Image sensor with a protection layer

An image sensor die comprises a substrate and an image sensor array formed over the substrate. Micro lens are disposed on the image sensor array. A protection layer is formed on the micro lens to prevent the micro lens from particle containment.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an image sensor, and more particularly to an image sensor structure free of particle contamination on micro lens, and the method for manufacturing the same.

2. Description of the Prior Art

The semiconductor technologies are developing very fast, and especially semiconductor dice have a tendency toward miniaturization. However, the requirements for the functions of the semiconductor dice have an opposite tendency to variety. Namely, the semiconductor dice must have more I/O pads into a smaller area, so the density of the pins is raised quickly. It causes the packaging for the semiconductor dice to become more difficult and decrease the yield. The main purpose of the package structure is to protect the dice from outside damages. Furthermore, the heat generated by the dice must be diffused efficiently through the package structure to ensure the operation the dice. Most of the package technologies divide dice on a wafer into respective dice and then to package and test the die respectively. Another package technology, called “Wafer Level Package (WLP)”, can package the dice on a wafer before dividing the dice into respective dice. The WLP technology has some advantages, such as a shorter producing cycle time, lower cost, and no need to under-fill or molding.

A digital image technique has been wildly applied to image shooting instrument such as digital camera, image scanner, etc. The conventional CMOS sensor is disposed on a circuit board. The CMOS sensor has a chip secured therein. The lens seat has a focusing lens for focusing the image onto the chip of the CMOS sensor. Through the lens, the image signal is sent by the chip to a digital processor for converting the analog signal into digital signal. The Chip of the CMOS sensor is relatively sensitive to infrared ray and dust particles. If the unwanted particles are not removed from the sensor, it leads to downgrade the quality of the device. In order to achieve the purpose, the removal by manual may damage the sensitive chip. Typically, the image sensor module is formed by using a method of COB or LCC. One drawback of the COB is lower yield rate during packaging process due to particle contamination on sensing area. Besides, the drawbacks of the LCC are higher packaging cost and lower yield rate due to particle contamination on sensing area.

Further, micro lenses are optical components on semiconductors utilized as solid state imaging devices. One of the most important considerations in designing and manufacturing micro lenses is photosensitivity. One reason micro lens photosensitivity may be reduced is that the area of each micro lens has been reduced below an optimum value. Moreover, SHELL CASE company also develops wafer level package technique, the image sensor dice packaged by the SHELL CASE is higher cost due to requiring two glass plate and complicate process. And, the transparency is bad due to epoxy wearing out, and the potential reliability may be reduced. U.S. Pat. No. 5,514,888 for ON-CHIP SCREEN TYPE SOLID STATE IMAGE SENSOR AND MANUFACTURING METHOD THEREOF; issued May 7, 1996 to Yoshikazu Sano, et al. teaches a method for forming charge-coupled devices (CCDS) on a silicon substrate. A micro lens array is formed over the CCD array using conventional lithography and re-flow techniques.

Therefore, what is desired is to provide a novel image sensor structure free of particle contamination on sensing area.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the above problems in the prior arts, and it is an objective of the present invention to provide an image sensor die structure without particle contamination on micro lens and method for manufacturing the same.

An image sensor die comprises a substrate and an image sensor array formed over the substrate. Micro lens are disposed on the image sensor array. A protection layer having character of water repellency and/or oil repellency is formed on the micro lens to prevent the micro lens from particle containment. The protection layer is preferably a low refractive index layer. The protection layer includes PMMA (Polymethylmethacrylat), SOG (Spin on Glass), PolyCarbonate, Fluoropolymer, SiO2, Al2O3. The image sensor array includes CMOS or CCD. The image sensor die further comprises a filtering layer formed on the protection layer. The image sensor die further comprises a color filter formed over the image sensor array.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Some sample embodiments of the invention will now be described in greater detail. Nevertheless, it should be recognized that the present invention can be practiced in a wide range of other embodiments besides those explicitly described, and the scope of the present invention is expressly not limited except as specified in the accompanying claims. Then, the components of the different elements are not shown to scale. Some dimensions of the related components are exaggerated and meaningless portions are not drawn to provide a more clear description and comprehension of the present invention.

A wafer level package structure is provided, as shown inFIG. 1. The package structure comprises an isolating base200, image sensor dice201and dice202, a first dielectric layer205, a second dielectric layer207, contact conductive layer206, an isolation layer209and solder balls208. The material of the isolating base200can be glass, silicon, ceramic or quartz crystal etc., and even have a round or a rectangular shape. The image sensor dice201and the dice202are packaged with a side by side structure. The image sensor dice201and the dice202are adhered to the isolating base200by an UV curing type and/or heat curing type adhesion material203with good thermal conductivity. The first dielectric layer205is formed on the isolating base200and filled in a space except the image sensor dice201and the dice202on the isolating base200. The material of the first dielectric layer205may be silicon rubber.

The second dielectric layer207is formed on the image sensor dice201to cover a sensing area of the image sensor dice201. The material of the second dielectric layer207is SiO2to be a protection film. Besides, a filtering film may be formed on the second dielectric layer207, and the filtering film is, for example IR filtering layer, to be a filter.

