Method for detecting germanium-silicon deep trench defects
By removing the hard mask layer to expose the sidewalls of SiGe deep trenches, the method enables effective SEM scanning for defect detection, overcoming the detection challenges posed by the hard mask obstruction.
Patent Information
- Application Number
- CN202411215478.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2024-12-13
AI Technical Summary
The roughness of the bottom and sidewalls of SiGe deep trenches is difficult to detect due to being obscured by the hard mask sidewalls, making traditional SEM electron scanning ineffective.
A method involving the removal of the hard mask layer to expose the sidewalls of the SiGe deep trench, followed by scanning for defects using a SEM electron scanning microscope.
Enhances the detectability of defects in SiGe deep trenches by exposing uneven surfaces for clear SEM scanning, improving defect detection accuracy.
Smart Images
Figure CN119132990A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of semiconductor manufacturing, and in particular to a method for detecting defects in silicon germanium deep trenches. Background Art
[0002] With the rapid development of VLSI technology, device size continues to shrink. In order to improve the performance of PMOS devices, silicon germanium (SiGe) is introduced into the CMOS process as a stress source for the source and drain regions of PMOS. It increases the operating current of PMOS devices by providing compressive stress to the channel and increasing the mobility of holes.
[0003] As the integration of chips becomes higher and higher and the speed becomes faster and faster, the shape of SiGe filled in the source and drain regions of PMOS has changed from U-shaped to Σ-shaped, similar to the shape of a diamond profile. This Σ-shaped morphology has a great impact on the performance of PMOS. The control of SiGe Σ-shaped brings great challenges to the dry etching process. On the one hand, we need to pay attention to whether the Σ-shaped meets the requirements, which is mainly confirmed by online measurement and slicing; on the other hand, we need to pay attention to the uniformity and stability of the Σ-shaped within the wafer surface and between wafers, which is mainly confirmed by online measurement and defect scanning technology.
[0004] However, in actual operation, the morphology of the SiGe trench after etching is located below the active area between the two polysilicon layers. Together with the height of the polysilicon layer, the total depth reaches 1300 angstroms to 1500 angstroms. The roughness of the bottom of the trench is difficult to detect with a traditional SEM electron scanning microscope. Moreover, the roughness of the sidewalls is blocked by the hard mask sidewalls and cannot be detected (e.g. Figure 1 shown). Summary of the invention
[0005] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for detecting defects in SiGe deep trenches, so as to solve the problem that the rough topography of the existing SiGe deep trenches is difficult to be scanned.
[0006] To achieve the above-mentioned object and other related objects, the present invention provides a method for detecting defects in silicon germanium deep trenches, the method comprising:
[0007] A semiconductor structure is provided, comprising a substrate, a gate structure formed on a surface of the substrate, a first mask layer formed on a surface of the gate structure, and a first spacer formed on a sidewall of the gate structure and the first mask layer;
[0008] forming a hard mask layer on the surface of the semiconductor structure, and patterning the hard mask layer to expose the substrate on both sides of the gate structure;
[0009] Etching the exposed substrate to form a Σ-shaped SiGe deep trench, wherein the bottom and sidewalls of the SiGe deep trench have a certain degree of roughness, and at this time, the hard mask layer forms a second sidewall on the surface of the first sidewall;
[0010] Removing the hard mask layer to remove the second sidewall spacer, so that there is no barrier on the sidewall of the rough silicon germanium deep trench;
[0011] The semiconductor structure is scanned for defects.
[0012] Optionally, before removing the second spacer, the method further comprises a step of wet cleaning the semiconductor structure.
[0013] Optionally, the material of the hard mask layer includes silicon nitride.
[0014] Optionally, the semiconductor structure is further formed with a lightly doped drain region.
[0015] Optionally, the gate structure includes a gate oxide layer and a polysilicon layer formed on a surface of the gate oxide layer.
[0016] Optionally, when etching the exposed substrate to form the SiGe deep trench, a plasma etching self-alignment process is firstly adopted, and then a wet etching process is adopted.
[0017] Optionally, the sidewalls of the SiGe deep trench are detected by conventional SEM scanning.
[0018] Optionally, the applicable technology node is less than or equal to 28 nm.
[0019] As described above, the method for detecting defects in the germanium silicon deep trench of the present invention, before scanning the defects, exposes the uneven defects on the side walls of the germanium silicon deep trench by removing the hard mask layer, so that the defects can be easily scanned by a SEM electron scanning microscope, thereby improving the detectability of the defects. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 The electron microscope image showing the existing semiconductor structure with a germanium-silicon deep trench formed after SEM scanning
[0021] Figure 2 Shown is a flow chart of a method for detecting defects in SiGe deep trenches according to the present invention.
[0022] Figure 3 It is a schematic cross-sectional structure diagram of the semiconductor structure of the present invention after the hard mask is removed.
