This application claims benefit of priority under 35 USC xc2xa7 119 to Korean Patent Application No. 2002-46613, filed on Aug. 7, 2002, the contents of which are hereby incorporated by reference in their entirety.
1. Field of the Invention
The present invention relates to a method for forming a contact in a semiconductor process, and more particularly to a method for forming a contact in a semiconductor device of minute size.
2. Description of the Related Art
Highly integrated semiconductor devices are required to maintain pace with today""s rapidly developing information society. As a result, the dimensions of the electrical wiring in a semiconductor device tends to become increasingly miniaturized, exhibiting a multi-layered construction. To achieve electrical connection between the wirings of the semiconductor device, contacts are necessary.
FIGS. 1A to 1E are cross-sectional views illustrating a conventional method for forming a contact in a semiconductor device.
Referring to FIG. 1A, an etching stop layer 12 having a thickness of approximately 100 to 2,000 xc3x85 is formed on a semiconductor substrate 10 including the portion 10a for the formation of a contact. An interlayer dielectric film 14 is formed on the etching stop layer 12. In this case, the portion 10a for the formation of the contact can include the upper face of a gate electrode, a source, or a drain. Also, the portion 10a for the contact may correspond to the surface of a contact plug.
Referring to FIG. 1B, an anti-reflective layer 16 is formed on interlayer dielectric film 14 to prevent scattering of light from the underlying films during a successive photolithography process. Then, a photoresist pattern 18 is formed on the anti-reflective layer 16. The photoresist pattern 18 opens the portion of the anti-reflective layer 16 corresponding to the portion 10a for the formation of the contact.
Referring to FIG. 1C, portions of the anti-reflective layer 16 and the interlayer dielectric film 14 are successively etched by using the photoresist pattern 18 as an etching mask until the etching stop layer 12 is exposed.
The photoresist pattern 18 is removed through a stripping process. The exposed etching stop layer 12 is etched so that a contact hole 20 exposing the portion 10a for the formation of the contact is formed, resulting in FIG. 1D. When the etching stop layer 12 is etched, the anti-reflective layer 16 is simultaneously removed.
Referring to FIG. 1E, a conductive material is filled in the contact hole 20 to form the contact 22.
According to the conventional method, the size of the contact is determined by means of the photolithography process executed in order to form the photoresist pattern. However, the smallest size of the contact hole may be limited because the photoresist pattern may not be formed to have extremely minute dimensions throughout a photolithography process. In particular, contact holes of recent semiconductor devices are required to have sizes below approximately 100 nm, but a contact hole of this size is difficult to form using conventional processes.
To form a contact smaller than that of the photoresist pattern provided by conventional means, a method has been suggested wherein an additional photoresist re-flow process is performed to flow the photoresist onto the sidewall of the photoresist pattern after the photoresist pattern is formed, as shown in FIG. 1B. However, because the photoresist lacks uniform flow on each region of the semiconductor substrate, the contacts are not the same size over the entire region of the substrate. Specifically, the contacts may have a relatively smaller size in regions where the contacts are closely arranged because the flow rate of the photoresist in those regions is greater than that of the photoresist in the region where the contacts are relatively widely dispersed.
In order to form a contact having minute size, a slant-etching method wherein the upper portion of the contact hole has a larger diameter than that of the lower portion of the contact hole has been suggested. However, the etching rate may be slower when a larger size contact is formed even though an identical film is etched for forming the contact hole through the slant etching process. Hence, a relatively large contact hole may be less etched to produce the contact non-open failure or a relatively small contact hole may be over-etched when contact holes of different sizes are formed in the same regions of the substrate with one etching process.
In order to solve the above-mentioned problem, U.S. Pat. No. 5,719,089 discloses a method for forming a contact hole by etching an insulation film while a polymer is formed on a mask pattern including a polysilicon pattern and a photoresist pattern. However, with this method, the contact may not have the desired size since the thickness of the polymer attached to the contact hole may be hard to control.
The invention solves the afore-mentioned problems and accordingly, it is an object of the invention to provide a method for forming a contact of a semiconductor device having a minute size.
According to an embodiment of the invention, in order to achieve this and other objects, a method is provided for forming a contact of a semiconductor device that includes the following steps. After forming an interlayer dielectric film on a semiconductor substrate including a portion for the formation of a contact, a polysilicon film and an anti-reflective layer are successively formed on the interlayer dielectric film. A first mask pattern is formed on the anti-reflective layer. The first mask pattern includes a first opened portion corresponding to the portion for the formation of the contact. A second mask pattern exposing the polysilicon film is formed via etching the anti-reflective layer exposed through the first mask pattern. A third mask pattern is formed by attaching polymer on a sidewall of the second mask pattern. The third mask pattern includes a second opened portion smaller than the first opened portion. A contact hole exposing the portion for the formation of the contact is formed via etching the polysilicon film and the interlayer dielectric film using the third mask pattern as an etching mask. Then, the contact hole is filled with a conductive material.
To achieve the objects of the invention, according to another embodiment, a method is provided for forming a contact of a semiconductor device comprising the following steps. After successively forming an etching stop layer and an interlayer dielectric film on a semiconductor substrate including a portion for the formation of a contact, a polysilicon film and an anti-reflective layer are successively formed on the interlayer dielectric film. A first mask pattern is formed on the anti-reflective layer. The first mask pattern includes a first opened portion corresponding to the portion for the formation of the contact. A second mask pattern exposing the polysilicon film is formed by etching the anti-reflective layer exposed through the first mask pattern. A third mask pattern is formed by attaching polymer on a sidewall of the second mask pattern. The third mask pattern includes a second opened portion smaller than the first opened portion. After etching the polysilicon film and the interlayer dielectric film using the third mask pattern as an etching mask to expose the etching stop layer, a contact hole exposing the portion for the formation of the contact is formed by etching the exposed etching stop layer while the anti-reflective layer remains on the polysilicon film. Then, the contact hole is filled with a conductive material.
To achieve objects of the invention according to yet another embodiment, a method is provided for forming a contact of a semiconductor device comprising the following steps. After forming an interlayer dielectric film on a semiconductor substrate including a portion for the formation of a contact, a polysilicon film and an anti-reflective layer are successively formed on the interlayer dielectric film. A first mask pattern is formed on the anti-reflective layer. The first mask pattern includes a first opened portion corresponding to the portion for the formation of the contact. A second mask pattern exposing the polysilicon film is formed by etching the anti-reflective layer exposed through the first mask pattern. A third mask pattern is formed by attaching polymer on a sidewall of the second mask pattern. The third mask pattern includes a second opened portion smaller than the first opened portion. After forming a contact hole exposing the portion for the formation of the contact by etching the polysilicon film and the interlayer dielectric film using the third mask pattern as an etching mask to expose the etching stop layer, films remaining on the interlayer dielectric film are removed. Then, the contact hole is filled with a conductive material.
According to the present invention, the polymer is attached to the sidewall of the second mask pattern, and the contact hole is formed using the third mask pattern where the polymer is attached as the etching mask. Therefore, the contact hole can have a smaller size than that of the contact provided by conventional photolithography processes. Additionally, the size of the contact hole can be adjusted by controlling the thickness of the polymer attached to the second mask pattern.