Contact pad processing method

Abstract

The invention relates to a contact pad processing method. Disclosed is an electronic circuit manufacturing method including, in order, forming an opening in a semiconductor substrate, the semiconductor substrate including a first surface and a second surface opposite the first surface, the opening being located between the first surface and the second surface, and forming a conductive pad, the conductive pad includes a first portion over the first surface and a second portion covering the flanks of the opening and defining a gap in the opening. And depositing a first layer covering the conductive pad and filling the gap, the first layer comprising a first resin, the first resin being non-photosensitive, and crosslinking the first resin in the first layer; and chemically etching the first layer by a plasma to define a first block of a first resin in the gap; and depositing a first protective layer on the first block.

Description

[0001] Cross - reference to related applications

[0002] This application is a translation of French Patent Application No. 23 / 15298, titled "Procédé de traitement de plots de reprise de contact", filed on December 26, 2023, and claims the benefit of its priority, which is hereby incorporated by reference in its entirety to the extent permitted by law. Technical field

[0003] The present disclosure generally relates to the field of electronic circuits, particularly to the field of image sensors including contact pads, and more particularly to methods of manufacturing image sensors. Background art

[0004] Image sensors typically include a plurality of photodetectors, such as photodiodes, integrated inside and on top of a semiconductor substrate. The top of the photodetectors may be covered by a layer of microlenses. This microlens layer enables focusing of incident radiation onto the photodetectors. The image sensor also includes contact pads that extend over one side of the substrate and through the semiconductor substrate, particularly when the image sensor is intended to be illuminated from this side. Such contact pads result in the presence of significant raised areas, which may particularly interfere with manufacturing steps after the formation of the contact pads, especially the formation of the microlens layer.

[0005] It is desirable to at least partially improve certain aspects of known methods for manufacturing image sensors including a microlens layer. Summary of the invention

[0006] Embodiments overcome all or part of the drawbacks of known image sensors.

[0007] Embodiments provide a method of manufacturing an electronic circuit, which successively includes the following steps:

[0008] a) forming an opening in a semiconductor substrate including a first surface and a second surface opposite the first surface, the opening extending from the first surface to the second surface, and forming at least one conductive pad including a first portion extending over the first surface and a second portion covering the flank of the opening and defining a gap in the opening;

[0009] b) depositing a first layer made of a first resin, the first resin being non - photosensitive, the first layer made of the first resin covering the conductive pad and filling the gap, and cross - linking the first layer made of the first resin;

[0010] c) chemically etching the first layer made of the first resin by plasma to define a first block of the first resin in the gap; and

[0011] d) Deposit a first protective layer on the first block.

[0012] According to one embodiment, the first surface includes a recess, the first portion is located in the recess, there is a groove between the first portion and the flank of the recess, a first layer made of a first resin fills the groove at step b), and at step c) a second block made of the first resin is further defined in the groove.

[0013] According to one embodiment, after step d), the method further sequentially includes the following steps:

[0014] e) Form a plurality of microlenses in a second layer made of a first resin and covering the first protective layer, wherein the plurality of microlenses do not cover the at least one conductive pad; and

[0015] f) Deposit a second protective layer on the plurality of microlenses and on the first protective layer around the plurality of microlenses.

[0016] According to one embodiment, forming a plurality of microlenses sequentially includes the following steps:

[0017] g) Deposit a second layer made of a first resin covering the first protective layer;

[0018] h) Form a mask made of a second resin, located on top of and in contact with the second layer made of the first resin;

[0019] i) Form a structure in the form of microlenses in the mask; and

[0020] j) Transfer the structure into the second layer made of the first resin by physical etching to form a plurality of microlenses in the second layer.

[0021] According to one embodiment, after step j), the mask is removed by means of a solvent.

[0022] According to one embodiment, after step f), the method further includes the following steps:

[0023] k) Remove the first protective layer and the second protective layer from at least a part of the first portion, while leaving the first protective layer and the second protective layer on the first block.

[0024] According to one embodiment, the method includes, at step k), removing the first protective layer and the second protective layer from at least a part of the first portion, while leaving the first protective layer and the second protective layer on the second block.

[0025] According to one embodiment, the method includes, before step a), forming a plurality of photodetectors in a semiconductor substrate.

[0026] According to one embodiment, the plasma includes oxygen.

[0027] According to one embodiment, the first protective layer is made of an oxide, for example, made of silicon oxynitride (SiON).

[0028] According to one embodiment, step b) successively includes: depositing a first sub-layer of a first resin having a first viscosity, crosslinking the resin of the first sub-layer, depositing a second sub-layer of a first resin having a second viscosity on the first sub-layer, and crosslinking the first resin of the second sub-layer.

[0029] According to one embodiment, the first viscosity is lower than the second viscosity, the first viscosity is in the range of 1 mPa·s to 30 mPa·s, and the second viscosity is in the range of 30 mPa·s to 150 mPa·s.

