GB2100511A - Detector for responding to light at a predetermined wavelength, and method of making the detector - Google Patents
Detector for responding to light at a predetermined wavelength, and method of making the detector Download PDFInfo
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- 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
- H01L27/148—Charge coupled imagers
- H01L27/14875—Infrared CCD or CID imagers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices 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; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/08—Semiconductor devices 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; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
- H01L31/10—Semiconductor devices 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; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by at least one potential-jump barrier or surface barrier, e.g. phototransistors
- H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
- H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier or surface barrier
- H01L31/108—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier or surface barrier the potential barrier being of the Schottky type
Abstract
A backside illuminated infrared detector has an n-type semiconducting substrate 10 on which is deposited a p-type semiconducting channel layer 16. A plurality of parallel insulating strips deposited on the channel layer 16 define therebetween a plurality of parallel channels in the channel layer 16, with a plurality of metallic contacts 90,92,94,96,98 deposited on the channels to establish a corresponding matrix of Schottky barriers 114,116,118,120,122 so that infrared light at the predetermined wavelength will be absorbed in the Schottky barriers which are so positioned that charges stored in the channels can be transferred to an end of the channels by the manipulation of voltages applied to the contacts. A row of metallic contacts 102, is deposited on the channel layer 16 to establish a corresponding row of transfer Schottky barriers, e.g. 124, such that charges transferred from the parallel channels may be transferred by the manipulation of voltages applied to this row of contacts. <IMAGE>
Description
SPECIFICATION
Detector for responding to light at a predetermined wavelength, and method of making the detector
The present invention relates to a detector for responding to light at a predetermined wavelength, and to methods of making the detector. The invention relates especially, but not exclusively, to solid state focal planes for imaging scenes through the detection of infrared light.
Advanced infrared imaging systems require a focal plane integration of large detector arrays and signal processing electronics. In addition, high density arrays are essential for various tactical and strategic target acquisition and surveillance applications.
In designing such an imaging system, there are basically two types of infrared focal planes from which to choose, monolithic and hybrid. The multiplexer for a monolithic focal plane is fabricated as an integral part of the structure, while the photodetector array and the signal multiplexer of a hybrid focal plane are fabricated separately, then joined together using an advanced interconnection technology.
Both types of focal planes serve the complimentary functions of photon detection, including prefiltering of the optical signal, and signal multiplexing.
In operation, the focal plane is irradiated with infrared background and signal energy. The optical signal is filtered and collected by the detectors, the resulting electrical signal from the detectors then being coupled to the multiplexerthrough interfacing electronics. Some signal processing, such as background suppression, is generally required to condition the incoming signal so that the multiplexer can be operated effectively. A serial video signal can thus be obtained at the output of the multiplexer which contains all the scene information within the field of view of the focal plane.
The first consideration in designing an infrared detector, whether following the monolithic or hybrid approach, is to provide for efficient illumination of the absorbing material by only those photons within the desired spectral band. Conventional detectors have employed a number of configurations to achieve this result, including, for example, frontside illumination of a bulk semiconductor, frontside illumination through a wide bandgap semiconductor, backside illumination by thinning the absorbing material, backside illumination through a wide bandgap semiconductor, spectral filtering byfundamen- tal absorption in an intermediate bandgap semiconductor, and constructive interference in an optically flat layer of an absorbing semiconductor.
Once the desired illumination of the detector has been accomplished in the design, the conventional approach to achieving photon detection has been to provide for the collection of minority carriers within a a diffusion length of a p-n homojunction. Significant advances in performance, however, have been made by employing heterostructure configurations in conjunction with the conventional photon detection approach, such as by placing a heteroface within an absorption length of the p-n homojunction or by placing the heteroface at the p-n junction.
After the detection function is satisfied, the next step is to arrange for the infrared signal from the detectors to be multiplexed by the focal plane. More advanced signal processing, such as precise nonuniformity compensation, target tracking, and bandwidth compression, can be performed on the raw video data output from the multiplexer through off-focal-plane electronics. Three types of multiplexers have been utilized: charge coupled device (CDD), charge injection device (CID), and X-Y addressed metal oxide semiconductor field effect transistor (MOSFET) switch arrays. In general, however, the
CCD has emerged as the preferred multiplexer due to the low noise characteristics of this device.
There are several approaches to incorporating charge coupled multiplexing into the design of an infrared imager. Charge coupled shift registers may be fabricated on materials having the desired intrinsic response, such as InAs, InSb, and HgCdTe. A second approach incorporates the use of extrinsic silicon, while a third provides charge coupled shift registers on a silicon wafer with separate infrared detectors prepared on the wafer.
