ADA 26 9 716

Fabrication Process for CantileverBeam Micromechanical Switches

by Timothy J. Mermagen andBernard J. Rod

ARL-MR-96 August 1993

DTVI~ELEC"I

93-21933

9 3 9 2 1 04 5ý ff1111111111 ~ 1h~f111 M f1I1Approved for public release; distribution unlimited.

The findings in this report are not to be construed as an official Department ofthe Army position unless so designated by other authorized documents.

Citation of manufacturer's or trade names does not constitute an officialendorsement or approval of the use thereof.

Destroy this report when it is no longer needed. Do not return it to theoriginator.

REPORT DOCUMENTATION PAGE IOMS No. 0704"18Pthe ~p~ig bdg 1 Iod. acmcot o wcwoit of eW*W ivtig IhiptM inw ct V., amwow~mVjtn 0 o~wg siu map*t .. "~g•~li are n.nbem, V. wheedd i dmi~ awl• e op. =weme it. me dectoe, of kodewywoo Seed ,me~ww wm• a'e. ' •hepo cE Be

o, mw. w, m o n d n. o6 •.., SW no Imw, Opeovime ew4 RP 1215 ,, -,w•,*~ W" Suh. I~ Arl ii o . torG nde Pmw ID704-MOM Wso~n DC 20503

I. AGENCY UIE ONLY ,L"nwbb*) 2. RPO DATE I PM 1TYPE NO DATM COvMV

August 1993 Final, 7/85 to 12/89

.. .T.I AND .L DING. NUIRS

Fabrication Process for Cantilever Beam Micromechanical Switches

&. AIOI(01S)

Timothy J. Mermagen and Bernard J. Rod

7. 11111ORInA 01GNZTINAK AMD ADOflESS(E) A, P OWFINIO ORGANZATIONU.S. Army Research Laboratory Rwom NUMER

Attn: AMSRL-WT-NG ARL-MR-962800 Powder Mill RoadAdelphi, MD 20783

t. SPONUORIGMOVORIIG AGENCY OMAEO) AND ADDSI&SES) 10. SPONS114GOISOMrORNG

U.S. Army Research Laboratory AGENCY MMrr NUS

2800 Powder Mill RoadAdelphi, MD 20783

. SIUP•U •UMWY NOTE

Approved for public release; distribution unlimited.

13. ABSTRACT Ikeomm "0 *owr*)

This report presents a detailed process description for fabrication of a micrornechanical acceler-ometer sensor switch. The switch consists of a metallic cantilever beam structure that is defined withsilicon micromachining processing technology. The beam is made up of a gold-nickel-gold tri-metallic structure, which is anchored at one end to a silicon substrate; the process was designed to becompatible with current integrated circuit technology used in industry.

14. UaBXT TOM it. MWUMIn Of PAGES18

Accelerometer, cantilever beam, switch 18 101o11 'OD

1?. SEUFTY CLASOMAICAON It SECUIMT CLASSIFCATION 116 ECUIMYCLAISRCATIO 20. LIMITATION OF ABSTRACTOPASPOF l OF PACE OF ABSTACTUnclassified Ur rlassified t inclassified SAR

HMO01 -26045 SUdr=•d Form 29 (Rov_ 249)Preowdby ANI Bid 2 -18256-lO2

Page

Contents

1. Itntroduction ........................................................................................................................................... 5

2. Cantilever Beam Fabrication Process .......................................................................................... 6

3. Results and Problem Areas ........................................................................................................... 10

4. Conclusions .......................................................................................................................................... 11

Acknowledgments ................................................................................................................................ 11

D istrib u tio n ............................................................................................................................................... 2 1

Appendices

A. Description 0'r'Thtiever Beam Design ................................................................... 13B. Chemistry and Materials Used in Cantilever Beam Process ........................................................... 17

Figures

1. Three-beam device (SEM photomnicrograph)............................................................... 52. Diagrammatic fabrication steps .......................................................................................................... 73. Photomask levels and composite ........................................................................................................ 84. Actual beam parameters .......................................................................................................................... 95. Die contact (TO-5) ................................................................................................................................ 106. Photograph of TO-5 header with beams ........................................................................................... 10

List

1. Steps in cantilever beam process ............................................................................ 6

A(oes.alan For

1 Ju: ;,.t

r, -,t

I By .------

If DA r~rr. .....

