KR100723457B1 - A semiconductor device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a semiconductor for providing a stacked photodiode structure to maximize photoelectric conversion efficiency for each wavelength band. The present invention is formed by forming a photodiode layer stacked in a plurality of layers on the upper layer, a total reflection layer below, and forming a transistor layer as a lower layer below the total reflection layer, and a filter on the upper stacked photodiode layer. The stack may be formed by separating the wavelength band, and the filter may be inserted therein. The filter stack may be formed as an anti-reflective coating or an infrared filter, and a color filter separated by the wavelength band may be installed outside. have.

Imaging Device, Photodiode, TDI, Stacking Type, Semiconductor

Description

Semiconductor device

1 is a characteristic diagram showing a transmission depth for each wavelength of incident light in a semiconductor substrate.

2 is a response curve relative to an incident wavelength band shown by a conventional imaging device.

3 is a structural diagram of a rear incident image device according to the prior art.

4A is a schematic cross-sectional view showing the structure of a stacked semiconductor device according to the present invention.

4B is a cross-sectional view for illustrating a manufacturing process of the stacked semiconductor device according to the present invention.

4C is a sectional view showing the principal parts of a buried structure photodiode in a stacked semiconductor device according to the present invention.

5 is a characteristic diagram illustrating a light detection situation of a general image device.

6 is a characteristic diagram for explaining a light detection situation of a stacked semiconductor device according to the present invention.

7A is a schematic cross-sectional view illustrating a parallel connection structure of a stacked semiconductor device according to the present invention.

7B is a schematic cross-sectional view illustrating an independent separate circuit connection structure of a stacked semiconductor device according to the present invention.

8 is an explanatory diagram illustrating a principle of operation of a time delay integrated (TDI) image device having a stacked structure according to the present invention.

9 is a configuration diagram of an internal filter insertion structure of a stacked semiconductor device according to the present invention.

10 is a configuration diagram of an external filter insertion structure of a stacked semiconductor device according to the present invention.

<Description of the symbols for the main parts of the drawings>

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly, to a semiconductor device capable of maximizing photoelectric conversion efficiency for each wavelength band in a semiconductor device that senses light by photoelectric conversion.

A semiconductor device that senses light and performs photoelectric conversion processes light as incident light, such as a CCD, and processes it as an image signal. An image device based on a semiconductor substrate such as silicon excites the electrons in the lattice structure in the semiconductor substrate. This creates twins of free electrons and holes. At this time, electrons or holes can be confined in one place through CCD or CMOS PD technology, and the amount of these electrons or holes is proportional to the intensity and energy of incident light.

On the other hand, the incident light particles are mutually reacted with the gratings in the semiconductor substrate, the transmission depth has a different probability for each wavelength.

1 is a characteristic diagram showing a transmission depth for each wavelength of incident light in a semiconductor substrate. That is, Figure 1 shows the transmission depth for each wavelength band in the visible light. That is, in the case of ultraviolet light, after about 1.5 μm in the case of a silicon substrate, most particles react with the silicon lattice to generate electrons and holes, and lose energy. Longer wavelengths reduce the probability of interacting with the lattice, allowing them to penetrate even deeper.

High-performance imaging devices usually embed a photodiode into areas away from the surface, usually in a single layer, to prevent leakage currents from incomplete coupling of the semiconductor substrate surface. If the photodiode has a certain thickness, it will respond particularly well to a particular wavelength in the incoming light spectrum. In other words, the other wavelength bands become relatively less responsive. This fact is better understood by looking at the frequency response of a typical imaging device.

FIG. 2 is a response curve relative to an incident wavelength band exhibited by a specific commercialized image device, and the device has the best conversion efficiency in the case of about 800 nm.

In general, in the case of a high-performance video device, photodiodes are buried and pinned to remove kTC noise. The buried type is a structure in which P or N surrounds another pole, and the pinned type is P. The doping materials of and N offset each other to completely deflate the N doped region, thus eliminating capacitance in this region. The size of this region is affected by the doping level and the driving voltage. Will receive.

Considering the semiconductor process characteristics and the situation in which the image device is used, the doping level and the size of the voltage that can be used are limited, the driving voltage for driving the photodiode cannot be increased indefinitely, and the photodiode has a finite thickness. In addition, the pinned photodiode having excellent noise performance is more limited in thickness. For this reason, it is very difficult to make an image device having perfect sensitivity over the entire spectrum.