[0030] The embodiment also provides an electronic circuit, including:

[0031] A semiconductor substrate, which includes a first surface, a second surface opposite to the first surface, and an opening extending from the first surface to the second surface;

[0032] A conductive pad, which includes a first portion extending above the first surface and a second portion covering the flank of the opening and defining a gap in the opening;

[0033] A first block made of a first resin in the gap, the first resin is non-photosensitive, and the first block made of the first resin is crosslinked; and

[0034] A first protective layer, which covers the first block.

[0035] According to one embodiment, the electronic circuit further includes:

[0036] A plurality of photodetectors located inside and on top of the semiconductor substrate;

[0037] A plurality of microlenses made of the first resin and covering the first protective layer, wherein the plurality of microlenses do not cover the at least one conductive pad; and

[0038] A second protective layer located above the plurality of microlenses and above the first protective layer surrounding the plurality of microlenses.

[0039] According to one embodiment, the first surface includes a depression, the first portion is located in the depression, there is a groove between the first portion and the flank of the depression, and the electronic circuit includes a second block of the first resin located in the groove, and the first protective layer covers the second block. Description of the Drawings

[0040] The foregoing features and advantages and other features and advantages will be described in detail in the remainder of the disclosure of specific embodiments given by way of illustration and not limitation, with reference to the accompanying drawings, in which:

[0041] Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 , Figure 12 and Figure 13 is a cross-sectional view illustrating a device obtained at the end of successive steps of an embodiment of a method for manufacturing an image sensor; and

[0042] Figure 14 is an image obtained by scanning electron microscopy, which illustrates another embodiment of an image sensor. DETAILED DESCRIPTION

[0043] In the various figures, the same features are indicated by the same reference numerals. In particular, common structural and / or functional features in various embodiments may have the same reference numerals and may have the same structure, size and material properties.

[0044] For the sake of clarity, only the steps and elements that are helpful for understanding the described embodiments are shown and described in detail. In particular, the formation of the photodetector of the described image sensor and its control circuit is not described in detail, and the formation of these elements is within the capabilities of those skilled in the art based on the instructions of the present disclosure.

[0045] Unless otherwise indicated, when two elements are referred to as being connected together, this means a direct connection without any intermediate elements except conductors, and when two elements are referred to as being coupled together, this means the two elements may be connected or they may be coupled via one or more other elements.

[0046] In the following description, when absolute position qualifiers such as "front", "back", "up", "down", "left", "right", etc., or relative position qualifiers such as "top", "bottom", "upper", "lower", etc., or orientation qualifiers such as "horizontal", "vertical", etc. are mentioned, unless otherwise indicated, they refer to the orientation of the drawing.

[0047] Unless otherwise indicated, the expressions "about", "approximately", "substantially" and "approximately" mean plus or minus 10%, preferably plus or minus 5%. Furthermore, the terms "insulating" and "conductive" are considered herein to mean "electrically insulating" and "conductive", respectively.

[0048] A method of manufacturing an electronic circuit corresponding to an image sensor will now be described. In general, embodiments of the manufacturing method are implemented for any type of electronic circuit including contact pads, in which case steps related to elements dedicated to an image sensor are not implemented.

[0049] Figures 1 to 13 Schematically and partially illustrates a device or structure obtained at the end of successive steps of an embodiment of an image sensor manufacturing method.

[0050] More specifically, Figure 1 corresponding to an initial structure that includes a semiconductor substrate 10, such as a silicon substrate, in which a photodetector 12 has been previously formed. As an example, the photodetector 12 is a photodiode, for example, adapted to capture infrared, visible, and / or ultraviolet radiation. As an example, the photodetector 12 is a photodetector made using CMOS (complementary metal oxide semiconductor) technology.

[0051] The substrate 10 includes an upper surface 10s and a lower surface 10i opposite the upper surface 10s. The substrate 10 is covered on one side of the upper surface 10s with one or more elements (not shown in the drawings), such as a dielectric protection layer, a color filter covering the photodetector 12, an opaque screen covering areas of the substrate 10 that do not contain the photodetector 12, etc. The substrate 10 is covered on one side of the lower surface 10i with an interconnect structure 14, which includes a stack of insulating layers having conductive tracks (not shown) extending between the insulating layers and having conductive vias (not shown) extending through the insulating layers. According to one embodiment, the thickness of the substrate 10 ranges from 3 μm to 10 μm.

[0052] In this example, the substrate 10 is intended to be illuminated through its upper surface 10s. The initial structure also includes one or more contact pads 13, Figure 1 a single contact pad 13 is shown. According to one embodiment, the contact pad 13 is electrically insulated from the substrate 10 by at least one insulating layer (not shown). The pad 13 is arranged to be offset from the photodetector 12 so as not to block the photodetector 12. As an example, in a top view, the photodetector 12 is located in the central region of the substrate 10, while the pad 13 is located in front of the peripheral region of the substrate 10.

