JP2002110613A - Plasma cleaning apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma cleaning apparatus that can reduce charge up damage given to a semiconductor chip at plasma cleaning by the composition or gas for plasma generation. SOLUTION: A cylindrical reaction pipe 7 is formed by a dielectric material. At the same time, one side of the reaction pipe 7 is opened as a supply opening 12, discharge electrodes 9 and 10 are provided outside the reaction pipe 7, the gas 8 for plasma generation, containing a reactive oxygen gas and a rare gas is introduced into the reaction pipe 7, and at the same time, voltage is applied between the discharge electrodes 9 and 10. As a result, discharge is generated in the reaction pipe 7 under pressure close to the atmospheric pressure, and the plasma 13 generated in the reaction pipe 7 by the discharge is blown out of the supply opening 12, thus setting the mixing ratio of the oxygen gas to the gas 8 for plasma generation to be 2 to 5 vol.% in the plasma cleaning apparatus, for supplying the plasma 13 to the semiconductor chip 14 where a junction electrode 20 is exposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the bonding property of an electronic component, improving the adhesion and wettability between the electronic component and a sealing resin, and forming a film. The present invention relates to a plasma cleaning apparatus used for modifying the surface with plasma and a plasma cleaning method using the same, particularly for a semiconductor chip which requires precise bonding with a mounting substrate such as an electronic circuit board. In order to improve the reliability, the method is suitably applied to cleaning of a surface of a semiconductor chip, a bonding electrode of the semiconductor chip, and a bump formed on the semiconductor chip.

[0002]

2. Description of the Related Art Conventionally, attempts have been made to perform plasma processing under atmospheric pressure. For example, Japanese Unexamined Patent Publication No.
No. 1, JP-A-3-241739 and JP-A-1-241.
JP-A-306569 discloses a method in which a pair of electrodes are arranged in a discharge space in a reaction tube, a dielectric is provided between the electrodes, and the discharge space is formed by a plasma mainly containing a rare gas such as He (helium) or Ar (argon). A plasma processing method has been disclosed in which a gas for generation is filled, an object to be processed is put into a reaction tube, and an AC electric field is applied between the electrodes. The glow-like discharge is generated stably by applying the voltage, and the plasma-generating gas is excited by the glow-like discharge to generate plasma in the reaction tube, and the object to be processed is processed by the plasma. Things.

[0003] Japanese Patent Application Laid-Open Nos. 4-358076 and 4-212253 also disclose that plasma generated by glow-like discharge under atmospheric pressure is jetted to an object to be processed to perform plasma processing. Has been proposed. Furthermore, Japanese Patent Application Laid-Open No. 9-167775 discloses a plasma generation gas containing (adding) an inert gas selected from He, Ar, Kr, and Xe, or O ₂ , CF ₄ , N ₂ , It is described that plasma processing is performed using a reactive gas selected from CO ₂ , SF ₆ and CHF ₃ , a gas containing at least O, H, F and Cl.

[0004]

However, in the above-described plasma processing method and apparatus, the plasma cleaning apparatus focuses on surface modification of an electronic component, and is particularly mounted (mounted) on the surface of a mounting substrate. No study has been made on the charge-up phenomenon when the surface of the semiconductor chip in the state or the semiconductor chip before mounting or the bonding electrode is subjected to plasma processing for the purpose of cleaning or the like. Irradiation of the semiconductor chip with plasma causes charge-up, which causes a semiconductor chip characteristic defect, which is also a problem in a semiconductor (manufacturing) process.

Hereinafter, charge-up will be described with reference to FIG. FIG. 8 shows a semiconductor chip (semiconductor element) 14.
3 is a schematic view of a gate electrode 2 formed on a silicon single crystal substrate 1. FIG. The charge-up is performed by injecting the charged particles 3 in the plasma into the wiring 6 electrically connected to the gate electrode 2 of the semiconductor chip 14 and accumulating in the gate oxide film 5 via the wiring 6 and the gate electrode 2. It is a phenomenon that occurs. The passivation film 4 is formed on the wiring 6 in order to protect the surface of the semiconductor chip 14. The passivation film 4 is formed at a position corresponding to a bonding electrode (bonding portion) 20 which is a part where wire bonding or bump bonding of the wiring 6 is performed. No passivation film 4 is formed, and the bonding electrode 20 is directly exposed to plasma during plasma processing, and the bonding electrode 20 plays a role of an antenna for picking up charged particles 3 in the plasma.

When the above-mentioned charge-up phenomenon proceeds excessively, the physical characteristics of the gate oxide film 5 will be affected. Specifically, as a result of a change in the physical characteristics of the gate oxide film 5, in the case of a MOSFET (field effect transistor), gm (conductance), Vth (threshold voltage), and the like change. This is a phenomenon called charge-up damage.

As an evaluation method of charge-up damage, there is a method of measuring a shift amount of VFB (flat band voltage) before and after plasma processing using an MNOS (metal-silicon nitride-silicon oxide film-silicon) element. A method of measuring the time until a breakdown occurs between a metal and silicon by applying a constant current to an oxide film (Q
bd evaluation method) and the like, and by these methods, the presence or absence and size of damage can be known by the amount of change in the oxide film life before and after plasma irradiation.

