JP3114759B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and, more particularly, to a photodetector formed on a compound semiconductor substrate and a semiconductor substrate having a different thermal expansion coefficient from that of the compound semiconductor substrate and detected by the photodetector. The present invention relates to a hybrid type semiconductor device in which signal processing elements for processing the processed signals are joined by metal bumps.

Conventionally, mercury / cadmium / tellurium (Hg) having a narrow energy gap and high sensitivity to infrared rays
_1-x Cd _x Te), a photodetector such as a photodiode is formed on a compound semiconductor substrate, and a signal processing element such as a charge transfer element that processes a signal obtained by the photodetector is formed of silicon. A light detection device such as a hybrid type solid-state image pickup device in which both elements are formed on a (Si) substrate and bonded by a metal bump such as indium (In) is formed.

In such a light detecting device, in order to increase the sensitivity and the resolution, the above-described light detecting element is formed on a single compound semiconductor substrate at a density as high as possible. It is desired to increase the area of itself, and therefore, a compound semiconductor substrate used for the device,
Alternatively, it is desired to increase the area of the Si substrate.

[0004]

2. Description of the Related Art FIG. 2A is a cross-sectional view of a conventional hybrid type photodetector. As shown, for example, p-type Hg
Boron (B) atoms, which are n-type impurity atoms, are ion-implanted into a _1-x Cd _x Te substrate 1 in a predetermined pattern to form an n-type layer 2, a pn junction is formed, and a photodiode 3 is formed. Is formed. An insulating film 4 made of zinc sulfide (ZnS) is formed on the surface of the substrate 1.

On the other hand, a charge transfer element for processing a signal obtained by the photodiode is formed on a p-type Si substrate 5, and an impurity atom such as phosphorus is ion-implanted into the p-type Si substrate 5 to form an n. An input diode 7 of the charge transfer element is formed by forming a mold layer 6.

An insulating film 8 made of a SiO ₂ film is formed on the substrate 5. The insulating films 4 and 8 are opened, and the n-type layer 2 of the photodiode 3 and the n-type layer 6 of the input diode are joined to each other using In metal bumps 9 and 10.

[0007]

By the way, such a solid-state imaging device usually has a temperature of 77 ° to avoid the influence of thermal noise.
Cooled and operated at K liquid nitrogen temperature. Above
Since the Si substrate 5 and the Hg _1-x Cd _x Te substrate 1 have different coefficients of thermal expansion, distortion occurs in both substrates 1 and 5 due to the temperature fluctuation between liquid nitrogen temperature during operation and room temperature during non-operation. Then, a stress due to this distortion is applied, and this stress shows a different value between the two substrates 1 and 5, so that the metal bumps 9,
If cracks or misalignment occurs in the substrate 10, or if it is severe, there is a problem that the metal bumps 9, 10 are peeled off from both substrates 1, 5.

For this reason, in a hybrid type photodetector which requires cooling during operation, the Si substrate 5 and the Hg _1-x Cd _x
Since thermal distortion occurs due to a difference in thermal expansion coefficient between different types of semiconductor substrates such as the Te substrate 1, there is a problem that only a small hybrid solid-state imaging device having a reduced substrate area can be manufactured.

Therefore, when the number of elements is increased in the hybrid type photodetector, stress is applied to the metal bumps due to thermal strain, and a connection failure occurs, or both substrates are damaged, resulting in an operation failure. There has been a problem that the reliability is reduced.

[0010] Therefore, in order to solve the above-mentioned problem, the present applicant has disclosed in Japanese Patent Application No. Hei 3-179301 the Hg _1-x Cd _x The Te substrate 1 and the Si substrate 5 on which the signal processing element is formed are thinned, and the thinned substrates 1 and 5 are adhered to a sapphire substrate 11 with an adhesive 12 so that A method for preventing the displacement of the metal bumps 9 and 10 due to the difference in thermal expansion coefficient of 5 has been proposed.

As shown in FIG. 2C, the Hg _1-x Cd _x Te substrate 1 on which the photodiode 3 is formed is thinned, and the thinned Hg _1-x Cd _x Te substrate 1 is Hg _1-x Cd _x Te which is attached to the substrate 5 using an adhesive to form the photodiode 3
The coefficient of thermal expansion of the substrate 1 is determined by the Si substrate 5 on which the signal processing element 13 is formed.
Metal bump 9,
It proposes a method to prevent 10 misalignments.

