200426930 玖、發·_顯 ； (给明說明湯ϋ明：發明所屬之技術領域、先前技術、內容、實施方式及圖式簡單說明) 一、發明所屬之技術領域 、 本發明係關於一種化學機械研磨終點判斷方法，尤 指一種結合終點偵測法（End-point Detection)與閉迴路控 制（Close Loop Control)之終點判斷方法。 二、先前技術200426930 玖 、 发 · 显; (Explain to Ming Ming Tang: the technical field to which the invention belongs, the prior art, the content, the embodiments, and the drawings briefly) 1. The technical field to which the invention belongs, the present invention relates to a chemical machine Grinding end point judgment method, especially an end point judgment method combining End-point Detection and Close Loop Control. Second, the prior art
目前用於半導體製造的化學機械研磨，採用的研磨 終點判斷方式主要有二，一是終點偵測法（End_p〇int Detection)，另一為閉迴路控制（cl〇se L〇〇p c〇ntr〇i)。終 點偵測法乃利用不同薄膜具不同性質，例如折射強度或 摩擦力的原理，藉由自動檢測或量測的子系統隨時量出 重要參數1後與標準值崎，並將結果回送而反應其 研磨終點，—般使用於多層膜結構，如淺溝渠隔離（STI) 之研磨。㈣迴路控制（C1〇se L〇〇p c_〇1)具有量出重 要製程參數的感測器，藉由回授的電子電路，其可進行 自我調整，而提供使製程維持在規格範圍内所需之研磨 時間’目前較常使用於單層薄膜之研磨，以使研磨過後 之薄膜厚度均一。 <舶识凋沄控制之STI研磨方式，雖可藉由 動檢測线研磨終點，但在實際生產操作時，量 =磨過後之4膜厚度，仍然:會有厚度不符合規格的情 务生’亦即單純終_測法並無法確保印之研磨是否 :。在此情況下，目前_般的補救方式是採用人工方 重工，即線上操作員藉由量測所得厚度，計算出所需: 200426930 再研磨時間，以進行士次研磨。但此方式會有發生人為 疏失或誤差的問題，而且，還會拉長石夕晶圓的製造時間， 提咼人力成本。因此’本發明利用閉迴路控制的加入， 來改善上述問題。 三、發明内容 本發明之主要目㈣在提供—種化學機械研磨終點 判斷方法，俾能降低研磨終點判斷之失誤率，排除人為 誤差發生的可能性，縮短生產時間，並降低人力成本二 〃為達成上述目的，本㈣—種化學機械研磨方法， 係配合一具有一厚度量測元件之化學機械研磨單元，用 以研磨具有多層薄膜結構之基板，其中該厚度量測元 件預設有-厚度範ϋ，該方法包含以下步驟··首先提供 -量測光學性質、電性、磁性、溫度、摩擦力或化學成 分之感測元件，其中該感測元件預設有一臨界強度或一 運算法則（algorithm);接著以該研磨單元研磨該基板，同 時以該Μ元件測量該基板，以得一量測強度或強度變 化曲線；之後比較該量測強度及該臨界強度，或以該強 度變化曲線比對該運算法則，當該量測強度大於該臨界 強度或該強度變化曲線符合該運算法則時，則以該厚度 量測元件量測該基板厚度，得一量測厚度值；然後再比 車又忒預设之厚度範圍與該量測厚度值，若該量測厚度值 未落入該預設之厚度範圍之内，則自一對照表或方程式 擷取出该置測厚度值對應之所需研磨時間，其中該對照 表係儲存複數個量測厚度值及其對應之所需研磨時間； 200426930 最後該研磨單元根據該研磨時間研磨該基板，直至該厚 度值落入該預設之厚度範圍内。 十 四、實施方式 本發明之化學機械研磨方法中，量測之薄膜光學性 質較佳為其折射強度或反射強度。本發明之化學機械研 磨方法中，量測之電性較佳為薄膜之片電阻、電容或電 堡。本發明之化學機械研磨方法之對照表較佳為紀錄複 數個厚度值及對應之所需研磨時間，對照表之内容更佳 為系統自動收集數據而得。本發明之化學機械研磨方法 為用以研磨具多層薄膜結構之基板，其基板較佳為一石夕 晶圓基板，其多層薄膜結構較佳為淺溝渠隔離（sti)結構。 為能讓貴審查委員能更瞭解本發明之技術内容，特 舉以下較佳具體實施例說明如下。 請同時參照圖丨與圖2,圖丨為本發明化學機械研磨終 點判斷方法之流程圖，圖2為待研磨基板，例如矽晶圓上 之薄膜結構剖視圖。本較佳具體實施例之目的 石夕層10研磨至氮化石夕層20，即可形成一淺溝渠隔離結 構。以下詳述其研磨過程。 首先將矽晶圓送入化學機械研磨機台之研磨室内進 行研磨，並以步驟100之終點偵測法控制。本較佳具體實 施例使用一般習用之化學機械研磨機台進行矽晶圓之研 磨，此研磨機台内除一研磨室之外，尚有一厚度量測元 件’厚度量測元件可於矽晶圓離開研磨室之後，量測其 薄膜厚度，此厚度量測元件内並已預設一厚度範圍，以 200426930 供測得之薄膜厚度做比較。而研磨機台内與一般習用之 研磨室相同，亦設置一可量測薄膜性質，例如反射率、 摩擦力、電阻、或化學成分之感測元件，於本較佳具體 貫施例中為雙光軸掃瞄式光譜儀，可於矽晶圓研磨過程 中隨時偵測薄膜之反射光強度頻譜，並收集訊號。 因氧化矽層10之光反射率約為RI1，氮化矽層20之光 反射率約為RI2,故可於光反射感測裝置内預設一反射光 強度頻邊變化比對之運算法則（algorithm)，例如正弦（8丨狀) 波形或正斜率，當測量之光強度頻譜變化比對符合所設 訂的運算法則時，表示已研磨至氮化矽層2〇，即停止研 磨。或者，光反射感測裝置内亦可預設一光反射率臨界 強度RI3，當測得之光反射率大於RI3時，即可停止研磨。 接著進行步驟200，將矽晶圓移至厚度量測元件量測 厚度，得一厚度值。此時厚度量測元件可依據其預設之 厚度範圍進行步驟300,判斷此厚度值是否已合乎製程規 格。若在規定厚度範圍内，則表示此研磨步驟已成功完 成，可進入步驟400。若厚度值未落入厚度範圍内，則進 入步驟500，進行閉迴路控制之二次研磨。 二次研磨之控制方式不同於步驟1〇〇之終點偵測法 控制，其係於研磨機台内之控制程式中，預先儲存一對 照表或方程式，此對照表係紀錄複數個 之所需研磨時間，其内容可由人為輸人或系統收集= 而得’而此方程式為依據薄膜特性或系統測試數據推演 而來’可由厚度值或研磨速率計算所需研磨時間。控制 系統會先至對照表擷取或經方程式計算上述厚度值對應 9 之所需研磨時間，再依據此所需研磨時間進行研磨。二 次研磨之後，如圖丨所示，再回到步驟200量測薄膜厚度， 之後再於步驟300判斷測得之厚度值是否已合乎製程規 格，直到厚度值落入厚度量測元件内預設之厚度範圍内。 目丽一般多層薄膜結構之研磨均未使用閉迴路控制 法控制，而本發明首創將閉迴路控制應用於多層薄膜結 構之研磨，其取代了原本當終點偵測法控制失敗時，須 由人為重工之作法，而改由閉迴路控制系統控制，使系 統控制能力提高，製程監控更為容易。除可降低人為誤 差發生的可能性之外，並可降低人為重工所需之人力成 本。因不需人為重工，故其生產時間可縮短並較易控制， 使生產量提高。此外，原本僅以終點偵測法控制之失誤 率亦大為減低，可使良率提高。 上述實施例僅係為了方便說明而舉例而已，本發明 所主張之權利範圍自應以申請專利範圍所述為準，而非 僅限於上述實施例。 五、圖式簡單說明 圖1係本發明化學機械研磨終點判斷方法之流程圖。 圖2係本發明待研磨之薄膜結構剖視圖。 