A focal plane array device and method of making the same to prevent signal cross-talk

Abstract

The application relates to a focal plane array device for preventing signal crosstalk and a manufacturing method thereof, which comprises the following steps: manufacturing an epitaxial layer comprising a first contact layer, an absorption layer, a second contact layer and an etching stop layer on a substrate surface in sequence; etching the epitaxial layer to form a focal plane array mesa; preparing a passivation film on the surface of the focal plane array mesa; etching and removing the passivation film at the bottom of the focal plane array mesa; then depositing a metal electrode layer on the bottom and the sidewall; sequentially performing In column manufacturing, readout circuit installation and colloid filling; removing the substrate and the etching stop layer; etching the second contact layer at the bottom to expose the metal electrode layer; manufacturing an anti-reflection film on the surface of the second contact layer; and manufacturing a back electrode on the surface of the exposed metal electrode layer. The metal electrode layer is grown on the sidewall of the mesa, and the etching back contact layer is used, so that two crosstalk paths existing in the prior deep mesa array device are shielded, and the purpose of further inhibiting signal crosstalk between focal plane array pixels is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of focal plane array devices, in particular to a focal plane array device for preventing signal crosstalk and a manufacturing method thereof. BACKGROUND

[0002] For a focal plane array photoelectric device, crosstalk is that when a light radiation signal acts on a certain pixel to generate a response signal, a response signal also appears on the adjacent pixel. Crosstalk is an important factor limiting the performance of the focal plane array photoelectric device, and directly affects the modulation transfer function of the focal plane device, especially for the focal plane array device with high pixel density and wide waveband. Crosstalk is generally divided into optical crosstalk and electrical crosstalk. The optical crosstalk refers to that part of the light radiation signal entering the target pixel is transmitted into the adjacent pixel, thereby introducing crosstalk, which is related to the light diffraction effect, uneven substrate, backside growth of dielectric film and metal film reflection to the light signal and other factors. The electrical crosstalk refers to that after the incident light radiation signal is absorbed by the target pixel and converted into non-equilibrium carriers, the non-equilibrium carriers enter the adjacent pixel area through lateral diffusion, and are absorbed by the adjacent pixel pn junction to form a photocurrent crosstalk output signal. In addition, for a Geiger mode avalanche photodiode, there is weak spontaneous light in the multiplication layer during the avalanche process, which is received by the nearby other pixels and generates an error signal, which is a special crosstalk combined with photoelectricity.

[0003] At present, the method for suppressing crosstalk of the focal plane array device is to perform substrate removal technology and deep mesa isolation technology. The substrate removal can reduce the scattering of the substrate surface to the light radiation signal or the full reflection effect of a specific angle range to cause optical crosstalk of the adjacent pixel. The deep mesa isolation can suppress the lateral diffusion effect of the non-equilibrium carriers. By means of the above two schemes, most of the crosstalk has been suppressed, but the crosstalk still cannot be completely eliminated. After the target pixel is excited, secondary photons are radiated outward. Even if there is physical isolation between the pixels, part of the secondary photons still transmit to the adjacent pixel through the space channel to form crosstalk. In addition, after the substrate is removed, the backside dielectric film and the metal film can also reflect the secondary photons passing through the narrow contact layer channel to the adjacent pixel to form crosstalk. SUMMARY

[0004] Embodiments of the present application provide a focal plane array device for preventing signal crosstalk and a manufacturing method thereof, to solve the problem of adjacent APD signal crosstalk in the focal plane array device in the related art, which affects the performance of the device.

[0005] The technical scheme provided by the present application is as follows:

[0006] In a first aspect, the present application provides a manufacturing method of a focal plane array device for preventing signal crosstalk, comprising the following steps:

[0007] An epitaxial layer is prepared on the surface of the substrate, and the epitaxial layer comprises, from top to bottom, a first contact layer, an absorption layer, a second contact layer, and a stop-etching layer;

[0008] The surface of the epitaxial layer is etched to form a focal plane array mesa;

[0009] A passivation film is prepared on the surface of the focal plane array mesa;

[0010] Etching is performed to remove the passivation film at the bottom of the focal plane array mesa;

[0011] A metal electrode layer is deposited on the bottom and sidewall of the focal plane array mesa;

[0012] An In column is prepared on the top of the focal plane array mesa, and a readout circuit is connected to the surface of the In column;

[0013] A colloid is filled between the readout circuit and the epitaxial layer;

[0014] The substrate and the stop-etching layer are removed;

[0015] The second contact layer at the bottom of the focal plane array mesa is etched to expose the metal electrode layer;

[0016] An anti-reflection film is prepared on the surface of the second contact layer, and the anti-reflection film is provided with a metal electrode layer exposure hole;

[0017] A back electrode is prepared on the surface of the exposed metal electrode layer.

