大面积PIN型超薄硅ΔE探测器的研制

Particle identification method is commonly used in the nuclear physics experiments to eliminate the experimental background effectively and thus pick out the target nuclides of interest. For the nuclear reaction in the light nuclide region, a telescope detector group is always used to fulfill the particle identification function. It's composed of an ultra-thin silicon ΔE detector and a thicker E detector. The ultra-thin silicon detector is thinner than 100μm at large, sometimes it's even as thin as 40μm. Gold surface-barrier silicon ΔE detector can be found anywhere, whereas the ultra-thin PIN ΔE detector is seldom seen in the experiments. The real reason is that the ultra-thin wafer is too fragile and easily broken in the microelectronic process line. It's well known that the PIN detector has some specific advantages that the Au-surface barrier silicon detector is short of. An ultra-thin PIN silicon ΔE detector with 100μm thickness or less, 30mmx30mm area or larger, and single sided 16 strips, is suggested to be developed in this project by combining of the MMES technique and the chemical etching technique. The key point is that only the central part of the wafer in one side is chemical etched to a proper thickness, keeping the other place unchanged.

为了有效地去除实验本底并挑选出感兴趣的目标核，在核物理实验中经常采用核素粒子鉴别的手段。在轻核区核反应研究中，常用的粒子鉴别方法是采用望远镜结构的硅半导体探测器组，即由一块超薄型的ΔE探测器和其后的E探测器构成。该薄ΔE探测器一般在100μm以下，最薄的甚至在40μm左右。它常采用金硅面垒结构的探测器，采用PIN结构的薄硅探测器很少见，原因是研制PIN型探测器需要采用微电子工艺生产线，在流片过程中超薄的硅片极易碎裂，成品率低。鉴于PIN型探测器具有某些金硅面垒探测器无法比拟的优点，本申请拟将MMES技术和化学腐蚀技术结合起来，采用硅片中心区域局部减薄的方法，研制出超薄型的单面16条的100微米以下厚度和30mmx30mm以上面积的PIN型硅ΔE探测器。

大面积PIN型超薄∆E探测器在核物理领域及核天体、核医学等领域正得到越来越广泛的应用，它是低能离子能谱测量和高能离子粒子鉴别的重要探测元件。由于超薄的硅片在MMES的工艺流片过程中极易碎裂，成品率低，这使其造价升高。PIN型超薄∆E探测器目前在国内核物理实验中有大量需求，但没有国内可研制超薄探测器的厂家或研制单位。本申请先将硅片整体减薄至一定厚度，然后利用MMES工艺设备进行流片，探索工艺设备流片时的硅片厚度下限。实践表明100μm硅片厚度是工艺设备的下限，但此时碎片率仍较高，保守估计硅片厚度应保持在150μm以上。我们提出局部刻蚀的方法，仅将硅片中心区域局部减薄并在此区间内研制探测器，力图研制出100μm以下厚度的超薄∆E探测器。我们用HNO3:HF:冰醋酸按一定比例进行中间区域局部腐蚀，实验表明在HNO3:HF:冰醋酸按4:1:1的比例进行化学腐蚀时硅片中心部位腐蚀可保证±2μm的厚度均匀度，但由于腐蚀效率较低，只能在150μm厚硅片基础上局部减薄后研制出符合实验要求的103μm±2μm厚的PIN型超薄∆E探测器来。经调研后新提出了如下方案：用标准厚度300μm硅片先完成正面图形的工艺流程，而后将蓝膜保护的硅片正面探测器图形的周边环绕半切，最后将硅片背面整体研磨减薄+湿法腐蚀的方案，最终成功研制出61μm±1μm的单面PIN型超薄∆E探测器，各项指标符合实验要求。