JPH0738207A - Formation of semiconductor element on diamond thin film - Google Patents

Abstract

PURPOSE: To accurately set an electronic component in a diamond mount by mechanically self aligning and coupling the component in a recess. CONSTITUTION: The top surface of a diamond film 20 is anisotropically etched to form a recess having vertical sidewall segments 21, 22. A patterned contact layer 15 partly extends to a part of the bottom surface of the recess to contact one or both segments 21, 22. A laser element 10 has side faces contacting a part of the contact layer 15 disposed on one side segment 21, 22 of the recess, or adjacent to the other segment 21, 22, or adjacent to a part of the contact layer 15 disposed on both the segments 21, 22 of the recess. Thus an electronic component is disposed and self-aligned along a special direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component such as a laser device, and more particularly to a method of forming an assembly including a diamond film submant and an integrated device (laser device).

[0002]

A free-standing diamond film is a submount that is formed on a metal die with a laser element formed thereon. During this laser operation, it can be in electrical contact with the laser element and can be a thermal heat sink. In particular, the diamond film is grown on a silicon or metal substrate by a CVD process and then the diamond film is removed from the substrate or
Alternatively, the substrate may be completely etched (melted), leaving only the free-standing diamond film. The top and bottom surfaces of the diamond film are then processed for a predetermined time by a material removal (thinning) process to remove a predetermined thickness from the top and bottom surfaces of the diamond film to transfer the bottom area of the film. It improves the heat resistance and improves the smoothness of the upper surface of the film.

A technical problem that occurs when bonding a laser element (or other electronic component) to this diamond film is that the laser element is mechanically attached to a metal bonding pad disposed on the upper surface of the diamond film. It is a point to adhere and to match. This process powers the laser during test and normal operation of the laser,
It is a process necessary for mechanical stabilization. Accurate alignment requires the laser element to be in place on the diamond film and properly aligned with the package containing the diamond film. In the prior art, in order to obtain such accurate matching, the laser element was arranged on the bonding pad and its position was determined by means of accurate optical inspection, but this was a time-consuming method. .

[0004]

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a self-aligning bonding method in which a laser element is accurately arranged on a diamond submant and then these are accurately bonded. Is. That is, it is necessary to provide an accurate alignment and a subsequent bonding method which do not require the means of the accurate optical inspection according to the prior art.

[0005]

SUMMARY OF THE INVENTION The method of the present invention comprises patterning recessed regions on an insulating (preferably heat conducting) substrate (eg, CVD diamond film submount),
The step of anisotropically etching and then mechanically self-aligning and coupling the electronic component (eg, laser element) into the recessed region. Further, the present invention provides that the material of the etching-resistant patterned protective mask has a predetermined electrical resistance, a portion of this mask being in its final assembled state and in its original state, during operation of the electronic component, the desired resistance. Alternatively, it functions as a conductor. Thus, the method of the present invention is as set forth in claim 1.

In this way, electronic components are arranged in a self-aligned manner along one spatial direction. That is, it is possible to dispose without the need for accurate optical inspection.
The substantially horizontal surface of this recessed area does not necessarily have to be perfectly smooth, as long as it can provide a good base, such as a patterned metal layer. Similarly, the sidewall segments need not be smooth as long as they provide a good base for electronic component integrity. Furthermore, the present invention has the features described in the claims 2 and 3.

An advantage of the present invention includes the further patterning of the patterned protective layer after step (b) to form a patterned resistive layer having a higher predetermined resistance than the patterned metal layer, The patterned resistive layer has a pair of opposite ends. Furthermore, the advantage is that the patterned resistance layer has a higher predetermined resistance everywhere than the patterned metal layer. In this way, the second patterned layer can provide the desired resistance during operation of the semiconductor device.

Further, an advantage of the present invention is that the patterned protective layer is made of, for example, tantalum nitride or tantalum silicate. Furthermore, the semiconductor device of the present invention can also be used as a laser device. The film is a diamond film. It is an advantage of the present invention that the metal coating is located on the bottom surface opposite the top surface. Furthermore, this diamond film is a diamond film formed by CVD.

