JPH06260438A - Boat for heat treatment - Google Patents

Abstract

PURPOSE:To obviate the surface defects called slips produced when a circular sheetlike work e.g. a semiconductor wafer is heat-treated. CONSTITUTION:Multiple wafer supporting members comprising the same material as that of a wafer W are provided at an up and down interval on upright mutual struts 41-44 using e.g. the trench parts formed in the struts 41-44 so that the outer peripheral edge of the wafer W may be brought into surface- contact with an arc or ring type wafer supporting members 5 to support the wafer W. Furthermore, the wafer supporting members 5 are quick disconnectably provided on the struts 41-44 using e.g. a fixing shaft 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment boat used for heat treatment of a circular plate-shaped object such as a semiconductor wafer.

[0002]

2. Description of the Related Art Semiconductor wafers (hereinafter referred to as "wafers")
There is a process of performing heat treatment at a high temperature in order to form an oxide film, diffuse a dopant, and the like. As a device for performing this heat treatment, a horizontal heat treatment furnace has hitherto been the mainstream, but recently, a vertical heat treatment furnace has come to be used more often because of less entrainment of outside air.

In a vertical heat treatment apparatus using a vertical heat treatment furnace, a vertical heat treatment boat (wafer) is used for loading and unloading a large number of wafers vertically mounted on the heat treatment furnace. Also called a boat) is used. FIG. 8 shows a conventional heat treatment boat. This heat treatment boat 1 is made of, for example, quartz between a circular top plate 11 and a bottom plate 12 which are vertically opposed to each other.
Two columns 13 to 16 are provided, of which two columns 1
3 and 14 support the left and right positions of the wafer W on the front side in the approach direction, and the remaining two columns 15 and 16 support the left and right positions on the back side of the wafer W in the entrance direction. And is provided on the heat insulating cylinder 2 which is a heat insulating material.

As shown in FIG. 9, each of the columns 13 to 16 is provided with a groove 17 having a width slightly above and below the thickness of the wafer W so that each wafer W is inserted and supports the lower surface of the peripheral edge thereof. The two columns 13 and 14 on the front side
The wafer W is attached to and detached from the groove 17 by the transfer arm 21 from between.

The structure of such a boat 1 for heat treatment is a structure in which the structure used in the conventional horizontal furnace is vertically used as it is. That is, in the horizontal furnace, the transfer of the wafer is performed by a mechanism that pushes up the wafer from the lower side of the heat treatment boat and a mechanism that holds the pushed-up wafer. Therefore, the structure of the heat treatment boat was decided.

In the heat treatment boat 1 of FIG. 8, when a predetermined number of unprocessed wafers W are loaded, the elevator 22 moves up and is introduced into a heat treatment furnace (not shown), whereby the wafers W are loaded and predetermined. Heat treatment is performed.

[0007]

By the way, during the heat treatment process of the wafer, for example, after performing ion implantation on the wafer, in order to diffuse the implanted dopant (impurity ion) to a predetermined depth, about 1200 ° C. May be heated at high temperature for a long time. When the base material of the wafer is silicon, the melting point of silicon is 1410 ° C., so that the yield stress of the silicon wafer is extremely small at a temperature of 1200 ° C.

On the other hand, the diameter of wafers is increasing,
The size has started to shift from 6 inches to 8 inches, and the shift to 12 inches is also being considered. When the diameter of the wafer is increased in this way, when heat treatment is performed at a temperature close to the melting point of the base material of the wafer as described above,
Crystal defects called slips are likely to occur on the wafer in the vicinity of the portion supported by the columns of the heat treatment boat. This slip is a minute slice that is difficult to confirm visually and can be seen with a magnifying glass or a microscope.

The cause of the slip is as follows.
Internal stress due to the weight of the wafer and thermal strain stress due to non-uniformity of the in-plane temperature of the wafer have been cited as probable causes. That is, with respect to the above, since the support position by the heat treatment boat is on the peripheral portion of the wafer and there are four partial supports, a large internal stress occurs due to the weight of the wafer in the vicinity of the support position, and this internal stress It is considered that slip occurs when a certain size is exceeded. Further, the wafer also has a warp within the standard value, and also has a warp due to the temperature distribution during heating. Further, there is a manufacturing error in the processing of the groove of the column. When one of the four wafer support points is separated due to these factors, the wafer support points become three, and the load at each support point becomes unbalanced as can be seen from the arrangement of the columns 13 to 16. However, a large stress exceeding the slip generation limit is generated at one of them.

With respect to the above, when the temperature of the wafer is raised, heat flows in and out via the columns of the boat for heat treatment, so that a temperature difference occurs between the central portion and the peripheral portion of the wafer, which causes thermal strain stress. It is considered that slip occurs when the thermal strain stress exceeds a certain level.

