JP4396209B2 - Plasma processing apparatus, plasma processing method, and electronic component manufacturing method - Google Patents

Description

  The present invention relates to a plasma processing apparatus and a plasma processing method for performing surface modification of a processing target surface including an inner surface of a narrow space by plasma processing, and an electronic component manufacturing method for manufacturing electronic components using this plasma processing method. is there.

  In mounting a semiconductor element connected to a substrate via a bump formed on the lower surface such as a flip chip, a structure in which a resin is filled in a gap between the semiconductor element and the substrate to be reinforced is widely used. When the gap is narrowed, the resin filling property is deteriorated. Therefore, a technique for modifying the surface of the upper surface of the substrate and the lower surface of the semiconductor element in the gap by plasma treatment prior to resin filling is known (for example, see Patent Document 1).

In this technology, an active substance such as oxygen radicals generated by plasma discharge enters the gap between the semiconductor element and the substrate and comes into contact with the upper surface of the substrate or the lower surface of the semiconductor element. The surface is modified. Thereby, the wettability with respect to the resin of a clearance inner surface is improved, and the filling property of resin can be improved.
JP 2000-91373 A

  However, according to the above-described conventional technology, the gap between the semiconductor element and the substrate is narrowed and the number of bumps is drastically increased with the demand for downsizing of electronic devices, and the following problems are caused. ing. In the plasma treatment for surface modification, oxygen radicals generated under reduced pressure diffuse and enter the aforementioned gap from the outer edge of the semiconductor element, and further diffuse in the gap toward the central portion, thereby oxygen radicals. Contacts the surface to be treated.

  However, under the condition of a narrow gap and a large number of bumps, it is difficult to reach a sufficient amount of oxygen radicals to the back of the gap by this diffusion, and a sufficient reforming effect cannot be obtained. Also, if the processing pressure is increased to reach a sufficient amount of oxygen radicals inside the gap, the density of oxygen radicals increases, but the outer edge of the semiconductor element is excessively etched by charged particles generated simultaneously by plasma discharge. This results in local damage to the outer edge of the semiconductor element. As described above, in the surface modification by the conventional plasma treatment, it is difficult to obtain a sufficient modification effect without damaging the object to be treated when the inner surface of the narrow space is the object to be treated.

  Therefore, an object of the present invention is to realize a plasma processing apparatus, a plasma processing method, and an electronic component manufacturing method using the plasma processing method, which can obtain a sufficient modification effect without damaging a processing target.

The plasma processing apparatus of the present invention is a plasma processing for performing surface modification of the inner surface of a narrow space, which is a gap between a semiconductor element having a bump formed on the lower surface and a substrate on which the semiconductor element is mounted, by plasma processing. An apparatus, a vacuum chamber capable of forming a hermetically sealed processing chamber, a pair of electrodes disposed opposite to each other in the vacuum chamber, and a substrate to be processed disposed between the electrodes. A work placement unit to be placed, a high frequency power supply unit for applying a high frequency voltage to the electrode, a vacuum exhaust unit for evacuating the processing chamber, and supplying a plasma generating gas containing a reactive gas into the processing chamber The processing pressure of the plasma generating gas in the plasma processing space formed by generating a plasma discharge between the gas supply unit and the electrode is changed from the first pressure lower than the atmospheric pressure to the first pressure. A boosting control for increasing the high second pressure than was the pressure reduction control for reducing the pressure to reach the second pressure and a pressure control means for performing a plurality of times repeatedly.

The plasma processing method of the present invention includes a vacuum chamber capable of forming a sealed processing chamber, a pair of electrodes arranged opposite to each other in the vacuum chamber, and a processing target disposed between these electrodes. A workpiece placement portion on which a substrate is placed, a high-frequency power supply portion for applying a high-frequency voltage to the electrode, a vacuum exhaust portion for evacuating the processing chamber, and a plasma generating gas containing a reactive gas in the processing chamber A semiconductor element having bumps formed on the lower surface thereof by a plasma processing apparatus comprising a gas supply unit for supplying gas and a pressure control means for controlling the processing pressure of the plasma generating gas in the processing chamber, and the semiconductor element is mounted A plasma processing method for modifying the inner surface of a confined space, which is a gap between a substrate and a plasma treatment, which is formed by generating a plasma discharge between the electrodes. The process pressure in the plasma generating gas in the space, several times the pressure reduction control for reducing the pressure from the first pressure below atmospheric pressure and the boost control for increasing the high second pressure than the first pressure, and reaches the second pressure Repeat it.

