JP2005026715A6 - Semiconductor device having low melting point metal bump and flip chip bonding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device provided with a high-quality low melting point metal ball and mounted on a substrate by flip chip bonding, and a flip chip bonding method.
A semiconductor device including an electrode 8 formed on a semiconductor chip 2 and a low-melting-point metal ball 3 having a predetermined size formed in a spherical shape, which is adhesively bonded to these electrodes by a flux, and a semiconductor device using the same This is a flip chip bonding method.
[Selection] Figure 2

Description

  The present invention relates to a semiconductor device provided with a low melting point metal bump and a method of manufacturing the same.

  Semiconductor devices are currently widely used in various fields. Usually, these semiconductor devices are used by being mounted on a substrate. These mounting methods include bonding methods such as tape automated bonding (TAB), wire bonding, and flip chip bonding.

  TAB and wire bonding are techniques for mounting a semiconductor device on a substrate via leads. The leads are arranged in one row per side around the semiconductor device. Therefore, these techniques are not suitable for high-density mounting of semiconductor devices. In contrast, flip-chip bonding is a technique for directly connecting an electrode of a semiconductor device to an electrode terminal on a substrate via a bonding metal. Since the electrodes of the semiconductor device can be provided in a lattice pattern on the entire surface, this technique is suitable for high-density mounting. As a bonding metal in flip chip bonding, various solders are generally used in order to perform bonding by melting at a low temperature.

  In flip chip bonding, a semiconductor device in which bumps of low melting point metal for bonding are provided on electrodes is used, and the semiconductor device is connected to the electrode terminals of the substrate by a reflow method in which the bumps are melted and resolidified.

  In general, the bump is formed by vapor deposition or plating. However, in any of these bump forming methods, complicated processing steps using a mask must be repeated. Further, in the method of forming bumps by vapor deposition, the bump material is deposited on the portion where the bump is not formed, and the amount of deposition on the portion is very large. Therefore, this method is not preferable in terms of cost and efficiency. Furthermore, wet plating such as electroplating and electroless plating causes contamination of the wafer and environmental problems, and countermeasures against such problems are indispensable. As described above, the normal bump forming method is relatively expensive, and its practical use is limited.

  As a bump forming method other than vapor deposition and plating, there is a stud bump method. In this method, since bumps are formed one by one, the manufacturing efficiency is low, and the amount of individual bumps tends to vary.

  Therefore, it is difficult to ensure the uniformity of bonding between the semiconductor device and the substrate.

  An object of the present invention is to provide a semiconductor device having a high-quality low melting point metal ball that can be mounted on a substrate by flip chip bonding, and a method for manufacturing the same.

The semiconductor device of the present invention includes an electrode formed on a semiconductor chip, and includes a low-melting-point metal ball having a predetermined size formed in a spherical shape and adhesively bonded to the electrode by a flux.
Preferably, the electrode on the semiconductor chip is formed of an electrode material of Cu or Cu alloy, Al or Al alloy, or Au or Au alloy.
When the electrode material is Al or an Al alloy, preferably, at least one metal or metal alloy layer having a melting point higher than that of the electrode material is laminated on the layer formed of the electrode material.
This stacked layer is preferably formed of a metal selected from Ti, W, Ni, Cr, Au, Pd, Cu, Pt, Ag, Sn and Pb or alloys of these metals.
Preferably, of the layers stacked on the electrode material layer, the layer in contact with the electrode material layer is formed of Ti, W, Ni, Cr, Pd, Cu, or Pt or an alloy of these metals and is in contact with the low melting point metal ball. The layer is formed of Ni, Au, Pd, Cu, Pt, Ag, Sn or Pb or an alloy of these metals.
A method for manufacturing a semiconductor device according to the present invention includes a semiconductor device having electrodes formed on a semiconductor chip and having a low-melting point metal ball of a predetermined size formed in a spherical shape and adhesively bonded to each electrode. A method of manufacturing, wherein a flux is applied to the electrode,
The low melting point metal ball,
Applying a small amplitude vibration to a container containing low melting point metal balls to float those low melting point metal balls;
The floating low melting point metal ball is adsorbed to the suction hole of the array plate provided with the suction port at a position corresponding to the position of the electrode of the semiconductor chip to which the low melting point metal ball is to be bonded and bonded. A process of arranging and supporting low melting point metal balls
Removing the extra low melting point metal balls attached to the array plate or adhering to the low melting point metal balls adsorbed to the suction port by vibrating the array plate; A step of bringing melting point metal balls into contact with the electrodes of the semiconductor chip in a lump;
And adhesively bonding to each of the electrodes.
In another aspect of the present invention, a method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device having a low melting point metal bump on an electrode of a semiconductor chip,
Applying flux to the electrode;
A process of floating low-melting metal balls of low-melting metal balls of a predetermined size formed into a spherical shape by applying minute amplitude vibration to a container containing the low-melting metal balls, floating the low-melting metal balls, A low melting point metal ball is adsorbed to the suction port of the array plate provided with a suction port at a position corresponding to the position of the electrode of the semiconductor chip to which the low melting point metal ball is to be adhesively bonded, and the low melting point metal ball is arranged on the array plate. A step of removing the extra low melting point metal ball attached to the array plate or adhering to the low melting point metal ball adsorbed to the suction port by vibrating the array plate, and on the array plate. A step of adhesively bonding the supported and arranged low-melting-point metal balls to the electrodes by a method including a step of bringing the balls into contact with the electrodes of the semiconductor chip in a lump, and these low-melting-point metals Reflowing the ball to form a hemispherical bump,
including.

