Flash memory capacity information

The amount of useful information that we can store in electronic form is determined by the capacity of a particular device. Very useful from this point of view is flash memory. A feature of the devices that use it is usually called a significant volume and a small physical size of the carrier.

What is flash memory?

This is the name of a kind of semiconductor technology for creating electrically reprogrammable memory. In circuitry, this is the term that is terminated from a technological point of view for constructing permanent storage devices.

In everyday life, the phrase "flash memory" is used to refer to a wide range of solid-state storage devices made using the same technology. Important advantages that have caused their wide distribution are:

1. Compactness.
2. Cheapness.
3. Mechanical strength.
4. Large volume.
5. Speed of work.
6. Low power consumption.

Thanks to this, all flash memory can be found in many digital portable devices, as well as in a number of storage media. Alas, there are drawbacks, such as a limited period of technical maintenance of the carrier and sensitivity to electrostatic discharges. But what is the capacity of flash memory? Hardly you can guess, but try. The maximum capacity of flash memory can reach huge sizes: so, despite the small size, data carriers at 128 GB on a free sale now few people will be surprised. Not so far the moment when 1 Tb is not very interesting.

History of creation

Predecessors consider permanent memory devices, which were erased with the help of ultraviolet and electricity. They also had transistor matrices that had a floating gate. Only here in them the engineering of electrons was carried out by creating a considerable electric field strength of a thin dielectric. But at the same time, the area of wiring of the components presented in the matrix increased sharply, when it was necessary to create a field of reverse tension.

It was difficult for engineers to solve the problem with the density of the components of the erasure chains. In 1984, it was successfully solved, and thanks to the similarity of processes with a flash, the new technology was called "flash" (in English - "flash").

Operating principle

It is based on recording and changing the electric charge, which is in the isolated region of the semiconductor structure. These processes take place between the source of a large potential and the gate to obtain the electric field voltage in a thin dielectric placed here, so that this is sufficient for the appearance of a tunnel effect between the pocket and the transistor channel. To enhance it, use a small acceleration of electrons, and then injection of hot carriers occurs. Reading information is entrusted to a field effect transistor. The pocket serves as a shutter for it. Its potential changes the threshold characteristics of the transistor, which are recorded by reading circuits. The design has elements with which it is possible to work with a large array of similar cells. Due to the small size of all the details, the capacity of the flash memory is impressive.

NOR- and NAND-devices

They are distinguished by the method that is used as the basis for joining cells into one array, as well as reading and writing algorithms. The construction of NOR is based on the classical two-dimensional matrix of conductors, where there is one cell at the intersection of columns and rows. During the action, the row conductor is connected to the drain of the transistor, and columns join the second gate. The source is connected to the substrate, which is common for all. This design makes it easy to read the state of a specific transistor by supplying a positive power to one line and one column.

To imagine what NAND is, imagine a 3D array. It is based on the same matrix. But not one transistor is located in each intersection, but a whole column is already installed, which consists of consecutively connected cells. This design has many gate chains in just one intersection. In this case, you can significantly increase (and this is used) the density of the components. The downside is that the algorithm of recording, accessing and reading the cell is much more complicated. For NOR, speed is the advantage, and the disadvantage is the maximum information capacity of flash memory. For NAND, the size is plus, and the minus is the speed.

SLC- and MLC-devices

There are devices that can store one or more bits of information. In the first type there can only be two levels of charge of the floating shutter. Such cells are called one-bit cells. In others, there are more. Often multi-bit cells are also called multi-level cells. Strange as it may seem, they differ in cheapness and volume (in a positive sense), although they respond more slowly, and also suffer a smaller number of overwrites.

Audio memory

As MLC developed, the idea arose to write an analog signal into a cell. The obtained result was obtained in microcircuits, which are engaged in reproduction of relatively small sound fragments in cheap products (toys, for example, sound cards and similar things).

Technological limitations

The processes of recording and reading differ in energy consumption. So, for the first one it is necessary to form a high voltage. At the same time, when reading energy costs are quite small.

Recording resource

When the charge changes, irreversible changes in the structure are copied. Therefore, the number of entries for a cell is limited. Depending on the memory and the technological process of operation, devices can survive hundreds of thousands of cycles (although there are individual representatives who do not even hold up to 1000).

In multi-bit devices, the guaranteed resource is quite low compared to the other type of organization. But why does the device itself degrade? The fact is that you can not individually control the charge, which has a floating gate in each cell. After all, recording and erasing are done for the set at the same time. Quality control is carried out by means of an average value or by a reference cell. Over time, a mismatch occurs, and the charge can go beyond the acceptable limits, after which the information becomes unreadable. Then the situation is only aggravated.

Another reason is the mutual diffusion of the conducting and insulating regions in the semiconductor structure. At the same time, there are periodic electrical breakdowns, which leads to blurring of the boundaries, and the flash memory card goes out of order.

Data retention period

Since the insulation in the pocket is not ideal, the charge is gradually dissipated. Usually the period that information can be stored is about 10-20 years. Specific external conditions adversely affect the storage period. Thus, elevated temperature, gamma radiation or high-energy particles can quickly destroy all data. Now the most advanced samples, which can boast that they have a significant information capacity of flash memory, have weak points. They have a lower shelf life than the already developed and corrected devices, which have been improved several times.

Conclusion

Despite the problems mentioned at the end of the article, flash memory technology is very effective, due to which it is widely used. And its advantages are more than enough to cover shortcomings. Therefore, the information capacity of flash memory has become very useful and popular in home appliances.