JP3503710B2 - Mounting jig for heat treatment of semiconductor wafer and heat treatment apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment mounting jig for mounting a semiconductor wafer when heat treating the semiconductor wafer, and a heat treatment apparatus using the heat treatment mounting jig. Is.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor wafer (hereinafter referred to as "wafer") on which a semiconductor device such as LSI is formed, its surface is formed with an oxide film or diffuses a dopant. BACKGROUND ART A process of subjecting a target wafer to a heat treatment at a high temperature is carried out, and a vertical heat treatment furnace with little entrainment of outside air is often used for such a heat treatment in recent years.

This vertical heat treatment furnace generally has a structure in which a reaction tube is provided in a vertically arranged tubular furnace for heating. A wafer to be processed is a wafer boat for heat treatment. A predetermined number (for example, 100) of the wafers are mounted horizontally on a so-called mounting jig at intervals vertically, and the wafer boat is inserted into the reaction tube and subjected to a predetermined heat treatment.

A conventional wafer boat of this type is shown in FIG.
It has the structure shown in FIG. In the wafer boat 101 shown in the figure, four columns 104, 105, 106, 107 made of, for example, quartz are provided between a circular top plate 102 and a bottom plate 103, which are vertically opposed to each other. Each of these columns is arranged so as to be located at each apex of the trapezoid when viewed from above. Then, as shown in FIG. 13, a groove portion 108 having a groove width slightly larger than the thickness of the wafer W is inserted into each of the columns so that the wafer W, which is an object to be processed, is inserted and supports the peripheral edge portion. The wafer W is formed at predetermined equal intervals.
Is the two columns 10 on the front side by the transfer arm 109.
The four columns 104, 105, 1 from between 4, 107
The wafer W to be mounted is placed and supported on the supporting portion 110 in the groove portion 108, as shown in FIG.

When a predetermined number (for example, 100) of wafers W are loaded on the wafer boat 101 in this way, the elevating mechanism 111 moves up and is delivered into the reaction tube.
As a result, the wafer W is loaded and heat treatment is performed in a temperature atmosphere of a predetermined temperature, for example, 1200 ° C.

[0006]

However, wafers today tend to have larger diameters, and their sizes are from 6 inches to 8 inches.
Inches and even 12 inches are being considered. When the diameter of the wafer is increased, the heat treatment is performed at a temperature close to the melting point (1410 ° C.) of silicon as described above, and the support portion 110 of the groove portion 108 of the pillars 104, 105, 106 and 107 supports the wafer. A surface defect called a slip may occur on the wafer W in the vicinity of the formed portion.

This slip is a minute slice that can be confirmed by a magnifying glass or a microscope. However, if such a slip occurs on the wafer, the yield may be reduced. Therefore, it is necessary to prevent the slip from occurring by some means.

Therefore, as a result of detailed examination of the cause of such slip, the inventors have found that the conventional problem
It was found that the surface shape and hardness of the holding portion 110 contributed to the occurrence of slip.

That is, the surface of the conventional supporting portion 110 has a CV
Although it is covered with the SiC film formed by the D coat, when it is enlarged, it can be seen that there are actually unevenness having a step difference of about 2 μm. On the other hand, the wafer is, for example, Si
In this case, the hardness of SiC is higher than that of Si, and since the surface of this SiC film has the unevenness, when the wafer is supported by the supporting portion, the SiC
It is conceivable that the convex portion on the film surface pierces the back surface of the wafer to form a minute flaw, which lowers the yield point in the vicinity of the punctured portion, and as a result, the shear stress causes the slip to occur in the vicinity of the punctured portion. Therefore, it is considered that the slip can be further prevented by improving the shape and hardness of the supporting portion itself.

[0010] The present invention has been made in view of the above, the shape of the actual support portion itself, with a hardness reviewing
And, it is an its object to prevent generation of the slip.

[0011]

[Means for Solving the Problems ]
Because, according to the present invention, used in the heat treatment of semiconductor wafers, and supports the lower surface of the semiconductor wafer at the support portion in the as configured for heat treatment installation jigs mounting the semiconductor wafer, said support part Formed against three columns
It was created by a groove that
One is a column with a rectangular cross section, and the other two are cylindrical.
It is a columnar body in which the
The inner peripheral surface side of the two columns is the center of the semiconductor wafer to be mounted.
Slightly more so that the cross section faces the side of the rectangular pillar
Provided is a mounting jig for heat treatment of a semiconductor wafer , which is arranged . On the upper surface of the support part,
Supporting a material having a hardness equal to or lower than the hardness of the semiconductor wafer
A member is provided, and the semiconductor wafer is supported by this supporting member.
It may be configured to support.