[0023] Figure 4 Shown as the present invention Figure 3 Scanning electron microscopy image of the structure shown. DETAILED DESCRIPTION
[0024] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.
[0025] See also Figures 1 to 4 It should be noted that the illustrations provided in this embodiment are only schematic illustrations of the basic concept of the present invention. Although the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation, the form, quantity and proportion of each component in actual implementation may be changed arbitrarily, and the component layout may also be more complicated.
[0026] like Figure 2 As shown, this embodiment provides a method for detecting defects in silicon germanium deep trenches, the method comprising:
[0027] A semiconductor structure is provided, comprising a substrate, a gate structure formed on a surface of the substrate, a first mask layer formed on a surface of the gate structure, and a first spacer formed on a sidewall of the gate structure and the first mask layer;
[0028] forming a hard mask layer on the surface of the semiconductor structure, and patterning the hard mask layer to expose the substrate on both sides of the gate structure;
[0029] Etching the exposed substrate to form a Σ-shaped SiGe deep trench, wherein the bottom and sidewalls of the SiGe deep trench have a certain degree of roughness, and at this time, the hard mask layer forms a second sidewall on the surface of the first sidewall;
[0030] Removing the hard mask layer to remove the second sidewall spacer, so that there is no barrier on the sidewall of the rough silicon germanium deep trench;
[0031] The semiconductor structure is scanned for defects.
[0032] In this embodiment, Figure 3 The semiconductor structure after the hard mask layer is removed is shown, and the structure is scanned by SEM. Figure 4 As shown in the figure, it can be seen that the rough morphology of the sidewall of the SiGe deep trench is scanned out. In this embodiment, the SiGe deep trench has a certain roughness, that is, the SiGe deep trench has high and low undulation defects.
[0033] Specifically, before removing the second sidewall spacer, the method further includes a step of wet cleaning the semiconductor structure.
[0034] Specifically, the material of the hard mask layer includes silicon nitride.
[0035] Specifically, the semiconductor structure further forms a lightly doped drain region.
[0036] Specifically, the gate structure includes a gate oxide layer and a polysilicon layer formed on the surface of the gate oxide layer.
[0037] Specifically, when etching the exposed substrate to form the SiGe deep trench, a plasma etching self-alignment process is firstly adopted, and then a wet etching process is adopted.
[0038] Specifically, the sidewalls of the SiGe deep trench are detected by conventional SEM scanning.
[0039] Specifically, the applicable technology node is less than or equal to 28nm.
[0040] In summary, the method for detecting defects in the germanium-silicon deep trench of the present invention exposes the uneven defects on the sidewalls of the germanium-silicon deep trench by removing the hard mask layer before scanning the defects, so that the defects can be easily scanned by a SEM electron scanning microscope, thereby improving the detection of defects. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.
[0041] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.
Claims
1. A method for detecting defects in deep trenches of silicon germanium, It is characterized in that The method comprises: A semiconductor structure is provided, comprising a substrate, a gate structure formed on a surface of the substrate, a first mask layer formed on a surface of the gate structure, and a first spacer formed on a sidewall of the gate structure and the first mask layer; forming a hard mask layer on the surface of the semiconductor structure, and patterning the hard mask layer to expose the substrate on both sides of the gate structure; Etching the exposed substrate to form a Σ-shaped SiGe deep trench, wherein the bottom and sidewalls of the SiGe deep trench have a certain degree of roughness, and at this time, the hard mask layer forms a second sidewall on the surface of the first sidewall; Removing the hard mask layer to remove the second sidewall spacer, so that there is no barrier on the sidewall of the rough silicon germanium deep trench; The semiconductor structure is scanned for defects.
2. The method for detecting defects in silicon germanium deep trenches according to claim 1, It is characterized in that Before removing the second spacer, the method further comprises a step of wet cleaning the semiconductor structure.
3. The method for detecting defects in silicon germanium deep trenches according to claim 1, It is characterized in that The material of the hard mask layer includes silicon nitride.
4. The method for detecting defects in silicon germanium deep trenches according to claim 1, It is characterized in that The semiconductor structure is also formed with a lightly doped drain region.
5. The method for detecting defects in silicon germanium deep trenches according to claim 1, It is characterized in that The gate structure includes a gate oxide layer and a polysilicon layer formed on the surface of the gate oxide layer.
6. The method for detecting defects in silicon germanium deep trenches according to claim 1, It is characterized in that When etching the exposed substrate to form the germanium silicon deep trench, a plasma etching self-alignment process is firstly adopted, and then a wet etching process is adopted.
7. The method for detecting defects in silicon germanium deep trenches according to claim 1, It is characterized in that The sidewalls of the SiGe deep trenches are detected by conventional SEM scanning.
8. The method for detecting defects in silicon germanium deep trenches according to claim 1, It is characterized in that Applicable technology nodes are less than or equal to 28nm.