Grinding method for semiconductor crystal and grinding wheel for grinding used in said grinding method

Abstract

The purpose of the present invention is to provide: a grinding method for a semiconductor crystal, with which it is possible to achieve higher grinding accuracy by more precisely and minutely managing plastic deformation as a plastic deformation mechanism of an end surface of a semiconductor crystal ingot or a wafer surface; and a grinding wheel for grinding, which is used in the grinding method. In a grinding method for an Si wafer 100, due to a grinding wheel 53 and a pressing force for pressing the wafer 100 against the grinding wheel 53 via a spindle 51, a plastic deformation region 100A is formed on the surface of the wafer 100 by a temperature rise that is caused by friction with the grinding wheel 53, and the plastic deformation region 100A is ground by the grinding wheel 53 while performing functional polishing of the surface of the plastic deformation region 100A by having the grinding wheel 53 contain a functional additive.

Description

Grinding method for semiconductor crystals and grinding stone used in said grinding method

[0001] The present invention relates to a grinding method for semiconductor crystals, which grinds the end face of a semiconductor crystal ingot ground into a cylindrical shape or the surface of a wafer sliced ​​from the semiconductor crystal ingot, and to a grinding wheel used in the grinding method.

[0002] Conventionally, as a grinding method for this type of semiconductor crystal wafer, as shown in Patent Document 1 below, a method developed by the present inventor forms a plastic deformation region on the surface of the wafer facing the platen (grinding table) by a temperature rise caused by friction between the platen and the diamond abrasive grains, based on (1) the grain size of the diamond abrasive grains (diamond grinding stone) used for grinding, (2) the pressing force with which the wafer is pressed against the platen via the spindle, and (3) the speed at which the spindle advances relative to the platen.

[0003] Patent No. 7285507

[0004] As a result of intensive research into the plastic deformation region in more detail, the inventors of the present application have discovered that higher grinding accuracy can be achieved by more precisely controlling the plastic deformation mechanism.

[0005] The present invention is based on this finding, and aims to provide a grinding method for semiconductor crystals that can achieve higher grinding accuracy by more precisely and in detail managing plastic deformation as a plastic deformation mechanism on the end face of a semiconductor crystal ingot or the surface of a wafer, and a grinding wheel for use in said grinding method.

[0006] The first invention relates to a method for grinding semiconductor crystals, which grinds an end face of a semiconductor crystal ingot ground into a cylindrical shape or a surface of a wafer sliced ​​from the semiconductor crystal ingot, and which comprises: a grinding wheel mounted on a grinding machine for grinding; and a pressing force for pressing the semiconductor crystal ingot or the wafer against the grinding wheel via a support base, which causes a temperature rise due to friction between the grinding wheel and the end face of the semiconductor crystal ingot facing the grinding machine or the surface of the wafer facing the grinding machine, and the grinding wheel grinds the plastically deformed region while functionally polishing the surface of the plastically deformed region by incorporating a functional additive into the grinding wheel, characterized in that the plastically deformed region is ground with the grinding wheel while an oxide film formed on the surface of the plastically deformed region is removed by incorporating cerium oxide into the grinding wheel.

[0007] According to the semiconductor crystal grinding method of the first invention, as a result of extensive research into the plastic deformation region in more detail, it has been discovered that various states can exist on the surface of the plastic deformation region.

[0008] Based on this knowledge, in order to integrate the functional polishing of the plastically deformed region with the grinding process, a surface treatment is carried out by adding a functional additive to the grinding stone, and the plastically deformed region is then ground.

[0009] Thus, according to the semiconductor crystal grinding method of the first invention, higher grinding accuracy can be achieved by controlling the plastic deformation mechanism more precisely and in detail.

[0010] Furthermore, according to the semiconductor crystal grinding method of the first invention, as a result of intensive research that analyzed the plastic deformation region in more detail, it was discovered that an oxide film formed by oxidizing the semiconductor crystal is constantly formed on the surface of the plastic deformation region.

[0011] Based on this knowledge, functional polishing is performed by incorporating cerium oxide into the grinding wheel as a functional additive, so as to combine the removal of the oxide film from the semiconductor crystal with the grinding of the plastic deformation region, and the plastic deformation region is ground.

[0012] Thus, according to the semiconductor crystal grinding method of the first invention, higher grinding accuracy can be achieved by controlling the plastic deformation mechanism more precisely and in detail.

[0013] The grinding stone of the second invention is a grinding stone used in any one of the semiconductor crystal grinding methods of the first invention, characterized in that it contains more than 0% and 10% or less of cerium oxide as its material composition.

