Microfabrication of cesium vapor cells with buffer gas for MEMS atomic clocks
Microfabrication of cesium vapor cells with buffer gas for MEMS atomic clocks
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DOI：
10.1016/j.sna.2011.02.039
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发表时间：
2011-06-01
影响因子：
4.6
通讯作者：
Mauri, L.
中科院分区：
文献类型：
--
作者：
Hasegawa, M.;Chutani, R. K.;Mauri, L.
本文报道了用硅玻璃阳极键合工艺在可控压力（20 kPa）下向微型铯蒸气室充入缓冲气体（Ar或Ne），这是微型原子钟铯蒸气室制作的关键技术之一。在这些气体的气氛中，由于气体电离引起的电击穿，可应用的键合电压不足以实现强键合。为了提高键合质量，提出了一种新颖的两步阳极键合方法。阳极键合的第一步。其旨在预密封微单元中的气体，在存在缓冲气体的情况下通过施加低于击穿电压的电压来进行。随后，在空气中以足够高的电压进行第二次键合，以提高密封质量。通过采用光谱学，证明了电池将缓冲气体保持在适合原子钟工作的压力下。加速老化试验表明，Cs蒸气以及缓冲气体保留在电池中，而压力没有任何显著变化，这使我们能够估计电池的寿命至少为3年。进一步的CPT实验表明，在125 ℃下超过3周的整个老化测试中，缓冲气体压力变化小于6.13 × 10（-4）kPa。这些结果表明，这些微单元是适当的原子频率基准的应用。(C)2011 Elsevier B. V.保留所有权利。
This paper reports on the Si-glass anodic bonding process to fill micro Cs vapor cells with a buffer gas (Ar or Ne) at a controlled pressure (up to 20 kPa), which is one of the technological key steps to fabricate Cs vapor cells for miniature atomic clocks. In the atmosphere of these gases, the applicable bonding voltage was not high enough to achieve strong bonding because of the electrical breakdown caused by ionization of the gas. To improve the bonding quality, an original two-step anodic bonding method was proposed. The first step of the anodic bonding. which intends to pre-seal the gas in microcells, is carried out in the presence of a buffer gas by applying a voltage lower than the breakdown voltage. Subsequently, the second bonding is performed in air at sufficiently high voltages to improve the sealing quality.By employing optical spectroscopy, it was demonstrated that the cells maintain the buffer gas at an appropriate pressure for atomic clock operation. The accelerated aging tests show that Cs vapor as well as the buffer gas remained in the cells without any significant change in the pressure, which allow us to estimate the lifetime of the cells to be at least 3 years. Further CPT experiments revealed that the buffer-gas pressure change is less than 6.13 x 10(-4) kPa throughout the aging test at 125 degrees C for more than 3 weeks. These results show that these microcells are appropriate for applications to atomic frequency references. (C) 2011 Elsevier B.V. All rights reserved.