WO2011089673A1 - Ultrasonic cleaning method - Google Patents

Ultrasonic cleaning method Download PDF

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Publication number
WO2011089673A1
WO2011089673A1 PCT/JP2010/007274 JP2010007274W WO2011089673A1 WO 2011089673 A1 WO2011089673 A1 WO 2011089673A1 JP 2010007274 W JP2010007274 W JP 2010007274W WO 2011089673 A1 WO2011089673 A1 WO 2011089673A1
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Prior art keywords
cleaning
ultrasonic
cleaned
output
tank
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PCT/JP2010/007274
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French (fr)
Japanese (ja)
Inventor
均 椛澤
達夫 阿部
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信越半導体株式会社
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Publication of WO2011089673A1 publication Critical patent/WO2011089673A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
    • B08B3/04—Cleaning involving contact with liquid
    • B08B3/10—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration
    • B08B3/12—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration by sonic or ultrasonic vibrations
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02041—Cleaning
    • H01L21/02043—Cleaning before device manufacture, i.e. Begin-Of-Line process
    • H01L21/02052—Wet cleaning only
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/67005—Apparatus not specifically provided for elsewhere
    • H01L21/67011—Apparatus for manufacture or treatment
    • H01L21/67017—Apparatus for fluid treatment
    • H01L21/67028—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like
    • H01L21/6704—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like for wet cleaning or washing
    • H01L21/67057—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like for wet cleaning or washing with the semiconductor substrates being dipped in baths or vessels

Definitions

  • the present invention relates to an ultrasonic cleaning method in which an object to be cleaned such as a semiconductor component such as a semiconductor wafer is immersed in a cleaning liquid and cleaned by irradiating with ultrasonic waves.
  • the ultrasonic cleaning called megasonic as described above has high directivity due to high frequency, and there is a problem that uneven cleaning (unwashed) occurs due to jigs in the cleaning tank. Due to the fact that megasonics are not irradiated on the wafer support jigs and piping shadows placed inside, cleaning irregularities have occurred depending on the arrangement of the megasonic vibrators.
  • the present invention has been made in view of the above circumstances, and an object thereof is to provide an ultrasonic cleaning method capable of solving the problem of uneven cleaning (unwashed) of the wafer surface, which has been a problem in ultrasonic cleaning. .
  • At least the object to be cleaned is immersed in the cleaning liquid in the cleaning tank, and the ultrasonic wave generated from the ultrasonic vibrator is propagated to the cleaning liquid in the cleaning tank to
  • An ultrasonic cleaning method for cleaning an object to be cleaned, wherein the object to be cleaned is cleaned with ultrasonic waves generated from the ultrasonic transducer under at least two ultrasonic output conditions. Provide a method.
  • the cleaning performed under the at least two ultrasonic output conditions is performed by changing the output of the ultrasonic wave generated from the ultrasonic vibrator continuously or stepwise during the cleaning of the object to be cleaned. Can do.
  • the object to be cleaned is cleaned under at least two ultrasonic output conditions. be able to.
  • the cleaning performed under the at least two ultrasonic output conditions can be performed by sequentially immersing the object to be cleaned in a plurality of cleaning liquids in the cleaning tanks having different ultrasonic output conditions between the cleaning tanks.
  • the object to be cleaned can be cleaned under at least two ultrasonic output conditions by sequentially immersing the object in the cleaning liquid in a plurality of cleaning tanks having different ultrasonic output conditions between the cleaning tanks. it can.
  • the cleaning liquid can be a mixed solution of ammonia, hydrogen peroxide solution, and water.
  • a mixed solution of ammonia, hydrogen peroxide and water (so-called SC-1 (Standard Clean 1) cleaning solution) can be used as the cleaning solution.
  • the ultrasonic wave generated from the ultrasonic vibrator is propagated to the cleaning liquid in the cleaning tank through an ultrasonic wave propagation tank filled with ultrasonic propagation water.
  • ultrasonic waves generated from the ultrasonic vibrator are propagated to the cleaning liquid in the cleaning tank through the ultrasonic wave propagation tank filled with the ultrasonic wave propagation water, so that the ultrasonic vibration is alleviated and the object to be cleaned. Excessive impact on the surface is suppressed, and ultrasonic waves can be uniformly propagated to the cleaning liquid in the cleaning tank.
  • the ultrasonic cleaning method of the present invention it is possible to realize powerful ultrasonic cleaning with suppressed cleaning unevenness. Thereby, particle removal can be performed effectively.
  • the ultrasonic cleaning method of the present invention even when high-frequency ultrasonic waves such as megasonic are used, effective particle removal with suppressed cleaning unevenness can be performed.
  • FIG. 6 is an observation view of a silicon wafer after ultrasonic cleaning in Comparative Example 1.
  • FIG. 6 is an observation view of a silicon wafer after ultrasonic cleaning in Comparative Example 2.
  • FIG. 6 is an observation view of a silicon wafer after ultrasonic cleaning in Example 2.
  • FIG. 6 is an observation view of a silicon wafer after ultrasonic cleaning in Example 3.
  • FIG. 6 is an observation view of a silicon wafer after ultrasonic cleaning in Comparative Example 3.
  • FIG. 6 is an observation view of a silicon wafer after ultrasonic cleaning in Comparative Example 4.
  • FIG. 4 is an observation view of a silicon wafer after ultrasonic cleaning in Comparative Example 4.
  • ultrasonic cleaning that is powerful and capable of cleaning the entire wafer surface evenly is required.
  • ultrasonic cleaning called megasonic has high directivity due to high frequency, and there is a problem that uneven cleaning occurs, and there is a need for an ultrasonic cleaning method capable of suppressing cleaning unevenness and effectively removing particles. It was done.
  • the present inventors increase the output of the oscillator and increase the ultrasonic wave, thereby causing cleaning unevenness due to the frequency, shape, arrangement, etc. of the ultrasonic transducer, and reducing the output. And the attenuation of the ultrasonic wave reduces the cleaning power in the area far from the ultrasonic transducer, and the entire wafer surface cannot be cleaned without uneven cleaning, that is, effectively depending on the output of the ultrasonic wave. We paid attention to the different areas where cleaning can be performed.
  • the inventor cleaned the object to be cleaned under two or more ultrasonic output conditions i.e., the region left unwashed in a specific ultrasonic output. It has been found that by cleaning with another output different from the ultrasonic output, the region that can be effectively cleaned can be changed, and cleaning unevenness can be suppressed. That is, in the past, ultrasonic cleaning was performed only on one output condition for the same object to be cleaned, but in the present invention, the ultrasonic output is changed during cleaning of the object to be cleaned. It was found that the surface to be cleaned can be cleaned uniformly by overlapping highly effective regions.
  • FIG. 1 is a diagram showing an ultrasonic cleaning apparatus used in the first embodiment of the ultrasonic cleaning method of the present invention.
  • the cleaning tank 11 in FIG. 1 is filled with a cleaning liquid 12 for cleaning an object to be cleaned 13 such as a substrate.
  • the ultrasonic vibrator 14 is driven by being applied with a high frequency voltage by an ultrasonic oscillator (not shown), and the ultrasonic wave generated thereby is propagated to the cleaning liquid 12 in the cleaning tank 11 through the ultrasonic wave propagation tank 16.
  • the object 13 to be cleaned held by the holding jig 17 is ultrasonically cleaned.
  • the output of the ultrasonic wave generated from the ultrasonic vibrator 14 is changed continuously or stepwise, and the ultrasonic cleaning is performed under at least two ultrasonic output conditions.