[0014] According to the grinding wheel of the second invention, by including cerium oxide in the material composition in a range of more than 0% to 10% or less, it is possible to actually perform the removal of the oxide film and the grinding of the plastic deformation region as a single unit.

[0015] According to the grinding wheel of the second invention, by including cerium oxide in the material composition in a range of more than 0% to 10% or less, it is possible to actually perform the removal of the oxide film and the grinding of the plastic deformation region as a single unit.

[0016] A third invention relates to a method for grinding semiconductor crystals, which grinds an end face of a semiconductor crystal ingot ground into a cylindrical shape or the surface of a wafer sliced ​​from the semiconductor crystal ingot, and which comprises: a grinding wheel mounted on a grinding machine for grinding; and a pressing force for pressing the semiconductor crystal ingot or the wafer against the grinding wheel via a support table, which causes a temperature rise due to friction between the grinding wheel and the end face of the semiconductor crystal ingot facing the grinding machine or the surface of the wafer facing the grinding machine, and the grinding wheel grinds the plastically deformed region while functionally polishing the surface of the plastically deformed region by adding a functional additive to the grinding wheel, characterized in that the method grinds the plastically deformed region with the grinding wheel by adding potassium permanganate in addition to cerium oxide to form an oxide film on the surface of the plastically deformed region while simultaneously removing the oxide film with the grinding wheel.

[0017] According to the semiconductor crystal grinding method of the third invention, as a result of extensive research into the plastic deformation region in more detail, it has been discovered that various states can exist on the surface of the plastic deformation region.

[0018] Based on this knowledge, in order to integrate the functional polishing of the plastically deformed region with the grinding process, a surface treatment is carried out by adding a functional additive to the grinding stone, and the plastically deformed region is then ground.

[0019] Thus, according to the semiconductor crystal grinding method of the third invention, higher grinding accuracy can be achieved by controlling the plastic deformation mechanism more precisely and in detail.

[0020] Furthermore, according to the semiconductor crystal grinding method of the third invention, as a result of intensive research into the plastic deformation region in more detail, it has been discovered that an oxide film formed by oxidation of the semiconductor crystal is constantly formed on the surface of the plastic deformation region.

[0021] Based on this knowledge, in order to integrate the removal of the oxide film of the semiconductor crystal and the grinding of the plastic deformation region as a functional polishing, potassium permanganate is added to the grinding wheel as a functional additive, which generates an oxide film on the surface of the plastic deformation region, and at the same time, the oxide film is removed with the grinding wheel while the plastic deformation region is ground.

[0022] Thus, according to the semiconductor crystal grinding method of the third invention, higher grinding accuracy can be achieved by controlling the plastic deformation mechanism more precisely and in detail.

[0023] The grinding stone of the fourth invention is a grinding stone used in any one of the grinding methods for semiconductor crystals of the third invention, characterized in that it contains more than 0% and 10% or less of potassium permanganate as a material composition.

[0024] According to the grinding wheel of the fourth invention, by including potassium permanganate in the material composition in a range of more than 0% and not more than 10%, it is possible to perform the grinding process of the formation and removal of an oxide film and the grinding of the plastic deformation region in one process.

[0025] In this way, with the grinding stone of the fourth invention, higher grinding accuracy can actually be achieved by controlling the plastic deformation mechanism more precisely and in detail.

[0026] The grinding stone of the fifth invention is the same as that of the fourth invention, characterized in that the potassium permanganate is replaced as a part of the material composition with calcium carbonate and / or calcium hydroxide.

[0027] According to the grinding stone of the fifth invention, by replacing potassium permanganate as part of the material composition with calcium carbonate and / or calcium hydroxide, the pH value of the aqueous solution used as the processing fluid can be controlled to make it alkaline enough for processing.

[0028] In this way, with the grinding wheel of the fifth invention, higher grinding accuracy can actually be achieved by more precisely and in detail managing the plastic deformation mechanism, including the processing conditions.

[0029] The sixth invention is a method for grinding semiconductor crystals according to the first or third invention, characterized in that, in the plastic deformation region, a plastic brittle intermediate layer present on the side opposite the grinding machine is used as a buffer region, and only the surface of the plastic deformation region is ground so as to leave the entire plastic brittle intermediate layer intact.

