CMOS覆晶式微磁通閘磁量計之設計與製程研究

A Study on the Design and Process of CMOS Flip-Chip Micro Fluxgate Magnetometers

趙方毓(Fang-Yu Jhao)

指導教授 ： 呂志誠

國立臺北科技大學/機電學院/機電整合研究所/碩士(2012年)

https://doi.org/10.6841/NTUT.2012.00612

摘要

本篇論文設計製作了運用CMOS製程、無電鍍及覆晶技術之雙磁芯微磁通閘感測器及感測器之磁芯磁通量及磁通密度模擬，我們透過螺線管形狀激發線圈之設計來得到更強的激發磁場來使磁芯更容易飽和。概念設計方面，微磁通閘晶片整體面積為2.5 mm×2.5 mm，包含磁芯、上下層平面感應線圈、下層激發線圈(CMOS製程的金屬鋁)、上層激發圈(CMOS製程的金屬鋁)。利用Ansoft Maxwell電磁模擬軟體分析磁芯之磁通量模擬中，可以發現磁芯愈細其磁通密度越大，但在磁通量方面則是磁芯越寬，其磁通量越大，在此模擬中可以用來判別爾後磁通閘之磁芯選擇，於磁通閘製程方面，我們使用了三種製程方式，其第一種為使用無電解電鍍銅之方式；第二種為使用微錫球將錫球植入PAD上來達成覆晶之概念；第三種方式為使用濺鍍之方式將銀鍍至PAD上並運用第二種之方法來完成，經由我們實驗發現，其晶片之設計上發生錯誤，導致我們運用晶片銲線技術將其訊號點拉出至PCB板上時無法拉出，且探究其第一種之製程方式於我們之微小晶片上為不可行之製程；第二種製程方式雖成功將其覆晶之概念完成，但完成後其內部無法導通；第三種之製程方式驗證了於鋁材上濺鍍銀可順利將上下層結構做導通，但其實驗結果於感應線圈部分有導通，於激發線圈部分則是沒有導通，其實驗結果將可供後續覆晶式微磁通閘之製作方面提供一參考價值。

關鍵字

磁通閘 ； 磁場感測器 ； CMOS ； 覆晶技術 ； 無電鍍 ； 微錫 ； 濺鍍 ； Maxwell電磁模擬

並列摘要

This paper presents a dual-core (Förster-type) micro-fluxgate magnetic field sensor fabricated on a silicon chip based on CMOS technology, electroless plating and flip-chip technology. The silicon chip is 2.5 mm × 2.5 mm in dimension. The sensor consists of magnetic cores, planar pick-up coils, bottom excitation coils (CMOS Al interconnections) and upper excitation coils (wire-bonding Al wires). By using Ansoft Maxwell to simulate the magnetic flux (Φ), it is found that by using a smaller core width it is able to obtain a higher magnetic flux density (B) at the expense of a reduced total magnetic flux (Φ). The simulation result helps optimizing the core size of microfluxgate in the future designs. In addition to the wire-bonded microfluxgate, we make use of the micro solder balls method to realize the flip-chip microfluxgate. Before collocating micro solder balls on to the pads, we tried two methods to improve the electrical contact between solder balls and pads. The first method is electroless plating of copper films, and the second one is sputtering deposition of silver films on the pads. Through experiments, it was found that the excitation circuit tends to open for both methods. The electroless-plated copper rapidly becomes insulating copper oxide on the surface, making it difficult to bond the solder balls. By using the silver coating process can successfully connect most of the pads of upper and lower chips. The experiment showed that the sensing coils in the upper and lower chips are successfully connected in series via solder balls, but the multi-turn excitation coil of the flip-chip sensor is an open circuit. Further works on improving the yield and efficiency of solder ball plating and wafer-to-wafer bonding with solder balls will be valuable for realization of the practical flip-chip microfluxgate.

並列關鍵字

micro fluxgate ； magnetic sensor ； CMOS ； Flip-chip ； Maxwell ； Electroless ； micro ball ； sputtering

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