Single chamber timing cycles

The first stage in a high-vacuum cycle is to evacuate the loaded chamber. Some cycles may require a single evacuation, others may require a pulsing cycle of evacuation followed by steam injection repeated several times. The nature of the load dictates the cycle. Evacuation may be controlled through a pressure switch or transducer or simply by a timer governing pump running time. It is usual to find a condenser positioned between the chamber and the pump for purposes of pump protection. 

Thermal cycle experiments are t5tpicaUy performed in single-chamber ovens. Dual-chamber systems are sometimes employed, but single-chamber equipment tends to dominate the test space. The main drawback of a dual-chamber oven is the lack of control over the thermal loading profile when transferring from one chamber (or thermal zone) to the other. Regardless of whether a single or dual chamber is used, temperature is cycled from a maximum to a minimum (T in) value. Temperature is ramped from one temperature extreme to another at a controlled rate, referred to as the ramp rate. Temperature is also held at the maximum and minimum values for a predetermined time known as the dwell time. Table 59.1 lists typical... 

The separation of the expansion chamber (with cold finger) from the compressor by a capillary ( 30cm) reduces vibration. Typical small split-cycle single-stage units have a cooling power of 1W near 80 K, a cool-down time of 5-10 min and a life of over 5000 h. 

The double promoter process involves the successive application of liquid promoter solutions of vinyltrichlorosilane (VTS) and 3-chloropropyltrimethoxy-silane followed by successive cure cycles in dry N2 at 90°C after each application and before photoresist application. The double promoter process evolved because it was felt that the silane reaction with the SiOH surface groups of low temperature oxides was incomplete for a single promoter application, and because vapor silane equipment did not exist at that time. Interestingly, a double HMDS liquid promoter process failed to yield adequate adhesion as well. Later in time, the successful but somewhat complex double promoter process was replaced by the vapor phase HMDS process in the Star 1000 (or 2000) then superior resist image adhesion was obtained on all four oxide substrates with all the photoresists tested. Before the advent of the HMDS vapor priming in standalone or wafer track equipment module chambers, liquid priming solutions were widely used, especially in development areas. 

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