JPH098269A - Hybrid type solid-state imaging device and manufacturing method thereof - Google Patents

Abstract

PURPOSE: To form a highly integrated hybrid solid-state image pickup device by press-fitting and connecting a substrate carrying signal processing elements in and to another substrate carrying photoelectric conversion elements by using bump electrodes and providing cavity sections below the bump electrodes. CONSTITUTION: At the time constituting a hybrid solid-state image pickup device by press-fitting and connecting a substrate 7 having signal processing elements in and to another substrate 1 having photoelectric conversion elements 2 by using bump electrodes 5 and 8, the bump electrodes 5 drop into cavity sections 6 and lateral expansion of the electrodes 5 can be prevented and, as a result, the occurrence of short circuits among the electrodes 5 can be prevented when the substrates 1 and 7 are press-contacted with each other, because the cavity sections 6 are provided below the electrodes 5. In addition, since the diameter d2 of the electrodes 8 on the substrate 7 is made smaller than the outside diameter d1 of the cavity section 6 provided below the electrodes 5 on the substrate 1, the electrodes 5 can be pushed in the cavity sections 6 and the expansion of the electrodes 5 can be prevented at the time of press-fitting the substrate 7 in the substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid type solid-state image pickup device and a method of manufacturing the same, and more particularly, to a substrate provided with an infrared photoelectric conversion element and a substrate provided with a signal processing element by a mechanical bump electrode. The present invention relates to an electrically coupled hybrid type solid-state imaging device and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a CCD type solid-state image pickup device using silicon has been mainly used as a solid-state image pickup device, but since silicon is not highly sensitive to infrared light having a relatively long wavelength such as 10 μm band. In addition, the infrared light solid-state imaging device mounted on the resource exploration satellite could not be used.

Therefore, in such an infrared light solid-state image pickup device, the photoelectric conversion device is composed of a compound semiconductor such as HgCdTe, and the signal processing device is composed of a CCD (charge coupled device) using silicon. A hybrid-type solid-state imaging device in which is coupled with In bump electrodes is used.

This conventional hybrid type solid-state image pickup device
This will be described with reference to FIG. See FIG. 6A. First, Hg is formed on the CdTe substrate._0.8Cd_0.2P type such as Te
An HgCdTe layer is provided, and a photoresist pattern (illustrated
B) on the p-type HgCdTe layer using ⁺(Boro
Ion) is selectively ion-implanted to form the n-type region 14.
Then, a ZnS film 12 to be an insulating film is deposited and
After forming tact holes, ohmic electrode such as Cr
The In bump electrode 26 is formed via the base electrode 29 that also serves as
The substrate 28 on which the photodiode is provided is completed.

Next, referring to FIG. 6B, an In bump electrode 31 corresponding to the In bump electrode 26 is formed on a predetermined portion of the substrate 30 on which the signal processing element is formed, and both substrates 28 and 30 are opposed to each other and pressure-bonded. As a result, the substrate 28 provided with the photodiode and the substrate 30 provided with the signal processing element are mechanically and electrically coupled to complete the hybrid type solid-state imaging device.

[0006]

However, in the conventional hybrid type solid-state image pickup device, there is a problem that a short circuit is likely to occur at the time of coupling as the degree of integration increases. This situation will be described with reference to FIGS. 6 (b) and 6 (c).

See FIG. 6B. When the substrate 28 provided with the photodiode and the substrate 30 provided with the signal processing element are crimped by the In bump electrodes 26, 31, the In bump electrodes 26, 31 are crushed by the crimping. At that time, the In bump electrode, especially the In bump electrode 2 provided on the substrate 28 provided with the photodiode is formed.
6 spreads in the lateral direction and may contact the adjacent In bump electrode 26 to cause a short circuit.

Further, as shown in FIG. 6C, since the In bump electrodes 26 and 31 are apt to be laterally deformed due to shear stress during pressure bonding, the displacement 32 due to the shear stress causes a positional shift, which is extremely likely to occur. Is
The In bump electrode 26 may contact the adjacent In bump electrode 26 to cause a short circuit.

In order to eliminate such a short circuit, it is sufficient to increase the distance between the In bump electrodes 26. However, if the distance is increased, the integration degree for increasing the number of pixels and the density of the solid-state image pickup device can be improved. There is a problem that improvement is hindered.

A method in which the In bump electrodes 26 and 31 are thermally melted and joined together is conceivable. However, the device characteristics of the substrate, particularly the device characteristics of the substrate 28 on which the photodiode is provided are different from those of the In bump electrode 26. It cannot be applied when the melting point changes.

