A method for fabricating a ferroelectric memory
By adjusting the via process and using a filling layer to isolate the ferroelectric memory from the metal interconnects, the problem of etching contamination in the CMOS back-end process was solved, achieving seamless integration and performance improvement of the ferroelectric memory.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PEKING UNIV
- Filing Date
- 2023-11-29
- Publication Date
- 2026-07-21
AI Technical Summary
When integrating ferroelectric memory in CMOS back-end processes, the problem of metal interconnect contamination caused by etching processes has not been effectively solved, affecting the performance and reliability of the memory.
By adjusting the via process, the ferroelectric memory is isolated from the metal interconnect using a filling layer. Then, chemical vapor deposition, photolithography, and reactive ion etching are used to fabricate the ferroelectric memory and integrate it into the CMOS back-end process, avoiding etching contamination.
This technology achieves seamless integration of ferroelectric memory with CMOS technology, solves the etching contamination problem, and improves the reliability and performance of the memory.
Smart Images
Figure CN117529114B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor memory technology, and specifically relates to a method for preparing a ferroelectric memory. Background Technology
[0002] Memory is an indispensable component of electronic information processing systems. In the past, thanks to continuous advancements in CMOS technology, memory performance has been constantly improved. However, in recent years, on the one hand, the leakage current problem of transistors caused by miniaturization has become increasingly serious, increasing memory power consumption and deteriorating the retention characteristics of memory cells, thus encountering a significant bottleneck in memory development; on the other hand, the rapid development of fields such as artificial intelligence and the Internet of Things has placed higher demands on the capacity, speed, and power consumption of memory. Against this backdrop, embedded ferroelectric random access memory (eFeRAM) has attracted much attention in recent years due to its non-volatility, high density, low power consumption, and fast read speed, which can improve the overall performance of the system.
[0003] Ferroelectric memories (FE-Ms) possess two distinct polarization states, both of which are retained after the voltage excitation is removed. Applying an external voltage excitation to a FE-M results in different response charges in the two polarization states. By defining the two polarization states as "0" and "1," non-volatile data storage can be achieved. Integrating FE-Ms onto an array, by applying voltages to the FE-Ms in different polarization states and collecting the voltage changes resulting from the response charges, storage functionality can be implemented at very low cost and high speed. However, FE-M fabrication often employs photolithography and etching for patterning. The copper interconnects in CMOS back-end processes and almost all the reactants generated by etching gases are non-volatile, leading to contamination of the metal interconnects. Therefore, how to integrate FE-Ms in CMOS back-end processes has become an urgent problem to solve. Summary of the Invention
[0004] To address the problems existing in the prior art, this invention proposes a method for fabricating ferroelectric memory. By using a specially designed process flow, the fabrication of ferroelectric memory is integrated into the traditional CMOS back-end process. By adjusting the original via process, the etching contamination problem caused by patterning of ferroelectric memory is solved.
[0005] The technical solution adopted in this invention is as follows:
[0006] A method for fabricating a ferroelectric memory specifically includes the following steps:
[0007] (1) Select a silicon wafer that has been fabricated with CMOS array and circuit as a substrate;
[0008] (2) A barrier layer and a fill layer are grown on the substrate using chemical vapor deposition (CVD);
[0009] (3) Photolithography and etching of the via location. The specific method is to use reactive ion etching (RIE) to etch the filling layer, then use buffered hydrofluoric acid to rinse the residual filling layer and etching reactants, then use hot phosphoric acid to etch the barrier layer exposed on the surface, and then use buffered hydrofluoric acid to rinse the etching reactants.
[0010] (4) Grow a deposited layer, fill a metal layer, and smooth the surface by chemical mechanical polishing;
[0011] (5) Grow the lower electrode layer, ferroelectric layer, and upper electrode layer;
[0012] (6) Patterning of ferroelectric capacitor stacks by photolithography and reactive ion etching (RIE);
[0013] (7) A barrier layer material is grown by chemical vapor deposition (CVD), and then a protective layer for a ferroelectric capacitor is formed by photolithography and reactive ion etching (RIE).