[0053] Each contact pad 13 includes a contact area 13c that extends in a recess 15 provided in the upper surface 10s of the substrate 10. The contact area 13c of each pad 13 is intended to be connected to an external device, for example by means of a conductive wire (e.g., a metal wire). The contact area 13c includes an upper surface 13s. For each contact pad 13, the substrate 10 includes a through hole 16 that extends from the upper surface 10s to the lower surface 10i. The opening 16 opens into the recess 15. According to one embodiment, the opening 16 has a substantially constant cross-section when viewed in a direction perpendicular to the surface 10s. As an example, the cross-section of the opening 16 is square or rectangular, in particular inscribed within a rectangle, the length of the short side of which varies from 2 μm to 10 μm and the length of the long side of which varies from 5 μm to 100 μm. The contact pad 13 includes a bonding portion 13j that extends through the opening 16. As an example, the bonding portion 13j of the contact pad 13 is connected to one or more metallization layers of an interconnect structure 14 disposed on one side of the lower surface 10i of the substrate 10. As an example, the contact pad 13 is made of a metallic material, such as aluminum. The bonding portion 13j covers the side wings of the opening 16. However, the opening 16 is not completely filled by the bonding portion 13j, so there remains an air-filled gap 17 that opens to the outside in the opening 16. As an example, the bonding portion 13j has a thickness in the range of 200 nm to 2 μm measured with respect to the side wings of the opening 16, for example equal to about 2 μm. As an example, the depth of the gap 17 is in the range of 3 μm to 10 μm and, for example, equal to about 6 μm. As an example, the thickness of the contact area 13c is equal to the thickness of the bonding portion 13j. As an example, the depth of the recess 15 is substantially equal to the thickness of the contact area 13c and is in the range of 200 nm to 2 μm.

[0054] As an example, the contact pad 13 can be used to exchange signals with an image sensor and / or for the power supply of an image sensor. According to another example, one of the contact pads 13 can form part of a protection structure such as a sealing ring, in which case the pad extends along the entire periphery of the image sensor.

[0055] According to one embodiment, the upper surface 10s is planar outside the recess 15 and the through hole 16. In the recess 15, there is an air-filled groove 18 between the side wings of the recess 15 and the contact pad 13.

[0056] Figures 2 to 4 The figure shows the device obtained at the end of a planarization step for the structure in Figure 1 order to obtain a substantially flat surface on one side of the upper surface 10s of the substrate 10.

[0057] Figure 2Illustrated is an apparatus obtained at the end of the step of forming a resin layer 19 on the upper surface 10s of a substrate 10.

[0058] For example, layer 19 is deposited by spin coating over the entire upper surface 10s of substrate 10. Thus, layer 19 covers contact pads 13 and photodetectors 12. In particular, for each contact pad 13, the resin layer 19 fills the gaps 17 and the trenches 18 (if the latter exist). For example, layer 19 has a thickness in the range of 1 μm to 6 μm outside the region where it covers the contact pads 13, for example approximately 4 μm. According to one embodiment, layer 19 has a substantially flat upper surface 19s.

[0059] The resin of layer 19 is, for example, a crosslinkable resin that is not soluble in the usual liquid solvents used for developing and / or etching the resin. The resin of layer 19 is, for example, a non-photosensitive resin. As an example, the resin of layer 19 is chosen such that it can be crosslinked, for example, by UV or by a certain temperature (for example, approximately 200 °C). As an example, the resin of layer 19 is chosen such that it can be etched using a plasma (for example, oxygen-based) by reactive ion bombardment (also known as RIE (reactive ion etching)). As an example, the resin of layer 19 includes polymers, such as polymers of the acrylic or polyhydroxystyrene type.

[0060] Advantageously, the viscosity of the resin forming layer 19 is chosen such that complete filling of the gaps 17 and the trenches 18 (if they exist) for each contact pad 13 is obtained, and a substantially flat upper surface 19s is obtained. According to one embodiment, layer 19 is formed by a single deposition operation. According to one embodiment, the formation of layer 19 includes the deposition of a first sub-layer 19a of the resin of layer 19 having a first viscosity, the crosslinking of the resin of the first sub-layer 19a, the deposition of a second sub-layer 19b of the resin of layer 19 having a second viscosity, and the crosslinking of the resin of the second sub-layer 19b. The first sub-layer allows the filling of the gaps 17. The first viscosity is lower than the second viscosity. According to one embodiment, the first viscosity is in the range of 1 mPa·s to 30 mPa·s, for example equal to 25 mPa·s. According to one embodiment, the second viscosity is in the range of 30 mPa·s to 150 mPa·s, for example equal to 50 mPa·s. The first viscosity advantageously serves to facilitate the filling of the gaps 17. The second viscosity advantageously serves to facilitate obtaining a substantially flat upper surface 19s.

