CN100423283C

CN100423283C - Novel channel structure phase change storage

Info

Publication number: CN100423283C
Application number: CNB200610029177XA
Authority: CN
Inventors: 林殷茵; 廖菲菲; 汤庭鳌; 陈邦明
Original assignee: Fudan University; Silicon Storage Technology Inc
Current assignee: Fudan University; Silicon Storage Technology Inc
Priority date: 2006-07-20
Filing date: 2006-07-20
Publication date: 2008-10-01
Anticipated expiration: 2026-07-20
Also published as: CN1901217A

Abstract

This invention relates to a storage unit of a new channel structure in a phase change storage device characterizing that the phase change material is distributed on side walls of the channel, different storage units share the lower electrode of the channel bottom and a same gate transistor connected with gate transistors, which utilizes the thickness of phase change material to control the contact area and nm diameter is reached to break through the limit of the photo-etch condition. This invented storage structure can reduce operation current and increase storage density without occupying extra silicon chip area.

Description

A kind of novel channel structure phase change storage

Technical field

The invention belongs to microelectronics technology, be specifically related to a kind of novel channel structure phase change storage.

Background technology

Along with progressively popularizing of portable electric appts, the market of nonvolatile memory is increasing.FLASH is the main flow in present nonvolatile memory market, accounts for more than 90%.But can not be owing to be used for the floating boom of stored charge among the FLASH along with the development of integrated circuit technology attenuate unrestrictedly, therefore can't be with the technology sustainable development.It is generally acknowledged that at present FLASH will be difficult to go beyond the 32nm process node.Therefore on research and development non-volatile memory technology of future generation, carrying out keen competition in the world.This is phase transition storage (Phase Change Memory wherein, abbreviation PCM) demonstrated great competitiveness, in all many-sides such as read or write speed, read-write number of times, data hold time, cellar area, many-valued realizations great superiority is arranged all, be considered to one of the strongest competitor of the non-volatile memory technology mainstream product in the market of future generation ⁽¹⁾

The basic principle of phase transition storage is: the chalcogenide compound material can be under signal of telecommunication effect, and at polycrystalline and amorphous two alternate generation reversible transitions, correspondingly, reversible variation takes place between low-resistance and high resistant resistance, thereby can be used for the storage of information 1 or 0.The chalcogenide compound material also often is called phase-change material, and what extensively adopt at present is GeSbTe (GST) compound or the material that obtains after mixing based on GeSbTe.Normally used phase change memory structure is the 1T1R structure, and its physical structure and circuit structure are respectively shown in Fig. 1 a and b.The subject matter that present restriction phase transition storage really is applied is that it is too big to convert the needed write-operation current of amorphous state to from crystalline state, causes peripheral circuit excessive, therefore is restricted at aspects such as power consumption and integration densities.Reducing phase transformation active area (active area) as far as possible is one of main thought that reduces write-operation current.In the structure shown in Figure 1, the phase transformation active area is as the metal closures of bottom electrode and the contact area of phase-change material, and the area size is to be determined by the photoetching technique of preparing the embolism figure.

At present in the world, utilize and to reduce phase-change material and electrode contact surface and amass the work that reduces write-operation current and mainly contain: SAMSUNG adopts ring type structure, and bottom electrode is done circlewise ⁽²⁾ST company adopts μ trench structure, and electrode material is laid in the groove ⁽³⁾These two kinds of structures all are to limit contact area with contact electrode thickness, effectively reduce write current.

Summary of the invention

The objective of the invention is to propose a kind of new channel structure phase change storage unit, this structure can utilize the thickness of phase-change material self to limit the phase transformation active area, therefore can break through the restriction of etching condition on thickness direction, drops to Nano grade.

The phase transition storage of the groove structure that the present invention proposes, its phase-change material is distributed in trenched side-wall, beneath trenches is the metal closures as bottom electrode, and metal closures links to each other with the memory cell gate tube, the shared bottom electrode of channel bottom and the gate tube that is communicated with bottom electrode of being positioned at of different memory cell; The trenched side-wall top is a top electrode, and the top electrode size is then controlled by etching condition.In this structure, the phase transformation active area of single memory cell is by the width decision of the thickness and the top electrode of phase-change material.The thickness of phase-change material can not retrained by etching condition to reduce size, therefore can utilize the thickness of phase-change material self to reduce the phase transformation active area, reduces write-operation current.Through it is carried out hot emulation, found that under identical contact area, groove structure reduces by 24% write-operation current (as Fig. 3) than conventional 1T1R structure.

Photoetching top electrode all on each limit of groove is worn a memory cell under the top electrode, so the present invention can form a plurality of memory cells, and number from 1 to 64.A plurality of phase-change memory cells are shared a gate tube, reach to reduce the memory cell area occupied, improve the purpose of memory integration density.

