Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor
Reexamination Certificate
2000-05-08
2001-10-09
Tsai, Jey (Department: 2812)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
C438S115000, C438S121000, C438S125000
Reexamination Certificate
active
06300162
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the manufacture of microelectronic devices. More particularly, the invention relates to protecting semiconductor components from various kinds of damage.
BACKGROUND OF THE INVENTION
The manufacture of microelectronics has become a major worldwide industry. A typical process in manufacturing a microelectronic component includes securing a semiconductor chip or die on a circuit board. Small wires, welded into place using an automated welding process known as wire bonding, connect the electronic circuitry on the chip to circuitry on the lead frame package. Such a process permits complex circuits to be made in a more standard durable package.
One issue that is of particular concern to the microelectronics industry is reverse engineering. Using readily available equipment, it is possible to analyze in detail the layout of a chip's circuitry and then copy the design for use in a competing product. Because reverse engineering a chip is significantly less expensive and may require less technology than designing a competing chip from scratch, the incentive to reverse-engineer a semiconductor chip is very great.
Various methods of defeating reverse engineering have been proposed. One such method is to cover a chip with an impermeable coating, such as a thermal spray, and then cure the coating using a predetermined cure schedule. The coating prevents analysis of the circuitry on the chip and cannot be removed without completely destroying the circuitry. One challenge of using impermeable coatings is that the ideal materials for such a coating behave quite differently from the silicon-based chip the coating is designed to protect. Of particular concern is the difference in the coefficient of thermal expansion of each of the many materials involved. If the difference between the materials' coefficients of thermal expansion is too great, the coating will destroy the circuitry during the curing process or damage the small bond wires connecting the chip to the lead frame package. Furthermore, some coatings may need to be applied to the chip at high temperatures. A chip exposed to high temperatures in the application stage, or in the curing stage mentioned above, may be adversely affected with respect to performance and may encounter unacceptable failure rates of the microelectronic chip or module.
Another issue, unrelated to reverse-engineering concerns, is that the top layer of microelectronic circuit lines on the chip is not designed to be resistant to scratching, impact, or temperature change. Even incidental contact with the chip may cause a failure of part of the circuitry in the chip.
It is therefore an object of the present invention to protect the integrity of an electronic chip or module while preventing the chip or module from being reverse-engineered.
It is another object of the invention to protect an electronic component from temperature damage during heat-intensive manufacturing processes.
It is another object of the invention to prevent damage to an electronic component due to impact, scratching, and/or temperature changes.
SUMMARY OF THE INVENTION
The invention provides a method of protecting an electronic component from damage, wherein the electronic component includes a semiconductor chip. According to the method, a first protective substance is applied to an outer surface of the semiconductor chip. The first protective substance has a coefficient of thermal expansion substantially similar to the coefficient of thermal expansion of the semiconductor chip. A second substance is then applied to an outer surface of the first protective substance. The first protective substance is applied such that it protects the semiconductor chip from damage during the application of the second substance.
According to another aspect of the invention, a method of increasing the tamper-resistance of an electronic component is provided. A first protective substance is applied to an outer surface of a semiconductor chip that forms part of the electronic component. The first protective substance has a coefficient of thermal expansion substantially similar to the coefficient of thermal expansion of the semiconductor chip. A second substance is applied to an outer surface of the first protective substance such that the second substance prevents access to the semiconductor chip. The first protective substance is applied so that it protects the semiconductor chip from damage during the application of the second substance.
According to still another aspect of the invention, A method of protecting an outer surface of a semiconductor chip is provided. According to the method, multiple layers of a protective substance are applied to an outer surface of the semiconductor chip. The protective substance has a coefficient of thermal expansion substantially similar to the coefficient of thermal expansion of the semiconductor chip. The semiconductor chip is cured or semi-cured after applying each of the layers of the protective substance.
REFERENCES:
patent: 4017340 (1977-04-01), Yerman
patent: 4633573 (1987-01-01), Scherer
patent: 5243756 (1993-09-01), Hambergen et al.
Tummala, R. et al., Microelectronics Packaging Handbook, Part III, 1997, Chapman & Hall, p. 364.
Shiel Roger R.
Smith Brian K.
Eppele Kyle
Jensen Nathan O.
Jones Josetta I.
Rockwell Collins
Tsai Jey
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