Name: Suzhou cycas Microelectronics Co., Ltd.
Address: 1st floor,B06 building,No.2,Fuxing Road,Zhangjiagang Economic Development Zone,Jiangsu Province 215600PRC
良好的刻蝕速率均勻性(Uniformity)，不僅僅是片內的均勻性(Within Wafer)，還包括片與片之間(Wafer to Wafer)，批次與批次之間(Lot to Lot)。
等離子體幹法刻蝕通常有三種形式：等離子體刻蝕、離子轟擊和兩種形式的結合反應離子刻蝕（Reactive Ion Etching），下表給出三種刻蝕的特點對照。
當刻蝕氣體被通入刻蝕反應腔中，在射頻電場的作用下產生等離子體輝光放電，反應氣體分解成各種中性的化學活性基團，分子、電子、離子；由於電子和離子的質量不同使得質量較輕的電子能夠響應射頻電場的變化而離子卻不能，正是這種差異在電極上產生負偏壓 Vdc(Negative DC bias) ，離子在負偏壓的加速下轟擊矽片表麵形成反應離子刻蝕；一個持續的幹法刻蝕必須要滿足這些條件：在反應腔內有源源不斷的自由基團；矽片必須靠等離子體足夠近以便反應基團可以擴散到其表麵；反應物應被矽片表麵吸附以持續化學反應；揮發性的生成物應可從矽片表麵解吸附並被抽出反應腔。上麵的任一種條件末達到刻蝕過程都會中斷。等離子刻蝕機刻蝕的具體過程可描述為如下六個步驟：
As we all know, in the process of chip manufacturing, the formation of silicon surface pattern mainly depends on two modules: lithography and etching. The aim of lithography is to form the pattern of photoresist on the surface of silicon wafer, and then the pattern of photoresist is transferred to the substrate or the film layer on the substrate. With the requirement of feature size becoming smaller and smaller, the requirement of lithography and etching is also higher and higher. Generally, an etching process includes the following characteristics:
good uniformity of etching rate, not only within wafer, but also between wafer to wafer, lot to lot.
With high selectivity, the etching rate of etched material is much higher than that of photoresist and substrate.
There is no residual free, and non-volatile and difficult to remove etching by-products and particles should not be generated in the etching process.
No damage (damage free), that is, there should be no electrical damage or plasma damage to the substrate, film and device during the etching process. It will not make photoresist difficult to remove after etching.
Controllable and good side profile. A good critical dimension controls the etching rate and ensures the amount of chips. There are generally three forms of plasma dry etching: plasma etching, ion bombardment and two forms of reactive ion etching. The following table shows the characteristics of three kinds of etching. As the name implies, ion bombardment is to bombard the surface of silicon wafer with high-energy inert gas ions to achieve the effect of sputtering and etching. Because of this method, very small feature size and vertical side wall morphology can be obtained. This is a "universal" etching method, which can form patterns on any material, such as titanium, gold, etc. unfortunately, ion bombardment has its fatal weakness: low etching rate and poor selectivity, which can reach 3:1 is rare.
The advantages of plasma etching are not only the fast etching rate and good physical morphology, but also the high selection ratio for photoresist and substrate through the selection of reactive gas. But because the whole process is completely chemical reaction, the etching of the material is isotropic. With the continuous reduction of the process size, this disadvantage becomes more and more prominent, which makes its application more and more limited. Generally, it is only used in the Ashing process which does not require the characteristic morphology.
Reactive ion etching is the product of the combination of the above two etching methods. It uses chemically reactive gases to produce chemically active groups and ions. The high energy ions accelerated by electric field bombard the etched material and produce the damaged surface, which further accelerates the reaction rate between the reactive etching reaction group and the etched material. It is the mutual promotion of chemical and physical reactions that makes the reactive ion etching have the advantages that the above two dry etching methods do not have: good morphology control ability (anisotropy); high selection The acceptable rate of engraving. Because of its advantages, it has become the most widely used dry etching at present, so the dry etching we mentioned now generally refers to reactive ion etching.
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:
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.
The etching substance diffuses to the surface of silicon wafer;
The etching substance is adsorbed on the surface of silicon wafer;
The etching substance reacts with the etched material on the surface of silicon wafer under the ion bombardment;
The by-product of etching reaction is desorbed from the surface of silicon wafer under the ion bombardment;
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 locations 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