[0012]

[0013]

[0014]

[0015]

[0016]

Regarding the support member in the heat treatment mounting jig for each semiconductor wafer configured as described above ,
It may also be detachably provided for the part, further
Further, the shape of the support member may be substantially spherical.

And according to claim 5 , a reaction vessel,
The reaction container has a mounting jig that can be delivered freely, and the mounting jig is delivered to the reaction tube with the semiconductor wafer mounted on the mounting jig. A heat treatment apparatus configured to perform heat treatment, wherein the heat treatment apparatus for heat treatment of a semiconductor wafer according to claim 1, 2, 3 or 4 is used as the heat treatment apparatus. Provided.

According to the present invention, the support portion has three
Created by a groove formed on the pillar, said pillar
One of them is a column with a rectangular cross section, the other two are
Is a columnar body in which the tubular body is halved vertically.
The inner peripheral surface sides of the other two columns are semiconductor wafers to be mounted.
Slightly from the center of the c
Since it is arranged so that it will not slip,
You can

[0020]

Further, according to the semiconductor wafer heat treatment mounting jig of the second aspect , since the semiconductor wafer is supported by the supporting member made of a material having a hardness equal to or lower than the hardness of the semiconductor wafer to be supported, the supporting member is the semiconductor wafer. There is no possibility that a minute flaw will get stuck inside and a slip can be prevented from this point.

[0022]

[0023]

If the support member is detachably attached to the support portion, it is easy to clean and replace the support member by removing the support member. If the support member is formed into a substantially spherical shape, its molding and surface are improved. It is easy to process, and it is possible to easily manufacture the one suitable for supporting the semiconductor wafer.

Further, according to the present invention , since the mounting jig for heat treatment of the semiconductor wafer according to any one of claims 1 to 4 is used as the mounting jig for mounting the semiconductor wafer, It is possible to perform heat treatment that does not cause slippage, and it is possible to perform various heat treatments with improved yield.

[0026]

Embodiments of the present invention will be described below with reference to the accompanying drawings. This embodiment is an example configured as a vertical heat treatment apparatus, and FIG. 1 shows an overview of the vertical heat treatment apparatus 1. In addition, a predetermined number of, for example, 100 wafers of Si single crystal semiconductor wafers (hereinafter, referred to as “wafers”) W that are objects to be processed are placed in a wafer boat 10 that is a mounting jig arranged below the vertical heat treatment apparatus 1. It is configured such that one sheet is mounted and loaded into the reaction tube inside 3 of the vertical furnace 2 of the vertical heat treatment apparatus 1 to perform a predetermined nitride film forming treatment.

As shown in FIG. 2, the vertical furnace 2 has a casing 4 forming its outer shape fixed to the upper surface of a base plate 5 and erected vertically. The casing 4 has a substantially cylindrical shape with a closed top surface, the inner surface of which is covered with a heat insulating material 6, and the inner peripheral surface of the heat insulating material 6 is heated by, for example, a resistance heating element. A body 7 is provided in a spiral shape so as to surround the reaction tube 3, and the inside of the reaction tube 3 is heated to a predetermined temperature, for example, 800 ° C. to 1 by an appropriate temperature control device (not shown).
It is constructed so that it can be heated and maintained at any temperature between 200 ° C.

The reaction tube 3 forming the processing region is composed of a cylindrical outer tube 31 having a closed upper end and a cylindrical inner tube 32 having an open upper end located on the inner circumference of the outer tube 31. The outer pipe 31 and the inner pipe 32 are airtightly supported by a tubular manifold 33 made of, for example, stainless steel. A flange 34 is integrally formed on the lower end of the manifold 33.

On the upper side surface of the manifold 33, gas is exhausted from the space between the outer tube 31 and the inner tube 32 to set and maintain the processing region in the reaction tube 3 in a predetermined reduced pressure atmosphere. For example, an exhaust pipe 36 leading to the vacuum pump 35 is airtightly connected.