' .I

1. IntroductionA process for fabricating advanced micromechanical sensors used in safety andarming devices, munitions, and electronic fuzes was designed at the ArmyResearch Laboratory (ARL). The main objective of this program was to develop aprocess for the fabrication of cantilever beam mechanical switches on a siliconsubstrate that is compatible with standard integrated circuit manufacturing tech-nology (app A). 1 2 The switch consists of a number of cantilever (diving-board-shaped) beams that are open in the up (relaxed) position and closed in the down(stressed) position. The switching mechanism was designed to close when a spe-cific acceleration threshold was exceeded and to remain open or to reopen whenbelow this threshold. Three cantilever beam sizes, for three different accelerationthresholds, were processed and tested. A comparison of this work with otherdesigns was presented at Transducers '87.3

A photomicrograph of an actual device is shown in figure 1.

Figure 1. Three-beamdevice.

1L. 1. Maissel and R. Glang, Handbook of Thin Film Technology, McGraw-Hill Book Co., New York (1970), pp7-37.2W. D. Frobenis, S. A. Zeitman, M. H. White, D. D. O'Sullivan, and R. G. Hamel, Microminiature Ganged Thresh-old Accelerometers Compatible with Integrated Circuit Technology, IEEE Trans. Electron Devices ED-19, No. I(January 1972).3. Robinson, D. Overman, R. Warner, and T. Blomquist, Problems Encountered in the Development ofa MicroscaleG-Switch Using Three Design Approaches, Proceedings, 4th International Conference on Solid-State Sensors andActuators, Transducers '87, pp 410-413.

5

2. Cantilever Beam Fabrication ProcessThe beam fabrication process incorporates four different photomasking levelswith 62 processing steps (see list 1). These steps are combinations of materialsdeposition and etching techniques (app B) used to control the film uniformity, thebeam lengtls and thicknesses, and the final gap parameters between the metalcontacts. The beam structure is a ti-metallic strip made up of a single layer ofnickel sandwiched between two layers of gold. The nickel film was integrated intothe beam structure as a means of enhancing the thermal and tensile characteristicsof the beam during deflection.

The process begins with removal of all organic and metallic contaminants from asilicon substrate in a standard MOS (metal oxide semiconductor) cleaning process(app B). After adequate rinsing in deionized water, a 1000-A layer of thermaloxide (SiO2) is grown (fig. 2a). This oxide acts as an insulation layer between theconduction pathways on the cantilever switch and the semiconductor silicon sub-strate. On top of this oxide, a 2000-A layer of polysilicon is deposited by LPCVD(low-pressure chemical vapor deposition) (fig. 2b). This layer is used as an etchbarrier to protect the lower SiO 2 insulator during final patterning of the cantileverswitch. The polysilicon layer makes a good etch barrier because of the selectivityof the polysilicon etch. After the electrical isolation layer and etch barrier aregrown and deposited, the cantilever structure is fabricated.

List 1. Steps in cantilever beam process.

1. MOS clean wafer 21. Develop and rinse 44. De-scum in plasma etcher in 022. Grow oxide to 1000 A 22. De-scum in plasma etcher in 02 45. Hard bake3. Deposit polysilicon to 2000 A 23. Hard bake 46. Etch gold-nickel-gold, 70 s

(LCVD) 24. Etch SiO2 in buffered HF 47. Hard bake 5 min.4. Evaporate chrome to 500 A 25. Plasma ash photoresist in 02 48. Etch CVD SiQ2 buffered HF,5. Evaporate gold to 3000 A 26. Evaporate chrome to 500 A 2.5 min.6. Apply HMDS 27. Apply HMDIS 49. Plasma ash photoresist in 02

(hexamethyldisilizane) 28. Apply negative photoresist 50. Etch CVD SiO2 buffered HF, 87. Apply negative photoresist 29. Soft bake min.8. Soft bake (90-C) 30. Expose mask level 2 51. Etch both chrome layers. 3 min.9. Expose mask level 1 31. Develop and rinse 52. Deionized (Di) H20 rinse, air

10. Develop and rinse 32. De-scum in plasma etcher in 02 dry11. De-scum in plasma etcher in 02 33. Hard bake 53. Examine beams12. Hard bake (134 to 140 0C) 34. Etch chrome, 45 s 54. Apply photoresist (secure13. Etch gold, 45 s 35. Plasma ash photoresist in 02 beams)14. Etch chrome, 30 s 36. Evaporate gold to 9000 A 55. Soft bake