All of these CCD approaches to infrared focal plane multiplexing are based on the charge coupling concept - the collective transfer of all mobile electric charge contained within a semiconductor storage element to a similar, adjacent storage element by the external manipulation of voltages. Atypical CCD consists of a p-type silicon substrate with a silicon dioxide insulating layer on its surface, and an array of conducting electrodes deposited on the surface of the insulator. When a periodic waveform, called the clock voltage, is applied to the electrodes, some of the electrons in the vicinity of each electrode will form a discrete package of charge and move a distance of one charge coupled element, or unit cell, for each full clock cycle.The packets of electron charge are thus transferred as a result of the continuous lateral displacement of the local potential wells created by the clocked voltage.
Advancements in the design of CCDs which are significant for imager multiplexing applications have resulted from the research and development which has been devoted to Ill-V compound semiconductors in recent years. Substantial improvements in CCD speed and imaging performance, for example, can potentially be realized by fabricating CCDs from Ill-V semiconductors instead of silicon. These improvements result from two properties of Ill-V materials: high room temperature electron mobility and the low intrinsic carrier concentration found in wide energy bandgap Ill-V alloys. Further gains in device performance are possible by eliminating the metalinsulator-semiconductor (MIS) structure used in traditional CCD devices. This concept of a CCD having no insulator interfaces was first suggested by
Schuermeyer et al. (New Structures for Charge
Coupled Devices, Proc.IEEE, Vol. 60, p. 1444(1972) and such a CCD, which is necessarily of the buried channel design, has been demonstrated in a Schottky barrier gate CCD fabricated in GaAs, is disclosed in Deyhimy, et al., U.S. Patent No. 4285000.
In addition to its utility as a multiplexing device in infrared focal planes and other applications, the charge coupled concept has also been applied to achieve image sensing directly. Since the charge coupling technique was first developed, imaging with charge coupled devices has been an area of intense activity, and imagers operating in the visible spectrum with full television resolution have been demonstrated. If there is present an array of potential wells, such as those formed by CCDs, photoemitted electrons will fill the wells to a level corresponding to the amount of light in their vicinity. These packets of electrons which are generated by the light can be transferred to a point of detection and converted to an electrical signal representative of the optical image incident on the device.
Even though devices with a variety of gate structures, channel types, and chip layouts have been reported, however, most designs use silicon as the photoabsorbing material. Whether the photosensitive region is located under the shift register gates, under separate photogates, or at separate photodiodes, minority carriers photoexcited in the silicon form the charge packets to be clocked out in these
CCD imagers. Since these devices basically exhibit the spectral response and quantum efficiency associated with silicon photodiodes, they are useful as infrared imagers only to wavelengths as long as approximately 1.1 um. Considerable interest exists, however, in imagers sensitive to longer wavelength infrared radiation.Imagers responsive in the 2-3 Rm range, for example, are useful to the military for viewing high contrast scenes involving jet and rocket plumes, while devices responsive to higher wavelength radiation can image 300 K scenes by their own thermal radiation, and are of interest for industrial and medical applications as well as in military devices.
One way in which silicon based devices may be employed for imaging tasks in the medium and long wavelength infrared range is through the use of the
Schottky barrier concept. A simple Schottky barrier device consists of a metal layer which has been evaporated onto a semiconductorwaferthrough an opening in an overlying insulator layer. This device exhibits electrical characteristics similar to those of the p-n junction, its properties depending upon the barrier height at the metal-semiconductor interface in much the same way that the characteristics of the p-n junction depend upon the bandgap. The barrier height is a function of the choice of metal and the choice and polarity of the semiconductor, and is nearly independent of the doping applied to the semiconductor.A reverse-biased Schottky barrier diode will generate a dark current resulting from the collection by the metal of minority carriers thermally generated in the semiconductor and from the thermal excitement of majority carriers in the metal over the barrier into the semiconductor. Moreover, since the barrier height for the infrared spectral range of interest is less than half the bandgap of silicon, the latter process will dominate. The Schottky barrier device can act as a photodetector by absorbing light either in the semiconductor or in the metal. In the latter case, carriers are photoexcited over the barrier from the metal to the semiconductor where they become majority carriers. With light incident through the semiconductor, absorption takes place at the metal-semiconductor interface.The Schottky electrodes may be either metals or metal silicides, the latter being formed by a solid state reaction. A potential barrier will exist between the metal or silicide and the silicon substrate, so that infrared photons will pass through the silicon and be absorbed at the Schottky electrode, resulting in the excitation of carriers which are then internally emitted over the Schottky barrier into the silicon.
The quantum efficiency for this mechanism is relatively low, but the response extends to photon energies as low as the barrier height, a value that can be considerably lower than the bandgap. Since the spectral yield in such a device depends almost entirely on the absorption process in the metal and the emission of majority carriers over the barrier, the sensitivity is almost independent of such parameters as semiconductor doping and minority carrier lifetime, thus eliminating some of the major sources of nonuniformity in conventional semiconductor detectors.
