CN114334688A - Method for detecting metal film defect - Google Patents
Method for detecting metal film defect Download PDFInfo
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- CN114334688A CN114334688A CN202111561816.8A CN202111561816A CN114334688A CN 114334688 A CN114334688 A CN 114334688A CN 202111561816 A CN202111561816 A CN 202111561816A CN 114334688 A CN114334688 A CN 114334688A
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Abstract
The invention provides a method for detecting defects of a metal film, which comprises the steps of firstly forming the metal film with copper precipitates on a semiconductor substrate, then executing a wet cleaning process to form holes corresponding to the copper precipitates on the surface of the metal film, wherein in the process of executing the wet cleaning process, a cleaning solution of the wet cleaning process can chemically react with the copper precipitates on the surface of the metal film to form the holes, and the defect distribution of the copper precipitates on the surface of the metal film can be simply, accurately and quickly obtained through the holes. Further, by scanning the metal thin film to obtain the number of voids in a predetermined region of the surface of the metal thin film, the copper precipitate defects of the surface of the metal thin film can be quantified, whereby the content of the copper precipitate defects of the metal thin film can be characterized, thereby evaluating the quality of the metal thin film by the content of the copper precipitates.
Description
Technical Field
The invention relates to the technical field of semiconductor manufacturing, in particular to a method for detecting defects of a metal film.
Background
In a manufacturing process of a semiconductor device, a metal thin film is generally formed on a semiconductor substrate, and the metal thin film may be used as a metal connection line. In order to ensure the electron transport property of the metal thin film, an alloy including copper is used as the material of the metal thin film. However, when the deposition of the metal thin film is performed, it is necessary to pass through a metal thin film deposition apparatus, a metal etching apparatus, a dry stripping apparatus, a chemical vapor deposition apparatus, and the like, and since the process has a high temperature of 200 degrees celsius or more, if the residence time of the semiconductor substrate is too long, copper is easily precipitated, and copper precipitates which are difficult to be etched are formed. On the one hand, the copper precipitates are more difficult to etch and more likely to cause short circuits between metal lines, thereby rendering the conductive metal interconnects ineffective. On the other hand, in the subsequent cleaning process, since the chemical potentials of the alloys in the metal thin film are different, if the metal thin film is placed in an electrolyte solution, a so-called galvanic reaction occurs, causing electrochemical corrosion.
At present, defect detection of copper precipitates in a metal thin film is analyzed and judged by a FIB (Focused Ion beam) analysis method. In the FIB, an ion beam generated by a liquid metal (Ga) ion source is accelerated by an ion gun, focused, and irradiated on the surface of a sample to generate a secondary electron signal, thereby obtaining an electron image. However, because FIB is costly and time-consuming, it requires precise positioning to capture the copper precipitation defect, and if the positioning is not accurate to capture the area of the copper precipitation defect, it is difficult to detect the area of the copper precipitation defect, which requires much time and is not quantitative, and the quality of the metal film cannot be evaluated.
Disclosure of Invention
The invention aims to provide a method for detecting defects of a metal film, which can simply, accurately and quickly obtain the defects of copper precipitates of the metal film.
It is another object of the present invention to quantify copper precipitation defects in a metal film to evaluate the quality of the metal film.
In order to achieve the above object, the present invention provides a method for detecting a defect of a metal thin film, the method comprising:
providing a semiconductor substrate;
forming a metal thin film on the semiconductor substrate, the metal thin film having copper precipitates on a surface thereof;
performing a wet cleaning process to form a void corresponding to the copper precipitate on the surface of the metal thin film;
and scanning the metal film to obtain the number of the holes in the preset area on the surface of the metal film.
Optionally, in the method for detecting defects of a metal film, the metal film is made of an aluminum-copper alloy, and the metal film is formed by a physical vapor deposition process.
Optionally, in the method for detecting defects of a metal film, the content of copper in the metal film is 0.1% to 0.5%.
Optionally, in the method for detecting defects of a metal thin film, the thickness of the metal thin film is 0.1 μm to 10 μm.
Optionally, in the method for detecting defects of a metal thin film, the wet cleaning process is a soaking cleaning process and/or a spraying cleaning process.
