JPH09148469A - Hermetic package with optical window and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hermetic sealed semiconductor package having an optical glass window sealable at a low temp. by patterning the surface of an optical glass and depositing a metal layer thereto. SOLUTION: An optical glass is polished, a metal pattern 26 is deposited on the polished glass 23 to form a cover assembly and the cover assembly is sealed to a base metal frame 21 with a non-processed solder 22. This assembly composed of the glass 23 having the pattern 26 and a frame 21 is mounted to a housing 20 by a low temp. hermetic sealing. When a hermetic solder is formed between the metallized glass 23 and the frame 21 by an infrared vacuum flow heat treatment, utilizing solder 22, the stress appearing during soldering to the glass 23 can be minimized and the air-tightness of the solder bond can be maximized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hermetically sealed semiconductor package, and more particularly to a hermetically sealed semiconductor package having a lid assembly with a glass window of optical properties and a temperature sensitive semiconductor optical element.

[0002]

BACKGROUND OF THE INVENTION In the past, hermetic seals for temperature sensitive semiconductor packages utilizing glass optical windows have required the glass to be fused at high temperatures to the package housing. In the sealing method, a glass frit is attached to the package or glass and the glass window is fused to the package through the glass frit.

[0003]

The high temperature required to fuse the glass to the glass frit reduces the optical properties of the glass window. Further, since high temperature is required, the quality or breakage of the semiconductor chip may occur. Conventional methods utilize a circular window in the lid of the device.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to a hermetically sealed semiconductor package with a glass window of optical properties that can be sealed at low temperatures, and a method of making a package with a glass window of optical properties.

A method of making a semiconductor device package having an optical property glass window includes the steps of polishing the optical property glass and then etching a defined area of the glass surface. A metal layer is deposited on this etched area. The metal layer is then sealed to the metal frame and the metal frame is sealed to the housing.

The technical progress of the invention and its objects will become apparent from the following description of a preferred embodiment of the invention in connection with the accompanying drawings and the novel features defined in the claims. .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1 and 2 show the steps and steps of a conventional development and method of encapsulating a glass window in a semiconductor package. Referring to FIGS. 1 and 2, in step 15, glass 10 is placed on a ceramic or metal lid 11 that covers semiconductor package 13. Glass lid assembly 9
Is burned or melted during the high temperature treatment of step 16,
The glass 10 is hermetically sealed in the lid 11. The glass frit green body 12 is then placed between the glass lid assembly 9 and the package 13. Therefore, the glass lid assembly 9, the glass frit green body 12 and the package 13 are
The lid 9 and the package 13 are hermetically sealed. The combustion steps 16, 17 and 18 are at temperatures above 400 ° C.
These high temperatures cause damage to the semiconductor elements in the package and reduce the optical properties of the glass window.

FIG. 3a is an exploded view of an optical window package according to the present invention, FIG. 3b shows the back side of optical glass 23 with a metallized surface 26, and FIG. 4 is the process used in the packaging process. The stages are shown. This packaging process has a metal or ceramic package 20 on which a semiconductor device is mounted. If the package 20 is ceramic, it has a metallic sealing ring 21 for a hermetic sealing process. The metal or ceramic package 20 should have a coefficient of thermal expansion that is well matched to the glass lid assembly. Examples of metallic materials are Cobal (nickel / iron / cobalt) or alloy 42 (nickel / iron), examples of ceramic materials are alumina oxide (Al ₂ O ₃ ) or alumina nitride (AlN).

The basic process is to polish the glass (step 30) and deposit the metal pattern 26 on the polished glass 23 (step 31), thereby providing a lid assembly (step 32). The lid assembly is then sealed to the base metal frame 21 by the solder blank 22 (step 33) and then the lid / metal frame is sealed to the package 20 (step 34).

The lid assembly comprises a metal frame 21, a green solder body 22 and a solderable optical glass 23. The optical glass that can be soldered is a CTE that closely matches the polished glass piece and the metal frame 21 that have good optical properties. For example, it is shot ZKN
7 glass or similar glass.

