ADVANCEMENTS IN LAPPING AND POLISHING WITH 

DIAMOND SLURRIES 

Kan-Yin Ng and Timothy Dumm 

Kan-yin.ng@diamondinnovations.com, 614-438-5620 

Timothy.dumm@diamondinnovations.com, 614-438-2903 

Diamond Innovations 

6325 Huntley Road Worthington, OH 43085 

Keywords: Diamond Slurry, HYPERIONTM, Lapping, Polishing, Sapphire, Silicon Carbide 

Abstract 

A new diamond micron powder HYPERIONTM and diamond 

slurry contains such powder was developed to improve fine 

lapping and polishing of advanced compound semiconductor 

materials such as sapphire and silicon carbide (SiC). Testing 

showed that the novel diamond and diamond slurry 

significantly increased effectiveness of fine lapping and 

polishing thereby allowing reduction in cost and increase in 

productivity. 

INTRODUCTION 

The compound semiconductor materials used for 

making light emitting diode substrates are among the 

hardest materials on earth. Therefore, it is necessary to use 

diamond abrasives for slicing, edge grinding, lapping, 

polishing and dicing of the wafers. From the growth of 

the boule to final chip production, a considerable amount 

of cutting, grinding, lapping and polishing is performed on 

these materials. In substrate production alone, a 

significant portion of the manufacturing cost can be 

attributed to these material removal processes as well as 

long cycle times. Improvements in the use of abrasives for 

achieving substrate dimensions and surface finish can 

significantly reduce costs and cycle time. This paper will 

focus on advancements made in diamond slurry products 

used for lapping of sapphire wafers. 

In the production line of silicon carbide or 

sapphire substrates, the fine lapping process is used for 

establishing the proper thickness of the wafers after the 

wire-sawing and rough lapping processes. Diamond 

slurries are used with lapping plates made from tin, copper 

or copper composite plates. Typical lapping times can 

range from 20 minutes to 3 hours depending on wafer 

diameter, required stock removal and surface finish. In the 

chip making production line, grinding process remove the 

bulk thickness from the backside of the substrates and fine 

lapping follows to achieve certain surface finish. Within 

the past two years, new diamond slurries have been 

developed that significantly reduce the cycle time without 

sacrificing surface quality. 

DIAMOND TYPES AND SLURRY 

 The type of diamond used in lapping and 

polishing slurries is an important factor in determining 

how the product will perform. Industrial diamond can be 

from natural or synthetic sources and can be produced in 

different ways. Natural diamond powder is derived from 

low-grade diamond that is of too poor quality for 

gemstones. Natural diamond is in relatively short supply 

and is subject to the variability inherent in natural sources. 

Synthetic industrial diamond can be produced using hightemperature/high-pressure processes that convert graphite 

to diamond using the help of metal catalysts. This type of 

diamond is commonly referred to as mono-crystalline 

diamond grit and varies in quality from very pure to highly 

impurity-included. Mono-crystalline micron diamond is 

made by crushing the grit into finer sizes and micronizing 

the fines into narrow size fractions. Mono-crystalline 

micron diamond is widely available. 

 Another type of synthetic diamond is produced by 

detonating explosives that are packed around a graphite 

rod. The intense heat and pressure of the explosion 

directly converts the graphite to a polycrystalline form of 

diamond. The diamond from this process is generally less 

than 10 microns in size. This material is also micronized 

into narrow fractions for lapping and polishing. 

Polycrystalline diamond is not as widely available as 

mono-crystalline diamond and is generally more 

expensive. Nano-crystalline diamond is another type of 

diamond powder that is derived by exploding plastic 

explosives in a controlled environment – usually a sealed 

chamber. The residue that results from the explosion 

contains a small amount of low-grade diamond commonly 

referred to nano-diamond. This material is usually less 

than 1um in size when cleaned and dispersed. Although 

not as difficult to make as either mono-crystalline or 

polycrystalline diamond, it lacks the performance that 

CS MANTECH Conference, April 23rd - 26th, 2012, Boston, Massachusetts, USA
micron-sized diamond provides in a lapping and polishing 

application. 

Of the characteristics that impact the ability of 

slurry to perform lapping or polishing, particle size plays a 

primary role. Particle mean size determines the workpiece 

material removal rate and the resulting surface roughness 

or extent of scratching. Both mono-crystalline and 

polycrystalline diamond can be graded to extremely 

precise mean size and percentile tolerances. 

