JP6135328B2 - Bonding equipment - Google Patents

Description

  The present invention relates to a bonding apparatus for heating and pressing a protruding electrode and a lead of a semiconductor chip.

  Conventionally, a TAB (Tape Automated Bonding) method for bonding a protruding electrode formed on the upper surface of a semiconductor chip and a lead of a mounting tape is known. In the TAB method, a semiconductor chip having a plurality of protruding electrodes formed on the upper surface is fixed to a bonding stage, and then a lead of a mounting tape is overlaid on the plurality of protruding electrodes. Then, the bonding tool heated to 500 ° C. from above is applied to the leads, and the leads and the protruding electrodes are pressure-bonded. By doing in this way, each lead | read | reed and each protrusion electrode are crushed to some extent, and are electrically and mechanically connected. And it becomes possible to take out the function which a semiconductor chip has via a lead.

  Forsterite and zirconia are used as materials for the bonding stage as described above. For example, the bonding apparatus described in Patent Document 1 uses a zirconia bonding stage to heat the bonding stage in advance to reduce the temperature difference between the bonding tool and the bonding stage.

Japanese Patent Laid-Open No. 7-50320

  However, in the bonding apparatus as described above, the heat of the bonding tool is transmitted to the upper surface of the bonding stage through the semiconductor chip while the lead and the protruding electrode are heat-bonded by the bonding tool, and the temperature distribution is generated in the bonding stage. The stage upper surface is deformed into a convex shape. Due to this stage deformation, the protruding electrodes and leads in the center of the semiconductor chip are crushed more than the end portions, and defects in the semiconductor chip occur such that adjacent protruding electrodes come into contact with each other.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a bonding apparatus that can uniform the collapse of the protruding electrode and the lead by suppressing deformation of the bonding stage.

  (1) In order to achieve the above object, a bonding apparatus according to the present invention is a bonding apparatus that heats and crimps a protruding electrode and a lead of a semiconductor chip, and a positive expansion material and a temperature that expand with a rise in temperature. A stage formed of a low thermal expansion ceramic composed of a composite of a negative expansion material that shrinks in response to a rise, and a bonding tool that is heated to a predetermined temperature and pressurizes the protruding electrodes and leads superimposed on the stage. The negative expansion material is made of zirconium tungstate phosphate, and the Young's modulus of the low thermal expansion ceramic is 85 GPa or more.

  Thus, by using a low thermal expansion ceramic in which a bonding stage material is a composite of a positive expansion material and a negative expansion material, deformation of the stage can be reduced even if temperature distribution occurs in the stage during bonding. Further, by using zirconium tungstate phosphate as the negative expansion material, low thermal expansion can be realized in a wide temperature range, and deformation of the bonding stage can be reduced.

  In addition, the coefficient of linear expansion of zirconium tungstate phosphate is −4.0 ppm / ° C. and has a large negative expansion property. Therefore, a stage material with low (zero) thermal expansion can be designed by adding a large amount of positive expansion material. If a high-rigidity material is selected as the positive expansion material, a high-rigidity characteristic can be imparted in addition to low thermal expansion, and the Young's modulus can be 85 GPa or more. In addition, a low thermal conductive material can be selected as the positive expansion material to provide a low thermal conductive stage.

  (2) The bonding apparatus of the present invention is characterized in that the positive expansion material is made of zirconium oxide or zirconium phosphate.

  As described above, by selecting a zirconium compound of zirconium oxide or zirconium phosphate as the positive expansion material, the reaction with the negative expansion material can be particularly suppressed and composited.

  (3) In the bonding apparatus of the present invention, the low thermal expansion ceramic has a linear expansion coefficient from room temperature to 500 ° C. of ± 1 ppm / ° C. or less and a thermal conductivity of 3 W / mK or less. .

  As described above, if the linear expansion coefficient from room temperature to 500 ° C. of the low thermal expansion ceramic of the bonding stage material is ± 1 ppm / ° C. or less, the stage deformation at the time of bonding is 0.5 μm / φ30 mm, and the protruding electrode and the lead are crushed. Can be made uniform.

  Furthermore, heat escape from the bonding tool can be reduced by setting the thermal conductivity of the bonding stage material to 3 W / mK or less. The load necessary for maintaining the temperature of the bonding tool can be reduced.

  The linear expansion coefficient of the bonding stage material can be designed by adjusting the addition ratio of the negative expansion material and the positive expansion material.For example, zirconium phosphate tungstate is selected as the negative expansion material and zirconium oxide is selected as the positive expansion material. When the addition amounts are 75 vol% and 25 vol%, respectively, the linear expansion coefficient from room temperature to 500 ° C. can be 0.0 ppm / ° C., and can be designed to be ± 1 ppm / ° C. or less.

