JP2012212803A - Plasma processing method and plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide film removal method capable of removing an oxide film at a high speed by irradiating an oxide film formed on an object to be treated with hydrogen radical of larger than a required amount for separating oxygen atoms included in an oxide film, and eliminating damage to the object to be treated or the like by adjusting temperatures of plasma containing the hydrogen radical.SOLUTION: A coating formed by bonding atoms of a surface of an object to be treated with at least one type of oxygen atoms, nitrogen atoms, or sulfur atoms is irradiated with plasma generated by applying a voltage to plasma generation gas to remove the oxygen atoms, nitrogen atoms, or sulfur atoms contained in the coating.

Description

  The present invention relates to a plasma processing method and a plasma processing apparatus.

  In recent years, with the miniaturization of electronic products, there is an increasing demand for miniaturization of parts. In order to cope with this, the influence of the surface condition of the parts on the quality of the product has been taken into consideration, and an ultra-precise cleaning technique is required. A film is formed on the surface of an object to be processed such as an electronic component by bonding atoms of the surface portion to at least one of oxygen atom, nitrogen atom and sulfur atom.

  In Patent Document 1, in order to remove the oxide film formed on the surface of the aluminum or copper metal electrode before wire bonding, a plasma generating gas containing 0.5 to 50% by volume of hydrogen is supplied, An oxide film is irradiated with plasma generated by applying a pulsed electric field to a plasma source having a fixed dielectric disposed on at least one opposing surface of a pair of counter electrodes, such as aluminum or copper. Has been removed.

  In addition to this, the plasma generated by using a plasma generating gas containing hydrogen gas is irradiated to the oxide film formed on the surface of the solder, thereby using the hydrogen plasma generated in the plasma. A method for removing an oxide film that reduces the oxide film is described (Patent Document 2).

JP 2002-151543 A JP 2008-041980 A

However, in Patent Document 1, when the hydrogen gas exceeds 50% by volume, the explosion limit at the time of atmospheric release is exceeded, so the amount of hydrogen gas added is limited to 0.5 to 50% by volume and is generated. The concentration of hydrogen radicals in the plasma cannot be made a certain amount or more.
Further, since the dielectric is provided in the plasma source, the power applied to the plasma generating gas is weakened, and the power of the generated plasma is weakened. Further, since power is applied to the plasma source by the pulsed electric field, the time average input power to the plasma generating gas is reduced. As a result, there are problems that the number of hydrogen atoms and / or hydrogen molecules to be radicalized is reduced, the concentration of hydrogen radicals contained in the generated plasma is reduced, and the processing time is increased.

  Further, in the method of removing a film according to Patent Document 2, in order to promote the reduction action of the oxide film by hydrogen plasma, the object to be processed is heated to a temperature higher than normal temperature and lower than the melting point of solder, for example, about Heated to 150 ° C. Such heating does not damage the solder, but if the oxide film is removed while the component is placed on the electronic board, it will damage the resin plate and other parts used on the board. Therefore, when the object to be processed is a component on the substrate, it cannot be heated, and there is a problem that the processing time becomes long.

  Furthermore, when the power applied to the plasma is increased to increase the concentration of hydrogen radicals in the plasma, the temperature of the plasma generated with the increase in power increases, and not only the oxide film is removed but also the object to be processed. Further, there is a problem that damage is given to the substrate on which the object and the object to be processed are placed.

  Therefore, in the present invention, a plasma generating gas is applied to a coating formed by bonding atoms on the surface of an object to be processed such as metal or alloy with at least one of oxygen atom, nitrogen atom and sulfur atom. Plasma processing method and plasma processing apparatus capable of irradiating plasma generated by electrical discharge to remove the coating at high speed and preventing damage to the object to be processed by plasma heat during plasma processing The purpose is to provide.

  In order to achieve the above object, the plasma processing method according to the first aspect of the present invention is formed by combining atoms on the surface of an object to be processed with at least one of oxygen atoms, nitrogen atoms and sulfur atoms. A plasma processing method for removing the oxygen atoms, nitrogen atoms or sulfur atoms in the coating by irradiating the coating with plasma generated by discharging to a plasma generating gas, wherein the plasma is the plasma The radical generated from the substance contained in the generating gas and the plasma generating gas itself, and the radical generated from the substance contained in the plasma generating gas includes the oxygen atom and nitrogen contained in the coating film. At least hydrogen radicals capable of separating atoms or sulfur atoms from the object to be treated, and the removal of the film is performed by removing the film to be removed. Characterized contains all of the oxygen atoms, the oxygen atom of the amount or more of the hydrogen radicals required for separating nitrogen atom or a sulfur atom, to make in contact with the nitrogen atom or sulfur atom in the.

  According to the plasma processing method of the first aspect of the present invention, sufficient to separate all oxygen atoms, nitrogen atoms or sulfur atoms contained in the coating film to be removed from the coating film to be removed. Since an amount of hydrogen radicals can be brought into contact with the coating, it is possible to efficiently separate oxygen atoms, nitrogen atoms or sulfur atoms contained in the coating from the coating, and the coating is removed from the object to be processed at high speed. Realize that.

  In the plasma processing method of the second aspect of the present invention, the separation of the oxygen atom, nitrogen atom or sulfur atom by the hydrogen radical is carried out by the collision of the hydrogen radical with the coating film and the oxygen atom, nitrogen atom or Separation by ejecting sulfur atoms and / or separation by reducing the film by a chemical reaction between the hydrogen radical and the oxygen atom, nitrogen atom or sulfur atom.

