Infrared detector, hybrid chip and back thinning scratch treatment method thereof

Abstract

The present invention discloses an infrared detector, a hybrid chip and a method for processing back thinning scratches thereof. The method for processing back thinning scratches of an infrared detector hybrid chip comprises: thinning the infrared detector hybrid chip to a preset thickness; removing the edge area of ​​the photosensitive chip in the infrared detector hybrid chip thinned to the preset thickness; grinding and polishing the infrared detector hybrid chip with the edge area of ​​the photosensitive chip removed to a target thickness, wherein the preset thickness is greater than the target thickness. According to the present invention, by thinning the infrared detector hybrid chip to a preset thickness, most of the thickness of the photosensitive chip can be removed, and the surface shape of the hybrid chip can be optimized due to a portion of stress release, and the overall flatness can be improved. In addition, an etching or corrosion process is added to form a smooth edge of the photosensitive chip device, thereby reducing the possibility of material slag and scratches in the subsequent grinding and polishing process, and at the same time, by removing a thickness of tens of microns, the scratches that appeared in the previous thinning process are removed.

Description

Technical Field

[0001] The invention relates to the field of preparation of hybrid chips for infrared detectors, and in particular to an infrared detector, a hybrid chip and a back thinning and scratch treatment method thereof. Background Art

[0002] The infrared detector hybrid chip is the core of the infrared detector. The hybrid chip is made by flip-chip interconnecting a photosensitive chip and a silicon readout circuit chip. Before interconnection, the thickness of the silicon circuit chip and the readout circuit chip are both several hundred microns. After interconnection, in order to maximize the quantum efficiency of the optical signal, the photosensitive chip needs to be thinned to a dozen or even several microns. At present, the more mature thinning processes such as Figure 16-Figure 17 As shown, the hybrid chip is turned upside down on the grinding and polishing disc or pad of the grinding and polishing equipment, and pressure is applied and grinding and polishing liquid is added. Under the action of the rotation and revolution of the grinding and polishing disc and the hybrid chip, a physical and chemical reaction is achieved between the photosensitive chip in the hybrid chip and the grinding and polishing liquid and the grinding and polishing pad. The photosensitive chip is gradually thinned to the required thickness through rough polishing and fine polishing processes.

[0003] However, it was found during the process that there is a certain probability that the photosensitive chip thinned to the target thickness has scratches on its surface. When the hybrid chip is packaged into the Dewar structure for imaging, the presence of the scratches will affect the performance of the corresponding pixel on the device, forming a line different from other normal areas on the image, affecting the image quality. The scratches are generated during the grinding and polishing process. If hard particles are mixed into the grinding and polishing liquid during the grinding and polishing process, there is a certain probability of leaving scratches on the surface of the wafer. If the scratches and their damage are not effectively removed after grinding and polishing, scratches will be left on the wafer or imaging. During the grinding and polishing process, the sources of hard particles are divided into two categories. One is the material residue that falls off the chip itself, and the other is the insufficient cleaning of the grinding and polishing pad, or the decrease in cleanliness after long-term use. For the cleaning problem of the grinding and polishing pad, the cleaning frequency of the grinding and polishing pad can be increased, and the use time of the grinding and polishing pad can be reduced to reduce the probability of contamination. The material residue mainly comes from the surrounding area of ​​the photosensitive chip. The photosensitive chip is cut by the scribing process, which is a physical cutting process of the material by a high-speed rotating blade. The device prepared by this process will have various burrs such as edge collapse, corner collapse, micro cracks, etc. caused by the cutting stress. Fig.18 As shown. The existence of the stress of the hybrid chip itself makes the chip present a morphology with a concave center and warped surroundings. When the hybrid chip with this morphology is turned upside down on the grinding and polishing pad for grinding and polishing, the microcracks and broken materials at the edges of the four sides of the smooth chip will fall off from the material surface under the action of grinding and polishing rotation and pressure, and remain on the grinding and polishing pad. Once it comes into contact with the chip during the grinding and polishing process, it is easy to leave a scratch on the surface of the chip. If the subsequent thinning thickness does not exceed the scratch and its damage depth, this scratch will exist on the surface of the photosensitive chip in the form of a scratch, affecting the optoelectronic performance of the device. Summary of the invention

[0004] The embodiment of the present invention provides an infrared detector, a hybrid chip and a back thinning scratch treatment method thereof, so as to solve the problem in the prior art that there is a certain probability of scratches on the surface of the photosensitive chip thinned to a target thickness during the photosensitive chip polishing process.

