Using a Hazard and Operability Study (HAZOP) - Semiconductor ...

Using a Hazard and Operability Study (HAZOP) to Evaluate a Copper Waste
Treatment System
Shree Dharasker and Joan Ning, Applied Materials
3135 Kifer Road, M/S 2763,Santa Clara,
California 95054
Abstract
Applied Materials (AMAT), the worlds largest manufacturer of wafer processing
equipment, announced the opening of a new Equipment and Process Integration
Center (EPIC) in 1998. The center houses several new products, including all
the technologies needed for making the copper interconnect (Barrier/Seed
Copper deposition, dielectric deposition, chemical mechanical polishing, and
electroplating of Copper). EPIC operations therefore generate a significant
amount of copper waste that must be addressed via treatment. Due to a low,
local discharge limit for Copper (0.4 mg/l), a specific copper treatment system
was needed to remove copper from the waste stream. Working together, Applied
Materials Facilities, Environmental, and Lab Operations designed and built a
Copper Waste Treatment System (CWTS) to effectively treat and minimize this
waste stream. The CWTS contains several unit operations that were new to
Applied Materials and local regulatory agencies. To evaluate and accept the new
treatment system, the design team conducted a Hazard and Operability Study
(HAZOP). The HAZOP provided an overall system review that enabled AMAT to
thoroughly understand, operate, and permit this system.
This paper will describe the final CTWS solution, the HAZOP process used, and
they key benefits of conducting this study. With the increasing importance of
Copper in semiconductor device structures, this paper will emphasize practical
solutions for addressing aqueous copper waste streams.
Introduction:
As device performance increases, line widths on semiconductors continue to
shrink. This has created problems for aluminum conductors that are currently
used on devices. At the 0.18 micron level, aluminum conductors experience
increased signal delays, reliability and heat generation, all of which can damage
the device. It is widely expected that copper will be the metal of choice for 0.18
micron devices and beyond. Copper has several advantages over aluminum
including a higher melting point (1083 0 C), low resistivity (1.77 umho/cm), and
high electromagnetic resistance. Along with the process advantages, copper also
has significant disadvantages such as a low etch rate, high diffusivity into Silicon,
and greater environmental impact. As a result of copper processing, there are

new wastes generated which often need special treatment that is not commonly
found at Semiconductor Fabrications Facilities.
Copper Processing and Waste Treatment at Applied Materials
In 1998, Applied Materials announced the opening of a new Equipment and
Process Integration Center (EPIC). The center had several tools and modules,
including all the technologies required to develop the copper interconnect. EPIC
would be used to demonstrate the capability of Applied Materials equipment to
build a copper-based semiconductor. Copper processes at EPIC are based on
the Copper Dual-Damascene Process which included the following processes:
• barrier layer deposition using PVD/IMP
• Copper Seed layer deposition using Copper CVD
• Copper Electroplating to fill the interconnect
• Copper CMP used to flatten the oxide layer
Operation of these processes resulted in several new waste streams that were to
be handled by the facility. These included, particulate air emissions from the
Copper CVD and PVD processes, dilute rinsewaters with low copper
concentration, concentrated copper sulfate solutions from the electroplating
processes, copper slurry wastes from CMP processes, and miscellaneous
contaminated solid wastes from maintenance activities. Based on the regulatory
requirements and design considerations, separate treatment technologies were
selected for each of the waste streams.
To remove particulate copper air emissions, hot and cold traps are used in pre
and post pump lines. The traps remove particulate air emissions from liquid
precursors that are used to deposit copper liners on the wafer substrate. While
eliminating air emissions, the traps also protect the pump from particulate
damage. For dilute copper wastewater, generated by wafer rinsing, an ionexchange
system was designed to remove copper from the waste stream. To
treat concentrated copper waste such as that generated by electroplating
processes, a traditional precipitation/filtration/evaporation system was designed
to reduce waste. CMP slurry is pumped to an ultrafiltration unit to remove solids
and then fed to the Ion exchange system for copper removal. Figure 1 is a flow
chart of the Copper treatment system. Effluent from the ion exchange system is
pumped to the Acid Waste Neutralization (AWN) System for treatment and
discharge to the City POTW. Solid waste generated from filtration and
evaporation activities are characterized and disposed of at approved disposal
sites. Table 1 summarizes the waste streams generated and the treatment
technologies used.
Due to the low waste discharge limit for Copper (0.4 mg/l), it was important that
the Copper Treatment System operate efficiently, and contain several checks
and balances to ensure that there was no release to the sanitary sewer that

