Mitsubishi Clean Room Robot-Clean Material Handling Originatedfrom Plant Equipment InspectionMASARU HIGUCHI* 1
TAKEYA KAWAMURA* 1
TAKAAKI KAIKOGI* 2
TADASHI MURATA*2
MASATAKA KAWAGUCHI*2

The size of the silicon wafers and LCD panels produced in semiconductor device and Liquid Crystal Display (LCD)
panel fabrication plants (hereunder referred to as fabs) are becoming consistently larger. As a result, obtaining
material handling robots of greater size and higher performance is a crucial technical challenge currently facingfabs. Mitsubishi Heavy Industries, Ltd. (MHI) has developed and sold various kinds of robots, such as special purpose robots for use in plant equipment inspection, and portable general-purpose arms (PA-10) for robotic R&D andgeneral industrial use. MHI has newly developed and released a brand new clean room robot to meet the growing
needs of the semiconductor and LCD industries. This paper describes the technical background of MHI robots andintroduces the features of the newly released clean room robot for handling semiconductor wafers and LCD panels.
Intelligent Arm PA10”. The PA10 robot is a light-weight
manipulator arm with seven rotational axes. As of April
2003, 310 units of the PA10 robot have been sold. Therobot has a reputation for being light-weight (approx.
40 kg body weight with a payload capacity as large as 10kg), industry’ first redundant 7-axis (first as a catalogued
industrial robot), and open and easy operability with aregular personal computer.
The PA10 robot has also been applied as a special
purpose robot with relatively small modification. It isvery useful for providing special robots with shorter leadtimes and smaller budgets than when the robot iscompletely tailor made.
Fig. 1 shows the PA10 applied in an underwater inspection vehicle, aimed to survey any structural flaws
inside a power plant pressure vessel. Fig. 2 shows another application of the PA10 as a spraying robot used
inside the hull of a ship.

1. Introduction
The size of the silicon wafers in leading semiconductorand LCD industry fabs is shifting from 200 mm to 300
mm in diameter, while the size of LCD panels is going toundergo a major shift from the current 1 m by 1 m (Generation 5) to 2 m by 2 m or greater size (Generation 7).
To meet this manufacturing trend, larger size robots
for clean material handling are obviously indispensable,and in fact, the detailed needs for such robot has beenplaced on MHI, as the company has large-sized clean
manufacturing facilities aimed for the production ofpower plant and space flight (aeronautical) equipment.
For more than twenty years, MHI has developed various kinds of special purpose robots in order to automate
the on-site inspection and repair of equipment in power
Table 1).
1 Through this experience, MHI has acplants (Tquired abundant knowledge and skill regarding robotic
products under special environments.
Since 1992, MHI has entered the general-purpose
market with a robot named “Portable General-purpose

Table 1 MHI robot products
PeriodMain robot products

From 1980
to 1989

Maintenance robot for power plantIndustrial spraying robot
Maintenance robot for seabed cable
Harsh environment robot with multi-finger hand

From 1990
to 1999

Tank wall inspection robot
Large telescope lens exchanging robot
Portable general-purpose arm PA10

On andafter 2000

Disaster prevention robot with crawler anddual arms
Fig. 1 Underwater plant inspection robot*1 Kobe Shipyard & Machinery Works*2 Takasago Research & Development Center, Technical Headquarters

1Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.5 (Oct. 2003)

Table 2 Comparison between Scalar robot and multi axis robot
Scalar robot

Multi axis robot

Degree offreedom(DOF)

Handling without
diverting wafer
orientation

Capable of diverting
wafer orientation withmore than 5 DOF

PayloadMax. approx. 5 wafers(small tolerance forarm tip sag)25 to 50 wafers(capable of adjustingarm tip sag)

Speed andaccuracy

Generally high speed
and high accuracy

Comparatively low speed
and low accuracy

Easy
installation

Requiring leveling

Not requiring levelingFig. 2 Vessel structure spraying robot(Courtesy of Nakata Mac Corporation)

Table 3 Specifications for PA10 robot (clean compatible)
Model
Number of joint axes

PA10-6C

PA10-7C

67

Maximum distance
between joints(mm)Self-weight(kg)

Payload(kg)10Operating speedo/s)

Base (shoulder) axis : 28.5
Elbow axis: 57 Wrist axis: 180(PA10C-7C

PA10-6C930
3840

Positioning repeatability (mm)Cleanliness
Protective structure
Built in tubing and cabling

