Wafer single-sided chemical plating method, semiconductor device manufacturing method and semiconductor device

Abstract

The invention relates to a wafer single-sided chemical plating method, a semiconductor device manufacturing method and a semiconductor device. The wafer single-sided chemical plating method comprises: providing a wafer with a Taiko ring formed on one side; providing a rigid support plate; closely connecting the end face of the Taiko ring with the rigid support plate; performing chemical plating on the closely connected wafer and the rigid support plate; and separating the wafer after chemical plating from the rigid support plate. The single-sided chemical plating method can be used to perform single-sided chemical plating on a wafer thinned by a Taiko thinning process, thereby eliminating the film sticking and film peeling procedures before and after the existing chemical plating process, and avoiding the occurrence of liquid leakage in the original chemical plating film sticking process; the rigid support plate is used to bond the end face of the Taiko ring of the wafer, which helps to reduce the warpage of the wafer during single-sided chemical plating, and can significantly reduce the color difference within the wafer after single-sided chemical plating, thereby improving the appearance of the product and the reliability of application.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a single-sided chemical plating method for a wafer, semiconductor device manufacturing and a semiconductor device. Background Art

[0002] Chemical plating is a common process in semiconductor manufacturing, which can be divided into single-sided plating and double-sided plating. Especially for the single-sided chemical plating process, it is necessary to coat the back of the wafer with a film, usually a UV film, and use the protective film to prevent the back metal layer from contacting the chemical agent. After the chemical plating is completed, the film is removed. Wafers usually need to be thinned before chemical plating. The Taiko thinning process was publicly developed by DISCO of Japan. The Taiko thinning process does not thin the entire surface of a certain surface of the wafer, but only thins the middle part of the wafer, so that a thicker support ring is formed on the edge of the wafer. This support ring is usually called a Taiko ring.

[0003] like Figure 1 As shown, the wafer is formed after the Taiko thinning process Figure 1 The structure in the middle, namely the middle thinning portion 1 and the Taiko ring 2 at the edge, forms a step at the connection between the Taiko ring 2 and the middle thinning portion 1. In the existing single-sided chemical plating process, the Taiko ring 2 has been formed when the film is attached to the back of the wafer. Due to the existence of the step difference of the Taiko ring 2, the protective film 3 attached to the back of the wafer cannot be well attached to the wafer, and the Taiko ring 2 step is prone to leakage in the chemical plating solution ( Figure 1 As shown in the middle circle, the metal layer on the back of the wafer comes into contact with chemicals, which will have a certain impact on the product's appearance and application reliability.

[0004] Furthermore, for large-sized wafers (such as 8-inch wafers), the warpage of the wafer is more obvious after thinning. The Taiko ring retained after the thinning process is completed has a certain effect on improving the warpage of the wafer, but for devices with larger die such as IGBTs, even with the presence of the Taiko ring, the wafer still has a certain warpage. Since the existing single-sided chemical plating operation is protected by attaching a protective film to the back of the wafer, the protective film is soft and has no rigidity, and cannot further eliminate the warpage of the wafer. In the single-sided chemical plating operation, the exchange and cleaning effects of the chemical plating solution at the warped edge of the wafer are poor, which can easily cause color difference within the wafer. For larger-sized wafers (such as 12 inches), the color difference will be more serious. Summary of the invention

[0005] The present invention firstly discloses a single-sided chemical plating method for a wafer, which eliminates the film attaching step before chemical plating and the film peeling step after chemical plating, simplifies the production process, and effectively avoids the leakage problem in the single-sided chemical plating link and the color difference problem within the wafer.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A single-sided chemical plating method for a wafer, comprising:

[0008] providing a wafer having a Taiko ring formed on one side;

[0009] Provide a rigid support plate;

[0010] Tightly connecting the end surface of the Taiko ring to the rigid support plate;

[0011] Performing chemical plating on the closely connected wafer and the rigid support plate;

[0012] The wafer after the chemical plating process is separated from the rigid support plate.

[0013] Furthermore, tightly connecting the end face of the Taiko ring to the rigid support plate includes: applying temporary bonding glue on one side surface of the rigid support plate and / or the end face of the Taiko ring, bonding the end face of the Taiko ring to the rigid support plate, and then curing.