Optionally, in the method for detecting defects of a metal film, the cleaning solution adopted in the wet cleaning process includes diluted hydrofluoric acid, hydrogen peroxide and hydrochloric acid.
Optionally, in the method for detecting defects of a metal thin film, the time for performing the wet cleaning process is 10min to 60 min.
Optionally, in the method for detecting defects of a metal thin film, the surface of the metal thin film is a flat surface, the copper precipitates are embedded in the surface of the metal thin film, and the copper precipitates are in the metal thin film.
Optionally, in the method for detecting defects of a metal thin film, the method for scanning the metal thin film includes:
scanning a preset area on the surface of the metal film through a scanning electron microscope to obtain the number of the holes in the preset area.
Optionally, in the method for detecting defects of a metal film, a cross section of a predetermined region on the surface of the metal film in the horizontal direction is rectangular, circular or triangular; the area of the predetermined region is 100 μm 2-1000 μm 2.
In the method for detecting the defects of the metal thin film, the metal thin film with the copper precipitates is firstly formed on the semiconductor substrate, then the wet cleaning process is carried out to form the holes corresponding to the copper precipitates on the surface of the metal thin film, and in the process of carrying out the wet cleaning process, the cleaning liquid of the wet cleaning process and the copper precipitates on the surface of the metal thin film are subjected to chemical reaction to form the holes, so that the defect distribution of the copper precipitates of the metal thin film can be simply, accurately and quickly obtained through the holes. Further, by scanning the metal thin film to obtain the number of voids in a predetermined region of the surface of the metal thin film, the copper precipitate defects of the surface of the metal thin film can be quantified, whereby the content of the copper precipitate defects of the metal thin film can be characterized, thereby evaluating the quality of the metal thin film by the content of the copper precipitates.
Drawings
FIG. 1 is a schematic flow chart of a method for detecting defects in a metal thin film according to an embodiment of the present invention;
FIG. 2 is a schematic cross-sectional view of a metal film in a method for detecting defects in a metal film according to an embodiment of the present invention;
FIG. 3 is a plan view of a metal thin film in the method for detecting defects in a metal thin film according to the embodiment of the present invention;
wherein the reference numerals are as follows:
100-a semiconductor substrate; 110-a metal thin film; 110A-copper precipitate; 110B-holes.
Detailed Description
The method for detecting defects of a metal thin film according to the present invention will be described in detail with reference to the accompanying drawings and specific examples. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
FIG. 1 is a schematic flow chart of a method for detecting defects in a metal thin film according to an embodiment of the present invention. As shown in fig. 1, the present embodiment provides a method for detecting a defect of a metal thin film, including:
step S1: providing a semiconductor substrate;
step S2: forming a metal thin film on the semiconductor substrate, the metal thin film having copper precipitates on a surface thereof;
step S3: performing a wet cleaning process to form a void corresponding to the copper precipitate on the surface of the metal thin film;
step S4: and scanning the metal film to obtain the number of the holes in the preset area on the surface of the metal film.
FIG. 2 is a schematic cross-sectional view of a metal film in a method for detecting defects in a metal film according to an embodiment of the present invention; fig. 3 is a plan view of a metal thin film in the method for detecting a defect in a metal thin film according to the embodiment of the present invention. Next, the above steps will be described in more detail with reference to FIGS. 2 to 3.
As shown in fig. 2, in step S1, a semiconductor substrate 100 is provided, and the semiconductor substrate 100 may be any suitable substrate known to those skilled in the art, such as at least one of the following materials: silicon, germanium, silicon carbon, silicon germanium carbon, indium arsenide, gallium arsenide, indium phosphide, silicon on insulator, silicon germanium on insulator, or the like. In this embodiment, the semiconductor substrate 100 is a silicon substrate.
