Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Assembly of plural semiconductive substrates each possessing...
Reexamination Certificate
2003-01-21
2004-10-19
Fourson, George (Department: 2823)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Assembly of plural semiconductive substrates each possessing...
C438S110000
Reexamination Certificate
active
06806118
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electrode connection methods, electrode surface activation apparatuses, electrode connection apparatuses, connection methods of electronic components, and more particularly to an electrode connection method, an electrode surface activation apparatus and an electrode connection apparatus that connect electrodes by solid state bonding, a method of directly connecting components to be connected via the respective electrodes, and a connected structure including electrical components connected by the method.
2. Description of the Related Art
The demand for high density mounting of electronic components is increasing based on smaller and thinner electronic equipment of these years. Thus, when connecting an electronic component such as a semiconductor chip to a board, a mounting method of flip chip bonding a bare chip provided with protruding electrodes (bumps) to a board is often employed. Protruding electrodes are formed on a semiconductor chip used for flip chip bonding, and it is necessary to electrically connect the protruding electrodes to the wiring on the board.
The major example of protruding electrodes of an electronic component is solder bumps. There is the reflow soldering method as a method of connecting the electronic component to the circuit board in a case where the solder bumps are used. In the reflow soldering method, flux for eliminating an oxide film on the solder is applied to the electrodes on a board so as to improve the solder bonding. Then, the electronic component is positioned and mounted on the board. Thereafter, the electronic component and the board are electrically connected by the reflow such that the solder bumps are melted in a furnace having an air atmosphere or a nitrogen atmosphere so as to wet the electrodes of the board with the melted solder and spread the solder on the electrodes. Generally, the electronic component and the circuit board are mechanically connected by filling and curing a resin for sealing between the electronic component and the circuit board. The reflow soldering method is also employed when forming a stacked structure by stacking electronic components.
Recently, solid state bonding has been attracting attention as a method of mounting a highly integrated smaller semiconductor device to a board at low temperature and low pressure with high reliability and low damage. As a specific connection method of solid state bonding, a method is known where bonding surfaces of electrodes (for example, the electrodes of a semiconductor device and the electrodes of a board to which electrodes the electrodes of the semiconductor are connected) are placed in direct contact with each other and pressed so as to form a solid state bond. More specifically, a method is known where a firm bond (solid state bond) is formed between metal atoms at room temperature, after activating the surface of the metal forming the electrodes by eliminating an oxide film existing on the surfaces of the electrodes.
However, when a pollutant or an oxide film such as an oxide exists on the bonding surfaces, it is impossible to form a firm solid state bond of metal atoms. Accordingly, when forming the solid state bond, the elimination of the oxide film and activation are performed on the bonding surfaces.
As specific methods of eliminating the oxide film of the bonding surfaces so as to activate the bonding surfaces, there are a method of irradiating an inert gas ion beam or an inert gas high-speed atom beam on the bonding surfaces, a method of applying ultrasonic waves to the bonding surfaces, a method of applying friction to the bonding surfaces, and so on.
In addition, after activating the electrodes by the above-described methods, until the electrodes are connected to each other, it is necessary to maintain the state where the surfaces of the electrodes are activated. This is because even if the elimination of the oxide film of the bonding surfaces and the activation process of the bonding surfaces are performed, when the bonding surfaces are returned (exposed) to the air, the oxide film is formed on the bonding surfaces again.
Therefore, conventionally, when the elimination of the oxide film and the activation process end, the activated electrodes are maintained in a vacuum or an inert gas atmosphere. Further, the connecting process of the electrodes is performed in the same atmosphere.
However, when the above-described conventional methods are employed, until the solid state bond is formed after the activation of the electrode surfaces, it is necessary to maintain the state where the electrodes are activated. For this reason, a mechanism is required for maintaining the electrode surfaces in the vacuum or the inert gas atmosphere.
Accordingly, it is impossible to use a flip chip bonder capable of connecting the components in the air and having a high mounting speed. Thus, there has been a problem in that the efficiency of the connecting process of the electrodes is degraded. In addition, in order to make the connecting process more efficient, when the mechanism for realizing the inactive gas atmosphere is provided to the flip chip bonder, the equipment becomes complex and expensive. Thus, the equipment cost increases.
In addition, in the above-described reflow soldering by the solder bumps, since the melting point of the solder is generally high such as equal to or more than 200° C., there is a possibility of the electronic component being thermally damaged. Moreover, shorts tend to occur between the adjacent electrodes when the solder melted in the reflow flows out from the electrode areas. Further, since the thermal expansion coefficient of the electronic component and the thermal expansion coefficient of the circuit board are different, shearing stress and strain are applied to the bonded parts connected by the reflow solder. Accordingly, the reliability of the connection is likely to be reduced.
On the other hand, in the method of forming the solid state bond such that the bonding surfaces are in direct contact with and pressed against each other after cleaning and activating the electrode surfaces of the components to be connected, it is difficult to achieve firm connection. The reason is that, since irregularities on the order of submicrons or microns originally exist on the electrode surfaces, the planarization of the electrode surfaces is difficult to achieve even if the electrode surfaces are cleaned, and thus the effective contact area of the electrodes is small. When the force on the connection is increased so as to improve the connection strength, the electronic component may be damaged. Additionally, when a polarization process such as the chemical-mechanical polishing (CMP) is performed so as to eliminate the irregularities on the electrode surfaces, problems such as an increase in the manufacturing cost and an increase in the TAT (turn around time) arise.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an improved and useful electrode connection method, electrode surface activation apparatus, electrode connection apparatus, and connection method of electronic components in which the above-mentioned problems are eliminated.
It is another and more specific object of the present invention to provide an electrode connecting method, electrode surface activation apparatus, and electrode connecting apparatus that can simply and inexpensively form a solid state bond between electrodes.
It is still another object of the present invention to provide a method enabling the connection between an electronic component and a mounting board such as a circuit board or between electronic components with high reliability at low temperature and low load in which the above-described problems in the prior art are eliminated.
In order to achieve the above-mentioned objects, according to one aspect of the present invention, there is provided an electrode connecting method of connecting a first electrode and a second electrode, including the steps of:
Mizukoshi Masataka
Okamoto Keishiro
Yamagishi Yasuo
Armstrong Kratz Quintos Hanson & Brooks, LLP
Fourson George
Fujitsu Limited
Toledo Fernando L.
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