Therefore, it is an object of the present invention to provide a bump electrode structure that enables a highly integrated hybrid type solid-state imaging device to be formed by pressure bonding.

[0012]

FIG. 1 is an explanatory view of the principle configuration of the present invention, and means for solving the problems of the present invention will be described with reference to FIG.

1 (1) In the hybrid solid-state image pickup device of the present invention, the substrate 1 provided with the photoelectric conversion element 2 and the substrate 7 provided with the signal processing element are connected by the bump electrodes 5 and 8. A feature is that a cavity 6 is provided under the bump electrode 5.

(2) Further, the present invention is characterized in that in the above (1), the cavity portion 6 is provided in the peripheral portion below the bump electrode 5.

(3) Further, in the present invention according to the above (1) or (2), the diameter d ₂ of the bump electrode 8 provided on one substrate 7 is set to be smaller than the diameter of the bump electrode 5 provided on the other substrate 1. It is characterized in that the diameter d ₁ of the outer circumference of the hollow portion 6 is less than or equal to d ₁ .

(4) Further, according to the present invention, in any one of the above (1) to (3), the wettability with the bump electrode 5 is used as the base electrode 4 of the bump electrode 5 provided with the cavity 6 thereunder. It is characterized in that the base electrode 4 made of two kinds of different metals is used.

(5) Further, according to the present invention, in the method for manufacturing a hybrid type solid-state image pickup device, the pattern of the insulating film 2 provided on one of the substrates 1 is utilized to obtain good wettability with the bump electrodes 5. No. 1 metal film is provided, and then a second metal film having a wettability with the bump electrode 5 worse than that of the first metal is provided so as to cover at least the central portion of the first metal film. The method further comprises the step of selectively depositing the bump electrode 5 so as to be in close contact with the exposed portion of the metal film and the second metal film, and then performing a heat treatment to form the cavity 6 under the bump electrode 5. Characterize.

(6) According to the present invention, in the above (5), the first metal film is a Cr film and the second metal film is A.
It is characterized in that it is made of an I film and the bump electrode 5 is made of an In bump electrode.

[0019]

When the hybrid type solid-state image pickup device is constructed by bonding the substrate 1 provided with the photoelectric conversion element 2 and the substrate 7 provided with the signal processing element by pressure bonding using the bump electrodes 5 and 8, Since the bump electrode 5 falls into the cavity 6 by providing the cavity 6 under the electrode 5, it is possible to prevent the bump electrode 5 from spreading in the lateral direction due to the pressure bonding, and thus a short circuit between the adjacent bump electrodes 5 is caused. Will not occur.

In the final structure of the hybrid type solid-state image pickup device, the bump electrode 5 falls into the cavity 6 so that the central portion of the cavity 6 is occupied by the bump electrode 5.
The cavity 6 remains in the peripheral portion below the bump electrode 5.

The bump electrode 8 provided on one of the substrates 7
By setting the diameter d ₂ of the bump electrode 5 to be equal to or smaller than the diameter d ₁ of the outer periphery of the cavity 6 below the bump electrode 5 provided on the other substrate 1, the bump electrode 5 can be pushed into the cavity 6 side during pressure bonding. Therefore, it is possible to surely prevent the bump electrode 5 from spreading in the lateral direction due to the pressure bonding.

Further, as the base electrode 4 of the bump electrode 5 having the cavity 6 formed thereunder, the base electrode 4 made of two kinds of metals having different wettability with the bump electrode 5 is provided, so that the cavity is formed. It can be reliably formed.

Further, by utilizing the pattern of the insulating film 2 provided on the one substrate 1, a first metal film having good wettability with the bump electrodes 5 is provided, and then at least this first metal film is formed. The wettability with the bump electrode 5 is first so as to cover the central portion.
After the second metal film, which is worse than the above metal, is provided, the bump electrodes 5 are selectively deposited so as to be in close contact with the exposed portions of the first metal film and the second metal film, and then heat treatment is performed. The bump electrode 5 reflows and tends to aggregate on the side of the second metal film having good wettability, and air enters between the bumpy electrode 5 and the second metal film having poor wettability. It is possible to form the cavity portion 6 underneath with good reproducibility.

A Cr film is used as the first metal film,
By using the Al film as the second metal film and the In bump electrode as the bump electrode 5, the cavity 6 can be formed inexpensively and with good reproducibility, and the short circuit between the adjacent bump electrodes can be surely performed. Can be prevented.

