JP2006066689A - Semiconductor device, and flattening method of bump electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device having flat bump electrodes, and a method of flattening the bump electrode. <P>SOLUTION: The method of flattening the bump electrode 101 includes a step of applying ultrasonic vibration in the horizontal direction while the semiconductor device 100 having a plurality of bump electrodes 101 is pressed against a flat stage 202. Then the bump electrode 101 is flattened by rubbing it against the stage 202. The semiconductor device 100 having the flat bump electrodes 101 is thus obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor element and a bump electrode flattening method, and more particularly to a semiconductor element having a flat bump electrode and a bump electrode flattening method.

  In recent years, with the miniaturization, high performance, and high functionality of electronic devices, a mounting method for mounting a semiconductor element on a mounting substrate such as a printed wiring board is required to have a higher density. In response to this requirement, flip chip mounting is widely adopted in which a semiconductor element provided with a bump electrode is aligned with a mounting substrate in a face-down state, and the bump electrode and the mounting substrate side electrode are connected. .

  In this method, since the occupied area on the mounting substrate is reduced as compared with the case of packaging in a form such as QFP (Quad Flat Package), the mounting density on the mounting substrate can be improved. As the flip-chip mounting, for example, a COG (Chip On Glass) system, a COF (Chip On Film) system, and the like are known.

  In general, for example, COG mounting is performed by thermocompression bonding with an anisotropic conductive film (ACF) interposed between a bump electrode provided on a semiconductor element and an electrode on the mounting substrate side. Has been done.

  The anisotropic conductive film contains a predetermined amount of conductive particles such as metal particles in an insulating adhesive. The anisotropic conductive film is placed on the electrode of the mounting substrate, and the semiconductor element is placed on the bump electrode of the semiconductor element and the electrode of the mounting substrate on the electrode, and pressed and heated. As a result, the bump electrode and the electrode of the mounting substrate are electrically connected, and insulation between adjacent electrodes is secured, and the semiconductor element and the mounting substrate are fixed.

In order to improve the reliability of the connection using the anisotropic conductive film, the conductive particles are made smaller than the distance between the adjacent electrodes to ensure the insulation between the adjacent electrodes, and the conductive particle content can be reduced. It is necessary that the particles do not come into contact with each other and that the conductive particles are surely present on the electrode (see, for example, Patent Document 1).
JP 2002-270641 A

  In the field of liquid crystal technology in which high definition and an increase in the number of pixels are required in recent years, for example, the above method is used as a method for mounting a driver IC that controls voltage switching related to liquid crystal display. When the number of bump electrodes of the driver IC increases due to the increase in the number of pixels, the pitch between the bump electrodes becomes narrower. Accordingly, since the connection area of the bump electrode decreases, it is necessary to increase the number of conductive particles in the anisotropic conductive film.

  However, this increases the conductive particles between the bump electrodes of the driver IC and increases the possibility of shorting between the bump electrodes. For example, when a driver IC having bump electrodes formed on a mounting substrate to which an anisotropic conductive film is bonded is heat-pressed, the viscosity of the anisotropic conductive film decreases due to heat, and there are many spaces between the bump electrodes. Of conductive particles flow in. At this time, if the interval between the bump electrodes is narrow, several conductive particles come into contact with each other, causing a short circuit between the bump electrodes.

  For this reason, when the space | interval between bump electrodes becomes narrow, the thing with a smaller particle diameter of the electrically-conductive particle in an anisotropic conductive film is used. By doing in this way, the insulation between adjacent electrodes can be ensured and the number of conductive particles involved in conduction can be increased.

  However, generally, the height of each bump electrode formed of Au varies. For example, when a bump electrode having a design value of 35 μm in length × 35 μm in width × 15 μm in height is formed in one chip, the height of each bump electrode has a variation of about 4 μm. When a driver IC having such a bump electrode is face-down mounted by the COG method, the bump electrode having a variation in height is opposed to the electrode of the mounting substrate. For this reason, the pressing force to the conductive particles in the anisotropic conductive film interposed between both electrodes differs between bump electrodes having different heights. That is, pressure non-uniformity occurs during mounting, causing contact failure.

  Further, the bump electrode surface is uneven and has a variation of about 2 μm. For this reason, the pressing force to the conductive particles in the anisotropic conductive film interposed between the bump electrode and the mounting substrate side electrode is slightly different between the concave portion and the convex portion. In addition, when small conductive particles are used, a portion where the conductive particles are not crushed is formed, and the electrical connection becomes unstable.

