JPH012375A - infrared detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an infrared detection device having a structure in which an infrared detection section and a detection signal processing section are stacked on a semiconductor substrate. The present invention relates to an infrared detection device suitable for detecting infrared rays.

[Prior Art] It gCd Te (mercury cadmium tellurium compound) is attracting attention as a semiconductor material for a highly sensitive photodetector for long wavelength infrared rays including the 8 to 14 μm band.

In particular, in order to realize a solid-state imaging device using such llgcdTe, it is important that the detection element or light receiving element and the electrical signal processing circuit are both formed on the same substrate. Also, if you do this, Si (silicon)
As is clear from the example of the imaging device using the , it is advantageous for increasing the number of pixels.

[Problems to be Solved by the Invention] However, although IIgCdTe described above is capable of photoelectric conversion in a long wavelength band, it has a small band gap, making it difficult to form signal processing circuit elements for signal transfer and the like. Therefore, it is not easy to realize a monolithic imaging device using HgCdTe.

Therefore, the Si substrate on which the elements constituting the signal processing circuit are formed, and the If
A widely used method is to electrically connect the two with a g Cd Te substrate by crimping them with In (indium) dots for coupling.

However, in this method, the bonding process is difficult and the bonding portion requires a considerable area.

If the area of this bonding portion is made small, poor bonding is likely to occur and reliability problems will occur, which is disadvantageous for realizing an imaging device with high pixel density.

On the other hand, if the device is an integrated device such as an 11gcdTe single crystal layer on which an infrared light receiving element is formed on a Si substrate on which a signal processing circuit element is formed, the above bonding process is not necessary.
Further, electrical connections can be easily and finely made using ordinary integrated circuit process technology, which is advantageous for increasing the number of pixels.

However, St and HgCdTe have significantly different lattice constants. For this reason, it has been impossible to grow a high-quality HgCdTe single crystal capable of forming a highly sensitive light-receiving element on a Si substrate, and it has been difficult to realize an integrated device.

This invention was made in view of the problems of the prior art, and is based on the J11 technology, which allows the formation of sufficiently high-quality infrared detection elements on a Si substrate on which signal processing circuit elements are formed.
The object of the present invention is to provide a laminated infrared detection device that allows crystal layers to grow well.

[Means for Solving the Problems] The present invention provides a buffer layer on a Si semiconductor substrate having a signal processing circuit element, and an lIg on which an infrared detection element is formed.
It is characterized in that a single crystal layer of either cdTc or 11gZnTe (mercury zinc telluride) is formed on the buffer layer.

[Function] According to the present invention, a buffer layer is provided on an element-forming Si substrate on which a signal processing circuit element is formed, and then an infrared detecting element is formed thereon.)IgcdTc or ItgZ
Either n Te can be grown as a single crystal layer, resulting in a highly sensitive pseudo-monolitic infrared detection device.

The buffer layer is made of a Si substrate (lattice constant: 5.43) and HgCdTe (lattice constant: approximately 5.47) or IgZnTe (lattice constant: 6) used for long wavelength infrared detection.
43 people) have a disparity in lattice constant, and if things continue as they are, Hg (
:dTe is a layer that exhibits a buffering effect that alleviates the difficulty in single crystal growth of HgZnTe, which is caused by the difference in lattice constant between the two.

In the present invention, the buffer layer preferably has a two-layer structure consisting of (1) a mixed crystal layer of CaF2 and BaF2 and (2) a CdZnTe (cadmium zinc telluride) single crystal layer thereon in order from the substrate side. The lattice constant of CaF2 in the mixed crystal layer is 5.46, which is close to that of the Si substrate, and that of BaF2 is 6.20, which is close to that of IgcdTe or HgZnTe. Therefore, it is preferable that the mixed crystal layer has CaF2 on the side in contact with the Si substrate, BaF2 on the opposite side, and a composition ratio that changes continuously from CaF2 to BaF in the middle (referred to as grading). As the composition ratio changes continuously, the lattice constant also changes from 5.46 (CaF2) to 6.20 (B
Good crystal growth is achieved that continuously changes to aF, ). Crystal growth is performed, for example, by a method called molecular beam epitaxy.

In addition, in some cases, Si substrate/Ca'F2 layer/BaF
The buffer layer may be composed of a two-layer film.

However, if a slight difference in lattice constant can be tolerated, a mixed crystal layer with a uniform composition without grading may be used. In this case, it is appropriate to use an equimolar composition ratio that provides an intermediate lattice constant between CaF2 and BaF2.

The CdZnTe layer cannot be used only as a mixed crystal layer.
It is provided because there is a slight difference in lattice constant from CdTe or lIgZnTe. The CdZnTe layer is CdTe
(lattice constant: 6.48) and ZnTe (lattice constant: 6
．． 10), and has a lattice constant between that of a CaF2/BaF2 mixed crystal layer and HgCdTe or llgZnTe, for example, a uniform layer having a composition ratio of 6.31 to 6.32. do. Otherwise, for the CdZnTe layer as well, the lattice constant at the edge of the CaF2/BaF2 mixed crystal layer,
For example, the grading layer may have a composition that changes continuously from 6.20 to about 6.43 for HgCdTe or about 6.43 for IgXnTe.