This problem becomes more serious in general front illumination devices, because the light transmission characteristics of poly-silicon gates and the like are worse than silicon, and they also cover light. To solve this problem, back-side illumination devices have been developed and the following figure shows an example of such a device.

3 is a structural diagram of a rear incident image device according to the prior art.

As shown therein, a P epitaxial layer 2 is formed on the upper surface of the wafer 1, P wells and N wells are formed on the upper surface thereof, thereby forming a photodiode layer 3, and the photodiode layer 3 The transistor layer 4 is formed in the upper part of (). Reference numeral 5 denotes a connection line between the transistors.

Such a conventional back incident imager needs to be scraped off the backside of the wafer 1 in order to make a back-side illumination device, although the existing mechanical grinding and chemical etching techniques are used. Likewise, a few um intervals are required. In this case, even if the silicon is not heavily doped, a large portion of the incident light is lost before entering the photodiode region, which leads to a decrease in the quantum efficiency.

In addition, since there is no etch stop during etching for the back incident, it is difficult to control the thickness of silicon to be left. As such, a few um intervals have a major influence on the decrease in sensitivity such as short wavelengths, that is, ultraviolet rays or blue wavelengths. In addition, in the case of the rear incident image device, since the light is incident on the transistor gate, noise characteristics are deteriorated, and there is a technical problem of making a local light shield to prevent this.

Accordingly, an aspect of the present invention is to provide a semiconductor device capable of maximizing photoelectric conversion efficiency for each wavelength band in a semiconductor device that receives light and detects it as an electrical signal.

The present invention provides a semiconductor device capable of sensing light having multiple wavelengths in one pixel region by forming a stacked photodiode on an upper layer and a transistor layer on a lower layer.

In addition, the present invention is to improve the photoelectric conversion efficiency of each wavelength band by short wavelength is mainly detected in the upper wavelength portion and the long wavelength band by the various photodiodes from the upper layer portion to the lower layer portion.

In addition, the present invention is to form an etch stop layer on the upper surface of the wafer to be removed when manufacturing the back-incidence stacked image device, to form a multi-layer photodiode and a transistor layer on top of the wafer, the etch stop layer at the time of device manufacturing By etching the wafer by using the desired thickness can be easily adjusted to increase the yield.

The semiconductor device according to the present invention,

Upper floor Find  Mold and landfill Photodiode  Laminated in multiple layers, underneath Transistor layer  Arranged to form a detection circuit, Stacked Photodiode  bracket Photo  The filter layer is interposed between the diode layers.

In addition, according to the present invention, in the method of manufacturing the semiconductor device, a buffer oxide film and an etch stop layer are formed on an upper surface of the handle wafer, a photodiode is laminated in multiple layers on the upper surface of the handle wafer, and a transistor layer is formed on the uppermost layer. After performing the pinned structure formation of the diode, the pixel separation, and the contact process, the silicon wafer of the handle wafer is etched and removed to the etch stop layer by inverting the handle wafer on which the plurality of photodiode and transistor layers are formed. do.

In addition, the semiconductor device of the present invention,

In a semiconductor device in which a multilayer photodiode layer is laminated on an upper layer and a transistor layer is formed on a lower layer,

In the transistor layer, a contact portion for connecting the respective photodiode layers is formed in common, the photodiode layers of each layer are connected in parallel, and the combined image information is read using a detection circuit.

In addition, the semiconductor device of the present invention,

In a semiconductor device in which a multilayer photodiode layer is laminated on an upper layer and a transistor layer is formed on a lower layer,

Forming a contact in the transistor layer separately from the photodiode layer so as to read the image signal as a separate circuit for each photodiode, and to acquire the entire image information by combining analog or digitally in or out of the pixel. It features.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

4A is a schematic cross-sectional view showing the structure of a semiconductor device according to the present invention.

As shown in the drawing, a plurality of photodiode layers are stacked on the upper layer, and a transistor layer is formed on the lower layer to form a back-illuminated image device.