  According to the plasma processing method of the second aspect of the present invention, oxygen atoms, nitrogen atoms or sulfur atoms can be physically and chemically separated from the film by hydrogen radicals. It is possible to remove the coating from the object at high speed.

  In the plasma processing method of the third aspect of the present invention, the amount of the hydrogen radicals controls the concentration of hydrogen atoms and hydrogen molecules in the plasma generating gas and the voltage value applied to the plasma generating gas. It is characterized by adjusting by doing.

  According to the plasma processing method of the third aspect of the present invention, the amount of hydrogen radicals can always be adjusted according to the state of the film to be removed. Can be removed.

  The plasma processing method of the fourth aspect of the present invention is characterized in that the plasma is adjusted to a predetermined temperature by controlling the temperature of the plasma generating gas.

  According to the plasma processing method of the fourth aspect of the present invention as described above, the plasma temperature is set at, for example, a temperature that does not cause thermal damage to the object to be processed, or a substrate on which the object to be processed is disposed. By adjusting the temperature so as not to cause thermal damage, it is possible to prevent damage to the object to be processed or the substrate from being damaged due to heat of the plasma when the object is irradiated with plasma. .

  The plasma processing method of the fifth aspect of the present invention is characterized in that the temperature of the plasma is adjusted to a temperature that does not damage the object to be processed.

  According to the plasma processing method of the fifth aspect of the present invention, it is possible to remove the coating film from the processing object at high speed without causing thermal damage to the processing object.

  The plasma processing method of the sixth aspect of the present invention is characterized in that the plasma is generated by applying a high frequency voltage to the plasma generating gas.

  According to the plasma processing method of the sixth aspect of the present invention, since the time average input power can be increased, a large amount of radicals generated from the substance contained in the plasma generating gas are generated. can do. As a result, the plasma having a high concentration of hydrogen radicals can be used to remove the coating from the object to be processed at high speed.

  The plasma processing method of the seventh aspect of the present invention is characterized in that the plasma generating gas is hydrogen gas.

  According to the plasma processing method of the seventh aspect of the present invention, since the radicals generated from the substance contained in the plasma generating gas in the plasma can be only hydrogen radicals, the concentration of hydrogen radicals By using high plasma, it is possible to remove the coating film from the object to be processed at high speed.

  In the plasma processing method of the eighth aspect of the present invention, the plasma generating gas is a base gas selected from at least one of argon gas, helium gas, nitrogen gas and air, hydrogen gas, methane gas and ethane gas. It is a mixed gas with at least one additive gas selected from the above.

  According to the plasma processing method of the eighth aspect of the present invention, hydrogen atoms and / or hydrogen contained in the additive gas are generated by the plasma-generated base gas by using the plasma generating gas as a mixed gas. Since it can be radicalized by applying energy to the molecule, it can be a plasma containing a high concentration of hydrogen radicals, and the life of the hydrogen radicals can be kept long, so that the plasma contains a lot of hydrogen radicals. Can be removed from the workpiece at high speed.

  The plasma processing method of the ninth aspect of the present invention is characterized in that the object to be processed is a metal.

  According to the plasma processing method of the ninth aspect of the present invention, the oxygen film, nitride film or sulfide film formed on the metal can be removed at high speed.

  In the plasma processing method according to the tenth aspect of the present invention, the object to be processed is placed or the object to be processed is disposed on the downstream side of the object to be processed in the plasma irradiation direction with respect to the object to be processed. A base on which a member to be mounted is placed, and applying a bias voltage to the electrode for applying a voltage to the plasma generating gas and applying a bias voltage to the base, the energy is applied to the plasma, and the hydrogen radical Is induced in the coating.

  According to the plasma processing method of the tenth aspect of the present invention, energy is applied to the plasma generated in the space between the electrode and the base by the bias voltage, so that it reaches the object to be processed after being ejected. It is possible to prevent the loss of hydrogen radical activity during the time period until Further, since hydrogen radicals are induced to the object to be processed, it is possible to prevent the hydrogen radicals after irradiation from diffusing. By these actions, hydrogen radicals can be efficiently brought into contact with the film, so that the film can be removed from the object to be processed at high speed.

  The plasma processing apparatus according to the first aspect of the present invention includes a plasma source that uses the plasma generating gas as plasma, a plasma generating gas temperature control unit that adjusts the temperature of the plasma generating gas supplied to the plasma source, A plasma generation gas temperature measurement unit for measuring the temperature of the plasma generation gas supplied to the plasma source; and a plasma temperature measurement unit for measuring the temperature of the plasma ejected from the plasma source. The temperature of the plasma generation gas is controlled by feeding back the measured plasma temperature to the plasma generation gas temperature control unit.

  According to the plasma processing apparatus of the first aspect of the present invention, when the plasma generating gas containing hydrogen gas is supplied to the plasma source, the coating is removed at high speed by the hydrogen radicals contained in the generated plasma. Furthermore, the temperature of the plasma can be set to a desired temperature, for example, to prevent the occurrence of thermal damage to a substrate made of a processing object and a resin material on which the processing object is placed. The film can be removed from the object to be processed at high speed.

