JP2007201058A - Boat for silicon wafer heat treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boat for a silicon wafer heat treatment capable of suppressing slip transition, with no application of a susceptor or an annular support. <P>SOLUTION: The boat 1 for a silicon wafer heat treatment comprises a plurality of posts 4 equipped with a plurality of silicon wafer supports 6 for loading silicon wafers parallel with constant intervals. A quartz tool 7 is placed on the silicon wafer supports 6. Thus, slip transition is suppressed which is caused by the in-plane temperature difference of a wafer due to welding between the wafer and the support as well as thermal conduction from the wafer to the boat. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a silicon wafer heat treatment boat used when heat treating a silicon wafer at a high temperature.

In recent years, vertical furnaces are frequently used in heat treatment in semiconductor manufacturing processes in place of conventional horizontal furnaces. In the vertical furnace, silicon wafers (hereinafter also referred to as wafers unless otherwise specified) are loaded and processed on a heat treatment boat (hereinafter also simply referred to as a boat) horizontally, in parallel and at equal intervals by a wafer support unit. For this reason, compared with a horizontal furnace, there exists the characteristic that the contact area of a boat and a wafer back surface becomes large.
A boat material used at this time is generally made of silicon, silicon carbide, or quartz having high purity and high heat resistance (see, for example, Patent Documents 1 to 3). Among them, silicon or silicon carbide having particularly excellent heat resistance is frequently used.

  FIG. 4 is a view showing a conventional boat for heat treatment of silicon wafers. FIG. 4A is a schematic view of a three-point support type silicon wafer heat treatment boat 1. An upper plate 2 having a ring shape and a lower plate 3 having the same shape are provided, and three support columns 4 are disposed and fixed between the upper and lower plates 2 and 3. FIG. 4B is an enlarged view of a part of the support column 4. A plurality of wafer support portions 6 for supporting the wafers horizontally and at equal intervals are formed on each of the columns 4 at a predetermined interval along the axial direction of the columns 4.

  Thus, when the boat is made of silicon or silicon carbide having excellent heat resistance, there is a problem that welding is likely to occur at the contact portion between the wafer and the support portion. When the wafer is chucked by the stepper in the lithography process, the wafer back surface protrusion generated by the welding interferes with the chuck stage and locally deteriorates the flatness. As a result, defocusing occurs, causing a defective device.

  By the way, when a wafer is loaded on a silicon wafer heat treatment boat and subjected to high temperature heat treatment, slip dislocation may occur in the wafer. Slip dislocation is likely to occur mainly from the wafer support portion of the boat where the self-weight stress of the wafer is concentrated. Therefore, recently, attempts have been made to alleviate the self-weight stress by holding the wafer in a wide range via a susceptor or a ring-shaped support, and to suppress the occurrence of slip dislocation (for example, Patent Documents). 1 and 2).

Further, another cause of occurrence of slip dislocation is a temperature difference generated in the wafer surface. In particular, in the case of a boat using a susceptor or a ring-shaped support portion, since the contact surface with the wafer is wide, the temperature difference in the wafer surface is likely to increase due to heat dissipation by heat conduction from the contact portion. In view of this, Patent Document 4 discloses a method in which the holding area is extremely reduced by inclining the susceptor in order to make the in-plane temperature distribution uniform during heat treatment.
However, this method increases stress concentration and is difficult to apply to a large-diameter wafer having a diameter of 200 mm or more.
JP-A-6-163440 JP 2003-173982 A Japanese Unexamined Patent Publication No. Sho 63-315596 Japanese Utility Model Publication No. 05-29129

  In the prior art in which a susceptor made of silicon or silicon carbide or a ring-shaped support portion is used to prevent slip dislocation generated by high-temperature heat treatment, in the initial state, the wafer is held in a wide range to reduce its own weight stress, The effect of suppressing the occurrence of slip dislocation can be obtained. However, as the heat treatment batch progresses, plastic deformation of the susceptor and the ring-shaped support itself occurs, making it impossible to support the wafer ideally, resulting in inconvenience that slip dislocation occurs where stress is concentrated. In addition, since the support portion becomes large, there is a problem that it costs more for manufacture or replacement as compared with a point support type boat.

  On the back surface of the wafer, when a susceptor or a ring-shaped support portion is used, the contact area with the wafer becomes large, so that the above-described welding problem is likely to occur. When welding occurs, in addition to the above-described defocus problem, there is also a problem that slip dislocation occurs starting from the welding mark.

  Furthermore, in the case of a support portion using silicon or silicon carbide, since the thermal conductivity of silicon or silicon carbide is high, a temperature difference in the wafer surface is likely to occur, and as described above, in particular, a susceptor or ring-shaped support is provided. When the portion is used, the problem becomes significant because the contact area with the wafer is large.

  The present invention has been made to solve the above problems, and an object thereof is to provide a silicon wafer heat treatment boat that can suppress the occurrence of welding and slip dislocation without using a susceptor or a ring-shaped support. To do.

