Formation method of semiconductor structure
By removing by-products of the metal silicide layer by using two pickling treatments and sonication treatments in semiconductor manufacturing, the problems of the impact of pollution sources in the prior art are solved, and product yield and stability are improved.
Patent Information
- Application Number
- CN202410011293.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-03
- Publication Date
- 2025-07-04
AI Technical Summary
The prior art is susceptible to a variety of pollution sources in the process of forming metal silicides, resulting in by-product residues, affecting product yields and being difficult to prevent. The existing air filters cannot effectively monitor and prevent trace pollution.
Two pickling treatments were used to remove the by-products generated by the initial metal silicide layer, and the metal layer was covered with the sonication and protective layer to isolate the oxygen to form the metal silicide layer.
It improves product yield, maintains good growth of metal silicides under different air filter efficiency conditions, reduces the impact of impurity pollution, and avoids product scrapping caused by environmental complexity.
Smart Images
Figure CN120261287A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular, to a method for forming a semiconductor structure. Background Art
[0002] The formation of self-aligned metal silicide is a key process in semiconductor integrated circuit manufacturing. The technology involved in this process is very complex, and the quality of the formed metal silicide directly affects the electrical performance, uniformity, and reliability of the devices on the entire semiconductor. Moreover, this process is sensitive to minute contamination, and the process undergoes two thermal reactions and one pickling with multiple acids. Minute contaminants from various sources are likely to participate in the reaction during the process and generate many by-products that are difficult to trace back to their sources. Therefore, in this process, it is crucial to control air pollution, reaction by-product residues, and metal contamination.
[0003] However, there are still many problems in the prior art during the formation of metal silicide. Summary of the Invention
[0004] The technical problem solved by the present invention is to provide a method for forming a semiconductor structure to improve the yield of products.
[0005] To solve the above problems, the technical solution of the present invention provides a method for forming a semiconductor structure, including: providing a substrate; forming a silicon layer in the substrate; forming a metal layer on the silicon layer; performing a first heat treatment on the metal layer and the silicon layer to form an initial metal silicide layer; removing the remaining metal layer by a first pickling treatment; after the first pickling treatment, performing a second pickling treatment on the initial metal silicide layer to remove by-products generated during the formation of the initial metal silicide layer; after the second pickling treatment, performing a second heat treatment on the initial metal silicide layer to form a metal silicide layer.
[0006] Optionally, before performing the first heat treatment, it further includes: forming a protective layer on the substrate, and the protective layer covers the metal layer.
[0007] Optionally, the substrate includes an active region; before forming the silicon layer, it further includes: forming a gate structure on the substrate, and the gate structure straddles the active region.
[0008] Optionally, the silicon layer is formed in the active regions on both sides of the gate structure.
[0009] Optionally, the material of the metal layer includes: cobalt, nickel, or titanium.
[0010] Optionally, the material of the protective layer includes: titanium nitride.
[0011] Optionally, the parameters of the first heat treatment include: the heat treatment temperature is 450 °C to 550 °C; the heat treatment time is 20 seconds to 40 seconds.
[0012] Optionally, the parameters of the first pickling treatment include: the pickling solution includes: nitric acid, phosphoric acid and acetic acid; the pickling temperature is 55 °C to 75 °C; wherein, the solution concentration of nitric acid is 55% to 65%; the solution concentration of phosphoric acid is 80% to 90%; the solution concentration of acetic acid is 55% to 65%; the flow rate ratio of nitric acid, phosphoric acid and acetic acid is (31.5 to 38.5):(0.9 to 1.1):(5.4 to 6.6).
[0013] Optionally, the parameters of the second pickling treatment include: the pickling solution includes: sulfuric acid and hydrogen peroxide; the pickling temperature is 15 °C to 35 °C; wherein, the solution concentration of sulfuric acid is 95% to 98%; the solution concentration of hydrogen peroxide is 20% to 35%; the flow rate ratio of sulfuric acid, hydrogen peroxide and water is (2.7 to 3.3):(6.3 to 7.7):(45 to 55).
