JPH0215635A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To make it possible to bond easily fellow metal bumps even if a high compressive force is not applied to the bumps for a long time by a method wherein the point part of the metal bump, which is provided on a semiconductor substrate on one side, is formed into a sharpened form. CONSTITUTION:An N-type layer 22 is formed on a mercury.cadmium.tellurium (Hg1-xCdxTe) substrate 21, which is a compound semiconductor substrate on one side, a protective film 23 consisting of zinc sulfide is formed on the surface of this substrate 21 and thereafter, an opening is provided in the layer 22 through the film 23. A metal film 24 for electrode connection use consisting of InP is formed at this opened region and a metal bump 29 consisting of InP on one side is formed on the film 24 in a state that the point of the bump 29 is sharpened. Moreover, an N-type layer 32 is formed on an Si substrate 31, which is a semiconductor substrate on the other side, an SiO2 film 33 is formed on the surface of the substrate 31 and an opening is provided on the layer 32. A metal film 34 for electrode connection use consisting of In is formed at this opened part and a metal bump 35, whose point part is formed into a cylindrical form and which consists of In, is formed on the film 34. Thereby, the bump 29 breaks through a thin metal oxide film formed on the bump 35 on the other side and the metal bumps are easily bonded to each other by low compression. Therefore, the bumps can be easily bonded to each other in a state that a distortion and a lattice defect are not generated in element formation regions of the substrates.

Description

[Detailed Description of the Invention] 1 Summary] A semiconductor device in which a photoelectric conversion element formed on a compound semiconductor substrate and a signal processing element such as a multiplexer formed on a silicon substrate are connected by metal bumps, and a method for manufacturing the same, A semiconductor element formed on one semiconductor substrate, with the aim of easily connecting metal bumps to each other without generating dislocations in the substrate on which the semiconductor element is formed and without causing plastic deformation in the metal bumps. In a semiconductor device in which a semiconductor element formed on the other semiconductor substrate is connected by a metal bump, the tip of the metal bump provided on the one semiconductor substrate is formed into a sharp shape; Areas other than the metal bump forming area are selectively coated with a metal, metal compound, or resin layer that has poor wettability with respect to the bump forming metal, and using the coating layer as a mask, the substrate is melted with the bump forming metal. It is constructed by immersing it in a liquid and pulling it up to form a metal bump with a pointed tip on the substrate.

[Industrial Application Field] The present invention relates to a semiconductor device and a method for manufacturing the same, and particularly relates to a photoelectric converter formed using metal bumps on a compound semiconductor substrate, which is one semiconductor substrate, and a silicon substrate, which is the other semiconductor substrate. The present invention relates to a semiconductor device in which a semiconductor element such as a multiplexer formed in the above is connected and integrated using metal bumps, and a method for manufacturing the same.

A compound semiconductor substrate that detects infrared rays with high sensitivity is used to form a photoelectric conversion element such as an infrared sensing element, and a silicon substrate is further used to form a signal processing device such as a charge coupled device. The elements are integrally formed by pressure bonding with low melting point metal bumps such as indium (In),
ζ is a well-known semiconductor device such as a solid-state imaging element that processes a detection signal obtained by photoelectric conversion using an infrared detection element using a charge-coupled device.

[Conventional technology]

As shown in FIG.
N-type impurity atoms are introduced into a substrate 1 made of +-Xctl After opening the N-type layer 2'' of the protective film 3, a connecting metal film 4 made of indium is formed to form an infrared sensing element 5.

On the other hand, a Sing film 7 is formed on a P-type Si substrate 6, on which a transfer electrode etc. of a predetermined pattern is formed (not shown), and an N-type layer 8 is further provided at a predetermined position on this substrate. An input diode serving as a signal input portion of this charge-coupled device is formed.

Then, the SiO□ film 7 on the N-type layer 8 is opened to form a connection metal film 9 to form a charge-coupled device 10. layer 8
A semiconductor device such as a solid-state imaging device is formed by forming In metal bumps 12 on top of each other and crushing and press-bonding the metal bumps I2 together.

