Sensor Integration on a W-CVD Cluster Tool for Real-Time Process Monitoring and Control

Transcription

1 Sensor Integration on a W-CVD Cluster Tool for Real-Time Process Monitoring and Control J.N. Kidder, Jr., Yiheng Xu. Nayanee Gupta, Theodosia Gougousi, Laurent Henn-Lecordier, G.W. Rubloff University of Maryland Department of Materials and Nuclear Engineering and Institute for Systems Research College Park, MD Supported by NSF, SRC, Texas Instruments, Leybold Inficon, Ulvac Corp., NIST AVS 1998 PC-FrM4 1

2 Outline APPLICATIONS In-situ Chemical Process Sensing and Sensor Integration Real-time Metrology (thickness, composition) Process Control Fault Management and Detection Process Dynamics and Mechanisms OUTLINE W-CVD Process, ULVAC cluster tool Syncronous collection of tool state and sensor signals In-situ mass spectrometry for downstream chemical sensing Application of a continuous acoustic sensor AVS 1998 PC-FrM4 2

3 Chemical Vapor Deposition for W Metallization Reaction Chemistry (1) WF 6 (g) + 3H 2 (g) > W (s) + 6HF (g) (2) WF 6 (g) + SiH 4 (g) > W (s) + SiF 4(g) + 2HF (g) + H 2 (3) WF 6 (g) + 3/2Si (s) > W (s) + 3/2SiF 4(g) Pressure (Torr) CVD Process Parameters Selective (Si over SiO 2 ) SiH 4, WF 6 Blanket H 2, WF Temperature (C) AVS 1998 PC-FrM4 3

4 Cluster Tool and Sensor Signals To Scrubber PROCESS PUMPS Leybold-Inficon AGM H3M CIS Quadrupole Mass Spectrometer PUMPS -3 AMU Mass Spectra Selected AMU vs. Time TMP TMP Temperature Pressure (Rxtr, L/UL, Buffer) Valve State Throttle Valve Position MFC Outputs REACTOR BUFFER REACTOR LOAD UNLOAD LabView Platform Synchronous Signal Collection TOP VIEW SCHEMATIC ULVAC CLUSTER TOOL AVS 1998 PC-FrM4 4

5 In-situ QMS: Downstream Sampling QMS Chamber P ~ Torr Closed Ion Source P ~ 1-3 Torr IG 2 µm orifice Process Exhaust Line P ~ 1-2 Torr QMS Sensor Electronics Quadrupole Mass Filter 5 l/s TMP Roots/Rotary Process Pumps AVS 1998 PC-FrM4 5

6 W-CVD Process Cycle Wafer T H 2 WF 6 P 6 s 9 s 24 s 9 s Time Load Heat W Deposition Cool Unload AVS 1998 PC-FrM4 6

7 Equipment States: One Process Cycle WF 6 Flow By-pass Reactor Wafer T H 2 WF 6 Rxtr P 12 W Deposition 562 Sensor Signals (a.u.) T H 2 MFC P WF 6 MFC Time (s) AVS 1998 PC-FrM4 7

8 Real-Time Mass Spectrometric Sensing QMS Ion current (a.u.) 6E-7 3E-7 4E-9 2E-9 81r2 81r2 W Deposition H + 2 (2) WF + 5 (279) HF + (2) 1E-1 5E-11 4E-11 2E-11 H 2 : 4 sccm WF 6 : 1 sccm 45 C.2 Torr 3 s deposition WF 6 (g) + 3H 2 (g) > W (s) + 6 HF (g) WF 6 (g) + 3/2Si (s) > W (s) + 3/2 SiF 4 (g) SiF 3 + (85) Time (s) AVS 1998 PC-FrM4 8

9 In-situ QMS: HF production, WF 6 depletion H 2 WF 6 Wafer T MFC out MFC out Step Flow T 1 H 2, WF 6 R.T. 2 H 2 Heat 3 H 2, WF 6 45 C 4 H 2 Cool 1E-1 WF 5 + (279) P =.2 Torr H 2 : 4 sccm WF 6 : 5 sccm 5E-11 QMS Ion current (a.u.) 4E-9 2E r2 HF + (2) Time AVS 1998 PC-FrM4 9

10 P:.2 Torr, 24 s deposition H 2 : 4 sccm, WF 6 : 4 sccm QMS Ion Current amu 2 (a.u.) 1x1-9 5x1-1 R.T C s 55 C Time (s) AVS 1998 PC-FrM4 1