[0061] Figure 3 Illustrated is an apparatus obtained at the end of the step of etching the resin layer 19 to expose the upper surface 10s of the substrate 10 and the upper surfaces of the contact pads 13. This etching step defines blocks 20 of the material forming layer 19 in the gaps 17 defined by each contact pad 13. When trenches 19 are present, this etching step also defines blocks 21 of the material forming layer 19 in the trenches 18.

[0062] According to one embodiment, the etching implemented during this step is remote (and thus isotropic) plasma etching (a method sometimes denoted by the terms "dry stripping" or "dry ashing"). The chemical etching plasma used preferably includes oxygen. As an example, the chemical etching plasma includes oxygen, nitrogen, and hydrogen. As an example, the temperature of the material etched during this step is in the range of 80 °C to 200 °C, for example, about 170 °C. The advantage of this embodiment is that it is selective for the material on the upper surface 10s.

[0063] According to one embodiment, the etching implemented during this step is ion bombardment etching, reactive dry etching, or dry etching. Such etching removes the material by bombardment, for example, by using an oxygen-based plasma.

[0064] When the upper surface 10s of the substrate 10 or the upper surface 13s of the contact pad 13 is exposed, the above etching is stopped.

[0065] Figure 4 Illustrated is the device obtained at the end of the step of depositing a protective layer 22 made of an electrically insulating material on the surface of the device shown in Figure 3 .

[0066] For example, the layer 22 continuously extends over the entire upper surface of the Figure 4 device. Thus, the layer 22 particularly covers the upper surface 13s of the pad 13, the blocks 20 and 21, and the upper surface 10s of the substrate 10. The layer 22 is made of an oxide, for example, silicon oxynitride (SiON) or silicon dioxide (SiO2) deposited at a low temperature (e.g., 150 °C).

[0067] As an example, the protective layer 22 is deposited on the upper surface of the device shown in Figure 3 by a conformal deposition method, for example, by chemical vapor deposition, such as plasma-enhanced chemical vapor deposition (PECVD). The thickness of the layer 22 ranges from 30 nm to 200 nm, for example, about 50 nm. As an example, the temperature range for forming the protective layer 22 is 150 °C to 250 °C, for example, about 150 °C.

[0068] Figures 5 to 7 Illustrated is the device obtained at the end of the step of forming an optical filter and a microlens layer in front of the photodetector 12 and on one side of the upper surface 10s of the substrate 10.

[0069] Figure 5 Illustrated is the device obtained at the end of the step of forming a filter 23 on the protective layer 22 and the step of forming a resin layer 24 on and around the filter 23 on the protective layer 22.

[0070] The filter 23 is formed on the protective layer 22 in vertical alignment with the photodetector 12. The filter includes a color filter and / or an interference filter. Advantageously, the protective layer 22 protects the blocks 20 and 21 during the formation of the filter 23 or during its reprocessing.

[0071] The resin layer 24 is deposited, for example, over the entire surface of the protective layer 22. The thickness of the layer 24 is, for example, in the range from 1 μm to 5 μm, for example, about 4 μm.

[0072] According to one embodiment, the resin of the layer 24 is the same as the resin of the layer 19. The resin of the layer 24 is, for example, a crosslinked resin that cannot be dissolved in the usual liquid solvents used for developing and / or etching the resin. The resin of the layer 24 is, for example, a non-photosensitive resin. As an example, the resin of the layer 24 is selected such that it can be crosslinked, for example, by UV or by a certain temperature (for example, about 200 °C). As an example, the resin of the layer 24 is selected such that it can be etched by RIE, in particular by means of an oxygen-based plasma. As an example, the resin of the layer 24 includes a polymer, for example, an acrylic-type polymer.

[0073] Figure 6 Illustrated is the device obtained at the end of the step of forming the etching mask 25 on the upper surface of the resin layer 24. The mask 25 includes structures in the form of microlenses intended to be transferred into the resin layer 24 during a subsequent etching step in order to form microlenses in the layer 24.

[0074] As an example, the mask 25 is formed by a resist layer. For example, first the resist of the mask 25 is deposited over the entire upper surface of the layer 24, on top of and in contact with the layer 24. At this stage, the resist of the mask 25 has, for example, a substantially uniform thickness over the entire surface of the structure. The deposition of the resist of the mask 25 can be carried out by a spin coating technique or any other suitable deposition technique. Then, the resist layer of the mask 25 is structured, for example, by photolithography to form individual resist disks 26 in front of the photodetectors 12. In this example, individual resist disks 26 are provided in front of each photodetector 12 of the sensor. Then a flow anneal is achieved, during which the resist disks 26 are deformed into the shape of microlenses. After the flow anneal, the resist disks 26 are, for example, separate. However, the embodiment is not limited to this specific case. For example, the thickness of the pads 26 is less than the thickness of the layer 24.