  It is apparent that the semiconductor device of the present invention includes low-melting point metal ball bumps that are directly bonded to the respective electrodes formed on the semiconductor chip. High quality bumps can be made by making the size of the metal balls uniform. The metal balls can be adhesively bonded to the electrodes instead of being formed on the electrodes of the semiconductor chip by plating or vapor deposition using conventional methods. Therefore, the semiconductor device of the present invention can be manufactured without using a mask and without concern about environmental pollution.

  Furthermore, by adjusting the size of the low melting point metal ball, the amount of bumps can be controlled easily and with high accuracy, and the reliability of the bumps can be improved.

  The present invention can be advantageously applied to flip chip bonding that enables high-density mounting on a substrate of a semiconductor device.

  FIG. 1 shows a semiconductor device 1 of the present invention. The semiconductor device 1 includes a low melting point metal ball 3 adhesively bonded on an electrode (not shown) formed on the surface of a semiconductor chip 2.

  The low melting point metal ball 3 can be formed from one of various solders used for mounting a semiconductor device on a substrate. Examples of such solders include solders such as Sn alloys such as Sn—Pb alloys and Sn—Ag alloys, and solders such as Pb alloys such as Pb—In alloys.

The electrode for adhesively bonding the bump 3 of the low melting point metal ball can be formed from an electrode material of Cu or Cu alloy, Al or Al alloy, or Au or Au alloy. In the semiconductor device of the present invention, it is preferable to use an electrode having a surface area of 900 to 22,500 μm ² . That is, when a square electrode is used, one side of the electrode has a size of 30 to 150 μm.

  When the electrode material is Al or an Al alloy, solder balls (hereinafter, this term shall indicate a low melting point metal ball, and this term will be used below) are reflowed and connected to the electrode. Adhesion with the electrode decreases. When Al or an Al alloy is used as the electrode material, in order to avoid this decrease, at least one metal or metal alloy layer having a melting point higher than that of the electrode material is laminated on the layer formed of the electrode material. Typical examples of materials used for this purpose are metals selected from Ti, W, Ni, Cr, Au, Pd, Cu, Pt, Ag, Sn and Pb or alloys of these metals. Of these substances, Ti, W, Ni, Cr, Pd, Cu or Pt or alloys of these metals are particularly effective for adhesion between the material and a layer made of Al or an alloy thereof. Therefore, it is preferable to use any of the above metals or alloys of these metals as the layer in contact with the Al or its alloy layer.

  Furthermore, solder generally exhibits good wettability to Ni, Au, Pd, Cu, Pt, Ag, Sn or Pb or alloys of these metals. Therefore, the layer in contact with the solder ball among the layers laminated on the electrode material layer of Al or Al alloy is preferably formed from these materials.

  As described above, when Al or Al alloy is used, the electrode has a multilayer structure as illustrated in FIG. In FIG. 2, an electrode 8 includes a first layer 5 made of Al (or an Al alloy) on the surface of the semiconductor chip 2, and a second layer 6 made of Cr on the first layer. A laminated structure including the third layer 7 made of Cu is formed on the second layer.

  As an example of an electrode laminated structure using Al or an alloy thereof as an electrode material, as shown in FIG. 2, a laminated structure having an Al (or Al alloy) layer, a Cr layer, and a Cu layer sequentially from the semiconductor chip side (this In addition to Al / Ni, Al / Ni / Au, Al / Ni / Cu / Au, Al / Cr / Cu / Au, and the like, in the following, such a laminated structure is indicated as Al / Cr / Cu). Al / Ti / Cu / Au, Al / Ti / TiW (alloy) / Cu / Au, Al / TiW (alloy) / Cu / Au, Al / Cr / Ni / Pd, Al / Pd / Au, Al / Ni / Sn, Al / Cr / Cu / Pd, and Al / Cr / Pt can be included. Needless to say, the electrode stacking structure effective in the semiconductor device of the present invention is not limited to the above-described structure.

  Flux is used to adhesively bond the solder balls to the electrodes. Any of the fluxes generally used in the manufacture of semiconductor devices can be used. The flux is applied to the electrode surface. As a method for applying the flux to the electrode surface, a standard method such as screen printing can be used.

When flip-chip bonding the semiconductor device of the present invention to a substrate, the bumps of the solder balls are opposed to the respective electrode terminals of the substrate, aligned, brought into contact with the bumps, and then the bumps are reflowed. . Such flip-chip bonding methods are widely known and need not be described in detail here.

  In the semiconductor device of the present invention, the solder balls may be reflowed once to form hemispherical bumps and then flip-chip bonded to the substrate. FIG. 3 shows an example of a hemispherical bump. The hemispherical bump 10 in FIG. 3 is formed by reflowing the solder ball bump 3 adhesively bonded to the laminated electrode 8 described in FIG.

