This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2011-145654 filed on Jun. 30, 2011, the entire contents of which are incorporated herein by reference.
The present invention relates to a method of vapor phase epitaxy and a vapor phase epitaxy device used for example in performing deposition by supplying a reaction gas to a surface of a semiconductor wafer while heating the semiconductor wafer from a back surface thereof.
In recent years, a high quality such as improved thickness uniformity has been required in addition to high productivity in a deposition process accompanied with a request for cost reduction and high performance of a semiconductor device.
A single wafer type of vapor phase epitaxy device is used to meet such a request. In the single wafer type of vapor phase epitaxy device, for example, deposition is performed on a wafer by a back side heating method in which a process gas is supplied while rotating a wafer at a high speed of 900 rpm or more in a reaction chamber and the wafer is heated from a back surface thereof using a heater.
In the deposition process as above, products are deposited not only on the wafer but also on a susceptor that is a supporting member for the wafer. When the products are deposited between the wafer and the susceptor, the wafer adheres to the susceptor, in which case the wafer may be lifted in a state with the susceptor being adhered thereto upon lifting the wafer by a push-up pin to unload the wafer. Further, if the wafer or the susceptor is damaged upon lifting the wafer or upon mounting it on a robot hand, there is a problem that an operation for removal performed by reducing a temperature in a reaction chamber becomes necessary, whereby an yield and a throughput are decreased.
A method of vapor phase epitaxy that is one embodiment of the present invention characteristically includes loading a wafer in a reaction chamber and mounting the wafer on a supporting section; heating the wafer by a heater provided under the supporting section; performing deposition on the wafer by supplying a process gas onto the wafer while rotating the wafer; detecting a temperature distribution at least in a circumferential direction at a peripheral edge section of the wafer; and determining a presence/absence of adhesion between the wafer and the supporting section based on the detected temperature distribution.
A vapor phase epitaxy device that is one embodiment of the present invention characteristically includes a reaction chamber into which a wafer is loaded; a supporting section on which the wafer is mounted in the reaction chamber; a rotation drive control section that rotates the wafer together with the supporting section; a gas supply section that supplies a process gas onto the wafer; a gas discharge section that discharges gases from the reaction chamber; a heater provided under the supporting section and that heats the wafer to a predetermined temperature; a temperature detecting section that detects a temperature distribution at least in a circumferential direction at a peripheral edge section of the wafer; and a calculation processing section that determines a presence/absence of adhesion between the wafer and the supporting section based on the temperature distribution detected by the temperature detecting section.
Reference will now be made in detail to the present embodiment of the invention, an example of which is illustrated in the accompanying drawings.
A gas supply inlet 12a connected to a gas supplying section 12 for supplying a process gas including a source gas and a carrier gas is provided at an upper portion of the reaction chamber 11. Further, at a lower portion of the reaction chamber 11, gas discharge outlets 13a connected to gas discharging sections 13 for discharging gases and controlling a pressure inside the reaction chamber 11 at a constant value (for example, an ordinary pressure) are provided for example at two positions.
A rectifying plate 14 having minute through holes for rectifying and supplying the supplied process gas is provided at under the gas supply inlet 12a.
Further, a susceptor 15 for example formed of SiC that is a supporting section for mounting the wafer w is provided under the rectifying plate 14. The susceptor 15 is mounted on a ring 16 that is a rotating member. The ring 16 is connected to a rotation drive control section 17 configured of a motor and the like via a rotation shaft that rotates the wafer w at a predetermined rotational speed.
A heater configured of an inner heater 18 and an outer heater 19 for example formed of SiC for heating the wafer w is provided inside the ring 16, and is connected to a temperature control section 24 that controls the inner heater 18 and the outer heater 19 respectively to be at a predetermined temperature at a predetermined temperature changing speed. Further, a disc-shaped reflector 20 for reflecting a downward heat from the inner heater 18 and the outer heater 19 and effectively heating the wafer w is provided. Further, a push-up pin 21 that supports a lower surface of the wafer w and moves the wafer w up and down is provided so as to penetrate the inner heater 18 and the reflector 20.
A radiation thermometer 22 that is a temperature detecting section for detecting a temperature distribution at a peripheral edge section of the wafer w is provided at the upper portion of the reaction chamber 11, and is connected to a calculation processing section 23. By using such a semiconductor manufacturing device, an Si epitaxial film is formed for example on the wafer w of φ200 mm.
Next, the wafer w is heated for example to be at 1100° C. by causing the inner heater 18 and the outer heater 19 respectively for example to be at 1500 to 1600° C. by the temperature control section, and the wafer w is rotated for example at 900 rpm by the rotation drive control section 17 (Step 2).
