JP2697181B2 - Manufacturing method of infrared detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] Among back-illuminated infrared detectors, the present invention relates to a method of manufacturing an infrared detection array provided with a lens, in particular, to simplify the manufacturing process and improve the performance of the detection array. Forming a spherical mask on the light receiving surface of the infrared transmitting substrate, ion milling the substrate together with the spherical mask to form a lens on the substrate surface, and then irradiating light through the lens. A step of locally heating the substrate by focusing on the opposite surface of the substrate, and a step of vapor-phase epitaxial growth for selectively growing the sensing element layer in the heated portion.

[Industrial applications]

The present invention relates to a method for manufacturing a back-illuminated infrared detector,
In particular, the present invention relates to a method for manufacturing an infrared detection array provided with a lens.

[Problems to be solved by conventional technology and invention]

With the rapid progress of infrared detectors used for infrared imaging and the like, wide applications to the high-tech industry are being developed. FIGS. 4 (a) and 4 (b) show such a back-illuminated infrared detector, wherein FIG. 4 (a) is a plan view and FIG. 4 (b) is a sectional view taken along the line AA. Symbol 1 in the figure is a CdTe substrate, 2 is a HgCdTe layer having a pn junction, 3 is an In bump electrode, and 4 is a signal readout CCD. Normally, the infrared detector has a light receiving portion and a charge transfer portion formed of a hybrid type of different materials, and the light receiving portion is formed of an array of photovoltaic elements. Further, as shown in the drawing, the light receiving surface of the CdTe substrate 1 is provided with one lens 5 per cell (element), and the amount of light incident on each cell is increased to improve the sensitivity. As shown in the lens partial view of FIG. 5, the lens 5 has, for example, a height t up to the lens 5 = 223 μm, a lens width d = 100 μm, a thickness 1 of the CdTe substrate 1 = 200 μm, and a distance between the lenses. The lens has a focal point f = 2 with p = 120 μm, and the focal point is focused on the HgCdTe portion 2.

The infrared detecting array serving as the light receiving portion is manufactured by a method of growing a HgCdTe layer 2 on a CdTe substrate 1 and then forming a lens. HgCd on the CdTe substrate 1
When the Te layer 2 is grown, a method of growing the HgCdTe layer over the entire surface and then patterning using a photolithography technique is employed, but a selective growth method is also used. The conventional selective growth of the HgCdTe layer 2 is a method in which a concave portion is formed in a CdTe substrate and HgCdTe is selectively grown in the concave portion by utilizing the fact that the reaction gas easily stays in the concave portion.

However, such a manufacturing method of forming a lens after growing the HgCdTe layer is not related to both steps, and the focus of the lens does not always coincide with the HgCdTe layer 2 due to fine processing.

The present invention proposes a manufacturing method for solving such problems, simplifying the manufacturing process, and improving the performance of the detection array.

[Means for solving the problem]

The problem is that as shown in FIGS. 1 and 2, a lens is formed by forming a mask 6 on a light receiving surface of an infrared transmitting substrate 1 and ion milling the substrate together with the mask to form a lens 5 on the substrate surface. Then, as shown in FIG. 3, light is radiated through the lens to focus on the opposite surface of the substrate to locally heat the light, and to selectively grow the sensing element layer 2 on the heated portion. The problem is solved by a manufacturing method including a phase epitaxial growth step.

(Operation)

That is, according to the present invention, a lens is prepared in advance using a mask (for example, a resist) on the light-receiving surface of the substrate, and then the sensing element layer is selectively grown by local heating using the lens. By doing so, a high-performance sensing array can be obtained by focusing on the sensing element layer, and the manufacturing process is simplified.

〔Example〕

Hereinafter, embodiments will be described in detail with reference to the drawings.

FIGS. 1 (a) to 1 (e) and 2 (a) to 2 (e) are a sectional view and a plan view in the order of steps of a lens manufacturing process according to the present invention, and are sectional views shown in FIG. The figure is a partial section,
The plan view shown in FIG. 2 shows the entire plan view. The lens manufacturing process will be described with reference to FIGS. 1A and 1A. First, a resist 6 (mask) is applied to the entire surface of the CdTe substrate 1 to reduce the thickness D. It is set to a required value (for example, about 30 μm). This thickness D can be determined by the viscosity of the resist before coating and the number of revolutions of the resist coating machine (spinner).

Referring to FIGS. 1B and 2B, the resist 6 is patterned by photolithography to form a columnar resist in an array.

See FIG. 1 (c) and FIG. 2 (c);
The solvent is evaporated by baking at 0 to 200 ° C., and the cylindrical resist is dried to be transformed into a hemispherical resist 6.
In the lens manufacturing process, the shape of the spherical resist is extremely important.

