Processing instructions for negative two-component system
The negative two-layer lift-off system is characterized by a particularly high temperature resistance up to 250 °C after development.
The substrate is at first coated with the co- polymer AR-BR 5400 and tempered. After cooling to room temperature, the negative resist SX AR-N 4340/7 which was specifically designed for two-layer systems is applied onto the copolymer. Dwell times are to be avoided; the liquid photoresist should not be left for more than 10 s on the standing wafer. The film thickness may be varied in a range between 1.0 – 2.5 μm. Subsequently, the two-component system is tempered.
基板(晶圓)上首先塗佈AR-BR 5400共聚物當底層並軟烤.待基板冷卻至室溫時塗佈負型光阻(SX AR-N 4340/7)於底層之上,光阻勢特別設劑用於塗佈於高分子底層之上.光阻滴定於基板後需避免延滯超過10秒. 否則膜厚變異可能介於1.0 – 2.5 um之間. 光阻塗佈後再對2層膜厚軟烤.
The ratio of film thicknesses of both films will affect the structural geometry. For a strong lift-off effect, a thin photoresist layer and a thick copolymer layer is advantageous. For a dimensionally accurate transfer of structures into the copolymer layer how- ever, both layers should have approximately the same thickness. The entire system always has to be optimized for the particular application.
兩層材料膜厚比例會影響結構. 薄光阻搭配較厚的底層共聚物可獲得較好的浮剝離(lift-off)效果. 兩層材料厚度一致則底層可獲得較佳的尺寸精確度. 使用者需依實際應用調整厚度比例.
SX AR-N 4340/7: Exposure and aqueous-alkaline development are carried out according to the general process descriptions which require an additional cross-linking bake in the negative mode.
AR-BR 5400: The copolymer itself is not sensitive in the UV-range between 300-450 nm. The properties of the layer are however adjusted such that the polymer will dissolve quickly in the recommended aqueous-alkaline developer.
SX AR-N 4340/7負型光阻曝光及鹼性水溶液顯影依產品基本參數. 負型光阻需要於曝光後烘烤以進行高分子架橋.
AR-BR 5400底層共聚物對紫外線波長300-450nm不感光. 但可在光阻鹼性水溶液顯影液中快速溶解.
After the upper photoresist layer is entirely developed in exposed areas, the developer begins to dissolve the copolymer.The dissolution process now takes place in undirected manner (isotropic).
AR-BR 5400 is in this process removed both towards the bottom and towards the left or right side so that the under-cut is formed. The longer the developer can exert its effect, the more of the copolymer under the photoresist film is removed by dissolution. For a reduction of the dissolving rate, a higher temperature of up to 180 °C must be chosen (instead of 150 °C). The desired undercut can thus be adjusted via the parameter‘s temperature and development time (👉see images below). In addition, the steepness can be influenced by the exposure time of the negative resist.
上層正光阻曝光區完全顯影後,顯影液開始溶解底層的共聚高分子. 但此時的溶解是等向性的. 即AR-BR 5400溶解的方向有向下及左右,因此型成下切結構. 顯影時間越長,底層溶解越多,下切效果越明顯. 底層材料軟烤溫度從150℃提高至180℃可降低溶解率. 因此下切結構可依軟烤溫度及顯影時間調整. (👉請參考下圖). 此外,負型光阻結構的垂直度會受曝光時間影響.
Selective removal of the photoresist layer (optional):
For transparent and temperature-stable films, the copolymer layer is used alone. In this case, the residual photoresist is selectively removed after development with remover AR 600-70. The substrate is briefly immersed in remover AR 600-70 and dried immediately with compressed air.
底層材料為耐溫透明結構,可依需求應用,因此光阻顯影後可單獨以AR 600-70去除. 以浸泡式將基本板置於AR 600-70去除液中並立即以壓縮空氣乾燥.
Lifting / Removal:
Removers AR 300-73 and AR 300-76 are both suitable for lifting. If lift-off structures are not thermally stressed during evaporation or sputtering, lifting will take place within a minute.
After high thermal load (> 250 °C), the time required for lifting increased considerably. Ultrasound and heating facilitate a removal. Remover AR 300-73 may in this case be heated up to 50 °C max.
AR 300-73及AR 300-76兩款去除劑都適合用於懸浮剝離的製程. 如果要被剝離的結構未受蒸鍍或濺鍍高溫影響,應該可在一分鐘之內剝離.
製程溫度如果高於250℃, 剝離所需時間會明顯增加. 可用超音波或加熱去除液改善. AR 300-73去除製程為例,最高可加熱至50℃