  According to the present invention, by using the low thermal expansion ceramic as the stage material of the bonding apparatus, the collapse of the protruding electrodes and the leads can be made uniform, and variations in their total height can be reduced.

It is the schematic which shows the bonding apparatus of this invention.

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

(Configuration of bonding equipment)
FIG. 1 is a schematic view showing a bonding apparatus. The bonding apparatus 101 includes a bonding stage 104, a bonding tool 105, and an apparatus base 106. As shown in FIG. 1, the bonding stage 104 is supported by an apparatus base 106, and a semiconductor chip 110 is placed on the bonding stage 104.

  The bonding stage 104 is fixed to the apparatus base 106 with high precision by a fixture. The bonding stage 104 is kept at room temperature (25 ° C.) before bonding. Note that the upper surface refers to the surface on the semiconductor chip side as viewed from the bonding stage 104, and the lower surface refers to the surface opposite to the upper surface. The material of the protruding electrode 111 formed on the semiconductor chip 110 is, for example, Au—Si, and the material of the lead 112 is, for example, a Cu alloy.

  With the semiconductor chip 110 placed on the bonding stage 104 as described above, the bump electrode 111 and the lead 112 can be bonded by the operation of the bonding apparatus 101 as described below. That is, first, the temperature of the bonding tool 105 is raised to about 500 ° C. prior to bonding. Then, the lead 112 and the protruding electrode 111 can be pressure-bonded by lowering the heated bonding tool 105 and pressurizing the lead 112 and the protruding electrode 111 superimposed on the bonding stage 104.

(Configuration of low thermal expansion ceramics)
The low thermal expansion ceramic constituting the bonding stage 104 is formed by combining a positive expansion material and a negative expansion material. A positive expansion material is a material that expands with increasing temperature. A negative expansion material is a material that shrinks with increasing temperature.

  Thus, by using a low thermal expansion ceramic in which a bonding stage material is a composite of a positive expansion material and a negative expansion material, deformation of the stage can be reduced even if temperature distribution occurs in the stage during bonding. Further, by using zirconium tungstate phosphate as the negative expansion material, low thermal expansion can be realized in a wide temperature range, and deformation of the bonding stage can be reduced.

  The positive expansion material is formed of a material having high rigidity and low thermal conductivity. Materials having high stiffness and low thermal conductivity include zirconium oxide or zirconium phosphate.

  In addition, the coefficient of linear expansion of zirconium tungstate phosphate is −4.0 ppm / ° C. and has a large negative expansion property. Therefore, a stage material with low (zero) thermal expansion can be designed by adding a large amount of positive expansion material. If a low thermal conductivity material or a high rigidity material is selected as the positive expansion material, it is possible to impart characteristics of low thermal conductivity and high rigidity in addition to low thermal expansion.

  The negative expansion material is formed of a material having a high negative expansion property. Examples of the material having a high negative expansion property include zirconium tungstate phosphate. In this way, a material having a low thermal expansion characteristic of a linear expansion coefficient from room temperature to 500 ° C. of ± 1 ppm / ° C. or less is prepared by mixing an appropriate amount of an appropriate positive expansion material with zirconium tungstate phosphate. be able to.

  By using such a low thermal expansion ceramic as the stage material of the bonding apparatus, variation in the total height of the bump electrode and the lead of the semiconductor chip after bonding can be reduced, and the bump of the bump electrode and the lead can be made uniform.

  The low thermal expansion ceramic has a Young's modulus of 85 GPa or more. Further, it preferably has a hardness of 7 GPa or more.

(Production method of low thermal expansion ceramics)
Next, the manufacturing method of the low thermal expansion ceramics comprised as mentioned above is demonstrated. First, the raw material of the negative expansion material made of zirconium phosphate tungstate is mixed in a predetermined composition. As the phosphorus source of zirconium phosphate tungstate, phosphate is preferable, and examples thereof include calcium phosphate and sodium phosphate. Ammonium phosphate that does not remain as an impurity in the calcined body after calcining is more preferable.

  As the tungsten source, tungsten trioxide or tungstate, for example, ammonium tungstate is preferable. As a zirconium source, a zirconium compound is preferable, and zirconia and zirconium chloride are more preferable.

  Each raw material powder is wet-mixed with an organic solvent, then calcined and pulverized to obtain a negative expansion material. Next, the positive expansion material and the negative expansion material are mixed and molded, and then fired at 1300 ° C. or lower. Baking is preferably performed at 1150 to 1300 ° C. Note that firing at a temperature higher than 1300 ° C. is not preferable because the negative expansion material decomposes.

  From the viewpoint of precisely adjusting the particle size of the negative expansion material, a method of mixing after the negative expansion material is adjusted in advance is suitable. On the other hand, from the viewpoint of workability, a method in which a positive expansion material is added to a calcined body of a negative expansion material and pulverized and mixed is suitable.

