JP2007110020A - Abnormality judging method in plasma etching treatment - Google Patents

Abnormality judging method in plasma etching treatment Download PDF

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JP2007110020A
JP2007110020A JP2005301747A JP2005301747A JP2007110020A JP 2007110020 A JP2007110020 A JP 2007110020A JP 2005301747 A JP2005301747 A JP 2005301747A JP 2005301747 A JP2005301747 A JP 2005301747A JP 2007110020 A JP2007110020 A JP 2007110020A
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cooling gas
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Kazuhiro Mizutani
和弘 水谷
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NEC Electronics Corp
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<P>PROBLEM TO BE SOLVED: To provide an abnormality judging method capable of setting such optimum reference values in a plasma etching treatment that they are affected hardly by the variation of the surface state of a stage, the deviation of the finishing result inherent in the manufacturing lot of a processed object, the difference existent between etching conditions, and the like, as the reference values for judging thereby the abnormality of the attracted state of the processed object to the stage, and the abnormality of the cooled state of the processed object by a cooling gas; and capable of performing therefore an accurate abnormality judgement in the plasma etching treatment. <P>SOLUTION: With respect to the process for so holding attractively a semiconductor wafer 5 on an electrostatically attracting stage 6 as to apply a predetermined etching treatment to it while making a cooling gas flow in the clearance between it and the stage 6, there is included as at least one of reference values a varied reference value set in succession every semiconductor wafer 5 subjected to an etching treatment; in an abnormality judging method for judging whether both the abnormalities of the attracted state of the semiconductor wafer 5 to the electrostatically attracting stage 6 and the cooled state of the semiconductor wafer 5 by a cooling gas are existent or not, by comparing in a judging way the measured value of the flow rate of the cooling gas with the reference values. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、プラズマエッチング装置のステージ上に被処理体を載置し、ステージと被処理体の隙間に被処理体を冷却するための冷却ガスを流しながら被処理体に所定のエッチング処理を施す際に、冷却ガスの実測流量値を基準値と比較して、ステージに対する被処理体の吸着状態および冷却ガスによる被処理体の冷却状態の異常の有無を判定するプラズマエッチング処理における異常判定方法に関する。 The present invention places a target object on a stage of a plasma etching apparatus, and applies a predetermined etching process to the target object while flowing a cooling gas for cooling the target object in a gap between the stage and the target object. In this regard, the present invention relates to an abnormality determination method in a plasma etching process in which an actual flow rate value of a cooling gas is compared with a reference value to determine whether there is an abnormality in the state of adsorption of the object to be processed and the state of cooling of the object to be processed by the cooling gas. .

先ず最初に、プラズマエッチング装置の概略構成と動作を説明する。図3は、プラズマエッチング装置の縦断面図である。   First, the schematic configuration and operation of the plasma etching apparatus will be described. FIG. 3 is a longitudinal sectional view of the plasma etching apparatus.

図3に示すように、プラズマエッチング装置1は、主に、真空チャンバ2と、その内部に対向配置された下部電極3及び上部電極4と、下部電極3上に配置され被処理体としての半導体ウェーハ5を吸着保持する静電吸着ステージ6と、真空チャンバ外部に配置されたプラズマ発生用のRF電源7とで構成されている。 As shown in FIG. 3, the plasma etching apparatus 1 mainly includes a vacuum chamber 2, a lower electrode 3 and an upper electrode 4 disposed facing each other, and a semiconductor as a processing object disposed on the lower electrode 3. An electrostatic chucking stage 6 for chucking and holding the wafer 5 and an RF power source 7 for plasma generation arranged outside the vacuum chamber are configured.

また、真空チャンバ2には、反応性ガスを導入するガス導入口8と、不要ガスを排気するガス排気口9とが設けられており、上部電極4は接地され、下部電極3はRF電源7に電気的接続され、下部電極3に高周波電圧を加えることにより下部電極3と上部電極4との間の空間にプラズマを励起するようになっている。 The vacuum chamber 2 is provided with a gas introduction port 8 for introducing a reactive gas and a gas exhaust port 9 for exhausting unnecessary gas, the upper electrode 4 is grounded, and the lower electrode 3 is an RF power source 7. The plasma is excited in the space between the lower electrode 3 and the upper electrode 4 by applying a high frequency voltage to the lower electrode 3.

また、静電吸着ステージ6と半導体ウェーハ5の隙間に冷却ガス(例えば、ヘリウム)を流すための静電吸着ステージ6に設けられた複数の開口部(図示せず)と繋がった配管10と、その配管10の先に接続された冷却ガス制御部11と、その冷却ガス制御部11の末端にそれぞれ接続された冷却ガスを排気する排気ポンプ12と、冷却ガスを貯留した冷却ガス供給源13とが配置されている。 A pipe 10 connected to a plurality of openings (not shown) provided in the electrostatic adsorption stage 6 for flowing a cooling gas (for example, helium) through the gap between the electrostatic adsorption stage 6 and the semiconductor wafer 5; A cooling gas control unit 11 connected to the tip of the pipe 10; an exhaust pump 12 for exhausting the cooling gas connected to each end of the cooling gas control unit 11; and a cooling gas supply source 13 storing the cooling gas; Is arranged.

