Name: 斯坦福納米加工設備：幹蝕刻 - 等離子體基礎知識和工具類型（第 2 部分，共 4 部分） (Stanford Nanofabrication Facility: Dry Etching - Basics of Plasmas & Types of Tools (Part 2 of 4))
Uploaded: 2025-06-07T15:32:50.000Z
Duration: 23 min 18 s

Hi, I'm Jim McVitie with the Stanford Nanofabrication Facility here at Stanford University.

大家好，我是斯坦福大學斯坦福納米加工設施的吉姆-麥克維蒂。

This is part two of a four-part lecture series on dry etching.

這是幹法蝕刻四部曲系列講座的第二部分。

In this part, I'm going to cover the basics of plasmas and the types of dry etching tools.

在這一部分，我將介紹等離子體的基礎知識和幹蝕刻工具的類型。

Previously, I talked about an introduction to dry etching, and following lectures will cover dry etching mechanisms and choosing dry etching processes and tools.

之前，我談到了幹蝕刻簡介，接下來的講座將介紹幹蝕刻機理以及幹蝕刻工藝和工具的選擇。

In this presentation, I'm going to cover the basics of plasmas, plasmas and sheath reasons, parallel plate configurations, inductive coupled plasmas or ICP configuration, and finally, downstream configuration.

在本講座中，我將介紹等離子體的基礎知識、等離子體和鞘的原因、平行板配置、電感耦合等離子體或 ICP 配置，以及下游配置。

Okay, let's start with the basics of plasmas.

好，我們先來了解一下等離子體的基本知識。

Plasma is commonly used for fluorescent lighting.

等離子體通常用於熒光燈照明。

Over here in the diagram, I show basically a vacuum chamber.

圖中顯示的基本上是一個真空室。

We're going to be limiting our discussion to RF power since we're DC, you can also generate a plasma using DC, but from a plasma etching standpoint, it can cause a DC plasma to cause damage to wafers or device wafers.

我們的討論僅限於射頻功率，因為我們使用的是直流電，您也可以使用直流電產生等離子體，但從等離子體蝕刻的角度來看，直流等離子體可能會對晶片或設備晶片造成損壞。

So we're going to be only talking about RF.

I show here the gases coming in, I show gases going out by way of the vacuum pump, I see light coming out, and in the plasma, I have neutrals, and then radicals, the initial gases, and sometimes I have multiple ions, and then I have electrons, and of course, I already talked about radicals.

我在這裡展示了氣體進入的過程，展示了氣體通過真空泵流出的過程，我看到了光的流出，在等離子體中，我看到了中性物，然後是自由基，最初的氣體，有時我看到了多個離子，然後是電子，當然，我已經談到了自由基。

Okay, the plasmas are a steady state process that results after a gas breakdown.

好吧，等離子體是氣體分解後產生的穩態過程。

The electrons gain energy from the applied field, so I'm going to be putting RF power that can generate fields that we're going to basically heat up or give energy to my electrons.

電子從外加磁場中獲得能量，是以我將使用能產生磁場的射頻功率，基本上可以加熱電子或為電子提供能量。

The higher energy electrons through collisions will have ionization and excitation and fragmentation of our source gas molecules.

能量較高的電子通過碰撞會使我們的源氣體分子發生電離、激發和破碎。

Okay, like I said, plasmas are a steady state process resulting after a breakdown.

好吧，就像我說的，等離子體是分解後產生的穩態過程。

In the plasma region, we mainly see the glow.

在等離子體區域，我們主要看到輝光。

We have a charged balance where the density of electrons are going to be balanced by equal to the density of positive ions.

我們有一個電荷平衡，電子密度將與正離子密度相平衡。

And typically, in the processing plasmas, we're talking about partially ionized gases, so there's less than 1% of the molecules or atoms in the chamber are ionized, so it's mainly neutral species.

通常，在加工等離子體中，我們討論的是部分電離的氣體，是以腔體內電離的分子或原子不到 1%，所以主要是中性物質。

The glow is from the decay of short lifetime excited species.

輝光來自短壽命激發物種的衰變。

So any place you see, when I say short lifetime, I'm talking about nanoseconds.

是以，在任何地方，當我說壽命短時，我指的是納秒。

So any place you see glow, that's where electrons are heating, are hot, they're basically breaking down and fragmenting the gas.

