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1、IC工艺技术系列讲座第二讲,PHOTOLITHOGRAPHY光刻,讲座提要,1.General 2.Facility (动力环境)3.Mask (掩膜版)4.Process step highlight (光刻工艺概述)5.BCD 正胶工艺6.History and 未来的光刻工艺,1.General,MASKING Process (光刻工艺)Photolithography (光学光刻) -Transfer a temporary pattern (resist)Defect controlCritical dimension controlAlignment accuracyCross
2、section profile Etch (腐蚀) -Transfer a permanent pattern (Oxide, Nitride, Metal),2.0Facility requirement,Temperature (温度) 70 oFHumidity (湿度)45%Positive pressure (正压) 0.02in/H2OParticle control (微粒) Class 100Vibration (震动)Yellow light environment (黄光区)DI water (去离子水) 17mhomCompress air and Nitrogen (加
3、压空气,氮气)In house vacuum(真空管道),3.0Mask (掩膜版),Design PG tapeMask making Plate - quartz, LE glass, Soda line glassCoating - Chrome, Ion oxide, EmulsionEquipment - E-beam, Pattern generatorMask storage -Anti static Box,Pellicle,Pellicle protection,4.0光刻工艺概述,Prebake and HMDS (前烘)Resist coating (涂胶)EBR (去胶
4、边), soft bake,3.Exposure (曝光)Alignment (校正)4.Develop (显影)Post e-bake, Hard bake, backside rinse 5.Develop inspection (显检),4.1Prebake and HMDS treatment,Purpose of Pre-bake and HMDS treatment is to improve the resist adhesion on oxide wafer. HMDS is adhesion promoter especially designed for positive
5、resist.HMDS (Hexamethyldisilane) can be applied on the wafers by1. Vapor in a bucket2.vapor in a vacuum box3.Directly dispense on wafer4.YES system - in a hot vacuum system5.Vapor in a hot plate (with exhaust)Too much HMDS will cause poor spin, vice versa will cause resist lifting,4.2Resist Coating
6、(涂胶),Resist coating specification (指标）Thickness（厚度）0.7u 2.0u (3.0以上for Pad layer)Uniformity（均匀度）+ 50A +200ASize of EBR （去胶边尺寸）Particle（颗粒）20 per waferBackside contamination(背后污染）三个主要因数影响涂胶的结果ResistProduct (产品） Viscosity （粘度）SpinnerDispense method （涂胶方法）Spinner speed (RPM) （转速）Exhaust （排气）Soft bake t
7、emperature （烘温）FacilityTemperature （室温）Humility （湿度）,4.2.1Coater (涂胶机）,Equipment module and special featurePre-bake and HMDS - Hot/Cold plateResist dispense - Resist pumpRPM accuracy - MotorEBR - Top/bottomHot plate - soft bake temperature accuracyExhaustWaste collectionTemperature/Humidity control
8、hoodTransfer system - Particle and reliabilityProcess step and process program - Flexible,SVG 8800,升降机,涂胶,HMDS,热板,冷板,升降机,升降机,升降机,涂胶,热板,热板,升降机,升降机,升降机,升降机,涂胶,热板,冷板,HMDS,冷板,冷板,冷板,涂胶,热板,热板,升降机,升降机,显影,热板,热板,热板,冷板,4.2.2 Coater (涂胶机）combination,4.2.3 Coater (涂胶机）,Resist dispense methodsStatic DynamicRadia
9、lReverse radialResist pump (Volume control - 2cc/wafer and dripping)Barrel pump -TritekDiaphragm pump - MilliporeN2 pressure control pump - IDLStep motor control pump - Cybot size of dispense head,4.2.4 Coater (涂胶机）,rpm (转速） and acceleration （加速） Maximum speed - Up to 10000 rpmStability - day to day
10、Acceleration - controllable number of stepsReliability - time to replacementEBR (Edge bead removal)（清边）Method - Top EBR or Bottom EBR or Top and bottom EBRProblem - DrippingChemical - Acetone, EGMEA, PGMEA, ETHLY-LACTATE,Resist Type,Negative resistPositive resistG-linei linereverse imageTAC - top an
11、ti-reflective coatingBARLI - bottom anti-reflective coatingChemical amplification resistX ray resist,4.3.1 Exposure (曝光),Transfer a pattern from the mask (reticle) to resistGoal1.Critical Dimension control (CD)条宽2.Alignment 校准- Mis-alignment, run in/out3.Pattern distortion 图样变形- Astigmatism4.Cross s