[0005] The method for processing back thinning and scratches of an infrared detector hybrid chip according to an embodiment of the present invention comprises:

[0006] Thinning the infrared detector hybrid chip to a preset thickness;

[0007] Removing the edge area of ​​the photosensitive chip in the infrared detector hybrid chip thinned to a preset thickness;

[0008] The infrared detector hybrid chip with the edge area of ​​the photosensitive chip removed is polished to a target thickness, wherein the preset thickness is greater than the target thickness to remove possible scratch damage and at the same time make the photosensitive chip reach the expected thickness.

[0009] According to some embodiments of the present invention, thinning the infrared detector hybrid chip to a preset thickness includes:

[0010] The back side of the infrared detector hybrid chip is bonded to the substrate, and the front side of the infrared detector hybrid chip is thinned by a single-point cutting process;

[0011] The infrared detector hybrid chip thinned to a preset thickness is separated from the substrate and cleaned.

[0012] According to some embodiments of the present invention, thinning the infrared detector hybrid chip to a preset thickness includes:

[0013] The back side of the infrared detector hybrid chip is bonded to the substrate, and the front side of the infrared detector hybrid chip is thinned by a grinding and polishing process;

[0014] The infrared detector hybrid chip thinned to a preset thickness is separated from the substrate and cleaned.

[0015] According to some embodiments of the present invention, removing the edge region of the photosensitive chip in the infrared detector hybrid chip thinned to a preset thickness includes:

[0016] Applying photoresist to the leakage area of ​​the readout circuit in the infrared detector hybrid chip;

[0017] Applying photoresist to the central area of ​​the photosensitive chip except the edge area;

[0018] The infrared detector hybrid chip coated with photoresist is processed by wet etching or dry etching process to remove the exposed photosensitive chip;

[0019] The photoresist is removed.

[0020] According to some embodiments of the present invention, applying photoresist to the leakage area of ​​the readout circuit in the infrared detector hybrid chip includes:

[0021] Apply photoresist to all the external leakage areas of the readout circuit.

[0022] According to some embodiments of the present invention, the step of grinding and polishing the infrared detector hybrid chip with the edge area of ​​the photosensitive chip removed to a target thickness includes:

[0023] The back side of the infrared detector hybrid chip with the edge area of ​​the photosensitive chip removed is bonded to the substrate, and the front side of the infrared detector hybrid chip is polished by a polishing process;

[0024] The infrared detector hybrid chip polished to a target thickness is separated from the substrate and cleaned.

[0025] According to the infrared detector hybrid chip of the embodiment of the present invention, the infrared detector hybrid chip is obtained by processing the infrared detector hybrid chip back thinning and scratching processing method as described above.

[0026] An infrared detector according to an embodiment of the present invention includes the infrared detector hybrid chip as described above.

[0027] By adopting the embodiment of the present invention, the infrared detector hybrid chip is thinned to a preset thickness to achieve the removal of most of the thickness of the photosensitive chip. The hybrid chip will be optimized due to the stress release of a part of the surface shape, and the overall flatness will be improved. At this time, in the subsequent undercut grinding and polishing process, the situation that the grinding and polishing pressure on the periphery of the photosensitive chip is greater than the grinding and polishing pressure on the central area will be alleviated, reducing the probability of slag falling off the edge of the device. In addition, an etching or corrosion process is added to form a smooth device edge, reducing the possibility of material slag and scratches in the subsequent grinding and polishing process. At the same time, by removing tens of microns of thickness, the scratches that appeared in the previous thinning process are removed.

[0028] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Various other advantages and benefits will become apparent to those skilled in the art by reading the detailed description of the embodiments below. The accompanying drawings are only used to illustrate the preferred embodiments and are not to be considered as limiting the present invention. In the accompanying drawings:

[0030] Figure 1 This is a flow chart of a method for processing back thinning and scratching of an infrared detector hybrid chip according to an embodiment of the present invention;

[0031] Figure 2-Figure 3 It is a schematic diagram of thinning the infrared detector hybrid chip to a preset thickness in the first embodiment of the present invention;

[0032] Figure 4-Figure 6 Schematic diagram of the edge area of ​​the photosensitive chip in the infrared detector hybrid chip which is thinned to a preset thickness in the first embodiment of the present invention;

