Pretreatment method for improving copper hill defect
By pretreating the copper surface with CO plasma, the copper oxide on the copper surface is reduced to pure copper, and an etching stop layer is formed on the copper surface, which solves the problem of copper hill defects in the prior art and improves the performance and reliability of semiconductor devices.
Patent Information
- Application Number
- CN202411905381.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-23
- Publication Date
- 2025-04-15
AI Technical Summary
In the prior art, copper hill defects are easily generated when pretreating copper surfaces with NH3 plasma, resulting in a high risk of current breakdown or short circuit, affecting the overall performance of the device.
The copper surface of the copper interconnect structure is pretreated by plasma using CO plasma, reducing the copper oxide on the copper surface to pure copper, and an etching stop layer is formed on the copper surface to reduce the occurrence of copper mound defects.
Through CO plasma pretreatment and the formation of etching stop layers, the occurrence of copper mound defects is effectively reduced and the overall performance and reliability of semiconductor devices are improved.
Smart Images
Figure CN119833474A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of semiconductor manufacturing, and in particular relates to a pretreatment method for improving copper hillock defects. Background Art
[0002] BEOL etch stop layer is an important step in the back end of semiconductor manufacturing process (Back End Of the Line). In the integrated circuit manufacturing process, BEOL mainly involves the vertical interconnection of transistors and connecting these interconnections with other parts of the circuit to form a complete circuit function. The etch stop layer (ESL) plays a protective role in this process to prevent damage to the underlying material during the etching process. Therefore, before the metal layer is deposited, a layer of etch stop layer will be deposited first. This layer of material will not be etched away in the subsequent etching process, thereby protecting the underlying metal interconnection from damage.
[0003] In the semiconductor manufacturing process, copper (Cu) is widely used as an interconnect material due to its excellent conductivity and low cost. In the copper interconnection process, since the copper surface is easily oxidized to form copper oxide (CuO / Cu2O) when exposed to air, the copper surface needs to be pretreated to remove these oxides and surface contaminants to ensure the copper surface is clean, thereby improving the quality and reliability of subsequent processes. In the prior art, ammonia (NH3) plasma is usually used to pretreat the copper surface. During the pretreatment process, the hydrogen ions (H+) dissociated from NH3 reduce the oxides on the copper surface (such as CuO and Cu2O) to pure copper; then the nitrogen ions (N+) in the plasma are used to remove the oxides and contaminants on the copper surface. + ) diffuses into the copper grain boundary and forms Cu-N compounds with copper. As the pretreatment process continues, copper absorbs plasma energy and the temperature rises. These compounds form compressive stress at the grain boundary and release it by forming a hillock structure, resulting in the formation of copper hillocks. See Figure 1 It is a copper hillock defect that is easily generated in the copper interconnection process of the prior art. The formation of copper hillock defects is closely related to the formation of Cu-N compounds at the copper grain boundaries. Copper hillock defects may cause short circuits or open circuits between metal lines, current breakdown risks, etc., which reduces product reliability and yield, thereby affecting the overall performance of semiconductor devices.
[0004] Therefore, the existing copper interconnection process faces the challenge of how to effectively reduce or eliminate copper hillock defects. Summary of the invention
[0005] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a pretreatment method for improving copper hill defects, which is used to solve the problem that copper hill defects are easily generated when pretreating the copper surface with NH3 plasma in the prior art, resulting in a high risk of current breakdown or short circuit and affecting the overall performance of the device.
[0006] To achieve the above-mentioned object and other related objects, the present invention provides a pretreatment method for improving copper hillock defects, comprising: using CO plasma to perform plasma pretreatment on the copper surface of the copper interconnect structure to reduce the copper oxide on the copper surface to pure copper.
