KR20090059879A - Die bonding structure and method thereof - Google Patents

Abstract

A die bonding structure and a method thereof are provided to obtain a die bonding structure having a high electrical property and a high adhesive force by selecting an optimum composition ratio and an optimum temperature range. An aluminum germanium alloy(120) is formed on a surface of a semiconductor die(110), and has thickness of 0.5~5um. The aluminum germanium alloy serves as a junction medium between the semiconductor die and a lead frame(140). Gold or silver(130) is formed on the surface of the aluminum germanium alloy, has thickness of 0.01~1um, and prevents oxidation of the aluminum germanium alloy. A vanadium is formed on the surface of the semiconductor die, and has thickness of 0.01~1um. A nickel is formed on the surface of the vanadium, and has thickness of 0.01~1um.

Description

DIE BONDING STRUCTURE AND METHOD THEREOF

The present invention relates to a die bonding structure and method thereof.

In general, die bonding means bonding a semiconductor die (active device or passive device) using an adhesive member on a lead frame or a circuit board. Here, the adhesive member may be broadly classified into an insulating adhesive member and a conductive adhesive member. Hereinafter, only the die bonding structure using the conductive adhesive member will be described.

In order to bond the semiconductor die on the lead frame, the following layer structure is usually formed on the bottom of the semiconductor die. That is, vanadium (V) / nickel (Ni) / gold germanium antimony (AuGeSb) alloy / gold or silver (Au or Ag), vanadium (V) / nickel (Ni) / gold or gold arsenide (AuAs) alloy / gold Or a layer of any one of three kinds of silver, vanadium / nickel / gold or silver / solder flux is formed on the bottom surface of the semiconductor die. Subsequently, when the semiconductor die is seated on the leadframe heated to a high temperature, the intermediate layer of the gold germanium antimony (AuGeSb) alloy or the gold arsenide (AuAs) alloy or nickel, or the solder flux is melted, and the semiconductor die and the leadframe are electrically and mechanically connected. Is connected by enemy.

However, this conventional die bonding structure has a problem that the cost and bonding process of each layer occupies approximately 20% or more of the semiconductor device manufacturing cost, thereby significantly increasing the manufacturing cost of the semiconductor device. In addition, in the conventional die bonding structure, since gold germanium antimony alloy, gold or gold arsenide alloy does not adhere well to the surface of the semiconductor die, the vanadium / nickel is formed on the bottom surface of the semiconductor die in advance, resulting in poor workability and thus a defective rate. There is also a problem that increases. In addition, in the case of using the solder plus in the conventional die bonding structure, the resistance between the semiconductor die and the lead frame is high, and the environment is contaminated by the use of solder (including lead).

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-mentioned conventional problems, and an object of the present invention is to provide a die bonding structure and a method capable of greatly reducing die bonding materials and process costs.

Another object of the present invention is to provide a die bonding structure and a method for easily bonding a semiconductor die and a lead frame without using a multilayer structure.

In order to achieve the above object, the present invention provides a die bonding structure for bonding a semiconductor die and a lead frame to each other, wherein the semiconductor die and the lead frame may be bonded to each other by an aluminum germanium (AlGe) alloy.

Gold (Au) or silver (Ag) may be further interposed between the aluminum germanium alloy and the lead frame.

Vanadium (V) and nickel (Ni), or a nickel vanadium alloy may be interposed between the semiconductor die and the aluminum germanium alloy.

The aluminum germanium alloy may be formed to a thickness of 0.5 ~ 5㎛ according to the size (chip size) of the semiconductor die. The gold or silver may be formed to a thickness of 0.01 ~ 1㎛.

The vanadium may be formed to a thickness of 0.01 ~ 1㎛, the nickel may be formed to a 0.01 ~ 1㎛ thickness.

The nickel vanadium alloy may be formed to a thickness of 0.01 ~ 1㎛.

The aluminum germanium alloy may be 35 to 55 wt.% Aluminum and 45 to 65 wt.% Germanium.

The aluminum germanium alloy may be formed only in a layered part without pure aluminum crystal parts.

