JPS63102225A - Wafer boat for vertical type semiconductor thermal treatment equipment - Google Patents

Abstract

PURPOSE:To prevent the effect of the turbulent flow region of a reaction gas generated in sections adjacent to connecting bars, and to equalize film thickness by erecting a plate, in which a wafer is housed into space with a recessed section slightly larger than the diameter of the wafer, between the connecting bars and separating the wafer from the connecting bars. CONSTITUTION:Upper and lower end plates 12, 14 are connected by connecting 16 e.g. six in a wafer boat 10. A plate 20 is erected onto a large number of notches 18 shaped separate in the axial direction of each connecting bar 16. The plate 20 has a ring 22 on a plate body 21, and the diameter and depth of a recessed section 23 in the ring 22 are formed in size slightly larger than a wafer. Consequently, since the periphery of the wafer is positioned separatedly by from the connecting bars 16 considerably, the effect of a reaction gas changed into turbulent flows generated in sections adjacent to the connecting bars is reduced. Since the circumferential surface of the wafer 24 is also exposed to the reaction gas having a normal flow in the same manner as the center, the equalization of the film thickness the periphery and the center is promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wafer boat that supports wafers and is carried into and out of a vertical semiconductor heat processing apparatus.

[Prior art]

Semiconductor substrates, such as silicon wafers (hereinafter referred to as wafers), are loaded and supported on a semiconductor substrate support device called a wafer boat, and are carried into a reaction tube of a vertical semiconductor heat treatment apparatus from above or below. Ru. Then, a reactive gas such as silane gas or oxygen gas is supplied into the reaction tube, and predetermined heat treatments (including chemical treatments) such as CVD, oxidation, and diffusion are performed on the wafer. Thereafter, the heat-treated wafer is carried out from the reaction tube while being supported by a wafer boat.

As shown in FIGS. 8 and 9, a known wafer boat 110 is constructed by connecting upper and lower end plates 112, 114 with a plurality of, for example, six connecting rods 116. Connecting rod 1
16 is arranged only on one side, for example, on the right side, so as to form an opening 111 through which wafers can be carried in and out. Additionally, a number of notches 118 are provided in each connecting rod 116 axially, typically spaced a distance apart. The wafers 124 inserted from the opening direction are loaded into the notches 118 and installed in parallel between the connecting rods 116, thereby being supported by the wafer boat 110.

As shown, a series of corresponding cuts 118 may be staggered so that the wafer 124 is supported at an angle α.

(Problems with the prior art) Reactive gases such as silane gas and oxygen gas are, for example,
It enters from above the reaction tube, flows through the gap between the wafers juxtaposed between the connecting rods, descends inside the reaction tube, and flows out from the bottom of the reaction tube. In order to prevent non-uniformity in film thickness and to ensure a high yield, it is necessary to heat-treat the center and periphery of each wafer uniformly over the entire surface.

However, although the connecting rods are molded from quartz glass, the lower end plate does not extend, and in order to support nearly 200 wafers, three to six connecting rods are used to ensure sufficient strength. It is also formed with a considerable diameter.

In this way, since the concatenation g115 of considerable thickness uses 3 to 6 trees, as shown in Figure 1A,
The flow of the reactant gas is disturbed near the connecting rod 115 under the influence of the connecting rod, and a turbulent region is formed near the connecting rod. In the known wafer boat 110, the wafer ends are supported by the notches 118 and inserted up to the center of the connecting rods 116. Therefore, there is a possibility that the thickness of the oxide film will be non-uniform between the peripheral edge 124a of the wafer exposed to the turbulent flow of the reaction gas and the center 124b of the wafer exposed to the normal flow of the reaction gas. Furthermore, since the reaction gas collides with the side surface of the wafer and flows, the flow of the reaction gas is disturbed on the side surface of the wafer, and the connecting rod 11δ
Also at the wafer periphery 24c other than near the wafer center 124b, a film thickness that is different from that at the wafer center 124b tends to be produced.

In particular, in low-pressure CVD performed at a low temperature using silane gas or oxygen gas as a reaction gas, mass transfer has a large effect on film thickness formation, and there is concern that it may be affected by a turbulent region.