[0007] Preferably, CO plasma is used to perform plasma pretreatment on the copper surface of the copper interconnect structure, and the specific steps include:
[0008] S1, forming a copper interconnect structure including a copper interconnect line;
[0009] S2, placing the copper surface of the copper interconnect line in a chemical vapor deposition reaction chamber;
[0010] S3, introducing CO gas into the reaction chamber, using a radio frequency power source to excite to form CO plasma, the CO plasma pre-treating the copper surface, and reducing the copper oxide on the copper surface to pure copper.
[0011] Preferably, the copper interconnect structure is formed by using a Damascus process.
[0012] Preferably, the flow rate of CO gas introduced into the reaction chamber is 200 sccm to 1000 sccm.
[0013] Preferably, the radio frequency power of the radio frequency power supply is 500W to 800W.
[0014] Preferably, during the pretreatment, the temperature inside the reaction chamber is 300° C. to 400° C., and the pressure is 2 Torr to 8 Torr.
[0015] Preferably, the CO plasma pretreatment time for the copper surface of the copper interconnect structure is 30s to 60s.
[0016] Preferably, after the copper surface of the copper interconnect structure is subjected to plasma pretreatment, the method further comprises: forming an etch stop layer on the copper surface, wherein the etch stop layer is one or a combination of SiN, SiCN and SiCO.
[0017] Preferably, the method for forming the etch stop layer comprises one of a plasma enhanced chemical vapor deposition method, a thermal chemical vapor deposition method, and an atomic layer deposition method.
[0018] Preferably, the thickness of the etch stop layer is
[0019] As described above, the pretreatment method for improving copper hillock defects of the present invention has the following beneficial effects:
[0020] The invention provides a more effective and reliable copper surface pretreatment method, thereby improving the overall performance and reliability of semiconductor devices; CO is used as a reducing gas, and a radio frequency power source is used to excite to form CO plasma, and the CO plasma performs plasma pretreatment on the copper surface to reduce copper oxide on the copper surface to pure copper; since CO does not contain nitrogen elements, Cu-N compounds cannot be formed, the formation of Cu-N compounds at copper grain boundaries is avoided, and the generation of copper hillock defects is effectively reduced; in addition, an etching stop layer is formed on the copper surface, and the compressive stress of the etching stop layer is used to further suppress the tendency of forming copper hillock protrusions. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 The SEM cross-sectional view shows a copper hillock defect formed in a prior art copper interconnect process.
[0022] Figure 2 Shown is a pretreatment process flow chart for improving copper hillock defects in the present invention. DETAILED DESCRIPTION
[0023] 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.
[0024] Before further describing the specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terms used in the examples of the present invention are intended to describe specific embodiments, rather than to limit the scope of protection of the present invention. The test methods in the following examples without specifying specific conditions are generally carried out under conventional conditions or under conditions recommended by the manufacturers.
[0025] When the embodiments give numerical ranges, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, according to the grasp of the prior art by those skilled in the art and the record of the present invention, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention can also be used to realize the present invention.
[0026] In the prior art, ammonia (NH3) plasma is used to pre-treat the copper surface, which easily generates copper hill defects, resulting in a greater risk of current breakdown or short circuit, affecting the overall performance of the device.
[0027] See also Figure 2 The present invention provides a pretreatment method for improving copper hillock defects, comprising: using CO plasma to perform plasma pretreatment on the copper surface of the copper interconnect structure to reduce the copper oxide on the copper surface to pure copper.
[0028] For details, please refer to the following chemical reaction formula:
[0029] CuO + CO → Cu + CO 2， Cu2O+CO→2Cu+CO2
[0030] CO is used as a reducing gas, which is excited to form CO plasma and then the copper surface is pretreated with plasma to reduce the copper oxide on the copper surface to pure copper. CO is used instead of NH3 for copper surface pretreatment. Since CO does not contain nitrogen, Cu-N compounds cannot be formed, which avoids the formation of Cu-N compounds at the copper grain boundaries and effectively reduces the generation of copper hillock defects.
