DISCO Technical Review March 2023

StayClean Anti-Particle and Anti-Corrosion Effects on Electrode Pads
Diamond R&D Department, Engineering R&D Division
Abstract
The dicing process is a process in which workpieces, etc. are singulated into die using a blade and cutting water. Challenges
within the dicing process are particle contamination caused by exposure to a large number of cutting particles and corrosionof electrode pads on the die caused by the cutting water.
To prevent these issues, DISCO has created StayClean, which is used by adding small amounts to the cutting water. In thispaper, StayClean effectiveness is examined.

1. Introduction
In the dicing process, Si semiconductor workpieces andpackage substrates are singulated into die by a blade. As
dicing is a mechanical process, particles such as processing
particles or blade wear fragments are produced duringon the surface of the die, which are used to stack these die
and to test electrical properties, will be exposed to thecutting water. This causes the issue of dissolved oxygen
and/or electrolytes in the cutting water corroding theelectrode pad (figure 2).

processing.
Generally, particles are flushed out by continuously
running water at the processing point. However, even if aFigure 2. Electrode pad (left) and an example of the corrosion thathigh level of workpiece cleanliness is maintained in theoccurs during dicing (right)

processes leading up to the dicing process, the workpieceis exposed to these particles during the dicing process.
Preventing contamination by these particles is one
challenge faced with image sensors in particular, which
require particle adhesion prevention after dicing as well.
As an example, figure 1 shows particles that had becomeadhered to a wafer during dicing. In addition to thematerials comprising the wafer, other particle sources thathave been observed are fractured blades and dicing tape.

Furthermore, the blades used in dicing are often hub-style
blades, which are comprised of an aluminum hub base anda metal bond, such as nickel. Similar to the electrode pads
mentioned earlier, the edge and hub in hub-style blades are
known to become corroded or dissolve, leading to blade
meandering and blade wear.
To prevent particle contamination and corrosion during
dicing, DISCO provides StayClean, which is added insmall amounts to the cutting water. This paper will
examinethefunctionalityandeffectivenessof

StayClean301, which is the latest DISCO technology inparticle and corrosion prevention.
Figure 1. Example of particles produced during dicing

2. StayClean Anti-Particle EffectAnti-corrosion countermeasures during dicing are also
important. When the materials to be processed aresemiconductor die or electronic devices, the electrode pads

To evaluate the level of particle contamination caused bydicing, a silicon wafer with polyimide film was prepared.

DISCO Technical Review March 2023
Polyimide materials are generally used on the outermost
surface of the die as surface protection for semiconductor
elements (including image sensors) or bump-side surface
protection film for packaging materials. Polyimide
materials are therefore exposed to particles on theoutermost surface of the workpiece during dicing.
Polyimidematerials

arecomparatively

low

Figure 4. Particle residue mapping after dicing with StayClean301

in(0.03%) (⌀6-inch Si wafer with polyimide film)hydrophilicity and, during dicing, attract polyimide cutting
particles originating from the polyimide film andAs you can see, a minute amount of StayClean is effectivehydrophobic silicon cutting particles originating from thein preventing particles.

wafers. Therefore, polyimide materials tend to experience

The fact that it is effective at a low concentration ismore cutting particle adhesion than materials withadvantageous from the point of view of operationshydrophilic surfaces, such as oxide wafers.

management, including cost of consumables and supply

Figure 3 shows the surface inspection results for a Si wafer

bottle replacement frequency. At the same time, however,with polyimide film and a Si wafer with oxide film thatprecision control of fluid supply is required. In practicalwere processed using cutting water (DI water) anduse, the DISCO-manufactured StayClean injector (figure

standard dicing conditions (table 1). Particles were5) is able to control concentration and supply StayClean

detected across the entire surface of the polyimide film Siwith high accuracy through the use of several types ofwafer, and as shown by a comparison with the oxide film

sensors, contributing to improved yield.

Si wafer, the polyimide film Si wafer clearly requires
further countermeasures against particle adhesion.

Figure 5. StayClean injector

3. StayClean Anti-Corrosion EffectFigure 3. Particle residue mapping after dicing

When there is metal on the surface of the dicing side of the(left: ⌀6-inch Si wafer with polyimide film; right: ⌀8-inch Si wafer withwafer to be processed, corrosion may occur in the metaloxide film)

section from the cutting water coming into contact withthis section during dicing. Metal sections can include

Next, dicing was performed on the same Si wafer withelectrode pads (e.g., probe pads located on the surface ofpolyimide film, but this time StayClean301 was added tothe wafer), lead frames, bumps, and bump pads. Rootthe cutting water. The amount added to the cutting water

causes of corrosion vary and can include cutting water

was only 0.03%. Surface inspection results are shown inquality, wafer structure, or electrochemical characteristics

figure 4.

of the wafer. For example, in order to prevent ESD damage(electrostatic discharge), CO2 gas is dissolved in thecutting water. This can cause several issues to occur. In

DISCO Technical Review March 2023
some cases, the metal section may weaken and dissolve. Inothers, if the workpiece is a semiconductor device,discoloration defects may be observed in only the electrodepads, which are connected to the transistors on the circuit,or elution may occur, possibly due to differences in themetals.
In response to these challenges, some StayClean products
have an anti-corrosion effect. As an example, the results ofa performance evaluation that used StayClean301 (newest
StayClean product) will be examined below.