According to experiments, this type of low pressure CVD
As shown in FIG. 0B and FIG. It has been pointed out that the periphery 124c of the wafer increases rapidly. It has also been pointed out that near the six-piece connecting rod 116, the film thickness at the periphery 124a of the wafer is thinner than at the center edge 124b.
OBJECT OF THE INVENTION The object of the present invention is to provide a wafer boat for a vertical semiconductor heat treatment apparatus that supports semiconductor substrates such as wafers so as to make film thickness uniform.

[Summary of the invention]

To achieve the above object, according to the present invention, the setting means for the wafer storage space includes, for example, a plate provided with a means for setting the space in which the wafer can be stored on the upper surface, which is installed between the connecting rods. This is formed from a recess provided on the top surface of the plate or three or more bins, and a space slightly larger than the diameter of the wafer is set, and the wafer is stored in the space.

〔Example〕

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

As shown in FIGS. 1 to 3, the wafer boat 10 according to the present invention includes upper and lower end plates 12.14 and, for example, six connecting rods 16 that connect the upper and lower end plates. are doing. Each connecting rod 16 is conventionally provided with a number of axially spaced notches 18.

A number of plates 20 are placed on each notch 18,
It is installed between connecting rods. Although a large number of plates 20 corresponding to the number of notches 18 are installed, only one plate 20 is illustrated in FIG. 1 to avoid complicating the drawing. Plate)-20 includes a plate body 21 and a semiconductor substrate to be subjected to heat treatment, such as a wafer 2.
It has four retractable parts 23 and a ring 22 disposed on the plate body. ring 22
The recess 23 is formed as a central hole, for example slightly larger than the diameter of the wafer, so as to leave a small gap on both sides. Further, it is preferable that the depth of the four parts 23 be the same as the thickness of the wafer 24 or slightly larger. Then, the wafer 24 is loaded using a loading arm (not shown) of the loading means.
It is housed within the four parts 23 of the ring and supported on the plate 20.

To illustrate the dimensions of each part in the wafer boat 10 for a 5-inch diameter (125 m+a) wafer 24, as shown in FIG. 2, the plate diameter is 151 m+i, the diameter of the recess 23 is 130 m+*, the plate body 21, The thickness of the rings 22 is 1+a each, and the pitch of the plates 20 is 14.
．． Each is formed to 28 mm.

In this way, the wafer 24 is attached to the recess 23 of the plate 20.
In the configuration housed in FIG. 2 and FIG.
As can be clearly seen by comparing Figure 0A, the periphery of the wafer is located at a considerable distance from the connecting rod 16. Therefore, the amount of turbulent reaction gas generated in the adjacent portion of the connecting rod 16 is reduced, and the film thickness can be made uniform.

In addition, the reactant gas flows against the side surface of the plate 20, and instead of colliding with the side surface of the wafer 24, it flows over the periphery of the wafer and reaches the center of the wafer. In this way, the peripheral surface of the wafer 24 as well as the center of the wafer,
Since the wafer is exposed to a normal flow of reaction gas, there is no difference in film thickness between the periphery and the center of the wafer, promoting uniformity of the film thickness.

Further, a recess 23 of the plate 20 that accommodates the wafer 24 is provided.
is formed slightly larger than the wafer diameter. Therefore, if the wafer 24 is placed in the recess 23 of the link,
Wafer center linking is done automatically and wafer loading can be done quickly and easily. In addition, in such a configuration in which only a small gap exists around the wafers 24, even if the wafer boat 10 is rotated during the heat treatment, only rotational deviation occurs in the wafers 24 on the plate 20.

The concave portion 23 of the link is a wafer storage space setting means 25.
However, this setting means is not limited to a recess, and may take various other forms. For example, as shown by the dashed line in FIG. 3, the setting means 25 may be formed from a plurality of bins 27 arranged on the plate 20 so as to leave a slight gap with the wafer 24. The bin 27 only needs to have a storage space for the wafers 24, and does not need to be strong and strong, and can be constructed from an extremely small diameter bin.