[0030] According to the semiconductor crystal grinding method of the sixth invention, as a result of intensive research that analyzed the plastic deformation region in more detail, it was discovered that there is a plastic brittle intermediate layer on the opposite side (crystal side) of the plastic deformation region from the grinding machine side, and that by using this as a buffer region, grinding that does not enter this buffer region leads to high-quality processing that does not cause cracks to propagate into the crystal.

[0031] Based on this knowledge, when grinding the plastic deformation region by using a grinding wheel containing cerium oxide to combine the removal of the oxide film of the semiconductor crystal and the grinding of the plastic deformation region, only the surface of the plastic deformation region is ground (the plastic brittle intermediate layer is not ground).

[0032] Thus, according to the semiconductor crystal grinding method of the sixth aspect of the invention, higher grinding accuracy can be achieved by controlling the plastic deformation mechanism more precisely and in detail.

[0033] FIG. 1 is a flowchart showing the entire manufacturing process of a Si wafer (semiconductor crystal wafer) according to the present embodiment. FIG. 2 is an explanatory diagram showing the contents of a first-side processing step and a second-side processing step in the manufacturing process of the Si wafer of FIG. 1. FIG. 3 is an explanatory diagram showing the contents of the first-side processing step and the second-side processing step in the manufacturing method of the Si wafer of FIG. 1. FIG. 4 is a schematic diagram showing the processed state in the first-side processing step and the second-side processing step in the manufacturing method of the Si wafer of FIG. 1. FIG. 5 is a schematic diagram showing the processed state in the first-side processing step and the second-side processing step in a conventional manufacturing method of a Si wafer. FIG. 6 is a schematic diagram showing the processed state in the first-side processing step and the second-side processing step in the manufacturing method of the Si wafer of FIG.

[0034] As shown in FIG. 1, in this embodiment, the method for manufacturing a Si wafer, which is a semiconductor crystal wafer, is a method for obtaining a Si wafer by slicing a wafer from a Si ingot that has been ground into a cylindrical shape and removing waviness from one surface of the wafer, and includes a groove processing step (STEP 100 / FIG. 1), a cutting step (STEP 110 / FIG. 1), a first surface processing step (STEP 120 / FIG. 1), and a second surface processing step (STEP 130 / FIG. 1).

[0035] The processing steps in STEP 120, the first surface processing step, and STEP 130, i.e., mechanical polishing (high-precision grinding), correspond to the semiconductor crystal wafer grinding method of the present invention (the grinding and grinding steps characteristic of the present invention). Meanwhile, the groove processing step in STEP 100 and the cutting step in STEP 110 are described in the applicant's Patent Nos. 7104909 and 7100864, ​​etc., and therefore detailed description thereof will be omitted here, and only an outline will be provided below.

[0036] First, in the groove processing step of STEP 100, a cylindrical Si ingot is prepared by determining the crystal orientation and performing cylindrical grinding on a pre-crystallized Si crystal in the ingot processing step.

[0037] Then, in the groove processing step of STEP 100, a plurality of grooves are formed around the entire side surface of the Si ingot.

[0038] Specifically, in the groove processing step of STEP 100, groove processing drum grinding wheels, each having a convex portion corresponding to the groove formed on its side, are rotated on parallel rotation axes and pressed against a Si ingot to form a groove.

[0039] It is desirable to subject the Si ingot (particularly the grooves) obtained in the groove processing step to a damage-free mirror finish by chemical processing.

[0040] Next, in the cutting step of STEP 110, the Si ingot is cut into slices by a plurality of wires arranged in the plurality of grooves formed in the groove processing step, to obtain Si wafers 100.

[0041] Specifically, in the cutting process, the wire saw device, which is a cutting processing device, has a wire saw section that aligns multiple wires with the multiple grooves formed in the groove processing process and moves the wires forward while circulating, thereby cutting the Si ingot into slices.

[0042] Next, as shown in FIG. 2, in the first surface processing step of STEP 120, one of the cut surfaces 110 is used as a support surface, and the other surface 120 is subjected to mechanical polishing (high-precision grinding).

[0043] Specifically, in the first surface processing step, grinding is performed by a mechanical polishing device 50 (ultra-high synthesis, high precision grinding device) that performs mechanical polishing.

[0044] 3, the mechanical polishing device 50 includes a spindle 51 and a platen 52, which is a grinding table, and stick-shaped grindstones 53 are radially arranged on the platen 52. More specifically, the stick-shaped grindstones 53 are fixed in recesses (not shown) formed in the platen 52 so that the lower sides of the stick-shaped grindstones 53 are partially fitted into the recesses.

