CN105489755B - Vertical stratification limits the autoregistration preparation method of phase transition storage entirely - Google Patents

Abstract

The present invention proposes a self-aligned preparation method for a fully confined phase change memory with a vertical structure. On the one hand, the method of filling, annealing and wet etching with a maskless phase change material to form a localized phase change material not only reduces the filling The aspect ratio in the hole process improves the filling quality of the film, and the phase change material filling process is a self-alignment process, which is less difficult to implement; on the other hand, the tapered electrode of this structure can integrate the The electric field is strengthened near the tip of the cone, which is equivalent to reducing the size of the contact electrode, reducing the effective phase transition volume, and reducing power consumption. In addition, due to the sufficient reserves of available phase-change materials, the structure also has good fatigue characteristics, which improves the working reliability of the device.

Description

Self-aligned Fabrication Method of Fully Confined Phase Change Memory with Vertical Structure

technical field

The invention relates to the field of micro-nano technology, in particular to a self-aligned preparation method of a vertical structure full-confinement phase-change memory.

Background technique

The accelerated development of high-tech industries and basic service facilities has higher and higher requirements for fast computing and efficient storage, and the improvement of CPU processing capabilities is increasingly dependent on the speed and power consumption of memory chips. Therefore, how to develop efficient storage It will become one of the key technologies that urgently need a breakthrough in the future. Phase change memory PCM (phase change random access memory) uses chalcogenide compounds as the storage medium, and relies on the thermal effect of the current to control the transformation of the phase change material between the crystalline state (low resistance) and the amorphous state (high resistance) to achieve information writing and Erasing relies on detecting changes in the resistance of the storage area to read out information. PCM is non-volatile, and compared with most current memories, it has many advantages such as small device size, low power consumption, fast reading speed, radiation resistance, multi-level storage, and compatibility with existing CMOS processes. With a similar device structure, the resistance memory RRAM based on metal oxide is considered to be the most likely to replace the current mainstream products such as SRAM, DRAM, and FLASH and become the mainstream in the future due to its simple structure, precise and controllable composition, and compatibility with logic processes. One of the semiconductor memories for storage.

At present, the main problem faced by PCM phase-change memory is that the operating current is too large and the requirements on the drive circuit are high, which limits the reduction of storage power consumption, the improvement of storage speed and the increase of storage density. One of the methods to reduce the effective phase change volume of PCM mass production structure is to prepare smaller nano-plug electrodes; the other method is to prepare phase change material confinement structures, by reducing the volume available for phase change Reduce the effective phase change volume. Both types of methods are limited by complex PVD, CVD hole filling processes and CMP surface planarization processes. The self-aligned preparation method of the vertical structure fully confined phase change memory proposed by the present invention, on the one hand, uses the method of filling, annealing and wet etching to form a localized phase change material with a maskless phase change material, which reduces the hole filling process The aspect ratio in the medium improves the filling quality of the film, and the preparation process is a self-alignment process, which reduces the difficulty of process implementation; on the other hand, the tapered electrode of this structure can transfer the electric field between the two electrodes near the tip Strengthening is equivalent to reducing the size of the contact electrodes, reducing the effective phase transition volume, and reducing power consumption. In addition, due to the sufficient reserves of available phase-change materials, the structure also has good fatigue characteristics, which improves the working reliability of the device.

Contents of the invention

In order to solve the above-mentioned problems existing in the prior art, the present invention proposes a self-aligned preparation method of a fully confined phase-change memory with a vertical structure. The invention has a very good industrial application prospect for quickly realizing the power consumption of small units, the working reliability of large devices, and being compatible with the existing CMOS technology.

The invention discloses a self-alignment preparation method of a vertical structure full-confinement phase-change memory. The concrete steps of this method include:

Step 1: Deposit the first electrothermal insulating material layer 102A on the substrate 101, and then prepare the bottom electrode layer 103 on the first electrothermal insulating material layer 102A by "photolithography-film deposition-lift-off" method, and deposit Passivate the surface of the second electrothermal insulating material layer 102B, and prepare the auxiliary electrode layer 104 by "photolithography-lift-off" method;

Step 2: On the upper surface of the second electrothermal insulation material layer 102B and the auxiliary electrode layer 104, spin-coat and photoetch a photoresist mask 100, and dry etch through the mask to a depth reaching the upper surface of the bottom electrode layer 103. through holes, and deposit a tapered electrode layer 105;

Step 3: removing the photoresist mask 100, and peeling off to form a tapered electrode 105A whose tapered tip is not higher than the upper surface of the auxiliary electrode layer 104;

Step 4: On the auxiliary electrode layer 104 and the tapered electrode 105A, a layer of phase change material layer 106 is prepared by the method of "photolithography-film deposition-lift-off";