The infrared rays introduced from the bottom of the infrared detecting element 5 as shown by the arrow are transmitted to the P-N of the boundary between the N type N2 and the substrate 1.
Photoelectric conversion is performed at the junction, and this photoelectrically converted signal is In
The input signal is input to the N-type layer 8 of the charge-coupled device 10 via the metal bump 11, and this input signal is transferred and signal-processed by applying a voltage to a predetermined transfer electrode of the charge-coupled device 10.

[Problem to be solved by the invention]

However, the metal bumps described above have a cylindrical flat head structure, and when a plurality of metal bumps are bonded with this shape, a thin metal oxide film of In is formed on the surface of each bump. is formed, and compressive stress is required to break these oxide films. However, if the head of the metal bump is flat, this compressive force is dispersed, so there is no compression stress that breaks the oxide film. A force of approximately I kg/mm" is required.

Furthermore, if there is an unevenness in the heights of the metal bumps, in order to reliably join all the metal bumps, it is necessary to continue compressing the other metal bumps until the metal bump with the lowest height is joined.

When compressive force is applied to the metal bump for a long time in this way, there arises a disadvantage that distortion, lattice defects, and dislocations are formed in the element forming region of the lower substrate.

The present invention eliminates the above-mentioned problems and has a structure in which the oxide film on the metal hump is easily broken when the metal bumps are pressure-welded together. The purpose of the present invention is to provide a method for manufacturing a semiconductor device in which metal humps can be bonded to each other.

[Means for Solving the Problems] The method of the present invention for achieving the above object connects a semiconductor element formed on one semiconductor substrate and a semiconductor element formed on the other semiconductor substrate with metal bumps. In the semiconductor device, the tip of the metal bump provided on the one semiconductor substrate is configured to have a pointed shape.

Furthermore, areas other than the metal bump formation area provided on one semiconductor substrate are selectively coated with a metal, metal compound, or resin layer that has poor wettability with respect to the metal bumps, and the substrate is coated with metal using the coating layer as a mask. It is characterized by forming metal bumps with pointed tips on a substrate by immersing it in a metal melt for bump formation and pulling it up.

[For production]

A portion of one semiconductor substrate excluding the element formation region is selectively coated with a metal compound film, such as aluminum oxide, which has poor wettability with respect to the metal for forming metal bumps, that is, In.

Using this aluminum oxide film as a mask, the substrate is immersed in an In melt and then pulled up to obtain an In metal bump with a sharp tip. When a metal bump with a sharp tip and a metal bump with a cylindrical tip are bonded to one semiconductor substrate in this way, the sharp tip of one metal bump is connected to the tip of the other metal bump. It is possible to easily break through the 7 oxide film of the metal bumps formed on the metal bump 1 without applying high compressive force between the metal bumps for a long time.
The materials can be easily joined without causing dislocation or distortion to the substrate.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing the structure of an embodiment of the semiconductor device of the present invention.

As shown in the figure, one of the compound semiconductor substrates,
N type 1 on cadmium/tellurium plate 21? After the protective film 23 made of zinc sulfide (ZnS) is formed on the surface of the substrate 21, an opening is made on the N-type layer 22 of the protective film 23, and a film made of In is formed in the opened region. A metal film 24 for electrode connection is formed, and one metal bump 29 made of In is formed on the metal film 24 with a pointed tip.

In addition, an N-type layer 3 is provided on the other semiconductor substrate, the St substrate 31.
2 is formed, a SiO□ film 33 is formed on the surface of the substrate 31, and after an opening is made on the N-type layer 32, In
A metal film 34 for electrode connection is formed, and the metal film 3
4-A metal bump 35 made of In with a cylindrical tip
is formed.

If the tip of the metal bump 29 formed on one semiconductor substrate 21 has a sharp shape as described above, the metal bump 29 may break through the thin metal oxide film formed on the other metal bump 35. Low compression force i.e. 200g/m
The metal bumps can be easily joined with a compressive force of about mz, and therefore can be easily joined without introducing distortion or lattice defects into the element formation region of the substrate.

A method for manufacturing such a semiconductor device of the present invention will be described.

First, as shown in FIG. 2(a), an N-type layer 22 is formed on one of the compound semiconductor substrates, an lIg+-x Cd)B Te substrate 21, and the surface of the substrate 21 is covered with a protective film such as a ZnS film. 23, and after opening the protective film 23 on the N-type layer 22, a connection metal film 24 is formed by vapor depositing In or the like on the N-type layer 22.

