JP2011151290A - Semiconductor device, and method of manufacturing the same - Google Patents

Abstract

In flip chip bonding using metal nanoparticles, excessive wetting and spreading of metal nanoparticles during printing and flip chip mounting is suppressed, and short-circuiting with adjacent electrodes is prevented.
A wiring board having a first electrode, a semiconductor element having a second electrode at a position facing the first electrode, and mounted on the wiring board, and the first A bonding material 4 interposed between and electrically connected to one electrode 2 and the second electrode 6, and a liquid repellent layer on the side surfaces of the first electrode 2 and the second electrode 6. 3 and the liquid repellent layer 3 is formed of a composite film made of Ni and PTFE (polytetrafluoroethylene) by electroless plating.
[Selection] Figure 1

Description

  The present invention relates to a flip chip bonding technique using metal nanoparticles, a semiconductor device that suppresses wet spread during printing of metal nanoparticles and wet spread during flip chip mounting, and prevents a short circuit with an adjacent electrode, and its manufacture Regarding the method.

  In recent years, downsizing and high functionality of electronic devices have been remarkably advanced, and as a bonding technology advantageous for high density, it is possible to realize miniaturization and miniaturization by face-down semiconductor elements and collectively connecting them to a wiring board. Possible flip-chip bonding technology is applied to semiconductor mounting.

  Usually, in the above technique, a metal bump is interposed between the semiconductor element and the wiring board, and ultrasonic bonding is performed by applying an ultrasonic wave at the time of bonding, or conductive between the bump and the electrode. The electrical connection between the semiconductor element and the wiring board is achieved by a pressure welding method in which a conductive resin is applied and a load is applied to make contact.

  As a problem in the flip chip bonding, there is damage to a semiconductor element due to ultrasonic waves or a load. The thickness of semiconductor elements tends to be reduced year by year, and the problem that stress due to ultrasonic waves or load damages the semiconductor elements and causes characteristic defects has become apparent. As a new bonding method for solving this problem, a method of using metal nanoparticles as a bonding material has been proposed.

  Metal nanoparticles are metal particles having a size of less than 100 nm, such as Au, Ag, and Cu. The metal nanoparticles have a higher surface activity than the bulk material due to the size effect and a low melting point, so that bonding at a low temperature is possible. In addition, metal nanoparticles have a high melting point equivalent to that of bulk materials when the metal nanoparticles are bonded to each other and have a large particle size. Therefore, a wide range is required to reduce heat stress when mounting electronic components and to improve heat resistance after mounting. Application to products is expected. Moreover, since excessive stress such as ultrasonic waves and load is not required at the time of joining metal nanoparticles, it is expected to be applicable to thinning of semiconductor elements.

  In addition, since the bulking of metal nanoparticles proceeds even at room temperature, a protective film is formed around the metal nanoparticles, and the protective film is decomposed by applying energy such as heat or light, and the metal nanoparticles Are agglomerated and sintered to form a joint. However, when using metal nanoparticles as a bonding material, there are the following problems.

  The metal nanoparticles are usually mixed with an organic solvent and handled in a paste form, and have fluidity because they are patterned by printing. In particular, when the ink jet method is used as a printing method, the viscosity of the metal nanoparticles must be lowered as compared with other printing methods because of the structure of the discharge part.

  Furthermore, since the surface energy of the metal is very large with respect to the surface tension of the organic solvent, the contact angle of the metal nanoparticles with the metal electrode becomes very small. For this reason, when printing metal nanoparticles on the electrode or when the semiconductor element is flip-chip mounted on the wiring board, the metal nanoparticles are wetted and spread more than necessary, and the adjacent electrodes of the wiring board and the semiconductor element There is a problem that it is easy to short-circuit with an adjacent electrode.

  A prior art for such a problem will be described with reference to FIG.

