BCB制程培训小结
BCB是一种介电材料,用来在Wafer的表面形成一个介电层,保护Wafer上的IC。
BCB的特征:
1低介电常数(2.65);
2低硬化烘烤温度(200~300℃),并且烘烤过程中没有副产品的气体产生;
3很好的潮湿抵抗能力;
4不活泼的化学性质,与很多化学材料不发生反应;
5与Cu有很好的黏着能力。
BCB的作用:
1减少在后续的PKG制程中的Chemical与Wafer上的IC发出影响;
2改善在接着的溅镀制程中Ti和Cu的溅镀效果;
3形成有序的WLCSP的工艺流程。
BCB制程的流程图:
Incoming Baking & Cleaning;BCB Layer Coating & Bake;BCB Layer Exposure;Pre-develop Baking;BCB Layer Develop;Post-develop Bake;BCB Layer Descum。
BCB制程中的Chemicals:
AP3000,助粘剂;BCB4024,用来Coating的介电材料,是聚合物;T1100,用来对Wafer进行洗边和显影前的对不需要的BCB的剥除;DS3000,显影剂;EKC922,这是在发现有Failure的时候可以用来剥除BCB做Rework。
BCB4024的特征:
1负光阻;
2对I-Line(365纳米)很敏感;
3温度在25摄氏度的时候,粘度是350;
4可以Coating的膜的厚度是3.5~7.5的微米。
制程中的Chemical一些需要注意的几点:
BCB需要保存在零下15度的环境中,有一年的寿命,而在室温的情况下就是只要7天的时间,而且是累积的。BCB在使用之前一定要回温到室温才是可以使用。
其他的Chemical是可以保存在室温中的,而且寿命也是会超过一年的。尤其重要的是EKC922不能够与水接触,会变成强酸。
制程中使用的设备:
涂布机:ModuTrack 2112;膜厚计:Nanospec 9200;
曝光机:Stepper Saturn Spectrum 3e;显影机:SEZ A1series;
烤箱:普通烤箱和无氧烤箱;显微镜:STM6。
涂布机的特征:
Cluster working mode(Piece by piece)
2 Coating Chamber,1 for AP3000,1 for BCB4204
3 hotplate & 1 chill plate for wafer coat process temperature control
software control
膜厚计的特征:
optic thickness measurement technology
high throughput 200pcs per hour
win NT platform
曝光机的特征:
cluster working mode
step and repeat
use 1× mask
software control
显影机的特征:
batch working mode(lot by lot)
wet process
temperature control (30℃)
develop time control(end point)
烤箱的特征:
Normal:temperature control & time control
无氧: O2〈100ppm,150℃。Need to fill with N2
显微镜:
optical microscope
visual inspection
各个制程中的参数:
BCB incoming baking & RIE cleaning
Baking parameter:temp 125℃;time 5sec
RIE parameter: power 400W;gas O2(80sccm)& CF4(20sccm);
Time 40sec; pressure 400mtorr
BCB Coating(3.5~6.5um)
AP3000 Coating:500rpm,5sec;2000rpm,30sec
AP3000 Baking: 125℃,60sec
BCB4024 Coating:1500rpm,10sec;2000rpm,15sec
T1100 EBR: 1000rpm,10sec;800rpm,10sec;Width 2mm
BCB Pre-baking: 70℃,90sec
BCB Exposure:
Use 1×BCB layer mask
Mask and wafer alignment
Different recipe:set exposure time and energy according the thickness of BCB
Step and repeat
BCB Develop:
Pre-develop Baking:60℃,30sec;adjust the endpoint of BCB
BCB develop:time=endpoint×(1.5~2.0);temperature 32~36℃
Time 1~2min in DS 3000,temperature RT
BCB Endpoint Measurement:
Coating a dummy wafer
Develop without exposure
Measure the time T from dipping to the point that the color ring disappear
The time T is needed endpoint time
BCB post-develop baking:
RT ramp to 50℃;
50 min soak at 50℃(fill nitrogen)
ramp to 210℃(N2 atmosphere)
40 min soak at 210℃
cool to 60℃
BCB exposure and develop rework
Use EKC922 acetone and DI water
Basin,spin dry and hotplate
RIE cleaning
Inspection by OM
Rework is done by handwork。
BCB RIE Descum intension:
Remove the passivation
Remove the oxide on Al pad of wafer
Promote the activity of BCB layer
BCB RIE Descum parameter
Energy:400W
Gas:O2(80sccm)+CF4(20sccm)
Time: 40sec
Pressure:400mtorr
BCB RIE Descum Inspection
Inspection position:Al pad opening
Inspection item:opening inner diameter,cusp end discharges,
Newton color ring
Criterion: 30um<r<X-10um,X:mask opening
OM 1000X to inspect the opening。No residue is permitted。