[0018] In some embodiments, the first contact layer is a P contact layer, and the second contact layer is an N contact layer;

[0019] Alternatively, the first contact layer is an N contact layer, and the second contact layer is a P contact layer.

[0020] In some embodiments, the focal plane array mesa comprises a plurality of protrusions, and an isolation groove is arranged between two adjacent protrusions, and the depth of the isolation groove reaches the second contact layer.

[0021] In some embodiments, the step of etching to remove the passivation film at the bottom of the focal plane array mesa comprises the following steps:

[0022] Etching is performed to remove the passivation film on the bottom wall and the sidewall of the isolation groove.

[0023] In some embodiments, the metal electrode layer covers the bottom wall and the sidewall of the isolation groove and extends to the top surface of the protrusion.

[0024] In some embodiments, the inclination angle of the protrusion is less than 70°.

[0025] In some embodiments, "etching the second contact layer at the bottom of the mesa of the focal plane array to expose the metal electrode layer" comprises the following steps:

[0026] Etching to remove the second contact layer at the bottom of the isolation groove to expose the metal electrode layer.

[0027] In some embodiments, "making the back electrode on the surface of the exposed metal electrode layer" comprises the following steps:

[0028] Depositing metal on the surface of the metal electrode layer at the bottom of the isolation groove away from the readout circuit to form the back electrode.

[0029] In some embodiments, and / or, the ICP etching is used to remove the etching stop layer (204);

[0030] And / or, the antireflection film (9) is grown by ICP-CVD technology.

[0031] In a second aspect, the application provides a focal plane array device for preventing signal crosstalk, which is prepared by the method described above.

[0032] The technical solutions provided by the application have the following beneficial effects:

[0033] After the metal electrode layer is covered on the sidewall of the focal plane array mesa in the application, the path channel of the photons transmitted to the adjacent APD through the sidewall of the mesa is completely shielded by the metal electrode layer covered by the sidewall of the mesa.

[0034] The application completely separates each pixel by etching the back contact layer, and blocks the transmission of the photons to the adjacent pixel through the contact layer channel by means of the reflection of the back medium film and the metal film, so that the application can further suppress the crosstalk problem of the adjacent APD in the focal plane array, and achieve the purpose of almost completely eliminating the crosstalk. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0036] Figure 1 The structure schematic diagram of the substrate and epitaxial layer in the embodiments of the application;

[0037] Figure 2 The structure schematic diagram of the focal plane array mesa after formation in the embodiments of the application;

[0038] Figure 3 The structure schematic diagram of the passivation film after formation in the embodiments of the application;

[0039] Figure 4 Structure schematic diagram of the structure after forming the metal electrode layer in the embodiment of the present application;

[0040] Figure 5 Structure schematic diagram of the structure after forming the In column, the readout circuit and the colloid in the embodiment of the present application;

[0041] Figure 6 Structure schematic diagram of the structure after removing the substrate in the embodiment of the present application;

[0042] Figure 7 Structure schematic diagram of the structure after etching the second contact layer in the embodiment of the present application;

[0043] Figure 8 Structure schematic diagram of the structure after forming the back electrode and the anti-reflection film in the embodiment of the present application;

[0044] Figure 9 Structure schematic diagram of the focal plane array device provided by the prior art;

[0045] Figure 10 Structure schematic diagram of the focal plane array device for preventing signal crosstalk provided by the present application;

[0046] Figure 11 Flow chart of the manufacturing method of the focal plane array device for preventing signal crosstalk provided by the present application.