  In the plasma processing apparatus according to the second aspect of the present invention, the plasma source is provided with a pair of counter electrodes, and in the irradiation direction in which the plasma is irradiated from the plasma source to the object to be processed. A base on which the object to be processed or a member on which the object to be processed is mounted is disposed on the downstream side of the object to be processed, one electrode of the pair of counter electrodes, and the base A power supply for applying a bias voltage is provided, and a potential difference is provided between the plasma source and the base by applying the bias voltage.

  According to the plasma processing apparatus of the second aspect of the present invention, energy can be applied from the bias voltage to the plasma generated in the space between the electrode and the base. Further, by providing a potential difference between the plasma source and the base, hydrogen radicals can be induced to the object to be processed. As a result, hydrogen radicals can be efficiently brought into contact with the film, and the film can be removed from the object to be processed at high speed.

  According to the plasma processing method and the plasma processing apparatus of the present invention, the film formed on the surface of the object to be processed can be removed at a high speed, and the object to be processed is processed without being damaged by the heat of the plasma. be able to.

  More specifically, according to the plasma processing method of the present invention, the film to be removed is removed from the film formed by bonding atoms on the surface of the workpiece with oxygen atoms, nitrogen atoms and sulfur atoms. Irradiate more hydrogen radicals than necessary to separate all oxygen, nitrogen or sulfur atoms contained in the film, so there is no shortage of oxygen, nitrogen or sulfur atoms in the coating to be removed. Hydrogen radicals are bonded and separated from the film, and the film can be removed from the object to be processed at high speed.

  Further, by adjusting the temperature of the plasma to a predetermined temperature, it is possible to prevent the occurrence of thermal damage to the workpiece and the substrate on which the workpiece is placed. For example, on the substrate made of a resin material When removing the film formed on the object to be processed made of the arranged metal, it is possible to remove the film by irradiating the plasma while the object to be processed is disposed on the substrate. .

  Furthermore, by applying a bias voltage to the electrode and the base of the plasma source, the active state of the hydrogen radical can be maintained for a long time, and a potential difference is provided between the plasma source and the base so that at least the hydrogen radical is generated. Since it can be guided to the object to be processed, it is possible to remove the film from the object to be processed at high speed by effectively bringing hydrogen radicals into contact with the film.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic explanatory drawing of isolation | separation of the oxygen atom by the plasma processing method of this invention, Comprising: (a) is an image figure of the crystal structure of copper (II) oxide (b) is an image figure (c) where oxygen atoms are repelled by a hydrogen radical, Image of oxygen atoms being reduced by hydrogen radicals Graph showing the relationship between the amount of power applied per unit volume and the density of each gas in the plasma The block diagram which shows the schematic of the plasma processing apparatus of this invention The block diagram which shows one Embodiment of the plasma temperature control apparatus of this invention Schematic sectional view showing a bias voltage application method of the plasma processing apparatus of the present invention Schematic sectional view showing another aspect of the bias voltage application method of the plasma processing apparatus of the present invention

  Hereinafter, detailed embodiments of the plasma processing method and the plasma processing apparatus of the present invention will be described with reference to FIGS.

  In the plasma processing method of the present invention, for example, the atoms on the surface of an object made of a metal or alloy such as copper, iron, tin, lead and solder are at least one kind such as oxygen atom, nitrogen atom and sulfur atom. Then, the plasma generated by discharging to the plasma generating gas is irradiated to the film made of oxide, nitride or sulfide formed by bonding with atoms forming a compound by combining with metal or alloy. And removing the film. At this time, the plasma includes radicals generated from substances contained in the plasma generation gas and the plasma generation gas itself.

The radicals generated from the substance contained in the plasma generating gas include one hydrogen atom H ^* and / or one hydrogen atom that can separate oxygen atoms, nitrogen atoms, sulfur atoms, and the like from the object to be processed. At least a hydrogen radical H ₂ ^* consisting of the following hydrogen molecules.

Specifically, a hydrogen radical consisting of one hydrogen atom in a radical generated from a substance (hydrogen) contained in hydrogen gas, which is a generated plasma generating gas, by using only hydrogen gas as the plasma generating gas. A hydrogen radical H ₂ ^* consisting of H ^* and / or one hydrogen molecule is included.

Further, the plasma generation gas is generated as a mixed gas of a base gas such as argon gas, helium gas, nitrogen gas and air and an additive gas containing hydrogen atoms such as hydrogen gas, methane gas and ethane gas. The radicals generated from the substance contained in the plasma generating gas may include hydrogen radicals H ^* consisting of one hydrogen atom and / or hydrogen radicals H ₂ ^* consisting of one hydrogen molecule. The gas selected as the additive gas may be any gas as long as it contains hydrogen atoms.

<Method of removing the film with hydrogen radicals>
In the removal of the coating film in the plasma processing method of the present invention, oxygen radicals, nitrogen atoms or sulfur atoms contained in the coating film to be removed are brought into contact with an amount of hydrogen radicals more than necessary to separate them. The oxygen atom, nitrogen atom or sulfur atom is removed from the object to be treated.

  Here, the form of separation will be described in detail with reference to FIG. 1 when the object to be treated is a copper plate and the atoms that form a film by bonding with copper atoms on the surface of the copper plate are oxygen atoms.

  As shown in FIG. 1A, copper oxide (II) has a monoclinic crystal structure in which oxygen atoms have entered the voids between copper atoms. In FIG. 1 (a), the oxygen atom is shown larger than the copper atom so as to pay attention to the oxygen atom, but actually, the atomic radius of the copper atom is larger than the atomic radius of the oxygen atom. Is also considered to be large.

