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Novel Slurry Injection System for Reduced Slurry Usage and Enhanced CMP Performance Ara Philipossian [Araca Incorporated, Tucson AZ USA]

Novel Slurry Injection System for Reduced Slurry …semieurope.omnibooksonline.com/2013/semicon_europa/SEMICON... · Novel Slurry Injection System for Reduced Slurry Usage and Enhanced

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Novel Slurry Injection System for Reduced Slurry Usage and Enhanced CMP Performance

Ara Philipossian [Araca Incorporated, Tucson AZ USA]

Problem Statement

Slurries are expensive and reducing their flow rate is among the top objectives of any CMP module leader and fab manager. Slurries vary in chemical and physical properties and they rely on different mechanisms for removal. Therefore, a simple reduction in slurry flow without understanding the nature of the slurry, and without fundamentally changing the method of slurry dispense, can cause adverse effects such as:

• Lower RR • Higher WIWRRNU • Higher wafer-level polishing defects • Slower displacement of rinse water from the pad surface

Each IC fab employs different processes and different sets of consumables (i.e. slurry, pad and conditioning discs). Therefore no universal technological solution exists for slurry flow rate reduction.

Effect of Rinsing Between Polishes (ILD)

1500

1700

1900

2100

2300

2500

2700

0 20 40 60 80 100 120 140

Rem

oval

Rat

e (A

/min

)

Slurry Flow Rate (ml/min)

No Rinse Between Polishes

Rinse Between Polishes

The Slurry Injection System (SIS)

Araca Incorporated has developed, and is selling, novel slurry injection systems for:

• Applied Materials Mirra and Reflexion LK

• Ebara EPO-222

• Ebara F-REX200 series • Ebara F-REX300 series • SpeedFam IPEC 472

Compared with standard slurry application methods (i.e. dispensing the slurry near the center of the pad or through a plurality of holes sprayed over the pad radius), SIS provides:

• Higher material removal rate at the same slurry flow rate • Same material removal rate at a lower slurry flow rate • Equivalent or lower wafer-level polishing defects

In this presentation, we highlight our latest results on the performance of the SIS technology with on various polishing platforms.

SIS for the Reflexion® LK Polisher

Quick disconnect

and three hand screws for pad

change

RR and Wafer-Level Defects Blanket 300 mm TEOS CMP Blanket 300 mm Copper CMP

0.0

0.2

0.4

0.6

0.8

1.0

Total Defects Scratches Area Defects

Def

ects

(Cop

per C

MP)

SIS Point Application

160 Wafer Mini-Marathon

SIS for the F-REX200® Polisher

RR and Wafer-Level Defects

Blanket 200 mm TEOS CMP Blanket 200 mm TEOS CMP

1500

1600

1700

1800

1900

2000

50 100 150 200 250

Rem

oval

Rat

e (A

/min

)

Slurry Flow Rate (ml/min)

SISPoint Application

50% Slurry Flow Rate Reduction

0.01

0.1

1

LPD Area Defects

Nor

mal

ized

Def

ect C

ount

Point ApplicationSIS

25 Wafer Mini-Marathon

SIS for the SpeedFam-IPEC® 472 Polisher

RR and Wafer-Level Defects

Blanket TEOS 25 Wafers

Mini-Marathon

SIS Principle of Operation Pad

Wafer

Injector

SIS squeegees the pad and significantly reduces the chances of the following to re-enter the pad-wafer interface: • Pad rinse water • Used slurry • Reaction products • Foam • Pad debris and particles

Injector bottom is made of PEEK or PPS. It contacts the pad. The air interface is eliminated; this means no dry slurry build-up. Fresh slurry is applied between the injector bottom and the pad through a thin fluid layer.

SIS can be configured to inject at multiple points to accommodate pad grooving differences. SIS is flexible and it conforms to the pad as the pad wears over time.

Bow Wave Characterization

Point Application SIS

SIS

Bow wave is formed at the retaining ring due to tortuosity in the pad-wafer interface. Higher bow wave at the retaining ring suggests greater slurry wastage as only a FIXED amount of slurry can enter the pad-wafer interface due to the slit design of the retaining ring. With ‘Point Application’ bow wave at the retaining ring is comprised of mixed old and new slurry along with water, pad debris, foam and particles! With ‘SIS’ the bow wave is mostly made of FRESH slurry!

Araca’s UVIZ-100 UV Fluorescence System

d

Bow Wave Thickness Results

SIS – 150 cc per min Top – 25 RPM

Bottom – 51 RPM

Point Application – 150 cc per min Top – 25 RPM

Bottom – 51 RPM

UVIZ-100 Image Browsing Software

Bow Wave Thickness Measurement

Bow Wave

Pad

Carrier Head

Bow Wave

Pad

Carrier Head

Grey Scale Image

Cropped Image

Raw Image 1 Frame Bow Wave

Carrier Head

Pad

UVIZ-100 Image Analysis Software

Point Application SIS-100

Example: 150 Frames of the Video

Film Thickness Calibration and Results

Injection Method

Mean Bow Wave Thickness (mm)

Maximum (mm)

Minimum (mm)

Point Application

0.38 0.74 0.28

SIS 0.23 0.24 0.22

Flow Patterns 10s After Start of Slurry

SIS 150 cc per min

25 RPM

Point Application 150 cc per min

25 RPM

Summary SIS significantly reduces slurry flow rate without adversely impacting RR. Defects are much lower than those observed at the POR flow rate using Point Application. Alternatively, SIS may be used to increase RR and decrease defects at the POR slurry flow rate. SIS is totally passive and can be added to existing polisher hardware in the most non-intrusive manner and be removed in less than 2 minutes during pad changes. Compared to POR, typical slurry savings of 25 to 50 percent are observed on all polisher models tested. Slurry film thickness at the bow wave is successfully measured by the UVIZ-100 UV fluorescence system. Results indicate that SIS generates a significantly thinner slurry film at the bow wave than Point Application. As such the ‘SIS’ the bow wave is mostly made of FRESH slurry which increases RR. By eliminating the slurry-air interface and by moving the bow wave containing debris, foam and pad fragments away from the retaining ring and to the upstream of the SIS, particles are also reduced.