JP6327519B2 - Method for processing silicon carbide single crystal substrate and silicon carbide single crystal substrate with jig - Google Patents

Description

  The present invention relates to a processing method suitable for manufacturing a silicon carbide single crystal substrate for forming a semiconductor element, and a silicon carbide single crystal substrate with a jig.

  In order to form a high-performance semiconductor element, a substrate processed with high precision is required. In particular, an element using a silicon carbide single crystal having a large band gap has attracted attention as a power semiconductor application. This silicon carbide has a higher hardness than silicon and is difficult to process with high accuracy.

By the way, in the planarization technique for the surface of a semiconductor wafer represented by a silicon wafer, silicon carbide is used as a jig for polishing such as a lap plate for the purpose of suppressing thermal deformation during surface polishing. Technology is known.
For example, Patent Document 1 describes a SiC wafer wrap plate using 0.05 to 0.015 wt% boron as a sintering aid as a lap plate used for polishing a semiconductor wafer.

Patent Document 2 describes a silicon carbide-based polishing plate having a thermal conductivity of 200 W / m · K or more and a Young's modulus of 450 GPa or more for the same purpose as Patent Document 1. Preferred configurations to achieve them, impregnated with molten Si into the silicon carbide sintered body having a bulk density of ^{2.60g / cm 3 ~2.90g / cm 3} , a bulk density of 3.05 g / ^cm 3 to 3 It is also described that a Si-SiC composite material having a flexural strength of 500 MPa or more at .15 g / cm ³ is used.

  Patent Document 3 describes a method in which a silicon carbide polycrystalline substrate made of a polycrystalline silicon carbide is bonded to a single crystal wafer by a heat-pressure bonding method through a coat layer.

  Patent Document 4 describes a method of thinning a single crystal silicon carbide substrate by bonding a single crystal silicon carbide substrate and a polycrystalline silicon carbide substrate by heat treatment.

JP-A-6-320415 JP 2007-283435 A JP 2010-235392 A JP 2009-117533 A

  The use of the silicon carbide sintered body of Patent Documents 1 and 2 described above was mainly intended to suppress deformation of the jig by utilizing the absolute low thermal expansion characteristics of silicon carbide. Therefore, the object to be polished is not limited, and no specific examples other than silicon are specified. Patent Documents 3 and 4 are all intended to bond a polycrystalline silicon carbide substrate to a single crystal silicon carbide substrate with high strength and bond them, and assume that the substrates are peeled off nondestructively. It is not done, and the damage when it peels is inevitable.

  On the other hand, in flattening a silicon carbide substrate that has low thermal expansion characteristics and a Young's modulus much higher than that of silicon, the material of the jig at the time of processing is not particularly problematic. Glass and the like have been used. However, according to the study of the present inventor, when the silicon carbide substrate and the jig are heat bonded, the jig side or the substrate side is warped, so that the reference surface is deformed and the processing accuracy is poor. Was confirmed. In addition, a silicon carbide single crystal substrate with a jig that can be applied to a semiconductor process while the substrate after processing is stuck to the jig without being caught by heat resistance and chemical resistance has not been proposed.

  An object of the present invention is to provide a silicon carbide single crystal substrate, a silicon carbide single crystal substrate, which is made of a material different from conventional silicon and capable of achieving a highly accurate surface planarization process, and a silicon carbide single crystal with a jig. It is to provide a crystal substrate.

In order to solve the above-described problems, the present invention has the following features.
In the first aspect of the present invention, the ratio of a coefficient of thermal expansion α _25-200 (CTE; Coefficient of Thermal Expansion) at 25 ° C. to 200 ° C. with respect to the substrate made of a silicon carbide single crystal and 25 to 200 ° C. is 1 or more. And a jig having a thermal conductivity ratio of 0.2 to 1.8 and having a major surface larger than the outer diameter of the substrate and serving as a support surface of the substrate. A step of heat-bonding one main surface of the substrate and the main surface of the jig via a thermoplastic or thermosetting adhesive member, and planarizing the other main surface of the substrate A method for processing a silicon carbide single crystal substrate, comprising: a step of separating the substrate and the jig.

According to a second aspect of the present invention, the ratio of the thermal expansion coefficient α _25-200 at 25 ° C. to 200 ° C. with respect to the substrate made of a silicon carbide single crystal and the substrate is from 0.7 to 1.3; Preparing a jig having a thermal conductivity ratio of 0.2 to 1.8 and having a major surface larger than the outer diameter of the substrate and serving as a support surface of the substrate; A step of heat-bonding the main surface and the main surface of the jig via a thermoplastic or thermosetting adhesive member, a step of flattening the other main surface of the substrate to Ra ≦ 1 nm, A method for processing a silicon carbide single crystal substrate, comprising: a step of peeling the substrate from a jig; and a step of forming an epitaxial growth surface of a silicon carbide film on the other main surface of the substrate.

  Moreover, it is preferable that GBIR (Global Back Ideal Ranges: 6SEMI M1-1013) of a board | substrate is 4 micrometers or less by the said planarization process.

  It is preferable that the planarization process of the said board | substrate includes the process of chemical mechanical polishing (CMP; Chemical Mechanical Polishing) process.

  Moreover, it is preferable that the said jig | tool is plate shape, thickness is 18 mm or less, and the parallelism between main surfaces is 10 micrometers or less.