The optical glass 23 shown in FIG. 3b has a metal pattern 26 deposited on its bottom surface, the central portion or opening 25 of which forms an unmetallized optical window. For example, a metallization layer 2 made of Cr, Ni and Au.
The 6 is deposited by a conventional plating process, such as Enhanced Ion Plating (EIP) 31 or other suitable metallization technique. The ion plating process is usually a vacuum deposition with a high energy glass particle bombardment with a thermal evaporation source. Traditional ion plating systems typically
A direct current (DC) bias potential (-2 to -5 kV) or radio frequency RF bias and an inert gas (typically Ar Ar) at a pressure of 5 to 200 mtorr is included. The EIP process uses an RF bias and, in some cases, a magnetic field as the ionization source, and the application of a negative DC bias. Although Ar is often used to increase ion bombardment, the metal vapor itself (about 1x1
It is ionized at a low pressure of 0 ⁻⁴ torr) without using Ar plasma. The glass is biased and thus becomes the cathode for the low voltage charge, resulting in plasma or ion assisted deposition. When ionized, the vapor particles are accelerated toward the glass and collide with energy from thermal to energies in the hundreds of electron volts. The advantage of using an ion plating process such as EIP is the increased adhesion obtained by the high arrival energy of the ionized vapor. The increased adhesion of the metallization to glass provides a strong hermetic solder joint.

Other metallization techniques such as electroplating, sputtering, or evaporation may be applied to the solderable metallization layer 2.
6 may be used to form 6. However,
EIPs have been shown to offer advantages over other technologies, including low temperature, low metallization stress, excellent adhesion, thickness uniformity and processing methods with reduced complexity and variability. EI
Another advantage of P is that it provides a critical aperture size for optical elements by forming a metallization layer that provides fine line dimensions (size, tolerance).

The unprocessed solder body 22 is made of, for example, 80% gold and 2
Raw body of 0% tin or other similar ratio, eg 70
% To 90% gold and 30 to 10% tin green body. For example, a 0.05 mm (0.002 inch) thick blank is utilized to form a hermetic solder between the metallized optical glass and the metal frame 21 by infrared vacuum reflow heat treatment 33. Infrared vacuum reflow heat treatment,
By slowly increasing or decreasing the resulting peak temperature, it has the advantage of minimizing the stresses that appear during optical glass and solder bonding. Another advantage of infrared vacuum reflow over conventional belt furnaces is that voids in hermetic solder joints can be minimized. Therefore,
The sealability of the solder joint can be maximized.

The lid assembly consisting of optical glass and metal frame with metallized garment 26 is then attached to housing 20 by a local or cold hermetic seal process 34. One method of local low temperature hermetic sealing is the NDYag laser sealing system. The lid assembly is aligned with the metal seal ring on the housing and an end-to-end hermetic seal weld is made.
The laser produces a high temperature melting point source in the base metal,
The temperature of the thermo-sensitive optical element depends on the heat dissipation from the metal
It does not rise above the atmosphere. Another method of hermetically sealing the lid assembly to the housing is seam welding or projection welding.

FIG. 5 shows a second embodiment in which no metal frame is used. Polished optical glass (step 40)
Is used. The etched areas of the optical glass are metallized (step 41) and the unetched areas of the optical glass define openings (openings 23 in FIG. 3). Optical glass with a metallized pattern forms the lid assembly (step 42). The solder blank is not used in this embodiment because the lid assembly is sealed to the housing by the vacuum reflow process (step 43). This process of sealing the metal areas deposited on the optical glass to the housing requires higher temperatures than the process 34 of FIG. 4 and places some restrictions on the type of semiconductor device that can be used in this package. If heating is not a limitation, this method has the advantages of low cost and few processing steps.

FIG. 6 shows the assembled element of FIG.
A lid of optical glass 23 with an optical opening 25 is sealed to the package 20. The package 20 has a plurality of leads 20a extending from at least two side surfaces. The metal frame 21 is shown to be sealed between the glass 23 and the package 20.

