DE2606108A1 - Burried channel charge injection device sensor - has imaging points, each with adjacent spaced overflow channel with threshold adjusting electrode inbetween - Google Patents

Abstract

The substrate of doped semiconductor material has a substrate terminal and one or several matrix-shaped separate imaging points in rows and columns. Each imaging point consists of an insulating layer capacitor(s). The capacitor electrodes are conductively connected in each imaging point row, or column. An overflow channel (9) passes each imaging point at a set distance. An electrode (90) is provided between the imaging point and the overflow channel for adjustment of variable potential thresholds. Preferably an overflow channel extends along each imaging point row and/or column at the longitudinal side. The adjusting electrode is strip-shaped and covers the entire intermediate space between the row and/or column and the overflow channel.

Description

CID or BCII) sensor arrangement

The present invention relates to a CID or BCID sensor arrangement, in the case of that on a surface of a substrate provided with a substrate connection made of doped semiconductor material one or more in matrix form in rows and columns arranged pixels separated by distances from one another are present, wherein each pixel consists of at least one insulating layer capacitor and in which the capacitor electrodes of these insulating layer capacitors in each row of pixels (column) are connected to one another in an electrically conductive manner.

Under a CIt sensor arrangement (CID stands for Charge Injection Device) one understands an arrangement of the type mentioned at the beginning, in which the in the pixels stored information charge carriers are injected into the substrate during readout.

Under a BCII) sensor arrangement (BCID stands for Buried Channel Charge Injection I) evice) is a special CII) sensor arrangement in which the in the substrate injected charge carriers doped opposite to the substrate buried channels. A CID sensor array is disclosed in publication Charge Injection Imaging "by G.J. Michon and H.K. Burke in 1973 IEEE International Solid State Circuits Conference, pp. 138 and 139 described and illustrated. To In Figure 1 of this publication, each pixel consists of the insulated capacitor (labeled Vy there) and an additional insulating layer capacitor arranged close to it (denoted there with Vx) to the one with the insulating layer capacitor through an opposite is coupled to the substrate doped region (p-region there). The capacitor electrodes the insulated film capacitors in each pixel line (column) are connected to one another in an electrically conductive manner. The capacitor electrodes of the additional Insulating capacitors in each pixel column (row) are also electrically connected to each other. While the picture is being taken, both of them Capacitor electrodes of a pixel have such voltages compared to the substrate potential created that a depletion zone arises underneath. Collect in this impoverishment zone the information charge carriers generated by the light and form on the surface of the substrate an inversion edge layer.

Reading is prepared by one of the two capacitor electrodes of an image point is brought in the direction of substrate potential - whereby the underneath stored information charge carriers via the opposite doped to the substrate Area under the other capacitor electrode and are stored there. When reading out, this other capacitor electrode is also at least at substrate potential brought, whereby the information charge carriers stored underneath it in the substrate injected. The substrate current is processed further to form the readout signal.

A BCID sensor array is in the release of your terminal Charge Injection Device "by Paul Jespers and Jean-Narie Millet in 1975 IEEE International Solid State Circuits Conference pp. 28 and 29 described and illustrated. The figure 1 on p. 29 of this publication shows a cross section through such a sensor arrangement: On a surface of an n-doped substrate provided with a substrate connection there are the insulating layer capacitors separated from each other by gaps. Each of these insulating layer capacitors represents a pixel. Below the Insulating layer capacitors run at a distance from the substrate surface buried channel in the form of a strip-shaped doped opposite to the substrate Area (referred to as Buried Collector in the publication). This buried one Channel is electrically conductive with an aluminum contact as an external connection contact tied together. The mode of operation a BCII) sensor arrangement is in essentially the following: The buried channel is opposite to that at the substrate connection applied potential biased in reverse direction. While the picture is being taken as with the CID sensor arrangement to the capacitor electrode of each pixel such a voltage applied to the substrate potential that underneath a depletion zone is produced. Holes generated by incident light collect in this depletion zone on the substrate surface under the capacitor electrode and form one again Inversion boundary layer. As with the CID sensor arrangement, the charge is this Inversion edge layer essentially proportional to the intensity of the incident Light. When reading out the information, like that of the CID sensor arrangement, the The capacitor electrode of the relevant pixel is at least at substrate potential placed, whereby the charge carriers collected in the inversion edge layer are restored injected into the substrate. However, these injected charge carriers are now picked up by the negatively biased buried canal and the one created therein Current is processed into the output signal. In Figure 5 on p. 29 of this Publication, a complete BCID sensor assembly is shown in plan view: In the substrate there are buried channels running next to one another at intervals (there Buried Collectors Stripes) present. On the surface of the substrate is a electrically insulating layer present on the transverse to the buried channels Silicon strips running next to each other at intervals (silicon gate strips) are upset. Each intersection of such a strip with a buried one Channel forms a pixel. These pixels are therefore in the form of a matrix in lines and columns arranged, the capacitor electrodes of the insulated film capacitors a pixel line (column) are connected to one another in an electrically conductive manner and whereby a buried channel runs under each pixel column (row).

