JP2018137483A - Plasma processing method and substrate produced using this method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a plasma processing method using plasma etching processing to allow a substrate chamfered at outer peripheral edges to be cut out, thereby allowing reduction in production cost of a substrate chamfered at outer peripheral edges; and a substrate produced using this method.SOLUTION: The method comprises: a front surface mask formation step for forming a front surface mask Mf having an opening Mf1 corresponding to a processing region D on a front surface of a substrate K; a front surface etching step for placing the substrate K on a base and isotropically etching the substrate K through the opening Mf1 of the front surface mask Mf; and, after performing the front surface etching step, a penetration step for anisotropically etching the substrate K through the opening Mf1 of the front surface mask Mf until penetrating to a rear surface of the substrate K.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a plasma processing method of cutting a substrate smaller than the substrate from the substrate by plasma etching, and a substrate manufactured using the method.

  There are various sizes of substrates used for manufacturing semiconductor chips. For example, when mass-producing semiconductor chips of the same type, productivity is improved by obtaining as many semiconductor chips as possible from a single substrate. For this reason, a relatively large-diameter substrate is used, whereas when producing a small amount of different types of semiconductor chips, the necessary processing is performed with equipment that is cheaper than equipment for performing processing such as etching on the large-diameter substrate. A relatively small-diameter substrate that can be applied is used. These substrates are generally subjected to beveling on the outer peripheral edge after slicing an ingot having a diameter corresponding to a desired substrate diameter.

  By the way, the small-diameter substrate may be manufactured by cutting out from the large-diameter substrate using, for example, a laser method. Even in a substrate manufactured in this way, the outer peripheral edge portions of the front and back surfaces thereof are angular, as in a general substrate. Therefore, there is a problem that chipping occurs at the outer peripheral edge when the substrate is handled.

  In addition, when the outer peripheral edge of the substrate is square, when a resist is applied to the surface by spin coating, a phenomenon called edge bead that the resist rises due to surface tension may occur at the outer peripheral edge of the substrate surface. In this case, the portion where the edge bead is generated (edge bead portion) is a portion that is not suitable for uniform processing, and the edge bead portion cannot be used for manufacturing a semiconductor chip. For this reason, the number of semiconductor chips obtained from a single substrate is reduced, resulting in a problem that production efficiency is lowered.

  Furthermore, while the types of single-element semiconductors are limited, there are many combinations of compound semiconductor elements, and it is also required to support high-mix low-volume production.

  Therefore, conventionally, a cutting process for cutting out a small-diameter substrate from a large-diameter substrate by a laser method or the like is performed, and then a polishing process for chamfering the outer peripheral edge of the cut-out small-diameter substrate with a rubber grindstone is performed. A method for manufacturing a semiconductor single crystal wafer has been proposed (Patent Document 1).

JP 2005-33190 A

  However, in order to manufacture a small-diameter substrate by the method disclosed in Patent Document 1, it is necessary to perform the cutting process and the polishing process separately, and thus there is a problem that the time required for manufacturing becomes long. .

  Further, when the substrate is cut out by the laser method, the substrate must be cut out one by one by scanning the laser along the shape of the substrate to be cut out. Therefore, as the size of the substrate to be cut out is reduced and the number of substrates that can be cut out from one substrate is increased, the cut-out length becomes longer and the time required for the cut-out process becomes longer.

  Further, in the polishing step, it is necessary to polish each of the cut out substrates, so that the time required for the step increases as the number of cut out substrates increases. Furthermore, when a substrate is cut out using a laser method, it is necessary to remove residues generated by cutting the substrate with a laser, so that the time required for the polishing process may be longer. In addition, the polishing process may be manually performed one by one by an operator, and in this case, labor and time required for the polishing process become enormous.

  Due to the above problems, when a substrate having a size smaller than the substrate is cut out from one substrate and the substrate is manufactured by a method of polishing the cut substrate, an increase in manufacturing cost is inevitable, and the price of one substrate Must be high.

  The present invention has been made in view of the above circumstances, and by using a plasma etching process, it is possible to cut out a substrate having a chamfered outer peripheral edge, and to manufacture a substrate having a chamfered outer peripheral edge. It is an object of the present invention to provide a plasma processing method capable of suppressing the above and a substrate manufactured by using this method.

The present invention for solving the above problems is as follows.
A plasma processing method of removing a processing region set on a substrate placed on a base in a processing chamber by plasma etching and cutting out a substrate smaller than the substrate,
A surface-side mask forming step of forming a surface-side mask having an opening corresponding to the processing region on the surface of the substrate;
A surface side etching step of placing the substrate on the base and isotropically etching the substrate through the opening of the surface side mask;
The present invention relates to a plasma processing method of performing a penetration step of anisotropically etching the substrate through an opening of the surface-side mask after performing the surface-side etching step until penetrating the back surface of the substrate.

  According to this plasma processing method, first, a surface-side mask is formed on the surface of the substrate, and then the substrate on which the surface-side mask is formed is placed on a base and a surface-side etching step is performed. The substrate may be held on the base using electrostatic adsorption, or may be held on the base using tape.

  In this surface-side etching step, the substrate is isotropically etched through the opening of the surface-side mask, that is, the substrate has a processing region located below the opening removed by etching, and the surface side The portion directly under the mask is etched to form a trench.

  In addition, the said process area | region is suitably set according to the planar shape of the board | substrate to cut out, and circular and a square can be illustrated as a planar shape of the board | substrate to cut out.

