PLASMA CVD & REACTIVE ION ETCHING SYSTEM

MODEL DRIE-1100-LL-ECR

The Tek-Vac DRIE-1100-LL-ECR series systems are designed for both high-density plasma chemical vapor deposition and reactive ion etching of sub-micron integrated circuits, optical devices and RF microwave electron devices.

APPLICATIONS:

CVD of diamond, diamond-like carbon, SiC, Si3N4, BN, and other refractory or high dielectric materials.
High-density plasma with low damage and high etching rates. Well suitable to devices sensitive to high energy electron damage, such as low-noise amplifiers. Various materials include aluminum, copper, gallium nitride, gallium arsenide, HeCdTe, and semiconductor dielectrics.
High uniformity of deposition and etching across large area substrates.

 

TECHNICAL SPECIFICATIONS:

Reaction Chamber

The reaction chamber is constructed of type 304 stainless steel with CF and/or ISO flanges with copper gaskets or elastomer seals. Interior and exterior surfaces are treated with proprietary high-vacuum passivation for corrosive protection coatings against chlorine or fluorine based etching chemistry.

The process chamber is provided with single or multiple view ports at the wafer loading level for inspection and analysis. The view ports are 2.75 inch or large enough for wafer position observation and for optical inspection or diagnostic access. Additional ports can be designed in such ways so as to aim at the wafer center for visual access to the substrate. These ports may be used for ellipsometry, interferometry, or for other diagnostic purposes.

The substrate is loaded and unloaded for processing through a load-lock. A rectangular slit valve accommodating 6 inch or larger size wafer transport is be utilized between the loadlock and the process chamber.

The load-lock and wafer transporting mechanism is available in a computer controlled automated version as standard. A manual version is available as an option.

 

ECR Source

The Tek-Vac DRIE-1100-LL-ECR system features a compact ECR microwave plasma source. This source is characterized by efficient internal cavity tuning resulting in a high density, high uniformity plasma distributed across a disk-shaped plane, and is transported downstream to the process chamber. A multi-polar permanent magnet produces 875 Gauss of magnetic field which generates electron resonance at 2.45 GHz microwave frequency inside of the compact source. This allows a short transport distance and achieves excellent uniformity. The combination of these two devices makes near perfect tuning of the ECR source and modal control, and assures production of the highest density plasma.

A microwave power supply with remote magnetron head is utilized for power generation. Output power is variable from 0 to 1.2 kW through the system computer. Appropriate circulator, isolator and matching circuits are also included. To achieve high-quality resonance and assure stable, high-density plasma delivery, a microwave power supply operating at 2.45 GHz is selected for DRIE-1100-LL-ECR system. This unit combines state-of-the-art technologies and generates extremely stable, minimal noise, low ripple microwave power to the system. All these are essential characteristics for the generation of high efficiency, high-quality ECR plasma. The microwave output power can be controlled locally by the front control panel, or remotely by the computerized interface. Various sensing devices are built into the microwave power generator making the equipment smart for process control and process automation. The following built-in sensing and protection features are available :

water-cooling fault detection
air- cooling fault detection
anodic current detection
high-voltage power supply detection
filament power supply detection
wave guide detection
external fault detection
maximal reflected power detection and setting
interlock detection (chamber, vacuum, safety switches, etc.)

The ECR plasma resonator, together with the low-ripple, high-quality microwave power supply, will allow highly reliable and reproducible production of the plasma.

The ECR plasma designed within the DRIE-1000 is optimized for both high density and high uniformity across the chamber cross-section, which is superior to any other schemes of plasma confinement mechanism. Excellent uniformity is achieved across 150 mm wafers. Etching rate variability's across a 6" wafer are typically less than 5%. Uniformity as low as 3% can be achieved under certain conditions.

There are two separate sets of gas manifolds and injectors to be individually selected or combined upon the user's request. One set of the manifolds introduces gases from the upstream and the other set from the downstream. The upstream gas injection will pass through the ECR zone and will produce the maximal reaction with the plasma. The downstream gas injection will be introduced to the process reactor by means of a gas ring and will minimize the exposure and reaction to the plasma.

RF Biased, Wafer Chuck and Wafer Back Cooling

The wafer susceptor ("RF Chuck") is powered by RF bias. A digital RF power generator and a digital automatic matching network with a built-in controller is included. Output power is variable from 0 to 300 watts (600 watts is used for large substrates susceptor) through the system computer. The RF power shall be able to deliver a power density on the electrode greater than 3.8 W/cm2.

The RF chuck and the wafer backside will be cooled for etching processes by a gas cooled heat exchanger. The wafer susceptor (RF chuck) is cooled by helium gas flowing through embedded gas cooling channels built in beneath the wafer susceptor, such that the susceptor temperature can be cooled to -15 C or lower. The wafer backside is also cooled with helium gas by flowing the gas in between the wafer and the susceptor surface. A mechanical wafer chuck will be used to clamp the wafer in place which allows the wafer to be properly pressed against the platen through a sealing medium, such as an elastomer ring.

A built-in resistor heater is utilized for heating the wafer to 450 C for standard CVD applications and to 750 C for special requirements.

The wafer's temperature is controlled and kept constant during processing in the temperature range of -15 C to 450 C with the combination of the helium backside cooling mechanism and a heat exchanger.

The wafer's temperature is monitored on the system computer by means of a thermocouple. The thermocouple will be immune from the RF power with an E-M wave decoupling technique such that the disturbance and noise will be avoided.