However, any of the above-mentioned methods needs to make the Si substrate 5 or the Hg _1-x Cd _x Te substrate 1 thinner. Then, as shown in FIG. 2 (b), Hg _1-x Cd _x Te
When the substrate 1 is polished or etched, when the sapphire substrate 11 is bonded, the amount of thermal expansion of the substrate to which the sapphire substrate 11 and the thinned Hg _1-x Cd _x Te substrate 1 are bonded is determined. It is necessary to polish the silicon substrate 5 to such a size that the amount of thermal expansion coincides therewith.

As shown in FIG. 2C, when the Hg _1-x Cd _x Te substrate 1 is thinned, the thinned Hg _1-x Cd _x Te substrate 1 and the Si substrate 5 are combined. The adhered thermal expansion must be polished and etched to a size that is equal to the thermal expansion of the Si substrate 5 on which the mating signal processing element 13 is formed, and the operation is complicated and difficult.

The present invention solves the above-mentioned problems, and for example,
When the Hg _1-x Cd _x Te substrate is thinned and bonded to another supporting substrate to form a synthesized substrate, the thermal expansion of the synthesized substrate is substantially equal to the thermal expansion of the mating Si substrate. It is an object of the present invention to provide a semiconductor device in which the amount of thermal expansion of the support substrate can be controlled.

[0015]

According to the present invention, there is provided a semiconductor device comprising:
2. A hybrid semiconductor device according to claim 1, wherein the semiconductor device formed on the first semiconductor substrate and the semiconductor device formed on the second semiconductor substrate are electrically coupled by using metal electrodes. In the apparatus, one of the first and second semiconductor substrates is thinned, and a support substrate having a thermal expansion coefficient close to that of the non-thinned semiconductor substrate is bonded to the thinned semiconductor substrate. It is characterized by the following.

According to a second aspect of the present invention, both the first and second semiconductor substrates are thinned to form a support substrate having a thermal expansion coefficient intermediate between the first and second semiconductor substrates. The support substrate is bonded to the first and second semiconductor substrates.

According to a third aspect of the present invention, the support substrate is formed by mixing powder of an element constituting the semiconductor substrate having a small coefficient of thermal expansion or oxide of the element with an organic resin. Things.

[0018]

According to the present invention, as shown in FIG.
Formed and thinned Hg_1-xCd _xSignal processing on Te substrate 1
It has a thermal expansion coefficient close to that of the Si substrate 5 on which the element 13 is formed, and
Powder or silicon dioxide (SiO_Two)
The support substrate 21 where the mixed epoxy resin is solidified is
Affix with an adhesive 12 such as resin.

Thus, the thermal expansion coefficient of the Hg _1-x Cd _x Te substrate 1 on which the photodiode 3 is formed is
The coefficient of thermal expansion of the composite substrate 22 to which the support substrate 21 and the Hg _1-x Cd _x Te substrate 1 are adhered is changed by changing the thickness of the support substrate 21. It becomes close to the coefficient of thermal expansion of the Si substrate 5 on which the signal processing element 13 is formed.

The coefficient of thermal expansion of the composite substrate 22 can be made closer to the coefficient of thermal expansion of the Si substrate 5 by changing the thickness of the supporting substrate 21. That is, when the coefficient of thermal expansion of the composite substrate 22 is separated from the coefficient of thermal expansion of the Si substrate 5,
This is possible by bringing the supporting substrate 21 in the direction of increasing the thickness.

Accordingly, the composite substrate 22 in which the Hg _1-x Cd _x Te substrate 1 and the supporting substrate 21 are bonded and the Si substrate 5 are connected to the metal bumps 9, 10.
Even if the temperature of the semiconductor device formed by bonding at the temperature changes from the temperature of liquid nitrogen during operation to the temperature of storage at room temperature during non-operation, the metal bumps 9 and 10 and both substrates 1 and 5 can be Since the applied stress is reduced, even when the number of elements is increased, the above-described phenomena such as displacement of the metal bumps 9 and 10 and separation are prevented.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1A is a cross-sectional view of a semiconductor device according to a first embodiment of the present invention.
_{The 1-x} Cd _x Te substrate 1 is thinned by etching or polishing to 20 μm or less. The reason why the thickness is reduced to 20 μm or less is that the supporting substrate having a thermal expansion coefficient close to that of the Si substrate is formed, and the difference in thermal expansion coefficient between the Si substrate and the Hg _1-x Cd _x Te substrate is kept small That's why.

The signal processing element 13 is formed by ion-implanting impurity atoms into the Si substrate 5. And this thinned
The Hg _1-x Cd _x Te substrate 1 is made of epoxy resin (trade name: Araldite, manufactured by Ciba Geigy) and S particles having a particle size of 10 to 50 μm.
A support substrate 21 having a thickness of about 100 μm solidified by mixing i or SiO ₂ is adhered by the adhesive 12 made of the epoxy resin. Mixing Si or SiO ₂ powder with the epoxy resin in this manner,
This is performed so as to have the same coefficient of thermal expansion as the substrate 5. The value of the coefficient of thermal expansion of the supporting substrate 21 is 1.4 × 10
^-6 (k ^-1 ), and the thermal expansion coefficient of the above epoxy resin is 3.4
× 10 ^-5 (k ^-1 ).

