Plasma Therm Etchers - General Operating Procedure
Plasma Therm Etchers - General Operating Procedure
This document is an overview of PlasmaTherm Etchers at SNF. There are three etchers on site. Pt-MTL for metal etch applications, PT-OX fr oxide etches and PT-DSE for deep silicon etch.
The PlasmaTherm Versaline ICP Etch system is a high density plasma (HDP) etch system. The most important characteristic of this system is that there are two power sources, a 2 MHz inductively coupled plasma (ICP) power and a 13.56 MHz bias power. This allows separate control of the plasma density through the top coil (ICP) and the sheath bias through the lower electrode (bias power). When the bias power is applied to the substrate or carrier, a self-bias DC voltage builds up on the substrate surface, independent of the substrate surface (conductive or non-conductive), thereby enabling etching of any material (conductive or non-conductive).
In the plasma processing world HDP means having at least two sources of plasma power. The first is used to generate the plasma, and is what is called a non-capacitive coupled source, such as inductively coupled (ICP) or ECR coupled, where power is transferred or coupled to the plasma without causing the voltage difference between the plasma and the wafer to be above about 50 V. This first source controls the plasma density (number of ions per cc) in the plasma and thus controls the ions flux (ions per sq cm per sec) bombarding the wafer. The second power source is connected through the wafer chuck/electrode and is capacitive coupled (CCP). This second source is often referred as the bias power in that it is used to control the voltage between the wafer and plasma. This voltage between wafer and plasma is important, it controls the energy and directionality of the ions bombarding the wafer surface. Thus, with high density plasmas we have the ability to control both ion flux and ion energy independently. Sometimes additional power sources are added to control the energy distribution of the ion for fine control in etching.
A process sequence is a recipe that is made up of several process steps. It gives information like gases, min/max flows, set points for RF, etc. Be warned that once you change a value in a process steps that value will be changed for all the steps with the same name. To be safe, if you copy a step be sure to give it a unique name.
- Load Lock.
- Reaction Chamber.
- Process Monitor/Control Computer.
- Mechanical Pumps – located in basement.
- Heat exchanger – located next to the tool.
Plasma-Therm ICP Etcher – Power Sources
The Plasma-Therm ICP source has a cylindrical coil configuration. In this configuration, an inductive coil encircles a dielectric vessel. The coil is connected to 2 MHz RF power source. When the coil is powered, a strong RF magnetic field is generated in the center of the chamber which in turn generates a high density plasma. The lower electrode is powered by a 13.56 MHz RF generator as in an RIE (Reactive Ion Etch) for independent control of substrate bias voltage. A schematic is shown in the figure below. Typical operating pressures are less than 10 mT in these systems.
In addition to the two RF power sources, the process chamber is supported by a gas box, vacuum system and temperature control units. The process module is connected to a load lock by a slit valve (VAT valve). Both the process chamber and the lid are made of Al. The chamber lid also houses the ICP coil, endpoint hardware and gas distribution hardware. The chamber lid, chamber walls and bottom electrode are all fitted with heating and cooling coil channels.
The system has a mechanical ceramic clamp which is used to hold the wafers down tight to the electrode. He is used to fill the space between the wafer and the electrode and acts as a thermal transfer media. The electrode has no lip seal (o-ring) so the He pressure is limited to 4 Torr and requires very smooth backsides. Due to sticking issues edge exclusion is required. The is best achieved by using EBR (Edge Bead Removal) during resist coat.
Wafer/ Substrate is loaded onto the load lock module (Figure 3) and is transferred to the process chamber under vacuum. The load lock is equipped with an automatic loading mechanism and is connected to the process chamber by a VAT valve.
This section describes the screen layout and functions of the shared panels. Here is the screen the tool is mostly likely to be up while the system is in stand-by;
The shared panels are A. Title Panel, B. Main Screen Panel and C. Menu Panel. The Title and Menu Panels will remain the same while the Main Screen will change as the user navigates through the different software screens.
Here is a description of the Tile Panel and what each of the items does;
Shows date and time. When clicked the program version is displayed
If activated text will appear when pointer is positioned on a command button.