15. Plasma ash (etch) photoresist in 37. Evaporate nickel to 1000 A 56. Separate die (wafer saw)02 38. Evaporate gold to 9000 A 57. DiH20 rinse, air dry

16. Deposit SiO2 to 10,000 A 58. Plasma ash photoresist in 02(CVD) 39. Apply HMDiS 59. Die bond to header package

17. Apply HMDS 40. Apply negative photoresist(-5)18. Apply negative photoresist 41. Soft bake 60. Bond die with gold wire19. Soft bake 42. Expose mask level 3 61. Cap TO-5 header20. Expose mask level 2 43. Develop and rinse 62. Perform centrifuge testing

6

____re_____(__I________ Grow thermal AuFigurea2. (a) oxide 1000 A MDiagrammatic Cfabrication steps. N So2

(b) Deposit polysilicon = Z*i ouj

(b) LPCVD 2000 A s=ubam

e + Au Evaporate Cr/Au and() Evaporate Cr A pattern bottom contact(c) Cr: 50o A

Au: 3oooA _ _.

Pattern Au I(d) ~bottom contact

Leave CrMask 1

(e) Deposit SiO2 Deposit CVD SiC2 andCVD: 1 .rm pattern spacer + gap

(f) SPattern deposited

(g) • Evaporate Cr

Cr: 500 A

Mask 2

Evaporate Cr layer + pattern,(h) Remove Cr then remove Cr from

from common contact area"contact only!

Evaporate Au-Ni-Aufor beama1. lg ir total

j• Mask 3

Pattern Au-Ni-Au

for beam(remove bulk Cr)

Evaporate Au-Ni-Aupattern 3 beams

(k) Etch SiO2

from underneathbeam

(I) 4 Remove bothlayers of Crunderneath beam

Mask 4

7

The cantilever switch consists of a beam structure that is anchored on one end andfloats at a distance called the "beam gap" above a contact pad on the other end.The contact and anchor consist of 3000 A of thermally evaporated gold. which sitsatop 500 A of thermally evaporated chrome (fig. 2c). The thin layer of chrome actsas a glue layer between the gold and the polysilicon. The gold and chrome layersare then patterned (fig. 2d) and etched with photomask I (fig. 3), which defines thebeam anchor and contact on top of the polysilicon.

Upon the beam anchor and contact, a 10,000-A layer of CVD (chemical vapordeposition) oxide is deposited to act as a spacer for the future beams (fig. 2e). Thisoxide defines the "beam gap" of the cantilever switch. The spacer oxide is pat-terned (fig. 2f) and etched with photomask 2 (fig. 3).

Deposited upon this spacer oxide is a sacrificial adhesion layer consisting of 500 Aof evaporated chrome (fig. 2g). This chrome layer is used as a glue layer forattaching the beam structure to the spacer oxide. The chrome is then patterned(fig. 2h) and etched with photomask 3 (fig. 3). The chrome is removed from on topof the anchor area to allow for a gold-to-gold adhesion (high-quality adhesion) ofthe beam to the anchor in subsequent steps.

The final metal depositions form the beam structure. This structure is built up ontop of the patterned chrome. The beam is basically a t-i-metallic strip made up of a1.9-.um-thick, thermally evaporated gold-nickel-gold sandwich (fig. 2i). The cen-ter nickel layer adds rigidity to the beam structure. The bottom layer of gold givesthe beam tri-metallic strip properties, allowing for uniform thermal expansion

Figure 3. Photomask f _

levels and composite.

Mask level I Mask level 2bottom contact spacer and gap

Mask level 3 Mask level 4common contact cantilever beams

Composite level

8

between the top and bottom surfaces of the beam. The beam structure is etchedand patterned (fig. 2j) with photomask 4 (fig. 3).

Once the beams have been defined, the spacer oxide is removed from underneathby a buffered HF etch solution (fig. 2k). The polysilicon layer protects the lowerSiO 2 layer or the bulk silicon substrate from being etched while the spacer oxideis being removed.

The chrome glue layer, under the beam and between the beam contact and anchor,

is removed next (fig. 21). This electrically isolates the beam from the contact. Oncethis final step is completed, the beams are finished and ready for dicing (individualdie separation).