[0075] Figure 7 Illustrated is the device obtained at the end of the step of physically etching the layer 24 and the mask 25 so as to transfer the pattern of the mask 25 to the upper part of the layer 24. For example, the etching stops when all the resin of the mask 25 is consumed.

[0076] Thus, inFigure 7 In the device shown, layer 24 includes a microlens 28 facing the photodetector 12. By way of example, the height of the microlens 28 ranges from 0.5 μm to 3 μm. At this stage, the connection pad 13 is still covered by the resin of layer 24.

[0077] Blocks 20 and 21 are made of a crosslinked non-photosensitive resin, which may be the same resin as that used for the microlens 28. Advantageously, there is no deterioration of the resin of blocks 20 and 21 during the formation of the filter 23 and the microlens 28.

[0078] Figures 8 to 13 The figure illustrates the device obtained at the end of the step of removing the resin of the resin layer 24 facing the pad 13, thus allowing electrical contact to be made on the pad 13.

[0079] Figure 8 The figure illustrates the device obtained at the end of the step of forming a masking layer 30 made of resin on the upper surface of layer 24.

[0080] By way of example, first the layer 30 is deposited on the entire upper surface of layer 24, for example in contact with the upper surface of layer 24. Then, for example by photolithography, the layer 30 is removed in front of the pad 13 in order to expose the part of the resin layer 24 covering the pad 13. The resin of the layer 30 is, for example, a resist. By way of example, the thickness of the layer 30 is greater than the maximum thickness of the layer 24. By way of example, the thickness of the layer 30 ranges from 4 μm to 10 μm, for example about 6 μm.

[0081] Figure 9 The figure illustrates the device obtained at the end of the step of etching layer 24 to layer 30. During this step, the layer 30 serves as an etching mask.

[0082] More particularly, during this step, the part of layer 24 not covered by layer 30 is removed to expose the protective layer 22. The protective layer 22 can act as an etch stop layer.

[0083] According to one embodiment, the etching implemented during this step is remote plasma etching (a method sometimes denoted by the terms "dry stripping" or "dry ashing"). This chemical etching is based on the use of free radicals generated by a remote plasma. This etching technique is currently used for removing, recovering or completely stripping resin layers. This technique is sometimes also used for performing chemical treatment on the entire exposed material. It is provided here for use in an uncommon way to perform local etching of the resin layer 24 through the mask formed by the resin layer 30. The advantage of this technique is that it is less aggressive than physical etching and does not produce fibers or filaments based on etch products and carbon on the flanks of the layer 24.

[0084] The etching plasma used preferably includes oxygen. As an example, the chemical etching plasma includes oxygen, nitrogen, and hydrogen. As an example, the temperature of the material etched during this step is in the range of 80°C to 200°C, for example, about 170°C.

[0085] According to one embodiment, the etching achieved during this step is an etching performed by ion bombardment, reactive dry etching, or dry etching. This etching causes the removal of material, for example, by using an oxygen-based plasma, by bombardment. The plasma used during this etching step has, for example, a different composition from the plasma used during the etching that results in the formation of the microlens 28. During the above step, the layers 30 and 24 are consumed simultaneously.

[0086] When the protective layer 22 is exposed, the above etching is stopped. At this stage, a part of the layer 30 still remains on the surface of the layer 24 in front of the microlens 28.

[0087] Figure 10 The figure shows the device obtained at the end of the step of removing the remaining part of the layer 30 to expose the upper surface of the microlens 28. This removal step is performed, for example, by wet etching using a solvent, by means of an etching solution that enables the selective etching of the material of the layer 30 with respect to the material of the layer 24.

[0088] Figure 11 The figure shows Figure 10 the device obtained at the end of the step of depositing a protective layer 32 made of an electrically insulating material on the surface of the device shown in

[0089] For example, the layer 32 extends continuously over the entire upper surface of the Figure 10 device shown. Thus, in particular, the layer 32 covers the microlens 28 of the layer 24, as well as covers the protective layer 22, especially on the pads 13. As an example, the layer 32 is made of a material that enables the protection of the layer 24 from moisture. The layer 32 is, for example, made of an oxide, for example, made of silicon oxynitride (SiON) or an oxide deposited at a low temperature (e.g., 150°C). According to one embodiment, the layer 32 is made of the same material as the layer 22.

[0090] As an example, the protective layer 32 is deposited on the upper surface of the Figure 10 device shown by a conformal deposition method, for example, by chemical vapor deposition, for example, plasma-enhanced chemical vapor deposition (PECVD). The thickness of the layer 32 ranges, for example, from 50 nm to 500 nm, for example, about 150 nm. Advantageously, the method for forming the layer 32 is the same as the method for forming the layer 22.