The electronic component manufacturing method of the present invention is an electronic component manufacturing method for manufacturing an electronic component by mounting a semiconductor element having a bump formed on a lower surface on a substrate, and bonding the bump to an electrode provided on the substrate. Mounting the semiconductor element on the substrate, and subjecting the substrate after the mounting process to plasma treatment to include the inner surface of the gap between the substrate and the semiconductor element as a target for surface modification. A vacuum chamber capable of forming a sealed processing chamber in the surface modification step, and a vacuum chamber that includes a resin filling step of filling an underfill resin in the gap after the surface modification step. A pair of electrodes disposed in opposition to each other, a workpiece placement unit disposed between these electrodes and on which a substrate to be processed is placed, a high-frequency power supply unit that applies a high-frequency voltage to the electrodes, , An evacuation unit that evacuates the chamber; a gas supply unit that supplies a plasma generating gas containing a reactive gas into the processing chamber; and a pressure control unit that controls a processing pressure of the plasma generating gas in the processing chamber. The plasma processing apparatus is equipped with a plasma processing apparatus, and a plasma processing gas is generated in a plasma processing space formed by generating a plasma discharge between the electrodes. The processing pressure of the plasma generating gas is changed from the first pressure lower than the atmospheric pressure to the first pressure. The pressure increase control for raising the pressure to a high second pressure and the pressure reduction control for reducing the pressure when the second pressure is reached are repeated a plurality of times.

  According to the present invention, the pressure increase control for increasing the processing pressure of the plasma generating gas in the plasma processing space for generating plasma discharge from the first pressure lower than the atmospheric pressure to the second pressure higher than the first pressure is performed. Thus, it is possible to ensure the surface modification effect by allowing oxygen radicals to enter the narrow space to be plasma-treated in the pressurization process.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a plasma processing apparatus according to a first embodiment of the present invention, FIG. 2 is a diagram for explaining a state of a plasma processing space in the plasma processing method of the first embodiment of the present invention, and FIG. 4 is a flow chart of the plasma processing method of the present embodiment, FIG. 4 is a time chart showing the boost control of the plasma generating gas in the plasma processing method of one embodiment of the present invention, and FIGS. 5 and 6 are one embodiment of the present invention. It is explanatory drawing of the diffusion state of the oxygen radical in the plasma processing method of this.

  First, the plasma processing apparatus will be described with reference to FIG. In FIG. 1, a pair of a lower electrode 3 and an upper electrode 6 are disposed inside the vacuum chamber 1 so as to face each other. A lower portion of the lower electrode 3 penetrates the bottom surface of the vacuum chamber 1 through the insulator 2 and protrudes to the outside, and an upper portion of the upper electrode 6 penetrates the upper surface of the vacuum chamber 1 and is connected to the ground portion 7. . A space between the lower electrode 3 and the upper electrode 6 is a plasma processing space 8, and a substrate 4 that is a workpiece to be plasma processed is placed on the upper surface of the lower electrode 3. The upper surface of the lower electrode 3 serves as a workpiece mounting portion for mounting the substrate 4 as a workpiece to be processed.

  A semiconductor element 5 having bumps formed on the lower surface is mounted on the substrate 4, and an inner surface of a gap (narrow space) between the substrate 4 and the semiconductor element 5 is a target for surface modification by plasma treatment. ing. The substrate 4 is in a state before being sent to the resin filling step of filling the gap between the semiconductor element 5 and the underfill resin. This is performed in order to improve the wettability to the stop resin and to facilitate the entry of the sealing resin.