Step 5: annealing and etching the phase-change material layer 106 with an alkaline solution to form a localized phase-change material layer 106A located only in the through holes;

Step 6: On the second electrothermal insulating material layer 102B, the auxiliary electrode layer 104 and the localized phase change material layer 106A, prepare the top electrode layer 107 by the method of "photolithography-film deposition-lift-off", and deposit Passivating the surface of the third electrothermal insulating material layer 102C;

Step 7: On the upper surface of the third electrothermal insulating material layer 102C, the first test electrode whose contact depth reaches the upper surface of the bottom electrode layer 103 and the top electrode layer 107 is prepared by the method of "photolithography-etching-film deposition-lift-off" 108A and the second test electrode 108B to complete the device preparation.

The implementation quality of the hole filling process is largely related to the aspect ratio of the hole. The preparation method of the present invention does not need to use a photolithographic mask to fill the hole of the phase change material, which reduces the aspect ratio of the hole to be filled. On the one hand , using maskless phase change material filling, annealing and wet etching to form a localized phase change material method, which reduces the aspect ratio in the hole filling process and improves the filling quality of the film, and the preparation process is self-aligned process, which reduces the difficulty of process implementation; on the other hand, the tapered electrode of this structure can strengthen the electric field between the two electrodes near the tip of the cone, which is equivalent to reducing the size of the contact electrode and reducing the effective phase transition volume. Reduced power consumption. In addition, due to the sufficient reserves of available phase-change materials, the structure also has good fatigue characteristics, which improves the working reliability of the device.

It solves the shortcomings of long research and development cycle, high difficulty, high cost and poor applicability caused by the research and development bottleneck of CMP technology in the past research and development of such vertical structures, and is compatible with the existing CMOS process in terms of preparation accuracy, preparation efficiency, economy and It has great advantages in terms of sex and so on.

Description of drawings

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings, wherein:

Fig. 1 is a flow chart of the self-aligned preparation method of the vertical structure fully confined phase change memory provided by the present invention;

2-8 are schematic diagrams of the self-aligned preparation process of the vertical fully confined phase-change memory.

detailed description

Please refer to Fig. 1, the present invention provides a self-aligned preparation method of a vertical fully-confined phase-change memory. On the one hand, a maskless phase-change material is used to fill, anneal and wet-etch to form a localized phase-change material. The method not only reduces the aspect ratio in the hole filling process and improves the filling quality of the film, but also the filling process of the phase change material is a self-alignment process, and the process is difficult to implement; on the other hand, the tapered electrode of the structure The electric field between the two electrodes can be strengthened near the tip of the cone, which is equivalent to reducing the size of the contact electrode, reducing the effective phase transition volume, and reducing power consumption. In addition, due to the sufficient reserves of available phase-change materials, the structure also has good fatigue characteristics, which improves the working reliability of the device.

FIG. 1 shows a flow chart of a self-aligned preparation method for a fully confined phase-change memory with a vertical structure proposed by the present invention. Figures 2-8 show a flow chart of a self-aligned fabrication process for a vertical fully confined phase-change memory proposed by the present invention. The invention provides a self-aligned preparation method of a vertical structure fully confined phase change memory, the method comprising:

Step 1: Deposit the first electrothermal insulating material layer 102A on the substrate 101, and then prepare the bottom electrode layer 103 on the first electrothermal insulating material layer 102A by "photolithography-film deposition-lift-off" method, and deposit Passivating the bottom electrode layer 103 with the second electrothermal insulating material layer 102B, and preparing the auxiliary electrode layer 104 by "photolithography-lift-off" method;

Wherein, the material of the substrate 101 can be silicon, gallium nitride, sapphire, silicon carbide, gallium arsenide or glass; the function is to provide planarization support necessary for device fabrication.

Among them, the design purpose of the first electrothermal insulation layer 102A is to provide an electrothermal insulation environment for the device, and its characteristic thickness is not more than 300 nanometers. The purpose of the design of the second electrical and thermal insulation material layer 102B is to form a tapered electrode in the hole and realize a confinement phase change material in the hole. The design thickness of the second electrothermal insulating material layer 102B directly determines the design thickness of the depositable phase change material, and its design thickness is 50 to 300 nanometers;

Among them, the design function of the bottom electrode layer 103 is to apply an electric pulse to induce a phase change in the localized phase change material, and its setting thickness is between 20 and 200 nanometers; the design function of the auxiliary electrode layer 104 is to provide phase change material wet etching The experiment found that the difference in the wet etching rate of the phase change material in the crystalline state on the conductive substrate and the insulating substrate in the alkaline solution exceeds an order of magnitude. The phase-change material after magnetron sputtering is in an amorphous state and is insoluble in alkaline solution. After annealing at 200-500°C, the phase-change material can be set to a crystalline state. Therefore, by depositing a thin layer of metal layer on the top of the round hole, it is used as a conductive substrate in the corrosion process of the phase change material to improve the corrosion rate of the phase change material in the alkaline solution, and its design thickness is less than 20 nanometers;

