JP7635708B2 - Tray for insulating film forming apparatus, insulating film forming apparatus, and insulating film forming method - Google Patents

Description

The present invention relates to a tray for an insulating film forming device, an insulating film forming device, and an insulating film forming method.

In recent years, epitaxial wafers, which are semiconductor wafers such as silicon wafers on which epitaxial layers of silicon or the like are formed, have become common as substrates for various semiconductor devices such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), DRAMs (Dynamic Random Access Memory), power transistors, and back-illuminated solid-state image sensors.

For example, epitaxial silicon wafers can be obtained by placing a silicon wafer in a single-wafer epitaxial growth furnace, supplying source gases such as dichlorosilane gas or trichlorosilane gas into the epitaxial growth furnace together with a carrier gas such as hydrogen gas, and growing a silicon epitaxial layer on the silicon wafer.

However, when forming a high resistivity epitaxial layer on the front surface of a low resistivity semiconductor wafer, so-called autodoping is likely to occur, in which dopants in the semiconductor wafer jump out from the back surface of the semiconductor wafer into the gas phase and are incorporated into the epitaxial layer. For this reason, prior to the growth of the epitaxial layer, an insulating film such as an oxide film is formed on the back surface of the semiconductor wafer as a protective film to suppress autodoping (see, for example, Patent Document 1).

The insulating film can be formed, for example, by a chemical vapor deposition (CVD) method. For example, in an atmospheric pressure CVD method in which CVD is performed at atmospheric pressure, a semiconductor wafer is placed on a tray with the surface on which the insulating film is to be formed (i.e., the back surface) facing up, and then, while the semiconductor wafer is heated, a source gas for the insulating film is supplied onto the semiconductor wafer to form the insulating film on the back surface of the semiconductor wafer.

In the conventional method, the insulating film source gas flows around to the outer edge of the front surface of the wafer, so the insulating film is formed not only on the back surface of the semiconductor wafer but also on the wafer edge (end face) and the outer edge of the front surface. On the other hand, when an epitaxial layer is formed on a semiconductor wafer in which an insulating film is formed on the outer periphery of the wafer from the outer edge of the back surface to the wafer end face and the outer edge of the front surface, cracks may occur on the outer periphery of the wafer, and the epitaxial layer may grow abnormally, resulting in so-called nodules. Therefore, when an insulating film is formed on the back surface of the wafer by the conventional method, the insulating film formed on the outer periphery of the wafer is subsequently removed. The insulating film on the outer periphery of the wafer can be removed by wiping using a nozzle soaked in a removing liquid such as hydrofluoric acid (HF) liquid.

International Publication No. 2011/070741

When removing the insulating film on the outer periphery of the wafer using the above-mentioned wiping method, the removal liquid may seep not only into the insulating film on the outer periphery of the wafer, but also into part of the insulating film on the back surface of the wafer, resulting in so-called "smearing." If such smearing occurs, the semiconductor wafer becomes a defective product and cannot be used as a substrate for an epitaxial wafer. For this reason, it is necessary to once remove the insulating film that has been formed, and then form an insulating film again, which creates the problem of reduced productivity.

In order to prevent the occurrence of bleeding as described above, it is preferable to form an insulating film only on the back surface of the semiconductor wafer, without forming an insulating film on the outer periphery of the semiconductor wafer.

The present invention was made in consideration of the above problems, and its purpose is to provide a tray for an insulating film forming device that can form an insulating film only on the back surface of a wafer, without forming an insulating film on the outer periphery of the wafer.

The present invention which solves the above problems is as follows.
[1] A tray for placing a semiconductor wafer in an insulating film forming apparatus for forming an insulating film on a back surface of a semiconductor wafer, comprising:
A tray body for placing a semiconductor wafer thereon is provided,
The tray body includes:
A cylindrical opening extending from the upper surface to the lower surface of the tray body;
a ring-shaped support portion located on the periphery of the opening portion and supporting an outer periphery of the semiconductor wafer;
A tray for an insulating film forming apparatus, comprising:

[2] The opening has a cylindrical first portion disposed on the lower surface side of the tray body and a cylindrical second portion disposed on the upper surface side for accommodating a semiconductor wafer, the second portion having the same central axis as the central axis of the first portion of the tray body and a diameter larger than the diameter of the first portion, and the periphery of the first portion constitutes the support portion, the tray for an insulating film forming apparatus described in [1].