In this embodiment, in order to better detect the defect of the metal thin film 110, before forming the metal thin film 110 on the semiconductor substrate 100, the method for detecting the defect of the metal thin film 110 further includes: firstly, cleaning the semiconductor substrate 100 to remove contaminants such as residual particles attached to the surface of the semiconductor substrate 100, for example, the surface of the semiconductor substrate 100 may be cleaned with a hydrofluoric acid or hydrochloric acid solution for 3min to 4min, and then the surface of the semiconductor substrate 100 is rinsed with deionized water; and then, drying the semiconductor substrate 100 to remove moisture attached to the surface of the semiconductor substrate 100, wherein the drying temperature can be 250-280 ℃, and the drying time can be 1-2 min.
As shown in fig. 2, in step S2, a metal thin film 110 is formed on the semiconductor substrate 100, and the surface of the metal thin film 110 has copper precipitates 110A. The surface of the metal thin film 110 is flat, the copper precipitates 110A are embedded in the surface of the metal thin film 110, and the copper precipitates 110A are contained in the metal thin film 110. Specifically, the metal film 110 is a copper-doped aluminum film, and the metal film 110 is formed by a physical vapor deposition process. The metal film 110 may be used as a metal layer in an interconnect structure for electrically connecting devices on the semiconductor substrate 100. In addition, a transistor and/or a dielectric layer are formed between the semiconductor substrate 100 and the metal thin film 110, and for better illustration of the present invention, in this embodiment, a description of a transistor and/or a dielectric layer between the semiconductor substrate 100 and the metal thin film 110 is omitted, and accordingly, in fig. 2 to 3, a diagram of a transistor and/or a dielectric layer between the semiconductor substrate 100 and the metal thin film 110 is omitted.
In the process of forming the metal thin film 110, the semiconductor substrate 100 is placed in a chamber of a physical vapor deposition process machine, and parameters such as temperature and power are set, for example, the temperature can be set to 400 ℃ to 700 ℃, and the power is 5000W to 8000W, wherein the higher the power is, the faster the rate of forming the metal thin film 110 is. In this embodiment, the thickness of the metal thin film 110 is 0.1 μm to 10 μm.
The metal thin film 110 may be formed by vacuum evaporation, sputtering or ion plating in a physical vapor deposition process, where the vacuum evaporation is to heat and evaporate a metal material to be evaporated in a vacuum chamber, so that evaporated atoms or atomic groups are condensed on a substrate with a low temperature to form the metal thin film 110. In the sputtering process, charged ions obtain sufficient energy under the action of an electromagnetic field to bombard the surface of a solid target (i.e., a metal material), and plasma is sputtered from the surface of the target and emitted to the surface of the semiconductor substrate 100 with certain kinetic energy, so as to form a metal thin film 110 on the semiconductor substrate 100. The ion plating is to partially separate a gas or an evaporated substance by gas discharge under vacuum, and deposit the evaporated substance or a reactant thereof on the semiconductor substrate 100 while bombarding the gas ions or the evaporated substance particles to form the metal thin film 110.
Taking the example of forming the metal thin film 110 by a sputtering plating method, the metal thin film 110 is a copper-doped aluminum film, an aluminum target material used for sputtering plating contains 0.1% to 0.5% of copper, and in this embodiment, an aluminum target material contains 0.5% of copper. When forming the metal thin film 110 on the semiconductor substrate 100, plasma of aluminum and copper is sputtered to the surface of the semiconductor substrate 100, and the metal thin film 110 is formed on the surface of the semiconductor substrate 100. Since the metal thin film 110 is a copper-doped aluminum film, and the copper-doped aluminum film is accumulated with the film thickness at a high temperature, the heat accumulation is increased, which seriously affects the lattice size of the metal thin film 110, and thus, after the temperature of the metal thin film 110 is reduced, copper is precipitated from the solid solution to form copper precipitates (i.e., copper-rich phases) 110A on the surface and inside of the metal thin film 110. The copper precipitates 110A are distributed in the form of grains on the surface and inside the metal thin film 110. It should be understood herein that the distribution of the copper precipitates 110A is non-uniform, a part of the regions is more densely distributed, and another part of the regions is more dispersedly distributed.
As shown in fig. 3, in step S3, a wet cleaning process is performed to form voids 110B corresponding to the copper precipitates 110A on the surface of the metal thin film 110. In this embodiment, the wet cleaning process is a soaking cleaning process and/or a spraying cleaning process.
