Patent Application
20210262119
The present invention relates to: a silicon carbide single crystal growth apparatus; and a method for manufacturing a silicon carbide single crystal.
Power devices that use a silicon carbide single crystal substrate have been attracting attention in recent years for having characteristics such as high breakdown voltage, low loss, and making a high-temperature operation possible.
Specifically, a method for growing a silicon carbide single crystal by a sublimation method is a method of placing a silicon carbide raw material 206 (solid raw material silicon carbide) inside a growth container 201 of the silicon carbide single crystal growth apparatus 200 shown in
The growth container 201 is disposed inside a vacuum quartz pipe or inside a vacuum chamber, is once filled with a gas with low activity, and an atmosphere thereof has a pressure lower than an atmospheric pressure so that the sublimation rate of the silicon carbide is raised.
On the outside of the growth container 201, a heat-insulating container 202 is disposed. A part of the heat-insulating container 202 has at least one hole for temperature measurement 209 for measuring temperature with a temperature measuring equipment 208 such as a pyrometer. The growth container 201 is mainly formed from carbon material, and has permeability so that the pressures inside and outside the growth container 201 become equal. The silicon carbide raw material 206 is disposed at the bottom of the growth container 201. The silicon carbide raw material 206 is solid, and is sublimed under high temperature and reduced pressure. The sublimed silicon carbide raw material 206 grows as the silicon carbide single crystal 205 on the seed crystal substrate 204 facing the silicon carbide raw material 206.
Here, a conventional method for manufacturing a silicon carbide single crystal using the above-described silicon carbide single crystal growth apparatus 200 will be described using
Single crystals of silicon carbide include a cubic crystal and a hexagonal crystal, and furthermore, among hexagonal crystals, 4H, 6H, and the like are known as typical polytypes.
In many cases, the same type of single crystal grows; for example, 4H grows on a 4H type seed crystal (Patent Document 2).
A warp occurs in the seed crystal substrate 204 as in a bimetal with the rise in temperature due to the difference in coefficient of thermal expansion between the seed crystal substrate 204 and the growth container 201 mainly made from a carbon material. This leads to bending the basal plane of a silicon carbide single crystal, which is a hexagonal crystal, etc. It is considered that if a silicon carbide single crystal is grown on a bent basal plane, the crystal grows, maintaining the bend, and that this causes basal plane dislocation (BPD) and threading edge dislocation (TED), etc. while growing and cooling. This is also considered to be a cause for threading screw dislocation (TSD). As described, many TSDs and TEDs that stretch continuously in the growth direction are present in a silicon carbide single crystal. BPDs are also present.
There is a problem that devices using a substrate manufactured from a silicon carbide single crystal with such dislocations present or even using a wafer with the quality of the crystal improved by further epitaxially growing an SiC on a substrate have a considerably lowered performance. For example, threading screw dislocation causes increase in the leakage current in a device. In addition, basal plane dislocation is said to become the source of killer defects in devices such as MOSFET.
To raise the yield in a substrate, it is important to reduce these dislocations.
The present invention has been made in view of the above-described problems, and an object thereof is to provide a silicon carbide single crystal growth apparatus and manufacturing method that can suppress the generation of threading screw dislocation, basal plane dislocation, and threading edge dislocation.
When an epitaxial growth is performed on a SiC substrate to make a device, threading screw dislocation and basal plane dislocation in particular are said to lead directly to the lowering of yields in a device.
To achieve the object, the present invention provides
a silicon carbide single crystal growth apparatus comprising:
a growth container comprising a growth container lid to which a seed crystal substrate is adhered and a growth container body for containing the seed crystal substrate and a silicon carbide raw material;
a heat-insulating container surrounding the growth container;
a temperature measuring equipment for measuring a temperature inside the growth container through a hole for temperature measurement provided in the heat-insulating container; and
a heater for heating the silicon carbide raw material, wherein
a silicon carbide single crystal is grown on the seed crystal substrate by heating and subliming the silicon carbide raw material by a sublimation method, wherein
the growth container lid has a pattern formed only within an adhesion region of the seed crystal substrate on the growth container lid, the pattern comprising at least one curved line or straight line that penetrates the growth container lid.
