Method for manufacturing silicon carbide wafer

Abstract

A method for manufacturing a silicon carbide wafer includes the following steps. A silicon carbide epitaxial layer is formed on the first silicon carbide substrate. And forming a weakening layer in the silicon carbide epitaxial layer by using an ion implantation process. A cavity weakening bond is created in the weakening layer using a laser lift-off process. And the cavity of the weakening layer is damaged to weaken the bonding, so that the silicon carbide epitaxial layer is divided into an upper silicon carbide epitaxial layer and a lower silicon carbide epitaxial layer. The laser lift-off technology of the process has the advantages of high processing efficiency and low material loss, and can replace a diamond wire cutting technology.

Description

Technical Field

[0001] The present invention relates to a semiconductor manufacturing method, in particular to a method for manufacturing a silicon carbide wafer. Background Art

[0002] Silicon carbide wafers are a substrate used in semiconductor manufacturing. This material possesses a range of advantageous properties, making it an ideal choice for high-temperature, high-voltage, and high-frequency applications. The silicon carbide wafer manufacturing process involves growing a single crystal of silicon carbide to a specific size and thickness, then forming it into disc-shaped chips for use in semiconductor devices.

[0003] One of the main advantages of silicon carbide is its high thermal stability. Its ability to maintain stability under extreme temperature conditions makes it an excellent choice for high-temperature applications. Furthermore, silicon carbide has a high electron mobility, meaning that electrons move more quickly within the crystal, thus improving overall device performance.

[0004] Silicon carbide wafers also excel in high-power and high-frequency applications. Their superior electrical conductivity and heat dissipation properties make them ideal for manufacturing power electronics, such as high-power converters and transmission lines. Furthermore, silicon carbide exhibits excellent performance in radio frequency (RF) applications, making it a top choice for manufacturing high-frequency wireless communication devices.

[0005] The mainstream processes for cutting the epitaxial layer of silicon carbide wafers include multi-wire cutting using diamond and mortar. These cutting methods all have problems such as high material loss rate, severe wear of the cutting wire and chip warping. Summary of the Invention

[0006] The present invention provides a method for manufacturing a silicon carbide wafer to solve the problems of the prior art.

[0007] According to some embodiments of the present invention, a method for manufacturing a silicon carbide wafer includes: forming a silicon carbide epitaxial layer on a first silicon carbide substrate; forming a weakened layer in the silicon carbide epitaxial layer using an ion implantation process; generating cavity-weakened bonds in the weakened layer using a laser lift-off process; and destroying the cavity-weakened bonds in the weakened layer to separate the silicon carbide epitaxial layer into an upper silicon carbide epitaxial layer and a lower silicon carbide epitaxial layer, wherein the lower silicon carbide epitaxial layer is located on the first silicon carbide substrate.

[0008] According to some embodiments of the present invention, ions used in the ion implantation process include argon ions, hydrogen ions, helium ions, or a combination thereof.

[0009] According to some embodiments of the present invention, the method of destroying the cavity-weakened bond of the weakened layer comprises high temperature heating.

[0010] According to some embodiments of the present invention, the method of destroying the cavity-weakening bond of the weakening layer includes ultrasonic vibration.

[0011] According to some embodiments of the present invention, an extension direction of the weakened layer is perpendicular to a central axis of the first silicon carbide substrate.

[0012] According to some embodiments of the present invention, the manufacturing method further comprises: before the laser lift-off process is performed, bonding the upper silicon carbide epitaxial layer using a temporary substrate.

[0013] According to some embodiments of the present invention, the manufacturing method further includes: bonding a second silicon carbide substrate on the upper silicon carbide epitaxial layer bonded to the temporary substrate, wherein the temporary substrate and the second silicon carbide substrate are respectively located on two opposite surfaces of the upper silicon carbide epitaxial layer.

[0014] According to some embodiments of the present invention, the manufacturing method further includes: removing the temporary substrate, so that the upper silicon carbide epitaxial layer is located on the second silicon carbide substrate.