[0014] (8) The filler layer is grown by chemical vapor deposition (CVD) and the surface is smoothed by chemical mechanical polishing.
[0015] (9) The locations of metal interconnects and vias in the non-ferroelectric memory portion are patterned using photolithography and reactive ion etching (RIE).
[0016] (10) A deposited layer is grown, a metal layer is filled, and the surface is smoothed by chemical mechanical polishing.
[0017] (11) A barrier layer was grown using chemical vapor deposition (CVD);
[0018] (12) Annealing;
[0019] (13) Enter the CMOS back-end process.
[0020] Furthermore, the filling layer material is silicon dioxide, fluorine-doped silicon dioxide, carbon-doped silicon dioxide, porous silicon dioxide, or other dielectric materials with a dielectric constant not greater than that of silicon dioxide, and the thickness is between 80 nm and 500 nm.
[0021] Furthermore, the barrier layer material is silicon nitride, carbon-doped silicon nitride, boron-doped silicon nitride, or silicon nitride material doped with other elements.
[0022] Furthermore, the metal layer material is copper or tungsten.
[0023] Furthermore, the deposited layer material is a titanium, titanium nitride, and copper multilayer material, or a tantalum, tantalum nitride, and tungsten multilayer material.
[0024] Furthermore, the upper electrode material is a metallic material such as titanium nitride, tantalum nitride, or tungsten, or a multilayer material composed of titanium and titanium nitride, or a multilayer material composed of tantalum and tantalum nitride.
[0025] Furthermore, the lower electrode material is a metallic material such as titanium nitride, tantalum nitride, or tungsten, or a multilayer material composed of titanium and titanium nitride, or a multilayer material composed of tantalum and tantalum nitride.
[0026] Furthermore, the ferroelectric layer material is zirconium oxide or hafnium oxide doped with impurities: hafnium zirconium oxide, hafnium aluminum oxide, hafnium silicon oxide, or a multilayer material composed of zirconium oxide and hafnium oxide doped with impurities.
[0027] Furthermore, the method for growing the deposited layer material in the above steps is magnetron sputtering, chemical vapor deposition (CVD), or atomic layer deposition (ALD).
[0028] Furthermore, the method for growing and filling the lower electrode layer and upper electrode layer materials in the above steps is magnetron sputtering, chemical vapor deposition (CVD), or atomic layer deposition (ALD).
[0029] Furthermore, the method for growing ferroelectric materials in the aforementioned steps is atomic layer deposition (ALD).
[0030] Furthermore, the method for filling the metal layer material in the above step is electroplating.
[0031] Furthermore, the annealing in the above step can be one or a combination of several of the following annealing methods: rapid thermal annealing (RTA), furnace tube annealing, laser annealing, or spike annealing.
[0032] This invention proposes a method for fabricating ferroelectric memory, integrating the fabrication of ferroelectric memory into the traditional CMOS back-end process. By adjusting the original via process, the filling layer forming the via isolates the ferroelectric memory from the metal interconnects, thus solving the etching contamination problem caused by patterning of ferroelectric memory. Attached Figure Description
[0033] Figures 1-12 A schematic diagram illustrating the steps of forming a ferroelectric memory monolithically integrated with a CMOS circuit according to the fabrication method proposed in this invention, wherein:
[0034] Figure 1A substrate diagram for the preparation of the embedded ferroelectric memory;
[0035] Figure 2 This is a rear view showing the growth barrier layer and the filler layer;
[0036] Figure 3 This is a rear view showing the location of the photolithography and etching vias;
[0037] Figure 4 Image showing the growth of the deposited layer, the filling of the metal layer, and the polishing process;
[0038] Figure 5 This is a diagram showing the growth of the lower electrode layer, ferroelectric layer, and upper electrode layer.