First, the form of separation of oxygen atoms from copper oxide (II) of the first embodiment is such that, as shown in FIG. 1 (b), hydrogen radicals collide with copper atoms and / or oxygen atoms to produce crystals. Oxygen atoms are separated from the structure and separated. Further, the hydrogen radical is very active, and two hydrogen radicals H ^* or one hydrogen radical H ₂ ^{* (} not shown) actively undergoes chemical reaction with respect to one separated oxygen atom. By waking up, water molecules are generated. In FIG. 1B, the inner I layer is an object layer made of copper atoms only, and the outer II layer is a copper oxide coating layer made of copper atoms and oxygen atoms.

  In addition, as shown in FIG. 1C, the form of separation of oxygen atoms from copper oxide (II) of the second embodiment is such that hydrogen radicals penetrate into the crystal lattice of copper oxide, and copper atoms and oxygen atoms To form an incommensurate state of the intermediate and combine with oxygen atoms to form OH. Further, hydrogen radicals cause a chemical reaction with this OH to generate water molecules, and oxygen atoms are separated by reducing copper oxide.

<Calculation of the number of necessary hydrogen radicals in an ideal state>
Specifically, the number of hydrogen radicals required for the separation is calculated. For example, the number of hydrogen radicals necessary for separating all oxygen atoms contained in the coating per 1 mm vertical x 1 mm wide x 1 nm thick is calculated. The density of copper (II) oxide is 6.31 g / cm ³ , the molar mass is 79.55 g / mol, and the Avogadro number is 6.02 × 10 ²³ .

で求めることができ、Ｘ＝２．３９×１０^１３個となる。この時、分離された酸素原子が全て水分子とされる反応は、２Ｈ＋Ｏ→Ｈ_２Ｏであるので、Ｘ＝２．３９×１０^１３個の酸素原子を全て水分子とするために必要な水素ラジカルの個数Ｙは、Ｙ＝２Ｘで求めることができ、Ｙ＝４．７８×１０^１３個となる。 The number X of oxygen atoms contained in 1 mm × 1 mm × 1 nm copper oxide is:

And X = 2.39 × 10 ¹³ pieces. At this time, since the reaction in which all the separated oxygen atoms are converted into water molecules is 2H + O → H ₂ O, X = 2.39 × 10 ¹³ hydrogen atoms necessary to make all the oxygen atoms into water molecules. The number Y of radicals can be determined by Y = 2X, and is Y = 4.78 × 10 ¹³ .

Accordingly, by bringing at least 4.78 × 10 ¹³ hydrogen radicals into contact with the film with respect to oxygen atoms contained in 1 mm × 1 mm × 1 nm of copper (II) oxide, oxygen in copper (II) oxide All atoms can be separated as water molecules.

Similarly, the number of hydrogen radicals required to separate iron oxide (II) formed on the surface is calculated using a pure iron plate as the object to be processed. In addition, the density of iron (II) is 5.24 g / cm ³ , the molar mass is 159.69 g / mol, and the Avogadro number is 6.02 × 10 ²³ .

で求めることができ、Ｘ＝１．１９×１０^１３個となる。この時、分離された酸素原子が全て水分子とされる反応は、２Ｈ＋Ｏ→Ｈ２Ｏであるので、Ｘ＝１．１９×１０^１３個の酸素原子を全て水分子とするために必要な水素ラジカルの個数Ｙは、Ｙ＝２Ｘで求めることができ、Ｙ＝２．３７×１０^１３個となる。 The number X of oxygen atoms contained in the coating of iron (II) per 1 mm vertical x 1 mm wide x 1 nm thick is:

And X = 1.19 × 10 ¹³ pieces. At this time, since the reaction in which all the separated oxygen atoms are converted into water molecules is 2H + O → H2O, X = 1.19 × 10 ¹³ of hydrogen radicals necessary to make all the oxygen atoms into water molecules. The number Y can be obtained by Y = 2X, and Y = 2.37 × 10 ¹³ .

That is, by bringing at least 2.37 × 10 ¹³ hydrogen radicals into contact with the film against oxygen atoms contained in 1 mm × 1 mm × 1 nm iron (II), oxygen in iron (II) oxide All atoms can be separated as water molecules.

Further, the number of hydrogen radicals necessary for separating the oxide film formed on the surface is calculated by using the object to be processed as solder. The solder is composed of 96.5% tin, 3% silver, and 0.5% copper, the density is 7.4 g / cm ³ , the molar mass is 118.11 g / mol, and the Avogadro number is 6.02 ×. 10 ²³ .