[0033] Figure 7-Figure 8 1 is a schematic diagram of grinding and polishing the infrared detector hybrid chip with the edge area of ​​the photosensitive chip removed to a target thickness in the first embodiment of the present invention;

[0034] Figure 9-10 is a schematic diagram of thinning the infrared detector hybrid chip to a preset thickness in the second embodiment of the present invention;

[0035] Figure 11-13 is a schematic diagram of removing the edge area of ​​the photosensitive chip in the infrared detector hybrid chip thinned to a preset thickness in the second embodiment of the present invention;

[0036] Figure 14-15 is a schematic diagram of grinding and polishing the infrared detector hybrid chip with the edge area of ​​the photosensitive chip removed to a target thickness in the second embodiment of the present invention;

[0037] Fig.16 It is a schematic diagram of the back thinning process of the hybrid chip of the infrared detector in the prior art;

[0038] Fig.17 It is a schematic diagram of the back thinning process of the hybrid chip of the infrared detector in the prior art;

[0039] Fig.18 It is a schematic diagram of edge collapse of a hybrid chip of an infrared detector in the prior art. DETAILED DESCRIPTION

[0040] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0041] The first embodiment of the present invention provides a method for processing back thinning scratches of an infrared detector hybrid chip, such as Figure 1 As shown, including:

[0042] S1, thinning the infrared detector hybrid chip to a preset thickness;

[0043] It should be noted here that the infrared detector hybrid chip has completed the interconnection process before being thinned to a preset thickness, that is, the flip-chip interconnection preparation process of the photosensitive chip and the silicon readout circuit chip has been completed.

[0044] S2, removing the edge area of ​​the photosensitive chip in the infrared detector hybrid chip thinned to a preset thickness;

[0045] S3, grinding and polishing the infrared detector hybrid chip with the edge area of ​​the photosensitive chip removed to a target thickness, wherein the preset thickness is greater than the target thickness to remove possible scratch damage and at the same time make the photosensitive chip reach the expected thickness.

[0046] By adopting the embodiment of the present invention, the infrared detector hybrid chip is thinned to a preset thickness to achieve the removal of most of the thickness of the photosensitive chip. The hybrid chip will be optimized due to the stress release of a part of the surface shape, and the overall flatness will be improved. At this time, in the subsequent undercut grinding and polishing process, the situation that the grinding and polishing pressure on the periphery of the photosensitive chip is greater than the grinding and polishing pressure on the central area will be alleviated, reducing the probability of slag falling off the edge of the device. In addition, an etching or corrosion process is added to form a smooth device edge, reducing the possibility of material slag and scratches in the subsequent grinding and polishing process. At the same time, by removing tens of microns of thickness, the scratches that appeared in the previous thinning process are removed.

[0047] On the basis of the above-mentioned embodiments, various variant embodiments are further proposed. It should be noted that, in order to make the description concise, only the differences from the above-mentioned embodiments are described in each variant embodiment.

[0048] like Figure 2-Figure 3 As shown, according to some embodiments of the present invention, thinning the infrared detector hybrid chip to a preset thickness includes:

[0049] The back side of the infrared detector hybrid chip is bonded to the substrate, and the front side of the infrared detector hybrid chip is thinned by a single-point cutting process;

[0050] The infrared detector hybrid chip thinned to a preset thickness is separated from the substrate and cleaned.

[0051] like Figure 9-10 As shown, according to some embodiments of the present invention, thinning the infrared detector hybrid chip to a preset thickness includes:

[0052] The back side of the infrared detector hybrid chip is bonded to the substrate, and the front side of the infrared detector hybrid chip is thinned by a grinding and polishing process;

[0053] The infrared detector hybrid chip thinned to a preset thickness is separated from the substrate and cleaned.

[0054] like Figure 4-Figure 6 , Figure 11-13 As shown, according to some embodiments of the present invention, removing the edge area of ​​the photosensitive chip in the infrared detector hybrid chip thinned to a preset thickness includes:

[0055] Applying photoresist to the leakage area of ​​the readout circuit in the hybrid infrared detector chip;

[0056] Applying photoresist on a central area of ​​a side of the photosensitive chip away from the readout circuit;

[0057] The infrared detector hybrid chip coated with photoresist is processed by wet etching or dry etching process to remove the exposed photosensitive chip material, that is, to remove the edge of the photosensitive chip to form a smooth photosensitive chip edge morphology;

[0058] The photoresist is removed.