In the third aspect of the present invention, the ratio of the coefficient of thermal expansion α _25-200 at 25 ° C. to 200 ° C. with respect to a substrate made of silicon carbide single crystal and having an element formed on one main surface is _25.degree . A jig having a main surface which is 7 or more and 1.3 or less and a thermal conductivity ratio is 0.2 or more and 1.8 or less and which is larger than an outer diameter of the substrate and serves as a support surface of the substrate; A step of heat-bonding one main surface of the substrate and the main surface of the jig via a thermoplastic or thermosetting adhesive member,
A step of planarizing the other main surface of the substrate, a semiconductor process step of performing at least one of cleaning, heat treatment, sputtering, etching, or plating, and peeling the substrate from the jig. A process for processing a silicon carbide single crystal substrate.

  It is preferable that the average thickness of the substrate is 500 μm or less by the planarization process.

  The planarization process of the substrate preferably includes a polishing process.

  The jig is plate-shaped and is 0.3 mm or more and 5 mm or less larger than the outer diameter of the substrate, the thickness is 0.5 mm or more and 3 mm or less, and the main surface SORI (SEMI M1-1013) is 30 μm or less. It is preferable.

Further, according to the present invention, a ratio of a thermal expansion coefficient α _25-200 at 25 ° C. to 200 ° C. with respect to a substrate made of a silicon carbide single crystal, a thermoplastic or thermosetting adhesive member, and the substrate is 0.7. A silicon carbide single crystal substrate with a jig, comprising: a jig having a thermal conductivity ratio of 0.2 to 1.8 and a thickness of 18 mm or less. is there.

  Furthermore, the parallelism between the main surfaces of the jig is preferably 10 μm or less.

  Further, an element is formed on one main surface of the substrate, the average thickness is 500 μm or less, the jig is 0.3 mm or more and 5 mm or less larger than the outer diameter of the substrate, and the thickness is 0.5 mm or more and 3 mm or less. The SORI of the main surface is preferably 30 μm or less.

  Here, it is preferable that the silicon carbide single crystal substrate with a jig has a flush annular wall made of the adhesive member at a peripheral portion of the substrate.

According to the processing method of the present invention, the warpage of the jig can be suppressed, and the main surface of the silicon carbide single crystal substrate can be planarized with high accuracy by suppressing the warpage and undulation on the substrate side. In addition, the jig can be peeled cleanly after the flattening process. As a result, it is possible to obtain a silicon carbide single crystal substrate with high efficiency and low cost.
Moreover, according to the silicon carbide single crystal substrate with a jig of the present invention, a silicon carbide single crystal substrate with a jig suitable for high-precision processing with high bonding strength between the substrate and the jig and less warpage can be obtained.

The silicon carbide single-crystal board | substrate with a jig | tool used for the processing method of this invention is shown, (a) is a perspective view, (b) is A-A 'sectional drawing. It is a figure explaining each process of embodiment in the processing method of the present invention. It is a figure explaining each process of another embodiment in the processing method of the present invention. The silicon carbide single-crystal board | substrate with a jig | tool of this invention is shown, (a) is before a planarization process, (b) is the schematic which shows after a planarization process. It is a photograph which shows the external appearance (no chipping) of the peripheral part of the silicon carbide single crystal substrate with a jig | tool of this invention. It is a photograph which similarly shows the outline (with chipping and a crack) of the peripheral part of a comparative example.

[First processing method]
The outline of the present invention will be described below.
First, the inventors have a problem that warpage occurs during flattening processing of a silicon carbide single crystal substrate (hereinafter, simply referred to as a substrate). The inventors have found that this is due to the difference in thermal expansion characteristics and the difference in thermal conductivity between the silicon carbide single crystal substrate and the jig accompanying this, and the inventors have conceived the present invention.
That is, in the present invention, a silicon carbide single crystal is used for the substrate. One jig has a thermal expansion coefficient α _25-200 from 25 ° C. to 200 ° C. of a ratio of 0.7 to 1.3 with respect to the substrate, and a thermal conductivity of 0. One feature is to use a material that is 2 or more and 1.8 or less. Note that the quality of the silicon carbide single crystal changes depending on the growth conditions and the like, and the thermal expansion coefficient α _25-200 and the thermal conductivity slightly vary accordingly. Therefore, as shown in Table 1, the silicon carbide single crystal in the following description is _handled with a thermal expansion coefficient α _25-200 of 4.2 × 10 ⁻⁶ m / K and a thermal conductivity of 490 W / m · K.
Here, the reason why the ratio of the thermal expansion coefficient α _25-200 is 0.7 or more and 1.3 or less is that an adhesive member such as wax is bonded in the range of 60 to 200 ° C. This is because the difference in thermal expansion due to the temperature difference is the main cause of warpage. Therefore, it is important to keep the ratio of the thermal expansion coefficient α _25-200 between 0.7 and 1.3. Preferably they are 0.8 or more and 1.2 or less, More preferably, they are 0.9 or more and 1.1 or less. Incidentally, as referred to herein a ratio of the thermal expansion coefficient alpha _25-200 A, multiplied by the value of the ratio of thermal expansion coefficient alpha _25-200 of the substrate becomes the thermal expansion coefficient alpha _25-200 jig That is. That is, if the thermal expansion coefficient α _25-200 of the substrate is 4.2 × 10 ⁻⁶ m / K, the thermal expansion coefficient α _25-200 of the _jig is 2.94 × 10 ⁻⁶ m / K or more. 46 × 10 ⁻⁶ m / K or less.

