The present invention relates generally to a coating process, and more specifically to a spin-on-dielectric (SOD) process.
Dielectric materials are often deposited by spin-on dielectric (SOD) process or chemical vapor deposition (CVD) process. While using the spin-on dielectric (SOD) process, a flowable dielectric material can be coated into gaps in a substrate easily through adjusting dibasic ester (DBE) system. This is an unique advantage of the spin-on dielectric (SOD) process, and thus the spin-on dielectric (SOD) process is widely used in nowadays industry.
Trenches with different sizes are usually formed in a substrate. A dielectric material covers the surface of the trenches while coating the dielectric material on the substrate by the spin-on dielectric (SOD) process. However, voids may occur in the films transformed by the dielectric material, which usually occurs at the bottom of the trenches. Thus, it becomes a challenge to eliminate the voids in the films.
The present invention provides a spin-on-dielectric process, which heats a flowable material spread during a spin-on-dielectric process for forming a dielectric, thereby increasing the fluidity of the flowable material and improving the gap filling capability of the flowable material.
The present invention provides a spin-on-dielectric process including the following steps. A substrate is provided. A flowable material is spread on a surface of the substrate to form a spin-on-dielectric layer on the substrate, wherein the flowable material is heated to a temperature higher than 25° C.
According to the above, the present invention provides a spin-on-dielectric process, which heats a flowable material while spread it on a surface of a substrate, especially for heating the flowable material to a temperature higher than 25° C., to form a spin-on-dielectric layer on the substrate. By doing this, the viscosity of the flowable material is reduced, the fluidity of the flowable material is increased and the gap filling capability of the flowable material is improved. Hence, voids in the formed spin-on-dielectric layer can be avoided.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
A plurality of trenches R1/R2/R3 are formed in the substrate 110, wherein methods of forming the trenches R1/R2/R3 may include the following, but it is not restricted thereto. A pad oxide layer (not shown) and a pad nitride layer (not shown) are formed blanketly and sequentially on the substrate 110, and the pad nitride layer and the pad oxide layer are patterned to form a pad oxide layer 2 and a pad nitride layer 4, thereby areas of the substrate 110 for forming the trenches R1/R2/R3 being exposed. The substrate 110 is then etched to form the trenches R1/R2/R3 . In this case, the plurality of trenches R1 are formed in the first area A1 of the substrate 110, the plurality of trenches R2 are formed in the second area A2 of the substrate 110, and the trench R3 is formed in the third area B of the substrate 110. There are six trenches R1, three trenches R2 and one trench R3 depicted in the figures, but the numbers of the trenches R1, the trenches R2 and the trench R3 are not restricted thereto. A width W1 of each of the trenches R1 is smaller than a width W2 of each of the trenches R2, and the width W2 of each of the trenches R2 is smaller than a width W3 of the trench R3. The widths W1/W2/W3 depend upon sizes of devices requiring to be isolated.
As shown in
As shown in
It is emphasized that, the flowable material 30′ is heated while is spread on the surface S1 of the substrate 10. Methods of heating the flowable material 30′ may include heating the surface S1 of the substrate 10 directly or heating a nozzle 5 spreading the flowable material 30′. In another case, the surface S1 of the substrate 10 and the nozzle 5 spreading the flowable material 30′ are heated at the same time, depending upon requirements.
Preferably, the flowable material 30′ is heated to a temperature higher than 25° C. while the flowable material 30′ is spread on the surface S1 of the substrate 110. By doing this, the viscosity of the flowable material 30′ is reduced, the fluidity of the flowable material 30′ is increased, thereby improving the gap filling capability of the flowable material 30′ to avoid voids in the spin-on-dielectric layer 30. In a preferred embodiment, the flowable material 30′ is heated to a temperature of 30° C.-100° C. while the flowable material 30′ is spread on the surface S1 of the substrate 110. In a still preferred embodiment, the flowable material 30′ is heated to a temperature of 30° C.-40° C. while the flowable material 30′ is spread on the surface S1 of the substrate 110. Since the viscosity of the flowable material 30′ decreases in a temperature range but increases higher than this temperature range, the viscosity of the flowable material 30′ decreases without solidification while the flowable material 30′ is heated in a temperature of 30° C.-100° C. Furthermore, while the flowable material 30′ is heated in a temperature of 30° C.-40° C., processing efficiency can be increased and processing costs can be reduced.