  • the output of the ultrasonic wave may be changed in any way as long as the object to be cleaned can be cleaned under two or more output conditions, for example, may be changed stepwise in the order of high output and low output. You may change in order of low output and high output. Furthermore, it is possible to repeatedly change the high output and the low output, for example, high output, low output, high output, and low output.
  • the ultrasonic wave generated from the ultrasonic vibrator 14 it is preferable to propagate the ultrasonic wave generated from the ultrasonic vibrator 14 to the cleaning liquid 12 in the cleaning tank 11 through the ultrasonic wave propagation tank 16 filled with the ultrasonic propagation water 15 such as deaerated water.
  • the ultrasonic vibrator 14 may be directly installed on the bottom surface or side surface of the cleaning tank 11.
  • FIG. 2 is an explanatory view showing a second embodiment of the ultrasonic cleaning method of the present invention.
  • the cleaning is performed under at least two ultrasonic output conditions by sequentially immersing the object to be cleaned 23 in a plurality of cleaning liquids in the cleaning tanks having different ultrasonic output conditions between the cleaning tanks.
  • the object to be cleaned 23 is first immersed in the cleaning liquid 22 of the cleaning tank 21 in which the ultrasonic wave generated from the ultrasonic transducer 24 is set to the first ultrasonic output condition, and the first output condition is set. Perform ultrasonic cleaning.
  • the object to be cleaned 23 is immersed in the cleaning liquid 22 ′ of the cleaning tank 21 ′ in which the ultrasonic wave generated from the ultrasonic transducer 24 ′ is set to the second ultrasonic output condition different from the first output condition.
  • the object to be cleaned 23 is cleaned under a second ultrasonic output condition different from the first output condition.
  • ultrasonic cleaning can be performed under at least two ultrasonic output conditions by sequentially immersing in cleaning liquids of cleaning tanks having different ultrasonic output conditions.
  • the ultrasonic waves generated from the ultrasonic transducers 24 and 24 ' are passed through the ultrasonic wave propagation tanks 26 and 26' filled with the ultrasonic wave propagation water 25 and 25 'such as deaerated water. It is preferable to propagate to the cleaning liquids 22 and 22 ′ in 21 ′.
  • the ultrasonic transducers 24 and 24 ' may be directly installed in the cleaning tanks 21 and 21'. In this case, the first output condition and the second output condition may change the outputs of the ultrasonic transducers 24 and 24 'stepwise or continuously.
  • the plurality of cleaning tanks that sequentially immerse the object 23 to be cleaned are not limited to two tanks as shown in FIG. Any number of tanks may be used as long as they can be washed under conditions.
  • the present invention is not limited to the above-described embodiment as long as ultrasonic cleaning is performed under two or more ultrasonic output conditions in a single cleaning tank or a plurality of cleaning tanks as described above.
  • the object to be cleaned is subjected to ultrasonic cleaning by gradually changing the ultrasonic output in one cleaning tank, and then the object to be cleaned in the cleaning liquid in another cleaning tank fixed to other output conditions. Can be immersed and subjected to ultrasonic cleaning.
  • a region left unwashed with a specific ultrasonic output is different from the ultrasonic output. Since cleaning can be effectively performed with other ultrasonic output, and unevenness in cleaning can be suppressed by canceling the portion that remains unwashed in this way, particles can be effectively removed.
  • the present invention is also suitable when the ultrasonic wave generated from the ultrasonic vibrator has a high frequency of 1 MHz or higher (so-called megasonic).
  • megasonic cleaning has a problem that unevenness in cleaning occurs due to high directivity and the wafer support jig and pipes placed in the cleaning tank are not irradiated with the megasonic, which causes uneven cleaning.
  • unevenness of cleaning occurred according to the arrangement of.
  • the use of the ultrasonic cleaning method of the present invention as described above is effective because effective particle removal with suppressed cleaning unevenness can be performed even with high frequency cleaning of 1 MHz or higher.
  • the shape and arrangement of the ultrasonic transducer used in the ultrasonic cleaning method of the present invention are not particularly limited, and can be changed as appropriate.
  • the cleaning liquid is not particularly limited, but is preferably a mixed solution of ammonia, aqueous hydrogen peroxide, and water, and is usually used as a cleaning liquid for pure water, semiconductor parts, and the like.
  • a chemical solution or the like can also be used.
  • a cleaning solution having a relatively low temperature for example, 50 ° C.
  • particles can be effectively removed.
  • Example 1 The 300 mm diameter silicon wafer after mirror polishing was washed as follows.
  • the silicon wafer was cleaned with ozone water, and ultrasonic cleaning was performed under the following conditions using the ultrasonic cleaning apparatus of FIG.
  • the cleaning liquid 12 in the ultrasonic cleaning was a mixed liquid (SC-1) of ammonia, hydrogen peroxide and water (mixing ratio 1: 1: 10), and the cleaning liquid temperature was 50 ° C.
  • the frequency of the ultrasonic wave generated from the ultrasonic vibrator 14 was 1 MHz (megasonic).
  • the silicon wafer that is the object to be cleaned 13 is immersed in the cleaning liquid 12, and the ultrasonic output is 1 minute at a time for a cleaning time of 6 minutes.
  • High output a (900 W) ⁇ Low output b (300 W) ⁇ High output a (900 W) ⁇ Low output b (300 W) ⁇ High output a (900 W) ⁇ Low output b (300 W) was changed in stages and washed. Thereafter, rinsing (no ultrasonic cleaning) and the dried silicon wafer were observed with a particle counter. An observation view of the cleaned silicon wafer is shown in FIG. The number of LPDs ( ⁇ 41 nm) was as small as 46, and it was found that the particle removal ability was improved and cleaning unevenness was suppressed.
  • Example 1 The silicon wafer was cleaned in the same manner as in Example 1 except that the ultrasonic cleaning step by SC-1 in Example 1 was performed with the output of ultrasonic wave being high output a (900 W) and the cleaning time being 6 minutes.
  • An observation view of the cleaned silicon wafer is shown in FIG. Irregularity of cleaning that appears to be caused by the ultrasonic vibrator occurred, and the number of LPD ( ⁇ 41 nm) was very large at 5034.
  • Example 2 In the ultrasonic cleaning process by SC-1 in Example 1, the silicon wafer was cleaned under the same conditions as in Example 1 except that the ultrasonic output was low output a (300 W) and the cleaning time was 6 minutes. It was. An observation view of the cleaned silicon wafer is shown in FIG. LPD ( ⁇ 41 nm) was seen as many as 332, and particles remained in the shadow of the holding jig on the outer periphery of the wafer.
  • Example 2 The silicon wafer was cleaned under the same conditions as in Example 1 except that the ultrasonic cleaning step by SC-1 in Example 1 was performed by the ultrasonic cleaning method shown in FIG. Using the two cleaning tanks (21, 21 ′) filled with the cleaning liquid (SC-1) used in Example 1, the silicon wafer as the object to be cleaned 23 was placed in the first cleaning tank 21. After ultrasonic cleaning at high output a (900 W) for 3 minutes, ultrasonic cleaning was performed at low output b (300 W) for 3 minutes in the second cleaning tank 21 ′. An observation view of the cleaned silicon wafer is shown in FIG. It was confirmed that the number of LPD ( ⁇ 41 nm) was as small as 57, the particle removal ability was improved, and cleaning unevenness was suppressed.
