Method for forming SOI (Silicon On Insulator) silicon wafer mixed substrate
By depositing SiOCN protective layer on the SOI silicon wafer, the problem of bulging at the boundary of the SOI region and the silicon substrate region is solved, and the effect of improving product yield and process uniformity is achieved.
Patent Information
- Application Number
- CN202410014314.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-04
- Publication Date
- 2025-07-04
AI Technical Summary
In the existing SOI silicon wafer hybrid substrate formation method, bulges are easily generated at the boundary of the SOI region and the silicon substrate region, which affects product yield.
SiOCN protective layer was deposited on the SOI silicon wafer, the silicon substrate region was flush with the SOI region by dry etching and epitaxial silicon growth, and SiOCN was removed in subsequent processes to prevent the generation of bulging at the boundary of the SOI region and the silicon substrate region.
The generation of bulges at the boundary of the SOI region and the silicon substrate region is effectively prevented, the product yield is improved, and the uniformity and reliability of the process are improved through the high conformal deposition of SiOCN.
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Figure CN120261391A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to semiconductor manufacturing technology, and particularly to a method for forming a hybrid substrate of an SOI (Silicon-On-Insulator) silicon wafer. Background Art
[0002] For the SOI (Silicon-On-Insulator) process, it is necessary to remove the BOX (buried oxide) and SOI in some regions to form a silicon substrate region, which is used as a well pickup region to apply a voltage to the well region and form structures such as diodes.
[0003] When the FDSOI (Fully Depleted SOI) adopts the Gate last process, it is necessary to make the silicon substrate region flush with the SOI region to ensure that subsequent CMP (Chemical Mechanical Polishing) can be carried out normally.
[0004] The process flow of the existing method for forming a hybrid substrate of an SOI silicon wafer is as follows:
[0005] (1) Deposit a layer of silicon oxide 4 on the SOI silicon wafer, and then deposit a layer of silicon nitride 5;
[0006] (2) Perform a lithography process to open the region where the silicon substrate needs to be formed;
[0007] (3) Dry-etch to remove the silicon nitride 5, silicon oxide 4, SOI (Silicon-On-Insulator) 3, and BOX (buried oxide) 2 in the silicon substrate region;
[0008] (4) Remove the photoresist;
[0009] (5) Wet-clean to remove possible by-products generated by dry-etching, and then grow epitaxial silicon 9 to make the silicon substrate region grow to be flush with the SOI region;
[0010] (6) Wet-clean to remove the silicon nitride 5 and silicon oxide 4 in sequence. When forming the active region through an etching process subsequently, the boundary between the SOI region and the silicon substrate region will be etched to form STI (Shallow Trench Isolation).
[0011] However, since the side of the SOI is exposed during the growth of epitaxial silicon 9, silicon will also grow epitaxially. After contacting and connecting with the silicon grown at the bottom, a relatively high bulge 6 will finally be formed at the boundary between the SOI and the silicon substrate, as shown in Figure 1As shown, after removing the silicon nitride 5 and silicon oxide 4, partial silicon peeling may occur, and moreover, during subsequent active area lithography (AA photo), the thickness of the Bottom Anti Reflection Coating (BARC) will be uneven, and excessive thickness in some areas will lead to Block etch. Summary of the Invention
[0012] The technical problem to be solved by the present invention is to provide a method for forming a hybrid substrate of an SOI silicon wafer, which can prevent the generation of bulges at the boundary between the SOI region and the silicon substrate region and improve the product yield.
[0013] To solve the above technical problem, a method for forming a hybrid substrate of an SOI silicon wafer provided by the present invention includes the following steps:
[0014] S1. Deposit a layer of masking silicon oxide 4 on the SOI silicon wafer, and then deposit a layer of masking silicon nitride 5.
[0015] S2. Perform a lithography process to open the silicon substrate region where the silicon substrate needs to be formed.
[0016] S3. Dry-etch to remove the masking silicon nitride 5, masking silicon oxide 4, SOI (Silicon on Insulator) 3, and BOX (Buried Oxide) 2 above the substrate silicon 1 in the silicon substrate region.