  Next, a penetration process is performed. In this penetration step, the substrate is anisotropically etched through the opening of the front side mask until it penetrates the back surface of the substrate. As a result, the processing region is removed by etching and trenches penetrating the front and back of the substrate are formed, so that a substrate smaller than the substrate is cut out from the substrate.

  In addition, as a method of anisotropically etching the substrate, for example, an etching process and a protective film forming process are alternately applied, or an etching process using an etching gas and a protective film forming gas is applied to the base. A method of gradually increasing the bias power to be performed can be exemplified. In addition, when the method of alternately performing the etching process and the protective film forming process is used, a so-called scallop shape appears on the sidewall of the trench.

  In this plasma processing method, in the surface side etching step, the portion directly under the surface side mask is also etched, and the portion directly under the surface side mask is a portion corresponding to the outer peripheral edge of the surface of the substrate to be cut out. It is. Therefore, the cut out substrate is in a state where the outer peripheral edge of the surface is chamfered by etching. Note that the shape immediately below the surface-side mask etched in the surface-side etching step, that is, the shape of the outer peripheral edge portion of the cut-out substrate varies depending on the processing conditions. Therefore, by adjusting the processing conditions in the surface side etching step, it is possible to optimize the desired shape of the outer peripheral edge of the surface of the substrate.

  As described above, in the plasma processing method, a substrate having a shape whose outer peripheral edge is chamfered can be cut out by a series of plasma etching processes in which isotropic etching and anisotropic etching are combined. Therefore, it is possible to manufacture a substrate with a chamfered outer peripheral edge without separately performing a step of cutting out the substrate and a step of polishing the cut-out substrate as in the prior art. Since a plurality of substrates can be cut out collectively by plasma etching without cutting out one by one, the manufacturing cost of the substrate can be kept low.

  Further, in the plasma processing method described above, when the processing region is anisotropically etched in the penetration process, a scallop shape appears on the sidewall of the trench if a method of alternately repeating the etching process and the protective film forming process is employed. . Therefore, in this case, the cut out substrate has a scallop shape on the outer peripheral surface corresponding to the trench side wall.

  If the substrate is unloaded from the processing chamber by a transport mechanism configured to integrally suck the cut substrates, it is possible to prevent the cut substrates from being scattered.

  In addition, if a support layer that is difficult to be etched in advance is formed on the back surface of the substrate, or a tape that is difficult to be etched in advance is bonded, the substrate is cut out without using a complicated transport mechanism equipped with suction means. It is possible to carry out the substrate cut out from the processing chamber while preventing the substrate from being scattered.

  In the plasma processing method, it is preferable that a finishing process for isotropically etching the substrate is performed after the penetration process.

  In this way, for example, when there is a corner between the portion etched in the surface side etching step and the portion etched in the penetration step, the corner can be rounded by isotropic etching. The outer peripheral edge of the surface of the substrate to be cut out can be rounded. The finishing step may be performed after removing the surface-side mask or may be performed before removing the surface-side mask. However, a corner between the surface of the cut substrate and the portion etched in the surface-side etching step may be used. In the case where there is a portion, it is preferable to remove the surface side mask in order to round the corner portion. Moreover, the surface roughness of the cut-out substrate can also be reduced by adjusting the processing conditions of this finishing process.

  In the plasma processing method, an insulating layer is formed on the back surface of the substrate on which the front-side mask is formed, or an insulating tape is adhered, and notching is generated in the penetration step. It is preferable.

  “Notching” means that when the substrate is etched, the surface of the insulating layer or the insulating seal is charged up, the direction of travel of ions contained in the plasma is bent, and a trench near the insulating layer or the insulating seal is formed. The side wall is etched and the shape generated by this phenomenon. In general etching, the processing conditions are adjusted so as not to generate as much as possible. The inventors of the present application pay attention to the fact that the portion to be etched when the notching phenomenon occurs corresponds to the outer peripheral edge of the back surface of the substrate to be cut out. And the outer peripheral edge of the back surface of the substrate is etched. Thereby, according to the said plasma processing method, since the back surface outer periphery part of the cut-out board | substrate will be in the state chamfered, the board | substrate with which the outer periphery part of the surface and the back surface was chamfered can be cut out. In this plasma processing method, an insulating layer is formed on the back surface of the substrate or an insulating tape is adhered, so that the cut out substrate is not scattered.

  Furthermore, since the notching shape changes depending on the processing conditions, in the plasma processing method described above, the processing conditions can be adjusted to optimize the outer peripheral edge of the back surface of the substrate to a desired shape.

  Examples of the insulating layer include a resist film and a silicon dioxide film. Examples of the insulating tape include so-called dicing tape made of polyimide, polyolefin, or the like.

  The plasma processing method according to the present invention is applied not only to a silicon substrate but also to a compound semiconductor substrate such as a gallium arsenide (GaAs) substrate, or a so-called wide gap semiconductor substrate such as a silicon carbide (SiC) substrate having a large band gap among compound semiconductors. For example, when a silicon substrate and a SiC substrate are compared, the SiC substrate is less likely to cause the notching phenomenon, and therefore the chamfering of the outer peripheral edge of the rear surface of the cut substrate may be insufficient. is there.

  Therefore, in the plasma processing method, after the back side mask forming step of forming a back side mask having an opening corresponding to the processing region on the back side of the substrate and the penetration step, the substrate is turned upside down. A reverse side etching process may be further performed in which the substrate is inverted and placed on the base and isotropically etched through the opening of the back side mask.