12、ection profile 侧面形貌- side wall angle5.Defect free无缺陷Equipment/mask/resist selection1.Resolution 分辨率- Expose character, Light source (wavelength), N/A,2.Auto-alignment skill 自动校准技术- Light field, dark field, laser3.Mask掩膜版- e-beam master, sub-master, spot size, quartz plate, defect density, CD require
13、ment4.Resist selection 胶选择,4.3.2Exposure (曝光),Aligner Technology1.Contact print (接触）Soft contact, hard contact, proximity2.Scanner (扫描）3.Stepper (重复）1X, 2X , 4X, 5X, 10X4.Step Scan (重复扫描)4X - reticle move, wafer move, reticle/wafer move5.X ray (X光） 1:16.E-beam (电子束）- Direct write,4.3.3Exposure (曝光),
14、Contact print (接触）1.Most of use for negative resist process - for 5u process and can be push to 3u.2.Positive resist can print smaller than 3u, and deepUV can push to 1u, but very high defect3.Equipment:- Canon PLA 501- Cobilt- Kasper- K&S,Contact print -Canon 501,4.3.4Exposure (曝光),Scanner (扫描）1.Mo
15、st of use for G line Positive resist process - for 3u process and can be push to 2u.2.Negative resist can print smaller than 4u 3.Equipment:- Canon MPA 500, 600- Perkin Elmer 100, 200, 300, 600, 700, 900,PE 240 Scanner,Canon 600 Scanner,4.3.5Exposure (曝光),Stepper (重复） 1.G line positive resist - for
16、0.8u process 2.i line positive resist - 0.5u process3.i line resist plus phase-shift mask - can be pushed to 0.354.deepUV resist process - 0.35u and below5.Equipment:- Ultratech- Canon - Nikon- ASML,4.3.6Exposure (曝光) 6,ASML Stepper list ModelWavelength ResolutionASML 2500 g0.8ASML 5000ASML 5500 20,
17、22,25,60,60B,80,80Bi0.55ASML 5500 100,100C,100D,150i0.45ASML 5000 200,200B,250,250B UV0.35ASML 5500 300,300B,C,D,TFH UV0.25ASML 5500-900 Step-ScanUV,4.4.1Develop (显影）,Develop process1.Post expose bake2.Resist Develop3.DI water rinse 4.Hard BakeDevelop equipment1.Batch develop2.Track developDevelop c
18、hemical1.KOH 2.Metal free (TMAH) - Tetramethylamoniahydroxide3.Wetting agent - with/without4.Concentration - 2.38%TMAHTrack develop method1.Spray2.Steam3.Signal-Paddle4.Double-Paddle,4.4.2 Develop (显影）,Develop Track1.Temperature control water jacket for Develop line2.Develop pump/develop pressure ca
19、nister3.Exhaust4.Hot plate temperature control5.Pre-wet - process program,4.4.3Develop (显影）,CD control in developing1.Post bake process2.Develop Time 3.Concentration of developer chemical (Higher fast)4.Developer temperature (lower faster 1o C/0.1u)5.Develop recipe - pre-wet, paddle, rotation6.Age o
20、f the develop chemical7.Rinse - DI water pressure8.Hard bake temperature,4.5.1Develop Inspection,Tool for inspection1.MicroscopeManually loadingAutomatic loading2.UV lamp Manually loadingAutomatic loading3.CD measurement equipmentManually measuring system - Vicker, Automatic measuring system - Nanol
21、ineCD SEM,4.5.2Develop Inspection,Inspection items1.Layer name2.Alignment3.Run in/out4.Pattern distortion5.Pattern integrity6.Defects lifting, particle, discoloration, scumming, bridging, excess resist, scratch7.CD (critical dimension),Nanoline - for CD measurement,Hitachi 8860 - CD SEM,Leitz Micros
22、cope inspect station,Autoload UV inspection system,5.0 BCD 正胶工艺,Equipment SSI, SVG8800, SVG 90Process steppre-bake/HMDS/cold platespin (5000rpm) -dynamic dispense -top (bottom) side EBR(2mm)soft bake (100oC)/cold/palteResist/specShipley 6112 (1.2u) 1818 (1.8u 1st metal) 6818 (2.4u 2nd metal)6118 (2.
