CN110299372B - Test structure for monitoring back-illuminated electronegativity strength and process integration method - Google Patents
Test structure for monitoring back-illuminated electronegativity strength and process integration method Download PDFInfo
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- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
- H01L22/30—Structural arrangements specially adapted for testing or measuring during manufacture or treatment, or specially adapted for reliability measurements
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- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14601—Structural or functional details thereof
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- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14601—Structural or functional details thereof
- H01L27/1464—Back illuminated imager structures
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- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14643—Photodiode arrays; MOS imagers
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- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof
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- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof
- H01L27/14689—MOS based technologies
Abstract
The invention discloses a test structure for monitoring the intensity of back-illuminated electronegativity, which comprises: the first electrode area has the same process conditions as the photosensitive doped area of the pixel area, and a first passivation layer comprising an electronegative material layer is formed on the back of the first electrode area; a back metal layer is formed on the back of the first passivation layer, and the first electrode region, the first passivation layer and the back metal layer on the back are superposed to form a monitoring capacitor; the first electrode region is connected to a first front side pad, and the first front side pad is connected to a first back side pad; a second back liner is formed on the back of the back metal layer on the back of the first electrode area; the first and second backside pads form a lead-out structure for both plates of the monitor capacitor. The invention also discloses a process integration method of the test structure for monitoring the back-illuminated electronegativity strength. The invention can realize the on-line continuous monitoring of the electronegativity strength of the back-illuminated image sensor, effectively shorten the test period and the feedback period, reduce the consumption of silicon chips and accelerate the research and development progress.
Description
Technical Field
The invention relates to the field of semiconductor integrated circuit manufacturing, in particular to a test structure for monitoring the intensity of back-illuminated electronegativity; the invention also relates to a process integration method of the test structure for monitoring the back-illuminated electronegativity strength.
Background
A conventional CMOS Image Sensor (CIS) is configured of a Pixel (Pixel) unit circuit formed in a Pixel region and a CMOS circuit formed in a peripheral region. Compared with a CCD image sensor, the CMOS image sensor has better integratability because of adopting a CMOS standard manufacturing process, can be integrated on the same chip with other digital-to-analog operation and control circuits, and is more suitable for future development.
The pixel unit circuit in the pixel region includes a Photodiode (PD) which is generally composed of an N-type doped photosensitive doped region and a P-type doped semiconductor substrate such as a silicon substrate, on the front surface of which a front metal layer is formed, which generally includes a plurality of layers and includes an interlayer film between the front metal layers.
With the decrease of the pixel unit, in order to increase the light input amount, a back-illuminated (BSI) configuration is adopted, so that light directly acts on the photodiode, and meanwhile, the blocking and reflection of metal in a front-illuminated (FSI) structure are avoided, the fill factor of the whole pixel unit is improved, and the fill factor is the ratio of the part of the passing light to the whole area, so that the sensitivity of the light can be improved.
In the BSI structure, a silicon wafer needs to be thinned, so that illumination is realized, after thinning, a plurality of interface states exist on the silicon surface, and passivation is needed to prevent the influence on the pixel quality. The initial passivation process is realized by heavily doped P-type ion implantation and then combining laser annealing, and the uniformity of the heavily doped P-type is poor after activation in the method, so that the performance among pixel units has large fluctuation; and for large pixel units, non-uniformity within the pixel unit caused by different local annealing points of the same pixel unit; and the conditions of ion implantation and annealing are optimized to meet the quantum efficiency requirement of short wave.
The existing passivation process adopts a lot of materials with electronegativity to cover the thinned high-density silicon oxide, the silicon oxide can realize partial interface state passivation, and simultaneously, positive charges with higher density are induced on the silicon surface by utilizing the strong electronegativity to prevent photoelectrons from entering a surface region, so that the effect of inhibiting leakage current is realized.
For BSI processes that use electronegative materials, the strength of the electronegativity of the material needs to be monitored from time to ensure the performance of subsequent pixels. In the prior art, because the monitoring of electricity or charges needs to be carried out on an optical sheet, and meanwhile, certain change exists along with time, the intensity of electronegativity cannot be accurately monitored, so that the quality of electronegativity materials can be verified only after all back-end processes including the manufacturing of color filters are completed on a silicon wafer and the testing function is finished. Therefore, the testing period of the electronegative material is long, the feedback of process adjustment has obvious hysteresis, and if problems occur, a large amount of silicon wafers are wasted and the development period is prolonged.