  A silicon wafer heat treatment boat according to one aspect of the present invention is a silicon wafer heat treatment boat including a plurality of support columns having a plurality of silicon wafer support portions for loading silicon wafers in parallel and at equal intervals. A quartz jig is placed on the silicon wafer support.

  By applying the silicon wafer heat treatment boat of the present invention, it is possible to provide a silicon wafer heat treatment boat that can suppress the occurrence of welding and slip dislocation without using a susceptor or a ring-shaped support portion.

(Embodiment)
Embodiments of a silicon wafer heat treatment boat according to the present invention will be described below with reference to the drawings.

(Constitution)
FIG. 1 is a diagram illustrating a silicon wafer heat treatment boat according to an embodiment of the present invention.
FIG. 1A is a view showing the appearance of a silicon wafer heat treatment boat for a three-point support type φ200 mm wafer made of silicon according to an embodiment of the present invention.
In FIG. 1 (a), a silicon wafer heat treatment boat 1 includes a ring-shaped upper plate 2, a ring-shaped lower plate 3, and three columns 4 made of silicon disposed between the upper and lower plates. And more fixed. Each support column 4 is provided with a plurality of support portions 6 for loading silicon wafers in parallel and at equal intervals. In addition, the plurality of support portions 6 formed on the pillars 4 of the silicon wafer heat treatment boat are formed to place the silicon wafers. Accordingly, the upper portion of the support portion 6 is connected to the silicon wafer holding surface 10. Is done.

  FIG. 1B is an enlarged perspective view of a portion of a boat column 4 in which a quartz jig 7 having a thickness of 1 mm is mediated by a wafer holding surface 10 according to an embodiment of the present invention. As shown in the figure, in the silicon wafer holding surface 10 of the silicon wafer heat treatment boat 1, a quartz jig 7 having a square outer shape with a thickness of, for example, 1 mm is mounted on the plurality of support portions 6 of the support column 2. Is placed. The quartz jig 7 is provided with a convex portion 8, and the quartz jig 7 is fixed and placed on the support portion 6 by fitting the convex portion 8 into the concave portion 9 provided on the support portion 6 of the boat. Yes.

(effect)
First, the quartz jig 7 made of a material different from that of the wafer is interposed between the wafer and the support portion 6, so that it is difficult to cause welding with the back surface of the wafer, and generation of protrusions on the back surface can be suppressed. Therefore, the slip dislocation caused by the back surface protrusion hardly occurs. In addition, it is possible to suppress device defects associated with defocusing caused by back surface protrusions.

Further, by interposing a quartz jig 7 made of quartz having a thermal conductivity lower than that of silicon, thermal conduction from the back surface of the wafer to the boat is suppressed, and a difference in temperature within the wafer surface is less likely to occur. Can be relaxed. Therefore, slip dislocation caused by thermal stress can also be suppressed.

  And in this Embodiment, the contact area of a wafer and the support part 6 is remarkably small compared with a susceptor or a ring-shaped support part. Therefore, the occurrence frequency of the back surface protrusions is remarkably suppressed, and the temperature difference in the wafer surface due to heat conduction is also suppressed. Therefore, it is possible to further suppress device failure and slip dislocation associated with defocusing.

  In addition, since the area of the support part is smaller than when using a susceptor or a ring-like support part, as the heat treatment batch proceeds, the support part itself undergoes plastic deformation, stress concentration occurs, and slip dislocation occurs. The fear is small. Certainly, quartz deforms faster than silicon in a high temperature region of 1000 ° C. or higher. However, even if the quartz jig 7 is deformed, only the deformed quartz jig 7 can be exchanged, so that there is an advantage that the replacement cost can be reduced.

  In the present embodiment, the thickness of the quartz jig 7 is 1 mm, but the thickness of the quartz jig 7 is preferably in the range of 1.0 to 1.5 mm. This is because if the thickness is 1 mm or less, the effect of suppressing heat conduction from the back surface of the wafer to the boat is reduced because it is too thin. Further, quartz has a specific heat larger than that of silicon, and if the thickness is 1.5 mm or more, the quartz jig 7 itself is deprived of heat and has an adverse effect.

  Further, it is desirable that the quartz of the quartz jig 7 is in an opaque state containing bubbles. This is because opaque quartz containing bubbles has lower thermal conductivity than transparent quartz. Therefore, the effect of suppressing slip dislocation increases.

And the material of a boat does not necessarily need to be silicon, For example, you may be another material excellent in heat resistance, such as silicon carbide.
In the present embodiment, the silicon wafer heat treatment boat having three support columns 4 has been described. However, the present invention is not limited to this, and any number of support columns may be used. Moreover, the support | pillar 4 can also be arrange | positioned in the position where workability | operativity is good at the time of wafer loading to the boat for silicon wafer heat processing.