As a result of these buffer layers, the present invention provides l! g
CdTe or HgZnTe single crystal layers can be laminated, and the single crystal can be used to form a light receiving element with high sensitivity to long wavelength infrared light.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Manufacturing method and structure of the first embodiment First, the manufacturing method of the device of this embodiment will be explained in Figs.
This will be explained with reference to FIG.

Note that FIG. 2 shows a part of an example of the configuration of an imaging device configured using the present invention, and FIGS. 1 and 3 are cross-sectional views of the main parts along line 1-1 in FIG. be.

First, as shown in FIG.
A substrate 10 is prepared.

This element-forming Si substrate 10 includes an input diode 16, an embedded CCD, and an input diode 16 on the main surface of a P-type Si substrate 12 and within an element isolation region formed by a P0 channel stop 14.
18 are formed at appropriate intervals.

Further, an electrode 20 is connected and formed on the input diode 16, and an input diode +6 and an embedded CC
A transfer electrode 22 is placed on the gap portion of D18.
is formed via the 5i02 layer 24, and furthermore, a CCD transfer electrode 26 is similarly formed on the embedded CCD 18.
It is formed through the i02 layer 24.

The above element-forming St substrate 10 is formed by a commonly used manufacturing process.

Next, as shown in the same figure (b), a mixed crystal layer of CaF2 and BaF2 (hereinafter referred to as "rCaF2-BaF2 layer") 28 is formed on the element-forming Si substrate 10 as described above. It is grown and formed by grading so that the composition ratio gradually increases.

In other words, the portion that contacts the element-forming Si substrate is CaF2.
The composition ratio of the surface (CdZnTe layer 30 described later)
The BaF2 composition ratio is set to 1 in the part (contacting part), and the middle part is a graded mixed crystal layer.

In this case, the suitable growth method is vacuum evaporation or single molecular beam epitaxy, but the CaF2-BaF2 layer 28 should be taxially grown at least on the region that is in direct contact with the Si crystal. A region 28c is formed.

Next, the ZnTe on the CaF2-BaF2 layer 28 is
Layer 30 is grown, for example, by molecular beam epitaxy. At this time, all 28 areas 28C of the CaF2-BaF2 layer 28
A CdZnTe single crystal film is laminated on the upper part, and a polycrystalline film is laminated on the other region.

Then, laser beam annealing or electron beam annealing is performed using this cdznTe single crystal region as a seed crystal, and the polycrystalline film portion of the CdZnTe layer 30 is made into a single crystal.

Note that the above Cd and ZnTe layers 30 may also be formed by grading.

Next, as shown in the same figure (D), the CdZnTe layer 30
On top of this, a P-type HgCdTe layer 32 is epitaxially grown, and then an N-type) IgcdTe layer 3 is grown.
4 was epitaxially grown, and then Zn5
Layer 36 is laminated.

) The epitaxial growth method for the IgCdTe layer 32, 34 is molecular beam epitaxy or OMVPE (
A method (organic metal vapor phase epitaxy) is suitable, and a sputtering method or a vacuum evaporation method is suitable for forming the Zn5 layer 36.

Next, the lIgcdTe layers 32, 34 and the Zn5 layer 36 are etched into a tapered shape by a dry or wet method, and then the CdZnTe layer 30 and the Ca
The entire 28 layers of F, -BaF2 layer 28 are etched to form a groove 40 having a length of 1/2. Further, a contact hole 38 is formed by anisotropic etching using a dry method, as shown in FIG.

Next, the CdZnTe layer 30 in the isolation trench 40 and the CaF, -
An insulating film 50 is formed so as to cover the entire BaF2 layer 28.

This absolute IJ-IBM is made of polyimide, spin-on glass,
5i02. SI3N4 or the like is suitable, and is formed by a normal device manufacturing process.

Next, as shown in FIG. 1, an In layer 42 is formed in the contact hole 38 by In evaporation and a lift-off method, and an In layer 42 is formed in the isolation trench 40 by Au evaporation and a lift-off method. An Au layer 44 is formed on the insulating film 50.

However, the width of this Au layer 44 is smaller than the width of the separation groove 40 and is formed so as not to contact the It g Cd Te layer 34 .

After the above, normal annealing is performed to form an ohmic contact between the input diode electrode 20 and the In layer 42, and to form an ohmic contact between the It g Cd Te layer 32 and 34 around the contact hole 38. In is diffused to form an N-type region 46.

Similarly, CdZn around the contact hole 38
The layer type 0 is also diffused into the Te layer 30 to form a diffusion region 48, but this does not affect the operation of the photoelectric conversion element in any way.

As described above, according to this embodiment, on the element-forming Si substrate 10, the CaF2-BaF2 layer 28, the CdZn
A Te layer 30 is formed in each layer, and further on top of that IgCd
The configuration is such that an infrared detecting element is formed by Te layers 32 and 34.