The present invention has been made in view of the above points, and uses a plasma cleaning apparatus and a plasma cleaning apparatus capable of reducing charge-up damage applied to a semiconductor chip during plasma cleaning by the composition of a plasma generating gas. An object of the present invention is to provide a plasma cleaning method.

[0009]

According to a first aspect of the present invention, there is provided a plasma cleaning apparatus in which a cylindrical reaction tube is formed of a dielectric material, and one side of the reaction tube is opened as a blow-out port to form a reaction chamber. A plurality of discharge electrodes 9 and 10 are arranged outside the tube 7, and a plasma generating gas 8 containing a reactive gas, an oxygen gas and a rare gas, is introduced into the reaction tube 7. A discharge is generated in the reaction tube 7 under a pressure close to the atmospheric pressure by applying a voltage to the junction electrode 20, and the plasma 13 generated in the reaction tube 7 by the discharge is blown out from the outlet 12, thereby exposing the bonding electrode 20. A plasma cleaning apparatus for supplying a plasma 13 to a semiconductor chip 14, wherein a mixing ratio of an oxygen gas in a plasma generating gas 8 is set to 2 to 5 vol%.

In the plasma cleaning apparatus according to a second aspect of the present invention, a cylindrical reaction tube 7 is formed of a dielectric material, and one side of the reaction tube 7 is opened as a blowout port 12 to open the outside of the reaction tube 7. A plurality of discharge electrodes 9 and 10 are disposed, and a plasma generating gas 8 containing a hydrogen gas and a rare gas as a reactive gas is introduced into the reaction tube 7 and a voltage is applied between the discharge electrodes 9 and 10. As a result, a discharge is generated in the reaction tube 7 under a pressure near the atmospheric pressure, and the plasma 13 generated in the reaction tube 7 by the discharge is blown out from the blowout port 12, thereby exposing the bonding electrode 20 to the semiconductor chip 14.
A plasma cleaning apparatus for supplying plasma 13 to the
The mixing ratio of the hydrogen gas in the plasma generating gas 8 is set to 0.3 to 3 vol%.

The plasma cleaning apparatus according to claim 3 of the present invention, in addition to the structure of claim 1 or 2, uses He and Ar together as rare gases of the plasma generating gas 8 and occupies He in the rare gases. Is 30 vol% or less.

A plasma cleaning method according to a fourth aspect of the present invention is characterized in that the semiconductor chip 14 from which the bonding electrode 20 is exposed is cleaned using the plasma cleaning apparatus according to any one of the first to third aspects. Things.

A plasma cleaning method according to a fifth aspect of the present invention is characterized in that, in addition to the structure of the fourth aspect, the semiconductor chip 14 in which the bonding electrode 20 is formed of copper or a copper alloy is cleaned. is there.

According to a sixth aspect of the present invention, there is provided a plasma cleaning method according to the first or third aspect, wherein a plasma generating gas containing a rare gas and an oxygen gas is used in addition to the constitution of the fourth or fifth aspect. After performing the first cleaning step using the plasma cleaning apparatus described above, the plasma generating gas 8 containing a rare gas and a hydrogen gas is used.
A second cleaning step is performed by the plasma cleaning apparatus according to claim 2 or 3, wherein a second cleaning step is performed.

According to a seventh aspect of the present invention, there is provided a plasma cleaning method comprising the steps of:
The semiconductor chip 14 is bonded to the mounting board 15 by a flip chip mounting method.

[0016]

Embodiments of the present invention will be described below.

FIG. 1 shows an example of the plasma cleaning apparatus of the present invention. This plasma cleaning apparatus is formed by arranging a plurality (one pair) of discharge electrodes 9 and 10 on the outside of a reaction tube 7 so as to face each other up and down.
A discharge space 21 is formed in the reaction tube 7 at a position corresponding to between 10. The discharge electrodes 9 and 10 are electrically connected to a power supply 11 via an impedance matching circuit (not shown). Note that any number of discharge electrodes 9 and 10 may be used as long as they are one or more.

The reaction tube 7 is made of a high melting point dielectric material (insulating material) and is formed in a flat, substantially rectangular tube shape. The dielectric constant of the dielectric material constituting the reaction tube 7 is an important factor in lowering the temperature of the plasma in the discharge space 21. Specifically, the dielectric material is a vitreous material such as quartz, alumina, or yttria partially stabilized zirconium. Examples include materials and ceramic materials. In addition, the upper surface of the reaction tube 7 is opened almost entirely as a gas inlet 51, and the lower surface of the reaction tube 7 is opened almost entirely as an outlet 12. Therefore, the outlet 12 is formed in a slit shape which is long and narrow in a direction parallel to the wide direction of the reaction tube 7, and thereby, the outlet 12
Compared to forming a small hole (spot shape)
A large area can be processed at a time. The outlet 12 and the gas inlet 51 are formed so as to communicate with the discharge space 21 in the reaction tube 7. The reaction tube 7
May be formed in a cylindrical shape.

