JP2003197545A - Wafer boat and furnace and method for heat-treating wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer boat that prevents the slip of semiconductor wafers by reducing the contact stresses or deflections caused by the own weights of the wafers. <P>SOLUTION: Prescribed heat treatment is performed on the semiconductor wafers W in a state where the wafers W are caused to generate Lorentz forces in the direction opposite to the gravitational force, by generating a magnetic field around the wafer boat 13 from the outside of a furnace core pipe 2 and making an electric current to flow to an electrode portion 24. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer boat used when heat-treating a semiconductor wafer, a wafer heat treatment furnace using the wafer boat, and a wafer heat treatment method.

[0002]

2. Description of the Related Art In a process for manufacturing a semiconductor wafer (hereinafter referred to as a wafer), a silicon single crystal is gradually pulled up from a heating furnace by a CZ (Czochralski) method or the like, as shown in a general flow chart of FIG. A single crystal is grown (S1), the pulled silicon ingot is cut into blocks, and the blocks are sliced (S).
2). The surface of the cut wafer is lapped, and then mirror-finished to form a mirror surface (S
3). After polishing, cleaning is performed (S4), and in order to secure a perfect crystal layer on the wafer surface, heat treatment is performed in a high temperature (1000 ° C. or higher) atmosphere using a wafer heat treatment furnace (S5). After that, final cleaning is performed (S6), and the wafer is completed (S7).

Wafer heat treatment in a wafer heat treatment furnace is to make the wafer suitable for forming semiconductor elements. Usually, the wafer heat treatment is carried out with a plurality of wafers placed on a wafer boat. It is carried out in a batch method.

However, due to the recent increase in the diameter of wafers,
Due to the increase in the weight of the wafer, there are problems such as slips which are considered to be caused by an increase in contact stress with the wafer holding portion.

[0005] Slip is a crystal defect caused by a phenomenon in which a slip occurs along a slip surface when thermal stress or contact stress exceeds a critical value, and is a minute fault that is difficult to visually confirm, such as a magnifying glass or a microscope. Can be seen by.

Further, the slip is apt to occur due to scratches and the like, and is often generated from the peripheral portion of the wafer to which stress is applied. The slip generated in the peripheral portion of the wafer is an intra-crystal slip that slips in an attempt to mitigate the internal strain generated inside the wafer, and a transition occurs at the slip generation site. There are various causes for the occurrence of the wafer slip, and one of the causes is considered to be bending due to the weight of the wafer. Therefore, as a method of supporting the wafer, the contact stress and the bending are reduced by optimizing the number of supporting tools, the supporting position, and the like.

[0007]

However, with respect to the increase in the weight of the wafer due to the increase in the diameter of the wafer as described above, the number of supporting members, the supporting position, etc. are optimized as the method of supporting the wafer in the wafer boat. However, it is difficult to reduce the bending due to the weight of the wafer because a simple method has not been developed at present. As a result, it is not possible to prevent the occurrence of slip on the wafer, and it is not possible to form a desired semiconductor device at the slip occurrence portion of the wafer, so that the manufacturing yield of the semiconductor device is extremely low.

The present invention has been made in view of these circumstances, and a wafer boat in which contact stress and bending due to the weight of the wafer are reduced to prevent the occurrence of slip, a wafer heat treatment furnace using the same, and a wafer heat treatment. It is intended to provide a way.

[0009]

According to the means of the present invention, the upper plate and the lower plate facing each other are fixed by a plurality of columns, and the semiconductor wafers are separated one by one through the columns. In the wafer boat to be loaded as a wafer, the upper plate and the lower plate are formed of an insulating member, and the support columns are formed of a conductive member.

According to the second aspect of the invention,
The pillar is a wafer boat characterized by being made of Si.

According to the means of the invention of claim 3,
The electrode on which the semiconductor wafer is mounted has a width A in the direction orthogonal to the direction of the current flow and a diameter Lw of the semiconductor wafer in order to allow a current to flow uniformly to the mounted semiconductor wafer. Then, the wafer boat has a relationship of 0.1 Lw <A <1.0 Lw.