After the beams were fully processed, the individual beam structures, which con-sist of three different-length cantilever beams on one common anchor with threeseparate contacts (fig. 4), must be separated into single dies for packaging and test-ing. As a first step, the beams are stabilized with poured on (not spun on) photo-resist; this supports the fragile, free-floating beams during the wafer dicingprocess. The photoresist is then soft baked at 900 C for 30 minutes before die sepa-ration. The die separation at ARL was performed on a Micro Automation waferdicing saw, which uses a water spray for cooling the saw blade and removingdebris from the surface of the wafer. After separation, the photoresist is removedfrom the individual dies by plasma ashing and wet chemistry. The cantilever beamgroup dies are then individually mounted and bonded into a test package. ARLused a TO-5 header package (fig. 5) for the electrical and centrifugal testing, andthe die were mounted on the header with epoxy (fig. 6).

Figure 4. Actual Beam lengths (3) A: 228.6 im

beam parameters. B: 177.8 gmC: 101.6 gm

Beam width D: 50.8 gmBeam thickness E: 1.9 gmBeam spacer and contact gap F: 1.0 gm

D

F1~H-AB 3 beams

[j= C

Commoncontact

Gold -- E contactNickel-

F

Figure 5. Die contactcr0O5).

Beam contacts contact

0 .0 1016 cm 7 10

0.01778cm --

0.02286 cm -

Figure 6. Photographof TO-5 header withbeams.

3. Results and Problem AreasThe laboratory fabrication of the metal beam cantilever switches on 2-in.-diametersilicon substrates yielded more than 800 di:.o per wafer. The final yield of func-tioning cantilever switches was approximately 40 percent per wafer. This lowyield is believed to be caused by imperfect fabrication techniques and stress-pointfailure.

After the wafer sawing procedure and the removal of the photoresist, a number ofthe cantilever beams were found to be broken off at the anchor point and otherswere bent or twisted; these problems were not evident before the photoresist wasremoved. We believe the deformities were caused by wafer handling that dis-closed stress points at the root of the beams. We would need to investigate further

10

to see whether wafer handling can be minimized in such procedures as die separa-tion and post-gap oxide removal processing. It should also be possible to alleviatethe stress point at the root of the beam, which may be caused by deposition of thetri-metallic stri- beam over a sharp edge of SiO2 gap spacer layer. This sharp edgecould cause tx.; beams to warp, resulting in larger than desired beam gap. Adjust-ing ti1 etciung of the SiO 2 to remove the sharp corners before metal depositioncould reduce the stress concentrations in this area.

Pa%;kaged devices from the initial wafer lots were tested in a laboratory centrifugeso that closure contact and resistance could be determined. The beams failed tomake switch contact at the target acceleration or even at three times the targetacceleration. This failure to make electrical contact was due either to an excessivebeam gap underneath the cantilever structure, combined with the enhanced stiff-ness of the beam, or to the presence of nonconductive material in the contact areaof the switch.

Another phenomenon was that switches that were measured to be electricallyshorted (closed) failed to open under high reverse acceleration. These closedswitches may have been mechanically bent in wafer-handling procedures or dur-ing die separation, or cold welding may have occurred between the gold surfaceson the beam and underlying contact pad.

4. ConclusionsWe have demonstrated a fabrication procedure for producing micromechanicalmultilevel metal cantilever beam switch arrays using semiconductor process tech-nology. These beams could be produced in large quantities at a low cosL Problemswith wafer-handling procedures, adequate residual removal, die separation proce-dures, and gold-to-gold cold welding contributed to statistically low yields andnonfunctioning switches. Studies on other beam materials, such as silicon, couldbe performed with the goal of creating more rigid beams with larger restoringforces and heavier end masses. Studies in electrical contact materials, such asevaporated platinum film, for the fixed side of the beam contact could correct thecold welding problem.

AcknowledgmentsThe authors wish to acknowledge Theodore Blomquist's leadership and efforts inthe design and fabrication of the micromechanical cantilever beam switches. Wealso wish to acknowledge the support of Robert B. Reams for his assistancetowards the original design concepts used during the development of thephotomasks used for the cantilever beam structure, and Judith McCullen for herhelp in the photolithography and wafer processing of the cantilever beams. Also,the authors wish to acknowledge the valuable support given by David Overman,Charles Robinson, and Robert Warner.

