JPH05315580A - Semiconductor photodetector and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a photodetector excellent in photosensitivity by a method wherein a recess is provided to the prescribed region of a semiconductor substrate, and a surface orientation selection layer formed of laminated zinc- containing compound semiconductor layers and a buffer layer formed of a Cd-containing compound semiconductor layer are provided inside the recess concerned. CONSTITUTION:A recess 21 is provided to a prescribed region of an Si substrate 3, and a ring-shaped source region 11 of a MOS type switching element is provided around the recess 21. A drain region 12 is provided onto the Si substrate 3 at a point separate from the source region 11 by a prescribed distance, and a gate electrode 14 is provided onto the substrate 3 through the intermediary of an insulating film 13. A surface orientation selection layer 22 composed of ZnTe layers or GaAs layers and ZnTe layers which are laminated and a buffer layer 23 composed of CdTe layers doped with N-type impurities are provided inside the recess 21. An N-type HgCdTe layer 16 and a P-type HgCdTe layer 17 are laminated on the buffer layer 23 to serve as a photodetecteing element 2, and a ring-shaped high density source region 11 is provided around the buffer layer 23 for the formation of a photodetector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor photodetection device and a method for manufacturing the same, and more particularly to a photodetection device arranged two-dimensionally and a predetermined position of the photodetection device selected to obtain the photodetection device. The present invention relates to a monolithic two-dimensional semiconductor photodetector in which a switching element for turning on / off the received signal to an external circuit is formed on the same semiconductor substrate.

For semiconductor photodetectors, particularly infrared detectors for detecting infrared light, development of a surface type photodetector (two-dimensional IR CCD) in which photodetectors are two-dimensionally arranged is under way. In such a two-dimensional IRCCD, infrared light is photoelectrically converted, and a two-dimensionally arranged photo-sensing element and a switching element for turning on and off a signal obtained by the photo-electric conversion by the photo-sensing element to an external circuit. And are needed.

[0003]

2. Description of the Related Art As shown in FIG. 3 (a), a conventional IR CCD is a photodetector formed by providing a pn junction on a compound semiconductor substrate 1 such as mercury cadmium tellurium (Hg _1-x Cd _x Te). An array of elements 2 and an input diode 4 of a charge transfer element (CCD), which processes a signal obtained by photoelectric conversion by the light detection element 2 and is formed on a silicon (Si) substrate 3,
The structure is such that bumps are connected by metal bumps 5 made of indium (In). Here, 6 in the figure is an insulating film of both substrates 1 and 3.

[0004]

By the way, the IR CCD having such a structure is normally operated at a very low temperature of liquid nitrogen, and when the IR CCD reaches a room temperature when it is not operating, the operating temperature and the room temperature are lowered. The expansion and contraction stresses are applied to the compound semiconductor 1 and the Si substrate 3 during the temperature cycle of.

The compound semiconductor substrate 1 is a Si substrate 3
Since the coefficient of thermal expansion is large, the above-mentioned stress becomes large, and due to the difference in the stress applied to the two substrates 1 and 3, the metal bump 5 of In connecting the two substrates 1 and 3 is displaced. In the case where the metal bumps 5 are cracked, cracked, or are severe, the problem that the metal bumps 5 are peeled off from the substrates 1 and 3 of both substrates occurs.

For this reason, if the areas of the substrates 1 and 3 are increased to form an IRCD having a large area, the difference in the amount of thermal expansion between the two substrates expands. .. Therefore, in order to form an IRCD having a large area, there is a demand for a technique of forming the IRCD without using the above metal bump bonding.

Therefore, in order to solve such a problem, as shown in FIG. 3B, the p-type Si substrate 3 is doped with a high concentration of n.
-Type impurity atoms are introduced by an ion implantation method or the like to obtain n ⁺
A source region 11 and a drain region 12 made of layers are formed, and a gate electrode 14 made of a poly-Si film is formed on the source region 11 and the drain region 12 with a SiO ₂ film 13 interposed therebetween.
To form a MOS type switching element.

On the other hand, the SiO ₂ film 13 on the source region 11 is opened to form an n-type CdTe layer 15 on the source region 11 by MOCVD (Metal).
Organic Chemical Vapor Deposition) method, molecular beam epitaxial growth method or the like, and then n-type HgCdTe layer 16 and p-type HgCd are formed on the CdTe layer 15.
The Te layer 17 is formed by using the MOCVD method, the molecular beam epitaxial growth method, or the like to form the photodetector element 2.