[3] The tray body further includes an annular member disposed on the support portion and having an inner diameter smaller than a diameter of the opening at the lower surface of the tray body,
The tray for an insulating film forming apparatus according to the above [1] or [2], wherein the support portion supports an outer periphery of the semiconductor wafer via the annular member.

[4] An apparatus for forming an insulating film on a back surface of a semiconductor wafer, comprising:
A tray according to any one of the above [1] to [3],
a source gas supply unit disposed below the tray and configured to supply a source gas for the insulating film toward a rear surface of the semiconductor wafer placed on the tray through the opening of the tray;
a heater disposed above the tray for heating the semiconductor wafer;
An insulating film forming apparatus comprising:

[5] The insulating film forming apparatus described in [4] above, further comprising an inert gas supply unit disposed above the tray and below the heater, for supplying an inert gas toward the front surface of the semiconductor wafer placed on the tray.

[6] A plurality of the trays are provided,
The insulating film forming apparatus according to [4] or [5] above, wherein the plurality of trays are continuously transported between the raw material gas supply unit and the inert gas supply unit so that the insulating film can be continuously formed on a plurality of semiconductor wafers.

[7] A method for forming an insulating film, comprising placing a semiconductor wafer on the tray of the insulating film forming apparatus described in any one of [4] to [6] above, then disposing the semiconductor wafer between the raw material gas supply unit and the heater, and then, while the semiconductor wafer is heated to a predetermined temperature by the heater, supplying an inert gas while supplying a raw material gas for the insulating film from the raw material gas supply unit, thereby forming an insulating film on the rear surface of the semiconductor wafer.

[8] The insulating film forming method described in [7] above, which includes placing a semiconductor wafer on the tray of the insulating film forming apparatus described in [5] above, then disposing the semiconductor wafer between the raw material gas supply unit and the inert gas supply unit, and then, while the semiconductor wafer is heated to a predetermined temperature by the heater, supplying an inert gas from the inert gas supply unit toward the front surface of the semiconductor wafer while supplying a raw material gas for the insulating film from the raw material gas supply unit, thereby forming an insulating film on the back surface of the semiconductor wafer.

[9] The method for forming an insulating film according to [7] or [8], wherein the semiconductor wafer is a silicon wafer.

[10] The insulating film forming method according to any one of [7] to [9], wherein the insulating film is an oxide film.

According to the present invention, an insulating film can be formed only on the back surface of a semiconductor wafer, without forming an insulating film on the outer periphery of the semiconductor wafer.

1A and 1B are diagrams showing an example of a tray for an insulating film forming apparatus according to the present invention, in which (a) is a top view and (b) is a cross-sectional view taken along the line AA of (a). 5A and 5B are diagrams showing another example of a tray for an insulating film forming apparatus according to the present invention, in which (a) is a top view and (b) is a cross-sectional view taken along the line AA of (a). 1A and 1B are diagrams showing yet another example of a tray for an insulating film forming apparatus according to the present invention, in which (a) is a cross-sectional view, and (b) and (c) are diagrams showing the relationship between the width of the annular member and the area where an insulating film is not formed. FIG. 1 is a diagram showing a preferred example of an insulating film forming apparatus according to the present invention. FIG. 2 is a diagram showing details of a tray used in an example of the invention. FIG. 1 is a diagram showing the relationship between the radial position of a silicon wafer and the thickness of an oxide film.

(Tray for insulating film forming equipment)
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A semiconductor wafer has a front surface which is a flat surface on which devices are formed, a back surface which is a flat surface opposite to the front surface, and a wafer end surface located on the outer side of the front surface and the back surface in the wafer radial direction and connecting the outer edge of the front surface and the outer edge of the back surface. A tray for an insulating film forming apparatus according to the present invention is a tray on which a semiconductor wafer is placed in an insulating film forming apparatus that forms an insulating film on the back surface of a semiconductor wafer. The tray for an insulating film forming apparatus includes a tray main body on which a semiconductor wafer is placed. Here, the tray main body is characterized by having a cylindrical opening penetrating from the upper surface to the lower surface of the tray main body, and an annular support portion located on the periphery of the opening and supporting the outer periphery of the semiconductor wafer.

