The present invention relates generally to methods of manufacturing semiconductor memory devices, and more particularly, to methods of manufacturing 3D programmable memory devices.
Various digital memory technologies including erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, NAND-flash memory, hard disk, compact disk (CD), digital versatile disk (DVD), and Blu-ray Discs registered by the Blu-ray Disc Association, have been widely used for data memory for more than 50 years. However, the lifetime of the memory media is usually less than 5 to 10 years. The anti-fuse memory technology developed for big data memory cannot meet the demand for massive data memory because of its high cost and low memory density.
The technical problem to be solved by the present invention is to provide a method for preparing a three-dimensional programmable memory with the characteristics of high density and low cost.
The manufacturing method of the three-dimensional programmable memory includes the following steps:
1) Form a basic structure: set a predetermined number of conductive medium layers and insulating medium layers in a way that the conductive medium layer and the insulating medium layer are vertically stacked one onto another to form the base structure body;
2) Form the interdigital structure on the basic structure body: the basic structure body is divided into two interdigitated interdigital structures by setting a segmenting structure that trenches from the top layer to the bottom layer of the basic structure body, and the interdigital structure includes at least two fingers and one commonly connecting strip, each finger strip in the same interdigitated structure is connected with the commonly connecting strip; the segmenting structure includes an array of cylindrical trench holes and an isolation trench filled with insulating material; The area between the fingers is called the inter-finger area, and the cylindrical trench holes in the same inter-finger area are the ones in the same row.
3) Forming the cylindrical memory unit: according to the preset memory structure, the required intermediate medium layer materials are set layer by layer onto the inner wall of the cylindrical trench hole, and finally the core medium material is filled in the cylindrical trench hole to form the core medium material layer.
In the step 2), in the cylindrical trench hole array, adjacent holes in the same row can encroach upon each other. The “nearest” edge of the encroaching hole is between the center point of the encroaching hole and the center point of the encroached hole. Here the “nearest” edge is the edge closest to the center of the invaded hole.
The insulating medium in the isolation trench and the isolation trench hole can be silicon dioxide or air.
The beneficial effects of the present invention are that the prepared semiconductor memory has high memory density, low process cost, being easy to fabricate.
The fabricating method of three-dimensional programmable memory includes the following steps:
Embodiment 1: This embodiment is a two-layer cylindrical structure, see
Embodiment 2: The cylindrical structure in this embodiment has a three-layer structure.
The materials of the conductive medium layer, the first and second medium layer and the core medium layer can be preselected in any one of the combinations in Table 2.
Embodiment 3: This embodiment has the following steps after Step 6 of Embodiment 2:
Step 7: Using the mask definition and deep trench etching process to set isolation trench holes between the center points of two adjacent cylindrical trench holes in the same array, and the isolation hole encroaches the two adjacent cylindrical holes, and the edge of the isolation hole locates in the middle of the center points of the two adjacent cylindrical holes, that is to say, after the isolation hole is trenched, the core medium layer in the cylindrical holes remains as a whole, as shown in
Step 8: Using the ALD method to fill the isolation trench holes with insulating materials, as shown in
The cylindrical holes in Embodiment 2 and Embodiment 3 are independent of each other. In Embodiment 4, adjacent cylindrical trench holes in the same array can encroach upon each other. Since the isolation hole will be set in the subsequent process, it will completely isolate the relevant memory media in the two adjacent cylindrical holes. The nearest edge of the encroaching party is between the center point of the invading party and the center point of the encroached party. Here the nearest edge refers to the edge closest to the center point of the encroaching party to maintain the integrity of the core medium, refer to
Embodiment 4: This is an improved embodiment. It specifically includes the following steps:
1: Forming a base structure body: a predetermined number of conductive medium layers and insulating medium layers are set in a manner that the conductive medium layer and the insulating medium layer are vertically stacked one onto another to form the base structure body; this step is the same as the second embodiment.
2: Using the mask definition and deep trench etching process to set an array of trench holes at the isolation trench to form cylindrical trench holes penetrating from top layer to the bottom layer of the base structure; the area between two adjacent arrays of cylindrical trench holes is in the finger strip region, shown in
3. Using the ALD process to grow a 0.5-5nm programmable dielectric on the inner wall surface of the cylindrical hole to form the first dielectric layer, as shown in
4. Using the ALD process to grow a layer of buffer layer on the inner wall of the cylindrical hole (that is, the surface of the first medium layer) as the second dielectric layer, the thickness of which is optimized according to the requirements of programming the leakage current of the reverse diode, shown in
5. The ALD process is used to deposit and fill the core medium material in the cavity left by previous steps inside the cylindrical hole to form the core medium material layer. The core medium material can be conducting semiconductor or Schottky metal, as shown in
6. Isolation trench holes are set between two adjacent cylindrical holes in the same row, and isolation trenches are set at the two ends of each array of cylindrical trench holes. The isolation trench holes encroach the core medium material in the cylindrical trench holes. The isolation trenches are alternately set at the two ends of each finger area, to form two staggered interdigitated structures, as shown in
7. Filling the isolation trench and the isolation trench hole with an insulating medium, as shown in
Embodiment 5: The interdigital structure of this embodiment is finally formed by trenching holes at the ends of the finger strips, refer to
Embodiments 2 and 3, where a complete interdigital structure with isolation trenches is form first. The hole at the end of the finger strip can be either a cylindrical trench hole as a memory unit, or an isolation trench hole. The former is equivalent to increasing the number of memory units.
This application claims the benefit of PCT Application No. PCT/CN2019/105517, filed Sep. 12, 2019, the contents of which are incorporated by reference.