JP5869280B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device.

  For example, SiC (silicon carbide) is known as a substrate material for semiconductor wafers. SiC is suitable for forming a semiconductor element because of its high hardness and thermal conductivity.

  The thickness of the substrate is, for example, about 500 (μm), but after the formation of the semiconductor element, it is ground by a grinding device called a back grinder and is finally reduced to about 100 to 150 (μm). . This is for adjusting the aspect ratio of the through hole formed inside the substrate and reducing the thickness of the semiconductor chip obtained from the wafer.

  For example, Patent Document 1 discloses a technique for grinding a wafer so that an inner peripheral portion of the wafer is thinner than an outer peripheral portion.

JP-A-5-121384

  The surface roughness of the substrate opposite to the surface on which the semiconductor element is formed is reduced by so-called mirror finish processing in order to improve thermal conductivity or adsorption. For this reason, in the grinding process by the grinding device, the grindstone of the device cannot slip effectively, and as a result, the operating current of the grinding device exceeds the upper limit value, or the operation of the device stops, or the device There is a problem that cracks occur in the substrate due to excessive pressing of the surface due to.

  This problem does not exist only in this type of grinding technique, but is common when the surface of the substrate is ground with a grindstone or abrasive grains.

  An object of the present invention is to provide a method for manufacturing a semiconductor device in which a substrate can be easily ground.

In order to achieve the above object, a method of manufacturing a semiconductor device according to claim 1 includes a step of forming a semiconductor element on one surface of a substrate, and dry etching the opposite surface of the substrate on which the semiconductor element is formed. Thus, the method includes a step of forming irregularities so that the roughness of the opposite surface of the substrate is increased, and a step of grinding the opposite surface of the dry-etched substrate.

  According to the above method for manufacturing a semiconductor device, the substrate is dry-etched on the surface opposite to the surface on which the semiconductor element is formed, whereby irregularities are formed on the opposite surface. And when grinding the opposite surface dry-etched, the unevenness | corrugation formed in this opposite surface and the grindstone for grinding, or the unevenness | corrugation of an abrasive grain can fully mesh | engage mutually. Therefore, the grindstone or the abrasive can effectively grind the surface of the substrate without slipping.

  In the method for manufacturing a semiconductor device, the substrate may include one selected from Si, SiC, GaN, GaAs, and sapphire.

  In the method for manufacturing a semiconductor device, the opposite surface of the substrate may be dry-etched with a fluorine-based gas.

In the method for manufacturing a semiconductor device, the fluorine-based gas may be one selected from CF ₄ , CHF ₃ , and SF ₆ O ₂ , or one in which oxygen is added to the selected one. Good. When oxygen is added in this way, for example, carbon on the SiC substrate can be efficiently removed.

  In the method of manufacturing a semiconductor device, an adhesive is applied to one surface of the substrate on which the semiconductor element is formed, before the step of grinding the opposite surface of the dry-etched substrate, and the substrate is supported. You may make it further include the process of sticking to.

  The method for manufacturing a semiconductor device may further include a step of forming a protective film that covers one surface of the substrate on which the semiconductor element is formed, prior to the step of attaching the substrate to a support.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the semiconductor device with easy grinding of a board | substrate can be provided.

It is a flowchart which shows the manufacturing method of a semiconductor device. It is sectional drawing which shows the structure of a semiconductor element. It is sectional drawing which shows the formation process of a protective film. It is sectional drawing which shows the sticking process to the support substrate of a board | substrate. It is a side view which shows an etching process. It is a side view which shows the grinding process of the surface of a board | substrate. It is the upper side figure and side view of a grinding wheel. It is an enlarged view of the part shown with the code | symbol P of FIG.

  FIG. 1 is a flowchart showing a method for manufacturing a semiconductor device. The manufacturing process of the present embodiment includes an element forming process St1, a protective film forming process St2, an attaching process St3, an etching process St4, a grinding process St5, and a dividing process St6.

  In the element formation step St1, the semiconductor element 2 is formed on one surface of the substrate 10 as shown in FIG. The substrate 10 includes, for example, one selected from Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), and sapphire. Among these, SiC, GAN, and sapphire are preferable because they have relatively high hardness. But the board | substrate 10 may be comprised with another material, if characteristics, such as thermal conductivity and hardness, satisfy | fill conditions.

  The semiconductor element 2 is a field effect transistor (FET), for example, and includes a nitride semiconductor layer 11, SiN layers 13, 14, a wiring layer 15, a gate electrode 16a, a source electrode 16b, and a drain electrode 16c. . The nitride semiconductor layer 11 includes a barrier layer 110, a channel layer 111, an electron supply layer 112, and a cap layer 113.

  The barrier layer 110 is made of, for example, AlN (aluminum nitride) with a thickness of 300 (nm), and the channel layer 111 is made of, for example, i-GaN (gallium nitride) with a thickness of 1000 (nm). The electron supply layer 112 is made of, for example, AlGaN (aluminum gallium nitride) having a thickness of 20 (nm), and the cap layer 113 is made of, for example, n-GaN having a thickness of 5 (nm).

