Application of silica sol in chemical mechanical polishing (CMP)

Application of silica sol in chemical mechanical polishing (CMP)

2021-07-29 16:22:49 23

For high-end grinding and polishing in the field of silicon carbide, aluminum nitride, silicon nitride, indium phosphide, gallium arsenide, gallium nitride, lithium niobate, lithium tantalate and other semiconductor materials, Grish specializes in the development of diamond grits and micronized powders containing wire-cutting, B₄C suspension, monocrystalline polycrystalline,rough-surface monocrystalline diamond grits and micronized powders, alumina polishing solution, CMP polishing solution, polyurethane & damping cloth grinding pads, etc.


Preface

At present, the rapid development direction of advanced manufacturing of electronic products is high precision (nano-level control accuracy, sub-nano-level processing accuracy), high performance (T-level storage and CPU main frequency), high integration (nano-level line width) and reliability (less than 1/109 thousand hours failure rate), therefore, the local flatness and overall flatness of the surface of the processed workpiece have put forward unprecedentedly high Therefore, the requirements for local flatness and overall flatness of the machined workpiece surface are unprecedentedly high (requiring sub-nanometer surface roughness), and presenting a serious challenge to the level of ultra-precision machining technology.


An important means of surface flattening processing is polishing, common polishing techniques such as mechanical polishing, chemical polishing, magnetic abrasive polishing, fluid polishing, electrochemical polishing, ion beam bombardment polishing, float polishing, etc., are local flattening technology, and the flattening capacity varies from a few microns to tens of microns, but it is generally accepted internationally that global flattening is necessary when processing workpiece feature size below 0.35μm flattening and the only surface finishing technology that can currently provide global flattening is the ultra-precision chemical mechanical polishing (CMP) technology.

For example, during the processing of silicon wafers, the wafer is fixed by adsorption on a polyurethane polishing pad rotating in the same direction as it, and the polishing slurry is continuously flowing onto the polishing pad through a peristaltic pump so that it continuously flows between the wafer and the polishing pad, and the wafer surface reacts with the polishing slurry, and the reactants are continuously removed through the high-speed movement of the polishing head to achieve the effect of making the wafer surface flat and with high finish.

Chemical mechanical polishing schematic


GRISH® Polyurethane Polishing Pad


Chemical mechanical polishing technology is a combination of chemical and mechanical action technology, in fact, its micro-process is quite complex, and there are many factors affecting the CMP equipment, polishing solution, polishing pad, post-cleaning equipment, polishing end-point detection equipment, etc. all have an important impact on the polishing rate and polishing quality of the wafer. Among them, the polishing fluid affects both the CMP chemical action process and the CMP mechanical action process, which is one of the decisive factors affecting the quality of CMP.


At present, the polishing solutions commonly used at home and abroad are SiO2 colloidal (silica sol) polishing solution, cerium dioxide polishing solution, alumina polishing solution, nano diamond polishing solution, etc.


Several polishing fluids have different application characteristics.


01

Silica sol polishing solution

Because the polishing slurry is selected to meet the characteristics of easy cleaning, fast polishing rate, and good polishing uniformity, and silica sol as a soft abrasive is coated with a layer of colorless transparent colloid on the surface of SiO2 abrasive particles, so that its hardness is softer than SiO2 abrasive particles, its particle size is about 0.01-0.1um, the polished surface is not easy to cause scratches when processing, while its colloid particles are nanometer in diameter, with a larger than The surface area, high dispersion and permeability, because of its particle surface often adsorbed OH- and negatively charged, has a very good hydrophilic and oleophobic, so it is widely used in silicon wafer, silicon dioxide, sapphire, and other precision optical device surface polishing treatment.


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CMP polishing solution for silicone solvents

Since the particle size of silica is very fine, about 0.01-0.1μm, the damage layer on the surface of the polished workpiece is minimal; in addition, the hardness of silica is similar to that of silicon wafers, so it is often used for polishing semiconductor wafers. In addition, the hardness of silica is similar to the hardness of silicon wafers, so it is often used for polishing semiconductor wafers. Instead of using micron-sized silica particles similar to those prepared by fumed polishing, nano-sized silica sols are used to reduce the surface roughness and the depth of the damage layer.


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GRISH®CMP Polishing Solution

Silicon dioxide is an important part of silica sol polishing solution, its particle size, density, dispersion and other factors directly affect the rate of chemical mechanical polishing and polishing quality.

