The Microlab operates five Lam dry etchers that represent three generations of Lam products, i.e. Autoetcher, Rainbow, and TCP. The specification table attached at the end, summarizes the important process and machine parameters of these etchers. Besides using different process gases to etch different target films, there are specific design differences among these etchers to achieve the process requirements, e.g. selectivity, etch rate, and deep sub-micron features. These design differences and other potential uses of each etcher will be discussed in the following paragraphs.
Originally, Lam1 was a Si/poly-Si etcher. It has been
modified and used as a thin Si-nitride etcher. However, the etch rate is low
(less than 1000 A/min). It is not able
to etch thick nitride (in micron meters) due to polymer deposition. The SF6
process gas also etches Si/poly-Si ten times faster than nitride.
Lam1 is still able to etch poly-Si. The recipes have been developed.
However, since it cannot handle HBr, the oxide selectivity is not as good as
Lam4 and Lam5.
Lam2 etches oxide and thick nitride using high RF
power, 850 W, which is 2 to 3 times higher than that of other etchers. It has a
graphite top electrode that provides carbon for high oxide to silicon
selectivity. The gap between the top and bottom electrodes is 0.38 cm, which is
several times smaller than on other etchers. To compensate for the small plasma
volume between the electrodes, the process pressure is set at 2.8 Torr. This is
higher, compared to pressures in other etchers, which are in the low hundreds
of mTorr range. Consequently, the gap and process pressure play important roles
in the etch rate and uniformity.
Lam3 is a true RIE (Reactive Ion Enhanced) etcher for aluminum. The RF power is connected to the bottom electrode where the wafer sits. The electrode temperature is set at around 65ēC to assist the desorption/evaporation of the etch byproducts.
Lam3 also has a PLL (Powered Load Lock), which is used to passivate
the etched aluminum sidewalls.
Lam4 is the second generation of Lam etchers
(Rainbow Platform). It has more
sophisticated robot, computer, controller, and gas handling system than its
predecessor, AutoEtcher. Lam4 is used for poly-Si/Si-nitride etch. Before the
Microlab acquired STS, Lam4 was also used as a deep silicon etcher.
Lam5
is one of the most advanced etcher in the Microlab. It is a TCP (Transformer
Coupled Plasma) system on a Rainbow platform. The control software has been upgraded
to Envision with GUI interface. There are two RF power supplies running at the
same time during the etch process. The result is high-density plasma with
adjustable bias. In order to obtain a vertical etch profile and high etch
aspect ratio, the mean free path of process gases need to be large. This is
accomplished by using a turbo pump to decrease the process pressure to the tens
mTorr range. The total volume of the plasma is also increased for total
available etching radicals. The gap between the electrodes during etch process
is set at 5.8 cm, compared to around or below 1 cm for other etchers.
|
|
Lam1 |
Lam2
|
Lam3 |
Lam3 |
Lam4 |
Lam5 |
|
Platform |
AutoEtch |
AutoEtch |
AutoEtch |
AutoEtch |
Rainbow |
TCP |
|
Model |
480 |
590 |
690 |
PLL |
4400 |
9400 |
Wafer Size
|
||||||
|
Current |
4"/6 |
4"/
6 |
4"/
6 |
4"/
6 |
4 |
6 |
|
Upgradeable |
6" |
6" |
6" |
6" |
8" |
8" |
Film Etched
|
||||||
|
Original
Design |
Poly |
Oxide |
Al |
Passivate |
Poly |
Poly |
Current Usage
|
||||||
|
Poly |
Yes |
|
|
|
Yes |
Yes |
|
Oxide |
|
Yes |
|
|
|
Yes* |
|
Thick
Nitride |
|
Yes |
|
|
|
|
|
Thin
Nitride |
Yes |
|
|
|
Yes |
|
|
Al |
|
|
Yes |
|
|
|
|
Al
Passivate |
|
|
|
Yes |
|
|
Process Gases/MFC Size
|
||||||
|
Ar |
|
|
|
|
Open |
500 |
|
BCl3 |
|
|
200 |
|
|
|
|
C2F6 |
Open |
Open |
|
|
|
|
|
CF4 |
Open |
200 |
50*** |
200 |
|
200 |
|
CHF3 |
|
200 |
|
|
100 |
200 |
|
Cl2 |
200 |
|
200 |
|
200 |
200 |
|
HBr |
|
|
|
|
200 |
200 |
|
He |
200 |
200 |
|
|
500 |
|