  Further, the SiN layers 13 and 14 function as insulating layers, and each thickness is formed to 40 (nm) and 20 (nm), for example. The wiring layer 32 is made of a metal such as Au.

  The source electrode 26 and the drain electrode 28 are ohmic electrodes, and are formed by, for example, stacking Ti, Al, or Ta, Al in this order. On the other hand, the gate electrode 30 is formed by stacking, for example, Ni and Au in this order.

  The above-described layers and electrodes are formed by, for example, an epitaxial growth method, a plasma CVD (Chemical Vapor Deposition) method, a thin film formation technique such as sputtering and vapor deposition, printing, plating, or a combination thereof, but the formation method is not limited. . The formation process is performed by adsorbing the substrate 10 to a stage and heating it to a temperature of several hundred degrees. At this time, as described above, since the substrate 10 has high thermal conductivity and the surface roughness of the surface opposite to the surface on which the element 2 is formed is low, the substrate 10 exhibits high thermal conductivity and adsorptivity. .

  Next, in the protective film forming step St2, as shown in FIG. 3, the protective film 3 is formed on the substrate 10 so as to cover the one surface 10a on which the semiconductor element 2 is formed. This protective film 3 protects the element 2 so that the element 2 is not damaged when the substrate 10 is peeled off from the support bonded in the subsequent bonding step St3. The protective film 3 preferably has a high melting point. For example, a resist film can be used, but is not limited thereto.

  Next, in the attaching step St3, as shown in FIG. 4, the adhesive 4 is applied to the one surface 10a on which the semiconductor element 2 is formed, and the substrate 10 is attached to the support 5. The support 5 is, for example, a glass plate, and supports the substrate 10 so that the substrate 10 does not warp in the subsequent grinding step St5. For example, a wax may be employed as the adhesive 4, but the present invention is not limited to this, and a resin adhesive or the like may be used. Further, the support 10 is not limited to a glass plate, and may be made of another material having a certain strength.

  Next, in the etching step St4, as shown in FIG. 5, the opposite surface 10b of the one surface 10a on which the semiconductor element 2 is formed is dry-etched. Thereby, irregularities are formed on the surface 10b of the substrate 10 so as to increase the surface roughness, thereby facilitating the subsequent grinding process. Note that this step St4 may be performed at any stage of the manufacturing process as long as it is after the element forming step St1 and before the grinding step St5.

Examples of the dry etching method include reactive ion etching (RIE) using high-density plasma, and plasma etching using a fluorine-based gas is particularly preferable. As an etching technique using high-density plasma, for example, inductively coupled RIE (ICP-RIE) or ECR-RIE (Electron Cyclotron Resonance-RIE) can be employed. The fluorine-based gas may be selected from, for example, CF ₄ , CHF ₃ , and SF _6, but is not limited thereto, and is a gas obtained by adding oxygen to CF ₄ , CHF ₃ , or SF _6. May be. When oxygen is added in this way, for example, carbon on the SiC substrate can be efficiently removed. However, the dry etching method is not limited, and for example, ion milling with Ar (argon) may be employed.

  Next, in the grinding process St5, as shown in FIG. 6, the dry etched opposite surface 10b is ground with a grindstone or abrasive grains. The figure illustrates the case of a grinding apparatus such as a back grinder using a grindstone. In addition, in the figure, the fixed base 6 is drawn as a cross section in a side view.

  The fixing table 6 fixes the support 5 and the substrate 10 bonded to each other by suction. The fixing base 6 has a suction surface 6a for fixing the support 5 and the substrate 10, and one or more through holes 6b extending perpendicularly to the suction surface 6a. The grinding device sucks the support 5 and the substrate 10 to the suction surface 6a by generating a negative pressure F in the through hole 6b by suction means such as a pump. However, the fixing method is not limited to this, and for example, a double-sided tape or the like may be used.

  A rotating shaft 71, a rotating plate 70, and a grinding wheel 72 are disposed on the back surface 10 b side of the substrate 10. The rotating shaft 71 is rotated in a direction d in the figure by driving means such as a spindle motor. The rotating plate 70 is a disc fixed to the rotating shaft 71 and rotates together with the rotating shaft 71. The grinding wheel 72 is an annular grinding member fixed to the rotating plate 70, and a plurality of grindstones 720 are provided on the circumference.

  The grinding wheel 72 rotates together with the rotary shaft 71 and grinds the back surface 10 b by bringing a plurality of grindstones 720 into contact with the back surface 10 b of the substrate 10. Note that the grinding liquid may be ejected toward the grinding portion of the back surface 10b by means such as a nozzle for the purpose of cooling, lubrication, and cleaning during grinding. The grinding fluid is pure water, for example.