[0091] Figures 12 to 13Illustrated is a device obtained at the end of a step of locally removing the protective layers 22 and 32 in front of each contact recovery pad 13 so as to enable electrical contact to be made on the pad 13.

[0092] Figure 12 Illustrated is the deposition of a resin layer 33 on the upper surface of the device of Figure 11 and the formation of a through-hole 34 in the resin layer 33, for each contact pad 13, the through-hole 34 exposing a part of the contact area 13c of the protective layer 32 covering the contact pad 13 (as an example, the contact area 13c is located on the left-hand side of the bonding portion 13j in Figure 12 ). For example, the through-hole 34 is formed by photolithography.

[0093] Figure 13 Illustrated is the device obtained at the end of the step of etching the protective layer 32 and the protective layer 22 in the opening 34 of the resin layer 33 used as an etching mask, followed by the step of removing the resin layer 33. Thus, openings 35 are formed in the protective layer 32 and the protective layer 22, aligned with each opening 34, so as to expose a part of the contact area 13c of the contact pad 13. According to one embodiment, the resin layer 33 can be removed by the same etching method as that described previously for Figure 9 etching the layer 24. The protective layer 32 enables the microlens 28 and the resin blocks 20 and 21 to be protected during the etching of the resin layer 33.

[0094] The resin block 20 is held in the gap 17 and the resin block 21 is held in the groove 18. This advantageously enables a relatively flat upper surface to be obtained above the bonding portion 13j of each contact pad 13 and around the groove 18 above each contact pad 13, or at least having a low undulation amplitude.

[0095] Figure 14 is Figure 13 an image of the electronic circuit of Figure 14 obtained by a scanning electron microscope, the gap 17 being substantially completely filled with the resin block 20 (not directly visible in Figure 14 ), covered by the protective layer 32, and the groove 18 being substantially completely filled with the resin block 21 (not directly visible in

[0096] In the embodiment described previously with respect to Figures 1 to 14 , the contact area 13c of each contact pad 13 is received in a recess 15 formed in the upper surface 10s of the substrate 10 such that the upper surface of the contact area 13c is substantially coplanar with the upper surface 10s of the substrate 10. As a variant, the contact area 13c of each contact pad 13 can be placed on the substantially flat upper surface 10s of the substrate 10 such that the contact area 13c protrudes relative to the upper surface 10s of the substrate 10.

[0097] The advantage of the above-described embodiment is that, after forming the blocks 20 and 21 and the protective layer 22, the upper surface of the obtained device is substantially flat, or in any case has raised areas with a low amplitude. Advantageously, the implementation of the subsequent steps of the image sensor manufacturing method is simpler. In particular, it is simpler to form the layer 24 with a substantially constant thickness, which makes it possible to avoid the phenomenon of striations of the (one or more) resins present above the photodetector array (at least in the region where the microlenses 28 are formed) (i.e., long-distance periodic perturbations in the diffusion of the resin during the centrifugal deposition method of the resin).

[0098] An advantage is that the resin used to form the resin blocks 20 and 21 can be the same as the resin used to form the microlens layer 28. Thus, the manufacturing, handling, crosslinking, and etching methods of such a resin can be advantageously well controlled.

[0099] In the above-described embodiment, the protective layer 22 is in direct mechanical contact with the contact pad 13. As a variant, the contact pad 13 can be covered with a dielectric layer, such as a silicon oxide layer, deposited before depositing the resin layer 19. In this case, during the formation of the protective layer 22 on the contact pad 13, the protective layer 22 is in direct mechanical contact with the dielectric layer on the contact area 13c, and the block 20 is interposed between the dielectric layer and the portion of the protective layer 22 covering the block 20.

[0100] Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these various embodiments and variants can be combined, and other variants will occur to those skilled in the art. In particular, the described embodiments are not limited to the above examples of dimensions and materials.

[0101] Finally, based on the functional indications given above, the actual implementation of the described embodiments and variants is within the capabilities of those skilled in the art.

[0102] A method for manufacturing an electronic circuit sequentially includes the following steps: a) forming an opening (16) in a semiconductor substrate (10) including a first surface (10s) and a second surface (10i) opposite to the first surface (10s), the opening (16) extending from the first surface (10s) to the second surface (10i), and forming at least one conductive pad (13), the conductive pad (13) including a first portion (13c) extending above the first surface (10s) and a second portion (13j) covering the side wings of the opening (16) and defining a gap (17) in the opening (16); b) depositing a first layer (19) made of a first resin, the first resin being non-photosensitive, the first layer (19) made of the first resin covering the conductive pad (13) and filling the gap (17), and crosslinking the first layer (19) made of the first resin; c) chemically etching the first layer (19) made of the first resin by plasma to define a first block (20) of the first resin in the gap (17); and d) depositing a first protective layer (22) on the first block (20).

