reflow简介reflow+review+and+process+suggetionHANL

1、REFLOW review and process suggestion,Prepared by HAN Lei,2020/7/23,2,Outline,REFLOW cleaning review REFLOW recipe configuration Inline low yield control,2020/7/23,3,Issue description: Verify reflow cleaning procedure, especially quartz window cleaning. The brief cleaning procedure as following chart

2、:,*The key step Cleaning is operated under “purge valve”state. After cleaning operator need to select “stand by” to make sure that susceptor load and unload normally.,REFLOW cleaning review,2020/7/23,4,REFLOW cleaning review,Heater: IR halogen lamp Lamp power: 6 kW/480V Lamp qty: 24 Temp zone: 6,The

3、 key parts of REFLOW is IR reactor as following images.,292 x 10mm Quartz window,2020/7/23,5,REFLOW cleaning review,*The images above show the 6 temperature zones of Infrared halogen lamps. *Halogen element of lamp enable the lamp durable and hi-temp-useful. *The heat transfers through quartz window

4、 and functions in chamber. *Two problems are concern: (1)Need to double confirm cleaning effective.,Clean Quartz window Reflow #5,Dirty Quartz window Reflow #6,2020/7/23,6,(2)What detergent is preferred? Inline detergent is alkaline, but quartz is weak acid. *The quartz is weak acid substance. *Smal

5、l traces of alkaline (finger prints!) will lead to unavoidable surface damage when heated over 900 . *Even at room temperature, the particular properties of quartz will be highly influenced by its purity and cleanliness, which impact heat transferring and lamp life. *so contact by skin and similar i

6、mpurities (especially detergents = soaps) should immediately be cleaned off by pure alcohol (isopropanol) and a clean, lint free cloth,REFLOW cleaning review,2020/7/23,7,REFLOW cleaning review,Action suggestion: (1)Clean chamber especially quartz window more than two times by pure alcohol . And need

7、 other person to double check. (2)Collect data to confirm whether the detergent impact quartz quality at both high temperature and room temperature.,2020/7/23,8,REFLOW recipe configuration,Issue description: how to study reflow recipe and brife recipe analysis *The following tables show some REFLOW

8、recipes for 250um solder & 300um solder devieces. 250um solder correspond to 400um pitch and 300um correspond to 500um pitch. *Difference of product code correspond to the difference of ball count on one dice, whose detail are all read from MBD. *The recipe partly correspond to the gross ball count

9、on one wafer.,2020/7/23,9,REFLOW recipe configuration,2020/7/23,10,Generally, REFLOW recipe mainly includes 4 tempeture variation zones. (1)Preheat, which consists of gradually ramping up the setting temperature. 13/s. (2)Tin Activation, which consists of bringing the solder ball to a temperature at

10、 which it is chemically activated, allowing SiF6 function sufficiently, uniforming the tempereture within wafer.,REFLOW recipe configuration,e.g: Recipe of EAG18V4,2020/7/23,11,(3)Actual Reflow, which consists of ramping up the temperature to the point at which the solder melts, causing the solder t

11、o sufficiently wet. The peak reflow temperature should be significantly 2040 higher than the solder alloys melting point to ensure good wetting. The area of peak is preferred to be smallest. (4) Cooldown, which consists of ramping down the temperature at optimum speed (fast enough to form small grai

12、ns that lead to higher fatigue resistance, but slow enough to prevent thermo-mechanical damage to the solder) until the solder becomes solid again. 80 is the final temperature.,REFLOW recipe configuration,2020/7/23,12,98.8%Sn Vs. 1.2%Ag,Assessed Ag - Sn phase diagram,REFLOW recipe configuration,Melt

13、ing point,2020/7/23,13,Inline low yield control,Issue description: Bumping inline low yield (99%)record 1st 14 July. Both holder release & V/I,2020/7/23,14,Inline low yield control,2020/7/23,15,Inline low yield control,Low yield reason maily: MISSING especially for 250um bumping device Root cause: n

14、onstability of manual operation and REFLOW issue. Action suggestion: (1)If there is no obvious missing pattern within wafer. List the low yield impacted wafers common path, such as which PLASMA and REFLOW ran from, when solder finish PLASMA washing.,250um bumping device low yield reasons from 1st14,

15、 July,300um bumping device low yield reasons from 1st14, July,Check yield of other wafer with same path,99.0%,99.0%,release,Check REFLOW history for temperature & gas flow,Check manual operation & mask,Do one more wafer sample to test shear & diameter,2020/7/23,16,Inline low yield control,Action sug

16、gestion: (2)Yield testing sample modify.,The first 3 wfs,The first 2 wfs + The last 2 wfs,Modify to,Modifying concern: *Match sample collecting rule of front end FAB inline defect auto scanning. *To make sure that solder/UBM layer is normal for wafer to wafer. *UBM is deposited by sputting & etch pr

17、ocess. One lot of 25 wafers run through different Chambers in one EQP. Eath process chamber need to do clean for every clean cycle (processing some pieces of wafers). Any shift of gas flow or RF power has risk of impacting UBM layer stress, uniformity, metallization distribution and so on.,Modify to

18、,2020/7/23,17,Inline low yield control,Action suggestion: (3)Vefify dummy rule: *Now when REFLOW idle time 1 hour, operator will routinely dummy chamber, dummy recipe remain be “temp-check”. *One cause of MISSING is purging/pumping mechanically when product process. *Suggesting to change dummy recipe to product running recipe, which