A SCID sensor arrangement differs from a CID sensor arrangement essentially just by its presence at least one buried Canal.

An insulating layer capacitor is understood to mean an arrangement which is constructed so that on a surface of a substrate made of doped semiconductor material at least one electrically insulating layer is applied, on which a capacitor electrode is applied from electrically conductive material.

Of course, with sensors of the type mentioned above translucent points must be present at least in the vicinity of the image points. Appropriately, it is used, as is also the case with those in the publications specified sensor arrangements is the case for the electrically insulating layers and the capacitor electrodes are translucent material so that the pixels themselves are translucent.

As with other optoelectronic sensor arrangements also occurs Irradiate (blooming) sensor arrangements of the type mentioned at the beginning. Under Over-irradiation is understood to mean the fact that with pointwise excessively brighter Lighting so many information carriers are generated that a part of it is no longer recorded by the inversion edge layer of the image point at this point can be.

The excess information charge carriers migrate through the substrate and are recorded in pixels with a not yet saturated inversion edge layer. This leads to disruptive information corruption. Appear in the evaluated image instead of the bright point stripes and / or spots. In extreme cases, the whole can Image will be disturbed. Of the optoelectronic sensor arrangements that are after Working principle of the charge coupled device displacement device is known that the excess charge carriers are picked up and discharged by overflow channels can. In the publication "Controle of Blooming in Charge Coupled Images" by W.F. Kosonocki et al.

in RCA Revue, Vol. 35, March 1974, pp. 3 to 24 are such sensor arrangements indicated with overflow channels. According to this, such an overflow channel consists of one opposite to the sub- strat-doped strip-shaped area on the substrate surface, which is on a row of pixels at a distance therefrom is guided along (see in particular Figure 4 on p. 4, Figure 6 on p. 10 and Figure 9 on p. 12 of the mentioned publication). The space between the row of picture dots (synonymous with the transmission channel of the charge coupled device) and the overflow channel is covered there by an electrode, by means of which one fixed potential threshold between the transmission channel and the overflow channel Applying a corresponding voltage to them is adjustable. To the overflow channel itself such a voltage is applied that it is almost of the majority charge carriers is completely cleared. Under one electrode of the charge coupled device displacement device information charge carriers (minority charge carriers) can only be collected for so long until the surface potential under this electrode equals the value of the potential threshold between her and the overflow channel. Additionally generated information carriers now flow over this threshold into the overflow channel and are from there discharged.

A simple adoption of the principle described above with Overflow channels is, however, in the sensor arrangements of the type mentioned not possible because with these the information charge carriers are injected into the substrate can be read out. With the aforementioned protective devices against over-exposure, an impermissibly large part of the stored data would be read out Information charge carriers flow off into the overflow channels and the entire sensor arrangement disable.

The object of the present invention is therefore to provide a protective device to indicate against over-irradiation for sensor arrangements of the type mentioned.

The object is achieved in that an overflow channel at each pixel is passed at a distance from it and that an electrode for setting variable potential thresholds between the pixel and the overflow channel is available.

Such a sensor arrangement is preferably constructed so that along an overflow channel of each pixel line and / or column on at least one longitudinal side is led along.