  • SC-1 cleaning liquid
  • Example 3 The 300 mm diameter silicon wafer after mirror polishing was washed as follows. The silicon wafer was cleaned with ozone water, and then ultrasonic cleaning was performed using the ultrasonic cleaning apparatus of FIG. In addition, the ultrasonic transducer
  • the cleaning liquid 12 in the ultrasonic cleaning was a mixed liquid (SC-1) of ammonia, hydrogen peroxide and water (mixing ratio 1: 1: 10), and the cleaning liquid temperature was 50 ° C.
  • the frequency of the ultrasonic wave generated from the ultrasonic vibrator 14 was 1 MHz (megasonic).
  • the silicon wafer as the object to be cleaned 13 is immersed in the cleaning liquid 12 in the cleaning tank 11, and the ultrasonic output is high output c (1000 W) ⁇ low output d (400 W) ⁇ high for 1 minute every 6 minutes. Washing was performed by changing the output c (1000 W) ⁇ low output d (400 W) ⁇ high output c (1000 W) ⁇ low output d (400 W) step by step. Thereafter, the rinsed (no ultrasonic cleaning) and dried silicon wafers were observed with a particle counter.
  • FIG. 7 shows an observation view after washing. The number of LPD ( ⁇ 41 nm) is as small as 58, and it can be seen that the particle removing ability is improved and the cleaning unevenness is suppressed.
  • Example 3 In the ultrasonic cleaning process by SC-1 in Example 3, the silicon wafer was cleaned under the same conditions as in Example 3 except that the ultrasonic output was high output c (1000 W) and the cleaning time was 6 minutes. It was. An observation view of the cleaned silicon wafer is shown in FIG. The cleaning unevenness which seems to be caused by the ultrasonic vibrator occurred, and the number of LPD ( ⁇ 41 nm) was 6814, which was very large.
  • Example 4 In the ultrasonic cleaning process by SC-1 in Example 3, the silicon wafer was cleaned under the same conditions as in Example 3 except that the ultrasonic output was low output d (400 W) and the cleaning time was 6 minutes. It was. An observation view of the silicon wafer after cleaning is shown in FIG. LPD ( ⁇ 41 nm) was seen as many as 451.
  • the present invention is not limited to the above embodiment.
  • the above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. It is contained in the technical range.

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
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Abstract

Disclosed is an ultrasonic cleaning method that, at the very least, cleans an object to be cleaned by immersing the aforementioned object to be cleaned in cleaning fluid that is within a cleaning tank and transmitting ultrasonic waves generated from an ultrasonic transducer to the cleaning fluid that is within the aforementioned cleaning tank, and is characterized by the cleaning of the object to be cleaned by means of the ultrasonic waves generated by the aforementioned ultrasonic transducer being performed under at least two ultrasonic output conditions. As a result, an ultrasonic cleaning method is provided that resolves the problem of uneven cleaning (missed spots), which has been a problem with ultrasonic cleaning, and that can effectively eliminate particles.

Description

超音波洗浄方法Ultrasonic cleaning method
　本発明は、半導体ウェーハを始めとした半導体部品等の被洗浄物を洗浄液に浸漬し、超音波を照射して洗浄する超音波洗浄方法に関する。
　 The present invention relates to an ultrasonic cleaning method in which an object to be cleaned such as a semiconductor component such as a semiconductor wafer is immersed in a cleaning liquid and cleaned by irradiating with ultrasonic waves.
　デバイスのデザインルール微細化に伴う品質改善要求の一つにウェーハパーティクルの低減がある。このパーティクル低減要求は、ウェーハ表面の個数のみではなく、デザインルールの微細化に合わせてサイズが小さくなり、ますます厳しいものとなっている。この品質要求を達成するためには、清浄度の高い洗浄技術が必要となる。半導体ウェーハを始めとした半導体部品等の被洗浄物の洗浄において、効率良くパーティクルを除去するために、超音波洗浄を併用するのが一般的となっている。この超音波洗浄は、付着パーティクルの種類やウェーハの状態、洗浄後の品質等によって、周波数、出力、超音波制御、超音波洗浄槽、洗浄時間等が決定され、現在まで様々な超音波洗浄方法が提案されている（特許文献１、特許文献２等）。 One of the quality improvement requirements accompanying the miniaturization of device design rules is the reduction of wafer particles. The demand for particle reduction is not only the number of wafer surfaces, but also the size becomes smaller as design rules become finer. In order to achieve this quality requirement, a cleaning technique with high cleanliness is required. In the cleaning of an object to be cleaned such as a semiconductor wafer and other semiconductor parts, it is common to use ultrasonic cleaning in order to efficiently remove particles. In this ultrasonic cleaning, frequency, output, ultrasonic control, ultrasonic cleaning tank, cleaning time, etc. are determined depending on the kind of adhered particles, wafer state, quality after cleaning, etc. Has been proposed (Patent Document 1, Patent Document 2, etc.).
　また、最近は、より微小なパーティクル除去、および、ウェーハ表面にダメージを与えないために、所謂メガソニックと呼ばれる１ＭＨｚといった高周波による超音波洗浄が行われる場合が多い。 Recently, in order to remove finer particles and not damage the wafer surface, ultrasonic cleaning with a high frequency of 1 MHz called so-called megasonic is often performed.
　半導体シリコンウェーハ表面の微小なパーティクルを除去するためには、強力でウェーハ表面全体をムラ無く洗浄できる超音波洗浄が必要である。
　しかし、現状の超音波洗浄は、振動子の周波数、出力、形状、配置等に起因する洗浄ムラ、洗浄槽、槽内の噴流管、ウェーハ保持冶具等の構造物による洗浄ムラが問題となっている。 In order to remove minute particles on the surface of the semiconductor silicon wafer, it is necessary to perform ultrasonic cleaning that is strong and can clean the entire surface of the wafer evenly.
However, in the current ultrasonic cleaning, cleaning unevenness due to the frequency, output, shape, arrangement, etc. of the vibrator, cleaning unevenness due to structures such as a cleaning tank, a jet pipe in the tank, and a wafer holding jig become problems. Yes.
　特に、上記のようなメガソニックと呼ばれる超音波洗浄は、高周波のため指向性が強く、洗浄槽内の治具等による洗浄ムラ（洗い残し）が発生する問題があり、詳述すると、洗浄槽内に配置されたウェーハ支持治具や配管の影となる部分にメガソニックが照射されないことに起因して、また、メガソニック振動子の配置に応じ、洗浄ムラが生じてしまっていた。 In particular, the ultrasonic cleaning called megasonic as described above has high directivity due to high frequency, and there is a problem that uneven cleaning (unwashed) occurs due to jigs in the cleaning tank. Due to the fact that megasonics are not irradiated on the wafer support jigs and piping shadows placed inside, cleaning irregularities have occurred depending on the arrangement of the megasonic vibrators.
　そこで、超音波洗浄で問題となっていた洗浄ムラの問題を解消し、パーティクル除去を効果的に行うことのできる超音波洗浄方法が求められている。 Therefore, there is a need for an ultrasonic cleaning method that can eliminate the problem of uneven cleaning, which has been a problem with ultrasonic cleaning, and can effectively remove particles.
特開平８－１３１９７８号公報JP-A-8-131978 特開２００９－１２５６４５号公報JP 2009-125645 A
　本発明は、上記事情に鑑みなされたもので、超音波洗浄で問題となっていたウェーハ表面の洗浄ムラ（洗い残し）問題を解消することができる超音波洗浄方法を提供することを目的とする。 The present invention has been made in view of the above circumstances, and an object thereof is to provide an ultrasonic cleaning method capable of solving the problem of uneven cleaning (unwashed) of the wafer surface, which has been a problem in ultrasonic cleaning. .