On the lower side surface of the manifold 33, for example, SiH ₄ which is a processing gas for forming a nitride film is used.
(Monosilane) gas or SiH ₂ Cl ₂ (dichlorosilane)
A gas and a first gas introduction pipe 37 and a second gas introduction pipe 38 for introducing the NH ₃ (ammonia) gas into the inner pipe 32 are connected to each other in an airtight manner.
Each gas nozzle 3 of the gas introduction pipe 37 and the second gas introduction pipe 38
7a and 38a respectively project into the inner pipe 32.
The first gas introduction pipe 37 and the second gas introduction pipe 38 respectively correspond to predetermined mass flow controllers 39,
It is connected via 40 to a predetermined supply source (not shown) of the processing gas.

The wafer boat 10 has a circular top plate 11 and a bottom plate 12 which are vertically opposed to each other, and a support column 13 made of, for example, quartz is provided between the top plate 11 and the bottom plate 12. 14 and 15 are provided. Each of these columns 1
3, 14, 15 may be installed at a position where the circumference of the top plate 11 (or the bottom plate 12) is divided into approximately three equal parts, but in the present embodiment, as shown in FIG. The opening angle (center angle) θ ₁ with 14 is 140 °.
4 and the angle theta ₂ opens the column 15, the opening angle theta ₃ between posts 15 and posts 13 are set to be respectively 110 °. Of course, each of the opening angles θ ₁ , θ ₂ , and θ ₃ may be set to 120 °.

The wafer W, which is the object to be processed, is allowed to enter at a right angle from between the columns 13 and 14 toward the column 15 as shown in FIG. 4 by the transfer arm 8, and these will be described in detail later. It is configured to be mounted on the wafer boat 10 by being supported by the supporting portions 19, 20, 21 created by the grooves 16, 17, 18 formed in the columns 13, 14, 15 of each of the columns. .

Each of the columns 13 and 14 is composed of a column body in which a thick cylindrical body is vertically divided into halves, while the other columns 15 are column bodies having a rectangular cross section. Further, the inner peripheral surface side of each of the columns 13 and 14 is arranged so as to be slightly closer to the column 15 side than the center of the wafer W to be mounted.

The support columns 13 thus arranged and arranged,
The grooves 16, 17, and 18 are formed in the grooves 14 and 15, respectively, at a predetermined interval in the vertical direction. The lower surface side of each of the grooves 16, 17, and 18 is shown in FIGS.
As shown in FIG. 5, the supporting portions 19, 20, and 21 are respectively configured. As shown in FIGS. 4 and 5, spherical support members 22 are provided on the support surfaces of the support portions 19, 20, 21 respectively, that is, the upper surfaces. This support member 2
2 is made of a single crystal of Si, and the lower half of each is a supporting portion 1
Embedded in 9, 20, and 21.

As shown in FIGS. 3 and 5, the support member 22 of each of the supporting portions 19, 20, and 21 extends from the edge of the wafer W in the radial direction when supporting the wafer W from the back surface. Each of the supporting portions 1 is set so that the distance L becomes 12.5 mm.
It is provided in 9, 20, and 21. Since this wafer W is an 8-inch wafer, the ratio is about 12.5 of the radius.
% Of the wafer W
Is set to support.

The wafer boat 10 configured as described above
Is detachably mounted on a heat retaining cylinder 24 having a flange portion 23 made of, for example, stainless steel, and the heat retaining cylinder 24 is mounted on a boat elevator 25 which can be raised and lowered. As the elevator 25 rises, the wafer W, which is the object to be processed, is transferred to the wafer boat 10
The whole is loaded into the reaction tube 3 in the vertical furnace 2.

The vertical heat treatment apparatus 1 according to the present embodiment is configured as described above. Next, the operation and operation thereof will be described. First, the heating body 7 is caused to generate heat, and the temperature in the reaction tube 3 is set to, for example, approximately. Heat to 800 ° C.

On the other hand, when a predetermined number of wafers W, which are the objects to be processed, are loaded on the wafer boat 10 by the transfer arm 8 as described above, the boat elevator 25 moves up, and is shown in FIG. As described above, the wafer boat 10 is raised to the position where the flange portion 25 of the heat insulating cylinder 24 is in close contact with the flange 34 at the lower end portion of the manifold 33,
The wafer W is loaded into the inner tube 32 of the reaction tube 3.

Next, the inside of the reaction tube 3 is evacuated by the vacuum pump 35, and a predetermined reduced pressure atmosphere, eg, 0.
After reducing the pressure to 3 Torr, for example, the first gas introducing pipe 37
SiH ₄ (monosilane) gas from the second gas introduction pipe 3
When NH ₃ (ammonia) gas is introduced into the inner pipe 32 from No. 8, Si ₃ N ₄ which is a silicon nitride film is formed on the surface of the wafer W which is the object to be processed mounted on the wafer boat 10. is there.