The thermal expansion coefficient of the Hg _1-x Cd _x Te substrate 1 is 3.87 ×
10 ^-6 (K ^-1 ), and the value of the thermal expansion coefficient of the supporting substrate made of epoxy resin mixed with Si powder or SiO ₂ powder thereon is 1.4 × 10 ^-6 (k ^-1 ). The coefficient of thermal expansion of the substrate synthesized by bonding the Hg _1-x Cd _x Te substrate 1 and the supporting substrate 21 has a value close to 1.21 × 10 ⁻⁶ (K ⁻¹ ) of the coefficient of thermal expansion of Si. As shown.

By changing the thickness of the support substrate, the coefficient of thermal expansion of the composite substrate 22 obtained by bonding the support substrate and the Hg _1-x Cd _x Te substrate can be reliably determined by the coefficient of thermal expansion of the Si substrate. , Closer to each other.

By doing so, the thermal expansion coefficients of the Hg _1-x Cd _x Te substrate 1 on which the photodiode 3 is formed and the Si substrate 5 on which the signal processing element 13 is formed become substantially equal, The displacement and cracking of the metal bumps 9 and 10 do not occur, so that a highly reliable semiconductor device can be obtained.

In addition to the above embodiment, a second embodiment shown in FIG.
As shown in (b), not only Hg _1-x Cd _x Te substrate 1 but also Si
The substrate 5 is also made thinner, and a support substrate 21 which is obtained by mixing Si or SiO ₂ powder with the above epoxy resin and is solidified is bonded to both the substrates 1 and 5 using the adhesive 12. By making the thermal expansion coefficients of the substrates 1 and 5 close to the thermal expansion coefficient of the support substrate 21, thermal distortion of the substrate due to temperature fluctuation of the semiconductor device may be reduced.

[0028]

As described above, according to the present invention, thermal distortion due to a difference in thermal expansion coefficient between different types of semiconductor substrates can be reduced, and a photodetector such as a formed solid-state image sensor can be used at 77 °.
Even when exposed to a storage temperature of room temperature from a low temperature of K, the displacement and cracking of the metal bumps connecting the two elements are less likely to occur, and a highly reliable hybrid photodetector is obtained. Has the effect.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a semiconductor device of the present invention.

FIG. 2 is a cross-sectional view of a conventional semiconductor device.

[Explanation of symbols]

1 Hg _1-x Cd _x Te substrate 3 Photodiode 4,8 Insulating film 5 Si substrate 9,10 Metal bump 12 Adhesive 13 Signal processing element 21 Support substrate 22 Composite substrate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01L 31/10 (72) Inventor Masahiko Narita 1015 Kamidadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited (56) References JP Hei 5-36966 (JP, A) JP-A-4-199877 (JP, A) JP-A-64-61056 (JP, A) IEEE TRANSACTIONS ON ELECTRON DEVIC ES, Vol. 38, No. 5 (1991), p. 1104-1109 (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 27/146 H01L 25/065 H01L 25/07 H01L 25/16 H01L 25/18 H01L 31/10

Claims (3)

(57) [Claims] A semiconductor device (3) formed on a first semiconductor substrate (1) and a semiconductor device (13) formed on a second semiconductor substrate (5) are connected to metal bumps (9). In the hybrid type semiconductor device electrically coupled by using the semiconductor substrate (1), the first or second semiconductor substrate (1, 5) is thinned, and the thinned semiconductor substrate (1) is formed. ), A supporting substrate (21) having a thermal expansion coefficient close to that of the non-thinned semiconductor substrate (5). 2. A semiconductor device (3) formed on a first semiconductor substrate (1) and a semiconductor device (13) formed on a second semiconductor substrate (5) are connected to metal bumps (9). , 10), the first and second semiconductor substrates (1, 5) are made thinner, and the first and second semiconductor substrates (1, 5) are thinned. A semiconductor device characterized in that a supporting substrate (21) having an intermediate thermal expansion coefficient is formed, and the supporting substrate (21) is bonded to the first and second semiconductor substrates (1, 5). 3. The support substrate (2) according to claim 1 or 2,
A semiconductor device, wherein 1) is formed by mixing powder of an element constituting the semiconductor substrate (5) having a small coefficient of thermal expansion or oxide of the element with an organic resin.