　上記課題を解決するために、本発明によれば、少なくとも、洗浄槽中の洗浄液に被洗浄物を浸漬し、超音波振動子から発生する超音波を前記洗浄槽中の洗浄液に伝播させて前記被洗浄物を洗浄する超音波洗浄方法であって、前記超音波振動子から発生する超音波による被洗浄物の洗浄を、少なくとも２以上の超音波出力条件で行うことを特徴とする超音波洗浄方法を提供する。 In order to solve the above problems, according to the present invention, at least the object to be cleaned is immersed in the cleaning liquid in the cleaning tank, and the ultrasonic wave generated from the ultrasonic vibrator is propagated to the cleaning liquid in the cleaning tank to An ultrasonic cleaning method for cleaning an object to be cleaned, wherein the object to be cleaned is cleaned with ultrasonic waves generated from the ultrasonic transducer under at least two ultrasonic output conditions. Provide a method.
　このように、超音波振動子から発生する超音波による被洗浄物の洗浄を、少なくとも２以上の超音波出力条件で行うことによって、ある特定の超音波出力で洗い残しとなっている領域を、当該超音波出力とは異なる他の効果的に洗浄できる超音波出力で洗浄することによって補完し、洗い残しとなっている領域を打ち消すことができ、被洗浄面内での洗浄ムラを抑制することができるため、パーティクルの除去を効果的に行うことができる。 In this way, by performing cleaning of an object to be cleaned with ultrasonic waves generated from an ultrasonic vibrator under at least two ultrasonic output conditions, an area left unwashed with a specific ultrasonic output, It can be complemented by cleaning with an ultrasonic output that can be effectively cleaned differently from the ultrasonic output, so that the area left unwashed can be canceled out, and uneven cleaning within the surface to be cleaned can be suppressed. Therefore, it is possible to effectively remove particles.
　また、前記少なくとも２以上の超音波出力条件で行う洗浄を、前記超音波振動子から発生する超音波の出力を、前記被洗浄物の洗浄中に連続的又は段階的に変化させることにより行うことができる。 In addition, the cleaning performed under the at least two ultrasonic output conditions is performed by changing the output of the ultrasonic wave generated from the ultrasonic vibrator continuously or stepwise during the cleaning of the object to be cleaned. Can do.
　このように、超音波振動子から発生する超音波の出力を、被洗浄物の洗浄中に連続的又は段階的に変化させることで、被洗浄物を少なくとも２以上の超音波出力条件で洗浄することができる。 In this way, by changing the output of the ultrasonic wave generated from the ultrasonic vibrator continuously or stepwise during the cleaning of the object to be cleaned, the object to be cleaned is cleaned under at least two ultrasonic output conditions. be able to.
　また、前記少なくとも２以上の超音波出力条件で行う洗浄を、前記被洗浄物を、洗浄槽間で超音波出力条件が異なる複数の前記洗浄槽中の洗浄液に順次浸漬することにより行うことができる。 Moreover, the cleaning performed under the at least two ultrasonic output conditions can be performed by sequentially immersing the object to be cleaned in a plurality of cleaning liquids in the cleaning tanks having different ultrasonic output conditions between the cleaning tanks. .
　このように、被洗浄物を、洗浄槽間で超音波出力条件が異なる複数の洗浄槽中の洗浄液に順次浸漬することで、被洗浄物を少なくとも２以上の超音波出力条件で洗浄することができる。 In this way, the object to be cleaned can be cleaned under at least two ultrasonic output conditions by sequentially immersing the object in the cleaning liquid in a plurality of cleaning tanks having different ultrasonic output conditions between the cleaning tanks. it can.
　また、前記洗浄液を、アンモニア、過酸化水素水、及び水の混合溶液とすることができる。 Further, the cleaning liquid can be a mixed solution of ammonia, hydrogen peroxide solution, and water.
　このように、本発明の超音波洗浄方法では、洗浄液として、アンモニア、過酸化水素水、及び水の混合溶液（所謂ＳＣ－１（Ｓｔａｎｄａｒｄ　Ｃｌｅａｎ　１）洗浄液）を用いることができる。 Thus, in the ultrasonic cleaning method of the present invention, a mixed solution of ammonia, hydrogen peroxide and water (so-called SC-1 (Standard Clean 1) cleaning solution) can be used as the cleaning solution.
　また、前記超音波振動子から発生する超音波を、超音波伝播水を満たした超音波伝播槽を介して前記洗浄槽中の洗浄液に伝播させることが好ましい。 Further, it is preferable that the ultrasonic wave generated from the ultrasonic vibrator is propagated to the cleaning liquid in the cleaning tank through an ultrasonic wave propagation tank filled with ultrasonic propagation water.
　このように、超音波振動子から発生する超音波を、超音波伝播水を満たした超音波伝播槽を介して洗浄槽中の洗浄液に伝播させることにより、超音波振動が緩和されて被洗浄物への過度の衝撃が抑制され、均一に超音波を洗浄槽中の洗浄液に伝播させることができる。 In this way, ultrasonic waves generated from the ultrasonic vibrator are propagated to the cleaning liquid in the cleaning tank through the ultrasonic wave propagation tank filled with the ultrasonic wave propagation water, so that the ultrasonic vibration is alleviated and the object to be cleaned. Excessive impact on the surface is suppressed, and ultrasonic waves can be uniformly propagated to the cleaning liquid in the cleaning tank.
　以上説明したように、本発明の超音波洗浄方法を用いれば、洗浄ムラが抑制された強力な超音波洗浄が実現できる。これにより、パーティクル除去を効果的に行うことができる。また、本発明の超音波洗浄方法を用いれば、メガソニック等の高周波の超音波を利用した場合にも、洗浄ムラが抑制された効果的なパーティクル除去を行うことができる。
　 As described above, by using the ultrasonic cleaning method of the present invention, it is possible to realize powerful ultrasonic cleaning with suppressed cleaning unevenness. Thereby, particle removal can be performed effectively. In addition, when the ultrasonic cleaning method of the present invention is used, even when high-frequency ultrasonic waves such as megasonic are used, effective particle removal with suppressed cleaning unevenness can be performed.
本発明の超音波洗浄方法で用いる超音波洗浄装置の１例を示す概略図である。It is the schematic which shows an example of the ultrasonic cleaning apparatus used with the ultrasonic cleaning method of this invention. 本発明の他の超音波洗浄方法の説明図である。It is explanatory drawing of the other ultrasonic cleaning method of this invention. 実施例１における超音波洗浄後のシリコンウェーハの観察図である。3 is an observation view of a silicon wafer after ultrasonic cleaning in Example 1. FIG. 比較例１における超音波洗浄後のシリコンウェーハの観察図である。6 is an observation view of a silicon wafer after ultrasonic cleaning in Comparative Example 1. FIG. 比較例２における超音波洗浄後のシリコンウェーハの観察図である。6 is an observation view of a silicon wafer after ultrasonic cleaning in Comparative Example 2. FIG. 実施例２における超音波洗浄後のシリコンウェーハの観察図である。6 is an observation view of a silicon wafer after ultrasonic cleaning in Example 2. FIG. 実施例３における超音波洗浄後のシリコンウェーハの観察図である。6 is an observation view of a silicon wafer after ultrasonic cleaning in Example 3. FIG. 比較例３における超音波洗浄後のシリコンウェーハの観察図である。6 is an observation view of a silicon wafer after ultrasonic cleaning in Comparative Example 3. FIG. 比較例４における超音波洗浄後のシリコンウェーハの観察図である。6 is an observation view of a silicon wafer after ultrasonic cleaning in Comparative Example 4. FIG.