[0031] As an example, CO plasma is used to perform plasma pretreatment on the copper surface of the copper interconnect structure, and the specific steps include:
[0032] S1, forming a copper interconnect structure including a copper interconnect line;
[0033] S2, placing the copper surface of the copper interconnect wire in a chemical vapor deposition reaction chamber;
[0034] S3, CO gas is introduced into the reaction chamber, and a radio frequency power source is used to excite to form CO plasma, and the CO plasma pre-treats the copper surface to reduce the copper oxide on the copper surface to pure copper.
[0035] First, step S1 is performed to form a copper interconnect structure including copper interconnect lines.
[0036] As an example, in step S1 , the copper interconnect structure is formed by using a damascene process.
[0037] Specifically, the Damascus process is a key technology for making copper interconnects in integrated circuits. First, a pattern of grooves and through-holes is formed in the dielectric layer through a photolithography process; then, copper is filled to form a copper interconnect structure to achieve multi-layer metal interconnection; after the grooves and through-holes are filled with copper, chemical mechanical polishing is used to smooth the surface, remove excess copper, achieve surface flatness, and then form a copper interconnect structure including copper interconnects.
[0038] Then, step S2 is performed to place the copper surface of the copper interconnection line in a chemical vapor deposition reaction chamber.
[0039] Then, step S3 is performed to introduce CO gas into the reaction chamber, and CO plasma is formed by excitation with a radio frequency power supply. The CO plasma pre-treats the copper surface and reduces the copper oxide on the copper surface to pure copper.
[0040] As an example, in step S3 , the flow rate of CO gas introduced into the reaction chamber is 200 sccm to 1000 sccm.
[0041] Specifically, the flow rate of the CO gas may include values within any range such as 200 sccm, 300 sccm, 400 sccm, 600 sccm, 800 sccm, 900 sccm, and 1000 sccm.
[0042] In the process of introducing CO gas, N2 is also required as a diluent or carrier gas, and the flow rate of N2 is 1000sccm~5000sccm (for example, 1000sccm, 1500sccm, 2000sccm, 3000sccm, 4000sccm, 4500sccm, 5000sccm, etc.); nitrogen is used as a diluent or carrier gas in the process of forming CO plasma to help stabilize the plasma and improve the energy distribution of electrons.
[0043] As an example, the RF power of the RF power supply in step S3 is 500W to 800W.
[0044] Specifically, high-frequency electric energy is applied to the CO gas through an RF power supply, so that the gas molecules are excited and ionized under the action of the electric field to form a plasma state. The RF power supply can provide continuous energy to maintain the stable existence of the plasma. In a specific embodiment of the present invention, the RF power of the RF power supply can include a value within any range such as 500W, 550W, 600W, 700W, 750W, 800W, etc.
[0045] As an example, during the pretreatment in step S3, the temperature inside the reaction chamber is 300° C. to 400° C., and the pressure is 2 Torr to 8 Torr.
[0046] Specifically, the temperature inside the reaction chamber during the pretreatment process may include values within any range of 300°C, 310°C, 320°C, 340°C, 360°C, 380°C, 400°C, etc., and the pressure may include values within any range of 2Torr, 2.5Torr, 3Torr, 5Torr, 7Torr, 8Torr, etc.
[0047] As an example, the CO plasma pretreatment time for the copper surface of the copper interconnect structure is 30 seconds to 60 seconds.
[0048] Specifically, the preprocessing time may include values within any range such as 30s, 35s, 40s, 45s, 50s, 55s, 60s, etc.
[0049] Finally, step S4 is performed to perform plasma pretreatment on the copper surface of the copper interconnect structure, and further includes: forming an etch stop layer on the copper surface, wherein the etch stop layer is one or a combination of SiN, SiCN, and SiCO.
[0050] Specifically, an etch stop layer with compressive stress is formed on the copper surface, and its compressive stress is used to further suppress the formation of copper hillocks, which helps to improve the reliability and performance of the copper interconnect structure; SiN, SiCN, and SiCO are used as etch stop layer materials for copper interconnect structures, so that the copper passivation performance of the etch stop layer and the copper interface is very good, and the density of copper hillocks is significantly reduced. The material selection of the etch stop layer plays a vital role in the semiconductor manufacturing process, ensuring the precise formation of the copper interconnect structure and the reliability of the device.