[0017] S4. Remove the photoresist.
[0018] S5. Deposit a layer of SiOCN 7.
[0019] S6. Dry-etch. Utilizing the directionality of dry-etching, remove the SiOCN 7 on the SOI region and the silicon substrate region. The sides of the masking silicon oxide 4, SOI (Silicon on Insulator) 3, and BOX (Buried Oxide) 2 are integrally covered with SiOCN, and the lower part of the side of the masking silicon nitride 5 is covered with SiOCN.
[0020] S7. Perform epitaxial silicon 9 growth to grow the upper surface of the substrate silicon 1 in the silicon substrate region to be flush with the upper surface of the SOI (Silicon on Insulator) 3 in the SOI region.
[0021] S8. Wet-etch to remove the silicon nitride and silicon oxide in the SOI region.
[0022] S9. When forming the active area through an etching process subsequently, etch and remove the SiOCN deposited at the boundary between the SOI region and the silicon substrate region, thereby forming STI (Shallow Trench Isolation).
[0023] Preferably, after S6, wet-etch to remove the by-products generated during the dry-etching process in step S6, and then perform step S7.
[0024] Preferably, a pickling agent with a first concentration is used for wet cleaning to remove the by-products generated in the dry etching process of step S6;
[0025] The pickling agent is phosphoric acid or hydrofluoric acid.
[0026] Preferably, in step S8, a pickling agent with a second concentration is used for wet cleaning to remove silicon nitride and silicon oxide in the SOI region, and the second concentration is higher than the first concentration.
[0027] Preferably, in step S5, the thickness of the deposited SiOCN 7 is 5-10 nm.
[0028] Preferably, in step S1, the thickness of the masking silicon oxide 4 is 3-10 nm, and the thickness of the masking silicon nitride 5 is 10-30 nm.
[0029] Preferably, in step S1, the thickness of the masking silicon oxide 4 is The thickness of the masking silicon nitride 5 is
[0030] In step S5, the thickness of the deposited SiOCN 7 is
[0031] The method for forming the SOI (silicon-on-insulator) silicon wafer hybrid substrate of the present invention removes the buried oxide layer and silicon-on-insulator in a partial area, protects the sidewall of the silicon-on-insulator by depositing a layer of SiOCN on the SOI sidewall, and then performs epitaxial silicon growth to make the silicon substrate area grow to be flush with the silicon-on-insulator area. The SiOCN on the SOI sidewall acts as a protective layer to prevent the growth of epitaxial silicon on the SOI sidewall, thereby preventing the generation of bulges at the boundary between the SOI area and the silicon substrate area and improving the product yield. Moreover, the SiOCN (silicon oxycarbide nitride) film can be deposited with high conformality, and the SiOCN deposited on the SOI sidewall has good uniformity (better uniformity than the silicon oxide formed on the SOI sidewall by RTO), and there will be no situation where Si epitaxially grows from the SOI during the subsequent epitaxial silicon 9 growth, which is beneficial to further improving the product yield. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.
[0033] Figure 1 It is a schematic structural diagram after epitaxial silicon growth of the existing method for forming an SOI silicon wafer hybrid substrate;
[0034] Figure 2Schematic diagram of the structure for depositing masking silicon oxide and masking silicon nitride on an SOI wafer;
[0035] Figure 3 Schematic diagram of the structure after dry etching to remove masking silicon nitride, masking silicon oxide, SOI, and BOX in the silicon substrate region;
[0036] Figure 4 Schematic diagram of the structure after depositing a layer of SiOCN in one embodiment of the method for forming the hybrid substrate of the SOI wafer of the present invention;
[0037] Figure 5 Schematic diagram of the structure after dry etching to remove SiOCN on the SOI region and the silicon substrate region in one embodiment of the method for forming the hybrid substrate of the SOI wafer of the present invention;
[0038] Figure 6 Schematic diagram of the structure when epitaxial silicon growth in the silicon substrate region of one embodiment of the method for forming the hybrid substrate of the SOI wafer of the present invention reaches the same level as the upper surface of the silicon in the SOI region;
[0039] Figure 7 Schematic diagram of the structure after wet cleaning to remove silicon nitride and silicon oxide in the SOI region in one embodiment of the method for forming the hybrid substrate of the SOI wafer of the present invention;
[0040] Figure 8 Schematic diagram of the structure for forming an active region by an etching process and etching to remove SiOCN at the boundary between the SOI region and the silicon substrate region to form STI in one embodiment of the method for forming the hybrid substrate of the SOI wafer of the present invention.