Disclosure of Invention
The invention aims to solve the technical problem of providing a test structure for monitoring the electronegativity strength of a back-illuminated image sensor, which can realize the on-line continuous monitoring of the electronegativity strength of the back-illuminated image sensor, effectively shorten the test period of electronegativity materials, shorten the feedback period, reduce the consumption of semiconductor substrates such as silicon wafers and accelerate the research and development progress. Therefore, the invention also discloses a process integration method of the test structure for monitoring the back-illuminated electronegativity strength.
In order to solve the above technical problem, the test structure for monitoring the intensity of the back-illuminated electronegativity provided by the invention comprises:
the first electrode area is formed on the front surface of the semiconductor substrate and has the same process conditions as the photosensitive doped area of the pixel area of the back-illuminated image sensor.
And a first passivation layer comprising an electronegative material layer is formed on the back surface of the first electrode region, and the process conditions of the first passivation layer are the same as those of a second passivation layer in the back process of the pixel region of the back-illuminated image sensor.
A back metal layer is formed on the back of the first passivation layer, a monitoring capacitor is formed by overlapping the first electrode region, the first passivation layer and the back metal layer on the back of the first passivation layer, the first electrode region forms a first electrode plate of the monitoring capacitor, and the back metal layer on the back of the first passivation layer forms a second electrode plate of the monitoring capacitor.
The first electrode area is connected with a front metal layer formed on the front surface of the semiconductor substrate, the front metal layer forms a first front liner, and a first back liner consisting of a back metal layer is formed on the back surface of the first front liner.
And a second back liner is formed on the back of the back metal layer on the back of the first electrode area.
The first back gasket forms an extraction structure of a first polar plate of the monitoring capacitor, and the second back gasket forms an extraction structure of a second polar plate of the monitoring capacitor.
In a further improvement, the semiconductor substrate is a silicon substrate.
The semiconductor substrate is doped in a P type mode, a photosensitive doped region of a pixel region of the back-illuminated image sensor is an N type ion implantation region, and the photosensitive doped region and the semiconductor substrate form a photosensitive diode.
In a further improvement, an isolation structure is formed in the semiconductor substrate on a peripheral side of the first electrode region.
In a further improvement, the isolation structure is a P-type injection layer; alternatively, the isolation structure is comprised of a dielectric material.
In a further refinement, the isolation structure is composed of silicon oxide.
In a further improvement, the first passivation layer and the second passivation layer are formed by laminating a first silicon oxide layer, the electronegative material layer and a second silicon oxide layer, and the electronegative material layer is aluminum oxide.
A back side groove is formed in a pixel area of the back side illumination type image sensor, the first silicon oxide layer of the second passivation layer is formed on the bottom surface and the side surface of the back side groove, the electronegative material layer is formed on the surface of the first silicon oxide layer, and the second silicon oxide layer is formed on the surface of the electronegative material layer; and filling tungsten in the back groove formed with the electronegative material layer.
The back metal layer is made of aluminum; the front metal layer is made of aluminum.
In a further improvement, a back-end process structure is further formed on the back surface of the second passivation layer, and the back-end process structure comprises a color filter and a micro lens.
The periphery of the pixel region of the back-illuminated image sensor is a peripheral region in which a CMOS circuit is formed.
A front side process Test-key (FSI Test-key) is also formed in the peripheral region.
The front side process test unit comprises an MOS transistor, a diode and a capacitor.
The front process test unit is led out by the corresponding front gasket formed by the front metal layer and the corresponding back gasket formed by the back metal layer.
In order to solve the technical problem, the process integration method of the test structure for monitoring the back-illuminated electronegativity strength provided by the invention comprises the following steps:
step one, in a front process of the back-illuminated image sensor, a first electrode area of the test structure is formed while a photosensitive doped area of a pixel area of the back-illuminated image sensor is formed by adopting an ion implantation process.
And step two, completing a front surface process of the back-illuminated image sensor, wherein the front surface process comprises the steps of forming a front surface metal layer and forming a front surface gasket consisting of the corresponding front surface metal layer, and the top of the first electrode area is connected with the corresponding front surface metal layer and is connected with the first front surface gasket.
And step three, thinning the back surface of the semiconductor substrate, and simultaneously forming a first passivation layer and a second passivation layer on the thinned back surface of the semiconductor substrate, wherein the first passivation layer and the second passivation layer both comprise electronegative materials, the second passivation layer is positioned in a pixel region of the back-illuminated image sensor, and the first passivation layer is positioned on the back surface of the first electrode region.