23、9u Pad)6124 (3.6u-4.5u ST)Everlight 533(1.2) Uniformity -+ 300A,Resist coating,升降机,冷板,HMDS,涂胶,热板,冷板,升降机,SVG 90,SVG 8800,5.1.1Positive Resist (正胶）,Component (成分）Resin （树脂）Diazonaphthoquinone(DNQ)/novolakPhoto-sensitizer （感光剂）Solvent （溶剂）Dye （染料）Manufacturing (制造商）Kodak Hunt Ash chemical (USA)TOK (Jap
24、an)JSR (Japan)Shipley (USA)AZ (USA, Germany)Sumitomo (Japan)Everlight (Taiwan),5.1.2Positive Resist (正胶）,Product Name and feature (产品称与特性）以everlight (永光）正胶为例Product SeriesEPG 510 SeriesExpose wavelengthG-Line (435nm) ThicknessName 2000rpm 5000rpmViscosity （粘度）EPG 510 - 12 cp1.25u0.80uEPG 512 - 21.5
25、cp2.00u1.25uEPG 516 - 50 cp3.25u2.00uEPG 518 - 105 cp4.50u2.75uEPG 519 - 460 cp9.00u5.5uResolution (分辨率） 0.8u (0.55u - the smallest)Depth of Focus (聚焦深度）+ 1.4u (1.0u line/space)Sensitivity (感光度）Eth = 60 mj/cm2Eop = 90 mj/cm2,5.1.4Positive Resist (正胶）,Select a positive resist1.Resolution （分辨率）2.Resis
26、t thickness - Spin curve （厚度）3.Photo speed(曝光速度)4.Expose latitude (曝光宽容度)5.Adhesion （粘附性）6.Reflective notch （反射缺口）6.Metallic content （金属含量）7.Thermal stability （热稳定性）8.Plasma resistance （抗腐蚀能力）9.How easy to be removed （清除能力）10.Price （價格）,5.2Expose,Equipment Ultratech stepper 1100 (6”)Ultratech steppe
27、r 1500 (6”)Canon 600 (6”)Perkin Elmer 240 (4”),Positive Resist reaction during expose,Positive Resist reaction during expose,5.2.1Ultratech Stepper,Ultratech stepperG-line N/A - 0.24 and 0.311:1 print ratio3 X 5 inch reticle - 3, 4, 5, 7 field4u depth of focusBlind step can be push to 5u (no spec)Ce
28、nter of array + 50u Dark field alignmentSite by Site alignment Alignment target *oat - 4mm X 4mm*K/T - 200u X 200u,Ultratech Stepper 1100,Ultratech Stepper 1500/1700,5.2.2Ultratch stepper specification,UTS-Reticle and Job file,Guide,Fiducials,UTS-primary lens,UTS AlignmentOptic,Ulratech stepper site
29、 by site alignment,UT alignment procedure,Load job file into computerLoad reticleStart iducials alignment - Guide, rotation(1500)OAT alignment OAT size = 4mmX4mmFast and slow scan 1000uSide by side alignment Key and target size 200uX200ushot scan 20ulong scan 100u (80u)Auto-focusGoble or localFailur
30、e alignment SkipExposeZmode,5.3 Perkin Elmer aligner,Micalign PE 100Micalign PE 200, 220, 240Micalign PE 300, 340, 340HTMicalign PE 500Micalign PE 600Micalign PE 700Micalign PE 900Micscan 100Micscan 200Micscan 300Micscan 400,PE 240 Specification,PE 240,PE 240,PMCenter of curvatureParallelismLight in
31、tensityFocusDistortionMask/wafer centeringView opticHPC rebuildCooling air flow rateVibration from HPC,FacilityVibration from environmentTemperature control hoodProcessReference waferAperture selectionResist build up on XYO pinsRoof mirror cleaningMask heat up during expose,PE - Focus wedge mask,PE
32、- distortion,PE - Projection optic,PE Mercury lamp,PE - Adjustable slit,PE alignment procedure,Set scanLoad maskLoad waferSwitch to maskUse microscope and carriage movement to find the alignment mark on mask (Test die)Move mask only to align the waferSwitch to waferMove wafer align to mask,5.4.1Resi
33、st develop,Equipment SSI, SVG8800, SVG 90Process steppose-e bake/cold platedevelop - double paddle - DI water rinse - back N2/rinsehard bake (110-130oC)/cold/palteDeveloperTMAH 2.35%,升降机,冷板,热板,冷板,升降机,热板,显影,SVG 8800,SVG 90,5.4.2 Resist develop,Equipment Develop sinkEquipment set upTemperatureN2 blank
34、etFilter sizeFilter changeDeveloperTMAH 2.38%Develop change Process step batch develop - immerse (1 & 15”)QDR DI water rinse (8 cycles)hard bake (110-130oC)/cold/palte,6. History and 未来的光刻工艺,Will imprint technology replace photolithography?In 1798, image was transferred by stone plate1940, Bell Lab
35、used resist developed by Eastman Kodak1960, San Francisco bay area becomes the silicon valley - AT &T, Raytheon, Fairchild, Negative resist contact print process wildly was used. End of 1970-early of 1980, positive resist Projection print (Perkin Elmer Micalign) started to be used in production. Bay
36、 area became cloudy - National, Intel and AMD. Outside bay area had Motolora, TI, IBM.From 1970 to early 2000, the technology of semiconductor is developed very fast. The smallest feature size from 10u reduced to 0.09u. 0.25u and 0.35u products were running mass production every where -USA, Europe,
