Method for reducing metal ion content of PECVD (plasma enhanced chemical vapor deposition) machine

Abstract

The invention provides a method for reducing the metal ion content of a PECVD (Plasma Enhanced Chemical Vapor Deposition) machine. The method comprises the following steps: providing a plasma enhanced chemical vapor deposition machine; a common oxide layer of a cavity pre-deposition layer is replaced by an oxide layer with tensile stress on the inner wall of a process cavity of a plasma enhanced chemical vapor deposition machine and the surface of each component in the process cavity, and the length of an atomic bond of the oxide layer with the tensile stress is larger than that of the common oxide layer. The oxide layer with tensile stress can be shrunk back to the original position to form a bowl shape; and transferring the product into a process cavity of a plasma enhanced chemical vapor deposition machine, and then carrying out plasma enhanced chemical vapor deposition to form a thin film layer. The metal ion content can be effectively reduced, and meanwhile the output of a machine table is effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a method for reducing the metal ion content in a PECVD machine. Background Art

[0002] PECVD is widely used in the integrated circuit manufacturing process. Its film formation principle is that the material source enters the process chamber in the form of gas. Under the condition of RF power addition, the reaction gas obtains activation energy from the glow discharge (Plasma: plasma field), activates and enhances the chemical reaction, thereby realizing chemical vapor deposition. In the plasma, high-energy electrons impact the reactant gas molecules, activate and ionize them, generate highly reactive radical groups, and make the substrate produce more reactive surface nodes, thus starting and accelerating the chemical reaction at low temperature.

[0003] When manufacturing CIS (image sensor) products, the front-end machine has particularly high requirements for the metal ion content. When the PECVD machine deposits a film, the inside of the chamber is in the atmosphere of the plasma field. The plasma field will increase the thermal load of the reaction chamber. In this case, it is easy to extract trace metal elements in the internal components of the reaction chamber. If the machine manufactures products such as CIS (CMOS image sensor), metal ions will cause abnormal white pixels, affecting the quality of the products.

[0004] To solve the above problems, a new method for reducing the metal ion content in a PECVD machine needs to be proposed. Summary of the Invention

[0005] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method for reducing the metal ion content in a PECVD machine, which is used to solve the problem that when the PECVD machine deposits a film in the prior art, the inside of the chamber is in the atmosphere of the plasma field, the plasma field will increase the thermal load of the reaction chamber, and in this case, it is easy to extract trace metal elements in the internal components of the reaction chamber, affecting the quality of the products.

[0006] To achieve the above purpose and other related purposes, the present invention provides a method for reducing the metal ion content in a PECVD machine, including:

[0007] Step 1: Provide a plasma-enhanced chemical vapor deposition machine;

[0008] Step 2: Replace the ordinary oxide layer of the cavity pre-deposition layer with an oxide layer with tensile stress on the inner wall of the process chamber of the plasma-enhanced chemical vapor deposition machine and the surfaces of various components in the process chamber. The atomic bond length of the oxide layer with tensile stress is longer than that of the ordinary oxide layer, and the oxide layer with tensile stress can shrink back to its original position to form a bowl shape;

[0009] Step 3: Transfer the product to the process chamber of the plasma-enhanced chemical vapor deposition machine tool, and then perform plasma-enhanced chemical vapor deposition to form a thin film layer.

[0010] Preferably, the components in Step 2 include: a sealing ring, a radio frequency plasma reaction tube, a fastener, and a gas mixing chamber.

[0011] Preferably, the thickness of the oxide layer with tensile stress in Step 2 is to

[0012] Preferably, the stress value of the oxide layer with tensile stress in Step 2 is 150 - 200 MPa.

[0013] Preferably, the formation method of the oxide layer with tensile stress in Step 2 includes: using a SiH4 / N2O mixed gas as a precursor, and by adjusting the gas volume ratio, making the Si - O bond network structure generated in the plasma field have a directional arrangement characteristic, generating an asymmetric chemical bond tension to form tensile stress.