  Here, the bumps 10 of FIG. 3 formed by reflowing solder balls are referred to as “hemispherical”. This term is mainly based on the vertical cross-sectional shape of the bump after reflow as shown in FIG. There are various shapes of electrodes on the semiconductor chip, such as a circle, a square, and other arbitrary shapes. For example, a bump formed by reflowing a solder ball on a square electrode has a hemispherical longitudinal cross-sectional shape as seen in FIG. However, since the melted solder wets the entire square electrode surface and solidifies, the shape seen from above (cross-sectional shape) is not a circle but a square or a shape close to a square. Therefore, the hemispherical bump referred to here is not only a bump that appears to have a circular cross-sectional shape when viewed from above after reflow, but also an arbitrary cross-sectional shape that reflects the electrode shape under the bump. It should be noted that it also includes the bumps it has. In other words, the “hemispherical bump” herein indicates all types of bumps formed by reflowing solder balls bonded and bonded to electrodes of an arbitrary shape.

In order to reflow the solder balls and appropriately form the hemispherical bumps on the electrodes, the radius R of the solder balls that are adhesively bonded to the electrodes is selected so that the surface area of the electrodes is A and the following formula is satisfied. Is desirable.
0.4 × A ^0.5 ≦ R ≦ 2 × A ^0.5
When the radius R of the solder ball is less than 0.4 × A ^0.5 , the amount of solder becomes insufficient, and it becomes difficult to form a good hemispherical bump after reflow. When the radius R of the solder ball exceeds 2 × A ^0.5 , the hemispherical bump is larger than the size of the electrode, and as a result, the joint between the electrode and the bump is easily stressed and easily broken.

When an electrode having a surface area of 900 to 22,500 μm ² is used in the semiconductor device of the present invention, the preferable radius R of the solder ball is 12 to 300 μm from the above formula.

Next, an example of manufacturing the semiconductor device of the present invention will be described with reference to FIG.
As shown in FIG. 4A, an electrode 42 of 100 × 100 μm Al alloy (Al—Si—Cu alloy) is formed on a semiconductor chip 41 to a thickness of 1.0 μm by sputtering. In this figure, reference numeral 43 denotes a passivation film that partitions the electrodes thus formed. Next, as shown in FIG. 4B, a Ni metal layer 44 and a Cu metal layer 45 are sequentially stacked on the chip electrode 42 with a thickness of 80 nm by sputtering.

  The above is the process of forming the base for forming the low melting point metal bump. Next, as shown in FIG. 4C, Pb—Sn alloy solder balls 46 having a diameter of 80 μm are adhesively bonded to the Cu metal layer 45. When the solder balls are bonded and bonded, a flux (not shown) is first applied to the surface of the metal layer 45 by screen printing. Next, a solder ball 46 is adhesively bonded to the flux. A method of adhesively bonding the solder ball to the electrode will be described later.

  The semiconductor device of the present invention thus manufactured has the solder balls opposed to the corresponding electrode terminals of the substrate, aligns the balls, brings the balls into contact with the electrode terminals, and reflows the balls. Can be flip-chip bonded to the substrate.

  The semiconductor device of the present invention having the solder ball 46 shown in FIG. 4 (c) has a substrate after the solder balls are reflowed to form hemispherical bumps 47 as shown in FIG. 4 (d). Flip chip bonding may be used.

  In the above example, since an Al alloy is used as the electrode material, a Ni layer and a Cu layer are laminated on the Al alloy layer in order to firmly bond the semiconductor device to the substrate by solder bumps. However, when the electrode material is neither Al nor an Al alloy, for example, Cu or Cu alloy, or Au or Au alloy, an underlayer for forming a low-melting point metal ball (1 or There is no need to form two or more metal (or alloy) layers. Therefore, as shown in FIG. 5, bumps of the solder balls 53 can be directly formed on the electrodes 52 of the semiconductor chip 51. This solder ball can also be used for flip chip bonding after being reflowed to form a hemispherical bump.

  Next, another example in which a solder ball bump having a diameter of 150 μm is formed on an electrode having a diameter of 50 μm will be described. In this case, a Cr layer, a Cu layer and an Au layer having the same diameter or a slightly larger diameter are sputtered onto an Al-Cu alloy electrode having a diameter of 50 μm and a thickness of 1.0 μm by a thickness of 80 nm, 80 nm and 30 nm, respectively. Then we will layer them one after another. Next, a flux is applied to the surface of the Au layer, and a solder ball of a Pb—Sn alloy having a diameter of 150 μm is adhesively bonded thereon. When a shear test was performed on the hemispherical bumps formed by reflowing the solder balls, all the breaks occurred in the solder balls, and no breaks were observed at the joints between the bumps and the electrodes.

  Next, a method for adhesively bonding solder balls to electrodes will be described. Here, adhesive bonding of a solder ball onto an electrode made of a single material as described with reference to FIG. 5 instead of an electrode having a multilayer structure will be described.

  As shown in FIG. 6A, the solder ball 53 is floated by applying a minute amplitude vibration to the container 60 containing the solder ball 53. Next, the floating solder ball 53 is adsorbed to the adsorbing port 61 of the array plate 63 provided with the adsorbing port 61 at a position corresponding to the position of the electrode of the semiconductor chip to which the solder ball 53 is to be bonded and bonded (soldering). A suction mechanism for adsorbing the balls is not shown), and the solder balls 53 are arranged and supported on the arrangement plate 63. As shown in FIG. 6A, when the solder balls are attracted / arranged, the extra solder balls 53 ′ are attached to locations other than the suction ports 61 of the array plate 63, or the solder that is attracted to the suction ports 61. Another extra solder ball 53 "adheres to the ball 53. Therefore, these extra solder balls 53 'and 53" are removed. For this purpose, it is possible to preferably remove the excess solder balls 53 ′ and 53 ″ by applying horizontal ultrasonic vibration to the array plate 63. The array plate 63 of FIG. For this reason, only two suction ports 61 are shown, but it should be noted that the actual array plate has the same number of suction ports as the number of solder balls to be adhesively bonded to the electrodes of the semiconductor chip.