　以下、本発明についてより具体的に説明する。
　前述のように、従来、半導体シリコンウェーハ表面の微小なパーティクルを除去するためには、強力でウェーハ表面全体をムラ無く洗浄できる超音波洗浄が求められている。特に、メガソニックと呼ばれる超音波洗浄は、高周波のため指向性が強く、洗浄ムラが発生する問題があり、洗浄ムラを抑制し、パーティクル除去を効果的に行うことのできる超音波洗浄方法が求められていた。 Hereinafter, the present invention will be described more specifically.
As described above, conventionally, in order to remove minute particles on the surface of a semiconductor silicon wafer, ultrasonic cleaning that is powerful and capable of cleaning the entire wafer surface evenly is required. In particular, ultrasonic cleaning called megasonic has high directivity due to high frequency, and there is a problem that uneven cleaning occurs, and there is a need for an ultrasonic cleaning method capable of suppressing cleaning unevenness and effectively removing particles. It was done.
　本発明者らは、超音波洗浄を強力にしようと、発振機の出力を上げ超音波を強くすると、超音波振動子の周波数、形状、配置等に起因する洗浄ムラが発生し、出力を下げると超音波の減衰により超音波振動子との距離が遠い領域の洗浄力が低下してしまい、ウェーハ全面を洗浄ムラなく洗浄することができないこと、即ち、超音波の出力に応じて効果的に洗浄ができる領域が異なることに着目した。 In order to enhance the ultrasonic cleaning, the present inventors increase the output of the oscillator and increase the ultrasonic wave, thereby causing cleaning unevenness due to the frequency, shape, arrangement, etc. of the ultrasonic transducer, and reducing the output. And the attenuation of the ultrasonic wave reduces the cleaning power in the area far from the ultrasonic transducer, and the entire wafer surface cannot be cleaned without uneven cleaning, that is, effectively depending on the output of the ultrasonic wave. We paid attention to the different areas where cleaning can be performed.
　そして、本発明者は、鋭意検討を行った結果、被洗浄物を２以上の超音波出力条件で洗浄することによって、即ち、ある特定の超音波出力では洗い残しとなっている領域を、当該超音波出力とは異なる他の出力で洗浄することによって、効果的に洗浄できる領域を変更することができ、洗浄ムラを抑制できることを見出した。即ち、従来は、同じ被洗浄物に対しては、１つの出力条件でしか超音波洗浄がなされていなかったが、本発明では、被洗浄物の洗浄中に超音波の出力を変化させ、洗浄効果の高い領域をオーバーラップさせることで、被洗浄面内を均一に洗浄できることを見出した。 And as a result of intensive studies, the inventor cleaned the object to be cleaned under two or more ultrasonic output conditions, i.e., the region left unwashed in a specific ultrasonic output, It has been found that by cleaning with another output different from the ultrasonic output, the region that can be effectively cleaned can be changed, and cleaning unevenness can be suppressed. That is, in the past, ultrasonic cleaning was performed only on one output condition for the same object to be cleaned, but in the present invention, the ultrasonic output is changed during cleaning of the object to be cleaned. It was found that the surface to be cleaned can be cleaned uniformly by overlapping highly effective regions.
　以下、本発明の超音波洗浄方法について、実施態様の一例として、図１を参照しながら詳細に説明するが、本発明はこれに限定されるものではない。図１は、本発明の超音波洗浄方法の第１実施形態に用いる超音波洗浄装置を示す図である。 Hereinafter, the ultrasonic cleaning method of the present invention will be described in detail with reference to FIG. 1 as an example of the embodiment, but the present invention is not limited thereto. FIG. 1 is a diagram showing an ultrasonic cleaning apparatus used in the first embodiment of the ultrasonic cleaning method of the present invention.
　図１の洗浄槽１１には、基板等の被洗浄物１３を洗浄するための洗浄液１２が満たされている。超音波振動子１４は超音波発振器（不図示）により高周波電圧を印加されて駆動し、これにより発生する超音波を超音波伝播槽１６を介して洗浄槽１１中の洗浄液１２に伝播させて、保持治具１７により保持されている被洗浄物１３を超音波洗浄する。
　この超音波洗浄の際、超音波振動子１４から発生する超音波の出力を連続的又は段階的に変化させ、超音波洗浄を少なくとも２以上の超音波出力条件で行う。 The cleaning tank 11 in FIG. 1 is filled with a cleaning liquid 12 for cleaning an object to be cleaned 13 such as a substrate. The ultrasonic vibrator 14 is driven by being applied with a high frequency voltage by an ultrasonic oscillator (not shown), and the ultrasonic wave generated thereby is propagated to the cleaning liquid 12 in the cleaning tank 11 through the ultrasonic wave propagation tank 16. The object 13 to be cleaned held by the holding jig 17 is ultrasonically cleaned.
At the time of this ultrasonic cleaning, the output of the ultrasonic wave generated from the ultrasonic vibrator 14 is changed continuously or stepwise, and the ultrasonic cleaning is performed under at least two ultrasonic output conditions.
　超音波の出力は、被洗浄物の洗浄を２以上の出力条件で行うことができれば、どのように変化させても良く、例えば高出力、低出力の順に段階的に変化させても良いし、低出力、高出力の順に変化させても良い。更に、例えば高出力、低出力、高出力、低出力のように、高出力と低出力とを繰り返し変化させることもできる。このように段階的に超音波の出力を変化させる場合、出力範囲は特に限定されないが、高出力／低出力＝１．５～３．５倍となるように出力を変化させることが好ましい。
　また、超音波の出力を連続的に変化させる場合にも、２以上の出力条件で洗浄することができれば、出力の変化方法は特に限定されない。 The output of the ultrasonic wave may be changed in any way as long as the object to be cleaned can be cleaned under two or more output conditions, for example, may be changed stepwise in the order of high output and low output. You may change in order of low output and high output. Furthermore, it is possible to repeatedly change the high output and the low output, for example, high output, low output, high output, and low output. When the output of the ultrasonic wave is changed step by step in this way, the output range is not particularly limited, but it is preferable to change the output so that high output / low output = 1.5 to 3.5 times.
Even when the output of the ultrasonic wave is continuously changed, the output changing method is not particularly limited as long as cleaning can be performed under two or more output conditions.
　尚、超音波振動子１４から発生する超音波を、脱気水等の超音波伝播水１５を満たした超音波伝播槽１６を介して洗浄槽１１中の洗浄液１２に伝播させることが好ましい。
　このように、超音波伝播槽１６を介することで、超音波振動が緩和されて被洗浄物１３への過度の衝撃が抑制され、また、より均一に洗浄することができる。
　もちろん、本発明では洗浄槽１１の底面や側面に超音波振動子１４を直接設置するようにしてもよい。 In addition, it is preferable to propagate the ultrasonic wave generated from the ultrasonic vibrator 14 to the cleaning liquid 12 in the cleaning tank 11 through the ultrasonic wave propagation tank 16 filled with the ultrasonic propagation water 15 such as deaerated water.
Thus, by passing through the ultrasonic wave propagation tank 16, the ultrasonic vibration is alleviated, an excessive impact on the object 13 to be cleaned is suppressed, and cleaning can be performed more uniformly.
Of course, in the present invention, the ultrasonic vibrator 14 may be directly installed on the bottom surface or side surface of the cleaning tank 11.
　また、本発明の超音波洗浄方法の第２実施形態について図２を参照しながら説明する。図２は、本発明の超音波洗浄方法の第２実施形態を示す説明図である。 Further, a second embodiment of the ultrasonic cleaning method of the present invention will be described with reference to FIG. FIG. 2 is an explanatory view showing a second embodiment of the ultrasonic cleaning method of the present invention.
