JP2017112206A - Method for manufacturing epitaxial wafer and epitaxial growth apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an epitaxial wafer and an epitaxial growth apparatus capable of managing an amount of metal of a member used in the epitaxial growth apparatus and stably producing a high quality epitaxial wafer with little contamination.SOLUTION: The method for manufacturing an epitaxial wafer uses the epitaxial growth apparatus in which an SiC coating member is used for a member constituting an epitaxial growth furnace. The tungsten concentration detected from a surface of the SiC coating member is managed to be greater than or equal to 1×10atoms/cmand less than or equal to 2.1×10atoms/cm.SELECTED DRAWING: Figure 1

Description

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

  In recent years, silicon epitaxial wafers in which a silicon film is vapor-phase grown on a silicon wafer have been used as an image sensor substrate such as a CCD or CIS. In such an epitaxial wafer for an image sensor, it is important to reduce the level of metal impurities in the wafer. This is because if a metal impurity is present in the wafer, a defect called white scratch (white spot) occurs.

  In general, in order to manufacture an epitaxial wafer, an epitaxial layer is vapor-phase grown at a high temperature. Therefore, when the epitaxial layer is formed, if the metal impurity is present in the reactor of the epitaxial growth apparatus, the manufactured epitaxial wafer is contaminated with the metal impurity. Examples of the contamination sources of these metals include, in addition to silicon crystals and silicon-containing compounds used as raw materials, metal impurities attached during the maintenance (cleaning) of the epitaxial growth apparatus, metal impurities contained in the material constituting the reactor, apparatus, and The stainless steel component etc. which are usually used for a piping system can be considered.

  By the way, it is necessary to periodically maintain the epitaxial growth apparatus. In the maintenance, for example, the epitaxial growth apparatus is opened to the atmosphere, and the reactor and piping are cleaned and the members in the reactor are replaced. Further, when the production of the epitaxial wafer is repeated, silicon deposits are gradually deposited in the reaction furnace, and the deposits cause generation of particles and the like. Therefore, it is necessary to periodically remove the silicon deposits accumulated in the reaction furnace (cleaning in the furnace). As a method for removing the silicon deposit, a method is known in which HCl gas is flowed into a reaction furnace, and the inside of the reaction furnace is vapor-phase etched with the HCl gas (see, for example, Patent Document 1).

  However, immediately after such maintenance and vapor phase etching, the metal contamination degree of the epitaxial growth apparatus is temporarily deteriorated, and the epitaxial growth is repeated, and the contamination is reduced by increasing the number of reaction. For example, it is known that the white defect of a product is gradually improved while reacting about several hundred sheets. Conventionally, cases where the degree of metal contamination immediately after maintenance is large or small are indeterminate, and the degree of contamination after maintenance cannot be suppressed, and a contaminated low-quality epitaxial wafer may be obtained.

JP 2004-87920 A

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and manages an amount of metal of a member used in an epitaxial growth apparatus and can stably manufacture a high-quality epitaxial wafer with less contamination and an epitaxial growth apparatus. The purpose is to provide.

  The present inventor has found that the metal contamination of the epitaxial wafer in the reaction furnace is aggravated immediately after the gas phase etching, and the metal adhering to the members constituting the epitaxial reactor is used in the gas phase etching. It was thought that metal contamination (reaction product) was generated due to corrosion by process gas such as hydrogen (HCl). Therefore, by evaluating the metal concentration of the epitaxial wafer and the degree of contamination of the reactor structural member itself that reacted with the epitaxial wafer, there is a relationship with the metal contamination of the epitaxial wafer, particularly the exchange of tungsten and SiC (silicon carbide) coating members. As a result, the present invention was reached.

FIG. 1 shows the relationship between the surface tungsten concentration in ICP-MS (ICP mass spectrometry) of an SiC coated member and the surface tungsten concentration of an epitaxial wafer produced in an epitaxial reactor in which the member was attached. When the surface tungsten concentration in the ICP-MS of the SiC coating member is 2.1 × 10 ⁹ atoms / cm ² or less, the surface tungsten concentration of the epitaxial wafer is 1 × 10 ⁷ atoms / cm ² or less, which is the lower limit of detection, but the SiC coating member It was found that the surface tungsten concentration of the epitaxial wafer increases when the surface tungsten concentration in the ICP-MS is higher than 2.1 × 10 ⁹ atoms / cm ² .