尚、静電吸着ステージ6と半導体ウェーハ5の隙間に冷却ガスを流し半導体ウェーハ5を冷却するのは、エッチング処理により半導体ウェーハ5が加熱され、半導体ウェーハ表面に塗布されたレジストが変質するレジスト焼けと呼ばれる不良やエッチング量のばらつきによる膜ムラと呼ばれる不良が生じることを防止するためである。 The reason why the semiconductor wafer 5 is cooled by flowing a cooling gas through the gap between the electrostatic adsorption stage 6 and the semiconductor wafer 5 is that the semiconductor wafer 5 is heated by the etching process and the resist applied on the surface of the semiconductor wafer is altered. This is to prevent the occurrence of defects called film irregularities due to variations in etching and variations in etching amount.

また、冷却ガス制御部11は、冷却ガスを供給/停止させる開閉バルブ14と、冷却ガスの圧力値を測定する圧力計15と、冷却ガスの流量値を測定したり流量調整するマスフローコントローラ16と、開閉バルブ14の開閉動作を制御したり、実測圧力値を設定圧力値に近づけるようにマスフローコントローラ16を制御したり、実測流量値を基準値と比較判定しその判定結果に基づいてエッチング処理を継続/中止したりする、記憶・演算機能や制御機能を有する制御機能部17とを内蔵している。 The cooling gas control unit 11 includes an opening / closing valve 14 for supplying / stopping the cooling gas, a pressure gauge 15 for measuring the pressure value of the cooling gas, a mass flow controller 16 for measuring the flow value of the cooling gas and adjusting the flow rate, The opening / closing operation of the opening / closing valve 14 is controlled, the mass flow controller 16 is controlled so that the actually measured pressure value approaches the set pressure value, and the actually measured flow value is compared with the reference value, and the etching process is performed based on the determination result. A control function unit 17 having a storage / arithmetic function and a control function for continuation / stopping is incorporated.

ここで、上述したように冷却構造が静電吸着ステージ6と半導体ウェーハ5の隙間に冷却ガスを流して冷却する構造となっているため、冷却ガスの実測流量値は、静電吸着ステージ6と半導体ウェーハ5の隙間から漏れる冷却ガスの量とほぼ等しい。また、実測流量値は、隙間の大きさに依存し隙間が大きくなればなるほど大きくなった。このため、実測流量値は、静電吸着ステージ6に対する半導体ウェーハ5の吸着状態および吸着状態によって大きく影響を受けると予想される冷却ガスによる半導体ウェーハ5の冷却状態の異常判定のための指標(代用特性)として用いることができた。 Here, as described above, the cooling structure has a structure in which the cooling gas is cooled by flowing the gap between the electrostatic adsorption stage 6 and the semiconductor wafer 5. The amount of cooling gas leaking from the gap between the semiconductor wafers 5 is almost equal. In addition, the measured flow rate value depends on the size of the gap and becomes larger as the gap becomes larger. For this reason, the measured flow rate value is an index (substitute) for determining an abnormality in the cooling state of the semiconductor wafer 5 by the cooling gas that is expected to be greatly affected by the suction state and the suction state of the semiconductor wafer 5 with respect to the electrostatic suction stage 6. Characteristic).

異常判定方法の詳細は後述するが、より具体的には、例えば半導体ウェーハ裏面に異物が付着し突発的に隙間が大きくなったような場合は、半導体ウェーハ裏面に十分な圧力が加わらず冷却不足となるため、実測流量値と基準値とを比較判定することでこれを検出しエッチング処理を中止するなどした。 The details of the abnormality determination method will be described later. More specifically, for example, when a foreign object adheres to the back surface of the semiconductor wafer and the gap suddenly increases, sufficient pressure is not applied to the back surface of the semiconductor wafer, resulting in insufficient cooling. Therefore, this was detected by comparing the measured flow rate value with the reference value, and the etching process was stopped.

このようなプラズマエッチング装置1の使用方法は、半導体ウェーハ5を静電吸着ステージ6上に吸着保持し、真空チャンバ2内を真空にしてガス導入口8より反応性ガスを導入した後、RF電源7をONにして下部電極3と上部電極4との間の空間にプラズマを励起させ、プラズマ中に発生するイオンや中性ラジカルで半導体ウェーハ5表面に所定のエッチング処理を施す。   The plasma etching apparatus 1 is used in such a manner that the semiconductor wafer 5 is adsorbed and held on the electrostatic adsorption stage 6, the inside of the vacuum chamber 2 is evacuated and a reactive gas is introduced from the gas inlet 8, and then the RF power source is used. 7 is turned on to excite plasma in the space between the lower electrode 3 and the upper electrode 4, and a predetermined etching process is performed on the surface of the semiconductor wafer 5 with ions or neutral radicals generated in the plasma.