[0014] Furthermore, the temporary bonding adhesive includes a photosensitive adhesive and a LTHC coating liquid, and the rigid support plate is a light-transmitting plate;

[0015] The LTHC coating liquid is coated on one side surface of the rigid support plate, and then first cured to form an LTHC coating;

[0016] The photosensitive adhesive is coated on the end surface of the Taiko ring, and the side of the rigid support plate having the LTHC coating is bonded to the photosensitive adhesive on the end surface of the Taiko ring, and then a second curing is performed.

[0017] Furthermore, the rigid support plate is made of a light-transmitting glass plate or a light-transmitting acrylic plate.

[0018] Furthermore, the first curing is performed by heating, the temperature of the first curing is 220° C. to 300° C., and the time of the first curing is 200s to 300s.

[0019] Furthermore, the second curing is performed by ultraviolet irradiation curing.

[0020] Furthermore, the wafer after the chemical plating process and the rigid support plate are separated by laser irradiation.

[0021] The invention also discloses a method for manufacturing a semiconductor device, comprising the above-mentioned single-sided chemical plating method for a wafer.

[0022] The present invention further discloses a semiconductor device manufactured by adopting the semiconductor device manufacturing method.

[0023] Furthermore, the semiconductor device is an IGBT.

[0024] The present invention is designed for wafers thinned by the Taiko thinning process and requiring single-sided chemical plating. In order to protect the back side of the wafer from being affected during chemical plating, the present invention adheres a rigid support plate to the end face of the Taiko ring on the back side of the wafer to shield the back side of the wafer. Compared with the existing single-sided chemical plating using a film protection method, the method of the present invention omits the film-sticking process for the wafer protection surface before chemical plating, and also omits the film-peeling process after chemical plating, effectively avoiding the occurrence of liquid leakage in the original chemical plating film-sticking process; and the present invention uses a rigid support plate to bond the end face of the Taiko ring of the wafer, which helps to reduce the warpage of the wafer during single-sided chemical plating, can significantly reduce the color difference within the wafer after single-sided chemical plating, and improves the appearance of the product and the reliability of application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the state of the Taiko ring and the protective film attached to the surface of the wafer in the prior art;

[0026] Figure 2 A flow chart of a single-sided chemical plating method according to an embodiment of the present invention;

[0027] Figure 3a to Figure 3e The device structure is shown in the embodiment at different process stages during the single-sided chemical plating method of the present invention, wherein:

[0028] Figure 3a It is a schematic diagram of the structure of the wafer and the rigid support plate on which the Taiko ring has been formed;

[0029] Figure 3b A schematic diagram of a LTHC coating formed on one side of a rigid support plate;

[0030] Figure 3c It is a schematic diagram of a structure in which a photosensitive adhesive is coated on the end surface of a wafer Taiko ring;

[0031] Figure 3d It is a schematic diagram of the structure after the rigid support plate is bonded to the end face of the wafer Taiko ring;

[0032] Figure 3e Schematic diagram of the structure for separating the wafer from the rigid support plate after single-sided chemical plating. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0034] This embodiment first discloses a single-sided chemical plating method for a wafer, which is applicable to any wafer thinned by the Taiko thinning process that needs to be subjected to single-sided chemical plating. Figure 2 , Figure 3a to Figure 3e As shown, the wafer single-sided chemical plating method includes the following steps:

[0035] Step S100: providing a wafer with a Taiko ring formed on one side, and providing a rigid support plate;

[0036] Step S200: tightly connecting the end surface of the Taiko ring to the rigid support plate;

[0037] Step S300: performing chemical plating on the closely connected wafer and the rigid support plate;

[0038] Step S400: separating the wafer after chemical plating from the rigid support plate.

[0039] In the above method, the rigid support plate 200 is made of a rigid plate, which is tightly connected to the end face of the Taiko ring 2 of the wafer 100, so that the back of the wafer 100 is sealed and protected from being exposed, and chemical plating can be directly performed without film pasting. Compared with the existing single-sided chemical plating process, the film pasting and film peeling steps are omitted, and there will be no leakage problem. In addition, compared with the protective film 3 in the prior art, the rigid support plate 200 can reduce the warpage of the wafer 100 after thinning, so that the wafer 100 can maintain a flat surface during single-sided chemical plating, and the color difference problem within the plated layer can be eliminated.