Further, the method of the present invention further includes the following steps. (1) electrically connecting the metal coating to a terminal of an element located on the top surface opposite the bottom surface, (2) connecting the metal coating to a conductive platform, (3) Electrically connecting a power source between the platform and a localized portion of the patterned metal layer, which is preferably adjacent to one of a pair of ends of the patterned resistive layer.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS.
Is a diamond film 20 formed by CVD.
And a laser element 10. This laser element 10 is
It has an active region 11, which emits light from the plane of FIG. 1 when fully forward biased. The metal pad 12 is disposed on the bottom surface of the recessed area,
This recessed region is formed in the upper surface of the diamond film 20 by anisotropic etching, and the vertical sidewall segment 2 is formed.
1 and 22. As shown in FIG. 1, vertical sidewall segments 21 and 22 intersect at an angle of approximately π / 2 radians (90 degrees). The laser element 10 has a pair of vertical sides that intersect at an angle whose apex is located adjacent the intersection of the vertical sidewall segments 21 and 22. This angle is at least equal to about π / 2 radians. Other angles are possible as long as the angle between the vertical sides of the laser element 10 is approximately equal to the angle formed by the intersection of the vertical sidewall segments 21 and 22.

On the upper surface of the diamond film 20, T
Patterned contact layer 13 made of i / Pt / Au and other Ti
/ Pt / Au patterned contact layer 15, a Ti / Pt conductive solder dam 14 connecting the patterned contact layer 13 and another patterned contact layer 15 made of Ti / Pt / Au, and Patterned contact layer 1 made of Ti / Pt / Au
6 and a locally patterned tantalum nitride resistive layer 18 are arranged. Au / Sn solder layer 1
7 is located between the bottom of the laser element 10 and the top surface of the patterned contact layer 15. Patterned contact layer 1
A portion of 5 extends into contact with one or both of the vertical sidewall segments 21 and 22 to a portion of the bottom surface of the recessed area. During heating of the laser element 10 to use the solder layer 17 that connects to the patterned contact layer 15, a portion of this solder moves toward the solder dam 14 and the resistive layer 18. The bottom surface of the laser element 10 is metallized with a Ti / Pt / Au contact layer (not shown).

The said side of the laser element 10 contacts a part of the patterned contact layer 15 arranged on one of the vertical sidewall segments 21 or 22 of the recessed region, respectively,
Or a portion of patterned patterned contact layer 15 disposed adjacent to vertical sidewall segment 22 or other of vertical sidewall segment 21, or on both vertical sidewall segments 21 and 22 in the recessed region. Adjacent to each other. The bottom surface of the diamond film is Ti /
It is metallized with a metal coating 23 such as Pt / Au. This metal coating 23 is bonded to a metal platform (not shown).

The diamond film 20 has a through hole extending between the top surface and the bottom surface, which is provided with a conductor 19 for electrically connecting the metal pad 12 to the metal coating 23 and also to the metal platform. It is filled. Alternatively, the walls of the through holes may be graphitized to make them conductive. Alternatively, the graphitized through holes may be filled with a conductor plug. The metal wire bond 24 made of metal is used for the laser element 10.
An ohmic contact layer (not shown) disposed on the upper surface of the metal pad 12 and the metal pad 12 to form an electrical connection path therebetween. In operation, the laser assembly 1
The metal elements shown at 00 have only negligible resistance compared to that of the resistive layer 18.

In the normal operating position, the power supply (not shown) has a dc power supply connected in series with an ac (RF) power supply, which is between the patterned contact layer 16 and the platform (not shown). Connected. The polarity of this dc power supply is such that a forward bias is applied to the laser element 10. Thereby, the platform, the metal coating 23, the conductor 19, the metal pad 12, the metal wire bond 24, the top contact layer to the bottom contact layer, the solder layer 17, the patterned contact layer 15, the resistive layer 1 of the laser device 10.
8. An electrical path is formed like the patterned contact layer 16.

