JP2885563B2 - Photodetector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photodetector, and more particularly to a photodetector having a test element group (hereinafter, referred to as TEG).

[0002]

2. Description of the Related Art FIG. 9 is a perspective view showing a conventional infrared imaging apparatus, and FIG. 10 is a schematic view showing a configuration of the infrared imaging apparatus shown in FIG. In these figures, 1 is a two-dimensional photodiode array composed of, for example, 128 × 128 pixels, and 2 is a silicon CC for reading signals.
D and 3 are indium bumps, 4 is an infrared ray, 5 is an output circuit, and 6 and 7 are a vertical CCD and a horizontal CCD constituting the silicon CCD 2.

Here, the two-dimensional photodiode array 1
The silicon CCD 2 is electrically connected to the silicon CCD 2 by an indium bump 3. The infrared rays 4 detected by the two-dimensional photodiode array 1 are stored in the silicon CCD 2 for a certain period of time, converted into a time-series signal, and output to an output circuit. 5 is output. The two-dimensional photodiode array 1 has Cd _0.2 Hg _0.8 T
e, whereby infrared imaging in the 10 μm band can be performed.

FIG. 7 is a plan view showing the structure of the two-dimensional photodiode array 1 using Cd _0.2 Hg _0.8 Te, and FIG. 8 is a sectional view taken along line AA ′ of FIG.

In these figures, 8 is Cd _0.2 Hg
_A semiconductor layer made of _0.8 Te, 9 a substrate made of CdTe, 10 a pn junction, 11 a light receiving region, 12 a TEG,
13 is an n-electrode pad, 14 is a p-electrode pad, 15 is TE
G12 is an n-electrode pad, 16 is a p-electrode pad of TEG12, 17 is an insulating film, and 18 is a p-side electrode metal. Here, for simplicity, the number of pixels of the light receiving area 11 is set to 3 × 3 pixels, but usually, the number of pixels of 128 × 128 pixels is often used. The TEG 12 monitors the characteristics of the pn junction 10 formed on the two-dimensional photodiode array 1 and includes a pn junction 10 ′ formed in the same step as the step of forming the pn junction 10. N
By setting the needle of the probe card on the electrode pad 15 and the p-electrode pad 16 of the TEG and measuring the IV characteristics of the TEG, the characteristics of the pn junction 10 of the light-receiving region 11 can be known in a pseudo manner. Has become.

[0006] Then, the 2 provided with such TEG12
In the two-dimensional photodiode array 1, the elements are evaluated and selected by evaluating the IV characteristics of the TEG 12 after the wafer process is completed, so that the non-defective two-dimensional photodiode array has n-electrode pads 13 and p-electrode pads 14 on it. The indium bump 3 is formed, and the silicon CCD is flip-chip bonded to obtain the infrared imaging device shown in FIG.

[0007]

As described above, in a photodiode array constituting a conventional infrared imaging element, a pn junction formed in the same step as the step of forming a pn junction in the light receiving area is provided near the light receiving area. A TEG having a junction is provided, and the IV characteristic of the TEG is measured after completion of the wafer process to monitor the characteristics of the pn junction 10 in the light receiving region. However, from the IV characteristics of the TEG, only information on whether or not a pn junction is formed in the light receiving region can be obtained. For example, the ion implantation region forming the pn junction 10 of the light receiving region can be obtained. Was diffused into the substrate too much and the adjacent pn junctions 10 were short-circuited, such a state could not be determined from the IV characteristics of the TEG, and the TEG was selected as a non-defective product. Despite being an infrared imaging device produced using a photodiode array,
There is a problem that an image is blurred or a defective device that does not form an image is included in the image.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a photodetector having a TEG capable of determining a diffusion state of a pn junction in a light receiving region. .

[0009]

According to the present invention, there is provided a photodetecting element comprising a metal electrode surrounding a pn junction forming region at a different distance from each of a plurality of pn junction forming regions constituting each element of the TEG. Is formed.

Further, the light detecting element according to the present invention has a T
Each of a plurality of pn junctions constituting each element of the EG is
It is formed at a position different from each other by a distance different from the position where the pn junction is formed at the edge of the light receiving region. Further, in the photodetector according to the present invention, two opposing pn junctions are formed on one test element constituting the TEG, and the distance between the two pn junction formation regions is changed for each test element. It was done.