[0041] Explanation of the reference numerals in the figure
[0042] 1 - Substrate silicon, 2 - BOX (buried oxide), 3 - SOI (silicon on insulator), 4 - Masking silicon oxide, 5 - Masking silicon nitride, 6 - Bulge formed by epitaxial silicon growth, 7 - SiOCN, 9 - Epitaxial silicon. Detailed implementation manners
[0043] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.
[0044] The "first", "second" and similar terms used in this application do not denote any order, quantity or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items. Terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper", "lower", "left" and "right" are only used to indicate relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.
[0045] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.
[0046] Embodiment 1
[0047] A method for forming a hybrid substrate of an SOI (silicon-on-insulator) silicon wafer, comprising the following steps:
[0048] S1. Deposit a layer of masking silicon oxide 4 on the SOI silicon wafer, and then deposit a layer of masking silicon nitride 5, as Figure 2 shown;
[0049] S2. Perform a photolithography process to open the silicon substrate area where the silicon substrate needs to be formed;
[0050] S3. Dry-etch to remove the masking silicon nitride 5, masking silicon oxide 4, SOI (silicon-on-insulator) 3 and BOX (buried silicon oxide) 2 above the substrate silicon 1 in the silicon substrate area;
[0051] S4. Remove the photoresist, as Figure 3 shown;
[0052] S5. Deposit a layer of SiOCN 7, as Figure 4 shown;
[0053] S6. Dry-etch, using the directionality of dry-etching, to remove the SiOCN 7 on the SOI area and the silicon substrate area. The sides of the masking silicon oxide 4, SOI (silicon-on-insulator) 3 and BOX (buried silicon oxide) 2 are integrally covered with SiOCN, and the lower part of the side of the masking silicon nitride 5 is covered with SiOCN, as Figure 5 shown;
[0054] S7. Perform epitaxial silicon 9 growth, so that the epitaxial silicon 9 grows on the upper surface of the substrate silicon 1 in the silicon substrate area until it is flush with the upper surface of the SOI (silicon-on-insulator) 3 in the SOI area, as Figure 6 shown;
[0055] S8. Wet cleaning is used to remove silicon nitride and silicon oxide in the SOI region. As shown in Figure 7 , although SiOCN is used as a protective layer and is not easily consumed by processes such as wet cleaning, the SiOCN at the top of the boundary between the SOI region and the silicon substrate region can be basically removed during wet cleaning;
[0056] S9. When forming the active region through an etching process subsequently, the SiOCN deposited at the boundary between the SOI region and the silicon substrate region is etched away, and then STI (shallow trench isolation) is formed, as shown in Figure 8 .
[0057] For the method of forming a hybrid substrate of an SOI (silicon on insulator) silicon wafer in Embodiment 1, the buried oxide layer and the silicon on insulator in a partial region are removed. A layer of SiOCN is deposited on the sidewalls of the SOI to protect the sidewalls of the silicon on insulator, and then epitaxial silicon growth is carried out to make the silicon substrate region grow flush with the silicon on insulator region. The SiOCN on the sidewalls of the SOI acts as a protective layer and can prevent the growth of epitaxial silicon on the sidewalls of the SOI, thereby preventing the generation of bulges at the boundary between the SOI region and the silicon substrate region and improving the product yield. Moreover, the SiOCN (silicon oxycarbide nitride) film can be deposited with high conformality, and the SiOCN deposited on the sidewalls of the SOI has good uniformity (better uniformity than the silicon oxide formed on the sidewalls of the SOI by RTO). When subsequent epitaxial silicon 9 growth is carried out, there will be no situation where Si epitaxially grows from the SOI, which is beneficial to further improving the product yield.