During a test operation, a power supply (not shown) is connected between the metal pad 12 and the patterned contact layer 13. And the electrical path is the metal pad 12,
Metal wire bonds 24, top contact layer to bottom contact layer of laser element 10, solder layer 17, patterned contact layer 15,
Formed like solder dam 14, patterned contact layer 13, power source. Thus, the resistive layer 18 is bypassed, but the resistive layer 18 can be incorporated in series with a current source if desired. The important point is that the laser device 10
The point is that the diamond film 20 can be tested without being bonded to the platform. Many assemblies similar to the laser assembly 100 can be formed at the same time, but as far as metallization patterned by anisotropic etching is concerned, a relatively large diamond area is used, and then this film is used in many cases. Dividing into small area film lasers, each of which is bonded with a diamond film 20 and metallized.

The following procedure is suitable for forming the laser assembly 100. First, a CVD diamond film having a flat top surface (not shown) is grown on a silicon body. This top surface is coated everywhere with a uniform thickness conductive protective layer made of tantalum nitride. Alternatively, it is coated with a layer of another suitable conductive material having the desired resistance (eg, tantalum silicate), and this coating is used as a protective mask during anisotropic etching of subsequent diamond films. And patterned. The conductive layer is then patterned by standard photolithography by selective masking and wet or dry etched. This allows the patterned conductive layer to
It then extends to vertical sidewall segments 21, 22 as etched into the diamond film (the patterned conductive layer is not over the recessed areas to be etched). By using this patterned conductive layer as a protective mask against etching,
This recessed region is anisotropically etched into the diamond film to a depth of 3-6 μm. The effective parameter values for anisotropic etching of this diamond film are as follows. 400W at 40s.ccm oxygen, 0.1 Pascal, 2.45GHz
Microweb power and -80v-150vdc bias voltage.

The patterned conductive (tantalum nitride) layer is then patterned by photolithographic partially selective masking and etching, the growth profile of which is the resistive layer 18. A through hole is then drilled by laser drilling from the bottom surface of the recessed area to the bottom surface of the diamond film. Thus, the walls of the through holes become graphitized and become electrically conductive.
To provide higher conductivity (ie, to provide negligible electrical resistance), the through-holes are made of metal,
For example, the conductor 19 is formed by plating or filling with a material such as W, Ti, Pt, or Au by low pressure CVD. The bottom surface of diamond film 20 is then metallized with a metal coating 23.

The entire top surface of the diamond film 20 includes the bottom surface of the recessed area and the vertical sidewall segments 21, 22.
, And then with Ti / Pt / Au metal layer to about 0.
Coated to a thickness of 5 μm. By this photolithography spatial selective masking and etching, Ti / P
The Au layer of the t / Au metal layer is completely removed from the area below. That is, about 1 area at all areas above the solder dam 14 and the four outer edges of the diamond film 20.
a μm wide edge (to allow the above cutting) and a gap of about 1 μm width between the vertical sidewall segment 22 and the metal pad 12, the patterned contact layers 13, 15, the ends of the solder dam 14. , Metal pad 12 and patterned contact layer 1
A gap of about 1 μm between the ends of 5 and the region of the gap over the resistance layer 18 is removed. This is to provide the desired electrical resistance between the patterned contact layers 15 and 16 when the regions of the Pt and Ti layers below this gap are subsequently removed. After that, the original Ti / Pt / Au
The Pt layer and the Ti layer of the layer are completely removed from a region similar to the Au layer except for the portion overlying the solder dam 14.

Next, a solder layer 17 is deposited with a thickness in the range of approximately 2-4 μm. The solder layer 17 includes at least three alternating layers of Au and Pt. The bottom and top surfaces of the laser device 10 are then metallized and placed on the side wall facing portions of the patterned contact layer 15 protruding from the vertical side wall segments 21,22. On the other hand, the plating is heated at about 320 ° C for 10 seconds to melt. After cooling, the metal wire bond 24 is bonded to the contact layer and the metal pad 1 on the upper surface of the laser assembly 100 by thermocompression bonding.
Join between 2 and. Then, this laser assembly 100
Enters test operation or normal operation. In normal operation, the metal coating 23 is bonded to the metal platform.

