Grinding wheel for insulating layer

Abstract

To provide a grinding wheel for an insulating layer, the grinding wheel quickly and mechanically polishing the front surface of a semiconductor wafer while preventing damage to the back surface of the semiconductor wafer due to pressure applied during a polishing process.SOLUTION: A grinding wheel 10 for an insulating layer is provided, which includes a wheel tip 11 including an abrasive, the abrasive including at least one of Si3N4 and ZrO2, and which enables mechanical grinding of an insulating layer provided on the front surface of a semiconductor wafer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a grinding wheel for insulating layers, and more particularly to a grinding wheel for insulating layers that can mechanically polish insulating layers formed on the front surface of semiconductor wafers. [Background technology]

[0002] Semiconductor wafers used to make semiconductor integrated circuits are produced through a specific process. After cutting an ingot made from high-purity silicon solution, the wafer surface undergoes a process of processing. Immediately after cutting, the wafer surface is scratched and rough, which can affect the precision of the circuit, so a precise polishing process is required.

[0003] Generally, semiconductor wafer polishing is the process of removing the silicon layer deposited on the backside of the wafer. By using a material with a relatively large particle size, such as diamond, as an abrasive, the backside of the wafer can be quickly removed.

[0004] Semiconductor elements can be stacked and bonded to the front surface of a semiconductor wafer. Therefore, the front surface does not undergo a separate grinding process, and the insulating layer formed on the front surface is removed through the CMP process. The CMP process is a chemical mechanical polishing process that involves a chemical reaction. Because a chemical reaction is involved, the polishing process takes longer and it is difficult to use commonly used diamond as an abrasive.

[0005] The need for a mechanical polishing process for insulating layers on the front side of semiconductor wafers is increasing due to the increase in stacking of semiconductor devices and the proliferation of bonding processes, and as the thickness of insulating layers continues to increase in the future, faster processes may be necessary. Summary of the Invention [Problem to be solved by the invention]

[0006] An embodiment of the present invention provides a grinding wheel for insulating layers that can quickly mechanically polish the front surface of a semiconductor wafer while preventing damage that may occur on the back surface of the semiconductor wafer due to pressure applied during the polishing process.

[0007] The problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned in this specification will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0008] Grinding wheels for insulating layers according to various embodiments of the present invention include wheel tips containing abrasives, and the abrasives include at least one of Si3N4 and ZrO2, and can mechanically grind an insulating layer provided on the front surface of a semiconductor wafer.

[0009] According to one embodiment, the abrasive material occupies 10% to 60% of the total volume of the wheel tip, with the remaining portion consisting of pores and binder material.

[0010] According to an embodiment, the binder may be a resin or glass material.

[0011] According to one embodiment, the abrasive may further comprise diamond.

[0012] According to one embodiment, the abrasive material can be a mixture of Si3N4 and diamond.

[0013] According to one embodiment, the abrasive may be a mixture of ZrO2 and diamond.

[0014] According to one embodiment, the insulating layer provided on the front surface of the semiconductor wafer may have a thickness of 300 to 1000 nanometers after polishing.

[0015] According to one embodiment, when the diameter of the grinding wheel is 300 mm, the rotation speed of the grinding wheel may be 1000 to 4000 rpm, and when the diameter of the grinding wheel is 200 mm, the rotation speed of the grinding wheel may be 1000 to 7000 rpm.

[0016] According to one embodiment, the abrasive may contain 10 to 100 vol % of Si3N4.

[0017] According to one embodiment, the abrasive can contain 10 to 100 vol % of ZrO2.

[0018] According to one embodiment, the abrasive may have a total volume ratio of Si3N4 and ZrO2 of 10 to 100%.

[0019] According to one embodiment, the Si3N4 and ZrO2 constituting the wheel tip may have an average particle size of 0.2 to 60 micrometers.

[0020] According to one embodiment, the abrasive may contain 0 to 50 vol % diamond.

[0021] According to one embodiment, the average particle size of the Si3N4 constituting the abrasive may be 0.2 to 60 micrometers.

[0022] According to one embodiment, the average particle size of the ZrO2 constituting the abrasive may be 0.2 to 60 micrometers.

[0023] According to one embodiment, the average particle size of the diamond constituting the abrasive may be 0.2 to 60 micrometers.

[0024] According to one embodiment, the depth of microcracks generated on the back surface of the polished semiconductor wafer may be 50 to 200 nanometers. [Effects of the Invention]

[0025] According to one embodiment of the present invention, Si3N4 is used as the abrasive material in the wheel tip used for grinding, allowing for mechanical grinding without damaging the underside of the wafer.