Preferably, the wet cleaning process is performed using a dip cleaning process. Specifically, the semiconductor substrate 100 is first soaked and cleaned, that is, the semiconductor substrate 100 with the metal thin film 110 is placed in a cleaning solution, and since the metal thin film 110 is a copper-doped aluminum film and the potentials of copper and aluminum are different, if the metal thin film 110 made of two metals, namely copper and aluminum, is placed in an electrolyte solution, a galvanic reaction occurs, resulting in electrochemical corrosion. The cleaning solution includes at least one of diluted hydrofluoric acid, hydrogen peroxide, and hydrochloric acid, and the diluted hydrofluoric acid, hydrogen peroxide, or hydrochloric acid has a higher etching rate for the copper precipitates 110A than for aluminum, and thus, the cleaning solution chemically reacts with the copper precipitates 110A on the surface of the metal thin film 110 during the wet cleaning process, thereby forming voids 110B at the copper precipitates 110A on the surface of the metal thin film 110.
In the cleaning process of the wet cleaning, it is possible to use one cleaning liquid at the same temperature, but in this case, the reaction rate of the copper precipitates 110A with the cleaning liquid is gradually decreased as the cleaning liquid is consumed, and at the same time, the reaction rate of the copper precipitates 110A with the cleaning liquid is decreased as the soaking time of the cleaning liquid is increased. Therefore, in order to increase the reaction rate between the copper precipitates 110A and the cleaning liquid, it is possible to use one cleaning liquid and raise the temperature from 20 ℃ to 50 ℃, but it is needless to say that a plurality of cleaning liquids may be used according to the reaction rates at different temperatures of the different cleaning liquids, and the order of changing the cleaning liquids may be changed in the order of the optimum cleaning temperatures of the different cleaning liquids from low to high.
For example, in the present embodiment, three kinds of cleaning liquids are common: the first cleaning solution has the best effect at 20 ℃, the second cleaning solution has the best effect at 30 ℃, and the third cleaning solution has the best effect at 40 ℃. The steps of performing the wet cleaning process are as follows: the semiconductor substrate 100 having the metal thin film 110 is first soaked with the first cleaning solution at 20 ℃ for a certain period of time, then the second cleaning solution is changed to soak the semiconductor substrate 100 at 30 ℃ for a certain period of time, and then the third cleaning solution is changed to soak at 40 ℃ for a certain period of time. The first middle cleaning liquid can be diluted hydrofluoric acid, the second cleaning liquid can be hydrogen peroxide, and the third cleaning liquid can be hydrochloric acid.
In the wet cleaning process, the cleaning solution may penetrate into the copper precipitates 110A from the surfaces of the copper precipitates 110A on the surface of the metal thin film, thereby forming the cavities 110B on the surface of the metal thin film 110. In this embodiment, the wet cleaning process is performed for 10min to 60min, for example, 20min, to ensure that the cleaning solution and the copper precipitates 110A can generate sufficient chemical reaction, so that the holes 110B in the metal thin film 110 have a certain size, and if the size of the holes 110B is smaller, the holes are not easily found in the subsequent scanning, thereby causing the problem of inaccurate detection result.
In another embodiment, the wet cleaning process is performed by a spray cleaning process, wherein the spray cleaning process is performed by spraying at least one cleaning solution of diluted hydrofluoric acid, hydrogen peroxide and hydrochloric acid onto the surface of the metal film 110, and the cleaning solution chemically reacts with the copper precipitates 110A on the surface of the metal film 110 to form the voids 110B on the surface of the metal film 110.
In step S4, the metal film 110 is scanned to obtain the number of cavities 110B in the predetermined area L on the surface of the metal film 110. Specifically, the method for scanning the metal thin film 110 includes: scanning a predetermined area L on the surface of the metal thin film 110 by a Scanning Electron Microscope (SEM) to obtain the number of the cavities 110B in the predetermined area L. The defect distribution of the copper precipitates 110A of the metal thin film 110 can be simply, accurately and rapidly obtained by the voids 110B. Further, by scanning the metal thin film 110 to obtain the number of voids 110B in the predetermined region L on the surface of the metal thin film 110, the copper precipitate 110A defects on the surface of the metal thin film 110 can be quantified, whereby the content of the copper precipitate 110A defects of the metal thin film 110 can be characterized, thereby evaluating the quality of the metal thin film 110 by the content of the copper precipitate 110A.
