This application claims the priority benefit of Taiwan application serial no. 96141209, filed on Nov. 1, 2007. The entirety the above-mentioned patent application is hereby incorporated by reference herein and made a part of specification.
1. Field of the Invention
The present invention relates to a memory and manufacturing method thereof, and more particularly, to a non-volatile memory and manufacturing method thereof.
2. Description of Related Art
Among various kinds of memory products, non-volatile memory is a kind of memory characterized by the advantages that it allows multiple data storing, reading, or erasing operations, and the stored data therein can be retained after the device is not powered. Hence, non-volatile memory has become a widely-adopted memory device in personal computers and electronic equipments.
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With scaling down integrated circuit devices, memory size is reduced with line width shrinkage. As a consequence, the space between neighboring floating gates is also narrowed as devices are miniaturized. A control gate material will not fully fill the space and easily result in the formation of holes 114 (as shown in
To overcome the above-mentioned issue, a planarizing floating gate structure (as shown in
With the present trend of miniaturizing devices, how to maintain the level of integration and reliability of the devices within a limited space is one of the important focuses of research.
Accordingly, the present invention provides a non-volatile memory and a manufacturing method thereof for increasing the space between the neighboring floating gates to avoid the formation of holes in subsequently filled layers without reducing the coupling ratio of the control gate and the floating gate, and furthermore, to comply with the current trend of miniaturizing devices.
The present invention is directed to a manufacturing method of non-volatile memory. First, a substrate is provided. An insulating layer, a first conductive material layer, and a polish stop layer are sequentially formed on the substrate. Then, a plurality of trenches is formed in the polish stop layer, the first conductive material layer, the insulating layer, and a portion of the substrate, and the first conductive material layer is segmented into a plurality of conductive blocks. A dielectric material layer is formed to cover the polish stop layer and fill the trenches. Then, a chemical mechanical polishing process is performed till the surface of the polish stop layer is exposed. A portion of the dielectric material layer is removed until the surface thereof is slightly higher than the surface of the insulating layer, so as to form a plurality of trench isolation structures. Thereafter, a portion of sidewalls exposed by each of the conductive blocks is removed to form a plurality of floating gates. The width of each floating gate decreases from bottom to top.
According to an embodiment of the present invention, the manufacturing method of the non-volatile memory further includes forming an inter-gate insulating layer on the floating gate and the trench isolation structure, and forming a second conductive material layer for covering the inter-gate insulating layer. A material of the inter-gate insulating layer is, for example, silicon oxide, silicon oxide/silicon nitride, or silicon oxide/silicon nitride/silicon nitride.
According to a manufacturing method of an embodiment in the present invention, a method for removing a portion of sidewalls exposed by each conductive block to form the floating gate is, for example, dry etching or wet etching.
According to a manufacturing method of an embodiment in the present invention, a material of the polish stop layer is, for example, silicon nitride or silicon oxynitride.
According to an embodiment of the present invention, the manufacturing method of the non-volatile memory further includes forming a hard mask layer on the polish stop layer before the formation of the above-mentioned trenches, and a material of the hard mask layer is, for example, amorphous carbon. In an embodiment, a forming method of the above-mentioned trenches is, for example, forming a patterned photoresist layer on the hard mask layer. Then, the patterned photoresist layer is used as a mask to etch the hard mask layer, the polish stop layer, the first conductive material layer, the insulating layer, and a portion of the substrate so as to form the trenches.
