a and 2b are cross-sectional views taken along lines A-A′ and B-B′ of the microlens pattern and microlens manufactured using the mask pattern of
a is a cross-sectional view of the phase shift mask according to the present invention.
b is a cross-sectional view of microlenses formed using the mask of
a to 5c are cross-sectional views sequentially showing an exemplary manufacturing process of the phase shift mask according to the present invention.
Hereinafter, a mask for manufacturing a plurality of microlenses according to the present invention will be described in detail with reference to the accompanying drawings.
Referring to
And, a planarization layer 116 is formed on the color filters 133a, 133b, and 133c. Thereafter, a plurality of microlenses 140 are formed on the planarization layer 116 so that each microlens 140 is located on a perpendicular line to the photodiode area 103a, 103b, or 103c.
Meanwhile, although not shown, the transistor comprises a light charge transmitter transmitting light charge generated from the photodiode, and a light color sensitivity calculator sensing an amount of light (e.g., red, green, or blue) received by the photodiode. The CMOS image sensor applies (multiple) back bias voltages to the rear surface of the semiconductor so that it varies the width of the depletion area of the photodiode and senses the red, green, or blue light received on the photodiode.
a is a cross-sectional view of an exemplary phase shift mask according to the present invention, and
As shown in
Each of the first to third phase shifting layers 251, 252, and 253 can have different sizes or dimensions (e.g., thickness and/or width), etc., according to the desired curvature of the microlens 240, and they are made of transflective phase shifting material (e.g., chrome or other material conventionally used to make transmission-reducing or light-blocking regions on a mask). It is preferable that the first to third phase shifting layers 251, 252, and 253 have (or define regions on the mask having) different light transmissivities and phase transition rates from each other.
If the microlens 240 is patterned on a substrate 200 using the mask of
a to 5c are cross-sectional views showing the fabrication process of an exemplary phase shift mask according to the present invention.
As shown in
As shown in
As shown in
Therefore, if the line width of the first phase shifting layer 251 is referred to as “c”, the line width of the second phase shifting layer 252 is referred to as “b”, and the line width of the third phase shifting layer 253 is referred to as “a”, the region of the mask corresponding to the line width “a” of the third phase shifting layer 253 (where the first, second and third phase shifting layers 251-253 are stacked) has the lowest light transmissivity. That region also has a phase shift that approaches 180°, as shown in
The first to third phase shifting layers 251, 252, and 253 (which are at least part of a mask pattern 255 of the phase shift mask according to the present invention) may have different transmissivities from each other. Independently, the transmissivity of a given phase shifting layer may be selected from values in the range of from 2% to 10%. The mask pattern 255 has a structure where at least two (or more) phase shifting layers are stacked, as a minimum condition.
c shows a graph showing the relation of light intensity according to locations of an exemplary phase shift mask according to the present invention. Herein, if the mask pattern 255 where the first to third phase shifting layers 251, 252, and 253 are stacked is irradiated, the light passing therethrough has a phase difference of 180° (or thereabout) from the light passing through a central portion of a light-transmitting region of quartz substrate 250 (e.g., passing through only the quartz substrate 250), and the offset interference of light occurs in the place where the transparent quartz substrate 250 semitransmitting film material (e.g., the region where only the first phase shifting layer 251 is formed, corresponding to line width “a”; optionally, a different material, not shown) to improve contrast, finally making it possible to obtain a desired microlens pattern on the semiconductor substrate regardless of the location of the microlens on the wafer or the corresponding phase shifting layer(s) in the mask pattern.
At this time, the present invention has advantages that the boundary between the lens unit and the non-lens unit is clearly differentiated, and a critical dimension (CD) of the microlens pattern is improved. Also, although the ends of the microlens pattern 240 become adjacent to each other, the present invention can evenly maintain the slope and/or curvature of the microlens. And, the present invention modifies the line width and/or thickness of the first to third phase shifting layers 251, 252, and 253, making it possible to form microlenses having a desired radius of curvature and increasing the receiving rate of the photodiode.
The mask pattern 255 of the phase shift mask is described by showing a structure where the first to third phase shifting layers 251, 252, and 253 are stacked in one embodiment of the present invention, but is not limited thereto. Therefore, the mask pattern 255 can be formed by stacking at least two (or more) phase shifting layers.
As shown in
As shown in
Each of the first to third phase shifting layers 251, 252, and 253 can have a different size or dimension (e.g., thickness and/or width, etc.), according to the desired curvature of the microlens 240. The phase shifting layers 251, 252, and 253 may also comprise or be made of transflective phase shifting material.
It is preferable that the first to third phase shifting layers 251, 252, and 253 have different light transmissivities and phase transition rates from each other.
If the microlens 240 having an even size is patterned on a substrate 200 using the phase shift mask of
When forming the microlens pattern using the phase shift mask according to the present invention, a defect that the microlens curvature in or near the edge of the mask becomes uneven can be prevented (e.g., by means of the high-temperature bake process).
With the present invention, the phase shift mask for forming the microlens in the CMOS image sensor is formed by stacking at least two or more phase shifting layers having different transmissivities from each other so that the microlens can have an even or more uniform size when forming the microlens using the phase shift mask, and/or the microlens can have an even or more uniform curvature regardless of the location on the mask pattern array. Also, when forming the microlens pattern using the phase shift mask according to the present invention, a defect that the microlens curvature on the edge of the mask becomes uneven is prevented (e.g., by means of a high-temperature bake process), and the microlens has even curvature (e.g., by means of a low-temperature bake process), regardless of the density of the microlens pattern, making it possible to improve manufacturing yield.
Also, present invention can clearly differentiate the boundary between the lens unit and the non-lens unit on the semiconductor substrate and can improve the CD of the microlens pattern. Also, although the end of the microlens pattern becomes close to the end of the microlens pattern adjacent thereto, the present invention can maintain the slope and/or curvature of the microlens, making it possible to improve resolution of the microlens.
Also, the present invention may modify one or more line widths and/or thicknesses of the phase shifting layer of the mask, making it possible to variously form microlenses having a desired radius of curvature and possibly increase the receiving rate of light at the photodiode.
Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.
Number | Date | Country | Kind |
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10-2006-0068696 | Jul 2006 | KR | national |