As described above, in conventional insulating film forming devices, the wafer is placed on a tray with the surface on which the insulating film is to be formed, i.e., the back side, facing up, and raw material gas is supplied from above the wafer to form an insulating film on the back side of the wafer. In this process, the insulating film is formed not only on the back side of the wafer, but also from the edge of the wafer to the front side. The insulating film formed on the periphery of the wafer, from the outer edge of the back side to the edge of the wafer and then to the outer edge of the front side, can cause nodules and must be removed.

The inventors of the present invention have thoroughly investigated a method for forming an insulating film only on the back surface of a wafer while suppressing the formation of an insulating film on the outer periphery of the wafer as described above. In the process, they focused on the tray on which the semiconductor wafer is placed, and came up with the idea of providing a cylindrical opening penetrating the tray, placing the semiconductor wafer so as to close this opening, and supporting the outer periphery of the wafer with the peripheral portion of the opening. As shown in the examples described below, they discovered that by using a tray such as the above, an insulating film can be formed only on the back surface of the wafer without forming an insulating film on the outer periphery of the wafer, and thus completed the present invention. The tray for an insulating film forming apparatus according to the present invention will be described in detail below.

Figure 1 shows an example of a tray for an insulating film forming apparatus according to the present invention, where (a) is a top view and (b) is a cross-sectional view taken along the line A-A of (a). The tray 1 for an insulating film forming apparatus shown in Figure 1 comprises a tray body 11 which constitutes the base of the tray. Both the upper surface 11a and the lower surface 11b of the tray body 11 are flat. The tray body 11 also has a cylindrical opening 11c which penetrates from the upper surface 11a to the lower surface 11b, and a support portion 11d which is located on the periphery of the opening 11c on the upper surface 11a and which supports a semiconductor wafer.

When a semiconductor wafer is placed on a tray 1 having such a configuration, the back side of the wafer, on which the insulating film is formed, faces downward, and the semiconductor wafer is placed so that the outer periphery of the semiconductor wafer is supported by the support portion 11d around the periphery of the opening 11c. As described above, the top surface 11a of the tray body 11 is flat, and therefore the top surface of the support portion 11d is also flat. Therefore, the top surface 11a of the tray body 11 comes into surface contact with the outer periphery of the back side of the semiconductor wafer.

When the tray 1 on which the semiconductor wafer is placed is viewed from below as described above, the back surface of the semiconductor wafer is exposed, while the outer periphery of the wafer is masked by the support portion 11d of the tray body 11. Therefore, when the source gas for the insulating film is supplied from below the tray 1, the source gas is supplied only to the area of the back surface of the wafer exposed by the opening 11c, and is not supplied to the outer periphery of the wafer. As a result, an insulating film can be formed only on the back surface of the wafer, without forming an insulating film on the outer periphery of the wafer.

It is preferable that the tray body 11 is made of a material that is heat-resistant and resistant to deformation at the temperature used to form the insulating film, and that does not contaminate the semiconductor wafer. For example, the tray body 11 can be made of sintered silicon carbide, or sintered silicon carbide whose surface is coated with a silicon carbide film.

The size of the tray body 11 can be appropriately set depending on the diameter and number of semiconductor wafers to be placed, the material that constitutes the tray body 11, etc.

As described above, the opening 11c defines the area in which the insulating film is formed on the back surface of the wafer when the semiconductor wafer is placed on it. The diameter of the opening 11c depends on the diameter of the semiconductor wafer to be placed and the size (width) of the outer peripheral area where the insulating film is not formed, but it is preferable to make the diameter of the opening 11c 2 mm to 6 mm smaller than the diameter of the semiconductor wafer.

In the tray 1 shown in FIG. 1, only one opening 11c is provided, but multiple openings 11c can be provided to make a tray for a continuous insulating film forming device for forming insulating films on the backsides of multiple semiconductor wafers.

2 shows another example of a tray for an insulating film forming apparatus according to the present invention, where (a) is a top view and (b) is an A-A cross-sectional view of (a). The tray 2 for an insulating film forming apparatus shown in FIG. 2 includes a tray body 21 that constitutes the base of the tray 2, similar to the tray 1 shown in FIG. 1, and both the upper surface 21a and the lower surface 21b of the tray body 21 are flat. The tray body 21 has a cylindrical opening 21c that penetrates from the upper surface 21a to the lower surface 21b. The opening 21c has a cylindrical first portion 21d arranged on the lower surface 21b side of the tray body 21, and a cylindrical second portion 21e arranged on the upper surface 21a side for accommodating a semiconductor wafer. The second portion 21e is defined by a side wall S and a bottom portion B, and the second portion 21e has the same central axis as the central axis of the first portion 21d, and has a diameter larger than the diameter of the first portion 21d. At least a portion of the bottom B, which is the periphery of the first portion 21d, constitutes the support portion 21f.

