JP6662571B2 - Epitaxial growth apparatus and epitaxial growth method - Google Patents

Description

  The present invention relates to an epitaxial growth apparatus and an epitaxial growth method, and more particularly, to an apparatus and a method for growing an epitaxial film on a surface of a circular substrate such as a silicon wafer.

  FIG. 1 is a sectional view of a conventional epitaxial growth apparatus. The epitaxial growth apparatus 21 includes a chamber 22 for receiving a silicon wafer W and growing an epitaxial film on the surface of the silicon wafer W, and a susceptor 23 disposed in the chamber 22 and supporting the silicon wafer W substantially horizontally. It has. The chamber 22 includes a top plate 29, and a lower surface of the top plate 29 forms a ceiling surface 29 a of the chamber 22. On the upper surface 23a of the susceptor 23, a concave portion 23c having substantially the same size as the silicon wafer W is formed.

When growing an epitaxial film on the surface of the silicon wafer W, the silicon wafer W is accommodated in the recess 23 c of the susceptor 23. Then, a mixed gas of source gas (for example, trichlorosilane (TCS)) and carrier gas (for example, H ₂ gas) (hereinafter referred to as “raw material mixed gas”) is supplied between silicon wafer W and ceiling surface 29a. Pour into the space.

  The raw material mixed gas is introduced into the chamber 22 from the raw material inlet 33a formed on the side of the chamber 22, passes over the silicon wafer W, and is formed on the side of the chamber 22 opposite the raw material inlet 33a. The raw material is discharged from the inside of the chamber 22 through the raw material discharge port 34a. In FIG. 1, the main direction in which the raw material mixed gas flows is indicated by black arrows.

  Next, the silicon wafer W is heated by a heater (not shown). Thereby, Si contained in the raw material mixed gas is supplied to the surface (upper surface) Wa of the silicon wafer W, and an epitaxial film is formed.

  In order to make the characteristics of the device manufactured from the silicon wafer W on which the epitaxial film is formed constant, it is necessary that the film thickness of the epitaxial film is uniform.

  Patent Literature 1 discloses a semiconductor vapor deposition apparatus including a plate-shaped susceptor on which a plurality of substrates are arranged and rotated. The plurality of substrates are arranged along the circumferential direction of the susceptor, and the lower surface, which is the growth surface of the substrate supported by the susceptor, faces the gas flow path. In this state, a source gas is flowed in the diameter direction of the susceptor, and the substrate is heated to epitaxially grow a semiconductor crystal on the substrate.

  Patent Literature 1 states that an epitaxial film having extremely high in-plane uniformity of the film thickness can be obtained by setting the crystal growth surface of the substrate at an angle to the flow direction of the source gas.

JP 2004-207545 A

  However, only by tilting the crystal growth surface of the substrate with respect to the flow direction of the source gas, a region having a small thickness is formed in the epitaxial film formed near the center of the susceptor, and the thickness of the epitaxial film is not sufficient. Become uniform. Further, since the apparatus of Patent Document 1 is of a batch type in which a plurality of substrates are processed at the same time, the uniformity of film thickness is controlled as compared with a single-wafer type apparatus in which substrates are processed one by one. hard.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide an apparatus and a method capable of growing an epitaxial film with improved thickness uniformity.

The gist of the present invention is the following epitaxial growth apparatus (1) and the following epitaxial growth method (2).
(1) a chamber for accommodating a circular substrate and growing an epitaxial film on the surface of the substrate;
A susceptor disposed in the chamber and supporting the substrate on an upper surface;
With
A gas inlet port for introducing a source gas into the chamber and a gas exhaust port for exhausting the source gas introduced into the chamber are provided at inner wall surfaces of the chamber at positions facing each other with the substrate interposed therebetween. And an exit is formed,
A ceiling surface, which is a lower surface of the ceiling constituting the chamber, is concave upward at an arbitrary cross section orthogonal to a facing direction of the gas inlet and the gas outlet,
In any cross section along the direction in which the gas inlet and the gas outlet face each other, the substrate is orthogonal to the substrate at a processing position when growing an epitaxial film on the surface of the substrate supported by the susceptor. distance between the surface and the ceiling surface of, over the entire opposing portion of the substrate and the ceiling surface, Ri a smaller toward from the gas inlet side to the gas outlet side,
Maximum Ru der less than 20 mm, epitaxial growth apparatus of the interval.