  Two openings 1a and 1b are provided on the bottom surface of the vacuum chamber 1, and the openings 1a and 1b are connected to the vacuum exhaust part 12 and the gas supply part 14 via the exhaust valve 11 and the gas supply valve 13, respectively. It is connected to the. The interior of the vacuum chamber 1 is evacuated by opening the exhaust valve 11 and driving the evacuation unit 12. Further, by opening the gas supply valve 13 and driving the gas supply unit 14, a plasma generating gas containing a reactive gas such as oxygen gas is supplied into the vacuum chamber 1.

  A high frequency power supply unit 15 is connected to the lower electrode 3, and a high frequency voltage is applied between the upper electrode 6 and the lower electrode 3 by driving the high frequency power supply unit 15. By driving the high frequency power supply unit 15 with the plasma generating gas supplied after the vacuum chamber 1 is evacuated, plasma of the plasma generating gas containing oxygen gas is generated in the plasma processing space 8.

  The exhaust valve 11, the gas supply valve 13, the vacuum exhaust unit 12, the gas supply unit 14, and the high frequency power supply unit 15 are controlled by the control unit 16. When the vacuum exhaust unit 12 and the gas supply unit 14 are driven, the control unit 16 controls the exhaust valve 11 and the gas supply valve 13 to arbitrarily set the processing pressure of the plasma generating gas in the plasma processing space 8 inside the vacuum chamber 1. Can be controlled according to the pressure pattern.

  As a result, as will be described later, it is possible to perform pressure increase control for increasing the processing pressure of the plasma generating gas in the plasma processing space 8 from the first pressure lower than the atmospheric pressure to the second pressure higher than the first pressure. It is possible. The exhaust valve 11, the gas supply valve 13, the vacuum exhaust unit 12, the gas supply unit 14, and the control unit 16 are pressure control means for performing the above-described pressure increase control.

Next, referring to FIG. 2, the state of the plasma processing space 8 when plasma is generated by a plasma generating gas containing oxygen gas will be described. As shown in FIG. 2, a plasma discharge is generated by applying a high frequency voltage between the lower electrode 3 and the upper electrode 6, thereby generating oxygen gas plasma (see broken line 17) in the plasma processing space 8. Then, charged particles such as oxygen ions O ⁺ and electrons e ⁻ and oxygen radicals O ^* are generated. Oxygen ions O ⁺ and electrons e ⁻ are particles having a positive charge and a negative charge, respectively. The oxygen radical O ^* is an electrically neutral particle in which oxygen atoms are activated. Here, an example is shown in which oxygen is used as the plasma generating gas, but chlorine, fluorine, bromine, or a mixture thereof may be used.

When the mounted substrate 4 to be processed is placed on the lower electrode 3 in a state where such plasma is generated, the upper surface of the substrate 4 is caused by charged particles such as the above-described oxygen ions O ⁺ and electrons e ^−. A physical effect, that is, a sputtering effect due to collision of these charged particles with the surface of the substrate 4 acts. Thereby, the surface of the resin material constituting the substrate 4 is partially removed. At the same time as the sputtering effect, oxygen radical O ^*, which is an active substance, enters the gap between the upper surface of the substrate 4 and the semiconductor element 5, and due to its chemical action, the surface in the gap, that is, the upper surface of the substrate 4. And the surface modification of the lower surface of the semiconductor element 5 is performed.

  Here, the semiconductor element 5 shown in this embodiment is a multi-pin fine-pitch flip chip having a plurality of bumps, and is mounted on the substrate 4 with a gap of 100 μm or less. For this reason, in the above-described plasma discharge occurrence state, the degree of oxygen radicals entering the gap is low, and oxygen radicals that have entered the gap are also prevented from diffusing by a large number of bumps. The effect of reforming is difficult to reach. For this reason, in the present embodiment, in the plasma processing for the purpose of surface modification in a narrow space such as the multi-pin fine pitch type semiconductor element 5, the surface modification effect is achieved using the method described below. To ensure.

