JP5889125B2 - Method for manufacturing SiC epitaxial substrate - Google Patents

Description

  The present invention relates to a method for manufacturing a SiC epitaxial substrate.

  In the manufacture of semiconductor devices, various inspections such as processing accuracy and cleanliness are performed in order to improve the yield. A dummy wafer is used as a wafer for performing these inspections. For example, Patent Document 1 discloses a wafer containing titanium or an alloy thereof as a dummy wafer of stable quality that is easy to process and has little warpage.

  If foreign matter adheres to the surface of the substrate, crystal defects and surface morphology anomalies are caused during epitaxial growth. In particular, in the case of a SiC substrate, since the epitaxial growth temperature is as high as 1400 ° C. or higher, by-products adhering to the inside of the reactor are desorbed due to a difference in thermal expansion coefficient and thermal history from the reactor, and float in the reactor to float the wafer. Adhere to the surface. Further, 3C type SiC grows on the susceptor in the reactor, and the fragments adhere to the wafer surface.

JP 2001-148334 A

  In the SiC device manufacturing process, it is conceivable to monitor the amount of foreign matter using a SiC substrate as a dummy wafer, but due to the difference in the wavelength used, it is impossible to use a conventional foreign matter inspection device for Si substrate for the SiC substrate. There was a problem. In addition, the SiC substrate itself has many crystal defects and is unsuitable for monitoring the amount of foreign matter.

  Furthermore, since the SiC substrate has an epitaxial growth temperature of 1400 ° C. or higher, some surface foreign matter is etched in the temperature rising and etching steps. For this reason, not all foreign matters adhering when transported into the etching apparatus cause defects or abnormal surface morphology, and the foreign matter management standards are unclear. It is desired to improve the accuracy of foreign matter management and improve the yield of SiC epitaxial substrate manufacturing.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for manufacturing an SiC epitaxial substrate with excellent yield.

The SiC epitaxial substrate manufacturing method of the present invention includes (a) a step of preparing a Si substrate and a production SiC substrate, (b) a step of inspecting the amount of foreign matter in the epitaxial growth apparatus using the Si substrate, and (c) a step (b) And a step of performing epitaxial growth on the production SiC substrate using an epitaxial growth apparatus when the amount of foreign matter inspected in step (b) is less than a predetermined amount, and the step (b) is a step of inspecting the amount of foreign matter having a diameter of 5 μm or more. , and the step (c), Ru steps der performing epitaxial growth to production SiC substrate at 1400 ° C. or higher.

The SiC epitaxial substrate manufacturing method of the present invention includes (a) a step of preparing a Si substrate and a production SiC substrate, (b) a step of inspecting the amount of foreign matter in the epitaxial growth apparatus using the Si substrate, and (c) a step (b) And a step of performing epitaxial growth on the production SiC substrate using an epitaxial growth apparatus when the amount of foreign matter inspected in step (b) is less than a predetermined amount, and the step (b) is a step of inspecting the amount of foreign matter having a diameter of 5 μm or more. , and the step (c), Ru steps der performing epitaxial growth to production SiC substrate at 1400 ° C. or higher. By performing the foreign matter amount inspection using the Si substrate, stable foreign matter management that is less affected by crystal defects can be performed. Further, the amount of foreign matter can be measured using a Si foreign matter measuring device. Therefore, the SiC epitaxial substrate can be manufactured with a high yield.

It is a figure which compares the foreign material adhesion number of a Si substrate and a SiC substrate. It is a figure which shows the influence which a surface foreign material has on film-forming of an epitaxial film. It is a figure which shows the defect map of a SiC wafer.

<A. Embodiment 1>
<A-1. Process>
The method for manufacturing an SiC epitaxial substrate according to the present embodiment includes a foreign matter amount inspection step for inspecting the amount of foreign matter in the SiC epitaxial apparatus, and a film formation step for forming a SiC epitaxial film on the SiC substrate surface.

