Role of mask on the contact etching for 14nm nodes

Transcription

1 Role of mask on the contact etching for 14nm nodes MEBARKI Mokrane 1,2,3 Maxime Darnon 2, Cecile Jenny 1, Nicolas Posseme 3, Delia Ristoiu 1,Germain Servanton 1, Olivier Joubert 2 1 ST Microelectronics 2 Laboratoire des technologies de la microélectronique (LTM) CNRS 3 CEA LETI PESM Monday, May Grenoble, France

2 Outline 2 Double patterning for contact etching Double patterning strategy Mask Opening Comparison between N 2 /H 2 vs COS/O 2 Silicon oxide etching Interaction with mask opening process Conclusion

3 Double patterning for contact etching: 3 Increase the number of transistors on a chip Reduce the transistors dimension Change of contacts patterning strategy Double patterning First patterning 1. deposition Si 3 N 4

4 Double patterning for contact etching: 3 Increase the number of transistors on a chip Reduce the transistors dimension Change of contacts patterning strategy Double patterning First patterning Si 3 N 4 1. deposition 2. Trilayer line pattern Cross section post etching

5 Double patterning for contact etching: 3 Increase the number of transistors on a chip Reduce the transistors dimension Change of contacts patterning strategy Double patterning First patterning Hard mask Si 3 N 4 2. Trilayerline 1. deposition pattern 3. Post etching of hard mask Cross section post etching

6 Double patterning for contact etching: 4 Increase the number of transistors on a chip Reduce the transistors dimension Change of contacts patterning strategy Double patterning Second patterning (Cross section) Hard mask Si 3 N 4 1. Post etching of hard mask Hard mask 2. Trilayer mask pattern Cross section post etching

7 Double patterning for contact etching: 4 Increase the number of transistors on a chip Reduce the transistors dimension Change of contacts patterning strategy Double patterning Second patterning (Cross section) Hard mask Si 3 N 4 1. Post etching of hard mask 2. Trilayer mask pattern Hard mask 3. Post mask etching

8 Double patterning for contact etching: 4 Increase the number of transistors on a chip Reduce the transistors dimension Change of contacts patterning strategy Double patterning Second patterning (Cross section) Hard mask Si 3 N 4 1. Post etching of hard mask 2. Trilayer mask pattern 3. Post mask etching Contact Hard mask 4. Post Silicon oxide etching

9 Double patterning for contact etching: 5 strip Post contact etching Double patterning opening Contact opening SEM Top view post contact etching SEM cross section post contact etching

10 Double patterning for contact etching: 6 Increase the number of transistors on a chip Reduce the transistors dimension Change of contacts patterning strategy Double patterning Second patterning (Cross section) Hard mask Hard mask Si 3 N 4 1. Post etching of hard mask 2. Trilayer mask pattern Hard mask 3. Post mask etching Contact 4. Post Silicon oxide etching

11 Characteristics of etching: etching With N 2 /H 2 etching With COS/O 2 (5%) 7 SiARC SiARC Etch rate of according the COS ratio Consumption of SiARC Presence of undercut on sidewalls of mask etching With COS/O 2 (17%) and shorter over etch The increase of COS ratio leads a better conservation of mask. SiARC

12 Characteristics of etching: EDX analysis after etching with COS/O 2 (5%) chemistry : 8 SiARC Ti SiARC observation : Presence of Ti elements Si 3 N 4 EDX analysis for Ti element S EDX analysis for S element EDX analysis after etching with N 2 /H 2 chemistry : SiARC No significant sputtering TEM cross section EDX analysis Interaction between etching and hard mask

13 Double patterning for contact etching: 9 Increase the number of transistors on a chip Reduce the transistors dimension Change of contacts patterning strategy Double patterning Second patterning (Cross section) Hard mask Si 3 N 4 1. Post etching of hard mask 2. Trilayer mask pattern 3. Post mask etching Contact Hard mask 4. Post Silicon oxide etching

14 Interaction with mask opening process: 10 Etch-stop presence after contact etching for the opening with COS/O 2 (5%) etching with COS/O 2 : Post contact etching Taper profiles The contacts are open after contact etching for the opening with N 2 /H 2 etching with N 2 /H 2 : Post contact etching Correct profiles

15 Interaction with mask opening process: EDX analysis after oxyde etching : 11 TiOF Contact Contact EDX after oxide etching with COS/O 2 (5%) for Opening Veil formation of TiO x F y on the holes patterned

16 Originof veil formation: 12 etching with COS/O 2 (5%) etching with N 2 /H 2 SiARC SiARC Ti sputtering Ti residue No significant sputtering EDX analysis Hypothesis : Ti sputtering during Over Etch induces veil EDX analysis After contact etching for formation etching during withsio COS/O 2 etching 2 (5%) Decrease OE time Lower OE Lower sputtering No TiOF veil

17 Conclusion: etch N 2 /H 2 COS/O 2 Taper mask profile Straight mask profile Increase ratio of COS/O 2 Low sputter Correct Etching Oxyde etch sputter Veil formation Etch stop At long OE Contacts open At short OE

18 PESM Monday,May Grenoble, France Thank you for your attention!