The discharge electrodes 9 and 10 are made of, for example, copper, aluminum, brass, stainless steel having high corrosion resistance (SUS30).
4) and the like. Although the discharge electrodes 9 and 10 are formed in a ring shape (annular shape), the inner peripheral shape is formed so as to match the outer peripheral shape of the reaction tube 7. And the discharge electrodes 9, 1
0, the reaction tube 7 is inserted into the inside of the reaction tube 7.
The discharge electrodes 9 and 10 can be attached to the outer periphery of.
At this time, the inner peripheral surface of each of the discharge electrodes 9 and 10 is brought into contact with the outer peripheral surface of the reaction tube 7 over the entire periphery.
As compared with the case where the discharge electrodes 9 and 10 are not brought into contact with the outer peripheral surface of the reaction tube 7 over the entire circumference, the discharge electrodes 9 and 10 and the reaction tube
The contact area can be increased to improve the contact property, and when a voltage is applied between the discharge electrodes 9 and 10, a discharge is easily generated in the discharge space 21 and the generation efficiency of the plasma 13 can be increased. Things. Further, by providing the discharge electrodes 9 and 10 outside the reaction tube 7, the discharge electrodes 9 and 10 can be prevented from being subjected to the sputtering or corrosive action by the plasma 13, and the discharge electrodes 9, 10 can be prevented.
5 to be treated with contaminants generated by sputtering
0 can be prevented from being contaminated, and the life of the discharge electrodes 9 and 10 can be extended.
The interval between the discharge electrodes 9 and 10 is preferably set to 3 to 20 mm in order to generate plasma stably.

The power supply 11 generates a high-frequency voltage or a pulse voltage and can apply a voltage required to continuously generate the plasma 13 in the discharge space 21 between the discharge electrodes 9 and 10. Used. The high-frequency voltage has a voltage waveform (for example, a sine wave) having no or almost no pause time (time during which the voltage is constant and in a steady state), and the pulse voltage has a voltage waveform having a pause time. is there. Further, the voltage required for continuously generating the plasma 13 in the discharge space 21 may be appropriately set because it varies depending on the thickness of the reaction tube 7 and the size of the discharge space 21, for example, 0.5 to 5 kV. Can be set to

When a high frequency voltage is used as the voltage applied between the discharge electrodes 9 and 10, the structure of the power supply device used as the power supply 11 can be simplified and the discharge electrodes 9 and 1 can be used.
This is preferable because the frequency of the voltage applied between zero and the magnitude of the power supplied to the discharge space 21 can be easily adjusted. When a pulse voltage is used as the voltage applied between the electrodes 9 and 10, the structure of the power supply device used as the power supply 11 becomes complicated, but there is a time during which the charged particles are not accelerated by the electric field. This is preferable because the time of staying in the discharge space 21 is prolonged, and discharge in the discharge space 21 is easily caused, the discharge efficiency is increased, and plasma can be easily generated. In particular, when He is not introduced into the discharge space 21, the breakdown voltage becomes higher than when He is introduced into the discharge space 21, and a discharge hardly occurs. Therefore, it is preferable to use a pulse voltage.

Gas for plasma generation (indicated by an arrow in FIG. 1)
As 8, a mixed gas of a rare gas and an oxygen gas or a rare gas and a hydrogen gas is used. When a mixed gas of a rare gas and an oxygen gas is used, organic substances can be removed.When a mixed gas of a rare gas and a hydrogen gas is used, the same organic substances can be removed and oxidized as when an oxygen gas is used. The oxide can be removed by reducing the substance (film). When the plasma generating gas 8 contains an oxygen gas or a hydrogen gas, the plasma 13
The oxygen gas or the hydrogen gas adsorbs the electrons therein to become negative ions by themselves, and acts to lower the electron density in the plasma 13. Generally, electrons have higher mobility and longer lifetime than ions compared to ions. Therefore, when performing plasma processing by blowing out a jet-like plasma (plasma jet) as in the present invention,
It has been confirmed that charge-up damage is mainly caused by electrons.

In the present invention, the oxygen gas or the hydrogen gas is added to the plasma generating gas 8 so that the electrons can be absorbed and extinguished by the oxygen gas or the hydrogen gas before reaching the semiconductor chip 14. As a result, charge-up of the semiconductor chip 14 by electrons can be reduced.
In addition, since the negative ions of oxygen and hydrogen disappear before reaching the semiconductor chip 14, they do not affect the charge-up. As described above, according to the present invention, electrons that reach the semiconductor chip 14 that causes charge-up can be reduced. Therefore, the semiconductor chip 14 is mounted on the mounting board 15 before mounting the semiconductor chip 14 on the mounting board 15. Even if plasma cleaning is performed later, the semiconductor chip 14
In addition, it is possible to suppress the occurrence of charge-up damage and reduce the characteristic failure of the semiconductor chip 14.

When a mixed gas of a rare gas and an oxygen gas is used as the plasma generating gas 8, the oxygen gas occupies the entire plasma generating gas 8 (total amount of the rare gas and the oxygen gas) introduced into the reaction tube 7. (Oxygen concentration in the plasma generation gas 8) is preferably set to 2 to 5 vol%. When a mixed gas of a rare gas and a hydrogen gas is used as the plasma generating gas 8, the hydrogen gas occupies the entire plasma generating gas 8 (total amount of the rare gas and the hydrogen gas) introduced into the reaction tube 7. The mixing ratio (the hydrogen concentration in the plasma generating gas 8) is preferably set to 0.3 to 3% by volume.