In this manner, when a pattern penetrating the growth container lid is formed only within the adhesion region of the seed crystal substrate on the growth container lid, the bend in the basal plane of the seed crystal substrate can be resolved by elastic deformation of the seed crystal substrate or silicon carbide single crystal while growing and cooling even if a warp occurs. It is considered that the stress that the seed crystal substrate receives from the growth container lid can thus be reduced further in each step of raising the temperature, growing at a high temperature, and cooling. It can also be considered that this is neared by elastic deformation rather than plastic deformation. It is said that there is a difference in coefficient of expansion between the seed crystal substrate and the growth container, being the adhesion base of the seed crystal substrate, and that the difference in the coefficients of expansion generates the dislocations. However, the difference in the coefficients of expansion itself is not the cause, and whether the seed crystal substrate is heated or cooled, a state of there being little stress is approached by forming a penetrating pattern on the growth container lid, being a base for sticking the seed crystal substrate onto, and therefore, the generation of threading screw dislocation and basal plane dislocation can be suppressed.
Furthermore, in this event, the pattern is preferably formed radially from a center of the growth container lid to which the seed crystal substrate is adhered.
When the penetrating pattern has such a shape, a uniform elastic deformation over the entire substrate is possible in the seed crystal substrate and the silicon carbide single crystal, and therefore, the generation of threading screw dislocation and basal plane dislocation can be suppressed more certainly.
In addition, the pattern is preferably formed concentrically.
When the penetrating pattern is formed concentrically as well, a uniform elastic deformation over the entire substrate is possible in the seed crystal substrate and the silicon carbide single crystal, and therefore, the generation of threading screw dislocation and basal plane dislocation can be suppressed more certainly.
Furthermore, the pattern preferably has a width of 5 mm or less.
When the width of the penetrating pattern is 5 mm or less, sufficient adhesive strength can be ensured between the seed crystal substrate and the growth container lid, and therefore, risk of the silicon carbide single crystal coming off and falling is reduced.
In addition, the present invention provides a method for manufacturing a silicon carbide single crystal by growing a silicon carbide single crystal on a seed crystal substrate adhered to a growth container lid of a growth container by a sublimation method, wherein
the silicon carbide single crystal is grown using, as the growth container lid, a growth container lid having a pattern formed only within an adhesion region of the seed crystal substrate, the pattern comprising at least one curved line or straight line that penetrates the growth container lid.
By such a method for manufacturing a silicon carbide single crystal, the bend in the basal plane of the seed crystal substrate can be resolved by elastic deformation of the seed crystal substrate or silicon carbide single crystal while growing and cooling even if a warp occurs. Thus, the generation of threading screw dislocation and basal plane dislocation can be suppressed, and therefore, a silicon carbide single crystal with a low dislocation density can be manufactured.
Furthermore, in this event, the pattern is preferably formed radially from a center of the growth container lid to which the seed crystal substrate is adhered. In addition, it is further preferable to form the pattern along the six or twelve crystal habit lines of a hexagonal crystal of SiC.
When a growth container lid having a penetrating pattern with such a shape formed is used, a uniform elastic deformation over the entire substrate is possible in the seed crystal substrate and the silicon carbide single crystal, and therefore, the bend in the basal plane of the seed crystal substrate can be resolved. Thus, the generation of threading screw dislocation and basal plane dislocation can be suppressed more certainly.
In addition, in this event, the pattern is preferably formed concentrically.
When a growth container lid having a concentrically formed penetrating pattern is used also, a uniform elastic deformation over the entire substrate is possible in the seed crystal substrate and the silicon carbide single crystal, and therefore, the bend in the basal plane of the seed crystal substrate can be resolved. Thus, the generation of threading screw dislocation and basal plane dislocation can be suppressed more certainly.
Furthermore, in this event, the pattern preferably has a width of 5 mm or less.