　被洗浄物２３を、洗浄槽間で超音波出力条件が異なる複数の前記洗浄槽中の洗浄液に順次浸漬することにより行うことで、少なくとも２以上の超音波出力条件で洗浄を行う。 The cleaning is performed under at least two ultrasonic output conditions by sequentially immersing the object to be cleaned 23 in a plurality of cleaning liquids in the cleaning tanks having different ultrasonic output conditions between the cleaning tanks.
　詳述すると、被洗浄物２３を、先ず、超音波振動子２４から発生する超音波を第１の超音波出力条件に設定した洗浄槽２１の洗浄液２２に浸漬し、第１の出力条件での超音波洗浄を行う。
　次いで、被洗浄物２３を、超音波振動子２４’から発生する超音波を前記の第１の出力条件とは異なる第２の超音波出力条件に設定した洗浄槽２１’の洗浄液２２’に浸漬し、再度洗浄を行うことで、第１の出力条件とは異なる第２の超音波出力条件で、被洗浄物２３の洗浄を行う。 More specifically, the object to be cleaned 23 is first immersed in the cleaning liquid 22 of the cleaning tank 21 in which the ultrasonic wave generated from the ultrasonic transducer 24 is set to the first ultrasonic output condition, and the first output condition is set. Perform ultrasonic cleaning.
Next, the object to be cleaned 23 is immersed in the cleaning liquid 22 ′ of the cleaning tank 21 ′ in which the ultrasonic wave generated from the ultrasonic transducer 24 ′ is set to the second ultrasonic output condition different from the first output condition. Then, by performing cleaning again, the object to be cleaned 23 is cleaned under a second ultrasonic output condition different from the first output condition.
　このように、超音波出力条件が異なる洗浄槽の洗浄液に順次浸漬することで、少なくとも２以上の超音波出力条件で超音波洗浄を行うことができる。 In this way, ultrasonic cleaning can be performed under at least two ultrasonic output conditions by sequentially immersing in cleaning liquids of cleaning tanks having different ultrasonic output conditions.
　また、各超音波振動子２４・２４’から発生する超音波は、脱気水等の超音波伝播水２５・２５’を満たした超音波伝播槽２６・２６’を介して各洗浄槽２１・２１’中の洗浄液２２・２２’に伝播させることが好ましい。もちろん、洗浄槽２１・２１’に直接超音波振動子２４・２４’を設置してもよい。また、この場合第１の出力条件及び第２の出力条件は、それぞれ超音波振動子２４・２４’の出力を段階的または連続的に変化させるようにしても良い。 Further, the ultrasonic waves generated from the ultrasonic transducers 24 and 24 'are passed through the ultrasonic wave propagation tanks 26 and 26' filled with the ultrasonic wave propagation water 25 and 25 'such as deaerated water. It is preferable to propagate to the cleaning liquids 22 and 22 ′ in 21 ′. Of course, the ultrasonic transducers 24 and 24 'may be directly installed in the cleaning tanks 21 and 21'. In this case, the first output condition and the second output condition may change the outputs of the ultrasonic transducers 24 and 24 'stepwise or continuously.
　ここで、被洗浄物２３を順次浸漬していく複数の洗浄槽は、図２に示すような２槽に限らず、被洗浄物２３を順次浸漬していく工程で、２以上の超音波出力条件で洗浄することができれば、何槽用いても良い。 Here, the plurality of cleaning tanks that sequentially immerse the object 23 to be cleaned are not limited to two tanks as shown in FIG. Any number of tanks may be used as long as they can be washed under conditions.
　尚、本発明は、上記のように単一洗浄槽や複数洗浄槽において、２以上の超音波出力条件で超音波洗浄を行うものであれば、上記実施形態に限られない。
　例えば、被洗浄物を一つの洗浄槽中で段階的に超音波出力を変化させて超音波洗浄を行い、その後、更に、他の出力条件に固定した他の洗浄槽中の洗浄液に被洗浄物を浸漬し、超音波洗浄を行うこともできる。 Note that the present invention is not limited to the above-described embodiment as long as ultrasonic cleaning is performed under two or more ultrasonic output conditions in a single cleaning tank or a plurality of cleaning tanks as described above.
For example, the object to be cleaned is subjected to ultrasonic cleaning by gradually changing the ultrasonic output in one cleaning tank, and then the object to be cleaned in the cleaning liquid in another cleaning tank fixed to other output conditions. Can be immersed and subjected to ultrasonic cleaning.
　このように、本発明によれば、少なくとも２以上の超音波出力条件で超音波洗浄を行うことによって、ある特定の超音波出力で洗い残しとなっている領域を、当該超音波出力とは異なる他の超音波出力で効果的に洗浄することができ、このように洗い残しとなる部分を打ち消すことによって、洗浄ムラを抑制することができるため、パーティクルの除去を効果的に行うことができる。 As described above, according to the present invention, by performing ultrasonic cleaning under at least two ultrasonic output conditions, a region left unwashed with a specific ultrasonic output is different from the ultrasonic output. Since cleaning can be effectively performed with other ultrasonic output, and unevenness in cleaning can be suppressed by canceling the portion that remains unwashed in this way, particles can be effectively removed.
　また、本発明は、超音波振動子から発生する超音波が、１ＭＨｚ以上の高周波（所謂メガソニック）である場合にも好適である。従来、メガソニック洗浄は、高い指向性が起因して洗浄槽内に配置されたウェーハ支持治具や配管の影となる部分にメガソニックが照射されず、洗浄ムラが発生する問題や、振動子の配置に応じた洗浄ムラが発生する問題があった。
　しかし、上記のような本発明の超音波洗浄方法を用いれば、１ＭＨｚ以上の高周波による洗浄であっても、洗浄ムラが抑制された効果的なパーティクル除去を行うことができるため、有効である。 The present invention is also suitable when the ultrasonic wave generated from the ultrasonic vibrator has a high frequency of 1 MHz or higher (so-called megasonic). Conventionally, megasonic cleaning has a problem that unevenness in cleaning occurs due to high directivity and the wafer support jig and pipes placed in the cleaning tank are not irradiated with the megasonic, which causes uneven cleaning. There was a problem that unevenness of cleaning occurred according to the arrangement of.
However, the use of the ultrasonic cleaning method of the present invention as described above is effective because effective particle removal with suppressed cleaning unevenness can be performed even with high frequency cleaning of 1 MHz or higher.
　尚、本発明の超音波洗浄方法に用いる超音波振動子の形状や配置は特に限定されず、適宜変更が可能である。 In addition, the shape and arrangement of the ultrasonic transducer used in the ultrasonic cleaning method of the present invention are not particularly limited, and can be changed as appropriate.
　また、本発明の超音波洗浄方法において、洗浄液は特に限定されないが、アンモニア、過酸化水素水、及び水の混合溶液とすることが好ましく、また、純水や半導体部品等の洗浄液として用いられる通常の薬液等も用いることができる。
　尚、ウェーハ等の洗浄において、ウェーハ表面粗さを低減するために、比較的低温（例えば５０℃）の洗浄液で洗浄を行う方法があるが、このような洗浄能力が低めの洗浄液の場合でも、本発明の超音波洗浄方法によれば、効果的にパーティクルの除去を行うことができる。
　 In the ultrasonic cleaning method of the present invention, the cleaning liquid is not particularly limited, but is preferably a mixed solution of ammonia, aqueous hydrogen peroxide, and water, and is usually used as a cleaning liquid for pure water, semiconductor parts, and the like. A chemical solution or the like can also be used.