The tray 2 having this configuration can accommodate the semiconductor wafer on which the insulating film is formed in the second portion 21e, and can better hold the semiconductor wafer and align the semiconductor wafer.

The diameter of the second portion 21e of the tray body 21 depends on the diameter of the semiconductor wafer to be stored, but is preferably larger than the diameter of the semiconductor wafer, and the difference between the diameter of the second portion 21e and the diameter of the semiconductor wafer is preferably 2 mm or more and 6 mm or less. This allows the semiconductor wafer to be held in a more aligned state and in a better condition. In addition, the depth of the second portion 21e is preferably designed so that the depth of the first portion 21d is 1 mm or more and 2 mm or less. This allows the semiconductor wafer to be held in a better condition.

The rest of the configuration of tray 2 can be the same as tray 1 shown in Figure 1.

When a semiconductor wafer is placed on a tray 2 having such a configuration, the back side of the wafer, on which the insulating film is formed, is placed in the second part 21e with the back side facing downward, and the semiconductor wafer is placed so that the outer periphery of the wafer is supported by the support part 21f on the periphery of the first part 21d. As a result, the upper surface of the support part 21f of the tray body 21 comes into surface contact with the outer periphery of the back side of the semiconductor wafer, and the outer periphery of the wafer is masked by the support part 21f.

When the source gas for the insulating film is supplied from below the tray 2 on which the semiconductor wafer is placed, the source gas is supplied only to the area of the back surface of the wafer exposed by the first portion 21d, and is not supplied to the outer periphery of the wafer. As a result, an insulating film can be formed only on the back surface of the wafer, without forming an insulating film on the outer periphery of the wafer.

Figure 3 shows another example of a tray for an insulating film forming apparatus according to the present invention, where (a) is a cross-sectional view, and (b) and (c) are diagrams showing the relationship between the width of the annular member and the area where the insulating film is not formed. In the tray 3 shown in Figure 3, an annular member 22 having an inner diameter smaller than the diameter of the opening 21c (i.e., the diameter of the first portion 21d) on the lower surface 21b of the tray body 21 is placed on the support portion 21f of the tray 2 shown in Figure 2. Both the upper surface 22a and the lower surface 22b of the annular member 22 are flat. In the tray 3 shown in Figure 3, the diameter of the first portion 21d is configured to be smaller than the diameter of the semiconductor wafer W, but as long as the inner diameter of the annular member 22 is configured to be smaller than the diameter of the semiconductor wafer W, the diameter of the first portion 21d may be configured to be the same as or larger than the diameter of the semiconductor wafer W.

When a semiconductor wafer is placed on a tray 3 having such a configuration, the back side of the wafer is placed on the annular member 22 by placing it in the second part 21e with the back side facing downward. Then, the upper surface 22a of the annular member 22 comes into surface contact with the outer periphery of the back side of the semiconductor wafer.

When the insulating film source gas is supplied from below the tray 3, the inner diameter of the annular member 22 is smaller than the diameter of the first portion 21d, so the outer periphery of the wafer is masked by the annular member 22, and the source gas is supplied only to the area of the wafer back surface exposed by the opening 22c of the annular member 22. As a result, an insulating film can be formed only on the wafer back surface, without forming an insulating film on the wafer outer periphery.

Since the inner diameter of the annular member 22 is smaller than the diameter of the first portion 21d of the tray body 21, the size of the area where the insulating film is formed on the back surface of the semiconductor wafer can be easily changed by changing the inner diameter of the annular member 22. Specifically, as shown in FIG. 3(b), when the diameter of the opening 22c of the annular member 22 (i.e., the inner diameter of the annular member 22) is relatively large, the area where the insulating film is not formed is small. On the other hand, as shown in FIG. 3(c), when the diameter of the opening 22c of the annular member 22 (i.e., the inner diameter of the annular member 22) is relatively small, the area where the insulating film is not formed is large.

