RU2153209C1 - Method and device for cooling down semiconductor wafers - Google Patents

Abstract

FIELD: microelectronics. SUBSTANCE: semiconductor wafers used in lithographic operations for manufacturing semiconductor devices and integrated circuits are cooled down as follows. Heat- conducting substance such as gas or air space is organized between substrate holder and semiconductor wafer by means of air-swirl centrifuge upon admission of excess pressure into its air chambers; semiconductor wafer to be cooled down is placed directly onto centrifuge; compressed gas or air flow through feed lines of peripheral and central chambers is chosen to ensure that peripheral-to-central chamber flowrate ratio is between 1.5 and 6. Proposed method is suitable for use at atmospheric pressure and within comprehensive temperature range. Device implementing proposed method is, essentially, air swirl centrifuge that has case accommodating central and peripheral air chambers connected to gas or air feed lines and to working zone on its one external side that receives wafer and communicates through nozzles with air chambers; it also has gas or air flow varying facility, control unit, sensors responding to low pressure in central and peripheral air chambers connected to gas or air flow varying facilities through control unit. Device is arranged so that uniform contact is ensured between entire surface of wafer and heat- conducting material, that wafer is not wetted by the latter, and that gas or air space is controlled more effectively. EFFECT: reduced labor consumption; simplified design and reduced cost of device. 2 cl, 3 dwg

Description

 The invention relates to microelectronics and can be used in lithographic operations in the manufacture of semiconductor devices and integrated circuits.

 A device is known for heat treatment of semiconductor wafers (SU N 1799196), comprising a substrate holder, a refrigerator with a cavity connected to means for supplying refrigerant located under the substrate holder, and a flat resistive heater located between the substrate holder and the refrigerator, the cavity in the refrigerator is made in the form of a spiral-shaped continuous channel square section.

 The disadvantage of this device is the occurrence of mechanical stresses in the film of the photoresist, leading to destructive changes due to temperature differences in places of uneven contact between the plate and the substrate holder.

 The closest in technical essence and the achieved effect is a device for applying a photoresist to plates (application RU N 2093921), comprising a housing with a pneumatic chamber inside it, connected to the compressed air and vacuum supply lines and with the working area from one of its outer sides for placing the plate communicating with the pneumatic chamber, a control unit connected to the compressed air and vacuum supply lines, and a dispenser for supplying the photoresist solution, the housing is stationary, and its pneumatic cam The unit is divided into central and peripheral parts, which are connected to the compressed air supply line and are equipped with nozzles, which are located on the side of the housing working area, the compressed air and vacuum supply lines are equipped with means for changing the compressed air flow, which are connected to the control unit, there is a gauge of the thickness of the gas layer located on the side of the working area of the housing, the working area for placing the plate is in communication with the Central part of the pneumatic chamber and with the peripheral part of the pneumatic chamber through its nozzles, the thickness gauge of the gas layer is connected to the control unit.

 The disadvantage of this device is the inability to control the flow of gas or air in the air supply lines or to control the pressure in the chambers, which reduces the efficiency of the process of controlling the vortex air gap.

 The closest is a method of cooling semiconductor wafers in a vacuum (application RU N 2076390), comprising placing between a substrate holder and a semiconductor wafer a heat-conducting substance that is placed in a tray and located between the wafer and the substrate holder, the diameter of the tray is larger than the diameter of the plate, and use as the heat-conducting substance gallium in liquid form.

 The disadvantage of this method is its high cost and the complexity of the implementation, the presence of the effect of wetting the semiconductor wafer with a heat-conducting substance, which is used as a low-melting metal, and the relatively narrow temperature range at which this method can be used.

 The technical task is to improve performance and reduce the cost of implementing this method.

 The problem is achieved in that in a method for cooling semiconductor wafers, including the placement between a substrate holder and a semiconductor wafer of a heat-conducting substance, it is new that a gas or air gap created on a pneumatic vortex centrifuge after applying excess pressure to its air chambers is used as a heat-conducting substance which is directly placed for cooling the semiconductor wafer, and the flow of compressed gas or air through the supply line eriferiynoy and central chambers are selected such that the ratio of the circumferential flow chamber for flow of the central chamber lies in the range 1.5 ... 6. The use of gas or air instead of liquid metal eliminates the effect of wetting and extends the temperature range of the use of this method.