As a modification of the above embodiment, the laser device 10 may be a semiconductor integrated circuit device. Further, the bottom surface of the laser element 10 may be incorporated into the solder layer 17 prior to placing the laser element 10 in the recessed region, which solder layer 17 may initially be part of the laser element 10. The laser device 10 also includes vertical sidewall segments 21 and 22.
It may be self-aligned to only one side and one side wall is not metallized. Further, only a single linear sidewall segment may be etched into the diamond film 20, after which the laser element 10 may self-align with the single sidewall segment after it is metallized. . Furthermore, the protective layer does not necessarily have to remain in contact with the resistive layer 18. It may be eliminated altogether if it is not needed while acting as this resistor or as a conductor. Finally, a portion of the protective layer may be left in place of the intact portion of the top surface of diamond film 20, or in addition to it as a recessed region.

[0021]

As described above, according to the present invention,
Accurately place the laser element on the diamond submount,
Then, it is possible to provide a self-aligning joining method for joining them accurately.

[Brief description of drawings]

FIG. 1 is a top view of a laser device according to an embodiment of the present invention.

2 is a cross-sectional view of the laser device of FIG. 1 taken along line 2-2.

3 is a cross-sectional view of the laser device of FIG. 1 taken along line 3-3.

[Explanation of symbols]

 10 Laser Element 11 Active Region 12 Metal Pad 13 Patterned Contact Layer 14 Solder Dam 15 Patterned Contact Layer 16 Patterned Contact Layer 17 Solder Layer 18 Resistive Layer 19 Conductor (Plug) 20 Diamond Film 21 Vertical Sidewall Segment 22 Vertical Sidewall Segment 23 Metal coating 24 Metal wire bond 100 Laser assembly

Front Page Continuation (72) Inventor Avischaik Katz United States 07090 New Jersey Westfield, St Marks Avenue 720

Claims (3)

[Claims] 1. (a) Diamond film (20)
Forming a patterned protective layer on the upper surface of the diamond film, the patterned protective layer having at least boundary segments, thereby exposing the unformed portion of the localized patterned protective layer of the diamond film (20). , (B)
Using the patterned protective layer as a protective layer against etching, anisotropically etching the diamond film (20) in a vertical direction to the exposed region to a predetermined depth, thereby forming an upper portion of the diamond film (20). The portion of the surface where the patterned protective layer is formed remains unetched, and a recessed region is formed in the film in the portion where the patterned protective layer is not formed, the recessed region having at least a first vertical sidewall segment (21). And diamond film (2
0) having a horizontal surface disposed at a predetermined depth from the upper surface thereof, and (c) forming a patterned contact layer (15) having first, second and third portions, said first portion Is arranged on at least a part of a horizontal plane of the concave region, and the second part is arranged on at least a part of an unformed part of the patterned protective layer on the surface of the diamond film (20). , The third portion is disposed on a portion of the first or second vertical sidewall segment (22) of the recessed region, the third portion being adjacent to the first and second portions ( d) disposing a laser element (10) having a bottom surface and at least a first vertical side surface at the location of the recessed area, whereby the bottom surface is patterned contact layer (15).
Of at least a portion of a first side wall segment of the recessed region or of a third portion of the patterned contact layer (15). A diamond thin film, characterized in that the diamond thin film is continuous with any one of at least a part, and Method for forming semiconductor device on top 2. The patterned protective layer has a second boundary segment forming a predetermined angle with the first boundary segment, whereby the first and second sidewalls are provided during step (b). The segments are formed at an angle with them, the laser element (10) having at least two intersecting vertical sides forming an angle between them, the step (d) The second vertical side is continuous with either at least a portion of the third portion of the patterned contact layer (15) or at least a portion of the second side of the recessed region during. the method of. 3. The patterned protective layer comprises a patterned conductor which is conductive and which is continuous with the first or second part of the resistive layer (18) or the patterned contact layer (15) after step (b). 3. The method of claim 1 or 2 which is further patterned to form.