could result in notices of violations and penalties. In addition, due to the complex
nature of the copper treatment system, it was important to ensure that
operations, facilities and environmental personnel fully understood system
operations. The design team therefore decided that a detailed review was
necessary to fully understand system operations and checks and balances
required to maintain compliance with the requirements.
Hazard and Operability Studies:
Hazard and Operability Studies (Hazops) are recommended by the American
Institute of Chemical Engineers (1) to evaluate the risk associated with automated
and semi-automated processes. There are a number of recommended
techniques for evaluating hazards such as, What- if analysis, Process Checklists,
Preliminary Hazard Analysis, and the Hazops guide word method. A Hazops
study identifies hazards and operability problems. It involves investigating how a
plant or treatment system might deviate from design intent. Solutions to these
deviations are discussed and noted if appropriate. A Hazops is based on the
principle that several experts with different backgrounds can interact and identify
more problems when working together than when working separately and
combining results, as in a typical design review. In most new facilities, the project
engineers and architects generate design drawings that are then reviewed in
parallel or in sequence by environmental, safety, industrial hygiene, maintenance
and operations personnel. In a Hazops study, the design drawings are reviewed
by key personnel together, greatly enhancing the effectiveness of the design
review.
The Hazops is conducted in a series of meetings where a multidisciplinary team
methodically “brainstorms” the plant design, following the structure provided by
the guide words and team leader’s experience. The primary advantage of this
brainstorming is that it stimulates creativity and generates ideas. Participation is
the key to a successful Hazops, (quantity breeds quality), and team members
must refrain from criticizing each other in the meetings. The Hazops team
focuses on specific points in the design (called “study nodes”), one at a time. At
each study node deviations in the process parameters are examined using guide
words. The guide words are used to ensure that the design is explored in every
conceivable way. The task of the team is to think about each node and what
possible deviations can occur, so that their potential causes and consequences
can be identified. The best time to conduct a Hazops is typically at the 60
percent design review stage, when the design is fairly firm and the cost is not
substantial to make changes from the Hazops. Key terms that are used during a
Hazops are:
a) Study Nodes: The locations on the drawings at which process parameters
are investigated for deviations (e.g. Equalization Tank)
b) Intention: The expected operation of the system in the absence of deviations
(e.g. No copper in effluent)

c) Deviations: These are departures from intentions that are obtained by
applying the guidewords (e.g., tank overflow)
d) Causes: The reasons why deviations might occur. There could be one or
many causes to deviations (e.g. hardware failure, human error, power failure)
e) Consequences: These are results of deviations should they occur (e.g.
release of copper to sanitary sewer, equipment damage). Since there will be
several consequences, it is important to consider only those that have serious
consequences relative to the study objective
f) Guide Words: These are words which are used to qualify or quantity the
intention in order to guide and stimulate the brain storming process and so
discover deviations (e.g., no, less, more, part of, reverse, other than)
g) Corrective Actions: These are actions assigned to prevent serious
consequences (e.g., increase maintenance, add redundancy)
h) Process Parameters: Variables that could cause deviations (e.g., pressure,
temperature, flow)
Copper Treatment System Hazard and Operability Study:
The Hazops concepts discussed above were put into practice using the following
methodology
1. Defining the purpose, objectives, and scope of the study:
The purpose of the Hazops study was to identify release scenarios that could
result in a discharge of copper wastewater to the sanitary sewer. The
objectives therefore were to understand the system operation, ensure
compliance with requirements and develop mitigation measures to eliminate
or reduce risks identified during the Hazops. Scope of this Hazops was
limited to the Copper Treatment System
2. Selecting the Hazop team:
A multidisciplinary team consisting of AMAT and contractor personnel was
formed to brainstorm the Copper Treatment System. These included
representatives from the manufacturer, construction contractor, maintenance,
ESH, building operations, and facilities. The team leader briefed the
participants on the Hazops methodology before starting the Hazops.
3. Preparing for the study:
Before starting the Hazops, the team leader reviewed the design drawings,
facility layout, flow charts, and operation and maintenance manuals to
understand the operations. The entire treatment process was divided into 4
sub system; dilute copper waste water treatment, Ion exchange regeneration
system, CMP slurry treatment, and concentrated copper sulfate waste
treatment. Process flow in each subsystem was broken into “nodes”, or points