Further, as shown in the figure, if there are at least three pins 27, a wafer storage space can be set. Therefore, compared to the connecting rod 16, the presence of the pin 27 has less influence on the reaction gas.
is mostly ignored.

In the embodiment, the plate 20 is housed in the notch 18 and installed between the connecting rods 16, but the installation method is as follows:
It is not limited to this. For example, the plate 20 may be welded to the connecting rod 16 and installed without providing a cut. Further, since the plate 20 is made of quartz glass, it can be easily molded by separating the plate body 21 and the ring 22 as shown in the figure. However, if necessary, the plate body 21 and the ring 22 may be integrated to form the plate 20.

Loading the wafers 24 into the wafer boat IO outside the furnace body of the vertical semiconductor heat treatment apparatus, and
Unloading from there is done using a loading means. Since a predetermined pattern is formed on the upper surface of the wafer 24, a vacuum suction cup, which may damage the pattern, is not used as a loading means. Usually, the loading means includes a pair of loading arms, and loads a wafer onto the loading arms to perform loading and unropping inking (hereinafter referred to as loading). Therefore, it is necessary to provide a loading hole 26 in the plate 20. The loading hole 26 may be, for example, a central hole 28 or a pair of parallel elongated holes 3, as shown by the dashed line in FIG.
It can be formed from 0. However, in the loading hole 26 having such a configuration, for example, during unloading, the lift arm is inserted into the rope ink hole from below to lift the wafer 24 from the plate 20.
It is necessary to transfer the wafer to the loading arm. On the other hand, if the loading hole 26 is formed from the elongated hole 32 that is open at one end, the loading arm can be inserted into the loading hole, and the wafer 24 is directly supported from the plate by the loading arm, and the wafer 24 is directly supported during unloading. It can be done quickly and easily. Heat theory and rope ink are also done quickly and easily.

It is expected that the presence of the loading holes 26 will affect the formation of the oxide film. The experimental results of low pressure CVD carried out at low temperature using silane gas and oxygen gas as reaction gases are shown below.

When the loading hole 26 was not provided in the wafer boat 10 for 5-inch wafers described above, the variation in the film thickness of 5i (h) produced on the test wafer was 1°5mm. On the other hand, diameter 110+sm
If the center hole 28 for rope ink is provided in the plate body 21, it will affect the film thickness of the wafer 24 located directly below, and the variation in film thickness of the wafer directly below will be 7° above.
It becomes a demon and the yield drops rapidly. However, central hole 2
If the diameter of the wafer 8 is set to 301111.20 mm, the variation in film thickness of the wafer 24 immediately below is improved to ±L, 2 $, and 2° 1 $ above.

On the other hand, there is no center hole 28, and the loading hole 2
Experimental results have shown that if 6 is a pair of elongated holes 32 with one end open, this affects the film thickness of the wafer 24 on the plate rather than the wafer 24 directly below. As shown in Fig. 4, if the long holes 32 are provided 110+sm apart and their width X is 5cm, then the variation in the film thickness of the wafer 24 on that plate is only 2°5z above. Ta. If the width of the elongated hole 32 is increased, it is expected that the variation in film thickness will increase.In fact, if the width is
Oni, in the case of 10 false 1, ±3.5 to 4. It was Oz.

In addition, the loading hole 26 has a width loam and a length 4.
When a pair of long holes 30 with a diameter of 0 mm are provided, both the wafer 24 on the plate and the wafer directly below the plate,
The variations in film thickness were all above 1°5z, and no influence due to the presence of rope ink holes was observed.

From the above experimental results, it is most preferable to provide the plate main body 21 with long holes 30 that do not open, with regard to variations in film thickness. However, on the other hand, it is necessary to transfer the wafer 24 during loading. On the other hand, if a pair of small-width open elongated holes 32 are provided, variations in film thickness can be relatively suppressed, and loading and unroping operations can be performed without transferring.

Note that reference numeral 34 indicates a support column fixed to the upper end plate 12.

In order to promote uniformity of the film thickness, it is preferable to improve not only the configuration of the wafer boat 10 but also the configuration of the vertical semiconductor heat treatment apparatus itself. In particular, in low-temperature, low-pressure CVD using silane gas or oxygen gas as a reaction gas, it is necessary to equalize the flow of one reaction gas.