  That is, in the present invention, in consideration of the above-described phenomenon, in the SiC coating member replacement at the time of maintenance, by using a member in which the tungsten concentration on the surface of the SiC coating member is controlled, the metal contamination of the epitaxial wafer that occurs immediately after the maintenance is performed. An epitaxial wafer manufacturing method and an epitaxial growth apparatus in which deterioration is suppressed are provided.

The method for producing an epitaxial wafer according to the present invention is a method for producing an epitaxial wafer using an epitaxial growth apparatus in which a SiC coating member is used as a member constituting the inside of an epitaxial growth furnace, and is detected from the surface of the SiC coating member. The tungsten concentration is controlled to be 1 × 10 ⁷ atoms / cm ² or more and 2.1 × 10 ⁹ atoms / cm ² or less.

Management range of the surface concentration of tungsten in the above-mentioned SiC coating member is 1 × 10 ⁷ atoms / cm ² or more and ^{2.1 × 10 9 atoms / cm 2} , 1 × 10 7 is lower than the atoms / cm ² is less than the detection limit Therefore, it cannot be used as a management value.

The epitaxial growth apparatus of the present invention is an epitaxial growth apparatus in which a SiC coating member is used as a member constituting the epitaxial growth furnace, and the tungsten concentration detected from the surface of the SiC coating member is 1 × 10 ⁷ atoms / cm ² or more. And 2.1 × 10 ⁹ atoms / cm ² or less.

  As a member constituting the inside of the epitaxial growth furnace, a susceptor is suitable.

  In the epitaxial wafer manufacturing method and epitaxial growth apparatus of the present invention, the metal contamination degree on the surface of the epitaxial wafer becomes below a certain level by managing the surface tungsten concentration of the SiC coating member. This makes it possible to stably manufacture a high-quality epitaxial wafer with little contamination.

  Advantageous Effects of Invention According to the present invention, it is possible to provide an epitaxial wafer manufacturing method and an epitaxial growth apparatus capable of controlling the metal amount of a member used in an epitaxial growth apparatus and stably manufacturing a high-quality epitaxial wafer with little contamination. Has a great effect.

It is a graph which shows the surface tungsten density | concentration of a SiC coating member, and the surface tungsten density | concentration of an epitaxial wafer. It is a side cross-sectional schematic diagram of an epitaxial growth apparatus. It is the flowchart of the Example which showed the manufacture example of the epitaxial wafer which uses an epitaxial growth apparatus, and a comparative example. It is the graph which showed transition by the number of wafer reaction of ICP-MS surface tungsten concentration in an example and a comparative example.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a side cross-sectional view of a single-wafer epitaxial vapor phase growth apparatus as a preferred example of the epitaxial growth apparatus according to the present invention. The vapor phase growth apparatus is an apparatus for vapor phase growth of a silicon single crystal film on the surface of a silicon wafer (an apparatus for producing a silicon epitaxial wafer). In the epitaxial growth apparatus, for example, an epitaxial wafer used for an image sensor substrate such as a CCD or CIS is manufactured.

  The epitaxial growth apparatus 1 includes a chamber base 2 made of SUS (stainless steel) and a transparent quartz member 3 that forms a reaction furnace 10 (chamber) sandwiched from above and a chamber base 2 provided inside the reaction furnace 10. An opaque quartz member 4 that covers from the inside, a susceptor 5 that horizontally supports the silicon wafer W, and a susceptor rotating mechanism 6 that rotates the susceptor 5 are provided. A SiC coating member is used as a member constituting the susceptor 5. The susceptor rotation mechanism is made of SUS and includes a mechanism for moving the silicon wafer W up and down for loading and unloading the silicon wafer W.

  In the reaction furnace 10, a vapor phase growth gas containing a raw material gas (for example, trichlorosilane (TCS)) and a carrier gas (for example, hydrogen) is introduced into the reaction furnace 10 into an upper region of the susceptor 5. A gas introduction pipe 7 for supplying the main surface of the silicon wafer W is provided. The same gas introduction pipe is also used for HCl (hydrogen chloride) gas used for in-furnace cleaning. Further, the reactor 10 is provided with a gas discharge pipe 8 on the side opposite to the side where the gas introduction pipe 7 is provided, so that the vapor growth gas flows in the direction of the vapor growth gas flow direction G. It is configured.