[0015] According to some embodiments of the present invention, the manufacturing method further includes: performing a chemical mechanical polishing process on the upper silicon carbide epitaxial layer on the second silicon carbide substrate.

[0016] According to some embodiments of the present invention, the manufacturing method further includes: performing a chemical mechanical polishing process on the lower silicon carbide epitaxial layer on the first silicon carbide substrate.

[0017] In summary, the present invention's method for manufacturing silicon carbide wafers utilizes epitaxial growth technology to grow a thicker, high-quality silicon carbide epitaxial layer. Using wafer separation technology, a high-dose Ar / H+ / He+ ion implant is used to form a weakened layer in the silicon carbide wafer. The silicon carbide epitaxial layer is bonded to a temporary substrate. Laser lift-off technology is used to create a cavity in the weakened layer to weaken the bond. Through heating or ultrasonic vibration, the weakened layer is separated into two silicon carbide wafers. The silicon carbide epitaxial layer on the temporary substrate is transferred to a permanent silicon carbide substrate. Chemical mechanical polishing (CMP) is used to remove the damaged layer and restore the epitaxial layer surface to a flat state, resulting in two high-quality silicon carbide wafers. The laser lift-off technology of this process offers the advantages of high processing efficiency and low material loss, and can replace diamond wire sawing technology.

[0018] The above description will be described in detail below with reference to implementation examples, and a further explanation of the technical solution of the present invention will be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To make the above and other objects, features, advantages and embodiments of the present invention more apparent, the accompanying drawings are described as follows:

[0020] Figure 1A 、 Figure 1BA cross-sectional view illustrating steps of a method for manufacturing a silicon carbide wafer according to an embodiment of the present invention; and

[0021] Figure 2 FIG1 is a flow chart illustrating a method for manufacturing a silicon carbide wafer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] For a more detailed and complete description of the present invention, reference is made to the accompanying drawings and various embodiments described below. Like numbers in the drawings represent like or similar elements. Well-known elements and steps are not described in the embodiments to avoid unnecessary limitations on the present invention. In the embodiments and claims, unless the context specifically dictates otherwise, the words "a," "an," and "the" may refer to either a single item or the plurality of items.

[0023] Please also refer to Figure 1A 、 Figure 1B and Figure 2 , Figure 1A 、 Figure 1B 1 is a cross-sectional view illustrating steps of a method 100 for manufacturing a silicon carbide wafer according to an embodiment of the present invention. Figure 2 The flowchart of a method 200 for manufacturing a silicon carbide wafer according to one embodiment of the present invention is shown. To address the issues of high material loss, severe wire wear, and chip warpage during multi-wire sawing of silicon carbide wafers using diamond or sandblasting, the present invention proposes a non-mechanical sawing method.

[0024] exist Figure 1A Step 110 and Figure 2 In step 210, a silicon carbide epitaxial layer 103 is formed on the first silicon carbide substrate 101. A silicon carbide wafer is a semiconductor wafer made of silicon carbide and is typically used to manufacture components for high-power, high-frequency applications, such as power amplifiers and radio frequency components. The silicon carbide epitaxial layer is formed using techniques such as chemical vapor deposition (CVD) or physical vapor deposition (PVD).

[0025] Chemical vapor deposition (CVD) is a common method for producing silicon carbide wafers. This method includes the following steps:

[0026] Pretreatment: Clean the wafer surface to ensure it is free of dust and impurities.

[0027] Introducing precursor gas: In a high vacuum or nitrogen environment, a silicon carbide precursor gas (such as monosilane, dimethylsilyl ether) is introduced into the reaction chamber.

[0028] Deposition of silicon carbide film: The precursor gas decomposes and deposits on the wafer surface, forming a silicon carbide film. This step is usually performed at high temperature to promote the reaction.

[0029] Epitaxial growth: Repeated introduction of precursor gases and thin film deposition gradually form a silicon carbide epitaxial layer. Reaction conditions, such as temperature and gas flow, are controlled to ensure uniformity and thickness of the epitaxial layer.