  In this way, since the portion directly under the back mask corresponding to the outer peripheral edge of the rear surface of the substrate to be cut out can be etched, the substrate in which the outer peripheral edge of the rear surface is chamfered by etching from the substrate in which notching phenomenon is unlikely to occur. Can be cut out.

  Note that the back side mask forming step may be performed after the penetrating step is performed, or may be performed before the front side etching step is performed.

  Further, the removal of the front surface side mask may be performed after the penetration process and before the back surface side etching process, or may be performed together with the removal of the back surface side mask after the completion of all the processes.

Further, the present invention for solving the above-described problems is a plasma processing in which a processing region set in a substrate placed on a base in a processing chamber is removed by plasma etching, and a substrate smaller than the substrate is cut out. A method,
A surface-side mask forming step of forming a surface-side mask having an opening corresponding to the processing region on the surface of the substrate;
A back side mask forming step of forming a back side mask having an opening corresponding to the processing region on the back side of the substrate;
A surface side etching step of placing the substrate on the base and isotropically etching the substrate through the opening of the surface side mask;
A deep digging step for anisotropically etching the substrate through the opening of the surface side mask after performing the surface side etching step;
After performing the deep digging step, the substrate is turned upside down and placed on the base, and a back side etching step for isotropically etching the substrate through the opening of the back side mask;
After performing the back surface side etching step, plasma processing is performed in which the substrate is anisotropically etched through the opening of the back surface side mask until it penetrates the bottom surface of the trench formed in the deep digging step Related to the method.

  According to this plasma processing method, first, a surface-side mask is formed on the surface of the substrate. Next, the substrate on which the surface-side mask is formed is placed on a base and a surface-side etching process is performed. As described above, examples of the method for holding the substrate on the base include a method using electrostatic adsorption and a method using a tape.

  In this surface-side etching process, the substrate is isotropically etched through the opening of the surface-side mask, so that the processing region located below the opening is removed by etching and the portion immediately below the surface-side mask is etched. And a trench is formed.

  Next, a deep digging step is performed, the substrate is anisotropically etched through the opening of the surface side mask, and the etching proceeds in the depth direction.

  Next, a back side etching process is performed. The back side mask forming process may be performed before the back side etching process is performed, or may be performed together with the front side mask forming process before the front side etching process is performed. Also good.

  In this back side etching step, the portion directly under the back side mask corresponding to the outer periphery of the back side of the substrate to be cut out is etched.

  Thereafter, the substrate is anisotropically etched through the opening of the back side mask until it penetrates the bottom surface of the trench formed in the deep digging step (penetration step). Thus, the processing regions are removed by etching over the front and back surfaces of the substrate, and trenches penetrating the front and back surfaces of the substrate are formed, so that a substrate smaller than the substrate is cut out from the substrate.

  In this plasma processing method, the front side etching step and the back side etching step, which are steps of isotropically etching the substrate, are performed, and are directly below the front side mask (corresponding to the outer peripheral edge portion of the surface of the substrate to be cut out). ) And the lower part of the back mask (corresponding to the outer peripheral edge of the back surface of the substrate to be cut out) are etched, and the cut out substrate has a state in which the outer peripheral edge portions of the front and back surfaces are chamfered by etching. It has become.

  As described above, in the plasma processing method, the chamfering of the outer peripheral edge portion and the cutting of the substrate can be performed together by the plasma etching process, and the step of cutting the substrate and the step of polishing the cut substrate as in the prior art Further, by performing plasma etching on the entire surface of the substrate, it is possible to cut out a plurality of substrates at once without cutting out the substrates one by one as in the prior art. Therefore, according to this plasma processing method, it is possible to manufacture a substrate in which the outer peripheral edge portions of the front and back surfaces are chamfered while keeping the cost low.

  In this plasma processing method, the front side mask may be removed after the deep digging step, or the front side mask and the rear side mask may be removed after the completion of all the steps.

  In this plasma processing method, after performing at least one of the deep digging step and the penetrating step, a finishing step of isotropically etching the substrate may be performed.

  If it does in this way, it occurred between the part etched in the surface side etching process and the part etched in the deepening process, the part etched in the back side etching process, and the part etched in the penetration process. Corners can be rounded by isotropic etching. Therefore, the outer peripheral edge portions of the front and back surfaces of the substrate to be cut out can be rounded. Moreover, the surface roughness of the cut-out substrate can also be reduced by adjusting the processing conditions of this finishing process.

  In the plasma processing method according to the present invention, a mask is not formed on at least one of the front surface and the back surface in order to adjust the thickness of the substrate to be cut out to a desired thickness in advance. A thinning process for etching the entire surface of the substrate on which the mask is not formed may be performed before the surface side etching process.

  The plasma processing method according to the present invention can be suitably used for manufacturing a substrate (substrate before forming a semiconductor element) used for manufacturing a semiconductor element, and can be used individually from a substrate on which a plurality of semiconductor elements are formed. It can also be used when cutting out these semiconductor elements.

  As described above, according to the plasma processing method of the present invention, the chamfering of the outer peripheral edge and the cutting of the substrate can be performed together by the plasma etching process. Since it is not necessary to separately perform the step of polishing the substrate, it is possible to manufacture a substrate whose outer peripheral edge is chamfered while keeping costs low.