Step 2: On the upper surface of the second electrothermal insulation material layer 102B and the auxiliary electrode layer 104, spin-coat and photoetch a photoresist mask 100, and dry etch through the mask to a depth reaching the upper surface of the bottom electrode layer 103. through holes, and deposit a tapered electrode layer 105;

Among them, the design function of the photoresist mask 100 is to provide an etching mask for the circular hole, on the other hand, to increase the aspect ratio of the film filling, so as to promote the parallel opening of the film above the hole and form a tapered shape in the hole. The designed thickness of the photoresist mask 100 is 200-500 nanometers. The material of photoresist mask 100 is SU-8 photoresist, ZEP photoresist, HSQ photoresist, PMMA photoresist, AZ series photoresist; Preparation by any one of electron beam exposure, ion beam direct writing or a combination of several methods;

Step 3: removing the photoresist mask 100, and peeling off to form a tapered electrode 105A whose tapered tip is not higher than the upper surface of the auxiliary electrode layer 104;

Among them, the top scale of the cone tip and the deposition thickness of the phase change material determine the size of the effective phase change volume. The top of the cone tip is not higher than the design of the auxiliary electrode layer 104, the purpose is to fill the phase change material in the circular hole in the later stage, and improve the heating efficiency of the phase change material;

Step 4: On the auxiliary electrode layer 104 and the tapered electrode 105A, a layer of phase change material layer 106 is prepared by the method of "photolithography-film deposition-lift-off";

Wherein, the phase-change material layer 106 is a GeSbTe series alloy, which is formed by sputtering, evaporation, chemical vapor deposition, laser-assisted deposition, atomic layer deposition, thermal oxidation or metal-organic thermal decomposition. a preparation of

Step 5: annealing and etching the phase-change material layer 106 with an alkaline solution to form a localized phase-change material layer 106A located only in the through holes;

Among them, the annealing method can be selected under vacuum, nitrogen, and argon atmosphere, rapid annealing, and the temperature is limited to 200-500 ° C; the initial deposition state of the phase change material is amorphous, and the first phase transition temperature of the phase change material is usually between At about 150°C, the phase change material can be set to a crystalline state by annealing at 200-500°C;

Step 6: On the second electrothermal insulating material layer 102B, the auxiliary electrode layer 104 and the localized phase change material layer 106A, prepare the top electrode layer 107 by the method of "photolithography-film deposition-lift-off", and deposit Passivating the top electrode layer 107 with the third electrothermal insulating material layer 102C;

Step 7: On the upper surface of the third electrothermal insulating material layer 102C, the first test electrode whose contact depth reaches the upper surface of the bottom electrode layer 103 and the top electrode layer 107 is prepared by the method of "photolithography-etching-film deposition-lift-off" 108A and the second test electrode 108B to complete the device preparation.

Wherein, the materials of the first, second, third, fourth and fifth electric insulation material layers 102A, 102B and 102C can be nitrogen oxide compounds, nitrides or oxides, or a combination of several of the above. It is to provide an electrothermal insulation environment for the device to work, which may be the same or different. Since their functions are the same, only the alphabetical order of the last digit is distinguished in the numbering. Wherein, in order to better realize the electric and thermal insulation properties, the first electric and thermal insulating material layer 102A is preferably selected from silicon nitride grown by LPCVD method or silicon oxide grown by thermal oxidation method. Considering the temperature compatibility of the film deposition process simultaneously, according to the order of the motor films (the second 102B and the third 102C), the deposition temperature of the film that is arranged behind is not higher than the deposition temperature of the film of the previous sequence; The first, second and third electrothermal insulating material layers 102A, 102B and 102C are formed by sputtering, vapor deposition, chemical vapor deposition, laser assisted deposition, atomic layer deposition or thermal oxidation or metal organic thermal One or a combination of several decomposition methods for preparation.

