JP2010129764A - Susceptor, semiconductor manufacturing apparatus, and semiconductor manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a susceptor, a semiconductor manufacturing apparatus and a semiconductor manufacturing method, capable of uniformly depositing a film on a wafer while suppressing metal contamination in a film deposition process, suppressing the decrease of manufacturing yield, and improving reliability of a semiconductor device. <P>SOLUTION: The susceptor 11 includes: a first susceptor part 12 which has an external diameter smaller than the diameter of the wafer w and holding the center part of the wafer w; a spacer 14 holding an outermost periphery of the wafer w; and a second susceptor part 13 holding the first susceptor part 12 and spacer 14. The thermal conductivity of the spacer 14 is lower than those of the first and second susceptor parts 12 and 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a susceptor for holding a semiconductor wafer, a semiconductor manufacturing apparatus, and a semiconductor manufacturing method, for example, used for film formation by supplying a reaction gas to the surface while heating from the back surface of a semiconductor wafer.

  In general, a CVD (Chemical Vapor Deposition) apparatus used for forming an epitaxial film in a semiconductor manufacturing process has a heat source and a rotating mechanism below the wafer and can supply a uniform process gas from above. The method is used.

  In recent years, with the miniaturization and high functionality of semiconductor devices, a high level of metal contamination is required in the film forming process. In the above-described backside heating method, the wafer has a heat source and a rotation mechanism below the wafer, and is not completely separated from the heat source and the rotation mechanism, so that the wafer contamination occurs due to diffusion and movement of metal atoms. There's a problem.

  Usually, a wafer is held by a susceptor in a film forming apparatus (reaction furnace), and is moved up by a push-up pin penetrating a pin hole provided in the susceptor during transport. Therefore, there is a problem that it is particularly difficult to block wafer contamination from the pin holes.

  On the other hand, for example, Patent Document 1 proposes a susceptor structure in which pin holes are not provided in order to achieve uniform wafer temperature distribution. However, if the susceptor structure does not actually have pin holes, a gas layer is formed at the bottom of the wafer when the wafer is placed, and the wafer rises, making it difficult to hold it stably. .

Therefore, it is conceivable to adopt a susceptor structure in which a gap is formed in the lower part of the wafer. However, when the wafer and the susceptor are separated from each other, there is a problem that the temperature distribution in the wafer surface becomes non-uniform and uniform film formation becomes difficult.
JP 2000-43302 A ([0019] to [0022], [0036], FIG. 1 etc.)

  As described above, in order to block contamination from the pin holes provided in the susceptor, if the susceptor structure is not provided with pin holes, it is difficult to stably hold the wafer and form a film uniformly. If a gap is provided under the wafer, there is a problem that the temperature distribution becomes non-uniform and uniform film formation becomes difficult.

  The present invention suppresses metal contamination in a film forming process, can form a film uniformly on a wafer, suppresses a decrease in yield, and improves the reliability of a semiconductor device, and semiconductor manufacturing An object is to provide an apparatus and a semiconductor manufacturing method.

  The susceptor of the present invention has an outer diameter smaller than the diameter of the wafer, a first susceptor part that holds the center of the wafer, a spacer that holds the outermost periphery of the wafer, a first susceptor part that holds the first susceptor part, and the spacer. 2 susceptor parts, and the thermal conductivity of the spacer is lower than that of the first and second susceptor parts.

  In the susceptor of the present invention, it is preferable that the first susceptor part has a disk shape and has a convex portion on which a wafer is placed.

  In the susceptor of the present invention, the spacer is preferably made of quartz.

  The semiconductor manufacturing apparatus of the present invention includes a reaction furnace into which a wafer is introduced, a gas supply mechanism for supplying process gas to the reaction furnace, a gas discharge mechanism for discharging gas from the reaction furnace, and an outer diameter of the wafer. Having a first susceptor part that holds the center of the wafer, a spacer that holds the outermost periphery of the wafer, a first susceptor part and a second susceptor part that holds the spacer. A susceptor having a thermal conductivity lower than that of the first and second susceptor parts, a heater for heating the wafer from below the first and second susceptor parts, and a rotation mechanism for rotating the wafer And a push-up pin for penetrating the heater and driving the first susceptor part up and down.

