Method for improving thick gate oxide residue
By using a hard mask layer instead of a photoresist layer in the thin gate oxide region, the problem of thick gate oxide residue caused by photoresist residue is solved, thereby improving the reliability of the device.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI HUALI INTEGRATED CIRCUIT CORP
- Filing Date
- 2023-03-14
- Publication Date
- 2026-07-14
AI Technical Summary
Existing technologies pose a risk of photoresist residue, which can lead to thick gate oxide residue and ultimately device failure.
In the area where the thin gate oxide layer is formed, a hard mask layer is used instead of a photoresist layer for protection. The hard mask layer is formed through photolithography and etching processes to avoid photoresist residue. Then, a first gate oxide layer covering the hard mask layer is formed, and the hard mask layer is removed to form a second gate oxide layer of different thickness.
It effectively avoids the thick gate oxide layer residue caused by photoresist residue, improves device reliability, and prevents device failure.
Smart Images
Figure CN116454026B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a method for improving the retention of thick gate oxide layers. Background Technology
[0002] The operating voltage of a standard CMOS sensor is divided into the Core (thin gate oxide) and I / O (output device) regions. A thin gate oxide layer is formed on the Core region, and its operating voltage is usually 0.9V or 1.8V. A thick gate oxide layer is formed on the I / O region, and its operating voltage is usually 0.9V or 2.5V.
[0003] Existing technology first grows a thick gate oxide layer, then removes the thick gate oxide layer by photolithography to open the thin gate oxide layer region, and then grows the thin gate oxide layer again. However, the existing technology has the risk of photoresist residue, which can lead to thick gate oxide layer residue on the thin gate oxide layer (e.g., Figure 1 (As shown), this ultimately leads to device failure.
[0004] To address the above problems, a novel method for improving the residual thick gate oxide layer is needed. Summary of the Invention
[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for improving the thick gate oxide layer residue, in order to solve the problem that there is a risk of photoresist residue in the prior art, which leads to a thick gate oxide layer residue on the thin gate oxide layer, and ultimately causes device failure.
[0006] To achieve the above and other related objectives, the present invention provides a method for improving the residual thick gate oxide layer, comprising:
[0007] Step 1: Provide a substrate, on which an STI is formed to define an active region, wherein at least a first device region and a second device region are formed on the active region;
[0008] Step 2: A hard mask layer is formed on the first device region and the region outside the first device region on the substrate. Then, a bottom anti-reflective coating and a photoresist layer on the bottom anti-reflective coating are formed on the hard mask layer.
[0009] Step 3: Photolithography opens the photoresist layer, exposing the bottom anti-reflective coating outside the first device area; etching removes the exposed bottom anti-reflective coating and the hard mask layer below it.
[0010] Step 4: Remove the remaining photoresist layer and the bottom anti-reflective coating, and then form a first gate oxide layer covering the hard mask layer on the substrate;
[0011] Step 5: Using photolithography and etching, the first gate oxide layer on the second device region of the substrate is retained, and the photoresist layer on the first device region is removed;
[0012] Step 6: Remove the hard mask layer to form a second gate oxide layer covering the substrate and the first gate oxide layer, wherein the thickness of the second gate oxide layer is lower than that of the first gate oxide layer;
[0013] Step 7: Use photolithography and etching to retain the second gate oxide layer on the first device region and the second device region on the substrate.
[0014] Preferably, the substrate in step one comprises a bulk semiconductor substrate or a silicon-on-insulator substrate.
[0015] Preferably, the material of the hard mask layer in step one is silicon nitride.
[0016] Preferably, the first device region in step one is the core device region.
[0017] Preferably, the second device area in step one is an input / output device area.
[0018] Preferably, step two further includes removing the pad oxide layer on the substrate before forming the hard mask layer in the first device region on the substrate.
[0019] Preferably, the material of the first gate oxide layer in step four is silicon dioxide.