で求めることができ、Ｘ_Ｓｎ＝１．５７×１０^１３個、Ｘ_Ａｇ＝３．２４×１０^１１個およびＸ_Ｃｕ＝８．１１×１０^１０個となる。この時、分離された酸素原子が全て水分子とされる反応は、２Ｈ＋Ｏ→Ｈ２Ｏであるので、Ｘ_Ｓｎ＝１．５７×１０^１３個、Ｘ_Ａｇ＝３．２４×１０^１１個およびＸ_Ｃｕ＝８．１１×１０^１０個の酸素原子を全て水分子とするために必要な水素ラジカルの個数Ｙ_Ｓｎ、Ｙ_ＡｇおよびＹ_Ｃｕは、Ｙ_{（Ｓｎ、Ａｇ、Ｃｕ）}＝２Ｘ_{（Ｓｎ、Ａｇ、Ｃｕ）}で求めることができ、それぞれＹ_Ｓｎ＝３．１３×１０^１３個、Ｙ_Ａｇ＝６．４９×１０^１１個およびＹ_Ｃｕ＝１．６２×１０^１１個となる。 Assuming that the film per 1 mm x 1 mm x 1 nm thickness formed on the solder is a complete crystal, 96.5% is tin oxide, 3% is silver oxide, and 0.5% is copper oxide. The number of oxygen atoms X _Sn , X _Ag and X _Cu contained in each oxide is:

X _Sn = 1.57 × 10 ¹³ pieces, X _Ag = 3.24 × 10 ¹¹ pieces and X _Cu = 8.11 × 10 ¹⁰ pieces. At this time, since the reaction in which all the separated oxygen atoms are converted into water molecules is 2H + O → H 2 O, X _Sn = 1.57 × 10 ¹³ , X _Ag = 3.24 × 10 ¹¹ and X _Cu = 8.11 × 10 ^{10 The} number of hydrogen radicals Y _Sn , Y _Ag, and Y _Cu required to make all ¹⁰ oxygen atoms water molecules are Y _{(Sn, Ag, Cu)} = 2X _{(Sn, Ag, Cu ) And} Y _Sn = 3.13 × 10 ¹³ , Y _Ag = 6.49 × 10 ¹¹ and Y _Cu = 1.62 × 10 ¹¹ respectively.

Therefore, with respect to the oxygen atoms contained in the 1 mm × 1 mm × 1 nm oxide film formed on the solder, at least 2.84 × 10 ¹³ hydrogen radicals, which is the total of Y _Sn , Y _Ag, and Y _Cu , are used as the coating. By contacting, all the oxygen atoms in the oxide film can be separated as water molecules.

Calculate the number of hydrogen radicals necessary to separate the aluminum nitride formed on the surface when the object to be processed is aluminum and the atoms that form a film by bonding with aluminum atoms on the surface are nitrogen atoms. To do. The density of aluminum nitride is 3.26 g / cm ³ , the molar mass is 40.99 g / mol, and the Avogadro number is 6.02 × 10 ²³ .

で求めることができ、Ｘ＝２．３９×１０^１３個となる。この時、分離された窒素原子が全てアンモニアとされる反応は、Ｎ＋３Ｈ→ＮＨ_３であるので、Ｘ＝２．３９×１０^１３個の窒素原子を全てアンモニアとするために必要な水素ラジカルの個数Ｙは、Ｙ＝３Ｘで求めることができ、Ｙ＝７．１８×１０^１３個となる。 The number X of nitrogen atoms contained in the film of aluminum nitride per 1 mm vertical x 1 mm wide x 1 nm thick is:

And X = 2.39 × 10 ¹³ pieces. At this time, since the reaction in which all the separated nitrogen atoms are converted to ammonia is N + 3H → NH ₃ , the number of hydrogen radicals necessary to make all X = 2.39 × 10 ¹³ nitrogen atoms ammonia. Y can be obtained by Y = 3X, and Y = 7.18 × 10 ¹³ pieces.

That is, at least 7.18 × 10 ¹³ hydrogen radicals are brought into contact with the coating with respect to nitrogen atoms contained in 1 mm × 1 mm × 1 nm aluminum nitride, thereby separating all nitrogen atoms in aluminum nitride as ammonia. can do.

In addition, the number of hydrogen radicals required to separate the copper sulfide formed on the surface when the workpiece is a copper plate and the atoms that form a film by bonding with copper atoms on the surface of the copper plate are sulfur atoms. Is calculated. The density of copper sulfide is 5.6 g / cm ³ , the molar mass is 159.16 g / mol, and the Avogadro number is 6.02 × 10 ²³ .

で求めることができ、Ｘ＝７．０６×１０^１２個となる。この時、分離された硫黄原子が全て硫化水素とされる反応は、Ｓ＋２Ｈ→Ｈ_２Ｓであるので、Ｘ＝７．０６×１０^１２個の硫黄原子を全て硫化水素とするために必要な水素ラジカルの個数Ｙは、Ｙ＝２Ｘで求めることができ、Ｙ＝１．４１×１０^１３個となる。 The number X of sulfur atoms contained in the copper sulfide coating per 1 mm vertical x 1 mm wide x 1 nm thick is:

X = 7.06 × 10 ¹² pieces. At this time, the reaction in which all of the separated sulfur atoms are converted to hydrogen sulfide is S + 2H → H ₂ S, and therefore X = 7.06 × 10 ¹² hydrogen atoms necessary to convert all ¹² sulfur atoms to hydrogen sulfide. The number Y of radicals can be obtained by Y = 2X, and is Y = 1.41 × 10 ¹³ .

That is, at least 1.41 × 10 ¹³ hydrogen radicals are brought into contact with the film with respect to sulfur atoms contained in 1 mm × 1 mm × 1 nm copper sulfide, so that all sulfur atoms in copper sulfide are converted into hydrogen sulfide. Can be separated.

Similarly, the object to be treated is a pure iron plate, and the number of hydrogen radicals necessary for separating the iron sulfide formed on the surface is calculated. The density of iron sulfide is 4.84 g / cm ³ , the molar mass is 87.911 g / mol, and the Avogadro number is 6.02 × 10 ²³ .