If the mixing ratio of the oxygen gas in the plasma generating gas 8 is less than 2 vol% or the mixing ratio of the hydrogen gas in the plasma generating gas 8 is less than 0.3 vol%, the oxygen gas or the hydrogen There is a possibility that the effect of adsorbing electrons by the gas is reduced and charge-up damage cannot be reduced.
The mixing ratio of oxygen gas to the total exceeds 5 vol%,
The mixing ratio of hydrogen gas in the plasma generating gas 8 is 3
If the concentration exceeds vol%, the effect of adsorbing electrons by oxygen gas or hydrogen gas becomes too high, and the elimination of ions or discharge space due to collision of negative ions of oxygen or hydrogen with positive ions of rare gas (Ar or He). There is a possibility that the electron efficiency in the inside 21 decreases, the discharge efficiency decreases, and the effect of removing (cleaning) organic substances and oxides by the plasma 13 decreases.

The mixing ratio of hydrogen gas in the plasma generating gas 8 supplied to the reaction tube 7 is set to 0.3 to 3 vol.
When the flow rate is set to 1%, the plasma 13 is efficiently generated in the reaction tube 7 and the reduction performance can be increased,
Further, even when the mounting substrate 15 on which the semiconductor chip 14 is mounted as the processing object 50 is subjected to plasma cleaning, the occurrence of charge-up damage is reliably suppressed and the semiconductor chip 14
Characteristic failure can be further reduced.
At the same time, it is possible to reliably prevent arc discharge to the processing object 50. If the mixing ratio of the hydrogen gas is less than 0.3 vol%, arc discharge may occur. This is because, when the concentration of hydrogen is low, the effect of adsorbing electrons by hydrogen decreases, and the density of charged particles in the plasma 13 increases. Further, since the generation of hydrogen radicals is reduced, the cleaning performance by hydrogen (radicals) may be reduced. On the other hand, if the mixing ratio of the hydrogen gas exceeds 3 vol%, the flow rate (gas velocity) of the plasma generating gas 8 in the reaction tube 7 increases, and the time of staying in the discharge space 21 decreases, and therefore, the plasma generation rate decreases. Since the energy of the high-frequency electric field is not efficiently transmitted to the use gas 8, the generation of hydrogen radicals is reduced, and there is a possibility that the cleaning property may be deteriorated similarly to the above. And 4% of the explosive limit of hydrogen
, The safety of the device may be reduced.

The rare gas of the plasma generating gas 8 is H
e, Ne, Ar, Kr, Xe, etc., can be used alone or in combination of a plurality of types.
It is preferable to use only r in terms of cost. Discharge electrode 9,
When the voltage applied between the electrodes 10 is a pulse voltage, the discharge efficiency is high, so that only Ar may be used as the rare gas of the plasma generating gas 8 (of course, He may be used together).
However, when the voltage applied between the discharge electrodes 9 and 10 is a high-frequency voltage, the discharge efficiency is not higher than the pulse voltage, so that He and A are rare gases of the plasma generation gas 8.
It is preferable to use r in combination. As described above, when He and Ar are used in combination as the rare gases of the plasma generating gas 8, the dielectric breakdown voltage in the discharge space 21 is reduced by He, so that the discharge efficiency can be increased and the plasma 13 can be easily generated. Thus, the efficiency of plasma processing such as removal (cleaning) of organic substances can be improved by increasing the generation efficiency of the plasma 13.

He is used as a rare gas of the plasma generating gas 8.
When both Ar and Ar are used, the mixing ratio of He in the rare gas (the total amount of He and Ar) is preferably 30 vol% or less. The mixing ratio of He in the rare gas is 30v
ol% may lead to cost increase,
Moreover, since He has a smaller atomic weight than Ar, the average atomic weight of the gas as a whole becomes smaller. Therefore, the processing target 50 (the semiconductor chip 14 and the mounting substrate) of the plasma 13 blown out from the outlet 12 15), the rate at which the active species to be cleaned is killed before the plasma 13 reaches the object to be processed 50 may decrease, and the cleaning performance may be reduced. Therefore, the mixing ratio of He in the rare gas is set to 30 vol.
The mixing ratio of He in the rare gas is preferably set to 10 vol% or more in order to improve the discharge efficiency.

As described above, the plasma generating gas 8
When only Ar is used as the rare gas of Ar, Ar is H
Since the atomic weight is larger than e, the average atomic weight of the gas as a whole becomes larger than that in the case of using He in combination, and therefore, the plasma 13 blown out from the blowout port 12 reaches the workpiece 50. The speed is improved, and before the plasma 13 reaches the object 50, the rate at which the active species to be cleaned is killed is reduced, and the cleaning performance can be improved.

In order to remove the organic substances and oxides adhering to the surface of the semiconductor chip 14 as the object to be processed 50 and perform plasma cleaning (surface modification) using the above-described plasma cleaning apparatus, the following steps are required. Do like this.
First, the plasma generating gas 8 is introduced into the reaction tube 7 from the gas inlet 51, and the plasma generating gas 8 flows from the top to the bottom in the reaction tube 7 to be introduced into the discharge space 21. Next, a high frequency voltage or a pulse voltage is applied between the discharge electrodes 9 and 10 by the power supply 11 to generate and apply a high frequency electric field or a pulse electric field to the discharge space 21 in the reaction tube 7. Under the pressure near the atmospheric pressure (93.3 to 106.7 kPa) by the electric field
(700 to 800 Torr)), a glow-like discharge is generated in the discharge space 21. Thereafter, the plasma generating gas 8 is turned into plasma by the glow-like discharge, and the plasma 13 containing the plasma active species is continuously generated in the discharge space 21.

