JP5348673B2 - Heating and cooling method of workpiece - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for heating or cooling an object to be treated, which can almost uniformly heat the object to be treated, without breaking the object to be treated, particularly in vacuum treatment equipment. <P>SOLUTION: A substrate W is electrostatically attracted by applying a predetermined voltage between a pair of positive and negative attraction electrodes 14a-14d provided on a substrate stage 2, and heated or cooled to a predetermined temperature by heating or cooling means incorporated in the substrate stage 2. The applied voltage of the attraction electrodes is changed to a triangular pulse by the time the temperature of the substrate reaches the predetermined temperature, and the attraction electrodes and an object to be treated are substantially separated from each other when the applied voltage becomes low. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to an object to be processed that can be used to heat or cool a Si wafer or a SiC wafer to a predetermined temperature in a vacuum processing apparatus that performs a predetermined process such as film formation on a Si wafer or a SiC wafer mainly in a vacuum. The present invention relates to a heating and cooling method.

  Conventionally, a substrate (processing object) such as a Si wafer or a SiC wafer to be processed is placed on a substrate stage installed in a processing chamber to be evacuated, and a predetermined thin film is formed on the substrate surface by, for example, a CVD method. The device is known. In such a processing apparatus, since the substrate temperature greatly affects the processing speed and the like, it is necessary to control the substrate to a substantially uniform temperature over the entire surface. Therefore, Japanese Patent Application Laid-Open No. H10-228688 discloses a technique in which a heating unit and a cooling unit using refrigerant circulation are incorporated in a substrate stage so that the substrate temperature can be controlled by heating and cooling the substrate.

  When controlling the temperature of a substrate in the processing apparatus as described above, an electrostatic chuck using electrostatic force is provided on the substrate stage, and a predetermined voltage is applied to a pair of positive and negative suction electrodes of the electrostatic chuck to attract the substrate. It is common to hold. Here, for example, when the substrate is heated by sucking and holding the substrate with the suction electrode, the region of the substrate that is sucked by the suction electrode (hereinafter referred to as “suction region”) is from the heating and cooling body that has passed through the suction electrode. Other areas heated by direct heat conduction and not adsorbed by the adsorption electrode (hereinafter referred to as “peripheral areas”) are heated by heat transfer from the adsorption area and radiant heat from the heating / cooling body (for this reason, The heating rate of the adsorption region is faster than that of the surrounding region).

However, when the substrate is continuously heated or cooled with the substrate held by suction as described above, that is, with the substrate locally restricted in the suction region, thermal stress caused by thermal expansion or contraction of the substrate The substrate may be damaged. Therefore, while applying a predetermined voltage between a pair of positive and negative adsorption electrodes provided on the heating / cooling body to electrostatically adsorb the substrate and heating or cooling the substrate to a predetermined temperature, the applied voltage to the adsorption electrode is stepwise. A method for heating and cooling a substrate that applies a voltage in the form of a rectangular pulse while increasing the voltage is known from Patent Document 2.

JP-A-5-13350 JP 2001-152335 A

  In the case of the above-mentioned Patent Document 2, the heating of the substrate to a predetermined temperature will be described as an example. The accumulated thermal stress is reduced to some extent by attenuating the adsorption force while no voltage is applied during the temperature rising process. Although it is dispersed, the temperature of the adsorption region rises linearly by direct heat conduction from the heating and cooling body even when no voltage is applied. For this reason, the temperature difference between the adsorption region and the peripheral region becomes large, and temperature unevenness easily occurs in the substrate surface. When large temperature irregularities occur, the substrate may be damaged due to thermal stress caused by the difference in thermal expansion between the adsorption region and the peripheral region, and becomes particularly prominent when the substrate is a SiC wafer.

  Accordingly, an object of the present invention is to provide a method for heating and cooling an object to be processed so that the object to be processed can be heated substantially uniformly without damaging the object to be processed.

In order to solve the above-described problems, the present invention provides a process of applying a predetermined voltage to the adsorption electrode to electrostatically attract the object to be processed, and heating the electrostatically adsorbed object to a predetermined temperature by the heating / cooling body. Or the step of cooling, the applied voltage of the adsorption electrode is changed in a triangular pulse shape with the same polarity until the temperature of the object to be processed reaches a predetermined temperature, and when the applied voltage becomes lower, the adsorption electrode And the object to be processed are substantially cut off.

  According to the present invention, the case where the substrate is heated to a predetermined temperature will be described as an example. The adsorption region of the substrate is heated by direct heat conduction from the heating / cooling body through the adsorption electrode, and the peripheral region is mainly from the adsorption region. The temperature is increased by heat conduction and radiation heat from the heating / cooling body. When the adsorption of the substrate is released in the temperature raising process, the thermal conductivity to the adsorption region is rapidly lowered, and the heat escapes to the peripheral region where the temperature raising rate is slow and the temperature is relatively low.