その後、エッチング処理が終了したら、RF電源7をOFFにして不要ガスをガス排気口9から排気した後、半導体ウェーハ5を静電吸着ステージ6から離脱させる。 Thereafter, when the etching process is completed, the RF power source 7 is turned off and unnecessary gas is exhausted from the gas exhaust port 9, and then the semiconductor wafer 5 is detached from the electrostatic adsorption stage 6.

尚、冷却ガスの供給は、RF電源7のONと同時に開始され、OFFと共に停止される。即ち、半導体ウェーハ5をエッチング処理する間のみ冷却ガスは供給される。 The supply of the cooling gas is started at the same time when the RF power source 7 is turned on and stopped when the RF power source 7 is turned off. That is, the cooling gas is supplied only while the semiconductor wafer 5 is etched.

以上の動作を繰返し、順次、半導体ウェーハ5に対してプラズマエッチング処理を行う。 The above operation is repeated, and the plasma etching process is sequentially performed on the semiconductor wafer 5.

次に、このようなプラズマエッチング処理における異常判定方法の一例を図4,図5を用いて説明する。尚、図4は、冷却ガスの実測流量値の変化と基準値の関係を示す説明図であり、図5は、異常判定の手順の一例を示すフロー図である。 Next, an example of an abnormality determination method in such a plasma etching process will be described with reference to FIGS. FIG. 4 is an explanatory diagram showing the relationship between the change in the actual measured flow rate value of the cooling gas and the reference value, and FIG. 5 is a flowchart showing an example of a procedure for determining an abnormality.

図4に示すように、冷却ガスはエッチング処理が開始されるまでは供給停止状態であり、エッチング処理が開始されると同時に供給が開始される(タイミングt)。その後、短時間で設定圧力値に到達させるように制御されるため、実測流量値は、供給開始当初はオーバーシュートし不安定となるが徐々に圧力調整がなされるに従い一定時間経過後には安定する。この安定領域の実測流量値は、静電吸着ステージと半導体ウェーハの隙間からほぼ定常的に漏れる冷却ガスの量であり、冷却ガスを供給停止するまでの間、この漏れ量に相当する冷却ガスを流すことで半導体ウェーハを安定して冷却できる。尚、異常判定のタイミングtは、この安定領域に設定する。 As shown in FIG. 4, the supply of the cooling gas is stopped until the etching process is started, and the supply is started at the same time as the etching process is started (timing t 0 ). After that, since it is controlled to reach the set pressure value in a short time, the actually measured flow value overshoots at the beginning of the supply and becomes unstable, but becomes stable after a certain period of time as the pressure is gradually adjusted. . The measured flow rate value in this stable region is the amount of cooling gas that leaks almost constantly from the gap between the electrostatic adsorption stage and the semiconductor wafer, and the cooling gas corresponding to this leakage amount is kept until the cooling gas supply is stopped. By flowing, the semiconductor wafer can be cooled stably. The abnormality determination timing t 1 is set in this stable region.

次に、基準値は、通常、静電吸着ステージの表面状態や半導体ウェーハの製造ロットやエッチング条件などに係らず、一定の固定基準値(上限S)を用いる。(例えば、特許文献1参照) Next, as the reference value, a fixed reference value (upper limit S U ) is usually used regardless of the surface state of the electrostatic adsorption stage, the manufacturing lot of the semiconductor wafer, the etching conditions, and the like. (For example, see Patent Document 1)

次に、異常判定の手順は、図5に示すように、先ず、任意の半導体ウェーハのエッチング処理を開始する。そして、タイミングtにおける実測流量値を固定基準値(上限S)で異常判定する。もし、固定基準値(上限S)を越えて異常と判定された場合は、即座にエッチング処理を中止する。あるいは、固定基準値(上限S)以内であり正常と判定された場合は、そのままエッチング処理を継続し完了し、次の半導体ウェーハをエッチング処理する。 Next, in the abnormality determination procedure, as shown in FIG. 5, first, etching processing of an arbitrary semiconductor wafer is started. Then, the measured flow rate value at timing t 1 is determined to be abnormal with a fixed reference value (upper limit S U ). If it is determined that the value exceeds the fixed reference value (upper limit S U ), the etching process is immediately stopped. Alternatively, if it is within the fixed reference value (upper limit S U ) and is determined to be normal, the etching process is continued and completed as it is, and the next semiconductor wafer is etched.

