# US 2018/0321087 A1 · Electromagnetic radiation detector encapsulated by transfer of thin layer

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- Number: US 2018/0321087 A1
- Document ID: US20180321087A1
- Status: Published application
- Kind: A1
- Application number: 15/962,549
- Filed: 2018-04-25
- Published: 2018-11-08
- Earliest claimed: 2017-05-02
- Assignees: Commissariat A L'energie Atomique Et Aux Energies Alternatives
- Applicants: Commissariat A L'energie Atomique Et Aux Energies Alternatives
- Inventors: Patrick Leduc; Jean-Jacques Yon
- Web page: https://patentgrep.com/patent/US20180321087A1

## CPC

- G01J 5/20: using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
- G01J 5/024: {Special manufacturing steps or sacrificial layers or layer structures}
- G01J 5/045: {Sealings; Vacuum enclosures; Encapsulated packages; Wafer bonding structures; Getter arrangements (getter arrangements per se H10W76/48, H10P36/03)}
- G01J 5/0875: Windows; Arrangements for fastening thereof
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)

## Abstract

An electromagnetic radiation detector comprising: at least one membrane suspended above a substrate; and a cap, closing a hermetic cavity including the at least one membrane. According to the invention: the thickness of the cap is less than or equal to 10 μm; the cap bears at least on support walls surrounding the membrane(s); and the detector has first and second metallic sealing layers intercalated on each other between the cap and the support walls, and between which a peripheral bonding zone extends. The invention also relates to a method of making such a detector. The invention provides an encapsulation solution using a thin cap, in which the membranes are not subjected to high temperatures.

## Claims

### Claim 1

Electromagnetic radiation detector (100) comprising:
at least one membrane (108) suspended above a substrate (101), configured to absorb incident electromagnetic radiation and convert it into heat; and
a cap (110) transparent in a spectral sensitivity range of the electromagnetic radiation detector, and closing a hermetic cavity (115) containing the at least one membrane;
characterised in that:
the thickness (E) of the cap (110) is less than or equal to 10 μm;
the cap is suspended above the substrate, bearing on at least support walls (106) surrounding the membrane(s);
the detector (100) has first and second metallic sealing layers (112A, 112B) intercalated on each other between the cap and the support walls, and between which a peripheral bonding zone (112C) extends.

### Claim 2 (depends on 1)

Detector (100) according to claim 1, characterised in that:
the cap (110) is suspended above the substrate, bearing on support walls (106) and on support pillars (104) located between the support walls; and
the detector comprises pairs of first and second metallic sealing pads (114A, 114B), each pair being located between the cap and one of the support pillars (104), the first and second sealing pads of each pair being superposed and separated by a corresponding internal bonding zone (114C).

### Claim 3 (depends on 2)

Detector (100) according to claim 2, characterised in that it comprises a plurality of membranes (108) suspended above the substrate, a membrane distribution pitch (P) being equal to a distribution pitch of the support pillars (104), in each dimension of the plane of the substrate.

### Claim 4 (depends on 2)

Detector (100) according to claim 2, characterised in that the membrane(s) (108) is (are) suspended above the substrate, each bearing on bearing pillars (105), and in that for each membrane, a pair of first and second sealing pads (114A, 114B) is located on one of the bearing pillars, such that said bearing pillar also forms a support pillar (104) for the cap.

### Claim 5 (depends on 1)

Detector (100) according to claim 1, characterised in that the cap (1110) has one or several through openings (1102) and in that a closing layer (111) covers the cap.

### Claim 6 (depends on 5)

Detector (100) according to claim 5, characterised in that the membrane(s) (108) is (are) suspended above the substrate, each bearing on bearing pillars (105), and in that for each membrane, there is a through opening (1102) in the cap above one of the bearing pillars (105).

### Claim 7 (depends on 1)

Detector (100) according to claim 1, characterised in that the combined thickness of the first and second sealing layers (112A, 112B) is between 1.5 μm and 2.5 μm.

### Claim 8

Method of encapsulating at least one sensitive element of an electromagnetic radiation detector (100), characterised in that it comprises the following steps:
a) fabrication of a stack, called the sensor stack (117), comprising:
a first substrate (101), called the principal substrate;
at least one membrane (108) extending above the principal substrate, forming the at least one sensitive element of the electromagnetic radiation detector, and configured to absorb an incident electromagnetic radiation and convert it into heat;
support walls (106) extending above the principal substrate and surrounding the at least one membrane; and
a first metallic sealing layer (112A) located above upper faces of the support walls, on the side opposite the principal substrate;
b) deposition of a layer called the cap layer (132), transparent in a spectral sensitivity range of the electromagnetic radiation detector and less than or equal to 10 μm thick, above a second substrate (130) called the transfer substrate;
c) production of a second metallic sealing layer (112B) on the cap layer;
d) transfer of the transfer substrate (130) onto the principal substrate (101), so as to align the first sealing layer (112A) and the second sealing layer (112B) and bond them to each other; and
e) removing of the transfer substrate (130).

### Claim 9 (depends on 8)

Method according to claim 8, characterised in that:
the sensor stack (117) also comprises support pillars (104), extending between the support walls, each with a corresponding first sealing pad (114A) on top of it;
step c) also comprises production of second sealing pads (114B) on the cap layer; and
step d) also includes alignment and bonding of first sealing pads (114A) with second sealing pads (114B), in pairs.

### Claim 10 (depends on 8)

Method according to claim 8, characterised in that it also comprises a step to etch the cap layer (132), to delimit the external contour of a cap (110) designed to close a cavity containing the at least one membrane, and to form at least one through opening (1102) in this cap.

### Claim 11 (depends on 10)

Method according to claim 10, characterised in that the step to etch the cap layer is implemented after the step e) to remove the transfer substrate.

### Claim 12 (depends on 10)

Method according to claim 10, characterised in that:
the step to etch the cap layer is implemented after step b) to deposit the cap layer (132) and before step d) to transfer the transfer substrate (130);
the step to etch the cap layer is followed by a step to fill the etched regions with a layer of sacrificial material, called a cap sacrificial layer (133); and
the cap sacrificial layer (133) is evacuated after step e) to remove the transfer substrate.

### Claim 13 (depends on 8)

Method according to claim 8, characterised in that:
the method comprises steps to deposit layers of sacrificial material, called sacrificial stop layers (121, 135), such that before step d) to transfer the transfer substrate, the first sealing layer (112A) and the second sealing layer (112B) are each located in one of these sacrificial stop layers;
step d) uses hybrid bonding; and
the sacrificial stop layers (121, 135) are evacuated after step e) to remove the transfer substrate.

### Claim 14 (depends on 8)

Method according to claim 8, characterised in that in the sensor stack (117) after step a), the at least one membrane (108) extends above a sacrificial material layer, called the membrane sacrificial layer (120), the membrane sacrificial layer being evacuated after step e) to remove the transfer substrate.

### Claim 15 (depends on 8)

Method according to claim 8, characterised in that it is implemented for several sensor stacks (117) sharing the same principal substrate (101) simultaneously, and using a single transfer substrate (130) and a single cap layer (132), a step to etch the cap layer delimiting the external contours of several caps (110) each intended to cover one of the several sensor stacks.