[0040] The following combination Figure 3a to Figure 3e The single-sided chemical plating method is further described in detail with reference to the figures and specific embodiments.

[0041] In step S100, the wafer 100 on which the Taiko ring 2 has been formed is Figure 3a As shown, the interior enclosed by the Taiko ring 2 is the middle thinning portion 1, and the Taiko ring 2 needs to be removed after the single-sided chemical plating. Therefore, during the single-sided chemical plating process, the middle thinning portion 1 actually needs to be protected. In addition, a rigid support plate 200 needs to be prepared so that the middle thinning portion 1 can be covered by the rigid support plate 200 to protect the back side of the wafer 100.

[0042] In step S200, the end face of the Taiko ring 2 is tightly connected to the rigid support plate 200 by coating a temporary bonding adhesive on the connecting surfaces of the two. The temporary bonding adhesive is coated on one side surface of the rigid support plate 200, or the temporary bonding adhesive is coated on the end face of the Taiko ring 2, or the surface of the rigid support plate 200 and the end face of the Taiko ring 2 are each coated with a temporary bonding adhesive. If the last coating method is used, the temporary bonding adhesive on the rigid support plate 200 and the temporary bonding adhesive on the end face of the Taiko ring 2 may not be the same. The end face of the Taiko ring 2 described in the present invention refers to Figure 1 The upper surface of the Taiko ring 2 in the direction shown. After the rigid support plate 200 is bonded to the end surface of the Taiko ring 2 of the wafer 100, a curing process is required to ensure a firm connection.

[0043] As a further explanation of step S200, the selected temporary bonding adhesive can be of many types, but in order to avoid the temporary bonding adhesive coated on the wafer 100 being cured by heating and baking, the wafer 100 will be more prone to warpage and parameter deterioration in a high temperature environment. Therefore, the selected temporary bonding adhesive coated on the wafer 100 should be cured at room temperature, and the debonding method is relatively simple and does not require a high temperature step. Figure 3a to Figure 3e As shown, the content of the present invention is further described by a preferred embodiment:

[0044] Embodiment 1:

[0045] Step (1), prepare the wafer 100 on which the Taiko ring 2 has been formed, and prepare the rigid support plate 200; the rigid support plate 200 in this embodiment adopts a light-transmitting plate, which is convenient for curing and debonding the temporary bonding glue by light irradiation; the plate material that meets the requirements of light transmission and has a certain rigidity, such as a light-transmitting glass plate or a light-transmitting acrylic plate, can be used, and has a certain acid and alkali corrosion resistance.

[0046] Step (2), selection of temporary bonding adhesive: The temporary bonding adhesive selected in this embodiment includes photosensitive adhesive 5 and LTHC coating liquid. The photosensitive adhesive 5 can be cured by ultraviolet irradiation, while the LTHC coating liquid can be easily debonded by laser irradiation.

[0047] LTHC (Light-To-Heat-Conversion) coating liquid is a photothermal conversion coating liquid produced by 3M. It has a certain viscosity at room temperature, but the viscosity is not strong. After curing, the viscosity of the LTHC coating 4 is enhanced. By irradiating the LTHC coating 4 with a laser at room temperature, the rigid support plate 200 and the photosensitive adhesive 5 on the wafer 100 can be easily separated at room temperature without stress, thereby separating the rigid support plate 200 and the wafer 100 from each other. The main components of the LTHC coating liquid include 1-methoxy-2-propyl acetate, 2-butoxyethanol, carbon black, silicon dioxide, styrene and acrylic acid polymers.

[0048] The inventors have found that although the LTHC coating liquid has a certain viscosity at room temperature, the viscosity is relatively weak. If only the LTHC coating 4 exists between the wafer 100 and the rigid support plate 200, it is easy to separate during single-sided chemical plating. High-temperature curing will enhance the viscosity, but the thermal process will affect the wafer warpage and device parameters. Although the photosensitive adhesive 5 has strong viscosity, it is difficult to remove. If only the photosensitive adhesive 5 exists between the wafer 100 and the rigid support plate 200, it is difficult to debond. Therefore, this embodiment uses the two in combination.

