Formation method of semiconductor device
Through the combination of dry and wet etching, the substrate recession problem caused by the removal of polysilicon material layer in semiconductor devices is solved, ensuring the improvement of device quality and data retention performance.
Patent Information
- Application Number
- CN202510397021.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-31
- Publication Date
- 2025-07-04
AI Technical Summary
The prior art may cause overetching of the first gate oxide material layer when removing the first polysilicon material layer in a semiconductor device, resulting in depression on the substrate surface, affecting the quality of the subsequently formed second gate oxide material layer and second polysilicon material layer, and even leading to data retention failure.
The first polysilicon material layer is removed by dry etching to ensure that the surface of the first gate oxide material layer is flat, and then the first gate oxide material layer is removed by wet etching to ensure that the surface of the substrate is flat, and then the second gate oxide material layer and the second polysilicon material layer are formed on the substrate surface.
Through the combination of dry and wet etching, the substrate surface is avoided, and the formed floating gate extends in an undirected substrate direction is ensured, the quality of the semiconductor device is improved, and the probability of data retention failure is reduced.
Smart Images
Figure CN120264833A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for forming a semiconductor device. Background Art
[0002] The formation of polysilicon layers is involved in many semiconductor devices, and generally semiconductor devices are based on being formed on the surface of a substrate. For example, split-gate flash memories. With the development of technology, the application of data storage media has shifted from some traditional non-volatile memories to flash memory type memories, and large-capacity solid-state storage devices with flash memory as the main storage medium have become one of the mainstream solutions for data storage today. Please refer to Figure 1 , the split-gate flash memory includes a substrate 101, and a gate oxide layer 102 is formed on the surface of the substrate 101. A floating gate 103 is formed on the surface of the gate oxide layer 102, a first sidewall 104 located on the surface of the floating gate 103, a word line 105 located between the openings formed by the floating gate 103, and a second sidewall 106 that separates both the word line 105 from the first sidewall 104 and the word line 105 from the floating gate 103. Among them, please refer to Figure 2 , the floating gate 103 is formed by depositing a first polysilicon material layer 108 on the surface of a first gate oxide material layer 107, and then etching the first polysilicon material layer 108, and etching the first gate oxide material layer 107 to form the gate oxide layer 102.
[0003] During the formation process of forming a semiconductor device, due to various reasons, the quality of the first polysilicon material layer 108 may have problems. It is necessary to first remove the existing first polysilicon material layer 108, and then remove the first gate oxide material layer 107 to expose the surface of the substrate 101. After the removal is completed, a new gate oxide material layer is regrown on the surface of the substrate 101, and a new second polysilicon material layer is regrown on the gate oxide layer. Finally, various structures of the split-gate flash memory are formed, such as gate oxide layer and floating gate and other structures. The prior art method for removing the first polysilicon material layer 108 uses a SEZ machine tool for wet etching to remove the first polysilicon material layer 108, and uses a wet etching method to remove the first gate oxide material layer 107.
[0004] However, since the SEZ machine tool is used for wet etching to remove the first polysilicon material layer 108, during the process of removing the first polysilicon material layer 108, since the concentration of the acid used in the wet etching may be unstable, it may cause over-etching of a part of the first gate oxide material layer 107 below a part of the first polysilicon material layer 108, resulting in a depression in the direction of the substrate 101 here. Then when using wet etching to remove the first gate oxide material layer 107, the part of the substrate 101 below will continue to be etched at the depression of the first gate oxide material layer 107, as Figure 3This causes depressions 109 to appear on the surface of the substrate 101, resulting in defects in the substrate 101. If these defects are not improved, the subsequently reformed second gate oxide material layer 110 and second polysilicon material layer 111 may both have tips extending towards the substrate 101 at the depressions on the surface of the substrate 101, as Figure 4 This will continue to cause the subsequently formed floating gate to have a tip extending towards the substrate 101 at this location, reducing the quality of the semiconductor device. Even during the CP2 test, data retention failures may occur. SUMMARY OF THE INVENTION
[0005] An object of the present invention is to provide a method for forming a semiconductor device, which can make the surface of the first gate oxide material layer flat after removing the first polysilicon material layer. Then, after removing the first gate oxide material layer, the surface of the substrate can be made flat. Thus, a qualified second gate oxide material layer and second polysilicon material layer can be formed again on the surface of the substrate, and finally a qualified floating gate can be formed to improve the quality of the semiconductor device.