And step four, completing a back process of the back-illuminated image sensor, wherein the back process comprises forming a back metal layer and forming a back pad consisting of the corresponding back metal layer, the back metal layer on the back of the first passivation layer is connected with the second back pad, and the first front pad is connected with the first back pad.
The first electrode region, the first passivation layer and the back metal layer on the back of the first passivation layer are overlapped to form a monitoring capacitor, the first electrode region forms a first electrode plate of the monitoring capacitor, and the back metal layer on the back of the first passivation layer forms a second electrode plate of the monitoring capacitor.
The first back gasket forms an extraction structure of a first polar plate of the monitoring capacitor, and the second back gasket forms an extraction structure of a second polar plate of the monitoring capacitor.
In a further improvement, the semiconductor substrate is a silicon substrate.
The semiconductor substrate is doped in a P type mode, a photosensitive doped region of a pixel region of the back-illuminated image sensor is an N type ion implantation region, and the photosensitive doped region and the semiconductor substrate form a photosensitive diode.
In a further improvement, an isolation structure is formed in the semiconductor substrate on a peripheral side of the first electrode region.
In a further improvement, the isolation structure is a P-type injection layer; alternatively, the isolation structure is comprised of a dielectric material.
In a further improvement, the first passivation layer and the second passivation layer are formed by laminating a first silicon oxide layer, the electronegative material layer and a second silicon oxide layer, and the electronegative material layer is aluminum oxide.
In a further improvement, a back trench is formed in a pixel region of the back-illuminated image sensor, the first silicon oxide layer of the second passivation layer is formed on the bottom surface and the side surface of the back trench, the electronegative layer is formed on the surface of the first silicon oxide layer, and the second silicon oxide layer is formed on the surface of the electronegative layer; and filling tungsten in the back groove formed with the electronegative layer.
The back metal layer is made of aluminum; the front metal layer is made of aluminum.
In a further improvement, a back-end process structure is further formed on the back surface of the second passivation layer, and the back-end process structure comprises a color filter and a micro lens.
The periphery of the pixel region of the back-illuminated image sensor is a peripheral region in which a CMOS circuit is formed.
A front process test unit is also formed in the peripheral region.
The front side process test unit comprises an MOS transistor, a diode and a capacitor.
The front process test unit is led out by the corresponding front gasket formed by the front metal layer and the corresponding back gasket formed by the back metal layer.
The passivation layer of the back-illuminated image sensor adopts an electronegative material layer, and a test structure of electronegative strength is added, wherein the test structure is that a first electrode area with the same process condition as a photosensitive doping area of a pixel area is arranged in a semiconductor substrate, a passivation layer, namely a first passivation layer, is formed on the back surface of the first electrode area, the process condition of the first passivation layer is the same as the process condition of a second passivation layer of the pixel area, monitoring of the second passivation layer can be realized by monitoring the first passivation layer, a back metal layer is formed on the back surface of the first passivation layer, so that monitoring capacitors are formed by overlapping the first electrode area, the first passivation layer and the back metal layer on the back surface of the first passivation layer, two electrode plates, namely a first electrode plate and a second electrode plate, of the first electrode plate and the corresponding back metal layer respectively correspond to the monitoring capacitors, the first electrode plate is connected with the front metal layer, and a first front gasket formed by the front metal layer is used for The first back pad formed by the back metal layer is led out, and the second pole plate is led out through the second back pad formed by the back metal layer, so that the test of the monitoring capacitor can be realized, and the test structure is formed; the test structure can be used for testing after the process of the back metal layer is finished, and all back-end processes are not required to be finished, so that the test structure can realize the on-line continuous monitoring of the electronegativity strength of the back-illuminated image sensor, can effectively shorten the test period of electronegativity materials, shortens the feedback period, reduces the consumption of semiconductor substrates such as silicon wafers, and quickens the research and development progress.
In addition, the process conditions of the first electrode area of the testing structure and the photosensitive doping area of the pixel area are the same, and the upper and lower leading-out structures are compatible with the existing process adopting the back-illuminated image sensor, so that the invention does not need to add extra process and mask plates, has low process cost,
in addition, the main body of the test structure is the monitoring capacitor, the test of the monitoring capacitor is convenient, the test can be carried out by utilizing the existing test card without adding a new test card, and therefore, the test cost of the test structure is lower.