In the cleaning of wafers and the like, there is a method of cleaning with a cleaning solution having a relatively low temperature (for example, 50 ° C.) in order to reduce the wafer surface roughness. According to the ultrasonic cleaning method of the present invention, particles can be effectively removed.
　以下、実施例と比較例を示して本発明を具体的に説明するが、本発明はこれらに限定されるものではない。 Hereinafter, the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited thereto.
（実施例１）
　鏡面研磨後の直径３００ｍｍのシリコンウェーハを以下のように洗浄した。
　上記シリコンウェーハをオゾン水で洗浄し、図１の超音波洗浄装置を用いて以下の条件で超音波洗浄を行った。
　尚、超音波洗浄における洗浄液１２はアンモニア、過酸化水素水、水の混合液（ＳＣ－１）とし（混合比　１：１：１０）、洗浄液温度を５０℃とした。超音波振動子１４から発生する超音波の周波数は１ＭＨｚ（メガソニック）とした。
　被洗浄物１３である上記シリコンウェーハを上記洗浄液１２に浸漬し、６分間の洗浄時間で超音波出力を１分間ずつ高出力ａ（９００Ｗ）→低出力ｂ（３００Ｗ）→高出力ａ（９００Ｗ）→低出力ｂ（３００Ｗ）→高出力ａ（９００Ｗ）→低出力ｂ（３００Ｗ）と段階的に変更して洗浄した。
　その後、リンス（超音波洗浄なし）、乾燥したシリコンウェーハを、パーティクルカウンターによって観察した。洗浄後のシリコンウェーハの観察図を図３に示す。ＬＰＤ（≧４１ｎｍ）は４６個と少なく、パーティクル除去能力が改善し、洗浄ムラが抑制されていることが判った。
　 Example 1
The 300 mm diameter silicon wafer after mirror polishing was washed as follows.
The silicon wafer was cleaned with ozone water, and ultrasonic cleaning was performed under the following conditions using the ultrasonic cleaning apparatus of FIG.
The cleaning liquid 12 in the ultrasonic cleaning was a mixed liquid (SC-1) of ammonia, hydrogen peroxide and water (mixing ratio 1: 1: 10), and the cleaning liquid temperature was 50 ° C. The frequency of the ultrasonic wave generated from the ultrasonic vibrator 14 was 1 MHz (megasonic).
The silicon wafer that is the object to be cleaned 13 is immersed in the cleaning liquid 12, and the ultrasonic output is 1 minute at a time for a cleaning time of 6 minutes. High output a (900 W) → Low output b (300 W) → High output a (900 W) → Low output b (300 W) → High output a (900 W) → Low output b (300 W) was changed in stages and washed.
Thereafter, rinsing (no ultrasonic cleaning) and the dried silicon wafer were observed with a particle counter. An observation view of the cleaned silicon wafer is shown in FIG. The number of LPDs (≧ 41 nm) was as small as 46, and it was found that the particle removal ability was improved and cleaning unevenness was suppressed.
（比較例１）
　実施例１におけるＳＣ－１による超音波洗浄工程を、超音波の出力を高出力ａ（９００Ｗ）、洗浄時間を６分間とした以外は上記実施例１と同様にシリコンウェーハの洗浄を行った。
　洗浄後のシリコンウェーハの観察図を図４に示す。超音波振動子に起因すると見られる洗浄ムラが発生し、ＬＰＤ（≧４１ｎｍ）は５０３４個と非常に多かった。
　 (Comparative Example 1)
The silicon wafer was cleaned in the same manner as in Example 1 except that the ultrasonic cleaning step by SC-1 in Example 1 was performed with the output of ultrasonic wave being high output a (900 W) and the cleaning time being 6 minutes.
An observation view of the cleaned silicon wafer is shown in FIG. Irregularity of cleaning that appears to be caused by the ultrasonic vibrator occurred, and the number of LPD (≧ 41 nm) was very large at 5034.
（比較例２）
　実施例１におけるＳＣ－１による超音波洗浄工程を、超音波の出力を低出力ａ（３００Ｗ）、洗浄時間を６分間とした以外は上記実施例１と同様の条件でシリコンウェーハの洗浄を行った。
　洗浄後のシリコンウェーハの観察図を図５に示す。ＬＰＤ（≧４１ｎｍ）は３３２個と多く見られ、ウェーハ外周部も保持冶具の影になる部分にパーティクルが残っていた。
　 (Comparative Example 2)
In the ultrasonic cleaning process by SC-1 in Example 1, the silicon wafer was cleaned under the same conditions as in Example 1 except that the ultrasonic output was low output a (300 W) and the cleaning time was 6 minutes. It was.
An observation view of the cleaned silicon wafer is shown in FIG. LPD (≧ 41 nm) was seen as many as 332, and particles remained in the shadow of the holding jig on the outer periphery of the wafer.
（実施例２）
　上記実施例１におけるＳＣ－１による超音波洗浄工程を、図２に示す超音波洗浄方法で行った以外は上記実施例１と同様の条件でシリコンウェーハの洗浄を行った。
　実施例１で用いた洗浄液（ＳＣ－１）が満たされた２槽の洗浄槽（２１、２１’）を使用して、被洗浄物２３であるシリコンウェーハを、１槽目の洗浄槽２１で高出力ａ（９００Ｗ）で３分間超音波洗浄した後に、２槽目の洗浄槽２１’で低出力ｂ（３００Ｗ）で３分間超音波洗浄を行った。
　洗浄後のシリコンウェーハの観察図を図６に示す。ＬＰＤ（≧４１ｎｍ）が５７個と少なく、パーティクル除去能力が改善し、洗浄ムラが抑制されていることが確認できた。
　 (Example 2)
The silicon wafer was cleaned under the same conditions as in Example 1 except that the ultrasonic cleaning step by SC-1 in Example 1 was performed by the ultrasonic cleaning method shown in FIG.
Using the two cleaning tanks (21, 21 ′) filled with the cleaning liquid (SC-1) used in Example 1, the silicon wafer as the object to be cleaned 23 was placed in the first cleaning tank 21. After ultrasonic cleaning at high output a (900 W) for 3 minutes, ultrasonic cleaning was performed at low output b (300 W) for 3 minutes in the second cleaning tank 21 ′.
An observation view of the cleaned silicon wafer is shown in FIG. It was confirmed that the number of LPD (≧ 41 nm) was as small as 57, the particle removal ability was improved, and cleaning unevenness was suppressed.
（実施例３）
　鏡面研磨後の直径３００ｍｍのシリコンウェーハを以下のように洗浄した。
　上記シリコンウェーハをオゾン水で洗浄し、次いで図１の超音波洗浄装置を用いて超音波洗浄を行った。
　尚、超音波洗浄における超音波振動子１４は実施例１、２、比較例１、２とは形状と配置が異なるものを用いた。超音波洗浄における洗浄液１２はアンモニア、過酸化水素水、水の混合液（ＳＣ－１）とし（混合比　１：１：１０）、洗浄液温度を５０℃とした。超音波振動子１４から発生する超音波の周波数は１ＭＨｚ（メガソニック）とした。
　被洗浄物１３である上記シリコンウェーハを上記洗浄槽１１中の洗浄液１２に浸漬し、６分間の洗浄時間で超音波出力を１分間ずつ高出力ｃ（１０００Ｗ）→低出力ｄ（４００Ｗ）→高出力ｃ（１０００Ｗ）→低出力ｄ（４００Ｗ）→高出力ｃ（１０００Ｗ）→低出力ｄ（４００Ｗ）と段階的に変更して洗浄した。
　その後、リンス（超音波洗浄なし）、乾燥をしたシリコンウェーハをパーティクルカウンターによって観察した。洗浄後の観察図を図７に示す。ＬＰＤ（≧４１ｎｍ）は５８個と少なく、パーティクル除去能力が改善し、洗浄ムラが抑制されたことがわかる。
　 (Example 3)
The 300 mm diameter silicon wafer after mirror polishing was washed as follows.