The present invention is directed to another manufacturing method of non-volatile memory. In the method, a substrate is provided first. The substrate has a memory cell region and a peripheral circuit region. An insulating layer, a first conductive material layer, and a polish stop layer are sequentially formed on the substrate. Then, a plurality of first trenches is formed in the polish stop layer, the first conductive material layer, the insulating layer, and a portion of the substrate of the memory cell region, and the first conductive material layer is segmented into a plurality of conductive blocks. Thereafter, a plurality of second trenches is formed in the polish stop layer, the first conductive material layer, the insulating layer, and a portion of the substrate of the peripheral circuit region. A dielectric material layer is formed to cover the polish stop layer, and fill the first trenches and the second trenches. A chemical mechanical polishing process is then performed till the surface of the polish stop layer is exposed. A portion of the dielectric material layer of the memory cell region is removed until the surface of the dielectric material layer is slightly higher than the surface of the insulating layer so as to form a plurality of trench isolation structures in the memory cell region. Thereafter, a portion of sidewalls exposed by each conductive block is removed to form a plurality of floating gates. The width of each floating gate decreases from bottom to top.
According to an embodiment of the present invention, the manufacturing method of the non-volatile memory further includes forming an inter-gate insulating layer on the floating gate and trench isolation structure of the memory cell region, and forming a second conductive material layer for covering an inter-gate insulating layer and a peripheral circuit region.
According to the manufacturing method of the embodiment in the present invention, a material of the inter-gate insulating layer includes, for example, silicon oxide, silicon oxide/silicon nitride, or silicon oxide/silicon nitride/silicon nitride.
According to the manufacturing method of the embodiment in the present invention, a method of removing a portion of sidewalls exposed by each conductive block to form the floating gate is, for example, dry etching or wet etching.
According to the embodiment of the present invention, the manufacturing method of the non-volatile memory further includes forming a hard mask layer on the polish stop layer before the formation of the first trenches. A material of the hard mask layer is, for example, amorphous carbon. In an embodiment, a forming method of the first trenches is, for example, forming a patterned photoresist layer on the hard mask layer of the memory cell region. Then, the patterned photoresist layer is used as a mask to etch the hard mask layer, the polish stop layer, the first conductive material layer, the insulating layer, and a portion of the substrate so as to form the trenches. In another embodiment, a forming method of the second trenches is, for example, forming an anti-reflective layer to cover the hard mask layer and fill the trenches after the formation of the first trenches. Then, a patterned photoresist layer is formed to expose a portion of the anti-reflective layer of the peripheral circuit region. The patterned photoresist layer is used as a mask to etch the anti-reflective layer, the hard mask layer, the polish stop layer, the first conductive material layer, a tunneling dielectric layer, and a portion of the substrate so as to form the second trenches.
According to an embodiment of the present invention, a material of the polish stop layer is, for example, silicon nitride or silicon oxynitride.
The present invention further provides a non-volatile memory including a substrate, a plurality of floating gates, a plurality of gate dielectric layers, and a plurality of trench isolation structures. The floating gates are disposed on the substrate, and the width of each floating gate decreases from bottom to top. The gate dielectric layers are disposed between each floating gate and the substrate respectively. The trench isolation structures are respectively disposed in the substrate between two neighboring floating gates, and the surface of each trench isolation structure is slightly higher than the surface of the gate dielectric layer.
In an embodiment, the non-volatile memory further includes an inter-gate insulating layer and a conductive material layer. The inter-gate insulating layer is disposed on the floating gates and the trench isolation structures. The conductive material layer is disposed on the inter-gate insulating layer. A material of the inter-gate insulating layer is, for example, silicon oxide, silicon oxide/silicon nitride, or silicon oxide/silicon nitride/silicon nitride.
The width of the floating gates decreases from bottom to top so that the space between the neighboring floating gates is increased to prevent the formation of holes in subsequently filled layers, and thereby affecting the performance of the device. Moreover, the present invention does not utilize a conventional fabricating process of the planarizing floating gate structure. Hence, the problem of an inferior coupling ratio between the control gate and the floating gate is prevented, so as to comply with the current trend of miniaturizing devices.
In order to make the above and other objectives, features, and advantages of the present invention more comprehensible, several embodiments accompanied with figures are described in details below.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
The following description further explains the process of manufacturing the non-volatile memory of the present invention. The example, however, is not intended to limit the present invention.