From below, the metal layer 160, the inverted transistor layer 151, the thermal oxide film 152 , the dielectric layer 143 which is a total reflection layer, the red diode layer 141, the thermal oxide film 142, the AR coating layer 133, green The diode layer 131, the thermal oxide film 132, the AR coating layer 123, the blue diode layer 121, and the thermal oxide film 122 are sequentially stacked, and an AR coating layer (anti-reflection coating) is formed thereon ( 113) is formed. Here, reference numeral 191 denotes a contact metal between the photodiode and the transistor. 162a represents a trench isolation film for pixel separation, and serves to distinguish each pixel.

Method for manufacturing a semiconductor device according to the present invention configured as described above, as shown in Figure 4b,

The oxide film 111 and the etch stop layer 112 are formed on the top surface of the handle wafer 110, and the filter stack AR 113 is formed on the upper surface of the handle wafer 110.

Subsequently, a semiconductor layer and an oxide film for a semiconductor device are formed on a donor wafer, a process for thin film transition is performed to prepare a donor wafer, the donor wafer is turned upside down and bonded to an upper surface of the handle wafer 110, and a thin film transition is performed. A thin film transition process is performed to remove the silicon layer of the donor wafer that is separated from the oxide film and the semiconductor layer. In this case, the semiconductor layer is a photodiode layer, and the oxide layer is an oxide layer for distinguishing each photodiode layer.

As described above, the first donor thermal oxide film 122 and the first donor transfer Si (blue PD) 121 are formed by the thin film transition process as described above. An AR coating layer 123 is formed on the upper surface.

In the same manner, the thin film transition process, the AR coating layer, and the filter stack forming process are repeated, and as shown in the drawing, the second donor thermal oxide film 132, the second donor transfer Si (Green PD) 131, the AR coating layer 133, The third donor thermal oxide film 142, the third donor transfer Si (Red PD) 141, the filter stack (All reflect) 143, the fourth donor thermal oxide film 152, the fourth donor transfer Si (151) Form in turn. Here, the fourth donor transfer 151 is formed of a transistor layer.

Subsequently, the metal layer 160 connecting the circuits with the photodiodes is formed on the upper surface of the transistor layer, and the solder bumper 161 is formed. In the drawings, the pixel isolation and the contact structure of each photodiode and transistor are not shown in detail, and description thereof is omitted.

Thereafter, the work substrate having the structure as shown in the drawing is removed from the inverted side by etching the handle wafer 110 and the buffer oxide layer 111 to the etch stop layer 112, and then the etch stop layer 112 is removed.

As a result, as shown in FIG. 4A, a semiconductor device having a structure in which a filter stack (AR) 113 is formed on the top is manufactured. The uppermost filter stack 113 becomes an antireflective coating layer, and the filter stack 143 formed on the transistor layer 151 in FIG. 4A is formed as an all reflecting filter layer.

On the other hand, the pinned and buried photo diodes form trench grooves for contact and pixel separation in the multilayer stacked structure, and form sidewall oxide films 208 on the side walls of the trench grooves. Subsequently, the "upper" 204-"lower" 202 layer of the "upper" 204-"middle" 203-"lower" 202 dope layer (PNP layer or NPN layer) constituting the photodiode is formed. The sidewall layer 209 is further formed by ion implantation so as to be connected to each other to form a buried and pinned photodiode.

In this manner, the photodiode in the stacked structure can be formed as a buried structure. Thus, when the buried structure of PNP or NPN is made, a junction deflation region is formed up and down about P or N in the center, and the pinned structure is not shown in the figure.

As shown in FIG. 4A, when a multi-layered pinned and buried image device is disposed and a transistor detection circuit is disposed in a lower layer, incident light has a short wavelength mainly in the upper layer and a long wavelength band in a plurality of photo diodes from the upper layer to the lower layer. It can be detected over time to minimize the loss of incident light. Even when light of a narrow wavelength band is incident, a much higher efficiency of detection can be obtained than in the case of one photodiode.

For example, long wavelengths, such as red or near-infrared, penetrate into the depths of more than a few microns (um) from the entrance of the silicon (epidermis), making it very difficult to detect them all. Shorter wavelengths, such as blue or purple, will be detected relatively in the epidermis. If multi-layer photodiodes can be used to read the charges from multiple photodiodes, detection efficiency over a wide wavelength range is maximized.