  As described above, the proportion of the conductive particles compressed between both electrodes is reduced in the insufficiently pressurized portion compared to the normal pressurized portion. As a result, the degree of contact between the electrode and the conductive particles may be relatively weak or may be in a non-contact state. In such a case, the electrical resistance at that portion becomes high, and sufficient electrical conductivity between the two electrodes is not ensured.

  The present invention has been made against the background of such circumstances, and the object of the present invention is to sufficiently provide electrical continuity between the bump electrode of the semiconductor element and the mounting substrate side electrode connected to the bump electrode. The purpose is to improve the flatness of the bump electrode used for mounting.

  The semiconductor element according to the present invention is a semiconductor element having a plurality of bump electrodes, wherein the bump electrode has a surface roughness of 1 μm or less, and a height difference of the bump electrodes is 1 μm or less. To do. Thereby, good conduction can be ensured. In addition, poor connection between the semiconductor element and the mounting substrate can be suppressed.

  The bump electrode preferably has a surface roughness of 0.5 μm or less. As a result, even better conduction can be ensured.

  Furthermore, the height difference of the bump electrodes is preferably 0.5 μm or less. As a result, connection failure between the semiconductor element and the mounting substrate can be further suppressed.

  The semiconductor element according to the present invention is a semiconductor element having a plurality of bump electrodes, wherein the bump electrodes are pressed against a flat stage and are subjected to ultrasonic vibration and rubbed against the stage. The bump electrode is flattened. As a result, a semiconductor element including a bump electrode with improved flatness can be provided.

  A bump electrode flattening method according to the present invention is a bump electrode flattening method for flattening a bump electrode of a semiconductor element having a plurality of bump electrodes, wherein the bump electrode is pressed against a flat stage in an ultra-high state. The surface roughness of the bump electrode is set to 1 μm or less and the difference in height of the bump electrode is set to 1 μm or less by oscillating the sound wave and rubbing the bump electrode against the stage. Thereby, the bump electrode can be flattened.

  According to the present invention, it is possible to provide a semiconductor element having a flat bump electrode and a bump electrode flattening method.

  Hereinafter, embodiments to which the present invention can be applied will be described. The following description is to describe the embodiment of the present invention, and the present invention is not limited to the following embodiment. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. Moreover, those skilled in the art can easily change, add, and convert each element of the following embodiments within the scope of the present invention. In addition, in each drawing, the same code | symbol is attached | subjected to the same element and the duplication description is abbreviate | omitted as needed for clarification of description.

  An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic view showing a configuration of a bump electrode 101 provided in the semiconductor element 100. As shown in FIG. 1, a wiring electrode 102 made of Al or the like is formed on the surface of a semiconductor substrate 100a. The wiring electrode 102 indicates an exposed electrode among a plurality of wiring layers provided in the semiconductor element 100. A passivation layer 103 having an opening for exposing a part of the surface of the wiring electrode 102 is provided on the wiring electrode 102.

  The wiring electrode 102 is electrically connected to the bump electrode 101 made of Au or the like via a bump base metal layer 104 provided on the exposed portion. Irregularities on the surface of the bump electrode 101 are flattened, and the height of each bump electrode 101 is substantially uniform. A method for planarizing the bump electrode 101 will be described later.

  The bump electrode 101 is formed so as to protrude from the passivation layer 103 using, for example, an electroplating method. The bump electrode 101 has, for example, a height of 15 μm, a width of 35 μm, and a pitch of 50 μm.

  Next, a connection structure between the bump electrode 101 and the mounting substrate 106 of the semiconductor element 100 according to the present embodiment will be described with reference to FIG. As shown in FIG. 2, the semiconductor element 100 is mounted face-down on the mounting substrate 106 via an anisotropic conductive film 105.

  The mounting substrate 106 is provided with a mounting substrate side wiring electrode 107 made of ITO or the like. An insulating resin 108 is provided on the mounting board side wiring electrode 107. A part of the mounting substrate side wiring electrode 107 on which the insulating resin 108 is not provided becomes a connection electrode 109 that is electrically connected to the bump electrode 101 provided on the semiconductor element 100.

  An anisotropic conductive film 105 is disposed on the connection electrode 109 of the mounting substrate 106. The semiconductor element 100 is placed on the bump electrode 101 of the semiconductor element 100 and the connection electrode 109 of the mounting substrate 106 in alignment with each other, and is pressed and heated. Thereby, the mounting substrate 106 and the semiconductor element 100 are fixed by the thermally cured anisotropic conductive film 105, and the bump electrode 101 and the connection electrode 109 of the mounting substrate 106 are included in the anisotropic conductive film 105. Conduction is performed through the conductive particles 110.