[0049] Step (3), spin-coating a layer of LTHC coating liquid on one side of the rigid support plate 200, and then performing the first curing to form the LTHC coating 4; the purpose of the first curing is to form the LTHC coating 4 firmly adhered to the surface of the rigid support plate 200, and the wafer 100 is not involved at this time, so the first curing adopts a high-temperature heating curing method and will not cause any impact on the wafer 100. The temperature of the first curing in this embodiment is 220°C to 300°C, and the time of the first curing is 200s to 300s.

[0050] Step (4), coating the photosensitive adhesive 5 on the end surface of the Taiko ring 2 of the wafer 100.

[0051] It should be noted that the order of step (3) and step (4) can be swapped or performed simultaneously.

[0052] The LTHC coating liquid selected in this embodiment is only suitable for coating on the surface of the rigid support plate 200, but not suitable for coating on the end face of the Taiko ring 2, because the LTHC coating liquid is cured by high-temperature heating. If it is applied to the end face of the Taiko ring 2, the warping and parameters of the wafer 100 will be affected during high-temperature curing, and the LTHC coating 4 formed on the end face of the Taiko ring 2 is difficult to remove and usually requires cleaning with alkaline solution.

[0053] Step (5), the side of the rigid support plate 200 having the LTHC coating 4 after step (3) is opposite to the end face of the Taiko ring 2 after step (4), and the two are bonded together, and then a second curing is performed. The purpose of the second curing is mainly to increase the adhesion of the photosensitive adhesive 5, so the second curing in this embodiment is achieved by curing the photosensitive adhesive 5 by irradiating the rigid support plate 200 which is transparent to ultraviolet light.

[0054] Step (6), performing single-sided chemical plating on the wafer 100 that has completed step (5) together with the rigid support plate 200, wherein the chemical plating is performed according to the existing process.

[0055] Step (7), taking out the wafer 100 and the rigid support plate 200 that have completed step (6) and drying them, irradiating the LTHC coating 4 between the two through the light-transmitting rigid support plate 200 with a laser at room temperature, so that the LTHC coating 4 can be easily separated from the photosensitive adhesive 5, thereby separating the rigid support plate 200 and the wafer 100 from each other.

[0056] After completing the single-sided chemical plating according to the above method, the Taiko ring 2 is removed according to the conventional process. Since the subsequent process belongs to the existing conventional process, it will not be described in detail here.

[0057] Based on the single-sided chemical plating method for wafer given above, this embodiment also provides a semiconductor device manufacturing method including the single-sided chemical plating method for wafer, and provides a semiconductor device made by the semiconductor device manufacturing method. Specifically, the semiconductor device can be an IGBT, but is not limited to this type of device.

[0058] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A single-sided chemical plating method for a wafer, characterized in that: include: providing a wafer having a Taiko ring formed on one side; Providing a rigid support plate, wherein the rigid support plate is a light-transmitting plate; Coating a LTHC coating liquid on one side of the rigid support plate, and after coating the LTHC coating liquid on one side of the rigid support plate, performing a first curing to form an LTHC coating; coating a photosensitive adhesive on the end face of the Taiko ring, bonding a side of the rigid support plate with the LTHC coating to the photosensitive adhesive on the end face of the Taiko ring, and then performing a curing treatment to make the end face of the Taiko ring tightly connected to the rigid support plate; Performing chemical plating on the closely connected wafer and the rigid support plate; The wafer after the chemical plating process is separated from the rigid support plate by laser irradiation.

2. The wafer single-sided chemical plating method according to claim 1, characterized in that: After the rigid support plate is bonded to the end surface of the Taiko ring, a second curing is performed.

3. The wafer single-sided chemical plating method according to claim 1, characterized in that: The rigid support plate is a glass plate or an acrylic plate.

4. The wafer single-sided chemical plating method according to claim 2, characterized in that: The first curing is performed by heating, the temperature of the first curing is 220° C. to 300° C., and the time of the first curing is 200s to 300s.

5. The wafer single-sided chemical plating method according to claim 2, characterized in that: The second curing is performed by ultraviolet irradiation curing.

6. A method for manufacturing a semiconductor device, characterized in that: The invention comprises a wafer single-sided chemical plating method as described in any one of claims 1 to 5.

7. A semiconductor device, characterized in that: The semiconductor device is manufactured by the method for manufacturing a semiconductor device as claimed in claim 6.

8. The semiconductor device according to claim 7, wherein: The semiconductor device is an IGBT.

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