As described above, when the wafer is heat-treated, particularly when it is heat-treated at a high temperature close to the melting point of the base material of the wafer, when the diameter of the wafer becomes large, a problem of slippage occurs, which is a major problem of the wafer. This is one of the major challenges that hinder the transition to caliber.

The present invention has been made based on the above circumstances, and an object thereof is a boat for heat treatment which can reduce the occurrence of slip when heat treating a circular plate-shaped object. To provide.

[0013]

According to a first aspect of the present invention, a large number of circular plate-shaped objects to be processed are mounted at intervals in the vertical direction to heat-treat the objects in a vertical heat treatment furnace. In the heat treatment boat used, an arc-shaped or ring-shaped support member, which is made of the same material as that of the object to be processed and is in surface contact with the lower surface of the peripheral edge of the object to support the object, is vertically spaced. It is characterized in that a large number of columns are provided.

According to a second aspect of the present invention, a large number of circular plate-shaped objects to be processed are mounted at intervals in the vertical direction and used for heat-treating the objects in a vertical heat treatment furnace. In the above, a large number of arc-shaped or ring-shaped support members that are in surface contact with the lower surface of the peripheral edge of the object to be processed and support the object to be processed are detachably provided on the column at vertical intervals.

[0015]

The outer peripheral edge of the object to be processed such as a wafer is supported in surface contact with the object to be processed support member. Therefore, the internal stress due to the weight of the object to be processed near the supporting point is relaxed as compared with the case of four-point support, and even if the object to be processed is warped, a large supporting surface does not apply a large load to one point. In addition, the non-uniformity of the temperature distribution along the outer peripheral edge of the object to be processed is alleviated. Further, since the object support member is made of the same material as the object to be processed, the temperature rise or decrease during the heat treatment is the same, the in-plane temperature difference is small, and the thermal strain stress is considerably relaxed.

Further, if the object support member is detachably attached to the column, the production is easier than that of an integrated type, and the object to be processed in various forms corresponding to each conveying method of the object. If the support member is prepared, the target object support member can be appropriately selected and used even when the transport method is changed.

[0017]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a schematic perspective view showing a part of a vertical heat treatment apparatus including a heat treatment boat according to an embodiment of the present invention, and FIGS. 2 to 4 are views showing a part of the heat treatment boat. The heat treatment boat 3 of this embodiment is used to heat-treat a wafer which is a circular plate-shaped object to be treated. Hereinafter, the heat treatment boat is referred to as a wafer boat, and the object-to-be-treated support member is referred to as a wafer support member. I will decide.

The wafer boat 3 is provided with a circular top plate 31 and a bottom plate 32, which are made of, for example, SiC, and are vertically opposed to each other, and between them, for example, four columns 41 to 44 made of SiC or polysilicon. Is fixed.
Between the top plate 31 and the bottom plate 32, for example, 150 wafer support members 5 are arranged in parallel at a predetermined interval, and these support members 5 are used when the wafer W is a silicon wafer. , Made of the same material, for example, polysilicon.

Each wafer support member 5 has an arcuate shape, for example, a notch 5a having a size large enough to allow the transfer arm 21 to be described later to enter between the columns 41 and 42, and the inner diameter of the wafer support member 5 is the outer diameter of the wafer W. It has a horseshoe shape that is smaller than each of the columns, and the outer peripheral edge of each of the columns 41 to 4 is as shown in FIG.
It is inserted into the four groove portions 45 provided in the No. 4 and held horizontally on the bottom surface of the groove portion 45 and abuts the side surface of the groove portion 45.

The columns 4 of each wafer supporting member 5
A portion located between 3 and 44 (a rear portion when the loading / unloading side of the wafer W is a front side) has a larger outer diameter than the other portions and projects outward, and a through hole 51 ( (See Figure 3)
The projecting piece portion 50 having the is formed. A fixed shaft 6 for fixing the position of the wafer supporting member 5 is inserted into the through hole 51 of each wafer supporting member 5 (however, it cannot be seen because it overlaps with the support column 41 in FIG. 1).

As shown in FIG. 2, a top plate 31 is provided on the fixed shaft 6 so as not to drop downward from the top plate 31.
While the lower part of the fixed shaft 6 penetrates the bottom plate 2 without being fixed, the fixed shaft 6 can be pulled out from the top plate 31. Is configured. The notch 5 a of each wafer support member 5 constitutes an entrance space S into which a transfer mechanism for transferring the wafer W to the wafer boat 3, for example, a transfer arm 21 enters.