尚、プラズマエッチング装置が、複数のチャンバと全チャンバ共通の冷却ガス制御部とを備えたマルチチャンバタイプのプラズマエッチング装置(図示せず)の場合でも、通常、全チャンバ共通の一定の固定基準値を用いていた。
特開平10−240356号公報 図3(b)
Even when the plasma etching apparatus is a multi-chamber type plasma etching apparatus (not shown) having a plurality of chambers and a cooling gas control unit common to all the chambers, a fixed reference value common to all the chambers is usually used. Was used.
Japanese Patent Laid-Open No. 10-240356 FIG. 3B

しかしながら、このような異常判定方法においては、当然ながら、固定基準値(上限S)がゆる過ぎる場合は、異常を見逃し製品不良を発生させるおそれが増加し、反対に、きびし過ぎる場合は、過剰にエッチング処理を中止することになり生産性が落ちるおそれがあった。 However, in such an abnormality determination method, of course, if the fixed reference value (upper limit S U ) is too loose, there is an increased risk of overlooking the abnormality and causing a product defect. In some cases, the etching process was stopped and the productivity could be lowered.

またさらに、冷却ガスの実測流量値を変動させる要因、即ち、静電吸着ステージと半導体ウェーハの隙間を変化させる要因としては、前述したような突発的な半導体ウェーハの裏面への異物付着だけではなく、それ以外に、多数の半導体ウェーハを連続してエッチング処理して行くに伴って静電吸着ステージ表面に徐々に堆積していく反応生成物による静電吸着ステージ表面の経時的な平面度の変化や半導体ウェーハの製造ロットごとに固有のソリ量などの出来映えの偏りやエッチング条件(圧力,反応ガス流量,温度など)の相違による差も技術的に無視できない重要な変動要因であった。 Furthermore, the factors that change the measured flow rate value of the cooling gas, that is, the factors that change the gap between the electrostatic adsorption stage and the semiconductor wafer are not only the sudden adhesion of foreign matter to the back surface of the semiconductor wafer as described above. In addition, changes in the flatness of the surface of the electrostatic adsorption stage over time due to reaction products that gradually accumulate on the surface of the electrostatic adsorption stage as many semiconductor wafers are continuously etched. Differences in workmanship such as the amount of warpage unique to each manufacturing lot of semiconductor wafers and differences due to differences in etching conditions (pressure, reaction gas flow rate, temperature, etc.) were also important fluctuation factors that cannot be ignored technically.

このため従来は、一定の固定基準値(上限S)を決定する際に、製品不良の発生のおそれを考慮しつつも過剰な生産性低下を避けるため、冷却ガスの実測流量値が影響を受けるであろうと予測される技術的要因である、静電吸着ステージの表面状態の変化や半導体ウェーハの製造ロットに固有の出来映えの偏りやエッチング条件の相違による差なども見込んだ基準値としなければならず、どうしても比較的ゆるめの基準値となる傾向にあり、技術的根拠に基づく判定精度の良い最適な基準値を決定することはきわめて困難であった。 For this reason, conventionally, when determining a fixed fixed reference value (upper limit S U ), the actual flow rate value of the cooling gas has an effect in order to avoid an excessive decrease in productivity while considering the possibility of product defects. It is necessary to use the standard value that also anticipates technical factors that are expected to be affected, such as changes in the surface state of the electrostatic chuck stage, deviations in workmanship inherent to the production lot of semiconductor wafers, and differences due to differences in etching conditions. However, it tends to be a relatively loose reference value, and it has been extremely difficult to determine an optimum reference value with good determination accuracy based on the technical basis.

本発明のプラズマエッチング処理における異常判定方法は、プラズマエッチング装置のチャンバ内に配置されたステージ上に被処理体を吸着保持し、ステージと被処理体の隙間に被処理体を冷却するための冷却ガスを流しながら被処理体に所定のエッチング処理を施す工程で、冷却ガスの実測流量値を基準値と比較判定して、ステージに対する被処理体の吸着状態および冷却ガスによる被処理体の冷却状態の異常の有無を判定するプラズマエッチング処理における異常判定方法において、基準値は、順次、エッチング処理する被処理体ごとに設定される変動基準値を少なくとも基準値のひとつとして含むことを特徴とするプラズマエッチング処理における異常判定方法である。 The abnormality determination method in the plasma etching process of the present invention is a cooling method for adsorbing and holding an object to be processed on a stage disposed in a chamber of a plasma etching apparatus and cooling the object to be processed in a gap between the stage and the object to be processed. In the process of performing a predetermined etching process on the object to be processed while flowing the gas, the measured flow rate value of the cooling gas is compared with the reference value, the adsorption state of the object to be processed with respect to the stage, and the cooling state of the object to be processed by the cooling gas In the abnormality determination method in the plasma etching process for determining whether there is an abnormality in the plasma, the reference value sequentially includes a fluctuation reference value set for each object to be etched as at least one of the reference values. This is an abnormality determination method in the etching process.