六、圖號說明 氧化矽層 10 氮化矽層 20 200426930 步驟 100,200,300,400,500At present, there are two main methods for determining the end point of the grinding of chemical mechanical polishing used in semiconductor manufacturing, one is End_p〇int Detection, and the other is closed-loop control (clOse L〇〇pc〇ntr〇). i). The endpoint detection method is based on the principle that different films have different properties, such as refraction strength or friction. The automatic detection or measurement subsystem measures the important parameter 1 and the standard value at any time, and returns the result to reflect its The polishing end point is generally used for multilayer film structures, such as shallow trench isolation (STI) polishing. ㈣Loop control (C1〇se L〇〇p c_〇1) has a sensor to measure important process parameters, through the feedback of the electronic circuit, it can self-adjust, and provide to maintain the process within the specification range The required grinding time is currently more commonly used for single-layer film grinding to make the film thickness uniform after grinding. < The STI grinding method controlled by the shipping company, although the end point of the grinding can be detected by moving the line, in actual production operations, the amount = 4 film thickness after grinding, still: there will be cases where the thickness does not meet the specifications. 'That is, the simple final test method does not ensure that the grinding of the seal is :. In this case, the current remedy is to use manual heavy work, that is, the online operator calculates the required thickness by measuring the obtained thickness: 200426930 re-grinding time to perform the grind. However, this method will cause human errors or errors, and will also lengthen the manufacturing time of Shi Xi wafers, which will increase labor costs. Therefore, the present invention uses the addition of closed loop control to improve the above problems. 3. Summary of the Invention The main objective of the present invention is to provide a method for determining the end point of chemical mechanical grinding, which can reduce the error rate of the end point of grinding, eliminate the possibility of human error, shorten production time, and reduce labor costs. To achieve the above object, this chemical mechanical polishing method is a chemical mechanical polishing unit having a thickness measuring element for grinding a substrate having a multilayer thin film structure. The thickness measuring element is preset to a thickness range. Alas, the method includes the following steps: First, a sensor element for measuring optical properties, electrical properties, magnetic properties, temperature, friction, or chemical composition is provided, wherein the sensor element is preset with a critical intensity or an algorithm (algorithm ); Then grind the substrate with the grinding unit, and measure the substrate with the M element to obtain a measured intensity or intensity change curve; then compare the measured intensity and the critical intensity, or compare with the intensity change curve In the algorithm, when the measured intensity is greater than the critical intensity or the intensity variation curve conforms to the algorithm, Use the thickness measuring element to measure the thickness of the substrate to obtain a measured thickness value; then compare the preset thickness range and the measured thickness value with the car. If the measured thickness value does not fall within the preset Within the thickness range, the required grinding time corresponding to the measured thickness value is retrieved from a look-up table or an