  The plasma processing method will be described with reference to FIGS. First, the evacuation unit 12 and the gas supply unit 14 are set in a driving state. In FIG. 3, the exhaust valve 11 is opened, and the inside of the vacuum chamber 1 is depressurized to an initial pressure P0 set to a level lower than a first pressure P1 described below (ST1). As shown in FIG. 4, at the timing t1 when the pressure in the vacuum chamber 1 reaches the initial pressure P0, the gas supply valve 13 is opened to supply the plasma generating gas into the vacuum chamber 1 (ST2).

  Next, a processing pressure in the vacuum chamber 1 is detected by a pressure sensor (not shown), and it is determined whether or not this pressure is lower than a preset first pressure P1 (ST3). At the timing t2 when the pressure reaches the first pressure P1, the high frequency power supply unit 15 is driven to turn on plasma discharge (ST4), and the exhaust valve 11 is closed (ST5). As a result, the processing pressure increases as shown in FIG. Then, the pressure is detected by the pressure sensor in this pressure increasing process, and it is determined whether or not the detected pressure exceeds the second pressure P2 set to a pressure higher than P1 (ST6). If the second pressure P2 is exceeded, at this timing t3, the exhaust valve 11 is opened to depressurize the inside of the vacuum chamber (ST7).

  Next, it is determined whether or not the predetermined plasma discharge time has elapsed (ST8). If the time has not yet increased, it is determined whether or not the pressure is equal to or lower than the first pressure P1. If the pressure is equal to or lower than P1, the process returns to ST5 and the exhaust valve 11 is closed. As a result, the pressure starts to rise again, and when the pressure reaches the second pressure P2, the exhaust valve 11 is opened again to reduce the pressure. The above-described pressure increase and pressure reduction are repeated until the predetermined plasma discharge time is up.

That is, in the plasma processing method shown in the present embodiment, the above-described pressure increase control and pressure reduction control are repeated a plurality of times during a predetermined plasma discharge time, and the process pressure in the process space is set to the first pressure P1 and the second pressure. It is made to move up and down between P2. Here, the pressure is raised and lowered by alternately opening and closing the exhaust valve 11 while continuing the supply of the gas for generating the plasma, but the method for adjusting the opening degree of the exhaust valve 11 and the gas supply A method of controlling the supply amount of the plasma generating gas itself by a mass flow controller provided in the section 14 may be used. In the process of raising and lowering the plasma processing pressure, the plasma discharge is continued in both the pressure increasing process and the pressure reducing process in the above example, but the plasma discharge may be generated only in the pressure increasing process.

  Here, a setting example of the first pressure P1 and the second pressure P2 will be described. The levels of the first pressure P1 and the second pressure are required to be pressure levels lower than atmospheric pressure and capable of stable plasma discharge using the plasma generating gas. In the present embodiment, a pressure of about 10 Pa is used as the first pressure P1, and a pressure of about 100 Pa is used as the second pressure P2. However, within the pressure level range where stable plasma discharge can be maintained, P2 / A combination of pressures such that P1 is 2 or more may be used.

  Next, the behavior of oxygen radicals in the vicinity of the semiconductor element 5 and in the gap between the substrate 4 and the semiconductor element 5 in the above-described pressure raising / lowering process will be described. In plasma treatment performed under reduced pressure, particles generated by plasma discharge diffuse in a molecular flow state in which the individual particles move with a relatively large mean free path. Therefore, the lower the plasma processing pressure is, and the narrower the gap between the semiconductor element 5 and the substrate 4, the lower the probability that oxygen radicals will flow into the gap.

FIG. 5 schematically shows the state of movement of oxygen radicals during the pressurization process. In the process of increasing the pressure from the first pressure P1 to the first pressure P2, the pressure rises, that is, oxygen generated from the plasma generating gas. The increase in density of radicals O ^* and oxygen ions O ⁺ occurs first from outside the gap of the semiconductor element 5. For this reason, in the pressurization process, high-density oxygen radicals O ^* generated at a high pressure P2 flow from the outside of the semiconductor element 5 into the gap of the pressure P1 lower than the outside. The inflowing oxygen radical O ^* moves toward the inside of the gap while repeatedly colliding with the bumps 5 a in the gap, the upper surface of the substrate 4, and the lower surface of the semiconductor element 5. In this movement process, the resin surface such as the upper surface of the substrate 4 or the lower surface of the semiconductor element 5 on which the oxygen radical O ^* collides is subjected to surface modification by the active action of the oxygen radical O ^* .