In this embodiment, the section of the predetermined region L on the surface of the metal thin film 110 in the horizontal direction is rectangular, circular or triangular, and in this embodiment, the section of the predetermined region L on the surface of the metal thin film 110 in the horizontal direction is illustrated as a rectangle (as shown in fig. 3). The predetermined region L has an area of 100 μm2～1000μm2Here, it should be noted that the area of the predetermined region on the surface of the metal thin film 110 can be determined according to the distribution of the holes 110B, if a certain region on the surface of the metal thin film 110 is selected for scanning, and the number of the holes 110B in the region is large, the range of the region can be reduced, and if the number of the holes 110B in the region is small, the range of the region can be expanded, so as to ensure that the holes 110B can pass through accuratelyThe quality of the metal thin film 110 was evaluated. By evaluating the quality of the metal film 110, the forming process of the metal film 110 can be modified, so that the metal film 110 with better quality is formed, and the reliability of the interconnection structure is optimized.
In summary, in the method for detecting defects of a metal thin film according to the present invention, a metal thin film having copper precipitates is formed on a semiconductor substrate, and then a wet cleaning process is performed to form voids corresponding to the copper precipitates on the surface of the metal thin film. Further, by scanning the metal thin film to obtain the number of voids in a predetermined region of the surface of the metal thin film, the copper precipitate defects of the surface of the metal thin film can be quantified, whereby the content of the copper precipitate defects of the metal thin film can be characterized, thereby evaluating the quality of the metal thin film by the content of the copper precipitates.
The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.
Claims (10)
1. A method for detecting a defect of a metal thin film, the method comprising:
providing a semiconductor substrate;
forming a metal thin film on the semiconductor substrate, the metal thin film having copper precipitates on a surface thereof;
performing a wet cleaning process to form a void corresponding to the copper precipitate on the surface of the metal thin film;
and scanning the metal film to obtain the number of the holes in the preset area on the surface of the metal film.
2. The method of claim 1, wherein the metal film is a copper-doped aluminum film, and the metal film is formed by physical vapor deposition.
3. The method for detecting defects in a metal film as claimed in claim 2, wherein the content of copper in the metal film is 0.1% to 0.5%.
4. The method for detecting defects in a metal thin film according to any one of claims 1 to 3, wherein the metal thin film has a thickness of 0.1 μm to 10 μm.
5. The method of claim 1, wherein the wet cleaning process is a dip cleaning process and/or a spray cleaning process.
6. The method for detecting defects in a metal film as claimed in claim 5, wherein the wet cleaning process employs a cleaning solution comprising at least one of diluted hydrofluoric acid, hydrogen peroxide and hydrochloric acid.
7. The method of claim 1, wherein the wet cleaning process is performed for a time period of 10min to 60 min.
8. The method according to claim 1, wherein the surface of the metal thin film is flat, the copper precipitates are embedded in the surface of the metal thin film, and the copper precipitates are present in the metal thin film.
9. The method of detecting defects in a metal film of claim 1, wherein the method of scanning the metal film comprises:
scanning a preset area on the surface of the metal film through a scanning electron microscope to obtain the number of the holes in the preset area.
10. The method of detecting defects in a metal film as set forth in claim 9, wherein the predetermined area of the surface of the metal film has a rectangular, circular or triangular cross-section in the horizontal direction; the predetermined region has an area of 100 μm2～1000μm2。
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| CN202111561816.8A CN114334688A (en) | 2021-12-16 | 2021-12-16 | Method for detecting metal film defect |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115876823A (en) * | 2023-01-19 | 2023-03-31 | 合肥晶合集成电路股份有限公司 | Film defect detection method, film defect detection device and film defect detection system |
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2021
- 2021-12-16 CN CN202111561816.8A patent/CN114334688A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115876823A (en) * | 2023-01-19 | 2023-03-31 | 合肥晶合集成电路股份有限公司 | Film defect detection method, film defect detection device and film defect detection system |
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