The inner diameter of the annular member 22 can be appropriately set according to the region in which the insulating film is to be formed, and is not particularly limited. On the other hand, it is preferable that the outer diameter of the annular member 22 is 2 mm or more smaller than the diameter of the second portion 21e and 1 mm or more larger than the diameter of the first portion 21d.

The annular member 22 is preferably made of a material that is heat-resistant and resistant to deformation at the temperatures used to form the insulating film, and that does not contaminate the semiconductor wafer. For example, the annular member 22 can be made of sintered silicon carbide, or sintered silicon carbide whose surface is coated with a silicon carbide film.

The tray 3 shown in FIG. 3 is configured as a tray in which the annular member 22 is placed on the support portion 21d of the tray 2 shown in FIG. 2, but it can also be configured as a tray in which the annular member 22 is placed on the support portion 14 of the tray 1 shown in FIG. 1. In this case, if the inner diameter of the annular member 22 is configured to be smaller than the diameter of the semiconductor wafer W, the diameter of the opening 11c does not need to be smaller than the diameter of the semiconductor wafer W, and may be configured to be the same as or larger than the diameter of the semiconductor wafer W.

(Insulating film forming device)
The insulating film forming apparatus according to the present invention is an apparatus for forming an insulating film on the back surface of a semiconductor wafer, and is characterized by comprising: a tray for the insulating film forming apparatus according to the present invention described above; a raw material gas supply unit arranged below the tray for supplying a raw material gas for the insulating film through the opening of the tray toward the back surface of the semiconductor wafer placed on the tray; and a heater arranged above the tray for heating the semiconductor wafer.

Figure 4 shows a preferred example of an insulating film forming apparatus according to the present invention. The insulating film forming apparatus 100 shown in Figure 4 includes a tray 2, a raw material gas supply unit 4, an inert gas supply unit 5, and a heater 6.

The tray 2 is the tray 2 according to the present invention shown in FIG. 2, and details thereof have already been explained, so they will be omitted. A conveying roller 2a is provided at the bottom of the tray 2 so that the tray 2 can be conveyed.

The source gas supply unit 4 is disposed below the tray 2, and supplies the source gas for the insulating film through an opening 21c (first portion 21d) of the tray 2 toward the rear surface of the semiconductor wafer W placed on the tray 2. In the example shown in Fig. 4, the unit is configured to supply silane ( _SiH4 ) and oxygen gas ( _O2 ), which are source gases for forming a silicon oxide film, but it may also be configured to supply other source gases to form other insulating films, such as a nitride film.

As shown in FIG. 4, the raw material gas supply unit 4 is preferably configured to supply an inert gas such as nitrogen or a rare gas so as to surround the raw material gas in order to reduce the inclusion of impurities in the raw material gas.

The heater 6 is disposed above the tray 2 and heats the semiconductor wafer W to a temperature at which the source gas supplied to the rear surface of the semiconductor wafer W is decomposed and an insulating film is formed on the rear surface of the semiconductor wafer W.

As shown in FIG. 4, it is preferable to provide an inert gas supply unit 5 that is disposed above the tray 2 and below the heater 6 and supplies an inert gas toward the front surface of the semiconductor wafer W placed on the tray 2. This makes it possible to prevent the semiconductor wafer W from floating up even when the semiconductor wafer W is pressed downward during the formation of the insulating film and the raw material gas is supplied to the rear surface of the semiconductor wafer W by the raw material gas supply unit 4.

The operation of the insulating film forming apparatus 100 will now be described. First, the semiconductor wafer W is placed in the second part 21e on the tray 2 with the back side on which the insulating film is to be formed facing downwards, and the first part 21d is closed and the semiconductor wafer is placed so that the outer periphery is supported by the support part 21f on the periphery of the first part 21d.

Then, the tray 2 is placed above the raw material gas supply unit 4 and below the inert gas supply unit 5. Next, the semiconductor wafer W is heated to a predetermined temperature by the heater 6, and then, while supplying an inert gas from the inert gas supply unit 5, the raw material gas for the insulating film is supplied from the raw material gas supply unit toward the rear surface of the semiconductor wafer W through the opening 21c (first portion 21d) of the tray 2. In this way, an insulating film can be formed on the rear surface of the semiconductor wafer W without forming an insulating film on the outer periphery of the semiconductor wafer W.

The insulating film forming apparatus 100 is preferably configured to include a plurality of trays 2 and to transport the plurality of trays 2 continuously between the raw material gas supply unit 4 and the inert gas supply unit 5. This allows the insulating film to be formed continuously on a plurality of semiconductor wafers W.