是以，任何你看到發光的地方，都是電子發熱的地方，它們基本上是在分解和破碎氣體。

And when it's dark, it means we don't have any hot electrons.

而當它是黑暗的時候，就意味著我們沒有任何熱電子。

Typically, such a plasma at 20 millitorr, we're talking about neutrals in the range of 10 to the 15th per cubic centimeter, a ratio of radicals to neutrals from 50% down to 10%, and ion to neutral ratios from 10 to the minus 3 to 10 to the minus 6.

通常情況下，在 20 毫摩爾的等離子體中，每立方厘米的中性物質在 10 到 15 個之間，自由基與中性物質的比例從 50%下降到 10%，離子與中性物質的比例從 10 到負 3 到 10 到負 6。

So basically, it's mainly neutrals in the chamber.

是以，會議室裡基本上都是中性人。

Now I'm going to talk about RF plasmas and the sheath reasons.

現在我要談談射頻等離子體和護套的原因。

The diagram here, I show a parallel plate type configuration.

這裡的圖表顯示的是平行板式結構。

So we're going to be basically showing that I have one electrode that can be grounded, and the opposite electrode, well, I'm going to be applying RF power.

是以，我們基本上要展示的是，我有一個電極可以接地，而另一個電極則要施加射頻功率。

And after the breakdown of the gas equilibrium, what I'm going to see, I'm going to have a central glow region, and then we have dark spaces on both sides of the plasma, between the plasma and the electrode, basically between the plasma and all surfaces.

氣體平衡打破後，我將看到一箇中心發光區，然後等離子體兩側、等離子體和電極之間，基本上等離子體和所有表面之間都會出現暗空間。

And the reason we developed the dark spaces is, well, the reason is the electrons, being very small, travel much faster than the ions.

我們開發暗空間的原因是，由於電子非常小，其傳播速度比離子快得多。

So numbers are like electrons have velocities about 100 times faster than ions.

是以，數字就像電子的速度比離子快約 100 倍。

So it means when we have the glow region, the first thing that's going to happen is the electron is going to start streaming out of this region, and they're going to charge up all the surfaces.

是以，當我們產生輝光區域時，首先會發生的事情就是電子開始從這個區域流出，並對所有表面充電。

So I'm showing charge here on the two electrodes.

是以，我這裡顯示的是兩個電極上的電荷。

As the surfaces charge up, we're going to develop an electric field that's going to be retarding for electrons.

隨著表面電荷的增加，我們將形成一個對電子有阻礙作用的電場。

So if the electric field is this way, electrons are going to want to start turning around and going the opposite direction.

是以，如果電場是這樣的，電子就會開始轉向相反的方向。

So we mean, so I'm showing here schematically, I have a high current of electrons coming out of the plasma, but most of that, those electrons get returned to the plasma, and only a small amount makes it to the surface.

是以，我們的意思是，我在這裡示意性地展示了從等離子體中流出的高電流電子，但其中大部分電子會返回等離子體，只有少量電子會到達表面。

But the amount that makes it to the surface, it can be balanced by the same amount of ions that make it to the surface.

但是，進入地表的離子數量可以與進入地表的離子數量相平衡。

So at the surface, the electron current and ion current will be equal.

是以，在表面，電子電流和離子電流將相等。

And so we have the electrons and ions move from the plasma towards all surfaces.

是以，電子和離子從等離子體向所有表面移動。

The electrons want to leave much faster because they're going, let's say, 100 times faster.

電子想以更快的速度離開，因為它們的速度，比方說，快了 100 倍。

And to maintain steady state balance in the plasma, we form a boundary layer that we're going to call the sheath or depletion region.

為了保持等離子體的穩態平衡，我們會形成一個邊界層，我們稱之為鞘或耗盡區。

And this makes the electron and ion current or loss rates from the plasma equal so we can maintain our steady state.

這使得等離子體中的電子和離子電流或損耗率相等，是以我們可以保持穩定狀態。

Here again, I'm showing our diagram of the plasma and the sheath region.

在這裡，我再次展示等離子體和鞘區的示意圖。

And so I talked about the electrons and how the electric field turned most of the electrons back so we have the balance at the electrodes.

是以，我談到了電子，以及電場如何將大部分電子轉回，從而在電極上達到平衡。

Well, the ions now are accelerated by the electric field.

And so they accelerate towards the surface, and they gain both energy and directionality.