[0051] As an example, a method of forming the etch stop layer includes one of a plasma enhanced chemical vapor deposition method (PECVD), a thermal chemical vapor deposition method (thermal CVD), and an atomic layer deposition method (ALD).
[0052] Preferably, the etch stop layer is deposited by PECVD, which has a high deposition rate and controllability over the refractive index. The method can be performed at a relatively low temperature, usually below 400°C.
[0053] As an example, the thickness of the etch stop layer is
[0054] Specifically, the thickness of the etch stop layer may include Any value in the range.
[0055] The present invention also provides an application of a pretreatment method for improving copper hillock defects in different technology nodes, and the method is applied to process methods of 55nm, 40nm, 28nm and 22nm technology nodes.
[0056] In summary, the present invention provides a more effective and reliable copper surface pretreatment method, thereby improving the overall performance and reliability of semiconductor devices; CO is used as a reducing gas, and a radio frequency power source is used to excite and form a CO plasma, and the CO plasma performs plasma pretreatment on the copper surface to reduce the copper oxide on the copper surface to pure copper; since CO does not contain nitrogen, it cannot form Cu-N compounds, thus avoiding the formation of Cu-N compounds at the copper grain boundary, and effectively reducing the generation of copper hill defects; in addition, an etching stop layer is formed on the copper surface, and the compressive stress of the etching stop layer is used to further suppress the tendency of forming copper hill protrusions. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.
[0057] 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 pretreatment method for improving copper hillock defects, characterized in that: The pretreatment method comprises: using CO plasma to perform plasma pretreatment on the copper surface of the copper interconnect structure to reduce the copper oxide on the copper surface to pure copper.
2. The pretreatment method for improving copper hillock defects according to claim 1, characterized in that: The copper surface of the copper interconnect structure is pretreated by plasma using CO plasma, and the specific steps include: forming a copper interconnect structure including a copper interconnect line; Placing the copper surface of the copper interconnect in a chemical vapor deposition reaction chamber; CO gas is introduced into the reaction chamber, and a radio frequency power source is used to excite the CO plasma, and the CO plasma pre-treats the copper surface to reduce the copper oxide on the copper surface to pure copper.
3. The pretreatment method for improving copper hillock defects according to claim 2, characterized in that: The copper interconnection structure is formed by using a Damascus process.
4. The pretreatment method for improving copper hillock defects according to claim 2, characterized in that: The flow rate of CO gas introduced into the reaction chamber is 200 sccm to 1000 sccm.
5. The pretreatment method for improving copper hillock defects according to claim 2, characterized in that: The radio frequency power of the radio frequency power supply is 500W to 800W.
6. The pretreatment method for improving copper hillock defects according to claim 2, characterized in that: During the pretreatment, the temperature inside the reaction chamber is 300° C. to 400° C., and the pressure is 2 Torr to 8 Torr.
7. The pretreatment method for improving copper hillock defects according to claim 1, characterized in that: The CO plasma performs plasma pretreatment on the copper surface of the copper interconnect structure for 30s to 60s.
8. The pretreatment method for improving copper hillock defects according to claim 1, characterized in that: After the copper surface of the copper interconnect structure is subjected to plasma pretreatment, the method further includes: forming an etch stop layer on the copper surface, wherein the etch stop layer is one or a combination of SiN, SiCN, and SiCO.
9. The pretreatment method for improving copper hillock defects according to claim 8, characterized in that: The method for forming the etch stop layer includes one of a plasma enhanced chemical vapor deposition method, a thermal chemical vapor deposition method, and an atomic layer deposition method.
10. The pretreatment method for improving copper hillock defects according to claim 8, characterized in that: The thickness of the etch stop layer is