Abrading – Precision device or process - or with condition responsive... – Controlling temperature
Reexamination Certificate
2000-02-29
2001-07-10
Eley, Timothy V. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
Controlling temperature
C451S053000, C451S060000, C451S446000
Reexamination Certificate
active
06257955
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to an apparatus and to a method for heating a liquid or viscous medium, in particular a polishing agent for a chemical mechanical polishing. Furthermore, the invention relates to an apparatus for polishing, in particular for a chemical mechanical polishing of wafers.
Depending on the strength of the chemical component of the polishing process, the temperature during chemical mechanical polishing (CMP) has a decisive influence on the process result. In this case, the process temperature, that is to say the temperature on the side of the wafer to be polished during the polishing operation, is influenced essentially by three thermal components: 1) the frictional heat occurring during the polishing process; 2) the heating of the polishing table; and 3) the temperature of the polishing agent (slurry).
The frictional heat produced during the polishing process can be influenced only in a limited manner, since the polishing pressure and the rotational speeds of the table and the carrier are generally subject to other process preconditions. Heating for the polishing table is usually provided in the apparatuses for polishing.
A specific and defined setting of the temperature of the polishing agent has so far not been taken into consideration. If the temperature of the polishing agent is controlled at all, this is done in such a way that the conduit for the polishing agent is guided through the heating device which is responsible for the temperature control of the polishing table. Such heating has, however, the disadvantage that it is not possible for the polishing agent and the polishing table to be heated independently.
In a further known apparatus, a heating coil is wound around the conduit for the polishing agent. However, this has the disadvantage that by comparison with the desired temperature of the polishing agent the heating coil operates at very high temperatures in order to be able to react quickly to temperature fluctuations. However, this can lead locally to very high temperatures in the polishing agent and thus to a degradation of the polishing agent.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and an apparatus for heating a liquid or viscous medium which overcome the above-mentioned disadvantages of the heretofore-known methods and apparatuses of this general type and which make it possible to set the temperature of the polishing agent in a defined manner independently of other process parameters.
It is furthermore an object of the invention to provide an apparatus for polishing wafers which allows to polish the wafers simply and satisfactorily while avoiding the abovementioned disadvantages.
The object of the invention is achieved by an apparatus for heating a liquid or viscous medium, in particular a polishing agent for chemical mechanical polishing, having a conduit for the medium to be heated and a heating device for the medium, the heating device being constructed as a heat exchanger which is disposed at the conduit for the medium to be heated.
With the heating apparatus according to the invention, it is possible to provide the polishing agent always at a precisely defined and constant temperature for the polishing process, virtually independently of the fact that the polishing agent is not continuously removed because of the polishing cycle which has a loading phase, a polishing phase and an unloading phase.
In accordance with a preferred embodiment, a heating agent, preferably a glycol-water mixture or deionized water, can flow through the heat exchanger. The selection of the heating agent is however not limited to these two variants. The temperature of the heating agent is advantageously set with a heating controller to a value between 30 and 90° C., preferably between 45 and 70° C., and most preferably between 55 and 60° C. The heating controller is advantageously a thermostat, and has a power of approximately 3 kW, for example. The transportation of the heating agent from a tank provided therefor into the heat exchanger can be supported, for example, by a pump which can have a performance of approximately 24 l/min. If the heating controller for the heating agent is disposed in the heating agent tank, then this configuration has the advantage that the heating agent temperature in the heat exchanger corresponds virtually to the heating agent temperature in the heating agent tank, wherein it is possible to provide the heating agent tank separated and away from the heat exchanger. However, the heating controller can also be provided directly in the heat exchanger.
In accordance with another feature of the invention, the conduit for the medium (polishing agent) to be heated can have a conduit region which is connected to a tank for the medium to be heated, and a conduit region which is connected to a distributor. The latter conduit region is advantageously short by comparison with the first-named conduit region. That is to say, the heat exchanger of the heating apparatus according to the invention is provided in the immediate vicinity of the distributor. The short length of the conduit ensures that the medium cannot cool down much after exiting from the heat exchanger and until entering the distributor. The defined adjustability of the temperature of the medium—for example the polishing agent—is therefore further increased.
In accordance with a further feature of the invention, the heat exchanger has a conduit section which is flushed on its outside by a heating agent. The conduit section is advantageously connected to the two conduit regions of the conduit for the medium (polishing agent) to be heated. The conduit section can, for example, be a spiral hose, but other configurations are also possible.
In accordance with another feature of the invention, the heat exchanger can have a cover with inlet openings on the incoming side. For example, two inlet openings for the heating agent conduit and the corresponding conduit region of the conduit for the medium (polishing agent) to be heated are provided. Furthermore, the heat exchanger can have a cover with outlet openings on the outgoing side. Again, two outlet openings can be provided for the conduits mentioned with regard to the incoming openings. Finally, the heat exchanger can have a medium pipe and at least one limiting rod. The limiting rod serves the purpose of holding the conduit section inside the heat exchanger in a precisely defined position, so that the conduit section is flushed on its outside simultaneously from all sides with heating agent, and the medium (polishing agent) to be heated, which is provided in it, is heated to a uniform, defined temperature.
The cover can advantageously have an outside diameter of approximately 126 mm and a maximum thickness in the region of the openings of 15 mm. An exemplary embodiment of the heat exchanger has a length of 510 to 540 mm.
According to another feature of the invention, the flow rate of the medium to be heated can be in the range of 100 to 1000 ml/min in the individual conduit regions and/or in the conduit section of the heat exchanger. Preferred flow rates are, for example, 150 ml/min, 200 ml/min and 250 ml/min.
The individual elements of the heat exchanger can advantageously be formed from a plastic, preferably from a polyurethane-based plastic or a PVA (polyvinyl alcohol) based plastic. The invention is not, however, limited to the use of these materials. Rather, any material can be used which has a suitable thermal conductivity, chemical stability with respect to the medium to be heated, and thermal stability. In particular, it is possible to use those materials which are, furthermore, compatible with the purity requirements and contamination requirements of the semiconductor industry.
According to the invention, the inside diameter of the conduit regions and/or of the conduit section can be 5 to 8 mm, preferably approximately 6.4 mm.
In accordance with another feature of the invention, the conduit region, leading towards the heat exchang
Diewald Wolfgang
Richter Andre
Springer Götz
Eley Timothy V.
Greenberg Laurence A.
Infineon - Technologies AG
Lerner Herbert L.
Nguyen Dung Van
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