NB SEMIPLATE CU 100 Copper electroplating process

Transcription

1 NB SEMIPLATE CU 100 Cpper electrplating prcess INTRODUCTION The NB SEMIPLATE CU 100 prcess is an acid cpper plating frmulatin engineered fr wafer plating applicatins including cpper bump plating, intercnnects fr VLSI/ULSI r MEMS. The NB SEMIPLATE CU 100 prcess prvides excellent thrwing pwer, imprved levelling characteristics, ductile lw stress depsits and ffers unique flexibility in its peratin. This prduct is frmulated, packaged, and quality cntrlled accrding t the needs f the semicnductr industry. The slutin is made up with CU 100 MAKE UP and the CU 100 additives described belw. NB SEMIPLATE CU 100 is shipped ready-fr-use, while the CU 100 xxx are cmpunds and used fr mixture and maintenance. READ ENTIRE TECHNICAL DATA SHEET BEFORE USING THIS PRODUCT. MATERIALS REQUIRED The fllwing materials are nrmally recmmended fr a typical start up and peratin: Prduct Name NB SEMIPLATE CU 100 CU 100 MAKE UP CU 100 MD CU 100 LO CU 100 COPPER SULPHATE ready-fr-use slutin Cmment supplied pretested and ready t use t make up the initial perating slutin. Brightening Carrier Cncentratins f this additive can be varied in wrking slutins based n specific perating preferences. Brightening Agent Cncentratins f this additive can be varied in wrking slutins based n specific perating preferences. used t replace cpper in heavy drag-ut situatins Materials are purified and packaged fr semicnductr applicatins in clean rm cmpatible packages In additin, there might be needed sulphuric acid (H 2 SO 4 ) and hydrchlric acid (HCl) needed fr maintenance (use nly reagent r semicnductr grade). Rev 1.4 / Page 1

2 EQUIPMENT REQUIRED The fllwing sectin is a guide fr usual peratin cnditins. The specific cnditins and requirements may depend n tl vendr specificatins and applicatin. Acid cpper sulphate slutins are highly crrsive Therefre, expsed metal materials in the fab area shuld be prtected frm the effects f these slutins. Several cats f a vinyl cating can prvide adequate prtectin. Tanks Leaching Agitatin Heating and Cling Filtratin Ventilatin Rectifiers Andes PVC, PVDC, plyprpylene r Tefln tanks can be used. Tanks, filter cartridges, ande bags, and peripheral equipment must be leached prir t installatin. Depending n tl status, this may include degreasing, base slutin treatment, DI water rinse, acidic treatment and final DI-water rinse. Slutin agitatin is necessary t achieve the best results. Slutin agitatin, withut air, is recmmended. Increased slutin flw rate can be imprtant fr unifrm plate distributin and plating rate. Cling cils may be cnsidered fr temperature adjustment. Cling and heating cils made f titanium r Tefln-cated cpper may be used. Tefln tube bundles, immersin type heat exchangers r external heat exchangers are preferred. Cntinuus filtratin is necessary fr maintaining lw particle cunts f the slutin. Use wven Dynel r plyprpylene filter cartridges (with a plyprpylene cre) with a 5 micrn r less retentin. Cttn filters must nt be used. Filter cartridges must be leached befre installatin in the tl (refer t next sectin). Ensure sufficient exhaust (acidic mists) and check with lcal regulatins. Direct current r pulse rectifiers (direct r reverse mde) may be used. Make sure t use pwer supply withut current ramping and ripple less than 2%. Cnsult NB Technlgies GmbH fr specific applicatin recmmendatins. Andes must be degrease and cnditined (refer t next sectin). Cpper andes with a certified unifrm phsphrus cntent f 0.045% t 0.06% must be used. Cpper andes with a certificatin f phsphrus cntent are available frm NB Technlgies GmbH. If cpper andes, ther than phsphrized cpper andes are t be used, btain certificatin verifying that phsphrus cntent is unifrm and within the specified range. Pure electrlytic r OFHC cpper cannt be used. Rev 1.4 / Page 2