[0047] The reference signs are as follows: 1, substrate; 2, epitaxial layer; 201, first contact layer; 202, absorption layer; 203, second contact layer; 204, etching stop layer; 3, focal plane array mesa; 301, boss; 302, isolation groove; 4, passivation film; 5, metal electrode layer; 6, In column; 7, readout circuit; 8, colloid; 9, anti-reflection film; 10, back electrode; 11, metal electrode. DETAILED DESCRIPTION

[0048] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in a clear and complete manner in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0049] Referring to Figures 1-8 and Figure 11 , the first aspect, the embodiment of the present application provides a manufacturing method of a focal plane array device for preventing signal crosstalk, comprising the following steps:

[0050] 101: An epitaxial layer 2 is made on the surface of the substrate 1, and the epitaxial layer 2 comprises, from top to bottom, a first contact layer 201, an absorption layer 202, a second contact layer 203, and an etching stop layer 204;

[0051] 102: The surface of the epitaxial layer 2 is etched to form a focal plane array mesa 3;

[0052] 103: A passivation film 4 is prepared on the surface of the focal plane array mesa 3;

[0053] 104: Etching is performed to remove the passivation film 4 at the bottom of the focal plane array mesa 3;

[0054] 105: A metal electrode layer 5 is deposited on the bottom and sidewall of the focal plane array mesa 3;

[0055] 106: An In column 6 is prepared on the top of the focal plane array mesa 3, and a readout circuit 7 is connected to the surface of the In column 6;

[0056] 107: A colloid 8 is filled between the readout circuit 7 and the epitaxial layer 2;

[0057] 108: The substrate 1 and the etching stop layer 204 are removed;

[0058] 109: The second contact layer 203 at the bottom of the focal plane array mesa 3 is etched to expose the metal electrode layer 5;

[0059] 110: An anti-reflection film 9 is prepared on the surface of the second contact layer 203, and the anti-reflection film 9 is provided with a metal electrode layer exposure hole;

[0060] 111: A back electrode 10 is prepared on the surface of the exposed metal electrode layer 5.

[0061] The applicant has found, through research, that the existing way of suppressing adjacent signal crosstalk of a focal plane array device by using a substrate removal technology and a deep mesa isolation technology (see Figure 9 The existing way still has two signal crosstalk paths, one is path 1 shown at arrow A, and the other is path 2 shown at arrow B. The secondary photons of the part of the secondary light emitted outward by the target pixel after excitation are transmitted to the adjacent pixel through the space channel of path 1 to form crosstalk. The secondary photons of the part of the secondary light emitted outward by the target pixel after excitation can be transmitted to the adjacent pixel through the reflection of the back medium film and the metal film from the narrow contact layer channel to form crosstalk.

[0062] In the method provided in the present application, the metal electrode layer 5 and the back electrode 10 can effectively block the above two crosstalk paths (see Figure 10The path 1 is shielded by the metal electrode layer 5 on the sidewall of the focal plane array device, and the path 2 is shielded by the back electrode 10 at the bottom of the focal plane array device and the metal electrode layer 5, so that the metal electrode layer 5 and the back electrode 10 completely isolate each pixel, effectively avoiding the problem of signal crosstalk between adjacent APDs, improving the performance of the focal plane array device, and improving the resolution of the focal plane array device to the target.

[0063] In some embodiments, the first contact layer 201 is a P contact layer, and the second contact layer 203 is an N contact layer.

[0064] Alternatively, the first contact layer 201 is an N contact layer, and the second contact layer 203 is a P contact layer.

[0065] The epitaxial layer in the focal plane array device provided by the present application can include, from top to bottom, a P contact layer, an absorption layer, an N contact layer, and a corrosion stop layer;

[0066] Alternatively, from top to bottom, the epitaxial layer can include an N contact layer, an absorption layer, a P contact layer, and a corrosion stop layer.

[0067] Specifically, referring to Figures 4-5 As shown in the figure, "preparing an In column 6 on the top of the focal plane array mesa 3, and connecting a readout circuit 7 to the surface of the In column 6" specifically includes:

[0068] Etching to remove part of the passivation film on the top of the focal plane array mesa 3, to expose the first contact layer 201, depositing a metal layer on the exposed first contact layer 201, and then making the In column 6 on the metal layer, and then installing the readout circuit 7 on the In column 6 through flip-chip technology.