  Next, as shown in FIG. 6B, the array plate 63 carrying the solder balls 53 in a predetermined position is moved onto the semiconductor chip 51, and the solder balls 53 and the respective electrodes 52 of the semiconductor chip 51 are appropriately connected. After alignment, the array plate 63 is moved downward to bring the solder balls 53 into contact with the respective electrodes 52. After the contact, the adsorption of the solder balls 53 to the array plate 63 is stopped (by stopping the suction mechanism), and the array plate 63 is moved upward.

  If a flux (not shown) is applied to the surface of the electrode 52, the solder ball 53 is adhesively bonded to the electrode due to its adhesiveness.

  This method is very advantageous for manufacturing the semiconductor device of the present invention because the solder bumps can be collectively bonded to a large number of electrodes of the semiconductor chip by the method described here.

  Semiconductor chips are generally made in large numbers on a single wafer and then cut into individual chips. The above-described method can be applied to a plurality of semiconductor chips before being separated from the wafer, or can be applied to individual semiconductor chips after being separated from the wafer. From what has been described here, it is apparent that the semiconductor chip according to the present invention includes not only individual semiconductor chips that have been separated but also a plurality of semiconductor chips that are manufactured on a single wafer.

It is a perspective view explaining the semiconductor device of this invention. It is a figure explaining the electrode in the semiconductor device of this invention. It is a figure explaining the hemispherical bump formed by reflowing the low melting metal ball of the semiconductor device of the present invention. It is a figure explaining the manufacturing method of the semiconductor device of this invention. It is a figure explaining the bump of the solder ball formed directly on the chip electrode of a single material. It is a figure explaining the preferable method of adhesive-bonding a low melting metal ball | bowl on each electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor device 2 Semiconductor chip 3 Low melting-point metal ball 5 1st layer 6 2nd layer 7 3rd layer 8 Electrode 10 Hemispherical bump 41, 51 Semiconductor chip 42, 52 Electrode 43 Passivation film | membrane 44, 45 Metal layer 46 53 Solder balls 47 Hemispherical bumps 60 Containers 61 Adsorption ports 63 Array plate

The present invention relates to a semiconductor device having a low melting point metal bump and a flip chip bonding method.

  Semiconductor devices are currently widely used in various fields. Usually, these semiconductor devices are used by being mounted on a substrate. These mounting methods include bonding methods such as tape automated bonding (TAB), wire bonding, and flip chip bonding.

  TAB and wire bonding are techniques for mounting a semiconductor device on a substrate via leads. The leads are arranged in one row per side around the semiconductor device. Therefore, these techniques are not suitable for high-density mounting of semiconductor devices. In contrast, flip-chip bonding is a technique for directly connecting an electrode of a semiconductor device to an electrode terminal on a substrate via a bonding metal. Since the electrodes of the semiconductor device can be provided in a lattice pattern on the entire surface, this technique is suitable for high-density mounting. As a bonding metal in flip chip bonding, various solders are generally used in order to perform bonding by melting at a low temperature.

  In flip chip bonding, a semiconductor device in which bumps of low melting point metal for bonding are provided on electrodes is used, and the semiconductor device is connected to the electrode terminals of the substrate by a reflow method in which the bumps are melted and resolidified.

  In general, the bump is formed by vapor deposition or plating. However, in any of these bump forming methods, complicated processing steps using a mask must be repeated. Further, in the method of forming bumps by vapor deposition, the bump material is deposited on the portion where the bump is not formed, and the amount of deposition on the portion is very large. Therefore, this method is not preferable in terms of cost and efficiency. Furthermore, wet plating such as electroplating and electroless plating causes contamination of the wafer and environmental problems, and countermeasures against such problems are indispensable. As described above, the normal bump forming method is relatively expensive, and its practical use is limited.

As a bump forming method other than vapor deposition and plating, there is a stud bump method. In this method, since bumps are formed one by one, the manufacturing efficiency is low, and the amount of individual bumps tends to vary. Therefore, it is difficult to ensure the uniformity of bonding between the semiconductor device and the substrate.
Prior art documents include the following Patent Documents 1 to 6.

JP 59-148352 A JP-A-2-180036 JP-A-8-139097 JP-A-8-118055 JP-A-8-139093 JP-A-8-162494

An object of the present invention is to provide a semiconductor device that includes a high-quality low melting point metal ball and can be mounted on a substrate by flip chip bonding, and a flip chip bonding method.