Drawings
The invention is described in further detail below with reference to the following figures and detailed description:
FIG. 1A is a schematic diagram of a conventional backside illuminated image sensor;
FIG. 1B is an enlarged view of the passivation layer region of FIG. 1A;
FIG. 2A is a schematic top view of a front side pad formed by a front side metal layer of a conventional front side process test unit;
FIG. 2B is a schematic top view of a conventional backside pad formed by a backside metal layer of a frontside process test unit;
FIG. 2C is a cross-sectional view of a conventional front side process test cell at the back side pad;
FIG. 3A is a cross-sectional view of a test structure for monitoring intensity of backside illuminated electronegativity in accordance with an embodiment of the invention;
fig. 3B is a top view of a backside liner formed from a backside metal layer according to an embodiment of the invention.
Detailed Description
First, a structure of a conventional backside illuminated image sensor is described with reference to the accompanying drawings:
fig. 1A is a schematic structural diagram of a conventional backside illuminated image sensor; the conventional back side illumination image sensor includes a pixel region 101 and a peripheral region 102, which are respectively located at left and right sides of a dotted line AA; a device structure is formed on a semiconductor substrate such as a silicon substrate 103, and the semiconductor substrate 103 is also called a device slice; the device structure in the pixel region 101 includes a photodiode, typically a P-type doped semiconductor substrate 103, and the photodiode is composed of an N-type photo-doped region formed in the P-type semiconductor substrate 103 and the P-type semiconductor substrate 103. CMOS devices are formed in the peripheral region 102.
A plurality of front metal layers 104 are formed on the front surface of the semiconductor substrate 103, and interlayer films are separated between the front metal layers 104.
The liner 105 covers the front surface of the semiconductor substrate 103 on which the front surface metal layer 104 is formed.
A back metal layer 106 is formed on the back surface of the semiconductor substrate 103.
Since the semiconductor substrate 103 is thinned by the back surface, the thinned back surface of the semiconductor substrate 103 has more interface states, and therefore a passivation layer for passivating the interface states is required to be used, in fig. 1A, the passivation layer is shown as a dashed circle 201, fig. 1B is an enlarged view of the dashed circle 201, the passivation layer is formed by stacking the first silicon oxide layer 107, the electronegative material layer 108 and the second silicon oxide layer 109, and the electronegative material layer 108 is usually made of aluminum oxide.
As shown in fig. 1B, a back trench is formed in the pixel region of the back-illuminated image sensor, the first silicon oxide layer 107 is formed on the bottom surface and the side surface of the back trench, the electronegative material layer 108 is formed on the surface of the first silicon oxide layer 107, and the second silicon oxide layer 109 is formed on the surface of the electronegative material layer 108; the back surface trench formed with the electronegative material layer 108 is filled with tungsten 111.
In the prior art, a front side process test unit for detecting a front side process is formed, as shown in fig. 2A, which is a schematic top view of a front side pad formed by a front side metal layer of the prior front side process test unit, wherein a plurality of front side pads 301 are shown, and a distance between the front side pads 301 is S. As shown in fig. 2B, which is a schematic top view of a back pad formed by a back metal layer of a conventional front process test unit, a back pad 302 is superimposed on a corresponding front pad 301. As shown in fig. 2C, which is a cross-sectional structure diagram of a back pad of a conventional front process test unit, a plurality of front metal layers are formed on the front surface of the semiconductor substrate 103, and a front pad 301 and a back pad 302 are formed after the back surface of the semiconductor substrate 103 is opened. The existing front side process test unit can only detect the front side process, and the structure of the back side pad 302 can only monitor the performance of the connected front side process test unit. And for the influence of the front process test unit on the back process and the influence of the back device structure on the back process, no corresponding test unit exists.
The embodiment of the invention provides a test structure for monitoring the intensity of back-illuminated electronegativity, which comprises the following steps:
referring to fig. 1A, as shown in fig. 3A, a structure of a backside illuminated image sensor according to an embodiment of the present invention is a cross-sectional structure diagram of a test structure for monitoring a backside illuminated electronegativity strength according to an embodiment of the present invention; as shown in fig. 3B, which is a schematic top view of a backside pad formed by the backside metal layer 106 according to an embodiment of the present invention, the test structure for monitoring backside illuminated electronegativity strength according to an embodiment of the present invention includes:
the first electrode region 1 is formed on the front surface of the semiconductor substrate 103 and has the same process conditions as the photosensitive doped region of the pixel region 101 of the back-illuminated image sensor.
The semiconductor substrate 103 is a silicon substrate.