[0069] After flip-chip, the readout circuit 7 and the epitaxial layer 2 are filled with a gel 8.

[0070] Further, the material of the gel 8 is preferably epoxy resin.

[0071] Further, the metal layer is not in contact with the metal electrode layer 5.

[0072] In some embodiments, the focal plane array mesa 3 includes a plurality of bosses 301, and each two adjacent bosses 301 has an isolation groove 302, and the depth of the isolation groove 302 reaches the second contact layer 203.

[0073] Specifically, each boss 301 is a pixel, and the depth of the isolation groove 302 reaches the second contact layer 203, so that the pixels on both sides are completely isolated.

[0074] Further, the epitaxial layer 2 can be etched by ICP to form the focal plane array mesa 3.

[0075] Referring toFigures 3-4 As shown in some embodiments, the step of etching the passivation film 4 at the bottom of the FPA mesa 3 includes the following steps:

[0076] The step of etching removes the passivation film 4 on the bottom wall of the isolation groove 302 and the side wall of the isolation groove 302 that is in contact with the surface of the second contact layer 203.

[0077] Further, the passivation film on the bottom wall of the isolation groove 302 and the passivation film on the side wall of the isolation groove 302 that is in contact with the second contact layer 203 can be removed by RIE etching method. Based on this, after the metal electrode layer 5 is deposited on the surface of the isolation groove 302, the metal electrode layer 5 can connect the second contact layers 203 on both sides.

[0078] Referring to Figure 4 As shown in some embodiments, the metal electrode layer 5 covers the bottom wall and the side wall of the isolation groove 302 and extends to the top surface of the boss 301.

[0079] By extending the metal electrode layer 5 to the top surface of the boss 301, the transmission of secondary photons along the path 1 can be maximally blocked.

[0080] In some embodiments, the inclination angle of the boss 301 is <70°.

[0081] The inclination angle of the boss 301 is <70°, which can ensure the operability of subsequent steps.

[0082] Specifically, the metal electrode layer 5 can be prepared by magnetron sputtering method.

[0083] Referring to Figure 7 As shown in some embodiments, the step of etching the second contact layer 203 at the bottom of the FPA mesa 3 to expose the metal electrode layer 5 includes the following steps:

[0084] The step of etching removes the second contact layer 203 at the bottom of the isolation groove 302 to expose the metal electrode layer 5.

[0085] Specifically, the second contact layer 203 below the bottom wall of the isolation groove 302 can be removed by photolithography and ICP etching method, so that the back surface of the FPA device exposes the metal electrode layer 5.

[0086] Further, under the support of the colloid 8, the exposed metal electrode layer 5 will not collapse and deform.

[0087] Specifically, after the metal electrode layer 5 is exposed, an antireflection film 9 is made on the surface of the second contact layer 203 away from the readout circuit 7, and the antireflection film is provided with a metal electrode layer exposure hole. Further, the position of the metal electrode layer exposure hole corresponds to the bottom wall of the isolation groove 302.

[0088] Referring to Figure 8 As shown in some embodiments, "forming the back electrode 10 on the surface of the bare metal electrode layer 5" includes the following steps:

[0089] Depositing metal on the surface of the metal electrode layer 5 at the bottom of the isolation groove 302 away from the readout circuit 7 to form the back electrode 10.

[0090] The surface of the metal electrode layer 5 exposed in the above step is deposited with metal by an electron beam evaporation device to form the back electrode 10.

[0091] Preferably, the top surface of the back electrode 10 is flush with the outer surface of the anti-reflection film 9.

[0092] In some embodiments, the anti-reflection film 9 is grown by ICP-CVD technology.

[0093] Further, the growth temperature of the anti-reflection film 9 is preferably lower than 100℃.

[0094] In some embodiments, the substrate 1 is removed by wet etching.

[0095] The etching stop layer 204 is removed by ICP etching.

[0096] In a second aspect, the application provides a focal plane array device for preventing signal crosstalk, which is prepared by the method as described above.