  In the prior art, as shown in FIG. 5A, first, the width of the first electrode 102 on the wiring board 101 side is made wider than the area of the second electrode 106 on the semiconductor element 105 side. Next, as shown in FIG. 5B, a liquid repellent layer 103 made of an amorphous fluorine-containing polymer is formed on the entire wiring substrate 101. Subsequently, as shown in FIG. 5C, the laser beam 107 is irradiated to peel off the unnecessary portion of the liquid repellent layer 103 and expose the portions other than the outer peripheral portion on the first electrode 102.

  In this way, as shown in FIG. 5 (d), by forming the liquid repellent layer 103 only on the outer peripheral portion of the first electrode 102, the metal nanoparticles on the insulating portion during ink jet printing by the liquid repellent layer 103. The spread of wetting is suppressed.

JP 2005-136375 A

  However, in the prior art as described above, it is necessary to widen the electrode width by the required liquid repellent region, and accordingly, the electrode pitch is increased accordingly, which hinders the narrowing of the pitch.

  In addition, wetting and spreading of metal nanoparticles occurs not only during ink jet printing but also due to the indentation of the semiconductor element during flip chip mounting. However, in the prior art, since the liquid repellent layer is not formed on the semiconductor element side, the semiconductor element side There is concern about short-circuiting at the electrodes.

  Furthermore, the process is complicated because the liquid repellent layer is formed even on unnecessary portions as a semiconductor and is removed by laser.

  The present invention has been made in view of such conventional problems, and suppresses the occurrence of short-circuiting due to wetting and spreading of metal nanoparticles during ink jet printing and flip chip mounting without changing the electrode width. It is an object of the present invention to provide a semiconductor device and a method for manufacturing the same that can achieve a narrow pitch of electrodes without complicating the process.

  In order to achieve the above object, a semiconductor device of the present invention includes a wiring board having a first electrode, and a semiconductor element mounted on the wiring board and having a second electrode at a position facing the first electrode. And a bonding material electrically interposed between the first electrode and the second electrode, and a liquid repellent layer on the side surfaces of the first electrode and the second electrode Is formed. The liquid repellent layer is formed of a composite film made of Ni and PTFE (polytetrafluoroethylene) by electroless plating.

  Furthermore, the method for manufacturing a semiconductor device of the present invention includes a step of forming a first electrode on a wiring substrate, a step of forming a second electrode on a semiconductor element, and a liquid repellent surface of the first electrode. Forming a layer, forming a liquid repellent layer on the side of the second electrode, printing a bonding material on the first electrode, and inverting the semiconductor element and holding it with a bonding tool While aligning, mounting the semiconductor element on the wiring substrate so that the first electrode and the second electrode face each other, heating and sintering the bonding material, Forming a joint between the first electrode and the second electrode.

  According to the present invention, wetting and spreading of metal nanoparticles can be suppressed without increasing the electrode width, and even when the electrode pitch is narrow, a short circuit with an adjacent electrode can be prevented by a simple process.

Schematic showing the structure of the semiconductor device according to the first embodiment of the present invention. Schematic diagram showing a method of manufacturing a semiconductor device according to the first embodiment of the present invention. Schematic diagram showing a method of manufacturing a semiconductor device according to the first embodiment of the present invention. Schematic showing the structure of the semiconductor device in the second embodiment of the present invention Schematic which shows the structure of the manufacturing process of the semiconductor device in Embodiment 3 of this invention. Schematic which shows the structure of the manufacturing process of the semiconductor device in Embodiment 3 of this invention. Schematic diagram showing the structure of a conventional semiconductor device

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic diagram of a semiconductor device according to Embodiment 1 of the present invention, FIG. 1A is a top view of the semiconductor device after ink jet printing, and FIG. 1B is AA in FIG. It is sectional drawing of a part.

  As shown in FIGS. 1A and 1B, a first electrode 2 that is square when viewed from above is formed on a wiring board 1, and the entire side surface of the first electrode 2 is formed on the entire side surface of the first electrode 2. A liquid repellent layer 3 is formed. The first electrode 2 is formed of Au, and the liquid repellent layer 3 is formed of a composite film in which fine particles of PTFE (polytetrafluoroethylene) are uniformly dispersed in Ni.