  When pulverizing with a ball mill, zirconia balls are preferred. When alumina balls other than zirconia balls are used, for example, contamination is likely to occur, and a predetermined thermal expansion coefficient may not be obtained. Details of the particle size adjustment of the negative expansion material will be described later. Then, the mixed material is molded and fired in an air atmosphere. By such a process, flatness can be maintained and a low thermal expansion ceramic excellent in chemical resistance can be produced.

  In the molding process, molding can be performed by various molding methods such as uniaxial pressure molding, isostatic pressing, cast molding, and the like. In the firing step, firing is preferably performed at a firing temperature of 1300 ° C. or lower. Furthermore, the firing temperature between 1150-1300 degreeC is more preferable. This can prevent tungsten in the negative expansion material from becoming tungsten oxide and decomposing at a high temperature. The heating rate in the firing step is preferably 100 ° C./hr or more and 800 ° C./hr or less. Thereby, the low thermal expansion ceramics of a dense sintered body can be manufactured.

(Example)
Based on the production method described above, a negative expansion material and a positive expansion material were blended in the blending amounts shown in Table 1 to produce a low thermal expansion ceramic. The relative density of the obtained low thermal expansion ceramic was measured by the Archimedes method. The linear expansion coefficient was measured by the method defined in JIS R 3251 “Method for measuring linear expansion coefficient by laser interferometer of low expansion glass”. The thermal conductivity was measured by a method defined in JIS R 1611 “Test method of thermal diffusivity / specific heat capacity / thermal conductivity of fine ceramics by laser flash method”. Moreover, about the reaction of the positive expansion material and negative expansion material at the time of composite, the crystal phase was identified by the X-ray diffraction method.

  In the configuration of the bonding apparatus shown in FIG. 1, the experiment was performed by changing the material of the bonding stage. First, as Examples 1 to 4, low thermal expansion ceramics in which zirconium phosphate tungstate and zirconium oxide are combined are used as the bonding stage material. As Examples 4 to 6, tungstic phosphate phosphate is used as the bonding stage material. A low thermal expansion ceramic compounded with zirconium and zirconium phosphate was used. Further, as Example 7, low thermal expansion ceramics in which zirconium tungstate phosphate and aluminum oxide were combined as the material for the bonding stage was used. The composition and characteristics of each material are as shown in Table 1. The shape of the bonding stage is φ30 mm × 10 mmt, and the bonding time is 3 seconds.

  As a result of numerical analysis using the configuration of Example 2, the temperature difference between the upper surface and the lower surface of the bonding stage was 235 ° C. with respect to the temperature 260 ° C. of the upper surface of the bonding stage immediately after the completion of bonding. As a result of numerical analysis of the warping amount of the bonding stage having this temperature difference with the lower surface fixed, it was 0.5 μm. From this, it is considered that the variation in the total height of the protruding electrode and the lead of the semiconductor chip is 0.5 μm.

  Moreover, the same measurement was performed using the bonding stage formed with the forsterite of the shape similar to an Example as a comparative example. As a result, the temperature of the upper surface of the bonding stage was 130 ° C., and the temperature difference between the upper surface and the lower surface of the stage at this time was 105 ° C. The warping amount of the bonding stage was 2.5 μm. From this, it is considered that the variation in the total height of the protruding electrode and the lead of the semiconductor chip is 2.5 μm.

  As described above, in the comparative example, the variation in the total height of the protruding electrode and the lead of the semiconductor chip was 2.5 μm, whereas in the configuration of Example 2, this was reduced to 0.5 μm. I was able to.

  Furthermore, in the comparative example, there was a lot of heat escape from the bonding stage, and a high load was applied to the tool heater to maintain the temperature of the bonding tool. In many embodiments, the heater load of the bonding tool was reduced. This is because the thermal conductivity of most low thermal expansion ceramics is lower than that of forsterite.

101 Bonding Device 104 Bonding Stage 105 Bonding Tool 106 Device Base 110 Semiconductor Chip 111 Projection Electrode 112 Lead

Claims (3)

A bonding apparatus that heats and crimps a protruding electrode and a lead of a semiconductor chip,
A stage formed of a low thermal expansion ceramic formed by combining a positive expansion material that expands in response to a temperature rise and a negative expansion material that contracts in response to a temperature increase;
A bumping tool heated to a predetermined temperature and pressurizing the protruding electrodes and leads superimposed on the stage, and
The negative expansion material is made of zirconium tungstate phosphate,
The Young's modulus of the low thermal expansion ceramic is 85 GPa or more.   The bonding apparatus according to claim 1, wherein the positive expansion material is made of zirconium oxide or zirconium phosphate. 3. The bonding apparatus according to claim 1, wherein the low thermal expansion ceramic has a linear expansion coefficient from room temperature to 500 ° C. of ± 1 ppm / ° C. or less and a thermal conductivity of 3 W / mK or more.

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