Next, the reason why the thermal conductivity ratio is 0.2 or more and 1.8 or less will be described below. As described above, by using a jig that satisfies the ratio of thermal expansion coefficient α _25-200 from 25 ° C. to 200 ° C. with respect to the substrate of 0.7 or more and 1.3 or less, both dimensions at each temperature can be set. You can get closer. However, when a temperature difference occurs between the jig and the substrate, the two have different dimensions. For example, a borosilicate glass jig having a thermal expansion coefficient of 3.3 × 10 ⁻⁶ m / K and a thermal conductivity of 1.2 W / m · K, and a thermoplastic adhesive member softened at 60 ° C. When used, in the cooling process after heating, only the substrate with high thermal conductivity is cooled first to a temperature near room temperature, and then the jig with low thermal conductivity is cooled. Then, in the process in which the temperature of the jig passes through the softening point of the adhesive member and cools, the adhesive member is solidified and bonded to the substrate, and further cooled from that temperature, the jig becomes smaller in size. On the other hand, since the dimensions of the substrate do not change, the difference in contraction between the two increases in this process. The result appears as warpage on the substrate side. For this reason, in the cooling process after heat-bonding the substrate and the jig, the thermal conductivity ratio between the substrate and the jig is set to 0.2 or more and 1.8 or less in order to suppress the temperature difference between the two. . Preferably they are 0.3 or more and 1.7 or less, More preferably, they are 0.5 or more and 1.5 or less. In addition, the ratio of thermal conductivity here means that the thermal conductivity of the jig is obtained by multiplying the thermal conductivity of the substrate by the value of the ratio. That is, assuming that the thermal conductivity of the substrate is 490 W / m · K, the thermal conductivity of the jig is 98 W / m · K or more and 882 W / m · K or less.
As another approach to this problem, a method of gradually cooling using a thermostatic bath or the like is conceivable to suppress the temperature difference. However, it takes time to cool down, and considering the deterioration of the adhesive member, the thermal conductivity is considered. It is more practical to set the ratio of 0.2 to 1.8. However, this method is not prevented from being used together.

As described above, a jig having both the thermal expansion coefficient α _25-200 and the thermal conductivity is used. In order to satisfy both conditions, it depends greatly on the selection of the material. In short, it is preferable to use a jig made of a material whose main component is the same composition as that of the substrate in order to make the above-mentioned range. For example, silicon carbide (single crystal, polycrystal), diamond, GaN, or ceramics mixed with a heat conductive filler may be Si ₃ N ₄ or BN. In particular, a composition having components other than silicon carbide as inevitable impurities is most preferable because the thermal expansion coefficient α _25-200 and the thermal conductivity can be made substantially the same. Further, if the structure is the same single crystal as the substrate, the thermal expansion characteristics and the thermal conductivity itself are substantially the same, which is further preferable in terms of characteristics. However, since a single crystal is very expensive, it is preferable from the viewpoint of cost to apply a dense polycrystal obtained by sintering without significant difference in these characteristics.

  Further, the jig is plate-shaped, usually disk-shaped, and needs a thickness of about 0.5 to 18 mm from the viewpoint of mechanical strength, warpage, and deformation. At this time, in order to process the substrate 1 with high accuracy, the parallelism between the principal surfaces of the jig is preferably 10 μm or less, preferably 5 μm or less, and more preferably 2 μm or less. Further, the surface roughness of one main surface on the side to which the substrate is attached may be of a level that can be used as a reference by contacting the substrate. For example, it is preferable that the surface roughness is small because the substrate is brought into contact with the reference and the surface is further scratched when further brought into contact with the substrate. Further, it is preferable that the surface roughness is large because the adhesive strength can be ensured while allowing the excess adhesive member to escape. Furthermore, a hole, a groove, or the like for allowing an extra adhesive member to escape may be provided on the main surface of the jig. Of course, the other main surface may have the same surface properties. As will be described later, after polishing by CMP, after peeling from the jig and forming a growth surface of the epitaxial film on the substrate, the thickness is 18 mm or less and the parallelism between the main surfaces is 10 μm or less. Those are preferred. This means that the thickness of the jig that is not deformed when performing precision polishing by CMP processing is secured, while the thinner the thickness is, the easier it is to handle and the lighter handling, the better the workability during processing, and the higher the parallelism. This is because the accuracy of the reference surface is increased.

  Further, the jig of the substrate with a jig to be flown through the semiconductor process has an outer diameter that is about 0.3 to 5 mm larger than the outer diameter of the substrate, a thickness of 0.5 to 3 mm, and a main surface SORI of 30 μm or less. Those are preferred. In order to protect the edge of the thinned silicon carbide single crystal substrate after processing, the outer diameter is preferably larger than the outer diameter by 0.3 mm or more. It is preferable that it is larger than 5 mm. The thickness is preferably 3 mm or less in order to be applied to a semiconductor process apparatus, and is preferably 0.5 mm or more in order to reduce handling properties. As for SORI on the main surface, the bonding layer for bonding the jig and the substrate is made uniform to increase the processing accuracy of the substrate, and further the dimensional accuracy such as the film thickness formed by the semiconductor process and the cooling efficiency are increased. Therefore, the thickness is preferably 30 μm or less. If it is a jig | tool which has sufficient rigidity, you may set it as the structure hold | maintained at three points of the other main surface of a jig | tool. By adjusting the height of the held points, it is possible to adjust the direction in which the load due to the weight is applied.