  Further, the bonding material 4 is printed on the first electrode 2 and spreads only on the upper surface of the first electrode 2. The bonding material 4 is a paste formed by mixing Au particles of 0.5 nm or more and 100 nm or less and an organic solvent such as phenylcyclohexane.

  Since the surface energy of Au, which is the material of the first electrode 2, is very large with respect to the surface tension of the organic solvent of the bonding material 4, printing the bonding material 4 shows very good wettability, and FIG. ) And (b), the entire upper surface of the first electrode 2 where Au is exposed spreads out. However, when the bonding material 4 reaches the liquid repellent layer 3, the wettability is remarkably lowered, so that further progress can be prevented. This is because the liquid-repellent layer 3 has fine irregularities formed on the film surface by the fine particles of PTFE in Ni, and has a high liquid-repellent effect. In addition, if the thickness of the liquid repellent layer 3 is 1.5 μm or more, a sufficient liquid repellent effect can be obtained, but if it is too thick, the electrode width will be increased, and therefore a thickness of about 1.5 to 5 μm is preferable. .

  FIG. 1C is a cross-sectional view after flip-chip mounting on the structure of FIGS. 1A and 1B.

  As shown in FIG. 1C, the second electrode 6 of the semiconductor element 5 is mounted so as to face the first electrode 2 of the wiring substrate 1. Similarly to the first electrode 2, the second electrode 6 is square and made of Au, and the side surface of the second electrode 6 is covered with a liquid repellent layer 3 made of Ni and PTFE. Further, the bonding material 4 is between the first electrode 2 and the second electrode 6 and wets and spreads on the side surfaces of both electrodes, but does not reach the insulating portion between adjacent electrodes.

  When flip-chip mounting is performed from the state shown in FIG. 1, the bonding material 4 protrudes from between the first electrode 2 and the second electrode 6 by pressing the semiconductor element 5. However, by setting both electrodes to an appropriate height, wetting and spreading can be stopped only on the side surfaces of the electrodes. Thereby, a short circuit due to the bonding material 4 being wet and spreading to the insulating portion between the adjacent electrodes can be prevented.

  In the present embodiment, the heights of the first electrode 2 and the second electrode 6 are the same and can be adjusted as appropriate. However, for example, when the bonding material 4 is printed so as to have a thickness of 5 μm with respect to an electrode size of 60 μm square, and the semiconductor element 5 is pushed in so as to have a thickness of 3 μm, the preferred first electrode 2 and second electrode The thickness of 6 is 10 μm or more. If such a thickness is set, wetting and spreading to the insulating portion between adjacent electrodes can be suppressed. The present embodiment can be applied to the case where the wet spread amount to the first electrode 2 and the second electrode 6 is the same.

  Thus, by providing the liquid-repellent layer 3 on the side surface of the electrode and having an appropriate height, wetting and spreading during ink jet printing can be suppressed in a limited region. Furthermore, by causing the bonding material 4 that protrudes to escape to the side surface of the electrode in the height direction during flip chip mounting, a short circuit between adjacent electrodes of the bonding material 4 can be prevented without increasing the electrode width. For this reason, the pitch between the electrodes can be reduced as compared with the prior art.

  Next, a method for manufacturing the semiconductor device of the present embodiment will be described with reference to FIGS. 2-1 (a) to (d) and FIGS. 2-2 (e) to (h).

  First, as shown in FIGS. 2-1 (a) and (b), the first electrode 2 is formed on the wiring substrate 1, and the second electrode 6 is formed on the semiconductor element 5. Although the first electrode 2 and the second electrode 6 are formed by Au plating, Ag and Cu can be used in addition to Au as the plating material. Moreover, the thickness of the 1st electrode 2 and the 2nd electrode 6 is given appropriate thickness as mentioned above.

