Study of cobalt etching speed controling by ph and oxidizer concentraion

Transcription

1 Study of cobalt etching speed controling by ph and oxidizer concentraion Kurita Water Industries Ltd. Yuichi Ogawa, Nobuko Gan, Toru Masaoka, Minami Yoshimura, Hideaki Iino imec vzw Quoc Toan Le, Els Kesters, Frank Holsteyns SCREEN Semiconductor Solutions., Ltd. Yuya Akanishi, Akihisa Iwasaki

2 Agenda 1. Introduction 2. upon test 3. Surface analysis 4. Mechanism mm wafer test 6. Summary 2

3 Introduction Process Innovation Scaling down Fin STI (shallow trench isolation) Gate Spacer S/D (source/drain) EPI ILD0 (inter-layer dielectric) RMG (replacement metal gate) MOL (middle-of-line) BEOL (back-end-of-line) New processes and structures are used in device. New materials are used in devices. Some materials are corroded in water. It is also necessary to develop the methods of cleaning new materials and new structures. 3

4 Introduction The transition of line width and material Trend in8 in7 in5 in5+ in3 PP/MP/FP 56/40/30 42/32/24 42/21/21 42/21/ /16-21/16-21 Channel n/p Device architecture Si/Si FF Si/Si FF Si/Si or SiGe FF Si/Si or SiGe FF or GAA Si/Si or SiGe GAA or CFET BEOL Lines (Fill/Liner/Barrier) Via Mx:Cu/TaN Vx:Cu Mint:/TiN Vint: Mx:Cu/TaN Vx:Cu, Mint:/TiN Vint: Mx:Ru, Cu/MnRu Vx: Mint:/TiN, Ru Vint:, Ru Mx:Ru, Cu/MnRu Vx:, Ru Mint:/TiN, Ru Vint:, Ru Mx:Ru, Cu/MnRu, Ru Vx:, Ru Mint:/TiN, Ru Ref,:imec PR ML PR ML MG HM ILD BL BL Litho Etch Post etch clean Litho Etch will replace W or Cu in MOL and BEOL. Post etch clean We have studied the new rinsing method for avoiding dissolution. 4

5 Agenda 1. Introduction 2. upon test 3. Surface analysis 4. Mechanism mm wafer test 6. Summary 5

6 upon test 1 (ph) Experimental Procedure <Purpose>To study the behavior of dissolution concerning ph. wafer coupon Rinsing Analysis of conc. in the solution N 2 gas Dipping coupons in various solution Analysis by ICP-MS () wafer upon (10mm 10mm) upon N 2 purged globe box ndition Range ph 2-10 ph2:dhf ph5:co 2 water PH8-10: NH 4 OH water < wafer> Method :PVD thickness: 28nm 6

7 etching rate [nm/min] upon test1 (ph) Result In dilute HF In CO 2 water 0.01 <1ppb H₂O₂ In NH 4 OH water DO:<30ppb (μg/l) ph The influence of ph on the etching rate of The etching rate significantly decreased as ph increased. 7

8 upon test1 (ph) Why can dissolution be avoided by increasing ph? ndition dissolution mechanism In acid As standard oxidation-reduction potential of is V, is etched easily. H 2 H + e - 2+ In alkali The concentration of OH - is higher in higher ph. reacts with OH - and forms a passivating (OH) 2 layer. The will not be dissolved. OH - (OH) 2 8

9 upon test2 (Oxidizer) Experimental Procedure <Purpose>To study the behavior of dissolution changing oxidizer concentration wafer coupon Rinsing Analysis of conc. in the solution N 2 gas Dipping coupon in DIW (+NH 4 OH + H 2 O 2 ) Analysis by ICP-MS () wafer upon (10mm 10mm) upon N 2 purged globe box ndition Range ph 6-10 The ph was adjusted by adding NH 4 OH H 2 O 2 conc, ppm (mg/l) < wafer> Method :PVD thickness: 28nm 9

10 etching rate [nm/min] upon test2 (Oxidizer) Results In dilute HF In CO 2 water <1ppb H₂O₂ 10ppm H₂O₂ DO: <30ppb ph The influence of H 2 O 2 on the etching rate of By adding 10 ppm H 2 O 2, the etching rate of gets lower. 10

11 upon test 2 (Oxidizer) Results 10ppm NH 4 OH :ph=9 The correlation between the concentration of H 2 O 2 and the etching rate of. About both solutions 0 10ppm : The etching rates of decreases as H 2 O 2 concentration increases. 10ppm :The etching rates is stable at lower level. 11

12 Agenda 1. Introduction 2. upon test 3. Surface analysis 4. Mechanism mm wafer test 6. Summary 12

13 Surface analysis upon test 1 ph influences etching strongly. In alkali, etching rate is significantly lowered. upon test 2 When an oxidizer exists in the solution, etching rate is lowered furthermore. Oxidizer control ( in H 2 O 2 water) To clarify the mechanism of dissolution, we analyzed etched surface by XPS (X-ray photoelectron spectroscopy). 13

