Optical Micro-Scanner Fabricated on Stainless Steel by Aerosol Deposition Method Maxim Lebedev, Harumichi Sato and Jun Akedo Advanced Manufacturing Research Institute National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba, Japan akedo-j@aist.go.jp Abstract— An optical micro scanner, having a high speed performance at high resonance frequency of 15.8 kHz and scan angle (peak to peak value) of 18 degree in atmospheric ambient, was successfully fabricated by depositing via the aerosol deposition method of the piezoelectric materials at a high deposition rate onto the metal scanner structure, which was fabricated by mechanical machining. Keywords-component optical scanner, micro electro mechanical systems, aerosol deposition method, PZT I. INTRODUCTION Optical micro scanners are very important for many applications reaching from laser-pointers, barcode readers to raster scanning laser displays. In these applications, high- speed operation, adequate mirror size, low driving voltage, large scanning angle without deformation of laser beam as well as the low cost are required. Many types of optical scanners have been proposed by now as micro electro mechanical systems (MEMS) device, most of them are usually operated at a resonant frequency of several kHz with ~30 degree optical scan angle. Scanners in such a low resonant frequency range are not applicable to high-resolution display. There are some reports of scanners operating at more high frequencies [1,2], however all such devices are requires MEMS fabrication technology, that is time consuming and expensive. Such scanners are made from silicon, and as a result can be easily broken due to high stress concentration near mirror. It is very attractive to use metal substrate instead of silicon one in applications of optical micro scanner devices due to the reduction of the device cost and improving the lifetime because of changing of brittle silicon to ductile stainless steel. Punching of base stainless steel sheet to make desired structure can reduce production cast as well. At the same time, the stainless steel and silicon have the approximately same value of Young’s modulus (Y) as about of 200 Gpa, densities of materials (ρ) of 7.81 g/cc for steel and of 2.33 g/cc for silicon so the ratio of ρ Y that determines the mechanical resonance for this material will be different only by factor of 2, however such difference in resonance characteristics can be adjusted by appropriate device design. Thus silicon can be replaced by stainless steel in the MEMS structures. However the integration of stainless steel and piezoelectric materials is difficult, because the bonding of bulk piezoelectric material on substrate by glue can be hardly applied for microstructure. At the same time the direct deposition of piezoelectric on steel by conventional thin film technique is limited the process temperature, which should be not exceeded 600 0 C. Recently Aerosol Deposition Method (ADM) [3,4] has become very attractive for deposition of piezoceramics thick films on different kinds of substrates. In ADM, sub-micron particles were accelerated by a gas flow in the nozzle and ejected onto substrate. During impaction with substrate, part of particle’s kinetic energy is transformed into bonding energy between particles. ADM is a dry process and it is done without any additional source of energy. No additional procedure for densification of layer is necessary. Having very high deposition rate as compare with conventional techniques, ADM is applicable for micro electro mechanical systems (MEMS) applications as well [3,4]. Particular feature of ADM is simple and fine patterning of piezoelectric films in deposition process and deposition on delicate structures. The density of deposited film is close to that of theoretical density and films has adhesion with substrate more than 30 MPa [4]. The films thickness is varied from less than 1 μm up to 500 μm that gives flexibility in optimization of piezoelectric layers thickness for microactuator application. The lead zirconate titanate (PZT) film deposited by ADM and annealed at 600 0 C shows piezoelectric properties as d 31 of about - 100 pm/V [5], good piezoelectric fatigue of more than 10 9 cycles [6]. The breakdown electrical voltage of piezoelectric films is very high and is more than 700 kV/cm for films thinner than 4 μm [7]. Previously we reported the microscanner fabricated on Si- based structure by ADM [8], in this paper we use another device design and reported for the first time the results of fabrication of a new type microscanner based on stainless steel. II. MICROSCANNER’S DESIGN The schematic of the scanner is shown in the Fig. 1. Piezoelectric layer which was deposited in some part of the sheet, excites vibration of the stainless sheet, due to the reflection of waves from the boarders of the sheet and waves interference with each other, the standing waves on the stainless steel was occurred; these waves induce the movement 0-7803-8410-5/04/$20.00 (c)2004 IEEE. 2004 IEEE International Ultrasonics, Ferroelectrics, and Frequency Control Joint 50th Anniversary Conference 165