  Next, as shown in FIGS. 2-1 (c) and (d), the liquid repellent layer 3 is formed on the side surfaces of the first electrode 2 and the second electrode 6. The liquid repellent layer 3 is formed by an electroless plating method including fine particles of Ni and PTFE. A known liquid composition can be used for this plating solution. For example, nickel sulfate can be used as nickel, carboxylic acid or a salt thereof as a complexing agent, sodium hypophosphite as a reducing agent, PTFE fine particles and a surfactant for dispersing them, and various kinds as required. A plating solution mixed with an additive can be used.

  By using the electroless plating method, the liquid repellent layer 3 can be easily and uniformly formed on the side surface of the electrode which is difficult to form three-dimensionally. In addition, a deposition method for selectively eutecting different materials such as Ni and PTFE is difficult except for electroless plating, and in that sense, a manufacturing method using electroless plating is preferable.

  Further, as the material of the liquid repellent layer 3 to be co-deposited with PTFE, metals such as Au, Ag, and Cu can be used in addition to Ni. However, the combination of Ni and PTFE exhibits a higher liquid repellent effect. It is preferable to use Ni. The liquid repellent layer 3 may be partially formed on the upper surfaces of the first electrode 2 and the second electrode 6, but prevents the bonding of the bonding material 4 to the first electrode 2 and the second electrode 6, Since the bonding strength is lowered, it is preferable that they are not formed on the upper surfaces of both electrodes as much as possible.

  Next, as shown in FIG. 2E, the bonding material 4 is printed on the upper surface of the first electrode 2. This bonding material 4 is printed by an ink jet printing method, and can be printed with two or three layers if necessary. In addition, screen printing or the like may be used as a printing method. However, since ink-jet printing is capable of maskless patterning on demand and is non-contact with a member, dust or other members, such as a semiconductor device, may be used. It is advantageous and preferable for the production of products that are easily affected by contact.

  Moreover, it is preferable that the viscosity of the bonding material 4 is adjusted to a viscosity of about 5 to 20 mPa · s so as to facilitate printing by inkjet. In addition to Au, Ag, Cu, Ni, or an alloy thereof can be used as the metal of the metal nanoparticle, but it is better to combine the material with the first electrode 2 and the second electrode 6 in the semiconductor device. It is preferable in terms of reliability.

  Next, as shown in FIG. 2-2 (f), the semiconductor element 5 is held by the bonding tool 8 and aligned so that the first electrode 2 and the second electrode 6 face each other.

  Subsequently, as shown in FIG. 2-2 (g), the semiconductor element 5 is flip-chip mounted on the wiring board 1. The mounting load at this time may be a load that allows the bonding material 4 to wet and spread on the second electrode 6 of the semiconductor element 5, and in consideration of damage to the semiconductor element 5, do not apply a load more than necessary. Is preferred.

  Finally, as shown in FIG. 2-2 (h), the bonding material 4 is heat-treated to decompose the protective film, and the particles are further bonded and bulked. Moreover, although the suitable conditions of heat processing differ for every kind of metal contained in the joining material 4, for example, if it is a metal particle of Au, the junction part 7 can be formed in 300 degreeC and 1 hour. In this way, the bonding material 4 is formed as the bonding portion 7 having sufficient conductivity and strength, and the semiconductor device is manufactured.

  As described above, according to the manufacturing method of the present embodiment, only the step of forming the liquid repellent layer 3 by electroless plating, which is an existing method, is added to the side surfaces of the electrodes 2 and 6. It is simpler than the step of forming the liquid repellent layer in the invention, and a semiconductor device can be manufactured without complicating the step.

(Embodiment 2)
FIG. 3 is a schematic view of the semiconductor device according to the second embodiment of the present invention, and is a cross-sectional view showing a state after flip-chip. The configuration is the same as that of the first embodiment except that the thickness of the second electrode 6 of the semiconductor element 5 is smaller than that of the first electrode 2 of the wiring board 1.