When a growth container lid formed with such a pattern width is used, sufficient adhesive strength can be ensured between the seed crystal substrate and the growth container lid, and therefore, risk of the silicon carbide single crystal coming off and falling is reduced.
The inventive silicon carbide single crystal growth apparatus has a pattern penetrating the growth container lid formed only within the adhesion region of the seed crystal substrate on the growth container lid so that the bend in the basal plane of the seed crystal substrate can be resolved by elastic deformation of the seed crystal substrate or silicon carbide single crystal while growing and cooling even if a warp occurs. Thus, the generation of threading screw dislocation and basal plane dislocation can be suppressed.
In addition, in the inventive method for manufacturing a silicon carbide single crystal, by using a growth container lid having a pattern penetrating the growth container lid formed only within the adhesion region of the seed crystal substrate, the bend in the basal plane of the seed crystal substrate can be resolved by elastic deformation of the seed crystal substrate or silicon carbide single crystal while growing and cooling even if a warp occurs. Thus, the generation of threading screw dislocation and basal plane dislocation can be suppressed, and therefore, a silicon carbide single crystal with a low dislocation density can be manufactured.
Hereinafter, the present invention will be described in detail as an example of an embodiment with reference to the drawings, but the present invention is not limited thereto.
As described above, a warp that occurs in a seed crystal substrate leads to a bend in the basal plane of a silicon carbide single crystal and basal plane dislocation (BPD) and threading screw dislocation (TSD), etc. are generated occur in conventional technology. There has been a problem that the performance of devices that use a substrate manufactured from a silicon carbide single crystal having such dislocations present therein is considerably degraded.
The present inventors have earnestly studied and found out that when a pattern is formed only within an adhesion region of a seed crystal substrate on a growth container lid, the pattern including at least one curved line or straight line that penetrates the growth container lid, the generation of threading screw dislocation and basal plane dislocation can be suppressed, completing the present invention.
That is, the present invention is a silicon carbide single crystal growth apparatus including:
a growth container including a growth container lid to which a seed crystal substrate is adhered and a growth container body for containing the seed crystal substrate and a silicon carbide raw material;
a heat-insulating container surrounding the growth container;
a temperature measuring equipment for measuring a temperature inside the growth container through a hole for temperature measurement provided in the heat-insulating container; and
a heater for heating the silicon carbide raw material, where
a silicon carbide single crystal is grown on the seed crystal substrate by heating and subliming the silicon carbide raw material by a sublimation method, where
the growth container lid has a pattern formed only within an adhesion region of the seed crystal substrate on the growth container lid, the pattern including at least one curved line or straight line that penetrates the growth container lid.
Hereinafter, the inventive silicon carbide single crystal growth apparatus will be described with reference to
The inventive silicon carbide single crystal growth apparatus 100 shown in
The growth container 101 is formed from a graphite with heat resistance, for example.
The inventive silicon carbide single crystal growth apparatus 100 has a pattern 111 penetrating the growth container lid 101a formed only within the adhesion region 112 of the seed crystal substrate 104 on the growth container lid 101a as shown in
In this manner, it is considered that when a pattern 111 penetrating the growth container lid 101a is formed within the adhesion region 112 of the seed crystal substrate 104 adhered to the growth container lid 101a, the bend in the basal plane of the seed crystal substrate 104 can be resolved by elastic deformation of the seed crystal substrate 104 or silicon carbide single crystal 105 while growing and cooling even if a warp occurs. Thus, the generation of dislocation can be suppressed.
Furthermore, when the penetrating pattern 111 has such shapes as those shown in
Furthermore, the width of the pattern 111 is preferably 5 mm or less (more than 0 mm and 5 mm or less). When the pattern width is 5 mm or less, the adhesive strength of the seed crystal substrate becomes sufficient, and there is no risk of falling.
In addition, when growing a silicon carbide single crystal 105, the crystal growth is performed in an inert gas atmosphere under reduced pressure by setting the growth container 101 inside an outer container 107 made from SUS or quartz and supplying an inert gas such as Ar or N2 while vacuum exhausting.