3 MAKE UP PROCEDURE 1. Prper leaching and cleaning f the tank is mandatry. Depending n the tl status (used r first time f use), the tank must be leached with a slutin cntaining 45 g/l trisdium phsphate and 7.5 g/l sdium hydrxide heated t 60 C fr 4 t 8 hurs. Scrub tank lining with slutin t remve any dirt, ils r surface sils. Be careful t flush thrughly with several rinses t remve all residues f sdium (filled and drained). 2. Then leach with 10% by vlume sulfuric acid heated t 50 C fr 8 hurs. Again flush tank with wate r. 3. Empty the tank. 4. Carefully pur r pump recmmended amunt f CU 100 MAKE UP int tank. 5. Cpper andes: new cpper andes must be cleaned f ils, rganic materials, dirt, xides and sulfides. If vapurs degreasing is pssible, this is the preferred first step tward remving grease and il and sils bund by these materials. As an alternative t vapur degreasing, the andes may be ttally immersed in a ht, alkaline sak cleaner fr at least ne hur, fllwed by thrugh rinsing. 6. The ande skin must then be etched t unifrm, matte pink cpper in a slutin f 120 g/l ammnium persulfate and 5 ml/l f cncentrated sulphuric acid. Etch the andes fr at least 1minute up t 20 minutes, fllwed by a thrugh water rinse 7. Sak in 10% by vlume sulphuric acid fr 30 t 60 sec with a final rinse in DI-water. 8. Evidence f any smth, shiny areas n the andes at this pint indicates an incmplete etch. Etch the andes nce again in a fresh persulfate slutin r use a mre aggressive etchant. Etchants f the perxide/sulphuric type act well in remving cpper ande skins due t their aggressive nature. Mst f the cmmercially available stabilized etchants are suitable when prepared and used accrding t the manufacturer's recmmendatins. Fllw the safety precautins given in the supplier's literature because these slutins are strngly acidic and are xidizers. Rinse the andes, treat in 10% by vlume sulphuric acid and rinse nce again as wuld be dne with the ammnium persulfate etch prcedure. 9. Rinse the andes with DI-water and install int plating tl. 10. Pre-leached ande bags may be used in sme applicatins where installatin is recmmended by the equipment vendr. 11. Clean, prepare and use a cpper dummy cathde panel r cpper blanket seeded wafer fr ande filming. Prepare enugh cathde area t prvide a cathde current density n greater than 10 ma/cm² (1.0 ASD) while filming the ande at 10 t 15 ma/cm² (1.0 t 1.5 ASD) ande current density. Plate the dummy cathde fr ½ t 1 hur befre adding CU 100 additin agents as described in the start up sectin f this manual. Cntinue electrdepsitin fr apprximately 4 hurs maintaining additive cncentratins by ampere hur r by tl supplier recmmendatin. During this time a black cntinuus film will frm n the andes. When a unifrm film n the andes is achieved, remve the dummy cathde panels. The panels shuld have a unifrm, satin, t bright pink depsit f cpper. 13. Inspect each individual ande fr the presence f the black film, taking care nt t disturb the film. If there are any andes which d nt have the prper film verall, repeat the abve filming prcedure. 14. Leach string wund plyprpylene filter cartridges at this time by immersing in biling DI-water fr 30 minutes, fllwed by thrugh rinsing with deinized water. This prcess must be repeated until there is n evidence f fam r turbidity f the biling water. The cartridges must then be immersed in a slutin f 10% by vlume reagent grade sulphuric acid, t which 2.5 ml/l f CU 100 MD has been added. The cartridges must be allwed t sak fr 1 hur. Fr sub-micrn filters fllw the manufacturer recmmendatin fr preparatin prir t installatin. 15. Add CU 100 MD and CU 100 LO starting dsages. Dispense the additives thrughut the tank and allw fr prper mixing while running the agitatin pumps. Air agitatin may be used in sme applicatins as recmmended by yur tl supplier. 16. Install leached filter cartridges and start filtering the slutin. The slutin is nw ready fr prductin peratin. 17. Take a sample f the slutin and send t NB Technlgies GmbH t check fr final additive cncentratins. Rev 1.4 / Page 3

4 BATH PARAMETERS The fllwing table shws the bath parameters, which shuld be maintained and checked with regular sample analysis. NBT analysis Units Max. upper Upper actin Optimum Lwer actin Lwest Cu X g/l Cpper sulphate (pentahydrate) X g/l Sulphuric acid X g/l Chlride In X mg/l CU 100 MD X ml/l CU 100 LO X ml/l ,5 1 PLATING CONDITIONS Parameter Optimum Range Cathde current density [ma/cm²] Flw (depending n tl) [l/h] Ande t cathde area rati 1:1 1:1 t 2:1 Ande t cathde spacing [cm] 5-15 (depend n tl and wafer size) Temperature [ C] OPERATION Cpper sulphate Cpper sulphate is used in the NB SEMIPLATE CU 100 prcess t prvide the prper cncentratin f cpper ins. In peratin, cpper is replenished frm the andes. Fluctuatins in the cpper cntent f the slutin may be cmpensated by adding CU 100 COPPER SULPHATE r bleeding slutin as necessary. Add nly specially pre-purified cpper sulphate, CU 100 COPPER SULPHATE t the slutin r CU 100 MAKE UP if bleed and-feed prcess cntrl is used. Cpper Cncentratin and Andes The cpper cncentratin f the electrlyte will change slightly with use and time. If there is an excessively high ande t cathde rati, r if the slutin is infrequently used, the cncentratin f cpper in the electrlyte will rise steadily. When a slutin is used infrequently and/r is taken ut f service fr lnger than 2 weeks, remve all andes and stre in a tank f clean, DI-water. If left in the electrlyte, the high free acid will disslve the cpper. Sulphuric Acid Sulphuric acid perfrms the principal functin f maintaining high slutin cnductivity. Add nly reagent r semicnductr grade acid t adjust the slutin. Chlride Ins Chlride ins are essential t the prmtin f prper ande crrsin characteristics. The prcess requires a nminal cncentratin f 45 mg/l (ppm) f chlride in. Excess f 60mg/l is detrimental t the prcess peratin and must be avided. The chlride cntent is easily increased, when necessary, by the additin f reagent grade hydrchlric acid. Fr increasing 1mg/l chlride add 0,0023ml/l HCL (37%). Rev 1.4 / Page 4