In order to achieve the above object, the die bonding method according to the present invention includes a semiconductor die preparation step of preparing a semiconductor die, an aluminum germanium alloy forming step of forming an aluminum germanium alloy on the surface of the semiconductor die, and the aluminum germanium alloy Gold or silver forming step of forming gold or silver on the surface, and die bonding step of placing the semiconductor die on the surface of the lead frame, die bonding at a temperature of 400 ~ 600 ℃, pressure 50 ~ 500gf / ㎠.

A vanadium and nickel forming step of forming vanadium and nickel or a nickel vanadium alloy on the surface of the semiconductor die may be further included between the semiconductor die preparation step and the aluminum germanium alloy forming step. The forming of the aluminum germanium alloy may include deposition. It may be made by an evaporation or sputtering method.

The gold or silver forming step may be performed by evaporation or sputtering.

The vanadium and nickel forming step may be performed by evaporation or sputtering.

As described above, the die bonding structure and method thereof according to the present invention can significantly reduce the die bonding material and the process cost by using an aluminum germanium alloy 1/10 of the conventional cost.

In addition, the present invention can easily bond the semiconductor die and the lead frame without using the conventional multilayer structure.

In addition, the present invention can obtain an aluminum germanium alloy having a random layered structure without aluminum precipitation by selecting the optimum composition ratio and the optimum temperature range, thereby obtaining a die bonding structure having excellent electrical properties and excellent adhesion. Can be.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings such that those skilled in the art may easily implement the present invention.

1 is a cross-sectional view illustrating a die bonding structure according to an embodiment of the present invention.

As shown in FIG. 1, the die bonding structure 100 according to the present invention includes a semiconductor die 110, an aluminum germanium (AlGe) alloy 120 formed on the semiconductor die 110, and the aluminum germanium alloy 120. ) Includes gold (Au) or silver (Ag), and a lead frame 140 bonded to the gold or silver 130.

The semiconductor die 110 may be a conventional active device, an integrated circuit, or an equivalent thereof, but is not limited thereto. In other words, the semiconductor die 110 is a concept including even passive elements.

The aluminum germanium alloy 120 is formed to a thickness of about 0.5 to 5㎛ on the surface of the semiconductor die 110, the role of common bonding (eutectic bonding) between the semiconductor die 110 and the lead frame 140. Do it. That is, the aluminum germanium alloy 120 serves as a bonding medium between the semiconductor die 110 and the lead frame 140. When the aluminum germanium alloy 120 has a thickness less than 0.5 μm, there may be a process defect (opening, deterioration of properties, etc.), and when the thickness of the aluminum germanium alloy 120 exceeds 5 μm, There may be a problem of process failure (chip tilting, short, etc. of the semiconductor die).

In addition, the aluminum germanium alloy 120 may be formed of 35 to 55 wt.% Aluminum and 45 to 65 wt.% Germanium. When the weight ratio of the aluminum is less than 35wt.% Or more than 55wt.%, The melting point of the aluminum germanium alloy 120 exceeds approximately 600 ° C., resulting in poor process conditions, and furthermore, the aluminum germanium alloy 120 in the die bonding process. ) Passes through all of the solid, solid + liquid and liquid phases, so that only crystals of aluminum or germanium (ie, aluminum or germanium precipitation) may be formed upon cooling. Similarly, when the weight ratio of germanium is less than 45 wt.% Or more than 65 wt.%, The melting point of the aluminum germanium alloy 120 exceeds approximately 600 ° C., resulting in poor process conditions, and furthermore, the aluminum germanium alloy in the die bonding process. Since 120 passes through all of the solid, solid and liquid phases and liquid phases, crystals of only aluminum or germanium (ie, aluminum or germanium precipitation) may be formed upon cooling.

The gold or silver 130 is formed on the surface of the aluminum germanium alloy 120 to a thickness of approximately 0.01 ~ 1㎛ to prevent oxidation of the aluminum germanium alloy 120, to be more strongly bonded to the lead frame 140 It plays a role. In this case, when the thickness of the gold or silver 130 is less than 0.01 μm, there may be a process defect (oxidation, open, etc.), and when the thickness of the gold or silver 130 exceeds 1 μm. There may be a process defect (chip tilting, short, bad bonding, etc. of the semiconductor die).

