JP7457486B2 - Method for manufacturing epitaxial wafer - Google Patents

Description

The present invention relates to an epitaxial wafer manufacturing method and an epitaxial wafer.

As semiconductor elements have become more highly integrated in recent years, wafers for cutting-edge devices are required to have a wafer shape that is highly flat all the way to the outermost periphery. Furthermore, depending on the device application, there is an increasing demand for epitaxial wafers with (111) major surfaces in addition to epitaxial wafers with (100) major surfaces (hereinafter referred to as "(100) epitaxial wafers"; the same applies to other surfaces), and therefore a method for manufacturing highly flat (111) epitaxial wafers is becoming important.

What is noteworthy about the flatness of epitaxial wafers is the difference in growth rate caused by changes in the crystal orientation of the wafer. First, the (111) plane of a silicon wafer will be explained. FIG. 1 is an explanatory diagram of the crystal orientation on the surface of a wafer W whose main surface is a (111) plane. As shown in FIG. 1, the crystal orientation of the (111) wafer W repeats the <110> orientation and the <112> orientation at intervals of 30° in the rotation direction with respect to the center of the wafer. Note that the reference numeral 5 in the figure indicates the outer peripheral portion in the <112> crystal direction. In a silicon wafer whose main surface is (111), when the <110> direction from the center to the outer periphery is used as the crystal orientation standard, the growth rate is high in the <112> direction, which is 30° from the crystal orientation standard, and the epitaxial The thickness of the layer increases, and the flatness of the outer periphery deteriorates.

In the conventional epitaxial wafer manufacturing process, the thickness of the epitaxial layer is 2 μm or more, and the reaction temperature for epitaxial growth is generally in the range of 800 to 1150°C. At high temperatures, slips occur and the effects of gas phase reactions of process gas become stronger, making them unsuitable as manufacturing conditions. In addition, the raw material gas concentration is generally in the range of 1 × 10 ^-4 to 1 × 10 ^-2 mol/L, and if the concentration is lower than the above raw material gas concentration, the productivity will decrease due to a decrease in the growth rate. At high concentrations, an increase in epitaxial defects occurs. Therefore, when producing an epitaxial wafer using a silicon wafer as a substrate, film formation is performed within the above reaction temperature and raw material gas concentration ranges.

On the other hand, the difference in growth rate at the wafer periphery caused by a change in crystal orientation also occurs within the above reaction temperature and raw material gas concentration ranges. The difference in growth rate at the wafer periphery caused by a change in crystal orientation is also noticeable in the variation in ΔESFQR, which is one of the indicators of site flatness, in the wafer circumferential direction.

Here, ESFQR (Edge Site Front Least Square Range) is an index of site flatness that focuses on edges where the flatness tends to deteriorate, and is calculated from the reference plane calculated from the thickness distribution by the least squares method. Defined by the maximum and minimum width of deviation. Further, ΔESFQR is defined as the difference in ESFQR before and after epitaxial growth.

In order to reduce the growth rate difference at the wafer periphery caused by changes in crystal orientation, Patent Document 1 recommends that the epitaxial reaction on (100) and (110) wafers be performed at a pressure of up to 2.66×10 ⁴ Pa (200 Torr) or less. By reducing the pressure, (100) and (110) epitaxial wafers with good peripheral flatness are manufactured. In the epitaxial reaction on the (111) wafer, there is a method of shifting the mounting position of the wafer so that the growth rate at the position where facets are generated in the (111) epitaxial growth is reduced, as in Patent Document 2. There were no examples of reducing the growth rate difference by reducing the pressure during the reaction.

JP 2016-100483 Publication Japanese Patent Application Publication No. 2002-261023

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a growth method and an epitaxial wafer for manufacturing a highly flat epitaxial wafer (111) wafer.