The plasma 13 thus generated is continuously jetted downward from the outlet 12 in the form of a jet, and the plasma 13 is discharged from the semiconductor chip 14 disposed below the outlet 12. By spraying and supplying the surface, organic substances and the like on the surface of the semiconductor chip 14 can be removed by sputtering active species such as radicals generated in the plasma 13, and the bonding electrode exposed on the surface of the semiconductor chip 14. The metal oxide formed at 20 can be reduced and returned to the original metal to remove the oxide, and the surface of the semiconductor chip 14 can be modified. For example, when the bonding electrode 20 is formed of copper or a copper alloy, a copper oxide (copper oxide film) may be formed on the bonding electrode 20, which may cause poor conduction. However, by performing the plasma cleaning as described above, the copper oxide can be reduced to the original copper or copper alloy, and the copper oxide can be removed. Further, as shown in FIG. 2, the above-described plasma cleaning can be performed while the semiconductor chip 14 is mounted on the surface of the mounting substrate 15. The organic substance adhering to the processing object 50 is, for example, an organic substance component contained in a silver paste material used for forming a bump or a circuit or the processing object 50 is washed with a cleaning liquid (for example, acetone). This is a cleaning liquid or the like remaining on the surface of the processing object 50 when cleaned, and can be removed by the above-described plasma cleaning.

Further, the mounting substrate 15 can be cleaned (surface modified) using the plasma cleaning apparatus of the present invention. In cleaning the mounting substrate 15, the mounting substrate 15 may be used as the object to be processed 50 instead of the semiconductor chip 14, whereby the mounting is performed by sputtering active species such as radicals generated in the plasma 13. Organic substances and the like on the surface of the substrate 15 can be removed, and the metal oxide formed on the bonding electrode 19 exposed on the surface of the mounting substrate 15 can be reduced and returned to the original metal to remove the oxide. The surface of the mounting substrate 15 can be modified.

Further, by continuously transporting the plurality of semiconductor chips 14 and the mounting substrate 15 below the outlet 12 while blowing out the plasma 13 from the outlet 12, the plurality of semiconductor chips 14 and the mounting substrate 15
Can be continuously plasma-cleaned in-line.

In performing the plasma cleaning as described above, the frequency of the high frequency voltage or the pulse voltage applied between the discharge electrodes 9 and 10 by the power supply 11 is 1 kHz to 20 kHz.
Preferably, it is set to 0 MHz. If the frequency of the high-frequency voltage or the pulse voltage is less than 1 kHz, the discharge in the discharge space 21 cannot be stabilized, and the plasma processing may not be performed efficiently. Further, the frequency of the high frequency voltage or the pulse voltage is 2
If it exceeds 00 MHz, the temperature of the plasma in the discharge space 21 rises remarkably, and the life of the reaction tube 7 and the discharge electrodes 9 and 10 may be shortened. In addition, the mounting substrate 15 and the semiconductor chip 14 may be thermally damaged. Or the plasma cleaning apparatus may be complicated and large.

The density of the power supplied (applied) to the discharge space 21 is preferably set to 20 to 3500 W / cm ³ . If the density of the power supplied to the discharge space 21 is less than 20 W / cm ³ , the plasma 13 cannot be sufficiently generated in the discharge space 21, and conversely,
The density of the power supplied to the discharge space 21 is 3500 W / c
If it exceeds m ³ , stable discharge may not be obtained in the discharge space 21. The power density (W / c
m ³ ) is (power supplied to discharge space 21 / discharge space 2)
1 volume).

In performing the above-described plasma cleaning, the semiconductor chip 14 and the mounting substrate 15 are subjected to plasma cleaning using a plasma cleaning apparatus using a mixed gas of a rare gas and an oxygen gas as the plasma generating gas 8. After performing the first cleaning process, the semiconductor chip 14 and the mounting substrate 1 after the first cleaning process are performed using a plasma cleaning device using a mixed gas of a rare gas and hydrogen gas as the plasma generating gas 8.
It is preferable to perform a second cleaning step of performing plasma cleaning on the surface of the semiconductor chip 14 and the mounting substrate 1 under the influence of oxygen radicals in the first cleaning step.
Even if an oxide (oxide film) is formed on the surface of the substrate 5 or the surfaces of the bonding electrodes 19 and 20, the oxide can be reduced and removed by the hydrogen radical used in the second cleaning step, and a good cleaning effect can be obtained. Is obtained.

An example of a flip chip mounting method using the above-described plasma cleaning apparatus will be described below. First, FIG.
As shown in (a), bumps 16 such as stud bumps are formed on the bonding electrodes 20 exposed on the surface of the semiconductor chip 14. The above-described plasma cleaning can be performed on the semiconductor chip 14 before the bumps 16 are formed. The bump 16 can be formed by an arbitrary method using various known materials. For example, the tip of the gold wire 32 is led out from the capillary 31 and the tip of the gold wire 32 is formed into a ball shape by arc discharge or the like. Then, the bump 16 which is a gold stud bump can be formed by thermocompression-bonding the tip of the ball-shaped gold wire 32 to the bonding electrode 20. Note that the bumps 16 may be formed on the surface of the bonding electrode 19 of the mounting board 15 described later. Also, bump 1
After the formation of 6, the semiconductor chip 14 can be subjected to the above-described plasma cleaning. In this case, the surface of the bump 16 can be modified by removing organic substances and oxides present in the bump 16.