  In the semiconductor manufacturing method of the present invention, the first susceptor part that carries the wafer into the reaction furnace, is installed in the reaction furnace, and holds the center of the wafer is lifted by the push-up pin, The wafer is placed on the susceptor part, the push-up pin is lowered, the first susceptor part is placed on the second susceptor part, and the outermost periphery of the wafer is heated by the first and second susceptor parts. It is placed on a spacer having low conductivity, the wafer is heated through first and second susceptor parts, the wafer is rotated, and a process gas is supplied onto the wafer.

  By using the susceptor, the semiconductor manufacturing apparatus, and the semiconductor manufacturing method of the present invention, metal contamination in the film forming process can be suppressed, and a film can be uniformly formed on the wafer. Can be improved.

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a cross-sectional view of the susceptor of this embodiment. As shown in the figure, the susceptor 11 is a first susceptor part, for example, an inner susceptor 12 made of SiC, and a second susceptor part provided on the outer periphery of the inner susceptor 12, for example, an outer susceptor made of SiC. 13 and is formed between an inner susceptor 12 and an outer susceptor 13, and is composed of a ring-shaped spacer 14 made of, for example, quartz.

  The inner susceptor 12 has a disk shape smaller than the diameter (for example, φ20 cm) of the wafer w to be placed, and is provided with a step portion 12a having a taper at the edge portion. Then, on the upper surface, for example, dot-like convex portions 12b having the same height are arranged at substantially equal intervals on the same circumference in four places.

  The outer susceptor 13 is provided with an opening, and a step portion 13a having a taper is provided at an edge portion of the inner wall. The inner susceptor 12 is placed on the stepped portion 13a so as to shield the opening, and a spacer 14 having a taper on the inner wall is placed on the outer periphery thereof. The cross-sectional shape of the spacer 14 is a rectangle having a width of 5 mm and a thickness of 1.3 mm, for example. The upper surface of the spacer 14 is the same height as the upper end of the convex portion 12 b of the inner susceptor 12 and is lower than the upper surface of the outer susceptor 13. The inner wall 13b of the outer susceptor 13 protruding from the spacer 14 has a taper so as to have an angle substantially equal to the bevel taper angle of 22 ° of the wafer w, for example.

  A wafer w is placed on the susceptor 11 having such a configuration. The wafer w is in contact with the convex portion 12 b of the inner susceptor 12 at the center of the back surface and the spacer 14 at the outermost periphery. The central portion indicates a region closer to the center than the outermost periphery. Then, the edge (outer periphery) of the wafer w is surrounded by the inner wall 13 b of the outer susceptor 13. At room temperature, the gap between the inner susceptor 12 and the spacer 14 and between the wafer w and the outer susceptor 13 are about 0.5 to 1.0 mm and 1.0 to 1.5 mm, respectively, in consideration of thermal expansion after heating. Is formed.

  Such a susceptor 11 is placed in a semiconductor manufacturing apparatus and used as follows.

  FIG. 2 shows a cross-sectional view of an epitaxial growth apparatus which is a semiconductor manufacturing apparatus of this embodiment. For example, in the reaction chamber 21 in which a wafer w having a diameter of 200 mm is formed, a gas supply mechanism (not shown) for supplying a process gas including a source gas such as TCS and dichlorosilane onto the wafer w from above the reaction chamber 21. A gas supply port 22 connected to (1) is installed. A gas discharge port connected to a gas discharge mechanism (not shown) for discharging gas to, for example, two places under the reaction chamber 21 and controlling the pressure in the reaction chamber 21 to be constant (normal pressure). 23 is installed.

  A rectifying plate 24 for supplying the process gas supplied from the gas supply port 22 to the wafer w in a rectified state is installed in the upper part of the reaction chamber 21.

  Below the reaction chamber 21, a rotation drive mechanism 25 for rotating a wafer w composed of a motor (not shown), a rotation shaft (not shown), a ring 25 a and the like is connected to the rotation drive mechanism 25. A susceptor 11 for holding the wafer w is installed.

  Below the susceptor 11, an in-heater 26a for heating a wafer w made of, for example, SiC is installed. Furthermore, between the susceptor 11 and the in-heater 26a, an out-heater 26b for heating a peripheral portion of a wafer w made of, for example, SiC is installed. A disc-shaped reflector 27 for efficiently heating the wafer w is installed below the in-heater 26a. Further, push-up pins 28 are provided so as to penetrate the in-heater 26a and the reflector 27 and move the wafer w up and down.