The semiconductor substrate 103 is doped in a P-type manner, the photosensitive doped region of the pixel region 101 of the back-illuminated image sensor is an N-type ion implantation region, and the photosensitive doped region and the semiconductor substrate 103 form a photosensitive diode.
An isolation structure 2 is formed in the semiconductor substrate 103 on the peripheral side of the first electrode regions 1. In the embodiment of the present invention, the isolation structure 2 is made of a dielectric material, such as silicon oxide. In other embodiments can also be: the isolation structure 2 is a P-type injection layer.
A first passivation layer including an electronegative material layer 108 is formed on the back surface of the first electrode region 1, and the process conditions of the first passivation layer are the same as those of the second passivation layer in the back process of the pixel region 101 of the back-illuminated image sensor.
A back metal layer 106 is formed on the back of the first passivation layer, the first electrode region 1, the first passivation layer and the back metal layer 106 on the back of the first passivation layer are overlapped to form a monitoring capacitor, the first electrode region 1 forms a first plate of the monitoring capacitor, and the back metal layer 106 on the back of the first passivation layer forms a second plate of the monitoring capacitor.
The first electrode region 1 is connected to a front metal layer 104 formed on the front surface of the semiconductor substrate 103, the front metal layer 104 forms a first front pad 301a, and a first back pad 302a composed of a back metal layer 106 is formed on the back surface of the first front pad 301 a.
A second backside liner 302b is formed on the backside of the backside metal layer 106 on the backside of the first electrode region 1.
The first backside pad 302a forms an extraction structure of a first plate of the monitoring capacitor, and the second backside pad 302b forms an extraction structure of a second plate of the monitoring capacitor.
The first passivation layer and the second passivation layer are formed by overlapping a first silicon oxide layer 107, the electronegative material layer 108 and a second silicon oxide layer 109, and the electronegative material layer 108 is aluminum oxide.
As shown in fig. 3A, in which the first silicon oxide layer 107 can implement partial interface state passivation, a higher density of positive charges as shown by reference numeral 303 is induced on the surface of the semiconductor substrate 103 by the strong electronegativity of the electronegative material layer 108, so that photoelectrons can be blocked from entering the surface region, and thus the effect of suppressing leakage current can be achieved.
A back side groove is formed in the pixel region 101 of the back side illumination type image sensor, the first silicon oxide layer 107 of the second passivation layer is formed on the bottom surface and the side surface of the back side groove, the electronegative material layer 108 is formed on the surface of the first silicon oxide layer 107, and the second silicon oxide layer 109 is formed on the surface of the electronegative material layer 108; tungsten is filled in the back trench in which the electronegative material layer 108 is formed.
The back metal layer 106 is made of aluminum; the front metal layer 104 is made of aluminum.
And a back-end process structure is formed on the back surface of the second passivation layer, and the back-end process structure comprises a color filter and a micro lens.
The periphery of the pixel region 101 of the back-illuminated image sensor is a peripheral region 102, and a CMOS circuit is formed in the peripheral region 102.
A front side process Test-key (FSI Test-key) is also formed in the peripheral region 102.
The front side process test unit comprises an MOS transistor, a diode and a capacitor.
The front side process test unit is led out through a corresponding front side pad 301 formed by the front side metal layer 104 and then superposed with a corresponding back side pad 302 formed by the back side metal layer 106.
As can be seen from a comparison between fig. 2B and fig. 3B, in the embodiment of the present invention, only one region needs to be formed in the front pad 301 of the conventional front process testing unit, and the ion implantation is performed in the formed region to form the first electrode region 1 under the same process conditions as the photosensitive doped region of the pixel region 101. In fig. 3B, the pitch of the front spacers 301 on both sides where the first electrode regions are formed is 2S, and the pitch of each of the other front spacers 301 is S; the spacing between the backside pads 302 is S. The first back side pad is identified individually by reference numeral 302a, the second back side pad is identified individually by reference numeral 302b, and the first front side pad is identified individually by reference numeral 301 a.