On the other hand, the lead frame 140 may be any one selected from ordinary copper, copper alloy and equivalents thereof, but is not limited thereto. That is, the lead frame 140 is a concept including a circuit board having a conventional copper wiring pattern.

2 is a cross-sectional view illustrating a die bonding structure according to another embodiment of the present invention.

As shown in FIG. 2, the die bonding structure 200 according to another embodiment of the present invention is almost similar to the die bonding structure 100 shown in FIG. 1. Therefore, only the difference is demonstrated.

As illustrated, vanadium (V) 210 that is firmly adhered to the silicon surface may be formed on the surface of the semiconductor die 110 to have a thickness of about 0.01 to 1 μm. The vanadium 210 serves as a glue metal. In addition, the vanadium 210 may have a metal lift problem when the thickness is less than 0.01 μm, and when the thickness of the vanadium 210 exceeds 1 μm, poor characteristics (increasing resistance) may cause problems. There can be.

In addition, nickel (Ni) 220 is formed on the surface of the vanadium 210 to a thickness of approximately 0.01 ~ 1㎛, may serve to improve the bonding force between the vanadium 210 and the aluminum germanium alloy (120). . The nickel 220 may have a metal lift problem when the thickness of the nickel 220 is less than 0.01 μm. When the nickel 220 has a thickness of more than 1 μm, there may be a problem of poor properties (increasing resistance). have.

In addition, although not shown, a nickel vanadium alloy may be interposed between the semiconductor die 110 and the aluminum germanium alloy 120 instead of the vanadium 210 and the nickel 220. Of course, when forming such a nickel vanadium alloy, the thickness is preferably formed to a thickness of 0.01 ~ 1㎛. The nickel vanadium alloy may have a metal lift problem when the thickness of the nickel vanadium alloy is less than 0.01 μm, and may cause a characteristic defect (increase in resistance) when the thickness of the nickel vanadium alloy exceeds 1 μm. Since such nickel vanadium alloy is already known to those skilled in the art, further detailed description thereof will be omitted.

3 is a flowchart illustrating a die bonding method according to another embodiment of the present invention.

4A through 4D are cross-sectional views sequentially illustrating the die bonding method illustrated in FIG. 3.

As shown in FIG. 3, the die bonding method according to the present invention includes a semiconductor die preparation step S11, an aluminum germanium alloy forming step S12, a gold or silver forming step S13, and a sawing step S14. And a bonding step S15.

In the preparing of the semiconductor die 110 (S11), as shown in FIG. 4A, one of a conventional active device, an integrated circuit, or an equivalent thereof is prepared, but the type thereof is not limited thereto. That is, the semiconductor die 110 is a concept including a passive element. Further, in practice, the semiconductor die 110 is suitably in the form of a semiconductor wafer. That is, a semiconductor wafer in which a plurality of semiconductor dies 110 are formed is preferable. However, in the drawings, only one semiconductor die is shown for convenience of description.

In the aluminum germanium alloy forming step (S12), as shown in FIG. 4B, the aluminum germanium alloy 120 is evaporated or sputtered on the surface of the semiconductor die 110 to a thickness of about 0.5 μm to 5 μm. sputtering). Here, the aluminum germanium alloy 120 may be formed of 35 to 55 wt.% Aluminum and 45 to 65 wt.% Germanium.

In one example, a target and a process condition for forming the aluminum germanium alloy 120 are presented. However, the present invention is not limited to these targets and working conditions.