And in this invention, one main surface of the said board | substrate and the main surface of the said jig | tool are heat-bonded through a thermoplastic or thermosetting adhesive member. For example, as shown in FIG. 1, one main surface 5 of the circular substrate 1 and one main surface 6 of the circular jig 2 are bonded together using an adhesive member 3. Therefore, the focus is on the problems caused by the difference between the thermal expansion characteristics and the thermal conductivity characteristics between the silicon carbide single crystal substrate and the jig accompanying the heating at the time of bonding. exclude. In FIG. 1, one substrate is bonded to one jig, but a plurality of substrates may be bonded to one jig and simultaneously polished.
The thermoplastic or thermosetting adhesive member used may be any adhesive, but since silicon carbide has high hardness, it can be bonded with high strength, and at least has sufficient adhesive strength during flattening processing. . However, it is preferable that the adhesive member can be easily removed from the substrate after processing. Since the adhesive strength depends on the contact area between the substrate and the jig in addition to the adhesive force of the adhesive member, it is preferable to select the adhesive strength appropriately according to the dimension to be processed and the shape of the jig. A lower viscosity at the time of heating is preferable because highly accurate adhesion can be performed. Furthermore, depending on the type of processing liquid used for flattening processing, etc., and the type of cleaning liquid used for cleaning, insolubility and solubility in water, organic solvents, acids, alkalis, etc. are selected, without peeling during processing, after processing Those that are easy to peel cleanly without causing damage or damage to the substrate are good. For example, when processing using a neutral processing liquid, a wax of a thermoplastic waxy substance that exhibits sufficient adhesive strength during processing and can be removed using a cleaning liquid such as an alkali after processing is used. An adhesive member such as a resin is preferable because it can be obtained at low cost. Specifically, it is softened at a temperature of about 60 ° C. to 140 ° C., but up to about 200 ° C., a chemical adhesive that is stable and can be washed with an organic solvent, such as PEG, PPG, various types There are synthetic waxes in which waxy substances such as fatty acids are mixed with resin components such as rosin, vinyl acetate, nylon, acrylic and various polymers.

Next, the planarization process can employ a processing method such as grinding, mechanical polishing with abrasive grains, or chemical mechanical polishing, but is not particularly limited. A combination of these techniques can also be used.
After the planarization process, the substrate and the jig are separated from each other and then another process is applied, or after the other process is applied to the substrate with the jig after the planarization process, the substrate and the jig are attached. It can also be peeled off. The peeling process is selected according to the bonding method and situation, such as a method of mechanical peeling such as pulling the substrate or dividing with a scraper, a method using heating, a method using a chemical for peeling and cleaning, etc. However, it can be performed by an appropriate method without damaging the substrate or the element.
Through the above steps, a highly accurate surface planarization process can be achieved with a material different from a conventional silicon substrate called a silicon carbide single crystal substrate.

[Second processing method]
The processing method according to the second aspect of the present invention is effective as a processing method for a silicon carbide single crystal substrate for forming an epitaxial growth surface of a silicon carbide film. Before the flattening process, it is almost the same as the first processing method described above, and therefore different processes will be described below.
That is, in this processing method, the surface roughness Ra (JIS B 0601 (1994)) of the other main surface of the substrate is planarized to Ra ≦ 1 nm,
And a step of forming an epitaxial growth surface of a silicon carbide film on the other main surface of the substrate after peeling.
Here, in the flattening process, the reason for flattening to Ra ≦ 1 nm is to flatten with an accuracy close to the atomic arrangement, and to suppress defects due to the surface shape during epitaxial growth. This flattening process is preferably performed by chemical mechanical polishing in order to suppress the work-affected layer and to improve the processing efficiency of the fine abrasive grains.
The reason why the epitaxial growth surface of the silicon carbide film is formed on the other main surface of the substrate is that it is easy to grow a crystal having the same crystal structure and few defects in accordance with the underlying crystal structure. Accordingly, an additive may be doped to bring out semiconductor characteristics. Epitaxial growth can be performed by various methods such as molecular beam epitaxy, metal organic vapor phase epitaxy, and liquid phase epitaxy.

  In this processing method, the GBIR of the substrate is desirably 4 μm or less by planarization. Preferably it is 3 micrometers or less, More preferably, it is 2 micrometers or less. If the GBIR is in the range of 4 μm or less, the difference in height will be 4 μm or less when the back surface is adsorbed, so that the epitaxial growth can be performed while suppressing the thickness variation of the silicon carbide single crystal film, and the subsequent device fabrication. In particular, it is particularly preferable because accuracy is improved. Furthermore, it is preferable to employ a chemical mechanical polishing process because Ra can be further reduced and the work-affected layer is also reduced.

  Further, as described above, the jig has a thickness of 18 mm or less, and the parallelism between the main surfaces is 10 μm or less, which makes a silicon carbide single crystal substrate processing method particularly suitable for epitaxial polishing. Preferably it is 5 micrometers or less, More preferably, it is 2 micrometers or less. Here, the thickness is defined as 18 mm or less in order to improve workability while ensuring the rigidity of the jig.

