Semiconductor structure and method for forming the same
By etching the polysilicon layer using a mixed liquid of hydrofluoric acid and ozone solution, the problem of insufficient accuracy and flatness of the etching process in the prior art is solved, and a more efficient polysilicon layer formation and protection effect is achieved.
Patent Information
- Application Number
- CN201910572512.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2019-06-28
- Publication Date
- 2024-12-24
- Estimated Expiration
- 2039-06-28
AI Technical Summary
In the existing semiconductor manufacturing process, the etching process of the polycrystalline silicon layer has problems of insufficient accuracy and flatness, which affects the layer thickness and surface quality.
The mixed solution of hydrofluoric acid and ozone solution is used as the etching solution, with a volume ratio of 1:4 to 4:1, and the etching process time is controlled from 1 minute to 30 minutes, and the temperature is 25°C to 50°C to remove part of the thickness. A polycrystalline silicon film forms a polycrystalline silicon layer.
It improves the accuracy of the etching process and the flatness of the polysilicon layer, ensures that the layer thickness meets the process requirements, and enhances the protection effect of the polysilicon layer and the convenience of subsequent processes.
Smart Images
Figure CN112151369B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a semiconductor structure and a forming method thereof. Background Art
[0002] Polycrystalline silicon is a form of elemental silicon. When molten elemental silicon solidifies under supercooling conditions, silicon atoms are arranged in the form of diamond lattices to form many crystal nuclei. These crystal nuclei grow into grains with different crystal plane orientations. These grains combine to form polycrystalline silicon.
[0003] In the manufacturing process of semiconductor structures, polysilicon materials can be used to form hard mask layers or shielding layers. In order to make the thickness of the formed polysilicon layer meet the process requirements, the polysilicon material needs to be etched.
[0004] However, the existing etching process still needs to be improved. Summary of the invention
[0005] The problem solved by the present invention is to provide a semiconductor structure and a method for forming the same.
[0006] To solve the above problems, the present invention provides a method for forming a semiconductor structure, comprising: providing a substrate; forming a polysilicon film on the substrate; removing a portion of the polysilicon film by an etching process to form a polysilicon layer, wherein the etching solution is a mixture of hydrofluoric acid and ozone solution, and the volume ratio of hydrofluoric acid to ozone solution is 1:4 to 4:1.
[0007] Optionally, the volume ratio of HF to H2O in the hydrofluoric acid is 1:200.
[0008] Optionally, the percentage concentration of the ozone solution is 30 ppm.
[0009] Optionally, the base includes a substrate and a device layer, and the device layer covers the surface of the substrate; in the process of forming the polysilicon film, the polysilicon film is formed on the surface of the device layer.
[0010] Optionally, the process time of the etching process is less than 30 minutes, and the process time is greater than or equal to 1 minute.
[0011] Optionally, the temperature of the etching solution is 25°C to 50°C.
[0012] Optionally, the thickness of the polysilicon layer is less than
[0013] Optionally, in the process of forming the polysilicon film, the thickness of the polysilicon film is
[0014] Correspondingly, the present invention also provides a semiconductor structure formed by the above method, comprising: a substrate; and a polysilicon layer located on the substrate.
[0015] Optionally, the base includes a substrate and a device layer, the device layer covers a surface of the substrate, and the polysilicon layer covers a surface of the device layer.
[0016] Compared with the prior art, the technical solution of the present invention has the following advantages:
[0017] The etching solution is a mixture of hydrofluoric acid and ozone solution. Among them, the ozone solution is used to oxidize the partially thick polysilicon film into silicon dioxide. Hydrofluoric acid is used to react with silicon dioxide to generate a reaction product soluble in water, thereby removing a partially thick polysilicon film. The volume ratio of hydrofluoric acid to ozone solution is 1:4 to 4:1. On the one hand, due to the small volume share of hydrofluoric acid, the etching rate is slow, which helps to improve the accuracy of the etching process and can improve the flatness of the surface of the polysilicon layer after etching. On the other hand, the etching process time is appropriate to avoid the etching process taking too long. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figures 1 to 3 It is a schematic structural diagram corresponding to each step in an embodiment of a method for forming a semiconductor structure of the present invention. DETAILED DESCRIPTION
[0019] A method for forming a semiconductor structure is now analyzed, including: providing a substrate (not shown in the figure); forming a polysilicon film (not shown in the figure) on the substrate; oxidizing a portion of the polysilicon film to form a silicon oxide layer, and using the remaining thickness of the polysilicon film as the polysilicon layer; and etching to remove the silicon oxide layer.
[0020] The oxidation process and the etching process are performed in separate steps, which results in low process efficiency. In addition, the process control becomes more difficult, which affects the formation quality of the polysilicon layer.