During production the status of the system modules (operating mode and actual pressure) and the name of the recipe are shown.
|D|| FA Connection Status
Provides information on host connection. This does not apply to the SNF systems and should read Disabled.
|E|| Login, Logout
Command button Login or Logout respectively to login and logout. The SNF tool is left logged in. Login and passwd are 3333.
|F|| Signal Lamp
Graphical reference to the status shown on the signal tower.
|G|| System Navigator
Allows for the selection of installed modules directly which determines what will be displayed sa the Main Screen Panel.
Interrupts the current process or aborpts the transfer in load lock.
|I|| Menu Button
Shortcut to the Jobs menu.
|J|| Active Alarm Display
The most severe alarm with a short description is displayed in the field. Clicking on the field will send you to the Alarm screen.
Command buttons are used select the individual menus and screens. The screen selection in the top line (A) depends on the particular menu selected in the bottom line.
Previously selected screens can be selected by using the Back and Forward buttons or by directly clicking the command button.
Job Start Screen from the Jobs Menu
This is the screen you will use to run the recipe. The system must be in PRODUCTION (green!). The Maintain button is where you will be able to put the system into Production.
- A Recipe selection
- B Graphic representation
- C Current job
- D Current parameters
- E Load lock control and status
- F process control
||Starts the selected recipe
||Interrupts the current process. Has the same function as the Stop button in the Title Panel
||Pumps the load lock to high vacuum
||Vents the load lock to atmospheric pressure
|Vent after Job
||If selected will transfer the wafer into the process module (or PM
also called process chamber), run the recipe, transfer the wafer into
the load lock upon completion and vent the load lock
|Process in PM No Transfer
||If selected requires manual transfer into PM from
Maintain/Transfer. The recipe will be run and the wafer stays in the
PM. This option is likely chosen if multiple recipes are to be run on
a single wafer
- Check for tool status and configuration in Badger and make sure it is available for processing.
- Enable the tool on Badger.
- Make sure that there are no active alarms on the system, the modules are initialized and the chamber is empty (refer to the picture below).
- On the Jobs/Jobs Start screen load the desired recipe and click on the Go To Recipe Temps button. This will set the tool to the temps required for the recipe, saving time.
Process Chamber Status Description
Job Start Screen
5. Check that the system is in PRODUCTION Mode as displayed in the Status bar (top of the screen)
6. If it is MAINTENANCE Mode you will need to go to Maintain/Mode screen and chose PRODUCTION All Chambers. MAINTENANCE Mode is used for manually loading and unloading wafers from the Load Lock, for loading the endpoint programs and for viewing the wafer surface using the camera.
7. Vent the load lock by clicking the “Vent” button under “Lock” control.
8. Once the load lock is vented, open the load lock door, remove the wafer in the arm and load your wafer.
9. Align the flat parallel to the line marked on the arm (away from the chamber). Ensure that the wafer is touching the pins near the flat area.
10. Close the load lock door.
11. In 'Jobs/Jobs Start' double check that the correct recipe has been selected from the Recipe list. Follow the link for instructions on creating/editing the recipe - PlasmaTherm - Creating/ Editing Recipes
12. Make sure the recipe sequence and recipe steps are correct and have the desired settings.
13. Make sure “Process in PM. No Transfer” box is unchecked and “Vent after Job” is selected.
14. Click on the “Start Job” button to start the processing.
15. Once the processing begins, details of the process recipe and the process parameters, set points and actuals, will appear on the right side of the Jobs screen.
16. Click the Jobs/Adjust button to monitor your process. You have a choice of monitoring three parameters in a real time plot. Typically, RF forward, reflected and power are plotted.
17. Monitor the process.
18. In case the processing has to be aborted, click the command button “Next Step” in the Jobs/Adjust screen.
19. When processing is completed, wafers will be transported back to the load lock and the load lock will be vented if “Vent after Job” is selected.
20. Continue with next wafer or if you are finished pump LL.
21. Fill out log sheet and Disable tool in Badger.