[0030] Physical vapor deposition can also be used to prepare silicon carbide films, in which a solid source material or target is used, and the source material is excited to form a vapor phase, which is then deposited on the wafer surface.

[0031] The fabrication of SiC wafers involves prior processing of the wafer and then depositing a SiC thin film using techniques such as CVD or PVD, ultimately forming a SiC epitaxial layer.

[0032] exist Figure 1A Step 112 and Figure 2 In step 212, a weakened layer 105 is formed in the silicon carbide epitaxial layer 103 using an ion implantation process. In some embodiments of the present invention, the weakened layer 105 extends perpendicular to the central axis 101a of the first silicon carbide substrate 101 (e.g., the central axis of a disc-shaped silicon carbide substrate). In some embodiments of the present invention, the ion implantation dose ranges from 1E15 to 5E17 [atom / cm2]. Forming a weakened layer in a silicon carbide epitaxial layer using an ion implantation process is a technique for modifying material properties, typically using argon ions, hydrogen ions, helium ions, or a combination thereof. The following is an example process.

[0033] Prepare the SiC epitaxial layer: Ensure that the SiC epitaxial layer has been grown on the wafer and is of the required thickness and quality.

[0034] Select ion species: Select appropriate ion species based on the characteristics of the weakened layer to be formed.

[0035] Energy and dose control: Adjust the energy and dose of ion implantation. Energy control affects the penetration depth of ions, while dose affects the density of implanted ions. Adjusting these parameters will affect the depth and properties of the weakened layer formed.

[0036] Ion implantation process: Under specific vacuum conditions, selected ions are implanted into the silicon carbide epitaxial layer. This introduces stress into the material, forming weakened areas.

[0037] Heat treatment: After ion implantation, heat treatment is performed to repair the crystal lattice and stabilize the weakened areas. This helps ensure the stability of the weakened layer in subsequent processes.

[0038] exist Figure 1A Step 114 and Figure 2 In step 214, a temporary substrate 106 is bonded to the silicon carbide epitaxial layer 103. This step facilitates the subsequent transfer of the divided half of the silicon carbide epitaxial layer 103 to another silicon carbide substrate when the silicon carbide epitaxial layer 103 is subsequently divided.

[0039] exist Figure 1A Step 116 and Figure 2 In step 216, a laser lift-off process is used to create a cavity-weakened bond 107 in the weakened layer 105. This step combines the laser lift-off process with the weakened layer to create a cavity-weakened bond. The following is an example of the steps. In some embodiments of the present invention, the structure includes a silicon carbide weakened layer and a cavity created by laser injection into the weakened layer. The laser injection location can include below, within, or above the weakened layer 105 to create a cavity-weakened bond.

[0040] After forming a weakened layer in the silicon carbide epitaxial layer through techniques such as ion implantation, a laser lift-off process is performed. This involves irradiating the surface of the wafer, specifically the area of ​​the weakened layer, with a high-energy, short-pulse laser beam.

[0041] The selected laser should create a localized absorption layer in the material of the weakened layer. This causes the local area to heat up, and due to the absorption properties of the material, the weakened area absorbs more energy than other areas. The increased temperature in the weakened area leads to the generation of gases, forming cavities. At the same time, the weakening of the weakened bond makes the material easier to peel off. Through the action of the laser, the material in the weakened area is peeled off, forming a cavity-weakened bond. This allows specific areas on the wafer to be separated without damaging other areas. Laser peeling can achieve high precision in the process and reduce mechanical stress, thereby improving the performance and reliability of the component.

[0042] exist Figure 1A Step 118 and Figure 2 In step 218, the cavity weakening bond 107 of the weakening layer is destroyed, thereby dividing the SiC epitaxial layer 103 into an upper SiC epitaxial layer 103b and a lower SiC epitaxial layer 103a. The cavity weakening bond 107 of the weakening layer can be destroyed in the following ways.

[0043] Mechanical stress or force: Using mechanical stress or force methods, such as mechanical peeling or mechanical impact, to apply force to the SiC epitaxial layer. This helps to break the cavity and weaken the bond, causing it to separate into upper and lower layers.