[Third processing method]
The processing method according to the third aspect of the present invention is characterized in that the thickness of the substrate on which the element 13 is formed on one main surface 5 of the substrate is reduced. The thickness of the substrate is reduced by reducing the electrical resistance through the substrate with respect to the element 13 on one main surface and further flattening the other main surface, and then providing a semiconductor process as it is to provide an electrode. It is effective as a processing method that can move to a process. The substrate used here has an integrated circuit and a diode element operating at a high voltage on one main surface 5 of the substrate, and various elements such as a film doped with a carrier opposite to the substrate, a groove, an electrode, and a wiring. Has been. The components formed in advance on these substrates are collectively referred to as elements in the present invention.
Since the third processing method is substantially the same as the first processing method described above until the flattening processing, different steps will be described below.
That is, this processing method is a semiconductor process in which at least one of cleaning, heat treatment, sputtering, etching, or plating is performed using a silicon carbide single crystal substrate with a jig after flattening as it is. It becomes a processing method to shift to the process. Here, the semiconductor process in which the temperature is increased, such as heat treatment or sputtering, is in a range that does not exceed the heat resistance temperature of the adhesive member, and epitaxial growth that requires a temperature higher than the melting point of silicon carbide is not included in the semiconductor process of the present invention. Also, processing or assembly processes may be performed as the semiconductor process. Furthermore, before and after the step of peeling is not questioned. With this configuration, the opposite side of the mounting surface of the element 13 can be precisely planarized, so that a semiconductor element using a thinner silicon carbide single crystal can be obtained. On the other hand, the silicon carbide single crystal substrate with a jig itself has the same external dimensions and rigidity as a conventional silicon substrate, so that it can be handled easily and can be applied as it is to an existing semiconductor manufacturing process apparatus.

  In the planarization process, it is desirable that the average thickness of the processed substrate is 500 μm or less. Although the thickness of the substrate after processing is arbitrarily determined according to the element 13 formed on one main surface, the average thickness of the substrate is 500 μm or less, preferably from the film thickness of the element 13 generally used. When the thickness is in the range of 50 to 100 μm, the electrical resistance of the substrate required for the semiconductor element is particularly preferable. In order to increase the pass rate of the thinned substrate 1, it is preferable that the substrate 1 after being processed and peeled off from the jig 2 has a thickness variation of 20 μm or less. Therefore, the thickness variation of the adhesive member is preferably 10 μm or less.

  The jig is larger than the outer diameter of the substrate in the range of 0.3 mm to 5 mm, the thickness is 0.5 mm to 3 mm, and the SORI of the main surface is 30 μm or less. While maintaining one main surface on which 13 is formed, only the other main surface of the substrate is ground to be suitable for thinning the substrate. Here, the reason why the outer diameter (diameter) of the substrate is set to be 0.3 mm or more and 5 mm or less is to avoid the outer peripheral portion where the accuracy may be deteriorated due to sagging when the main surface of the jig is processed. This is because the substrate can be adhered to the center of the substrate with high accuracy. Furthermore, application of adhesive and thermocompression bonding can be easily performed. The thickness is defined as 0.5 mm or more and 3 mm or less when the jig is attached to a semiconductor process in which at least one of cleaning, heat treatment, sputtering, etching, or plating is performed. This is because the silicon carbide single crystal substrate is passed through as it is, and it is preferable that the thickness be equal to the thickness obtained by subtracting the thickness of the silicon carbide single crystal substrate and the adhesive member from the thickness of a generally used semiconductor substrate. Furthermore, the SORI of the main surface of the jig is set to 30 μm or less because the bonding layer for bonding the jig and the substrate is made uniform to increase the processing accuracy of the substrate, and the film thickness formed by the semiconductor process, etc. This is to improve the dimensional accuracy and cooling efficiency.

[Silicon carbide single crystal substrate with jig]
Further, the silicon carbide single crystal substrate with a jig of the present invention is not limited to that used in the above-described processing method of the present invention, but is suitable for use in the third processing method, 5 illustrates a silicon carbide single crystal substrate with a jig in the third processing method. In other words, the silicon carbide single crystal substrate having the element 13 is thinned, further through a semiconductor process, and after passing through an appropriate process, the silicon carbide with a jig that can be easily separated from the substrate It is a single crystal substrate. The substrate is made of silicon carbide single crystal, and elements 13 and the like are formed in advance on one main surface. One jig has a thermal expansion coefficient α _25-200 ratio of 25 to 200 ° C. relative to the substrate of 0.7 or more and 1.3 or less, and a thermal conductivity ratio of 0.2 or more. It is 1.8 or less, and warpage is unlikely to occur during the process of thermocompression bonding the substrate. Furthermore, by adjusting the heat conduction ratio to the above range, an effect of effectively radiating the generated heat can be obtained in a dry process where heat is generated particularly in the semiconductor process.

  Further, it is larger than the outer diameter of the substrate by not less than 0.3 mm and not more than 5 mm, and the thickness is not less than 0.5 mm and not more than 3 mm. Further, the SORI of the main surface is set to 30 μm or less. This makes it easy to manage the film thickness in dry processes and sputtering, and further increases the contact area with the cooling plate. can get. One main surface of the substrate provided with the element 13 and one main surface of the jig are bonded by a thermoplastic or thermosetting adhesive member. Thereby, both are easily peeled after processing, and can be peeled without damaging the element 13 at the time of peeling and without polluting the main surface of the substrate. The thickness of the thermoplastic or thermosetting adhesive member is preferably 2 μm or more and 200 μm or less, and particularly preferably 10 μm or more and 100 μm or less. If the thickness of the adhesive member is 2 μm or more and 200 μm or less, the unevenness due to the elements 13 formed on one main surface can be absorbed by the adhesive member, and the average thickness of the substrate can be ground to 500 μm or less. It is easy to adjust the entire thickness of the substrate with tools to 0.5 mm or more and 3 mm or less.