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An insulating layer 406 is formed on the substrate 400 as a tunneling dielectric layer of the memory cell region 402 and a gate dielectric layer of the peripheral circuit region 404. A material of the insulating layer 406 is, for example, silicon oxide. A forming method of the insulating layer 406 is well-known to those skilled in the art, and is not further described herein.
Then, a conductive material layer 408 is formed on the substrate 400. A material of the conductive material layer 408 is, for example, doped polysilicon. A forming method of the conductive material layer 408 is, for example, performing a chemical vapor deposition (CVD) first to form an un-doped polysilicon layer and then performing an ion implanting process to form the conductive material layer 408. Alternatively, the conductive material layer 408 may also be formed by adopting an in-situ ion implanting operation and performing a chemical vapor deposition (CVD) process.
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Please note that the bottom width of the formed floating gates 409 is approximately equal to the width of the conductive block 408a, and the top width of the floating gates 409 is smaller than the bottom width thereof, and the width of the floating gates 409 decreases from bottom to top. Therefore, the space between the neighboring floating gates 409 can be enlarged to prevent the control gate material from causing holes in the space because of the miniaturization of the conventional manufacturing method. In another aspect, the method of the present embodiment does not require the conventional manufacturing process of a planarizing floating gate structure. Therefore, the method does not incur the problem of reduced the coupling ration between the control gate and the floating gate.
The manufacturing process of the other elements, such as an inter-gate dielectric layer and a control gate, can proceed further after the floating gates 409 are formed.
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Thereafter, a conductive material layer 426 is formed above the substrate 400 to cover the inter-gate dielectric layer 424, and the trench isolation structures 421 and the conductive material layer 408 of the peripheral circuit region 404. The conductive material layer 426 is used as the control gate of the memory cell region 402 and is combined with the conductive material layer 408 of the peripheral circuit region 404 to constitute the gate structure of the device. Similarly, a material and forming method of the conductive material layer 426 are the same as those of the conductive material layer 408.
In an embodiment, a metal silicide layer 428 is selectively formed above the conductive material layer 426 to reduce the resistance of the device. A material of the metal silicide layer 428 includes, for example, tungsten silicide, titanium silicide, cobalt silicide, tantalum silicide, nickel silicide, platinum silicide, or palladium silicide. A forming method of the metal silicide layer 428 is, for example, the chemical vapor deposition process.
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The present embodiment provides a non-volatile memory, including a substrate 400; a floating gate 409, disposed on the substrate 400, whose width decreases from bottom to top; a gate dielectric layer (an insulating layer 406), which is respectively disposed between the floating gate 409 and the substrate 400; a trench isolation structure 423, respectively disposed in the substrate 400 between two neighboring floating gates, whose surface is slightly higher than the surface of the insulating layer 406; an inter-gate insulating layer (an inter-gate dielectric layer 424), which is disposed on the floating gate 409 and the trench isolation structure 423; and a conductive material layer 426, which is disposed on the inter-gate dielectric layer 424. Moreover, in other embodiments, a metal silicide layer 428 can be formed on the conductive material layer 426 to reduce the resistance of the device. In summary, the present invention at least has the following advantages:
1. In the present invention, the width of the floating gates decreases from bottom to top, which increases the space between two neighboring floating gates and prevents the holes from being created when layers are filled in the space subsequently.
2. The present invention avoids reducing the coupling ratio between the control gate and the floating gate, and enhances the device performance.
3. The present invention applies self-alignment and critical simplification to form the floating gates, which simplifies the manufacturing process and complies with the current trend of device miniaturization.
Although the present invention has been disclosed above by the embodiments, they are not intended to limit the present invention. Anybody skilled in the art can make some modifications and alteration without departing from the spirit and scope of the present invention. Therefore, the protecting range of the present invention falls in
Number | Date | Country | Kind |
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96141209 | Nov 2007 | TW | national |