JP2006313929A - Method for manufacturing flip-chip ic and method for manufacturing flip-chip ic mounting circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a flip-chip IC which can suitably form individual solder bumps and can increase a productivity by effectively preventing a flow of solder paste. <P>SOLUTION: The method for manufacturing a flip-chip IC includes the steps of applying a flux paste on a barrier metal layer 3 formed on a circuit pattern 2 of a semiconductor substrate 1, forming a flux layer 8 by drying the flux paste, applying a solder paste 5' on the flux layer 8 through pattern holes of a stencil, and heating the flux layer 8 and the solder paste 5' to form solder bumps 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a flip chip type IC used for face-down bonding to a circuit board, and a method of manufacturing a flip chip type IC mounted circuit board.

  Conventionally, an IC is face-down bonded to the upper surface of a circuit board having a circuit pattern, that is, the IC is mounted on the circuit board with the surface on which the integrated circuit of the IC is formed facing the circuit board. Has been done.

  An IC used for such face-down bonding is called a flip-chip type IC and generally has a terminal connected to a circuit pattern on a circuit board via solder.

  As such a conventional flip chip type IC, for example, as shown in FIG. 3, a plurality of barrier metal layers 22 made of nickel or the like are formed on one main surface of a semiconductor substrate 21 on which an integrated circuit is provided. A structure in which a passivation layer 23 made of silicon nitride or the like is deposited on a region where the metal layer 22 does not exist and a solder bump 24 is selectively formed on the barrier metal layer 22 is known. When mounting the chip type IC on the circuit board, the flip chip type IC is placed on the circuit board so that the solder bumps 24 of the flip chip type IC face the corresponding circuit pattern on the circuit board. Thereafter, the solder bump 24 is heated and melted at a high temperature so that the barrier metal layer 22 of the flip chip IC is formed on the circuit board. It is soldered to turn.

  When the solder bump 24 is formed on the barrier metal layer 22, a predetermined solder paste obtained by adding / mixing an organic solvent or flux to a large number of solder particles (particle size: 2 μm to 12 μm) is conventionally used. By printing and applying directly on the upper surface of the barrier metal layer 23 by well-known screen printing or the like, the solder particles are bonded to each other and bonded to the barrier metal layer 22 through drying and reflow processes. It was formed in a spherical shape.

  The flux contained in the solder paste is for cleaning the metal surface during soldering and maintaining the metal surface in a good state where no oxide film is present. A rosin type is used.

  However, in the conventional flip-chip type IC described above, the surface state of the barrier metal layer 22 and the passivation layer 23 is very smooth when the solder bump 25 is formed. However, part of the solder paste flows and spreads around. In this case, the defect that a solder bridge is formed between adjacent solder bumps is induced.

  Further, when the solder bumps of the flip chip type IC are formed by the above-described conventional forming method, the stencil such as a metal mask used for printing the solder paste directly contacts the barrier metal layer 22 and the like. The barrier metal layer 22 and the like may be damaged, which has been one of the causes of reducing the productivity of flip chip ICs.

  The present invention has been devised in view of the above-mentioned drawbacks, and its purpose is to effectively prevent the flow of solder paste, to form individual solder bumps satisfactorily, and to improve productivity. It is an object of the present invention to provide a method of manufacturing a flip chip type IC capable of performing the above and a method of manufacturing a flip chip type IC mounting circuit board.

  The flip chip type IC manufacturing method according to the first aspect of the present invention includes a step of applying a flux paste on a barrier metal layer formed on a circuit pattern of a semiconductor substrate on which a circuit pattern is formed, A step of drying the flux paste to form a flux layer, a step of applying a solder paste on the flux layer through the pattern holes of a stencil having pattern holes, and a heat treatment of the flux layer and the solder paste. And a step of forming solder bumps.

  In this manufacturing method, it is preferable to apply the flux paste so as to cover the entire barrier metal layer.

  In the present manufacturing method, the barrier metal layer is preferably constituted by a zinc layer made of zinc and a nickel layer made of nickel and laminated on the zinc layer.

  According to a second aspect of the present invention, there is provided a method for manufacturing a flip chip type IC mounting circuit board, wherein the flip chip type IC manufactured by the method for manufacturing a flip chip type IC according to the first aspect of the present invention is replaced with the solder bump. Mounting on a circuit board having a circuit pattern to be bonded to the board, and soldering the flip chip type IC to the circuit board by heating and melting the solder bumps. It is a feature.