It is sectional drawing which shows schematic structure of the plasma processing apparatus used for implementation of the plasma processing method which concerns on one Embodiment. It is a top view which shows typically the board | substrate after surface side mask formation. It is a fragmentary sectional view of a substrate for explaining a process of cutting out a substrate by a plasma processing method concerning one embodiment. It is a fragmentary sectional view of a substrate for explaining a process of cutting out a substrate by a plasma processing method concerning one embodiment. It is an enlarged view of the A section in FIG.4 (c). It is the table | surface which put together the process conditions of each process in the experiment which applied the plasma processing method which concerns on one Embodiment. It is a top view which shows typically the board | substrate after surface side mask formation. It is a fragmentary sectional view of a substrate which shows the state where notching has not occurred. It is a fragmentary sectional view of a substrate for explaining a process of cutting a substrate by a plasma processing method concerning other embodiments. It is a fragmentary sectional view of a substrate for explaining a process of cutting a substrate by a plasma processing method concerning other embodiments. It is a fragmentary sectional view of a substrate for explaining a process of cutting a substrate by a plasma processing method concerning other embodiments. It is explanatory drawing for demonstrating the aspect which cuts out each semiconductor element from the board | substrate with which the semiconductor element was formed, (a) shows the board | substrate before surface side mask formation, (b) shows the board | substrate after surface side mask formation. It is a figure.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[Plasma processing equipment]
First, the plasma processing apparatus 1 used for implementation of the plasma processing method according to one embodiment of the present invention will be described. As shown in FIG. 1, the plasma processing apparatus 1 of this example has a cylindrical processing chamber in which a plasma generation space 5 is set above an internal space and a processing space 6 is set below the plasma generation space 5. 2, a processing gas supply mechanism 10 for supplying a processing gas to the plasma generation space 5, an annular coil 15 for generating an induction electric field in the plasma generation space 5, and high-frequency power to the coil 15 A coil power supply mechanism 20; a base 25 disposed in the processing space 6 for placing the substrate K; a base power supply mechanism 30 for supplying high-frequency power to the base 25; and a processing chamber. 2 is provided with an exhaust device 35 for exhausting the gas in 2.

  The processing chamber 2 includes an upper chamber 3 and a lower chamber 4 made of an aluminum alloy. The upper chamber 3 and the lower chamber 4 each have an internal space communicating with each other. The internal space of the upper chamber 3 is a plasma generation space 5, and the internal space of the lower chamber 4 is a processing space 6. . The upper chamber 3 is formed smaller than the lower chamber 4.

The processing gas supply mechanism 10 includes a processing gas supply source 11 in which processing gas is stored, one end connected to the processing gas supply source 11, and the other end connected to a discharge port formed on the top plate of the upper chamber 3. It consists of a connected supply pipe 12. According to the processing gas supply mechanism 10, the processing gas is discharged from the processing gas supply source 11 through the supply pipe 12 from the discharge port vertically downward, and the processing gas is supplied to the internal space of the upper chamber 3. . The processing gas differs depending on the type of substrate to be etched. When the substrate is a silicon substrate, an etching gas such as SF ₆ gas, IF ₅ gas, NF ₃ gas, or F ₂ gas, C Examples of the protective film forming gas include ₄ F ₈ gas, O ₂ gas, and 2,3,3,3-tetrafluoropropene gas (HFO-1234yf). As the protective film forming gas, 2,3,3,3-tetrafluoropropene gas is preferable from the viewpoint of reducing greenhouse gas emissions and improving the etching rate. Further, in the case of a silicon carbide substrate, SF ₆ gas, SiF ₄ gas, CF ₄ gas, CH ₃ F gas are exemplified as etching gas, and O ₂ gas, SiF ₄ gas, SiCl ₄ gas, etc. are exemplified as protective film forming gas. One or more processing gas supply sources 11 may be provided depending on the number of processing gases used.

  The coil 15 is wound around the outer periphery of the upper chamber 3, and high frequency power is supplied by a coil power supply mechanism 20.

  The coil power supply mechanism 20 includes a matching unit 21 connected to the coil 15 and a high-frequency power source 22 connected to the matching unit 21, and supplies high-frequency power to the coil 15. According to the coil power supply mechanism 20, when high frequency power is supplied to the coil 15, an induction electric field is generated in the plasma generation space 5, and the processing gas supplied in the plasma generation space 5 is converted into plasma. A so-called inductively coupled plasma (ICP) is generated.

  The base 25 is composed of an upper member 26 on which the substrate K is placed and a lower member 27 to which an elevating cylinder 28 is connected, and is disposed in the inner space (processing space 6) of the lower chamber 4. .

  The base power supply mechanism 30 includes a matching unit 31 connected to the base 25 and a high frequency power source 32 connected to the matching unit 31, and supplies high frequency power to the base 25. . According to the base power supply mechanism 30, a bias potential is applied between the base 25 and the plasma by supplying high frequency power to the base 25.

  The exhaust device 35 includes a vacuum pump 36 that exhausts gas, and an exhaust pipe 37 that has one end connected to the vacuum pump 36 and the other end connected to an exhaust port that opens to the side surface of the lower chamber 4. According to the exhaust device 35, the gas in the processing chamber 2 is exhausted by the vacuum pump 36, and the internal space of the processing chamber 2 is maintained at a predetermined pressure.