[0103] The first surface (10s) includes a depression (15), the first portion (13c) is located in the depression (15), a groove (18) exists between the first portion (13c) and the side wings of the depression (15), the first layer (19) made of the first resin fills the groove (18) in step b), and further defines a second block (21) of the first resin in the groove (18) in step c).

[0104] After step d), the method further sequentially includes the following steps: e) forming a plurality of microlenses (28) in a second layer (24) made of the first resin and covering the first protective layer (22), wherein the plurality of microlenses (28) do not cover the at least one conductive pad (13); and f) depositing a second protective layer (32) on the plurality of microlenses (28) and on the first protective layer (22) around the plurality of microlenses (28).

[0105] Forming the plurality of microlenses (28) sequentially includes the following steps: g) depositing a second layer (24) made of the first resin covering the first protective layer (22); h) forming a mask (25) made of a second resin, located on top of and in contact with the second layer (24) made of the first resin; i) forming a structure (26) in the form of microlenses in the mask (25); and j) transferring the structure (26) into the second layer (24) made of the first resin by physical etching to form a plurality of microlenses (28) in the second layer (24).

[0106] After step j), the mask (25) is removed by means of a solvent.

[0107] The method further includes the following steps after step f): k) removing the first protective layer (22) and the second protective layer (32) from at least a part of the first portion (13c), while keeping the first protective layer (22) and the second protective layer (32) on the first block (20).

[0108] The method includes, in step k), removing the first protective layer (22) and the second protective layer (32) from at least a part of the first portion (13c), while keeping the first protective layer (22) and the second protective layer (32) on the second block (21).

[0109] The method includes, before step a), forming a plurality of photodetectors (12) in the semiconductor substrate (10).

[0110] The plasma includes oxygen.

[0111] The first protective layer (22) is made of an oxide, for example, made of silicon oxynitride (SiON).

[0112] Step b) successively includes: depositing a first sub-layer (19a) of a first resin having a first viscosity, cross-linking the resin of the first sub-layer (19a), depositing a second sub-layer (19b) of a first resin having a second viscosity on the first sub-layer (19a), and cross-linking the first resin of the second sub-layer (19b).

[0113] The first viscosity is lower than the second viscosity, the first viscosity is in the range of 1 mPa·s to 30 mPa·s, and the second viscosity is in the range of 30 mPa·s to 150 mPa·s.

[0114] The electronic circuit includes: a semiconductor substrate (10) including a first surface (10s), a second surface (10i) opposite to the first surface (10s), and an opening (16) extending from the first surface (10s) to the second surface (10i); a conductive pad (13) including a first portion (13c) extending above the first surface (10s) and a second portion (13j) covering the flank of the opening (16) and defining a gap (17) in the opening (16); a first block (20) made of a first resin in the gap (17), the first resin being non-photosensitive and the first block (20) made of the first resin being cross-linked; and a first protective layer (22) covering the first block (20).

[0115] The electronic circuit further includes: a plurality of photodetectors (12) located inside and on top of a semiconductor substrate (10); a plurality of microlenses (28) made of a first resin and covering a first protective layer (22), wherein the plurality of microlenses (28) do not cover the at least one conductive pad (13); and a second protective layer (32) located on the plurality of microlenses (28) and on the first protective layer (22) surrounding the plurality of microlenses (28).

[0116] The first surface (10s) includes a recess (15), the first portion (13c) is located in the recess (15), and there is a groove (18) between the first portion (13c) and the flank of the recess (15). The electronic circuit includes a second block (21) of the first resin located in the groove (18), and the first protective layer (22) covers the second block (21).

[0117] The various embodiments described above can be combined to provide further embodiments. Based on the above detailed description, these and other changes can be made to the embodiments. Generally speaking, in the following claims, the terms used should not be construed as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be construed as including all possible embodiments and the full scope of equivalent forms enjoyed by these claims. Therefore, the claims are not limited by the disclosure.

Claims

1. A method comprising: forming an opening in a semiconductor substrate, the semiconductor substrate comprising a first surface and a second surface opposite to the first surface, the opening being located between the first surface and the second surface, and forming a conductive pad comprising a first portion located above the first surface and a second portion covering flanks of the opening and defining a gap in the opening; Depositing a first layer, the first layer covers the conductive pad and fills the gap, the first layer comprising a first resin, and the first resin is non-photosensitive; cross-linking the first resin in the first layer; chemically etching the first layer using plasma to define a first block comprising a first resin in the gap; as well as A first protective layer is deposited on the first block.

2. The method of claim 1 , wherein the first surface comprises a recess forming a trench between the first portion and the first surface of the semiconductor substrate, wherein a first layer comprising a first resin is deposited in the trench, defining a second mass of the first resin in the trench.