[0021] The inventor has studied the method for forming the above-mentioned semiconductor structure. After creative work, the inventor has noticed that a polysilicon film of partial thickness can be etched by etching with a mixture of hydrofluoric acid and ozone solution. The rate of the etching process can be controlled by controlling the volume ratio of hydrofluoric acid to ozone solution. When the volume ratio of hydrofluoric acid to ozone solution is 1:4 to 4:1, the etching process can be conveniently controlled to improve the etching accuracy. In addition, the surface roughness of the polysilicon layer can be reduced, thereby improving the formation quality of the polysilicon layer.
[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.
[0023] Figures 1 to 3 It is a schematic structural diagram corresponding to each step in an embodiment of a method for forming a semiconductor structure of the present invention.
[0024] refer to Figure 1 , providing a substrate 100.
[0025] In this embodiment, the base 100 includes a substrate 110 and a device layer 120 , and the device layer 120 covers the surface of the substrate 110 .
[0026] The material of the substrate 110 is silicon, germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium. In this embodiment, the material of the substrate 110 is silicon.
[0027] The material of the device layer 120 is silicon oxide, silicon nitride or silicon oxynitride. In this embodiment, the material of the device layer 120 is silicon oxide.
[0028] The device layer 120 has transistors (not shown in the figure) or passive devices (not shown in the figure).
[0029] In this embodiment, a chemical vapor deposition process is used to form the device layer 120. In other embodiments, an atomic layer deposition process or a physical vapor deposition process may also be used to form the device layer.
[0030] refer to Figure 2 , a polysilicon film 200 is formed on the substrate 100 .
[0031] In this embodiment, a polysilicon film 200 is formed on the surface of the device layer 120 .
[0032] The polysilicon film 200 covers the surface of the device layer 120 , and the polysilicon film 200 can protect the surface of the device layer 120 , thereby preventing the surface of the device layer 120 from being directly exposed to the subsequent process environment, thereby preventing the surface of the device layer 120 from being damaged or contaminated.
[0033] Subsequently, an etching process is used to remove a portion of the polysilicon film 200. Since the thickness of the retained polysilicon film 200 is a fixed value, if the thickness of the polysilicon film 200 is too large, the thickness of the polysilicon film 200 removed in the etching process will be too large, resulting in a long etching process time. If the thickness of the polysilicon film 200 is too small, in the subsequent etching process of the polysilicon film 200, the entire polysilicon film 200 is easily etched away, so that the surface of the device layer 120 is directly exposed to the subsequent process environment. In this embodiment, the thickness H1 of the polysilicon film 200 is
[0034] refer to Figure 3 , using an etching process to remove a portion of the polysilicon film 200 (reference Figure 2 ), forming a polysilicon layer 300.
[0035] The polysilicon film 200 is etched and removed to a predetermined thickness, so that the thickness of the formed polysilicon layer 300 meets the process requirements.
[0036] If the thickness of the polysilicon layer 300 is too large, the polysilicon layer 300 occupies too much space, affecting the subsequent process; if the thickness of the polysilicon layer 300 is too small, the protective effect of the polysilicon layer 300 on the surface of the device layer 120 is affected. In this embodiment, the thickness H2 of the polysilicon layer 300 is less than
[0037] In this embodiment, in the etching process, the etching solution is a mixture of hydrofluoric acid and ozone solution. The etching process includes two stages, which are explained in detail below.
[0038] The first stage: Ozone reacts with the partially thick polysilicon film 200 material to cause the partially thick polysilicon material to be converted into silicon oxide. The chemical reaction formula is:
[0039] Si+2O3+H2O→SiO2+2O2+H2O.
[0040] The second stage: Hydrogen fluoride reacts chemically with the converted silicon oxide to generate H2SiF6 and H2O, and H2SiF6 dissolves in water. The chemical reaction formula is:
[0041] SiO2+6HF→H2SiF6+2H2O.
[0042] The above two stages are repeated until the thickness of the polysilicon film 200 removed by etching reaches a predetermined value. The overall chemical reaction formula is:
[0043] Si+2O3+6HF→2O2+H2SiF6+2H2O.
[0044] If the volume ratio of HF to H2O in the hydrofluoric acid is too large, the concentration of the hydrofluoric acid is too high, resulting in a violent chemical reaction in the second stage, making the etching rate too fast, and over-etching is likely to occur, resulting in the polysilicon film 200 exceeding the predetermined thickness being etched away. In addition, a too fast etching rate will also affect the flatness of the surface of the polysilicon layer 300 after the etching process. If the volume ratio of HF to H2O in the hydrofluoric acid is too small, the concentration of the hydrofluoric acid is too low, and the chemical reaction between hydrogen fluoride and the converted silicon oxide is too slow, making the etching process time too long. In this embodiment, the volume ratio of HF to H2O in the hydrofluoric acid is 1:200.