[0011]

In the present invention, a metal electrode surrounding the pn junction forming region constituting each element of the TEG is provided, and each electrode is formed at a different distance from the position where the pn junction is formed. If the junction formation region is too wide, short-circuiting is sequentially performed from the metal electrodes that are closer to the position where the pn junction is formed, making it impossible to obtain a normal IV characteristic.
It is useful to know the diffusion state of n-bonds.

Further, in the present invention, since each of the plurality of pn junctions constituting each element of the TEG is formed at a different distance from the pn junction at the edge of the light receiving region, the formation region of the pn junction is small. If it spreads too much, the TE at a position close to the pn junction at the edge of the light receiving area portion
Short-circuiting in order from the pn junction constituting the element of G makes it impossible to obtain a normal IV characteristic.
It is possible to know the diffusion state of the pn junction in the substrate.

Further, in the present invention, since two opposing pn junctions having different distances between respective forming positions are formed for each element constituting the TEG, the formation of the pn junction is prevented. If the region is excessively widened, short-circuit current can be obtained in order from the element in which the two pn junction formation positions are close to each other. From this result, the diffusion state of the pn junction in the substrate can be known. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing the structure of a photodiode array according to the present invention, and FIG. 2 is a sectional view taken along line BB 'in FIG. In these figures, the same reference numerals as those in FIGS. 7 and 8 indicate the same or corresponding parts, and reference numerals 15a, 15b,
Reference numeral 15c denotes an n-electrode pad, and 20 denotes a metal electrode pattern. The metal electrode pattern 20 is provided on the upper surface of the semiconductor layer 8, and forms the pn junction 10 'so as to surround the ion implantation region of the pn junction 10' below the n electrode pads 15a, 15b, 15c. An opening 20a having the same diameter as the opening of the mask pattern at the time, an opening 20b having a diameter slightly larger than the opening 20a, and an opening 20c having a diameter several times the diameter of the opening of the mask pattern at the time of forming the pn junction 10 '. Each is formed.

Then, as in the conventional case, n
When a probe card needle is set between any one of the electrode pads 15a, 15b, and 15c and the p electrode pad 16, and the IV characteristics are measured for the n electrode pads 15a, 15b, and 15c, respectively, pn The degree of diffusion of the ion-implanted region forming the junction 10 can be known. That is, if the respective IV characteristics obtained for the respective n-electrode pads 15a, 15b, 15c are all normal, the formation state of the pn junction 10 in the light receiving region 11 is good, and the ion implantation region It can be determined that there is no unnecessary enlargement. For example, the IV characteristics corresponding to the n-electrode pad 15a and the n-electrode pad 15b become linear, and the IV characteristics corresponding to the n-electrode pad 15c.
If the characteristics are normal, the ion-implanted region of the pn junction 10 ′ under the n-electrode pad 15 a and the n-electrode pad 15 b has expanded to such an extent as to short-circuit with the metal electrode pattern 20,
From this, it can be seen that the ion-implanted region forming the pn junction 10 of the light-receiving region 11 has expanded to about the same as the diameter of the opening 20b.

In the photodiode array according to the present embodiment, n constituting the TEG 12 is formed on the upper surface of the semiconductor layer 8.
With respect to the periphery of the pn junction 10 ′ corresponding to the electrode pads 15 a, 15 b, 15 c, the openings 20 a, 20 a, 20 d, 20 d, which are equal to or larger than the opening diameter of the mask when forming the pn junctions 10, 10 ′ are different from each other. Since the metal pattern 20 having 20b and 20c is formed, the n-electrode pad 15
By measuring the IV characteristics corresponding to each of a, 15b, and 15c, it is possible to know the degree of diffusion of the ion-implanted region forming the pn junction 10 '.
It is possible to determine whether the pn junction 10 in the light receiving region 11 is short-circuited by comparing the relationship between the formation position of the pn junction 10 'in the light receiving region at the time of forming the junction and the opening diameter of the ion implantation mask. .

