Wafer forming method

Abstract

A method of forming a wafer includes cutting the ingot in a direction parallel to an upper surface of the ingot to form a first wafer, bonding an upper surface and a lower surface of the first wafer to a first carrier plate and a second carrier plate, respectively, cutting the first wafer in a direction parallel to the upper surface of the first wafer to form a second wafer, and bonding the second wafer to the second carrier plate. Wherein a first one of the second wafers contacts the first carrier and a second one of the second wafers contacts the second carrier, and removing the second carrier from the second one of the second wafers. The method can be used for solving the problem that when a wafer with a large size is cut to be thin, the formed wafer is prone to warping.

Description

TECHNICAL FIELD

[0001] Some embodiments of the present disclosure relate to a method of forming a wafer. BACKGROUND

[0002] A wafer is a common semiconductor component, which can be formed by cutting a rod-shaped ingot. As the size of the wafer is larger, the number of integrated circuits formed on each wafer is larger. However, the thickness of the wafer needs to be thicker as the size of the wafer is larger, to avoid the warping problem of the wafer. It is desirable to find a way to form a wafer with both large size and small thickness. SUMMARY

[0003] Some embodiments of the present disclosure provide a method of forming a wafer, comprising cutting an ingot along a direction parallel to an upper surface of the ingot to form a first wafer, bonding an upper surface and a lower surface of the first wafer to a first carrier plate and a second carrier plate, respectively, cutting the first wafer along a direction parallel to the upper surface of the first wafer to form a second wafer, wherein a first one of the second wafer contacts the first carrier plate and a second one of the second wafer contacts the second carrier plate, and removing the second carrier plate from the second one of the second wafer.

[0004] In some embodiments, a diameter of the first carrier plate is larger than a diameter of the first wafer.

[0005] In some embodiments, before the second carrier plate is removed, the method further comprises reducing a thickness of the second one of the second wafer.

[0006] In some embodiments, before the thickness of the second one of the second wafer is reduced, the thickness of the second one of the second wafer is between 225 micrometers and 250 micrometers.

[0007] In some embodiments, after the thickness of the second one of the second wafer is reduced, the thickness of the second one of the second wafer is between 150 micrometers and 170 micrometers.

[0008] In some embodiments, reducing the thickness of the second one of the second wafer comprises performing a grinding process on the second one of the second wafer, and after performing the grinding process, performing a planarization process on the second one of the second wafer.

[0009] In some embodiments, the grinding process reduces a first thickness of the second one of the second wafer, and the planarization process reduces a second thickness of the second one of the second wafer, the first thickness being larger than the second thickness.

[0010] In some embodiments, a diameter of the first wafer is between 8 inches and 12 inches.

[0011] In some embodiments, a thickness of the first wafer is between 450 micrometers and 500 micrometers.

[0012] In some implementations, the first and second carrier plates are made of quartz or sapphire. Attached Figure Description

[0013] The scope of this invention is best understood from the following detailed description when read with reference to the accompanying drawings. Note that, in accordance with standard practice in the industry, the various features are not drawn to scale. In fact, for clarity of explanation, the dimensions of the various features may be arbitrarily increased or decreased.

[0014] Figures 1 to 5 A cross-sectional view illustrating a method of forming a wafer in some embodiments of the present invention is shown. Detailed Implementation

[0015] Some embodiments of the present invention relate to a method of forming a wafer. Specifically, the present invention addresses the problem that when a large wafer is cut into a thinner section, the resulting wafer is prone to warping, which can hinder subsequent processes. The present invention is applicable to forming wafers with diameters between 8 inches and 12 inches and thicknesses between 150 micrometers and 170 micrometers.