Area arrays for infrared detection utilizing the
Schottky barrier concept have been achieved. One such device, for example, includes Schottky barrier metalizations and a charge coupled shift register fabricated on a p-type silicon substrate. Infrared photons from backside illumination are absorbed in a metal silicide Schottky barrierfilm underneath the metalization regions Holes are photoemitted over the Schottky barrier, thereby causing external current flow (or charge buildup in the diode storage mode). The barrier height determines the cutoff wavelength of the detection limit, while the short wavelength cutoff is determined by intrinsic absorption in the silicon substrate. Retina operation is completed by multiplexing the readout current to each cell, as by integrating the Schottky cell array with multiplexing circuitry by a charge coupled line readout.
For a PtSi2/p-Si system (Pt metalization on a p type silicon substrate) the barrier height is approximately 0.25 eV, corresponding to a cutoff wavelength of# 5.0 lim. This use of silicon monolithic processing technology in the fabrication of Schottky retinas can lead to good photoresponse uniformities with significant reductions in the cost and complexity of a thermal imaging sytem. The techniques proposed in the prior art, however, exhibit several shortcomings which limit their applicability in some infrared systems. The Schottky detector approach exhibits a low (.5-1%) quantum efficiency, although this deficiency can be alleviated by providing large arrays. More troublesome problems arise from the necessity for a large (80 x 160 um) cell size and a characteristically low "fill factor" (which may be defined as the amount of light detecting area taken as a percentage of total focal plane area) of approximately 15-30%. Consequently, an infrared focal plane design incorporating the advantages of utilizing well developed silicon processing techniques while avoiding the disadvantages of large cell size and a low fill factor would find ready acceptance in many infrared focal plane applications.
It is a general objective of this invention to provide a new and improved detector design.
A detector for responding to light at a predetermined wavelength includes, according to the present invention, a semiconducting substrate of a first conductivity type with a semiconducting channel of a second conductivity type disposed on the substrate. A plurality of metallic contacts are disposed on the channel to establish a corresponding plurality of
Schottky barriers, the contacts being selected so that light at the predetermined wavelength will be absorbed in the barriers and the contacts being positioned so that charge stored in the channel may be transferred by the manipulation of voltages applied to the contacts.
In a more particular embodiment, the detector includes a region of the second conductivity type in the substrate which defines the semiconducting channel.
If the substrate and the channel are transparent to light at the predetermined wavelength, light can reach the Schottky barriers by travelling through the substrate and the channel in a backside illuminated mode. In addition, the plurality of metallic contacts may be fabricated from a plurality of different metals, so that various wavelengths of light can be absorbed and detected.
In another embodiment, a backside illuminated detector includes a semiconducting substrate of a first conductivity type which is transparent to the light and a transparent semiconducting channel layer of a second conductivity type deposited on the substrate. A row of metallic contacts is deposited on the channel layer to establish a corresponding row of Schottky barriers so that light at the predetermined wavelength can be absorbed in the barriers, the contacts being positioned so that charges stored in the channel layer may be transferred by the manipulation of voltages applied to the contacts.
A first relatively heavily doped region of the second conductivity type is located in the channel layer at a first end of the row, while a second relatively heavily doped region of the second conductivity type is located in the channel layer at a second end of the row. Deposited on these regions are an input and an output electrode contact. A relatively heavily doped isolation region of the first conductivity type extends through the channel layer to surround the electrodes and the Schottky barriers.
A detector focal plane for responding to light at a predetermined wavelength includes a semiconducting substrate of a first conductivity type with a plurality of parallel semiconducting channels of a second conductivity type disposed on the substrate.
A plurality of parallel metallic contacts are disposed across the channels to establish a matrix of Schottky barriers so that light at the predetermined wavelength can be absorbed in the barriers, the contacts being positioned so that charges stored in the channels may be transferred by the manipulation of voltages applied to the contacts.
In a more particular embodiment, a plurality of parallel regions of the second conductivity type are located in the substrate to define the plurality of parallel channels, and a charge transfer region of the second conductivity type in the substrate defines a charge transfer channel along an end of each of the channels.
In another more particular embodiment, a backside illuminated focal plane includes a semiconducting substrate of a first conductivity type which is transparent to the light, with a semiconducting transparent channel layer of a second conductivity type deposited on the substrate. A plurality of parallel insulating strips are deposited on the channel layer to define therebetween a plurality of parallel channels in the channel layer, while a plurality of parallel metallic contacts are deposited across the channels to establish a matrix of Schottky barriers. A first relatively heavily doped region of the second conductivity type is located in the channel layer along a first end of each of the channels, with an input electrode contact deposited on the region.A row of metallic contacts deposited on the channel layer along a second end of each of the channels establishes a row of transfer Schottky barriers so that charges stored in the channel layer may be transferred by the manipulation of voltages applied to the row of contacts. A second relatively heavily doped region of the second conductivity type is located in the channel layer at an end of the row of metallic contacts with an output electrode contact deposited on the second region.
