As is known in the art, many semiconductor and biological devices require rapid and precise temperature control during processing and testing. To provide such control, the device is typically disposed in a temperature control structure. The temperature control structure regulates the temperature of the device.
Devices, such as integrated circuits, have become increasingly smaller while at the same time the devices dissipate increasingly more power. This results in devices having a relatively low thermal mass which tend to rapidly heat during operation.
Temperature control structures, on the other hand, do not typically have a low thermal mass since the structures must include a heating apparatus and a heat sink. U.S. Pat. No. 5,821,505, for example, describes a typical temperature control structure which utilizes an electric blanket-type heater having first and second opposing faces. A heat sink makes contact with a first face of the electric heater and an electronic device under test makes contact with the second face of the electric heater. This approach results in a built-up, layered serial component structure in which the heater is disposed between the electronic device under test and the heat sink.
A temperature sensor is coupled to the electronic device and a control circuit is coupled to the temperature sensor and to the heater. The temperature sensor senses the device temperature Td and the control circuit decreases the power to the heater when the sensed temperature of the electronic device is above a set point, and vice-versa. When the heater temperature Th is less than the device temperature Td, then heat flows from the electronic device through the heater to the heat sink and the rate of heat flow increases as Td−Th increases. When Th is greater than Td, then heat flows to the electronic device from the heater; and the rate of heat flow increases as Th−Td increases. By electrically controlling just the heat power, heat flow to from the electronic device can be adjusted and that in turn regulates the device temperature.
Since the devices being heated and cooled have relatively low thermal mass and the temperature control structure on which the devices are disposed for processing and/or testing have many times the thermal mass of the device, the device itself does not greatly effect the thermal dynamics of the system. Instead, the thermal dynamics of the system are dominated by the temperature control structure. Thus, the principal task in maintaining a device at a particular temperature is to servo control the temperature of the temperature control structure on which the device is disposed.
As a consequence of the thermal mass of the temperature control structure being much greater than the thermal mass of the device, there is a delay in the thermal response time in controlling the temperature of the device. Furthermore, since the temperature control structure is many times the thermal mass of the device itself, significant energy is wasted in heating and/or cooling a low thermal mass device by using a high thermal mass temperature control structure.
Further, if the heater is provided as the type which includes an electrical trace separated from surroundings by a layer of dielectric material on each side, another problem with this layered component approach is that the dielectric layers of the heater represent a thermal resistance between the metal heating element and the electrical device and heat sink. Also the dielectric layers of the heating element are repeatedly heated and cooled and thus repeatedly expand and contract. These regions thus represent areas of potential mechanical failure due to the repeated expansion and contraction of the dielectric due to temperature changes.
It would, therefore, be desirable to provide a temperature control structure and system having a relatively low thermal mass which allows the temperature of a device to be rapidly changed. It would also be desirable to provide a system which provides fast thermal response, but good temperature stability once a desired temperature is reached. It would be further desirable to provide a compact temperature control structure which can be utilized in a relatively small test chamber and which allows good electrical contact to be made to a device under test and which can be used to in an environment in which a plurality of devices can be tested simultaneously.