Introduction

This document serves as a user manual  for  the Denton RF/DC sputter  tool. The  tool  is a  three-target sputter

system that allows single layer, multilayer and co-sputtering processes, in reactive or passive mode.

One of the cathodes is energized by a radio-frequency  (RF) power  source whereas  the other  two are direct  current  (DC) powered.

This means  that the DC cathodes can only sputter from conductive targets whereas the RF cathode can sputter from insulators or semi-insulators. 

A large collection of targets is available for this tool but obviously, only three can be installed at any given time.

In  the event  that a  target  is  required which  is not currently  installed  in  the machine,  the user must submit a

target change request via email  to  the Microfab User List. The request must be submitted at  least  two weeks

prior to needing the target.

Process Capabilities

Associated Documents & References

• MSDS of argon, oxygen and nitrogen in addition to the MSDS of the required target material
• User manual
• Microfab Regulations and Procedures document
• Denton Vacuum Explorer® coating system operating manual (factory manual) p.31-66.

Equipment Used

• Denton sputter located in the etch/dep cleanroom
• XP-200 profiler located in the etch/dep cleanroom

This equipment must be reserved through the online software: Coral.

If you need to be assisted by technicians, check their availability before reserving the equipment.

Users must receive equipment-specific training before using this equipment alone.

Verifications Prior to Processing

• Verify that the needed target(s) are installed in the chamber. The targets currently installed can be checked on the Denton computer’s main screen, or via correspondence with fab staff.
• If the required target(s) is(are) not in place, submit a request via email to the Microfab User list so that other users have the opportunity to complete their work with the existing targets. Staff will install the necessary targets within two weeks of your request.
• Review the desired recipe to check that every parameter is set as required, especially the deposition time which determines the coating thickness.
• The following recipe parameters must be set within regular process limits, unless approved by the staff:
• • Current  <= 1.0 A
  • RF Power <= 500 W
  • Temperature <= 300 C
  • Total deposition time <= 3000 s
  • Total deposition thickness <= 500 nm
• Verify that the liquid nitrogen (LN₂) container is full: this will be used to help pump the chamber and also to prevent any material from coating the inner part of the vacuum hose that goes to the turbo pump. For safety purposes the use of LN₂ is temporarily suspended.

Editing Recipes (engineer privilege only)

(Note: refer to section  to get to the recipe editing window.)

The software that controls the sputter is able to store thousands of different recipes. The recipe editor is conceived in such a way that a sputter process, called a master recipe, is made up of different “sub-recipes”. The sub-recipes are of two types: Automatic non-programmable sequence and Deposition T(ime)-steps programmable sequences.

Non-programmable sequences

There are only 2 automatic non-programmable sequences:

• auto_pump: this sequence is programmed to pump the chamber to high vacuum through a well established sequence of actions. The master recipe performing the auto pump of the chamber is “A_pump”.
• auto_vent: this sequence is programmed to vent the chamber to atmosphere through a well established sequence of actions. The master recipe performing the auto pump of the chamber is “A_Vent”.

Programmable sequences

The deposition process in the Explorer system is designed to follow a programmable timeline. The programming of the automatic process is organized in a spreadsheet format. Each column is a programmable time segment. The programmable data in the column is active for the time period programmed into the first cell of the column.

To access the Programmable sequences Editor, click on the “Recipe” tab at the bottom of the screen and click on the “Edit/Create” button located just above “Deposition T-step”.

Here is a description of the fields needed to program the recipe:

• Step Time: each column is a time segment of the process. The time will start to count down only after
• Min Vacuum Setpoint (Torr) AND Heat Setpoint are satisfied.