The invention also includes a method of making a detector which is responsive to light at predetermined wavelength, including the steps of:
providing a semiconducting substrate of a first conductivity type,
depositing a semiconducting channel layer of a second conductivity type on the substrate,
depositing a plurality of metallic contacts on the channel layer to establish a corresponding plurality of Schottky barriers, and
positioning the contacts so that charges stored in the channel layer may be transferred by the manipulation of voltages applied to the contacts.
In a more particular embodiment, the step of depositing metallic contacts involves
depositing a plurality of parallel insulating strips on the channel layer to define therebetween a plurality of channels in the channel layer and
depositing a plurality of parallel metallic contacts across the insulating strips to establish a matrix of
Schottky barriers, while the method further includes the steps of::
forming a first relatively heavily doped region of the second conductivity type in the channel layer along a first end of each of the plurality of channels,
depositing a metallic input electrode contact in the first region,
depositing a row of metallic contacts on the channel layer along a second end of each of the plurality of channels to establish a row of transfer
Schottky barriers,
forming a second relatively heavily doped region of the second conductivity type in the channel layer at an end of the row of transfer Schottky barriers, and
depositing a metallic output electrode contact on the second region.
In another embodiment, the method includes the steps of:
providing a semiconducting substrate of a first conductivity type,
forming a region of a second conductivitytype in the substrate to define a channel,
depositing a plurality of metallic contacts on the channel to establish a corresponding plurality of
Schottky barriers, and
positioning the contacts so that charges stored in the channel may be transferred by the manipulation of voltages applied to the contacts.
In the latter method, the steps of forming a region and depositing contacts may further include:
forming a plurality of regions of the second conductivity type in the substrate to define a plurality of channels, and
depositing a plurality of parallel metallic contacts across the channels to establish a matrix of Schottky barriers.
These examples summarize some of the more important features of this invention. There are, of course, additional details of the invention, which are further described below and which are included within the subject matter of the appended claims.
Additional objectives, features, and advantages of the present invention will be evident from the description below of the preferred embodiments and the accompanying drawings, wherein the same numerals are used to refer to like elements throughout all the Figures. In the drawings:
Figure 1 is a cross-sectional view illustrating one channel of a backside illuminated detector,
Figure 2 is an energy level diagram representing the Schottky barrier/p-type channel layer interface,
Figures 3-5 are plan views illustrating various steps in a method of fabricating an infrared focal plane according to the present invention,
Figures 6 and 7 are cross-sectional side views illustrating the structure of a focal plane fabricated according to the steps shown in Figures 3-5, and
Figures 8 and 9 are cross-sectional side views analogous to Figures 6 and 7, but illustrating the structure of an alternative embodiment of the invention.
A preferred embodiment of the present invention will now be described which constitutes a new
Schottky barrier detector design which is particularly advantageous because both the detection and multiplexing functions are accomplished by the same
Schottky barriers. Figure 1 illustrates, in a crosssectional view, one channel of a backside illuminated infrared detector constructed in accordance with the invention. The most important applications for this invention are believed to be in the detection of infrared light, and this discussion will focus on those applications. Those skilled in the art, however, will recognize that the invention is not necessarily limited to the infrared portion of the spectrum.This device includes a n-type semiconducting silicon substrate 10 which has a bandgap greater than the energy of the light which is to be detected, so that the light, as indicated by the photon paths 12 and 14, will pass through the substrate. Deposited on the substrate 10 is a p-type silicon channel layer 16 which, like the substrate, is transparent to the infrared radiation to be detected. A row of metallic contacts 18,20,22, and 24 is deposited on an upper surface 26 of the channel layer 16, thereby establishing a corresponding row of Schottky barriers 28, 30,32, and 34 between the contacts and the channel layer. As those skilled in the art will appreciate, and as indicated by the break 36 in the drawing, an actual device may have a significantly larger number of contacts than can be effectively illustrated.An input ohmic contact is established by means of a metallic contact 38 deposited on a p±doped region 40 of the channel layer. Although an input device for the CCD function of this detector is not essential, since the signal charges for the Schottky barriers are themselves derived from the detection function of the same barriers, as is explained further below, an input electrode can be used to improve the functioning of the detector by supplying a constant DC input to the CCD. A similar output ohmic contact is created by a metallic contact 42 deposited on the channel layer over a p±doped region 44. Isolation of the channel layer is accomplished by the n±doped regions 46 and 48, which are portions of an isolation region extending through the channel layer and surrounding the electrodes and the Schottky barriers.
It is an outstanding feature of this invention to provide a detector design which utilizes the same charge coupled device for both the detection function and the multiplexing function. As illustrated by the photon paths 12 and 14, when a photon at the desired wavelength enters the detector, the photon travels through the substrate 10 and the channel layer 16 and is absorbed at one of the Schottky barriers 28-34. The absorption process excites a hole, such as the holes 50 and 52, overthe barrier and into the channel layer 16. The collected charge in the channel layer, which is thus representative of the appropriate wavelength light intensity impinging on each corresponding portion of the focal plane, can be transferred out of the channel layer by connecting the proper clocking signals, as is well known in the art, to the contacts 18-24.The lines 54,56 and 58, for example, illustrate a three phase clocking arrangement consisting of phases " 2, and 3. This invention may also readily be adapted to provide a multicolor detector. If the detector were to be sensitive to four different wavelengths of light, for example, each of the barriers 28,30, 32, and 34 could be made responsive to different light by selecting the appropriate metal for each of the contacts 18,20, 22 and 24.
