刻蚀的具体过程可描述几个步骤？How many steps can be described in the etching process?

当刻蚀气体被通入刻蚀反应腔中，在射频电场的作用下产生等离子体辉光放电，反应气体分解成各种中性的化学活性基团，分子、电子、离子；由于电子和离子的质量不同使得质量较轻的电子能够响应射频电场的变化而离子却不能，正是这种差异在电极上产生负偏压 Vdc(Negative DC bias) ，离子在负偏压的加速下轰击硅片表面形成反应离子刻蚀；一个持续的干法刻蚀必须要满足这些条件：在反应腔内有源源不断的自由基团；硅片必须靠等离子体足够近以便反应基团可以扩散到其表面；反应物应被硅片表面吸附以持续化学反应；挥发性的生成物应可从硅片表面解吸附并被抽出反应腔。上面的任一种条件末达到刻蚀过程都会中断。等离子刻蚀机刻蚀的具体过程可描述为如下六个步骤：

1. 刻蚀物质的产生；

射频电源施加在一个充满刻蚀 气体的反应腔上，通过等离子体辉光放电产生电子、离子、活性反应基团。

2. 刻蚀物质向硅片表面扩散；

3. 刻蚀物质吸附在硅片表面上；

4. 在离子轰击下刻蚀物质和硅片表面被刻蚀材料发生反应；

5. 刻蚀反应副产物在离子轰击下解吸附离开硅片表面；

6. 挥发性刻蚀副产物和其它未参加反应的物质被真空泵抽出反应腔；

整个过程中有诸多的参数影响刻蚀工艺，其中最重要的是：压力、气体比率、气体流速、射频电源（RF　POWER）。另外硅片的位置和刻蚀设备的结构也会对刻蚀工艺，因此在实际生产中，针对不同的刻蚀膜质设备厂家设计不同的设备，提供不同的气体配比以达到工艺要求

    When the etching gas is introduced into the etching reaction chamber, a plasma glow discharge is generated under the action of RF electric field, and the reaction gas is decomposed into various neutral chemical active groups, molecules, electrons and ions; because of the different mass of electrons and ions, the lighter electrons can respond to the change of RF electric field, while the ions cannot, which is the difference that produces negative bias on the electrode Voltage VDC (negative DC bias) Under the acceleration of negative bias voltage, ions bombard the surface of silicon wafer to form reactive ion etching; a continuous dry etching must meet these conditions: there are continuous free groups in the reaction chamber; silicon wafer must be close enough to the plasma so that the reactive groups can diffuse to its surface; reactants should be adsorbed on the surface of silicon wafer for continuous chemical reaction; volatile products should be able to Desorption from the wafer surface and extraction of the reaction chamber. Any of the above conditions will interrupt the etching process. The specific process of plasma etching can be described as follows: 

1. The generation of etching materials; RF power supply is applied to a reaction chamber full of etching gas, through the glow discharge of plasma to produce electrons, ions, active reaction groups.

2. The etching substance diffuses to the surface of silicon wafer;

3. The etching substance is adsorbed on the surface of silicon wafer;

4. The etching substance reacts with the etched material on the surface of silicon wafer under the ion bombardment;

5. The by-product of etching reaction is desorbed from the surface of silicon wafer under the ion bombardment;

   6. The volatile etching byproducts and other substances not involved in the reaction are pumped out of the reaction chamber by vacuum pump; 

     There are many parameters affecting the etching process in the whole process, the most important of which are: pressure, gas ratio, gas flow rate, RF power. In addition, the location of silicon wafer and the structure of etching equipment will also affect the etching process. Therefore, in actual production, different equipment and gas ratio are designed for different etching film equipment manufacturers to meet the process requirements