In this case, the electrode is preferably made variable for setting Potential thresholds from a strip-shaped electrode covering the entire space covered between the pixel line or column and the overflow channel. Appropriate it is when the overflow channel at the same time the overflow channel for one to its other Forms line or column of image points guided along the long side. In this context To save space, it is advantageous if it is used as an electrode for setting variable potential thresholds a single electrode strip is used, the the entire space between the two pixel rows or columns completely covered.

Furthermore, for reasons of space saving, it is generally advantageous if an overflow channel only in every second pixel row harvester column space is present and if in every other pixel row or column space a blocking device is present, the flow of information carriers prevented across this pixel line or column space. Preferably This blocking device consists of a substrate that is identical to the substrate, but is also highly doped strip-shaped area that runs parallel to the rows or columns of pixels.

Preferably each overflow channel is as opposed to the substrate doped strip-shaped area formed on the substrate surface.

A CID or BCID sensor arrangement noted above becomes so operated that the sensor arrangement itself and the overflow channel in known per se Operated manner that during image acquisition to each of the electrodes Setting variable Potential thresholds such a voltage applied is that, in a manner known per se, an overflow potential threshold is generated below it and that during the period of reading out a pixel line (column) such a voltage to the associated electrode (s) for setting variable Potential thresholds is applied that underneath an accumulation layer between the pixels and the adjacent overflow channel or channels is generated.

The specified CID or BCID sensor arrangements have protection against over-exposure and still know without significant loss of information can be read out. The protective device itself is just as simple as the protective devices already known from other sensor arrangements and required therefore no additional process steps compared to these in their production. Another advantage is that the resolution of the CID or BCID sensor arrangements is only insignificantly reduced compared to those without protection against over-irradiation. The mode of operation is extremely simple and only requires insignificant additional ones Circuit effort.

The invention is illustrated by means of two exemplary embodiments in the figures explained in more detail.

FIG. 1 shows a top view of a section from a CID sensor arrangement with overflow channels.

Figure 2 shows a cross section through the embodiment according to Figure 1 along the section line I - I.

FIG. 3 shows a top view of a detail from a BCID sensor arrangement with overflow channels.

Figure 4 shows a cross section through the embodiment according to Figure 3 along the section line III - III.

In the figure 1 is a top view of a detail from a CID sensor arrangement shown with overflow channels. On a surface of a substrate 1 made of doped Semiconductor material, for example p-detected silicon, is meaningfully translucent electrically insulating layer 2, for example silicon dioxide, upset. This electrically insulating layer carries electrodes 11 to 16 at intervals, for example made of aluminum, which are arranged in a matrix in rows and columns. In each case electrodes a row (column) are each through a row line (column line) 3, 4, for example made of aluminum, electrically connected to each other. Each of the electrodes 11 through 16, the capacitor electrode forms one of the insulating film capacitors. Along of each column (row) is on one long side close to the electrodes an electrically conductive electrode strip 5, 6, for example made of polysilicon, as Column line (row line) led along. In each case the area of one of these The strip next to one of the electrodes located close to it forms the capacitor electrode one of the additional insulating film capacitors.

These areas are shown with a dashed frame in FIG and provided with the reference numerals 21 to 26. Each of the electrode pairs 11 and 21, 12 and 22 to 16 and 26 form a pixel of the sensor arrangement. The row lines are passed over the column lines and from these through a not shown here electrically insulating layer separated. The coupling of the two insulating layer capacitors of a pixel can as in the aforementioned publication by Michon and Burke be carried out by a region doped opposite to the substrate. In this area but can be dispensed with if the space between the two capacitor electrodes is removed makes it sufficiently narrow (i.e. so narrow that the electrical fringing fields of the electrodes reach over this gap when operating the sensor) or even themselves can overlap. Along one long side of each pixel column (row) is an overflow channel 8, 9, 10 led along at a distance from the image points. In FIG. 1, this is the longitudinal side opposite the column line.