FIG. 3 is a sectional plan view showing the structure of a photodiode array according to a second embodiment of the present invention.
FIG. 4 is a sectional view taken along line CC ′ of FIG. 3. And
In this photodiode array, the n-electrode pad 15
pn junction 1 where a, 15b and 15c are respectively connected
0's are formed at positions different from the p-electrode pad 16 by different distances.

In the photodiode array of the present embodiment, n constituting the TEG 12 is formed on the upper surface of the semiconductor layer 8.
Since the pn junctions 10 'corresponding to the electrode pads 15a, 15b, 15c are formed at positions different from each other by a distance from the p electrode pad 16, the degree of diffusion of the ion implantation region constituting the pn junction 10' is increased. At the same time, a pn junction 10 'under the n-electrode pad 15b, a pn junction 10' under the n-electrode pad 15b, and a pn junction 10 'under the n-electrode pad 15c are formed in order from the p-electrode pad 16 near the p-electrode pad 16. In order to short-circuit with p electrode pad 16, I corresponding to each of n electrode pads 15a, 15b, 15c
By measuring the -V characteristic, it is possible to know the degree of diffusion of the ion implantation region forming the pn junction 10 ′, and to determine the degree of diffusion of the pn junction 10 in the light receiving region when forming the pn junction and the ion implantation mask. Of the pn junction 1 in the light receiving region 11 by comparing the
It can be determined whether 0 is short-circuited.

FIG. 5 is a plan view showing the structure of a photodiode array according to a third embodiment of the present invention.
FIG. 6 is a sectional view taken along line DD ′ in FIG. 5. And
In this photodiode array, the elements forming the TEG 12 are a pn junction 10 'under the n-electrode pad 15a, a pn junction 10' under the n-electrode pad 15d, and the n-electrode pad 15
b, the pn junction 10 'under the n-electrode pad 15e, the pn junction 10' under the n-electrode pad 15c, and n
It has two opposing pn junctions like a pn junction 10 ′ below the electrode pad 15 f, and the distance between these two pn junctions differs between elements.

In the photodiode array of the present embodiment, each element constituting the TEG 12, ie, the elements corresponding to the n-electrode pad 15a and the n-electrode pad 15d, n
Elements corresponding to the electrode pad 15b and the n-electrode pad 15e, and elements corresponding to the n-electrode pad 15c and the n-electrode pad 15f have two pn junctions 10 'opposed to each other, and each of these elements has two pn junctions. Since the distance between the formation positions of the pn junctions 10 ′ is different, if the degree of diffusion of the ion implantation region constituting the pn junction 10 ′ is increased, the two pn junctions 1
Since the short-circuit current is obtained in order from the element including the n-electrode pad 15c and the n-electrode pad 15f in which the distance between the formation positions of 0 'is small, it is necessary to know the degree of diffusion of the ion-implanted region forming the pn junction 10'. By comparing this with the relationship between the formation position of the pn junction 10 in the light receiving region when the pn junction is formed and the opening diameter of the ion implantation mask, it is determined whether the pn junction 10 in the light receiving region 11 is short-circuited. Can be determined.

In each of the above embodiments, the TEG element corresponding to each row of the pixels (pn junction) constituting the light receiving region of the photodiode array is changed to a predetermined configuration, which corresponds to each column. The same effect as in the above embodiment can be obtained for the TEG element corresponding to both the row and the column, or for the TEG element corresponding to both the row and the column.

In each of the above embodiments, the light receiving area is 3
Although a photodiode array of × 3 pixels (pn junction) is used, even if the number of pixels (pn junction) constituting the light receiving region is larger, a TEG similar to that of the above-described embodiment is formed corresponding to each pixel (pn junction). Needless to say, it can be formed.

[0023]

As described above, according to the present invention, the TE
For each of the plurality of pn junction forming regions constituting each element of G, the metal electrodes surrounding the pn junction forming regions are formed at different distances from each other. Therefore, if the pn junction forming region is too wide, It is impossible to obtain a normal IV characteristic by short-circuiting in order from a metal electrode that is closer to the position where the pn junction is formed.
The diffusion state of the pn bond in the light receiving area can be known. For example, the short-circuit state of the pn bond in the light receiving area of the light detecting element used for assembling the infrared device can be known. It can be used as a final product and has the effect of improving productivity. Further, since the diffusion state of the pn coupling in the light receiving region can be known, there is an effect that the obtained light detecting elements can be classified according to the performance according to the diffusion state of the pn coupling.