(1) An electrode made of only Cu or Cu alloy or Au or Au alloy formed on a semiconductor chip, and a low-melting point metal ball of a predetermined size formed in a spherical shape, which is adhesively bonded to these electrodes by flux. Including semiconductor devices .
(2) At least a layer of electrode material made of Al or Al alloy formed on the semiconductor chip and a metal layer or metal alloy layer laminated on this electrode material layer and having a melting point higher than that of the electrode material A semiconductor device comprising an electrode including one (excluding a solder layer) and a low melting point metal ball of a predetermined size formed in a spherical shape, which is adhesively bonded to these electrodes by a flux .
(3) at least one layer laminated on said layer of electrode material, Ti, W, Ni, Cr , Au, Pd, Cu, In Pt or A g or we selected metal or an alloy of these metals The semiconductor device according to (2), which is formed.
(4) The at least one layer laminated on the electrode material and in contact with the electrode material layer is formed of Ti, W, Ni, Cr, Pd, Cu or Pt or an alloy of these metals, and from the electrode material layer farthest wherein the at least one layer in contact with the low melting point metal balls Ni, Au, Pd, Cu, Pt or a g or is an alloy of these metals (3) the semiconductor device according.
(5) An electrode made of Cu or Cu alloy or Au or Au alloy formed on a semiconductor chip, or a layer of electrode material composed of Al or Al alloy and the electrode laminated on the electrode material layer An electrode including at least one metal layer or metal alloy layer (excluding a solder layer) having a melting point higher than that of the material, and a low-melting-point metal ball having a predetermined size formed in a spherical shape, adhesively bonded to these electrodes A method of manufacturing a semiconductor device including :
Applying a flux to the electrode, and then applying the low-melting metal balls to the container containing the low-melting metal balls by applying a minute amplitude vibration to float the low-melting metal balls.
The floating low melting point metal ball is adsorbed to the suction hole of the array plate provided with the suction port at a position corresponding to the position of the electrode of the semiconductor chip to which the low melting point metal ball is to be bonded and bonded. A process of arranging and supporting low melting point metal balls
Removing the extra low melting point metal balls attached to the array plate or adhering to the low melting point metal balls adsorbed to the suction port by vibrating the array plate; A step of bringing melting point metal balls into contact with the electrodes of the semiconductor chip in a lump;
Manufactured by the semiconductor device manufacturing method comprising adhesively bonding before Symbol electrodes by a process comprising,
A semiconductor device comprising a low melting point metal ball adhesively bonded to each electrode of a semiconductor chip .
(6) A method of manufacturing a semiconductor device having a low melting point metal bump on a semiconductor chip ,
An electrode made of only Cu or Cu alloy or Au or Au alloy, or a layer of electrode material composed of Al or Al alloy and a metal layer or metal alloy having a melting point higher than that of the electrode material laminated on the electrode material layer Applying flux to an electrode including at least one layer (excluding a solder layer) ;
A step of suspending low-melting metal balls of low-melting metal balls of a predetermined size formed into a spherical shape by applying micro-amplitude vibration to a container containing the low-melting metal balls to float the low-melting metal balls, A low melting point metal ball is adsorbed to the suction port of the array plate provided with a suction port at a position corresponding to the position of the electrode of the semiconductor chip to which the low melting point metal ball is to be bonded and bonded, and the low melting point metal ball is arranged on the array plate A step of removing the extra low melting point metal ball attached to the array plate or adhering to the low melting point metal ball adsorbed to the suction port by vibrating the array plate, and on the array plate. A step of adhesively bonding the supported and arranged low melting point metal balls to the electrode by a method including the step of bringing the low melting point metal balls into contact with the electrodes of the semiconductor chip in a lump; The process of forming a hemispherical bump by reflowing
Manufactured by a method of manufacturing a semiconductor device including
A semiconductor device provided with a low melting point metal in an electrode of a semiconductor chip .
(7) The low melting point metal ball of the semiconductor device described in (1) is opposed to the corresponding electrode terminal of the substrate, aligned, and the ball is brought into contact with the electrode terminal, and then reflow is performed. Flip chip bonding method.
(8) The low melting point metal ball of the semiconductor device according to (5) is opposed to each corresponding electrode terminal of the substrate, aligned, brought into contact with the electrode terminal, and then reflowed. Flip chip bonding method.
(9) The hemispherical bumps of the semiconductor device according to (6) are made to face each corresponding electrode terminal of the substrate, aligned, the hemispherical bump is brought into contact with the electrode terminal, and then reflow is performed. Flip chip bonding method characterized.

  It is apparent that the semiconductor device of the present invention includes low-melting point metal ball bumps that are directly bonded to the respective electrodes formed on the semiconductor chip. High quality bumps can be made by making the size of the metal balls uniform. The metal balls can be adhesively bonded to the electrodes instead of being formed on the electrodes of the semiconductor chip by plating or vapor deposition using conventional methods. Therefore, the semiconductor device of the present invention can be manufactured without using a mask and without concern about environmental pollution.

  Furthermore, by adjusting the size of the low melting point metal ball, the amount of bumps can be controlled easily and with high accuracy, and the reliability of the bumps can be improved.

  The present invention can be advantageously applied to flip chip bonding that enables high-density mounting on a substrate of a semiconductor device.

  FIG. 1 shows a semiconductor device 1 of the present invention. The semiconductor device 1 includes a low melting point metal ball 3 adhesively bonded on an electrode (not shown) formed on the surface of a semiconductor chip 2.

  The low melting point metal ball 3 can be formed from one of various solders used for mounting a semiconductor device on a substrate. Examples of such solders include solders such as Sn alloys such as Sn—Pb alloys and Sn—Ag alloys, and solders such as Pb alloys such as Pb—In alloys.