The present invention has been made to achieve the above object, and provides an epitaxial wafer in which a silicon layer is epitaxially grown by supplying a process gas containing a silicon-based raw material gas to the surface of a silicon wafer whose main surface is a (111) plane. In the manufacturing method, in epitaxial growth, the reaction temperature is 800 to 1150°C, the concentration of silicon-based raw material gas in the process gas is 1.0 × 10 ^-4 to 1.0 × 10 ^-2 mol/L, Provided is a method for manufacturing an epitaxial wafer in which the internal pressure of a reactor is 1.33×10 ⁴ Pa (100 Torr) or less.

This method makes it possible to produce (111) epitaxial wafers with good peripheral flatness.

At this time, a silicon wafer with a diameter of 300 mm can be used as the silicon wafer.

Using such a silicon wafer, it is possible to manufacture a large diameter (111) epitaxial wafer with high productivity and better peripheral flatness.

In this case, trichlorosilane (TCS), dichlorosilane (DCS), or monosilane can be used as the silicon-based source gas.

This makes it possible to inexpensively manufacture a (111) epitaxial wafer with even better peripheral flatness.

The present invention also provides a silicon epitaxial wafer whose main surface is a (111) plane, in which, when the amount of variation in the wafer circumferential direction of ΔESFQR, which is the difference in site flatness before and after epitaxial growth, is X and the thickness of the epitaxially grown film is T, the ratio of the variation in the wafer circumferential direction of ΔESFQR to the thickness T of the epitaxially grown film (X/T) x 100 is 0.6% or less.

This results in a (111) epitaxial wafer with reduced circumferential variation around the wafer.

As described above, according to the method for manufacturing an epitaxial wafer of the present invention, by reducing the pressure inside the reactor to 1.33×10 ⁴ Pa (100 Torr) or less during epitaxial growth of a (111) wafer, <110> , the difference in growth rate at the edge in the <112> direction is reduced, the variation in the circumferential direction of the wafer is corrected to less than two-thirds of that when grown at normal pressure, and the (111) epitaxial wafer has good peripheral flatness. You can get

FIG. 2 is an explanatory diagram of crystal orientation on a wafer surface whose main surface is a (111) plane. FIG. 1 is a diagram showing an example of a general epitaxial growth apparatus.

As mentioned above, there is a need for a growth method for producing highly flat epitaxial wafers in (111) wafers.

As a result of intensive studies on the above-mentioned problems, the present inventors have discovered an epitaxial wafer method in which a silicon layer is epitaxially grown by supplying a process gas containing a silicon-based raw material gas to the surface of a silicon wafer whose main surface is a (111) plane. In the manufacturing method, in epitaxial growth, the reaction temperature is 800 to 1150°C, the concentration of silicon-based raw material gas in the process gas is 1.0 × 10 ^-4 to 1.0 × 10 ^-2 mol/L, and the reaction is performed. We have completed a method for manufacturing epitaxial wafers that reduces the internal pressure of the furnace to 1.33×10 ⁴ Pa (100 Torr) or less. This manufacturing method reduces the growth rate difference between the edges in the <110> and <112> directions, corrects the variation in the circumferential direction of the wafer to less than two-thirds of that when grown under normal pressure, and improves the peripheral flatness. A (111) epitaxial wafer with good quality was completed.

The present invention will be described in detail below with reference to the drawings, but the present invention is not limited thereto.

The (111) plane of the present invention includes a plane that is substantially equivalent to this, and includes, for example, not only a (111) plane with a just angle, but also a plane with a desired off angle.

As the (111) wafer W of the present invention, a silicon wafer whose main surface is a (111) plane is used.

Epitaxial growth will be explained with reference to FIG. FIG. 2 is a diagram showing an example of a general epitaxial growth apparatus. The epitaxial growth apparatus 10 includes a reaction furnace (reaction chamber) 11 and a process gas supply section 12 for performing epitaxial growth. Note that the structure of the epitaxial growth apparatus 10 is not particularly limited. A process gas is supplied from the process gas supply section 12, and epitaxial growth can be performed on the (111) wafer W whose temperature has been adjusted.

In epitaxial growth, when the reaction temperature of the (111) wafer W is lower than 800° C., epitaxial defects increase. On the other hand, at temperatures higher than 1150° C., the effects of slip generation and gas phase reactions of the process gas become stronger. Therefore, in epitaxial growth, the reaction temperature is set at 900 to 1150°C.