本発明のプラズマエッチング処理における異常判定方法によれば、ステージに対する被処理体の吸着状態および冷却ガスによる被処理体の冷却状態の異常を判定する基準値として、ステージの表面状態の変化や被処理体の製造ロットに固有の出来映えの偏りやエッチング条件の相違による差などの影響を受けにくい最適な基準値を設定でき判定精度の良い異常判定をすることができる。 According to the abnormality determination method in the plasma etching process of the present invention, the change in the surface state of the stage or the process target is used as a reference value for determining the abnormality in the adsorption state of the process object on the stage and the cooling state of the process object by the cooling gas. It is possible to set an optimum reference value that is not easily affected by the deviation of the workmanship inherent in the production lot of the body or the difference due to the difference in the etching conditions, and the abnormality determination with high determination accuracy can be performed.

本発明は、ステージに対する被処理体の吸着状態および冷却ガスによる被処理体の冷却状態の異常を判定する基準値として、ステージの表面状態の変化や被処理体の製造ロットに固有の出来映えの偏りやエッチング処理条件の相違による差の影響を受けにくい最適な基準値を設定し判定精度の良い異常判定をするという目的を、基準値として、順次、エッチング処理する被処理体ごとに設定される変動基準値を少なくとも基準値のひとつとして含むことで実現した。   The present invention provides a reference value for determining an abnormality in the state of adsorption of the object to be processed and the state of cooling of the object to be processed by the cooling gas. Variations that are set for each workpiece to be etched sequentially, with the goal of setting an optimal reference value that is not easily affected by differences due to differences in etching process conditions and making an abnormality determination with good determination accuracy. Realized by including at least one reference value as one of the reference values.

本発明のプラズマエッチング処理における異常判定方法の一例を図1,図2を用いて説明する。尚、図1は、冷却ガスの実測流量値の変化と基準値の関係を示す説明図であり、図2は、異常判定の手順の一例を示すフロー図である。また、図4,図5と同一部分には同一符号を用い、プラズマエッチング装置の概略構成および動作については、従来技術で説明した内容と同様であるため説明を省略する。 An example of an abnormality determination method in the plasma etching process of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory diagram showing the relationship between the change in the actual measured flow rate value of the cooling gas and the reference value, and FIG. 2 is a flowchart showing an example of a procedure for determining abnormality. Also, the same reference numerals are used for the same parts as in FIGS. 4 and 5, and the schematic configuration and operation of the plasma etching apparatus are the same as those described in the prior art, and thus description thereof is omitted.

図1に示すように、冷却ガスはエッチング処理が開始されるまでは供給停止状態であり、エッチング処理が開始されると同時に供給が開始される(タイミングt)。その後、短時間で設定圧力値に到達させるように制御されるため、実測流量値は、供給開始当初はオーバーシュートし不安定となるが徐々に圧力調整がなされるに従い一定時間経過後には安定する。この安定領域の実測流量値は、静電吸着ステージと半導体ウェーハの隙間からほぼ定常的に漏れる冷却ガスの量であり、冷却ガスを供給停止するまでの間、この漏れ量に相当する冷却ガスを流すことで半導体ウェーハを安定して冷却できる。尚、異常判定のタイミングtは、この安定領域に設定する。 As shown in FIG. 1, the supply of the cooling gas is stopped until the etching process is started, and the supply of the cooling gas is started at the same time as the etching process is started (timing t 0 ). After that, since it is controlled to reach the set pressure value in a short time, the actually measured flow value overshoots at the beginning of the supply and becomes unstable, but becomes stable after a certain period of time as the pressure is gradually adjusted. . The measured flow rate value in this stable region is the amount of cooling gas that leaks almost constantly from the gap between the electrostatic adsorption stage and the semiconductor wafer, and the cooling gas corresponding to this leakage amount is kept until the cooling gas supply is stopped. By flowing, the semiconductor wafer can be cooled stably. The abnormality determination timing t 1 is set in this stable region.