Next, the process gas whose flow rate is controlled by the gas supply control section 12 and mixed is supplied onto the wafer w in a rectified state through the rectifying plate 14. The process gas has dichlorosilane (SiH2Cl2) as a source gas diluted to a predetermined concentration (for example, 2.5%) by a diluent gas such as an H2 gas, for example, and is supplied for example at 50 SLM.
On the other hand, a discharge gas formed of the excessive process gas, reaction by-products, and the like is discharged from the gas discharging openings 13a through the gas discharging sections 13, and the pressure inside the reaction chamber 11 is controlled to be constant (for example, the ordinary pressure). Accordingly, the Si epitaxial film with a predetermined film thickness is formed on the wafer w (Step 3).
Next, for the wafer w onto which the Si epitaxial film has been formed, a temperature distribution in the circumferential direction at the peripheral edge section of the wafer w is detected by measuring a temperature at predetermined positions of the peripheral edge section of the wafer w (for example, with a distance from a wafer edge of 5 mm) by the radiation thermometer 22 while rotating the wafer w (Step 4). Note that, the measurement is not limited to one cycle; an accuracy of the temperature distribution can further be improved by performing the measurement for two cycles or more and calculating an average value.
Next, in the calculation processing section 23, a presence/absence of adhesion between the peripheral edge section of the wafer w and the susceptor 15 is determined based on the temperature distribution detected in Step 4 (Step 5). Hereinafter, the determination on the presence/absence of the adhesion will be explained in detail with reference to
Contrary to this,
Accordingly, if the fluctuation in the temperature (ΔT=T(max)−T(min)) exceeds a predetermined value (for example, 5° C.), it is determined in the calculation processing section 23 that the adhesion is present between the wafer w and the susceptor 15 (Step 5: YES). In this case, the wafer w is cooled to a temperature (for example, 500° C.) lower than a regular wafer unload temperature (for example, 800° C.), and the adhered state with the susceptor 15 is released by a contracture difference caused by a difference in coefficients of thermal expansion between the wafer w formed of Si and the susceptor 15 formed of SiC (Step 6).
Then, the wafer w whose adhered state with the susceptor 15 has been released is lifted by the push-up pin 21, and thereafter is unloaded from the reaction chamber 11 by the robot hand and the like (Step 8).
On the other hand, if the temperature increase is within the predetermined value (for example, 5° C.), it is determined in the calculation processing section 23 that the adhesion is absent between the wafer w and the susceptor 15 (Step 5: NO). In this case, the wafer w is cooled to the regular wafer unload temperature (for example, 800° C.) (Step 7), and the wafer is lifted by the push-up pin 21, and is unloaded from the reaction chamber 11 by the robot hand and the like (Step 8).
As described, according to the present embodiment, upon performing the deposition, even in the case of having the adhesion between the wafer w and the susceptor 15, the adhesion can be detected, and the wafer w can be unloaded after having released the adhesion. Due to this, the operation for releasing the adhesion can be performed only when it is necessary. That is, although the temperature reduction for example to 500° C. for releasing the adhesion had generally been performed for an entire lot including the adhesion, herein the operation for releasing the adhesion is performed only on the ones to which the adhesion has been detected. By performing the control as described, about two minutes of time loss caused for each wafer in connection to the temperature reduction and temperature increase can be omitted. Accordingly, damages to the wafer and the susceptor 15 can be suppressed, and the decrease in the yield and throughput can be suppressed.
In the present embodiment, although a vapor phase epitaxy device similar to the first embodiment is used, the temperature distribution at the peripheral edge section of the wafer before the deposition is detected in addition to the temperature distribution after the deposition.
That is, similar to the first embodiment, after the wafer w is loaded in the reaction chamber 11 and is mounted on the susceptor 15, the wafer w is heated for example to be at 1100° C., and the wafer w is rotated for example at 900 rpm by the rotation drive control section 17.
Then, before the process gas is supplied, the temperature distribution at the peripheral edge section of the wafer w is detected by measuring the temperature at the predetermined positions of the peripheral edge section of the wafer w (for example, with the distance from the wafer edge of 5 mm) by the radiation thermometer 22 while rotating the wafer w.
Further, similar to the first embodiment, the process gas is supplied onto the wafer w at the predetermined concentration and the predetermined flow rate, and the Si epitaxial film with the predetermined film thickness is formed on the wafer w. Then, for the wafer w onto which the Si epitaxial film has been formed, the temperature distribution in the circumferential direction at the peripheral edge section of the wafer w is similarly detected.