[0016] Figures 1 to 5 A cross-sectional view illustrating a wafer formation method in some embodiments of the present invention is shown. (Reference) Figure 1 An ingot 100 is provided, and the ingot 100 is cut along a direction parallel to its upper surface 100T to form a plurality of first wafers 110. Specifically, the ingot 100 is made of a semiconductor material, such as silicon carbide. The ingot 100 may be cylindrical, and therefore its upper surface 100T is circular. Whether the first wafers 110 have a warpage problem depends on the thickness T1 of the first wafers 110 and the size of the ingot 100. The larger the size of the ingot 100, the larger the thickness T1 of the first wafers 110 needs to be to avoid warpage problems. In some embodiments, the diameter of the ingot 100 (or the first wafer 110) may be between 4 inches and 12 inches. In some embodiments, the method of the present invention is particularly suitable for larger ingots 100 (or first wafers 110), such as ingots 100 (or first wafers 110) with a diameter between 8 inches and 12 inches. In some embodiments, the thickness T1 of the first wafer 110 is between 450 micrometers and 500 micrometers. When the thickness T1 of the first wafer 110 is less than the above range, warping of the first wafer 110 may occur due to the thickness T1 being too small within the dimensions of the ingot 100 of the present invention. When the thickness T1 of the first wafer 110 is greater than the above range, excessive wafer thinning in subsequent processes may occur due to the thickness T1 being too large (e.g., ...). Figure 4 This would waste materials due to the process (often referred to as "processing"). However, the thickness of the first wafer 110 needs to be further reduced to decrease the power consumption and on-resistance of the resulting semiconductor device.

[0017] Referring to Figure 2 The upper surface 110T of the first wafer 110 is bonded to the first carrier 122, and the lower surface 110B of the first wafer 110 is bonded to the second carrier 124. Specifically, an adhesive can be applied on the upper surface 110T of the first wafer 110, and the upper surface 110T of the first wafer 110 is gently pressed against the first carrier 122. Then, an adhesive is applied on the lower surface 110B of the first wafer 110, and the lower surface 110B of the first wafer 110 is gently pressed against the second carrier 124. Then, the first wafer 110, the first carrier 122 and the second carrier 124 are heated to cure the adhesive that bonds the first wafer 110 and the first carrier 122, and the first wafer 110 and the second carrier 124. In this way, the first carrier 122 and the second carrier 124 can be firmly bonded to the first wafer 110. In some embodiments, the first carrier 122 and the second carrier 124 can be made of quartz or sapphire. In some embodiments, the adhesive can be a high molecular polymer or a siloxane-based material. In some embodiments, the diameter D1 of the first carrier 122 and the second carrier 124 is greater than the thickness T1 of the first wafer 110, and the diameter D1 of the first carrier 122 and the second carrier 124 is greater than the diameter D2 of the first wafer 110.

[0018] Then, the first wafer 110 is cut along a direction parallel to the upper surface 110T of the first wafer 110 to form a plurality of second wafers 130, wherein a first one of the second wafers 130 contacts the first carrier 122, and a second one of the second wafers 130 contacts the second carrier 124. The second wafers 130 formed by cutting the first wafer 110 are shown in Figure 3 some embodiments, each first wafer 110 can be cut into two second wafers 130, such that one surface of the second wafer 130 can be bonded to the first carrier 122 or the second carrier 124. The first carrier 122 or the second carrier 124 can directly serve as a carrier in subsequent processing without the need to attach additional carriers. In Figures 3 to 5 Hereinafter, the second one of the second wafers 130 and the second carrier 124 will be used as an example. However, the first one of the second wafers 130 and the first carrier 122 can also be processed in a similar manner.

[0019] Referring to Figure 2 With Figure 3After the second wafer 130 is formed, one side of the second wafer 130 contacts the first carrier 122 or the second carrier 124, while the other side is exposed. Specifically, when the first carrier 122 and the second carrier 124 are bonded to the first wafer 110 and the first wafer 110 is cut, the first carrier 122 and the second carrier 124 can provide sufficient rigidity, thus allowing the first wafer 110 to be cut thinner without warping. Furthermore, since the diameter D1 of the first carrier 122 and the second carrier 124 is larger than the diameter D2 of the first wafer 110, the first carrier 122 and the second carrier 124 can more completely cover the upper surface 110T and the lower surface 110B of the first wafer 110, providing better rigidity to the first wafer 110. In this way, each ingot 100 can be cut into more second wafers 130, improving the yield of the second wafers 130. In some implementations, the thickness T2 of the second wafer 130 can be between 225 micrometers and 250 micrometers before the thickness of the second wafer 130 is reduced.