  Further, heaters 9 for heating the silicon wafer W to an epitaxial temperature (for example, 900 ° C. to 1200 ° C.) at the time of epitaxial growth are provided above and below the reaction furnace 10. A plurality of heaters are provided in the horizontal direction. For example, a halogen lamp is used as the heater.

  As described above, it is necessary to periodically perform gas phase etching (cleaning in the furnace) in the reactor using the maintenance of the epitaxial growth apparatus and the HCl gas. In the maintenance, the epitaxial growth apparatus may be opened to the atmosphere, and the members in the reaction furnace may be replaced. In this case, there is a possibility that the surface is replaced with a member having a large metal contamination. In particular, a susceptor composed of a SiC coating member is repeatedly subjected to vapor phase etching processing during wafer manufacture, and is gradually consumed. Therefore, it is necessary to replace the susceptor with a certain reaction frequency. When a SiC coating member with large metal contamination on the surface is brought into the furnace at the time of replacement, a reaction product of metal impurities is generated due to the reaction between HCl gas and the introduced contamination source when vapor phase etching is performed. Corrosion is caused by HCl remaining in the reaction furnace to generate metal impurities. Therefore, immediately after maintenance or vapor phase etching, metal contamination of the epitaxial growth apparatus is temporarily deteriorated. Since devices such as an image sensor are very strongly affected by metal impurities in the epitaxial layer, it is necessary to suppress the deterioration of metal contamination of the epitaxial growth apparatus, and the present invention is implemented for that purpose.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, these do not limit this invention.

(Description of process)
Next, the process of the Example of an epitaxial wafer manufacture example using the epitaxial growth apparatus mentioned later and a comparative example is demonstrated. FIG. 3 is a flowchart showing the steps of the manufacturing example and the comparative example.

First, a susceptor whose surface tungsten concentration is known and the surface tungsten concentration is 2.1 × 10 ⁹ atoms / cm ² or less (the embodiment of FIG. 3) and a susceptor having a surface tungsten concentration greater than 2.1 × 10 ⁹ atoms / cm ^2. Prepare one each (comparative example of FIG. 3) and attach it to the reactor (FIG. 3 (a)).

  Next, a silicon wafer serving as a substrate for a semiconductor wafer for contamination evaluation is prepared (FIG. 3B). The diameter, plane orientation, conductivity type, resistivity, and the like of the silicon wafer prepared here are not particularly limited. For example, the diameter can be the same as that of the silicon wafer processed by the epitaxial growth apparatus to be evaluated. Further, the processing conditions of the surface of the silicon wafer may be standard conditions, but it is preferable to avoid processes that affect the contamination evaluation, such as sandblasting and formation of a polycrystalline silicon film.

  Thereafter, the prepared substrate is transported to the reaction furnace and carried in (FIG. 3C). A source gas TCS of 10 L / min and a carrier gas of hydrogen of 50 L / min are flown at the time of forming the epitaxial layer, and a non-doped layer having a thickness of 10 μm is reacted to perform epitaxial growth (FIG. 3D). The contamination evaluation epitaxial wafer thus produced was taken out (FIG. 3E), and the surface tungsten concentration was measured using the ICP-MS method on the contamination evaluation epitaxial wafer (FIG. 3). (F)), the amount of contamination of the epitaxial growth apparatus is evaluated (FIG. 3G).

(Example)
First, a silicon wafer having a diameter of 200 mm and a thickness of 725 μm was prepared. Next, an epitaxial growth apparatus to be evaluated was prepared, opened to the atmosphere, and so-called maintenance work was performed. At that time, the susceptor having a surface tungsten concentration of 2.1 × 10 ⁹ atoms / cm ² or less prepared as described above, specifically, a susceptor having a surface tungsten concentration of 8.8 × 10 ⁸ atoms / cm ² was attached to the epitaxial growth apparatus. .

  After preparing an epitaxial growth apparatus for which maintenance work was performed in this manner, epitaxial growth was performed on the above silicon wafer in the same manner as described above using this apparatus, and an epitaxial wafer for contamination evaluation was produced.

  Further, after the maintenance in the same manner as in the above-described example, an epitaxial wafer for contamination evaluation was prepared every time an appropriate number of wafers were reacted. In addition, while the epitaxial wafer for contamination evaluation was not produced, the epitaxial growth processing for the silicon wafer for contamination removal was continued in the same order as the growth of the silicon epitaxial layer for the normal product.