  As shown in FIG. 7, the grinding wheel 72 includes an outer peripheral annular portion 721, an inner peripheral annular portion 722, and a plurality of grindstones 720. Each of the plurality of grindstones 720 has a rectangular parallelepiped shape and is provided at equal intervals on the circumference of the outer circumferential ring portion 721. Each of the plurality of grindstones 720 includes diamond and can suitably cut the hard substrate 10. The particle diameter of diamond is, for example, 5 to 10 (μm).

  The inner circumferential ring portion 722 is a thin plate portion projecting inward from the inner circumferential surface of the outer circumferential ring portion 721. The inner ring portion 722 has a plurality of screw holes 722a formed at equal intervals on the circumference. The plurality of screw holes 722a are used to fix the grinding wheel 72 to the rotating plate 70 by screwing.

  The grinding wheel 72 grinds the back surface 10b evenly by changing the position on the back surface 10b of the substrate 10 while rotating the grindstone 720 against the back surface 10b of the substrate 10 while rotating. Thereby, the thickness of the board | substrate 10 is reduced from about 500 (micrometer) to about 100-150 (micrometer), for example.

  FIG. 8 is an enlarged view of the contact portion P between the back surface 10b of the substrate 10 and the grindstone 720 in FIG. As can be understood from the drawing, the unevenness formed on the back surface 10b by the etching step St4 and the unevenness on the surface of the grindstone 720 are meshed with each other. Therefore, the grindstone 720 can be prevented from sliding on the back surface 10b, and the back surface 10b can be effectively cut. After cutting, the substrate 10 is peeled off from the support 5.

  Next, in the dividing step St6, the substrate 10 is diced in order to divide the substrate 10 to obtain a plurality of semiconductor chips which are electronic components. However, the dividing method is not limited to dicing, and scribing may be used.

  According to the method for manufacturing a semiconductor device described so far, the substrate 10 is dry-etched on the opposite surface 10b of the one surface 10a on which the semiconductor element 2 is formed, whereby irregularities are formed on the opposite surface 10b. Then, by grinding the oppositely etched opposite surface 10b with the grindstone 720, the irregularities formed on the opposite surface 10b and the irregularities of the grindstone 720 can sufficiently mesh with each other. Therefore, the grindstone 720 can effectively grind the surface 10b of the substrate 10 without slipping.

  In the present embodiment, in the grinding step St5, the grindstone 720 is disposed below the substrate 10 and cut. However, the present invention is not limited to this. As in the so-called infeed method, the substrate may be fixed on a table called a rotary chuck by suction, and the grindstone may be lowered from above to be ground.

  Moreover, although the grinding method using a grindstone was illustrated in this embodiment, the same effect is acquired also in the case of grinding methods, such as lapping using an abrasive grain, instead of this. In this case, for example, the substrate is sandwiched between a pair of fixing plates via a stainless steel carrier. Then, a lapping liquid containing abrasive grains such as alumina or silicon carbide is poured into the target surface of the substrate, and the surface and the abrasive grains are rubbed together to grind the surface.

  This lapping enables high-precision surface processing, for example, flatness of 0.001 (mm) or less, surface roughness of 0.0003 (mm) or less, and dimensional accuracy of 0.002 (mm) or less. Is obtained. Note that after lapping, the surface of the substrate may be polished with a polishing cloth holding an abrasive to polish the surface.

  Although the contents of the present invention have been specifically described above with reference to the preferred embodiments, it is obvious that those skilled in the art can take various modifications based on the basic technical idea and teachings of the present invention. It is.

DESCRIPTION OF SYMBOLS 10 Substrate 10a Opposite surface 2 Semiconductor element 3 Protective film 4 Adhesive 5 Support body 720 Grinding stone

Claims (6)

Forming a semiconductor element on one surface of the substrate;
Forming an irregularity so as to increase the roughness of the opposite surface of the substrate by dry-etching the opposite surface of the substrate on which the semiconductor element is formed;
And a step of grinding the opposite surface of the substrate that has been dry-etched.   The method of manufacturing a semiconductor device according to claim 1, wherein the substrate includes one selected from Si, SiC, GaN, GaAs, and sapphire.   3. The method of manufacturing a semiconductor device according to claim 1, wherein the opposite surface of the substrate is dry-etched with a fluorine-based gas. 4. The semiconductor device according to claim 3, wherein the fluorine-based gas is one selected from CF ₄ , CHF ₃ , and SF ₆ , or one in which oxygen is added to the selected one. Manufacturing method.   Prior to the step of grinding the opposite surface of the substrate that has been dry-etched, the method further includes the step of applying an adhesive to one surface of the substrate on which the semiconductor element is formed and attaching the substrate to a support. The method for manufacturing a semiconductor device according to claim 1, wherein the method is a semiconductor device manufacturing method.   The semiconductor device according to claim 5, further comprising a step of forming a protective film covering one surface of the substrate on which the semiconductor element is formed, prior to the step of attaching the substrate to a support. Manufacturing method.

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