Then, a signal obtained by photoelectrically converting the light detecting element 2 is transmitted to the source region 11 and a voltage is turned on / off to the gate electrode 14, so that the signal transmitted to the source region 11 is transferred to the drain region. It is transmitted to 12 and is led to an external circuit through a wiring layer (not shown) which is electrically connected to the drain region 12.

By the way, the above-mentioned silicon substrate 3 is provided with MO.
To form an S-type switching element, a Si substrate 3 having a plane orientation of (100) plane is used so that the element has good electrical characteristics.

However, when the CdTe layer 15 is epitaxially grown on the Si substrate 3 having such a (100) plane orientation, the CdTe layer 15 having the (111) plane orientation grows in the literature ["Molecular beam epitaxial growth of Cd
Te and HgCdTe on Si (100) ", Appl.Phys.Lett.55 (18),
30 October 1989 page 1879-1881, by R. Sporken, etc.)
It is described in.

CdTe layer having the (111) plane orientation
In No. 15, crystal defects such as twins are likely to occur, and therefore,
The n-type or p-type HgCdTe layers 16 and 17, which are formed on the CdTe layer 15 and are used as the material for forming the photodetector 2, are naturally prone to crystal defects such as twins, and a leak current is generated. Inconveniences such as occurrence occur, and there arises a problem that it becomes a light detecting element having poor light receiving characteristics.

The present invention eliminates the above-mentioned problems and makes it possible to obtain a HgCdTe layer having few crystal defects by making the CdTe layer and the HgCdTe layer have (100) planes, and to provide a photodetector having excellent light receiving characteristics. An object of the present invention is to provide a semiconductor photodetection device and a method of manufacturing the same.

[0014]

According to another aspect of the present invention, there is provided a semiconductor photodetecting device, wherein a recess is provided in a predetermined region of a semiconductor substrate and a ring-shaped source of a MOS type switching element is provided around the recess. A region is provided, and a drain region is provided on the semiconductor substrate at a predetermined position from the source region,
A gate electrode is provided on the substrate via an insulating film, and a plane orientation selection layer formed by stacking a compound semiconductor layer containing zinc, or a compound semiconductor layer containing gallium and a compound semiconductor layer containing zinc in the recess, and an impurity A buffer layer comprising a compound semiconductor layer containing cadmium to which atoms are added is provided, and a compound semiconductor layer containing mercury having different conductivity types for forming a photo-detecting element is laminated on the buffer layer. It is a thing.

Further, as described in claim 2, the thickness of the plane orientation selection layer is set smaller than the depth of the recess, and the sum of the thickness of the plane orientation selection layer and the buffer layer is equal to or equal to the depth of the recess. It is characterized in that it is provided with a thickness greater than that.

According to a third aspect of the present invention, in the method of manufacturing a semiconductor photodetecting device of the present invention, a recess is formed in a predetermined region of a semiconductor substrate, and impurity atoms are introduced in a predetermined pattern around the recess. A ring-shaped source region of a MOS type switching device is formed, impurity atoms are introduced into the semiconductor substrate at a predetermined position from the source region to form a drain region, and a gate electrode is formed on the substrate via an insulating film. After forming a compound semiconductor layer containing zinc or a compound semiconductor layer containing gallium and a compound semiconductor layer containing zinc in the recess, a plane orientation selection layer is formed, and impurity atoms are formed on the plane orientation selection layer. Forming a buffer layer composed of a compound semiconductor layer containing cadmium added thereto, and depositing a compound semiconductor layer containing mercury having different conductivity types for forming a photodetection element on the buffer layer. It is characterized in that to form.

[0017]

According to the semiconductor device of the present invention, a recess is formed in a Si substrate having a (100) plane orientation, and a ring-shaped high-concentration n-type layer is formed in the Si substrate around the recess to form a source. A drain region is formed at a position separated from the region and the source region. The SiO ₂ to form an SiO ₂ film on the Si substrate
A poly-Si gate electrode is embedded in the film to form a MOS type switching element.

On the other hand, the SiO ₂ film on the recess of the Si substrate is removed, and a ZnTe layer as a plane orientation selection layer having a lattice constant approximately in the middle of the Si substrate and the CdTe layer is formed in the recess. Here, the lattice constant of Si on the (100) plane is 5.43Å, and (10
The lattice constant of ZnTe in the (0) plane is 6.10Å, and the lattice constant of CdTe in the (100) plane is 6.481Å.

This ZnTe layer is described in (10)
A ZnTe layer having a (100) plane orientation can be formed on a Si substrate having a (0) plane orientation. However, it is difficult to obtain an n-type conductivity type crystal in the ZnTe layer of this plane orientation selection layer.

