1、IC工藝技術(shù)系列講座第二講,PHOTOLITHOGRAPHY 光刻,講座提要,1.General 2.Facility (動(dòng)力環(huán)境) 3.Mask (掩膜版) 4.Process step highlight (光刻工藝概述) 5.BCD 正膠工藝 6.History and 未來(lái)的光刻工藝,1.General,MASKING Process (光刻工藝) Photolithography (光學(xué)光刻) -Transfer a temporary pattern (resist) Defect control Critical dimension control Alignment accur

2、acy Cross section profile Etch (腐蝕) -Transfer a permanent pattern (Oxide, Nitride, Metal),2.0Facility requirement,Temperature (溫度) 70 oF Humidity (濕度)45% Positive pressure (正壓) 0.02in/H2O Particle control (微粒) Class 100 Vibration (震動(dòng)) Yellow light environment (黃光區(qū)) DI water (去離子水) 17mhom Compress ai

3、r and Nitrogen (加壓空氣,氮?dú)? In house vacuum(真空管道),3.0Mask (掩膜版),Design PG tape Mask making Plate - quartz, LE glass, Soda line glass Coating - Chrome, Ion oxide, Emulsion Equipment - E-beam, Pattern generator Mask storage -Anti static Box,Pellicle,Pellicle protection,4.0光刻工藝概述,Prebake and HMDS (前烘) Res

4、ist coating (涂膠) EBR (去膠邊), soft bake, 3.Exposure (曝光) Alignment (校正) 4.Develop (顯影) Post e-bake, Hard bake, backside rinse 5.Develop inspection (顯檢),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 espec

5、ially designed for positive resist. HMDS (Hexamethyldisilane) can be applied on the wafers by 1. Vapor in a bucket 2.vapor in a vacuum box 3.Directly dispense on wafer 4.YES system - in a hot vacuum system 5.Vapor in a hot plate (with exhaust) Too much HMDS will cause poor spin, vice versa will caus

6、e resist lifting,4.2Resist Coating (涂膠),Resist coating specification (指標(biāo)） Thickness（厚度）0.7u 2.0u (3.0以上for Pad layer) Uniformity（均勻度）+ 50A +200A Size of EBR （去膠邊尺寸） Particle（顆粒）20 per wafer Backside contamination(背后污染） 三個(gè)主要因數(shù)影響涂膠的結(jié)果 ResistProduct (產(chǎn)品） Viscosity （粘度） SpinnerDispense method （涂膠方法） Spi

7、nner speed (RPM) （轉(zhuǎn)速） Exhaust （排氣） Soft bake temperature （烘溫） FacilityTemperature （室溫） Humility （濕度）,4.2.1Coater (涂膠機(jī)）,Equipment module and special feature Pre-bake and HMDS - Hot/Cold plate Resist dispense - Resist pump RPM accuracy - Motor EBR - Top/bottom Hot plate - soft bake temperature accurac

8、y Exhaust Waste collection Temperature/Humidity control hood Transfer system - Particle and reliability Process step and process program - Flexible,SVG 8800,升降機(jī),涂膠,HMDS,熱板,冷板,升降機(jī),升降機(jī),升降機(jī),涂膠,熱板,熱板,升降機(jī),升降機(jī),升降機(jī),升降機(jī),涂膠,熱板,冷板,HMDS,冷板,冷板,冷板,涂膠,熱板,熱板,升降機(jī),升降機(jī),顯影,熱板,熱板,熱板,冷板,4.2.2 Coater (涂膠機(jī)）combination,4.2

9、.3 Coater (涂膠機(jī)）,Resist dispense methods Static Dynamic Radial Reverse radial Resist pump (Volume control - 2cc/wafer and dripping) Barrel pump -Tritek Diaphragm pump - Millipore N2 pressure control pump - IDL Step motor control pump - Cybot size of dispense head,4.2.4 Coater (涂膠機(jī)）,rpm (轉(zhuǎn)速） and accel

10、eration （加速） Maximum speed - Up to 10000 rpm Stability - day to day Acceleration - controllable number of steps Reliability - time to replacement EBR (Edge bead removal)（清邊） Method - Top EBR or Bottom EBR or Top and bottom EBR Problem - Dripping Chemical - Acetone, EGMEA, PGMEA, ETHLY-LACTATE,Resist

11、 Type,Negative resist Positive resist G-line i line reverse image TAC - top anti-reflective coating BARLI - bottom anti-reflective coating Chemical amplification resist X ray resist,4.3.1 Exposure (曝光),Transfer a pattern from the mask (reticle) to resist Goal 1.Critical Dimension control (CD)條寬 2.Al