於是，它們加速衝向地表，同時獲得能量和方向性。

So the ions come in isotropically into the boundary between the plasma and the sheath.

是以，離子會各向同性地進入等離子體和鞘之間的邊界。

And at the surface, they're very directional.

在表面上，它們的方向性很強。

In addition, they gain energy, and there can be hungry EV coming from the ions crocking the sheath.

此外，它們還能獲得能量，鞘內的離子會產生飢餓的電動汽車。

So the ion gain, the energy gain, depends on the voltage across the sheath and the collisions.

是以，離子增益、能量增益取決於鞘上的電壓和碰撞。

So if I go low pressure, I'm going to have a few collisions or no collisions, and the ions are going to get the full energy across the sheath.

是以，如果我使用低壓，就會有少量碰撞或沒有碰撞，離子將獲得穿過鞘的全部能量。

And this energy, so if I integrate the electric field here, I have what we call the sheath voltage across the sheath, and that's basically the voltage between the plasma and the electrode.

這種能量，如果我在這裡對電場進行積分，就會得到我們所說的跨鞘電壓，基本上就是等離子體和電極之間的電壓。

And with no collisions, the ions will basically gain the sheath voltage in terms of energy.

在沒有碰撞的情況下，離子基本上會獲得鞘電壓的能量。

So lower pressure, less collisions, more directionality, more ion energy.

是以，壓力越低，碰撞越少，方向性越強，離子能量越大。

The sheath voltage depends on the system configuration, the applied power and pressure, and we're going to talk a little bit more of that in the next slide.

護套電壓取決於系統配置、應用功率和壓力，我們將在下一張幻燈片中詳細介紹。

Oh, and I'll talk about it actually in a couple slides.

哦，我將在幾張幻燈片中詳細介紹。

So first I want to talk about, give you an overview of the four configurations I'll be going into more detail.

所以，首先我想談談，給大家介紹一下我將要詳細介紹的四種配置。

So I have, first I have what we call a CCP plasma, and this can mean charged coupled plasma.

首先，我有我們所說的 CCP 等離子體，這可能意味著帶電耦合等離子體。

And I'll talk about a capacitive coupled plasma, and I'll talk about the meaning of that in the following slides.

我將談談電容耦合等離子體，並在下面的幻燈片中闡述其含義。

And I have what we call a plasma mode, where you have equal electrodes.

我有一個所謂的等離子模式，在這種模式下，電極是相等的。

RIE mode, where you have one electrode much smaller than the other electrode.

RIE 模式，其中一個電極比另一個電極小得多。

And then I'll talk about ICP case, inductive coupled plasmas.

然後我會談談 ICP 案例，即電感耦合等離子體。

And finally I'll talk about downstream plasmas.

最後，我要談談下游等離子體。

So let's start talking about the CCP case.

那麼，讓我們開始討論 CCP 案吧。

So we have the CCP, or capacitive coupled plasmas, and again I'm showing the parallel plate case, where our plasma is sitting between the electrodes with a sheath on both sides.

是以，我們有 CCP，即電容耦合等離子體，我再次展示平行板情況，我們的等離子體位於電極之間，兩側有護套。

So the plasma is driven by RF currents going through the electrodes.

是以，等離子體是由通過電極的射頻電流驅動的。

So we have the RF supply here, the RF current going through the top electrode, it goes across the sheath region, through the plasma, and then out the other side.

是以，我們這裡有射頻電源，射頻電流穿過頂部電極，穿過鞘區，穿過等離子體，然後從另一側流出。

And this is RF current, if we're going to be driving, keeping the plasma going.

如果我們要開車，這就是射頻電流，讓等離子體繼續運轉。

So we never use DC supply for action because of the damage issue.

是以，由於損壞問題，我們從不使用直流電源進行操作。

RF, we normally use 13.56 megahertz, it's an inductive plasma frequency, set up by the

射頻，我們通常使用 13.56 兆赫，這是一種感應等離子體頻率，由

FCCC, and although some of the time, there are special cases where we use lower frequency at the wafer.

儘管在某些特殊情況下，我們會在晶圓上使用較低的頻率。

We also use lower frequency for the ICP, but at the wafer, typically 13 megahertz.

我們還在晶圓上使用較低頻率的 ICP，通常為 13 兆赫。

RF current flow determines the sheath voltage, okay, let's talk about what this means.

射頻電流決定了護套電壓，好，讓我們來談談這意味著什麼。

So the electrons carry the RF current in the plasma region.