で求めることができ、Ｘ＝１．７２×１０^１３個となる。この時、分離された硫黄原子が全て硫化水素とされる反応は、Ｓ＋２Ｈ→Ｈ_２Ｓであるので、Ｘ＝１．７２×１０^１３個の硫黄原子を全て硫化水素とするために必要な水素ラジカルの個数Ｙは、Ｙ＝２Ｘで求めることができ、Ｙ＝３．４３×１０^１３個となる。 The number X of sulfur atoms contained in the iron sulfide coating per 1 mm vertical x 1 mm wide x 1 nm thick is:

And X = 1.72 × 10 ¹³ pieces. At this time, since the reaction in which all separated sulfur atoms are converted to hydrogen sulfide is S + 2H → H ₂ S, X = 1.72 × 10 ¹³ hydrogen atoms required to convert all ¹³ sulfur atoms to hydrogen sulfide. The number Y of radicals can be obtained by Y = 2X, and is Y = 3.43 × 10 ¹³ .

That is, by bringing at least 3.43 × 10 ¹³ hydrogen radicals into contact with the film against sulfur atoms contained in 1 mm × 1 mm × 1 nm iron sulfide, all the sulfur atoms in iron sulfide are converted into hydrogen sulfide. Can be separated.

  As described above, the amount (number) of hydrogen radicals required by the coating is different, and the method for adjusting the amount of hydrogen radicals will be described in detail below with reference to FIGS.

のように電離し、この時のそれぞれの物質の存在数の関係は、以下であると考えられる。

For example, when a voltage is applied to a plasma generating gas composed of a mixed gas of argon gas as a base gas and hydrogen gas as an additive gas

The relationship between the number of each substance present at this time is considered to be as follows.

That is, by increasing the concentration of hydrogen gas in the plasma generating gas, the amount of hydrogen atoms and hydrogen molecules in the plasma generating gas is increased, and one hydrogen atom contained in the resulting plasma is generated. The amount of hydrogen radicals H ^* consisting of and / or hydrogen radicals H ₂ ^* consisting of one hydrogen molecule can be increased.

Further, the amount of hydrogen radical H ^* consisting of one hydrogen atom and / or hydrogen radical H ₂ ^* consisting of one hydrogen molecule contained in the plasma, that is, the density of all hydrogen radicals in the plasma is shown in FIG. Thus, it increases in proportion to an increase in the amount of power applied per unit volume. This is because the ratio of hydrogen electrons and hydrogen molecules ionized or excited is increased by increasing the power applied to the plasma generating gas.

  Furthermore, since the plasma based on the components of the base gas exists in the entire plasma, the base gas plasma can be an energy source for maintaining the radical state of the hydrogen radical, and the lifetime of the hydrogen radical can be extended. Therefore, hydrogen radicals can be brought into contact with the coating at a high concentration even in a portion away from the plasma source.

<Method for adjusting the amount of hydrogen radicals>
In the plasma processing method of the present invention, hydrogen in a plasma generating gas supplied to a plasma source having a plasma generating gas as plasma in order to adjust the amount (number) of hydrogen radicals brought into contact with the film. The concentration of atoms and hydrogen molecules and the voltage value applied to the plasma source are controlled.

  Specifically, when increasing the amount of hydrogen radicals, for example, when supplying a mixed gas of argon gas as a base gas and hydrogen gas as an additive gas to a plasma source at 10 L / min, the hydrogen gas And the argon gas flow rate is decreased by the increased amount to increase the proportion of hydrogen gas in the mixed gas to increase the existence ratio of hydrogen atoms and hydrogen molecules as hydrogen radicals.

Furthermore, the amount of hydrogen radicals is increased by increasing the amount of hydrogen atoms and hydrogen molecules that are ionized or excited by increasing the amount of power from DC to AC, high frequency, and microwave power sources that input power to the plasma source. Increase. In particular, a high-frequency power source is preferably used as a power source for inputting power to the plasma source, and a power amount of 60 to 240 W / cm ³ with respect to the volume in the plasma generation chamber for generating a plasma with a frequency of 20 kHz or higher. It is most preferable to input so that

The control of the hydrogen gas concentration in the plasma generating gas and the voltage value of the high frequency voltage applied to the plasma source by the high frequency power source are appropriately performed according to the film to be removed, and an optimum plasma is applied to the film. Irradiation is performed to separate oxygen atoms, nitrogen atoms and sulfur atoms by hydrogen radicals. Specifically, the voltage applied so that the power input to the plasma source is about 120 W / cm ^{3 with} respect to the volume in the plasma generation chamber is controlled, and the plasma generation gas flowing into the plasma source is 10 L. Most preferably, it is about / min.

  As described above, the amount of hydrogen radicals can be adjusted by controlling the concentration of hydrogen atoms and hydrogen molecules in the plasma generating gas and the voltage value applied to the plasma generating gas. Hydrogen radicals can be brought into contact with oxygen atoms, nitrogen atoms and sulfur atoms without deficiency, and the coating can be removed from the object to be processed at high speed.

<Plasma temperature adjustment method and apparatus configuration>
As described above, when a large amount of electric power is applied to the plasma generating gas in order to increase the amount of hydrogen radicals in the plasma, the temperature of the plasma increases as the applied electric power increases.

  Therefore, in the plasma processing method of the present invention, the temperature of the plasma generating gas is controlled to control the plasma temperature to an arbitrary temperature.