[0014] Optionally, during the second pickling treatment, ultrasonic treatment is further included.
[0015] Optionally, the parameters of the ultrasonic treatment include: the ultrasonic frequency is 200 W to 500 W.
[0016] Optionally, the parameters of the second heat treatment include: the heat treatment temperature is 750 °C to 850 °C; the heat treatment time is 10 seconds to 30 seconds.
[0017] Optionally, the by-products include: one or more of fluoride ions, chloride ions, sulfide ions, sulfate ions and ammonia gas generated with the metal layer.
[0018] Optionally, the forming process of the metal layer includes: physical vapor deposition process.
[0019] Compared with the prior art, the technical solution of the present invention has the following advantages:
[0020] In the method for forming a semiconductor structure of the technical solution of the present invention, the second pickling treatment is added to remove the by-products generated during the formation of the initial metal silicide layer. Starting from the process flow itself, without artificial intervention in unpredictable environmental indicators, good growth of metal silicide can be achieved under any filtration efficiency conditions of the air filter, changing the current situation that the metal silicide process is sensitive to impurity pollution and has no way to prevent complex environmental sources, and thereby improving the product yield.
[0021] Further, before performing the first heat treatment, it further includes: forming a protective layer on the substrate, and the protective layer covers the metal layer. The metal layer is covered by the protective layer to isolate oxygen, thereby reducing the by-products of metal oxide formation during the first heat treatment.
[0022] Further, during the second pickling treatment, it further includes: ultrasonic treatment. Since the sulfuric acid solution used in the second pickling treatment has strong viscosity, the ultrasonic treatment is cooperated to improve the pickling effect. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figures 1 to 9 It is a schematic diagram of the structures of the steps in the formation process of the semiconductor structure in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0024] As described in the background art, there are still many problems in the prior art during the formation of metal silicide. The following will be specifically described.
[0025] Currently, the metal element used in the self-aligned metal silicide formation process is mostly cobalt. After elemental cobalt is deposited on the wafer surface by physical vapor deposition, titanium nitride is covered to isolate oxygen, and then rapid heat treatment is performed to form cobalt silicide. After removing the excess elemental cobalt by various pickling processes, further rapid heat treatment is performed to form cobalt disilicide with lower resistance phase. This process is extremely vulnerable to pollution sources from various sources. For example, ammonia often exists near chemical mechanical polishing, sulfate in the air due to coal burning in winter in the north, and chloride ions and fluoride ions that may exist near the pickling machine. All of these will chemically react with elemental cobalt at room temperature and cause the formation of self-aligned cobalt silicide to deviate from the preset in the subsequent process, resulting in the phenomenon of cobalt by-product residue or cobalt silicide deficiency, thereby causing yield loss and scrapping. According to long-term production and practical experience, once such problems occur, depending on the concentration of air pollutants near the execution process, the yield loss ranges from 10% to 30%. Moreover, since the wafer per hour (WPH) of this process is extremely high and the grown cobalt silicide cannot be reworked, if it cannot be monitored and stopped in time, it will cause a large-scale scrapping. There have been records of large-scale scrapping of hundreds or thousands of wafers in multiple factories.
[0026] Because the sources of pollution are diverse, and the by-products after ambient-temperature reaction, heating reaction, pickling, and secondary heating reaction of trace amounts of pollution are diverse and impossible to trace back to the source, it is generally impossible to monitor a certain type of pollution separately and prevent it specifically in a clean room. Currently, the commonly used air filters for each machine provided by the factory are all unified. Such filters adsorb impurities through targeted acid-base reactions and chemical reactions of inorganic compounds. Therefore, there is a certain adsorption limit. As the service life increases, the adsorption efficiency decreases, and such filters will gradually become ineffective. Under normal pollution source exposure conditions, the service life of the filter is about three years. Under conditions of increasing pollutant concentration, the service life will drop to one year or even several months. Because the pollution sources in the air will change with conditions such as surrounding machines, weather, and seasons, without real-time monitoring of the adsorption efficiency, it is impossible to estimate its service life, often resulting in unexpected failures of the filter within its service life, affecting the self-aligned cobalt silicide process, the product yield, and causing scrapping. The existing detectors have a monitoring lower limit of 0.1 ng / L for pollution sources such as sulfate radicals in the environment. Contents below this unit will not be detected, but about 0.1 ng / L * 10^-5 content of sulfate radicals is sufficient to cause cobalt deficiency on one side of the self-aligned cobalt silicide process. The research on the environment itself has also exceeded the requirements of a conventional clean room. Using higher-precision equipment to monitor the environment for a long time is beyond the budget and unrealistic.
