Bonding method and SOI substrate preparation method

Abstract

The present application provides a bonding method and an SOI substrate preparation method. The bonding method comprises the following steps: providing a first silicon substrate and a second silicon substrate; performing activation treatment on the surface of the first silicon substrate and / or the surface of the second silicon substrate, such that an -OH group can be adsorbed on the surface of the first silicon substrate and / or the surface of the second silicon substrate; pre-bonding the first silicon substrate and the second silicon substrate to form a combined substrate; and heating the pre-bonded combined substrate and maintaining for a predetermined time, and performing thermal insulation and dehydration on a bonding interface. In the present application, by means of activation and thermal insulation, the van der Waals force at an interface is converted into chemical bonding force, enhancing the strength of a bonding interface, and reducing the width of an unbonded region. The present invention is applied in the field of SOI substrate preparation, such that a better supporting environment can be provided for a stripping process.

Description

A bonding method and a method for preparing an SOI substrate

[0001] Related application citations

[0002] This application claims priority to Chinese patent application No. 202311629938.5, filed on November 30, 2023, entitled “A bonding method and a method for preparing an SOI substrate,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of semiconductor technology, and in particular to a bonding method and a method for preparing an SOI substrate. Background Art

[0004] Low-temperature pre-bonding technology already exists in the semiconductor industry. This involves directly peeling the bonded wafer from the hydrogen-implanted surface after high-temperature annealing to obtain an SOI substrate. However, this process leaves a wide, unbonded, overhanging area at the edge of the SOI substrate after peeling. Therefore, improving the bonding process and reducing the width of this unbonded area at the SOI edge is a challenge currently underway.

[0005] Summary of the Invention

[0006] The technical problem to be solved by the present application is to provide a bonding method and a method for preparing an SOI substrate, which can reduce the width of the unbonded area at the edge of the bonding process.

[0007] In order to solve the above problems, an embodiment of the present application provides a bonding method, comprising the following steps: providing a first silicon substrate and a second silicon substrate; activating the surface of the first silicon substrate and / or the second silicon substrate so that -OH groups are adsorbed on the surface; pre-bonding the first silicon substrate and the second silicon substrate to form a combined substrate; heating the pre-bonded combined substrate and maintaining it for a predetermined time to insulate and dehydrate the bonding interface.

[0008] Optionally, the pre-bonded assembled substrate is heated to 60-120°C.

[0009] Optionally, the predetermined time is 3-8 hours.

[0010] Optionally, surfaces of the first silicon substrate and the second silicon substrate are both activated.

[0011] Optionally, at least one surface of the first silicon substrate and the second silicon substrate has an oxide layer.

[0012] In order to solve the above problems, an embodiment of the present application also provides a method for preparing an SOI substrate, comprising the following steps: providing a first silicon substrate and a second silicon substrate; performing ion implantation on the first silicon substrate to form a device layer; forming an oxide layer on the surface of the first silicon substrate and / or the second silicon substrate; performing activation treatment on the surface of the first silicon substrate and / or the second silicon substrate so that -OH groups are adsorbed on its surface; pre-bonding the first silicon substrate and the second silicon substrate to form a combined substrate; heating the pre-bonded combined substrate and maintaining it for a predetermined time to insulate and dehydrate the bonding interface.

[0013] Optionally, the pre-bonded assembled substrate is heated to 60-120°C.

[0014] Optionally, the predetermined time is 3-8 hours.

[0015] Optionally, surfaces of the first silicon substrate and the second silicon substrate are both activated.

[0016] Optionally, an oxide layer is formed on the surfaces of both the first silicon substrate and the second silicon substrate.

[0017] This application uses activation and heat preservation to convert the van der Waals force at the interface into chemical bonding force, thereby enhancing the strength of the bonding interface and reducing the width of the unbonded area. Its application in the field of SOI substrate preparation can provide a better support environment for the stripping process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a schematic diagram showing the implementation steps of a specific embodiment of the bonding method described in this application.

[0019] FIG2 is a schematic diagram showing a specific embodiment of the bonding method described in this application.

[0020] FIG3 is a schematic diagram showing the implementation steps of a specific embodiment of the method for preparing an SOI substrate described in this application. DETAILED DESCRIPTION

[0021] The specific implementation of the bonding method and the SOI substrate preparation method provided in this application is described in detail below with reference to the accompanying drawings.

[0022] Figure 1 is a schematic diagram of the implementation steps of a specific embodiment of the bonding method described in the present application, including: step S10, providing a first silicon substrate and a second silicon substrate; step S11, activating the surface of the first silicon substrate and / or the second silicon substrate so that -OH groups are adsorbed on the surface; step S12, pre-bonding the first silicon substrate and the second silicon substrate to form a combined substrate; step S13, heating the pre-bonded combined substrate and maintaining it for a predetermined time to insulate and dehydrate the bonding interface.

[0023] Specifically, in step S11, the surface of the first silicon substrate and / or the second silicon substrate is activated to allow -OH groups to adsorb on the surface. In this step, the activation treatment may be performed on both the first silicon substrate and the second silicon substrate. Furthermore, at least one surface of the first silicon substrate and the second silicon substrate may have an oxide layer. Regardless of whether or not an oxide layer is present, the surface contains silicon atoms, and therefore does not affect the adsorption of -OH groups on the silicon on the surface.

[0024] In step S12, the first silicon substrate and the second silicon substrate are pre-bonded to form a combined substrate. The bonding environment must be very clean and free of particle and metal contamination, and the bonding wave has a certain propagation time.