FIG. 5 shows a light detection state of a general image device, and the detection efficiency in a specific band such as a long wavelength and a short wavelength is inferior. That is, in the figure, in the case of the blue index of short wavelength in the sensing area of the photodiode (area indicated by dotted line in the figure), the detection is performed only on the surface side of the photodiode, and in the case of long wavelength, light is detected only in a part of the wavelength region. This reduces the detection efficiency.

 On the other hand, in FIG. 6, since the plurality of image device layers are disposed, the image elements may be detected with high efficiency evenly regardless of the wavelength characteristic of the incident light. For example, as shown in the figure, for example, the first and second photodiodes PD1 and PD2, the first and third photodiodes PD1-PD3, and the first and fourth photodiodes PD1 for each wavelength band. -PD4), it can be seen that the first-fourth photodiode (PD1-PD4) can be detected. Therefore, even if the wavelength is short, the photodiode can sufficiently detect light, and in the case of the long wavelength band, it is possible to accurately detect the entire light intensity.

Thus, as shown in FIG. 4A, it can be seen that the fabrication of the image device in the stacked structure can be detected with high efficiency even irrespective of the wavelength characteristic of the incident light.

In addition, in the case of an etch stop for etching a back incident type device, as shown in FIG. 4B, an nitride film and an oxide film are disposed on a handle wafer (work substrate) as an appropriate etch stop. By operating, the thickness of the oxide layer on the silicon can be controlled very accurately. By doing so, it is possible to solve the problem of lowering light sensing efficiency (particularly short wavelength) and lowering yield caused by difficulty in controlling thickness of silicon. In actual etching, most of the thickness of the working board is removed by mechanical grinding, and the etching technique is used to solve the thickness which is difficult to control mechanically.

The circuit for reading image information that senses light reads using a single detection circuit by connecting several photodiodes in parallel as shown in FIG. 7A, and reads a plurality of photodiodes as a separate circuit as shown in FIG. 7B. There are ways to combine and combine them analogly or digitally in or out of pixels. Or there may be a mix of the two.

7A is a structural diagram showing an overview of a detection circuit of a stacked semiconductor device according to the present invention. As shown here,

As the upper layer, the first to fourth photodiode layers 310 to 340 are stacked, the total reflection filter layer 350 is formed below the fourth photodiode layer 340, and the transistor layer 360 is formed as the lower layer. And constitutes a stacked semiconductor device.

In the stacked semiconductor device configured as described above, the photodiodes of each layer are formed as buried and pinned structures as described in FIG. 4C), and the four layers are connected to the photodiodes and transistors of each layer. Forming trench grooves are connected to all the photodiode layer of the structure is connected in parallel to the contact portion (401). In other words, several photodiodes are connected in parallel and read using one detection circuit. The detection circuit here refers to a circuit of a metal layer (not shown) of the transistor layer 360.

7B is a structural diagram showing another example of a detection method of a stacked semiconductor device according to the present invention. As shown therein, the first to fourth photodiode layers 310 to 340 are stacked as an upper layer, and the total reflection filter layer 350 is formed below the fourth photodiode layer 340, and the transistor is formed as a lower layer. A layer 360 is formed to form a stacked image element, and a contact portion 501 for connecting each photodiode layer and the transistor layer is formed to form a plurality of photodiodes in separate detection circuits to read information. It is configured to pay. Thereafter, there is a method of combining the signals of the respective detection circuits analog or digitally in or out of the pixel. Or there may be a mix of the two.

In the meantime, the total reflection layer 350 may be provided before the transistor layer, thereby minimizing transistor malfunction or noise. As there is no need to make a local light shield like a general back-incidence image device, it is technically easy to implement.

In addition, the semiconductor device of the present invention is not limited to one to four photodiode layers, but may be further increased or reduced as necessary.

TDI (Time delayed integration) device is a kind of line scan camera. It was developed to increase effective exposure in the case of very low amount of light. The line camera scans an object and acquires an image. In this case, it works by moving charges at the speed of the object or reading images at high speed and combining them analog or digital.

FIG. 8 is an explanatory diagram illustrating a principle of operation of a time delayed integration (TDI) semiconductor device having a stacked structure according to the present invention.