(2) A method of growing an epitaxial film on a surface of a circular substrate using the epitaxial growth apparatus according to (1),
Supporting the substrate on the susceptor;
Accommodating a substrate supported on the susceptor in the chamber;
Introducing a source gas into the chamber from the gas inlet, and discharging the source gas in the chamber from the gas outlet,
With the substrate supported on the susceptor is housed in said chamber, at any cross section perpendicular to the opposing direction of the said gas inlet and said gas outlet, said interval, while along the opposing direction An epitaxial growth method, which is largest on a center line passing through the center region of the substrate and becomes smaller as the distance from the center line to the side becomes smaller.

  Using this epitaxial growth apparatus, an epitaxial film with improved thickness uniformity can be grown. Further, by this epitaxial growth method, an epitaxial film having improved thickness uniformity can be grown.

FIG. 1 is a sectional view of a conventional epitaxial growth apparatus. FIG. 2 is a cross-sectional view showing a structure of an epitaxial growth apparatus according to an embodiment of the present invention, showing a cross section orthogonal to a wafer supported on a susceptor along a direction in which a gas inlet and a gas outlet face each other. ing. FIG. 3 is a cross-sectional view of the susceptor and the top plate, and shows a cross section orthogonal to the facing direction of the gas inlet and the gas outlet. FIG. 4 is a diagram illustrating the relationship between the distance from the center of the wafer and the film thickness of each of the epitaxial films obtained by the epitaxial growth apparatuses of Example 1, Example 2, Comparative Example 1, and Comparative Example 2. .

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 2 is a sectional view showing the structure of the epitaxial growth apparatus according to one embodiment of the present invention.

  This epitaxial growth apparatus 1 is for growing an epitaxial film on a surface of a silicon wafer (hereinafter, simply referred to as a “wafer”) W which is a circular substrate in a single-wafer manner. The epitaxial growth apparatus 1 includes a chamber 2 that houses a wafer W. The chamber 2 includes a ring-shaped main body 8, a top plate 9 and a bottom plate 10 attached to the main body 8. A lower surface 9 a of the top plate 9 (hereinafter, referred to as a “ceiling surface”) forms a part of an inner wall surface of the chamber 2.

  Through the bottom plate 10, a bearing 11 is provided substantially along the vertical direction. A through hole is formed in the bearing 11 along the axial direction, and the susceptor support shaft 7 is inserted into the through hole. In the chamber 2, a disk-shaped susceptor 3 is arranged coaxially with a susceptor support shaft 7. At the upper end of the susceptor support shaft 7, a support member 7a that supports the vicinity of the outer periphery of the susceptor 3 is provided. On the upper surface 3a of the susceptor 3, a concave portion 3c having substantially the same size as the wafer W is formed. The bottom surface of the concave portion 3c is a substantially horizontal flat surface.

  The motor 5 is attached to the lower end of the susceptor support shaft 7. The susceptor support shaft 7 can be rotated around its axis by the motor 5, whereby the susceptor 3 and the wafer W supported on the susceptor 3 can be rotated around its axis.

  Further, the epitaxial growth apparatus 1 includes a plurality of infrared lamps 4 above and below the chamber 2. The top plate 9, the bottom plate 10, and the support portion 7a are made of a material that transmits infrared rays, for example, quartz. Therefore, the susceptor 3 and the wafer W mounted on the susceptor 3 can be heated from above and below by the infrared lamp 4.

On the inner wall surface of the chamber 2, a gas inlet 13a and a gas outlet 14a are formed at positions facing each other with the wafer W interposed therebetween. A source gas (for example, trichlorosilane (TCS)) serving as a raw material for growing an epitaxial film can be introduced into the chamber 2 through the gas inlet 13a. The source gas is introduced as a mixed gas with a carrier gas (for example, H ₂ gas) (hereinafter, referred to as “raw material mixed gas”). The raw material mixed gas can be discharged from the chamber 2 through the gas discharge port 14a.