Preparation process of the present invention is: make the metal closures 2 that is used to connect above gate tube 1 one sides, deposit insulating medium layer 3 and chemico-mechanical polishing (CMP) stop layer 4 successively then, perforate on metal closures (being groove 5), toward groove 5 interior deposit skim phase-change materials 6, in the groove that has covered phase-change material, fill up dielectric 7 more then.With CMP device surface is polished afterwards, grind off outer unnecessary phase-change material and the dielectric of groove.CMP stops at stop layer 4, at last at device surface deposition insulating material 8, carves electrode hole 9 above investing the phase-change material of recess sidewall, and plated metal forms the top electrode 10 of phase change resistor.

Description of drawings

(a) and (b) are respectively the physical structure and the circuit diagram of traditional phase transition storage 1T1R memory cell among Fig. 1.

Fig. 2 is novel channel structure phase change storage element circuit schematic diagram.

Fig. 3 is the novel channel structure phase change storage of simulation and traditional 1T1R memory write electric current comparison diagram.

Fig. 4 is for forming metal-oxide-semiconductor.

Fig. 5 is for forming metal closures.

Fig. 6 is deposit dielectric and CMP stop layer material.

Fig. 7 is perforate on metal closures.

Fig. 8 deposit phase-change material.

Fig. 9 deposit dielectric.

Figure 10 CMP stops at stop layer.

Figure 11 deposit dielectric.

The perforate of Figure 12 top electrode.

Figure 13 makes up top electrode.

Two electrode vertical views of the novel channel structure phase change storage band of Figure 14.

Number in the figure: 1-gate tube (metal-oxide-semiconductor); 2-metal closures (bottom electrode); The 3-dielectric; 4-CMP stop layer material; The 5-groove; The 6-phase-change material; The 7-dielectric; The 8-dielectric; The perforate of 9-top electrode; The 10-top electrode

Embodiment

Fig. 3～Figure 12 has provided a kind of concrete operations flow process diagram of the inventive method.Further introduce this novel channel structure phase change storage unit below in conjunction with diagram.Its making step is as follows:

Produce the MOS gate tube according to 0 25 μ m CMOS technologies,, deposit insulating medium layer 0.5 μ mSiO then as Fig. 4 ₂, carve the contact hole of diameter 0 25 μ m, then depositing metal tungsten in the hole, the formation connector is as Fig. 5.The 0.1 μ m SiO of deposit successively ₂Insulating medium layer and 0.01 μ m chemico-mechanical polishing (CMP) stop layer SiN are as Fig. 6.Perforate on metal closures again (being groove 5), length and width all are 0.25 μ m, as Fig. 7.Toward groove 5 interior deposit one deck 50nmGST, as Fig. 8.In the groove that has covered phase-change material, fill up SiO again ₂, as Fig. 9.With CMP device surface is polished afterwards, grind off outer unnecessary GST and the SiO of groove ₂, CMP stops at stop layer SiN, as Figure 10.0.5 μ mSiO in the last device surface deposit ₂, as Figure 11, investing above the GST of recess sidewall and carving diameter 0.25 μ m electrode hole, as Figure 12.Splash-proofing sputtering metal in the electrode hole forms the top electrode contact of phase change resistor, as Figure 13.

List of references:

(1)Stefan?Lai，Current?status?of?the?phase?change?memory?and?its?future，in?IEEE?IEDM2003-255.

(2)Y.J.Song?etal.Advanced?Ring?Type?Contact?Technology?for?High?DensityPhase?Change?Memory，Proceedings?of?ESSDERC，Grenoble，France，2005.

(3)F.Pellzzer?etal.NovelμTrench?Phase-Change?Memory?Cell?for?Embedded?andStand-Alone?Non-Volatile?Memory?Applications，Symposium?on?VLSI?Technology?Digest?ofTechnical?Papers，2004，18.

(4) a kind of method that improves phase transition storage density and realize circuit Chinese patent application numbers 200510110252.0, the blue or green Li Ying soup of the woods Yin Yin Liu Xin fourth benefit front yard old nation of huge legendary turtle is bright.

Claims

1. channel structure phase change storage, it is characterized in that: phase-change material is distributed in trenched side-wall, beneath trenches is the metal closures as bottom electrode, and metal closures links to each other with the memory cell gate tube, the shared bottom electrode of channel bottom and the gate tube that is communicated with bottom electrode of being positioned at of different memory cell; The trenched side-wall top is a top electrode, and the top electrode size is controlled by etching condition; The phase transformation active area of single memory cell is by the width decision of the thickness and the top electrode of phase-change material.

2. channel structure phase change storage according to claim 1 is characterized in that utilizing phase-change material self thickness to control the phase transformation active area.

3. channel structure phase change storage according to claim 1 is characterized in that a plurality of top electrodes are arranged simultaneously on the trenched side-wall that phase-change material depends on, form a plurality of memory cells, and the number of memory cell is 1 to 64.