Therefore, the photocurrent obtained by the photodetection element to be formed thereon does not flow into this ZnTe layer,
No photocurrent flows into the source region of the switching element formed around the recess. Therefore, the plane orientation selection layer of the ZnTe layer is formed thinner than the depth of the recess, and (1
00) plane-oriented high-concentration n-type CdTe layer is formed to be thicker than the depth of the recess as a buffer layer, and the photocurrent flowing from the photodetector to be formed on the CdTe layer of the buffer layer is
It flows into the surrounding source region that is in contact with the CdTe layer. Then, an n-type and p-type HgCdTe layer having a (100) plane orientation is formed on this CdTe layer to form a photodetecting element.

By doing so, both the CdTe layer and the HgCdTe layer have a (100) plane orientation in which crystal defects such as twins are unlikely to occur, and a high-performance photodetector can be obtained. Further, the photocurrent obtained by the photodetector is collected in the buffer layer of the n-type CdTe layer, and the photocurrent is composed of a high-concentration Si n ⁺ layer provided in a ring shape around the CdTe layer. Easily flows into the source region. In this way, it is difficult to obtain the n-type conductivity type, but it is easy to obtain the (100) plane orientation.
A ZnTe layer is formed as a plane orientation selection layer, and (10
It is possible to form an n-type CdTe layer having a plane orientation of 0) and use this CdTe layer as a buffer layer to form p-type and n-type HgCdTe layers with few crystal defects thereon.

Further, since the ring-shaped source region is provided in contact with the periphery of the n-type CdTe layer, the photocurrent collected in the CdTe layer easily flows into the source region.

[0023]

[Embodiment] An embodiment of a semiconductor photodetector of the present invention is shown in FIG.
A cross-sectional view and a perspective view of FIG. 1 (b) are shown.

As shown in FIGS. 1 (a) and 1 (b), a p-type Si substrate 3 having a resistivity of 10 to 20 Ω-cm and a plane orientation of (100) has a depth of 5 μm. The recess 21 with a diameter of 20 μm is
Provide at the pitch of. A MOS is formed around the recess 21.
Ring-shaped switching element 18 of
A source region 11 of an n ⁺ layer of 10 ¹⁸ / cm ³ and a drain region 12 are provided at a predetermined position from the source region 11, and SiO ₂ is formed on the substrate.
Gate electrode made of poly-Si via insulating film 13 made of a film
Provide 14

In the recess 21, ZnTe having a thickness smaller than the depth of the recess, or a plane orientation selection layer 22 in which a GaAs layer and a ZnTe layer are stacked, and an n-type impurity atom, that is, In, are added thereon. A buffer layer 23 made of the CdTe layer is provided. The total thickness of the plane orientation selection layer 22 and the buffer layer 23 is equal to or greater than the depth of the recess 21.

On the buffer layer 23, an n-type HgCdTe layer 16 and a p-type HgCdTe layer 17 for forming a photodetector are laminated and provided. According to such a semiconductor photodetector of the present invention, since the n-type HgCdTe layer 16 and the p-type HgCdTe layer 17 having few crystal defects are provided in a laminated manner, a highly reliable photodetector can be obtained.

In addition, since the ring-shaped high-concentration source region 11 is formed around the buffer layer 23 of the n-type CdTe layer, the photocurrent obtained by the photodetector is collected in the buffer layer 23, The semiconductor photodetector with high performance can be obtained because it easily contacts the buffer layer and flows into the source region 11 provided in the periphery.

A method of manufacturing such a semiconductor photodetector of the present invention will be described. As shown in Fig. 2 (a), the resistivity is 10
Recesses 21 having a depth of 5 μm and a diameter of 20 μm are formed at a pitch of 50 μm on the p-type Si substrate 3 having a surface orientation of (100) by 20 Ω-cm by an ion etching method or the like.

Next, as shown in FIG. 2 (b), phosphorus atoms are ion-implanted around the recess 21 at an impurity concentration of 10 ¹⁸ / cm ³ to form M.
A ring-shaped n ⁺ type source region 11 of the OS type switching element is formed, and phosphorus atoms are similarly ion-implanted into the Si substrate 3 at a predetermined position from the source region 11 to form a drain region 12.

Next, an insulating film 13 made of a SiO ₂ film is formed on the substrate by a CVD method or a sputtering method, a poly Si film is formed on the insulating film by a CVD method, and the poly Si film is formed into a predetermined pattern. Then, a gate electrode 14 is formed by etching, and an insulating film 13 is further formed thereon.

Next, as shown in FIG. 2C, the insulating film 13 on the recess 21 is removed by etching, and then the recess 21 is filled with the insulating film 13.
The plane orientation selection layer 22 made of ZnTe is formed by MOCVD or molecular beam epitaxial growth to have a dimension smaller than the depth of the recess 21, that is, a thickness of 1 μm. The plane orientation of the plane orientation selection layer 22 made of ZnTe is the (100) plane.