Next, as shown in FIG. 3B, a known conductive paste 17 such as a silver paste is applied to the surface of the bump 16 by transferring or the like. Next, as shown in FIG. 3C, the above-described plasma cleaning is performed on the mounting substrate 15.
Next, as shown in FIG. 3D, the semiconductor chip 14 is placed close to the mounting substrate 15 from above, and the plurality of bonding electrodes 19 formed on the surface of the mounting substrate 15 correspond to each bonding electrode 19. The predetermined bump 16 and the conductive paste 17 are brought into contact with each other. Next, as shown in FIG. 3E, the conductive paste 17 is cured by applying heat to the conductive paste 17 so that the bonding portion 20 of the semiconductor chip 14 and the electrode 19 of the mounting board 15 are electrically connected. The semiconductor chip 14 and the mounting substrate 15 are joined together by the bumps 16 and the cured conductive paste 17.

Next, as shown in FIG. 3F, underfill is performed. As the underfill material 33 injected into the gap 30 between the semiconductor chip 14 and the mounting board 15, a known resin or resin composition for underfill, such as a liquid resin or a liquid resin composition, can be used. An epoxy resin composition containing a filler such as calcium carbonate can be used. The method of injecting the underfill material 33 is also optional. For example, the nozzle 35 is brought close to the side opening of the gap 30 and
, The underfill material 33 can be blown out and injected into the gap 30. Then, by heating and curing the underfill material 33 injected into the gap 30, a semiconductor package as shown in FIG. 3G can be formed.

In the above-described flip-chip mounting method, the surface of the semiconductor chip 14 and the surface of the mounting substrate 15 which face each other with the gap 30 formed between the mounting board 15 and the semiconductor chip 14 interposed therebetween, and Bump 1
Since the surface of the substrate 6 is plasma-cleaned, dirt such as organic substances and oxides that hinder the flow of the underfill material 33 or hinder the adhesion of the underfill material 33 is reduced. It is possible to prevent the underfill material 33 from flowing easily and to prevent the unfilled portion of the underfill material 33 from being formed, and to adhere the underfill material 33 to the surface of the semiconductor chip 14, the surface of the mounting substrate 15, or the surface of the bump 16. Thus, the effect of reinforcing the bumps 16 with the underfill material 33 and the tightness of the gap 30 can be enhanced. Therefore, a semiconductor package having high bonding strength between the semiconductor chip 14 and the mounting substrate 15 and excellent in moisture resistance can be formed.

[0041]

The present invention will be described below in detail with reference to examples.

Example 1 A plasma cleaning apparatus having the structure shown in FIG. 1 was formed. The reaction tube 7 was formed of quartz glass.
The upper electrode 9 and the lower electrode 10 were made of copper, and were electrically connected to the power supply 11 such that the electrode 9 was a high-voltage electrode and the electrode 10 was a low-voltage (ground) electrode. As the plasma generating gas 8, a mixed gas of He, Ar, and oxygen gas (O ₂ ) was used. At this time, the flow rate of He was 2 liters / minute and Ar
Was introduced into the reaction tube 7 at a flow rate of 10 liter / minute and an oxygen gas flow rate of 0.4 liter / minute, and the mixing ratio of the oxygen gas in the plasma generating gas 8 was about 3.2 vol%.

The frequency is 13.56M under the atmospheric pressure.
Hz, 700 W power between the electrodes 9 and 10 (discharge space 2
1) to apply a high-frequency voltage (sinusoidal waveform) between the electrodes 9 and 10 so that the discharge space 2 in the reaction tube 7 is
1, a glow-like discharge is generated, and a plasma 13 is generated in the discharge space 21 by the discharge.
3 was formed so as to be jetted from the jet port 12 in a jet shape.

Example 2 A mixed gas of He, Ar and hydrogen gas (H ₂ ) was used as the plasma generating gas 8. At this time, the flow rate of He was 0.29 l / min, the flow rate of Ar was 1.46 l / min, and the flow rate of hydrogen gas was 0.017 l / min.
The reaction mixture was introduced into the reaction tube 7 at a rate of 1 liter / min.
And The electric power supplied between the electrodes 9 and 10 (discharge space 21) was 100 W.

The other conditions were the same as in Example 1.

Comparative Example 1 Example 1 was repeated except that the flow rate of oxygen gas was set at 0.12 liter / min and the mixing ratio of oxygen gas in the plasma generating gas 8 was set at 1.0 vol%.
Same as.

Comparative Example 2 The procedure was the same as in Example 2 except that no hydrogen gas was used.

Then, the above Examples 1 and 2 and Comparative Example 1
Qbd evaluation was performed using the plasma cleaning apparatus of No. 1. This Qbd evaluation uses a glass substrate epoxy resin substrate on which a gate oxide film of a MOSFET is formed as a processing object for Qbd evaluation, and supplies plasma to the processing object for 5 seconds to perform plasma processing. After that, the life of the gate oxide film was measured, and the damage due to the charge-up damage was evaluated based on the difference in the life of the gate oxide film before and after the plasma treatment. The results are shown in FIGS.