Target: Al55wt.% Ge45wt.% (Al55Ge)

Basic Pressure: 5.0E-6Torr

Preliminary Sputtering: 5 minutes

Power (DC, RF): 120 W

Argon flow rate: 15sccm

Working pressure: 3.0E-3Torr

Thickness: 15,000Å

By such targets and working conditions, an aluminum germanium alloy 120 having a sheet resistance of 4.5 to 5.5 kW / cm 2 can be obtained. This sheet resistance value is within the range of the sheet resistance value of the conventional gold germanium antimony (AuGeSb) alloy, gold or gold arsenide (AuAs) alloy. Therefore, it can be seen that the aluminum germanium alloy 120 according to the present invention has the same electrical characteristics as that of the conventional material, and thus can replace the conventional expensive material. In fact, the die bonding structure can be realized at 1/10 of the conventional price. In addition, the aluminum germanium alloy 120 has passed both the scratch and taping tests used in conventional material property evaluation. That is, the aluminum germanium alloy 120 has sufficient adhesive force as a die bonding material. Therefore, it can be seen that the aluminum germanium alloy 120 can sufficiently replace the conventional expensive materials. Moreover, this aluminum germanium alloy 120 was also dense and hard with no voids in compositional structure and distribution. In addition, it was confirmed that the inside of the chamber used in the sputtering process of the aluminum germanium alloy 120 and the target used were not contaminated. In sum, the aluminum germanium alloy according to the present invention has the same electrical properties and adhesive strength as in the prior art, and can be realized at a price of 1/10 of the conventional.

Subsequently, in the gold or silver forming step (S13), as illustrated in FIG. 4C, gold or silver is deposited or sputtered on the surface of the aluminum germanium alloy 120 at a thickness of about 0.01 to 1 μm. )do. The gold or silver prevents oxidation of the aluminum germanium alloy 120 and is well adhered to the lead frame 140 in the die bonding process.

In the sawing step S14, the individual semiconductor dies 110 are sawed and separated from the wafer. Of course, such a sawing process is not necessary if the above operation is performed on the individual semiconductor dies 110 from the beginning.

Finally, in the die bonding step S15, as shown in FIG. 4D, the semiconductor die 110 is placed on the lead frame 140, and die-bonded at a temperature of 400 to 600 ° C. and a pressure of 50 to 500 gf / cm 2. Cool. In this case, when the temperature is less than 400 ° C., the aluminum germanium alloy 120 may remain in a solid state and may not reach an eutectic state. In addition, when the temperature exceeds 600 ° C., the eutectic state may be reached and the aluminum germanium alloy 120 may flow out of the semiconductor die 110. Of course, too high a process temperature risks other elements to melt. As a result of the actual experiment, the aluminum germanium alloy 120 was observed to start the eutectic state from about 423 ℃, but the optimum electrical properties and adhesive strength was obtained at about 450 ~ 550 ℃.

5 is a flowchart illustrating a die bonding method according to another embodiment of the present invention.

6A through 6E are cross-sectional views sequentially illustrating the die bonding method illustrated in FIG. 5.

5 and 6A to 6E, the die bonding method according to another embodiment of the present invention includes a semiconductor die preparation step (S21), a vanadium and nickel formation step (S22), and an aluminum germanium alloy formation step ( S23, gold or silver forming step S24, sawing step S25, and bonding step S26.

Here, the remaining steps except for the vanadium and nickel forming step (S22) is the same as the step shown in FIG. Therefore, only the differences will be described.

As illustrated in FIGS. 5 and 6B, the vanadium 210 may be formed on the surface of the semiconductor die 110 to have a thickness of about 0.01 μm to 1 μm by deposition or sputtering. The vanadium 210 serves as a glue metal. In addition, nickel 220 may be formed on the surface of the vanadium 210 to a thickness of about 0.01 μm to about 1 μm by deposition or sputtering. The nickel 220 serves to improve the bonding force between the vanadium 210 and the aluminum germanium alloy 120.

In addition, although not shown in the drawing, instead of the vanadium 210 and the nickel 220, a nickel vanadium alloy may be formed on the surface of the semiconductor die 110 by deposition or sputtering. Of course, when the nickel vanadium alloy is formed, its thickness is formed to a thickness of 0.01 ~ 1㎛.

7 is a graph showing the characteristics of the aluminum germanium alloy disclosed in the present invention.