Further, according to the present invention, each of the plurality of pn junctions constituting each element of the TEG is formed at a position different from the formation position of the pn junction at the edge constituting the light receiving region. Therefore, if the formation region of the pn junction is too wide, the pn junction of the TEG element located closer to the pn junction at the edge of the light receiving region is short-circuited in order to obtain a normal IV characteristic. Can no longer do
From this result, it is possible to know the diffusion state of the pn bond in the light-receiving region, to use only a good-quality photodetector as a final product as described above, and to improve the productivity of the device using the photodetector, Further, there is an effect that the obtained light detecting elements can be classified by performance according to the diffusion state of the pn coupling.

Further, according to the present invention, the photodetector according to the present invention forms two pn junctions facing each other on one test element constituting the TEG, and a distance between the two pn junction formation regions. Since the interval is changed for each test element, if the formation region of the pn junction is too wide, short-circuit current can be obtained in order from the element in which the formation position between the two pn junctions is close to each other. It is possible to know the diffusion state of the pn-coupling in the substrate, to improve the productivity of the device using the light-sensing element, and to classify the obtained light-sensing element by performance according to the diffusion state of the pn-coupling. effective.

[Brief description of the drawings]

FIG. 1 is a plan view showing the structure of a photodiode array according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line BB 'of FIG.

FIG. 3 is a plan view showing a structure of a photodiode array according to another embodiment of the present invention.

FIG. 4 is a sectional view taken along line CC ′ of FIG. 3;

FIG. 5 is a plan view showing the structure of a photodiode array according to another embodiment of the present invention.

FIG. 6 is a sectional view taken along line DD ′ of FIG. 5;

FIG. 7 is a plan view showing the structure of a conventional photodiode array.

FIG. 8 is a sectional view taken along the line AA ′ in FIG. 7;

FIG. 9 is a perspective view showing a conventional infrared imaging device.

FIG. 10 is a schematic diagram showing the structure of the infrared imaging device of FIG. 9;

[Explanation of symbols]

1 photodiode array 2 silicon CCD 3 indium bumps 4 Infrared 5 output circuit 6 vertical CCD 7 horizontal CCD 8 Cd _0.2 Hg _0.8 semiconductor layer 9 substrate 10 pn junction consisting of CdTe 11 light receiving area 12 TEG 13 consisting of Te n electrode pad 14 p Electrode pads 15, 15a, 15b, 15c, 15d, 15e, 15
f n electrode pad 16 p electrode pad 17 insulating film 18 p-side electrode 19 TEG 20 metal electrode pattern 20a, 20b, 20c opening

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-314974 (JP, A) JP-A-1-314975 (JP, A) JP-A-1-291441 (JP, A) JP-A-62-162 179737 (JP, A) JP-A-54-18693 (JP, A) JP-A-55-95336 (JP, A) JP-A-50-1640 (JP, A) JP-A-61-64138 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/66 H01L 27/148 H01L 31/10

Claims (3)

(57) [Claims] 1. A pn forming a light receiving region on a semiconductor substrate
A photodetector having a junction and a pn junction formed in the same step as the pn junction, and a test element group for monitoring characteristics of the pn junction in the light receiving region; A photodetector, wherein metal electrodes are formed at different distances from each other so as to surround the respective pn junction forming regions. 2. A pn which forms a light receiving region on a semiconductor substrate
A photodetector having a junction and a pn junction formed in the same step as the pn junction, and a test element group for monitoring characteristics of the pn junction in the light receiving region; A photodetector, wherein each of the constituent pn junctions is formed at a different distance from a position where the pn junction is formed at an edge of the light receiving region. 3. A pn forming a light receiving area on a semiconductor substrate.
A photodetector element having a junction and a pn junction formed in the same step as the pn junction, and a test element group for monitoring characteristics of the pn junction in the light receiving region; A light detecting element having two pn junctions facing each other, and a distance between formation positions of the two pn junctions is different for each element.