Preparation method of hafnium oxide-based MIM capacitor and hafnium oxide-based MIM capacitor

Abstract

The nitrogen-doped hafnium oxide is adopted as the dielectric layer of the MIM capacitor, the phase change temperature of the dielectric layer of the capacitor can be increased and can reach up to 1000 DEG C, electric leakage can be reduced due to the high phase change temperature, the high temperature resistance of the MIM capacitor is improved, and the reliability of the MIM capacitor is improved; doped nitrogen can improve the hafnium oxide dielectric constant and further improve the device performance; and the annealing temperature of hafnium oxide can be improved by improving the phase transition temperature of hafnium oxide, so that the annealing time is shortened, and the performance of the hafnium oxide material is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method for forming a MIM capacitor and a hafnium oxide-based MIM capacitor. Background Technology

[0002] Existing capacitors can be broadly categorized into front-end capacitors and back-end capacitors. Front-end capacitors include MOS capacitors and PN junction capacitors, while back-end capacitors include MIM (metal-insulator-metal) capacitors and MOM (metal-oxide-metal) capacitors. Among these, MIM capacitors offer superior frequency and temperature-dependent characteristics and can be fabricated using interlayer metal and copper interconnect processes, reducing the difficulty and complexity of integration with CMOS front-end processes. Consequently, they are widely used in various integrated circuits, such as analog-logic, analog-digital, mixed-signal, and radio frequency circuits, especially in CMOS image sensor (CIS) chips.

[0003] MIM capacitor structures typically consist of a lower electrode (metal layer), a dielectric layer (insulating layer), and an upper electrode (metal layer), forming a sandwich structure with an insulating dielectric layer sandwiched between the two metal electrodes. Hafnium oxide is used in the fabrication of the dielectric layer due to its high dielectric constant. Conventional CMOS image sensor fabrication processes require temperatures of 450°C or even higher. However, at high temperatures, the amorphous hafnium oxide in MIM capacitors undergoes a phase transition. This phase-transitioned hafnium oxide becomes a fast channel for oxygen or impurity diffusion, causing leakage current and severely damaging device performance and reliability.

[0004] Therefore, increasing the hafnium oxide phase transition temperature, thereby improving the high-temperature resistance of capacitors, has become a key technical issue that needs to be addressed by those skilled in the art. Summary of the Invention

[0005] Based on the problems described above, this invention proposes a method for preparing a hafnium oxide-based MIM capacitor and a hafnium oxide-based capacitor.

[0006] On one hand, the present invention proposes a method for fabricating a hafnium oxide-based MIM capacitor, comprising: providing a substrate; forming a lower electrode layer on the substrate; forming a hafnium oxide layer on the lower electrode layer, and then performing nitrogen doping to increase the phase transition temperature of the hafnium oxide layer; and forming an upper electrode layer on the nitrogen-doped hafnium oxide layer.

[0007] Optionally, the phase transition temperature exceeds 600°C.

[0008] Alternatively, hafnium oxide can be formed by atomic layer deposition (ALD), metal-organic vapor deposition (MOCVD), chemical vapor deposition (CVD), or physical vapor deposition (PVD).

[0009] Optionally, the nitrogen doping method may be decoupled plasma nitriding (DPN), rapid thermal doping (RTN), in-furnace doping, long-distance plasma doping (RPN), or trap implantation.

[0010] Optionally, the nitrogen doping method is decoupled plasma nitriding (DPN), and the gas used includes N2 or N2. x O y , where x is greater than 0 and y is greater than 0.

[0011] Optionally, after forming a nitrogen-doped hafnium oxide layer, a decoupled plasma nitridation (DPN) process is performed.

[0012] Optionally, the annealing temperature is higher than the phase transition temperature of undoped hafnium oxide and lower than the phase transition temperature of nitrogen-doped hafnium oxide.

[0013] Optionally, the lower electrode layer and the lower electrode layer are selected from one or more of titanium, tantalum, titanium nitride, tantalum nitride, copper and tungsten.

[0014] Optionally, the MIM capacitor is used in a CMOS image sensor chip.