  A filter stack 300; A plurality of photodiode layers 310-340 stacked below the filter stack 300, a total reflection layer 350 formed under the photodiode layer 340, and a transistor formed under the total reflection layer 350. The transistor layer 360 and the stacked photodiode layers 310 to 340 each have a photodiode independently connected to a detection circuit of a transistor layer for each pixel. The detection circuit is configured to be connected in parallel with a detection circuit at a later stage so that the charges generated in the photodiode layer by exposure are transferred to the next pixel and detected as the sum of the charges.

Therefore, the charge detected by the exposure in the previous pixel is transferred to the next pixel, and the total charge is detected by the sum of the previous charges in the final output terminal. The stacked image device can perform the same operation. Image information of pixels read from the transistor may be transferred to neighboring pixels and merged with image information of a new exposure in various ways. There is also a method of transmitting analog signals, or digital information.

The conversion to digital and the accumulation of information can occur in pixels, in other parts of the chip, or externally. In this technique, as shown in FIG. 7B, each photodiode is configured as a separate detection circuit to combine signals in a circuit of a transistor layer, and is combined with image information detected by a new exposure.

  On the other hand, the TDI imaging device of the present invention can be selectively detected for each wavelength by an external color filter combination.

9 is a configuration diagram of an internal filter insertion structure of a stacked semiconductor device according to the present invention.

An oxide film 370 for protecting the filter stack; A plurality of filter stacks 301-303 which are separately provided for each wavelength band under the oxide film 370; Each of the plurality of photodiode layers 310-340 and the photodiode layer 340, which are separately formed in correspondence with the filter stacks 301-303, are respectively stacked below the filter stacks 301-303. The total reflection layer 350 is formed integrally connected to the lower portion and the transistor layer 360 is formed in the lower portion of the total reflection layer 350 to correspond to the separation of the filter stack to read the image signal for each wavelength band. Here, each photodiode layer and the transistor layer are separated in a lower part according to the filter stack, and the detection circuits are configured independently. Here, the portions indicated as the isolation regions in the drawing are pixel isolation and contact regions, each of which has a parallel connection contact portion for parallel connection of each photodiode layer and a transistor layer in one pixel, or each photodiode layer and transistor layer in one pixel, respectively. A serial connection contact portion connected to each other is formed. (See FIGS. 7A and 7B).

In addition, the color filter can be installed outside. 10 is a configuration diagram of an external filter insertion structure of a stacked semiconductor device according to the present invention.

An oxide film 370 for protecting the filter stack; A filter stack 300 which is an antireflective coating or an infrared cut filter formed under the oxide film 370; A plurality of stacked photodiode layers 310-340 and a lower portion of the photodiode layer 340 that are formed in a stacked structure under the filter stack 300 and are separated to correspond to the external filter separation structure. A total reflection layer 350 formed integrally connected to the transistor, and a transistor layer 360 separated from the total reflection layer 350 to correspond to the separation structure of the photodiode layer, and formed on the upper portion of the oxide film 370. And a plurality of external color filters 301'-303 'separately provided for each wavelength band. Here, each photodiode layer and the transistor layer are separated in a lower part according to the filter stack, and the detection circuits are configured independently. Here, the portions indicated as the isolation regions in the drawing are pixel isolation and contact regions, each of which has a parallel connection contact portion for parallel connection of each photodiode layer and a transistor layer in one pixel, or each photodiode layer and transistor layer in one pixel, respectively. A serial connection contact portion connected to each other is formed. (See FIGS. 7A and 7B).

As described above, the stacked semiconductor device according to the present invention basically implements a filter stack after the nitride film so as to be used as an anti-reflection coating or an infrared ray elimination (IR-Cut) filter. This concept can be further expanded to select different wavelength bands by placing different color filters on the upper portion of the image device unit, and can be optimized to obtain an optimal light conversion efficiency according to each wavelength as a stacked type device. Installation after the nitride film has the advantage of minimizing the complexity of the system, but can be installed externally. In this case, there is an advantage that the wavelength band can be selected relatively freely, but care must be taken during assembly. In addition, thickness and material properties can be freely selected for the purpose of optimizing the color filter or system focus.