  Further, it is effective to form a flush annular wall made of the adhesive member on the peripheral edge of the substrate. This is an adhesive member when bonding the substrate and the jig, and an annular wall is formed on the substrate, and the bonding member is processed together with the substrate to provide a flush annular wall. With this annular wall, it is possible to obtain an effect of protecting the peripheral portion of the substrate that has been cut and thinned during the flattening process, and suppressing chipping and further cracks originating from the chipping. Furthermore, when chemical mechanical polishing is performed thereafter, the peripheral portion can be protected and defects such as edge chips can be suppressed. In addition, since the outer peripheral portion of the jig is used for holding and transporting the semiconductor process, damage to the outer peripheral portion of the extremely thin silicon carbide single crystal substrate can be prevented. It should be noted that it is sufficient that the surface is flush and does not turn up, and it is sufficient if the above-described effects can be obtained. Further, as shown in FIG. 9, for example, as shown in FIG. 9, a sheet-shaped adhesive member is used as the adhesive member, and the means for forming the annular wall is bonded and polished so as to be wound around the peripheral edge of the substrate before processing. The annular wall may be formed by processing the surface together with the substrate by, for example. Alternatively, a liquid adhesive member may be applied to the peripheral edge of the substrate and similarly processed to be flush with the substrate by polishing or the like.

  As described above, also in the first and second processing methods, the silicon carbide single crystal substrate with a jig can be used under conditions suitable for each processing method.

  Embodiments of the present invention will be described below in detail with reference to the drawings, but the present invention is not limited thereto. The description of each embodiment is applicable to other embodiments unless otherwise specified.

[1] Example 1
A silicon carbide single crystal substrate for forming a surface for epitaxial growth was processed using the processing method of the present invention. The applied conditions will be described below with reference to FIG.
(A) Step of Preparing Substrate 1 and Jig 2 In FIG. 2, the substrate 1 is made of a single crystal of silicon carbide. In this example, a single crystal ingot is processed into a cylindrical shape using an outer cylinder grinding device, and then sliced using a wire saw, and has an outer diameter of 100 mm (φ4 inches) having the other main surface 4 and one main surface 5. ) To obtain a substrate 1 having a thickness of about 0.5 mm. In addition, in order to change the orientation of the silicon carbide single crystal when slicing, or to increase the parallelism of the other main surface 4 and one main surface 5 of the substrate after slicing, it is processed using a double-side polishing apparatus or the like. Also good.
On the other hand, the jig 2 has a thermal expansion coefficient α _25-200 ratio of 0.7 to 1.3 with respect to the substrate of 25 ° C. to 200 ° C. and a thermal conductivity ratio of _0.1 . It consists of 2 or more and 1.8 or less material. In this example, a polycrystalline silicon carbide sintered body was used. For example, the sintered body is formed by molding a powder with a dimension taking into account the shrinkage rate, followed by hot press sintering, further adjusting the parallelism by a double-side polishing apparatus, and having an outer diameter having one main surface 6 and the other main surface 7. A jig 2 having a thickness of about 150 mm and a thickness of 8 mm was obtained. Here, the one main surface 6 of the jig 2 serves as a reference when the other main surface 4 of the substrate 1 is flattened by bringing the main surface 5 of the substrate 1 into contact with the jig 1 later. The main surface 6 of No. 2 was made larger in outer diameter than one main surface 5 of the substrate 1, and the parallelism was processed so that the parallelism between both surfaces was 10 μm or less using a double-side polishing apparatus.

(B) Step of pressure bonding the substrate and the jig through the adhesive member Next, the prepared substrate 1 and the jig 2 were bonded through the adhesive member 3 while applying heat and pressure.
First, one main surface 5 of the substrate 1 and the main surface 6 of the jig 2, which are adhesion surfaces, are washed with water, an organic solvent, or the like to remove deposits and the like. Next, the substrate 1 and the jig 2 are heated to the working temperature using a hot plate. The working temperature is preferably in the range where the adhesive member is sufficiently softened and the dimensional change of the substrate 1 and the jig 2 due to thermal expansion is small, and is preferably about 20 to 50 ° C. higher than the softening point of the adhesive member. The temperature was 100 ° C. The substrate 1 and the jig 2 are sufficiently heated, and after the entire surface becomes uniform at 100 ° C., the adhesive member 3 is applied to the main surface 6 of the jig 2. In this example, the softening wax at 80 ° C. is applied to the main surface of the jig. It applied to the 6th side. Here, bubbles are not caught between the main surfaces of the substrate 1 and the jig 2, and the wax does not remain at the contact portion between the main surfaces, and the bonding strength that does not peel off during processing can be ensured. Note that the coating amount is moderated.
Next, one main surface 5 of the substrate 1 was brought into contact with the main surface 6 of the jig 2 via the adhesive member 3. At this time, the substrate 1 and the jig 2 were brought into contact with each other while being pressed and slid to each other to remove excess wax along with air and dust from between the jig and the substrate, and a sufficient load was applied. Subsequently, the adhesive member is solidified and fixed by cooling the substrate 1 and the jig 2. At this time, it is further cooled after the softening point of the adhesive, but the ratio of the thermal expansion coefficient α _25-200 between the substrate 1 and the jig 2 is 0.7 or more and 1.3 or less, and the thermal conductivity is Since the ratio is set to 0.2 or more and 1.8 or less, the amount of warpage due to thermal expansion difference or temperature difference is suppressed. In order to prevent adhesion of abrasive grains and the like, extra adhesive members were removed after complete adhesion.