Electrodes for adhesively bonding bumps 3 of low melting point metal balls, Cu or Cu coupling Kimua Rui is formed only Au or an Au alloy, or a layer of an electrode material composed of Al or an Al alloy, the electrode material It includes at least one metal layer or metal alloy layer (excluding the solder layer) laminated on the layer and having a melting point higher than that of the electrode material . In the semiconductor device of the present invention, it is preferable to use an electrode having a surface area of 900 to 22,500 μm ² . That is, when a square electrode is used, one side of the electrode has a size of 30 to 150 μm.

When the electrode material is Al or an Al alloy, solder balls (hereinafter, this term shall indicate a low melting point metal ball, and this term will be used below) are reflowed and connected to the electrode. Adhesion with the electrode decreases. When Al or an Al alloy is used as the electrode material, in order to avoid this decrease, at least one metal or metal alloy layer having a melting point higher than that of the electrode material is laminated on the layer formed of the electrode material. Representative examples of materials used for this, a Ti, W, Ni, Cr, Au, Pd, Cu, Pt or A g or we selected metals or alloys of these metals. Of these substances, Ti, W, Ni, Cr, Pd, Cu or Pt or alloys of these metals are particularly effective for adhesion between the material and a layer made of Al or an alloy thereof. Therefore, it is preferable to use any of the above metals or alloys of these metals as the layer in contact with the Al or its alloy layer.

Furthermore, solder generally shows Ni, Au, Pd, Cu, good wettability to Pt or A g or alloys of these metals. Therefore, the layer in contact with the solder ball among the layers laminated on the electrode material layer of Al or Al alloy is preferably formed from these materials.

  As described above, when Al or Al alloy is used, the electrode has a multilayer structure as illustrated in FIG. In FIG. 2, an electrode 8 includes a first layer 5 made of Al (or an Al alloy) on the surface of the semiconductor chip 2, and a second layer 6 made of Cr on the first layer. A laminated structure including the third layer 7 made of Cu is formed on the second layer.

As an example of an electrode laminated structure using Al or an alloy thereof as an electrode material, as shown in FIG. 2, a laminated structure having an Al (or Al alloy) layer, a Cr layer, and a Cu layer sequentially from the semiconductor chip side (this In addition to Al / Ni, Al / Ni / Au, Al / Ni / Cu / Au, Al / Cr / Cu / Au, and the like, in the following, such a laminated structure is indicated as Al / Cr / Cu). Al / Ti / Cu / Au, Al / Ti / TiW (alloy) / Cu / Au, Al / TiW (alloy) / Cu / Au, Al / Cr / Ni / Pd, Al / Pd / Au , Al / Cr / Cu / Pd, and Al / Cr / Pt. Needless to say, the electrode stacking structure effective in the semiconductor device of the present invention is not limited to the above-described structure.

  Flux is used to adhesively bond the solder balls to the electrodes. Any of the fluxes generally used in the manufacture of semiconductor devices can be used. The flux is applied to the electrode surface. As a method for applying the flux to the electrode surface, a standard method such as screen printing can be used.

  When flip-chip bonding the semiconductor device of the present invention to a substrate, the bumps of the solder balls are opposed to the respective electrode terminals of the substrate, aligned, brought into contact with the bumps, and then the bumps are reflowed. . Such flip-chip bonding methods are widely known and need not be described in detail here.

  In the semiconductor device of the present invention, the solder balls may be reflowed once to form hemispherical bumps and then flip-chip bonded to the substrate. FIG. 3 shows an example of a hemispherical bump. The hemispherical bump 10 in FIG. 3 is formed by reflowing the solder ball bump 3 adhesively bonded to the laminated electrode 8 described in FIG.

  Here, the bumps 10 of FIG. 3 formed by reflowing solder balls are referred to as “hemispherical”. This term is mainly based on the vertical cross-sectional shape of the bump after reflow as shown in FIG. There are various shapes of electrodes on the semiconductor chip, such as a circle, a square, and other arbitrary shapes. For example, a bump formed by reflowing a solder ball on a square electrode has a hemispherical longitudinal cross-sectional shape as seen in FIG. However, since the melted solder wets the entire square electrode surface and solidifies, the shape seen from above (cross-sectional shape) is not a circle but a square or a shape close to a square. Therefore, the hemispherical bump referred to here is not only a bump that appears to have a circular cross-sectional shape when viewed from above after reflow, but also an arbitrary cross-sectional shape that reflects the electrode shape under the bump. It should be noted that it also includes the bumps it has. In other words, the “hemispherical bump” herein indicates all types of bumps formed by reflowing solder balls bonded and bonded to electrodes of an arbitrary shape.

In order to reflow the solder balls and appropriately form the hemispherical bumps on the electrodes, the radius R of the solder balls that are adhesively bonded to the electrodes is selected so that the surface area of the electrodes is A and the following formula is satisfied. Is desirable.
0.4 × A ^0.5 ≦ R ≦ 2 × A ^0.5
When the radius R of the solder ball is less than 0.4 × A ^0.5 , the amount of solder becomes insufficient, and it becomes difficult to form a good hemispherical bump after reflow. When the radius R of the solder ball exceeds 2 × A ^0.5 , the hemispherical bump becomes larger than the size of the electrode, and as a result, the joint between the electrode and the bump is easily stressed and easily broken. .