  FIG. 2 shows a cross section orthogonal to the wafer W supported on the susceptor 3 along the direction in which the gas inlet 13a and the gas outlet 14a face each other (hereinafter, referred to as “opening facing direction”). In this cross section, the distance D between the front surface Wa of the wafer W and the ceiling surface 9a of the chamber 2 becomes smaller from the gas inlet 13a to the gas outlet 14a. This relationship for the spacing D holds for any cross section parallel to the cross section of FIG. In this embodiment, a ceiling surface 9a in a cross section orthogonal to the wafer W supported on the susceptor 3 along the opening facing direction is substantially flat.

  The maximum value of the interval D, that is, the interval D in the portion closest to the gas inlet 13a is less than 20 mm and 5 mm or more. The minimum value of the interval D, that is, the interval D at the portion closest to the gas outlet 14a is smaller than the maximum value of the interval D by, for example, 2 to 8 mm.

  FIG. 3 is a cross-sectional view of the susceptor 3 and the top plate 9 and shows a cross section orthogonal to the opening facing direction.

  In this cross section, the ceiling surface 9a is bent convexly upward, that is, concave upward. The distance D between the front surface Wa of the wafer W supported on the susceptor 3 and the ceiling surface 9a of the chamber 2 is determined by a center line passing through the center region of the wafer W along the opening facing direction (see FIG. .).), And decreases as the distance from the center line C to the side. Here, the “center region of the wafer W” includes a circular region within a radius of 20% of the radius of the wafer W with respect to the center of the wafer W.

  Next, a method for growing an epitaxial film using the epitaxial growth apparatus of the present invention will be described.

  First, the wafer W is placed on the susceptor 3. More specifically, the wafer W is accommodated in the recess 3c of the susceptor 3 so that the wafer W is supported on the susceptor 3 substantially horizontally. Subsequently, the susceptor support shaft 7 is rotationally driven by the motor 5 to rotate the susceptor 3 and the wafer W. Then, in this state, the raw material mixed gas is introduced into the chamber 2 from the gas inlet 13a. The raw material mixed gas flows through the space S between the wafer W and the ceiling surface 9a, and is discharged out of the chamber 2 via the gas discharge port 14a. In FIG. 2, the main direction in which the raw material mixed gas flows is indicated by black arrows.

  Then, the wafer W is heated to a predetermined temperature by the infrared lamp 4 while the introduction and discharge of the raw material mixed gas are continued. As a result, Si generated by thermal decomposition or reduction of the source gas contained in the raw material mixed gas precipitates on the surface Wa of the wafer W, and an epitaxial film grows.

  In the conventional epitaxial growth apparatus 21 (see FIG. 1), the distance D between the surface Wa of the wafer W placed on the susceptor 23 and the ceiling surface 29a of the chamber 22 is constant at any position on the wafer W. Yes, for example, 20 mm. On the other hand, in the epitaxial growth apparatus 1 according to the embodiment of the present invention, as described above, the interval D is less than 20 mm, that is, smaller than the conventional epitaxial growth apparatus.

  Thus, when the flow rate (volume velocity) and concentration of the raw material mixed gas on the wafer W are the same, when the epitaxial growth apparatus 1 is used, the wafer W is smaller than when the conventional epitaxial growth apparatus 21 is used. The flow velocity (linear velocity) of the raw material mixed gas above becomes large. Therefore, when the epitaxial growth apparatus 1 is used, the growth rate of the epitaxial film can be increased as compared with the case where the conventional epitaxial growth apparatus 21 is used. In other words, the time required for growing an epitaxial film having a constant thickness can be reduced. When the epitaxial growth apparatus 1 is used, the growth rate of the epitaxial film can be increased without increasing the concentration of the source gas in the raw material mixed gas and without increasing the flow rate of the mixed gas.

  As described above, in the epitaxial growth apparatus 1, the interval D is 5 mm or more. If the maximum value of the interval D is less than 5 mm, the flow of the mixed gas cannot be controlled, and the film thickness distribution becomes uneven.

  The present inventors have found that in the conventional epitaxial growth apparatus 21, when the interval D is reduced while the interval D is kept constant at any position on the wafer W, the unevenness of the thickness of the epitaxial film becomes remarkable. I learned. As the film thickness is non-uniform, specifically, the film thickness is smallest at the center of the wafer W, and increases as the distance from the center increases.