12、ignment 校準(zhǔn)- Mis-alignment, run in/out 3.Pattern distortion 圖樣變形- Astigmatism 4.Cross section profile 側(cè)面形貌- side wall angle 5.Defect free無(wú)缺陷 Equipment/mask/resist selection 1.Resolution 分辨率- Expose character, Light source (wavelength), N/A, 2.Auto-alignment skill 自動(dòng)校準(zhǔn)技術(shù)- Light field, dark field, lase

13、r 3.Mask掩膜版- e-beam master, sub-master, spot size, quartz plate, defect density, CD requirement 4.Resist selection 膠選擇,4.3.2Exposure (曝光),Aligner Technology 1.Contact print (接觸） Soft contact, hard contact, proximity 2.Scanner (掃描） 3.Stepper (重復(fù)） 1X, 2X , 4X, 5X, 10X 4.Step Scan (重復(fù)掃描) 4X - reticle m

14、ove, wafer move, reticle/wafer move 5.X ray (X光） 1:1 6.E-beam (電子束）- Direct write,4.3.3Exposure (曝光),Contact print (接觸） 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 defect 3.Equ

15、ipment: - Canon PLA 501 - Cobilt - Kasper - K in this first process, the pattern, or image, was transferred from a stone plate (the word litho comes 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 tim

16、e, polyvinylcinnamate, developed by Eastman Kodak, was used as a resist. However, device yields were low because of the poor adhesion of the polyvinylcinnamate to the silicon and oxide surface. The Kodak chemists then turned to a synthetic rubber based material-a partially cyclized isoprene and adde

17、d 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 unexposed 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 pl

18、ate, therefore, the new material was then referred as the negative resist. The cyclized rubber/bisazide resist was widely used in the contact printing 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.

19、 The industry therefore decided to switch to contactless projection printing in 1972 for producing the 16k DRAM. Projection printing, however, was 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

20、 printing. In order to preserve the same quality of image structure, the contrast of the image material must be increased.,Lithographic lore has 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 w

21、ord novo, meaning new) made their way from the blue print paper industry to the microelectronic through family ties: at that times, the offices of 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

22、 technician at Azoplate worked as a technician at Bell Labs. Apparently the father had complained one day about the poor resolution quality of the 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 fa

23、ther 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 Azoplate 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 mater

24、ial. The use of DNQ/novolak system increased rapidly after the introduction of the projection lithography. By 1980s, the DNQ resist had completely 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

25、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 material 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 DN

26、Q/novolak resist application, but rather the loss in the depth of focus with the ever increasing NA of the stepper. Deep UV and chemical amplification negative tone resist slowly erode the market place of the DNQ/novolak resist. By the end of the 1990s, the DNQ/novolak resist was no longer be used i

27、n the technologically most advanced applications-the printing of the critical levels of the 256M DRAM.,6.2 Future,Introduction of nanoimprint technology Fabricating microstructures and nanostructure is important in many fields of science and technology, including electronics, data storage, flexible

28、displays, microelectromechanical systems, microfluidics, photonics and biosensors. Traditionally, optical or electron beam lithography systems are used to print the relevant structures. However, new printing methods such as imprint lithography and soft lithography have recently been explored in some

29、 detail to lower the costs of fabricating low volumes of structures with very small features and to increase the range of printing application. The soft lithography schemes, in general, use a soft template pattern made of silicone elastomer, polydimethylsiloxane (PDMS), which is placed into contact

30、with the substrate in a variety of ways, to pattern a surface film, to transfer a material, or for direct integration into the final part, with a range of innovative applications. Challenges in this area are generally concerned with the inherent limitations of the PDMS material including resolution

31、limitations when curing due to differences in thermal expansion between the master and mold; adhesion to common master materials like silicon; significant time, about an hour, to fabricate a mold; elasticity of the mold, which may impact multilevel alignment; insolubility with common solvents; conta

32、mination issues and incompatibility with some organic materials.,The imprint methods utilize heat or UV curable liquids to mold patterns onto a substrate from a rigid template. Research groups have demonstrated sub-100nm resolution, some have down to 10nm. Imprint process; however, do not transfer m

33、aterials from the template to the substrate like the soft lithography schemes. Another hesitation with the imprint technique concerns the lifetime of the master pattern. The problem is similar to that encountered in the contact photolithography, where it has been found that the defect free lifetime is only limited to less than 1000 passes, despite the application of coatings and lubricants. This concern arises from the important requirements that the substrate must