Laser-induced backside wet etching (LIBWE) has been proposed to fabricate high-quality micromachined components on transparent materials. However, the process is limited by poor repeatability when fabricating high-aspect-ratio structures, even under the same conditions due to uncertainties arising from the thermal process and the complex mechanisms associated with the indirect irradiation of the etching process. Such errors could lead to redundant trials and wastages when trying to achieve the desired dimension. To identify the factors causing these variations, we targeted the process sounds generated during the etching. This study uses a microphone to measure factors that result in variations in material removal quantity during the etching process under the same conditions. The sound was filtered at frequencies between 3 and 6 kHz, which were selected as characteristic frequencies for the process under various laser conditions. By integrating the root mean squared value of the detail coefficient of the wavelet transform, the depth estimation closely matched the measured depth of the fabricated part. This finding suggests that determining the etching rate from sound at a certain characteristic frequency during the LIBWE process is feasible; this approach can improve the accuracy and repeatability of the process. Based on this estimation mechanism, we designed a closed-loop feedback control system capable of fabricating highly accurate microchannels in the range of 80–120 μm with a maximum error of 5.6%.

激光诱导背面湿法蚀刻（LIBWE）已被提议用于在透明材料上制造高质量的微机械部件。然而，由于热处理过程产生的不确定性以及与蚀刻过程的间接照射相关的复杂机制，即使在相同的条件下，该工艺在制造高深宽比结构时也受到重复性差的限制。在尝试达到所需尺寸时，此类错误可能会导致重复试验和浪费。为了确定导致这些变化的因素，我们针对蚀刻过程中产生的过程声音。本研究使用麦克风来测量在相同条件下蚀刻过程中导致材料去除量变化的因素。声音在 3 至 6 kHz 之间的频率进行过滤，这些频率被选为各种激光条件下工艺的特征频率。通过对小波变换细节系数的均方根值进行积分，深度估计与制造零件的测量深度紧密匹配。这一发现表明，在 LIBWE 过程中通过特定特征频率的声音确定蚀刻速率是可行的；这种方法可以提高过程的准确性和可重复性。基于这种估计机制，我们设计了一种闭环反馈控制系统，能够制造80-120μm范围内的高精度微通道，最大误差为5.6%。