According to the means of the invention of claim 4,
A wafer heat treatment furnace in which the entire structure of heating a semiconductor wafer mounted on a wafer boat installed on a heat-retaining cylinder erected on the hearth tube in a furnace core tube by a heater is covered by the wafer boat. The wafer mounting portion is formed of a positive electrode and a negative electrode, and a magnetic field applying means is provided at a position facing the wafer boat housed in the casing while being separated from the outside of the casing. Is a wafer heat treatment furnace.

According to the means of the invention of claim 5,
The magnetic field applying means is a wafer heat treatment furnace in which a surface facing the casing is formed by a curved surface corresponding to the curved surface of the casing.

According to the means of the invention of claim 6,
The heat insulation cylinder is a wafer heat treatment furnace characterized in that a plurality of heat insulating spacers are provided by a member capable of adjusting an interval between the spacers.

According to the means of the invention of claim 7,
In a wafer heat treatment method of subjecting each semiconductor wafer placed separately to the electrode portion of the wafer boat in the core tube to a predetermined heat treatment, a magnetic field is generated from the outside of the core tube around the wafer boat, and, A wafer heat treatment method is characterized in that a predetermined heat treatment is applied to the semiconductor wafer in a state in which a Lorentz force opposite to gravity is generated by applying a current to the electrode portion.

According to the means of the invention of claim 8,
When a plurality of current flow vectors are generated in the electrode portion of the wafer boat, the magnitudes of the respective vectors are equal and are plane-symmetric with respect to a plane perpendicular to the magnetic field direction. This is a heat treatment method.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of a vertical wafer heat treatment furnace of the present invention.

The vertical wafer heat treatment furnace 1 is made of quartz glass.
A cylindrical furnace core tube 2 made of a material such as SiC or carbon and having a closed upper part is provided, and a lower side wall of the furnace core tube 2 has a predetermined size for performing a heat treatment on a wafer W as an object to be processed. A gas introduction tube 3 for introducing the heat treatment gas G from above from inside the furnace core tube 2 is arranged. Also the furnace core tube 2
Gas discharge ports 4 for discharging the heat treatment gas G introduced from the gas introduction pipe 3 to the outside of the furnace core tube 2 are arranged on the lower side walls facing each other.

Inside the furnace core tube 2, a lower heat retaining cylinder 11, an upper heat retaining cylinder 12, and a wafer board 13 are sequentially arranged in a stacked state on a stainless steel hearth 5. In the hearth floor 5, two positive electrodes 7 and two negative electrodes 8 made of Si are provided at positions corresponding to columns 9a (details will be described later) shown in FIG. The arrangement of the electrodes is, for example, a positional relationship of the vertices of an isosceles trapezoid. The position of the vertices on the long side is + electrode 7, and the position of the vertices on the short side is − electrode 8.

The lower heat retaining cylinder 11 is provided with four columns which are erected and electrically connected to the positions of the apexes of the trapezoid of the isosceles trapezoid of the hearth 5 on which the + electrode 7 and the − electrode 8 are arranged. 9a
The four holes formed in the quartz glass plate 17a via the spacers 18 (made of quartz glass) are pierced in a skewered manner, and the quartz glass plates 17a are laminated.

The upper heat retaining cylinder 12 is provided at a position corresponding to the support 9a of the lower heat retaining cylinder 11, and a spacer 19 (made of quartz glass or Si) is attached to the support 9b electrically connected to the support 9a. The four holes formed in the quartz glass plate 17a are pierced in a skewered manner, and the quartz glass plates 17b are laminated and formed.

The heat insulating cylinder is for preventing heat from escaping downward when the wafer W stored in the wafer board 13 is heat-treated. The upper heat retaining cylinder 1 is provided separately from the lower heat retaining cylinder 11 and the upper heat retaining cylinder 12.
2 is exposed to high temperature and changes with time
This is due to the ease of replacement at that time and the economics of partial replacement.