[0026] The various beneficial advantages and effects of the present invention are not limited to the above, but will be more easily understood in the course of describing specific embodiments of the present invention. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a diagram showing an insulating layer grinding wheel according to an embodiment of the present invention. FIG. [Figure 2] FIG. 2 is an enlarged view of a wheel tip of an insulating layer grinding wheel according to an embodiment of the present invention. [Figure 3] FIG. 2 is a diagram showing an insulating layer grinding wheel according to an embodiment of the present invention grinding the front surface of a wafer. [Figure 4] FIG. 1 is a diagram showing a semiconductor wafer polished with a grinding wheel for insulating layers according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] Since the present invention can be modified in various ways and can have various embodiments, specific embodiments are shown in the drawings and described in detail. However, it should be understood that this is not intended to limit the present invention to the specific embodiments, and that it includes all modifications, equivalents, and alternatives within the spirit and technical scope of the present invention. In describing the present invention, if a detailed description of related publicly known technology is considered to obscure the gist of the present invention, the detailed description will be omitted.

[0029] Terms such as "first" and "second" may be used to describe various components, but the components should not be limited by the terms. The terms are used only to distinguish one component from another.

[0030] The terms used in this application are merely used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as "comprise" or "have" specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but should be understood not to preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0031] Furthermore, throughout the specification, when the term "connected" is used, it does not only mean that two or more components are directly connected, but also that two or more components are indirectly connected via other components, that two or more components are not only physically connected but also electrically connected, or that two or more components are referred to by different names depending on their position or function but are integrated.

[0032] Furthermore, when it is described as being formed or located "above (top) or below (bottom)" each component, above (top) or below (bottom) includes not only the case where two components are in direct contact with each other, but also the case where one or more other components are formed or located between the two components. Also, when it is expressed as "above (top) or below (bottom)," it can mean not only the upward direction but also the downward direction relative to one component.

[0033] Hereinafter, one embodiment of a grinding wheel for insulating layers according to the present invention will be described in detail with reference to the accompanying drawings. In the description with reference to the accompanying drawings, the same or corresponding components will be given the same drawing numbers, and duplicate descriptions thereof will be omitted.

[0034] Semiconductor wafers undergo a polishing process during the manufacturing process. Generally, wafers are polished from the backside, but the front side, where the substrate and elements are located, can be damaged if polished.

[0035] A semiconductor wafer may have a plurality of semiconductor elements and a substrate disposed on the front surface thereof, and may have an insulating layer covering the substrate and elements. The insulating layer may be formed of silicon dioxide or the like, and covers the front surface of the semiconductor wafer to protect the wafer surface, separate the elements, and maintain electrical insulation of the wafer.

[0036] However, as stacking and bonding processes for semiconductor devices proliferate, changes in manufacturing processes are occurring, creating a need to grind the insulating layer on the front side of the semiconductor.

[0037] The insulating layer on the front of a semiconductor wafer is currently polished using the CMP process, but as the insulating layer continues to thicken, there may be limits to how much polishing the front of the wafer can be achieved using only the CMP process, which takes a long time to polish.

[0038] In addition, grinding wheels used for back grinding of semiconductor wafers generally use diamond as an abrasive, but when diamond is used as an abrasive to polish the front surface of a semiconductor wafer, there is a risk of direct damage to the semiconductor element.

[0039] The insulating layer grinding wheel according to one embodiment of the present invention is capable of mechanically polishing the insulating layer on the front side of a semiconductor wafer.

[0040] FIG. 1 is a diagram showing an insulating layer grinding wheel according to one embodiment of the present invention, and FIG. 2 is an enlarged view of a wheel tip of the insulating layer grinding wheel according to one embodiment of the present invention.

[0041] The grinding wheel 10 may be circular and may have a wheel tip 11 formed on one side. The wheel tip 11 may be arranged in a circular shape on the grinding wheel 10. Referring to FIGS. 1 and 2, a grinding wheel 10 for insulating layers according to an embodiment of the present invention may be made of a material selected to be able to polish the front surface of a semiconductor wafer. This material may be Si3N4 or ZrO2. Diamond, which is commonly used as an abrasive, has such high hardness and strength that it may apply strong pressure to elements and substrates placed on the front surface when polishing the front surface of a semiconductor wafer, resulting in damage.

[0042] When Si3N4 is used as an abrasive as in this embodiment, efficient grinding is performed and damage to the lower part of the semiconductor wafer is not likely to occur.