[0027] On this basis, the present invention provides a method for forming a semiconductor structure, adding the second pickling treatment to remove the by-products generated during the formation of the initial metal silicide layer. By starting from the process flow itself and not artificially interfering with unpredictable environmental indicators, good growth of metal silicide can be achieved regardless of the filtration efficiency of the air filter, changing the current situation that the metal silicide process is sensitive to impurity pollution and unable to prevent complex environmental sources, and thereby improving the product yield.
[0028] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following specifically describes the embodiments of the present invention in detail with reference to the accompanying drawings.
[0029] Figures 1 to 9 It is a schematic diagram of the structures of each step in the formation process of the semiconductor structure in the embodiment of the present invention.
[0030] Please refer to Figure 1 , provide a substrate 100, and the substrate 100 includes an active region (not labeled).
[0031] In this embodiment, the material of the substrate 100 is silicon; in other embodiments, the material of the substrate may also be germanium, silicon germanium, or silicon carbide; or the substrate may also be other materials, such as III-V compounds such as gallium arsenide.
[0032] Please refer to Figure 2 to form a gate structure 101 on the substrate 100, and the gate structure 101 straddles the active region.
[0033] The gate structure 101 includes: a gate dielectric layer and a gate layer (not labeled) located on the gate dielectric layer.
[0034] In this embodiment, the material of the gate dielectric layer is silicon oxide, and the material of the gate layer is polysilicon.
[0035] Please refer to Figure 3 to form a silicon layer 102 in the substrate 100.
[0036] The silicon layer 102 is formed in the active regions on both sides of the gate structure 101 to serve as source and drain electrodes on both sides of the gate structure 101.
[0037] The forming method of the silicon layer 102 includes: etching the active region using the gate structure 101 as a mask to form a groove (not labeled) in the active region; forming the silicon layer 102 in the groove.
[0038] Please refer to Figure 4 to form a metal layer 103 on the silicon layer 102.
[0039] The material of the metal layer 103 includes: cobalt, nickel or titanium; in this embodiment, the material of the metal layer 103 is cobalt.
[0040] The forming process of the metal layer 103 uses physical vapor deposition process.
[0041] Please refer to Figure 5 to form a protective layer 104 on the substrate 100, and the protective layer 104 covers the metal layer 103.
[0042] By covering the metal layer 103 with the protective layer 104 to isolate oxygen, thereby reducing the by-products of forming metal oxides during the subsequent first heat treatment process.
[0043] The material of the protective layer 104 is titanium nitride.
[0044] Please refer to Figure 6 to perform a first heat treatment 200 on the metal layer 103 and the silicon layer 102 to form an initial metal silicide layer 105.
[0045] The parameters of the first heat treatment 200 include: the heat treatment temperature is 450 °C to 550 °C; the heat treatment time is 20 seconds to 40 seconds.
[0046] In this embodiment, the parameters of the first heat treatment 200 include: the heat treatment temperature is 500 degrees Celsius; the heat treatment time is 30 seconds. The first heat treatment 200 causes the silicon layer 102 and the metal layer 103 to form cobalt silicide.
[0047] Please continue to refer to Figure 6 , after the first heat treatment 200, the protective layer 104 is removed.
[0048] Please refer to Figure 7 , the remaining metal layer 103 is removed by the first pickling treatment 201.
