Patent Application
20210118726
The present invention relates to the field of wafer technology, and more particularly, to a method for transferring a thin film.
In addition to traditional food heating, many novel applications of multimode microwave cavity bodies for material heating have been found, such as microwave-enhanced chemical reactions, ceramic sintering, and polymer curing for semiconductor packaging.
It is proposed to transfer a thin Si layer to a handle wafer by using a fixed frequency (2.45 MHz, 900 MHz or 2.45 GHz) or 2.45 MHz-900 MHz variable frequency microwaves (referring to U.S. Pat. No. 6,486,008 and China Patent ZL2003 10123080.1). However, due to uneven heating (see
Aiming at the deficiencies of the prior art, the present invention provides a method for transferring a thin film, and solves the problem of the poor transferring quality of the existing thin layer.
In order to solve the above object, the present invention is implemented with the following technical solution. A method for transferring a thin film comprises: providing a supply substrate; performing ion implantation process to form an ion layer at the defined depth in the supply substrate, the ion depth defining a thin layer in the supply substrate: a thin film, which is a defined portion of the supply substrate by implanted ions, and a remnant substrate, which is a remaining portion of the supply substrate without the thin film; performing a direct wafer bonding process to join a handle substrate onto the supply substrate, forming a bonded substrate pair; and separating the thin film from the remnant substrate by using variable frequency microwave irradiation, the thin film transferring from the supply substrate to the surface of the handle substrate.
Preferably, the method further comprises a pre-heat process performed after the formation of the ion separation layer and before the thin film separation from the supply substrate, wherein the pre-heat process is configured to polymerize the implanted ions and to generate crystal fractures; and the polymerized ions form bubbles within the supply substrate.
Preferably, the pre-heat process is performed by variable frequency microwave irradiation or thermal treatment.
Preferably, the ion implantation process is a standard ion implantation process, which is performed at a different temperature for each treatment step.
Preferably, the ions used in the ion implantation process comprise hydrogen ions, oxygen ions, nitrogen ions, fluorine ions, chloride ions, helium ions or neon ions.
Preferably, the ions used in the ion implantation process are ions or molecular ions.
Preferably, the wafer bonding process is a direct bonding process, which is performed at a low temperature, in a vacuum or on a bonding surface enhanced by plasma treatment.
Preferably, the microwave irradiation is applied by a variable frequency microwave generating device, and the variable frequency microwave generating device increases the kinetic energy of the implanted ions, the molecular ions or reactants generated by the reactions between the ions and the substrates in a bonded structure.
Preferably, the variable frequency microwave irradiation is capable of being combined with direct thermal heating of the bonded structure, wherein the temperature in the direct heating is at most 450° C.
Preferably, the kinetic energy of the implanted ions, the molecular ions or the reactants generated by the reaction between the ions and the substrate in the bonded structure is increased by direct excitation but not by thermally heating the bonded structure.
Preferably, the variable frequency microwave generating device is configured to generate a high frequency alternating electromagnetic field, and variable frequency microwaves are generated by frequency sweeping between 2 GHz and 24 GHz.
Preferably, the variable frequency microwave generating device generates a high frequency alternating electromagnetic field, and the variable frequency microwaves are generated by frequency sweeping between 4 GHz and 12 GHz.
Preferably, the variable frequency microwave generating device is configured to generate a high frequency alternating electromagnetic field, and the variable frequency microwaves are generated by frequency sweeping between 5 GHz and 7 GHz.
Preferably, the variable frequency microwave generating device is configured to generate a high frequency alternating electromagnetic field, and the variable frequency microwaves are generated by frequency sweeping between 5.85 GHz and 6.65 GHz.
Preferably, the variable frequency microwaves are generated by frequency sweeping at 0.1 sec cycle time between each frequency.
Preferably, the bonded structure is exposed to microwave irradiation for more than 1 minute.
The present invention provides a method for transferring a thin film, and has the following beneficial effects. The method for transferring the thin film can improve wafer bonding, a larger wafer is transferred to the handle wafer with a uniform thin layer thickness and a larger surface roughness, and the bonded wafer can be treated from 100° C. to 450° C. to achieve different service lives. By the lower power with the maximum value of 1 kW, in an initial step, the bonding strength can be improved, and the problem of relatively poor thin film transferring effect in the prior art is solved.
The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only part but not all of the embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative efforts based on the embodiments in the present invention are within the protection scope of the present invention.
Referring to
A person skilled in the art uses wires to connect all electrical components in the solution to a power supply adapted to the all electrical components; and an appropriate controller is selected according to an actual situation to meet control requirements. The specific connecting and control sequence may refer to the following working principle, in which the respective electrical components are electrically connected in sequence based on a work order of the electrical components. The detailed connection means of the electrical components is well known in the art. The following mainly introduces the working principle and the process, and does not describe the electrical control any more.
Embodiments: in the present invention, the new variable frequency microwaves (VFM) of 2 GHz-18 GHz are used to improve wafer bonding. For larger wafers (with diameters>200 mm), the thin layer is transferred to the handle wafer with a uniform thin layer thickness and a larger surface roughness.
1) The supply substrate 101 has an implantation layer 103, and the implanted ions may be hydrogen ions and/or helium ions. Optionally, the supply substrate 101 is covered with a dielectric layer 102, which may be an oxide, nitride or oxynitride layer. The supply substrate 101 may be a semiconductor of Si, Ge, SiC, SiGe, III-V or II-VI, etc. The handle substrate 201 may be a semiconductor, glass, Al2O3, AlN, BeO or even ceramic.
Optionally, the substrate 201 is covered with a dielectric layer 202, which may be an oxide, nitride or oxynitride layer.
2) The substrates 101 and 201 are joined by direct bonding at room temperature. The wafer can be cleaned with a wet chemical (for example, RCA1, RCA2, and/or a dilute HF solution) before bonding. The wafer surface can further be activated by O2, N2, Ar or NH3 plasma to promote direct bonding.
3) Optionally, the bonding pair 101/201 may be subjected to thermal treatment at the temperatures from 100° C. up to 450° C. for various periods of time.
4) The bonding pair 101/201 is then treated by VFM irradiation. The VFM can sweep in the frequency band from 2 GHz to 18 GHz with the maximum power of 2 kW.
The VFM treatment may be a single treatment condition or multiple steps. In the last embodiment, the initial step is of a relatively low power up to 1 kW, so as to increase the bonding strength. The single step or the subsequent multiple steps is to activate the implanted H or He ions to form a thin layer of gas molecules and split the thin layer 110 from the substrate 101 onto the substrate 201.
It is to be understood that the term “includes”, “containing” or any other variants thereof is intended to cover non-exclusive including, such that the process, method, article, or device including a plurality of elements includes not only those elements but also other elements that are not explicitly listed, or also includes the elements that are inherent to such a process, method, item, or device. Without more limitations, the element defined by the phrase “including a . . . ” does not exclude the presence of additional equivalent elements in the process, method, item, or device that includes the element.
The foregoing is only the preferred embodiments of the present disclosure, and is not intended to limit the present disclosure. Various changes and modifications may be made to the present disclosure for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present disclosure should be included within the scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201910986159.8 | Oct 2019 | CN | national |
