Precise Control of Nucleation and Growth in Lead Zirconate Titanate Thin Films by Scanning Rapid Thermal Annealing
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Precise Control of Nucleation and Growth in Lead Zirconate Titanate Thin Films by Scanning Rapid Thermal Annealing Jang-Sik Lee and Seung-Ki Joo School of Materials Science and Engineering, College of Engineering, Seoul National University, Seoul 151-742, Korea, [email protected] ABSTRACT In this paper, a novel annealing method, scanning-rapid thermal annealing (RTA), for the selectively nucleated lateral crystallization (SNLC) of Pb(Zr,Ti)O3 (PZT) thin films is discussed. The effects of lamp power and scan speed on the SNLC were investigated. It was found that scanning-RTA was very effective method for SNLC in reducing the process time and preventing undesirable nucleation at other than pre-determined positions.
INTRODUCTION We previously reported the selectively nucleated lateral crystallization (SNLC) of Pb(Zr,Ti)O3 (PZT) thin films and their electrical characteristics [1-3]. By the SNLC method, we could control the nucleation site, thereby the grain-location in PZT thin films. The SNLC was based on the selective nucleation and growth between the template layer and the perovskite seed. The SNLC annealing was carried out in a conventional diffusion furnace. However, the selective growth was very difficult, because the annealing temperature should be low enough not to nucleate at other regions and thus, growth rate was too low due to low annealing temperature. Also, there was undesirable nucleation at other than artificial nucleation sites, as shown in Fig. 1. Thus, a novel type annealing method, that scanning rapid thermal annealing is provided in this study to reduce the process time and prevent the undesirable nucleation. In this paper, the effects of preheating temperature, scan-lamp power and scan speed on the crystallization and microstructure of PZT thin films are discussed in detail.
EXPERIMENTAL PROCEDURE PZT(65/35) thin films were formed by radio-frequency magnetron sputtering at 350℃ using targets of Pb, PbZrO3 and PbTiO3. PZT thin film (200 nm) was deposited on Pt/SiO 2/Si(100) substrate. The detailed sample preparation method and fabrication process of SNLC are described in elsewhere [1]. SNLC annealing was carried out by scanning-RTA with tungsten-halogen lamps, as shown in Fig. 2. [4] A line-shaped light, which was focused with an elliptical reflector, was scanned over the specimen that had been preheated by bottom lamps. The temperature was monitored by a computer-based temperature measurement system using a DT2811 D/A converter (Data Translation, Inc.). The growth behavior of the films was investigated using a Normarski microscope (polarized light).
C1.3.1
Scan
Guiding Rail Upper Elliptical Reflector
Upper Halogen Lamp
Substrate Quartz Plate
Compressed air cooling Water cooling
Figure 1. SNLC of PZT thin films annealed at 580ºC for 2 h. The arrows show the undesirable nucleation at other than nucleation sites.
Bank of Lower Halogen Lamps
Lower Planar Reflector
Figure 2. Scanning rapid thermal annealing apparatus.
RESULTS AND DISCUSSION When the upper lamp scanned, the substrat
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