equation, wherein the look-up table stores a plurality of measured thickness values and their corresponding required grinding time; 200426930 the last The grinding unit grinds the substrate according to the grinding time until the thickness value falls within the preset thickness range. XIV. Embodiment In the chemical mechanical polishing method of the present invention, the optical property of the thin film to be measured is preferably its refractive strength or reflection strength. In the chemical-mechanical grinding method of the present invention, the measured electrical property is preferably a sheet resistance, a capacitor, or an electric fort of a thin film. The comparison table of the chemical mechanical polishing method of the present invention preferably records a plurality of thickness values and the corresponding required grinding time, and the content of the comparison table is more preferably obtained by the system automatically collecting data. The chemical mechanical polishing method of the present invention is for polishing a substrate having a multilayer thin film structure. The substrate is preferably a wafer substrate, and the multilayer thin film structure is preferably a shallow trench isolation (STI) structure. In order to make your reviewing committee better understand the technical content of the present invention, the following preferred embodiments are described below. Please refer to FIG. 丨 and FIG. 2 at the same time, which is a flowchart of the method for determining the end point of chemical mechanical polishing according to the present invention. FIG. 2 is a cross-sectional view of a thin film structure on a substrate to be polished, such as a silicon wafer. The purpose of this preferred embodiment is to grind the stone layer 10 to the nitride layer 20 to form a shallow trench isolation structure. The grinding process is detailed below. First, the silicon wafer is sent to the grinding chamber of the chemical mechanical polishing machine for polishing, and controlled by the endpoint detection method of step 100. In this preferred embodiment, a conventional chemical mechanical polishing machine is used for polishing silicon wafers. In addition to a grinding chamber, there is a thickness measuring element in the polishing machine. The thickness measuring element can be used on silicon wafers. After leaving the grinding chamber, measure the thickness of the film. A thickness range has been preset in the thickness measuring element, and the thickness of the film provided by 200426930 is compared. The grinding machine is the same as the conventional grinding room, and a sensing element that can measure the properties of the film, such as reflectance, friction, resistance, or chemical composition, is provided in the preferred embodiment. The optical axis scanning spectrometer can detect the reflected light intensity spectrum of the film at any time during the silicon wafer grinding process and collect signals. Since the light reflectance of the silicon oxide layer 10 is about RI1 and the light reflectance of the silicon nitride layer 20 is about RI2, an algorithm for comparing the frequency-edge variation of the reflected light intensity can be preset in the light reflection sensing device ( algorithm), such as a sine (8) shape or positive slope, when the measured light intensity spectrum change comparison is in accordance with the set algorithm, it means that the silicon