Flash memory device with multi-level cells and method of writing data therein

• US 7,970,981 B2
• Filed: 02/06/2007
• Issued: 06/28/2011
• Est. Priority Date: 10/30/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Park, Chan-Ik, Cheon, Won-Moon, Kim, Seon-Taek, Choi, Sung-up
• Primary Examiner(s): Bragdon; Reginald G
• Assistant Examiner(s): Bernard; Daniel J
• Application Number:
  US11/702,573
• Publication Number:
  US 20080104309A1
• Time in Patent Office: 1,603 Days
• Field of Search: None
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/1021 Hit rate improvement
• CPC Class Codes: G06F 2212/2022 Flash memory
• CPC Class Codes: G06F 2212/7202 Allocation control and policies
• CPC Class Codes: G06F 2212/7208 Multiple device management, e.g. distributing data over multiple flash devices
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/0631 by allocating resources to storage systems
• CPC Class Codes: G06F 3/0632 by initialisation or re-initialisation of storage systems
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 2211/5641 Multilevel memory having cells with different number of storage levels

Abstract

In one aspect, a method of writing data in a flash memory system is provided. The flash memory system forms an address mapping pattern according to a log block mapping scheme. The method includes determining a writing pattern of data to be written in a log block, and allocating one of SLC and MLC blocks to the log block in accordance with the writing pattern of the data.

Claims

1. A method of writing data in a flash memory system including a single-level cell (SLC) block and a multi-level cell (MLC) block, the flash memory system forming an address mapping pattern according to a log block mapping scheme, the method comprising:

determining a writing pattern of data to be written in a log block; and

selectively allocating one of the SLC block and the MLC block to the log block in accordance with the writing pattern of the data,

wherein the writing pattern includes a sequential-writing pattern in which data are sequentially written into the log block in a unit of a page, and a random-writing pattern in which data are written into the log block out of sequence in a unit of a page, and

wherein the MLC block is allocated to the log block when the writing pattern of the data is the sequential-writing pattern, and the SLC block is allocated to the log block when the writing pattern of the data is the random-writing pattern.

2. The method as set forth in claim 1, wherein determining the writing pattern of the data comprises:

(a) determining whether the data is a first writing-unit data which has been requested for writing;

(b) determining wherein an offset is 0 when the data is the first writing-unit data; and

(c) determining whether the data is successive to previous page data when either the data is not the first writing-unit data in step (a) or when the offset is 0 in step (b).

3. The method as set forth in claim 2, wherein the writing-unit is a page unit in the flash memory.

4. The method as set forth in claim 3, wherein the writing pattern of the data is determined as the random-writing pattern when the offset of the page is determined to be different from 0 in step (b).

5. The method as set forth in claim 3, wherein the writing pattern of the data is determined as the sequential-writing pattern when the data is determined to be successive to the previous page data in the step (c), and the writing pattern of the data is determined as the random-writing pattern when the data is determined to be discontinuous to the previous page data in the step (c).

6. The method as set forth in claim 1, wherein the SLC block is contained in a cell array independent from the MLC block.

7. The method as set forth in claim 1, wherein the SLC block is defined by a portion of the MLC block that is operable in an SLC mode.

8. The method as set forth in claim 1, wherein the MLC block is allocated to a data block corresponding to the log block.

9. A method of writing data in multi-level cell (MLC) flash memory system including a first MLC block and a second MLC block, the flash memory system forming an address mapping pattern according to a log block mapping scheme, the method comprising:

determining a writing pattern of data to be written in the MLC flash memory;

selectively allocating one of the first MLC block and the second MLC block to a log block for a write buffer hi accordance with the writing pattern of the data,

wherein the writing pattern includes a sequential-writing pattern in which data are sequentially written into the log block in a unit of a page., and a random-writing pattern by which data are written into the log block out of sequence in a unit of a page,

wherein the first MLC block is an MLC block with fast pages selected as available storage fields and the second MLC block is an MLC block with fast and slow pages selected as available storage fields, and

wherein a slow page among the slow pages of the second MLC block is allocated to the log block when the writing pattern of the data is the sequential-writing pattern, and a fast page among the fast pages of the first and second MLC blocks is allocated to the log block when the writing pattern of the data is the random-writing pattern.

10. The method as set forth in claim 9,

wherein the second MLC block includes plural least significant bit (LSB) pages and plural most significant bit (MSB) pages, and wherein the fast pages of the second MLC block are the LSB pages, and the slow pages of the second MLC block are the MSB pages.

11. The method as set forth in claim 9, wherein determining the writing pattern comprises:

(a) determining whether the data is a first writing-unit data which has been requested for writing;

(b) determining wherein an offset is 0 when the data is the first writing-unit data; and

(c) determining whether the data is successive to previous page data when either the data is not the first writing-unit data in step (a) or when the offset is 0 in step (b).

12. The method as set forth in claim 11, wherein the writing unit is a unit of a page in the flash memory.

13. The method as set forth in claim 12, wherein the writing pattern of the data is determined as the random-writing pattern when the offset of the page is determined to be different from 0 in step (b).

14. The method as set forth in claim 12, wherein the writing pattern of the data is determined as the sequential-writing pattern when the data is determined to be successive to the previous page data in the step (c), and the writing pattern of the data is determined as the random-writing pattern when the data is determined to be discontinuous to the previous page data in the step (c).

15. The method as set forth in claim 9, wherein the first and second MLC blocks are allocated to a data block corresponding to the log block.

16. A method of mapping addresses in a flash memory system, the flash memory system forming an address mapping pattern in accordance with a log block mapping scheme, the method comprising:

including a plurality of single-level cell (SLC) blocks in a log block; and

using an multi-level cell (MLC) block for a data block corresponding to the log block,

wherein an SLC block is allocated to the log block when page data to be written into the flash memory is in a random-writing pattern, and

wherein the MLC block is allocated to the log block when the page data to be written into the flash memory is in a sequential-writing pattern.

17. The method as set forth in claim 16, wherein, during a merged operation in which data is copied into the data block from the log block, allocation information changes to assign the data block with the MLC block.

18. A memory system which forms an address mapping pattern in accordance with a log block mapping scheme, comprising:

a flash memory device including pluralities of single-level cell (SLC) and multi-level cell (MLC) blocks as storage fields; and

a controller which detects a writing pattern of externally supplied data and which selects a part of the SLC blocks or one of the plural MLC blocks as a log block in accordance with the detected writing pattern,

wherein the writing pattern includes a sequential-writing pattern in which data are sequentially written into the log block in a unit of a page, and a random-writting pattern in which data are written into the log block out of sequence in a unit of a page, and

wherein the controller allocates one of the plural MLC blocks to the log block when the writing pattern of the data is detected as the sequential-writing pattern, and allocates one of the plural SLC blocks to the log block when the writing pattern of the data is detected as the random-writing pattern.

19. The memory system as set forth in claim 18, wherein the plural SLC blocks are provided in a flash memory cell array which is independent from the plural MLC blocks.

20. The memory system as set forth in claim 18, wherein the SLC blocks are defined by a portion of the MLC blocks that are operable in an SLC mode.

21. The memory system as set forth in claim 18, wherein the plural SLC blocks and pages of the MLC blocks operable in a fast writing mode are selected as writing fields.

22. The memory system as set forth in claim 21, wherein the pages of the MLC blocks operable in the fast writing mode are least significant bit (LSB) pages of the MLC blocks.

23. The memory system as set forth in claim 18, wherein a data block corresponding to the log block is partially allocated with the plural MLC blocks.