The fluidity of a solute of the flowable material 30′ is increased, or/and the viscosity of a solvent of the flowable material 30′ is reduced while the flowable material 30′ is heated, thereby improving the gap filling capability of the flowable material 30′, and avoiding voids in the spin-on-dielectric layer 30. The solute of the flowable material 30′ may include polysilazane (PSZ, SiH2NH), but it is not limited thereto. The solvent of the flowable material 30′ may include aromatic hydrocarbons, aliphatic hydrocarbons or ether-type solvents, but it is not limited thereto. The flowable material 30′ can be constituted by the solute and the solvent, but it is not limited thereto.
Please refer to
According to the above, the improved spin-on-dielectric process of the present invention is applied to form isolation structures isolating the Dynamic Random Access Memory (DRAM) cells having recessed gate structures from each other.
Another embodiment applying the present invention to form an interdielectric layer of a dynamic random access memory (DRAM) device having recessed gate structures is presented, but the present invention can also be applied in other layers of the dynamic random access memory (DRAM) device.
A plurality of embedded word lines 220 are disposed in the substrate 210 and trenches R4 are formed in the substrate 210 for forming bit line contacts in later processes. Isolation materials covering a surface of the substrate 210 may include a plurality of silicon oxide layers 232, silicon nitride layers 234, silicon oxide layers 236 and etc, but it is not limited thereto.
As shown in
As shown in
As shown in
As shown in
As the flowable material 30′ is spread on the surface S1 of the substrate 10, the flowable material 30′ is heated as well. Methods of heating the flowable material 30′ may include heating the surface S1 of the substrate 10 directly, or heating the nozzle 5 for spreading the flowable material 30′. In another embodiment, the surface S1 of the substrate 10 and the nozzle 5 for spreading the flowable material 30′ are heated at the same time, depending upon practical requirements.
In a preferred embodiment, the flowable material 30′ is heated to a temperature higher than 25° C. as the flowable material 30′ is spread on the surface S1 of the substrate 10. This can decrease the viscosity of the flowable material 30′, increases the fluidity of the flowable material 30′ and improves the gap filling capability of the flowable material 30′ to prevent the spin-on-dielectric layer 264 from having voids therein. In a still preferred embodiment, the flowable material 30′ is heated to a temperature of 30° C.-100° C. as the flowable material 30′ is spread on the surface S1 of the substrate 10. Preferably, the flowable material 30′ is heated to a temperature of 30° C.-40° C. as the flowable material 30′ is spread on the surface S1 of the substrate 10. The viscosity of the flowable material 30′ decreases gradiently in a temperature range, but the flowable material 30′ solidifies beyond the temperature range. Therefore, as the flowable material 30′ is heated to a temperature of 30° C.-100° C., the viscosity of the flowable material 30′ is decreased without solidified. As the flowable material 30′ is heated to a temperature of 30° C.-40° C., process efficiency is improved and processing cost is reduced.
More precisely, the fluidity of a solute of the flowable material 30′ is increased, or/and the viscosity of a solvent of flowable material 30′ is reduced as the flowable material is heated, thereby the gap filling capability of the flowable material 30′ can being improved to avoid voids in the spin-on-dielectric layer 264. The solute of the flowable material 30′ may include polysilazane (PSZ, SiH2NH), and the solvent of the flowable material 30′ may include aromatic hydrocarbons, aliphatic hydrocarbons or ether-type solvents, but it is not limited thereto. The flowable material 30′ can be constituted by the solute and the solvent, but it is not limited thereto.
As shown in
To summarize, the present invention provides a spin-on-dielectric process, which heats a flowable material while spread it on a surface of a substrate, especially for heating the flowable material to a temperature higher than 25° C., to form a spin-on-dielectric layer on the substrate. By doing this, the viscosity of the flowable material is reduced, the fluidity of the flowable material is increased and the gap filling capability of the flowable material is improved. Hence, voids can be avoided in the formed spin-on-dielectric layer.
In a preferred embodiment, the flowable material is heated to a temperature of 30° C.-100° C. to reduce the viscosity of the flowable material and prevent the flowable material from being solidified. In a still preferred embodiment, the flowable material is heated to a temperature of 30° C.-40° C. to improve processing efficiency and reduce processing cost.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
Number | Date | Country | Kind |
---|---|---|---|
201710455942.2 | Jun 2017 | CN | national |