11 QMS Downstream Sensing Reactant: WF Wafer T Rxtr to Pump o Valve State c H 2 MFC out WF 6 MFC out Step Gas Flow Wafer T 1 Vacuum Heat 2 H 2 < 45 C 3 H 2, WF 6 45 C 4 H 2 Cool 5 Vacuum ~R.T. QMS Ion Current, amu 279 (a.u.) 6x x Time (s) AVS 1998 PC-FrM4 11

12 Process Monitoring: Mass Spectrometry 6x1-11 WF 5 + (279) 12 QMS Ion Current, amu 279 (a.u.) 3x Time (s) AVS 1998 PC-FrM4 12

13 QMS Downstream Sensing: HF Wafer T Rxtr to Pump o Valve State c H 2 MFC out WF 6 MFC out Step Gas Flow Wafer T 1 Vacuum Heat 2 H 2 < 45 C 3 H 2, WF 6 45 C 4 H 2 Cool 5 Vacuum ~R.T. QMS Ion Current, amu 2 (a.u.) 2x1-9 HF + (2) 1x Time (s) AVS 1998 PC-FrM4 13

14 Downstream Sensing CVD By-Product: HF QMS Ion Current, amu 2 (a.u.) 1x1-9 2x1-9 HF + (2) Time (s) AVS 1998 PC-FrM4 14

15 Acoustic Sensor for Downstream Sensing Acoustic sensor measures gas composition via speed sound Speed of sound dependent on average molecular weight Schematic of Leybold Composer Gas Composition Sensor Inlet Transmitter Receiver Resonance Chamber Outlet AVS 1998 PC-FrM4 15

16 Acoustic Sensor Data 3 Composer Resonant Frequency vs Time (WF 6 /H 2 /Helium) data graph 5 29 Frequency (Hz) //2 2/4/2 25/4/2 3/4/2 35/4/2 25 Flow WF6/H2 mixture in 2 sccm He Temperature=6C Pressure=27 Torrs 4/4/ :15 12:22 12:29 12:36 12:43 12:5 Time (hour:min) AVS 1998 PC-FrM4 16

17 Acoustic Sensor Data 3 29 Resonant Frequency vs WF6 Flow Rate WF6 flowed in 4 sccm H2 / 2 sccm Helium Temperature = 6C Pressure = 27 Torrs Frequency (Hz) WF6 flow (sccm) Detection of WF6 flow with a sensitivity of.1 sccm/hz (25 sccm WF 6 equivalent to PP WF6 11 x 1-3 Torr) Response time and sensitivity dependent on sampling configuration, gas stream composition. AVS 1998 PC-FrM4 17

18 Summary and Conclusions Equipment state and chemical sensor signals have been used to monitor events and dynamics through the process cycle on a W-CVD cluster tool. In-situ mass spectrometry was used to sense reactant (WF 6 ) depletion and reaction product (HF) generation. Effects of residual reactant species (WF 6 ) in the sampled exhaust line and generation of HF in the sensor were present in the QMS signal. An acoustic sensor has been used for downstream chemical sensing and demonstrated a significant sensitivity to reactant concentration variations. AVS 1998 PC-FrM4 18

19 Acoustic Sensor Data WF6 / H2 mixture in N2 purge gas data Graph Example: 35/4 => 35 sccm WF6 + 4 sccm H /4 2.5/4 5/4 7.5/4 5/4 Frequency (Hz) /4 3/4 35/4 4/4 2/4 1/4 1/4 H2 flow= 4 sccm N2 flow= 1 sccm Temp= 6 C Inlet Pressure= 365/335 Torrs 11: 11:1 11:2 11:3 11:4 11:5 Time (hour:min) AVS 1998 PC-FrM4 19

20 Acoustic Sensor Data Frequency Vs WF6 flow rate (WF6 / 4 sccm H2 / 1 sccm N2) data graph 2 Frequency (Hz) WF6 / H2 mixture in 1 sccm N2 H2 flow = 4 sccm Temp= 6 C Inlet Pressure= 365/335 Torrs Depletion profile WF6 flow (sccm) 9/17/98 13:13:22 AVS 1998 PC-FrM4 2

21 Acoustic Sensor Data Process with WF6 flow in 4 sccm H2 / 2 sccm He data Graph 1 Room temperature (WF6 flow manually changed) 2 sccm WF6 flow = constant Temperature modulated from 2 to 45 C 36 5 sccm 45 C 2 C 45 C 2 C Frequency (Hz) sccm 5 sccm 33 12:1 12:2 12:3 12:4 12:5 Time (hour:min) 9/1/98 14:37:14 AVS 1998 PC-FrM4 21