[0015] Secondly, the present invention proposes a hafnium oxide-based MIM capacitor, which is prepared using the above-described preparation method.

[0016] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: The MIM capacitor of the present invention uses nitrogen-doped hafnium oxide as the capacitor dielectric layer, which can increase the phase transition temperature of the capacitor dielectric layer, reaching up to 1000°C. The high phase transition temperature can reduce leakage current, improve the high temperature resistance of the MIM capacitor, and improve its reliability. Furthermore, nitrogen doping can increase the dielectric constant of hafnium oxide, further improving the device performance. Increasing the phase transition temperature of hafnium oxide can also increase the annealing temperature of hafnium oxide, thereby reducing the annealing time and improving the performance of hafnium oxide material. Attached Figure Description

[0017] The accompanying drawings, which form part of this specification, are used to further understand the invention. The drawings illustrate embodiments of the invention and, together with the specification, serve to explain the principles of the invention.

[0018] Figure 1 This diagram illustrates the steps of the preparation method for the hafnium oxide-based MIM capacitor of the present invention.

[0019] Figure 2 This is a cross-sectional view of the hafnium oxide-based MIM capacitor of the present invention. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0021] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0022] In traditional CMOS image sensor chips, the hafnium oxide dielectric layer in MIM capacitors has a low phase transition temperature. However, the high temperatures involved in CMOS image sensor chip fabrication processes can cause phase transitions in the hafnium oxide dielectric layer, thus affecting the capacitor's performance. Furthermore, due to the low phase transition temperature of the hafnium oxide dielectric layer, it is typically subjected to low-temperature annealing or no annealing after fabrication, which is detrimental to improving the material properties of the hafnium oxide dielectric layer. Therefore, this application proposes a method to increase the phase transition temperature of the hafnium oxide dielectric layer in MIM capacitors.

[0023] See appendix Figure 1 and appendix Figure 2 First, a lower electrode layer 200 is formed on a substrate 100, then a hafnium oxide layer 300 is formed, followed by nitrogen doping of the hafnium oxide, and finally an upper electrode layer 400 is formed.

[0024] The substrate is typically a Si substrate, Ge substrate, SiGe substrate, SiC substrate, III-V compound substrate, or other suitable semiconductor substrates known in the art. An insulating isolation layer is deposited on the substrate surface, within which metal lines and conductive vias are formed. Specifically, the wafer surface can be polished first using chemical mechanical polishing (CMP), then the insulating isolation layer can be formed using one or more combinations of physical vapor deposition (PVD), chemical vapor deposition (CVD), and atomic layer deposition (ALD). Metal lines and metal interconnect vias are then fabricated using etching or filling methods. Finally, the insulating isolation layer is further refined and planarized using CMP to ensure that the subsequent MIM capacitor structure is fabricated on a flat and clean substrate surface. Furthermore, the lower electrode layer is selected from one or more of titanium, tantalum, titanium nitride, tantalum nitride, copper, and tungsten.

[0025] The hafnium oxide layer 300 is prepared using conventional thin film preparation methods, such as atomic layer deposition (ALD), metal-organic vapor deposition (MOCVD), chemical vapor deposition (CVD), or physical vapor deposition (PVD). For example, the hafnium oxide dielectric layer 300 is formed using atomic layer deposition, with HfCl4 as the hafnium source and H2O as the oxygen source.

[0026] Nitrogen doping processes include decoupled plasma nitriding (DPN), rapid thermal doping (RTN), furnace doping, long-distance plasma doping (RPN), or trap implantation. For example, decoupled plasma nitriding is used, where the nitriding gas includes N2 or N2. x O y Where x is greater than 0, y is greater than 0, and N is preferred. x O y .

[0027] Specifically, the inventors discovered that nitrogen doping can increase the phase transition temperature of hafnium oxide, raising it to over 600°C, and even over 1000°C. This high phase transition temperature allows hafnium oxide-based MIM capacitors to be compatible with high-temperature CMOS processes, such as CMOS image sensor technology, preventing leakage and deformation problems caused by the hafnium oxide phase transition in high-temperature CMOS processes. Furthermore, nitrogen doping can further increase the K-value of hafnium oxide and reduce EOT. x O y The oxygen in the hafnium oxide dielectric layer can fill oxygen vacancy defects, reduce the probability of defect generation, and thus help improve the reliability of the device.