  As an application example of the connection having such a configuration, for example, COG (Chip On Glass) using a glass substrate as the mounting substrate 106, COF (Chip On Film) using a film substrate, or the like can be given.

  When the anisotropic conductive film 105 is used with the above-described configuration of COG and COF, by improving the flatness of the bump electrode 101, the collapsed shape of the conductive particles at the time of mounting can be optimized, and the connection Defects can be suppressed.

  Here, a method for flattening the bump electrode 101 according to the embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic diagram showing the configuration of the ultrasonic vibration device 200.

  For example, an ultrasonic vibration device 200 shown in FIG. 3 is used for planarizing the bump electrode 101 according to the present embodiment. As shown in FIG. 3, the ultrasonic vibration device 200 performs planarization of the bump electrode 101 in a state where the head 201 that sucks and holds the semiconductor element 100 and vibrates ultrasonically and the bump electrode 101 of the semiconductor element 100 are in contact with each other. And a flat stage 202.

  Here, an example in which a horn 203 that is both-side supported is used for the head 201 is shown. The head 201 includes a transducer 205 in which an ultrasonic transducer 204 and a vibration transmitting horn 203 are connected. The transducer 205 is connected and supported horizontally at a lower portion of a holding member 206 made of a metal material such as stainless steel or aluminum. Further, a suction tool 207 is vertically attached to the horn 203.

  The horn 203 is made of a material having excellent acoustic characteristics such as an alloy such as aluminum or titanium, or hardened iron. The horn 203 is a rod-shaped member having a length of at least one wavelength of the resonance frequency of the ultrasonic transducer 204.

  At a position corresponding to the maximum amplitude point of the horn 203, a suction tool connecting portion is provided and a suction tool 207 is attached. In addition, a holding connecting portion 208 for connecting to the holding member 206 is provided at a position corresponding to a vibration node (a point where the horn 203 does not vibrate). The horn 203 and the holding connecting portion 208 are integrally formed as a single body.

  The suction tool 207 is inserted into the horn 203 so as to protrude vertically, and is fastened and fixed widely by a pair of upper and lower bolts (not shown). A suction hole (not shown) opened downward is provided at the lower end of the suction tool 207. The lower end of the suction tool 207 protrudes slightly (about 1 mm) from the lower surface of the horn 203.

  In the lower part of the holding member 206, an inverted U-shaped recess opened downward is formed. In a state where the transducer 205 is fitted into the concave portion from below, the holding connecting portion 208 and the holding member 206 are fastened and fixed with bolts 209. As a result, the transducer 205 is fixed horizontally with respect to the holding member 206.

  The holding member 206 is connected to the head body 211 via a spacer 210 made of a material having a different specific acoustic impedance, for example, a resin material such as an acrylic plate. The vibration of the transducer 205 is reflected by a spacer 210 having a different specific acoustic impedance that is interposed between the holding member 206 and the head body 211. As a result, the influence of the minute vibration between the holding member 206 and the head body 211 on the vibration characteristics of the transducer 205 is reduced.

  A suction pipe 212 is attached to the holding member 206 at the upper end of the suction tool 207. The suction pipe 212 is connected to a vacuum device (not shown) and sucks the semiconductor element through the suction hole at the lower end of the suction tool 207.

  Next, a method for planarizing the bump electrode 101 of the semiconductor element 100 using the ultrasonic vibration device 200 having the above-described configuration will be described.

  First, the semiconductor element 100 is held by suction with the bump electrode 101 on the lower side of the suction tool 207 in the head 201. At this time, the suction pipe 212 is sucked by the vacuum device, and when the suction hole at the lower end of the suction tool 207 is closed by the semiconductor element 100, the vacuum passage in the tool and the suction pipe 212 are negatively charged. A vacuum passage that is blocked from outside air is formed between the suction hole and the vacuum device, and the semiconductor element 100 is securely held by the suction tool 207 by a sufficient negative pressure.

  Then, the head 201 holding the semiconductor element 100 moves on the stage 202 and descends. The bump electrode 101 of the semiconductor element 100 held at the lower end of the suction tool 207 is pressed against the stage 202 with an appropriate load, and the transducer 205 is driven to cause horizontal ultrasonic vibration (in the direction of the arrow in the figure) to the suction tool 207. Communicated. As a result, this ultrasonic vibration is applied to the semiconductor element 100, and the bump electrode 101 is rubbed against the flat stage 202. Then, only the surface of the bump electrode 101 is softened by the frictional force generated between the stage 202 and the bump electrode 101, and planarization can be performed. That is, the unevenness of the surface of the bump electrode 101 and the variation in the height of the bump electrode can be reduced.