[Plasma processing method]
Next, a process of plasma etching the substrate K using the plasma processing apparatus 1 having the above configuration and cutting out a smaller substrate K1 from the substrate K will be described with reference to FIGS. In this example, the substrate K is a silicon substrate before the semiconductor element is formed. 2 is a plan view of the substrate K. FIGS. 3 and 4 are diagrams schematically showing a process of cutting out the substrate K1. In FIG. 2 to FIG. Are cut out (cut out) substrates, Mf is a surface side mask, S is a tape, D is a processed region, T is a trench, and T1 and T2 are corners of the trench T, respectively.

First, in order to obtain a desired thickness of the substrate K1 to be cut out, the substrate K is loaded into the plasma processing apparatus 1 and placed on the base 25, and the entire surface of the substrate K is etched (thinning ( Thinning) process). Specifically, SF ₆ gas is supplied into the processing chamber 2 at a predetermined flow rate by the processing gas supply mechanism 10, and high-frequency power is supplied to the coil 15 and the base 25 by the coil power supply mechanism 20 and the base power supply mechanism 30. Apply. Note that the pressure in the processing chamber 2 is reduced to a predetermined pressure by the exhaust device 35.

Thereby, SF ₆ gas supplied into the processing chamber 2 is turned into plasma, and the entire surface of the substrate K is etched by a chemical reaction between the etching species contained in the plasma and silicon atoms.

  Next, the substrate K is unloaded from the processing chamber 2 and a surface side mask forming step is performed. In this surface side mask forming step, for example, an opening is formed only in a portion corresponding to the processing region D by vapor deposition (chemical vapor deposition (CVD) or physical vapor deposition (PVD)), photoresist coating, or the like. A surface-side mask Mf having a predetermined pattern on which Mf1 is formed is formed (see FIG. 2). In FIG. 2, the processing area D is shown by shading. Examples of the surface-side mask Mf include a resist mask, an oxide film, a metal mask, and a laminated film.

  In this example, the annular processing region D is set so that the planar shape of the cut out substrate K1 is circular, but may be appropriately set according to the required planar shape of the substrate K1. . In addition, the width h of the processing region D and the minimum interval p between the processing regions D can be efficiently cut out in consideration of the number of substrates that can be cut out and the etching rate and etching uniformity. For example, the width h of the processing region D is about 10 to 200 μm, and the minimum interval pd between the processing regions D is about 1 to 2 mm.

  Next, the substrate K on which the surface-side mask Mf is formed is placed on the base 25 in the processing chamber 2 and a surface-side etching process is performed on the substrate K. In this example, an insulating tape S is affixed to the back surface of the substrate K (see FIG. 3A) so that the substrate K1 is not scattered when cut out.

In the surface side etching process, SF ₆ gas, C ₄ F ₈ gas and O ₂ gas are supplied into the processing chamber 2 at a predetermined flow rate by the processing gas supply mechanism 10, and the coil power supply mechanism 20 and the base power supply are supplied. High frequency power is applied to the coil 15 and the base 25 by the mechanism 30, and the gas in the processing chamber 2 is exhausted by the exhaust device 35 so that the pressure in the processing chamber 2 becomes a predetermined pressure.

As a result, the SF ₆ gas, C ₄ F ₈ gas, and O ₂ gas supplied into the processing chamber 2 are turned into plasma, and the formation and removal of the protective film on the substrate K is performed in parallel through the opening of the surface side mask Mf. The substrate K is isotropically etched by the chemical reaction of the etching species (for example, fluorine radicals) generated by converting the SF ₆ gas into plasma. By performing this surface-side etching step for a predetermined time, the processing region D is etched and the portion directly under the surface-side mask Mf is also etched as shown in FIG. T is formed. Since the shape immediately below the mask etched in the surface side etching process varies depending on the processing conditions, the processing condition of the surface side etching process can be adjusted to make the outer peripheral edge of the surface a desired shape.

  Next, a penetration process is performed. Specifically, in this penetration step, a process of forming a protective film in the trench T formed in the surface side etching process (protective film forming process), removing the protective film from the bottom of the trench T, and performing the processing A cycle in which the region D is etched (etching process) is repeated a plurality of times.

First, in the protective film forming process, C ₄ F ₈ gas is supplied into the processing chamber 2 at a predetermined flow rate, high frequency power is applied to the coil 15 by the coil power supply mechanism 20, and the pressure in the processing chamber 2 is increased. The gas in the processing chamber 2 is exhausted by the exhaust device 35 so as to be a predetermined pressure. Thereby, a protective film is formed on the inner wall of the trench T formed by the surface side etching process.

Next, an etching process is performed. In this etching process, SF ₆ gas is supplied into the processing chamber 2 at a predetermined flow rate, high frequency power is supplied to the coil 15 and the base 25 by the coil power supply mechanism 20 and the base power supply mechanism 30, and the processing chamber The gas in the processing chamber 2 is exhausted by the exhaust device 35 so that the pressure in 2 becomes a predetermined pressure.

Thus, SF ₆ gas supplied into the processing chamber 2 is plasma, the SF ₆ fluorine ions generated by the plasma of the gas that enters the substrate K, the protective film of the trench T bottom is removed. Further, the generated fluorine ions are incident on the substrate K, or the etching species generated by making the SF ₆ gas into plasma chemically react with silicon atoms, whereby the substrate K is etched (see FIG. 3C).

  Thereafter, the protective film forming process and the etching process are repeated a certain number of times until the processing region D is removed by etching and the trench T penetrating the front and back surfaces is formed in the substrate K.