As shown in
On the other hand, as shown in
As described, according to the present embodiment, even in the case where the temperature variations are present to begin with in the circumferential direction of the wafer w, the operation to release the adhesion can be performed only when it is necessary by more accurately detecting the adhesion upon the deposition, and taking the wafer w out after having released the adhesion; thus, the time loss can be omitted similar to the first embodiment. Accordingly, the damages to the wafer and the susceptor can be suppressed, and the decrease in the yield and throughput can be suppressed.
Although the vapor phase epitaxy device similar to the first embodiment is used in the present embodiment, it detects the temperature difference of the peripheral edge section of the wafer also in a diameter direction.
That is, similar to the first embodiment, after the wafer w is loaded in the reaction chamber 11 and is mounted on the susceptor 15, the wafer w is heated for example to be at 1100° C., and the wafer w is rotated for example at 900 rpm by the rotation drive control section 17.
Further, similar to the first embodiment, the process gas is supplied onto the wafer w at the predetermined concentration and the predetermined flow rate, and the Si epitaxial film with the predetermined film thickness is formed on the wafer w. Then, for the wafer w onto which the Si epitaxial film has been formed, as shown in
Similarly, a measurement position by the radiation thermometer 22 is changed to an outer circumferential side, and a temperature at a position b having the distance from the wafer edge of 10 mm and a temperature at a position c having the distance from the wafer edge of 5 mm are detected.
On the other hand, if the temperature increase is within the predetermined value (for example 5° C.), it is determined that the adhesion is absent, and similar to the first embodiment, the wafer w is cooled, and the wafer w is lifted by the push-up pin 21 and is unloaded from the reaction chamber 11 by the robot hand.
As described, according to the present embodiment, even in the case where the adhesion with the susceptor 15 is present at an entire outer circumferential surface of the wafer w, the adhesion upon the deposition can be detected and the wafer w can be unloaded after having released the adhesion by detecting the temperature distribution in the diameter direction, thus, the time loss can be omitted similar to the first embodiment. Accordingly, the operation for releasing the adhesion can be performed only when it is necessary, the damages to the wafer w and the susceptor 15 can be suppressed, and the decrease in the yield and throughput can be suppressed.
Note that, in the present embodiment, although only the temperature distribution after the deposition has been detected, by also detecting the temperature distribution before the deposition similar to the second embodiment, the adhesion upon the deposition can more accurately be detected even in the case of having the temperature variations to begin with in the circumferential direction of the wafer w.
In these embodiments, although the wafer w formed of Si and the susceptor 15 formed of SiC are used, there is no limitation regarding combinations thereof. Any combination is allowable so long as a difference in coefficients of thermal expansion resides between the wafer w and the susceptor 15, so other than the above, for example, a combination of the wafer formed of SiC and the susceptor 15 formed of TaC may be used.
Further, in these embodiments, although the presence/absence of the adhesion is determined by the temperature differences, the presence/absence of the adhesion may be determined by a deviation of the temperatures or the temperature increases. Such a deviation can be calculated from the following formula for example in the example of the second embodiment. It is determined that the adhesion is present between the wafer w and the susceptor 15 if the deviation exceeds the predetermined value.
Further, in these embodiments, although the presence/absence of the adhesion is determined and the operation for releasing the adhesion is performed in the presence of the adhesion, they are not limited to being used in the determination on whether the releasing operation is necessary or not. For example, information regarding the presence/absence of the adhesion may be stored as history information of the wafer w in the calculation processing section 23 or an externally provided memory. Accordingly, by being stored as the history information of the wafer w, for example, for the wafer to which the adhesion had been present, an internal warpage thereof is assumed to have enlarged due to the operation for releasing the adhesion; thus, for the wafer w as above, a test accuracy thereof can be improved by conducting a reexamination of a wafer state and the like.
According to these embodiments, it becomes possible to stably form films such as the epitaxial film on the semiconductor wafer w at a high productivity. Further, in addition to an improvement in a wafer yield, improving a yield of a semiconductor device to be formed through an element forming step and an element separating step and stabilizing an element performance also become possible. By being adapted especially to an epitaxial forming step for a power semiconductor device such as a power MOSFET, IGBT, and the like in which a thick film growth of 100 μm or more is required for an N type base region, a P type base region, an insulating isolation region and the like, it becomes possible to achieve a satisfactory element performance.
In these embodiments, although examples of forming the Si epitaxial film have been exemplified, other than the above, for example, an adaptation to an epitaxial layer of compound semiconductors such as GaN, GaAlAs, InGaAs, SiC, and the like, an amorphous layer thereof, or a polycrystal layer is also possible. Further, an adaptation to deposition of an insulation film such as SiO2 layer, Si3N4 layer and the like is also possible. Further, the teachings herein may be carried out with various modifications thereto within a scope that does not go beyond a gist thereof.
Number | Date | Country | Kind |
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2011-145654 | Jun 2011 | JP | national |