[0043] As mentioned above, when diamond is used as an abrasive, the coefficient of friction between the diamond and the front surface of the wafer is low, which can cause the abrasive to slip on the wafer surface, and in this case, large scratches can be generated on the front surface of the wafer due to the high hardness of diamond.

[0044] The coefficient of friction between Si3N4 and the front surface of the wafer is higher than that of diamond. The hardness of Si3N4 is lower than that of diamond. Therefore, when an abrasive is made of Si3N4, it can prevent the abrasive from slipping on the front surface of the wafer, and its low hardness allows for precise grinding.

[0045] In terms of material hardness and rigidity, diamond has values ​​more than 10 times higher than the front surface material of the wafer, and Si3N4 has values ​​three times higher than the front surface material of the wafer, so when the abrasive is made of Si3N4, the surface quality of the polished wafer can be better.

[0046] To achieve the above effects, the average particle size of Si3N4 used as an abrasive can be selected from the range of 0.2 to 60 micrometers. When the particle size is determined within this range, good quality can be ensured during polishing. If the particle size is too large, precise polishing becomes difficult and fine scratches may occur. If the particle size is too small, the polishing speed becomes slow and polishing itself may become impossible. Therefore, by appropriately selecting the particle size, a fast process speed and a high-quality ground surface without scratches can be obtained.

[0047] To achieve the above effects, the tip 11 of the grinding wheel 10 uses Si3N4 as an abrasive, and the Si3N4 content can be in the range of 10% to 100% by volume. When the Si3N4 content is determined within this range, the front surface of the polished semiconductor wafer is free of scratches and excellent surface quality can be obtained. Another advantage is that it is possible to polish the surface of a composite workpiece containing silicon dioxide depending on the Si3N4 content.

[0048] The above-mentioned effects can also be obtained when ZrO2 is used instead of Si3N4.

[0049] Therefore, the grinding wheel 10 for insulating layers according to another embodiment of the present invention can use ZrO2 as an abrasive.

[0050] In order to obtain the above-mentioned effects, the average particle size of ZrO2 used as an abrasive can be selected in the range of 0.2 μm to 60 μm.

[0051] To achieve the above-mentioned effects, the tip 11 of the grinding wheel 10 utilizes ZrO2 as an abrasive, and the ratio of ZrO2 contained may be in the range of 10% to 100% based on the volume ratio.

[0052] Abrasives can be made from a mixture of multiple materials. For example, Si3N4 and diamond can be used together. If diamond alone is used, too much load is placed on the front surface of the semiconductor wafer, which can cause damage. Therefore, by ensuring the proportion of Si3N4, the grinding load applied to the front surface of the wafer can be reduced.

[0053] Similarly, it is possible to use a mixture of ZrO2 and diamond. If only diamond is used, a large load is placed on the front surface of the semiconductor wafer, which can cause breakage. Therefore, by ensuring the ratio of ZrO2, the grinding load applied to the front surface of the wafer can be reduced.

[0054] Alternatively, a mixture of Si3N4 and ZrO2 can be used as the abrasive.

[0055] As mentioned above, the abrasive can be a mixture of multiple materials, so it is also possible to mix and use abrasive materials other than Si3N4 or ZrO2. As an example, the abrasive can be Si3N4, ZrO2, and diamond, either singly or in combination.

[0056] The abrasive material may occupy 10% to 60% of the total volume of the wheel tip, with the remainder consisting of pores and a binder, which may be a resin or glass material.

[0057] Figure 2 shows a close-up SEM image of the inside of a grinding wheel tip. The wheel tip can contain abrasives, a bond that bonds the abrasives, and pores, which are empty spaces. The composition of the abrasives and bond can be adjusted to tailor the grinding quality provided by the wheel tip.

[0058] FIG. 3 is a diagram showing how an insulating layer grinding wheel according to one embodiment of the present invention grinds the front surface of a wafer.

[0059] Referring to FIG. 3, it can be seen that a semiconductor element 21 and a substrate 22 are disposed on the front surface of a semiconductor wafer 20. The semiconductor element 21 and the substrate 22 are covered with an insulating layer 23, which may be formed to have a predetermined thickness. The insulating layer 23 can be ground to an appropriate thickness, and thus a polishing wheel according to an embodiment of the present invention can polish the insulating layer 23. The thickness of the insulating layer provided on the front surface of the semiconductor wafer after polishing may be 300 to 1000 nanometers.