In this case, as described above, the 8-inch wafer W
Is supported by the three support members 22 at a portion radially displaced from the edge by about 12.5% of the radius,
The shear stress in each part is reduced as compared with the conventional mounting jig of this type. When the wafer W was supported at a portion deviated by about 12.5% of the radius as in this example, no actual slippage was observed. Further, when the inventors actually measured, when an 8-inch wafer W was supported at a portion deviated by about 12.5% of the radius without using the supporting member 22, the shear stress in the vicinity of each supporting portion was It was 0.036 kgf / mm ² . In this regard, the shear stress when a conventional 8-inch wafer was supported at a portion 4 mm from the edge (a portion displaced by about 4% of the radius) was about 0.064 kgf / mm ² . Therefore, it can be seen that the shear stress is reduced in the present example in which the support is provided at the portion deviated by about 12.5% of the radius.

The inventors of the present invention have verified on another occasion that the shear stress is 0.0 in a normal Si wafer.
It has been found that slip occurs when the pressure exceeds 41 kgf / mm ² . Therefore, even if illuminated, the wafer W is deviated by about 12.5% of the radius as described above.
It can be seen that the slip does not occur if the above is supported.

Further, in the above embodiment, the wafer W has the support portion 1 in which the three columns 13, 14, 15 are formed.
Although the structure is supported by each of the supporting members 22, 20, and 21, that is, the structure is supported at three points, in the heat treatment of a wafer having a size of about 8 inches, the warp of the wafer itself due to thermal expansion, Even if there are four support points due to undulations, it is considered that the wafer is actually supported at three points. Therefore, even when compared with the case of the conventional boat for heat treatment by four-point support described in the section of the prior art, the shear stress of each support portion hardly changes even at the same support point, and therefore, as in the present embodiment, 3 offset by a length of about 12.5% of the radius
Even if it is supported by points, the shear stress is reduced and the occurrence of slip is suppressed as compared with the conventional 4-point support that is supported by about 4% inside.

Moreover, in this embodiment, since the supporting member 22 made of the same material as the wafer W, that is, the single crystal of Si, is used for the actually supporting portion, the supporting member is provided at the contact supporting portion on the back surface of the wafer W. There is no fear that 22 will attach a flaw,
Also from this point, the occurrence of slip is suppressed, and as a result,
It is possible to carry out a heat treatment in which no slip occurs. Therefore, the yield can be improved more than ever before.

In the above embodiment, the support member 22
Although a spherical member is used as the support member, it is needless to say that the shape of such a supporting member may not be such a spherical member.
It is also possible to use a support member 26 having an insertion portion 26a at the lower portion and a locking portion 26b having a larger diameter at the upper portion, and the upper surface of the locking portion 26b is formed flat as shown in FIG. As shown, a simple columnar or prismatic support member 27 may be used. In any case, if it is provided so as to be attachable to and detachable from the supporting portion, it can be easily replaced and washed.

By the way, the above-mentioned embodiment was applied to the 8-inch wafer W, but the present invention is also effective for a 12-inch large-diameter wafer. To explain this by a simulation conducted by the inventors, FIG. 8 shows that a circular 12-inch wafer is supported at regular intervals of 120 ° at points 18.8 mm from the edge (a length of about 12.5% of the radius). The displacement distribution is shown in the case of being supported at a position shifted inward by a certain amount), and FIG. 9 shows the shear stress distribution in that case. The maximum displacement width in this case is +22.1 μm
The area where the shear stress is large is −82.3 μm, as shown by the shaded area in FIG. 9, and the maximum value is 0.
It was 0618 kgf / mm ² .

On the other hand, according to the present invention, the circular 12-inch wafer is supported at equal intervals of 120 ° from the edge 4 times.
When supported at a point of 4.0 mm (a point displaced inward by a length of about 29.3% of the radius), the displacement distribution is as shown in FIG. 10, and the shear stress distribution is shown in FIG. It became so. And the maximum displacement width is +12.7 μm-
-41.5 μm, and the maximum value of shear stress is 0.
It was 0308 kgf / mm ² . Therefore, even in a 12-inch wafer, if the wafer is supported at a position displaced inward by a length of about 30% of the radius, no slip will occur.

The wafer boat in the above embodiment is
The present invention is applied to a vertical heat treatment apparatus that performs oxidation and diffusion treatments, but the present invention is not limited to this and is also applied to a heat treatment mounting jig used in a heat treatment apparatus that performs CVD treatment, etching treatment, or the like. It is possible.

