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Thin film analyzer

IP.com Disclosure Number: IPCOM000014734D
Original Publication Date: 2002-Apr-11
Included in the Prior Art Database: 2003-Jun-20
Document File: 3 page(s) / 72K

Publishing Venue

IBM

Abstract

In the semcinductor wafer fab such as 200mm line, Chemical vapor deposion (CVD) insulator film has been used for many process step like interlayer dielectric between multi-layer Aluminum(Al) line , belween Al and polysilicon line (silicide etc) , barrier nitride film at contact hole and final passivation film.

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Thin film analyzer

    In the semcinductor wafer fab such as 200mm line, Chemical vapor deposion (CVD) insulator film has been used for many process step like interlayer dielectric between multi-layer Aluminum(Al) line , belween Al and polysilicon line (silicide etc) , barrier nitride film at contact hole and final passivation film.

And there are so many kinds of CVD film like barrier silicon nitride (SixNy),Phospo silicate glass(PSG) or Boro-phospho silicate glass (BPSG) and Non-doped silicon oxide (SixOy) and which is called Plasma enhansed CVD (PECVD) film. But PECVD tool has multi-process parameter as shown below.

1: Chamber pressure
2. Heater stage for wafer chamber
3. Reactive gass kinds/flow/mixing ratio
4. Design of shower head
5.Plasma frequency
6.Pumping speed

So PECVD film deposition rate sometimes fluctuate at the production because of not only unstablity of above parameters and also deterioration by aging (reactive compounds sometimes deposits onto the chamber surface itself and/or shower head /inside of gas tube/ gas valve/ vaccum meter joint)

So as for production line monitoring (tool monitoring), regular base deposition rate check is necessary to see accurate deposition rate. To find accurate deposition rate, manufacturing (MFG) line uses recycled wafer for cost reduction program. Recycled wafer means physically polished wafer and having thinner wafer thickness. Normal wafer thickness is 725 um usually for 200mm line. But recycled wafer has the Thickness range of 610-725um for example.

Very thin wafer can not be used for PECVD tool because of machine handling error and wafer crack problem due to deposited film stress. So these thickness range are being used for 200 mm line.

However eventough doing these regular base deposition rate monitoring, this rate fluctuation has been still observed.

This time, I found wafer(wf) thickness itself has strong correlation w/ this deposition rate. Following fig 1. is one example for PSG film (Fixed time depostion thickness and wafer thickness by Applied Materils AME5000 PECVD machine)

1

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Thickness relation

This corelation root cause was investigated and found
1. Wafer temperature variance due to wf thickness change is not relate w/ this.

but

2.Plasma space volume (distance between upper and lower RF elctrode) is root cause

due to wafer thickness variation. I...