(Comparative example)
First, a silicon wafer having a diameter of 200 mm and a thickness of 725 μm was prepared. Next, in the epitaxial growth apparatus to be evaluated, maintenance work was performed with the atmosphere opened. At that time, the susceptor having a surface tungsten concentration prepared in the above-described manner and having a surface tungsten concentration higher than 2.1 × 10 ⁹ atoms / cm ² , specifically, a susceptor having a surface tungsten concentration of 3.3 × 10 ¹⁰ atoms / cm ² was attached to the epitaxial growth apparatus.

  After preparing an epitaxial growth apparatus in which maintenance work was performed in this way, an epitaxial wafer for contamination evaluation was produced using this apparatus in the same manner as in the examples. Furthermore, after the maintenance, a semiconductor wafer for contamination evaluation was produced every time an appropriate number of wafers were reacted. In addition, it was set as the Example also about the process while the epitaxial wafer for pollution evaluation is not produced.

  With respect to the epitaxial wafer for contamination evaluation thus produced, the surface tungsten concentration was measured using the ICP-MS method. FIG. 4 is a graph showing the measurement results, and specifically shows the transition of the tungsten concentration on the surface of the epitaxial wafer in the examples and comparative examples between 0 and 2000 reaction sheets.

As shown in FIG. 4, in the example, the tungsten concentration on the surface of the epitaxial wafer immediately after maintenance (reaction number of 20) is not more than the detection lower limit of 1.0 × 10 ⁷ atoms / cm ² , and was not detected even immediately after maintenance.

On the other hand, in the comparative example, the tungsten concentration on the surface of the epitaxial wafer immediately after maintenance (reaction number 20) is 2.7 × 10 ⁷ atoms / cm ² , and thereafter the surface tungsten concentration decreases with the progress of the reaction number, and the reaction number 700 It decreased to about 1.0 × 10 ⁷ atoms / cm ² which is the lower limit of detection. Thereafter, the number of reaction was 2000 or less, which was below the lower limit of detection.

As described above, in the embodiment of the present invention, the use of a member having a surface tungsten concentration of 2.1 × 10 ⁹ atoms / cm ² or less as the SiC coating member provided in the reaction furnace reduces the deterioration of tungsten contamination immediately after maintenance. It was shown that it can be suppressed. In the above-described embodiment, the SiC coating member is a susceptor.

  Thus, according to the present embodiment, by managing the surface tungsten concentration of the SiC coating member to be replaced at the time of maintenance, it is possible to suppress the deterioration of metal contamination of the epitaxial wafer even immediately after the maintenance. Therefore, it is shown that a high-quality epitaxial wafer with little contamination can be manufactured stably.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and has the same configuration as the technical idea described in the claims of the present invention, and can produce any similar effects. It is included in the technical scope of the present invention. For example, the epitaxial growth apparatus using the SiC coating member is not limited to the single wafer type, and the present invention is also applied to the case where the SiC coating member is used for various vapor phase growth apparatuses such as a vertical type (pancake type) and a barrel type (cylinder type). it can. Moreover, although the susceptor which mounts a wafer as a SiC coating member is mentioned as an example in the above-mentioned embodiment, this invention may be applied if it is a SiC coating member and a member used in a reaction furnace. . For example, as the SiC coating member, lift pins used for supporting a wafer can also be applied.

  1: epitaxial growth apparatus, 2: chamber base, 3: transparent quartz member, 4: opaque quartz member, 5: susceptor, 6: susceptor rotating mechanism, 7: gas introduction pipe, 8: gas outlet pipe, 9: heater, 10: Reactor, G: vapor growth gas flow direction, W: silicon wafer.

Claims (2)

It is a method of manufacturing an epitaxial wafer using an epitaxial growth apparatus in which a SiC coating member is used as a member constituting the inside of the epitaxial growth furnace,
A method for producing an epitaxial wafer, wherein a tungsten concentration detected from the surface of the SiC coating member is controlled to 1 × 10 ⁷ atoms / cm ² or more and 2.1 × 10 ⁹ atoms / cm ² or less. An epitaxial growth apparatus in which a SiC coating member is used as a member constituting the inside of the epitaxial growth furnace, and the tungsten concentration detected from the surface of the SiC coating member is 1 × 10 ⁷ atoms / cm ² or more and 2.1 × 10 ⁹ atoms / An epitaxial growth apparatus characterized by being controlled to be cm ² or less.

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