The contact conductive layer206is formed on metal pads210of the image sensor dice201and metal pads204of the dice202to cover the metal pads210,204. Namely, the contact conductive layer206may be electrically coupled to the metal pads210,204, respectively. The material of the contact conductive layer206may be selected from Ni, Cu, Au and the combination thereof. The metal pads210,204are, for example Al pads. The isolation layer209is formed on the contact conductive layer206, and the isolation layer209has openings on the contact conductive layer206. The material of the isolation layer209is selected from epoxy, resin, SINR(Siloxane polymer) or BCB. The metal soldering balls208are formed on the openings by welding method so that the metal soldering balls208are electrically coupled with the contact conductive layer206, respectively. The metal soldering balls208may be solder balls208.

The dice202may be selected from DSP die, active die, passive die, support die, CPU die or processor die, and the image sensor dice201are CMOS image sensor dice. The image sensor dice201are packaged with the dice202with a side by side structure.

Moreover, another wafer level package structure is provided, as shown inFIG. 2. The dice, in one embodiment, are packaged with a stacking structure. The package structure comprises an isolating base300, image sensor dice301and dice302, a first dielectric layer303, a second dielectric layer304, a third dielectric layer311, contact conductive layer305a,305b, an isolation layer306and solder balls307. The material of the isolating base300is glass, silicon, ceramic or quartz crystal etc., and even has a round or a rectangular shape. The image sensor dice301and the dice302are packaged with a stacking structure. The dice302are adhered to the isolating base300by an UV curing type and/or heat curing type adhesion material310awith good thermal conductivity. The first dielectric layer303is formed on the isolating base300and filled in a space except the dice302on the isolating base300. The material of the first dielectric layer303may be silicon rubber.

The contact conductive layer305ais formed on metal pads309of the dice302to cover the metal pads309to electrically couple to the metal pads309, respectively. The image sensor dice301are adhered to the dice302by an UV curing type and/or heat curing type adhesion material310bwith good thermal conductivity. The second dielectric layer304is formed on the first dielectric layer303and filled in a space except the image sensor dice301, and the second dielectric layer304has via hole312formed on the contact conductive layer305a. The material of the second dielectric layer304is SiO2.

Besides, the third dielectric layer311is formed on the image sensor dice301to cover a sensing area of the image sensor dice301. However, the third dielectric layer311should not affect function of the image sensor dice301. The material of the third dielectric layer311is SiO2to be a protection film. Specially, a filtering film may be formed on the third dielectric layer311on the image sensor dice301, and the filtering film is, for example IR filtering layer, to be a filter.

The contact conductive layer305bis formed on metal pads308of the image sensor dice301and filled in the via hole312to cover the metal pads308. Namely, the contact conductive layer305bis electrically coupled to the metal pads308and the contact conductive layer305a. The material of the contact conductive layer305a,305bmay be selected from Ni, Cu, Au and the combination thereof. The metal pads308,309are, for example Al pads. The isolation layer306is formed on the contact conductive layer305b, and the isolation layer306has openings on the contact conductive layer305b. The material of the isolation layer306is selected from epoxy, resin and the combination thereof.

The metal soldering balls307are formed on the openings by welding method so that the metal soldering balls307are electrically coupled with the contact conductive layer305b, respectively. The metal soldering balls307may be solder balls307.

The dice302may be selected from DSP die, active die, passive die, support die, CPU die or processor die, and the image sensor dice301are CMOS image sensor dice. The image sensor dice301are packaged with the dice302with a stacking structure.

Referring toFIG. 3, micro lens arrays140are generally formed on the top surfaces of silicon chips. The substrate100bears a plurality of CMOS devices in sensing area102. The image sensor includes an isolation layer110formed over a substrate100. A color filter layer120is next formed over the isolation layer100with sub-pixel areas properly aligned with active devices in the substrate100. Another layer130is generally formed over the color filter layer120. There are several ways well known to those skilled in the art to proceed with the formation of a micro lens array. The layer of lens forming material140is applied to the substrate. One material found suitable for this application is a mixture of melamine resin and generic novolac base resin. Individual lens areas are formed in the lens material layer140by masked exposure and developing. For example, a photo resist (PR; not shown) is deposited over the lens material layer140. Conventional lithographic techniques are then utilized to form patterns in the PR by using exposure and development step. PR is then stripped. The devices are hard baked to re-flow the micro lenses140into the proper optical form by controlling time and temperature. Individual Red/Green/Blue (RGB) sub-pixel areas120R,120G,120B, respectively, are shown aligned over corresponding CMOS devices in substrate100as known in the art.

The present invention provides an image sensor device as shown inFIG. 3. The material of the substrate100can be glass, semiconductor material, ceramic or quartz etc. Moreover, a protection layer150can be covered on the micro lenses140. The material of the protection layer150includes SiO2or Al2O3formed by spin coating. Further, the material for the protection layer150could be PMMA (Polymethylmethacrylat), SOG (Spin on Glass), PolyCarbonate or Fluoropolymer. The thickness of the protection layer150is controlled less than 0.5 micron meters (μm) so that it will not affect the function of the CMOS sensor. Alternatively, the protection layer150may comprise a filtering layer160, for example IR filtering layer, formed on the protection layer150to act as a filter, as show inFIG. 4. The protection layer150may prevent the micro lens from particle containment. The user may use liquid or air flush to remove the particles on the protection layer150without damaging the micron lens. The protection layer is a water repellency and/or oil repellency. Preferably, the protection layer is a low refractive index layer.

An isolation layer (not shown) is formed over the substrate100and it has openings to not cover the image sensor area for conveniently sensing the image. The material of the isolation layer is selected from epoxy, resin and the combination thereof.