  The foreign matter amount inspection process will be described. In this step, a Si wafer (Si substrate) is used as a dummy wafer. The reason why the Si wafer is used here is that since the number of crystal defects is smaller than that of the SiC wafer, the number of adhered foreign substances can be inspected with high accuracy. Further, as shown in FIG. 1, since the number of adhered foreign substances of the Si wafer and the SiC wafer in the foreign substance inspection of the same batch is almost the same, the Si wafer can be used as a foreign substance management dummy substrate of the SiC epitaxial growth apparatus. is there.

  The Si substrate is carried into the SiC epitaxial growth apparatus and left for a predetermined time, and then the Si substrate is carried out from the SiC epitaxial growth apparatus. And the number of foreign matter adhesion before carrying in and after carrying out is counted, respectively. From the difference in the number of adhering foreign matters, the number of foreign matters adhering as a result of being transferred into the SiC epitaxial growth apparatus is calculated. If the calculated number of foreign substances is equal to or greater than a predetermined number (for example, 500), the film forming process is not performed and the in-reactor coating and the cleaning by the dummy run are performed.

  Here, a foreign matter having a diameter of 5 μm or more is set as a management target foreign matter, that is, a count target, and other foreign matters are set as non-control target foreign matters, ie, not counted. The reason will be described with reference to FIG. FIG. 2A shows a state in which foreign matter is attached to the surface of the SiC substrate 1. In the process of raising the temperature of the SiC substrate 1 to the growth temperature of the epitaxial film, the surface of the SiC substrate 1 is etched as shown in FIG. At that time, the small foreign matter (non-management foreign matter 2) is removed, but the large foreign matter (management foreign matter 3a, 3b) still remains and causes crystal defects and morphological abnormalities. FIG. 2C shows a state in which a crystal defect occurs without epitaxial growth on the management target foreign material 3a, and a surface morphology abnormality occurs due to the management target foreign material 3b. As a result of investigation by the applicant, it was found that when the etching amount was 300 nm, foreign matters having a diameter of 5 μm or more remained even after the temperature rising process. Therefore, in the present invention, foreign matter having a diameter of 5 μm or more is set as a management target foreign matter.

  In the foreign matter amount inspection step, it is desirable to introduce a gas into the SiC epitaxial growth apparatus in order to bring the state close to that in the film formation step, thereby improving the accuracy with which the foreign matter adheres. The temperature in the SiC epitaxial growth apparatus is preferably 600 ° C. or higher and lower than 1200 ° C. If the growth temperature of the SiC epitaxial film is 1400 ° C. or higher, the Si substrate melts, so it remains below 1200 ° C. However, by reducing the temperature difference from the film formation step, the film formation step and the foreign matter amount inspection step The temperature raising / lowering time can be shortened. Further, it is desirable to allow foreign matter to adhere to the surface while rotating, revolving, or revolving the Si substrate.

  Under the above conditions, when the number of foreign objects to be managed attached to the surface of the Si substrate is less than a predetermined number, the process proceeds to the film forming process. The Si substrate is taken out from the SiC epitaxial growth apparatus, and instead, the SiC substrate 1 is carried into the SiC epitaxial growth apparatus and a film forming process is performed.

  Generally, a by-product made of Si, C, or O in a furnace (SiC epitaxial growth apparatus), or a 3C-type is formed on the surface of the SiC substrate 1 by a carry-in process, a subsequent temperature raising process, a gas introduction process, or the like. SiC, C caused by a heat insulating material or a susceptor, etc. adhere as non-management target foreign matter 2 and management target foreign matters 3a and 3b (FIG. 2A). As the SiC substrate 1, one having a growth surface that is off-cut at an off-cut angle inclined by 4 ° from the (0001) plane toward the (11-20) plane is generally used.

  After the SiC substrate 1 is carried into the SiC epitaxial growth apparatus, H2 gas is introduced as an etching gas, and the temperature in the SiC epitaxial growth apparatus is raised to the growth temperature (1400 ° C. or higher) and thereafter before the epitaxial crystal growth is started. In the process of holding at the growth temperature, the surface of the SiC substrate 1 is etched by about 300 nm (FIG. 2B).

