Method for permanent bonding of infrared chip and reading circuit without dielectric layer

Abstract

The invention provides a method for permanent bonding of an infrared chip and a readout circuit without a dielectric layer. The method comprises the following steps: passivating the surface of the infrared chip; depositing an intermediate layer on the surface of the infrared chip; cleaning and drying the surface of the infrared chip on which the intermediate layer is currently deposited; activating the surface of the infrared chip and the surface of the readout circuit wafer; enabling the middle layer of the infrared chip to face downwards, and carrying out pre-bonding with the readout circuit wafer; and carrying out annealing treatment on the pre-bonded infrared chip and the reading circuit. According to the method provided by the invention, the process problem of etching the through hole in the detector with the ring hole structure due to the existence of the dielectric layer is avoided, and meanwhile, the situation that the performance of the chip is reduced and blind pixels are increased due to stress accumulation formed on the tellurium-cadmium-mercury chip due to the existence of the bonding glue is also avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor processes, and in particular, to a method for permanent bonding without a dielectric layer between an infrared chip and a readout circuit. Background Art

[0002] The ring aperture structure has great advantages in the manufacturing processes of ultra-large area arrays, ultra-small pitch, and dual / multi-color infrared detectors. The ring aperture structure is as Figure 1 shown. The bonding of a mercury cadmium telluride (MCT) chip and a readout circuit is one of the key processes for realizing the fabrication of ring aperture structure detectors. When bonding an infrared detector with a ring aperture structure between an MCT chip and a readout circuit, factors such as bonding strength, via etching depth, and metal sidewall coverage need to be considered. Generally, an epoxy resin adhesive bonding method is used (such as Figure 1 the black part).

[0003] However, the epoxy resin adhesive bonding process has many drawbacks. Its process flow can be referred to Figures 2a - 2d : 1) Both the MCT chip and the silicon readout circuit chip are square chips. The spin coating uniformity of square chips cannot be guaranteed, so it is difficult to ensure the uniformity of the bonding thickness. 2) During backside via etching, it is difficult to remove the epoxy resin adhesive by plasma etching, which affects electrical conduction. 3) The thermal expansion coefficient of the epoxy resin adhesive is quite different from that of the MCT chip and the readout circuit, which will cause stress accumulation in the MCT chip, and ultimately lead to a decrease in chip performance and an increase in blind pixels during repeated power-on and power-off operations. Summary of the Invention

[0004] The technical problem to be solved by the present invention is how to avoid the influence of the traditional dielectric layer on the bonding thickness uniformity and the via preparation difficulty in the fabrication of ring aperture structure detectors. In view of this, the present invention provides a method for permanent bonding without a dielectric layer between an infrared chip and a readout circuit.

[0005] The technical solution adopted by the present invention is a method for permanent bonding without a dielectric layer between an infrared chip and a readout circuit, including: Step S1, passivating the surface of the infrared chip; Step S2, depositing an intermediate layer on the surface of the infrared chip; Step S3, cleaning and drying the surface of the infrared chip on which the intermediate layer is currently deposited; Step S4, activating the surfaces of the infrared chip and the readout circuit wafer; Step S5, pre-bonding the infrared chip with the intermediate layer downwards to the readout circuit wafer; Step S6: Anneal the pre-bonded infrared chip and the readout circuit.

[0006] In one embodiment, the infrared chip is a mercury cadmium telluride chip.

[0007] In one embodiment, the intermediate layer is a silicon dioxide layer.

[0008] In one embodiment, an ICP device is used to perform surface activation on the surface of the infrared chip and the readout circuit wafer.

[0009] In one embodiment, the process parameters of the annealing treatment are at least: 200 °C / 30 min.

[0010] In one embodiment, the thickness of the silicon dioxide layer is 200 nm ± 10%.

[0011] Another aspect of the present invention also provides an infrared detector, including: an infrared chip and a readout circuit, wherein the infrared chip and the readout circuit are bonded by the method for permanent bonding of an infrared chip and a readout circuit without a dielectric layer as described in any one of the above.

[0012] Compared with the prior art, the present invention has at least the following advantages: The method provided by the embodiments of the present invention can be used to avoid the process problems of via etching in the ring hole structure detector caused by the presence of the dielectric layer, and at the same time avoid the stress accumulation caused by the presence of the bonding glue in the mercury cadmium telluride chip, which reduces the chip performance and increases the number of blind pixels. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic structural diagram of a ring hole structure infrared detector chip in the prior art; Figures 2a - 2d is a process flow chart of the epoxy resin bonding process of the ring hole structure infrared detector chip in the prior art; Figure 3 is a schematic flow chart of the method for permanent bonding of an infrared chip and a readout circuit without a dielectric layer according to an embodiment of the present invention; Figure 4 is a schematic diagram of the implementation principle of the method for permanent bonding of an infrared chip and a readout circuit without a dielectric layer according to an embodiment of the present invention; Figures 5a - 5e is a schematic process flow chart of the method for permanent bonding of an infrared chip and a readout circuit without a dielectric layer according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined purpose, the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0015] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms (such as those defined in a common dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0016] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments may be combined with each other. The following will describe this application in detail with reference to the drawings and in combination with the embodiments.