[0059] According to some embodiments of the present invention, applying photoresist to the leakage area of ​​the readout circuit in the hybrid infrared detector chip includes:

[0060] Apply photoresist to all the external leakage areas of the readout circuit.

[0061] like Figure 7-Figure 8 , Figure 14-15 As shown, according to some embodiments of the present invention, the step of grinding and polishing the infrared detector hybrid chip with the edge area of ​​the photosensitive chip removed to a target thickness includes:

[0062] The back side of the infrared detector hybrid chip with the edge area of ​​the photosensitive chip removed is bonded to the substrate, and the front side of the infrared detector hybrid chip is polished by a polishing process;

[0063] The infrared detector hybrid chip polished to a target thickness is separated from the substrate and cleaned.

[0064] Refer to the following Figure 2-Figure 15 The method for processing back thinning and scratching of a hybrid chip of an infrared detector according to an embodiment of the present invention is described in detail with two specific embodiments. It is worth noting that the following description is only an exemplary description and is not a specific limitation of the present invention. All similar structures and similar variations of the present invention should be included in the protection scope of the present invention.

[0065] The method for processing back thinning and scratches of an infrared detector hybrid chip according to the first embodiment of the present invention comprises the following steps:

[0066] The hybrid chip is bonded to the substrate with the front side facing up, and the photosensitive chip with a thickness of several hundred microns is thinned to several tens of microns by a single-point cutting process (the retained thickness is greater than the sum of the chip surface roughness and damage thickness caused by the single-point cutting process and the target chip thickness that needs to be removed by the subsequent grinding and polishing process). The hybrid chip is removed and cleaned. Figure 2-Figure 3 shown.

[0067] The photolithography process is used to protect the central area of ​​the photosensitive chip and the silicon circuit, and a certain width of area is left around the photosensitive chip (to ensure that the exposed area is away from the working area of ​​the photosensitive chip). Figure 4 shown.

[0068] Use wet etching or dry etching process to remove the material around the photosensitive chip that is not protected by the photoresist. This process removes the device edge formed by the dicing process, such as Figure 5 shown.

[0069] Remove the photoresist. At this time, the photosensitive chip has smooth edges formed by wet or dry etching process. Figure 6 shown.

[0070] The hybrid chip photosensitive chip is mounted face down on the grinding and polishing equipment to continue grinding and polishing, further reducing the thickness while removing the single-point car contamination and single-point car damage, and finally through fine polishing and chemical polishing to achieve a smooth and damage-free photosensitive chip surface preparation, such as Figure 7-Figure 8 shown.

[0071] The essence of the above embodiment is to remove most of the thickness of the photosensitive chip through a single-point diamond cutting process. As the thickness of the photosensitive chip decreases, the surface shape of the hybrid chip will be optimized due to the stress release of a part, and the overall flatness will be improved. At this time, in the subsequent undercut grinding and polishing process, the situation where the grinding and polishing pressure on the periphery of the photosensitive chip is greater than the grinding and polishing pressure on the central area will be alleviated, reducing the probability of chipping at the edge of the device. On the other hand, by smoothing the edges of the device after single-point cutting, the probability of chipping at the edge of the subsequent undercut grinding and polishing device is further reduced.

[0072] The method for processing backside thinning and scratches of an infrared detector hybrid chip according to the second embodiment of the present invention comprises the following steps:

[0073] Use grinding and polishing process to thin the photosensitive chip - bond the hybrid chip to the substrate, put it face down on the grinding and polishing equipment, and use grinding and polishing liquid of different particle sizes and grinding and polishing pads applied under different conditions to thin the photosensitive chip to tens of microns. The determination of the thickness to be retained depends on the roughness of the grinding and polishing surface to be removed by the subsequent fine polishing process, the maximum depth of the possible scratches and the target thickness of the chip, such as Figure 9-10 shown.

[0074] Remove the hybrid chip and clean it;

[0075] The photolithography process protects the central area of ​​the photosensitive chip and the silicon circuit, leaving a certain width around the photosensitive chip, such as Fig.11 shown.

[0076] Use wet etching or dry etching process to remove the material around the photosensitive chip that is not protected by the photoresist. This process removes the device edge formed by the dicing process, such as Fig.12 shown.

[0077] Remove the photoresist, and the photosensitive chip will be surrounded by smooth edges formed by wet or dry etching process, such as Fig.13 shown.