Each overflow channel consists of one opposite to the substrate doped strip-shaped area with a connection contact, not shown here is electrically connected. The distance d between a pixel column (-row) and the overflow channel is of a strip-shaped electrode 80, 90, 100 for setting variable potential thresholds, for example made of polysilicon, covered.

Of course, this electrode must be from the substrate and thus the Be isolated overflow channel and the capacitor electrodes.

In FIG. 2, there is now a cross section through that shown in FIG Exemplary embodiment shown along the section line I-1. Using this figure a manufacturing process is also explained as an example. The substrate 1 consists of p-doped silicon with a doping of about 1015 com'3. In a The overflow channels 8, 9, 10 become the surface of this substrate by means of diffusion or ion implantation. Phosphorus is preferably used as the dopant used. The doping is chosen to be about 1018 to 102 ° cm 3. Then will a silicon dioxide layer 2 with a layer thickness on the surface by oxidation of about 0.12 # µm. The surface of this layer is covered with a polysilicon layer of about 0.6 / µm, which is then covered by diffusion or ion implantation is endowed. Phosphorus is preferably used as the dopant. The doping is chosen approximately 1018 to 1020cm # 3. The polysilicon layer is now down to the Electrode strips 5, 6, 7 and 80, 90, 100 are etched away using an etching mask.

The resulting surface is oxidized again, so that the Cover polysilicon regions with an oxide layer 20 with a thickness of 0.12 μm. It will now at suitable places (e.g. on the periphery of the entire arrangement) contact holes for contacting the overflow channels and the polysilicon areas and then opened the electrodes 11 to 16 and the row lines connecting them by means of metal vapor deposition (Gap lines) 3, 4 and the contacts made. For example, it can be used for steaming Aluminum can be used. Photolaek is preferably used as a pedal mask.

FIG. 3 shows a top view of a detail from a BCID sensor arrangement. On a substrate 101 made of doped semiconductor material, for example p-doped Silicon, is also a translucent, electrically insulating layer 102, for example silicon dioxide applied. This electrically insulating layer carries electrode strips 31 to 36 from electrically running next to one another at intervals conductive material, for example made of doped polysilicon. Across these electrode strips run at intervals next to one another opposite to the substrate doped buried Channels 41 to 43. A pixel of the sensor arrangement is in each case through a crossover area of an electrode strip with an underlying buried channel. These crossover areas are provided with the reference numerals 311 to 363. To here the specified sensor arrangement completely agrees with the one mentioned in the above Publication by Paul Jespers and Jean-Marie Millet, p. 29, Figure 5, agree. In every second of the electrode strip gaps 51 to 55, which the pixel rows (columns) gaps correspond, there is an overflow channel each. These overflow channels are with the Reference numerals 61 to 63 are provided. Each of these overflow channels consists of one opposite to the substrate doped strip-shaped area on the substrate surface. Each of these overflow channels is also designed so that its lateral spacing to the electrode strips to the left and right of it and thus the pixels is available. Over each of the spaces 51, 53 and 55 is an electrode 71, 72 and 73 for setting variable potential thresholds arranged in such a way that each of the distances between the electrode strip area and thus the pixel area and Overflow channel is covered. Of course, this electrode must also be dated here Substrate and thus the overflow channel and the electrode strip and thus the capacitor electrodes the picture pods must be electrically isolated. The overflow channels are again with a To connect connection contact electrically conductive.

