1. Field of Invention
The present invention relates to a process for forming semiconductor devices. More particularly, the present invention relates to a gap-filling process for forming semiconductor devices.
2. Description of Related Art
Gap-filling process is a technique that has many applications in semiconductor production. In semiconductor manufacturing, the gap-filling process is often used after openings are formed. Different material is deposited into the openings according to the type of structure desired. For example, insulating material is deposited into the trenches of a shallow trench isolation (STI) structure and conductive material is deposited into the contact window of an inter-metal dielectric (ILD) structure, the via of an inter-metal dielectric (IMD) structure or the metallic interconnect opening of a dual damascene structure.
FIGS. 1A to 1D are schematic cross-sectional views showing the progression of steps for forming a gap-filled material layer in the via opening of a via first dual damascene (VFDD) structure using a conventional gap-filling method. As shown in FIG. 1A, a substrate 100 having a conductive line 102 thereon is provided. A protective layer 104, a dielectric layer 106, an etching stop layer 108, a second dielectric layer 110, a cap layer 112 are sequentially formed over the substrate. A via opening 114 that passes through the cap layer 112, the second dielectric layer 110, the etching stop layer 108, the dielectric layer 106 and exposes the protective layer 104 is formed.
As shown in FIG. 1B, a gap-filling material is deposited into the via opening 114 to form a gap-filling material layer 116.
As shown in FIG. 1C, a polishing or etching process is conducted to remove excess gap-filling material from the gap-filling material layer 116 and expose the cap layer 112. Hence, a gap-filled material layer 118 is formed inside the via opening 114.
As shown in FIG. 1D, a bottom anti-reflection coating (BARC) 120 is formed over the cap layer 112 and the gap-filled material layer 118.
However, the aforementioned method of forming a gap-filling material layer 118 inside the via opening 114 has a few problems. When the gap-filling material layer 116 is formed over the substrate 100, a downward caving surface is formed near the mouth of the via opening 114 leading to the formation of a recess cavity in the gap-filling material layer 118 even after polishing or etching. The presence of this recess cavity in the gap-filling material layer 118 results in the production of a similar cavity in the subsequently formed bottom anti-reflection coating 120 and photoresist layer above the gap-filling material layer 118. A non-planar profile is a major factor that intensifies the so-called striation effect. The striation effect contributes to a worsening of thickness uniformity in an overlying photoresist layer. Ultimately, critical dimensions (CD) and the dimensions measured in the after etching inspection (AEI) may deviate too much from the desired range because an accurate pattern is no longer reproduced.
In addition, the gap-filling material layer 118 may also be subjected to the damaging effects caused by the overlying bottom anti-reflection coating 120 or photoresist layer. In other words, the material in the bottom anti-reflection coating 120 or the photoresist layer and the material in the gap-filling material layer 118 may intermix leading to a loss of gap material. As a result, there is a further intensification of the striation effect and/or a distortion of the pattern profile after etching the inter-metal dielectric layer rendering the formation of an accurate pattern difficult.
Accordingly, one object of the present invention is to provide a gap-filling process capable of producing a gap-filling material layer with an improved surface planarity so that a subsequently formed bottom anti-reflection coating or photoresist layer over the gap-filling material layer also has a better surface planarity.
A second object of this invention is to provide a gap-filling process capable of preventing the loss of gap-filling material from a gap-filling material layer due to contact with a bottom anti-reflection coating or a photoresist layer. Consequently, the gap-filling material layer and the bottom anti-reflection coating or the photoresist layer can have a better surface planarity.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a gap-filling process. A substrate having a dielectric layer thereon is provided. An opening is formed in the dielectric layer. A gap-filling material layer is formed over the dielectric layer and inside the opening. A portion of the gap-filling material layer is removed to expose the dielectric layer. The gap-filling material layer and the surface of the dielectric layer undergo a gap-filling material treatment.
The gap-filling material treatment may include etching the dielectric layer and the gap-filling material layer to planarize the gap-filling material layer.
In addition, the gap-filling material treatment may also include performing a plasma processing, an ultraviolet curing or a chemical immersion of the gap-filling material layer to form a protective layer over the gap-filling material layer.
Furthermore, the gap-filling material treatment may involve etching the dielectric layer and the gap-filling material layer to planarize the gap-filling material layer and then performing a plasma processing, an ultraviolet curing or a chemical immersion of the gap-filling material layer to form a protective layer over the gap-filling material layer.
In this invention, the gap-filling material layer is etched to form a planar surface. Hence, any layer deposited over the gap-filling material layer can have a high level of planarity that facilitates the formation of a correct pattern in subsequent photolithographic and etching operation.
Since a protective layer is formed over the gap-filling material layer, intermixing of material between the bottom anti-reflection coating or the photoresist layer with the gap-filling material layer is stopped. Thus, the gap-filling material layer and the bottom anti-reflection coating or the photoresist layer can have a high degree of surface planarity. Ultimately, an accurate pattern is reproduced after a photolithographic and etching operation.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.