[0006] To achieve the above object, the present invention provides a method for forming a semiconductor device, including:
[0007] Providing a semiconductor substrate, the semiconductor substrate including a substrate, a first gate oxide material layer located on the surface of the substrate, and a first polysilicon material layer located on the surface of the first gate oxide layer;
[0008] Dry-etching the first polysilicon material layer to expose the surface of the first gate oxide material layer, and the surface of the first gate oxide material layer is flat;
[0009] Wet-etching the first gate oxide material layer to expose the surface of the substrate, and the surface of the substrate is flat;
[0010] Sequentially forming a second gate oxide material layer and a second polysilicon material layer on the surface of the substrate;
[0011] Forming a first sidewall on the surface of a part of the second polysilicon material layer, and the first sidewall encloses a first opening;
[0012] Etching the second polysilicon material layer and the second gate oxide material layer exposed in the first opening to form a word line opening;
[0013] Forming a word line and a second sidewall in the word line opening, and the second sidewall separates both the word line and the second gate oxide material layer and the word line and the second polysilicon material layer;
[0014] Etching the second polysilicon material layer and the second gate oxide material layer not covered by the first sidewall to form a floating gate and a gate oxide layer.
[0015] Optionally, in the method for forming the semiconductor device, the thicknesses of both the first polysilicon material layer and the second polysilicon material layer are 500 angstroms to 800 angstroms.
[0016] Optionally, in the method for forming the semiconductor device, the first polysilicon material layer is dry-etched with CF4 gas to expose the surface of the first gate oxide material layer.
[0017] Optionally, in the method for forming the semiconductor device, the flow rate of the CF4 gas is 100 sccm to 200 sccm.
[0018] Optionally, in the method for forming the semiconductor device, the time for dry-etching the first polysilicon layer is less than 30 s.
[0019] Optionally, in the method for forming the semiconductor device, both the first gate oxide material layer and the first gate oxide material layer include silicon dioxide.
[0020] Optionally, in the method for forming the semiconductor device, both the first polysilicon material layer and the first polysilicon material layer include polysilicon.
[0021] Optionally, in the method for forming the semiconductor device, the substrate includes a wafer.
[0022] Optionally, in the method for forming the semiconductor device, the materials of both the first sidewall and the second sidewall include silicon dioxide.
[0023] Optionally, in the method for forming the semiconductor device, the material of the word line includes polysilicon.
[0024] In the method for forming a semiconductor device provided by the present invention, it includes providing a semiconductor substrate, the semiconductor substrate including a substrate, a first gate oxide material layer located on the surface of the substrate, and a first polysilicon material layer located on the surface of the first gate oxide layer; dry-etching the first polysilicon material layer to expose the surface of the first gate oxide material layer, and the surface of the first gate oxide material layer is flat; wet-etching the first gate oxide material layer to expose the surface of the substrate, and the surface of the substrate is flat; sequentially forming a second gate oxide material layer and a second polysilicon material layer on the surface of the substrate; forming a first sidewall on the surface of a part of the second polysilicon material layer, and the first sidewall encloses to form a first opening; etching the second polysilicon material layer and the second gate oxide material layer exposed in the first opening to form a word line opening; forming a word line and a second sidewall in the word line opening, and the second sidewall separates the word line from the second gate oxide material layer and the word line from the second polysilicon material layer; etching the second polysilicon material layer and the second gate oxide material layer not covered by the first sidewall to form a floating gate and a gate oxide layer. By the method of dry-etching, the present invention removes the first polysilicon material layer again to obtain a flat first gate oxide material layer. Then, when the first gate oxide material layer is removed by wet-etching to expose the surface of the substrate, a flat substrate can be obtained. Furthermore, the formed second gate oxide layer and second polysilicon layer will not have tips extending towards the substrate, and the formed floating gate does not have a tip extending towards the substrate, thereby improving the quality of the semiconductor device and reducing the probability of data retention failure during the CP2 test. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 is a schematic structural diagram of a semiconductor device of the prior art;
[0026] Figure 2 is a schematic structural diagram of a semiconductor device after forming the first polysilicon material layer of the prior art;
[0027] Figure 3 is a schematic structural diagram of a substrate after removing the first polysilicon material layer and the first gate oxide material layer of the prior art;
[0028] Figure 4 is a schematic structural diagram of a semiconductor device after forming the second polysilicon material layer of the prior art;
[0029] Figure 5 is a flowchart of the method for forming a semiconductor device according to an embodiment of the present invention;
[0030] Figure 6 is a schematic structural diagram of a semiconductor device after forming the first polysilicon material layer according to an embodiment of the present invention;
[0031] Figure 7It is a schematic structural diagram of a semiconductor device after removing the first polysilicon material layer and the first gate oxide material layer according to an embodiment of the present invention;
[0032] Figure 8 It is a schematic structural diagram of a semiconductor device after forming the second polysilicon material layer according to an embodiment of the present invention;
[0033] Figure 9 It is a schematic structural diagram of a semiconductor device according to an embodiment of the present invention;
[0034] In the figure: 101 - substrate, 102 - gate oxide layer, 103 - floating gate, 104 - first sidewall, 105 - word line, 106 - second sidewall, 107 - first gate oxide material layer, 108 - first polysilicon material layer, 109 - depression, 110 - second gate oxide material layer, 111 - second polysilicon material layer, 201 - substrate, 202 - first gate oxide material layer, 203 - first polysilicon material layer, 204 - second gate oxide material layer, 205 - second polysilicon material layer, 206 - gate oxide layer, 207 - floating gate, 208 - first sidewall, 209 - word line, 210 - second sidewall. Detailed Embodiments
[0035] The following will describe the detailed embodiments of the present invention in more detail with reference to the schematic diagrams. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the drawings are all in a very simplified form and use non - precise ratios, only for conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention.