Wherein, the materials of bottom electrode layer 103, auxiliary electrode layer 104, tapered electrode layer 105, tapered electrode 105A, top electrode 107, first test electrode 108A and second test electrode 108B are tungsten, titanium nitride, nickel, aluminum , titanium, gold, silver, copper, platinum metal, and one or more combinations of oxides, can be used by sputtering, evaporation, chemical vapor deposition, atomic layer deposition, metal organics One or several preparations in the thermal decomposition method.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (10)

1. a kind of vertical stratification limits the autoregistration preparation method of phase transition storage entirely, this method includes：

Step 1：The first electric insulating material layer (102A) is deposited on substrate (101), then with " photoetching-thin-film deposition-stripping From " method the first electric insulating material layer (102A) on prepare bottom electrode layer (103), and deposit the second electric heating insulation material The bed of material (102B) passivation bottom electrode layer (103), and prepare auxiliary electrode layer (104) with the method for " photoetching-stripping "；

Step 2：In the upper surface of the second electric insulating material layer (102B) and auxiliary electrode layer (104), spin coating and photoetching light extraction Resist mask (100), and the through hole that depth reaches bottom electrode layer (103) upper surface is gone out by mask (100) dry etching, And deposit one layer of tapered electrode layer (105)；

Step 3：Photoresist mask (100) is removed, peels off and forms the taper electricity that cone is not higher than auxiliary electrode layer (104) upper surface Pole (105A)；

Step 4：In the top of auxiliary electrode layer (104) and tapered electrode (105A), using " photoetching-thin-film deposition-stripping " Method prepares one layer of phase-change material layers (106)；

Step 5：Anneal and corrode phase-change material layers (106) with alkaline solution, form the localization phase transformation material being only located in through hole The bed of material (106A)；

Step 6：In the second electric insulating material layer (102B), auxiliary electrode layer (104) and localization phase-change material layers (106A) Top, top electrode layer (107) is prepared by the method for " photoetching-thin-film deposition-stripping ", and insulated with the 3rd electric heating of deposit Material layer (102C) passivation top electrode layer (107)；

Step 7：In the 3rd electric insulating material layer (102C) upper surface, using the side of " photoetching-etching-thin-film deposition-stripping " Method prepares the first test electrode (108A) that contact depth reaches bottom electrode layer (103) and top electrode layer (107) upper surface With the second test electrode (108B), complete device and prepare.

2. vertical stratification according to claim 1 limits the autoregistration preparation method of phase transition storage, wherein photoresist entirely The material of mask layer (100) is SU-8 photoresists, ZEP photoresists, PMMA photoresists, AZ6130 photoresists or S9912 photoresists.

3. vertical stratification according to claim 2 limits the autoregistration preparation method of phase transition storage, wherein photoresist entirely Mask layer (100) is by any one or a few side in optical lithography, laser direct-writing, electron beam exposure and ion beam direct write It is prepared by the combination of method.

4. vertical stratification according to claim 1 limits the autoregistration preparation method of phase transition storage, wherein substrate entirely (101) material is silicon, gallium nitride, sapphire, carborundum or glass.

5. vertical stratification according to claim 1 limits the autoregistration preparation method of phase transition storage entirely, wherein first, The material of two and the 3rd electric insulating material layer (102A), (102B) and (102C) is oxynitrides, nitride or oxide In any one or a few combination.

6. vertical stratification according to claim 5 limits the autoregistration preparation method of phase transition storage entirely, wherein first, Two and the 3rd electric insulating material layer (102A), (102B) and (102C) is by sputtering method, vapour deposition method, chemical vapor deposition It is prepared by one kind in method, laser-assisted deposition method, atomic layer deposition strategy, thermal oxidation method or metallo-organic decomposition process.

7. vertical stratification according to claim 1 limits the autoregistration preparation method of phase transition storage, wherein bottom electricity entirely Pole layer (103), auxiliary electrode layer (104), tapered electrode layer (105), tapered electrode (105A), top electrode layer (107), first The material for testing electrode (108A) and the second test electrode (108B) is tungsten, titanium nitride, nickel, aluminium, titanium, gold, silver, copper or platinum One or more of combinations in simple substance and its oxide.

8. limit the autoregistration preparation method of phase transition storage entirely according to any described vertical stratifications of claim 1-7, wherein Bottom electrode layer (103), auxiliary electrode layer (104), tapered electrode layer (105), tapered electrode (105A), top electrode layer (107), first test electrode (108A) and second test electrode (108B) be by sputtering method, vapour deposition method, chemical vapor deposition One or several kinds of preparations in method, atomic layer deposition method, metallo-organic decomposition process.

9. vertical stratification according to claim 1 limits the autoregistration preparation method of phase transition storage, wherein phase transformation material entirely The material of the bed of material (106) and localization phase-change material layers (106A) is GeSbTe series alloys.

10. vertical stratification according to claim 9 limits the autoregistration preparation method of phase transition storage, wherein phase transformation material entirely The bed of material (106) and localization phase-change material layers (106A) are by sputtering method, vapour deposition method, CVD method, laser assisted One or several kinds of preparations in sedimentation, atomic layer deposition strategy, thermal oxidation method or metallo-organic decomposition process.