3. The method according to claim 1, further comprising: A plurality of micro lenses are formed in the second layer, wherein the second layer comprises the first resin and covers the first protective layer, and wherein the plurality of microlenses do not cover the conductive pad; as well as A second protective layer is deposited on the plurality of microlenses and the first protective layer.

4. The method according to claim 3, wherein forming the plurality of microlenses further comprises: depositing a second layer, the second layer covering the first protective layer; forming a mask atop and in contact with the second layer, the mask comprising a second resin; forming the plurality of structures in the form of microlenses in the mask; as well as The structure is transferred into the second layer by physical etching to form the plurality of microlenses in the second layer. The method of claim 4 , wherein the mask is removed using a solvent.

6. The method according to claim 3, further comprising: The first protective layer and the second protective layer are removed from a portion of the first portion, the first protective layer and the second protective layer covering the first block.

7. The method according to claim 6, further comprising: The first protective layer and the second protective layer are removed from a portion of the first portion, the first protective layer and the second protective layer covering the second block. The method of claim 1 , wherein the semiconductor substrate comprises a plurality of photodetectors.

9. The method of claim 1, wherein the plasma comprises oxygen.

10. The method of claim 1, wherein the first protective layer comprises an oxide.

11. The method of claim 1 , wherein depositing the first layer further comprises: Depositing a first sublayer comprising a first resin, the first sublayer covering the conductive pad and filling the gap, the first sublayer having a first viscosity; cross-linking the first resin of the first sub-layer; depositing a second sublayer comprising the first resin, the second sublayer covering the first sublayer, the second sublayer having a second viscosity; and The first resin of the second sub-layer is cross-linked.

12. The method according to claim 11, wherein the first viscosity is lower than the second viscosity, the first viscosity is in the range of 1 mPa.s to 30 mPa.s, and the second viscosity is in the range of 30 mPa.s to 150 mPa.s.

13. An electronic circuit comprising: A semiconductor substrate comprising a first surface, a second surface opposite to the first surface, and an opening between the first surface and the second surface; a conductive pad including a first portion located above the first surface and a second portion covering the sides of the opening and defining a gap in the opening; a first block including a first resin located in the gap in the opening, the first resin being non-photosensitive, and the first resin in the first block being cross-linked; as well as A first protective layer covers the first block.

14. The electronic circuit according to claim 13, further comprising: a plurality of photodetectors located within and on top of the semiconductor substrate; a plurality of micro lenses, comprising a first resin, covering a first protective layer, wherein the plurality of micro lenses do not cover the conductive pad; as well as The second protection layer covers the plurality of micro lenses and the first protection layer.

15. The electronic circuit of claim 13, wherein the first surface comprises a recess forming a groove between the first portion and the first surface of the semiconductor substrate, wherein depositing the first layer forms a second block comprising the first resin in the groove, the second block being covered by the first protective layer.

16. A method comprising: forming an opening in a semiconductor substrate, the semiconductor substrate comprising a first surface, a second surface opposite to the first surface, and a recess in the first surface, the opening being located between the first surface and the second surface, the semiconductor substrate further comprising a plurality of photodetectors, the opening being offset from the plurality of photodetectors; forming a conductive pad in the opening, the conductive pad comprising a first portion located above a portion of a recess, the portion of the recess forming a trench between the conductive pad and the first surface of the semiconductor substrate, the conductive pad further comprising a second portion located above the second surface of the semiconductor structure and defining a gap in the opening; depositing a first layer including a first resin over the conductive pad and the semiconductor substrate, the first layer filling the gap and the trench; etching the first layer to expose the first portion and the first surface of the semiconductor substrate and to define a first block containing the first resin in the gap and a second block containing the first resin in the trench; depositing a first protective layer over the conductive pad and the semiconductor substrate; depositing a second layer comprising a first resin over the first protective layer; forming a first mask over a portion of the second layer, the mask comprising a microlens structure aligned over the plurality of photodetectors; physically etching the first mask and the second layer to transfer the microlens structure into the second layer above the plurality of photodetectors; forming a second mask over the microlens structure in the second layer; as well as The second layer not covered by the second mask is etched to expose the first protective layer.

17. The method according to claim 16, further comprising: removing the second mask to expose the microlens structure; forming a second protective layer on the first protective layer and the microlens structure; forming a third mask on the microlens structure; as well as The second protection layer and the first protection layer not covered by the third mask are etched to expose a portion of the first portion of the conductive pad.

18. The method of claim 16, wherein an interconnect structure is disposed below the second surface, and the second portion of the conductive pad is located above the interconnect structure.

19. The method of claim 16, wherein forming a first mask over the portion of the second layer further comprises: depositing a first mask over the second layer; forming aligned resist disks over the plurality of photodetectors using photolithography; as well as The resist disks are annealed to form the microlens structures.

20. The method of claim 16, wherein the first protective layer and the second protective layer comprise oxide.

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