[0036] In the following text, terms such as "first" and "second" are used to distinguish between similar elements and are not necessarily used to describe a specific order or time sequence. It should be understood that, under appropriate circumstances, these terms can be replaced. Similarly, if the methods described herein include a series of steps, and the order of these steps presented herein is not necessarily the only order in which these steps can be executed, and some of the described steps can be omitted and / or some other steps not described herein can be added to the method.
[0037] Moreover, it should be understood that when a layer (or film), region, pattern or structure is referred to as being "on" a substrate, layer (or film), region and / or pattern, it can be directly on another layer or substrate, and / or there can also be an intervening layer. Additionally, it should be understood that when a layer is referred to as being "under" another layer, it can be directly under another layer, and / or there can also be one or more intervening layers. Additionally, the references to "on" and "under" each layer can be based on the drawings.
[0038] Please refer to Figure 5 , the present invention provides a method for forming a semiconductor device, including:
[0039] S11: Provide a semiconductor substrate, the semiconductor substrate including a substrate, a first gate oxide material layer located on the surface of the substrate, and a first polysilicon material layer located on the surface of the first gate oxide layer;
[0040] S12: Dry-etch the first polysilicon material layer to expose the surface of the first gate oxide material layer, and the surface of the first gate oxide material layer is flat;
[0041] S13: Wet-etch the first gate oxide material layer to expose the surface of the substrate;
[0042] S14: Sequentially form a second gate oxide material layer and a second polysilicon material layer on the surface of the substrate;
[0043] S15: Form a first sidewall on the surface of a part of the second polysilicon material layer, and the first sidewall encloses a first opening;
[0044] S16: Etch the second polysilicon material layer and the second gate oxide material layer exposed in the first opening to form a word line opening;
[0045] S17: Form a word line and a second sidewall in the word line opening, and the second sidewall separates both the word line and the second gate oxide material layer and the word line and the second polysilicon material layer;
[0046] S18: Etch the second polysilicon material layer and the second gate oxide material layer not covered by the first sidewall to form a floating gate and a gate oxide layer.
[0047] Specifically, please refer to Figure 6 , first provide a substrate 201, the substrate 201 can be a silicon material substrate, specifically it can be a wafer. Form a first gate oxide material layer 202 on the surface of the substrate 201, and the forming method can be a method of depositing a layer of silicon oxide such as silicon dioxide. Then, form a first polysilicon material layer 203 on the surface of the first gate oxide material layer 202, and the forming method can be a method of depositing polysilicon material. At this time, if it is found that there are quality problems with the first polysilicon material layer 203, the first polysilicon material layer 203 needs to be removed and a second polysilicon material layer needs to be re-formed.
[0048] Next, please refer to Figure 7, the first polysilicon material layer 203 is removed by dry etching. The etching gas can be CF4, and the gas flow rate of CF4 can be 100 sccm to 200 sccm, and the etching time can be within 30 s. After etching, the surface of the exposed first gate oxide material layer 202 is flat and no depression occurs. Then, wet etching is used to remove the first gate oxide material layer 202 to expose the surface of the substrate 201. Since the surface of the first gate oxide material layer 202 was flat before, when continuously etching the first gate oxide material layer 202, no defect of depression will appear on the surface of the substrate 201 either. That is, the surface of the substrate 201 after removing the first polysilicon material layer 203 and the first gate oxide material layer 202 in the embodiment of the present invention is flat.
[0049] Next, please refer to Figure 8 , a second gate oxide material layer 204 is formed on the surface of the substrate 201, and the forming method can be depositing a layer of silicon oxide such as silicon dioxide. Then, a second polysilicon material layer 205 is formed on the surface of the second gate oxide material layer 204, and the forming method can be depositing a polysilicon material.