In the embodiment of the invention, the passivation layer of the back-illuminated image sensor adopts the electronegative material layer 108, and the test structure of electronegative strength is added, the test structure is that the first electrode region 1 which has the same process condition with the photosensitive doping region of the pixel region 101 is arranged in the semiconductor substrate 103, the passivation layer, namely the first passivation layer, is formed on the back surface of the first electrode region 1, the process condition of the first passivation layer is the same as the process condition of the second passivation layer of the pixel region 101, in the embodiment of the invention, the second passivation layer is an object to be monitored, the monitoring of the second passivation layer can be realized by monitoring the first passivation layer, the back metal layer 106 is formed on the back surface of the first passivation layer, thus, the monitoring capacitors are formed by overlapping the first electrode region 1, the first passivation layer and the back metal layer 106 on the back surface of the first passivation layer, and the two electrode plates of the monitoring capacitors, namely the first electrode plate and the second electrode plate, which correspond to the first electrode The first pole plate is led out through a first front pad 301a which is connected with the front metal layer 104 and formed through the front metal layer 104 and a first back pad 302a formed by the back metal layer 106, and the second pole plate is led out through a second back pad 302b formed by the back metal layer 106, so that the test of the monitoring capacitor can be realized, and the test structure of the invention is formed; the test structure of the embodiment of the invention can carry out the test after the process of the back metal layer 106 is finished, and all back-end processes are not required to be finished, so the embodiment of the invention can realize the on-line continuous monitoring of the electronegativity strength of the back-illuminated image sensor, effectively shorten the test period of electronegativity materials, shorten the feedback period, reduce the consumption of a semiconductor substrate 103 such as a silicon wafer, and accelerate the research and development progress.
In addition, the process conditions of the first electrode area 1 of the test structure and the photosensitive doped area of the pixel area 101 are the same, and the upper and lower lead-out structures are compatible with the existing process adopting the back-illuminated image sensor, so that no additional process or mask is required to be added in the embodiment of the invention, the process cost is low,
in addition, the main body of the test structure of the embodiment of the invention is the monitoring capacitor, the test of the monitoring capacitor is convenient, the test can be carried out by utilizing the existing test card without adding a new test card, and therefore, the test cost of the embodiment of the invention is lower.
The embodiment of the invention provides a process integration method of a test structure for monitoring back-illuminated electronegativity strength, which comprises the following steps:
the process integration method of the test structure for monitoring the back-illuminated electronegativity strength comprises the following steps of:
step one, in the front process of the back-illuminated image sensor, a first electrode region 1 of the test structure is formed while a photosensitive doped region of a pixel region 101 of the back-illuminated image sensor is formed by adopting an ion implantation process.
The front side process of the back side illuminated image sensor is performed on the surface of a semiconductor substrate such as a silicon substrate 103. The semiconductor substrate 103 is a silicon substrate.
The semiconductor substrate 103 is doped in a P-type manner, the photosensitive doped region of the pixel region 101 of the back-illuminated image sensor is an N-type ion implantation region, and the photosensitive doped region and the semiconductor substrate 103 form a photosensitive diode.
An isolation structure 2 is formed in the semiconductor substrate 103 on the peripheral side of the first electrode regions 1. The isolation structure 2 is composed of a dielectric material such as silicon oxide. Can also be: the isolation structure 2 is a P-type injection layer.
And step two, completing a front surface process of the back-illuminated image sensor, wherein the front surface process comprises forming a front surface metal layer 104 and forming a front surface gasket 301 composed of the corresponding front surface metal layer 104, and the top of the first electrode region 1 is connected with the corresponding front surface metal layer 104 and is connected with a first front surface gasket 301 a.
The front metal layer 104 is made of aluminum.
And step three, thinning the back surface of the semiconductor substrate 103, and simultaneously forming a first passivation layer and a second passivation layer on the back surface of the thinned semiconductor substrate 103, wherein the first passivation layer and the second passivation layer both comprise electronegative materials, the second passivation layer is located in the pixel region 101 of the back-illuminated image sensor, and the first passivation layer is located on the back surface of the first electrode region 1.
The first passivation layer and the second passivation layer are formed by overlapping a first silicon oxide layer 107, the electronegative material layer 108 and a second silicon oxide layer 109, and the electronegative material layer 108 is aluminum oxide.
A back side groove is formed in the pixel region 101 of the back side illumination type image sensor, the first silicon oxide layer 107 of the second passivation layer is formed on the bottom surface and the side surface of the back side groove, the electronegative layer is formed on the surface of the first silicon oxide layer 107, and the second silicon oxide layer 109 is formed on the surface of the electronegative layer; and filling tungsten in the back groove formed with the electronegative layer.
And step four, completing a back process of the back side illumination type image sensor, wherein the back process comprises forming a back side metal layer 106 and forming a back side pad consisting of the corresponding back side metal layer 106, wherein the back side metal layer 106 on the back side of the first passivation layer is connected with a second back side pad 302b, and the first front side pad 301a is connected with a first back side pad 302 a.
The material of the back metal layer 106 is aluminum.