The process gas according to the present invention contains a silicon-based source gas, a carrier gas, a dopant, and the like, and is capable of epitaxial growth of silicon. If the concentration of the silicon-based source gas in the process gas is lower than 1.0×10 ⁻⁴ mol/L, the productivity decreases due to a decrease in growth rate. If the concentration is higher than 1.0×10 ⁻² mol/L, epitaxial defects increase. Therefore, the concentration of the silicon-based source gas in the process gas is set to 1.0×10 ⁻⁴ to 1.0×10 ⁻² mol/L.

Further, during the epitaxial reaction, the pressure inside the reactor is set to 1.33×10 ⁴ Pa (100 Torr) or less. This reduces the growth rate difference between the edges in the <110> and <112> directions, corrects the variation in the circumferential direction of the wafer to less than two-thirds of that when grown under normal pressure, and improves the peripheral flatness. (111) epitaxial wafers can be manufactured. Further, the lower limit of the internal pressure of the reactor is not particularly limited, but it is preferably 1.33×10 ² Pa (1 Torr) or higher. It takes a long time to reduce the pressure to less than 1.33×10 ² Pa (1 Torr), which leads to a decrease in productivity.

As the silicon wafer whose main surface is the (111) plane, a silicon wafer with a diameter of 300 mm can be suitably used. By using such a silicon wafer, it is possible to manufacture a (111) epitaxial wafer with high productivity and a large diameter but with better peripheral flatness.

As the silicon-based raw material gas, trichlorosilane (TCS), dichlorosilane (DCS), or monosilane can be suitably used. By using these compounds, it becomes possible to manufacture (111) epitaxial wafers with even better peripheral flatness at low cost.

The epitaxial wafer obtained by the present invention is a silicon epitaxial wafer whose main surface is a (111) plane, and when the variation in the wafer circumferential direction of ΔESFQR, which is the difference in site flatness before and after epitaxial growth, is X and the thickness of the epitaxially grown film is T, the ratio of the variation in the wafer circumferential direction of ΔESFQR to the thickness T of the epitaxially grown film (X/T) x 100 is 0.6% or less.

The above-mentioned epitaxial wafer is a (111) epitaxial wafer with good circumferential flatness, and the variation in the circumferential direction of the wafer has been corrected to two-thirds or less of that when grown at normal pressure.

The following description will be made with reference to Examples and Comparative Examples.

(Example 1)
As the silicon wafer to be evaluated, a (111) silicon wafer having a diameter of 300 mm and having a polished surface with a mirror finish was used. In a single-wafer epitaxial growth apparatus, trichlorosilane (TCS) was used as a reaction gas, the gas concentration of the reaction gas was 9.4×10 ⁻⁴ mol/L, the reaction temperature was 1080°C, and the furnace pressure was 6.66×10 ³ Pa. (50 Torr) and epitaxial film formation was performed. When we measured the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation using Wafer-Sight2 (manufactured by KLA Tencor), we found that there was a variation in ΔESFQR in the wafer circumferential direction with respect to the film thickness of the epitaxial film. The ratio was 0.43%.

(Example 2)
As the silicon wafer to be evaluated, a polished (111) silicon wafer with a mirror surface and a diameter of 300 mm, similar to that in Example 1, was used. In the single-wafer epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1, except that the furnace pressure was set to 1.33×10 ⁴ Pa (100 Torr). When the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, the ratio of variation in the wafer circumferential direction of ΔESFQR to the film thickness of the epitaxial film was 0.60. %.

(Example 3)
As the silicon wafer to be evaluated, a polished (111) silicon wafer with a mirror surface and a diameter of 300 mm, similar to that in Example 1, was used. In a single-wafer epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1, except that dichlorosilane (DCS) was used as the reaction gas. When the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, the ratio of variation in the wafer circumferential direction of ΔESFQR to the film thickness of the epitaxial film was 0.43. %.