[0045] The grindstone 53 is, for example, a diamond grindstone suitable for grinding Si wafers, and contains cerium oxide in an amount of more than 0% and not more than 10% in its material composition in order to remove an oxide film, which will be described later.

[0046] Furthermore, the material composition may contain potassium permanganate in an amount greater than 0% and not greater than 10%. Here, the total amount of cerium oxide and potassium permanganate in the material composition is greater than 0% and not greater than 20%, but is preferably greater than 0% and not greater than 15%. Furthermore, it is preferable that the grinding wheel 53 contains calcium carbonate and / or calcium hydroxide instead of potassium permanganate as part of its material composition, thereby controlling the pH value of the aqueous solution used as the machining fluid and making it alkaline enough for machining.

[0047] First, one surface 110 is used as the upper surface and is supported by adsorption to a vacuum porous chuck 54, which is an adsorption plate of a spindle 51, which is a support base that supports the wafer, and the other surface 120 is used as the lower surface and is ground using a grinding wheel 53.

[0048] At this time, the spindle 51 and the platen 52 are rotated by a drive unit (not shown), and the spindle 51 is pressed against the platen 52 by a compressor (not shown) or the like, thereby grinding the other surface 120 .

[0049] After the grinding process, the grindstone 53 may be dressed using a dresser or the like.

[0050] Furthermore, the mechanical polishing device 50 may have a functional water supply pipe so that multiple types of functional water can be used during processing, if necessary.

[0051] Next, in the second surface processing step of STEP 130, the other surface 120 that has been subjected to high-precision grinding in the first surface processing step is used as the upper surface, and high-precision grinding similar to that in the first surface processing step is performed on the one surface 110.

[0052] That is, the other surface 120 is attached to a vacuum porous chuck 54 which is an attachment plate of the spindle 51 with the other surface 120 as the upper surface, and the one surface 110 is attached to the lower surface with the grindstone 53 to grind the one surface 110 .

[0053] In this case, too, dressing may be performed by pressing a dresser or the like against the grindstone 53, if necessary.

[0054] In this embodiment, in the mechanical polishing (high-precision grinding) process of the first surface processing step of STEP 120 and the second surface processing step of STEP 130, as shown in particular in FIG. 4, a plastic deformation region 100A is formed on the surface of the wafer 100 due to a temperature rise caused by friction between the grinding wheel 53 and the wafer 100, using the grinding wheel 53 and the pressing force that presses the wafer 100 against the grinding wheel 53 via the spindle 51, and the plastic deformation region 100A is ground using the grinding wheel 53 while the oxide film 100B that forms on the surface of the plastic deformation region 100A is removed by the grinding wheel 53 by adding cerium oxide to the grinding wheel 53.

[0055] Here, by adding potassium permanganate in addition to cerium oxide to the grinding wheel 53, an oxide film 100B can be generated on the surface of the plastic deformation region 100A, and the generated oxide film 100B can be removed by the grinding wheel 53 by adding cerium oxide to the grinding wheel 53, while the plastic deformation region 100A is ground with the grinding wheel 53.

[0056] At this time, within the plastic deformation region 100A, there is a plastic brittle intermediate layer 100C present on the side opposite the platen 52, and this plastic brittle intermediate layer 100C is used as a buffer region, and only the surface of the plastic deformation region 100A is ground with a grinding wheel 53 so as to leave the entire plastic brittle intermediate layer 100C remaining.

[0057] According to the above-described configuration, as shown in FIG. 5A, in the case of a normal grinding wheel 53' that does not contain cerium oxide, the oxide film 100B cannot be removed, and the wafer 100 is not ground. However, as shown in FIG. 5B, in the case of the grinding wheel 53 of this embodiment that contains cerium oxide, the oxide film 100B is removed (as shown by the arrow in the figure relatively due to the wafer 100 being pressed against the platen 52), and the grinding wheel 53 reaches the plastic deformation region 100A, and only the surface of the plastic deformation region 100A is ground.

[0058] In this way, by using the plastic brittle intermediate layer 100C as a buffer region and performing grinding that does not enter this buffer region, high-quality processing can be achieved that does not cause cracks to propagate into the crystal of the wafer 100.

[0059] That is, in the plastically deformed region 100A of the wafer 100 from which the oxide film 100B has been removed, the grinding efficiency by the grindstone 53 is significantly improved, unlike surface polishing in a state without plastic deformation, and a highly flat mirror finish can be achieved in one go. In other words, the complicated manufacturing process, such as multiple lapping steps (first to fourth), can be greatly simplified.