The detection mechanism for the device illustrated in Figure 1 is represented in Figure 2 by an energy level diagram for the Schottky barrier/p-type channel layer interface. The line Ec represents the conduction band energy level for the n-type silicon substrate 10 and the p-type silicon channel layer 16. The valence band energy level for these layers is shown by the line Ev, while the Fermi level is represented by the dashed line 60, so that the energy barrier QBP must be surmounted for a hole 62 to be excited from the metal 64 into the potential well 66 and stored in the p silicon channel 16.
It should be noted that the barrier energy QBP for this photoemission absorption process is considerably lower than the bandgap transition energy Ec#Ev for silicon. As a consequence, silicon can be used as the semiconducting material in an infrared focal plane constructed according to this invention, although conventional silicon based band-to-band transition type detectors are limited to wavelengths less than 1.1 um. For a PtSi2/p-Si system, for example, the barrier height QBP is approximately 0.25 eV, corresponding to a cutoff wavelength of XcO z um. Therefore, the focal plane of this invention can be fabricated with the well developed processing techniques available for silicon devices, yet can be designed to respond to wavelengths within the infrared portion of the spectrum.
Other types of Schottky barrier photodetectors have been demonstrated in the infrared focal plane art. A major limitation of these prior art designs, however, has been their inherently low fill factor, i.e., the percentage of light sensitive area available in the detector relative to the total area of the device which is exposed to incident radiation. With the Schottky barriers of the present invention performing both detecting and multiplexing functions, however, this limitation is eliminated. Since the light sensing
Schottky barrier contacts are the only portion of the present device which must occupy the area of the focal plane exposed to the incident light, the fill factor for a focal plane constructed according to the present invention can approach 100%.
The fill factor advantage of the present design can be further appreciated by referring to Figures 3-7, which illustrate a method of fabricating an infrared focal plane according to the present invention.
Figure 3 is a plan view illustrating a channel layer 16 of p-type silicon which has been deposited on a substrate of n-type silicon. An n+ region 46 is diffused or implanted around the periphery of the layer 16 in order to provide isolation for the device.
Next, p+ doped regions 40 and 44 are implanted in the layer 16 to provide ohmic contact areas for input and output electrodes, respectively.
Proceeding as illustrated in Figure 4, parallel insulating strips 68, 70,72, 74,76, and 78 of SlO2 are deposited on the layer 16 to establish channels 80, 82,84,86, and 88 in the channel layer. In Figure 5, metallic contact strips 90, 92, 94, 96, and 98 are deposited on the layer 16 and across the insulating strips so that a Schottky barrier detector is established under each contact strip between each two adjacent insulating strips to create a matrix of
Schottky barriers. In this manner, a two-dimensional detector/CCD array is formed on the device. An input electrode is established by applying a metallic contact 38 over the p + region 40 (shown in Figure 3).
Similarly, an output electrode is formed by a metallic contact 42 deposited over the p+ doped region 44. A row of metallic contacts 100,102,104, 106, and 108 is deposited on the layer 16 to establish a row of transfer Schottky barriers which form a CCD for transferring charge out of the channels 80-88 and into the output electrode 42. The break lines 110 and 112 are provided to indicate that an operational focal plane may include a considerably iarger array of detectors than can be effectively illustrated.
Figures 6 and 7 are cross-sectional side views, along the lines 6-6 and 7-7 of Figure 5, which further illustrate the structure of the focal plane shown in
Figures 3-5. In Figure 6, the metallic contact strips 90-98 form Schottky barriers 114, 116, 118, 120, and 122 in conjunction with the p-type channel layer 16.
This view illustrates how the n+ doped region 46 extends through the channel layer to provide isolation for the focal plane. Also shown are the metallic contact 38 on the p+ doped region 40 and the metallic contact 102 which forms a Schottky barrier 124 (part of the row of transfer Schottky barriers) with the channel layer 16.
Figure 7 is another cross-sectional side view, similar to that of Figure 6, but along the line 7-7 of
Figure 5. This view illustrates the manner in which the metallic contact strip 92 is deposited over the insulating strips 68,70,72, 74,76, and 78, forming
Schottky barriers 126, 128, 130, 132, and 116 in conjunction with the channel layer 16.