[0014] Preferably, the formation method of the oxide layer with tensile stress in Step 2 includes: controlling the deposition rate and temperature to achieve the differential thermal expansion of the oxide layer crystal phase and the metal matrix, thereby generating a continuous tensile stress gradient.

[0015] Preferably, the formation method of the oxide layer with tensile stress in Step 2 includes: by applying a high-frequency bias voltage to promote the lattice distortion induced by ion bombardment.

[0016] Preferably, the product in Step 3 is a CMOS image sensor.

[0017] Preferably, the metal ion includes the Cu element.

[0018] As described above, the method for reducing the metal ion content of the PECVD machine tool of the present invention has the following beneficial effects:

[0019] The present invention can effectively reduce the metal ion content and effectively improve the output of the machine tool. Brief Description of the Drawings

[0020] Figure 1 It shows a schematic process flow diagram of the present invention;

[0021] Figure 2 It shows a schematic diagram of the bowl-shaped oxide layer with tensile stress of the present invention. Detailed Description of the Invention

[0022] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the 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. 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.

[0023] Please refer to Figure 1 , the present invention provides a method for reducing the metal ion content in a PECVD machine, including:

[0024] Step 1: Provide a plasma-enhanced chemical vapor deposition machine;

[0025] Step 2: On the inner wall of the process chamber of the plasma-enhanced chemical vapor deposition machine and the surfaces of various components in the process chamber, replace the ordinary oxide layer of the cavity pre-deposition layer with an oxide layer having tensile stress. The atomic bond length of the oxide layer having tensile stress is longer than that of the ordinary oxide layer, and the oxide layer having tensile stress can shrink back to its original position, forming a bowl shape (as Figure 2 shown);

[0026] In some embodiments, the components in Step 2 include: sealing rings, radio frequency plasma reaction tubes, fasteners, gas mixing chambers, etc.

[0027] The sealing ring is used for sealing the vacuum system or gas pipeline to prevent the reaction gas from leaking or the external air from polluting the process chamber. In low-pressure or plasma environments such as PECVD and LPCVD, the sealing performance directly affects the vacuum degree and process stability. Usually, high-temperature and corrosion-resistant elastic materials (such as fluororubber or perfluoroether) are used to adapt to the chemical reactions and temperature fluctuations in the CVD process.

[0028] In plasma-enhanced chemical vapor deposition (PECVD), the radio frequency plasma reaction tube is a connecting component between the radio frequency (RF) power supply and the reaction chamber, used to transfer radio frequency energy to excite the gas to form plasma. Its design affects the plasma uniformity and deposition efficiency. Usually, it is used in conjunction with a capacitive coupling (CCP) or inductive coupling (ICP) structure, and a dual-frequency power supply (such as 13.56 MHz high frequency + 400 kHz low frequency) can optimize the plasma stability.

[0029] The fastener is used to fix the equipment components, such as the vacuum chamber flange, gas pipeline interface, or heating system components, to ensure the mechanical structure stability and airtightness. It needs to have heat resistance and anti-relaxation characteristics in high-temperature or vibration environments. It is commonly found in positions such as reaction chamber assembly and pump valve connection, and the materials are mostly stainless steel or corrosion-resistant alloys.

[0030] The gas mixing chamber is responsible for uniformly mixing multiple reaction gases (such as SiH4, NH3, etc.), ensuring the consistency of gas ratio and distribution before feeding them into the reaction chamber. Its design affects the film composition and uniformity.

[0031] In some embodiments, the thickness of the oxide layer with tensile stress in step two is to For example

[0032] In some embodiments, the stress value of the oxide layer with tensile stress in step two is 150 - 200 MPa, for example 185 Mpa.

[0033] In some embodiments, the method for forming the oxide layer with tensile stress in step two includes: using a SiH4 / N2O mixed gas as a precursor, by adjusting the gas volume ratio (1:2 to 1:4), making the Si - O bond network structure generated in the plasma field have a directional arrangement characteristic, generating an asymmetric chemical bond tension to form tensile stress.

