氢氧化钾(KOH)是一种用于各向异性湿法蚀刻技术的碱金属氢氧化物，是用于硅晶片微加工常用的硅蚀刻化学物质之一。各向异性蚀刻优先侵蚀衬底。也就是说，它们在某些方向上的蚀刻速度比在其他方向上的蚀刻速度快，而各向同性蚀刻(如HF)会向所有方向侵蚀。

Potassium hydroxide (KOH) is an alkali hydroxide used in anisotropic wet etching technology, and is one of the silicon etching chemicals commonly used in silicon wafer micromachining. Anisotropic etching prioritizes substrate erosion. That is to say, their etching speed in certain directions is faster than that in other directions, while isotropic etching (such as HF) erodes in all directions.

使用KOH工艺是因为其在制造中的可重复性和均匀性，同时保持了较低的生产成本。异丙醇(IPA)经常添加到溶液中，以改变从{110}壁到{100}壁的选择性，并提高表面光滑度。

The use of KOH process is due to its repeatability and uniformity in manufacturing, while maintaining lower production costs. Isopropanol (IPA) is often added to the solution to change the selectivity from {110} wall to {100} wall and improve surface smoothness.

氧化物和氮化物在KOH中都蚀刻缓慢。氧化物可以在KOH蚀刻浴中用作短时间的蚀刻掩模。对于更长的时间，氮化物是更好的掩模，因为它在KOH中蚀刻得更慢。另一种选择(对许多其他功能有用)是用硼掺杂晶片。这也将降低蚀刻速率，实际上停止富硼硅的蚀刻。

Both oxides and nitrides etch slowly in KOH. Oxides can be used as short-term etching masks in KOH etching baths. For longer periods of time, nitrides are better masks because they etch more slowly in KOH. Another option (useful for many other functions) is to use boron doped wafers. This will also reduce the etching rate, effectively stopping the etching of boron rich silicon.

当KOH浓度在80℃时达到18wt%时，蚀刻速率随着KOH浓度的增加而增加。当KOH浓度增加超过18wt%时，蚀刻速率降低。蚀刻过程中发生的化学反应就是这种变化的结果。这将在后面更深入地讨论。然而，通常不使用大蚀刻速率的浓度，因为表面光滑度随着浓度的增加而提高(明显高于30%)。Si{100}在KOH中的蚀刻速率可以使用下面的等式来计算:

When the KOH concentration reaches 18wt% at 80 ℃, the etching rate increases with the increase of KOH concentration. When the KOH concentration increases by more than 18wt%, the etching rate decreases. The chemical reaction that occurs during the etching process is the result of this change. This will be discussed in more depth later. However, concentrations with high etching rates are usually not used, as surface smoothness increases with increasing concentration (significantly higher than 30%). The etching rate of Si {100} in KOH can be calculated using the following equation:

r =[H2O]4[氢氧化钾]1/4实验值(-个/kT)

R=[H2O] 4 [potassium hydroxide] 1/4 experimental value (- pieces/kT)

等式1: {100}蚀刻速率

Equation 1: {100} Etching rate

其中浓度以摩尔/升为单位，k0 = 413米/分钟*(摩尔/升)-4.25，EA = 0.595电子伏。KOH的密度和分子量分别为2.055克/立方厘米和56.11克/摩尔，水的密度和分子量分别为1.00克/立方厘米和18.02克/摩尔。

The concentration is measured in moles per liter, with k0=413 meters per minute * (moles per liter) -4.25 and EA=0.595 electron volts. The density and molecular weight of KOH are 2.055 grams per cubic centimeter and 56.11 grams per mole, respectively, while the density and molecular weight of water are 1.00 grams per cubic centimeter and 18.02 grams per mole, respectively.

使用KOH蚀刻有几个缺点。大的问题是蚀刻过程中H2气泡的产生。这些H2气泡充当了一个伪面具。这增加了粗糙度，并可能损坏微结构。与KOH蚀刻相关的另一个问题是KOH含有碱离子。KOH是MOS器件的终生杀手。使用KOH的人必须小心不要污染任何其他过程。KOH还会腐蚀铝，这可能是片上电路的一个问题。

There are several drawbacks to using KOH etching. The big problem is the generation of H2 bubbles during the etching process. These H2 bubbles act as a fake mask. This increases the roughness and may damage the microstructure. Another issue related to KOH etching is the presence of alkali ions in KOH. KOH is the lifelong killer of MOS devices. People using KOH must be careful not to contaminate any other processes. KOH can also corrode aluminum, which may be a problem with on-chip circuits.

KOH蚀刻速率与成分和温度的关系

The Relationship between KOH Etching Rate and Composition and Temperature

蚀刻速率随着温度的增加而增加；然而，随着蚀刻速率的增加，会导致不太理想的蚀刻行为。当KOH浓度增加超过18wt%时，蚀刻速率降低。这是因为发生了蚀刻反应。当强碱，如KOH(含有大量的OH-离子)存在时，硅-硅键断裂。该蚀刻导致Si(OH)4的形成、四个水分子的消耗和两个氢气分子的释放。

The etching rate increases with the increase of temperature; However, as the etching rate increases, it can lead to less ideal etching behavior. When the KOH concentration increases by more than 18wt%, the etching rate decreases. This is because an etching reaction occurred. When strong bases such as KOH (containing a large amount of OH ions) exist, the silicon silicon bond breaks. This etching leads to the formation of Si (OH) 4, the consumption of four water molecules, and the release of two hydrogen molecules.

氢氧化钾(KOH)的硅湿法蚀刻事项就讲解到这里了，希望能够帮助到您，更多事项就来我们网站http://qxu1539600089.my3w.com咨询！

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