In the figure 4 is a cross section through the Ausführungsbei game shown according to Figure 3 along the section line III - III. Using this figure a manufacturing process is also explained at the same time. The substrate 1 is manufactured so that a surface of a p-doped silicon substrate with a Doping of about 5 x 1014 cm 3 in the areas of the buried channels is, with a doping of 1018 to 102 ° cm 3 is used. Preferably will phosphorus is used as a dopant. On this surface is a p-doped epitaxial silicon layer also produced with a doping of about 5 x 10 cm. The surface of this layer is in the areas of the electrode strip gaps, under which there are no overflow channels, highly p-doped, with one doping for example 1018 to 1020cm # 3 is used. These highly endowed areas represent so-called "channel stop diffusions" and serve for isolation and renn.ung the pixels lying to the left and right of these spaces. In 4 are these channel stop diffusions with the reference numerals 82 and 84 Mistake. A silicon dioxide layer is placed on the surface of the epitaxial silicon layer produced by a layer thickness of about 0.12 # µm as an electrically insulating layer 102. This layer is covered with a polysilicon layer with a layer thickness of approximately 0.6 / µm covered. By etching away this layer in the right places, it becomes the electrode strips 31 to 36 generated. Only the electrode strips are shown in FIG 32 to 35 shown in full or in part in cross section. The electrically insulating Layer is now in the places under which the buried channels are, etched away. The polysilicon strips are made conductive by diffusion and the buried channels self-generated. As a dopant is preferred Phosphorus used and the doping made about 1018 to 102 ° cm 3. The whole Surface is by oxidation with a second silicon dioxide layer 103 of a layer thickness of about 0.3 / µm. After opening contact holes for necessary contacts, the electrodes are used to set variable potential values by means of metal vapor deposition, for example by vapor deposition with aluminum. Only the electrode 72 is shown in FIG.

It should be expressly pointed out at this point that the in The sensor arrangements shown in the figures represent exemplary embodiments. It a number of variants are possible in the structure. For the CID sensor arrangement, see Figure i it is possible, for example, the overflow channel 8 as a common overflow channel to be used for both rows (columns) of pixels. It is then the row line 4 and swap the electrode for setting variable potential thresholds.

With this arrangement, a slightly higher resolution can be achieved. In another variant, the overflow channels and the electrodes run for adjustment variable potential thresholds parallel to the column lines. In this case it is it because of the inevitable crossings of the row lines with the electrodes useful for setting variable potential thresholds, the latter made of polysilicon and making the electrodes 11 to 36 from aluminum, the aluminum electrodes overlap the polysilicon strip. Designs with overflow channels are also conceivable parallel to the row lines and parallel to the column lines. Such Arrangement would have advantages in terms of information loss, but it is very difficult to manufacture and requires great effort. Otherwise are Channel stop diffusions are generally superfluous with the CID sensor arrangements.

Such channel stop diffusions could essentially only be used for the Case be required that an arrangement is chosen in which, for example, the Electrodes 11 and 12 are immediately adjacent. Such arrangements are however usually avoided.

In the case of the BCID sensor arrangement shown in FIG. 3, there are also a number of variants are possible. Thus, in every pixel rows (columns) -gap an overflow channel and electrodes for setting variable potential thresholds are arranged will. However, this variant requires considerably more space than the one in Figure 3 and Figure 4 illustrated embodiment. On the channel stop diffusions in the embodiment of Figure 4 can be omitted if the distance between the electrodes in question is chosen to be sufficiently large. Such a variant wtfrde, however, also require considerably more space.

As already mentioned, the overflow channels must have a connection contact be electrically connected. Each individual overflow channel has its own connection contact assigning is inexpedient, it is advantageous to all overflow channels to a single one Connect terminal contact. In Figure 3, this is done in such a way that the overflow channels at one edge of the sensor matrix into one that runs along there, opposite strip-shaped region 8 doped to the substrate and having a connection contact, merge. In this way, only a single contact hole becomes the periphery of the Sensor matrix required. This solution is for all sensor arrangements, including for CID sensor arrangements, suitable.

In general, the overflow channel can be in the form of a strip instead of a doped region by an electrode connected to a suitable voltage an electrically insulating layer can be realized. Such a variant requires but generally a high manufacturing cost.