14 Surface analysis <Preparation of XPS> XPS spectrum for data analysis The binding energy concerning compounds are close each other, We obtained the binding energy of (OH) 2, O and 3 O 4 originally. Each sample was prepared as follow. (OH) eV O 780.0eV 3 O eV Water plasma Heating in O 2 atmosphere XPS result of surface O 2 plasma mpounds Deposition method Binding energy (ev) (OH) 2 Water plasma O Heating in O 2 atmosphere O 4 O 2 plasma

15 Surface analysis Experimental Procedure wafer coupon Rinsing Analysis of surface N 2 gas Dipping coupon in Rinsing solution wafer upon upon Analysis by XPS upon (10mm 10mm) N 2 purged globe box No. ndition 1 No rinsing % DHF % DHF 10ppm NH 4 OH % DHF 10ppm H 2 O % DHF 10ppm NH 4 OH+10ppm H 2 O 2 15

16 Surface analysis Results Rinsing condition and compound ratio on the surface after rinsing No. ndition compound ratio [%] O (OH) 2 1 No rinsing N.D % DHF 24.2 N.D % DHF 10ppm NH 4 OH 3.2 N.D % DHF 10ppm H 2 O % DHF 10ppm NH 4 OH+10ppm H 2 O Based on these results, we assumed reactions by rinsing. 16

17 Agenda 1. Introduction 2. upon test 3. Surface analysis 4. Mechanism mm wafer test 6. Summary 17

18 Mechanism (DHF) No. ndition compound ratio [%] O (OH) 2 1 No rinsing N.D % DHF 24.2 N.D Hypothetical mechanism of surface rinsed with DHF (OH) % DHF (OH) 2 is formed by atmospheric water vapor by the time XPS measurement was performed. (OH) 2 (OH) 2 + 2H H 2 O +2H H 2 +2H 2 O (OH) 2 + H 2 18

19 Mechanism (NH 4 OH) No. ndition compound ratio [%] O (OH) 2 1 No rinsing N.D % DHF 24.2 N.D % DHF 10ppm NH 4 OH 3.2 N.D Hypothetical mechanism of surface rinsed with NH 4 OH water. (OH) % DHF 10ppm NH 4 OH (OH) 2 (OH) 2 + 2H H 2 O +2H H 2 + 2H 2 O (OH) 2 + H 2 +2H H 2 :Fast, :No react 19

20 Mechanism (H 2 O 2 ) No. ndition compound ratio [%] O (OH) 2 1 No rinsing N.D % DHF 24.2 N.D % DHF 10ppm H 2 O Hypothetical mechanism of surface rinsed with H 2 O 2 water. (OH) % DHF 10ppm H 2 O 2 (OH) 2 O (OH) 2 + 2H H 2 O +2H H 2 + H 2 O 2 O+H 2 O O+H 2 O (OH) 2 +2H H 2 (OH) 2 + 2H H 2 O :Fast, :Slow 20

21 Mechanism (NH 4 OH+H 2 O 2 ) No. ndition compound ratio [%] O (OH) 2 1 No rinsing N.D % DHF 24.2 N.D % DHF 10ppm NH 4 OH+10ppm H 2 O Hypothetical mechanism of surface rinsed with NH 4 OH and H 2 O 2 water. (OH) % DHF 10ppm NH 4 OH + 10ppm H 2 O 2 O (OH) 2 (OH) 2 (OH) 2 + 2H H 2 O +2H H 2 + 2H 2 O (OH) 2 + H 2 + H 2 O 2 O+H 2 O O+H 2 O (OH) 2 +2H H 2 (OH) 2 + 2H H 2 O :Fast, :No react 21

22 Agenda 1. Introduction 2. upon test 3. Surface analysis 4. Mechanism mm wafer test 6. Summary 22

23 300mm Wafer test Functional water unit (dnh 4 OH, H 2 O 2 control) Wafer cleaning tool Analytical tool Measuring the weight of wafer Etching rate of 23

24 etching rate [nm/min] 300mm Wafer test ppm NH4OH 10ppm NH4OH + 10ppm H + 10ppm H2O2 2 O 2 DIW CO2 Water 10ppm NH 4 OH 10ppm NH 4 OH DIW CO 2 water Result of 300mm wafer test ndition 10ppm NH 4 OH +10ppm H 2 O 2 nductivity μs/cm CO 2 water 10 μs/cm dissolution is avoided by rinsing with NH 4 OH and H 2 O 2 water in the wafer test. 300mm wafer test reproduced the result of coupon test. 24

25 Agenda 1. Introduction 2. upon test 3. Surface analysis 4. Mechanism mm wafer test 6. Summary 25

26 Summary ph and/or H 2 O 2 existence influence dissolution strongly. O, which is formed by oxidizer, functions as the passivation film. 300mm wafer test reproduced the result of coupon test. 26

27 Thank you for your attention. ntact: Yuichi Ogawa (Kurita)