Metrology challenges in High volume ULK production Ulrich Mayer, Michael Hecker, Holm Geisler

Transcription

1 Metrology challenges in High volume ULK production Ulrich Mayer, Michael Hecker, Holm Geisler

2 outline ILD material choice in GLBALFUNDRIES New ULK processes and parameters Mechanical frontiers with ULK LAB technologies for mechanical properties Inline technologies for mechanical properties Summary ctober 13,

3 GLBALFUNDRIES ILD selection in BEL metallization New ILD materials have been introduced almost with every new technology nodes ULK has been introduced in 45nm technology in GLBALFUNDRIES ULK Volume production has started in Q ctober 13,

4 Porosity introduction in low k materials by UV Cure 1. Deposition of PECVD low k SICH + organic additive CH 3 H 3 C CH 3 H 3 C 2. Removal of organic additives by UV Cure process (=> shrinkage) ctober 13,

5 Porosity introduction in low k materials by UV Cure CH 3 CH 2 H 3 C CH 3 CH 2 H 3 C 1. Deposition of PECVD low k SICH + organic additive 2. Removal of organic additives by UV Cure process (=> shrinkage) 3. Enhancing mechanical properties by extended UV Cure (=> shrinkage) ctober 13,

6 Porosity introduction in low k materials by UV Cure CH 2 CH 2 1. Deposition of PECVD low k SICH + organic additive 2. Removal of organic additives by UV Cure process (=> shrinkage) 3. Enhancing mechanical properties by extended UV Cure (=> shrinkage) => densification, C-loss and shrinkage induced by UV Cure ctober 13,

7 Effects of UV Cure process Shrinkage is strongly correlated to UV Cure effects like mechanical properties Shrinkage can easily be derived by classic ellipsometry on product post deposition and UV Cure However accuracy for shrinkage measurement will decrease with smaller ILD thickness Shrinkage is not a real material property shrinkage [a.u.] shrinkage vs. Cure-time , UV Cure duration [a.u.} ctober 13, Young's Modulus by Nanoindentation [GPa] Youngs's Modulus vs. Curetime UV Cure duration [a.u.]

8 Young s Modulus on ILDs K value reduction goes along with lower density and weaker molecular bonds As a consequence mechanical properties also get lower Risk of getting too weak k/k0 (normalized) k vs. Young's Modulus Reduced Young's Modulus [GPa] Nylon Line wiggling cracks ctober 13,

9 Nanoindentation on thin ILDs LAB Metrology Challenge: lower Modulus thinner ILDs (45nm ->28nm) no plateau any more => extrapolation for d-> 0 E r refers to reduced Young Modulus Less than 10% difference for ~ 6x film thickness variation for low k / ~2x thickness variation for low k Normalized Modulus E r /E 0 Thickness vs Modulus Thickness [nm] Low k ILD ULK ILD Assumption: real mechanical film properties do not depend on film thickness! ctober 13,

10 Nanoindentation on patterned ULK LAB Metrology Densified surface layer visible with E r / E 0 > 1.43 at smallest contact depths NI as a (local) sensor for modified ILD surface Post Cu CMP Post Metal Etch > 500nm ULK CN ULK > 500nm *) Characterization of Mechanics of Ultralow-k Films and Advanced Cu/low-k Interconnect Structures ; Holm Geisler et al.; MRS

11 Adhesion measurement for ULK characterization LAB Metrology 4-point-bending technique: energy release rate G c as measure of the fracture toughness of materials / interfaces P L P epoxy for meas. prep. (EPTEK) release layer silicon silicon sample delamination b h film stack to be measured (e.g. dielectric barrier/ulk) load pin P P mixed mode (I+II) external load simple measurement independent of crack length - does not enter G c accurate for mean G c, e.g. ULK adhesion load steady state crack growth final stiffness initial stiffness displacement

12 Adhesion: Influence of ULK material and deposition process LAB Metrology type 1 failure: interface delamination of ULK/dielectric barrier -> low fracture toughness type 2 failure: cohesive delamination within ULK -> high fracture toughness ULK weak interface without adhesion promoter 2 ULK strong interface with adhesion promoter effect of reducing k huge effect of introducing adhesion promoter AES: dielectric barrier on cracked surface 12 -> sensitive proof of effects of process optimization needed and possible! AES: no dielectric barrier at crack

13 Metapulse I inline Metrology ptoaccoustic technology gnal amplitude is depending on position of sound wave inside ILD Measurement delivers sound velocity ν s, Young s Modulus Y and ILD thickness destructive interference constructive interference λ, θ tool constants n, ρ, ν given Min/Max for Time Period Phase Change for Thickness ctober 13,

14 Metapulse II inline Metrology correlation to Nanoindentation established Good repeatability < 0.5 % for sound velocity <1% for Young s Modulus Young's Modulus by Metapulse [GPa] correlation plot Young's Modulus by Nanoindentation [GPa] Both shrinkage and Young s Modulus show expected trend for different UV Cure conditions shrinkage [a.u] shrinkage & Young s Modulus vs. UV-utput-Power shrinkage 105 UV utput Power [%] Young's Modulus Youngs Modulus by Metapulse [GPa] ctober 13,

15 Mass metrology inline Metrology Density provided by Mass of ILD layer + ILD thickness density vs. Deposition conditions Sensitivty to Deposition and UV Cure process changes shown density [g/cm³] density post Dep density post Cure 1.1 Mass metrology will get more challenging with thinner ILDs Conclusions for k value based on density measurement by Clausius-Musotti relation *) *) G.Ditmer et al. : Application of Mass Metrology in Advanced Device Manufacture ASTS Symposium 2007 density [g/cm³] gas flow [a.u.] density post Cure density post Cure UV Cure time [a.u.] ctober 13,

16 Summary Growing ILD complexity with every new technology Mechanical frontiers are getting visible with further reduction of mechanical properties LAB techologies as Nanoindentation and 4pt-bend-test can be extended to ULK applications for further technologies New inline metrology available to accomodate higher complexity of new ILD processes ctober 13,