As is apparent from FIGS.
In the case of No. 2, the life of the gate oxide film was hardly reduced and the damage due to the charge-up damage was reduced as compared with that before the plasma treatment (untreated).
In Comparative Example 1, the life of the gate oxide film was significantly reduced as compared with that before the plasma treatment (untreated), and damage due to charge-up damage occurred.

The charge-up charge of the above-mentioned Example 2 and Comparative Example 2 was measured. The charge-up charge was measured as shown in FIG. That is, an aluminum foil tape 71 is provided on the surface of a substrate 52 which is a glass base epoxy resin substrate, a lead 72 is led out from the aluminum foil tape 71, and the lead 72 is connected to one end of the capacitor 73. By using an end connected to the ground and connecting a charge measuring device 74 such as a digital multimeter in parallel with the capacitor 73, the plasma 13 is sprayed on the surface of the aluminum foil tape 71, so that the charges in the plasma are reduced by the capacitor. The amount of charge-up charge generated was considered by forming the capacitor 73 so as to accumulate it and measuring the voltage across the capacitor 73 with a charge measuring device 74. The results are shown graphically in FIG.

As is clear from FIG. 7, the potential (voltage) of Example 2 decreases more slowly with time than that of Comparative Example 2, and Example 2 using hydrogen gas uses hydrogen gas. It can be seen that the content of the charged particles (electrons) in the plasma 13 is smaller than that in Comparative Example 2 in which no plasma was used.

(Embodiment 3) As a result of manufacturing a semiconductor package according to the steps shown in FIGS. 3A to 3G using the plasma cleaning apparatus of Embodiment 1, the underfill material 33 is not injected into the gap 30. There is no portion, and the adhesion of the underfill material 33 to the surface of the semiconductor chip 14, the surface of the mounting substrate 15, and the surface of the bump 16 is increased, and the effect of reinforcing the bump 16 with the underfill material 33 and sealing the gap 30 are provided. I was able to improve the sex.

[0053]

As described above, according to the first aspect of the present invention, a cylindrical reaction tube is formed of a dielectric material, and one side of the reaction tube is opened as an outlet, and a plurality of the reaction tubes are provided outside the reaction tube. The reaction electrode is placed under a pressure near the atmospheric pressure by introducing a plasma generating gas containing a reactive gas of oxygen gas and a rare gas into the reaction tube and applying a voltage between the discharge electrodes. A plasma cleaning apparatus that generates a discharge in a tube and blows out plasma generated in the reaction tube by the discharge from a blowout port to supply plasma to a semiconductor chip in which a bonding electrode is exposed. Gas mixture ratio 2-5 vol%
Therefore, electrons generated in the plasma can be eliminated by adsorbing the oxygen gas with oxygen gas, and charge-up due to electrons applied to the semiconductor chip during plasma cleaning can be reduced, thereby reducing charge-up damage of the semiconductor chip. Can be done.

According to the invention of claim 2 of the present invention, a cylindrical reaction tube is formed of a dielectric material, and one side of the reaction tube is opened as an outlet, and a plurality of discharge electrodes are arranged outside the reaction tube. A discharge gas is generated in the reaction tube at a pressure near the atmospheric pressure by introducing a plasma generating gas containing a reactive gas, a hydrogen gas and a rare gas, into the reaction tube and applying a voltage between the discharge electrodes. A plasma cleaning apparatus for supplying plasma to a semiconductor chip in which a bonding electrode is exposed by blowing out plasma generated in a reaction tube by discharge from a blowout port, wherein a mixing ratio of hydrogen gas in a plasma generation gas is reduced. Since the concentration is set to 0.3 to 3 vol%, electrons generated in the plasma can be eliminated by adsorbing the hydrogen gas, and the electron beam applied to the semiconductor chip during plasma cleaning can be reduced. It is capable of reducing the charge-up damage of the semiconductor chip can be reduced Jiappu.

In the invention of claim 3 of the present invention, He and Ar are used together as the rare gas of the plasma generating gas, and the mixing ratio of He in the rare gas is made 30 vol% or less. By doing so, the dielectric breakdown voltage is reduced by He, the discharge efficiency can be increased, plasma can be easily generated, and the plasma generation efficiency can be increased to improve the performance of plasma cleaning. And He in the rare gas
By setting the mixing ratio to 30 vol% or less, it is possible to prevent the velocity of the plasma blown out from the outlet from reaching the semiconductor chip, and to reduce the active species in the plasma before the plasma reaches the semiconductor chip. Can be reduced, and the performance of plasma cleaning can be prevented from lowering.

Further, the invention of claim 4 of the present invention is directed to claim 1
The semiconductor chip in which the bonding electrode is exposed is cleaned by using the plasma cleaning apparatus according to any one of (1) to (3), so that electrons generated in the plasma can be eliminated by adsorbing the oxygen gas or the hydrogen gas with the oxygen gas or the hydrogen gas. The charge-up due to electrons applied to the semiconductor chip can be reduced, and the charge-up damage of the semiconductor chip can be reduced.