Figures 8 and 9 are cross-sectional side views analogous to Figures 6 and 7, but which illustrate the structure of an alternative embodiment of the invention which may be utilized if it is desirable to eliminate the need for depositing insulating strips on the channel layer 16. In Figure 8, it can be seen that the metallic contacts 38, 90-98, and 102 are depo- sited directly on substrate 10. The necessary channels are formed by a p-doped region 134 in the substrate, so that the need for depositing a channel layer is eliminated. Figure 9 shows the manner in which the p-doped channels 134, 136, 138, 140, and 142 are isolated by the intermediate areas of the substrate 10 for transferring charge detected by the
Schottky barrier array.
Although the embodiments which have been illustrated and described are typical of this invention modifications and other embodiments of the invention will undoubtedly be apparent to those skilled in the art. The embodiments disclosed are fabricated from silicon, for example, because it is considered a major advantage of the present invention to enable the use of silicon, and the well developed processing techniques developed for that material, in focal planes for the detection of infrared radiation which previously required more exotic materials, such as the Ill-V and Il-VI groups of compounds. The invention may also be employed to advantage, however, in devices made with these other materials. In addition, the preferred embodiments, which have been described above, are arranged in the backside illuminated configuration, although the invention may be used as well in other approaches, such as frontside illumination. Various changes, of course, may be made in the configurations, sizes, arrangements of the components of the invention without departing from the scope of the invention. Furthermore, equivalent elements may be substituted for those illustrated and described herein, parts or connections might be reversed or otherwise interchanged, and certain features of the invention might be utilized independently of the use of other features. Consequently, the exameples presented herein, which are provided to teach those skilled in the art how to construct the apparatus and perform the method of this invention, should be considered as illustrative only and not inclusive, the appended claims being more indicative of the full scope of the invention.
Claims (29)
1. Adetectorforrespondingto lightata predetermined wavelength, comprising: a semiconducting substrate of a first conductivity type; a semiconducting channel of a second conductivity type disposed on the substrate; and a plurality of metallic contacts disposed on the said channel to establish a corresponding plurality of Schottky barriers so that light at the predetermined wavelength can be absorbed in the barriers, the contacts being so positioned that charges stored in the channel can be transferred by the manipulation of voltages applied to the contacts.
2. A detector according to claim 1, wherein the plurality of metallic contacts further comprises contacts fabricated from a plurality of metals, so that different wavelengths of light can be absorbed in particular ones of the said barriers.
3. A detector according to claim 1, wherein the metallic contacts define a row of contacts on the channel, an input electrode is disposed on the substrate at a first end of the said row and an output electrode is disposed on the substrate at a second end of the said row.
4. A detector according to claim 3, wherein the input electrode and the output electrode each further comprise: a relatively heavily doped region of the second conductivity type in the channel and a metallic electrode contact disposed on the channel and communicating with the said region.
5. A detector according to claim 4, wherein there is a relatively heavily doped isolation region of the first conductivity type extending through the channel and surrounding the said electrodes and the
Schottky barriers.
6. A detector according to claim 4, wherein there is a region of the second conductivity type in the substrate, this region defining the channel.
7. A detector according to claim 4 or 6, wherein the substrate and the channel comprise silicon.
8. A detector according to claim 7, wherein the plurality of metallic contacts comprise platinum contacts.
9. A detector according to claim 8, wherein the substrate and the channel are transparent to light at the predetermined wavelength, so that light can reach the Schottky barriers by travelling through the substrate and the channel.
10. A backside illuminated detector for respond ingto light ate particularwavelength,comprising: a semiconducting substrate of a first conductivity type which is transparent to the said light; a semiconducting channel layer of a second conductivity type which is transparent to the said light and is deposited on the substrate; a row of metallic contacts deposited on the channel layer to establish a corresponding row of Schottky barriers so that light at the predetermined wavelength can be absorbed in the barriers, the contacts being so positioned that charges stored in the channel layer can be transferred by the manipulation of voltage applied to the contacts; a first relatively heavily doped region of the second conductivity type in the channel layer at a first end of the said row; an input electrode contact deposited on the first region; a second relatively heavily doped region of the second conductivity type in the channel layer at a second end of the said row; an output electrode contact deposited on the second region; and a relatively heavily doped isolation region of the first conductivity type extending through the channel layer and surrounding the electrodes and the Schottky barriers.
11. A detector focal plane for responding to light at a predetermined wavelength, comprising: a semiconducting substrate of a first conductivity type; a plurality of parallel semiconducting channels of a second conductivity type disposed on the substrate; and a plurality of parallel metallic contacts disposed across the channels to establish a matrix of Schottky barriers so that light at the predetermined wavelength can be absorbed in the barriers, the contacts being so positioned that charges stored in the channels can be transferred by the manipulation of voltages applied to the contacts.
12. A focal plane according to claim 11,wherein an input electrode is disposed on the substrate along a first end of each of the plurality of channels; a semiconducting charge transfer channel of the second conductivity type is disposed on the substrate along a second end of each of the plurality of channels; a row of metallic contacts is disposed on the charge transfer channel to establish a row of transfer Schottky barriers so that charges stored in the charge transfer channel can be transferred by the manipulation ofvoltages applied to the row of contacts; and an output electrode disposed on the substrate at an end of the charge transfer channel.