[0078] Place the hybrid chip photosensitive chip face down on the grinding and polishing equipment, replace the grinding and polishing pad (avoid the material residue on the previously used grinding and polishing pad), continue grinding and polishing, further reduce the thickness while removing the damage caused by the previous grinding and polishing, reduce the surface roughness, and eliminate the scratch damage that may have occurred in the previous process by removing enough thickness, and finally achieve the preparation of a smooth and damage-free photosensitive chip surface, such as Figure 14-15 shown.

[0079] The grinding and polishing process can be roughly divided into rough polishing, fine polishing, chemical polishing and even chemical etching. The specific process details are further subdivided into grinding and polishing of different granularities. The process design of this embodiment is based on the original mature grinding and polishing process of the process line, and an etching process step is added to achieve the preparation of the smooth edge of the photosensitive chip before the fine polishing process.

[0080] The essence of the above embodiment is to add an etching or corrosion process before removing the final tens of microns of material thickness to form a smooth device edge, thereby reducing the possibility of material slag and scratches in the subsequent grinding and polishing process. At the same time, by removing tens of microns of thickness, the scratches that appeared in the previous thinning process are removed.

[0081] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0082] A second aspect of the present invention provides an infrared detector hybrid chip, which is obtained by processing the infrared detector hybrid chip back thinning and scratching processing method as described in the first aspect of the present invention.

[0083] A third aspect of the present invention provides an infrared detector, comprising the infrared detector hybrid chip as described in the second aspect of the present invention.

[0084] It should be noted that, in the description of this specification, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and form different embodiments. The specific features, structures, materials or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. For example, in the claims, any one of the claimed embodiments can be used in any combination.

[0085] In addition, in the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

Claims

1. A method for processing back thinning and scratches of a hybrid infrared detector chip, characterized in that: include: The infrared detector hybrid chip comprises a flip-chip interconnected photosensitive chip and a silicon readout circuit chip, wherein the photosensitive chip in the infrared detector hybrid chip is thinned to a preset thickness; the infrared detector hybrid chip comprises a flip-chip interconnected photosensitive chip and a silicon readout circuit chip; Removing the edge area of ​​the photosensitive chip in the infrared detector hybrid chip thinned to a preset thickness to form a smooth device edge; The photosensitive chip in the infrared detector hybrid chip with the edge area of ​​the photosensitive chip removed is polished to a target thickness, wherein the preset thickness is greater than the target thickness to remove possible scratch damage and at the same time make the photosensitive chip reach the expected thickness.

2. The method according to claim 1, characterized in that The step of thinning the infrared detector hybrid chip to a preset thickness includes: The back side of the infrared detector hybrid chip is bonded to the substrate, and the front side of the infrared detector hybrid chip is thinned by a single-point cutting process; The infrared detector hybrid chip thinned to a preset thickness is separated from the substrate and cleaned.

3. The method according to claim 1, characterized in that The step of thinning the infrared detector hybrid chip to a preset thickness includes: The back side of the infrared detector hybrid chip is bonded to the substrate, and the front side of the infrared detector hybrid chip is thinned by a grinding and polishing process; The infrared detector hybrid chip thinned to a preset thickness is separated from the substrate and cleaned.

4. The method according to claim 1, characterized in that The method of removing the edge area of ​​the photosensitive chip in the infrared detector hybrid chip thinned to a preset thickness includes: Applying photoresist to the leakage area of ​​the readout circuit in the infrared detector hybrid chip; Applying photoresist to the central area of ​​the photosensitive chip except the edge area; The infrared detector hybrid chip coated with photoresist is processed by wet etching or dry etching process to remove the exposed photosensitive chip; The photoresist is removed.

5. The method according to claim 4, characterized in that The step of applying photoresist to the leakage area of ​​the readout circuit in the hybrid infrared detector chip comprises: Apply photoresist to all the external leakage areas of the readout circuit.

6. The method according to claim 1, characterized in that The step of grinding and polishing the infrared detector hybrid chip with the edge area of ​​the photosensitive chip body removed to a target thickness comprises: The back side of the infrared detector hybrid chip with the edge area of ​​the photosensitive chip removed is bonded to the substrate, and the front side of the infrared detector hybrid chip is polished by a polishing process; The infrared detector hybrid chip polished to a target thickness is separated from the substrate and cleaned.

7. An infrared detector hybrid chip, characterized in that: The infrared detector hybrid chip is obtained by processing the infrared detector hybrid chip back thinning and scratching processing method according to any one of claims 1 to 6.

8. An infrared detector, characterized in that: Comprising the infrared detector hybrid chip as described in claim 7.

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