Joint development of SANYO Semiconductor Manufacturing Co., Ltd. (hereunder『SSMC』, President : Norihiro Shigeta ) and Hayashi Pure Chemical Ind., Ltd. (hereunder『HPC』, President : Masakatsu Irie ) succeeded in development of high performance chemical which can etch Al Thin Film with easy control.
Desirable Edge Taper Angle from 20°to 60°of Al interconnection under photo resist is obtained with keeping precise geometry by using this chemical on Al interconnection etching process. HPC is successfully supplying this newly developed chemical to SSMC for improvement of precise processing and reliability of the IC and LSI products.
HPC is going to present this new chemical not only to SSMC, but also to many other companies in expanding field of MEMS product which needs precise etching process on hands.
One of the factors for semiconductor reliability (IC and LSI) is coverage of interconnection pattern (Step Coverage) by insulation layer which is processed in under layer on silicon wafer surface. In usual process, coverage properties depend on edge angle (taper angle) in the under layer, and better coverage can be obtained on smaller taper angle.
In dry process with etching gas, edge angle of Al interconnection is nearly 90°. This dry etching process needs filling up the gap between Al interconnection with insulation material to make flat surface.
On the other hand, in wet process, etching chemical can make small taper angle on Al pattern edge and it is known as relatively low cost process to obtain excellent coverage of final insulation layer. But this wet process has difficulties on control and uniformity of etching. In view of this background, our joint development started aiming easy control, precise etching and uniformity with reasonable cost of wet etching chemical filling the role of developing chemical by HPC and evaluating the chemical by SSMC.
Ⅲ.Results of Development
Results of developed chemical are shown as below.
(1) Etching can be easily controlled for less than 1μm thin film of pure Al, Al-Cu, Al-Si-Cu etc.
Etching of film more than 1μm can be also controlled with proper pre-treatment.
(2) Desirable taper angle can be obtainable from 20°to 60°as shown below.
(3) Desirable profile after etching with precise dimension accuracy is obtained.
(4) Neither surface damage on etched and tapered surface nor partial inferiority on insulation layer coming next
(5) No damage on photo resist
(6) Long life by containing no surfactant
(7) Superior step coverage of insulation layer by tapered angle of Al edge
Explanation of items
(1) MEMS (Micro-Electro-Mechanical Systems)
MEMS means the technology that forms minute machine elements on the silicon substrate by micro processing technology of semiconductor, and formed structure with this technology.
It is sometimes called Micro Machine.
Applications are acceleration sensors and pressure sensors, also medical application is expected.
(2) Step Coverage
Index of coverage when metal layer or insulation layer is deposited on the surface of material which has its own step. It is shown as below.
Step Coverage(%) = (Layer thickness of step／Layer thickness of flat area) x 100
Hayashi Pure Chemical Ind., Ltd.
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