma.
 A negatively biased grid is used to accelerate ions that pass through the grid to
form the ion beam.
7

8. Ion Beam Source(Conti.)
 After the accelerator grid, a Neutralizer filament is used to introduce electrons to
balance the positively charged ions.
 A vacuum of 10-6 Torr to 10-5 Torr is accomplished with a roughing pump and a
high vacuum molecular pump.
 The vacuum is required to produce the Ion Beam plasma as well as minimize
contamination to the substrate during the etching process.
 A pressure of 10-4 Torr is typical while the Gas is flowing to produce the Ion Beam.
8

9. Ion Beam Etch System Diagram 9

10.  Ions that impact the exposed material with sufficient energy will
dislodge atoms or molecules.
 The number of atoms etched by each ion is referred to as the
"Sputter Yield" This process also generates significant heat.
Ion Beam Etch
10
Photo Resist
Substrate

11. How ion beam Removing Surface
area
11

12.  Tilting of the substrate holder can be done between -
90°, the loading position, and up to about +65°. The
maximum angle depends on the chamber and
endpoint options.
 In figure the platen is shown in loading position and
at +45°.
 Indeed, tilt offers further control over the sidewall
profile as well as radial uniformity optimization.
 The substrate holder can rotate up to 20 rpm in order
to provide an axisymmetric etch rate profile.
 The substrate and platen shaft are cooled by a
dedicated chiller and helium is used as a conductive
medium to transfer heat during etching.
12Loading Positions

13. Applications
 Traditionally, ion beam etching has been applied to higher
value added devices, which require long operational lifetimes
as well as precise performance specifications.
 These devices include commercial disk drive products, military
and commercial communication components, microelectronic
circuits and sensor products for automotive, medical and
aerospace applications
13

14. Other methods of etching or cutting such as the chemical
process or laser simply do not deliver the same level of precision
that an ion beam etch can.
Furthermore, some materials such as Platinum cannot be
etched effectively using a chemical process
The Ion Beam Milling process comes as close as possible
to a universal etching solution.
14

15. Some benefits from IBM/IBE
Some benefits from IBM/IBE
 All materials can be etched including those that are not
plasma etched
 Sidewall shaping is possible through sample tilting
 Etch rate can be improved by adding chemically reactive gases
 Independent ion beam current and energy control
 Excellent run for high repeatability
 Excellent uniformity
 Wide process versatility
15

16. Conclusion
 Ion beam etching is clearly an enabling process technology for
precision micro devices and micro-circuitry.
 As demands for higher density continue, ion beam etching will
be the best option for offering quick and reliable prototyping
solutions as well as batch production.
 The trend is evident, high-density packaging is here, ion beam
etching provides the solution
16

17. Reference
 http://www.microfabnh.com/ion_beam_etch_technology.php
 https://plasma.oxinst.com/campaigns/technology/ion-beam-
etching/
 Puckett/Michel/Hughes, "Ion Beam Etching", Commonwealth
Scientific Corporation, Alexandria, VA 1991 back to article
 https://www.azom.com/article.aspx?ArticleID=7533
17

18. 18