  At this time, the behavior of the oxygen radical in the pressurization process is more viscous as a viscous flow in which particles move while the density increases, and oxygen radicals from the outside with higher density. It flows in the form of being forcibly fed into the gap having a lower density. Therefore, a sufficient amount of oxygen radicals can reach the back of the gap even under conditions of a narrow gap and a large number of bumps as in the semiconductor element 5, and a sufficient modification effect can be obtained.

  Further, in this plasma processing process, the processing pressure in the processing space once rises and then drops again, so that the semiconductor element 5 is continuously exposed to charged particles such as high-density oxygen ions and electrons. do not do. Therefore, the outer edge portion of the semiconductor element 5 is not excessively etched by the charged particles, and local damage to the outer edge portion of the semiconductor element 5 can be prevented.

  Thus, in the plasma processing intended for surface modification in the gap between the substrate 4 and the semiconductor element 5, the processing pressure of the plasma generating gas in the plasma processing space is changed from the first pressure P1 lower than the atmospheric pressure to the first pressure P1. By performing the pressure increase control to increase the pressure to a second pressure P2 higher than the first pressure P1, a sufficient amount of oxygen plasma is allowed to flow into the gap without continuously exposing the outer edge of the gap to high-density charged particles. And a sufficient modification effect can be obtained without damaging the object to be treated.

  As a plasma processing apparatus for applying the above-described plasma processing method, since the uniformity of plasma generation distribution in the plasma processing space is required, as shown in FIG. 1, a flat plate-like lower electrode 3 and upper electrode A parallel plate electrode type plasma processing apparatus in which 4 is opposed in parallel is suitable.

  Next, with reference to FIG. 6, the electronic component manufacturing method using the surface modification by the plasma treatment described above will be described. This electronic component manufacturing method manufactures an electronic component by mounting a semiconductor element having a bump formed on the lower surface on a substrate.

As shown in FIG. 6A, the bumps 5a provided on the lower surface of the semiconductor element 5 are bonded to the electrodes 4a provided on the substrate 4, and the semiconductor element 5 is mounted on the substrate 4 (mounting process). Next, as shown in FIG. 6B, the substrate 4 after the mounting process is subjected to plasma treatment, so that the inner surface of the gap between the substrate 4 and the semiconductor element 5 is included in the processing target, and surface modification processing is performed. (Surface modification step). That is, the substrate 4 is carried into the plasma processing apparatus shown in FIG. 1 and the substrate is placed on the lower electrode 3. Then, plasma processing is performed by the plasma processing method described in FIGS.

  Thereafter, as shown in FIG. 6C, an underfill resin 17 is applied on the substrate 4, and is filled by entering the gap after the surface modification step by capillary force (resin filling step). In this resin filling step, the wettability of the inner surface in the gap is improved by the surface modification, so that the filling property of the underfill resin 17 can be improved. Then, as shown in FIG. 6 (d), the substrate 4 is heated to thermally cure the underfill resin 17, thereby mounting the semiconductor element 5 having the bumps 5a formed on the lower surface thereof on the substrate 4. An electronic component in which the space between the substrate 5 and the substrate 4 is sealed is completed.

  In the above embodiment, an example is shown in which the gap between the semiconductor element after mounting and the substrate is the target of plasma processing for surface modification, but the inner surface of the narrow gap is the target of processing. If it is. For example, an inner surface of a fine recess formed on a processed surface after fine processing is also an application target of the present invention.

  The plasma processing apparatus and the plasma processing method of the present invention have an effect that oxygen radicals can be forcibly entered into a narrow space to be plasma processed to ensure a surface modification effect. The present invention is useful for a plasma processing apparatus and a plasma processing method for performing surface modification of a surface to be processed including the inner surface of the semiconductor by plasma processing, and for manufacturing a semiconductor device using this plasma processing method.