When an electrode having a surface area of 900 to 22,500 μm ² is used in the semiconductor device of the present invention, the preferable radius R of the solder ball is 12 to 300 μm from the above formula.

Next, an example of manufacturing the semiconductor device of the present invention will be described with reference to FIG.
As shown in FIG. 4A, an electrode 42 of 100 × 100 μm Al alloy (Al—Si—Cu alloy) is formed on a semiconductor chip 41 to a thickness of 1.0 μm by sputtering. In this figure, reference numeral 43 denotes a passivation film that partitions the electrodes thus formed. Next, as shown in FIG. 4B, a Ni metal layer 44 and a Cu metal layer 45 are sequentially stacked on the chip electrode 42 with a thickness of 80 nm by sputtering.

  The above is the process of forming the base for forming the low melting point metal bump. Next, as shown in FIG. 4C, Pb—Sn alloy solder balls 46 having a diameter of 80 μm are adhesively bonded to the Cu metal layer 45. When the solder balls are bonded and bonded, a flux (not shown) is first applied to the surface of the metal layer 45 by screen printing. Next, a solder ball 46 is adhesively bonded to the flux. A method of adhesively bonding the solder ball to the electrode will be described later.

  The semiconductor device of the present invention thus manufactured has the solder balls opposed to the corresponding electrode terminals of the substrate, aligns the balls, brings the balls into contact with the electrode terminals, and reflows the balls. Can be flip-chip bonded to the substrate.

  The semiconductor device of the present invention having the solder ball 46 shown in FIG. 4 (c) has a substrate after the solder balls are reflowed to form hemispherical bumps 47 as shown in FIG. 4 (d). Flip chip bonding may be used.

  In the above example, since an Al alloy is used as the electrode material, a Ni layer and a Cu layer are laminated on the Al alloy layer in order to firmly bond the semiconductor device to the substrate by solder bumps. However, when the electrode material is neither Al nor an Al alloy, for example, Cu or Cu alloy, or Au or Au alloy, an underlayer for forming a low-melting point metal ball (1 or There is no need to form two or more metal (or alloy) layers. Therefore, as shown in FIG. 5, bumps of the solder balls 53 can be directly formed on the electrodes 52 of the semiconductor chip 51. This solder ball can also be used for flip chip bonding after being reflowed to form a hemispherical bump.

  Next, another example in which a solder ball bump having a diameter of 150 μm is formed on an electrode having a diameter of 50 μm will be described. In this case, a Cr layer, a Cu layer and an Au layer having the same diameter or a slightly larger diameter are sputtered onto an Al-Cu alloy electrode having a diameter of 50 μm and a thickness of 1.0 μm by a thickness of 80 nm, 80 nm and 30 nm, respectively. Then we will layer them one after another. Next, a flux is applied to the surface of the Au layer, and a solder ball of a Pb—Sn alloy having a diameter of 150 μm is adhesively bonded thereon. When a shear test was performed on the hemispherical bumps formed by reflowing the solder balls, all the breaks occurred in the solder balls, and no breaks were observed at the joints between the bumps and the electrodes.

  Next, a method for adhesively bonding solder balls to electrodes will be described. Here, adhesive bonding of a solder ball onto an electrode made of a single material as described with reference to FIG. 5 instead of an electrode having a multilayer structure will be described.

  As shown in FIG. 6A, the solder ball 53 is floated by applying a minute amplitude vibration to the container 60 containing the solder ball 53. Next, the floating solder ball 53 is adsorbed to the adsorbing port 61 of the array plate 63 provided with the adsorbing port 61 at a position corresponding to the position of the electrode of the semiconductor chip to which the solder ball 53 is to be bonded and bonded (soldering). A suction mechanism for adsorbing the balls is not shown), and the solder balls 53 are arranged and supported on the arrangement plate 63. As shown in FIG. 6A, when the solder balls are attracted / arranged, the extra solder balls 53 ′ are attached to locations other than the suction ports 61 of the array plate 63, or the solder that is attracted to the suction ports 61. Another extra solder ball 53 ″ adheres to the ball 53. Therefore, these extra solder balls 53 ′ and 53 ″ are removed. For this purpose, it is possible to preferably remove the extra solder balls 53 ′ and 53 ″ by applying horizontal ultrasonic vibration to the array plate 63. The array plate 63 of FIG. For this reason, only two suction ports 61 are shown, but it should be noted that the actual array plate has the same number of suction ports as the number of solder balls to be adhesively bonded to the electrodes of the semiconductor chip.

  Next, as shown in FIG. 6B, the array plate 63 carrying the solder balls 53 in a predetermined position is moved onto the semiconductor chip 51, and the solder balls 53 and the respective electrodes 52 of the semiconductor chip 51 are appropriately connected. After alignment, the array plate 63 is moved downward to bring the solder balls 53 into contact with the respective electrodes 52. After the contact, the adsorption of the solder balls 53 to the array plate 63 is stopped (by stopping the suction mechanism), and the array plate 63 is moved upward.

  If a flux (not shown) is applied to the surface of the electrode 52, the solder ball 53 is adhesively bonded to the electrode due to its adhesiveness.

  This method is very advantageous for manufacturing the semiconductor device of the present invention because the solder bumps can be collectively bonded to a large number of electrodes of the semiconductor chip by the method described here.