Figure 7. Anti-corrosion evaluation results for Cu film when StayClean
was added to cutting water (optical microscope images)

An anti-corrosion evaluation was performed using Al film
(containing 1–3% Cu) and Cu plating film to examine theAs seen in figure 6, it was confirmed that pitting corrosion

effect on electrode pads and lead frames, which areoccurred in the Al film when dicing was performed using

commonly seen dicing materials. However, actual dicing

DI water. On the other hand, with cutting water containing

was not performed. Instead, the workpieces were soaked in

0.03% StayClean301, this pitting corrosion was notrunning cutting water for a certain length of time whileobserved, and the original state of the Al film wasvacuumed on the chuck table and then subjected to themaintained, which confirms that StayClean301 has an anti-standard processes of DI water cleaning and drying on thecorrosion effect on Al film.

spinner table. Following that, the wafer surface wasMoreover, as seen in figure 7, it was confirmed that theinspected for corrosion.

surface became rough (micro-pits at high density) in theNext, the same operation was conducted using cutting

Cu film when dicing was performed using DI water. On

water containing StayClean, after which wafer appearance

the other hand, with cutting water containing 0.03%

was inspected using an optical microscope.

StayClean301, this roughness was not observed, which

As before, the amount of StayClean added was 0.03%.

confirms that StayClean301 has an anti-corrosion effect on

Figures 6 and 7 show the results after soaking for both theCu film as well.

Al film and Cu film.

4. Blade Corrosion by Lubricant
In some cases, even when dicing is not being performed(warmup), the equipment is operated with cutting watercontinuously running and a constant spindle rpm tomaintain processing accuracy.
In this case, when the blade is in contact with cutting wateror CO2 water (see below) for a long period of time, theeffects of the cutting water or lubricant on that type ofFigure 6. Anti-corrosion evaluation results for Al film when StayClean

blade need to be considered. For example, in dicing usingwas added to cutting water (optical microscope images)

an electroformed or metal blade, it is important to selectlubricant that does not chemically attack the blade bondmaterials. If the lubricant and blade are not compatible, theDISCO Technical Review March 2023
blade edge, which is in contact with the lubricant at all

Table 1. Conditions for evaluating effects on hub-style blades

times (figure 8), will become tapered, which can cause
issues such as the required processing accuracy not being
obtained or meandering. If this effect is strong, it will leadto blade breakage.
StayClean301 is designed with importance placed oncompatibility with DISCO blades over long periods ofcontact.

Figure 8. An example of blade tapering caused by lubricant(SEM image of DISCO-manufactured hub-style blade edge)

Figure 9 shows results from the evaluation of StayClean
Next, the results from an evaluation of lubricant effects oneffects on DISCO’s main hub-style blades (ZH05 series).

DISCO’s main hub-style blades (ZH05, ZHZZ, ZH14) will
be examined below.
Testing methods and procedures are shown in table 1. In
this evaluation, CO2 water was injected into cutting water
to which StayClean had been added. CO2 water isgenerally used to supply electrolytes in order to prevent
ESD damage to semiconductor devices during dicing orspinner table cleaning. CO2 water exhibits a certain acidity
depending on the amount of CO2 dissolved, leading toelution and corrosion of hub-style blade bond materials.
In this evaluation, DISCO StayClean products that have anFigure 9. Decrease in blade weight for ZH05 blades by type of cutting

anti-corrosion effect (StayClean-F and StayClean301)

waterwere added to CO2 water, which tends to cause corrosion,and anti-corrosion performance was evaluated.

When only CO2 water was injected into the cutting water,
blade weight decreased by more than 15 g after the idlingtest. The suspected root cause of this weight decrease isblade bond elution caused by the CO2 water.
On the other hand, it was confirmed that this weightdecrease was suppressed to two-thirds the amount when
StayClean-F was added. Then, when StayClean301

DISCO Technical Review March 2023
(newest StayClean product) instead was added, it wasAs seen in figure 11, even after the long idling test, blade

confirmed that blade weight decrease was almostedge shape was maintained with StayClean301. However,completely suppressed.

the blade edge became tapered, and the blade itself

Using the same testing method, the decrease in blade

became thinner with the other supplier’s lubricant, whichwidth was evaluated for the three major types of DISCO

has not been designed with effects on or compatibility

hub-style blades.

with the blade in mind. To prevent issues such as

Results for StayClean301 (newest StayClean product) andmeandering or blade breakage, it is very important toconventional DISCO products are shown in figure 10.

select a lubricant that is designed with blade compatibilityin mind.

5. Summary
DISCO’s StayClean has anti-particle and anti-corrosion
functions, and has been designed with DISCO hub-style
blade compatibility in mind.
This paper has clearly demonstrated the effectiveness of
StayClean in performing these functions. In addition, theuse of StayClean during the dicing process can beconsidered an effective way to prevent unexpected issues.
Figure 10. Decrease in blade thickness for each hub-style blade by typeof lubricant

It was confirmed that StayClean301 also suppressed blade
thickness decrease for these hub-style blades. In addition,
the reason that blade thickness decrease in the ZH05
blades was greater than in the other blades was that more
CO2 gas was dissolved in the CO2 cutting water (loadtest on ZH05; refer to table 1).
Next, a similar evaluation was performed using anothersupplier’s lubricant and the ZH05 hub-style blade. In thisevaluation, blade edge shape after the idling test wasexamined using an electron microscope. Results areshown in figure 11.

Figure 11. SEM image of hub-style blade edge after idling test