  As described above, in the state where the adsorption of the substrate is released, the temperature of the adsorption region temporarily decreases, and the temperature increase rate of the peripheral region becomes transiently high. As a result, when the substrate is heated, the adsorption region and the peripheral region are not heated. The temperature difference between them becomes smaller. Therefore, according to the present invention, by heating the substrate as described above, the occurrence of temperature unevenness within the substrate surface that has reached a predetermined temperature is suppressed, and the thermal expansion within the substrate surface during the temperature rising process. It is possible to effectively prevent the substrate from being damaged by the thermal stress caused by the difference between the two, which is particularly effective when the substrate is a SiC wafer.

  In the present invention, while the substrate temperature is low during the temperature rising process and the amount of thermal expansion is small, the adsorption force of the substrate is reduced, the thermal stress caused by the thermal expansion is suppressed, and the substrate temperature is kept at a predetermined temperature. In order to reduce the total amount of thermal stress accumulated in the substrate when it reaches, the applied voltage to the adsorption electrode may be increased stepwise.

Sectional drawing which shows typically the processing apparatus which can implement the heating-cooling method of the board | substrate of this invention. The figure explaining adsorption holding of the substrate on a substrate stage in the processing apparatus of FIG. The graph explaining the heating control of a board | substrate. The graph explaining the voltage control to the adsorption | suction electrode at the time of the board | substrate heating which concerns on another form.

  FIG. 1 shows a processing apparatus capable of implementing the substrate heating and cooling method of the present invention. This processing apparatus includes a vacuum chamber 1 that defines a processing chamber 1a, and a substrate stage 2 installed in the processing chamber 1a. A substrate W such as a Si wafer or a SiC wafer is placed on the substrate mounting surface 2a, which is the upper surface of the substrate stage 2, and a film forming process is performed for forming a thin film on the surface of the substrate W by a CVD method.

  The processing chamber 1a is evacuated by the evacuation means 3 connected to the bottom thereof. A gas supply means 4 for supplying a processing gas composed of a raw material gas and a reaction gas to the processing chamber 1a is provided at the ceiling of the processing chamber 1. The gas supply means 4 includes a gas diffusion chamber 5 to which a processing gas is supplied via a supply pipe 5 a and a shower plate 6 on the lower surface of the gas diffusion chamber 5. Then, the processing gas is ejected toward the substrate W from a large number of holes 6 a formed in the shower plate 6.

  The substrate stage 2 is supported by a hollow column 7 standing on the bottom of the processing chamber 1a. Below the substrate stage 2, a lifting plate 9 that is lifted and lowered by a cylinder 8 is provided. The lift plate 9 is provided with a plurality of lift pins 10 penetrating the substrate stage 2 in the vertical direction. Further, a transfer port 11 with a gate valve is provided in the peripheral wall portion of the vacuum chamber 1, and a transfer means (not shown) moves forward and backward through the transfer port 11 into the processing chamber 1 a. Then, the processed substrate W is lifted from the substrate stage 2 by the lift pins 10 when the elevating plate 9 is lifted, and in this state, it is transferred to the transfer means and unloaded from the processing chamber 1a, and a new substrate W is processed by the transfer means. The substrate W is carried into the chamber 1 a and transferred to the lift pins 10, and the substrate W is placed on the substrate placement surface 2 a of the substrate stage 2 as the elevating plate 9 is lowered.

  The substrate stage 2 incorporates a resistance heating type heating means 12 connected to a known heater power supply device 12a installed outside the vacuum chamber 1, and circulates a coolant such as cooling gas or cooling water. A refrigerant circulation path 13 is formed. As a result, the temperature of the substrate W can be controlled by heating and cooling the substrate W. In this case, the substrate stage 2 itself including the heating means 12 and the refrigerant circulation path 13 constitutes a heating / cooling body.

  As shown in FIG. 2, the substrate mounting surface 2a of the substrate stage 2 is provided with a pair of positive and negative suction electrodes 14a to 14d for electrostatic chuck in order to suck the substrate S by static electricity. The pair of positive and negative suction electrodes 14 a to 14 d is connected to a chuck power supply device 15 disposed outside the vacuum chamber 1 by a power cable 15 a penetrating the inside of the column 7. The chuck power supply device 15 has a known structure, and includes a voltage control circuit 15b that controls application of a DC voltage to each pair of adsorption electrodes 14a to 14d with an arbitrary waveform, and each pair of adsorption electrodes 14a to 14d. A reverse voltage application circuit for applying a reverse voltage. In the present embodiment, the chuck power supply device 15 applies a triangular pulse voltage whose polarity changes at a constant cycle to the pair of suction electrodes 14a and 14d (see FIG. 3).

  Next, a method for heating the substrate W will be described by taking as an example the case where the substrate W is heated to a predetermined temperature in the processing apparatus. A new substrate W is carried into the processing chamber 1 a by the transfer means and transferred to the lift pins 10. After the lift plate 9 is lowered, the substrate W is placed on the substrate placement surface 2 a of the substrate stage 2, and then sucked by the chuck power supply device 15. The electrodes 14a to 14d are energized to hold the substrate W by suction. Then, the heater power supply device 12a is operated to start heating the substrate W.