The CID and SCID sensor assemblies with overflow channels are shown in operated in a manner known per se (see the corresponding publications cited). During the image acquisition (with the CID sensor arrangement also during the phase in which is preparing the readout) are variable to the electrodes for setting Potential thresholds voltages applied, the appropriate potential threshold values tg between the pixels and generate the overflow channels. At a voltage is continuously applied to each overflow channel, which is drawn from the majority charge carriers almost or completely clears it up. Under the corresponding capacitor electrodes of the pixels can only accommodate so many information charge carriers generated by light and stored and stored until the surface potential in the pixels reaches the threshold value s. Additionally generated charge carriers flow over the Threshold away into the overflow channel. In the exemplary embodiments specified in the figures are a voltage of, for example, 10 volts compared to the substrate potential for the Capacitor electrodes and a voltage of +2 volts compared to the substrate potential suitable for the electrodes for setting variable potential thresholds. When reading out one or more image points becomes the capacitor electrode in question in a manner known per se brought at least to substrate potential, whereby the information charge -, carrier stored underneath inäicated in the substrate. At the same time, at least the relevant Electrodes immediately adjacent to pixels for setting variable potential thresholds such a voltage is applied that in the spaces between the pixels and a shielding accumulation layer is created in the overflow channel, which prevents that the information charge carriers injected into the substrate enter the overflow channel can get. In the exemplary embodiments given in the figures, this is the case a voltage of about -2 volts relative to the substrate potential is suitable. The in The embodiment shown in FIG. 5 and FIG. 4 is the potential double wave, respectively set together for two pixel rows (columns).

While reading out the one pixel line (column) in the other only so much charge is generated that the potential wells underneath it do not run over. In a variant, each pixel line (column) has its own electrode assigned to setting variable potential thresholds, this problem occurs not on. However, this solution requires a considerably larger amount of space.

10 claims 4 figures L e r s e i t e

Claims (10)

ratentbedarfc he SJCID or BCII? -Sensor arrangement, in which on a Surface of a substrate made of doped semiconductor material and provided with a substrate connection one or more arranged in a matrix in rows and columns by spacing separate pixels are present, each pixel from at least an Isolierschiohtkondensator and in which the capacitor electrodes this Isoliersohicbtkondensatoren electrically conductive in each pixel row (column) are connected to each other, thereby g e k e n n -z e i c h n e t that at each Pixel an overflow channel (8,9,10,61, 62,63) passed at a distance therefrom is, and that an electrode (80,90,100,71,72,73) for setting variable potential thresholds exists between the pixel and the overflow channel. 2. CID or BCID sensor arrangement according to claim 1, characterized g e k e n n z e i n e t that line and / or pixel column along each pixel an overflow channel is guided along at least one longitudinal side. 3. CID oder.-BCID sensor arrangement according to claim 2, characterized g e k It is noted that the electrode is used to set variable potential thresholds consists of a strip-shaped electrode covering the entire space between the pixel line and / or pixel column and the overflow channel. 4. CID or BCID sensor arrangement according to claim 2 or 3, characterized it is noted that the overflow channel is also the overflow channel for a pixel line and / or pixel column guided along the other side forms. 5. CID or BCID sensor arrangement according to claim 4, characterized g e -k E n n e i c h n e t that as an electrode for setting variable potential thresholds a single electrode strip (71, 72, 73) is used which covers the entire gap between completely covered the two lines of pixels or columns of pixels. 6. CID or BCID sensor arrangement according to claim 4 or 5, characterized in that g E k e n n n e i c b n e t that only in every other pixel row or column space there is an overflow channel. 7. BCID sensor arrangement according to claim 6, characterized in that g e k e n n -z e i c h n e t that in every other pixel row or column space a Locking device is present, which has a plus of information carriers prevents these pixel lines (columns) -gap away. 8. SCID sensor arrangement according to claim 7, characterized in that g e k e n t -z e i c h n e t that this locking device is made of a material similar to the substrate, but more highly doped strip-shaped area that is parallel to the rows of pixels or columns runs. 9.CID or BCII) sensor arrangement according to one of claims 1 to 8, in that each overflow channel is viewed as opposite strip-shaped region doped to the substrate is formed on the substrate surface is. 10. Procedures for operating a CID or BCID sensor arrangement according to one of claims 1 to 8, characterized in that the sensor arrangement itself and the overflow channel are operated in a manner known per se that during the image recording at each of the electrodes for setting variable potential thresholds such a voltage is applied that a t} occupational potential threshold is known per se is generated below and that during the period of reading out a line of pixels (column) such a voltage to the associated electrode (s) for setting variable potential thresholds is applied that underneath an accumulation layer generated between the pixels and the adjacent overflow channel or channels will.