[0025] In step S13, the pre-bonded composite substrate is heated and maintained for a predetermined time to dehydrate the bonding interface. This step can be performed by using a constant temperature and humidity incubator to dehydrate the bonded wafers (i.e., the pre-bonded composite substrate) at 60-120°C for 3-8 hours. The intermolecular forces (van der Waals forces) gradually form chemical forces (chemical bonds), enhancing the bonding strength. The surface reaction equation is as follows:

[0026] Si-OH+HO-Si=Si-O-Si+H2O

[0027] Figure 2 is a schematic diagram showing the principle of the above reaction at the interface.

[0028] At the edges of the bonded substrates, water can be evaporated by heating, thereby strengthening the bond strength at the edges and reducing the width of the unbonded area. Experiments have shown that this method can reduce the width of the unbonded area from 3mm to less than 1.5mm.

[0029] Figure 3 is a schematic diagram of the implementation steps of a specific embodiment of the method for preparing an SOI substrate described in the present application, which includes the following steps: step S20, providing a first silicon substrate and a second silicon substrate; step S21, ion implanting the first silicon substrate to form a device layer; step S22, forming an oxide layer on the surface of the first silicon substrate and / or the second silicon substrate; step S23, activating the surface of the first silicon substrate and / or the second silicon substrate so that -OH groups are adsorbed on its surface; step S24, pre-bonding the first silicon substrate and the second silicon substrate to form a combined substrate; step S25, heating the pre-bonded combined substrate and maintaining it for a predetermined time to insulate and dehydrate the bonding interface.

[0030] Specifically, the ion implantation in step S21 may be one or a combination of H and He to form a bubble layer, thereby defining a device layer.

[0031] In step S22, an oxide layer is formed on the surface of the first silicon substrate and / or the second silicon substrate. The oxide layer serves to provide a buried oxide layer for the SOI substrate, so the oxide layer can be formed on the surface of either the first silicon substrate or the second silicon substrate, or can be formed simultaneously.

[0032] In step S23, the surfaces of the first silicon substrate and / or the second silicon substrate are activated to allow -OH groups to adsorb on their surfaces. In this step, the activation treatment can be performed on both the first silicon substrate and the second silicon substrate. Regardless of whether the surfaces of the first silicon substrate and the second silicon substrate have an oxide layer, they still contain silicon atoms, and therefore, the adsorption of -OH groups on the silicon on their surfaces is not affected.

[0033] In step S25, the pre-bonded composite substrate is heated and maintained for a predetermined time to dehydrate the bonding interface. This step can be performed by using a constant temperature and humidity incubator to dehydrate the bonded wafers (i.e., the pre-bonded composite substrate) at 60-120°C for 3-8 hours. The intermolecular forces (van der Waals forces) gradually form chemical forces (chemical bonds), enhancing the bonding strength. The surface reaction equation is as follows:

[0034] Si-OH+HO-Si=Si-O-Si+H2O

[0035] Figure 2 is a schematic diagram showing the principle of the above reaction at the interface.

[0036] At the edge of the bonded substrate, water evaporates through heating, strengthening the bond strength and reducing the width of the unbonded area. This provides a more effective support environment for subsequent peeling of the substrate from the blister layer. Experiments have shown that this method can reduce the width of the unbonded area from 3mm to less than 1.5mm.

[0037] After the above steps are completed, an annealing and stripping step is required to strip the first silicon substrate from the blister layer to form an SOI substrate. Due to the implementation of the heat preservation step, the width of the unbonded area at the edge is reduced, so the stripping step can be carried out more smoothly.

[0038] The above is only a preferred embodiment of the present application. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A bonding method, wherein: The steps include: providing a first silicon substrate and a second silicon substrate; Activating the surface of the first silicon substrate and / or the second silicon substrate so that -OH groups can be adsorbed on the surface; pre-bonding the first silicon substrate and the second silicon substrate to form a combined substrate; The pre-bonded combined substrate is heated and maintained for a predetermined time to heat and dehydrate the bonding interface.

2. The method of claim 1, wherein: The pre-bonded combined substrate is heated to 60-120°C.

3. The method of claim 1, wherein: The predetermined time is 3-8 hours.

4. The method of claim 1, wherein: The surfaces of the first silicon substrate and the second silicon substrate are both activated.

5. The method of claim 1, wherein: At least one surface of the first silicon substrate and the second silicon substrate has an oxide layer.

6. A method for preparing an SOI substrate, wherein: The steps include: providing a first silicon substrate and a second silicon substrate; Performing ion implantation on the first silicon substrate to form a device layer; forming an oxide layer on a surface of the first silicon substrate and / or the second silicon substrate; Activating the surface of the first silicon substrate and / or the second silicon substrate so that -OH groups can be adsorbed on the surface; pre-bonding the first silicon substrate and the second silicon substrate to form a combined substrate; The pre-bonded combined substrate is heated and maintained for a predetermined time to heat and dehydrate the bonding interface.

7. The method of claim 6, wherein: The pre-bonded combined substrate is heated to 60-120°C.

8. The method of claim 6, wherein: The predetermined time is 3-8 hours.

9. The method of claim 6, wherein: The surfaces of the first silicon substrate and the second silicon substrate are both activated.

10. The method of claim 6, wherein: Oxide layers are formed on the surfaces of the first silicon substrate and the second silicon substrate.

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