X-axis in the graph of Figure 7 refers to the weight ratio of germanium in the aluminum germanium alloy. Therefore, 0 in the X axis means 100 wt.% Aluminum and 0 wt.% Germanium. In addition, 55 in the X axis means aluminum 45wt.%, Germanium 55wt.%. Of course, 100 in the X-axis means 0wt.% Aluminum, 100wt.% Germanium. In addition, Y-axis means temperature. Experiments were carried out in the temperature range 300 ~ 700 ℃.

Meanwhile, the upper region formed by b-a-c in the graph means a liquid region of the aluminum germanium alloy. In addition, the region formed by d-b-a and a-c-e means a liquid phase + solid state region of the aluminum germanium alloy. Of course, the lower region of the line formed by d-a-e means the solid region of the aluminum germanium alloy.

As can be seen in Figure 7, when the weight ratio of germanium is less than approximately 55wt.% It can be seen that the aluminum germanium alloy is eutectic in the order of solid phase, liquid phase + solid phase and liquid phase with increasing temperature. As such, when eutectic in the order of solid phase, liquid phase + solid phase, and liquid phase, aluminum is precipitated during cooling and aluminum only crystals are formed, which is not suitable as a die bonding material. Furthermore, in order to obtain a complete liquid aluminum germanium alloy, a temperature of 423 ° C to 656 ° C or higher is required, resulting in a process temperature that is too high.

In addition, even when the weight ratio of germanium exceeds about 55 wt.%, It can be seen that the aluminum germanium alloy is eutectic in the order of a solid phase, a liquid phase + a solid phase, and a liquid phase as the temperature increases. As such, when eutectic in the order of solid phase, liquid phase + solid phase, and liquid phase, germanium is precipitated during cooling, and only germanium crystals are formed, which is not suitable as a die bonding material. Similarly, in order to obtain a complete liquid aluminum germanium alloy temperature of 423 ~ 700 ℃ or more, there is a disadvantage that the process temperature is too high.

However, when the weight ratio of germanium is about 55 wt.%, It can be seen that the aluminum germanium alloy 120 is eutectic in the order of solid phase and liquid phase. That is, in the die bonding process, the aluminum germanium alloy has a property of being eutectic in the order of liquid phase from solid phase to liquid phase without solid phase. As such, when the state changes from the solid phase to the liquid phase during the die bonding process, aluminum or germanium does not occur during the cooling process. Thus, an optimal die bonding structure can be obtained. In fact, the die bonding process was able to obtain a solid aluminum germanium alloy having a uniform composition as a whole by increasing the temperature to approximately 400 ° C. to 600 ° C. or more and then cooling it.

8a and 8b are SEM images showing the aluminum germanium alloy formed at the optimum composition ratio.

As shown in FIGS. 8A and 8B, when the die bonding is performed using an aluminum germanium alloy having an optimum composition ratio, that is, 45 wt.% Aluminum and 55 wt.% Germanium, the structure has a random layered shape. That is, the crystal part only of aluminum or the crystal part only of germanium is not observed. The aluminum germanium alloy having such a layered structure has a sheet resistance equal to or better than a sheet resistance containing conventional gold, and the adhesion is also equal to or better than that containing conventional gold.

9A and 9B are SEM photographs showing aluminum germanium alloy formed when the optimum composition ratio is out of range.

As shown in FIGS. 9A and 9B, when the composition ratio is out of the optimum composition ratio, that is, when the weight ratio of germanium is less than 55 wt.% Or more than 55 wt.%, Aluminum or germanium is precipitated, and aluminum or layer is deposited between layers. Germanium crystal parts are formed. The aluminum or germanium crystal part not only increases the sheet resistance but also lowers the adhesive force and is not suitable as a die bonding structure.

Therefore, it can be seen that in order to use the aluminum germanium alloy disclosed in the present invention as a die bonding material, an optimum composition ratio and an optimal die bonding temperature are required. In the above description, the optimum composition ratio was 45 wt.% Aluminum and 55 wt.% Germanium, and the die bonding temperature was 400-600 ° C. However, those skilled in the art will recognize that the present invention is not limited to these composition ratios and temperatures. That is, in the process, the aluminum germanium alloy or the target is provided with a small amount of impurities (for example, iron, carbon, silicon, sodium, arsenic, antimony, bismuth, etc.), and also a semiconductor die, nickel, gold, silver or leadframe This is because the actual optimum composition ratio and the actual die bonding temperature of the aluminum germanium alloy may be shifted slightly depending on the surface characteristics of the aluminum alloy.