Further, the lower heat retaining cylinder 11 and the upper heat retaining cylinder 12
Is the spacer 1 when it is desired to change the distance between the quartz glass plates 17a (or the quartz glass plates 17b) to improve the thermal environment.
The thickness of 8 (or spacer 19) may be changed.

Further, as shown in FIG. 1, a heater 21 is provided outside the core tube 2 at a position facing the wafer boat 13, and the outside of the core tube 2 and the heater 21 is covered by a casing 22. ing.

Wafer boat 13 outside casing 22
An electromagnet 23 using a coil for applying a magnetic field to the wafer W placed on the wafer boat 13 is arranged at a position facing to.

The wafer heat treatment furnace 1 has these configurations.
When heat-treating the wafer W, a voltage is applied to the electromagnet 23 to generate a magnetic flux density of 0.1 T inside the core tube 2. This causes a current of 6.1 A to flow through the wafer W loaded on the wafer boat 13 in the core tube 2.

As shown in the plan view of FIG. 3, the pillars 14 of the wafer boat 13 have, as described above, two adjacent poles of the four pillars 14 as a positive pole and the other two poles as a negative pole. Therefore, such an arrangement of the pillars (electrodes) 14 forms an electric field that is substantially orthogonal to the applied magnetic field.

As a result, as shown in FIG.
In addition, a Lorentz force of 0.61 N can be generated in the direction opposite to gravity. The Lorentz force is represented by F = I × B (F: Lorentz force, I: current, B: magnetic flux density) according to Fleming's left-hand rule.

For example, when the weight of the wafer W is 125 g, a force of 1.225 N is applied downward due to gravity, but the wafer W has a force of 0.
By generating a Lorentz force of 61N, 50% of the weight of the wafer W is canceled. This makes it possible to significantly reduce the contact stress generated in the contact portion of the wafer with the wafer boat due to the effect of its own weight, and suppress the occurrence of slip.

Further, in order to obtain a uniform and more parallel magnetic flux density, a plurality of electromagnets 23 using a ferroelectric material having a shape shown in FIG. 4 as a core material are used to process a plurality of wafers W. Also in this case, the magnetic field can be uniformly applied to each wafer W.

If three or more silicon pillars 14 are used for the wafer boat 13, a plurality of current flow vectors may occur. In that case, it is desirable that the respective vectors have the same magnitude and are plane-symmetric with respect to a plane perpendicular to the magnetic field direction.

Further, as shown in the perspective view of FIG. 5, the electrode portion 2 which is a portion of the wafer boat 13 on which the wafers W are loaded.
4, the width A of the electrode portion 24 in which a current can be uniformly applied to the wafer W by widening the width A of the electrode portion 24 is A = when the diameter of the wafer W to be processed is Lw. Lw is desirable, but 0.1 Lw <A <
In the range of 1.0 Lw, it is preferable to make the range of the width A of the electrode portion 24 as large as possible.

Further, according to the above-described embodiment, in order to realize the wafer boat 13 having the function of energizing the wafer W, the upper and lower heat insulating cylinders 11 at the bottom of the wafer boat 13,
Only the columns 9 of 12 are made of silicon, and the upper and lower heat insulating cylinders 11 and 1
A holding ring 18 made of quartz glass is inserted between two spacers 17 of the quartz glass plate. Further, the portions of the hearth 5 (usually made of stainless steel) that come into contact with the columns 9 of the lower heat insulating cylinder 11 are formed on the electrodes 7 and 8 made of silicon. With such a structure, it is possible to energize the column 9 of the lower heat insulating cylinder 11 that is in contact with the electrodes 7 and 8 of the hearth 5 and the column 14 of the wafer boat 13 that is in contact with the column 9.

As described above, according to the above-described embodiment, the Lorentz force is generated on the wafer placed on the wafer boat to reduce the apparent weight of the wafer and reduce the wafer-to-wafer relationship. It has become possible to reduce the contact stress at the contact portion of the boat and suppress the occurrence of slips that may occur on the wafer.