  Here, generally, when an insulating tape is adhered to the back surface of the substrate or an insulating layer is formed, the surface of the insulating tape or insulating layer is charged up unless a predetermined processing condition is adopted. As a result, the traveling direction of ions contained in the plasma is bent, and a notching phenomenon occurs in which the insulating tape and the trench side wall near the insulating layer are etched. In general etching processing, the occurrence of notching phenomenon is suppressed by taking measures such as applying pulse-shaped base high-frequency power, but in this embodiment, the back surface of the substrate K is insulated. A notching phenomenon is intentionally generated by bonding the adhesive tape S and performing the etching process without applying a pulse.

  That is, in this embodiment, since the insulating tape S is bonded to the back surface of the substrate K, the surface of the tape S is charged up, and the traveling direction of ions contained in the plasma is bent, The side wall of the trench T in the vicinity of the tape S is etched. As a result, the outer peripheral edge of the back surface of the cut out substrate K1 is rounded (see FIG. 4A).

Thereafter, the surface-side mask Mf is removed and a finishing process is performed (see FIG. 4B). In this finishing step, SF ₆ gas, C ₄ F ₈ gas, and O ₂ gas are supplied into the processing chamber 2 at a predetermined flow rate, and the coil power supply mechanism 20 and the base power supply mechanism 30 supply the coil 15 and the base 25 to each other. The high-frequency power is supplied, and the gas in the processing chamber 2 is exhausted by the exhaust device 35 so that the pressure in the processing chamber 2 becomes a predetermined pressure.

  Thereby, corner T1 between the portion etched in the surface side etching step and the portion etched in the penetration step, and corner T2 between the surface of the substrate K and the portion etched in the surface side etching step. Is rounded by isotropic etching, and the outer peripheral edge of the cut surface of the substrate K1 is rounded. The surface roughness of the substrate K1 can be reduced by appropriately adjusting the processing conditions of the finishing process.

  Thus, as shown in FIG. 4C, the substrate K1 whose outer peripheral edge portions on the front and back surfaces are rounded off is cut out from the substrate K. In this plasma processing method, since the trench T is formed by alternately performing the protective film forming process and the etching process in the penetration process, the outer peripheral surface of the cut out substrate K1 (on the side wall of the trench T). As shown in FIG. 5, it has a so-called scallop shape.

  According to this plasma processing method, for example, a substrate having a diameter of about 12.5 to 150 mm can be cut out from a substrate on which a semiconductor element having a diameter of about 100 to 450 mm is not formed.

  Incidentally, the inventors of the present application applied the plasma processing method of the present embodiment and performed each process under the processing conditions summarized in FIG. 6, and cut out a silicon substrate smaller than the silicon substrate from the silicon substrate. Successful. Note that the scallop shape formed on the outer peripheral surface of the cut out substrate had a height t and a pitch ps (see FIG. 5) of about 250 to 400 nm and about 400 to 600 nm, respectively.

  When the thickness of the substrate K is 200 μm, the time required for the surface side etching process is 2 minutes, the time required for the penetration process is 10 minutes for etching in the depth direction, and 1 minute for forming the notching shape. Minutes, the time required for the finishing process was 2 minutes, and the time required for these processes (total etching time) was 15 minutes. When the thickness of the substrate K is 600 μm, the time required for the surface side etching process is 2 minutes, the time required for the penetration process is 30 minutes for the etching in the depth direction, and 3 minutes for the formation of the notching shape 33 in total. Minutes, the time required for the finishing process was 2 minutes, and the total etching time was 37 minutes. Note that the time required for etching in the depth direction includes the time required for over-etching in consideration of uniformity.

  As described above, according to the plasma processing method according to the present embodiment, the surface side etching process for performing isotropic etching and the penetration process for performing anisotropic etching are combined, and a notching phenomenon is generated in the penetration process. By doing so, it is possible to cut out the substrate K1 in which the outer peripheral edges of the front and back surfaces are rounded. Therefore, unlike the conventional method, it is possible to manufacture a substrate having a shape in which the outer peripheral edge of the front and back surfaces are chamfered without separately performing the step of cutting out the substrate and the step of polishing the cut out substrate. Since a plurality of substrates can be cut out collectively by plasma etching without cutting out each piece, the manufacturing cost of the substrate can be kept low.

  As mentioned above, although one Embodiment of this invention was described, the aspect which can take this invention is not limited to this at all.

  In the above example, the thinning process is performed. However, when it is not necessary to adjust the thickness as in the case where the thickness of the substrate K1 to be cut out may be the same as the thickness of the original substrate K, etc. The thinning process may be omitted.

  In the above example, the pattern of the front-side mask Mf is a pattern having an opening Mf1 only in a portion corresponding to the processing region D, and a portion other than the processing region D is also covered with a mask in a portion where the substrate is not cut out. I have to. However, for example, as shown in FIG. 7, a portion other than the portion corresponding to the substrate K1 to be cut out is set as the processing region D so that only the substrate K1 having a predetermined planar shape (circular in FIG. 7) remains by etching. Only the portion corresponding to the substrate K1 to be covered may be covered with the mask. In FIG. 7, the shaded area is the machining area D.

  Furthermore, in the above example, a tapered trench is formed in the surface side etching step, but the portion directly under the surface side mask is etched, and the outer peripheral edge portion of the cut substrate is chamfered. If it is, the shape of the trench formed in a surface side etching process will not be specifically limited. Therefore, the method and processing conditions for isotropically etching the substrate in the surface side etching step may be appropriately selected according to the material of the substrate, the shape of the target trench, and the like.

