1. Field of the Invention
This invention relates to a method of gap filling between metal-metal lines, and more particularly to utilize a method of HDP-IMD in the back end process to fill a gap between metal-metal lines.
2. Description of the Prior Art
Generally, as semiconductor dimensions continue to shrink and device densities increase, the depositing technique in the back end process of ultra large scale integration (ULSI) can not achieve the gap fill without voids because of the shrinkage in the gap between metal-metal lines. However, a method of high density plasma-chemical vapor deposition (HDP-CVD) is utilized to fill the narrow gap and to prevent the production of voids due to its excellent ability in filling the gap. Consequently, the oxide is generally decomposed to be a material of inter-metal dielectric and passivation for filling the gap between the metal-metal lines.
The HDP-CVD is the method of chemical vapor deposition for executing the depositing and etching process in the meantime. When the size of pattern is reduced, the width of the metal line and the gap between the metal lines are become smaller. However, due to the fact that the resistor of the metal line can not be increased so that the height of the metal line can not be relatively decreased, and therefore causes a bigger aspect ratio. Accordingly, it makes a larger challenge in the process of inter-metal dielectric (IMD) deposition.
The method for depositing the second inter-metal dielectric layer 111 utilizes a method for depositing a thin film, for instance HDP-CVD. Nevertheless, when the integrity of the devices become higher and the aspect ratio of the gap become larger, an overhang is easily produced while depositing the thin film, as a result the device has variable geometric shapes thereon, and the material's low migration. When the second inter-metal dielectric layer 111 is depositing, the rate of deposition is quite different at different positions, for instance the top of the hole with a bigger arriving angle has faster rate for depositing, but the bottom of the hole with the smaller arriving angle has a slower one. If the material has a reaction as soon as it absorbs on the device and not migrate anywhere, the top of the hole with the bigger arriving angle will have an overhang. Therefore, when the thickness of the film is getting enhanced, the overhang is getting bigger due to the arriving angle effect and material's low migration and HDP process re-deposition issue. Accordingly, the gap between the metal-metal lines will be quickly sealed so that causes the voids 113 produced inside the gap, as shown in
As mentioned above, due to the fact that the conventional method of HDP-IMD does not have the ability in satisfactorily filling the gap and the advanced process, and as a result, a problem with producing the voids in the gap between the metal-metal lines occurs. Therefore, an improved method of filling the gap between the metal-metal lines is necessary to require in order to overcome the problems of the process in the prior art.
According to the background of the invention as in the prior art, some drawbacks in the process of filling the gap occurs, therefore this invention makes efforts in the improvement of the process for filling the gap between the metal-metal lines. Hence, the present invention is provided.
To resolve the problem with the voids in the gap between the metal-metal lines while gap filling, the present invention provides a method of HDP-IMD process, which improves the ability in filling of the gap. It can satisfy the ability of filling the gap in the advanced process, and not damage the surface of the metal lines.
To resolve the problem with the voids in the gap between the metal-metal lines while gap filling, the present invention further provides a method of HDP-IMD process, which improves the ability in filling of the gap. It utilizes a recipe to accomplish the sputter and HDP silicon oxide deposition process in situ.
To resolve the problem with the voids in the gap between the metal-metal lines while gap filling, the present invention still provides a method of HDP-IMD process, which improves the ability in filling of the gap. It performs the deposition twice to avoid the voids producing in the gap.
According to the objectives as mentioned above, one embodiment provides a method of high density plasma-chemical vapor deposition which has high ability of gap filling that comprises the steps at least: providing a semiconductor structure, and the surface of the semiconductor structure has a plurality of metal lines thereon. Then, utilizing a first high density plasma to partially deposit a first dielectric layer on the surface and side wall of the plurality of metal lines. Afterwards, before forming the voids, a second high density plasma is utilized to remove a portion of the first dielectric layer until a portion of the side wall of metal lines are exposed, wherein the portion of the first dielectric layer is remained on the portion of the metal lines. Next, a second dielectric layer is deposited on the first dielectric layer by a third high density plasma and covering on the metal lines. The first high density plasma has the same composition with the third high density plasma that comprises an inert gas, an oxidative gas and a depositing gas.
The objectives and features of the present invention as well as advantages thereof will become apparent from the following detailed description, considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings, which are not to scale, are designed for the purpose of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.
The present invention can be the best understood through the following description and accompanying drawings, wherein:
The preferred embodiment is explained with reference to the drawings of
Besides, an adhesive layer 205 is formed on the underside of the metal lines 207 before forming the plurality of metal lines 207, for instance titanium nitride (TiN) layer that provides a way of adhesive with the inter-metal dielectric layer 203, and then the process for depositing metal lines 207 is performed. Moreover, in order to avoid influencing the process with a light reflection by the metal layer, an anti-reflection layer (ARC) 211 is formed on the top of the metal lines 207, for instance a silicon-oxy-nitride (SiOxNy) layer that ensures the accuracy in the process of mask transferring.
Following that, performing the first step of gap filling in the present invention, please refer to
Subsequently, performing the second step of gap filling in the present invention, please refer to
After removing the portion of the first dielectric layer 213, a third step in the present invention is performed, as shown in
Due to the fact that the present invention utilizes the method of high density plasma-chemical vapor deposition, and performing the “etching” and “deposition” processes in situ in the same chamber so that the film, which is deposited, has higher density. The first dielectric layer 213 is partially removed before depositing the second dielectric layer 217 so that the portion of the first dielectric layer 213 still remains within the gap between the metal lines 207 that causes the gap between the metal lines 207 has smaller aspect ratio. After that, the gap between metal lines 207 will be completely filled with no voids after depositing the second dielectric layer 207. Accordingly, the present invention can satisfy the ability of filling in advanced process, and accomplish the Ar/O2 sputter and HDP silicon oxide deposition process in situ in the same chamber. It notes that the 1st HDP oxide deposition and the following Ar/O2 sputter process also can be performed in different chamber.
It notes that the method of filling in the present invention is not only utilized in filling the gap between the metal-metal lines, but also utilized in other methods for filling the notch such as the process of shallow trench isolation (STI). In other embodiments, the depositing gas, oxidative gas and inert gas are the same as in filling the gap between metal-metal lines. And the RF power is also added therein to produce the high density plasma, moreover; utilizing twice deposition to fill the notch and not produce voids.
The preferred embodiments are only used to illustrate the present invention, not intended to limit the scope thereof. Many modifications of the preferred embodiments can be made without departing from the spirit of the present invention.