[0039] Figure 6 This is a diagram showing the stacked ferroelectric capacitors after photolithography and etching.
[0040] Figure 7 Image after photolithography and etching of the growth barrier layer;
[0041] Figure 8 Image showing the growth of the filler layer and subsequent polishing;
[0042] Figure 9 The image shows the locations of metal interconnects and vias in the non-ferroelectric memory portion, as determined by photolithography and etching.
[0043] Figure 10 Image showing the growth of the deposited layer, the filling of the metal layer, and the polishing process;
[0044] Figure 11 Image showing the growth barrier layer;
[0045] Figure 12 This is a diagram showing the process after entering the CMOS back-end manufacturing process;
[0046] In the picture:
[0047] 1—Barrier layer; 2—Filling layer;
[0048] 3 – Deposition layer; 4 – Metal layer;
[0049] 5—Lower electrode layer; 6—Ferroelectric layer;
[0050] 7—Upper electrode layer; 8—Substrate. Detailed Implementation
[0051] An exemplary embodiment of the present invention will now be further described with reference to the accompanying drawings. It should be noted that the purpose of disclosing the embodiments is to aid in further understanding the present invention; however, those skilled in the art will understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection of the present invention is defined by the claims.
[0052] Figures 1-12 This is a schematic diagram illustrating the steps of a specific embodiment of the fabrication method proposed according to the present invention to form a ferroelectric memory monolithically integrated with a CMOS circuit. The specific steps are as follows:
[0053] First, such as Figure 1 As shown, a wafer with a CMOS circuit already fabricated is prepared as a substrate for subsequent fabrication of ferroelectric memory.
[0054] Secondly, such as Figure 2 As shown, a 30 nm thick silicon nitride (Si3N4) layer and a 100 nm thick silicon oxide (SiO2) layer were grown on the substrate using plasma-enhanced chemical vapor deposition (PECVD).
[0055] Next, as Figure 3 As shown, silicon oxide (SiO2) is etched using photolithography and reactive ion etching (RIE). Then, residual SiO2 and etching products are rinsed with buffered hydrofluoric acid. Then, exposed Si3N4 is removed by hot phosphoric acid etching. Finally, metal oxides generated during the etching process are rinsed with buffered hydrofluoric acid.
[0056] Next, as Figure 4 As shown, a 30 nm Ti / TiN / Cu layer was grown by magnetron sputtering, and then Cu was filled by electroplating as a metal layer. The surface was then smoothed by chemical mechanical polishing.
[0057] Next, as Figure 5 As shown, 20 nm titanium nitride (TiN) was grown by magnetron sputtering, 8 nm hafnium zirconium oxide (HZO) was grown by atomic layer deposition (ALD), and 20 nm TiN was grown by magnetron sputtering as the lower electrode layer, ferroelectric layer and upper electrode layer.
[0058] Next, as Figure 6 As shown, the ferroelectric capacitor stack is patterned using photolithography and reactive ion etching (RIE).
[0059] Next, as Figure 7 As shown, a 30 nm thick silicon nitride (Si3N4) layer was grown as a barrier layer using plasma-enhanced chemical vapor deposition (PECVD), and then a protective layer for the ferroelectric capacitor was formed by photolithography and reactive ion etching (RIE).
[0060] Next, as Figure 8 As shown, a 200 nm thick silicon oxide (SiO2) layer was grown using plasma-enhanced chemical vapor deposition (PECVD) as a filler layer, and then the surface was planarized by chemical mechanical polishing.
[0061] Next, as Figure 9 As shown, the locations of metal interconnects and vias in a non-ferroelectric memory portion are patterned using photolithography and reactive ion etching (RIE).
[0062] Next, as Figure 10 As shown, a 30 nm Ti / TiN / Cu layer was grown by magnetron sputtering, and then Cu was filled by electroplating as a metal layer. The surface was then smoothed by chemical mechanical polishing.