[0049] The parameters of the first pickling treatment 201 include: the pickling solution includes: nitric acid, phosphoric acid and acetic acid; the pickling temperature is 55 degrees Celsius to 75 degrees Celsius; among them, the solution concentration of nitric acid is 55% to 65%; the solution concentration of phosphoric acid is 80% to 90%; the solution concentration of acetic acid is 55% to 65%; the flow rate ratio of nitric acid, phosphoric acid and acetic acid is (31.5 to 38.5):(0.9 to 1.1):(5.4 to 6.6).
[0050] In this embodiment, the parameters of the first pickling treatment 201 include: the pickling solution includes: nitric acid, phosphoric acid and acetic acid; the pickling temperature is 70 degrees Celsius; among them, the solution concentration of nitric acid is 60%; the solution concentration of phosphoric acid is 85%; the solution concentration of acetic acid is 60%; the flow rate ratio of nitric acid, phosphoric acid and acetic acid is 35:1:6.
[0051] It should be noted that in this embodiment, since the metal layer 103 will generate cobalt hydroxide at room temperature under the condition of trace ammonia and cobalt oxide at 200 degrees Celsius, and the heat treatment temperature of the first heat treatment 200 can be as high as 500 degrees Celsius, the generated cobalt oxide will continue to absorb oxygen atoms to become high-valent cobalt (cobalt trioxide or cobalt tetroxide) at continuous high temperature, and cobalt higher oxide cannot be dissolved by pickling with nitric acid, phosphoric acid and acetic acid, so there will be a bulging or stacking morphology, deviating from the preset.
[0052] Please refer to Figure 8 , after the first pickling treatment 201, the initial metal silicide layer 105 is subjected to a second pickling treatment 202 to remove by-products (not shown) generated during the formation of the initial metal silicide layer 105.
[0053] By starting from the process flow itself and not artificially interfering with unforeseeable environmental indicators, good growth of metal silicide can be achieved regardless of the filtration efficiency of the air filter, changing the current situation that the metal silicide process is sensitive to impurity pollution and has no way to prevent complex environmental sources, and improving the yield of products accordingly.
[0054] The parameters of the second pickling treatment 202 are as follows: The pickling solution includes sulfuric acid and hydrogen peroxide; the pickling temperature is 15°C to 35°C; among them, the solution concentration of sulfuric acid is 95% to 98%; the solution concentration of hydrogen peroxide is 20% to 35%; the flow rate ratio of sulfuric acid, hydrogen peroxide and water is (2.7 to 3.3):(6.3 to 7.7):(45 to 55).
[0055] In this embodiment, the parameters of the second pickling treatment 202 are as follows: The pickling solution includes sulfuric acid and hydrogen peroxide; the pickling temperature is 125°C; among them, the solution concentration of sulfuric acid is 98%; the solution concentration of hydrogen peroxide is 30%; the flow rate ratio of sulfuric acid, hydrogen peroxide and water is 3:7:50.
[0056] In this embodiment, the second pickling treatment 202 can remove the by-products generated by the metal layer 103 due to contact with contaminants containing one or more of fluoride ions, chloride ions, sulfide ions, sulfate ions and ammonia.
[0057] It should be noted that in this embodiment, the conditions of the second pickling treatment 202 are determined by experiments, and precise control of concentration and temperature is required to ensure complete removal of cobalt oxide, thereby eliminating the bulging or stacking morphology of the subsequently formed metal silicide layer.
[0058] During the second pickling treatment 202, ultrasonic treatment is also included. Since the sulfuric acid solution used in the second pickling treatment 202 has strong viscosity, ultrasonic treatment is used to improve the pickling effect.
[0059] The parameters of the ultrasonic treatment include: the ultrasonic frequency is 200 W to 500 W.
[0060] In this embodiment, the ultrasonic frequency in the ultrasonic treatment is 300 W.
[0061] Please refer to Figure 9 , after the second pickling treatment 202, the initial metal silicide layer 105 is subjected to a second heat treatment 203 to form a metal silicide layer 106.