[0045] If the percentage concentration of the ozone solution is too high, the oxidation reaction rate is too fast, resulting in an oxidation reaction of the polysilicon film 200 material exceeding the predetermined thickness, causing silicon oxide residues on the surface of the formed polysilicon layer 300, affecting the subsequent process. If the percentage concentration of the ozone solution is too low, the oxidation reaction rate is too slow, affecting the progress efficiency of the etching process. In this embodiment, the volume ratio of HF to H2O in the hydrofluoric acid is 1:200.
[0046] If the volume ratio of hydrofluoric acid to ozone solution is too large, the concentration of hydrogen fluoride in the mixed solution is too high, resulting in a violent chemical reaction in the second stage, making the etching rate too fast, affecting the accuracy of the etching process, and easily causing the thickness of the formed polysilicon layer 300 to be too small. In addition, a too fast etching rate will also cause the surface of the formed polysilicon layer 300 to have a high roughness, affecting the subsequent process. In this embodiment, the volume ratio of hydrofluoric acid to ozone solution is 1:4 to 4:1.
[0047] If the process time of the etching process is too long, the polysilicon film 200 exceeding the predetermined thickness is etched away, resulting in the thickness of the formed polysilicon layer 300 being too thin, affecting the protective effect of the polysilicon layer 300 on the surface of the device layer 120. If the process time of the etching process is too short, the polysilicon film 200 below the predetermined thickness is etched away, resulting in the thickness of the formed polysilicon layer 300 being too thick, resulting in the polysilicon layer 300 occupying too much space, causing difficulty in the subsequent process. In this embodiment, the process time of the etching process is less than 30 minutes, and the process time is greater than or equal to 1 minute.
[0048] If the temperature of the etching solution is too high, the chemical reactions in the two stages will be too intense, and over-etching will easily occur, resulting in the thickness of the formed polysilicon layer 300 being too thin; in addition, the surface of the formed polysilicon layer 300 will be rough, reducing the formation quality of the polysilicon layer 300. If the temperature of the etching solution is too low, the chemical reactions in the two stages will be slow, and it may even be difficult to trigger the chemical reactions, affecting the etching rate. In this embodiment, the temperature of the etching solution is 25°C to 50°C.
[0049] Reference Figure 3 The present invention also provides a semiconductor structure obtained by the above-mentioned formation method. The semiconductor structure comprises: a substrate 100; and a polysilicon layer 300 located on the substrate 100.
[0050] In this embodiment, the base 100 includes a substrate 110 and a device layer 120 . The device layer 120 covers the surface of the substrate 110 , and the polysilicon layer 300 covers the surface of the device layer 120 .
[0051] The material of the substrate 110 is silicon, germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium. In this embodiment, the material of the substrate 110 is silicon.
[0052] The material of the device layer 120 is silicon oxide, silicon nitride or silicon oxynitride. In this embodiment, the material of the device layer 120 is silicon oxide.
[0053] The device layer 120 has transistors or passive devices therein.
[0054] The polysilicon layer 300 can protect the surface of the device layer 120 and prevent the surface of the device layer 120 from being contaminated or damaged.
[0055] In this embodiment, the thickness H2 of the polysilicon layer 300 is less than The polysilicon layer 300 has an appropriate thickness. On the one hand, it can ensure the protective effect of the polysilicon layer 300 on the surface of the device layer 120; on the other hand, the polysilicon layer 300 occupies an appropriate space, which is convenient for subsequent processes.
[0056] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.
Claims
1. A method for forming a semiconductor structure, characterized in that: include: providing a substrate; forming a polysilicon film on the substrate; An etching process is used to remove a part of the thickness of the polysilicon film to form a polysilicon layer, and the etching solution is a mixture of hydrofluoric acid and ozone solution, and the volume ratio of hydrofluoric acid to ozone solution is 1:4 to 4:1; The volume ratio of HF to H2O in the hydrofluoric acid is 1:
200.
2. The forming method according to claim 1, characterized in that: The percentage concentration of the ozone solution is 30 ppm.
3. The forming method according to claim 1, characterized in that: The base comprises a substrate and a device layer, wherein the device layer covers the surface of the substrate; in the process of forming the polysilicon film, the polysilicon film is formed on the surface of the device layer.
4. The forming method according to claim 1, characterized in that: The process time of the etching process is less than 30 minutes, and the process time is greater than or equal to 1 minute.
5. The forming method according to claim 1, characterized in that: The temperature of the etching solution is 25°C to 50°C.
6. The forming method according to claim 1, characterized in that: The thickness of the polysilicon layer is less than 7. The forming method according to claim 1, characterized in that: In the process of forming the polysilicon film, the thickness of the polysilicon film is 8. A semiconductor structure formed by the method for forming a semiconductor structure according to any one of claims 1 to 7, characterized in that: include: substrate; The polysilicon layer is located on the substrate.
9. The semiconductor structure according to claim 8, characterized in that The base comprises a substrate and a device layer, wherein the device layer covers the surface of the substrate, and the polysilicon layer covers the surface of the device layer.