[0097] In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise specified and limited, the terms "mounting", "connecting", "connecting" should be interpreted broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected internally between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0098] It should be noted that, in the present application, the relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another, without necessarily requiring or implying any actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0099] The foregoing is merely illustrative of the principles of the application and various modifications can be made by those skilled in the art without departing from the spirit and scope of the application. The above embodiments are illustrative, and not restrictive, of the scope of the application.

Claims

1. A method of fabricating a focal plane array device that prevents signal cross-talk, comprising: The method comprises the following steps: An epitaxial layer (2) is prepared on the surface of a substrate (1), and the epitaxial layer (2) comprises, from top to bottom, a first contact layer (201), an absorption layer (202), a second contact layer (203), and a corrosion stop layer (204); The surface of the epitaxial layer (2) is etched to form a focal plane array mesa (3); A passivation film (4) is prepared on the surface of the focal plane array mesa (3); Etching is performed to remove the passivation film (4) at the bottom of the focal plane array mesa (3); A metal electrode layer (5) is deposited on the bottom and sidewall of the focal plane array mesa (3); An In column (6) is prepared on the top of the focal plane array mesa (3), and a readout circuit (7) is connected to the surface of the In column (6); A colloid (8) is filled between the readout circuit (7) and the epitaxial layer (2); The substrate (1) and the corrosion stop layer (204) are removed; The second contact layer (203) at the bottom of the focal plane array mesa (3) is etched to expose the metal electrode layer (5); An anti-reflection film (9) is prepared on the surface of the second contact layer (203), and the anti-reflection film (9) is provided with a metal electrode layer exposure hole; A back electrode (10) is prepared on the surface of the exposed metal electrode layer (5). The focal plane array mesa (3) comprises a plurality of bosses (301), and an isolation groove (302) is arranged between two adjacent bosses (301), and the depth of the isolation groove (302) reaches the second contact layer (203).

2. The method for fabricating a focal plane array device for preventing signal crosstalk as described in claim 1, characterized in that, The first contact layer (201) is a P contact layer, and the second contact layer (203) is an N contact layer. Alternatively, the first contact layer (201) is an N contact layer, and the second contact layer (203) is a P contact layer.

3. The method of claim 1, wherein the step of forming a plurality of signal lines comprises the step of: forming a plurality of signal lines on the substrate, wherein the plurality of signal lines are formed in a pattern that is substantially the same as a pattern of the plurality of signal lines formed on the substrate of the infrared focal plane array device. The etching to remove the passivation film (4) at the bottom of the focal plane array mesa (3) comprises the following steps: Etching is performed to remove the passivation film (4) on the bottom wall of the isolation groove (302) and the sidewall of the isolation groove (302) located on the surface of the second contact layer (203).

4. The method for fabricating a focal plane array device for preventing signal crosstalk as described in claim 1, characterized in that, The metal electrode layer (5) covers the bottom wall and sidewall of the isolation groove (302) and extends to the top surface of the boss (301).

5. The method for fabricating a focal plane array device for preventing signal crosstalk as described in claim 1, characterized in that, The inclination angle of the boss (301) is less than 70°.

6. The method for fabricating a focal plane array device for preventing signal crosstalk as described in claim 1, characterized in that, The etching of the second contact layer (203) at the bottom of the focal plane array mesa (3) to expose the metal electrode layer (5) comprises the following steps: Etching is performed to remove the second contact layer (203) at the bottom of the isolation groove (302) to expose the metal electrode layer (5).

7. The method of claim 1, wherein the signal crosstalk prevention FPA device is a complementary metal-oxide-semiconductor (CMOS) device. The preparation of the back electrode (10) on the surface of the exposed metal electrode layer (5) comprises the following steps: Metal is deposited on the surface of the metal electrode layer (5) at the bottom of the isolation groove (302) away from the readout circuit (7) to form the back electrode (10).

8. The method for fabricating a focal plane array device for preventing signal crosstalk as described in claim 1, characterized in that, The substrate (1) is removed by wet etching; And / or, the corrosion stop layer (204) is removed by ICP etching; And / or, the anti-reflection film (9) is grown by ICP-CVD technology.

9. A focal plane array device for preventing signal cross-talk, comprising: The focal plane array mesa (3) is prepared by the method according to any one of claims 1-8.

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