Class 1(not requiring inside pneumatic suction)
Dust and drip proof (IP54)
Complete (till arm tip)
built in cables available

Fig. 3 Appearance of PA10 robot (clean compatible)

sion during handling and simplifies installation proceTable 2dures without the need for leveling work (T2).
To meet this new demand, MHI has released a brandnew Clean Compatible PA10-6C/7C Robot since summer 2002. The appearance of a PA10-6C/7C robot isshown in Fig. 3 and its specifications are outlined inTable 33.
An O-ring seal structure has been adopted in thePA10robot for all axes. The O-ring seal structure is the mostcompact and easiest to maintain compared with otherstructures. This structure also enables the underwateruse of the robot and almost zero emission of internallygenerated particles.
The newly released PA10 robot has been confirmed tocomply with Clean Class 1 standards (per Fed Std.209,
0.1 μm), as a result of the use of renewed grease material, rotational joint bearing structure, and other specialfeatures.
Some other clean robots adopt a negative-pressure
suctioning installation instead of the joint sealing structure. One of the advantages of the PA10 robot is that it
does not require such additional installation, and thus
contributes to the reduction of operating costs.

2. Development of Semiconductor Wafer Handling
Robots
Semiconductor fabs are in fact an assemblage of multiple (min. dozens to max. hundreds) wafer processing
equipments which are running individually. Within eachequipment unit, the wafer is exposed and handled one
by one or on a batch basis. However, the wafers arehoused in a unified cassette, which normally contains
twenty-five wafers, while being transported between
equipment units.
As the pattern width of the circuit formed on a semiconductor wafer is now less than 0.1 μm, wafer handlingrobots must be capable of achieving almost zero emission of particles larger than 0.1 μ m.
Currently most of the wafer handling robots in conventional use have a scalar type structure. The technicaladvantages of the scalar type robot are its higher speed
and accuracy, because it only allows planar motion. However, recently, the demand for multi axis robots has beenemerged, due to their larger degree of freedom and easeof installation. In fact, the adoption of a multi axis robot
instead a scalar robot enables wafer orientation diver-Mitsubishi Heavy Industries, Ltd.
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Coordination change

Angle and angular speed

TargettrajectoryNo. 1 joint speed control
No. 2 joint speed control
No. 3 joint speed control
No. 4 joint speed control

Digitalmock up(mechanismmodel)

No. 5 joint speed control
No. 6 joint speed control

Fig. 4 Example of PA10 robot dynamics analyzing modelFig. 5 Example of handling of 25 pieces of wafer using
PA10 robot

In addition, any robot used for semiconductor wafer
handling must be able to achieve low acceleration andhigh positioning accuracy in order not to damage the finest pattern etched on the wafer. To satisfy theserequirements, the control parameters of the PA10 robot
Fig. 4are optimized through dynamic analysis (Fig.
4).
A PA10 robot with a high clean class can be applied tothe following applications in the semiconductor field:Fig. 5batch wafer handling (up to 25 wafers) (Fig.
5),wafer cassette handling, andFig. 6
handling of reticules for exposing machines (Fig.
6).
MHI is currently concentrating efforts on the development of a robot system with optimized handling speed
and accuracy for the aforementioned applications.

..
.

Fig. 6 Handling of reticule using PA10 robot(Courtesy of Ulvac Coating Corporation)

3. Development of LCD panel handling robots

panels, because every handling robot or cassette is aslarge as 3 m in size.
MHI is currently focusing efforts on the developmentof a large LCD panel handling robot based on thecompany’s special purpose robot technology. It is also
engaged in the development of ultra thickness electro
beam welding technology which will pave the way tothe cheaper production of large LCD processing chambers.
As with semiconductor wafer handling, LCD panel
handling is a combination of cassette handling between
different equipment units and single panel handlingwithin a single unit. The typical structure of a LCD panel
handling robot used in the vacuum process is shown inFig. 77.
The LCD panel handling robot consists of an atmospheric robot, which operates between the cassette andthe load lock (vacuum preparation) chamber, and avacuum robot, which operates between the load lockchamber and the vacuum process chamber. Generally,
the atmospheric robot is very tall due to the height of
the LCD panel cassette. The vacuum robot, on the otherhand, must be capable of planar motion with very low
acceleration shock to the panel, because the suctioning
chuck of the panel is not applicable.
The appearance and specifications of the LCD panel
handling robot now being developed by MHI are given