  According to the flip chip type IC manufacturing method of the present invention, when forming solder bumps, the solder paste is applied onto the flux layer, and part of the organic solvent, etc. in the solder paste penetrates into the flux layer. Therefore, the plate slipping property when printing the solder paste is extremely good, and the spread of the solder paste can be effectively prevented. Accordingly, individual solder bumps can be formed satisfactorily.

  Further, according to the flip chip type IC manufacturing method of the present invention, when solder paste is applied by stencil printing at the time of forming solder bumps, the stencil such as a metal mask comes into contact with the surface of the flux layer, and the barrier metal layer or the like is contacted. There is no direct contact. Therefore, the barrier metal layer and the like are hardly damaged by the solder paste application operation, and the productivity of the flip-chip IC can be improved.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of a flip chip type IC manufactured by the manufacturing method of the present invention, in which 1 is a semiconductor substrate, 2 is a circuit pattern, 3 is a barrier metal layer, 4 is a passivation layer, and 5 is a solder bump. is there.

  The semiconductor substrate 1 is made of single crystal silicon or the like, and a circuit pattern 2 made of aluminum or the like and semiconductor elements (not shown) are formed on one main surface with a high density. The barrier metal layer 3 and the passivation layer 4 are deposited in the region where the barrier metal layer 3 does not exist.

  The semiconductor substrate 1 functions as a supporting base material for supporting a semiconductor element, a circuit pattern 2, a barrier metal layer 3, a passivation layer 4, and the like. A single crystal silicon ingot (lumb) is formed by the (pulling up method) or the like, and thereafter, the ingot is manufactured by slicing the ingot to a predetermined thickness.

  The barrier metal layer 3 on the semiconductor substrate 1 has, for example, a two-layer structure in which zinc (Zn) and nickel (Ni) are sequentially laminated from the semiconductor substrate 1 side, and the total thickness of the barrier metal layer is, for example, 1 μm. It is set to ˜4 μm.

  When the flip-chip type IC is mounted on the circuit board, the barrier metal layer 3 is eroded by solder on aluminum or the like that forms the circuit pattern 2 as the solder bumps 5 provided on the barrier metal layer 3 are melted. It works to prevent this.

  Such a barrier metal layer 3 is formed on the circuit pattern 2 exposed in the opening of the passivation layer 4, that is, in the region where the passivation layer 4 does not exist, after the formation of the passivation layer 4 described later. By adopting plating or the like and sequentially depositing Zn and Ni, the whole is formed in a substantially cylindrical shape.

  Of the two layers constituting the barrier metal layer 3, the lower Zn layer is formed by replacing the Ni layer with a conventionally known electroless plating method, thereby converting the Ni layer into an efficient layer. The thickness is set to 0.01 μm to 0.1 μm.

On the other hand, the passivation layer 4 effectively prevents the above-described semiconductor element and circuit pattern 2 from being corroded by contact with moisture contained in the atmosphere by blocking well from the atmosphere. For example, it is formed of an electrically insulating material having excellent sealing properties such as silicon nitride (Si ₃ N ₄ ), and the thickness thereof is set to 0.5 μm to 1.5 μm, for example.

  The passivation layer 4 is deposited on the semiconductor substrate 1 provided with the circuit pattern 2 or the like by employing a conventionally well-known thin film forming technique, for example, a vacuum deposition method or a sputtering method. Thereafter, this is processed into a predetermined pattern by a well-known photolithography and etching technique or the like, that is, by forming a through-hole in a place where the barrier metal layer 3 is formed.

  Then, substantially spherical solder bumps 5 are individually formed on each upper surface of the barrier metal layer 3 described above.

  The solder bump 5 is an alloy for metal bonding in which Sn, Ag, and Cu are melted and solidified at a ratio of 96.5: 3.0: 0.5, and a flip chip type IC is mounted on a circuit board. In doing so, it is melted by being heated in a furnace, and the circuit pattern 2 of the flip chip type IC and the circuit pattern on the circuit board are joined by soldering.

  The surface of the solder bump 5 and the passivation layer 4 described above is thinly coated with a flux 8a made of rosin-based flux, and this flux 8a cleans the metal surface when soldering to the circuit board. The metal surface is maintained in a good state with no oxide film.

  Thus, the flip chip type IC described above is placed on the circuit board so that a large number of solder bumps 5 provided on one main surface thereof face the corresponding circuit pattern on the circuit board, and then soldered. The bump 5 is heated and melted at a high temperature, and the melted solder is solder-bonded to a circuit pattern or the like on the circuit board to be mounted on the circuit board.

  Next, a method for forming the above-described flip-chip IC solder bump 5 will be described with reference to FIG.