Another key characteristic of diamond powder 

and subsequent slurry performance is particle shape or 

surface morphology. In a lapping or polishing application, 

the edges and corners interact with the workpiece and do 

the abrading. Particle shape also affects the ability of the 

particle to embed in the lapping plate. Once the particles 

are embedded in the plate, they become much more 

effective in abrading the workpiece as shown in Figure 1 

FIGURE 1 

ILLUSTRATION OF LAPPING MECHANISM 

Mono-crystalline micron powders typically have 

sharp edges and corners as shown in Figure 3a. As can be 

seen, each particle will have a few corners that will have 

some potential or probability for interacting with the 

workpiece. Polycrystalline diamond powders have a 

rougher surface texture than mono-crystalline particles and 

therefore have more cutting points as shown in Figure 3b. 

This feature increases the probability of embedding into 

the plate and interacting with the workpiece. It is the 

surface texture of polycrystalline diamond that allows it to 

achieve a significantly higher material removal rate than 

mono-crystalline diamond. In addition to the higher 

material removal rates, the resulting surface roughness of 

the workpiece will be lower than with mono-crystalline 

diamond. 

 

This paper describes a new type of diamond 

powder HYPERIONTM and results obtained with it. 

HYPERIONTM diamond has been developed by surface 

modifying mono-crystalline diamond that transforms the 

surface texture of mono-crystalline diamond from having 

just a few cutting points to one where there are many fine 

and distinct features as shown in Figure 2 [1]. Figure 3c is 

a SEM image of a modified HYPERIONTM diamond 

powder. The surface-modified, mono-crystalline diamond 

with the increased numbers of pits and spikes out-performs 

polycrystalline diamond in lapping and polishing of 

semiconductor materials. 

FIGURE 2

TYPICAL PROFILE OF MONO-CRYSTALLINE DIAMOND 

PARTICLE (2a) SHOWS A FEW EDGES THAT ACT AS CUTTING 

POINTS IN LAPPING AND POLISHING. BUT SURFACE 

MODIFIED DIAMOND PROFILE HAS MANY FINE MICRO-POINTS 

THAT INCREASES THE EFFECTIVENESS OF THE DIAMOND. 

FIGURE 3 

SEM IMAGES OF MONOCRYSTALLINE, POLYCRYSTALLINE 

AND HYPERIONTM DIAMOND 

Lapping and polishing slurries or suspensions are 

made from liquid media and diamond powder. The liquid 

component of the slurry has several important functions. 

The liquid provides the means for uniform dispersion and 

controlled distribution of the diamond onto the lapping 

plate or polishing cloth. The slurry vehicle also provides 

a lubricating effect that prevents heat build-up when the 

workpiece interacts with the embedded abrasives. Finally, 

the liquid media carries away the fine debris that results 

from abrasion. In addition to diamond size and shape 

effects, slurry vehicle composition can add significant 

value to the performance of slurries. 

Tests have shown that different slurry formulation 

works differently on various types of plates or pad. 

Specific slurry formulations with HYPERIONTM diamond 

have been developed to be used on tin, copper or copper 

composite plates. Specific slurry was also developed to be 

used on a polishing pad. 

LAPPING AND POLISHING PERFORMANCE 

Extensive lapping and polishing tests were 

performed to demonstrate the differences between monocrystalline, poly-crystalline and surface-modified diamond. 

Table 1 is a list of general test conditions and parameters. 

The following are several case-studies that show how 

HYPERIONTM diamond powder greatly advances lapping 

and polishing performance. 

CS MANTECH Conference, April 23rd - 26th, 2012, Boston, Massachusetts, USA
TABLE 1 

GENERAL LAPPING AND POLISHING TEST CONDITIONS 

Parameters Lapping Polishing 

Lapper/Polisher Model 15” 

LapMaster 

Model 15” 

LapMaster 

Lapping 

Plate/Polishing 

Pad 

Tin and Copper 

Composite 

Suba 500 

Workpieces 2” as-lapped 

sapphire wafers 

3” as-cut SiC 

wafers 

Table rotation 

speed 

60rpm 60rpm 

Wafer mounting Free Free 

Pressure 3.2psi 5.7psi 

Slurry flowrate 4ml/min 15ml/min 

Process time 60 minutes 90 minutes 

Example 1 – Polishing of Silicon Carbide Wafers 

 Polishing tests were performed using a LapMaster 

15” lapping machine with conditions listed in Table 1. One 

wafer was polished at a time for 90 minutes and tests were 

repeated 3 times. Wafers were weighed before and after 

polishing. Surface roughness on polished workpieces was 

measured on Veeco Wyko. Figure 4 shows the test results 

of SiC wafers polished with K285T slurries containing 

mono-crystalline, poly-crystalline and HYPERIONTM 

diamond powder with the same particle size and diamond 

concentration. The results in Figure 4 show that 

HYPERIONTM slurry had an average material removal rate 

of nearly 350 mg in 90 minutes using the test setup. This 

is an increase in the removal rate of over two times 

compared to the mono-crystalline diamond slurry and an 

increase of eighty percent as compared to poly-crystalline 

diamond slurry. Figure 4 also shows that even though the 

material removal rate of the HYPERIONTM slurry is 

significantly higher than the poly-crystalline slurry, the 

resulting surface finish on the wafers was equivalent or 

better.