1 (b) and 2 (d); next, the entire surface is milled by an ion milling method using an argon gas, and the resist 6 and the CdTe substrate 1 are simultaneously removed. This figure illustrates the ion milling process.

1 (e) and 2 (e); thus, the resist 6 is completely removed, and the lens 5 is formed on the surface of the CdTe substrate 1.

Next, FIGS. 3A and 3B show HgCdTe according to the present invention.
FIGS. 4A and 4B are diagrams for explaining a layer selective growth process, wherein FIG. 4A shows a vapor phase epitaxial growth apparatus, and FIG. 4B shows CdTe after selective growth.
FIG. 4 shows a partial cross-sectional view of the substrate.

In the vapor phase epitaxial growth apparatus shown in FIG. 3 (a), reference numeral 1 denotes a CdTe substrate on which the lens 5 is formed, 10 denotes a reaction chamber, 11 denotes a high-frequency heating coil, 12 denotes a reaction gas inlet, 1
3 is an exhaust port, 14 is a light transmission window, and 15 is a mercury lamp. The selective growth method will be described. A CdTe substrate 1 having a lens array formed therein is accommodated in a reaction chamber 10, and a lens 5 is provided with a light transmitting window.
Attach so as to face 14. Dimethyl cadmium (approximately
10 ^-5 atm), diisopsopirtellurium (about 10 ^-5 atm), and mercury (about 10 ^-3 atm). First, the CdTe substrate 1 is heated to 350 ° C. by the high-frequency heating coil 11. HgC of about 0.2 μm is formed on the entire surface of the CdTe substrate 1 opposite to the lens array.
A dTe layer 2 ′ (this HgCdTe layer 2 ′ is formed to be a common electrode) is grown, and then the temperature is lowered to 300 ° C., and a mercury lamp 15 is irradiated from a light transmission window 14 to form a CdTe substrate. Focus on the opposite surface and heat locally, and add an island
The HgCdTe layer 2 is selectively grown. Thus, the selective growth was performed for 12 hours by irradiating a mercury lamp 15 to obtain a Hg _1-x C of about 50 μm.
A d _x Te layer (x = 0.22) 2 can be grown. Third
FIG. 2B shows a partial cross-sectional view thereof.

If an infrared detection array serving as a light receiving unit is formed as in the above-described embodiment, it is possible to use an already manufactured lens array.
The HgCdTe layer can be selectively grown, and the formation method according to the present invention requires alignment compared to the conventional method in which a lens array is formed so as to match the initially formed HgCdTe layer in the form of an array. For example, the manufacturing process is simplified. Moreover, a high-performance detection array in which the focal point of the lens matches the HgCdTe layer can be obtained.

Note that, in addition to CdTe crystal, sapphire, GaAs, Si, etc. were used as the infrared transmitting substrate, and HgCd was used as the detecting element.
In addition to Te, PbSnTe, InSb, InAs and the like can be used.

〔The invention's effect〕

As is apparent from the above description, the manufacturing method according to the present invention is a manufacturing method in which a lens array is first manufactured, and the sensing element layer is selectively grown using the lens array. A high-performance sensing array having the same focal point is formed, and the manufacturing process is simplified. Therefore, high performance and low cost of the infrared detector can be realized at the same time.

[Brief description of the drawings]

1 (a) to 1 (e) are sectional views in the order of steps in a lens manufacturing process according to the present invention, and FIGS. 2 (a) to 2 (e) are plan views in the order of steps in a lens manufacturing process according to the present invention. 4A and 4B are views for explaining a selective growth process of the HgCdTe layer according to the present invention, FIGS. 4A and 4B are views showing an infrared detector, and FIG. 5 is a partial view of a lens. is there. In the figure, 1 is a CdTe substrate (infrared transmitting substrate), 2, 2 'is a HgCdTe layer (detection element layer), 3 is an In bump electrode, 4 is a signal readout CCD, 5 is a lens, 6 is a resist (mask), 10 Denotes a reaction chamber, 11 denotes a high-frequency heating coil, 12 denotes a reaction gas inlet, 13 denotes an exhaust port, 14 denotes a light transmission window, and 15 denotes a mercury lamp.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-308927 (JP, A) JP-A-63-150976 (JP, A) JP-A-62-1111416 (JP, A) JP-A-61-1 267313 (JP, A)

Claims (1)

(57) [Claims] A lens forming step of forming a mask on the light receiving surface of the infrared transmitting substrate, ion milling the substrate together with the mask to form a lens on the substrate surface, and then irradiating light through the lens; A method of manufacturing an infrared detector, comprising: a step of locally heating a focus on the opposite surface of the substrate, and a step of selectively growing a sensing element layer in the heated portion.