The first electrode region 1, the first passivation layer and the back metal layer 106 on the back of the first passivation layer are overlapped to form a monitoring capacitor, the first electrode region 1 forms a first plate of the monitoring capacitor, and the back metal layer 106 on the back of the first passivation layer forms a second plate of the monitoring capacitor.
The first backside pad 302a forms an extraction structure of a first plate of the monitoring capacitor, and the second backside pad 302b forms an extraction structure of a second plate of the monitoring capacitor.
And a back-end process structure is formed on the back surface of the second passivation layer, and the back-end process structure comprises a color filter and a micro lens.
The periphery of the pixel region 101 of the back-illuminated image sensor is a peripheral region 102, and a CMOS circuit is formed in the peripheral region 102.
A front side process test unit is also formed in the peripheral region 102.
The front side process test unit comprises an MOS transistor, a diode and a capacitor.
The front side process test unit is led out through a corresponding front side pad 301 formed by the front side metal layer 104 and then superposed with a corresponding back side pad 302 formed by the back side metal layer 106.
The present invention has been described in detail with reference to the specific embodiments, but these should not be construed as limitations of the present invention. Many variations and modifications may be made by one of ordinary skill in the art without departing from the principles of the present invention, which should also be considered as within the scope of the present invention.
Claims (15)
1. A test structure for monitoring intensity of back-illuminated electronegativity, the test structure comprising:
the first electrode area is formed on the front side of the semiconductor substrate and has the same process conditions as the photosensitive doped area of the pixel area of the back-illuminated image sensor;
a first passivation layer comprising an electronegative material layer is formed on the back surface of the first electrode region, and the process conditions of the first passivation layer are the same as those of a second passivation layer in the back process of the pixel region of the back-illuminated image sensor;
a back metal layer is formed on the back of the first passivation layer, the first electrode region, the first passivation layer and the back metal layer on the back of the first passivation layer are overlapped to form a monitoring capacitor, the first electrode region forms a first electrode plate of the monitoring capacitor, and the back metal layer on the back of the first passivation layer forms a second electrode plate of the monitoring capacitor;
the first electrode area is connected with a front metal layer formed on the front surface of the semiconductor substrate, the front metal layer forms a first front liner, and a first back liner consisting of a back metal layer is formed on the back surface of the first front liner;
a second back liner composed of the back metal layer is formed on the back of the back metal layer on the back of the first electrode area;
the first back gasket forms an extraction structure of a first polar plate of the monitoring capacitor, and the second back gasket forms an extraction structure of a second polar plate of the monitoring capacitor.
2. The test structure for monitoring intensity of back-illuminated electronegativity of claim 1, wherein: the semiconductor substrate is a silicon substrate.
3. The test structure for monitoring intensity of back-illuminated electronegativity of claim 2, wherein: the semiconductor substrate is doped in a P type mode, the photosensitive doped region of the pixel region of the back-illuminated image sensor is an N type ion implantation region, and the photosensitive doped region and the semiconductor substrate form a photosensitive diode.
4. The test structure for monitoring intensity of back-illuminated electronegativity of claim 3, wherein: an isolation structure is formed in the semiconductor substrate on a peripheral side of the first electrode region.
5. The test structure for monitoring intensity of back-illuminated electronegativity of claim 4, wherein: the isolation structure is a P-type injection layer; alternatively, the isolation structure is comprised of a dielectric material.
6. The test structure for monitoring intensity of back-illuminated electronegativity of claim 1, wherein: the first passivation layer and the second passivation layer are formed by laminating a first silicon oxide layer, the electronegative material layer and a second silicon oxide layer, and the electronegative material layer is aluminum oxide;
a back side groove is formed in a pixel area of the back side illumination type image sensor, the first silicon oxide layer of the second passivation layer is formed on the bottom surface and the side surface of the back side groove, the electronegative material layer is formed on the surface of the first silicon oxide layer, and the second silicon oxide layer is formed on the surface of the electronegative material layer; filling tungsten in the back groove formed with the electronegative material layer;
the back metal layer is made of aluminum; the front metal layer is made of aluminum.
7. The test structure for monitoring intensity of back-illuminated electronegativity of claim 6, wherein: a rear-end process structure is further formed on the back of the second passivation layer, and the rear-end process structure comprises a color filter and a micro lens;
the periphery of a pixel area of the back-illuminated image sensor is a peripheral area, and a CMOS circuit is formed in the peripheral area;
a front process test unit is also formed in the peripheral area;
the front process test unit comprises an MOS transistor, a diode and a capacitor;
the front process test unit is led out by the corresponding front gasket formed by the front metal layer and the corresponding back gasket formed by the back metal layer.