• Min Vacuum Setpoint (Torr): This pressure setpoint MUST be reached before this step will execute.
• Heat Setpoint - This temperature setpoint MUST be reached before this step will execute.
• Gas - (PID or Fixed):
• • When Fixed is selected, gas flows setpoints (sccm) have to be set for each gas. The chamber pressure is not controlled by the software and will depend on the total gas flow.
  • When PID mode is selected, the mass flow controller will operate in a control loop with the chamber pressure. A pressure set point has to be input into the Gas PID Pressure row. For more detailed info on this feature, contact a staff member and refer to the Denton vacuum explorer® coating system operating manual (factory manual).
• Gas 1 Set Point (sccm): input the desired gas (Argon) set point in sccm.
• Gas 2 Set Point (sccm): input the desired gas (Nitrogen) set point in sccm.
• Gas 3 Set Point (sccm): input the desired gas (Oxygen) set point in sccm.
• Gas PID Pressure: input the desired pressure if PID mode is chosen.
• Source power setting (RF and DC):
• • Input a PreSputter power setting for the preparation of the target material before source shutter is opened.
  • Input a Sputter power setting for operation of the cathode after the shutter is opened.

Note: the individual source shutters will open on the transition from PreSputter to Sputter for each active source.

• Pressure control: select <Yes> to activate the Pressure Control Mode (PCM). In the PCM, the gate valve is not totally opened allowing a control on the chamber pressure during process.
• Ignition pressure: usually the RF cathode requires a higher pressure to ignite than the ones set for processing. Enter here the ignition pressure between 20 and 50mT depending on the total gas flow during process.
• Bias forward Power (Watts): if a substrate bias is desired, enter a set point in this row. This will energize the substrate bias power supply during the deposition process.
• Rotation Speed (%): enter here a rotation speed during process. Commonly a value of 50% is used which corresponds to 10rpm.
• End Process: A ‘Yes’ selection is required in the last column of every Deposition T-step file. The Save function will not permit you to save a file without a ‘Yes’ selection in the End Process row.

In the left part of the screen, there are a set of control buttons to “open”, “save”, “save as...”, “delete” files and also to delete and insert columns.

Creating and editing a master recipe

Once the deposition recipe(s) has been created, a master recipe has to be built and downloaded to the tool. 

To create a recipe:

• choose a sequence type in the drop down menu (Auto Pump, Auto dep, Auto Vent)
• Choose a “user defined sequence”
• Click “Add” to add the sequence’s steps in the Master sequence list.
• Once this done, Save the Master recipe and Download to the tool.
• Close the window.

To edit a recipe:

• open the recipe. It will display in the master sequence list
• “Add”, “Insert” or “Replace” sequences.
• Once this is done, Save the Master recipe and Download to the tool. For the master recipe, use the same convention as per the deposition sub-recipe.
• Close the window.

Generally speaking, master recipes are made of an Auto Pump sequence, followed by one or more deposition recipe(s) and the last step is an Auto Vent sequence.

Provided that the process concerning the needed material has been characterized and documented, the only parameter that will be subject to change is the deposition time which controls the coating thickness.

Operation

The software is controlled by a task bar located at the bottom of the screen.

Login: gives access to the login screen (see below for different user privileges).

• To log in: First look at top right corner of the screen, a frame with “USER ID: User logged in” whereuser logged in should be either OPERATOR or ENGINEER. If the previous user is already logged in as you wanted to, do nothing.

Otherwise, click on the “login” button, click on “LOGIN” on the next window.

Overview: displays the overall tool state along with all live parameters (base pressure, gas flows, valves and pumps states, cathodes ON or OFF, shutter opened or closed, heating ON/OFF, temperature set point and actual reading, stage rotation ON/OFF, vacuum and other interlocks, alarms screen)

Recipe: opens the recipe manager. Refer to recipe editing (section 4) for details; this capability is only available for ENGINEER users. OPERATOR can only run pre-established recipes.

Alarm view: displays alarm in full screen mode. The ACK button role is to acknowledge the alarm blinking signal.

Tolerance Alarms: displays the tolerance alarms set for different parameters.

Open Datalog: opens Microsoft Access for data logging analysis.

PLC racks: displays the PLC states in full screen mode.

The most used screens for regular users are the login, overview and recipe screens.

User privileges

The tool offers three levels of user: operator, engineer and service.