  In flip chip mounting, the semiconductor element 5 is inverted and mounted face down, so that the bonding material 4 protruding from between the first electrode 2 and the second electrode 6 is placed on the side surface of the second electrode 6. In this case, the bonding material 4 is in a state of creeping up, and the amount of wetting and spreading on the side surface of the second electrode 6 may be smaller than the amount of wetting and spreading on the side surface of the first electrode 2 due to the influence of gravity.

  In that case, the thickness of the 2nd electrode 6 may be formed thinner than the thickness of the 1st electrode 2, and each thickness can be suitably adjusted according to the amount of wet spread. For example, when the bonding material 4 is printed so as to have a thickness of 5 μm with respect to a 60 μm square electrode size as in the first embodiment, and the semiconductor element 5 is pushed in so that the thickness becomes 3 μm, the preferred first The total thickness of the electrode 2 and the second electrode 6 may be 20 μm. If the thickness of the first electrode 2 is required to be 15 μm, the second electrode 6 may be 5 μm. However, if the thickness of the second electrode 6 is 5 μm or less, it is difficult to obtain the effect of suppressing wetting and spreading, and therefore the thickness is preferably 5 μm or more.

(Embodiment 3)
4A and 4B are schematic views of the semiconductor device according to the third embodiment of the present invention. FIG. 4A is a top view of the semiconductor device after inkjet printing, and FIG. ) Is a cross-sectional view taken along line AA ′ in FIG. 4A, and FIG. 4C is a cross-sectional view taken along line BB ′ in FIG. 4A.

  The first electrode 2 on the wiring substrate 1 is formed long in the X direction perpendicular to the electrode pitch direction (Y direction) and has a rectangular shape. Further, the bonding material 4 spreads wet until it reaches the liquid repellent layer 3 in the Y direction, but stops before the wet spread reaches the liquid repellent layer 3 in the X direction. As shown in FIG. 1C, a non-wetting region 9 in which the bonding material 4 is not spread out is formed in a part of the first electrode 2.

  The bonding material 4 first isotropically wets and spreads after landing on the first electrode 2, but when the bonding material 4 reaches the liquid repellent layer 3 in the Y direction, the wet spreading stops due to the above-described effect. However, if the length of the first electrode 2 in the X direction is set sufficiently longer than the Y direction, the bonding material 4 stops before reaching the liquid repellent layer 3 in the X direction.

  FIGS. 4-2 (d), (e), and (f) are schematic views of the semiconductor device after flip-chip mounting on the structure of FIGS. 4-1 (a), (b), and (c). 4-2 (d) is a top perspective view of the semiconductor device after flip chip, FIG. 4-2 (e) is a cross-sectional view of the AA ′ portion in FIG. 4-2 (d), and FIG. 4-2 (f). FIG. 4B is a cross-sectional view taken along the line BB ′ in FIG.

  As shown in FIG. 4B, the second electrode 6 of the semiconductor element 5 is mounted so as to face the first electrode 2 of the wiring board 1. Further, the second electrode 6 is formed of Au in a rectangular shape that is long in the X direction, like the first electrode 2, and the side surface is covered with the liquid repellent layer 3. The bonding material 4 is between the first electrode 2 and the second electrode 6 and covers all the upper surfaces of both electrodes, but does not reach the insulating portion between adjacent electrodes.

  When flip-chip mounting is performed from the state shown in FIG. 4B, the bonding material 4 tries to further spread by wetting of the semiconductor element 5, but does not wet and spread on the side surface of the electrode in the Y direction. It spreads wet against the region 9. This is because wetting and spreading preferentially from the part with high wettability.

  In the first and second embodiments, the desired effect of the present invention is obtained by releasing the wet spread after flip chip mounting to the side surface of the electrode. In the third embodiment, the wet spread is applied to the non-wetting region 9, that is, the electrode. The desired effect of the present invention is obtained by letting it escape to the upper surface of the electrode that has not yet spread out.