  For example, a Si epitaxial film is formed on the wafer w using such a semiconductor manufacturing apparatus. First, as shown in FIG. 3, for example, a wafer w having a diameter of 20 cm is held by the transfer arm 29 at the outer peripheral portion and is carried into the reaction furnace 21. Then, the inner susceptor 12 is raised by the push-up pin 28. At this time, the wafer w is held by the transfer arm 29 outside the inner susceptor 12, and the wafer w is placed on the inner susceptor 12 by raising the inner susceptor 12. Then, the inner susceptor 12 is lowered by the push-up pins 28, thereby holding the wafer w and the inner susceptor 12 on the outer susceptor 13.

  At this time, the wafer w is placed on the convex portion 12 b of the inner susceptor 12 and the outermost periphery is placed on the spacer 14, and a gap is formed between the back surface of the wafer w and the inner susceptor 12. .

  Next, based on the temperature of the wafer w measured by a temperature measurement mechanism (not shown), the temperature of the in-heater 26a and the out-heater 26b is appropriately controlled within a range of, for example, 1400 to 1500 ° C. by a temperature control mechanism (not shown). Then, the temperature of the wafer w is controlled to be 1100 ° C., for example. Further, the wafer w is rotated by, for example, 900 rpm by the rotation mechanism 25.

Then, from the gas supply port 23, for example, a carrier gas: H ₂ of ₂₀ to 100 SLM, a deposition gas: SiHCl ₃ of 50 sccm to ₂ SLM, a dopant gas: B ₂ H ₆ , and a PH ₃ : trace amount of process gas are rectified. It is introduced onto the plate 22 and supplied onto the wafer w in a rectified state. At this time, the pressure in the reaction furnace 21 is controlled to, for example, 1333 Pa (10 Torr) to normal pressure by adjusting the valves of the gas supply port 23 and the gas discharge port 24. In this way, each condition is controlled, and an epitaxial film is formed on the wafer w.

  FIG. 4 shows the position dependency of the wafer w temperature during the formation of the epitaxial film. As a comparative example, FIG. 5 shows the position dependency of the wafer w temperature when an epitaxial film is similarly formed without providing a spacer. As shown in these figures, according to the present embodiment, it is possible to suppress the temperature rise particularly at the outermost periphery of the wafer to about 1/10 of the conventional one. For example, the in-plane film thickness variation is 0.5% or less. It is possible to form a uniform epitaxial film.

  In order to suppress the temperature rise at the outermost periphery, it is conceivable to simply lower the temperature of the outheater 26b. In this case, however, the temperature in the region closer to the center of the wafer w is excessively lowered. Therefore, it is necessary to reduce only the temperature at the outermost periphery. In the present embodiment, since the outermost periphery of the wafer w is in contact with the spacer 14 having a low thermal conductivity, a rapid temperature rise from the outermost periphery can be suppressed.

  As a result, it is possible to form a uniform epitaxial film having a thickness variation of 0.5% or less on the wafer w, for example.

  In addition, the slip stress defined by the shear stress in the crystal direction due to temperature distribution variation is defined as the stress at which the slip progresses when there is a starting point, using the maximum value in the wafer w plane as a guide. It can be made smaller than the dislocation stopping critical stress. Further, the slip stress at the contact position (outermost circumference) with the susceptor 11 can be suppressed to nearly 1/10 of the conventional one, and the occurrence of slip to the wafer w can be suppressed.

  Further, in the epitaxial film formed in this way, the diffusion length of Fe by the SPV (Surface Photovoltage) method becomes, for example, 400 μm, and metal contamination can be sufficiently suppressed.

  When a semiconductor device is formed through an element formation process and an element isolation process, variations in element characteristics can be suppressed, and yield and reliability can be improved. In particular, an epitaxial formation process of a power semiconductor device such as a power MOSFET or IGBT (insulated gate bipolar transistor) that requires a thick film growth of several tens to 100 μm in an N-type base region, a P-type base region, an insulating isolation region, or the like. As a result, good device characteristics can be obtained.

  In this embodiment, as shown in FIG. 1, the cross-sectional shape of the spacer 14 is a predetermined rectangle, but the amount of heat conduction to the wafer w can be changed by changing the step area. Accordingly, the cross-sectional area of the spacer 14 can be optimized as appropriate according to the temperature rise at the outermost periphery, and the temperature distribution of the wafer w can be uniformly controlled.

  In addition, as shown in the partial enlarged view of the susceptor in FIG. 6, the cross-sectional shape of the spacer 64 may be a trapezoidal shape having a taper on the inner peripheral side. The spacer 64 is disposed on the step of the outer susceptor 63, and the inner susceptor 62 can be easily centered by forming a taper in the opposite portion of the inner susceptor 62 in accordance with the taper.