  At this time, the adsorption area A1 of the substrate W is heated by direct heat conduction from the substrate stage 2 through the adsorption electrodes 14a to 14d, and the peripheral area A2 is mainly due to heat conduction from the adsorption area A1 and radiation heat from the substrate stage 2. The temperature rises. Then, immediately after the heating of the substrate W is started, the chuck power supply 15 applies a triangular pulse voltage whose polarity changes at a constant cycle.

  When a reverse voltage is applied by the chuck power supply device 15 during the temperature raising process and the adsorption of the substrate W is released, the amount of heat conduction to the adsorption region A1 decreases rapidly and the temperature raising rate is slow and the temperature is relatively low. The heat escapes to the lower peripheral area. When a positive voltage is applied by the chuck power supply device 15 and the substrate W is attracted again, the attracting region A1 is heated by direct heat conduction from the substrate stage 2 (that is, the temperature rise rate is increased).

  When the substrate W reaches a set temperature, a constant positive voltage is continuously applied to each of the pair of suction electrodes 14a to 14d by the chuck power supply device 15 so that the substrate W is held by suction. At that time, the operation of the heating means 12 is stopped, and the temperature of the substrate W is controlled by circulating the refrigerant in the refrigerant circulation path 13 as necessary.

  As described above, in the present embodiment, when the temperatures at the measurement points of the adsorption region A1 and the peripheral region A2 in the temperature raising process are measured, as shown in FIG. As the temperature of the adsorption region A1 decreases once, the temperature increase rate of the peripheral region A2 becomes transiently high, and as a result, the temperature difference between the adsorption region A1 and the peripheral region A2 becomes small when the substrate W is heated. Therefore, by heating the substrate W while repeating the above-described control, the occurrence of temperature unevenness in the surface of the substrate W that has reached a predetermined temperature is suppressed, and thermal expansion in the surface of the substrate W during the temperature rising process is suppressed. It is possible to effectively prevent the substrate from being damaged by the thermal stress caused by the difference.

  In this embodiment, since reverse voltage is periodically applied to the suction electrodes 14a to 14d when the suction of the substrate W is released, it remains even if the suction electrodes 14a to 14d are grounded. In some cases, the adsorption of the substrate W cannot be completely released due to the electric charge. However, by applying a reverse voltage, the residual charge is canceled and the adsorption of the substrate W can be completely released.

  Further, in the present embodiment, since a triangular pulse voltage is applied to the chucking electrodes 14a to 14d by the chuck power supply device 15, when a rectangular pulse voltage is applied, the peak voltage (the chucking force is maximized). Is applied for a predetermined time, and during this time, the temperature rise rate of the adsorption region A1 becomes faster and the temperature difference from the peripheral region A2 becomes larger, but the peak voltage (maximum adsorption force) is applied. Immediately after being done, the voltage is lowered to lower the suction force, so that the temperature rise of the suction region A1 during suction can be suppressed.

  In this embodiment, the case of using the film forming process by the CVD method has been described. However, the present invention is not limited to this, and the present invention is not limited to this, and also when other processes such as etching and sputtering are performed while controlling the substrate temperature. Applicable.

  In the present embodiment, the chuck power supply 15 applies a triangular pulse voltage whose polarity changes at a constant cycle, and the adsorption electrodes 14a to 14d and the substrate W are cut off to completely remove the adsorption. As described above, the period can be arbitrarily set, and as shown in FIG. 4, when the applied voltage is lowered by applying a triangular pulse voltage to release the adsorption of the present invention, the deposition is performed. This includes a case where the adsorption electrodes 14a to 14d and the substrate W are substantially cut off without being affected by the charge to be generated.

  At that time, while the substrate W temperature is low in the temperature rising process of the substrate W and the thermal expansion amount is small, the adsorption force of the substrate W is reduced, the thermal stress caused by the thermal expansion is suppressed to a small level, and the substrate W temperature is kept at a predetermined temperature. In order to reduce the total amount of thermal stress accumulated in the substrate W when reaching the value, the voltage applied to the adsorption electrodes 14a to 14d may be increased stepwise.

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 1a Processing chamber 2 Substrate stage 2a Substrate mounting surface 12 Heating means 13 Refrigerant circulation path (cooling means)
14a to 14d Suction electrode 15 Chuck power supply device A1 Suction area A2 Peripheral area W Substrate

Claims (2)

A step of applying a predetermined voltage to the adsorption electrode to electrostatically attract the object to be processed, and a step of heating or cooling the electrostatically adsorbed object to be processed to a predetermined temperature by a heating / cooling body,
Until the temperature of the object to be processed reaches a predetermined temperature, the applied voltage of the adsorption electrode is changed in a triangular pulse shape with the same polarity, and when the applied voltage is lowered, the adsorption electrode and the object to be processed are substantially A method for heating and cooling an object to be processed, characterized by:   The method for heating and cooling an object to be processed according to claim 1, wherein the voltage applied to the adsorption electrode is increased stepwise.

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