  (1) First, a flux paste 8 ′ is prepared, and this is applied to the entire upper surface of the semiconductor substrate 1 on which the barrier metal layer 3 and the passivation layer 4 are formed, thereby forming the flux layer 8.

  As the flux paste 8 ', for example, a rosin-based flux dissolved and adjusted with an organic solvent such as isopropyl alcohol (IPA) is preferably used, and the flux paste 8' is used as a barrier metal by a conventionally known spin coating method or the like. The upper surface of the semiconductor substrate 1 having the layer 3 and the like is applied to a substantially uniform thickness of 1 μm to 3 μm, for example, and dried to completely cover the barrier metal layer 3 and the passivation layer 4 with the flux layer 8. To be formed.

  (2) Next, a solder paste 5 ′ and a stencil for printing solder paste are prepared, and the solder paste 5 ′ is applied to the upper surface of the flux layer 8 located in a region on the barrier metal layer 3.

  As the solder paste 5 ', a solder paste prepared by adding and mixing an organic solvent such as IPA to a large number of solder particles to have a predetermined viscosity is used, and the stencil is formed of, for example, stainless steel. A metal mask or the like is used. In this stencil, a plurality of pattern holes corresponding to the pattern of the barrier metal layer 3 are formed, and these pattern holes are formed with high accuracy by adopting conventionally known photo-etching or laser processing. The

  When the solder paste 5 'is applied onto the flux layer 8, the semiconductor substrate 1 with the flux layer obtained in the step (1) is first placed and fixed on the stage of the stencil printing machine, and then the above-mentioned. Is placed on the semiconductor substrate 1 so that the individual pattern holes are located on the corresponding barrier metal layer 3, and then the squeegee placed on the stencil is moved together with the solder paste 5 '. As a result, the solder paste 5 'is printed and applied onto the flux layer 8 through the pattern holes of the stencil.

  At this time, since part of the organic solvent or the like in the solder paste 5 'penetrates into the flux layer 8, the spread of the solder paste 5' after coating is effectively prevented, and the plate is missing. The properties are extremely good.

  Further, in this case, the lower surface of the stencil comes into contact with the surface of the flux layer 8 when a pressing force from the squeegee is applied, and does not directly contact the barrier metal layer 3 or the like. Therefore, the barrier metal layer 3 and the like are hardly damaged by the application work of the solder paste 5 ′, and the productivity of the flip chip type IC can be improved.

  (3) Next, the solder paste 5 'applied on the flux layer 8 is dried, and finally, the solder bump 5 is formed by heating it at a high temperature.

  The heat treatment for the solder paste 5 ′ and the flux layer 8 is performed at a temperature of, for example, 230 ° C. to 260 ° C., and the heating causes the flux layer 8 to be in a molten state, and the solder particles in the solder paste 5 ′ are self-weighted. Move to the vicinity of 3. Then, these solder particles are also heated and melted to be bonded to each other and bonded to the upper surface of the barrier metal layer 3. By cooling this as it is, substantially spherical solder bumps 5 are individually formed on the barrier metal layer 3. Will be.

  In addition, this invention is not limited to the above-mentioned embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention.

  For example, in the above-described embodiment, a metal mask is used as the stencil plate 6, but instead of this, another screen plate formed of a polyester resin or the like may be used.

  In the above-described embodiment, a rosin flux or the like may be separately added and mixed in the solder paste 5 ′ applied on the flux layer 8.

It is sectional drawing of the flip chip type IC manufactured by the manufacturing method of this invention. (A)-(c) is sectional drawing for every process for demonstrating the formation method of the solder bump 5. FIG. It is sectional drawing of the conventional flip chip type IC.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Circuit pattern 3 Barrier metal layer 4 Passivation layer 5 Solder bump 5 'Solder paste 8 Flux layer 8' Flux paste

Claims (4)

Applying a flux paste on the barrier metal layer formed on the circuit pattern of the semiconductor substrate on which the circuit pattern is formed;
Drying the flux paste to form a flux layer;
Applying a solder paste on the flux layer through the pattern holes of the stencil having pattern holes;
And a step of heat-treating the flux layer and the solder paste to form solder bumps. The method of manufacturing a flip chip type IC according to claim 1, wherein the flux paste is applied so as to cover the entire barrier metal layer. 3. The method of manufacturing a flip-chip IC according to claim 1, wherein the barrier metal layer includes a zinc layer made of zinc and a nickel layer laminated on the zinc layer and made of nickel. Placing the flip chip type IC manufactured by the manufacturing method according to any one of claims 1 to 3 on a circuit board having a circuit pattern bonded to the solder bump;
And a step of soldering the flip chip type IC to the circuit board by heating and melting the solder bumps.

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