(Method of forming insulating film)
The insulating film forming method according to the present invention is characterized in that a semiconductor wafer is placed on the tray for the insulating film forming apparatus according to the present invention described above, and then the semiconductor wafer is disposed between a raw material gas supply unit and a heater. After that, while the semiconductor wafer is heated to a predetermined temperature by the heater, a raw material gas for the insulating film is supplied from the raw material gas supply unit to form an insulating film on the back surface of the semiconductor wafer.

Below, an example of the insulating film forming method according to the present invention will be described using the preferred insulating film forming apparatus 100 according to the present invention shown in Figure 4 as an example. First, the semiconductor wafer W is placed in the second part 21e on the tray 2 with the back side on which the insulating film is to be formed facing downward, and the first part 21d is closed and the semiconductor wafer is placed so that the outer periphery is supported by the support part 21f on the periphery of the first part 21d.

The semiconductor wafer W is not particularly limited and may be a silicon wafer, a germanium wafer, a silicon carbide wafer, a gallium arsenide wafer, or the like. In particular, a silicon wafer can be suitably used as the semiconductor wafer W.

The insulating film is not particularly limited, but can be an oxide film, a nitride film, or the like. For example, in the case of an epitaxial silicon wafer in which a silicon epitaxial layer is formed on a silicon wafer, the oxide film can be a silicon oxide film or a silicon nitride film.

Then, the tray 1 is placed above the raw gas supply section 4 and below the inert gas supply section 5.

Then, the heater 6 heats the semiconductor wafer W to a predetermined temperature, and then the inert gas is supplied from the inert gas supply unit 5 while the raw material gas for the insulating film is supplied from the raw material gas supply unit 4 through the opening 21c (first portion 21d) of the tray 2 toward the rear surface of the semiconductor wafer W. The temperature of the semiconductor wafer during the formation of the insulating film depends on the type of insulating film to be formed, but for example, when a silicon oxide film is formed on the rear surface of a silicon wafer, it is preferably set to 380°C or higher and 460°C or lower.

The source gas supplied from the source gas supply unit 4 can be an appropriate gas depending on the source material of the insulating film. For example, when the insulating film is a silicon oxide film, the source gas can be _SiH4 gas and _O2 gas. When the insulating film is a silicon nitride film, the source gas can be _SiH4 gas and _N2 gas or ammonia ( _NH3 ) gas.

The inert gas supplied from the inert gas supply unit 5 may be _N2 gas, a rare gas, or the like.

In this way, an insulating film can be formed on the back surface of the semiconductor wafer W without forming an insulating film on the outer periphery of the semiconductor wafer W.

The following describes examples of the present invention, but the present invention is not limited to these examples.

(Example of the Invention)
A silicon oxide film was formed only on the back surface of a silicon wafer using the insulating film forming apparatus 100 shown in Fig. 4 equipped with the tray 2 shown in Fig. 2. The detailed dimensions of the tray 2 are shown in Figs. 5(a) and (b).

Specifically, a silicon wafer with a diameter of 200 mm was first prepared and placed in the second part 21e with the back side on which the insulating film was to be formed facing downwards, and the first part 21d was closed and the outer periphery of the silicon wafer was supported by the support part 21f on the periphery of the first part 21d.

Then, the tray 2 was placed above the raw material gas supply unit 4 and below the inert gas supply unit 5 of the insulating film forming apparatus 100.

Next, the silicon wafer was heated to 450° C. by the heater 6 and maintained at that temperature, and _N2 gas was supplied from the inert gas supply unit 5 while _SiH4 gas and _O2 gas were supplied from the raw material gas supply unit 4. In this way, a silicon oxide film was formed on the back surface of the silicon wafer only in an area 196 mm in diameter from the center.

(Conventional example)
A silicon oxide film was formed on the back surface of the silicon wafer in the same manner as in Example 1. However, the silicon oxide film was formed using the apparatus described in Patent Document 1, and as a result, the silicon oxide film was formed on the back surface and the outer periphery of the silicon wafer.

<Evaluation of oxide film thickness>
The thickness of the oxide film formed on the silicon wafers of the invention and the conventional example was measured. Specifically, using a film thickness measuring device (Nanospec 8000XSE, manufactured by NANOMETRICS), the thickness of the oxide film was measured at the center of the back surface of the wafer, at a position 50 mm from the center of the back surface in the wafer radial direction, and at a position 99 mm from the center of the back surface in the wafer radial direction, as shown in Fig. 5(c). The obtained measurement results are shown in Fig. 6.