As the heater 103, a heater for performing RH (resistance heating) or RF (radiofrequency) heating can be used. In addition, by using a pyrometer as the temperature measuring equipment 108, temperature measurement can be performed with precision through the hole for temperature measurement 109 in the heat-insulating material from outside the growth container without contact.
A method for manufacturing a silicon carbide single crystal for manufacturing a silicon carbide single crystal 105 using the inventive silicon carbide single crystal growth apparatus 100 as described will be described using the flow diagram of
Firstly, the silicon carbide raw material 106 is contained in the growth container body 101b as shown in
By such a method for manufacturing a silicon carbide single crystal, the bend in the basal plane of the seed crystal substrate 104 can be resolved by elastic deformation of the seed crystal substrate 104 or silicon carbide single crystal 105 while growing and cooling even if a warp occurs. Thus, the generation of threading screw dislocation and basal plane dislocation can be suppressed, and therefore, a silicon carbide single crystal with a low dislocation density can be manufactured.
Furthermore, in this event, the pattern 111 is preferably formed radially from the center of the growth container lid 101a to which the seed crystal substrate 104 is adhered as shown in
When a growth container lid 101a having a penetrating pattern 111 with such a shape formed is used, a uniform elastic deformation over the entire substrate is possible in the seed crystal substrate 104 and the silicon carbide single crystal 105, and therefore, the bend in the basal plane of the seed crystal substrate 104 can be resolved. Thus, the generation of threading screw dislocation and basal plane dislocation can be suppressed more certainly.
In addition, in this event, the pattern 111 is preferably formed as a concentrically penetrating pattern.
When a growth container lid having a concentrically penetrating pattern 111 is used also, a uniform elastic deformation over the entire substrate is possible in the seed crystal substrate 104 and the silicon carbide single crystal 105, and therefore, the bend in the basal plane of the seed crystal substrate 104 can be resolved. Thus, the generation of threading screw dislocation and basal plane dislocation can be suppressed more certainly.
Furthermore, in this event, the pattern 111 preferably has a width of 5 mm or less (more than 0 mm and 5 mm or less).
When a growth container lid 101a formed with such a pattern 111 width is used, sufficient adhesive strength can be ensured between the seed crystal substrate 104 and the growth container lid 101a, and therefore, risk of the silicon carbide single crystal 105 coming off and falling is eliminated.
Hereinafter, the present invention will be described more specifically with reference to an Example and a Comparative Example, but the present invention is not limited thereto.
A silicon carbide seed crystal substrate with a 4-inch (101.6 mm) diameter was adhered to a growth container lid having a radially penetrating pattern formed as shown in
With a silicon carbide seed crystal substrate having a 4-inch (101.6 mm) diameter, a silicon carbide single crystal was grown according to the flow shown in
The examination results of the densities of threading screw dislocation (TSD) in the silicon carbide single crystal substrates in the Example and the Comparative Example are shown in Table 1, the examination results of the densities of basal plane dislocation (BPD) in Table 2, and the examination results of the densities of threading edge dislocation (TED) in Table 3.
In addition, observation photographs of dislocation pits in the Example are shown in
As clearly seen from Table 1, Table 2, and Table 3, the Example had an extremely low result for every dislocation density compared with the Comparative Example, and all of the dislocation densities were improved considerably. In the Example, since a pattern penetrating the growth container lid was formed only within the adhesion region of the seed crystal substrate on the growth container lid, it was possible to resolve the bend in the basal plane of the seed crystal substrate by elastic deformation of the seed crystal substrate or silicon carbide single crystal while growing and cooling even if a warp had occurred. Thus, it was possible to suppress the generation of threading screw dislocation, basal plane dislocation, and threading edge dislocation.
In addition, as clearly seen from
It should be noted that the present invention is not limited to the above-described embodiments. The embodiments are just examples, and any examples that have substantially the same feature and demonstrate the same functions and effects as those in the technical concept disclosed in claims of the present invention are included in the technical scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-117328 | Jun 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/021189 | 5/29/2019 | WO | 00 |