An example of a double reaction tube type vertical semiconductor heat treatment apparatus 40 configured to uniformize the flow of reaction gas is shown in FIGS. 5 and 6. This vertical semiconductor heat treatment apparatus 40 has the following features:
A supply pipe 42,44 for supplying a reaction gas, for example silane gas (Sill), oxygen gas (02), extends in the axial direction within the gap 49 between the outer reaction tube 46 and the inner reaction tube 48. It is arranged. Silane gas, oxygen gas,
ft. each exits through a series of holes 50 drilled at predetermined intervals in the inner ends of the supply tubes 42,44. The silane and oxygen flowing out from the hole 50 then flow through the elongated hole 52 formed in the peripheral wall of the internal reaction tube 48, respectively. Note that a shielding wall 53 is disposed behind the supply pipes 42 and 44 to close the gap 4.
This prevents the reactant gas from directly flowing out to 9. Although not shown in order to avoid complicating the drawing, the wafer boat 10 supporting the wafers 24 is suspended within the reaction tube, and silane gas and oxygen gas flow through the internal reaction tube 48 to reach the upper surface of each wafer. An oxide film is grown in a vapor phase.

A large number of discharge holes 54 spaced apart from each other by a predetermined distance in the axial direction are bored in the peripheral wall of the inner reaction tube 48, facing the supply tubes 42, 44, and the inside of the outer reaction tube 46 is provided with
It is depressurized. Therefore, silane gas and oxygen gas are
It is sucked and flows out of the internal reaction tube 48 from the discharge hole 54, flows in the gap 49 with the external reaction tube 46, and then,
It passes through the pressure reducing pipe 56 and is discharged to the outside of the reaction tube.

As described above, in the configuration in which a large number of the holes 50 of the reaction gas supply pipes 42 and 44 and the discharge holes 54 of the internal reaction tube 48 are provided in a number separated from each other in the axial direction, the flow of the reaction gas within the reaction tube is , easily laminarized, in the axial direction,
Equalized. Therefore, irrespective of the level (height) at which the wafers 14 are supported on the wafer boat 10, the vapor phase growth occurs in the same way whether the wafers 14 are supported at the top, center, or bottom of the wafer boat. , the film thickness can be made uniform.

Providing a large number of holes 50, 54 is preferable because the flow of the reaction gas in the reaction tube becomes more uniform in the axial direction. Therefore, for example, it is preferable to provide the same number of holes 50, 54 as there are plates, ie, wafers 24, so as to be located in the center of adjacent plates 20. However, since the internal reaction tube 48 is made of quartz glass and drilling is not easy, one hole 50, 54 may be provided for several wafers 24. In theory, it is not necessary to provide the same number of holes 50, 54 symmetrically.

Note that reference numeral 58 indicates a thermocouple protection tube into which a thermocouple for measuring the temperature of the reaction tube is inserted.

In general, wafers supported at the upper and lower portions of the wafer boat tend to have different thicknesses of oxide film than wafers 24 supported at the center of the wafer boat 10 . This is because the same amount of reaction gas flows in the upper, middle, and lower parts of the reaction tube, even though the temperatures at the upper and lower ends of the reaction tube are different from the center.

Therefore, as shown in FIG. 7, for example, 42a, 4
Supply pipe 42 from the branch pipe branched into three trees 2b and 42c
can be configured. A series of holes 50 are provided in the upper part of the branch pipe 42a, in the center of the branch pipe 42b, and in the lower part of the branch pipe 42c. In such a configuration, by adjusting the throttle valve 60, a different appropriate amount of silane gas is supplied to the branch pipes 42a and 42c compared to the branch pipe 42b.
will be supplied to.

In this way, an appropriate amount of silane gas that is different from the center part of the internal reaction tube 48 is supplied to the upper and lower parts of the internal reaction tube, so that the reaction in the upper part, middle part, and lower part of the internal reaction tube is uniformized, and the inside reaction tube is uniform. The thickness of the film produced on the wafer can be made uniform.