[0025]

EXAMPLE A manufacturing process of an HgCdTe-based hybrid type solid-state image pickup device which is an example of the present invention will be described with reference to FIGS. 2 (b) to 4 (f) are explanatory views of the main part in which the inside of the broken line circle in FIG. 2 (a) is enlarged.

Referring to FIG. 2A, first, an epitaxial layer is formed on a CdTe substrate (not shown).
Lengthened Hg_0.8Cd _0.2P-type HgCd made of Te
A photoresist pattern (not shown) is formed on the surface of the Te layer 11.
No.) is formed, and this photoresist pattern is used as a mask.
Then B⁺Are ion-implanted to form the n-type region 14. What
The area of the n-type region 14 in this case is 15 to 25 μm.
□, preferably 20 μm □.

Next, a polycrystalline ZnS film 12 serving as a surface protective film is deposited to a thickness of 3 to 7 μm, preferably 5 μm, and then selectively etched to have an area of 5 to 15 μm □, preferably 10 μm □, and n. An opening 13 smaller than the area of the mold region 14 is formed.

Next, as shown in FIG. 2B, a photoresist is applied and patterned to form a photoresist pattern 15 having an opening 16, and then a Cr film 1 having good wettability with In is formed.
7 is deposited to a thickness of 100 to 300 nm, preferably 200 nm, and an ohmic electrode 18 is formed at a contact portion with the HgCdTe layer 11.

Next, referring to FIG. 3C, a photoresist pattern (15 in FIG. 2B).
After the ohmic electrode 18 is left by lift-off to remove the photoresist, a new photoresist is applied and patterned to form a second photoresist pattern 19 having an opening 20 smaller than the area of the ohmic electrode 18. Later, an Al film 2 having poor wettability with In
1 is deposited to 300-700 nm, preferably 500 nm.

See FIG. 3D. In this case, the second photoresist pattern (see FIG.
In 19) of (c), it is necessary to provide a lacking portion corresponding to the extending portion 22 of the Al film 21, and air will flow in through the extending portion 22 in the subsequent cavity forming step. Will be done.

4E, the ohmic electrode 1 is formed by lift-off for removing the second photoresist pattern (19 in FIG. 3C).
After the Al film 21 deposited on 8 is left, a third photoresist pattern 23 having an opening 24 corresponding to the ohmic electrode 18 is formed by applying a new photoresist and patterning. Later, I
The n film 25 is deposited to 10 to 20 μm, preferably 15 μm, and the In film deposited in the opening 24 is used as the In bump electrode 2
6

Next, as shown in FIG. 4F, the In bump electrode 2 is formed by lift-off for removing the third photoresist pattern (23 in FIG. 4E).
After leaving 6 remaining, 160 to 170 ° C., preferably 17
The In bump electrode 26 is reflowed by heat treatment at 0 ° C.

In this case, since Al has a poor wettability with In, the reflowed In bump electrode has a good wettability with Cr.
It tends to aggregate on the ohmic electrode 18 side, and at that time,
Air flows between the In bump electrode 26 and the Al film 21 through the extending portion 22 of the Al film 21 shown in FIG. 3D to form a cavity 27 under the bump electrode 26.

Next, referring to FIG. 5G, the substrate 28 provided with the photodiode thus completed and the substrate 30 provided with the signal processing element, that is, the silicon CCD device are opposed to each other, and the In bumps are provided respectively. In having a diameter smaller than the diameter of the electrode 26 and the cavity 27
The bump electrode 31 is pressure bonded. Note that, in FIG. 5, the Cr ohmic electrode 18 and the Al film 21 shown in FIG. 4 are shown together as a base electrode 29.

See FIG. 5 (h). At the time of this pressure bonding, the diameter of the In bump electrode 31 depends on the cavity 2.
Since the diameter of the In bump electrode 26 is smaller than that of the In bump electrode 26, the In bump electrode 26 can be surely pushed into the cavity portion 27 side, so that the In bump electrode 26 can be prevented from being depressed and laterally expanding. , 31 even if the density is increased, it is possible to reliably prevent a short circuit between the adjacent In bump electrodes 26, 31.

Further, when the In bump electrode 26 is depressed toward the cavity 27 side, the In bump electrode 31 is fitted into the depressed portion, so that the displacement 32 due to the shear stress occurs.
Since it can be reduced, the deviation due to shear stress 3
It is possible to prevent a short circuit between the adjacent bump electrodes 26 and 31 due to 2.

Further, in the embodiment of the present invention, the cavity 27 is formed under the In bump electrode 26 on the side of the substrate 28 on which the photodiode is provided, but the In on the side of the substrate 30 on which the signal processing element is provided. It may be formed under the bump electrode 31.