at which deviations could be studied. Nodes in the dilute copper waste
treatment system included, feed tank, carbon polishing, ion exchange resins,
and treated water storage tank. Nodes for the Ion exchange regeneration
system included chemical rinse tanks, regeneration process, and storage
tank. Nodes studied for CMP slurry treatment included equalization tank,
slurry concentration tank, ultrafiltration process, filter press, and storage tank.
Lastly, nodes for the concentrated Copper waste treatment were the feed
tank and transfer pumps, evaporator holding tank, filter press, evaporators,
and drum evaporator. Information available was rearranged based on the
nodes and sub-systems
4. Conducting the team meetings:
A series of meetings were conducted to brainstorm the Copper Treatment
Systems. One meeting was devoted to each sub system to limit the time
spent at one sitting. At the Hazops meeting, each node was thoroughly
evaluated using guide words such as “more”, “less”, and “none” to process
parameters pressure, temperature, reaction, time, and flow. Combining the
guide words with process parameters led to possible deviations that might
occur. Consequences of the deviations and suggested corrective actions
were discussed by the Hazops team. The guide-word procedure was
continued for each node and suggested actions noted for any deviations.
5. Recording the results:
The results of the Hazops meetings were recorded on spreadsheets for each
node and sub system. Entries were made into the spreadsheets as the
Hazops study progressed. All corrective actions suggested were recorded in
the spreadsheets
6. Selecting and Assigning Action Items
There are several ways to select and assign action items. The conservative
approach is to assign all action items to an owner for correction. Due to time
restraints however, it is better to rank each consequence in terms of
probability and severity. Each consequence of a deviation is considered by
the Hazops team and given a probability of “unlikely”, “possible”, or “likely”.
Similarly, severity of occurrence is rated as, “insignificant”, “moderate”, and
“significant”. The results are plotted on a probability/severity graph 2 (see
figure 2). Consequences that are both probably and severe are considered
credible, and action items to mitigate these are assigned to appropriate
personnel. At Applied Materials, the conservative approach was used and all
action items generated during the Hazops were assigned to plant personnel
for completion.
Conclusions:

The Hazops technique was found to be effective for this design review,
particularly since the system was new and relatively complex. It greatly increased
the understanding, safety and environmental compliance of the Copper waste
treatment systems, particularly for maintenance personnel who are responsible
for keeping the system up an running. In addition, specific modifications to
design were made based on the Hazops study results. A detailed Hazops
however, can take significant time and resources. It is difficult to schedule, and
follow up on action items becomes difficult as the team disbands. At least a
minimum version of a Hazop study however, is recommended for all new and
complex environmental protection and abatement systems.
As a result of Copper Treatment System Hazop, certain proposed actions
included, increased alarm notifications with tighter alarm parameters, increased
preventive maintenance procedures (PM’s) on transfer pumps, installation of
sight glass for visual monitoring of all tanks, heat jackets on caustic tanks to
prevent freezing, reevaluation of design parameters, emergency power to critical
systems to prevent failure in power outage, and installation of fluoride sensors.
This form of detailed evaluation is not possible without a thorough hazard and
operability study.
The team agreed to revisit the study and installation within a year of operation.
Maintenance personnel agreed to keep the necessary records with this review in
mind. The follow up review will determine if the recommended changes did
indeed improve the operation of the system and if any additional changes to
procedure or modification of the system is warranted based on this period of
operation. As a key system with clear environmental aspects and impacts, the
study and operational findings are expected to exceed Environmental
Management System (ISO14001) requirements when certification is obtained for
this area of our business.
Attachments:
Table 1:
Figure 1:
Figure 2:
Copper Waste Streams and Treatment Technologies Used
Flow Chart of Copper Treatment Process
Probability/Severity Graph
References
1) The Center for Chemical Process safety of the American Institute of
Chemical Engineers, 1985 “Guidelines for Hazard Evaluation Procedures”,.

2) United States Environmental Protection Agency, 1987, “Technical Guidance
for Hazard Analysis, Emergency Planning, and Extremely Hazardous
Substances”
Authors:
Shree Dharasker, P.E., REA
Shree is Member of Technical Staff at Applied Materials,
Santa Clara, California. He is currently responsible for Product Environmental
Support at Applied Materials. Previously, he was responsible for Applied
Materials-Santa Clara environmental and emergency response management. He
has a BS in Chemical Engineering from the Indian
Institute of Technology in Bombay, India, and an MS in
Environmental Engineering from New Jersey Institute of Technology,
Newark, New Jersey.
Shree is a Registered Professional Engineer (Chemical) and a
Registered Professional Assessor in California. He is an active
member of SSA, SEMI, and other professional associations.
Joan Ning
Joan is an environmental engineer in Applied Materials Lab Operations
group, responsible for environmental compliance in the laboratories.
Joan has a BS in Environmental Science from San Jose State
University, San Jose California. Joan is an active member of SSA
and other professional associations.