Further, since the thermal stress is allowed to some extent due to the reduction of the contact stress with the contact portion of the wafer, the temperature rise / fall of the wafer can be further speeded up, and the processing time can be shortened. Thereby, productivity can be improved.

[0037]

According to the present invention, it is possible to realize a wafer boat capable of suppressing the occurrence of slip during heat treatment and efficiently manufacturing wafers with few defects.

Further, a wafer heat treatment furnace and a wafer heat treatment method having excellent productivity using the wafer boat can be realized.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a wafer heat treatment furnace of the present invention.

FIG. 2 is a perspective view of the wafer boat and the heat insulating cylinder of the present invention.

FIG. 3 is a plan view of the wafer boat of the present invention.

FIG. 4 is an explanatory diagram of Lorentz force generation.

FIG. 5 is a plan view of a wafer loading portion.

FIG. 6 is a flow chart of an outline manufacturing process of a semiconductor wafer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer heat treatment furnace, 2 ... Reactor tube, 5 ... Hearth floor, 7 ... + electrode, 8 ...- Electrode, 9a, 9b ...
Lower heat retaining cylinder, 12 ... Upper heat retaining cylinder, 13 ... Wafer boat,
14 ... Prop (wafer boat), 15 ... Upper plate, 16 ... Lower plate, 17 ... Quartz glass plate, 18, 19 ... Spacer, 23
… Electromagnet, 24… Wafer loading area

Continued front page    (72) Inventor Junichi Koyamauchi             378 Oguni Town, Oguni Town, Nishiokitama District, Yamagata Prefecture               Toshiba Ceramics Co., Ltd. Oguni Office F-term (reference) 5F045 BB13 DP19 EM08 EM09

Claims (8)

[Claims] 1. A wafer boat in which an upper plate and a lower plate facing each other are fixed by a plurality of columns, and semiconductor wafers are separated and loaded one by one through the columns, wherein the upper plate and the lower plate are A wafer boat, wherein the wafer boat is formed of an insulating member, and the pillar is formed of a conductive member. 2. The wafer boat according to claim 1, wherein the pillar is made of Si. 3. The electrode on which the semiconductor wafer is mounted has a width A in a direction orthogonal to the direction in which the current flows in order to allow a current to flow uniformly to the mounted semiconductor wafer,
The wafer boat according to claim 1, wherein the relationship is 0.1 Lw <A <1.0 Lw, where Lw is the diameter of the semiconductor wafer. 4. A wafer heat treatment furnace in which a casing entirely covers a structure for heating semiconductor wafers mounted on a wafer boat installed on a heat-retaining cylinder erected on a hearth inside a core tube by a heater. In the above, the wafer mounting portion of the wafer boat is formed of a positive electrode and a negative electrode, and a magnetic field applying means is provided at a position facing the wafer boat housed in the casing while being separated from the outside of the casing. A wafer heat treatment furnace characterized by being provided. 5. The wafer heat treatment furnace according to claim 4, wherein a surface of the magnetic field applying unit facing the casing is formed by a curved surface corresponding to the curved surface of the casing. 6. The wafer heat treatment furnace according to claim 4, wherein the heat insulating cylinder is provided with a plurality of heat insulating spacers by a member capable of adjusting a distance between the spacers. 7. A wafer heat treatment method in which a predetermined heat treatment is applied to each semiconductor wafer separately placed on the electrode portion of the wafer boat in the core tube, wherein a magnetic field is applied from the outside of the core tube to the periphery of the wafer boat. A wafer heat treatment method, wherein a predetermined heat treatment is performed in a state in which a Lorentz force in the direction opposite to gravity is generated in the semiconductor wafer by causing a current to flow through the electrode portion. 8. When a plurality of current flow vectors are generated in the electrode portion of the wafer boat, the respective vectors have the same magnitude and are plane-symmetric with respect to a plane perpendicular to the magnetic field direction. The wafer heat treatment method according to claim 7.