CS204875B1 - Method of acceleration of the reaction of the plasma with the hard substance surface and device for executing the same - Google Patents

Description

The invention relates to a method for accelerating the reaction of a plasma to a solid surface (e.g., ICs) and an apparatus for performing the method used in the diagnostics of ICs damage.

Upon completion, the microelectronic circuitry is encapsulated with epoxy resins to protect the circuit elements from both mechanical damage and environmental corrosion. The non-disassembly of such a structure is an obstacle to the failure analysis of these integrated circuits. Therefore, there has also been a demand in technical practice to remove the epoxy housing without damaging both the electronic components and their connections.

The least suitable method of removing the IC circuitry is mechanical, which simultaneously damages the components of the IC itself. Much more often, the chemical method of removing the IC circuit is used, but the joints and circuit elements themselves are attacked by an aggressive environment. Therefore, the specific action of ionized gas on solids with which it comes into contact has recently been utilized (Wilson D.D., Beal JR., XVth Annual Proceedings Reliability Physics 1978, p. 82 Las Vegas, Nevada). In particular, the thermodynamically unbalanced state of partially ionized gases is used.

The plasma itself is generated by the flow of electric current through the gaseous medium, thereby producing a series of active particles which cause the desired chemical changes. In addition to charged particles, ionization, dissociation, and excitation give rise to new neutral particles in both the ground and excited states, which can then form or break chemical bonds even at low temperatures.

The methods used so far have always led to an increase in the temperature of the solid, so that the usable concentration of the active particles was very low and limited by the heat resistance of the measured sample. A low temperature is necessary to avoid disturbing the electrical components and connections of the integrated circuit itself. When working at low temperatures, the entire decomposition process is lengthy and labor productivity is very low.

The above-mentioned drawbacks of the prior art are eliminated by the method of accelerating the reaction of the plasma to the solid surface according to the invention, which consists in increasing the power input to the reaction space and at the same time its walls, thereby cooling the solid so that the substance did not exceed a predetermined limit. The principle of the device according to the invention consists of a discharge tube provided with a reaction gas inlet and outlet and electrodes for supplying energy to the system, the discharge tube being provided with a cooling jacket.

Increasing the power input of the supplied energy simultaneously increases the energy of the individual particles, their number and thus the plasma density. Simultaneously cooling the walls of the reaction space also leads to a decrease in the temperature of the sample itself, which again allows to increase the energy input and thus the plasma density. This increase results in faster removal of the IC housing without destroying the IC itself and its electrical connections. Simultaneously with the supply of electrical energy, a gas, preferably oxygen, is introduced into the reaction space, which removes the products of reaction of the plasma with the solid surface.

The invention is further elucidated in Fig. 1, where a particular embodiment of the invention is shown, and Fig. 2, where the shear rate of a sheath for different concentrations of active particles is compared.

FIG. 1 shows a particular embodiment of a discharge tube 6 which is provided with a supply and outlet of reaction gas 2, 6 supplied to the reaction system and electrodes 6, 6 for supplying electrical energy. The discharge tube 8 is further provided with a cooling jacket 1, with a coolant inlet and outlet 2, 8 (preferably water). A solid sample g is introduced into the central portion of the reaction space of the discharge tube 6, wherein one p-n of the insert sample transition is used to measure the sample temperature using the meter 10.

Fig. 2 shows the polymer loss rates at lower active particle density in the uncooled tube (curve 1) and at high particle density while cooling the discharge tube (curve 2). By comparing the two curves, it can be seen that the rate of removal of the IC integrated circuit will increase by approximately 20x against the uncooled tube. The invention is further illustrated by way of example.

Example 1

A sample of the encapsulated integrated circuit was inserted into the discharge tube shown in Figure 1, provided with lead electrodes and a cooling jacket, in which one p-n junction was used simultaneously to measure the temperature of the integrated circuit. An RF generator operating at a frequency of 4 MHz with a maximum power of 200 W was used to generate a high-frequency field. The plasma-enclosure reactive products were carried away by oxygen, which was introduced into the tube at a pressure of 133 Pa.

The method can also be used to remove a polymer layer in a predetermined area using an appropriate mask (e.g., silicone grease) that does not react with the plasma.

Claims (3)

SUBJECT OF THE INVENTION What is claimed is: 1. A method for accelerating the reaction of a plasma to a solid surface, characterized in that the power input to the reaction space and the walls thereof is increased, thereby cooling the solid so that its temperature does not exceed a predetermined limit. Device for carrying out the method according to claim 1, characterized in that it consists of a discharge tube (1) provided with a reaction gas inlet and outlet (2, 6) and electrodes (4, 5) for supplying energy to the system, the discharge tube (1) is provided with a cooling jacket (3). Device according to claim 2, characterized in that a sample (9) is inserted into the central part of the discharge tube (1), one p-n junction of which is connected to the temperature meter (10). 2 sheets of drawings