The shape of the quartz jig 7 is shown by taking a rectangular outer shape as an example in accordance with the wafer holding surface 10, but is not limited thereto, and may be a circular shape, an elliptical shape, a triangular shape, a polygonal shape, or other shapes. It doesn't matter. Further, the method of placing the quartz jig 7 on the support portion 6 is not necessarily the method of fitting the convex portion 8 into the concave portion 9, for example, fitting the entire quartz jig 7 into the concave portion provided in the support portion 6. Any method may be used as long as the quartz jig 7 is fixed to the support 6 during the heat treatment.
There is no particular limitation on the shape of the wafer support 6.

  In this embodiment, a silicon wafer heat treatment boat for φ200 mm wafers is described, but the present invention can also be applied to a silicon wafer heat treatment boat for φ200 mm or more wafers.

  The above-described embodiment is merely an example, and the present invention is not limited to the above-described embodiment, and any modifications and changes by those skilled in the art based on the above-described embodiment will be described. It goes without saying that it is included in the category.

Sample preparation:
(Example)
In this example, a three-point support type φ200 mm silicon wafer heat treatment boat made of silicon of the present invention shown in FIG. 1 (hereinafter, the present invention boat) was used. A quartz jig 7 having a thickness of 1 mm was placed on the wafer holding surface 10 of the support 6.
In this boat of the present invention, 100 silicon wafers having an oxygen concentration of 1.2E18 atoms / cm ³ were loaded, and heat treatment was performed at 1200 ° C. for 1 hour in an Ar gas atmosphere in a vertical furnace.
(Comparative example)
In this comparative example, a three-point support type φ200 mm silicon wafer heat treatment boat (hereinafter referred to as a conventional boat) made of silicon as shown in FIG. 4 was used. The quartz jig 7 was not placed on the wafer holding surface 10 of the support 6.
This conventional boat was loaded with 100 silicon wafers having an oxygen concentration of 1.2E18 atoms / cm ³ and heat-treated at 1200 ° C. for 1 hour in an Ar gas atmosphere in a vertical furnace.

Slip length, back projection height evaluation and evaluation results:
Among the silicon wafers prepared in the above-mentioned Examples and Comparative Examples, the slip length and the height of the back protrusion were evaluated for 10 silicon wafers loaded on the middle portion of the boat in each of the Examples and Comparative Examples.

Regarding the slip length, “Rigaku X-ray topography” was used as a measuring device.
FIG. 2 is a diagram showing the slip length of the wafer after the heat treatment, and shows a comparison between when the conventional boat is used and when the boat of the present invention is used. In this figure, the vertical axis indicates the slip length (mm) as the sum of slip dislocation lengths (mm) existing in one wafer.

As shown in FIG. 2, when 10 samples of the in-furnace Middle portion processed by a conventional boat were measured, the total slip length per wafer was 21 to 38 mm.
On the other hand, the slip length of the wafer processed with the boat of the present invention was very small at the maximum of 15 mm, and the superiority of the example over the comparative example was confirmed. That is, the slip dislocation suppressing effect of the boat of the present invention was clarified.

Next, as for the height of the back surface protrusion, the height of the back surface protrusion that was revealed on the back surface of the wafer by contact with the boat for silicon wafer heat treatment was measured by the “KLA-Tencor fine shape measuring device P-15”. did.
FIG. 3 is a diagram showing the height of the wafer rear surface protrusion after the heat treatment, and shows a comparison between when the conventional boat is used and when the boat of the present invention is used. In this figure, the vertical axis indicates the maximum value of the height (μm) of the back projection measured for one wafer as the back projection height (μm).

  As shown in FIG. 3, when 10 samples of the in-furnace Middle portion processed in the conventional boat were measured, protrusions having a height of 5 to 15 μm were confirmed on the wafer processed in the conventional boat. On the other hand, the protrusion height of the wafer processed by the boat of the present invention was very small, 1 to 3 μm, and the superiority of the example over the comparative example was confirmed. That is, the wafer back surface protrusion suppression effect of the boat of the present invention was clarified.

It is a figure which shows the boat for a silicon wafer heat processing of embodiment of this invention. FIG. 2 is a diagram showing the slip length of the wafer after the heat treatment. FIG. 3 is a view showing the height of the wafer rear surface protrusion after the heat treatment. It is a figure which shows the boat for silicon wafer heat processing of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon wafer heat treatment boat 2 Upper plate 3 Lower plate 4 Support column 6 Support portion 7 Quartz jig 8 Protrusion portion 9 Recess portion 10 Wafer holding surface

Claims (4)

  A silicon wafer heat treatment boat having a plurality of pillars having a plurality of silicon wafer support portions for loading silicon wafers in parallel and at equal intervals, wherein a quartz jig is placed on the silicon wafer support portions A boat for heat treatment of silicon wafers.   The silicon wafer heat treatment boat according to claim 1, wherein the boat is made of silicon or silicon carbide.   The silicon wafer heat treatment boat according to claim 1 or 2, wherein the thickness of the quartz jig is 1.0 to 1.5 mm. 4. The boat for heat treating a silicon wafer according to claim 1, wherein the quartz forming the quartz jig is in an opaque state containing bubbles. 5.

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