Next, after forming a first photoresist film 25 by coating on the substrate 21, an aluminum film 26 is formed thereon by vapor deposition.

Next, as shown in FIG. 2(b), a second photoresist film 27 is formed on the substrate, and then the photoresist film 27 is opened using photolithography.

Furthermore, using the opened photoresist film 27 as a mask, the aluminum film 26 is etched with a mixed solution of phosphoric acid and nitric acid to form a predetermined pattern.

Further, as shown in FIG. 2C, the photoresist film 27 is removed, and the surface of the aluminum film 26 is oxidized thinly by irradiating oxygen plasma using a plasma CVD apparatus.

Next, as shown in FIG. 2(d), the second photoresist film 27 used as a mask is removed using a removing agent. In this way, the aluminum oxide film 4, which has poor wettability with In, can be formed in areas other than the In metal bump formation region.
It is selectively covered with 0.

Further, as shown in FIG. 2(e), this substrate is turned over and placed so that only the surface of the substrate is immersed in the In melt 28 using the aluminum oxide film 40 as a mask. The substrate is at the melting temperature of In (156°C).
), the substrate is lifted vertically above the melt surface and left to stand until room temperature.

Then, as shown in FIG. 2(f), since aluminum oxide has poor wettability with In, In is repelled in the area where aluminum oxide is formed, and the electrode connecting metal film 24
in remains only in h. Furthermore, when pulling up the board,
The tip of the In deposited on the connection electrode film 24 becomes sharp due to gravity, and when the substrate moves away from the surface of the melted In, the temperature of the deposited In immediately drops below the melting point, so the surface tension causes the tip of the In to become sharp. The tip does not become rounded and remains pointed.

Next, as shown in FIG. 2(6), by removing the first photoresist film 25, the aluminum oxide film 40 thereon is removed by a lift-off method, and a semiconductor substrate having In metal bumps with sharp tips is obtained. can be easily obtained.

In this example, an aluminum oxide film was used as the coating layer that has poor wettability with the In melt, but a resin layer that can withstand the temperature of the In melt or a metal film such as tungsten may be used as the coating layer. It's okay.

〔Effect of the invention〕

As is clear from the explanation below, according to the present invention, In
Since the metal bumps can be easily bonded to each other with low compressive force, a highly reliable semiconductor device that is less likely to generate lattice defects or dislocations in the element formation region of the substrate can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a semiconductor device of the present invention, FIG. 2(a) to FIG. 2(2) are cross-sectional views showing the manufacturing process of the semiconductor device of the present invention, and FIG. FIG. 3 is a cross-sectional view showing the structure. In the figure, 21 is a Hg+-, CdXTe substrate, 22.32 is an N-type layer, 23 is a protective film, 24 and 34 are metal films for electrode connection, and 2
5 is the first photoresist film, 26 is the AN film, 27 is the second photoresist film, 28 is the In melt, 29.35 is the metal bump, 31 is the Si substrate, 33 is the SiO□ film, 40 is Aβ2
03 coating is shown. This invention-1 details Takashi F, T
Figure 2 (Wholesale 1) <f> /f g sum 1/2 times 4 times αn mai seven ozo ni pickle Figure 2 (Part 2)

Claims (2)

[Claims] (1) In a semiconductor device in which a semiconductor element formed on one semiconductor substrate (21) and a semiconductor element formed on the other semiconductor substrate (31) are connected by metal bumps (29, 35), the above-mentioned Metal bumps (2) provided on one semiconductor substrate (21)
9) A semiconductor device characterized in that the tip of item 9) has a pointed shape. (2) A method for manufacturing a semiconductor device in which a semiconductor element formed on one semiconductor substrate (21) and a semiconductor element formed on the other semiconductor substrate (31) are connected by metal bumps (29, 35). selectively covering a portion of the one semiconductor substrate (21) other than the metal bump (29) formation region with a metal, metal compound, or resin layer that has poor wettability with respect to the bump-forming metal; Using the coating layer (26) as a mask, the substrate (21) is immersed in the melt (28) of the bump-forming metal and pulled up, and the metal bumps (29) with pointed tips are placed on the substrate (2).
1) A method for manufacturing a semiconductor device, characterized in that it is formed on a semiconductor device.