Active solid-state devices (e.g. – transistors – solid-state diode – Physical configuration of semiconductor – Mesa structure
Reexamination Certificate
1999-01-20
2002-01-01
Tran, Minh Loan (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Physical configuration of semiconductor
Mesa structure
C257S638000, C257S641000, C257S650000
Reexamination Certificate
active
06335561
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device. More particularly, the present invention relates to a semiconductor device having a passivation film formed on a semiconductor substrate layer in which circuit elements are provided.
2. Description of the Related Art
IC chips are well known in which a large number of circuit elements such as transistors, aluminum wirings and pads are provided on one semiconductor substrate.
FIG. 11
is a cross-sectional view showing a portion of a related IC chip. An insulating film
4
is formed on an element formation layer
2
on which transistors (not shown) and other elements are provided. On a surface of IC chip, a a passivation film
14
is formed.
By forming the passivation film
14
, it is possible to physically protect the transistors and aluminum wirings
6
,
8
, and it is also possible to prevent water from infiltrating IC chips.
However, the above conventional IC chip has the following disadvantages. When transistors arranged in IC chip is operated, the transistors generate heat. A portion of the thus generated heat is emitted outside through the passivation film
14
. However, an upper surface of the passivation film
14
is almost flat except for portions in the peripheries of the aluminum wirings
6
,
8
and pads
10
,
12
.
Therefore, the heat radiation efficiency is not sufficient because heat is emitted through the passivation film
14
. Accordingly, an increased temperature of the chip causes limitations for further enhancement of the transistor performance. The above problem is very serious especially in IC chips, which generate a large amount of heat, such as IC chips having power transistors or CPU. Also, the above problem is very serious especially in IC chips, having a passivation film formed on a base layer of the insulating film
4
, planalized by the method of CMP (chemical and mechanical polishing) for the purpose of high integration.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to solve the above problems and provide a semiconductor device having a passivation film (protective film), the heat radiation efficiency of which is improved.
In the first aspect of the semiconductor device of the present invention, at least part of the passivation film being uneven shaped film, an upper surface of which is formed into an uneven shape independent of a shape of a lower surface of the passivation film layer.
Accordingly, even in the case that a base layer on which the passivation film is formed is flat, it is possible to form an upper surface of the passivation film into an uneven surface. For the above reasons, it is possible to increase a surface area of the passivation film per unit projected area. Consequently, a heat radiating area of the passivation film can be increased. As a result, a larger amount of heat can be emitted outside through the passivation film. In other words, it is possible to enhance the heat radiation efficiency through the passivation film. As a result, it is possible to enhance the performance of the semiconductor device.
In the second aspect of the semiconductor device, the passivation film is formed so as to include thick portions having large thickness of the film and thin portions having small thickness of the film, in an area in which the circuit element is formed.
In the third aspect of the semiconductor device, the passivation film is formed on a planarized insulating layer as a base layer.
In the fourth aspect of the semiconductor device, the base layer is planarized by the CMP method.
In the fifth aspect of the semiconductor device, the base layer includes an insulating layer planarized by the CMP method and a wiring section formed on a part of the insulating layer.
Recently, planarization of the surface of the semiconductor device is regarded as important in view of micronization and high-integration of the semiconductor device.
According to the above configuration, even in the semiconductor device in which the base layer is planarized, the heat radiation area can be increased and thereby the efficiency of the heat radiation through the passivation film can be enhanced. Further, as the film thickness is varied in accordance with a state of circuit elements formed in the base layer, so as to have large thickness at that portions such thickness is required and so as to have small thickness at any portions other than the portions at which the large thickness is required, the heat radiation efficiency can be enhanced while keeping reliability thereof.
In the sixth aspect of the semiconductor device, wherein at least one of the thin portions and the thick portions are arranged so as to be a closest packing structure.
In the seventh aspect of the semiconductor device, the thin or thick portions are regularly arranged such that the each center of adjacent thin or thick portions form a regular triangle.
Accordingly, the surface area of the uneven passivation film can be made maximum within a range of restriction of processing technique. Accordingly, it is possible to further enhance the heat radiation efficiency through the passivation film.
In the eighth aspect of the semiconductor device, the thin portion is formed so as to be the minimum thickness capable of protecting the circuit element.
Accordingly, even if the surface area is the same, it is possible to obtain the passivation film, the average film thickness of which is thinner. Therefore, it is possible to further enhance the heat radiation efficiency through the passivation film.
In the ninth aspect of the semiconductor device, the uneven shaped area may be formed into a shape such that a plurality of independent thick portions are provided on the passivation film which is substantially planar.
Accordingly, as compared with a case that a plurality of independent thin portions are provided on an upper surface of a flat passivation film, even if the surface area, the film thickness of the thin portion and the film thickness of the thick portion are respectively the same, it is possible to obtain an uneven passivation film, the average film thickness of which is thinner. Therefore, it is possible to further enhance the heat radiation efficiency through the the passivation film.
In the tenth aspect of the semiconductor device, at least one of corner portions of the each thin portion and each thick portion defined by the each thin portion may be rounded.
When the corner portions of the each thin portion is rounded, stress concentration caused in the corners of the thin portion can be reduced. Therefore, even if the passivation film is deformed, it is possible to reduce a possibility that the thin portion of the uneven passivation film is broken.
When the corners of the each thick portion are tapered, even if an upper surface of the semiconductor device is covered with a sealing material, stress concentration caused in the sealing material at a position opposed to the corner of the thick portion can be reduced. Therefore, even if the sealing material is deformed, it is possible to reduce a possibility that the sealing material is broken. As a result, it is possible to reduce a possibility that the semiconductor device itself is broken.
That is, while a function of protecting the circuit elements are protected physically, the heat radiation efficiency through the passivation film can be enhanced.
In the eleventh aspect of the semiconductor device, the uneven shaped film is formed in a vicinity of the circuit element generates a large amount of heat generation, the vicinity includes at least a part of above the circuit element.
Therefore, it is possible to emit heat generated by the circuit elements more effectively. Accordingly, while a portion in which the uneven passivation film is formed is minimized, the heat radiation efficiency through the passivation film can be enhanced, which is effective when it is necessary to reduce a portion in which the uneven surface film is formed.
In the twelfth aspect of the semiconductor device, a base layer on whic
Morgan & Lewis & Bockius, LLP
Rohm & Co., Ltd.
Tran Minh Loan
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