5 Replenisher CU 100 MD and CU 100 LO are the additin agent replenishment slutins fr the prcess and are cnsumed during prcess. CU 100 LO is the brightening agent and is cnsumed at the rate f 0,2 t 0,8 ml per ampere-hur. CU 100 MD is the brightening carrier and is cnsumed at the rate f 1 t 3 ml/l per ampere-hur. The additin rate depends n the specific plating cnditins. Fllwing the initial additin f CU 100 MD and CU 100 LO at start up, it may be determined that the higher replenishment figure will be required. Leached tanks and filter cartridges will have a tendency t absrb the additive until a saturatin equilibrium is reached. Temperature Cntrl the temperature f the slutin between 21 and 27 C. The ptimum perating temperature is 24 C. Temperatures abve 27 C cause cluding f the brig ht depsit. Temperatures belw 21 C lwer the cnductivity f the slutin and cause graininess in the high current density areas. Hwever, cling r heating may nt be required if ambient temperature is within the range as indicated. Filtratin Cntinuus filtratin fr the remval f particulate matter is strngly recmmended. Clean and leach cartridges r filter bags prir t use accrding t the slutin make-up sectin f this dcument. D nt perate cntinuusly with carbn filter cartridges, r additin agent will be remved frm the slutin. Capacity f the pump and filter must be sufficient t turn ver the cmplete vlume f slutin at least nce per hur, preferably tw r mre times per hur. Pumps, fittings, pipes, valves, cnnectins and filter must be f inert acid resistant materials. Plastic and hard rubber are recmmended fr pumps. PVC, PVDC, plyprpylene and apprved grades f rubber are suitable materials f cnstructin fr filter chambers and baffles. Andes Maintain the ande area between 0.5 t 2.0 times (1:1 ptimum) the cathde plating area (wafer) fr NB SEMIPLATE CU 100 prcess. Exercise care in the riginal determinatin f the ande area and take int cnsideratin the increase in area due t fine features including vias and trenches. Andes facing tank walls have nly 85% f their full surface area andically effective. Establish a maintenance prgram t replace andes as cnsumed t keep the ande t cathde rati within the perating s. A black film is frmed n the andes when the slutin is plating. This film will remain n the ande when the slutin is nt in use. Take care nt t disturb this film as it plays a majr rle in the perfrmance f the slutin. Prperly filmed andes effectively prevent the additin agents frm being cnsumed at the surface f the ande and thereby decrease brightener cnsumptin. If the film is disturbed, small cpper fines will be set free causing rughness f the depsit and higher brightener cnsumptin until a new film is frmed. The use f incrrect andes will result in an inadequate film frmatin, high brightener cnsumptin, pr levelling and rugh depsits. Ande-t-Cathde Spacing Nrmal ande-t-cathde spacing fr wafer plating is 5 t 15cm depending n wafer size and ande shape. Current Density The nrmal current density range f 10 t 40 ma/cm² (1.0 t 4.0 ASD) is recmmended fr mst applicatins. Lwer currents may be desirable during filling f damascene structure. Rev 1.4 / Page 5

6 SPECIFIC PROCEDURES Oxygen plasma befre plating chemical pre-treatment nt recmmended/nrmally nt needed Cleaning f all items with DI befre insertin in electrlyte Wetting f wafer surface with DI water befre insertin int bath (check fr wetting) CUSTOMER SUPPORT Further custmer supprt n the prcess with this prduct is available by cntacting NB Technlgies GmbH. BATH ANALYSIS SERVICE NB Technlgies supprts the bath analysis and prvides special shipping kits including shipping bx, sample bttles and labels. DATA LOGGING Keep a recrd f ampere-hurs f use t determine replenishment vlumes. Examples f prcess lg sheets are available by cntacting NB Technlgies GmbH. HANDLING AND SAFETY INSTRUCTIONS Fr detailed infrmatin cnsult the material safety data sheets fr this prduct. Please read material safety data sheets carefully befre using this prduct. DISCLAIMER All recmmendatins and suggestins in this bulletin cncerning the use f ur prducts are based upn tests and data believed t be reliable. Since the actual use by thers is beynd ur cntrl, n guarantee expressed r implied, is made by NB Technlgies GmbH, its subsidiaries f distributrs, as t the effects f such use r results t be btained, nr is any infrmatin t be cnstrued as a recmmendatin t infringe any patent. ADDRESS NB Technlgies GmbH Fahrenheitstr Bremen Tel Fax inf@nb-technlgies.de Rev 1.4 / Page 6