GRISH®CMP Polishing Solution Product Specifications

Product

 Model

Particle 

size

Particle 

shape

pH value

Viscosity

Concentration

SOQ-12D

110nm-130nm

Spherical

10.5±

0.5

<20cst

20%

SO-100

90nm-120nm

<10cst

20-50%

SO-80

70nm-90nm

SO-60

50nm-70nm

SO-40

30nm-50nm

SO-20

10nm-30nm

<30cst

10-40%

Test 

Method

Laser 

Particle 

Sizer

SEM/

TEM

pH 

Viscosity

Concentration

Note: In addition to the above specifications, customized products are available according to customers' needs.


GRISH®CMP polishing solution product features


★Uniform spherical SiO2 particles


★High removal rate, stable polishing performance


★Precise polishing quality, Ra<0.2nm, TTV<3μm


★Can be recycled for many times


★Applicable to low temperature polishing process below 35℃


★Neutral or weakly acidic polishing solution can be used to correspond


02 Cerium dioxide polishing solution

As the size of the workpiece shrinks, the traditional silicon is easy to form butterfly defects at the larger size of the integrated circuit STI (shallow trench isolation), the second generation of polishing solution using cerium oxide as the abrasive particles, with high selectivity and polishing end point automatic stop characteristics, with rough polishing and fine polishing, can be very effective in solving the shortcomings of the first generation of STI process.


Cerium dioxide hardness, good stability, good dispersion uniformity, can get a high surface quality, but because the commercial cerium dioxide is generally prepared by crushing process, there are particles are not uniform, affecting the polishing quality, so the need to study the preparation of good uniformity of nanoscale cerium dioxide. However, because cerium is a rare metal, and cerium dioxide purification is difficult, resulting in expensive cerium dioxide, the prepared polishing solution is not cost-effective.


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Cerium dioxide polishing solution

GRISH® Cerium Dioxide Polishing Solution Product Specifications


Series

Model

Particle size(D50)

Applications

Cerium dioxide

(CO)

CO-1/3

0.2-0.4μm

Optical fiber connectors, lenses, carbide, 

gemstones, optical glass, etc.

CO-1/2

0.4-0.6μm

CO-1

0.8-1.2μm

Package specification

250ml/bottle, 500ml/bottle, 1L/bottle, 1Gallon/bottle 

Note: In addition to the above specifications, customized products are available according to customers' needs.



03 Aluminum oxide polishing solution

Nano alumina is widely used for precision polishing of optical lenses, single-core fiber optic connectors, microcrystalline glass substrates, crystal surfaces, etc. At present, most of the chips of blue and white LEDs use sapphire wafers, and the use of Al2O3 polishing solution to finish grinding and polishing sapphire wafers at one time is also very common in today's applications.


Because of the high hardness of nano-α-alumina (corundum), polishing causes serious damage to the surface of the workpiece; and because the surface energy of nano-alumina is relatively high, nano-particles are easy to agglomerate, causing surface defects such as scratches and pits on the polished workpiece, usually in the application of nano-alumina surface modification is required. At the same time, due to the hardness of alumina abrasive, it is easy to scratch the surface of the workpiece when polishing the soft workpiece, so it is not suitable for the polishing of the softer workpiece.


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GRISH® Aluminum Oxide Polishing Solution

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GRISH® Aluminum Oxide Polishing Solution Product Specifications


Series

Model

Particle size(D50)

Applications

Aluminum oxide

(AO)

AO-1/3

0.2-0.4μm

Fiber optic connectors,

 crystals (Si, Ge, GaAs, InP, SiC), 

hard disk substrates, 

ceramics, cemented carbide, 

stainless steel and optical glass

AO-1/2

0.4-0.6μm

AO-1

0.8-1.2μm

AO-2

1.6-2.4μm

AO-3

2.6-3.6μm

Package specification

250ml/battle, 500ml/battle, 1L/battle, 1Gallon/battle 

Note: In addition to the above specifications, customized products are available according to customers' needs.


Supplementary:

GRISH® Silicon Carbide Polishing Solution Product Specifications


Series

Model

Particle size(D50)

Applications

Silicon Carbide

(SC)

SC-1/2

0.5-1μm

Optical fiber connector, hard disk, ceramics, carbide, 

various gemstones, optical glass, etc.

SC-1

0.8-1.2μm

Note: In addition to the above specifications, customized products are available according to customers' needs.

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Grish also provides cerium dioxide, alumina, silicon carbide and other fine polishing powder, specific specifications, please call 010-51653168 or in-store consultation:GRISH online store at Alibaba

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