1. Field of the Invention
This present invention relates to a structure of corner free, and more particularly to a corner free structure of nonvolatile memory.
2. Description of the Prior Art
In recent years, it is well known for employing trench isolation devices, such as shallow trench isolation (STI), to isolate the semiconductor devices. However, corners of the trench isolation devices always come with the trench isolation devices. In the prior art, due to the corners of the trench isolation devices, many unwanted issues of the semiconductor devices will occur.
For instance,
Hence, it is an important object of developing a corner free structure for raising the reliability of a nonvolatile memory. Moreover, the above-mentioned corner free structure can increase the efficiency of the nonvolatile memory.
In accordance with the present invention, a corner free structure of a nonvolatile memory is provided, wherein the corner free structure efficient isolates the nonvolatile memory and trench isolation devices, and the reliability of the nonvolatile memory is increased.
It is another object of this invention to provide a corner free structure of a nonvolatile memory. According to the definition of coupling ratio, through changing the width of the tunnel oxide layer and the dielectric layer of the nonvolatile memory in this present invention, the efficiency of the above-mentioned nonvolatile memory can be improved.
In accordance with the above-mentioned objects, the invention provides a corner free structure of a nonvolatile memory. The above-mentioned corner free structure of a nonvolatile memory comprises a substrate, at least one trench isolation device, and a plurality of nonvolatile memory. The trench isolation device comprises a corner free structure for complete isolating the nonvolatile memory and the trench isolation device, and thus the reliability of the nonvolatile memory is improved. Additionally, the above-mentioned corner free structure is helpful for modifying the width of the tunnel oxide layer of the nonvolatile memory. Therefore, the corner free structure according to this invention can improve the efficiency of the nonvolatile memory.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
Some sample embodiments of the invention will now be described in greater detail. Nevertheless, it should be recognized that the present invention can be practiced in a wide range of other embodiments besides those explicitly described, and the scope of the present invention is expressly not limited except as specified in the accompanying claims.
Then, the components of the semiconductor devices are not shown to scale. Some dimensions are exaggerated to the related components to provide a more clear description and comprehension of the present invention.
One preferred embodiment of this invention is a corner free structure of a nonvolatile memory. The above-mentioned corner free structure of a nonvolatile memory comprises a substrate, and a plurality of trench isolation device. The trench isolation device comprises a first portion on the substrate, and a second portion in the substrate. The above-mentioned trench isolation structure of a nonvolatile memory further comprises a spacer at a sidewall of the first portion of the trench isolation device. The spacer is employed for covering a corner between the sidewall of the first portion of the trench isolation device.
In this preferred embodiment, due to the spacer at the sidewall of the first portion of the trench isolation device, the tunnel oxide layer of a nonvolatile memory between two trench isolation device is kept from the corner of the trench isolation device, and thus the reliability of the nonvolatile memory is improved. On the other hand, the width of the nonvolatile memory is modified by the spacer of the trench isolation device. In other words, the width of the tunnel oxide layer of the nonvolatile memory is decreased, and the width of the dielectric layer of the nonvolatile memory is increased. According to the definition of coupling ratio, the above-mentioned width modification of the nonvolatile memory can improve the coupling ratio of the nonvolatile memory. Hence, the efficiency of the nonvolatile memory according to this present embodiment is better than the efficiency of the nonvolatile memory in the prior art.
Another preferred embodiment of this present invention is about a corner free structure of a nonvolatile memory. Referred to
Corners 230 are formed between the first portion 222 of the trench isolation device 220 and the substrate 200. In the prior art, because the corner 230 is close to the tunnel oxide layer of the nonvolatile memory or touched with the tunnel oxide layer of the nonvolatile memory, the reliability of the nonvolatile memory will be decreased. Therefore, in this present embodiment, a spacer 240 is at a sidewall of the first portion 222 of the trench isolation device 220, and covers the corner 230 between the sidewall of the first portion 222 of the trench isolation 220 and the substrate 200. The spacer 240 is consisted of deposited silicon dioxide, deposited silicon nitride, and the like dielectric materials. The spacer 240 can be formed by the technology in the prior art. For example, the spacer 240 may be formed at the sidewall of the first portion 222 by a depositing step and an etching step. In this manner, the trench isolation device 220 and the tunnel oxide layer of the nonvolatile memory can be efficiently isolate the spacer 240, and thus the reliability of the nonvolatile memory can be improved.
Another preferred embodiment according to this invention is a corner free structure of a nonvolatile memory. As shown in
Referred to
coupling ratio=B/B+A (equation 1)
In the equation 1, A is the capacitive value of the tunnel oxide layer 342, and B is the capacitive value of the dielectric layer 346. In the point of a nonvolatile memory, coupling ratio is relative to the efficiency of the nonvolatile memory. From
According to the preferred embodiments, this invention discloses a corner free structure of a nonvolatile memory. The corner free structure of a nonvolatile memory comprises a substrate, at least a trench isolation device, and a plurality of nonvolatile memory, wherein each of the nonvolatile memory is disposed between two trench isolation devices. The above-mentioned trench isolation device comprises a first portion on the substrate, and a second portion in the substrate. The corner free structure of a nonvolatile memory further comprises a spacer at a sidewall of the first portion of the trench isolation device. The spacer is utilized for covering a corner between the substrate and the sidewall of the first portion of the trench isolation device. The trench isolation device and the tunnel oxide layer of the nonvolatile memory can be efficiently isolated by the spacer. Hence, the reliability of a nonvolatile memory can be advanced by the corner free structure according to this invention. On the other hand, as a result of the spacer according to this invention, the width of the tunnel oxide layer of the nonvolatile memory is decreased, and the width of the dielectric layer of the nonvolatile memory is increased. Therefore, based on the definition of coupling ratio, the nonvolatile memory according to this present invention can achieve higher efficiency than the nonvolatile memory in the prior art.
Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from what is intended, but not to be limited solely by the appended claims.