8. A process integration method for a test structure for monitoring the intensity of back-illuminated electronegativity is characterized in that the forming process of the test structure integrated back-illuminated image sensor comprises the following steps:
in the front process of the back-illuminated image sensor, a first electrode area of the test structure is formed while a photosensitive doped area of a pixel area of the back-illuminated image sensor is formed by adopting an ion implantation process;
step two, completing a front surface process of the back-illuminated image sensor, wherein the front surface process comprises forming a front surface metal layer and forming a front surface gasket consisting of the corresponding front surface metal layer, and the top of the first electrode area is connected with the corresponding front surface metal layer and is connected with the first front surface gasket;
thinning the back surface of the semiconductor substrate, and simultaneously forming a first passivation layer and a second passivation layer on the back surface of the thinned semiconductor substrate, wherein the first passivation layer and the second passivation layer both comprise electronegative materials, the second passivation layer is positioned in a pixel region of the back-illuminated image sensor, and the first passivation layer is positioned on the back surface of the first electrode region;
step four, completing a back process of the back-illuminated image sensor, wherein the back process comprises forming a back metal layer and forming a back pad consisting of the corresponding back metal layer, the back metal layer on the back of the first passivation layer is connected with the second back pad, and the first front pad is connected with the first back pad;
the first electrode region, the first passivation layer and the back metal layer on the back of the first passivation layer are overlapped to form a monitoring capacitor, the first electrode region forms a first electrode plate of the monitoring capacitor, and the back metal layer on the back of the first passivation layer forms a second electrode plate of the monitoring capacitor;
the first back gasket forms an extraction structure of a first polar plate of the monitoring capacitor, and the second back gasket forms an extraction structure of a second polar plate of the monitoring capacitor.
9. The process integration method for monitoring the test structure for intensity of backside illuminated electronegativity of claim 8, wherein: the semiconductor substrate is a silicon substrate.
10. The process integration method for monitoring the test structure for intensity of backside illuminated electronegativity of claim 9, wherein: the semiconductor substrate is doped in a P type mode, the photosensitive doped region of the pixel region of the back-illuminated image sensor is an N type ion implantation region, and the photosensitive doped region and the semiconductor substrate form a photosensitive diode.
11. The process integration method for monitoring the test structure for intensity of backside illuminated electronegativity of claim 10, wherein: an isolation structure is formed in the semiconductor substrate on a peripheral side of the first electrode region.
12. The process integration method for monitoring the test structure for intensity of backside illuminated electronegativity of claim 11, wherein: the isolation structure is a P-type injection layer; alternatively, the isolation structure is comprised of a dielectric material.
13. The process integration method for monitoring the test structure for intensity of backside illuminated electronegativity of claim 8, wherein: the first passivation layer and the second passivation layer are formed by laminating a first silicon oxide layer, the electronegative material layer and a second silicon oxide layer, and the electronegative material layer is aluminum oxide.
14. The process integration method for monitoring the test structure for intensity of backside illuminated electronegativity of claim 13, wherein: a back side groove is formed in a pixel area of the back side illumination type image sensor, the first silicon oxide layer of the second passivation layer is formed on the bottom surface and the side surface of the back side groove, the electronegative layer is formed on the surface of the first silicon oxide layer, and the second silicon oxide layer is formed on the surface of the electronegative layer; filling tungsten in the back groove formed with the electronegative layer;
the back metal layer is made of aluminum; the front metal layer is made of aluminum.
15. The process integration method for monitoring the test structure for intensity of backside illuminated electronegativity of claim 8, wherein: a rear-end process structure is further formed on the back of the second passivation layer, and the rear-end process structure comprises a color filter and a micro lens;
the periphery of a pixel area of the back-illuminated image sensor is a peripheral area, and a CMOS circuit is formed in the peripheral area;
a front process test unit is also formed in the peripheral area;
the front process test unit comprises an MOS transistor, a diode and a capacitor;
the front process test unit is led out by the corresponding front gasket formed by the front metal layer and the corresponding back gasket formed by the back metal layer.
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| CN104051478A (en) * | 2013-03-14 | 2014-09-17 | 台湾积体电路制造股份有限公司 | Backside structure for a BSI image sensor device |
| CN106920810A (en) * | 2015-12-11 | 2017-07-04 | 台湾积体电路制造股份有限公司 | Image sensor devices and manufacture method |
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