Optimization of chip back metallization process using Schottky diodes for eutectic soldering
[Objective]As a pivotal process in semiconductor device fabrication,the metallization with its conditions and parameters directly impacts the performance of these devices.To reduce fabrication costs,diminish environmental pollution,and improve the efficiency of backside metallization for Schottky diodes,we have undertaken a comprehensive study.Exploring an optimal non-thermal plating metallization technique,we advocate the use of tin-antimony alloy as a viable alternative to conventional gold-based alloys.Finally,this approach aims to enhance the sustainability without compromising on quality or performance.[Methods]Through comparative experiments between temperature-controlled and non-temperature-controlled plating,we analyze the effect of substrate temperatures during the electron beam evaporation on the adhesion between cathode metal layers,as well as the impact of tin-antimony alloy layer thickness on the void rate of subsequent eutectic soldering.Consequently,the main contribution of our study lies in the determination of optimal-process parameters for backside metallization of Schottky diodes suitable for mass eutectic soldering.[Results]The influence of substrate temperatures on the shear force is pronounced,with both coating techniques exhibiting lower shear forces at reduced substrate temperatures.The shear force increases as the substrate temperature rises,peaking at 64.53 N for non-isothermal coating and 64.41 N for isothermal coating at 180 ℃.Beyond this temperature,the shear force paradoxically diminishes with further temperature increases.In metallization processes,thicker tin-antimony alloy films correspond to lower soldering void rates.A film thickness of 3 pm results in a void rate of less than 5％during chip eutectic soldering,satisfying the criteria for eutectic bonding.The sheet resistance of the metal layer on the reverse side,produced by electron beam evaporation,initially decreases and subsequently increases along with rising substrate temperature.Between 180 ℃ and 240 ℃,the sheet resistance varies gradually with the substrate temperature,and attains a minimum of 11.8 Ω/sq at 210 ℃.However,the sheet resistance escalates rapidly when the substrate temperature surpasses 240 ℃.[Conclusions]The optimal process for the back metallization of Schottky diodes used in eutectic soldering is involved with increasing the substrate temperature to 180 ℃,followed by multi-layer metal coating during natural cooling,with a tin-antimony alloy film thickness of 3 pm.The non-isothermal coating process,in which the tin-antimony alloy is used as a substitute for gold-based alloys,not only reduces manufacturing costs but also minimizes the environmental pollution.This outcome secures significant implications for the mass production of Schottky diodes.
Schottky diodemetallization processelectron beam evaporation coatingsheet resistancevoid rateshear force
万方数据
维普