With regard to the above description, the following items will be disclosed. (1) A method of manufacturing a semiconductor device package having an optical property window, which comprises providing a glass having an optical property, patterning a defined area on one surface of the glass, and the glass. A method as described above comprising the steps of depositing a metal layer on the patterned surface of, sealing the metal layer to a metal frame, and sealing the metal frame to a housing. (2) The method according to (1), wherein the attached metal layer is sealed to the metal frame by the unworked solder body. (3) The method according to (1), wherein the metal frame is sealed to the metal housing by local heating. (4) The method according to (1), wherein the metal frame is sealed to the metal housing by vacuum reflow. (5) The method according to item (1), wherein the deposited metal layer is selected from the group consisting of Cr, Ni and Au. (6) The attached metal layer is a metal ion plating layer,
The method according to item (1). (7) A method of manufacturing a semiconductor device package having an optical property window, comprising: polishing an optical property glass; etching a defined area on one surface of the glass; The foregoing method comprising depositing a metal layer on the etched surface, sealing the metal layer to a metal frame, and sealing the metal frame to a housing. (8) The method according to item (7), wherein the attached metal layer is sealed to the metal frame by the unworked solder body. (9) The method according to (7), wherein the metal frame is sealed to the metal housing by local heating. (10) The method according to (7), wherein the metal frame is sealed to the metal housing by vacuum reflow. (11) The method according to item (7), wherein the deposited metal layer is one of Cr, Ni and Au. (12) The attached metal layer is an ion plating layer,
The method according to item (7). (13) A semiconductor package having a window of optical properties, comprising a housing and an optical glass with a metallization pattern to be sealed to the housing plated between the optical glass and the housing. The semiconductor package described above, which is hermetically sealed. (14) The semiconductor package according to item (13), which has a metal frame between the optical glass and the housing. (15) The semiconductor package according to the item (14), wherein the metal frame and the housing are base metals. (16) A semiconductor package having a window of optical properties, a housing, an optical glass having a metallization pattern thereon, and a metal frame attached to the metallization pattern and the housing on the optical glass. And an optical glass and a semiconductor package having a metal frame that provides a hermetic seal between the metal frame and the housing. (17) The semiconductor package according to the item (16), wherein the metal frame and the housing are base metals. (18) A method of making a semiconductor package having an optical property window on a lid of a package fixed to a package base, comprising polishing an optical property glass window,
The above method comprising plating a metal pattern on the glass window and hermetically sealing the metal pattern to the package base at a low temperature. (19) The method according to item (18), wherein the plating step is achieved by an ion plating treatment. (20) The method according to item (18), wherein the plated glass window is sealed to the base metal frame, and the base metal frame is sealed to the package base. (21) The optical glass window 23 keeps the housing 20 at a low temperature.
Package fixed to and method of making it.
The optical glass window 23 is etched and a metal layer 26 is formed on the etched surface. The metal layer is sealed to the metal frame 21, and the frame is the housing 2
The metal layer 26, which is sealed or attached to zero, is directly sealed to the housing 20.

[Brief description of the drawings]

FIG. 1 is an exploded view of a prior art device providing a window of non-optical nature in a semiconductor package utilizing a high temperature glass frit.

FIG. 2 illustrates steps in a prior art method of providing a window of non-optical properties in a semiconductor package utilizing a high temperature glass frit.

FIG. 3a is an exploded view of a semiconductor package with an optical glass lid assembly according to one embodiment of the present invention. b shows a metallization layer on optical glass.

FIG. 4 illustrates steps of the method of the present invention for providing a semiconductor package with an optical quality lid assembly and sealing process.

FIG. 5 is a diagram showing another embodiment of the present invention.

FIG. 6 shows an assembled element with an optical property window made according to the invention shown in FIG. 3a.

[Explanation of symbols]

 20 Housing 21 Metal Frame 23 Optical Glass 25 Opening 26 Metal Layer

Claims (2)

[Claims] 1. A method of making a semiconductor device package having an optical property window, comprising providing a glass of optical property, patterning a defined area on one surface of the glass. A method as described above comprising depositing a metal layer on the patterned surface of the glass, sealing the metal layer to a metal frame, and sealing the metal frame to a housing. 2. A method of making a semiconductor device package having an optical property window, comprising: polishing an optical property glass; etching a defined area on one surface of the glass; A method as described above comprising depositing a metal layer on the etched surface of the glass, sealing the metal layer to a metal frame, and sealing the metal frame to the housing.