37、Japan, Taiwan, Korea i-line,and deepUV - 5X stepper and step-scan (4X) aligner became the major tools.Now, 0.09u technology become mature. 0.065u, 0.045u and 0.035u technology are being developed. Immersion lithography and imprint technology will be used to print these nano feature.Imprint technolog
38、y claims that it is able to print 0.01u (10nm) - It may be the future masking.,6.1History,Lithography, as used in the manufacture of the integrated circuit, is the process of transferring geometric shapes on a mask to the surface of a silicon wafer. These shapes make up the parts of the circuit, suc
39、h as gate electrodes, contact windows, metal interconnections, and so on. Although most lithography techniques used today were developed in the past 40 years, the process was actually invented in 1798; in this first process, the pattern, or image, was transferred from a stone plate (the word litho c
40、omes from). The first practical two dimensional device patterning on a silicon wafer was actually carried out in the late 1940s at the Bell Lab. At that time, polyvinylcinnamate, developed by Eastman Kodak, was used as a resist. However, device yields were low because of the poor adhesion of the pol
41、yvinylcinnamate to the silicon and oxide surface. The Kodak chemists then turned to a synthetic rubber based material-a partially cyclized isoprene and added a UV active sensitizer-a bis-aryl-azide into it to crosslink the rubber matrix and created a new class of photoresist material. Since the unex
42、posed area of the new material was the only part of the polymer matrix that will dissolve in an organic solvent and yielding a negative image of the mask plate, therefore, the new material was then referred as the negative resist. The cyclized rubber/bisazide resist was widely used in the contact pr
43、inting age. However, the contact mode of printing created severe wear of the mask plate and the defect density of the photomask and the wafer was very high. The industry therefore decided to switch to contactless projection printing in 1972 for producing the 16k DRAM.Projection printing, however, wa
44、s carried out in the Fraunhoffer or the so called far field diffraction region and the aerial image was much poorer than the contact or proximity method of printing. In order to preserve the same quality of image structure, the contrast of the image material must be increased.,Lithographic lore has
45、it that the diazonaphthoquinone/novolak resist (the term novolak is derived from the Swedish word lak, meaning lacquer or resin and prefixed by the Latin word novo, meaning new) made their way from the blue print paper industry to the microelectronic through family ties: at that times, the offices o
46、f Azoplate, the American outlet for Kalle printing plate, was located at Murray Hill, NJ, just across the street from the famous Bell Labs. The father of a technician at Azoplate worked as a technician at Bell Labs. Apparently the father had complained one day about the poor resolution quality of th
47、e solvent developed resist system used at the Bell Labs and the son had boasted the properties of the Azoplate DNQ/novolak material; anyway, one day the father took a bottle of the material with him to the Bell Labs, and the age of the DNQ/novolak resist began. The new material was marketed by Azopl
48、ate under the trade name of AZ photoresist. It was always referred as the positive resist for a positive tone of image would be reproduced by the new material. The use of DNQ/novolak system increased rapidly after the introduction of the projection lithography. By 1980s, the DNQ resist had completel
49、y supplanted the old negative resist as the workhorse of the semiconductor industry in the high-end applications. The DNQ/novolak resist has held sway for 6 device generations, from the introduction of the 16K DRAM to the large scale production of the 64M DRAM in 1994 to 1995. The success of such ma
50、terial was the indicative of it supreme performance and potential. Today, it appears that it is not really the resolution which defines the limit of the DNQ/novolak resist application, but rather the loss in the depth of focus with the ever increasing NA of the stepper. Deep UV and chemical amplific
