Some communication equipment is capable of processing only voice signals, while other more complex equipment processes both voice signals and image signals. Recently, more communication equipment is cable of possessing both voice signals and image signals at the same time. Accordingly, a semiconductor device for an image sensor that can process image signals is in increasing demand, and its importance is gradually increasing.
FIGS. 1A to 1E are cross-sectional drawings illustrating a procedure of fabricating a semiconductor device for an image sensor according to the related art.
Referring to FIG. 1A, an insulating material may be deposited on semiconductor substrate 102 and may form lower insulating film 104 on the entire surface of semiconductor substrate 102. A photoelectric element and a logic circuit may be formed in semiconductor substrate 102.
Referring to FIG. 1B, an insulating material may be deposited on lower insulating film 104 to form upper insulating film 106. During the formation of upper insulating film 106, a metal interconnection (not shown) may be formed. That is, after upper insulating film 106 may be formed, via holes or contact holes may be formed. Then, metal may be buried in the formed via holes or contact holes and the metal interconnection may be formed by performing a planarization process such as a CMP process. Accordingly, upper insulating film 106 may be formed to be flat.
Referring to FIG. 1C, a photoresist may be coated on the entire surface of semiconductor substrate 102. Then, an exposure process may be performed using a mask to selectively remove a portion of the photoresist, thereby forming a photoresist pattern.
Further, color filters 108, which may have a specified pattern, may be formed on upper insulating film 106 using the photoresist pattern.
Referring to FIG. 1D, a photoresist may be coated on semiconductor substrate 102, Planarization layer 110 may be formed over color filters 108.
Referring to FIG. 1E, a photoresist may be coated on semiconductor substrate 102. An exposure process may then be performed using a mask to selectively remove a portion of the photoresist, thereby leaving the photoresist only at positions corresponding to color filters 108 formed below the photoresist, i.e., on the portions where color filters 108 may be formed.
Next, a heat treatment process may be performed on the remaining photoresist. Accordingly, through the photoresist flow process, convex micro lenses 112 having a specified radius of curvature may be formed on planarization layer 110.
In the related art semiconductor device for an image sensor formed through the above process, micro lenses 112 that may be used to collect light may be formed on the planar surface of planarization layer 110.
Thus, a light-receiving region may be small. That is, there may be a limited area onto which light may be projected, which may limit a range of real images to be captured.
Color filters 108 may receive light which has passed through micro lenses 112 and may transmit only a specified wavelength of light. Accordingly, photodiodes may convert light which has passed through color filters 108 into signals, and may then output the signals.
However, in the above-described related art technology, all of the projected light may not pass through color filters 108 and the light may leak between color filters 108 as natural light, which may cause noise in the signals.
Further, light having a substantially short wavelength which has passed through color filters 108 may be also incident on another photodiode under the neighboring color filter, which may cause a crosstalk phenomenon. The crosstalk phenomenon may deteriorate the characteristics of the image sensor.