Next, the infrared detection element and signal processing circuit element formed as described above constitute a plurality of photoelectric conversion elements arranged in the X-Y direction shown in FIG.

The above-mentioned Au layer 44 is commonly connected to each photoelectric conversion element, and a COD shift register R is constituted by the embedded CCD I 8 of each optical conversion element in the X direction. .

Operation of First Embodiment Next, the operation of the imaging device configured as described above will be explained.

First, when infrared rays are incident on any of the photoelectric conversion elements, the generated electron/hole pairs are separated in the infrared detection element by the II g Cd Te layer 32, 34, and the carrier or human diode 16 corresponding to the amount of incident light is separated. Move to.

The carriers are transferred to the embedded CCD 18 by applying a signal to the transfer electrode 22 . Then, the transferred carrier is further transferred from the imaging device by a CCD shift register R.

Here, considering the lattice constant of each layer constituting each photoelectric conversion element, first of all, in the GaF2 BaF2 layer 28, the lattice constant of CaF2 is 5.46, and the lattice constant of Si is 5.46.
Close to 3 people <, 'The lattice constant of BaF2 is 6.20 people
(close to 6.47 people in gcdTe).

Next, the CdZnTe layer 30 has a layer type 0. The CdZnTe is a mixed crystal of CdTe (cadmium-tellurium) with a lattice constant of 6.48 and ZnTe (zinc-tellurium) with a lattice constant of 6.10.

Therefore, if the composition ratio of both is appropriate, it can be used as a buffer layer between IgcdTe and BaF (with a lattice mismatch of 4%).

For this reason, the above-described CdZnTe layer 30 can be formed as a single layer type 0, and furthermore, the IgCdTe layer 32 can be laminated thereon as a single crystal film with lattice matching.

Further, the CdZnTe single crystal layer 30 is made of )IgCdTe
It not only lattice-matches BaF2 and BaF2, but also has the function of preventing impurity diffusion from BaF and layers below it into the It g Cd Te layer 32 .

Effects of the first embodiment As described above, the CaF2-BaF2 layer 28, Il
:dZnTe By layering ZnTe, element formation S
I, g of high quality with few defects and impurities on the i substrate 10
It is now possible to form an infrared detection element using a CdTe layer 32, 34, which facilitates the connection between the infrared detection element and the signal processing circuit element, simplifies the manufacturing process, and further improves pixel density and reliability. This makes it possible to improve performance.

Furthermore, since it is a stacked type, it has a high aperture ratio and a high degree of freedom in element design.

Second Embodiment Next, with reference to FIG. 4, a second embodiment of the present invention will be described. Note that the same reference numerals are used for the same parts as in the first embodiment described above.

In this example, compared to the above-mentioned example, an N-type l
The second embodiment is the same as the first embodiment except that the lgcdTe layer 50 is formed by diffusion of N-type impurities using a normal planar technique instead of epitaxial growth.

Other Embodiments It should be noted that the present invention is not limited to the above-mentioned embodiments; however, in the above-mentioned embodiments, the infrared detection element was constructed of llgcdTe; You can also obtain similar effects.

In addition, as an electric signal processing circuit formed on a Si substrate, although the case of an embedded CCD as a transfer function element is shown, it is not limited to this, and various types such as a surface type CCD, MOS transistor switch, etc. Applies to.

In addition, although a photovoltaic type was shown as the light receiving element in the example,
It may also be of photoconductive type.

Furthermore, the present invention can be used not only as a one-dimensional or two-dimensional imaging device as shown in FIG. 2, but also as a single photoelectric conversion element.

Further, the conductivity type of each part is not limited to the above embodiment, and even if other conductivity types are used, a device having similar effects can be constructed.

[Effect of the invention] As described above, according to the present invention, HgCdTe.

An infrared detection element made of either HgZnTe or Si
As a result, the number of pixels can be increased and the reliability can be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an infrared irradiation detection device according to a first embodiment of the present invention, FIG. 2 is a plan view showing a part of an imaging device according to the first embodiment, and FIG. 3 is a plan view showing a part of an imaging device according to the first embodiment. FIG. 4 is a sectional view showing a second embodiment of the present invention. [Description of symbols of main parts] 10...Element forming Si substrate, 16...Human power diode, 18...Embedded CCD, 28 =-CaF2-
BaF2 layer, 30- CdZnTe layer, 32 ・P-type Hg Cd Te layer, 34...N-type HgCdTe
Layer, 36 ・= ZnS layer, 46 ・N type diffusion region, 4
2...In layer, 44...U layer, D...photoelectric conversion element, R...CCD shift register. Agent Patent Attorney Tadashi Sato Figure 1 Figure 2 r-m=(-m=, Figure 3 (D) Figure 3 (E) Figure 4

Claims (1)

[Claims] In an infrared detection device having an infrared detection element formed of a single crystal layer of either HgCdTe or HgZnTe, and a signal processing circuit element formed on a Si semiconductor substrate, the infrared detection element is formed of HgC
An infrared detection device characterized in that a buffer layer is provided between a single crystal layer of either dTe or HgZnTe and the Si substrate.