  Further, in the above penetration process, the substrate K is anisotropically etched by repeating the protective film formation process and the etching process, but other modes in which the anisotropic etching is performed in the penetration process are described. For example, a method of forming the protective film and etching the substrate K at the same time and gradually increasing the voltage applied to the base 25 can be exemplified, and the substrate is anisotropically etched in the penetration process. The technique and processing conditions to be performed can be appropriately selected according to the material of the substrate.

  In the above example, the notch phenomenon is generated so that the outer peripheral edge of the back surface of the substrate K is rounded, but it is not necessary to chamfer the outer peripheral edge of the back surface of the substrate K. In some cases. In that case, it is not necessary to intentionally generate the notching phenomenon, and the substrate in a state where the outer peripheral edge of the front surface of the substrate K is chamfered by forming the trench T penetrating the front and back surfaces of the substrate K in the penetration process. K1 may be cut out.

  Furthermore, in the above example, the finishing process is performed so that the outer and outer peripheral edges of the front and back surfaces are rounded, in other words, a smooth state with no corners, but rounded chamfering is necessary. In the case where there is no problem, or when it can be dealt with by adjusting the processing conditions of the surface side etching step and the penetration step, the finishing step may not be performed.

  In the above example, the insulating tape S is attached to the back surface of the substrate K. However, for example, an insulating layer may be formed on the back surface of the substrate K.

  Furthermore, in the above example, by intentionally generating a notching phenomenon in the penetration process, the outer peripheral edge of the back surface of the substrate to be cut out is chamfered. However, in a substrate that is relatively difficult to etch, such as a silicon carbide substrate, notching is unlikely to occur, so that the outer peripheral edge of the rear surface of the cut out substrate may not be chamfered (see FIG. 8). Therefore, after performing the penetration process, a back surface side etching process for isotropically etching the substrate from the back surface side may be further performed.

  Specifically, as shown in FIG. 9A, after the surface side mask Mf is removed after the penetration process is performed, the tape S is pasted on the surface of the substrate K, and the cut out substrate K1 is scattered. Then, the substrate K is turned upside down and the back side mask forming step is performed. In this back side mask forming step, a back side mask Mb having a predetermined pattern in which an opening Mb1 is formed in a portion corresponding to the processing region D is formed by a predetermined method as in the front side mask forming step (FIG. 9 ( b)). In this case, the tape S attached to the surface does not need to have insulating properties. Further, examples of the back side mask Mb include a resist mask, an oxide film, a metal mask, and a laminated film.

  Next, the substrate K on which the back-side mask Mb is formed is placed on the base 25 in the processing chamber 2, and a back-side etching step for isotropically etching the substrate K is performed, and the back-side mask Mb The portion immediately below the back-side mask Mb on the substrate K is etched through the opening Mb1. In this backside etching process, the method of isotropically etching the substrate K and the processing conditions may be appropriately selected according to the material of the substrate and the like as in the frontside etching process.

  Thereby, as shown in FIG.9 (c), the front-and-back outer peripheral part of the cut-out board | substrate K1 will be in the state chamfered.

  In this case as well, if the finishing process is performed after removing the front-side mask Mf, the front and back outer peripheral edges of the cut out substrate K1 can be rounded, and the processing conditions can be adjusted. Thus, the surface roughness can be reduced.

  As described above, even with this plasma processing method, a substrate with front and back outer peripheral edges is chamfered without separately performing a substrate cutting step and a step of polishing each cut substrate. In addition, a plurality of substrates can be cut out collectively without cutting out the substrates one by one. Therefore, it is possible to manufacture a substrate whose outer peripheral edge portions on the front and back surfaces are chamfered while suppressing costs.

  Further, in the plasma processing method of the above example, the substrate K1 is cut out by performing the surface side etching step and the penetration step. However, the present invention is not limited to this, and the surface side etching step was performed. Then, you may make it perform a deep digging process, a back surface side etching process, and a penetration process. This will be described below with reference to FIGS. 10 and 11.

  After performing the surface side etching process in the above example, a deep digging process for anisotropically etching the substrate K through the opening Mf1 of the surface side mask Mf is performed, and as shown in FIG. A trench T is formed. In this deep digging step, as a method of anisotropically etching the substrate K, a method of repeating a protective film forming process and an etching process can be exemplified as in the case of the penetration process. The method for anisotropically etching the substrate K and its processing conditions can be selected as appropriate.

  Next, after removing the mask Mf from the surface of the substrate K, a tape S is affixed to the surface of the substrate K, the substrate K is turned upside down, and a back side mask forming step is performed (see FIG. 10B). In this back side mask forming step, the back side mask Mb in which the opening Mb1 is formed in a portion corresponding to the processing region D is formed by a predetermined method, as in the front side mask forming step (see FIG. 10C). . The back side mask Mb is a resist mask, an oxide film, a metal mask, a laminated film, or the like as described above.

  Next, the substrate K on which the back-side mask Mb is formed is placed on the base 25, and a back-side etching process for isotropically etching the substrate K is performed to open the opening Mb1 of the back-side mask Mb. Then, the portion directly under the back-side mask Mb of the substrate K is etched. As a result, a tapered trench T is formed on the back side of the substrate K as shown in FIG. In this backside etching process, the method of isotropically etching the substrate K and its processing conditions may be selected as appropriate.