11

Appendix A. Description of Cantilever Beam Design

13

' • " II II II I I

Appendix A

To facilitate the cantilever beam process development work, we chose a designbased on work done by Westinghouse researchers in 1972,1 in which they devel-oped a similar device using electroplated gold to build the cantilever beams. Al-though the beam lengths and widths used in our work are similar to those in theWestinghouse designs, the beam metallurgy and thicknesses are different. It wasnot within the scope of this work to attempt a detailed analysis of the structures todetermine the actual closing forces that could be expected. Our focus was ondeveloping a procedure to demonstrate that these types of beams could be suc-cessfully fabricated in a manner compatible with commerial integrated circuitprocessing.

The actual beam design used for our work is shown in figure 4 in the main body ofthe report. The three different beam lengths are used to give three different closingaccelerations. As shown in the fabrication flow diagram (see fig. A- i), the beam iscomposed of a gold-nickel-gold sandwich that is 1.9 jim thick and 50.8 tm wide,in lengths of 228.6, 177.8, and 101.6 tun each, with a contact gap of I Pi.

Figure A-1. Flow Starting wi Gi c& Ddiagram for cantilever imet,-3 nf. CosI oxid UI11Dsi,,o, -7o, Clan100ACr(A)beam fabrication 2 in. P-e 2 AuMprocess.

Aadeinmask I Am corf&•s a

1W.D. Frobenis, S. A.. Zeitman, M. H. White, D. D. O'Sullivan, and R. G. Hamel, Microminiature Gancged ThresholdAccelerometers Compatible with Integrated Circuit Technology, [Ep Trans. Electron Devices ED-19, No. 1 (January1972).

15

phwwSt oomo dpoiton phlireix bo

Appendix B. Chemistry and Materials Used in

Cantilever Beam Process

17

Appendix B

B-1. Chemical Solutions

B-1.1 MOS Clean

The MOS (metal oxide semiconductor) cleaning process consists of three cleaningand rinsing steps.

a Solution of 5 parts Di (deionized) H20 to I part NH4Oi to I part H20 2; immersefor 20 min at 80WC;rinse in DiH20

* lpart DiH 20 to 50 parts HF; immerse for 10 s;rinse in DiH20

0 6 parts DiH20 to I part HCL to I part H20 2; immerse for 15 min at 80 0C;rinse in DiH20

B-I.2 Gold and Nickel Etch

The gold etch solution diluted from full strength yields better control of metalbeam line edges.

Solution: 400 gm KI potassium iodide, 100 gm 12 iodine, and 400 Mal H20Etch rate: 400 to 1600 nm/min

B-1.3 Chrome Etch

Solution: 9 parts saturated ceric sulfate solution to I part HNO3Etch rate: 80 nm/min

B-1.4 SiO2 Chemical Vapor Deposited (CVD) Oxide (Buffered HF)

Solution: 10 parts NH4F to I part 48-percent HF

Etch rate: -65 to 75 nminmin for thermal silicon dioxide, -180 to 220 nm/min forambient pressure CVD oxide

B-1.5 Polysilicon Etch

Solution: 100 ml DiH20, 250 ml -NO 3, and 4 ml HFEtch rate: 310 nm/min (undoped polysilicon)

B-2. Materials

The following materials are needed for the cantilever beam process.

Photoresist: KTI 757 negative photoresistChemical etches: stored in plastic polyethylene containersDishes: Teflon (Petri type)Tweezers: flat-tipped stainless steelWater rinses: DiH20, 18 MCQ-cm resistivityGol&d 99.999-percent pure gold 0.1016-cm-diameter wireChrome: 99.999-percent pellet formNickeL Grade A sheet 0.00254 cm thickEvaporator filaments: Tungsten coils

19

Distribution

Administrator DirectorDefense Technical Information Center US Army Research LaboratoryAttn: DTIC-DDA (2 copies) Attn: SLCBR-AMCameron Station, Building 5 Attn: SLCBR-TB-VLAlexandria, VA 22304-6145 Attn: SLCBR-X