The silicon wafer was cleaned with ozone water, and then ultrasonic cleaning was performed using the ultrasonic cleaning apparatus of FIG.
In addition, the ultrasonic transducer | vibrator 14 in ultrasonic cleaning used what differs in a shape and arrangement | positioning from Examples 1, 2 and Comparative Examples 1 and 2. The cleaning liquid 12 in the ultrasonic cleaning was a mixed liquid (SC-1) of ammonia, hydrogen peroxide and water (mixing ratio 1: 1: 10), and the cleaning liquid temperature was 50 ° C. The frequency of the ultrasonic wave generated from the ultrasonic vibrator 14 was 1 MHz (megasonic).
The silicon wafer as the object to be cleaned 13 is immersed in the cleaning liquid 12 in the cleaning tank 11, and the ultrasonic output is high output c (1000 W) → low output d (400 W) → high for 1 minute every 6 minutes. Washing was performed by changing the output c (1000 W) → low output d (400 W) → high output c (1000 W) → low output d (400 W) step by step.
Thereafter, the rinsed (no ultrasonic cleaning) and dried silicon wafers were observed with a particle counter. FIG. 7 shows an observation view after washing. The number of LPD (≧ 41 nm) is as small as 58, and it can be seen that the particle removing ability is improved and the cleaning unevenness is suppressed.
（比較例３）
　実施例３におけるＳＣ－１による超音波洗浄工程を、超音波の出力を高出力ｃ（１０００Ｗ）、洗浄時間を６分間とした以外は上記実施例３と同様の条件でシリコンウェーハの洗浄を行った。
　洗浄後のシリコンウェーハの観察図を図８に示す。超音波振動子に起因すると見られる洗浄ムラが発生し、ＬＰＤ（≧４１ｎｍ）は６８１４個と非常に多かった。
　 (Comparative Example 3)
In the ultrasonic cleaning process by SC-1 in Example 3, the silicon wafer was cleaned under the same conditions as in Example 3 except that the ultrasonic output was high output c (1000 W) and the cleaning time was 6 minutes. It was.
An observation view of the cleaned silicon wafer is shown in FIG. The cleaning unevenness which seems to be caused by the ultrasonic vibrator occurred, and the number of LPD (≧ 41 nm) was 6814, which was very large.
（比較例４）
　実施例３におけるＳＣ－１による超音波洗浄工程を、超音波の出力を低出力ｄ（４００Ｗ）、洗浄時間を６分間とした以外は上記実施例３と同様の条件でシリコンウェーハの洗浄を行った。
　洗浄後のシリコンウェーハの観察図を図９に示す。ＬＰＤ（≧４１ｎｍ）は４５１個と多く見られた。 (Comparative Example 4)
In the ultrasonic cleaning process by SC-1 in Example 3, the silicon wafer was cleaned under the same conditions as in Example 3 except that the ultrasonic output was low output d (400 W) and the cleaning time was 6 minutes. It was.
An observation view of the silicon wafer after cleaning is shown in FIG. LPD (≧ 41 nm) was seen as many as 451.
　上記のように、超音波の出力を強くすると、ウェーハ外周下部から上部に向ってクシ状のパターンでパーティクルが除去できない部分が出てくる（比較例１、３）。一方、出力を弱くすると、全体的（特に、超音波振動子との距離が遠い領域）にパーティクル除去能力が弱くなることがわかる（比較例２、４）。
　一方、実施例のように、超音波振動子から発生する超音波による被洗浄物の洗浄を、少なくとも２以上の超音波出力条件で行うことによって、洗浄ムラの問題を解消することができるため、パーティクルの除去を効果的に行うことができる。 As described above, when the output of the ultrasonic wave is increased, a portion in which particles cannot be removed in a comb-like pattern appears from the lower periphery of the wafer toward the upper portion (Comparative Examples 1 and 3). On the other hand, it can be seen that when the output is weakened, the particle removal capability is weakened as a whole (particularly, a region far from the ultrasonic transducer) (Comparative Examples 2 and 4).
On the other hand, as in the embodiment, the problem of uneven cleaning can be solved by performing cleaning of an object to be cleaned with ultrasonic waves generated from an ultrasonic vibrator under at least two ultrasonic output conditions. Particles can be effectively removed.
　なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に含有される。 The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. It is contained in the technical range.

Claims (5)

  1. 　少なくとも、洗浄槽中の洗浄液に被洗浄物を浸漬し、超音波振動子から発生する超音波を前記洗浄槽中の洗浄液に伝播させて前記被洗浄物を洗浄する超音波洗浄方法であって、
    　前記超音波振動子から発生する超音波による被洗浄物の洗浄を、少なくとも２以上の超音波出力条件で行うことを特徴とする超音波洗浄方法。
    　     At least, an ultrasonic cleaning method for cleaning the object to be cleaned by immersing the object to be cleaned in a cleaning liquid in a cleaning tank and propagating ultrasonic waves generated from an ultrasonic vibrator to the cleaning liquid in the cleaning tank,
    An ultrasonic cleaning method, wherein cleaning of an object to be cleaned with ultrasonic waves generated from the ultrasonic vibrator is performed under at least two ultrasonic output conditions.
  2. 　前記少なくとも２以上の超音波出力条件で行う洗浄を、前記超音波振動子から発生する超音波の出力を、前記被洗浄物の洗浄中に連続的又は段階的に変化させることにより行うことを特徴とする請求項１に記載の超音波洗浄方法。
    　     The cleaning performed under the ultrasonic output conditions of at least two or more is performed by changing the output of the ultrasonic wave generated from the ultrasonic vibrator continuously or stepwise during the cleaning of the object to be cleaned. The ultrasonic cleaning method according to claim 1.
  3. 　前記少なくとも２以上の超音波出力条件で行う洗浄を、前記被洗浄物を、洗浄槽間で超音波出力条件が異なる複数の前記洗浄槽中の洗浄液に順次浸漬することにより行うことを特徴とする請求項１又は請求項２に記載の超音波洗浄方法。
    　     Cleaning performed under the at least two or more ultrasonic output conditions is performed by sequentially immersing the object to be cleaned in a plurality of cleaning liquids in the cleaning tanks having different ultrasonic output conditions between the cleaning tanks. The ultrasonic cleaning method according to claim 1 or 2.
  4. 　前記洗浄液を、アンモニア、過酸化水素水、及び水の混合溶液とすることを特徴とする請求項１乃至請求項３のいずれか一項に記載の超音波洗浄方法。
    　     The ultrasonic cleaning method according to any one of claims 1 to 3, wherein the cleaning liquid is a mixed solution of ammonia, hydrogen peroxide water, and water.
  5. 　前記超音波振動子から発生する超音波を、超音波伝播水を満たした超音波伝播槽を介して前記洗浄槽中の洗浄液に伝播させることを特徴とする請求項１乃至請求項４のいずれか一項に記載の超音波洗浄方法。
     
          The ultrasonic wave generated from the ultrasonic transducer is propagated to the cleaning liquid in the cleaning tank through an ultrasonic wave propagation tank filled with ultrasonic propagation water. The ultrasonic cleaning method according to one item.

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