[0044] Heat treatment: Apply appropriate heat treatment to promote the expansion of the cavity or the expansion of the material. This helps to further weaken the cavity and weaken the bond, making it easier to separate.

[0045] Chemical treatment: Chemical treatments, such as specific solutions or gases, are used to erode or decompose cavities and weaken bonds. This can introduce cracks into the material, allowing for separation.

[0046] Combining multiple methods can improve the segmentation effect. For example, mechanical stress can be used to weaken the bonds, followed by heat treatment or light exposure to further segment.

[0047] Ensuring these steps are performed meticulously requires precise and controlled separation of the silicon carbide epitaxial layer, a technique often used in the manufacture of microelectromechanical systems (MEMS) and other components.

[0048] In some embodiments of the present invention, the method of destroying the cavity-weakening bond 107 of the weakened layer includes high-temperature heating. In other embodiments of the present invention, the method of destroying the cavity-weakening bond 107 of the weakened layer includes ultrasonic vibration.

[0049] exist Figure 1A Step 120 and Figure 2 In step 220, a second silicon carbide substrate 109 is bonded onto the upper silicon carbide epitaxial layer 103b bonded to the temporary substrate 106. In some embodiments of the present invention, the second silicon carbide substrate 109 and the first silicon carbide substrate 101 are made of the same material.

[0050] exist Figure 1B Step 122 and Figure 2 In step 222, the temporary substrate 106 is removed so that the upper silicon carbide epitaxial layer 103b is located on the second silicon carbide substrate 109. The temporary substrate 106 may be removed in the following manner, for example.

[0051] Chemical wet etching uses specific chemical solutions that selectively attack the temporary substrate without damaging the upper SiC epitaxial layer. For example, wet etching can selectively etch silicon or other substrate materials. This requires careful selection of chemical solutions to ensure that only the temporary substrate is removed without affecting the upper SiC layer.

[0052] Mechanical peeling: Using mechanical force to separate the temporary substrate. This may involve applying mechanical shock or stress to peel the substrate. This requires careful control of the direction and magnitude of the force to avoid damaging the SiC epitaxial layer.

[0053] Thermal treatment: By treating the temporary substrate with high temperature, the substrate material will have specific thermal expansion characteristics, thus facilitating separation. This method is usually combined with chemical wet etching to enhance the effect.

[0054] Laser lift-off: This method uses a laser beam to focus on a temporary substrate, generating heat in the light-absorbing areas that facilitate lift-off. This process also requires careful control of energy and timing.

[0055] Ion implantation: Similar to the process of forming a weakened layer, the ion implantation process changes the properties of the temporary substrate material, making it easier to peel off.

[0056] When performing these methods, special attention needs to be paid to selecting appropriate parameters to ensure effective and controlled removal of the temporary substrate while protecting the integrity of the upper SiC epitaxial layer.

[0057] exist Figure 1B Step 124 and Figure 2 In steps 224 and 226, a chemical mechanical polishing process is performed on the lower silicon carbide epitaxial layer 103a on the first silicon carbide substrate 101, and a chemical mechanical polishing process is performed on the upper silicon carbide epitaxial layer 103b on the second silicon carbide substrate 109. Steps 224 and 226 can be performed simultaneously or separately. The chemical mechanical polishing process removes damaged layers from the lower silicon carbide epitaxial layer 103a and the upper silicon carbide epitaxial layer 103b, restoring the surface of the epitaxial layers to a smooth state, thereby obtaining two silicon carbide wafers.