As described in detail above, the stacked semiconductor device according to the present invention may provide a semiconductor device capable of sensing light having multiple wavelengths in one pixel region by forming a stacked photodiode on an upper layer and a transistor layer on a lower layer. It can be effective.

In addition, in the image device using the stacked photodiode structure according to the present invention, short wavelengths are mainly detected in the upper portion and long wavelength bands are detected by various photodiodes from the upper portion to the lower portion, thereby improving photoelectric conversion efficiency for each wavelength band over a wide wavelength range. It can be effective.

In addition, the present invention is to form an etch stop layer on the upper surface of the wafer to be removed when fabricating the back-incidence stacked semiconductor device, to form a multi-layered photodiode and transistor layer on top, the etch stop layer during device manufacturing By etching the wafer, the desired thickness can be easily adjusted and the yield can be increased.

Claims (8)

In a semiconductor device that receives light incident photoelectric conversion, First to fourth photodiode layers 310 to 340 that receive light and detect light intensity for each wavelength band; A total reflection filter layer 350 formed below the fourth photodiode layer 340; A transistor layer 360 formed below the total reflection filter layer 350 to detect information of light detected by each photodiode layer as an electrical signal; And a contact unit 401 connecting the photodiode layers 310-340 to the transistor 360 layer in parallel for each pixel so as to integrate and detect a signal detected in each photodiode in a transistor. Stacked semiconductor device, characterized in that configured. In a semiconductor device that receives light incident photoelectric conversion, First to fourth photodiode layers 310 to 340 that receive light and detect light intensity for each wavelength band; A total reflection filter layer 350 formed below the fourth photodiode layer 340; A transistor layer 360 formed below the total reflection filter layer 350 to detect information of light detected by each photodiode layer as an electrical signal; And a contact unit 501 connecting the photodiode layers 310 to 340 and the transistor 360 to each other so as to separately detect a signal detected by each photodiode in a transistor. Laminated semiconductor device, characterized in that. The method according to claim 1 or 2, wherein the first to fourth photodiode layers 310 to 340, The semiconductor device of claim 1, further comprising an antireflective coating layer formed between the photodiode layers. In a semiconductor device that receives light incident photoelectric conversion, An oxide film 370 for protecting the lower filter stack; A plurality of filter stacks 301-303 formed separately from the oxide film 370 by respective wavelength bands; A plurality of photodiode layers 310-340 respectively separated from each other in correspondence with the filter stacks 301-303 and stacked thereon; Filter layers 311, 321, and 331 inserted into and between each photodiode layer; A total reflection layer 350 formed under the photodiode layer 340; Stacked semiconductor device, characterized in that consisting of a transistor layer 360 separated from the total reflection layer (350) to correspond to the photodiode layer (310-340). In a semiconductor device that receives light incident photoelectric conversion, An oxide film 370 for protecting the filter stack; A filter stack 300 which is an antireflective coating or an infrared cut filter formed under the oxide film 370; A plurality of stacked photodiode layers 310-340 formed below the filter stack 300 in a stacked structure and separated to correspond to an external filter separation structure; Filter layers 311, 321, and 331 inserted between and between each photodiode layer; A total reflection layer 350 integrally connected to a lower portion of the photodiode layer 340; A transistor layer 360 is formed below the total reflection layer 350 to correspond to the separation configuration of the photodiode layer. Stacked semiconductor device, characterized in that it comprises a plurality of external color filters (301'-303 ') that are installed separately for each wavelength band on the oxide film (370). The method according to claim 4 or 5, A parallel connection contact unit for connecting the photodiode layers 310-340 to the transistor 360 layer in parallel for each pixel so as to integrate and detect a signal detected at each photodiode in a transistor; Laminated semiconductor device, characterized in that. The method according to claim 4 or 5, And a series connection contact unit for connecting the photodiode layers 310 to 340 and the transistor 360 layers individually to connect a signal sensed by each photodiode so as to be separated from the transistor. A laminated semiconductor device characterized by the above-mentioned. The method according to claim 4 or 5, Each of the photodiode layers 310 to 340 and the transistor 360 layer may be selectively connected to each pixel, and a series connection contact unit for connecting each pixel may be selectively applied to each pixel. Multi-layer semiconductor device characterized in that the composite configuration in the device.

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