(C) Step of flattening the other main surface of the substrate The other main surface 4 of the substrate 1 was polished. First, a rough polishing process is performed using rough diamond abrasive grains until the entire surface is touched. Thereafter, polishing with a diamond abrasive having a particle diameter of 1 μm and CMP were performed to reduce the surface roughness.

  In order to perform epitaxial growth with good quality, the other main surface 4 needs to be flattened at the atomic level, that is, surface roughness Ra ≦ 1 nm. At this time, it is preferable to adjust the GBIR of the substrate to about 4 μm or less because it contributes to high accuracy in forming an element using an epitaxially grown film. Therefore, the jig 2 is a jig in which the parallelism between the main surfaces is 10 μm or less, the surface roughness Ra of the main surface 6 is 0.1 mm or less, and an adhesive member relief portion is formed on the main surface 6. Using.

  When processing the other main surface of the substrate after bonding, it is processed by CMP using a slurry containing an oxidant and colloidal silica after planarization by mechanical polishing and peeling the substrate from the jig. A more suitable surface can be obtained for epitaxial growth with a deteriorated layer and less scratches. When the epitaxial growth surface of the silicon carbide film is not formed, the planarization process by CMP may be usually omitted, but it may be performed to relieve stress or the like due to the work-affected layer.

Next, there is a step of forming an epitaxial growth surface of a silicon carbide film on the other main surface of the substrate. Since this step can be performed by using an existing apparatus and method, description thereof is omitted here.

(D) The process of peeling a board | substrate and a jig | tool Then, it peels in the procedure reverse to an adhesion | attachment process. That is, first, the silicon carbide single crystal substrate with a jig from which the attached abrasive grains are completely removed is heated to 100 ° C. to soften the adhesive member. Since it becomes easy to peel by overheating and softening the adhesive member, the substrate is slid to peel from the jig. The adhesive member 3 attached to the substrate 1 after being peeled may be cleaned using a solvent or the like.

  Under the conditions described above, a substrate for epitaxial growth was obtained using a polycrystalline silicon carbide jig. On the other hand, as Comparative Example 1, the material was processed under the same conditions as in Example 1 except that alumina was used. Table 2 shows GBIR (measured by SEMI M1-1013) of the other main surface of the substrate 1 after processing. The substrate which was processed accurately with respect to Comparative Example 1 and was suitable for epitaxial growth of the silicon carbide film was obtained.

[2] Example 2
Using the method of the present invention, back grinding was performed to reduce the thickness of the substrate 1 by polishing the other main surface 4 while protecting the various elements 13 formed on the one main surface 5 of the substrate 1. . Specific conditions used will be described below with reference to FIG.

(A) Step of Preparing Substrate and Jig Substrate 1 is made of a single crystal of silicon carbide as in Example 1 above.
A jig 2 having a thickness of 1 mm was used as a sufficiently thin film that can be passed through a semiconductor process while ensuring rigidity. Since the thinned substrate 1 is easily damaged, the jig 2 serves as a protective member when passing through a semiconductor process. Therefore, a jig whose outer diameter is approximately 1 mm larger than the outer diameter (diameter) of the substrate 1 was used. Since other manufacturing methods and conditions are the same as those in the first embodiment, description thereof will be omitted, and different parts will be described.

(B) Step of pressure bonding the substrate and the jig through the adhesive member Next, the prepared substrate 1 and jig 2 are pressure bonded by applying heat through the adhesive member. At this time, the adhesive member is bonded so as to cover the outer periphery of the substrate. When backgrinding is performed, the substrate thickness is made extremely thin by grinding to about 100 μm, so it is necessary to take measures against defects at the peripheral edge that become particularly brittle. In addition, since the element 13 is formed on one main surface 5 of the substrate 1, an adhesive sheet in which a thermosetting adhesive as described below is formed into a sheet shape is used as the adhesive member 3 here. The adhesive member passes through the semiconductor process with the substrate 1 and the jig 2 bonded, and thus has high heat resistance to the extent that heat treatment, sputtering, vapor phase etching, or the like can be passed through, or cleaning, liquid phase etching, or A material that is resistant to chemicals such as acid and alkali can be used to such an extent that it can be passed through plating. Here, an adhesive sheet having acid resistance and alkali resistance and a heat resistant temperature of 200 ° C. was used.

(C-1) Step of flattening the other main surface of the substrate The other main surface 4 of the substrate 1 was polished. First, rough polishing was performed using coarse diamond abrasive grains. The peripheral edge of the substrate 1 is chipped, and cracks are easily generated. Therefore, in order to suppress the occurrence of chipping at the peripheral portion, polishing was performed using polishing abrasive grains. Here, the substrate 1 was processed until the thickness became 100 μm.

(C-2) Step through a semiconductor process After polishing, a metal film was sputtered using a general metal film sputtering apparatus. Since the peripheral portion of the jig was set in the apparatus, the peripheral portion of the substrate was less likely to be chipped by contact.

  As described above, in Example 2, the other main surface of the substrate on which the element 13 was formed on one main surface was polished using a polycrystalline silicon carbide jig. On the other hand, as Comparative Example 2, the jig was processed using the same method as Example 2 except that borosilicate glass was used. Table 3 shows the reduction rate of GBIR of the silicon carbide single crystal substrate with the jig before and after each processing and the SORI after processing (measured by SEMI M1-1013). GBIR after processing was smaller in Example 2, and a silicon carbide single crystal substrate with a jig could be thinned with high accuracy. Also, the processed SORI was smaller than that of Comparative Example 2.