Further, although the polycrystalline ZnS film is used as the surface protection film, it does not have to be polycrystalline, and high resistance single crystal ZnS may be used. Furthermore, besides the ZnS, a SiO ₂ film may be used. Alternatively, a Si ₃ N ₄ film may be used.

Although the In bump is used as the bump electrode, the In electrode is not necessarily limited to In, and the combination of Cr and Al is used as the base electrode. However, the combination is not limited to this combination. Any combination of conductive materials having different wettability with respect to the electrodes may be used. For example, Cr may be replaced with a Cr / Au alloy.

In the embodiment of the present invention, Hg
An infrared solid-state image pickup device in the 10 μm band using _0.8 Cd _0.2 Te has been described, but it is not limited to the 10 μm band, and HgCdTe whose mixed crystal ratio is changed according to the required wavelength band is used. Is also good.

Further, in the above embodiment, the photodiode in which the n-type impurity is ion-implanted in the p-type substrate has been described, but the conductivity type is reversed and the p-type impurity is ion-implanted in the n-type substrate. A diode may be formed.

Furthermore, the present invention is not limited to the HgCdTe-based infrared light solid-state image pickup device, but may be IIS such as InSb.
It is also applied to an infrared light solid-state image pickup device using an IV compound semiconductor.

[0043]

According to the present invention, since the cavity is provided under one of the bump electrodes on the substrate on which the photodiode is provided and the substrate on which the signal processing element is provided, the In bump electrode can be formed during the bonding by pressure bonding. Since it is depressed toward the cavity side, it is possible to reduce the lateral spread of the In bump electrode or the shift due to shear stress, thereby preventing a contact short circuit between the adjacent bump electrodes, which is a hybrid type. It greatly contributes to the improvement of the integration of the solid-state imaging device.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a principle configuration of the present invention.

FIG. 2 is an explanatory view of a manufacturing process up to the middle of the embodiment of the present invention.

FIG. 3 is an explanatory view of a manufacturing process up to the middle of FIG. 2 and subsequent steps of the embodiment of the present invention.

FIG. 4 is an explanatory view of a manufacturing process up to the middle of FIG. 3 and subsequent steps of the embodiment of the present invention.

FIG. 5 is an explanatory view of the manufacturing process after FIG. 4 of the embodiment of the present invention.

FIG. 6 is an explanatory diagram of a conventional hybrid type solid-state imaging device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Photoelectric conversion element 3 Insulating film 4 Base electrode 5 Bump electrode 6 Cavity 7 Substrate provided with a signal processing element 8 Bump electrode 11 HgCdTe layer 12 ZnS film 13 Opening 14 n-type area 15 Photoresist pattern 16 Opening 17 Cr film 18 Ohmic electrode 19 Second photoresist pattern 20 Opening 21 Al film 22 Extended portion 23 Third photoresist pattern 24 Opening 25 In film 26 In bump electrode 27 Cavity 28 Substrate provided with photodiode 29 Base electrode 30 Substrate provided with signal processing element 31 In bump electrode 32 Misalignment due to shear stress

Claims (6)

[Claims] 1. A hybrid-type solid-state image pickup device comprising: a substrate provided with a photoelectric conversion element and a substrate provided with a signal processing element, which are connected by a bump electrode; and a cavity is provided below the bump electrode. 2. The hybrid solid-state imaging device according to claim 1, wherein the cavity is provided in a peripheral portion below the bump electrode. 3. The diameter of the bump electrode provided on one of the substrates is set to be equal to or less than the diameter of the outer circumference of the cavity provided under the bump electrode provided on the other substrate of the substrates. The hybrid type solid-state imaging device according to claim 1 or 2. 4. The base electrode made of two kinds of metals having different wettability with the bump electrode is used as the base electrode of the bump electrode provided with the hollow portion. 2. The hybrid type solid-state imaging device according to item 1. 5. A first metal film having good wettability with a bump electrode is provided by using an insulating film pattern provided on one substrate, and then at least a central portion of the first metal film is covered. A second metal film having a wettability with the bump electrode worse than that of the first metal is provided, and then the bump electrode is adhered to the exposed portions of the first metal film and the second metal film. The method for manufacturing a hybrid solid-state imaging device, further comprising the step of selectively depositing, and then performing a heat treatment to form a cavity under the bump electrode. 6. The first metal film is a Cr film, the second metal film is an Al film, and the bump electrode is an In bump electrode.
A method for manufacturing the hybrid-type solid-state imaging device described.