  Semiconductor chips are generally made in large numbers on a single wafer and then cut into individual chips. The above-described method can be applied to a plurality of semiconductor chips before being separated from the wafer, or can be applied to individual semiconductor chips after being separated from the wafer. From what has been described here, it is apparent that the semiconductor chip according to the present invention includes not only individual semiconductor chips that have been separated but also a plurality of semiconductor chips that are manufactured on a single wafer.

It is a perspective view explaining the semiconductor device of this invention. It is a figure explaining the electrode in the semiconductor device of this invention. It is a figure explaining the hemispherical bump formed by reflowing the low melting metal ball of the semiconductor device of the present invention. It is a figure explaining the manufacturing method of the semiconductor device of this invention. It is a figure explaining the bump of the solder ball formed directly on the chip electrode of a single material. It is a figure explaining the preferable method of adhesive-bonding a low melting metal ball | bowl on each electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor device 2 Semiconductor chip 3 Low melting-point metal ball 5 1st layer 6 2nd layer 7 3rd layer 8 Electrode 10 Hemispherical bump 41, 51 Semiconductor chip 42, 52 Electrode 43 Passivation film | membrane 44, 45 Metal layer 46 53 Solder balls 47 Hemispherical bumps 60 Containers 61 Adsorption ports 63 Array plate

Claims (12)

  A semiconductor device comprising: an electrode formed on a semiconductor chip; and a low-melting point metal ball of a predetermined size formed in a spherical shape, which is adhesively bonded to these electrodes by a flux.   The semiconductor device according to claim 1, wherein the electrode is formed of an electrode material of Cu or Cu alloy, Al or Al alloy, or Au or Au alloy.   The electrode includes at least one layer of an electrode material composed of Al or an Al alloy, and at least one metal layer or metal alloy layer laminated on the electrode material layer and having a melting point higher than that of the electrode material. The semiconductor device described.   The at least one layer stacked on the electrode material layer is formed of a metal selected from Ti, W, Ni, Cr, Au, Pd, Cu, Pt, Ag, Sn, or Pb or an alloy of these metals. The semiconductor device according to claim 3.   The at least one layer stacked on the electrode material layer and in contact with the electrode material layer is formed of Ti, W, Ni, Cr, Pd, Cu, or Pt, or an alloy of these metals. The semiconductor device according to claim 4, wherein the at least one layer that is in contact with the low melting point metal ball is formed of Ni, Au, Pd, Cu, Pt, Ag, Sn, or Pb or an alloy of these metals. A method of manufacturing a semiconductor device comprising electrodes formed on a semiconductor chip and low-melting-point metal balls of a predetermined size formed in a spherical shape, adhesively bonded to these electrodes,
After applying flux to the electrode,
The low melting point metal ball,
Applying a small amplitude vibration to a container containing low melting point metal balls to float those low melting point metal balls;
The floating low melting point metal ball is adsorbed to the suction hole of the array plate provided with the suction port at a position corresponding to the position of the electrode of the semiconductor chip to which the low melting point metal ball is to be bonded and bonded. A process of arranging and supporting low melting point metal balls
Removing the extra low melting point metal balls attached to the array plate or adhering to the low melting point metal balls adsorbed to the suction port by vibrating the array plate; A step of bringing melting point metal balls into contact with the electrodes of the semiconductor chip in a lump;
A method of manufacturing a semiconductor device, comprising: adhesively bonding to the electrode by a method including: A method of manufacturing a semiconductor device having a low melting point metal bump on a semiconductor chip,
Applying flux to the electrode;
A step of suspending low-melting metal balls of low-melting metal balls of a predetermined size formed into a spherical shape by applying micro-amplitude vibration to a container containing the low-melting metal balls to float the low-melting metal balls, A low melting point metal ball is adsorbed to the suction port of the array plate provided with a suction port at a position corresponding to the position of the electrode of the semiconductor chip to which the low melting point metal ball is to be bonded and bonded, and the low melting point metal ball is arranged on the array plate A step of removing the extra low melting point metal ball attached to the array plate or adhering to the low melting point metal ball adsorbed to the suction port by vibrating the array plate, and on the array plate. A step of adhesively bonding the supported and arranged low melting point metal balls to the electrode by a method including the step of bringing the low melting point metal balls into contact with the electrodes of the semiconductor chip in a lump; The process of forming a hemispherical bump by reflowing
A method of manufacturing a semiconductor device.   A semiconductor device comprising a low melting point metal ball manufactured by the method according to claim 6 and adhesively bonded to each electrode of a semiconductor chip.   A semiconductor device manufactured by the method according to claim 7, wherein a low melting point metal is provided on an electrode of a semiconductor chip.   2. A flip characterized in that the low melting point metal ball of the semiconductor device according to claim 1 is opposed to each corresponding electrode terminal of the substrate, aligned, brought into contact with the electrode terminal, and then reflowed. Chip bonding method.   9. A flip characterized in that the low melting point metal ball of the semiconductor device according to claim 8 is opposed to each corresponding electrode terminal of the substrate, aligned, brought into contact with the electrode terminal, and then reflowed. Chip bonding method.   The hemispherical bump of the semiconductor device according to claim 9 is made to face each corresponding electrode terminal of the substrate, alignment is performed, and the hemispherical bump is brought into contact with the electrode terminal, and then reflow is performed. Flip chip bonding method.

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