13. Afocal plane according to claim 12, wherein there are a semiconducting channel layer of the second conductivity type deposited on the substrate; and a plurality of parallel insulating strips deposited on the channel layer; the insulating strips defining therebetween in the channel layer the parallel semiconducting channels.
14. A focal plane according to claim 13, where there is a relatively heavily doped isolation region of the first conductivity type extending through the channel layer and surrounding the semiconducting channels and the Schottky barriers.
15. Afocal plane according to claim 12, where there are a plurality of parallel regions of the second conductivity type in the substrate, these regions defining the plurality of parallel semiconducting channels; and a charge transfer region of the second conductivity type in the substrate, this charge transfer region defining the charge transfer channel.
16. Afocal plane according to claim 13 or 15, wherein the input electrode and the output electrode each further comprise: a relatively heavily doped region of the second conductivity type in the channel and a metallic electrode contact disposed on the channel and communicating with this region.
17. Afocal plane according to claim 16, wherein the semiconducting substrate and the semiconducting channel comprise silicon.
18. Afocal plane according to claim 17, wherein the plurality of parallel metallic contacts comprise platinum contacts.
19. A focal plane according to claim 18, wherein the substrate and the channel are transparent to ligh at the predetermined wavelength, so that light may reach the Schottky barriers by travelling through the substrate and the channel.
20. A backside illuminated focal plane for responding to light at a predetermined wavelength, comprising: a semiconducting substrate of a first conductivity type which is transparent to the said light; a semiconducting channel layer of a second conductivity type which is transparent to the said light and is deposited on the substrate; a plurality of parallel insulating strips deposited on the channel layer to define therebetween a plurality of parallel channels in the channel layer; a plurality of parallel metallic contacts deposited across the channels to establish a matrix of Schottky barriers so that light al the predetermined wavelength can be absorbed in the barriers, the contacts being so positioned that charges stored in the channels can be transferred by the manipulation of voltages applied to the contacts: a first relatively heavily doped region of the second conductivity type in the channel layer along a first end of each of the channels; an input electrode contact deposited on the first region; a row of metallic contacts deposited on the channel layer along a second end of each of the channels to establish a row of transfer Schottky barriers so that charges stored in the channel layer can be transferred by the manipulation of voltages applied to the row of contacts; a second relatively heavily doped region of the second conductivity type in the channe layer at an end of the row of metallic contacts; and an output electrode contact deposited on the second region.
21. A method of making a detector for responding to light at a predetermined wavelength, comprise ing the steps of: providing a semiconducting substrate of a first conductivity type; depositing a semiconducting channel layer of a second conductivity type on the substrate; depositing a plurality of metallic contacts on the channel layer to establish a corresponding plurality of Schottky barriers so that light at the predetermined wavelength can be absorbed in the barriers; and so positioning the contacts that charges stored in the channel layer can be transferred by the manipulation of voltages applied to the contact.
22. A method according to claim 21, wherein the step of depositing metallic contacts further comprises the steps of: depositing a plurality of parallel insulating strips on the channel layer to define therebetween a plurality of channels in the channel layer; and depositing a plurality of parallel metallic contacts across the insulating strips to establish a matrix of Schottky barriers.
23. A method according to claim 22, further comprising the steps of: forming a first relatively heavily doped region of the second conductivity typ in the channel layer along a first end of each of the plurality of channels; depositing a metallic input electrode contact on the first region; depositing a row of metallic contacts on the channel layer along a second end of each of the plurality of channels to establish a row of transfer Schottky barriers; forming a second relatively heavily doped region of the second conductivity type in the channel layer at an end of the row of transfer Schottky barriers; and depositing a metallic output electrode contact on the second region.
24. A method of making a detector for responding to light at a predetermined wavelength, comprising the steps of: providing a semiconducting substrate of a first conductivity type; forming a region of a a second conductivity type in the substrate to define a channel; depositing a plurality of metallic contacts on the channel to establish a corresponding plurality of Schottky barriers so that light at the predetermined wavelength can be absorbed in the barriers; and so positioning the contacts that charges stored in the channel can be transferred by the manipulation of voltages applied to the contacts.
25. A method according to claim 24, wherein the steps of forming a region and depositing contacts further comprise: forming a plurality of regions of the second conductivity type in the substrate to define a plurality of channels; depositing a plurality of parallel metallic contacts across the channels to establish a matrix of Schottky barriers.
26. A method according to claim 25, further comprising the steps of: forming a first relatively heavily doped region of the second conductivity type in the substrate and into a first end of each of the plurality of channels; depositing a metallic input electrode contact on the first region; forming a charge transfer region of the second conductivity type in the substrate and into a second end of each of the plurality of channels; depositing a row of metallic contacts on the charge transfer region to establish a row of transfer Schottky barriers; forming a second relatively heavily doped region of the second conductivity type in the substrate and into an end of the charge transfer region; and depositing a metallic output electrode contact on the second region.
