Specific Process Knowledge/Characterization/SEM: Scanning Electron Microscopy

Etching using the dry etch technique RIE (Reactive Ion Etch)

File:Cluster1.jpg

RIE1 (part of Cluster1) - positioned in cleanroom2

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RIE2 (part of Cluster2)- positioned in cleanroom3

At Danchip we have three RIE's. Two (RIE1 and RIE2) for etching silicon based materials, resist and polymers (mainly RIE2) and one (III-V RIE) for etching III-V materials. Here only RIE1 and RIE2 will be described.

The hardware of RIE1 and RIE2 is very similar, but you cannot count on that identical recipes on RIE1 and RIE2 perform exactly the same. In addition to that the main difference between RIE1 and RIE2 is the cleanness of the two equipment. In rough terms RIE1 is the clean system and the RIE2 is the dirty system. This means that in RIE2 opposed to RIE1 it is allowed to have small amounts of metals exposed to the plasma.

The user manuals, quality control procedures and results, user APVs, technical information and contact information can be found in LabManager:

RIE1 info page in LabManager,

RIE2 info page in LabManager

Process information

• Etch of silicon using RIE
• Etch of silicon oxide using RIE
• Etch of silicon nitride using RIE
• Etch of photo resist using RIE

Equipment performance and process related parameters

Equipment		RIE1	RIE2
Purpose	Dry etch of	Silicon Silicon oxide Silicon (oxy)nitride Resist	Silicon Silicon oxide Silicon (oxy)nitride Resist and other polymers
Performance	Etch rates	Silicon: ~0.04-0.8 µm/min Silicon oxide: ~0.02-0.15 µm/min Silicon (oxy)nitride: ~0.02-? µm/min	Silicon: ~0.04-0.8 µm/min Silicon oxide: ~0.02-0.15 µm/min Silicon (oxy)nitride: ~0.02-? µm/min
	Anisotropy	Can vary from isotropic to anisotropic with vertical sidewalls and on to a physical etch where the sidewalls are angled but without etching under the mask.	Can vary from isotropic to anisotropic with vertical sidewalls and on to a physical etch where the sidewalls are angled but without etching under the mask.
Process parameter range	Max pressure	800 mTorr	949 mTorr
	Max R.F. power	600 W	600 W
	Gas flows	SF6: 0-52 sccm O2: 0-99 sccm CHF3: 0-100 sccm CF4: 0-42 sccm Ar: 0-146 sccm N2: 0-100 sccm C2F6: 0-24 sccm	SF6: 0-130 sccm O2: 0-99 sccm CHF3: 0-99 sccm CF4: 0-84 sccm Ar: 0-145 sccm N2: 0-99 sccm
Substrates	Batch size	1 4" wafer 1 2" wafer (use Al carrier with Si dummy wafer) Several smaller samples (use Al carrier with Si dummy wafer)	1 4" wafer (use Al carrier with Si dummy wafer) 1 2" wafer (use Al carrier with Si dummy wafer) 1 6" wafer (requires 6" setup) Several smaller samples (use Al carrier with Si dummy wafer)
	Allowed materials	Silicon Silicon oxide (with boron, phosphorous and germanium) Silicon nitrides (with boron, phosphorous and germanium) Pure quartz, fused silica (not Pyrex, Tempax and other glasses) Resists: AZ resists, e-beam resists, SU8, DUV resists Aluminium as thin film layer on your sample	Silicon Silicon oxide (with boron, phosphorous and germanium) Silicon nitrides (with boron, phosphorous and germanium) Pure quartz, fused silica (not Pyrex, Tempax and other glasses) Resists: AZ resists, e-beam resists, SU8, DUV resists Other olymers (ask the Plasma group for permission) Aluminium as thin film layer on your sample Other metals (<5% coverage of the wafer)

The Scanning Electron Microscopes at Danchip

The Leo SEM has its own dedicated room: Cleanroom 9

We have four SEM's at Danchip. Together they cover a wide range of needs both in the cleanroom and outside: From the fast in-process verification of different process parameters such as etch rates, step coverages or lift-off quality to the ultra high resolution images on any type of sample intended for publication.