Wafer boat 3 constructed as described above
1 is detachably mounted on a heat retaining tube 2 having a flange portion 20 at the bottom as shown in FIG.
Is mounted on the boat elevator 22. A vertical furnace 7 is arranged above the wafer boat 3. 7
Reference numeral 1 is a gas supply pipe for supplying a predetermined gas into a reaction tube which is not visible in the vertical furnace 7, and 72 is an exhaust pipe for exhausting the reaction tube.

Next, the operation of the above embodiment will be described. First, the wafer W before processing is introduced into the boat 3 from the notch 5a (entry space S) of the wafer support member 5 by the transfer arm 21 and positioned immediately above the wafer support member 5, and then the transfer arm 21 is placed in the wafer boat. The wafer W is transferred to the wafer supporting member 5 of the wafer boat 3 by slightly lowering it relative to the wafer supporting member 3. As a result, the peripheral portion of the wafer W is brought into surface contact with the upper surface of the wafer supporting member 5.

Such transfer of the wafers W is sequentially carried out, for example, from the upper side of the wafer boat 3, and a predetermined number of wafers, for example 150, are loaded on the wafer boat 3, and then the boat elevator 22 is raised to lift the wafers W in the vertical furnace 7. To load.
For example, when the heat treatment is performed at a temperature of about 1200 ° C., the inside of the vertical furnace 7 is heated to, for example, about 800 ° C.
Is loaded, the temperature is raised to about 1200 ° C., and a predetermined heat treatment is performed. Thereafter, the boat elevator 22 descends to unload the wafer W, and the wafer W is taken out of the wafer boat 3 by the operation reverse to the above.

According to such an embodiment, each wafer W
Is supported by surface contact with a wide surface of the wafer supporting member 5 that spreads in an arc shape, so that the internal stress applied to the wafer W is small, and even if the wafer W is warped and a part of the outer peripheral edge floats. Since the remaining portion is supported by the surface along the circumferential direction, an excessive load is not applied to one position of the wafer W as in the case of the conventional four-point support, and as a result, the occurrence of slip is reduced. You can In the case of a silicon wafer, since the melting point of silicon is 1410 ° C., the above-described structure is very effective when heat-treated at a temperature of about 1000 ° C. or higher.

Further, since the supporting surface of the wafer supporting member 5 is wide, the uneven temperature distribution along the outer peripheral edge of the wafer W can be alleviated.
Since the same material is used, the degree of temperature increase or decrease during heat treatment is the same, and the temperature difference between the peripheral portion and the central portion of the wafer W is small, and therefore the thermal strain stress is considerably relaxed. That is, the wafer W and the wafer supporting member 5 have the same absorptance and thermal conductivity with respect to radiant heat, so that the thermal strain (temperature difference) between the portion in contact with the wafer supporting member 5 and the other portions is suppressed, Therefore, the occurrence of slip due to this can be reduced.

Further, the wafer supporting member 5 has a fixed shaft 6
Since it can be attached to and detached from the columns 41 to 44 by pulling out, it is easy to manufacture. In the present invention, the wafer supporting member and the support may be integrally formed. However, in the case of integrally forming, the shape is considerably restricted, so that it is better to make them detachable as described above.

Further, the maintenance of the wafer supporting member 5 is easy. For example, when a part of the wafer supporting member 5 is damaged, the fixed shaft 6 is extracted and only the damaged wafer supporting member 5 is removed and replaced with a new one. It can be done and is very economical as compared to the case where all must be replaced. Further, as will be described later, since various types of wafer supporting members can be manufactured, the wafer supporting members can be exchanged according to the wafer transfer method.

Next, another embodiment will be described. Figure 5
Shows a wafer supporting member according to another embodiment, and in this example, the wafer supporting member 5 is constituted by two independent semicircular members 5A and 5B. Semi-circular members 5A, 5
B has its outer peripheral edge inserted into the groove portion 45 provided in the columns 41 to 44 and held horizontally by its own weight, and the through holes 51A and 51B provided in the semi-circular members 5A and 5B, respectively.
The fixed shafts 6A and 6B are inserted into and fixed in position. Between one semi-arcuate member 5A and the other semi-arcuate member 5B, an entrance space S is formed in which the transfer arm 21 which is a transfer mechanism for transferring the wafer W to the wafer boat 3 enters. is doing.

FIG. 6 shows a wafer supporting member according to still another embodiment. In this example, the wafer supporting member 5 has a ring shape. In this case, since the wafer support member 5 is not provided with the entrance space S into which the transfer arm 21 is inserted as shown in FIG. 1, the transfer method shown in FIG. 1 cannot be used as it is. Therefore, the push-up device 8 as shown in FIG. 7 is arranged below the boat stage 9.