Then, as shown in FIG. 2 (d), a buffer layer 23 made of a CdTe layer, which is an n-type layer formed by adding In to the plane orientation selection layer 22, is formed by MOCVD to a thickness of 7 μm, or It is formed by the molecular beam epitaxial growth method. This CdTe
The layer has a (100) plane, and crystal defects are unlikely to occur.

On the buffer layer 23, In is added as an impurity atom to form an n-type HgCdTe layer 16 with a thickness of 1 μm, and arsenic (As) is added as an impurity atom to form a p-type HgCdTe layer 16. HgCd
The Te layer 17 is deposited to a thickness of 10 μm to form a photodetector element. Since both of these HgCdTe layers 16 and 17 have (100) planes, crystal defects are less likely to occur, and a highly reliable photodetector can be obtained.

In this embodiment, Zn is used as the plane orientation selection layer.
Although only the Te layer is used, a GaAs layer may be formed in the recess 21 provided in the Si substrate, and a ZnTe layer may be stacked on the GaAs layer.

[0035]

As described above, according to the semiconductor photodetection device of the present invention, since a crystal defect such as twin is unlikely to occur in the HgCdTe layer forming the photodetection device, a highly reliable photodetection device can be obtained. can get.

Further, by providing the concave portion and the source region of the ring-shaped high-concentration impurity layer provided around the concave portion, even if the ZnTe layer is difficult to form n-type conductivity type crystals, This ZnTe layer is formed to be thinner than the depth of the recess, and an n-type CdTe layer is formed thereon to form the ZnTe layer,
It can be applied as a plane orientation selection layer for forming a CdTe layer having a plane orientation of the (100) plane, and has an effect of obtaining a semiconductor photodetector with high performance and high reliability.

[Brief description of drawings]

FIG. 1 is a sectional view and a perspective view of a semiconductor photodetector of the present invention.

FIG. 2 is a cross-sectional view showing the method of manufacturing the device of the present invention.

FIG. 3 is an explanatory diagram of a conventional device.

[Explanation of symbols]

2 Photodetector 3 Si substrate 11 Source region 12 Drain region 13 Insulating film (SiO ₂ film) 14 Gate electrode 16 n-type HgCdTe layer 17 p-type HgCdTe layer 18 Switching device 21 Recess 22 Face orientation selection layer 23 Buffer layer

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 31/10

Claims (3)

[Claims] 1. A semiconductor substrate (3) is provided with a recess (21) in a predetermined region, and a ring-shaped source region (11) of a MOS type switching element is provided around the recess (21). A drain region (12) is provided on the semiconductor substrate (3) at a predetermined position from (11), a gate electrode (14) is provided on the substrate (3) through an insulating film (13), and inside the recess (21). A compound semiconductor layer containing zinc, or a plane orientation selection layer (22) formed by stacking a compound semiconductor layer containing gallium and a compound semiconductor layer containing zinc, and a buffer layer including a compound semiconductor layer containing cadmium to which impurity atoms are added (23) is provided, and a compound semiconductor layer (16, 17) containing mercury having different conductivity types for forming a photodetection element is laminated on the buffer layer (23) to provide a semiconductor photodetection. apparatus. 2. The plane orientation selection layer (22) according to claim 1, wherein the plane orientation selection layer (22) has a thickness smaller than the depth of the recess (21).
The semiconductor photodetecting device is characterized in that the total thickness of the buffer layer (23) and the buffer layer (23) is equal to or greater than the depth of the recess (21). 3. A ring-shaped source region of a MOS type switching device in which a recess (21) is formed in a predetermined region of a semiconductor substrate (3) and impurity atoms are introduced around the recess (21) in a predetermined pattern. (11) is formed, impurity atoms are introduced into the semiconductor substrate (3) at a predetermined position from the source region (11) to form a drain region (12), and an insulating film () is formed on the substrate (3). Gate electrode through (13) (14)
And forming a plane orientation selection layer (22) formed by stacking a compound semiconductor layer containing zinc, or a compound semiconductor layer containing gallium and a compound semiconductor layer containing zinc in the recess (21), A buffer layer (23) made of a compound semiconductor layer containing cadmium to which impurity atoms are added is formed on the orientation selection layer (22), and mercury having different conductivity types for forming a photodetecting element is formed on the buffer layer (23). A method for manufacturing a semiconductor photodetecting device, which is characterized in that the compound semiconductor layers (16, 17) containing are laminated.