(Example 4)
As the silicon wafer to be evaluated, a polished (111) silicon wafer with a mirror surface and a diameter of 300 mm, similar to that in Example 1, was used. In a single-wafer epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1, except that the reaction gas was dichlorosilane (DCS) and the furnace pressure was 1.33×10 ⁴ Pa (100 Torr). When the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, the ratio of variation in the wafer circumferential direction of ΔESFQR to the film thickness of the epitaxial film was 0.59. %.

(Example 5)
As the silicon wafer to be evaluated, a polished (111) silicon wafer with a mirror surface and a diameter of 300 mm, similar to that in Example 1, was used. In a single-wafer epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1, except that the reaction gas was monosilane (SiH ₄ ) and the reaction temperature was 900°C. When the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, the ratio of variation in the wafer circumferential direction of ΔESFQR to the film thickness of the epitaxial film was 0.38. %.

Example 6
The silicon wafer to be evaluated was a (111) silicon wafer with a diameter of 300 mm that had been polished and had a mirror surface, similar to that in Example 1. In a single-wafer epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1, except that the reaction gas was monosilane (SiH ₄ ), the reaction temperature was 900° C., and the furnace pressure was 1.33×10 ⁴ Pa (100 Torr). The ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, and the ratio of the wafer circumferential variation of ΔESFQR to the epitaxial film thickness was 0.52%.

(Comparative example 1)
As the silicon wafer to be evaluated, a polished (111) silicon wafer with a mirror surface and a diameter of 300 mm, similar to that in Example 1, was used. In a single-wafer type epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1 except that the furnace pressure was set to 2.66×10 ⁴ Pa (200 Torr). When the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, the ratio of variation in the wafer circumferential direction of ΔESFQR to the film thickness of the epitaxial film was 0.83. %.

(Comparative example 2)
As the silicon wafer to be evaluated, a polished (111) silicon wafer with a mirror surface and a diameter of 300 mm, similar to that in Example 1, was used. In a single-wafer type epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1 except that the furnace pressure was set to 5.33×10 ⁴ Pa (400 Torr). When the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, the ratio of variation in the wafer circumferential direction of ΔESFQR to the film thickness of the epitaxial film was 0.90. %.

(Comparative example 3)
As the silicon wafer to be evaluated, a polished (111) silicon wafer with a mirror surface and a diameter of 300 mm, similar to that in Example 1, was used. In a single-wafer type epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1 except that the furnace pressure was set to 1.01×10 ⁵ Pa (760 Torr). When the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, the ratio of variation in the wafer circumferential direction of ΔESFQR to the film thickness of the epitaxial film was 0.95. %.

(Comparative example 4)
As the silicon wafer to be evaluated, a polished (111) silicon wafer with a mirror surface and a diameter of 300 mm, similar to that in Example 1, was used. In a single-wafer type epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1 except that the reaction gas was dichlorosilane (DCS) and the furnace pressure was 2.66×10 ⁴ Pa (200 Torr). When the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, the ratio of variation in the wafer circumferential direction of ΔESFQR to the film thickness of the epitaxial film was 0.80. %.

(Comparative example 5)
As the silicon wafer to be evaluated, a polished (111) silicon wafer with a mirror surface and a diameter of 300 mm, similar to that in Example 1, was used. In a single-wafer epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1, except that the reaction gas was dichlorosilane (DCS) and the furnace pressure was 5.33×10 ⁴ Pa (400 Torr). When the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, the ratio of variation in the wafer circumferential direction of ΔESFQR to the film thickness of the epitaxial film was 0.85. %.

(Comparative example 6)
As the silicon wafer to be evaluated, a polished (111) silicon wafer with a mirror surface and a diameter of 300 mm, similar to that in Example 1, was used. In a single-wafer epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1, except that the reaction gas was dichlorosilane (DCS) and the furnace pressure was 1.01×10 ⁵ Pa (760 Torr). When the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, the ratio of variation in the wafer circumferential direction of ΔESFQR to the film thickness of the epitaxial film was 0.90. %.