次に、基準値は、従来の一定の固定基準値(上限S)に加えて、これからエッチング処理する予定の半導体ウェーハ(以降、次ウェーハと呼ぶ)と同一製造ロットであり、かつ、次ウェーハと同一静電吸着ステージで、同一エッチング条件で、直前にエッチング処理した半導体ウェーハ(以降、直前ウェーハと呼ぶ)の処理時のタイミングtにおける実測流量値に一定の許容範囲aを加算・減算して求めた変動基準値(上限J,下限J)を併用する。変動基準値(上限J,下限J)は、直前ウェーハのタイミングtにおける実測流量値をもとに順次、新たに算出し次ウェーハの基準値として用いる。(尚、製造ロットとは、半導体製造プロセスをいっしょに流れ、単一ワークとしてトレースされる半導体ウェーハのグループをいう。) Next, in addition to the conventional fixed fixed reference value (upper limit S U ), the reference value is the same production lot as the semiconductor wafer to be etched (hereinafter referred to as the next wafer), and the next wafer. A certain permissible range a is added to or subtracted from the measured flow rate value at the timing t 1 when processing a semiconductor wafer (hereinafter referred to as the immediately preceding wafer) that has been subjected to the last etching process under the same etching conditions at the same electrostatic adsorption stage. The fluctuation reference values (upper limit J U , lower limit J L ) obtained in the above are used together. The fluctuation reference values (upper limit J U , lower limit J L ) are newly calculated sequentially based on the measured flow rate value at the timing t 1 of the immediately preceding wafer and used as the reference value for the next wafer. (Note that a production lot refers to a group of semiconductor wafers that flow through a semiconductor manufacturing process and are traced as a single workpiece.)

次に、異常判定の手順は、図2に示すように、先ず、同一の静電吸着ステージで、同一のエッチング条件で処理予定の同一製造ロットの半導体ウェーハのうち、最初にエッチング処理する予定の先頭の半導体ウェーハ(以降、先頭ウェーハと呼ぶ)のエッチング処理を開始する。そして、そのタイミングtにおける実測流量値を固定基準値(上限S)で異常判定する。もし、実測流量値が固定基準値(上限S)を越えて異常と判定した場合は、即座にエッチング処理を中止する。あるいは、実測流量値が固定基準値(上限S)以内であり正常と判定した場合は、そのままエッチング処理を継続し完了する。 Next, as shown in FIG. 2, the abnormality determination procedure is as follows. First, among the semiconductor wafers of the same production lot scheduled to be processed under the same etching conditions at the same electrostatic adsorption stage, the etching process is first scheduled. The etching process for the first semiconductor wafer (hereinafter referred to as the first wafer) is started. Then, the measured flow rate value at the timing t 1 is determined to be abnormal with a fixed reference value (upper limit S U ). If the measured flow rate value exceeds the fixed reference value (upper limit S U ) and is determined to be abnormal, the etching process is immediately stopped. Alternatively, when the measured flow rate value is within the fixed reference value (upper limit S U ) and is determined to be normal, the etching process is continued and completed as it is.

またこのとき、正常判定された場合は、先頭ウェーハのタイミングtにおける実測流量値を記憶し、例えばそれに一定の許容範囲aを加算・減算して、次ウェーハ(2枚目)のための変動基準値(上限J,下限J)を算出し設定する。尚、許容範囲aは、例えば予め、同一静電吸着ステージで、同一エッチング条件でエッチング処理した同一製造ロットの半導体ウェーハの処理時の実測流量値のばらつきを別に取得しておき、それを一般的な統計的手法(例えば3σ法)で算出した一定の許容範囲とする。 At this time, if it is determined as normal, the actual flow rate value at the timing t 1 of the first wafer is stored, and for example, a certain allowable range a is added to or subtracted from it to change for the next wafer (second wafer). Reference values (upper limit J U , lower limit J L ) are calculated and set. In addition, for example, the allowable range a is obtained by separately obtaining a variation in the measured flow rate value during processing of a semiconductor wafer of the same manufacturing lot that is etched under the same etching conditions on the same electrostatic adsorption stage in advance. A certain allowable range calculated by a statistical method (for example, 3σ method).

その後、引き続き、次ウェーハ(2枚目)のエッチング処理を開始する。そして、そのタイミングtにおける実測流量値を固定基準値(上限S)と変動基準値(上限J,下限J)の両方の基準値で異常判定する。もし、実測流量値がそれらの基準値(上限S,上限J,下限J)のいずれかを越えて異常と判定された場合は、即座にエッチング処理を中止する。あるいは、すべての基準値(上限S,上限J,下限J)以内であり正常と判定された場合は、そのままエッチング処理を継続し完了する。 Subsequently, the etching process for the next wafer (second sheet) is started. Then, the measured flow rate value at the timing t 1 is determined to be abnormal based on both the fixed reference value (upper limit S U ) and the fluctuation reference value (upper limit J U , lower limit J L ). If the measured flow rate value exceeds any of those reference values (upper limit S U , upper limit J U , lower limit J L ), the etching process is immediately stopped. Alternatively, if it is determined that the value is within all the reference values (upper limit S U , upper limit J U , lower limit J L ) and is normal, the etching process is continued and completed.

またこのとき、正常判定された場合は、2枚目の半導体ウェーハのタイミングtにおける実測流量値を記憶し、それに前述した許容範囲aを加算・減算して、次ウェーハ(3枚目)のための変動基準値(上限J,下限J)を新たに算出し設定する。 In this case also, if it is normal determination, it stores the measured flow rate value at the timing t 1 of the second sheet of the semiconductor wafer, by adding, subtracting the allowable range a as described above to, the following wafer (3rd) Fluctuation reference values (upper limit J U , lower limit J L ) are newly calculated and set.