  Further, the present inventors obtained the velocity distribution of the source gas in the chamber 2 by simulation under the condition that the thickness of the epitaxial film becomes non-uniform as described above. As a result, it has been found that the velocity of the raw material gas becomes the smallest near the line connecting the center of the raw material inlet 33a and the center of the raw material outlet 34a, and becomes larger away from this part. This tendency becomes more remarkable as the interval D becomes smaller. It is considered that this is because the raw material mixed gas introduced from the gas inlet 13a spreads laterally and flows easily.

  As shown in FIG. 3, the present inventors set the distance D between the surface Wa of the wafer W and the ceiling surface 9a of the chamber 2 to be the largest on the center line C of the wafer W in a cross section orthogonal to the opening facing direction. In addition, it has been found that when the distance from the center line C is reduced toward the side, unevenness in the thickness of the epitaxial film can be reduced or eliminated. This is because, as compared with the case where the interval D is constant at any position on the wafer W, the larger the interval D, the easier the material mixture gas flows, and the variation in the flow rate of the material mixture gas on the wafer W becomes smaller. It is thought that this is because it becomes smaller.

  The cross-sectional shape can be defined, for example, by the difference ΔD between the maximum interval and the minimum interval among the intervals D in the cross section. When the diameter of the wafer W is about 200 mm, ΔD can be, for example, 2 to 6 mm. The ceiling surface 9a may not be a single concave curved surface as a whole, but may be, for example, substantially two flat surfaces.

  Further, the present inventors have found that the growth rate of the epitaxial film is reduced on the downstream side of the flow of the raw material mixed gas. In the epitaxial growth apparatus 1, as described above, the distance D decreases from the gas inlet 13a toward the gas outlet 14a. As a result, the flow rate of the raw material mixed gas increases toward the downstream side of the flow of the source gas. Therefore, by appropriately selecting the distribution of the interval D along the opening facing direction, for example, the inclination of the ceiling surface 9a with respect to the surface Wa of the wafer W, the unevenness of the growth rate of the epitaxial film along the opening facing direction can be reduced or Can be eliminated.

  As shown in FIGS. 2 and 3, in the above embodiment, the thickness of the top plate 9 is substantially constant, but as long as the ceiling surface 9 a is recessed upward, the thickness of the top plate 9 is 9 may be changed depending on the in-plane position. For example, the ceiling surface 9a may be recessed upward when the top surface of the top plate 9 is flat and the thickness of the top plate 9 changes depending on the in-plane position of the top plate 9.

  In order to confirm the effect of the present invention, an epitaxial film growth test was performed on a silicon wafer using various chambers.

  As the epitaxial growth apparatus according to the first embodiment of the present invention, an apparatus having a structure shown in FIGS. 2 and 3 and having a ceiling surface 9a that can be regarded as consisting of two flat surfaces was used. In this apparatus, the maximum value of the height D is 12 mm, the height difference ΔD in a cross section orthogonal to the opening facing direction is 4 mm, and the height D is orthogonal to the wafer W supported on the susceptor 3 along the opening facing direction. The difference in height D in the cross section was 4 mm. With this apparatus, an epitaxial film was grown on a wafer W having a diameter of about 200 mm.

Trichlorosilane was used as a source gas, H ₂ was used as a carrier gas, and a raw material mixed gas of trichlorosilane and H ₂ was introduced into the space S from the gas inlet 13a at a flow rate of 36 slm.

  Then, the wafer W accommodated in the recess 3 c of the susceptor 3 is rotated at 30 to 50 rpm by the motor 5 via the susceptor support shaft 7 and the susceptor 3, and the wafer W is heated to 1000 to 1150 ° C. by the infrared lamp 4. And held for 1-2 minutes. Thus, an epitaxial film was formed on the surface Wa of the wafer W.

  Example 1 Example 1 of an epitaxial growth apparatus according to Example 2 of the present invention, except that the difference in height D of the ceiling surface 9a in a cross section orthogonal to the wafer W supported on the susceptor 3 along the opening opposing direction was 0 mm. An epitaxial film was grown on the wafer W using the same apparatus as that used in the above. Except for the structure of the epitaxial growth apparatus used, the film forming conditions were the same as in the case of using the apparatus of Example 1 of the present invention.

  As an epitaxial growth apparatus of Comparative Example 1, an apparatus having the structure shown in FIG. 1 and having a distance D of 20 mm (a height difference ΔD is substantially 0) in any part on the wafer W was used. An epitaxial film was grown thereon. Except for the structure of the epitaxial growth apparatus used, the film forming conditions were the same as in the case of using the apparatus of Example 1 of the present invention.