[0028] Following nitrogen doping, a decoupled plasma nitridation (DPN) annealing process is preferably included, with the annealing atmosphere being an inert gas such as Ar or N2. The annealing temperature is preferably higher than the phase transition temperature of undoped hafnium oxide but lower than the phase transition temperature of nitrogen-doped hafnium oxide. Because the annealing temperature is higher than the phase transition temperature of undoped hafnium oxide, it can better repair hafnium oxide defects and improve material properties. Furthermore, a higher annealing temperature can reduce annealing time and save costs.

[0029] Using the hafnium oxide MIM capacitor prepared by the above method in CMOS image sensors can improve the performance of MIM capacitors and better accommodate the high-temperature manufacturing process of CMOS image sensors.

[0030] In summary, using nitrogen-doped hafnium oxide as the capacitor dielectric layer can increase the phase transition temperature of the capacitor dielectric layer, reduce high-temperature leakage, improve the high-temperature resistance of MIM capacitors, and enhance their reliability. Furthermore, nitrogen doping can increase the dielectric constant of hafnium oxide, further improving device performance. Increasing the phase transition temperature of hafnium oxide can also increase its annealing temperature, thereby improving the performance of hafnium oxide materials and reducing annealing time.

[0031] The basic concepts have been described above. It is clear that the detailed disclosure above is merely illustrative and does not constitute a limitation of the present invention. Although not explicitly stated herein, various modifications, improvements, and corrections may be made to the present invention by those skilled in the art. Such modifications, improvements, and corrections are suggested in this invention and therefore remain within the spirit and scope of the exemplary embodiments of the present invention.

[0032] It should be understood that the embodiments described in this invention are merely illustrative of the principles of the invention. Other modifications may also fall within the scope of this invention. Therefore, alternative configurations of the embodiments of this invention are considered as examples and not limitations, and are regarded as consistent with the teachings of this invention. Accordingly, the embodiments of this invention are not limited to those explicitly described and illustrated herein.

Claims

1. A method for preparing a hafnium oxide-based MIM capacitor, characterized in that, include: Provide a substrate; A lower electrode layer is formed on the substrate; A hafnium oxide layer is formed on the lower electrode layer, and then nitrogen doping is performed to increase the phase transition temperature of the hafnium oxide layer; An upper electrode layer is formed on the nitrogen-doped hafnium oxide layer.

2. The method according to claim 1, characterized in that, The phase transition temperature exceeds 600°C.

3. The method according to claim 2, characterized in that, Hafnium oxide can be formed by atomic layer deposition (ALD), metal-organic vapor deposition (MOCVD), chemical vapor deposition (CVD), or physical vapor deposition (PVD).

4. The method according to claim 2, characterized in that, The nitrogen doping methods include decoupled plasma nitriding (DPN), rapid thermal doping (RTN), in-furnace doping, long-distance plasma doping (RPN), or trap implantation.

5. The method according to claim 4, characterized in that, The nitrogen doping method is decoupled plasma nitriding (DPN), and the gas used includes N2 or N2. x O y , where x is greater than 0 and y is greater than 0.

6. The method according to claim 5, characterized in that, After forming a nitrogen-doped hafnium oxide layer, a decoupled plasma nitridation (DPN) process is performed.

7. The method according to claim 6, characterized in that, The annealing temperature is higher than the phase transition temperature of undoped hafnium oxide, but lower than the phase transition temperature of nitrogen-doped hafnium oxide.

8. The method according to claim 1, characterized in that, The lower electrode layer and the lower electrode layer are selected from one or more of titanium, tantalum, titanium nitride, tantalum nitride, copper and tungsten.

9. The method according to claim 1, characterized in that, The MIM capacitor is used in CMOS image sensor chips.

10. A hafnium oxide-based MIM capacitor, prepared by the method described in any one of claims 1 to 9.

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