According to the invention of claim 5 of the present invention, since the semiconductor chip having the bonding electrode formed of copper or a copper alloy is washed, copper oxide formed on the surface of the semiconductor chip or the bonding electrode is reduced and removed. Cleaning performance can be improved.

According to a sixth aspect of the present invention, there is provided a plasma cleaning apparatus according to the first or third aspect, wherein the first cleaning step is performed by using a plasma generating gas containing a rare gas and an oxygen gas. The second cleaning step by the plasma cleaning apparatus according to claim 2 or 3, wherein a plasma generation gas containing a gas and a hydrogen gas is used, so that the surface of the semiconductor chip and the mounting substrate are affected by oxygen radicals in the first cleaning step. Even if oxides are formed on the surface of
The oxide can be reduced and removed by the hydrogen radical used in the second cleaning step, and a good cleaning effect can be obtained.

According to the invention of claim 7 of the present invention, since the semiconductor chip is bonded to the mounting substrate by the flip chip mounting method, the semiconductor chip is mounted on the mounting substrate after the plasma cleaning, thereby reducing the underfill. When the underfill material flows, the amount of dirt such as organic substances and oxides that hinder the adhesion of the underfill material is reduced, so that the underfill material flows easily and the underfill material is not injected. It is possible to prevent the formation of parts and to improve the adhesion of the underfill material to the surface of the semiconductor chip and the surface of the mounting substrate. The bonding strength between the semiconductor chip and the mounting substrate is high, and the moisture resistance is high. It is possible to form a semiconductor package having excellent characteristics.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an embodiment of the present invention.

FIG. 2 is a perspective view showing another embodiment of the same.

FIGS. 3A to 3G are schematic front views showing an example of a flip chip mounting method according to the embodiment.

FIG. 4 is a graph showing Qbd evaluations of Example 1 and Comparative Example 1 according to the first embodiment.

FIG. 5 is a graph showing Qbd evaluation of Example 2 of the same.

FIG. 6 is a schematic diagram showing a method for measuring charge-up charge according to the first embodiment.

FIG. 7 is a graph showing measurement results of charge-up charges in Example 2 and Comparative Example 2 of the above.

FIG. 8 is an explanatory diagram illustrating charge-up.

[Explanation of symbols]

 Reference Signs List 7 reaction tube 8 plasma generation gas 9 discharge electrode 10 discharge electrode 12 outlet 13 plasma 14 semiconductor chip 15 mounting board 20 bonding electrode

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/60 H01L 21/302 N H05H 1/24 21/92 604J (72) Inventor Kazunori Kuzuhara Osaka 1048 Kadoma Kadoma Kadoma Matsushita Electric Works F-term (reference) 3B116 AA02 AA46 BB02 BB89 BB90 BC01 5F004 AA06 AA14 BA06 BA20 CA02 DA22 DA23 DA24 DA26 EA28 5F044 KK19 QQ04 QQ06

Claims (7)

[Claims] 1. A tubular reaction tube is formed of a dielectric material, and one side of the reaction tube is opened as an outlet, and a plurality of discharge electrodes are disposed outside the reaction tube. A gas for generating a plasma containing a gas and a rare gas is introduced into the reaction tube, and a voltage is applied between the discharge electrodes to generate a discharge in the reaction tube under a pressure close to the atmospheric pressure. A plasma cleaning apparatus for supplying plasma to a semiconductor chip in which a bonding electrode is exposed by blowing out plasma that has been blown out from a blowing port,
The mixing ratio of oxygen gas in the plasma generation gas is 2 to
A plasma cleaning apparatus characterized by comprising 5 vol%. 2. A tubular reaction tube is formed from a dielectric material, and one side of the reaction tube is opened as an outlet, and a plurality of discharge electrodes are disposed outside the reaction tube. A gas for generating a plasma containing a gas and a rare gas is introduced into the reaction tube, and a voltage is applied between the discharge electrodes to generate a discharge in the reaction tube under a pressure close to the atmospheric pressure. A plasma cleaning apparatus for supplying plasma to a semiconductor chip in which a bonding electrode is exposed by blowing out plasma that has been blown out from a blowing port,
The mixing ratio of hydrogen gas in the plasma generating gas is set to 0.1.
A plasma cleaning apparatus characterized by comprising 3 to 3 vol%. 3. He is used as a rare gas of a plasma generating gas.
The plasma cleaning apparatus according to claim 1, wherein a mixture ratio of He and the rare gas is 30 vol% or less, together with Ar and Ar. 4. A plasma cleaning method using the plasma cleaning apparatus according to claim 1 to clean a semiconductor chip from which a bonding electrode is exposed. 5. The plasma cleaning method according to claim 4, wherein a semiconductor chip having a bonding electrode made of copper or a copper alloy is cleaned. 6. A method for producing a plasma containing a rare gas and a hydrogen gas after performing a first cleaning step by a plasma cleaning device according to claim 1 or 3, wherein a plasma generating gas containing a rare gas and an oxygen gas is used. The plasma cleaning method according to claim 4 or 5, wherein the second cleaning step is performed by the plasma cleaning apparatus according to claim 2 or 3 using a gas. 7. The plasma cleaning method according to claim 4, wherein the semiconductor chip is bonded to the mounting substrate by a flip chip mounting method.