[0034] In some embodiments, the method for forming the oxide layer with tensile stress in step two includes: controlling the deposition rate and temperature, for example, depositing in a medium - temperature range of 300 - 450 °C, ensuring that the oxidation reaction rate remains at 0.1 - 0.3 μm / min, realizing the differential thermal expansion between the oxide layer crystal phase and the metal matrix, thereby generating a continuous tensile stress gradient.

[0035] In some embodiments, the method for forming the oxide layer with tensile stress in step two includes: by applying a high - frequency bias voltage of 500 - 800 W, promoting the lattice distortion induced by ion bombardment.

[0036] Step three: Transfer the product to the process chamber of a plasma - enhanced chemical vapor deposition machine tool, and then perform plasma - enhanced chemical vapor deposition to form a thin film layer.

[0037] In some embodiments, the product in step three is a CMOS image sensor.

[0038] In some embodiments, the metal ions include Cu element.

[0039] The Cu content of individual devices is 17.06E10 atoms / cm 2 and 16.9E10 atoms / cm 2 , and by using this method, it can basically be optimized to a level within 8E10 atoms / cm 2 , for example 6.49E10 atoms / cm 2 and 7.44E10 atoms / cm 2, it can be seen that the method of the present invention can effectively reduce the metal ion content.

[0040] It should be noted that the illustrations provided in this embodiment only schematically illustrate the basic concept of the present invention. Therefore, only the components related to the present invention are shown in the drawings, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and proportion of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0041] In summary, the present invention can effectively reduce the metal ion content and at the same time effectively improve the output of the machine. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0042] The above embodiments are only illustrative of the principles and effects of the present invention, and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for reducing the metal ion content in a PECVD machine, characterized in that, At least including: Step 1: Provide a plasma-enhanced chemical vapor deposition machine tool; Step 2: On the inner wall of the process chamber of the plasma-enhanced chemical vapor deposition machine tool and the surfaces of various components in the process chamber, replace the ordinary oxide layer of the cavity pre-deposition layer with an oxide layer having tensile stress. The length of the atomic bond of the oxide layer having tensile stress is longer than that of the ordinary oxide layer. The oxide layer having tensile stress can shrink back to its original position to form a bowl shape; Step 3: Transfer the product to the process chamber of the plasma-enhanced chemical vapor deposition machine tool, and then perform plasma-enhanced chemical vapor deposition to form a thin film layer.

2. The method for reducing the metal ion content in a PECVD machine according to claim 1, characterized in that: The components in Step 2 include: a sealing ring, a radio frequency plasma reaction tube, a fastener, and a gas mixing chamber.

3. The method for reducing the metal ion content in a PECVD machine according to claim 1, characterized in that: The thickness of the oxide layer with tensile stress in Step 2 is to 4. The method for reducing the metal ion content in a PECVD machine according to claim 1, characterized in that: The stress value of the oxide layer having tensile stress in Step 2 is 150 - 200 MPa.

5. The method for reducing the metal ion content in a PECVD machine according to claim 1, wherein: The formation method of the oxide layer having tensile stress in Step 2 includes: using a SiH4 / N2O mixed gas as a precursor, and by adjusting the gas volume ratio, making the Si-O bond network structure generated in the plasma field have a directional arrangement characteristic, and generating an asymmetric chemical bond tension to form tensile stress.

6. The method for reducing the metal ion content in a PECVD machine according to claim 1, wherein: The formation method of the oxide layer having tensile stress in Step 2 includes: controlling the deposition rate and temperature to realize the differential thermal expansion of the oxide layer crystal phase and the metal matrix, thereby generating a continuous tensile stress gradient.

7. The method for reducing the metal ion content in a PECVD machine according to claim 1, wherein: The formation method of the oxide layer having tensile stress in Step 2 includes: by applying a high-frequency bias voltage to promote the lattice distortion induced by ion bombardment.

8. The method for reducing the metal ion content in a PECVD machine according to claim 1, characterized in that: The product in Step 3 is a CMOS image sensor.

9. The method for reducing the metal ion content in a PECVD machine according to claim 1, wherein: The metal ion includes the Cu element.

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