[0048]

According to the present invention , the slip of a semiconductor wafer is performed.
Can be prevented from occurring. Further, since the supporting member is detachably attached to the supporting portion, it is easy to wash and replace the supporting member after removing the supporting member. Further, if the supporting member has a substantially spherical shape, the supporting member itself is molded. Further, the surface processing is easy, and the one suitable for supporting the semiconductor wafer can be easily manufactured. With the semiconductor wafer heat treatment apparatus according to the present invention, it is possible to perform the heat treatment on the semiconductor wafer in which slip does not occur, and it is possible to perform various heat treatments with improved yield.

[0049]

[0050]

[Brief description of drawings]

FIG. 1 is a perspective view showing an outline of a vertical heat treatment apparatus according to an embodiment of the present invention.

2 is a vertical cross-sectional explanatory view schematically showing the inside of a vertical furnace of the vertical heat treatment apparatus of FIG.

FIG. 3 is a plan view of the wafer showing the support points of the wafer in the embodiment of the present invention.

FIG. 4 is a perspective view of relevant parts showing a state where a wafer boat according to an embodiment of the present invention supports a wafer.

FIG. 5 is a side view of the essential parts showing how the wafer boat according to the embodiment of the present invention supports wafers.

FIG. 6 is a side view illustrating a main part of another example of the support member.

FIG. 7 is a side view illustrating the main part of another example of the support member.

FIG. 8 is an explanatory diagram showing a displacement distribution when a 12-inch wafer is supported by a conventional technique.

FIG. 9 is an explanatory diagram showing a shear stress distribution when a 12-inch wafer is supported by a conventional technique.

FIG. 10 is an explanatory diagram showing a displacement distribution when a 12-inch wafer is supported according to the present invention.

FIG. 11 is an explanatory diagram showing a shear stress distribution when a 12-inch wafer is supported according to the present invention.

FIG. 12 is a perspective view showing an overview of a conventional wafer boat.

FIG. 13 is an explanatory side view of the main parts, showing a state where a wafer boat of a conventional technique supports a wafer.

[Explanation of symbols]

1 Vertical heat treatment equipment 2 Vertical furnace 3 reaction tubes 7 heating body 10 wafer boat 13, 14, 15 support 16, 17, 18 groove 19, 20, 21 Support 22 Support member 25 boat elevator W wafer

   ─────────────────────────────────────────────────── ─── Continued front page       (56) References JP-A-6-168902 (JP, A)                 JP-A-5-238882 (JP, A)                 JP-A 1-272112 (JP, A)                 JP-A-2-102523 (JP, A)                 JP-A-1-134915 (JP, A)                 JP-A-61-206232 (JP, A)

Claims (5)

(57) [Claims] 1. A heat treatment mounting jig, which is used when a semiconductor wafer is heat-treated and is configured to support the lower surface of the semiconductor wafer by a supporting portion and mount the semiconductor wafer, the supporting portion including three supporting portions. Grooves formed on the columns of
Was created by one of the columns
Is a columnar body with a rectangular cross section, and the other two are vertical cylinders.
It is a columnar body that is halved into two, and the inner peripheral surface side of the other two columns is the semi-conductor to be mounted.
A pillar whose cross section is rectangular, slightly above the center of the body wafer
A jig for heat treatment of a semiconductor wafer, which is arranged so as to face the side . 2. The semiconductor wafer is provided on the upper surface of the supporting portion.
Provide a support member made of a material with a hardness not higher than the
So that the semiconductor wafer is supported by the supporting member of
The mounting jig for heat treatment of a semiconductor wafer according to claim 1, wherein the jig is formed. 3. The support member is detachable from the support portion.
Any one of claims 1 to 2, characterized in that it is provided.
A mounting jig for heat treatment of a semiconductor wafer according to any one of them . 4. The supporting member has a substantially spherical shape.
The mounting jig for heat treatment of a semiconductor wafer according to any one of claims 1 to 3 . 5. A reaction vessel and free delivery to this reaction vessel
And a semiconductor wafer mounted on the mounting jig.
Deliver this mounting jig into the reaction tube in the mounted state, and
As if a predetermined heat treatment was applied to the semiconductor wafer in the reaction tube.
In the configured heat treatment apparatus, the mounting jig is
The semiconductor wafer according to any one of items 1, 2, 3 and 4.
Heat treatment, characterized by being a mounting jig for heat treatment of c
apparatus.