  In the first embodiment of the plasma processing apparatus of the present invention, as shown in FIG. 3, a plasma generation gas supply unit 2, a plasma generation gas temperature control unit 3, a plasma source 4, a power source 5 and the like are provided. The temperature of the plasma is adjusted by controlling the temperature of the plasma generating gas supplied from the plasma generating gas supply unit 2 in the operating gas temperature control unit 3.

  More specifically, as shown in FIG. 4, the plasma generating gas is cooled using liquid nitrogen via a gas pipe 6 so as to reduce the temperature of the plasma, which becomes high when a large amount of power is input. Through the vessel 7, the plasma generating gas is introduced into the plasma source 4 in a state where the temperature is low. In this state, the temperature of the plasma generating gas is measured by the plasma generating gas temperature measuring unit 9 in the gas pipe 8 in front of the plasma source 4 and the temperature of the plasma is adjusted in the outlet 10 from which the plasma of the plasma source 4 is ejected. By measuring with the plasma temperature measuring unit 11 and feeding back the temperature of the plasma generating gas and the plasma temperature to the plasma generating gas temperature control unit 3 to control the temperature of the plasma generating gas appropriately. The plasma temperature is adjusted precisely.

  In particular, the plasma temperature is preferably set to a temperature that does not damage the workpiece. Specifically, by cooling the plasma generating gas to a low temperature of 0 ° C. or lower, for example, −70 ° C., and setting the plasma temperature at the injection port 10 to about 100 ° C., the temperature that contacts the object to be processed 12 is increased. The melting point is below the melting point of the workpiece.

  In this manner, by making the plasma temperature adjustable, it is possible to prevent the occurrence of thermal damage to the object to be processed 12 when performing the plasma processing. For example, the object to be processed 12 is made of a resin material. Even when plasma processing is performed in a state of being placed on a substrate having a low heat-resistant temperature such as a substrate, not only the object to be processed 12 but also a substrate having a low heat-resistant temperature such as a resin material is not thermally damaged. The coating film can be removed from the workpiece 12 at high speed while the workpiece 12 is placed on the substrate.

<Method and apparatus for strengthening / inducing hydrogen radicals>
Further, in the second embodiment of the plasma processing apparatus of the present invention, as shown in FIG. 5, in the direction of plasma irradiation from the plasma source 4 to the object 12 (downward direction in FIG. 5), the object 12 is processed. A base 13 on which the workpiece 12 is placed or a member on which the workpiece 12 is disposed is placed on the downstream side.

  At this time, the plasma source 4 is connected to a hollow housing 14, an insulating pipe 15 made of alumina fitted to the inner peripheral surface of the housing 14, and a distal end portion of the housing 14, thereby forming a jet port 10. And the other counter electrode 17 accommodated in the housing 14 and the one counter electrode 16. At this time, one counter electrode 16 and the other counter electrode 17 are a pair of counter electrodes.

  The plasma generating gas introduced from the plasma generating gas supply unit 2 to such a plasma source 4 is supplied to the discharge unit 19 after passing through the gas flow path 18 in the housing 14. Further, when a voltage is applied between one counter electrode 16 and the other counter electrode 17, it is uniform in a direction extending radially from the center of the spherical portion of the other counter electrode 17 (hereinafter referred to as the discharge direction). Discharge occurs. And it is ejected from the ejection port 10 as jet-like plasma.

  Further, a power source 5a for applying a voltage to the plasma generating gas is provided between one counter electrode 16 and the other counter electrode 17, and between one counter electrode 16 and the base 13, A power supply 5b for applying a bias voltage is provided.

  In the plasma processing method of the present invention using the second embodiment, a bias voltage is provided, for example, by applying a high-frequency voltage between one counter electrode 16 and the base 13 by the power source 5b. By applying energy to the plasma generated in the space between the two, it is possible to prevent the hydrogen radical activity from being lost after it is ejected until it reaches the object to be processed. Further, a potential difference is provided between one counter electrode 16 and the base 13 so that at least hydrogen radicals are directed toward the object 12 to be diffused after irradiation. Can be prevented. By these actions, hydrogen radicals can be efficiently brought into contact with the film, so that the film can be removed from the object to be processed at high speed.

  In this way, energy is given to the plasma generated in the space between the one counter electrode 16 and the other counter electrode 17 and the base 13 by the bias voltage by the bias voltage. Thus, it is possible to prevent the activity of hydrogen radicals from being lost until reaching to the object 12, so that plasma having a high concentration of hydrogen radicals can reach the workpiece 12.

  In addition, by providing a potential difference between the plasma source 4 and the base 13 by a bias voltage so that at least hydrogen radicals are induced toward the workpiece 12, diffusion of hydrogen radicals after irradiation is prevented. Thus, since the hydrogen radicals are efficiently brought into contact with the film formed on the object to be processed 12, the film can be removed from the object to be processed 12 at a high speed.

  Further, as a third embodiment of the plasma processing apparatus of the present invention, as shown in FIG. 6, a positive or negative voltage is applied from the power source 5 to the other counter electrode 17 disposed in the plasma source 4. To do. Further, the negative or positive power supply 5 to which the other counter electrode 17 of the power supply 5 is not connected is branched into two, and one of the branches is connected to one counter electrode 16 through the capacitor 20 and branched. The other is connected to the base 13 to apply a voltage. As a result, a bias voltage is applied between the plasma source 4 and the base 13.