The push-up device 8 is screwed into a fixed base 81 and has a ball screw 83 having a push-up portion 82 at the upper end.
And a pulley 86 that is screwed onto a ball screw 83 and that is rotated by the motor 84 via a belt 85. When such a push-up device 8 is used, the wafer boat 3 is placed on the boat stage 9 provided separately from the boat elevator 22, and the wafer W before processing is adjacent to the wafer support member 5 by the transfer arm 21. The wafer supporting member 5 is moved into the space between the wafers 5 and positioned immediately above the wafer supporting member 5. Then, the motor 84 is driven to rotate the ball screw 83, and
Is raised in the wafer boat 3 and the wafer W on the transfer arm 21 is pushed up from below. With the wafer W floating, the transfer arm 21 is pulled out, the motor 84 is reversely rotated to lower the push-up portion 82, and the wafer W is transferred to the wafer support member 5. As a result, the peripheral portion of the wafer W is supported in surface contact with the upper surface of the ring-shaped wafer supporting member 5. Such transfer of the wafers W is sequentially performed from the upper stage side of the wafer boat 3, for example, after mounting a predetermined number of wafers, for example, 150, on the wafer boat 3, the wafer boat 3 is transferred to the boat elevator 22, and the wafer boat 3 is raised to raise the wafers. W
Is loaded into the vertical furnace 7 and a predetermined heat treatment is performed. After that, the boat elevator 22 is lowered to unload the wafer W, and the wafer W is taken out from the wafer boat 3 by the reverse operation to the above.

Even if the wafer transfer methods are different as described above, the wafer supporting member 5 is detachably attached to the columns 41 to 44, so that it includes the top plate 31, the bottom plate 32, and the columns 41 to 44. By using the wafer boat main body as it is and exchanging only the wafer supporting member 5 as appropriate, it is possible to easily adapt to various transfer systems, and a universal wafer boat can be obtained.

In the above embodiments, the wafer support member is made of the same material as the wafer, and the wafer support member is detachably attached to the plurality of columns to form the wafer boat. However, the present invention is not limited to this. According to the present invention, the wafer support member is made of the same material as the wafer, and the wafer support member is fixedly provided on the support, and the wafer support member is made of a material different from that of the wafer. A configuration in which it is detachably attached to the column may be adopted.

[0034]

According to the first aspect of the present invention, the outer peripheral edge of the object to be processed is supported by the arcuate or ring-shaped object supporting member in surface contact, so that the internal stress of the object to be processed is relaxed. In addition, since the object support member is made of the same material as the object to be processed, the thermal strain stress is relieved considerably, and as a result, the occurrence of slip of the object can be reduced.

According to the invention of claim 2, the internal stress of the object to be processed is relieved, and the occurrence of slip of the object to be processed can be reduced. Furthermore, since the object support member can be attached to and detached from the column, it is easy to manufacture, and even if a part of the object support member is damaged, it can be easily replaced, and in addition to various transfer systems. Correspondingly, it is possible to obtain an effect that the object support member can be easily replaced.

[Brief description of drawings]

FIG. 1 is a perspective view showing an overall outline of an embodiment of the present invention.

FIG. 2 is a perspective view showing a heat treatment boat according to an embodiment of the present invention.

FIG. 3 is a plan view showing a wafer supporting member according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a part of a heat treatment boat.

FIG. 5 is a plan view showing a wafer supporting member according to another embodiment of the present invention.

FIG. 6 is a plan view showing a wafer supporting member according to still another embodiment of the present invention.

FIG. 7 is an explanatory view showing a wafer transfer system using the wafer support member of FIG.

FIG. 8 is a perspective view showing an overview of a conventional heat treatment boat.

FIG. 9 is a cross-sectional view showing a part of a conventional boat for heat treatment.

[Explanation of symbols]

 W Wafer (Processing Object) 21 Transfer Arm 3 Wafer Boat 41 to 44 Support 45 Groove 5, 5A, 5B Wafer Supporting Member (Processing Object Supporting Member) 6 Fixed Shaft

Claims (2)

[Claims] 1. A heat treatment boat in which a large number of circular plate-shaped objects to be processed are mounted at intervals in the vertical direction and used for heat-treating the objects in a vertical heat treatment furnace. A plurality of arc-shaped or ring-shaped support members, which are made of the same material and are in surface contact with the lower surface of the peripheral edge of the target object to support the target object, are provided on the column at intervals vertically. A boat for heat treatment. 2. A heat treatment boat for mounting a large number of circular plate-shaped objects to be processed vertically in a vertical heat treatment furnace, wherein A boat for heat treatment, characterized in that a large number of arc-shaped or ring-shaped supporting members, which are in surface contact with the lower surface of the peripheral portion and support the object to be processed, are removably provided on the support columns at intervals vertically.