 The drawing (Fig. 1) schematically shows a device of a pneumatic vortex centrifuge for cooling semiconductor wafers on a pneumatic vortex gas or air gap, with which the proposed method is implemented.

 The device for cooling the semiconductor wafers is a two-chamber pneumatic vortex centrifuge containing a housing 1 with a central 2 and peripheral 3 pneumatic chambers connected to the gas or air supply lines 9 and with a working area from one of its outer sides to accommodate the semiconductor plate 4 communicating with pneumatic chambers by nozzles 10, control unit 7, characterized in that it contains low pressure sensors 5 and 6, connected to means for changing the flow of gas or air 8 through the unit the board 7.

 The device operates as follows. Overpressure is supplied to the peripheral and central chambers by changing the gas or air flow rate in the respective lines so that the ratio between the flow rates lies in the range of ratios determined experimentally for a particular diameter of the semiconductor wafer, configuration and diameter of the air supply nozzles based on the minimum temperature spread over the plate area during the cooling process. Expiring through the air supply nozzles of the peripheral and central chambers, the gas or air forms a vortex flow onto which the semiconductor wafer is placed. The swirling stream flowing around the plate cools it. When a semiconductor wafer is placed on a gas interlayer formed by a vortex flow, the pressure in the pneumatic chambers changes. The low-pressure sensor 5 of the central pneumatic chamber and the low-pressure sensor 6 of the peripheral pneumatic chamber gives the values of gas or air pressure in the chambers to the control device, which recalculates these values into costs, and comparing their ratio with the set one, gives a control action on the means for changing the gas or air consumption 8 , thus maintaining a given ratio of gas or air flow rates. Formed by the vortex flow causes the plate to rotate, thereby increasing the stability of the plate and the uniformity of heat transfer between the plate and the gas or air gap.

 Example. The method was tested for plates with a diameter of 100 mm.

 For this, a semiconductor wafer model was made, which is an ordinary semiconductor wafer with microthermocouples implanted into it.

The operating ranges of flow rates were determined experimentally, which for the central pneumatic chamber lie within 0.0012 ... 0.0018 m ³ / s, and for the peripheral pneumatic chamber within 0.0033 ... 0.0062 m ³ / s, and the optimal the ratio of the flow of gas or air in the peripheral pneumatic chamber to the flow of gas or air in the central pneumatic chamber from the point of view of the minimum temperature spread over the area of the semiconductor wafer is in the range of 1.5. . .6. For example, for a pneumatic vortex centrifuge, the geometric parameters of the working surface of which are shown in Fig. 2, the optimal ratio of gas or air flow of the peripheral pneumatic chamber to the gas or air flow of the central pneumatic chamber from the point of view of the minimum temperature dispersion over the area of the semiconductor wafer was 3.6 (Fig. 3 )

Thus, the proposed method for cooling semiconductor wafers and a device for its implementation provide:
- uniform contact over the entire area of the plate with a heat-conducting material;
- the use of this method at atmospheric pressure and in a wide temperature range;
- a significant reduction in the complexity of the method and the cost of the device while maintaining its simplicity;
- the absence of the effect of wetting the semiconductor wafer with a thermally conductive substance;
- more efficient control of the gas or air gap in comparison with the prototype device.

Claims (2)

 1. A method of cooling semiconductor wafers, comprising placing between a substrate holder and a semiconductor wafer a heat-conducting substance, characterized in that as a heat-conducting substance, a gas or air layer is used that is created on a pneumatic vortex centrifuge after applying excess pressure to its air chamber, on which a semiconductor is directly placed for cooling plate, and the flow rate of compressed gas or air through the supply lines of the peripheral and central chambers are selected such that the ratio of the flow rate of the peripheral camera to the flow rate of the Central camera was in the range of 1.5 to 6.  2. The device for implementing the method according to claim 1, which is a pneumatic vortex centrifuge containing a housing with a central and peripheral pneumatic chambers connected to the gas or air supply lines and with a working area from one of its outer sides to accommodate a plate communicating with pneumatic chambers through nozzles , means for changing the flow of gas or air, a control unit, characterized in that it contains low pressure sensors of the central and peripheral pneumatic chambers connected to means for changing p descent of gas or air through the control unit.

Images