  After a predetermined time has elapsed since the temperature in the SiC epitaxial growth apparatus reached the growth temperature, epitaxial growth is performed (FIG. 2C). SiH4 gas, C3H8 gas or the like is used as the growth gas, and N2 gas is used as the dopant gas. Moreover, H2 gas is used as carrier gas.

  FIG. 3 shows a defect map of the SiC epitaxial substrate. A circle indicates a portion where there was a foreign material on the surface but did not cause a defect in the epitaxial film. A cross indicates a portion where the surface foreign matter causes a crystal defect or a surface morphology. Further, the triangle marks indicate crystal defects formed due to factors other than the surface foreign matter.

<A-2. Effect>
The SiC epitaxial substrate manufacturing method of the present invention includes (a) a step of preparing a Si substrate as a dummy wafer and a production SiC substrate, (b) a step of inspecting the amount of foreign matter in the SiC epitaxial growth apparatus using the Si substrate, and (c And a step of performing epitaxial growth on the actual SiC substrate using a SiC epitaxial growth apparatus when the amount of foreign matter inspected in the step (b) is less than a predetermined amount. Therefore, a SiC epitaxial substrate can be manufactured with a high yield. Further, since the inspection process of the foreign matter 3a, 3b to be managed is performed using a Si substrate with few crystal defects, it is possible to use a foreign matter inspection apparatus for Si and to detect the foreign matter with high accuracy.

  Step (b) is a step of inspecting the amount of foreign matter having a diameter of 5 μm or more, and step (c) is a step of performing epitaxial growth on a production SiC substrate at a temperature of 1400 ° C. or more. Foreign matter having a diameter of 5 μm or more remains even in the process of raising the temperature in the SiC epitaxial growth apparatus to 1400 ° C. or more, and causes crystal defects and surface morphology in the epitaxial film. Therefore, by examining the amount of foreign matter having a diameter of 5 μm or more, a SiC epitaxial substrate can be manufactured with a high yield.

  In addition, the foreign matter amount inspection step can be performed between the film forming step and the foreign matter amount inspection step by shortening the temperature rise / fall time by performing the temperature measurement at a temperature of 600 ° C. or more and less than 1200 ° C. within a range where the Si substrate does not melt.

  The foreign matter amount inspection step includes a step of carrying the Si substrate into the SiC epitaxial growth apparatus, leaving it for a predetermined period, and then carrying it out of the SiC epitaxial growth apparatus. When the Si substrate is left in the SiC epitaxial growth apparatus, by introducing a gas into the SiC epitaxial growth apparatus, the foreign matter amount inspection process can be performed under conditions as close as possible to the film forming step, thereby improving the accuracy of the foreign matter amount inspection. it can.

  In the present invention, the embodiments can be appropriately modified and omitted within the scope of the invention.

  1 SiC substrate, 2 foreign matter not to be managed, 3a, 3b foreign matter to be managed, 4 SiC epitaxial film.

Claims (3)

(A) preparing a Si substrate that is a dummy wafer and a production SiC substrate;
(B) a step of inspecting the amount of foreign matter in the epitaxial growth apparatus using the Si substrate;
(C) when the amount of foreign matter inspected in the step (b) is less than a predetermined amount, performing epitaxial growth on the production SiC substrate using the epitaxial growth apparatus;
Equipped with a,
The step (b) is a step of inspecting the amount of foreign matter having a diameter of 5 μm or more,
Wherein step (c), Ru steps der performing epitaxial growth on the production SiC substrate at 1400 ° C. or higher,
Manufacturing method of SiC epitaxial substrate. The step (b) is a step of inspecting the amount of foreign matter at a temperature of 600 ° C. or higher and lower than 1200 ° C.,
The manufacturing method of the SiC epitaxial substrate of Claim 1. The step (b)
  (B1) carrying the Si substrate into the epitaxial growth apparatus;
  (B2) leaving the Si substrate in the epitaxial growth apparatus;
  (B3) carrying the Si substrate out of the epitaxial growth apparatus;
With
  The step (b2) is a step of leaving the Si substrate while introducing a gas into the epitaxial growth apparatus.
The manufacturing method of the SiC epitaxial substrate of Claim 1 or 2.

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