Attn: SLCBRUS Army Electronics Technology & Devices Abdn Pr

Aberdeen Proving Ground, MD 21005-.5066Laboratory

Attn: SLCET-E Naval Research LaboratoryAttn: SLCET-ER Attn: Code 2620, Tech Library BrAttn: SLCET-ER-S Washington, DC 20375Attn SLCET-I, Microelectronics CommanderAttn: SLCET-IAComneFT Monmouth, NJ 07703-5601 Naval Surface Warfare Center

Attn: Code WA501, Navy Nuc Prgns OfcUnder Secretary of Defense for Research & Attn: Code WA52

Engineering Attn: Microelectronics, R. GoetzAttn: Research & Advanced Tech Attn: E-43, Technical LibraryAttn: Asst to Sec/Atomic Energy Attn: WA50Attn: Dept Asst Sec/Energ., Environment & White Oak, MD 20910

Safety CommanderAttn: Dep Under Sec /Res & Advanced Tech ComneAttn: Dep Under Sec/Test & Evaluation Naval Surface Warfare CenterDepartment of Defense Attn: Code WR, Research & Technology DeptWashington, DC 20301 Attn: DX-21 Library Div

Dahlgren Laboratory

Commander Dahlgren, VA 22448US Army Materiel CommandAttn: AMCDE, Dir for Dev & Engr Booz-Allen & Hamilton, IncAttn: J. TerrellAttn: AMCDE-R, Sys Eval & Testing 8283 Greensboro DriveAttn: AMCNC, Nuclear-Chemical Ofc McLean, VA 221025001 Eisenhower AveAlexandria, VA 22333-0001 Micrion Corporation

Commander Attn: D. Stewart

CECOM R&D Tech Library One Corporation Way, Centennial Park

Attn: ASQNC-ELC-IS-L-R Peabody, MA 01960-7990

Ft Monmouth, NJ 07703-5018 U.S. Army Research Laboratory

Director Attn: AMSRL-D-C, Legal Office

US Army Electronic Warfare Laboratory, Attn: AMSRL-OP-CI-AD, Library (3 copies)

LABCOM Attn: AMSRL-OP-CI-AD, Mail & Records

Attnu SLCET-D, Electronic Tech & Devices Lab Mgmt

Attn: ASQNC-ELC-IS, Information Services Attn: AMSRL-OP-CI-AD, Tech Pub

Div Attn: AMSRL-EP-EE, G. Simonis

FT Monmouth, NJ 07703-5601 Attn: AMSRL-EP-EE, M. SteadAttn: AMSRL-SL-NC, J. McCullen

21

Distribution (cont'd)

US Army Research Laboratory (cont'd) US Army Research Laboratory (cont'd)Attn: AMSRL-SS-F, R. B. J. Goodman Attn: AMSRL-WT-NG, H. BoeschAttn; AMSRL-SS-IA, T. Tayag Attn: AMSRL-WT-NG, H. EisenAttn. AMSRL-SS-IA, N. Gupta Attn: AMSRL-WT-NG, J. BenedettoAttn. AMSRL-WT-CS, Chief Attn: AMSRL-WT-NG, K. W. BennettAttn: AMSRL-WT-E, Chief Attn: AMSRL-WT-NG, M. DeLanceyAttn: AMSRL-WT-EH, Chief Attn: AMSRL-WT-NG, R. B. ReamsAttn: AMSRL-WT-EP, Chief Attn: AMSRL-WT-NG, R. MooreAttn: AMSRL-WT-ES, Chief Attn: AMSRL-WT-NG, T. GriffinAttn: AMSRL-WT-L, R. Gilbert Attn: AMSRL-WT-NG, T. MermagenAttn: AMSRL-WT-N, J. M. McGarrity (10 copies)Attn: AMSRL-WT-NB, D. Davis Attn: AMSRL-WT-NG, T. OldhamAttn: AMSRL-WT-ND, J. R. Miletta Attn: AMSRL-WT-NG, T. TaylorAttn: AMSRL-WT-NG, A. J. Lelis Attn: AMSRL-WT-NH, H. BrandtAttn: AMSRL-WT-NG, B. Geil Attn: AMSRL-WT-P, ChiefAttn: AMSRL-WT-NG, B. J. Rod Attn: AMSRL-WT-RS, ChiefAttn: AMSRL-WT-NG, B. McLean Attn: AMSRL-WT-TN, ChiefAttn: AMSRL-WT-NG, C. Pennise Attn: AMSRL-WT-TS, ChiefAttn: AMSRL-WT-NG, Chief

22