  By adopting such a third embodiment, it is possible to simultaneously apply a voltage for generating plasma using one power supply 5 and a bias voltage between the plasma source 4 and the base 13. Therefore, no further power source for applying the bias voltage is required.

  When the electrode applied to one counter electrode 16 and the base 13 is branched, not only the capacitor 20 but also a resistor or a coil can be used.

<Example>
The results of removing the oxide film using the plasma processing method of the present invention are shown below.

  Using the workpiece 12 as a copper plate, the oxide film formed on the surface was removed. In addition, the thickness of the film before a process was 30 nm.

Helium gas (flow rate 4 L / min) is added to the plasma generating gas mixed with argon gas (flow rate 5 L / min) as the base gas and hydrogen gas (flow rate 0.3 L / min) as the additive gas. Using plasma generated by applying a power of 120 W / cm ³ using a power source, the plasma was irradiated while the copper plate was moved at a feed speed of 1 μm / min to remove the oxide film.

  As a result, the oxide film of 30 nm was reduced to 1.5 nm, and the oxide film was removed at high speed. The plasma temperature at this time was 200 ° C., and no thermal damage was observed on the copper plate.

DESCRIPTION OF SYMBOLS 1 Plasma generator 2 Plasma generation gas supply part 3 Plasma gas temperature adjustment part 4 Plasma source 5 Power supply 6 Gas piping 7 Cooler 8 Gas piping 9 Plasma generation gas temperature measurement part 10 Injection port 11 Plasma temperature measurement part 12 Processed Object 13 Base 14 Housing 15 Insulating pipe 16 One counter electrode 17 The other counter electrode 18 Gas flow path 19 Discharge part 20 Capacitor I Processed object layer II Coating layer

Claims (12)

A coating formed by bonding atoms on the surface of the object to be processed with at least one of oxygen atom, nitrogen atom or sulfur atom is irradiated with plasma generated by discharging to a plasma generating gas. A plasma treatment method for removing the oxygen atom, nitrogen atom or sulfur atom in the film,
The plasma includes a radical generated from a substance contained in the plasma generating gas, and the plasma generating gas itself,
The radical generated from the substance contained in the plasma generating gas contains at least a hydrogen radical capable of separating the oxygen atom, nitrogen atom or sulfur atom contained in the coating from the object to be processed,
The removal of the film involves contacting the oxygen atom, nitrogen atom or sulfur atom with the hydrogen radical in an amount more than necessary to separate all the oxygen atoms, nitrogen atoms or sulfur atoms contained in the film to be removed. And performing the plasma processing method.   Separation of the oxygen atom, nitrogen atom or sulfur atom by the hydrogen radical is performed by separating the hydrogen radical by colliding with the coating and expelling the oxygen atom, nitrogen atom or sulfur atom from the coating and / or the hydrogen radical. 2. The plasma processing method according to claim 1, wherein the film is separated by reducing the film by a chemical reaction between the oxygen atom, the nitrogen atom, and the sulfur atom.   The amount of the hydrogen radical is adjusted by controlling the concentration of hydrogen atoms and hydrogen molecules in the plasma generating gas and the voltage value applied to the plasma generating gas. Or the plasma processing method of Claim 2.   The plasma processing method according to any one of claims 1 to 3, wherein the plasma is adjusted to a predetermined temperature by controlling a temperature of the plasma generating gas.   The plasma processing method according to claim 4, wherein the temperature of the plasma is adjusted to a temperature that does not damage the object to be processed.   6. The plasma processing method according to claim 1, wherein the plasma is generated by applying a high frequency voltage to the plasma generating gas.   The plasma processing method according to claim 1, wherein the plasma generation gas is hydrogen gas.   The plasma generating gas is a mixed gas of a base gas selected from at least one selected from argon gas, helium gas, nitrogen gas and air and an additive gas selected from at least one selected from hydrogen gas, methane-based gas and ethane-based gas. The plasma processing method according to any one of claims 1 to 6, wherein the plasma processing method is provided.   The plasma processing method according to claim 1, wherein the object to be processed is a metal. In the plasma irradiation direction with respect to the object to be processed, on the downstream side of the object to be processed, there is a base for mounting the object to be processed or a member on which the object to be processed is disposed,
The bias voltage is applied to the electrode for applying a voltage to the plasma generating gas and the base, thereby applying energy to the plasma and inducing the hydrogen radicals in the coating. The plasma processing method according to any one of claims 1 to 9. A plasma source using the plasma generating gas as plasma;
A plasma generation gas temperature controller for adjusting the temperature of the plasma generation gas supplied to the plasma source;
A plasma generation gas temperature measurement unit for measuring the temperature of the plasma generation gas supplied to the plasma source;
A plasma temperature measuring unit for measuring the temperature of the plasma ejected from the plasma source,
A plasma processing apparatus, wherein the plasma temperature measured by the plasma temperature measurement unit is fed back to the plasma generation gas temperature control unit to control the temperature of the plasma generation gas. The plasma source is provided with a pair of counter electrodes,
In the irradiation direction in which the plasma is irradiated from the plasma source to the object to be processed, a member on which the object to be processed is mounted or the object to be processed is mounted on the downstream side of the object to be processed. A base to be placed,
A power source for applying a bias voltage to one electrode of the pair of counter electrodes and the base is disposed, and a potential difference is provided between the plasma source and the base by applying the bias voltage. The plasma processing apparatus according to claim 11.

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