  As an epitaxial growth apparatus of Comparative Example 2, a wafer having a structure shown in FIG. 1 and having an interval D of 10 mm (a height difference ΔD is substantially 0) in any portion on the wafer W was used. An epitaxial film was grown on W. Except for the structure of the epitaxial growth apparatus used, the film forming conditions were the same as in the case of using the apparatus of Example 1 of the present invention.

  FIG. 4 is a diagram showing the relationship between the distance from the center of the wafer and the film thickness of each of the epitaxial films obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 2. The film thickness was measured using an infrared spectrophotometer (FT-IR).

When the apparatus of Comparative Example 1 was used, the thickness of the obtained epitaxial film was approximately 3.8 μm, which was almost uniform. When the apparatus of Comparative Example 2 was used, the thickness of the obtained epitaxial film was larger than that when the apparatus of Comparative Example 1 was used. However, the thickness of this epitaxial film was small at the center of the wafer and increased toward the outer periphery of the wafer. This is considered to be due to the following reasons (a) and (b).
(A) Due to the smaller spacing D in the apparatus of Comparative Example 2 compared to the apparatus of Comparative Example 1, the flow rate of the raw material mixed gas decreases on the center line C of the wafer W along the opening facing direction. The larger the distance from the center line C, the larger it became.
(B) In the apparatus of Comparative Example 2, the growth rate of the epitaxial film was significantly lower on the downstream side in the opening facing direction than in the apparatus of Comparative Example 1.

  On the other hand, when the devices of Examples 1 and 2 of the present invention were used, the thickness of the obtained epitaxial film was larger than that when the devices of Comparative Examples 1 and 2 were used. Was approximately 4.7 to 4.8 μm. Further, the film thickness was almost uniform. That is, it was confirmed that even when the film thickness was increased, an epitaxial film with improved film thickness uniformity could be grown by using the apparatuses of Examples 1 and 2.

  When the apparatus of Example 1 was used, the uniformity of the film thickness was improved as compared with the case where the apparatus of Example 2 was used. That is, at an arbitrary cross section orthogonal to the wafer W along the opening facing direction, the distance between the surface of the wafer W and the ceiling surface 9a is reduced from the gas inlet 13a toward the gas outlet 14a. It was confirmed that the uniformity of the film thickness could be improved.

1: epitaxial growth apparatus, 2: chamber, 3: susceptor,
9a: ceiling surface, 13a: gas inlet, 14a: gas outlet,
W: silicon wafer, Wa: surface of silicon wafer,
C: Center line of silicon wafer

Claims (2)

A chamber for accommodating a circular substrate and growing an epitaxial film on the surface of the substrate;
A susceptor disposed in the chamber and supporting the substrate on an upper surface;
With
A gas inlet for introducing a source gas into the chamber and a gas exhaust for exhausting the source gas introduced into the chamber are provided on the inner wall surface of the chamber at positions facing each other with the substrate interposed therebetween. And an exit is formed,
A ceiling surface that is a lower surface of the ceiling configuring the chamber is upwardly concave in an arbitrary cross section orthogonal to a facing direction of the gas inlet and the gas outlet,
In any cross section along the direction in which the gas inlet and the gas outlet are opposed to each other while being perpendicular to the substrate at a processing position when growing an epitaxial film on the surface of the substrate supported by the susceptor, the substrate distance between the surface and the ceiling surface of, over the entire opposing portion of the substrate and the ceiling surface, Ri a smaller toward from the gas inlet side to the gas outlet side,
Maximum Ru der less than 20 mm, epitaxial growth apparatus of the interval. A method for growing an epitaxial film on a surface of a circular substrate by using the epitaxial growth apparatus according to claim 1,
Supporting the substrate on the susceptor;
Accommodating a substrate supported on the susceptor in the chamber;
Introducing a source gas into the chamber from the gas inlet, and discharging the source gas in the chamber from the gas outlet,
In a state in which the substrate supported on the susceptor is housed in the chamber, in any cross section orthogonal to the direction in which the gas inlet and the gas outlet face each other, the interval is set along the facing direction. An epitaxial growth method, which is largest on a center line passing through the center region of the substrate and becomes smaller as the distance from the center line to the side becomes smaller.

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