An electrostatic chuck can be provided for wafer back cooling and RF bias control, as an option.

Process Control

A vacuum gauge is mounted on the reaction chamber for pressure measurement and control. The vacuum gauge is an MKS Instruments Baratron capacitance manometer. The system pressure will be controlled by a throttling valve and adaptive pressure controller, such as an MKS series control set. The pressure will be smoothly controlled in the range from 0.5 mTorr to 100 mTorr within 1.0 mTorr of the set point.

An ionization gauge with set points for monitoring base pressure in the range from 10-3 to 10-9 torr is mounted just downstream of the reaction chamber.

Each of the six standard gas lines will consist of one MKS Instruments (or equivalent) mass flow controller (MFC) and a set of valves for MFC bypass and nitrogen purge. Each gas line can be independently connected to an upstream or a downstream injector.

Six MFC's will be included, each to be specified by the user for process gases to be used. The suitable full scale of flow rate of the MFC's will be selected in order to meet the process specifications. Additional MFC's may be incorporated upon request.

An additional oxygen gas line shall be included for plasma reaction chamber cleaning. The oxygen flow rate will be controlled by a metering valve.

Vacuum and Pumping Systems

An Alcatel corrosive series turbo-molecular pump (TMP) with nitrogen gas purge is utilized for high-rate, anisotropic etch processing. The corresponding electronics drive unit is provided.

An Alcatel rotary vane backing pump with nitrogen gas circulation and Fomblin oil charge for corrosive service is provided. Included will be oil filtration and inert gas purge.

Conflat , ISO, and ASA flanges with copper gaskets or elastomer seals are included on all chamber and exhaust components.

Gas lines are electro-polished 316L stainless steel with weld and VCR fittings. All gas inlet ports are complete with nuts, glands, and gaskets. Nitrogen lines will be included for purging and venting of the reaction chamber and pumps. A set of high vacuum valves for rough pumping without stopping the TMP are included. The pressure of the reaction chamber is monitored on the system computer.

The pumping speed will maintain the processing pressure of the reaction chamber in the low millitorr range, thus allowing high-quality, high-rate anisotropic etching.

The leak rate (as determined by a mass spectrometer leak detector) of the reaction chamber and that of the load lock chamber will be less than 4.0 x 10-7 mTorr-l/min. when all valves are closed and all pumps are isolated.

Load Lock

A load-lock (L/L) will be used for substrate loading and unloading. An automatic transferring mechanism to the process chamber is offered as an option. The wafer location is sensed and determined by the computer. The computer program will show the status of the wafer. A transparent load lock lid is provided to facilitate the observation of the processing sample.

An independent rotary vane pump is equipped with the L/L. The L/L vacuum system will be pressure controlled by an MKS Baratron gauge with digital display. The pressure of the load lock chamber will be monitored on the system computer.

The load lock chamber shall be constructed of type 304 stainless steel with Conflat and ISO flanges with copper gaskets or elastomer seals. The interior surface will be treated with Tek-Vac UHV passivation and will be suitable for operations under high vacuum conditions.

Automatic Computer Control

An IBM compatible personal computer shall , to be equipped with:

One Dell laptop is included.
One HP ink jet printer is included.
Two sets of control software. One is operated through the hard drive on the etching system and the other is for programming on a separate PC.
Control System Software

Multi-tasking, real time control software operating under Windows will be utilized.

The control software will automatically switch between steps in a multi-step process according to signals coming from the end point detector or from process timers.

Real time sensor and drive display of all sensors and drives.

Diagnostic functions and manual control of all operations in a user-friendly manner.

Control of the 6 (or more) MFCs . Controllable parameters include size, gas type, flow rate from 0% to 100% of full scale, automatic zero point calibration prior to processing, real time monitoring of mass flow controller outputs, etc.

Control of process time in 1 second increments from 0 to 9999 seconds, real time display of remaining process time.

Smooth control of the microwave power delivery from 0 watt to 1.2 kilowatts at the step of 12 watts or a finer scale.

Smooth control of the RF bias power delivery from 0 to 600 watts at the step of 6 watts or a finer scale.

Process Programming Capability

The program includes DIAGNOSTICS, EDITING, EXECUTION, and ADJUST modes for processing.

In DIAGNOSTICS mode, all functions are activated through the keyboard or mouse to calibrate the system.

The EDITING mode is for customizing recipes or for creation of new recipes. The number of process steps available for any process shall be greater than 20. The recipes can be stored in hard disk and floppy disk.

EXECUTION mode with real time process control of any parameter and display of all process parameters versus time.

ADJUST mode is use to develop new process by interactive process control and editing.

Interlocks

Interlocks are included for safety consideration. Two types of interlocks are utilized on the system: hardware and software. In all areas, the hardware interlocks shall override any software interlocks.

Utilities

System size: The system's dimensions, including integrated electronics rack, mechanical vacuum pumps, heat exchanger, and PC set is 8 ft. wide X 6 ft. deep X 5 ft. high.

Electrical: The etching system shall use 230 VAC, 3 phase, 30 amp, 50-60 Hz electrical power. A complete power distribution box shall be provided with the system, allowing a single point of electrical access to the system.

Water: 10 liters/minute
Pneumatic: 80 psi
Pump purge gas: 5 SCFM minimum
Exhaust: 2 separate 1" tube bulkheads
Weight: 1500 lbs

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