FIGURE 4 

SLURRY PERFORMANCE ON POLISHING SIC WAFERS 

Example 2 – Lapping Sapphire Wafers on Tin Plate 

 Lapping tests were performed on a LapMaster 

15” lapping machine with conditions listed in Table 1. For 

each test, three wafers were lapped at a time for 60 

minutes and the tests were repeated. Wafers were weighed 

before and after lapping to determine material removal rate 

(MRR). The surface roughness on lapped workpieces was 

measured on a Veeco Wyko. Figure 5 shows the test 

results on sapphire wafers with DI3300 slurries containing 

mono-crystalline, poly-crystalline and HYPERIONTM 

diamond powder with the same particle size and diamond 

concentration. 

FIGURE 5 

DIAMOND SLURRY PERFORMANCE OF LAPPING SAPPHIRE 

WAFERS ON TIN PLATE 

Results showed that the HYPERIONTM slurry 

achieved a material removal rate of over 170mg in 60 

minutes. In the same test, the mono-crystalline slurry only 

achieved a removal rate of 30mg and the poly-crystalline 

slurry was 80mg. Therefore, the HYPERIONTM slurry 

almost doubled the removal rate compared to the polycrystalline diamond slurry and the surface finish was 

significantly improved. 

Example 3 – Lapping Sapphire Wafers on Copper 

 Composite Plate 

Similar lapping tests were performed using a 

copper composite lapping plate with DI950 slurries 

containing mono-crystalline, poly-crystalline and 

HYPERIONTM slurry having the same particle size and 

diamond concentration. As shown in Figure 6, the material 

removal rate with the HYPERIONTM slurry was 270mg in 

60 minutes whereas the mono-crystalline slurry provided a 

rate of 50mg per hour and the poly-crystalline slurry a rate 

of 180mg per hour. Even though the removal rate of the 

HYPERIONTM slurry was nearly double that of the polycrystalline diamond, the resulting surface roughness of the 

wafers was lower compared with the mono-crystalline 

slurry and about the same as the poly-crystalline slurry. 

CS MANTECH Conference, April 23rd - 26th, 2012, Boston, Massachusetts, USA
FIGURE 6 

DIAMOND SLURRY PERFORMANCE ON LAPPING SAPPHIRE 

WAFERS ON TIN PLATE 

CONCLUSIONS 

Diamond slurry is a critical material for lapping 

and polishing advanced compound semiconductor 

materials. Diamond Innovations has successfully 

developed a novel diamond and diamond slurry that 

significantly increases lapping and polishing effectiveness, 

allowing reduced processing costs through reduced cycle 

times, improved capacity without sacrificing surface 

quality. Table 2 shows a general guideline for choosing 

the proper HYPERIONTM slurry for each lapping and 

polishing system. 

TABLE 2 

SELECTION OF HYPERION DIAMOND SLURRY FOR LAPPING 

AND POLISHING 

DI3300 

Series 

DI900/950 

Series 

K285T Series 

Application Precision 

lapping 

Precision 

lapping 

Polishing 

Workpieces Sapphire, 

SiC, GaN 

Sapphire, SiC, 

GaN 

Sapphire, SiC, 

GaN 

Plate Types Tin Copper and 

Copper 

composite 

Polishing pad 

Slurry type Watersoluble Water-soluble Water-soluble 

Diamond 

size 

2 – 10um 2 – 10um 2 – 10um 

Handling Easy 

Cleaning and 

dispersing 

Easy Cleaning 

and dispersing 

Good 

suspension and 

easy cleaning 

ACKNOWLEDGEMENT 

The authors would like to thank all colleagues who have 

performed lapping and polishing tests and analyzing 

diamond powder, slurry and workpieces. 

REFERENCES 

[1]. US Patent Application #US20100064593A1 and 

#US20100068974A1 

CS MANTECH Conference, April 23rd - 26th, 2012, Boston, Massachusetts, USA