The 'old workhorse' SEM that will cover most users needs is the Leo SEM. It is a very reliable and rugged instrument that provides high quality images of most samples. Due to its robustness new users only need a mandatory two hour training session before they are free to use it by themselves. It is a standard high vacuum instrument equipped with a field emission gun, 3 high vacuum electron detectors (Se2, Inlens and RBSD) and a Röntec EDX system. You can obtain excellent images on a large variety of materials such as semiconductors, semiconductor oxides or nitrides, metals, thin films and some polymers. We prefer that new users that have no prior SEM experience get trained on the Leo SEM before they start using the FEI or Zeiss.

The FEI SEM has its own dedicated room: Cleanroom 10

The FEI SEM has been acquired to cope with the growing need for polymer and e-beam related imaging. It is an extremely versatile microscope with two vacuum modes (High Vacuum and Low Vacuum) and 7 different detectors, offering excellent resolution on any type of sample or material. This great performance, however, requires a skilled operator that knows how to achieve it. Also, we have learned that the high degree of sophistication and the great number of detectors make it much less robust compared to the other SEM's. It is therefore the intention that only users with special needs (for instance thick polymers, glass substrates or EDX/micromanipulator experiments) that will be trained. Furthermore, the instrument is equipped with a Oxford Inca EDX system and a Kleindiek micromanipulator with a Capres 4 point probe.

The Zeiss SEM is the newest SEM in the cleanroom.

The Jeol SEM is located outside the cleanroom in the basement

Jeol SEM The less advanced Jeol SEM offers a great alternative for many types of SEM needs. If you have to check the result of an etch process, a lift-off etc. before you proceed with the process sequence, the Jeol SEM is a much better choice. It is simple, faster to use, has a very low sample exchange time and is by far more accessible than any of the other SEMs. There is a very good chance that it is free when you need it. On heavily charging polymers such as SU-8 it even does a better job than the Leo SEM. To use it, a 1-2 hour training session is necessary.

	SEM - Zeiss	SEM - FEI	SEM - Leo	SEM - Jeol
Model	Zeiss Supra 55 VP	FEI Nova 600 NanoSEM	Leo 1550 SEM	Jeol JSM 5500 LV SEM
Electron emitter type	FEG (Field Emission Gun)	FEG (Field Emission Gun)	FEG (Field Emission Gun)	Tungsten filament
Vacuum modes		High vacuum (>2*10$^{-4}$mbar) and Low vacuum (0.1-1.9 mbar)	High vacuum (>2*10$^{-5}$mbar)	High vacuum and Low vacuum
Detectors		High and Low vacuum detectors of SE and BSE electrons, HiVac Inlens SE detector and high resolution Low vacuum detector	SE, Inlens SE and BSE detectors	High vacuum SE and BSE detector
Substrate size		Up to 6" wafer with full view	Up to 6" wafer with 4" full view	Up to 4" wafer with full view
Additional equipment		Kleindiek micromanipulator with Capres 4 point probe
Best obtainable lateral resolution (strongly dependent on user skills and sample type)		Down to 1-2 nm (Limiting factor: Beam)	Down to 10 nm (Limiting factor: Vibrations)	Down to 20-30 nm (Limiting factor: Vibrations)
General availability		Good	Poor	Excellent
Ease of use		A sophisticated user interface with many features and many different detectors: Complicated	A simple user interface with joystick and a limited number of detectors: Relatively simple	A simple user interface with joystick with one detector: Very simple
User level access		Only experienced SEM users, masters/Ph.D students with special needs will be trained	Any cleanroom user	Any cleanroom user
Best usage		High resolution imaging of any sample	High resolution imaging of any non-polymer sample	Fast in-process imaging
EDX analysis		Oxford Inca system	Röntec system	Not available