Sectional drawing of the plasma processing apparatus of Embodiment 1 of this invention State explanatory drawing of the plasma processing space in the plasma processing method of one embodiment of this invention The flowchart of the plasma processing method of one embodiment of this invention FIG. 3 is a time chart showing the boost control of the plasma generating gas in the plasma processing method according to the embodiment of the present invention. Explanatory drawing of the diffusion state of oxygen radicals in the plasma processing method of one embodiment of the present invention Process explanatory drawing of the electronic component manufacturing method of one embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 3 Lower electrode 4 Substrate 5 Semiconductor element 5a Bump 8 Plasma processing space 11 Exhaust valve 12 Vacuum exhaust part 13 Gas supply valve 14 Gas supply part 15 High frequency power supply part

Claims (3)

A plasma processing apparatus for performing surface modification of the inner surface of a narrow space, which is a gap between a semiconductor element having a bump formed on a lower surface and a substrate on which the semiconductor element is mounted, by plasma processing, and is sealed A vacuum chamber capable of forming a processing chamber; a pair of electrodes disposed opposite to each other in the vacuum chamber; and a workpiece placement unit disposed between these electrodes and on which a substrate to be treated is placed. A high-frequency power supply unit that applies a high-frequency voltage to the electrodes, a vacuum exhaust unit that evacuates the processing chamber, a gas supply unit that supplies a plasma generating gas containing a reactive gas into the processing chamber, and a gap between the electrodes The processing pressure of the plasma generating gas in the plasma processing space formed by generating the plasma discharge in the step is increased from the first pressure lower than the atmospheric pressure to the second pressure higher than the first pressure. That a step-up control, the plasma processing apparatus characterized by comprising a pressure control means for performing by the pressure reduction control for reducing the pressure to reach the second pressure several times repeated. A vacuum chamber capable of forming a sealed processing chamber, a pair of electrodes arranged opposite to each other in the vacuum chamber, and a workpiece mounting on which a substrate to be processed is placed. A placement unit, a high-frequency power supply unit that applies a high-frequency voltage to the electrode, a vacuum exhaust unit that evacuates the processing chamber, a gas supply unit that supplies a plasma generating gas containing a reactive gas into the processing chamber, A gap between a semiconductor element having a bump formed on the lower surface by a plasma processing apparatus having a pressure control means for controlling a processing pressure of the plasma generating gas in the processing chamber and a substrate on which the semiconductor element is mounted. A plasma processing method for modifying the inner surface of a narrow space for generating plasma in a plasma processing space formed by generating a plasma discharge between the electrodes. The process pressure of the scan, and the step-up control for increasing the first pressure lower than the atmospheric pressure to a higher second pressure than the first pressure, be performed under reduced pressure control to reduce the pressure to reach the second pressure several times repeated A plasma processing method characterized by the above. An electronic component manufacturing method for manufacturing an electronic component by mounting a semiconductor element having a bump formed on a lower surface on a substrate, wherein the bump is bonded to an electrode provided on the substrate to mount the semiconductor element on the substrate A surface modification step of performing a surface modification process including the inner surface of the gap between the substrate and the semiconductor element as a processing target by performing a plasma treatment on the substrate after the process and the mounting step; and after the surface modification step A resin filling step of filling an underfill resin in the gap of
In the surface modification step, a vacuum chamber capable of forming a sealed processing chamber, a pair of electrodes arranged opposite to each other in the vacuum chamber, and a substrate to be processed disposed between these electrodes A work placement portion on which a high-frequency voltage is applied to the electrode, a vacuum exhaust portion for evacuating the processing chamber, and a plasma generating gas containing a reactive gas in the processing chamber Plasma processing formed by generating a plasma discharge between the electrodes using a plasma processing apparatus having a gas supply section to supply and a pressure control means for controlling a processing pressure of a plasma generating gas in the processing chamber the process pressure in the plasma generating gas in the space, and a step-up control for increasing the first pressure lower than the atmospheric pressure to a higher second pressure than the first pressure, and reaches the second pressure Electronic component manufacturing method characterized by performing pressure reduction control for pressurizing a plurality of times repeated.

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