このようにして、先頭ウェーハについてのみ従来の固定基準値(上限S)で異常判定し、2枚目以降の半導体ウェーハについては固定基準値(上限S)に加えて、順次、直前ウェーハの実測流量値を元に新たに算出した変動基準値(上限J,下限J)を用いて異常判定しながらエッチング処理を繰り返す。 In this way, the top wafer only conventional fixed reference value abnormality determination and with (upper S U), the second and subsequent semiconductor wafer is in addition to the fixed reference value (an upper limit S U), sequentially, immediately before the wafer The etching process is repeated while making an abnormality determination using a fluctuation reference value (upper limit J U , lower limit J L ) newly calculated based on the actually measured flow rate value.

ここで、変動基準値(上限J,下限J)を算出する実測流量値として直前ウェーハの実測流量値を用いるのは、技術的観点から見て、直前ウェーハが次ウェーハに最も近い環境と条件で処理され、次ウェーハの基準値を決める上で最も信頼度が高いと考えるためである。 Here, the measured flow rate value of the immediately preceding wafer is used as the measured flow rate value for calculating the fluctuation reference value (upper limit J U , lower limit J L ), from the technical point of view, the environment where the immediately preceding wafer is closest to the next wafer. This is because the reliability is highest in determining the reference value of the next wafer processed under the conditions.

尚、上記では、プラズマエッチング装置を枚葉式のプラズマエッチング装置とし、静電吸着ステージが1つの場合について説明したが、複数のチャンバと静電吸着ステージを備えたマルチチャンバタイプの場合は、各静電吸着ステージごとに平面度などが異なることが予想されるため各チャンバごとに変動基準値(上限J,下限J)を決定するとよい。 In the above description, the case where the plasma etching apparatus is a single-wafer type plasma etching apparatus and one electrostatic adsorption stage is described. However, in the case of a multi-chamber type including a plurality of chambers and an electrostatic adsorption stage, Since flatness and the like are expected to be different for each electrostatic adsorption stage, it is preferable to determine a variation reference value (upper limit J U , lower limit J L ) for each chamber.

また、上記では、変動基準値(上限J,下限J)を算出するのに、直前ウェーハ1枚の実測流量値をもとに算出することで説明したが、必ずしもこれに限るわけではなく、処理予定の半導体ウェーハと近い環境・条件で以前に処理された半導体ウェーハの実測流量値を元に算出するならばよく、例えば、以前に処理された一定枚数分の実測流量値を記憶しその平均値を元に算出するようにしてもよい。 In the above description, the fluctuation reference value (upper limit J U , lower limit J L ) is calculated based on the actual flow rate value of the immediately preceding wafer. However, the present invention is not necessarily limited to this. It may be calculated based on the measured flow rate value of the previously processed semiconductor wafer in the environment and conditions close to the semiconductor wafer to be processed.For example, the measured flow rate value for a certain number of previously processed wafers is stored and stored. You may make it calculate based on an average value.

また、異常判定の手順についても、上記の例に限るわけではなく、変動基準値(上限J,下限J)を少なくとも基準値のひとつとして用いて異常判定する方法であればよく、例えば、判定時間を短縮するために、2枚目以降の半導体ウェーハは、固定基準値(上限S)を用いずに変動基準値(上限J,下限J)だけで異常判定するようにしてもよい。 Also, the abnormality determination procedure is not limited to the above example, and any abnormality determination method using the fluctuation reference values (upper limit J U , lower limit J L ) as at least one reference value may be used. In order to shorten the determination time, the second and subsequent semiconductor wafers may be determined to be abnormal using only the fluctuation reference value (upper limit J U , lower limit J L ) without using the fixed reference value (upper limit S U ). Good.

本発明は、被処理体をプラズマエッチング処理するに際し、冷却ガスの実測流量値を基準値と比較して、ステージに対する被処理体の吸着状態および冷却ガスによる被処理体の冷却状態の異常の有無を精度よく判定できる異常判定方法に適用できる。   The present invention compares the measured flow rate value of the cooling gas with the reference value when plasma processing is performed on the object to be processed, and whether there is an abnormality in the state of adsorption of the object to be processed and the cooling state of the object to be processed by the cooling gas. It can be applied to an abnormality determination method that can accurately determine.