  The variation in height of the bump electrode 101 is reduced, so that when the connection electrode 109 of the mounting substrate 106 and the bump electrode 101 of the semiconductor element 100 are connected by the anisotropic conductive film 105, The pressure applied to the conductive particles 110 becomes uniform, and connection failure can be suppressed.

  Further, the time required for the flattening process using the ultrasonic vibration is 0.2 to 1.0 s, and the time required for the flattening process of the bump electrode 101 can be shortened. Further, since the planarization process can be performed at a low pressure, only the surface of the bump electrode 101 can be reliably processed.

  In recent years, with the fine pitch, the area of the bump electrodes 101 has become smaller and the pitch between the bump electrodes 101 has also become narrower. For example, the pitch of the bump electrodes 101 is 100 μm to 50 μm. In this case, the particle diameter of the conductive particles 110 included in the anisotropic conductive film 105 needs to be 4 μm to 3 μm.

  By using the method for planarizing the bump electrode 101 according to the present invention, the unevenness on the surface of the bump electrode 101 can be planarized. Therefore, even when the conductive particles 110 having a small particle diameter are used, there is no variation in the shape of the conductive particles 110 during mounting, and the connection reliability can be improved. It is preferable that the surface unevenness of the bump electrode 101 is 1 μm or less. More preferably, it is 0.5 μm or less. This further suppresses connection failures.

  In the present embodiment, the vibration frequency of the ultrasonic vibrator 204 is 40 to 100 kHz, the pressing pressure per bump is 20 to 30 g, and the vibration amplitude is 3 to 5 μm. Conventionally, when the height of the bump electrode 101 is 15 μm, a variation of ± 2 μm has occurred. That is, among the plurality of bump electrodes, the height difference between the highest bump electrode and the lowest bump electrode was 4 μm. However, by using the bump electrode flattening method according to the present invention, the variation in the height of the bump electrode 101 could be ± 0.25 μm. That is, among the plurality of bump electrodes, the difference in height between the highest bump electrode and the lowest bump electrode could be 0.5 μm. Further, the bump surface irregularities could be reduced from 2 μm to 0.5 μm.

  In addition, although an example in which the horn 203 with both ends is used is shown here, a horn with a cantilever may be used. However, in order to make the height of the bump electrodes more uniform, it is preferable to use a horn that supports both ends.

It is a schematic diagram which shows the structure of the bump electrode of the semiconductor element concerning this embodiment. It is a schematic sectional drawing which shows the structure of the connection of the semiconductor element concerning this embodiment, and a mounting board | substrate. It is a schematic diagram which shows the structure of the ultrasonic vibration apparatus used for planarization of the bump electrode concerning this embodiment.

Explanation of symbols

100 Semiconductor element 101 Bump electrode 102 Wiring electrode 103 Passivation layer 104 Bump foundation metal layer 105 Anisotropic conductive film 107 Mounting substrate side wiring electrode 108 Insulating resin 109 Connection electrode 110 Conductive particle 200 Ultrasonic vibration device 201 Head 202 Stage 203 Horn 204 Ultrasonic vibrator 205 Transducer 206 Holding member 207 Suction tool 208 Holding connecting portion 209 Bolt 210 Spacer 211 Head body 212 Suction pipe

Claims (5)

A semiconductor element having a plurality of bump electrodes,
A semiconductor element, wherein the bump electrode has a surface roughness of 1 μm or less, and a height difference of the bump electrodes is 1 μm or less.   The semiconductor element according to claim 1, wherein the bump electrode has a surface roughness of 0.5 μm or less.   The semiconductor element according to claim 1, wherein a difference in height between the bump electrodes is 0.5 μm or less. A semiconductor element having a plurality of bump electrodes,
A semiconductor element, wherein the bump electrode is flattened by being applied with ultrasonic vibration while being pressed against a flat stage and being rubbed against the stage. A bump electrode planarizing method for planarizing a bump electrode of a semiconductor element having a plurality of bump electrodes,
The bump electrode is ultrasonically vibrated in a state of being pressed against a flat stage, and the bump electrode is rubbed against the stage, thereby reducing the surface roughness of the bump electrode to 1 μm or less and the difference in height of the bump electrode. The bump electrode flattening method is characterized in that the thickness is 1 μm or less.

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