[0020] refer to Figure 4 A processing technique is performed on the second wafer 130 to reduce its thickness. In some embodiments, reducing the thickness of the second wafer 130 includes performing a grinding process on the second wafer 130, followed by a planarization process. Specifically, with Figure 4 For example, when the lower surface 110B of the second wafer 130 is bonded to the second carrier 124, a grinding process is performed on the exposed surface of the second wafer 130 to thin the second wafer 130. Next, a planarization process is performed on the second wafer 130 to flatten the exposed surface. In some embodiments, the grinding process reduces the first thickness of the second wafer 130, while the planarization process further reduces the second thickness of the second wafer 130, wherein the first thickness is greater than the second thickness. In some embodiments, the grinding process reduces the first thickness of the second wafer 130 by 80 to 100 micrometers. The planarization process reduces the second thickness of the second wafer 130 by 0.1 to 10 micrometers. After reducing the thickness of the second wafer 130, the thickness T3 of the second wafer 130 is between 150 and 170 micrometers.

[0021] refer to Figure 5 The second substrate 124 is then removed from the second wafer 130. Specifically, the adhesive between the second wafer 130 and the second substrate 124 can be removed by heating or using a solvent. At this point, the second substrate 124 can be removed from the second wafer 130, resulting in a second wafer 130 that is large in size and thin in thickness.

[0022] The second wafer 130 can then be subjected to subsequent processes to form integrated circuits on the second wafer 130. The subsequent processes can include ion implantation processes, deposition processes, etching processes, etc. Finally, the second wafer 130 with the integrated circuits is cut into a plurality of dies. The second wafer 130 of the present application has a large size, so that more dies can be formed from each second wafer 130. In this way, the efficiency of forming dies can be improved.

[0023] In summary, some embodiments of the present application can be used to cut a large ingot into thin wafers. Specifically, the ingot can be first cut into first wafers having a first thickness, and then the upper and lower surfaces of the first wafers are bonded to carrier plates, respectively. The carrier plates can increase the rigidity of the first wafers, so that when the first wafers are cut subsequently, the second wafers formed therefrom will not have warping problems due to the small thickness. In this way, not only the number of wafer dies formed from each ingot can be improved, but also the yield of forming wafers can be improved. In addition, since the ingot and the second wafers formed therefrom have a large size, the number of dies formed from each wafer can also be improved.

[0024] The above description is only some embodiments of the present application, not all embodiments. Any equivalent changes made by those skilled in the art to the technical solutions of the present application by reading the description of the present application are covered by the claims of the present application.

[0025]

Symbol Description

[0026] 100: ingot

[0027] 100T, 110T: upper surface

[0028] 110: first wafer

[0029] 110B: lower surface

[0030] 122: first carrier plate

[0031] 124: second carrier plate

[0032] 130: second wafer

[0033] D1, D2: diameter

[0034] T1, T2, T3: thickness

Claims

1. A method for forming a wafer, characterized in that, Include: The ingot is cut along a direction parallel to the upper surface of the ingot to form a first wafer; The upper and lower surfaces of the first wafer are respectively bonded to the first substrate and the second substrate; The first wafer is cut along a direction parallel to the upper surface of the first wafer to form a plurality of second wafers, wherein a first of the plurality of second wafers contacts the first substrate, and a second of the plurality of second wafers contacts the second substrate. as well as Remove the second carrier from the second of the plurality of second wafers.

2. The method according to claim 1, characterized in that, The diameter of the first carrier plate is larger than the diameter of the first wafer.

3. The method according to claim 1, characterized in that, Before removing the second carrier board, it also includes: Reduce the thickness of the second of the plurality of second wafers.

4. The method according to claim 3, characterized in that, Before reducing the thickness of the second of the plurality of second wafers, the thickness of the second wafer is between 225 micrometers and 250 micrometers.

5. The method according to claim 4, characterized in that, After reducing the thickness of the second of the plurality of second wafers, the thickness of the second wafer is between 150 micrometers and 170 micrometers.

6. The method according to claim 3, characterized in that, Reducing the thickness of the second of the plurality of second wafers includes: A polishing process is performed on the second of the plurality of second wafers; and After the grinding process is performed, a planarization process is performed on the second of the plurality of second wafers.

7. The method according to claim 6, characterized in that, The grinding process reduces the second first thickness of the plurality of second wafers, and the planarization process reduces the second second thickness of the plurality of second wafers, wherein the first thickness is greater than the second thickness.

8. The method according to claim 1, characterized in that, The diameter of the first wafer is between 8 inches and 12 inches.

9. The method according to claim 1, characterized in that, The thickness of the first wafer is between 450 micrometers and 500 micrometers.

10. The method according to claim 1, characterized in that, The first and second carrier plates are made of quartz or sapphire.

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