[0020] Preferably, the material of the second gate oxide layer in step six is silicon dioxide.
[0021] As described above, the method for improving the residual thick gate oxide layer of the present invention has the following beneficial effects:
[0022] This invention forms a hard mask layer in the area where a thin gate oxide layer needs to be formed, replacing the photoresist layer as protection, thus avoiding the thick gate oxide layer residue caused by photoresist residue, thereby improving the problem of device failure. Attached Figure Description
[0023] Figure 1 This is a schematic diagram showing the residual thick gate oxide layer in the prior art;
[0024] Figure 2 The diagram shows a hard mask layer on the retained first device region of the present invention.
[0025] Figure 3 The diagram shown is a schematic representation of the first gate oxide layer of the present invention.
[0026] Figure 4 The diagram shown is a schematic representation of the graphical second gate oxide layer of the present invention.
[0027] Figure 5 The diagram shown is a schematic representation of the process flow of this invention. Detailed Implementation
[0028] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
[0029] Please see Figure 5 The present invention provides a method for improving the residual thick gate oxide layer, comprising:
[0030] Step 1: Provide a substrate 101, and form an STI 102 on the substrate 101 to define an active region. At least a first device region and a second device region are formed on the active region.
[0031] In embodiments of the present invention, the substrate 101 in step one comprises a bulk semiconductor substrate or a silicon-on-insulator (SOI) substrate. The SOI substrate includes an insulating layer located beneath a thin semiconductor layer serving as the active layer of the SOI substrate. The semiconductor of the active layer and the bulk semiconductor typically comprise the crystalline semiconductor material silicon, but may also include one or more other semiconductor materials, such as germanium, silicon-germanium alloys, compound semiconductors (e.g., GaAs, AlAs, InAs, GaN, AlN, etc.) or alloys thereof (e.g., GaxAl1-xAs, GaxAl1-xN, InxGa1-xAs, etc.), oxide semiconductors (e.g., ZnO, SnO2, TiO2, Ga2O3, etc.), or combinations thereof. The semiconductor material may be doped or undoped. Other substrates that may be used include multilayer substrates, gradient substrates, or mixed-orientation substrates.
[0032] In an embodiment of the present invention, the material of the hard mask layer 103 in step one is silicon nitride, and the hard mask layer 103 can usually be formed by chemical vapor deposition.
[0033] In an embodiment of the present invention, the first device region in step one is the core device region, and the gate oxide layer on this region is relatively thin.
[0034] In an embodiment of the present invention, the second device region in step one is an input / output device region, and the gate oxide layer on this region is relatively thick.
[0035] Step 2: A hard mask layer 103 is formed on the first device region and the region outside the first device region on the substrate 101. Then, a bottom anti-reflection coating 104 and a photoresist layer 105 located on the bottom anti-reflection coating 104 are formed on the hard mask layer 103.
[0036] In an embodiment of the present invention, before forming the hard mask layer 103 in the first device region on the substrate 101 in step two, the pad oxide layer on the substrate 101 is removed. Typically, after forming the STI 102, the pad oxide layer on the surface of the substrate 101 needs to be removed by wet etching.
[0037] Step 3: Photolithography (exposure, development, vertical film formation, baking, etc.) The photoresist layer 105 is opened, exposing the bottom anti-reflective coating 104 outside the first device area. The exposed bottom anti-reflective coating 104 and the underlying hard mask layer 103 are etched away. The hard mask layer 103 is etched using either dry etching or wet etching, thereby forming... Figure 2 The structure shown is such that a hard mask layer 103 is retained on the first device region to form a protective layer and prevent the surface of the first device region from being oxidized.
[0038] Step 4: Remove the remaining photoresist layer 105 and bottom anti-reflective coating 104. The remaining photoresist layer 105 and bottom anti-reflective coating 104 can be removed by ashing process and wet cleaning. Then, a first gate oxide layer 106 covering the hard mask layer 103 is formed on the substrate 101.