[0063] Next, as Figure 11 As shown, a 30 nm thick silicon nitride (Si3N4) layer was grown as a barrier layer using plasma-enhanced chemical vapor deposition (PECVD).
[0064] Next, rapid thermal annealing (RTA) was used to crystallize the ferroelectric layer 6 and give it ferroelectric properties;
[0065] Next, as Figure 12 As shown, it enters the CMOS back-end process.
[0066] As can be seen from the above steps, the present invention proposes a method for fabricating ferroelectric memory. By adjusting the original through-hole process, the filling layer forming the through-hole is used to isolate the ferroelectric memory from the metal interconnect, thus solving the etching contamination problem caused by the patterning of ferroelectric memory.
[0067] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, shall still fall within the protection scope of the present invention.
Claims
1. A method for fabricating a ferroelectric memory, characterized in that, Specifically, the following steps are included: (1) Select a silicon wafer that has been fabricated with CMOS array and circuit as a substrate; (2) A barrier layer and a filler layer are grown on the substrate using chemical vapor deposition; (3) Photolithography and etching of the via location. The specific method is to use reactive ion etching to etch the filling layer, then use buffered hydrofluoric acid to rinse the residual filling layer and etching reactants, then use hot phosphoric acid to etch the barrier layer exposed on the surface, and then use buffered hydrofluoric acid to rinse the etching reactants. (4) Grow a deposited layer, fill a metal layer, and smooth the surface by chemical mechanical polishing; (5) Grow the lower electrode layer, ferroelectric layer, and upper electrode layer; (6) Patterning of ferroelectric capacitor stacks by photolithography and reactive ion etching; (7) A barrier layer material is grown by chemical vapor deposition, and then a protective layer for a ferroelectric capacitor is formed by photolithography and reactive ion etching. (8) The filler layer is grown by chemical vapor deposition and the surface is smoothed by chemical mechanical polishing; (9) The positions of metal interconnects and vias in the non-ferroelectric memory are patterned by photolithography and reactive ion etching. (10) A deposited layer is grown, a metal layer is filled, and the surface is smoothed by chemical mechanical polishing. (11) A barrier layer was grown using chemical vapor deposition; (12) Annealing; (13) Enter the CMOS back-end process.
2. The method as described in claim 1, characterized in that, The filling layer material is silicon dioxide, fluorine-doped silicon dioxide, carbon-doped silicon dioxide, porous silicon dioxide, or other dielectric materials with a dielectric constant not greater than that of silicon dioxide, and the thickness is between 80 nm and 500 nm.
3. The method as described in claim 1, characterized in that, The barrier layer material is silicon nitride, carbon-doped silicon nitride, boron-doped silicon nitride, or silicon nitride material doped with other elements.
4. The method as described in claim 1, characterized in that, The metal layer material is copper or tungsten.
5. The method as described in claim 1, characterized in that, The deposited layer material is a titanium, titanium nitride, and copper multilayer material, or a tantalum, tantalum nitride, and tungsten multilayer material.
6. The method as described in claim 1, characterized in that, The upper electrode material is a metallic material such as titanium nitride, tantalum nitride, or tungsten, or a multilayer material composed of titanium and titanium nitride, or a multilayer material composed of tantalum and tantalum nitride.
7. The method as described in claim 1, characterized in that, The lower electrode material is a metallic material such as titanium nitride, tantalum nitride, or tungsten, or a multilayer material composed of titanium and titanium nitride, or a multilayer material composed of tantalum and tantalum nitride.
8. The method as described in claim 1, characterized in that, The ferroelectric layer material is zirconium oxide or hafnium oxide doped with impurities: hafnium zirconium oxide, hafnium aluminum oxide, hafnium silicon oxide, or a multilayer material composed of zirconium oxide and hafnium oxide doped with impurities.