The above-mentioned embodiments are for illustrating the present invention, and are not intended to limit the present invention in any way, and any modifications, modifications, etc. made within the technical scope of the present invention are also included in the present invention. Needless to say.

(Effects of the Invention) As described above, according to the wafer boat of the present invention, semiconductor substrates such as wafers are supported with their peripheries separated from the connecting rods, so that reactions occur in adjacent portions of the connecting rods. This makes it less susceptible to the effects of gas turbulence, making it possible to make the film thickness more uniform.

Also, the reactant gas flows against the side of the plate and does not collide with the side of the wafer. 1. The reaction gas is
Flows above the periphery of the wafer to the center of the wafer,
The wafer periphery, like the wafer center, is exposed to a normal flow of reactant gas. Therefore, uniformity of the film thickness at the periphery and center of the wafer is promoted.

Furthermore, the wafer storage space is formed slightly larger than the wafer diameter by the recesses and bins provided on the top surface of the plate, so if the wafer is stored in the plate storage space, the wafer will be automatically centered. done to. Therefore, wafer loading can be performed quickly and easily.

[Brief explanation of the drawing]

FIG. 1 is a schematic longitudinal sectional view of a wafer boat according to the present invention, FIG. 2 is a longitudinal sectional view of the wafer boat taken along line II-11 in FIG. 1, and FIG. 3 shows an upper end plate. A plan view of the removed wafer boat, Figure i4 is a plan view of the plate, Figure 5 is a schematic cross-sectional view of the vertical semiconductor heat treatment equipment in which the wafer port is housed, and Figure 6 is the line VI-- 7 is a schematic longitudinal sectional view of a vertical semiconductor heat treatment apparatus along VI, FIG. 8 is a schematic diagram showing a modified example of the reaction gas supply pipe, FIG. 8 is a plan view of a known wafer port, and FIG. 10A is a partial longitudinal section of the wafer port along line XA-XB of FIG. 8; FIG. 10B is a partial longitudinal section of the wafer port along line A plan view of the wafer showing the thickness of the oxide film. FIG. 10C is a cross-sectional view of the wafer taken along line xc-xc in FIG. 10B(7). 10: wafer boat, 12.14: upper and lower end plates of wafer boat, 16: connecting rod of wafer port, 18: notch of wafer boat, 20 nibrate, 21 niblet main body, 22: ring, 23: recess of ring, 24: Wafer (semiconductor substrate), 25: Wafer storage space setting means, 26: Loading hole, 27: Pin, long hole with one end open at 32, 42.44: Reaction gas supply pipe, 46;
External reaction tube, 48: Internal reaction tube, 50: Hole, 54: Discharge hole. Applicant Disco Sair Japan Co., Ltd. Agent Patent Attorney Takao Warashina, ゛-゛-枦6
two. , 22 Figure 1 Figure 2 Figure 4 ○ N (T)
1 size Lr>
Dimension LIIO\T\1 Hour=

Claims (6)

[Claims] (1) In a wafer boat of a vertical semiconductor heat processing apparatus in which wafers are installed and supported between connecting rods, a plate is provided with a means for setting a space in which wafers can be stored on the upper surface.
A wafer boat for vertical semiconductor heat treatment equipment, characterized in that it is installed between connecting rods. (2) A wafer boat for a vertical semiconductor heat processing apparatus according to claim 1, wherein the setting means for the wafer storage space comprises a recess provided on the upper surface of the plate. (3) A wafer boat for a vertical semiconductor heat processing apparatus according to claim 2, wherein the plate includes a ring having a recessed portion capable of storing wafers, and a plate body on which the ring is loaded. (4) A wafer boat for a vertical semiconductor heat treatment apparatus according to claim 1, wherein the setting means for the wafer storage space comprises three or more pins provided on the upper surface of the plate. (5) The wafer of the vertical semiconductor heat treatment apparatus according to any one of claims 1 to 4, wherein the plate is provided with a loading hole into which a loading arm for loading and unloading the wafer can be inserted. boat. (6) A wafer boat for a vertical semiconductor heat treatment apparatus according to claim 5, wherein the loading holes are two parallel long holes with one end open.