What has been described above is just one embodiment for carrying out the die bonding structure and method thereof according to the present invention, and the present invention is not limited to the above-described embodiment, and as claimed in the following claims, the present invention Without departing from the gist of the present invention, those skilled in the art to which the present invention pertains to the technical spirit of the present invention to the extent that various modifications can be made.

1 is a cross-sectional view illustrating a die bonding structure according to an embodiment of the present invention.

2 is a cross-sectional view illustrating a die bonding structure according to another embodiment of the present invention.

3 is a flowchart illustrating a die bonding method according to another embodiment of the present invention.

4A through 4D are cross-sectional views sequentially illustrating the die bonding method illustrated in FIG. 3.

5 is a flowchart illustrating a die bonding method according to another embodiment of the present invention.

6A through 6E are cross-sectional views sequentially illustrating the die bonding method illustrated in FIG. 5.

7 is a graph showing the characteristics of the aluminum germanium alloy disclosed in the present invention.

8a and 8b are SEM images showing the aluminum germanium alloy formed at the optimum composition ratio.

9A and 9B are SEM photographs showing the aluminum germanium alloy formed when the optimum composition ratio is out of range.

<Description of Symbols for Main Parts of Drawings>

100,200; Die bonding structure according to the present invention

110; Semiconductor die

120; Aluminum germanium alloy

130; Gold or silver

140; Leadframe

210; vanadium

220; nickel

Claims (14)

In a die bonding structure in which a semiconductor die and a lead frame are bonded to each other, And the semiconductor die and the lead frame are bonded to each other by an aluminum germanium (AlGe) alloy. The method of claim 1, Die bonding structure, characterized in that gold (Au) or silver (Ag) is further interposed between the aluminum germanium alloy and the lead frame. The method of claim 1, And a vanadium (V) and nickel (Ni) or a nickel vanadium alloy interposed between the semiconductor die and the aluminum germanium alloy. The method of claim 1, The aluminum germanium alloy is a die bonding structure, characterized in that formed in a thickness of 0.5 ~ 5㎛. The method of claim 2, The gold or silver is a die bonding structure, characterized in that formed in a thickness of 0.01 ~ 1㎛. The method of claim 3, wherein The vanadium is 0.01 ~ 1㎛, the nickel is die bonding structure, characterized in that formed in a thickness of 0.01 ~ 1㎛. The method of claim 3, wherein The nickel vanadium alloy is a die bonding structure, characterized in that formed in a thickness of 0.01 ~ 1㎛. The method of claim 1, The aluminum germanium alloy is a die bonding structure, characterized in that aluminum is 35 ~ 55wt.%, Germanium 45 ~ 65wt.%. The method of claim 1, The aluminum germanium alloy is a die bonding structure, characterized in that formed only in the layered portion without pure aluminum crystal. A semiconductor die preparation step of preparing a semiconductor die; An aluminum germanium alloy forming step of forming an aluminum germanium alloy on a surface of the semiconductor die; Gold or silver forming step of forming gold or silver on the surface of the aluminum germanium alloy; And a die bonding step of placing the semiconductor die on the surface of the lead frame and die bonding at a temperature of 400 to 600 ° C. and a pressure of 50 to 500 gf / cm 2. The method of claim 10, Between the semiconductor die preparation step and the aluminum germanium alloy forming step And a vanadium and nickel forming step of forming vanadium and nickel, or a nickel vanadium alloy on a surface of the semiconductor die. The method of claim 10, And the aluminum germanium alloy is formed by evaporation or sputtering. The method of claim 10, The gold or silver forming step is a die bonding method, characterized in that by the evaporation (evaporation) or sputtering (sputtering) method. The method of claim 11, The vanadium and nickel forming step is a die bonding method, characterized in that by the evaporation (evaporation) or sputtering (sputtering) method.

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