[0058] In summary, the present invention's method for manufacturing silicon carbide wafers utilizes epitaxial growth technology to grow a thick, high-quality silicon carbide epitaxial layer. Using wafer separation technology, high-dose Ar / H+ / He+ ion implantation is used to form a weakened layer in the silicon carbide wafer. The silicon carbide epitaxial layer is bonded to a temporary substrate. Laser lift-off technology is used to create cavities in the weakened layer to weaken the bond. The weakened layer is separated into two silicon carbide wafers through heating or ultrasonic vibration. The silicon carbide epitaxial layer on the temporary substrate is transferred to a permanent silicon carbide substrate. Chemical mechanical polishing (CMP) is used to remove the damaged layer and restore the epitaxial layer surface to a flat state, resulting in two high-quality silicon carbide wafers. This process not only reduces material loss, but also eliminates the need for cutting wires and eliminates the need to address chip warpage.

[0059] Although the present invention has been disclosed above in terms of embodiments, this is not intended to limit the present invention. Any person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0060]

Explanation of symbols

[0061] 100: Manufacturing method

[0062] 101: first silicon carbide substrate

[0063] 101a: Central axis

[0064] 103: Silicon carbide epitaxial layer

[0065] 103a: Lower silicon carbide epitaxial layer

[0066] 103b: Upper silicon carbide epitaxial layer

[0067] 105: Weakened layer

[0068] 106: Temporary substrate

[0069] 107: Cavity weakens bond

[0070] 109: Second silicon carbide substrate

[0071] 110: Steps

[0072] 112: Steps

[0073] 114: Steps

[0074] 116: Steps

[0075] 118: Steps

[0076] 120: Steps

[0077] 122: Steps

[0078] 124: Steps

[0079] 200: Manufacturing method

[0080] 210: Steps

[0081] 212: Steps

[0082] 214: Steps

[0083] 216: Steps

[0084] 218: Steps

[0085] 220: Steps

[0086] 222: Steps

[0087] 224: Steps

[0088] 226: Steps.

Claims

1. A method for manufacturing a silicon carbide wafer, characterized in that: Include: forming a silicon carbide epitaxial layer on a first silicon carbide substrate; forming a weakened layer in the silicon carbide epitaxial layer using an ion implantation process; creating cavity-weakened bonds in the weakened layer using a laser lift-off process; as well as The cavity of the weakened layer is destroyed to weaken the bonding, so that the silicon carbide epitaxial layer is divided into an upper silicon carbide epitaxial layer and a lower silicon carbide epitaxial layer, wherein the lower silicon carbide epitaxial layer is located on the first silicon carbide substrate.

2. The method for manufacturing a silicon carbide wafer according to claim 1, wherein: Ions used in the ion implantation process include argon ions, hydrogen ions, helium ions, or a combination thereof.

3. The method for manufacturing a silicon carbide wafer according to claim 1, wherein: Methods for destroying the cavity-weakened bonds of the weakened layer include high temperature heating.

4. The method for manufacturing a silicon carbide wafer according to claim 1, wherein: The method of destroying the cavity weakening bond of the weakening layer includes ultrasonic vibration.

5. The method for manufacturing a silicon carbide wafer according to claim 1, wherein: An extending direction of the weakened layer is perpendicular to a central axis of the first silicon carbide substrate.

6. The method for manufacturing a silicon carbide wafer according to claim 1, wherein: The method further comprises: using a temporary substrate to bond the upper silicon carbide epitaxial layer before the laser lift-off process is performed.

7. The method for manufacturing a silicon carbide wafer according to claim 6, wherein: The method further comprises bonding a second silicon carbide substrate on the upper silicon carbide epitaxial layer bonded to the temporary substrate, wherein the temporary substrate and the second silicon carbide substrate are respectively located on two opposite surfaces of the upper silicon carbide epitaxial layer.

8. The method for manufacturing a silicon carbide wafer according to claim 7, wherein: The method further comprises: removing the temporary substrate so that the upper silicon carbide epitaxial layer is located on the second silicon carbide substrate.

9. The method for manufacturing a silicon carbide wafer according to claim 8, wherein: The method further comprises: performing a chemical mechanical polishing process on the upper silicon carbide epitaxial layer on the second silicon carbide substrate.

10. The method for manufacturing a silicon carbide wafer according to claim 1, wherein: The method further comprises: performing a chemical mechanical polishing process on the lower silicon carbide epitaxial layer on the first silicon carbide substrate.

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