[0062] The initial metal silicide layer 105 is heat-treated at a higher temperature to form the metal silicide layer 106.
[0063] The parameters of the second heat treatment 203 include: the heat treatment temperature is 750°C to 850°C; the heat treatment time is 10 seconds to 30 seconds.
[0064] In this embodiment, the parameters of the second heat treatment 203 include: the heat treatment temperature is 840 degrees Celsius; the heat treatment time is 30 seconds. The second heat treatment 203 causes the cobalt silicide to form cobalt disilicide with a lower resistance phase.
[0065] 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 should be subject to the scope defined by the claims.
Claims
1. A method for forming a semiconductor structure, characterized in that, Comprising: Providing a substrate; Forming a silicon layer within the substrate; Forming a metal layer on the silicon layer; Performing a first heat treatment on the metal layer and the silicon layer to form an initial metal silicide layer; Removing the remaining metal layer by a first pickling treatment; After the first pickling treatment, performing a second pickling treatment on the initial metal silicide layer to remove by-products generated during the formation of the initial metal silicide layer; After the second pickling treatment, performing a second heat treatment on the initial metal silicide layer to form a metal silicide layer.
2. The method for forming a semiconductor structure according to claim 1, wherein Before performing the first heat treatment, further comprising: forming a protective layer on the substrate, the protective layer covering the metal layer.
3. The method for forming a semiconductor structure according to claim 1, wherein, The substrate includes an active region; before forming the silicon layer, further comprising: forming a gate structure on the substrate, the gate structure spanning the active region.
4. The method for forming a semiconductor structure as described in claim 3, wherein The silicon layer is formed within the active regions on both sides of the gate structure.
5. The method for forming a semiconductor structure according to claim 1, wherein, The material of the metal layer includes: cobalt, nickel or titanium.
6. The method for forming the semiconductor structure according to claim 2, wherein The material of the protective layer includes: titanium nitride.
7. The method for forming a semiconductor structure as claimed in claim 1, wherein The parameters of the first heat treatment include: the heat treatment temperature is 450 °C to 550 °C; the heat treatment time is 20 seconds to 40 seconds.
8. The method for forming a semiconductor structure as described in claim 1, wherein, The parameters of the first pickling treatment include: the pickling solution includes: nitric acid, phosphoric acid and acetic acid; the pickling temperature is 55 °C to 75 °C; wherein, the solution concentration of nitric acid is 55% to 65%; the solution concentration of phosphoric acid is 80% to 90%; the solution concentration of acetic acid is 55% to 65%; the flow rate ratio of nitric acid, phosphoric acid and acetic acid is (31.5 to 38.5):(0.9 to 1.1):(5.4 to 6.6).
9. The method for forming a semiconductor structure as claimed in claim 1, wherein, The parameters of the second pickling treatment include: the pickling solution includes: sulfuric acid and hydrogen peroxide; the pickling temperature is 15 °C to 35 °C; wherein, the solution concentration of sulfuric acid is 95% to 98%; the solution concentration of hydrogen peroxide is 20% to 35%; the flow rate ratio of sulfuric acid, hydrogen peroxide and water is (2.7 to 3.3):(6.3 to 7.7):(45 to 55).
10. The method for forming a semiconductor structure according to claim 9, wherein, During the second pickling treatment, further comprising: ultrasonic treatment.
11. The method for forming the semiconductor structure according to claim 10, wherein The parameters of the ultrasonic treatment include: the ultrasonic frequency is 200 watts to 500 watts.
12. The method for forming a semiconductor structure according to claim 1, wherein, The parameters of the second heat treatment include: the heat treatment temperature is 750 °C to 850 °C; the heat treatment time is 10 seconds to 30 seconds.
13. The method for forming a semiconductor structure as described in claim 1, wherein, The by-products include: those generated by one or more of fluoride ions, chloride ions, sulfide ions, sulfate ions and ammonia gas with the metal layer.
14. The method for forming a semiconductor structure as described in claim 1, wherein, The forming process of the metal layer includes: physical vapor deposition process.