(Comparative Example 7)
As the silicon wafer to be evaluated, a polished (111) silicon wafer with a mirror surface and a diameter of 300 mm, similar to that in Example 1, was used. In a single-wafer epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1, except that the reaction gas was monosilane (SiH ₄ ), the reaction temperature was 900° C., and the furnace pressure was 2.66×10 ⁴ Pa (200 Torr). went. When the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, the ratio of variation in the wafer circumferential direction of ΔESFQR to the film thickness of the epitaxial film was 0.70. %.

(Comparative example 8)
As the silicon wafer to be evaluated, a polished (111) silicon wafer with a mirror surface and a diameter of 300 mm, similar to that in Example 1, was used. In a single-wafer epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1, except that the reaction gas was monosilane (SiH ₄ ), the reaction temperature was 900° C., and the furnace pressure was 5.33×10 ⁴ Pa (400 Torr). went. When the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, the ratio of variation in the wafer circumferential direction of ΔESFQR to the film thickness of the epitaxial film was 0.75. %.

(Comparative Example 9)
As the silicon wafer to be evaluated, a polished (111) silicon wafer with a mirror surface and a diameter of 300 mm, similar to that in Example 1, was used. In a single-wafer epitaxial growth apparatus, epitaxial film formation was performed under the same conditions as in Example 1, except that the reaction gas was monosilane (SiH ₄ ), the reaction temperature was 900° C., and the furnace pressure was 1.01×10 ⁵ Pa (760 Torr). went. When the ESFQR of the silicon wafer before film formation and the ESFQR of the epitaxial wafer obtained after film formation were measured using Wafer-Sight2, the ratio of variation in the wafer circumferential direction of ΔESFQR to the film thickness of the epitaxial film was 0.82. %.

Table 1 shows the results of Examples 1 to 6 and Comparative Examples 1 to 9 above.

From the results in Table 1, it can be seen that in Examples 1 to 6, the rate of variation in ΔESFQR in the wafer circumferential direction relative to the epitaxial film thickness was 0.60% or less, which is a significant improvement compared to Comparative Examples 1 to 9. In this way, by using the epitaxial wafer manufacturing method of the present invention, it is possible to obtain an epitaxial wafer with reduced variation in the wafer circumferential direction. In other words, when epitaxially growing on a (111) silicon wafer, it was found that the pressure inside the reactor needs to be 100 Torr or less in order to obtain a highly flat epitaxial wafer.

Note that the present invention is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any embodiment that has substantially the same configuration as the technical idea stated in the claims of the present invention and has similar effects is the present invention. covered within the technical scope of

5... <112> Outer peripheral end in crystal direction, 10... Epitaxial growth apparatus,
11... Reactor (reaction chamber), 12... Process gas supply section,
W...(111) wafer.

Claims (3)

A method for manufacturing an epitaxial wafer in which a process gas containing a silicon-based raw material gas is supplied to a surface of a silicon wafer whose main surface is a (111) plane to epitaxially grow a silicon layer, the method comprising:
In the epitaxial growth, the reaction temperature was 800 to 1150°C, the concentration of silicon-based raw material gas in the process gas was 1.0 × 10 ^-4 to 1.0 × 10 ^-2 mol/L, and the internal pressure of the reactor was 1.33×10 ⁴ Pa (100 Torr) or less ,
When the amount of variation in the wafer circumferential direction of ΔESFQR, which is the difference in site flatness before and after epitaxial growth, is X and the film thickness of the epitaxially grown film is T, the ratio of the variation in ΔESFQR in the wafer circumferential direction to the film thickness T of the epitaxially grown film is ( A method for manufacturing an epitaxial wafer, characterized in that X/T)×100 is 0.6% or less . 2. The method for manufacturing an epitaxial wafer according to claim 1, wherein a silicon wafer having a diameter of 300 mm is used as the silicon wafer. 3. The method for manufacturing an epitaxial wafer according to claim 1, wherein trichlorosilane (TCS), dichlorosilane (DCS), or monosilane is used as the silicon-based source gas.

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