nitride layer has been ground to 20, and the grinding is stopped. Alternatively, a light reflectance critical intensity RI3 can also be preset in the light reflection sensing device. When the measured light reflectance is greater than RI3, the grinding can be stopped. Then, step 200 is performed to move the silicon wafer to the thickness measuring element to measure the thickness to obtain a thickness value. At this time, the thickness measuring element can perform step 300 according to its preset thickness range to determine whether the thickness value has met the process specifications. If it is within the specified thickness range, it means that the grinding step has been successfully completed, and the process may proceed to step 400. If the thickness value does not fall within the thickness range, the process proceeds to step 500 to perform the secondary grinding of the closed-loop control. The control method of secondary grinding is different from the end point detection method control of step 100, which is stored in a control program in the grinding machine, and a comparison table or equation is stored in advance. This comparison table records multiple required grindings. Time, its content can be collected by human input or system = 'and this equation is derived from the film characteristics or system test data' can be calculated from the thickness value or grinding rate. The control system will first take the comparison table or calculate the required grinding time for the thickness value corresponding to 9 through the equation, and then perform grinding according to the required grinding time. After the second grinding, as shown in Figure 丨, return to step 200 to measure the film thickness, and then determine whether the measured thickness value meets the process specifications at step 300 until the thickness value falls into the thickness measurement element and is preset. Range of thickness. Muli's general multilayer film structure grinding is not controlled by closed-loop control method, and the present invention first applies closed-loop control to the polishing of multilayer film structure, which replaces the original manual heavy-duty process when the endpoint detection method fails Instead, it is controlled by a closed-loop control system, which improves the system control ability and makes process monitoring easier. In addition to reducing the possibility of human error, it can also reduce the labor costs required for human heavy work. Since no heavy industry is needed, its production time can be shortened and easier to control, which increases the production volume. In addition, the error rate originally controlled by the endpoint detection method is also greatly reduced, which can increase the yield. The above embodiments are merely examples for the convenience of description. The scope of the claimed rights of the present invention shall be based on the scope of the patent application, rather than being limited to the above embodiments. V. Brief Description of the Drawings Figure 1 is a flowchart of the method for judging the end point of chemical mechanical polishing according to the present invention. FIG. 2 is a sectional view of a thin film structure to be polished according to the present invention. VI. Description of drawing number Silicon oxide layer 10 Silicon nitride layer 20 200426930 Step 100, 200, 300, 400, 500
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