本発明の異常判定方法における冷却ガスの流量変化と基準値の関係を示す説明図Explanatory drawing which shows the relationship between the flow volume change of the cooling gas in the abnormality determination method of this invention, and a reference value 本発明の異常判定方法の手順の一例を示すフロー図The flowchart which shows an example of the procedure of the abnormality determination method of this invention プラズマエッチング装置の縦断面図Vertical section of plasma etching system 従来の異常判定方法における冷却ガスの流量変化と基準値の関係を示す説明図Explanatory drawing which shows the relationship between the reference | standard value and the change of the flow volume of the cooling gas in the conventional abnormality determination method 従来の異常判定方法の手順の一例を示すフロー図Flow chart showing an example of the procedure of a conventional abnormality determination method

符号の説明Explanation of symbols

1 プラズマエッチング装置
2 真空チャンバ
3 下部電極
4 上部電極
5 半導体ウェーハ
6 静電吸着ステージ
7 RF電源
8 ガス導入口
9 ガス排気口
10 配管
11 冷却ガス制御部
12 排気ポンプ
13 冷却ガス供給源
14 開閉バルブ
15 圧力計
16 マスフローコントローラ
17 制御機能部
固定基準値
冷却ガス供給開始タイミング
判定タイミング
a 許容範囲
,J 直前ウェーハの実測流量値を元に算出した変動基準値
DESCRIPTION OF SYMBOLS 1 Plasma etching apparatus 2 Vacuum chamber 3 Lower electrode 4 Upper electrode 5 Semiconductor wafer 6 Electrostatic adsorption stage 7 RF power supply 8 Gas introduction port 9 Gas exhaust port 10 Pipe 11 Cooling gas control part 12 Exhaust pump 13 Cooling gas supply source 14 Open / close valve 15 pressure gauge 16 mass flow controller 17 control function unit S U fixed reference value t 0 start cooling gas supply timing t 1 determined timing a tolerance J U, J L immediately before the wafer actually measured flow rate value variation reference value calculated based on the

Claims (5)

プラズマエッチング装置のチャンバ内に配置されたステージ上に被処理体を吸着保持し、前記ステージと前記被処理体の隙間に前記被処理体を冷却するための冷却ガスを流しながら前記被処理体に所定のエッチング処理を施す工程で、前記冷却ガスの実測流量値を基準値と比較判定して、前記ステージに対する前記被処理体の吸着状態および前記冷却ガスによる前記被処理体の冷却状態の異常の有無を判定するプラズマエッチング処理における異常判定方法において、前記基準値は、順次、エッチング処理する被処理体ごとに設定される変動基準値を少なくとも基準値のひとつとして含むことを特徴とするプラズマエッチング処理における異常判定方法。 An object to be processed is adsorbed and held on a stage disposed in a chamber of a plasma etching apparatus, and a cooling gas for cooling the object to be processed is supplied to a gap between the stage and the object to be processed. In the step of performing a predetermined etching process, the measured flow rate value of the cooling gas is compared with a reference value, and the state of adsorption of the object to be processed with respect to the stage and the abnormality of the cooling state of the object to be processed by the cooling gas are determined. In the abnormality determination method in the plasma etching process for determining the presence or absence, the reference value includes, as at least one of the reference values, a variation reference value that is sequentially set for each object to be etched. Abnormality judgment method. 前記変動基準値は、エッチング処理予定の被処理体と同一製造ロットであり、かつ、前記処理予定の被処理体と同一ステージで、同一エッチング条件で、以前にエッチング処理した被処理体の処理時の実測流量値を元に算出することを特徴とする請求項1に記載のプラズマエッチング処理における異常判定方法。 The variation reference value is the same manufacturing lot as the target object to be etched, and at the same stage as the target object to be processed, under the same etching conditions, at the time of processing the target object previously etched The abnormality determination method in the plasma etching process according to claim 1, wherein the abnormality is calculated on the basis of the actual flow rate value. 前記処理予定の被処理体の以前にエッチング処理した被処理体は、前記処理予定の被処理体の直前にエッチング処理した被処理体であることを特徴とする請求項2に記載のプラズマエッチング処理における異常判定方法。 3. The plasma etching process according to claim 2, wherein the object to be processed that has been etched before the object to be processed is an object to be processed that has been etched immediately before the object to be processed. Abnormality judgment method. 前記変動基準値と一定の固定基準値とを併用することを特徴とする請求項1から3のいずれかに記載のプラズマエッチング処理における異常判定方法。 The abnormality determination method in the plasma etching process according to any one of claims 1 to 3, wherein the fluctuation reference value and a fixed fixed reference value are used in combination. 前記プラズマエッチング装置が、複数のチャンバ(およびステージ)を備えたマルチチャンバタイプの場合、前記変動基準値は、各チャンバ(各ステージ)ごとに設定されることを特徴とする請求項1から4のいずれかに記載のプラズマエッチング処理における異常判定方法。

When the plasma etching apparatus is a multi-chamber type having a plurality of chambers (and stages), the variation reference value is set for each chamber (each stage). An abnormality determination method in the plasma etching process according to any one of the above.

JP2005301747A 2005-10-17 2005-10-17 Abnormality judging method in plasma etching treatment Withdrawn JP2007110020A (en)

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