The size of LCD glass panels is expected to becomelarger from the current 1 m by 1 m class (Generation 5)
to the 2 m by 2 m class (Generation 7) within a few years.
In fact, this pace of enlarging LCD panels is remarkable
compared to that of semiconductor wafers, which took
almost ten years to change from 200 mm to 300 mm insize. This rapid enlarging of the LCD panel is due toexplosive demand by consumers for larger LCD displays.
However, to meet this demand, a drastic review and revision is required for every handling process of the LCD

Process chamber

Vacuumprocess

Vacuum robot(transfer chamber)

Load lock chamber
Atmospheric robot
Atmosphericprocess
Cassette station
Fig. 7 Configuration of LCD panel handling system

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.5 (Oct. 2003)

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Table 4 Specifications for LCD panel handling robot
Specifications for atmospheric handling robot
Size of LCD panel
Structure

2.0 X 2.0 m or over
Vertical axis + Traversing hand (2 pieces)

Operation range

Vertical: 1 800 mm

Horizontal: 2 500 mm or over

Equivalent to class 100

Cleanliness classSpecifications for vacuum handling robot
2.0 X 2.0 m or overSize of LCD panel

Vertical axis + Traversing hand (2 pieces)

Structure
Operation range

Vertical: 200 mm

Equivalent to class 100

Cleanliness class

Fig. 8 LCD panel handling robot

Horizontal: 2 500 mm or over

Dynamics model
Control unit

Mechanism section

Drive torqueAngle
controlAngular
speed
control

Generationof target
trajectoryMotorcharacteristics

Gear
characteristics

Link
characteristics
Arm angle

Motor angle (encoder value)
5: T Company: H Company

4Planar sway of arm chip

3210-1-2Fig. 9 Simulation of dynamics
for planar handling ofthe robot in atmosphere-3-4-5
00.5

11.5

22.5

33.5

4Time (s)4 respectively. The technical targets
in Fig. 8 and Table 4,of the large-size LCD panel handling robot are as given
below:
development of vertical drive structure that allows
large payload, higher speed and long life;
development of planar drive structure that allows 0.1
mm positioning accuracy of a 2 m by 2 m LCD panel;development of light-weight fork hand that is sufficiently “thin” allowed by the cassette pitch; and#cleanliness technology which minimize the particle
emission from the robot driving joints.
Of these technical targets, the development of a planar drive structure with high positioning accuracy isespecially important. MHI has performed dynamic analysis of the driving structure, which had been applied to
the wafer-handling robot, in order to achieve the optimal selection of robotic components.
Fig. 9 shows an example of the dynamic simulation of
the trajectory accuracy of LCD panel handling by a threeaxis planar atmospheric robot, with two different typesof reducing gear adopted inside the robot. The result ofthe simulation shows that a robot with a planocentric
type reducing gear provides better trajectory accuracy
than a robot with the other type of gear.However, thetwo types of gears have their own advantages regarding
the amount of backlash or rigidity and could not be pri-.
.
.

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oritized by the gear alone.
Further, the three-dimensional model shown in Fig
Fig.. 10was used to check the mutual interference between eachrobotic component before starting production of the robot so as to minimize the cost of trial and error.
As for the substrate handling robot in a vacuum, MHI
has concluded technical collaboration with American
Brooks-PRI Automation Inc., and is engaged in the development of a Generation 7 LCD panel handling robot
with original mechanism and control.

4. Conclusion
This article has presented a brief review of the history of MHI’s special purpose robot technology, and has
unveiled the semiconductor wafer handling robot system using the clean compatible PA10-6C/7C robotic arm,and the LCD panel handling robot which are both being
newly developed.
The field of semiconductor wafer and LCD panel handling is undergoing severe competition and drasticchange in terms of both technology and cost. However,
MHI is determined to make an all- out effort and use
our diversified technologies and equipment in the hopethat they will be of some service to our customers.

Masaru Higuchi

Fig. 10 Three-dimensional evaluation (assessment)
model of atmospheric handling robot

References(1) The Development of the Portable General-Purpose Intelligent
Arm, The Journal of The Robotics Society of Japan Vol. 18
No. 1 (2000) pp. 55-66(2) The Next-Generation LCD Panel Handling Robot, The Journal of Japan Robot Association “ROBOT” No.151 (2003) p.42
(3) The website for “MHI General Purpose Robot PA10 Series”
by Mitsubishi Heavy Industries, Ltd.
http://www.robot-arm.com

Takeya Kawamura

Takaaki Kaikogi

Tadashi Murata

Masataka Kawaguchi

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.5 (Oct. 2003)

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