  For example, on the first electrode 2 formed of Au, the bonding material 4 having a viscosity of 10 mPa · s, which is covered with a liquid repellent layer 3 and mixed with Au particles and phenylcyclohexane, is printed to a thickness of 5 μm. Assuming that the semiconductor element 5 is pushed in so as to have a thickness of 3 μm, when the electrode length in the Y direction is 60 μm and the electrode length in the X direction is 220 μm, the effect of suppressing wetting and spreading can be obtained.

  Specifically, when the bonding material 4 is printed, the wet spread spreads up to the liquid repellent layer 3 in the Y direction, but the wet spread stops at 130 μm in the X direction. Therefore, if the electrode in the X direction is 220 μm, the non-wetting region 9 can be formed.

  After that, when flip chip mounting is performed, the bonding material 4 wets and spreads with respect to the non-wetting region 9, and the wet spreading stops when the bonding material 4 reaches the entire upper surface of the electrode. If the length of the electrode in the X direction satisfies the relationship of “length in the X direction = 13083 / length in the Y direction”, the effect of suppressing wetting and spreading is sufficiently obtained.

  In the case of the third embodiment, the thicknesses of the first electrode 2 and the second electrode 6 can be set thinner than those in the first and second embodiments, but it is preferable to set the thickness to 5 μm or more. It is preferable because the effect of suppressing wetting and spreading can be obtained more reliably. The third embodiment has an effect of improving the bonding strength because the electrode area, that is, the bonding area is increased.

  INDUSTRIAL APPLICABILITY The semiconductor device and the manufacturing method thereof according to the present invention have an effect of suppressing a short circuit with an adjacent electrode with respect to flip chip bonding using metal nanoparticles, and reduce the size of the semiconductor device by narrowing the pitch of the electrodes. Useful for this.

DESCRIPTION OF SYMBOLS 1 Wiring board 2 1st electrode 3 Liquid repellent layer 4 Bonding material 5 Semiconductor element 6 2nd electrode 7 Bonding part 8 Bonding tool 9 Non-wetting area | region

Claims (10)

  A wiring board having a first electrode; a semiconductor element mounted on the wiring board and having a second electrode at a position facing the first electrode; and the first electrode and the second electrode. A semiconductor device comprising: a bonding material interposed between and electrically bonded to each other, wherein a liquid repellent layer is formed on side surfaces of the first electrode and the second electrode.   The semiconductor device according to claim 1, wherein a thickness of the second electrode is smaller than a thickness of the first electrode.   3. The semiconductor device according to claim 1, wherein the first electrode and the second electrode are rectangular when viewed from above.   2. The semiconductor device according to claim 1, wherein the liquid repellent layer is formed of a composite film made of a metal and fluorine-based fine particles.   2. The semiconductor device according to claim 1, wherein the liquid repellent layer is formed of a composite film made of Ni and PTFE (polytetrafluoroethylene).   The semiconductor device according to claim 1, wherein the bonding material includes metal particles of 0.5 nm to 100 nm.   The semiconductor device according to claim 1, wherein the bonding material is Au, Ag, Cu, Ni, or an alloy thereof.   Forming a first electrode on the wiring substrate; forming a second electrode on the semiconductor element; forming a liquid repellent layer on a side surface of the first electrode; and the second electrode. A step of forming a liquid repellent layer on the side surface of the substrate, a step of printing a bonding material on the first electrode, a step of reversing and aligning the semiconductor element while holding it with a bonding tool, and the first step A step of mounting the semiconductor element on the wiring substrate so that the electrode and the second electrode face each other, and heating and sintering the bonding material, and the first electrode and the second electrode And a step of forming a bonding portion between the semiconductor devices.   The method of manufacturing a semiconductor device according to claim 8, wherein the liquid repellent layer is formed by electroless plating.   The method for manufacturing a semiconductor device according to claim 8, wherein the bonding material is formed by an inkjet printing method.

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