[0060] The grinding wheel 10 can be polished by rotating at a high speed, causing friction between the wheel tip 11 and the insulating layer 23, thereby scraping the outer periphery of the insulating layer 23. If the tip 11 of the grinding wheel 10 uses Si3N4 or ZrO2 as an abrasive instead of diamond, the load generated during the polishing process is reduced, and the grinding wheel 10 can be rotated at a faster speed.

[0061] The rotation speed of the grinding wheel 10 may be selected from 1,000 to 4,000 rpm when the wheel diameter is 300 mm. The rotation speed of the grinding wheel 10 may be selected from 1,000 to 7,000 rpm when the wheel diameter is 200 mm. When the grinding wheel 10 is rotated at a rotation speed within the above range, excellent grinding quality can be ensured.

[0062] If the rotation speed of the grinding wheel 100 is below a certain level, the wheel tip 11 and insulating layer 23 are in contact for a long time, and the wafer 20 may be pushed out without being polished due to the slow speed. If the rotation speed of the grinding wheel 10 is above a certain level, the grinding load may be too high, causing damage to the wafer 20. When the rotation speed of the grinding wheel 10 is selected at an appropriate level as described above, a uniform amount of polishing can be obtained across the entire area of ​​the wafer 20. Another advantage is that excellent surface quality can be obtained through a low grinding load.

[0063] FIG. 4 is a diagram showing a semiconductor wafer polished with a grinding wheel for insulating layers according to one embodiment of the present invention.

[0064] Referring to FIG. 4, (a) shows a wafer polished with a grinding wheel 10 using diamond as an abrasive, and (b) shows a wafer polished with a grinding wheel 10 using Si3N4 as an abrasive.

[0065] Below, (a) and (b) will be compared and explained.

[0066] Looking at the photo of the ground surface taken with a laser microscope, when Si3N4 was used as the abrasive, the surface was polished smoothly and no scratches occurred.In contrast, when looking at the ground surface (a) where diamond was used as the abrasive, it can be seen that cracks C occurred in the area indicated by the dotted line due to the large grit size.

[0067] Diamond has a low coefficient of friction with the workpiece, so it can easily slide on the surface. Also, due to its high hardness, diamond can slide on the surface during the polishing process, causing numerous large scratches. If the diamond grain size is made small to prevent this, there is a problem that the workpiece is hardly polished at all.

[0068] When diamond is used as an abrasive, damage can be transmitted to the bottom of the substrate. Because the abrasive presses the substrate hard while polishing, the polishing quality deteriorates and the force is transmitted to the bottom of the substrate, which can cause damage to the bottom of the substrate.

[0069] In the case of (a), where diamond is used as the abrasive, the surface roughness (curvature) of the front surface of the wafer is 1 micrometer or more, and the depth of the microcracks that occurred in the wafer is 10 micrometers or more.

[0070] In contrast, in case (b) where Si3N4 is used as the abrasive, the surface roughness of the front surface of the wafer can be on the order of 10 nanometers.When Si3N4 is used as the abrasive, the depth of the microcracks that occur on the wafer is on the order of 50 to 200 nanometers.

[0071] While the present invention has been described above with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications and variations of the present invention may be made without departing from the spirit and scope of the present invention as set forth in the following claims. [Explanation of symbols]

[0072] 10: Grinding wheel 11: Wheel tip 20: Semiconductor wafer 21: Semiconductor element 22: Circuit board 23: Insulating layer

Claims

1. Includes a wheel tip containing abrasive material, The abrasive material includes at least one of Si3N4 and ZrO2, and the insulating layer grinding wheel is used to mechanically grind the insulating layer provided on the front surface of a semiconductor wafer.

2. The insulating layer grinding wheel of claim 1 , wherein the abrasive material further comprises diamond.

3. 3. The grinding wheel for insulating layers according to claim 2, wherein the wheel tip contains 10 to 100 vol % of Si3N4.

4. 3. The grinding wheel for insulating layers according to claim 2, wherein the wheel tip contains 10 to 100 vol % ZrO2.

5. 4. The grinding wheel for insulating layers according to claim 3, wherein the Si3N4 constituting the wheel tip has an average particle size of 0.2 to 60 micrometers.

6. 5. The grinding wheel for insulating layers according to claim 4, wherein the average particle size of the ZrO2 constituting the wheel tip is 0.2 to 60 micrometers.

7. 2. The grinding wheel for insulating layers according to claim 1, wherein the abrasive has a total volume ratio of Si3N4 and ZrO2 of 10 to 100%.

8. 8. The grinding wheel for insulating layers according to claim 7, wherein the Si3N4 and ZrO2 constituting the wheel tip have an average particle size of 0.2 to 60 micrometers.

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