[0039] In an embodiment of the present invention, the material of the first gate oxide layer 106 in step four is silicon dioxide, which can be formed by methods such as plasma-enhanced chemical vapor deposition (PECVD) and thermal oxidation.
[0040] Step 5: Using photolithography and etching, the first gate oxide layer 106 on the second device region of the substrate 101 is retained, while the photoresist layer 105 on the first device region is removed, forming a structure as shown in the figure. Figure 3 The structure shown has improved the problem of residual second gate oxide layer 107 and its photoresist layer 105 because the hard mask layer 103 was retained on the first device area as protection in the previous step. The photolithography in this step can expose the photoresist on the first device area and then remove it.
[0041] Step 6: Remove the hard mask layer 103. The removal method can be wet etching. At the same time, a small amount of residual photoresist and the first gate oxide layer 106 can be further removed to form a second gate oxide layer 107 covering the substrate 101 and the first gate oxide layer 106. The thickness of the second gate oxide layer 107 is lower than that of the first gate oxide layer 106.
[0042] In an embodiment of the present invention, the material of the second gate oxide layer 107 in step six is silicon dioxide, which can be formed by methods such as plasma-enhanced chemical vapor deposition (PECVD) and thermal oxidation.
[0043] Step 7: Using photolithography and etching, the second gate oxide layer 107 on the first device region and the second device region on the substrate 101 is retained, forming a structure as shown in the figure. Figure 4 The structure shown.
[0044] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.
[0045] In summary, this invention forms a hard mask layer instead of a photoresist layer in the area where a thin gate oxide layer needs to be formed, thus avoiding the thick gate oxide layer residue caused by photoresist residue and improving the device failure problem. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.
[0046] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A method for improving residual thick gate oxide layer, characterized in that, At least including: Step 1: Provide a substrate, on which an STI is formed to define an active region, wherein at least a first device region and a second device region are formed on the active region; Step 2: A hard mask layer is formed on the first device region and the region outside the first device region on the substrate. Then, a bottom anti-reflective coating and a photoresist layer on the bottom anti-reflective coating are formed on the hard mask layer. Step 3: Photolithography opens the photoresist layer, exposing the bottom anti-reflective coating outside the first device area; etching removes the exposed bottom anti-reflective coating and the hard mask layer below it. Step 4: Remove the remaining photoresist layer and the bottom anti-reflective coating, and then form a first gate oxide layer covering the hard mask layer on the substrate; Step 5: Using photolithography and etching, the first gate oxide layer on the second device region of the substrate is retained, and the photoresist layer on the first device region is removed; Step 6: Remove the hard mask layer to form a second gate oxide layer covering the substrate and the first gate oxide layer, wherein the thickness of the second gate oxide layer is lower than that of the first gate oxide layer; Step 7: Use photolithography and etching to retain the second gate oxide layer on the first device region and the second device region on the substrate.
2. The method for improving residual thick gate oxide layer according to claim 1, characterized in that: The substrate in step one includes a bulk semiconductor substrate or a silicon-on-insulator substrate.
3. The method for improving residual thick gate oxide layer according to claim 1, characterized in that: The material of the hard mask layer in step one is silicon nitride.
4. The method for improving residual thick gate oxide layer according to claim 1, characterized in that: The first device area in step one is the core device area.
5. The method for improving the residual thick gate oxide layer according to claim 4, characterized in that: The second device area in step one is the input / output device area.
6. The method for improving residual thick gate oxide layer according to claim 1, characterized in that: Step two, before forming a hard mask layer in the first device region on the substrate, also includes removing the pad oxide layer on the substrate.
7. The method for improving residual thick gate oxide layer according to claim 1, characterized in that: The material of the first gate oxide layer in step four is silicon dioxide.
8. The method for improving residual thick gate oxide layer according to claim 1, characterized in that: The material of the second gate oxide layer in step six is silicon dioxide.