  Although the inner susceptor 12 has a disk shape, it may have a ring shape. The convex portions 12b provided on the upper surface of the inner susceptor 12 have four dot-like portions. However, the shape and arrangement are not particularly limited as long as the wafer w can be held horizontally. For example, in order to make the contact area with the wafer w as small as possible, it is preferable to hold it at three dot-shaped convex portions. Moreover, the ring shape which has a notch (non-continuous part) in one or more places may be sufficient.

  Moreover, although SiC was used as a material for the inner susceptor and the outer susceptor, it is preferable from the viewpoint of workability and high-temperature stability. For SiC, a sintered body can be used, and high purity SiC may be coated. Also, carbon coated with high purity SiC can be used. On the other hand, quartz is used as the spacer, but it is preferable because it has lower thermal conductivity than SiC and carbon and is excellent in high-temperature stability.

In the present embodiment, the case of forming the Si single crystal layer (epitaxial growth layer) has been described. However, the present embodiment can also be applied when forming the poly-Si layer. Furthermore, the present invention can be applied to other compound semiconductors such as a GaAs layer, GaAlAs, InGaAs, and the like. Further, the present invention can be applied to the case of forming a SiO ₂ film or a Si ₃ N ₄ film. In the case of a SiO ₂ film, in addition to monosilane (SiH ₄ ), N ₂ , O ₂ , and Ar gas are used as the Si ₃ N ₄ film. In this case, NH ₃ , N ₂ , O ₂ , Ar gas and the like are supplied in addition to monosilane (SiH ₄ ). Various other modifications can be made without departing from the scope of the invention.

FIG. 6 is a cross-sectional view of a susceptor according to one embodiment of the present invention. 1 is a cross-sectional view of a semiconductor manufacturing apparatus in one embodiment of the present invention. 4A and 4B illustrate a manufacturing process of a semiconductor device according to one embodiment of the present invention. The figure which shows the position dependence of the wafer w temperature at the time of epitaxial film formation in 1 aspect of this invention. The figure which shows the position dependence of the wafer w temperature at the time of epitaxial film formation in a comparative example. The elements on larger scale of the susceptor in 1 aspect of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Susceptor 12, 62 ... Inner susceptor 12a, 13a ... Step part 12b ... Convex part 13, 63 ... Outer susceptor 14, 64 ... Spacer 21 ... Reactor 22 ... Gas supply port 23 ... Gas discharge port 24 ... Current plate 25 ... Rotating mechanism 26a ... in heater 26b ... out heater 27 ... reflector 28 ... push-up pin 29 ... conveying arm

Claims (5)

A first susceptor part having an outer diameter smaller than the diameter of the wafer and holding the center of the wafer;
A spacer for holding the outermost periphery of the wafer;
A second susceptor part for holding the first susceptor part and the spacer;
The susceptor according to claim 1, wherein a thermal conductivity of the spacer is lower than a thermal conductivity of the first and second susceptor parts.   2. The susceptor according to claim 1, wherein the first susceptor part has a disk shape and has a convex portion on which the wafer is placed.   The susceptor according to claim 1, wherein the spacer is made of quartz. A reactor into which the wafer is introduced;
A gas supply mechanism for supplying process gas to the reactor;
A gas discharge mechanism for discharging gas from the reactor;
A first susceptor part having an outer diameter smaller than the diameter of the wafer and holding a central portion of the wafer; a spacer holding the outermost periphery of the wafer; and a second holding the first susceptor part and the spacer. A susceptor having a thermal conductivity of the spacer lower than that of the first and second susceptor parts;
A heater for heating the wafer from below the first and second susceptor parts;
A rotation mechanism for rotating the wafer;
A semiconductor manufacturing apparatus comprising a push-up pin that penetrates the heater and drives the first susceptor part up and down. Bring wafers into the reactor,
The first susceptor part that is installed in the reaction furnace and holds the center of the wafer is raised by a push-up pin, and the wafer is placed on the first susceptor part,
The push-up pin is lowered, the first susceptor part is placed on the second susceptor part, and the outermost periphery of the wafer is on a spacer having a lower thermal conductivity than the first and second susceptor parts. Placed on the
Heating the wafer through the first and second susceptor parts;
Rotate the wafer,
A semiconductor manufacturing method, wherein a process gas is supplied onto the wafer.

Images