是以，電子在等離子體區域攜帶射頻電流。

So in the plasma, I have a lot of electrons, they're very mobile, they carry the current.

是以，在等離子體中，我有很多電子，它們流動性很強，攜帶著電流。

But at the two sheath region, the depletion region, there's not enough electrons to carry the RF current.

但在兩個鞘區，即耗盡區，沒有足夠的電子來承載射頻電流。

And so how does the RF current get across the region?

那麼，射頻電流是如何穿過該地區的呢？

And by what we call displacement current, or capacitive current.

我們稱之為位移電流或電容電流。

And that's a way RF current gets across a capacitor, where we build up a charge on one side of a capacitor, and the two plates of the capacitor, the charge on one side induces a charge on the other side, and we have basically an oscillating charge across the capacitor.

這是射頻電流穿過電容器的一種方式，我們在電容器的一側積累電荷，電容器的兩塊極板上，一側的電荷誘導另一側的電荷，電容器上的電荷基本上是振盪的。

So if we start to look at our sheath region, we have electrodes here, so it's easy to have an oscillating charge building up and going away on the metal electrode.

是以，如果我們開始觀察我們的鞘區，我們這裡有電極，所以很容易在金屬電極上產生振盪電荷，然後消失。

But at the boundary layer, I don't have any electrodes.

但在邊界層，我沒有任何電極。

So the way I get my oscillating charge, the QDT, is by the sheath oscillating.

是以，我獲得振盪電荷（QDT）的方法就是通過鞘的振盪。

I deplete into the plasma, and then I undeplete.

我把能量消耗到等離子體中，然後再把能量消耗掉。

And so the sheath will be oscillating up and down, and that's going to give me a charge per unit of time that's going to allow the displacement current, the capacitive current to go across the sheath region.

是以，鞘將上下襬動，這將在組織、部門時間內產生電荷，使位移電流、電容電流穿過鞘區域。

Now if we go in and integrate that charge, that gives us a voltage across it.

現在，如果我們對電荷進行積分，就能得到它兩端的電壓。

So what I'm going to get at here is that RF current, this oscillating charge here, is what gives us our voltage across the sheath.

是以，我要在這裡說明的是，射頻電流，即這裡的振盪電荷，就是我們跨鞘電壓的來源。

And that, basically if you work out the details of it, you're going to get that the sheath voltage goes into RF current density divided by the electron density.

基本上，如果你能計算出其中的細節，你就會發現鞘電壓會轉化為射頻電流密度除以電子密度。

So if I have a higher RF current density, I'm going to have a higher voltage.

是以，如果射頻電流密度越大，電壓也就越高。

And this is where the area comes into play, because now if I change the area of my electrode,

這就是面積發揮作用的地方，因為現在如果我改變電極的面積、

I can increase my current density and increase my voltage.

我可以增加電流密度，提高電壓。

So let's talk about it a little bit more.

那麼，讓我們再來談談這個問題。

So we're seeing that the RF of the sheath voltage depends on the RF current density.

是以我們可以看到，鞘電壓的射頻取決於射頻電流密度。

Reducing the electrode area increases the sheath voltage, and therefore I'm going to be able to increase my ion energy across the sheath.

減小電極面積會增加鞘電壓，是以我就能增加離子穿過鞘的能量。

Okay, there's going to be two ways we do this.

So I forgot to mention that the capacitive coupling across the sheath, the displacement current or capacitive current is where we get the name.

所以，我忘了說，穿過護套的電容耦合、位移電流或電容電流就是我們的名稱由來。

Capacitive coupled plasma means that it refers to the capacitive current across the sheath.

電容耦合等離子體指的是護套上的電容電流。

好吧，我們來談談等離子模式。

The plasma mode is where we have parallel plate electrodes but equal area.

等離子模式是指平行板電極的面積相等。

So I have the two electrodes at equal area, and in this case we're going to have, we get relatively low voltage across the sheath, and so we get low ion energies.

是以，我讓兩個電極的面積相等，在這種情況下，我們會在鞘上獲得相對較低的電壓，從而獲得較低的離子能量。

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斯坦福納米加工設備：幹蝕刻 - 等離子體基礎知識和工具類型（第 2 部分，共 4 部分） (Stanford Nanofabrication Facility: Dry Etching - Basics of Plasmas & Types of Tools (Part 2 of 4))

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