[0060] It is important that the speed at which the spindle 51 advances relative to the grindstone 53 (platen 52) does not exceed the depth of the plastic deformation region 100A.

[0061] In this way, according to the grinding method for Si wafers, which are semiconductor crystal wafers, of this embodiment, it is possible to actually provide a grinding method for semiconductor crystal wafers that can achieve higher grinding accuracy by more precisely and in detail managing plastic deformation, which has been conventionally shunned, as a plastic deformation mechanism on the wafer surface.

[0062] In this embodiment, a method for grinding a Si wafer has been described in which a Si wafer is manufactured from a Si ingot. However, the semiconductor crystal is not limited to Si, and may be gallium phosphate, indium phosphide, silicon carbide (SiC), or other compound semiconductors.

[0063] Furthermore, in this embodiment, the case where the grooves are formed in the groove processing step and then the cutting is performed in the cutting step has been described, but the groove processing step may be omitted as appropriate.

[0064] Furthermore, in this embodiment, the grinding wheel 53 containing cerium oxide and potassium permanganate (which may contain calcium carbonate, calcium hydroxide, or both) is stick-shaped, but the shape of the grinding wheel 53 is not limited to this, and various shapes such as a cup shape (cup wheel shape) can be adopted as long as they are suitable for the purpose of grinding the end surface of the wafer 100 or ingot.

[0065] Furthermore, in this embodiment, the functional polishing of the surface of the plastic deformation region is described as an example of forming and removing an oxide film using potassium permanganate and cerium oxide as functional additives, and a case where CMP (chemical mechanical polishing) is performed in conjunction with grinding processing, but the functional polishing (surface treatment) and the functional additives used therefor are not limited to this.

[0066] 50... mechanical polishing device (ultra-high synthesis high precision grinding processing device), 51... spindle (support base), 52... platen (grinding surface plate), 53... grinding stone, 54... vacuum porous chuck (suction plate), 100... Si wafer (semiconductor crystal wafer), 110... one side, 120... other side.

Claims

1. A method for grinding a semiconductor crystal, which grinds an end face of a semiconductor crystal ingot ground into a cylindrical shape or the surface of a wafer sliced ​​from the semiconductor crystal ingot, comprising: a grinding wheel mounted on a grinding machine for grinding; and a pressing force applied to press the semiconductor crystal ingot or the wafer against the grinding wheel via a support base, which causes a temperature rise due to friction between the grinding wheel and the end face of the semiconductor crystal ingot facing the grinding machine or the surface of the wafer facing the grinding machine, and the surface of the plastically deformed region is ground with the grinding wheel while functionally polishing the surface of the plastically deformed region by incorporating a functional additive into the grinding wheel, characterized in that an oxide film formed on the surface of the plastically deformed region is removed by incorporating cerium oxide into the grinding wheel while the plastically deformed region is ground with the grinding wheel.

2. A grinding stone used in the method for grinding semiconductor crystals according to claim 1, characterized in that the grinding stone contains cerium oxide in an amount of more than 0% and not more than 10% as a material composition.

3. A method for grinding a semiconductor crystal, which grinds an end face of a semiconductor crystal ingot ground into a cylindrical shape or a surface of a wafer sliced ​​from the semiconductor crystal ingot, comprising: a grinding wheel mounted on a grinding machine for grinding; and a pressing force for pressing the semiconductor crystal ingot or the wafer against the grinding wheel via a support base, which causes a temperature rise due to friction between the grinding wheel and the end face of the semiconductor crystal ingot facing the grinding machine or the surface of the wafer facing the grinding machine, and the surface of the plastically deformed region is ground with the grinding wheel while functionally polishing the surface of the plastically deformed region by adding a functional additive to the grinding wheel, characterized in that the method grinds the plastically deformed region with the grinding wheel by adding potassium permanganate in addition to cerium oxide to form an oxide film on the surface of the plastically deformed region and simultaneously removing the oxide film with the grinding wheel.

4. A grinding stone for use in the semiconductor crystal grinding method described in claim 3, characterized in that the material composition contains more than 0% and not more than 10% of potassium permanganate.

5. A grinding stone according to claim 4, characterized in that the potassium permanganate is replaced as part of the material composition by calcium carbonate and / or calcium hydroxide.

6. A method for grinding semiconductor crystals according to claim 1 or 3, characterized in that a plastic brittle intermediate layer present on the side of the plastic deformation region opposite the grinding machine side is used as a buffer region, and only the surface of the plastic deformation region is ground so as to leave the entire plastic brittle intermediate layer intact.

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