[0058] Embodiment 2
[0059] Based on the method of forming a hybrid substrate of an SOI silicon wafer in Embodiment 1, after S6, wet cleaning is used to remove the by-products generated during the dry etching process in step S6, and then step S7 is carried out.
[0060] Preferably, an acid cleaning agent with a first concentration is used for wet cleaning to remove the by-products generated during the dry etching process in step S6;
[0061] The acid cleaning agent is phosphoric acid or hydrofluoric acid.
[0062] Preferably, in step S8, an acid cleaning agent with a second concentration is used for wet cleaning to remove silicon nitride and silicon oxide in the SOI region, and the second concentration is higher than the first concentration.
[0063] Embodiment 3
[0064] Based on the method of forming a hybrid substrate of an SOI silicon wafer in Embodiment 1, in step S5, the thickness of the deposited SiOCN 7 is 5 - 10 nm.
[0065] Preferably, in step S1, the thickness of the mask silicon oxide 4 is 3 - 10 nm, and the thickness of the mask silicon nitride 5 is 10 - 30 nm.
[0066] Preferably, in step S1, the thickness of the masking silicon oxide 4 is The thickness of the masking silicon nitride 5 is
[0067] In step S5, the thickness of the deposited SiOCN 7 is
[0068] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.
Claims
1. A method for forming a hybrid substrate of an SOI silicon wafer, characterized in that, It includes the following steps: S1. Deposit a layer of masking silicon oxide on the SOI wafer, and then deposit a layer of masking silicon nitride; S2. Perform a photolithography process to open the silicon substrate area where the silicon substrate needs to be formed; S3. Dry etch to remove the masking silicon nitride, masking silicon oxide, SOI, and BOX above the substrate silicon in the silicon substrate area; S4. Remove the photoresist; S5. Deposit a layer of SiOCN; S6. Dry etch. Utilize the directionality of dry etching to remove the SiOCN on the SOI area and the silicon substrate area. The masking silicon oxide, SOI, and BOX sides are entirely covered with SiOCN, and the lower part of the masking silicon nitride side is covered with SiOCN; S7. Perform epitaxial silicon growth to make the upper surface of the substrate silicon in the silicon substrate area grow flush with the upper surface of the SOI in the SOI area; S8. Wet clean to remove the silicon nitride and silicon oxide in the SOI area; S9. When forming the active area through an etching process subsequently, etch and remove the SiOCN deposited at the boundary between the SOI area and the silicon substrate area, thereby forming STI.
2. The method for forming the SOI wafer hybrid substrate according to claim 1, wherein, After S6, wet clean to remove the by-products generated during the dry etching process in step S6, and then perform step S7.
3. The method for forming the SOI wafer hybrid substrate according to claim 2, wherein, Use an acid cleaning agent with a first concentration to wet clean and remove the by-products generated during the dry etching process in step S6; The acid cleaning agent is phosphoric acid or hydrofluoric acid.
4. The method for forming the SOI wafer hybrid substrate according to claim 3, wherein, In step S8, use an acid cleaning agent with a second concentration to wet clean and remove the silicon nitride and silicon oxide in the SOI area, and the second concentration is higher than the first concentration.
5. The method for forming the SOI wafer hybrid substrate according to claim 1, wherein, In step S5, the deposited SiOCN has a thickness of 5 - 10 nm.
6. The method for forming the SOI wafer hybrid substrate according to claim 5, wherein, In step S1, the masking silicon oxide has a thickness of 3 - 10 nm, and the masking silicon nitride has a thickness of 10 - 30 nm.
7. The method for forming the SOI wafer hybrid substrate according to claim 6, wherein, In step S1, the thickness of the masking silicon oxide is and the thickness of the masking silicon nitride is In step S5, the thickness of the deposited SiOCN is