As is clear from Figure 6, in the conventional example, an oxide film with a thickness of about 3,500 Å is formed over the entire silicon wafer. On the other hand, in the inventive example, the thickness of the oxide film at a position 99 mm from the center is zero, and it can be seen that an oxide film is formed only on the back surface of the wafer, without forming an oxide film on the outer periphery of the wafer.

The present invention is useful in the semiconductor wafer manufacturing industry because it allows an insulating film to be formed only on the back surface of a wafer without forming an insulating film on the outer periphery of the wafer.

Reference Signs List 1, 2, 3 Tray 2a Transport roller 4 Raw material gas supply section 5 Inert gas supply section 6 Heater 11, 21 Tray body 11a, 21a Upper surface 11b, 21b Lower surface 11c, 21c Opening 11d, 21f Support section 21d First portion 21e Second portion 22 Annular member 21a Upper surface 21b of annular member Lower surface 21c of annular member Opening B of annular member Bottom portion S Side wall W Semiconductor wafer

Claims (9)

A tray for placing a semiconductor wafer in an insulating film forming apparatus for forming an insulating film on a back surface of a semiconductor wafer, comprising:
A tray body for placing a semiconductor wafer thereon ,
The tray body includes:
A cylindrical opening extending from the upper surface to the lower surface of the tray body;
a ring-shaped support portion located on the periphery of the opening portion and supporting an outer periphery of the semiconductor wafer;
A tray body having
an annular member disposed on the support portion of the tray body, the entire upper surface of the annular member being located within one plane, and the annular member having an inner diameter smaller than a diameter of the opening at the lower surface of the tray body;
The tray for an insulating film forming apparatus , wherein the support portion supports an outer periphery of the semiconductor wafer via the annular member . The tray for an insulating film forming apparatus according to claim 1, wherein the opening has a cylindrical first portion disposed on the lower surface side of the tray body and a cylindrical second portion disposed on the upper surface side for accommodating a semiconductor wafer, the second portion having the same central axis as the central axis of the first portion of the tray body and a diameter larger than that of the first portion, and the periphery of the first portion constitutes the support portion. An apparatus for forming an insulating film on a back surface of a semiconductor wafer, comprising:
A tray according to claim 1 or 2 ;
a source gas supply unit disposed below the tray and configured to supply a source gas for the insulating film toward a rear surface of the semiconductor wafer placed on the tray through the opening of the tray;
a heater disposed above the tray for heating the semiconductor wafer;
An insulating film forming apparatus comprising: 4. The insulating film forming apparatus according to claim 3 , further comprising an inert gas supply unit disposed above the tray and below the heater, for supplying an inert gas toward a front surface of the semiconductor wafer placed on the tray. A plurality of the trays are provided,
5. The insulating film forming apparatus according to claim 4, wherein the plurality of trays are continuously transported between the raw material gas supply unit and the inert gas supply unit so that the insulating film can be continuously formed on a plurality of semiconductor wafers. 6. An insulating film forming method comprising the steps of: placing a semiconductor wafer on the tray of the insulating film forming apparatus according to claim 3 ; arranging the semiconductor wafer between the raw material gas supply unit and the heater; and, while the semiconductor wafer is heated to a predetermined temperature by the heater, supplying a raw material gas for the insulating film from the raw material gas supply unit to form an insulating film on a back surface of the semiconductor wafer. 6. The insulating film forming method according to claim 5, which relies on claim 5, comprising the steps of: placing a semiconductor wafer on the tray of the insulating film forming apparatus according to claim 4 or 5 ; arranging the semiconductor wafer between the raw material gas supply unit and the inert gas supply unit; and, in a state in which the semiconductor wafer is heated to a predetermined temperature by the heater, supplying an inert gas from the inert gas supply unit toward the front surface of the semiconductor wafer while supplying a raw material gas for the insulating film from the raw material gas supply unit, thereby forming an insulating film on the back surface of the semiconductor wafer . 8. The method for forming an insulating film according to claim 6 , wherein the semiconductor wafer is a silicon wafer. The insulating film forming method according to claim 6 , wherein the insulating film is an oxide film.

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