[0017] An embodiment of the present invention, a method for permanent bonding of an infrared chip and a readout circuit without a dielectric layer, as Figure 3 shown, includes: Step S1, passivate the surface of the infrared chip; Step S2, deposit an intermediate layer on the surface of the infrared chip; Step S3, clean and dry the surface of the infrared chip on which the intermediate layer is currently deposited; Step S4, surface activate the surface of the infrared chip and the readout circuit wafer; Step S5, with the intermediate layer of the infrared chip facing downwards, perform pre-bonding with the readout circuit wafer; Step S6, perform annealing treatment on the pre-bonded infrared chip and the readout circuit.

[0018] In this embodiment, the infrared chip is a mercury cadmium telluride chip.

[0019] In this embodiment, the intermediate layer is a silicon dioxide layer.

[0020] In this embodiment, an ICP device is used to surface activate the surface of the infrared chip and the readout circuit wafer.

[0021] In this embodiment, the process parameters of the annealing treatment are at least: 200 °C / 30 min.

[0022] In this embodiment, the thickness of the silicon dioxide layer is 200 nm ± 10%.

[0023] The following will describe the method provided in this embodiment in detail.

[0024] Referring to Figure 4 , in a specific implementation of this embodiment, the bonding method can be specifically implemented by the following method: a) Clean the surface impurities to increase the contact area and thus promote bonding; b) Change the surface chemical properties and introduce active groups to increase the bonding strength; Reference Figures 5a to 5e , the process flow of a specific embodiment of this embodiment is as follows: 1) Deposit a 200-nm-thick silicon dioxide layer on the surface of the mercury cadmium telluride chip after surface passivation; 2) Clean and dry the surface of the chip deposited with silicon dioxide; 3) Use an ICP device to perform surface activation on the surface of the infrared chip and the readout circuit wafer; 4) Pre-bond the infrared chip face down with the readout circuit wafer; 5) Anneal the pre-bonded chip and the readout circuit, and the process parameters are: 200 °C / 30 min.

[0025] That is: infrared material sheet → deposit SiO2 → surface activation → pre-bonding → annealing, permanent bonding completed.

[0026] Compared with the prior art, this embodiment has at least the following effects: The bonding method provided in this embodiment avoids the process difficulties of via etching in the ring hole structure detector caused by the existence of the dielectric layer, and also avoids the stress accumulation formed on the mercury cadmium telluride chip due to the existence of the bonding glue, which reduces the chip performance and increases the number of blind pixels.

[0027] In the second embodiment of the present invention, corresponding to the first embodiment, there is an infrared chip and a readout circuit, wherein the infrared chip and the readout circuit are bonded by the method for permanent bonding without a dielectric layer between the infrared chip and the readout circuit as described in the first embodiment.

[0028] Through the description of the specific embodiments, it should be possible to have a more in-depth and specific understanding of the technical means and effects adopted by the present invention to achieve the predetermined purpose. However, the accompanying drawings are only for reference and illustration, and are not used to limit the present invention.

Claims

1. A method for permanent bonding of an infrared chip and a readout circuit without a dielectric layer, characterized in that, Including: Step S1, passivate the surface of the infrared chip; Step S2, deposit an intermediate layer on the surface of the infrared chip; Step S3, clean and dry the surface of the infrared chip on which the intermediate layer is currently deposited; Step S4, perform surface activation on the surface of the infrared chip and the readout circuit wafer; Step S5, place the intermediate layer of the infrared chip downward and perform pre-bonding with the readout circuit wafer; Step S6, perform annealing treatment on the pre-bonded infrared chip and the readout circuit.

2. The method for permanent bonding without a dielectric layer between an infrared chip and a readout circuit according to claim 1, wherein The infrared chip is a mercury cadmium telluride chip.

3. The method for permanent bonding without a dielectric layer between an infrared chip and a readout circuit according to claim 1, characterized in that, The intermediate layer is a silicon dioxide layer.

4. The method for permanent bonding without a dielectric layer between an infrared chip and a readout circuit according to claim 1, characterized in that, Use an ICP device to perform surface activation on the surface of the infrared chip and the readout circuit wafer.

5. The method for permanent bonding without a dielectric layer between an infrared chip and a readout circuit according to claim 1, characterized in that, The process parameters of the annealing treatment are at least: 200 °C / 30 min.

6. The method for permanent bonding without a dielectric layer between an infrared chip and a readout circuit according to claim 3, characterized in that, The thickness of the silicon dioxide layer is 200 nm ± 10%.

7. An infrared detector, characterized in that, Including: An infrared chip and a readout circuit, wherein the infrared chip and the readout circuit are bonded by the method for permanent bonding of an infrared chip and a readout circuit without a dielectric layer according to any one of claims 1 to 6.

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