Thereafter, a penetration process is performed. In this penetration process, the substrate K is anisotropically etched through the opening Mb1 of the back-side mask Mb until it penetrates the bottom of the trench T formed in the deep digging process. As a result, the substrate K is formed with a trench T having a tapered shape penetrating the front and back surfaces and having upper and lower portions tapered, and the front and back outer peripheral edges are chamfered (see FIG. 11B). ).

  In this plasma processing method, after removing the front side mask Mf, a finishing process is performed on the front side of the substrate K. After performing the penetration process, the back side mask Mb is removed and then the rear side of the substrate K is moved to the rear side. A finishing step may be performed so that the front and back outer peripheral edges of the cut out substrate K1 are rounded. Further, the surface roughness of the substrate K can be reduced by adjusting the processing conditions of the finishing process.

  As described above, this plasma processing method also has the same effects as described above.

  In the above example, a smaller substrate is cut out from the substrate before the formation of the semiconductor element. However, in the plasma processing method according to the present invention, for example, a plurality of semiconductor elements H as shown in FIG. It can also be used when individual semiconductor elements (also referred to as “dies”) H are cut out from the formed substrate K. Specifically, as shown in FIG. 12B, a surface-side mask Mf having an opening Mf1 only in a portion corresponding to the processing region D set between the semiconductor elements H formed on the substrate K is formed. Then, by performing each step in the above example, the processing region D is removed by etching through the opening Mf1 of the mask Mf, thereby dividing the semiconductor element H into pieces (also referred to as “plasma dicing”). it can. And the semiconductor element H separated into pieces using this plasma processing method will be in the state by which the outer peripheral edge part of the surface side and the back surface side was chamfered.

  As described above, according to this plasma processing method, it is possible to manufacture a semiconductor element that is a substrate with a chamfered outer peripheral edge while keeping costs low. More specifically, the outer peripheral edge is chamfered. Thus, a semiconductor element with improved bending strength can be manufactured at low cost.

  In this case, the processing conditions of each step may be adjusted so that the chamfer width on the front surface side or the back surface side is a width that can improve the bending strength of the semiconductor element H. For example, the chamfer width May be about 1 μm. In addition, the semiconductor element H to be singulated is relatively small and the dicing line becomes long, in other words, the processing region D becomes wide, so that the amount of gas necessary for processing increases. Therefore, from the viewpoint of reducing greenhouse gas emissions, it is preferable to use 2,3,3,3-tetrafluoropropene gas as the protective film forming gas.

DESCRIPTION OF SYMBOLS 1 Plasma processing apparatus 2 Processing chamber 5 Plasma generation space 6 Processing space 10 Processing gas supply mechanism 15 Coil 20 Coil power supply mechanism 25 Base 30 Base power supply mechanism K Substrate K1 Cut-out substrate D Processing area Mf Surface side mask Mf1 Opening Mb Back side mask Mb1 Opening T Trench T1, T2 Corner S Tape

Claims (8)

A plasma processing method of removing a processing region set on a substrate placed on a base in a processing chamber by plasma etching and cutting out a substrate smaller than the substrate,
A surface-side mask forming step of forming a surface-side mask having an opening corresponding to the processing region on the surface of the substrate;
A surface side etching step of placing the substrate on the base and isotropically etching the substrate through the opening of the surface side mask;
A plasma processing method comprising: performing a penetrating step of anisotropically etching the substrate through the opening of the surface-side mask after performing the surface-side etching step until penetrating the back surface of the substrate.   The plasma processing method according to claim 1, wherein after the penetrating process is performed, a finishing process isotropically etching the substrate is performed. On the back surface of the substrate, an insulating layer is formed or an insulating tape is adhered,
3. The plasma processing method according to claim 1, wherein notching is generated in the penetration step. A back side mask forming step of forming a back side mask having an opening corresponding to the processing region on the back side of the substrate;
After carrying out the penetration step, the substrate is turned upside down and placed on the base, and a back side etching step of isotropically etching the substrate through the opening of the back side mask is further performed. The plasma processing method according to claim 1 or 2, wherein A plasma processing method of removing a processing region set on a substrate placed on a base in a processing chamber by plasma etching and cutting out a substrate smaller than the substrate,
A surface-side mask forming step of forming a surface-side mask having an opening corresponding to the processing region on the surface of the substrate;
A back side mask forming step of forming a back side mask having an opening corresponding to the processing region on the back side of the substrate;
A surface side etching step of placing the substrate on the base and isotropically etching the substrate through the opening of the surface side mask;
A deep digging step for anisotropically etching the substrate through the opening of the surface side mask after performing the surface side etching step;
After performing the deep digging step, the substrate is turned upside down and placed on the base, and a back side etching step for isotropically etching the substrate through the opening of the back side mask;
After performing the back side etching step, performing a through step of anisotropically etching the substrate through the opening of the back side mask until it penetrates the bottom surface of the trench formed in the deep digging step. A plasma processing method.   6. The plasma processing method according to claim 5, wherein after performing at least one of the deep digging step and the penetrating step, a finishing step of isotropically etching the substrate is performed.   A thinning process for etching the entire surface of the substrate on which at least one of the front surface and the back surface is not formed with a mask is performed before the front surface side etching step. The plasma processing method according to claim 1, wherein: The outer peripheral edge of at least one of the front and back surfaces is chamfered,
A substrate characterized by having a scalloped shape on the outer peripheral surface.

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