[3] Example 3
The pasting sheet 9 was used as an adhesive member, and the substrate was processed so that a part was wound around the outer periphery of the substrate as shown in FIG. For comparison, the substrate was processed without winding a sheet around the outer periphery. FIG. 5 shows a photograph of a portion where the peripheral edge is wound, and FIG. 6 shows a photograph when the periphery is not wound. In the case of winding, the annular wall 10 was formed on the peripheral edge of the substrate, and the edge chip 11 and the crack 12 as shown in FIG. 6 were not generated. In particular, it was confirmed that the edge chip 11 was not generated despite the presence of crystal defects. On the other hand, when not wound, the crack 12 was generated together with the edge chip 11, and the edge chip 11 was also generated at the crystal defect portion.

  It is suitable as a highly accurate method for processing a silicon carbide single crystal substrate. Further, the present invention can be applied to a silicon carbide single crystal substrate with a high-precision jig that can form an epitaxial growth surface, and a silicon carbide single crystal substrate with a jig that can be easily adapted to a semiconductor manufacturing process without defects such as edge chips.

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Jig 3 ... Adhesive member 4 ... First main surface 5 of substrate ... Second main surface 6 of substrate ... First main surface of jig Surface 7 ... Second main surface 8 of the jig 8 ... Main surface 9 after the semiconductor process (cleaning + sputtering) ... Paste sheet (adhesive member)
10 ... annular wall 11 ... edge chip 12 ... crack 13 ... element

Claims (13)

The ratio of thermal expansion coefficient α _25-200 at 25 ° C. to 200 ° C. with respect to the substrate made of silicon carbide single crystal and the substrate is 0.7 to 1.3, and the ratio of thermal conductivity is Preparing a jig having a main surface which is 0.2 to 1.8 and larger than the outer diameter of the substrate and serves as a support surface of the substrate;
Heat bonding the one main surface of the substrate and the main surface of the jig through a thermoplastic or thermosetting adhesive member;
Flattening the other main surface of the substrate;
Peeling the substrate and the jig;
A method for processing a silicon carbide single crystal substrate, comprising: The ratio of thermal expansion coefficient α _25-200 at 25 ° C. to 200 ° C. with respect to the substrate made of silicon carbide single crystal and the substrate is 0.7 to 1.3, and the ratio of thermal conductivity is Preparing a jig having a main surface which is 0.2 to 1.8 and larger than the outer diameter of the substrate and serves as a support surface of the substrate;
Heat bonding the one main surface of the substrate and the main surface of the jig through a thermoplastic or thermosetting adhesive member;
Flattening the other main surface of the substrate to Ra ≦ 1 nm;
Peeling the substrate from the jig;
Forming an epitaxial growth surface of a silicon carbide film on the other main surface of the substrate;
A method for processing a silicon carbide single crystal substrate, comprising: By the planarization process, the GBIR of the substrate is set to 4 μm or less.
A method for processing a silicon carbide single crystal substrate according to claim 1. The planarization of the substrate includes a chemical mechanical polishing process,
The method for processing a silicon carbide single crystal substrate according to any one of claims 1 to 3. The jig is plate-shaped and has a thickness of 18 mm or less, and the parallelism between main surfaces is 10 μm or less.
The method for processing a silicon carbide single crystal substrate according to claim 1. The ratio of the thermal expansion coefficient α _25-200 at 25 ° C. to 200 ° C. with respect to the substrate made of silicon carbide single crystal and having an element formed on one main surface is from 0.7 to 1.3 And providing a jig having a thermal conductivity ratio of 0.2 to 1.8 and having a main surface larger than the outer diameter of the substrate and serving as a support surface of the substrate;
Heat bonding the one main surface of the substrate and the main surface of the jig through a thermoplastic or thermosetting adhesive member;
Flattening the other main surface of the substrate;
A semiconductor process step for performing at least one of cleaning, heat treatment, sputtering, etching, or plating; and
Peeling the substrate and the jig;
A method for processing a silicon carbide single crystal substrate, comprising: By the planarization process, the average thickness of the substrate is set to 500 μm or less.
A method for processing a silicon carbide single crystal substrate according to claim 6. The planarization process of the substrate includes a polishing process,
A method for processing a silicon carbide single crystal substrate according to claim 6 or 7. The jig is plate-shaped and is 0.3 mm or more and 5 mm or less larger than the outer diameter of the substrate, the thickness is 0.5 mm or more and 3 mm or less, and the SORI of the main surface is 30 μm or less.
The method for processing a silicon carbide single crystal substrate according to any one of claims 6 to 8. The ratio of thermal expansion coefficient α _25-200 at 25 ° C. to 200 ° C. with respect to the substrate made of silicon carbide single crystal, the thermoplastic or thermosetting adhesive member, and the substrate is from 0.7 to 1.3 And a silicon carbide single crystal substrate with a jig, comprising: a jig having a thermal conductivity ratio of 0.2 to 1.8, a plate shape and a thickness of 18 mm or less.   The silicon carbide single crystal substrate with a jig according to claim 10, wherein the jig has a parallelism between main surfaces of 10 μm or less.   The substrate has an element formed on one main surface and an average thickness of 500 μm or less. The jig is 0.3 mm or more and 5 mm or less larger than the outer diameter of the substrate, and the thickness is 0.5 mm or more and 3 mm. The silicon carbide single crystal substrate with a jig according to claim 10 or 11, wherein SORI of the main surface is 30 µm or less.   The silicon carbide single crystal substrate with a jig according to any one of claims 10 to 12, wherein a peripheral wall portion of the substrate has a flush annular wall made of the adhesive member.