27. A method according to claim 21 or 24, wherein the step of depositing metallic contacts further cr-rnprises depositing a plurality of different metals to establish different Schottky barriers in which different wavelengths of light can be absorbed.
28. A method of making a detector for responding to light at a predetermined wavelength, substantially as described hereinbefore with reference to
Figures 3 to 7 or Figures 8 and 9 of the accompanying drawings.
29. A detector for responding to light at a predetermined wavelength, substantially as described hereinbefore with reference to Figure 1, or
Figures 3 to 7, or Figures 8 and 9 of the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US26415681A | 1981-05-15 | 1981-05-15 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2100511A true GB2100511A (en) | 1982-12-22 |
| GB2100511B GB2100511B (en) | 1985-02-27 |
Family
ID=23004854
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8213498A Expired GB2100511B (en) | 1981-05-15 | 1982-05-10 | Detector for responding to light at a predetermined wavelength and method of making the detector |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS57198656A (en) |
| DE (1) | DE3217895A1 (en) |
| FR (1) | FR2506077A1 (en) |
| GB (1) | GB2100511B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001052329A1 (en) * | 2000-01-14 | 2001-07-19 | Centre National De La Recherche Scientifique | Vertical metal-semiconductor microresonator photodetecting device and production method thereof |
| EP1634110A1 (en) * | 2003-05-29 | 2006-03-15 | Research Triangle Institute | Electromagnetic radiation detectors having a microelectromecanical shutter device |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5961959A (en) * | 1982-09-30 | 1984-04-09 | Mitsubishi Electric Corp | Infrared ray solid-state image pickup element |
| JPH0658952B2 (en) * | 1984-06-22 | 1994-08-03 | 三菱電機株式会社 | Solid-state image sensor |
| US4602158A (en) * | 1984-10-26 | 1986-07-22 | Itek Corporation | PbS-PbSe IR detector arrays |
| JPH0644578B2 (en) * | 1984-12-21 | 1994-06-08 | 三菱電機株式会社 | Charge transfer device |
| DE102007046501A1 (en) * | 2007-09-28 | 2009-04-09 | Siemens Ag | Image sensor for use in e.g. digital camera, has detector chip provided at side of light entrance and contacting side, where side of light enterance on lower side of wafer is different from contacting side on upper side of wafer |
| CN113161442B (en) * | 2021-04-22 | 2022-10-14 | 合肥工业大学 | Silicon schottky junction line array near infrared photoelectric detector |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3739240A (en) * | 1971-04-06 | 1973-06-12 | Bell Telephone Labor Inc | Buried channel charge coupled devices |
| US4210922A (en) * | 1975-11-28 | 1980-07-01 | U.S. Philips Corporation | Charge coupled imaging device having selective wavelength sensitivity |
| DE2740996A1 (en) * | 1977-09-12 | 1979-03-22 | Siemens Ag | Sensor cell for opto-electronic transducer - has semiconductor chip with two parallel strips, with doping opposite to that of substrate |
| DE2743245A1 (en) * | 1977-09-26 | 1979-04-05 | Siemens Ag | CHARGE-COUPLED COMPONENT |
| EP0025658A3 (en) * | 1979-09-18 | 1983-04-20 | The Secretary of State for Defence in Her Britannic Majesty's Government of the United Kingdom of Great Britain and | Improvements in or relating to charge storage and transfer devices and their fabrication |
-
1982
- 1982-05-10 GB GB8213498A patent/GB2100511B/en not_active Expired
- 1982-05-12 JP JP57080814A patent/JPS57198656A/en active Pending
- 1982-05-12 DE DE19823217895 patent/DE3217895A1/en not_active Ceased
- 1982-05-14 FR FR8208511A patent/FR2506077A1/en active Granted
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001052329A1 (en) * | 2000-01-14 | 2001-07-19 | Centre National De La Recherche Scientifique | Vertical metal-semiconductor microresonator photodetecting device and production method thereof |
| FR2803950A1 (en) * | 2000-01-14 | 2001-07-20 | Centre Nat Rech Scient | VERTICAL METAL-SEMICONDUCTOR MICRORESONATOR PHOTODETECTION DEVICE AND METHOD OF MANUFACTURING THE SAME |
| US6713832B2 (en) | 2000-01-14 | 2004-03-30 | Centre National De La Recherche Scientifique | Vertical metal-semiconductor microresonator photodetecting device and production method thereof |
| EP1634110A1 (en) * | 2003-05-29 | 2006-03-15 | Research Triangle Institute | Electromagnetic radiation detectors having a microelectromecanical shutter device |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2506077A1 (en) | 1982-11-19 |
| FR2506077B1 (en) | 1985-01-04 |
| DE3217895A1 (en) | 1982-12-02 |
| GB2100511B (en) | 1985-02-27 |
| JPS57198656A (en) | 1982-12-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19920510 |