[0050] Finally, please refer to Figure 8 and Figure 9 , a first sidewall 208 is formed on the surface of a part of the second polysilicon material layer 205, and the first sidewall 208 encloses a first opening. Forming the first sidewall 208 is a prior art and will not be elaborated here. Then, the second polysilicon material layer 205 and the second gate oxide material layer 204 exposed in the first opening are etched to form a word line opening. Then, a word line 209 and a second sidewall 210 are formed in the word line opening, and the second sidewall 210 separates the word line 209 from the second gate oxide material layer 204 and the word line 209 from the second polysilicon material layer 205. Then, the second polysilicon material layer 205 and the second gate oxide material layer 204 not covered by the first sidewall 208 are etched to form a floating gate 207 and a gate oxide layer 206.
[0051] In summary, in the method for forming a semiconductor device provided by an embodiment of the present invention, it includes providing a semiconductor substrate, where the semiconductor substrate includes a substrate, a first gate oxide material layer located on the surface of the substrate, and a first polysilicon material layer located on the surface of the first gate oxide layer; dry-etching the first polysilicon material layer to expose the surface of the first gate oxide material layer, and the surface of the first gate oxide material layer is flat; wet-etching the first gate oxide material layer to expose the surface of the substrate, and the surface of the substrate is flat; sequentially forming a second gate oxide material layer and a second polysilicon material layer on the surface of the substrate; forming a first sidewall on the surface of a part of the second polysilicon material layer, and the first sidewall encloses a first opening; etching the second polysilicon material layer and the second gate oxide material layer exposed in the first opening to form a word line opening; forming a word line and a second sidewall in the word line opening, and the second sidewall separates the word line from the second gate oxide material layer and the word line from the second polysilicon material layer; etching the second polysilicon material layer and the second gate oxide material layer not covered by the first sidewall to form a floating gate and a gate oxide layer. In the present invention, the first polysilicon material layer is removed again by dry-etching to obtain a flat first gate oxide material layer. Then, when the first gate oxide material layer is removed by wet-etching to expose the surface of the substrate, a flat substrate can be obtained. Furthermore, the formed second gate oxide layer and second polysilicon layer will not have tips extending towards the substrate, and the formed floating gate does not have a tip extending towards the substrate, thereby improving the quality of the semiconductor device and reducing the probability of data retention failure during the CP2 test.
[0052] The above is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any person skilled in the art, without departing from the technical solution of the present invention, makes any form of equivalent substitution or modification and other changes to the technical solution and technical content disclosed by the present invention, all of which belong to the content of the technical solution of the present invention and are still within the protection scope of the present invention.
Claims
1. A method for forming a semiconductor device, characterized in that, Comprising: Providing a semiconductor substrate, the semiconductor substrate including a substrate, a first gate oxide material layer located on the surface of the substrate, and a first polysilicon material layer located on the surface of the first gate oxide layer; Dry etching the first polysilicon material layer to expose the surface of the first gate oxide material layer, and the surface of the first gate oxide material layer is flat; Wet etching the first gate oxide material layer to expose the surface of the substrate, and the surface of the substrate is flat; Sequentially forming a second gate oxide material layer and a second polysilicon material layer on the surface of the substrate; Forming a first sidewall on the surface of a part of the second polysilicon material layer, and the first sidewall encloses to form a first opening; Etching the second polysilicon material layer and the second gate oxide material layer exposed in the first opening to form a word line opening; Forming a word line and a second sidewall in the word line opening, and the second sidewall separates the word line from the second gate oxide material layer and also separates the word line from the second polysilicon material layer; Etching the second polysilicon material layer and the second gate oxide material layer not covered by the first sidewall to form a floating gate and a gate oxide layer.
2. The method for forming a semiconductor device according to claim 1, wherein, The thicknesses of both the first polysilicon material layer and the second polysilicon material layer are 500 angstroms to 800 angstroms.
3. The method for forming a semiconductor device according to claim 1, wherein, Dry etching the first polysilicon material layer using CF4 gas to expose the surface of the first gate oxide material layer.
4. The method for forming a semiconductor device according to claim 3, wherein, The flow rate of the CF4 gas is 100 sccm to 200 sccm.
5. The method for forming a semiconductor device according to claim 1, wherein, The time for dry etching the first polysilicon layer is less than 30 s.
6. The method for forming a semiconductor device according to claim 1, wherein, Both the first gate oxide material layer and the first gate oxide material layer include silicon dioxide.
7. The method for forming a semiconductor device according to claim 1, wherein, Both the first polysilicon material layer and the first polysilicon material layer include polysilicon.
8. The method for forming a semiconductor device according to claim 1, wherein, The substrate includes a wafer.
9. The method for forming a semiconductor device according to claim 1, wherein, The materials of both the first sidewall and the second sidewall include silicon dioxide.
10. The method for forming a semiconductor device according to claim 1, wherein The material of the word line includes polysilicon.