EP025. Endpoint detection: OES怎麼設定？什麼是IB訊號？

Keywords： spectrum, 光譜, OES, IB7

參考資料：202-037878-001, Rev. G, Endpoint Detection

本文大綱列表

Endpoint Detection

用中文簡單說：質譜儀能夠提供高精度的氣體分析結果，這使得在蝕刻過程中氣體相變化的特定時刻被準確地檢測。當特定氣體成分的峰值或變化率達到預定值時，可以判定蝕刻終點已經達到。

Every step within a wafer-processing recipe has a number of user-defined parameters for controlling the process of endpoint detection. In order to define a step as an endpoint step, you must select the parameter variable named Step Type for that step as EndPT. Otherwise, all optical emission spectra (OES) parameters are processed but no endpoint detection is performed.

There are four major groups of user-defined parameters used by the OES system to perform an endpoint detection test. These four parameter groups are integration bands, basis functions, filters, and algorithms. All these four parameters are defined in the Editors\Endpoint Param window. See Figure 7.

OES 設定的主要參數

Integration Bands (IB訊號）

用中文簡單說：就是常聽到的 IB訊號，

軟體可藉由設定波長、波寛，設定8組訊號，IB1, IB2, IB3, IB4～IB8.

IB訊號訊定範圍：from 200 nm to 900 nm

IB訊號設定，舉例”波長 256 nm，波寬 6 for IB1，在 253 nm to 259 nm 這區域收為IB1訊號。

An integration band (IB) defines a contiguous wavelength band in the spectrograph. The value of the IB is the sum of the spectrographic intensity in the defined contiguous wavelength band.

An IB is defined by providing a wavelength position and a width band centered at the selected wavelength. You can define up to eight IBs (IB1, IB2, and so forth).

Once an IB is defined, its value can then be used by the basic function. The valid range of the wavelength is from 200 nm to 900 nm.

For example, if a wavelength of 256 nm is chosen and the width is 6 for IB1, then the value of IB1is obtained by adding all the intensity values from the contiguous band of 253 nm to 259 nm.

Basis Functions

用中文簡單說：看出此步驟偵測哪個IB訊號，或代數計算之設定

A basis function (BF) combines one or more IBs in a simple algebraic equation. The value of a basis function (endpoint signal) at each sampling interval is used as basis for endpoint detection.

The OES system provides several predefined algebraic equations for selection. In addition, you can also specify user-defined equations. The predefined algebraic equations are:

IB1
IB2
IB1 – IB2
IB1 / IB2
User definedAn example of a user-defined basic function is as follows:

0.5 * IB1 + 0.9 * IB2

Filters

用中文簡單說：不常用，再找專家研究

Filters are used to smooth out the incoming data and to reduce noise. You can apply the filters individually to integration bands and/or basis functions.

Fourteen different types of filters are defined in the current version of OES system:

Algorithms

用中文簡單說：該步驟偵測End Point 的演算法，偵測IB訊號變化、波峰、波谷等等，達到偵測點後，結束此EndPt step，進入下一步驟。大致上演算法包含三階段：經過幾後後開始偵測（Delay time), IB 訊號趨於穩定( Normalization Time）, and 基於Endpoint設定條件（Endpoint Detecting）.

For each endpoint step, select an algorithm for the OES system to use for detecting the occurrence of endpoint. There are ten pre-defined algorithms for selection in the current OES system—Value Change,Percent Change, Value Slope, Percent Slope, Direction Detection, Interferometer, Peak and Valley, Twin Peaks, Percent Slope Change, and WAC Detection.

In general, the process of finding the endpoint involves three stages: Delay Time, Normalization Time, and Endpoint Detecting.