Package semiconductor device using chalcogenide glass sealing

A semiconductor device includes a package hermetically sealed with a chalcogenide-based glass sealing agent. A semiconductor element is housed within the package, and the respective electrodes of the semiconductor element are connected through bonding wires to leads extending to the outside of the package.

The present invention relates to a packaged semiconductor device and, more 
particularly, to a semiconductor device hermetically sealed in a package. 
Semiconductor elements are packaged to be placed under usable condition as 
well as to be protected from mechanical shocks and the external 
environment (humidity, contamination, temperature and the like) so as to 
improve the reliability. As one of the packaging techniques, it has been 
proposed to mount a semiconductor chip or pellet on which a predetermined 
circuit is formed to a base body of a package, to connect the electrodes 
of the semiconductor elements with the leads of the package and then to 
hermetically bond a lid body to the base body of the package with a 
bonding agent. As such a bonding agent, an oxide glass is known which 
contains lead oxide, boron trioxide and the like as main components, and 
further includes silicon oxide, titanium oxide, zirconium oxide, aluminum 
oxide and the like. 
When such an oxide glass is used as a bonding agent, bonding must be 
performed at a temperature higher than the glass transition point but 
lower than the melting point of the oxide glass. However, the glass 
transition point of the oxide glass is relatively high (for example, there 
is one with a glass transition point of over 300.degree. C.). This results 
in a considerably complicated sealing operation and damage to the 
semiconductor characteristics due to heat. Further, since bonding must be 
performed in an oxidizing atmosphere so as not to change the oxides 
constituting the glass, bonding wires tend to be degraded. With a 
conventional semiconductor device sealed with an oxide glass, a small 
electrical leak tends to be generated between the leads of the package, 
presenting problems in reliability. 
It is, therefore, the primary object of the present invention to provide a 
packaged semiconductor device which may be fabricated in a relatively 
simple manner and which has high reliability. 
A packaged semiconductor device of the present invention comprises: 
a base body of a package; 
a semiconductor element mounted on said base body; 
a lid body of said package for sealing said semiconductor element; 
a layer of a bonding agent hermetically sealing said base body and said lid 
body, said bonding agent including a glass of a chalcogenide of at least 
one element selected from the group consisting of IVA and VA group 
elements; and 
leads, each having one end connected to electrodes of said semiconductor 
element and the other end extending outside said package.

The present invention will now be described in more detail with reference 
to the accompanying drawings. 
FIGS. 1 to 3 show a case where the present invention is applied to a 
semiconductor device sealed in a CIRDIP type package. The same reference 
numerals designate the same parts in these FIGS. This semiconductor device 
has a package consisting of a ceramic base body 11 and a ceramic lid body 
13. As shown in FIG. 2 and particularly in FIG. 3, a recess 12 is formed 
at the center of the base body. A semiconductor element 15 with a 
predetermined circuit formed thereon is mounted inside this recess 12 with 
a bonding material 16 (FIG. 3) by a general bonding method such as 
soldering or resin bonding and in particular, by eutectic bonding. 
The lid body 13 has a recess 14 at the center for defining a space with the 
recess 12 of the base body 11 for housing the semiconductor element 15. 
Respective electrodes of the semiconductor element 15 are connected to 
respective one ends of external leads 18 with bonding wires 17 as shown in 
FIG. 3. The front ends of the external leads 18 protrude inside the space 
and contact the wires 17. The external leads 18 extend parallel to each 
other between the base body 11 and the lid body 13, and bend downward 
outside the base and lid bodies. These leads 18 are assembled with a frame 
19 (FIG. 2), which supports them and is formed integrally therewith. The 
frame 19 is cut away after assembly. 
In a semiconductor device of such a construction, the base body 11 and the 
lid body 13 are hermetically sealed with bonding agent layers 20. These 
bonding agent layers 20 fix the leads 18. According to the present 
invention, the bonding agent is a glass of a chalcogenide (i.e., sulfide, 
selenide, and/or telluride) of at least one element selected from the 
group consisting of IVA group elements (for example, silicon and 
germanium) and VA group elements (for example, arsenic). Such chalcogenide 
glass is described in A. R. Hilton et al, Physics and Chemistry of 
Glasses-, Vol. 7 [4]pp. 105-126, 1966 under the item "Non-oxide IVA-VA-VIA 
chalcogenide glasses". The chalcogenide glass is also described in H. 
Rawson, Inorganic Glass-Forming Systems pp. 249 -286, Academic Press, 1967 
under the item "Chalcogenide Glasses". 
Examples of such a chalcogenide glass are As-Se, As-S, Si-As-Te, AsS-AsSe, 
Si-As-Se, and Ge-As-Se. It is of course to be understood that each 
component is contained in a ratio suffucient to provide a glass. As an 
example, the glass region for the Si-As-Te system is shown in a phase 
equilibrium diagram plotted along triangular coordinates in FIG. 4. The 
area surrounded by the broken lines in FIG. 4 is the glassification 
region. The particularly preferable glasses for the purpose of the present 
invention are Si (10 to 20 atomic %) - As (30 to 50 atomic %) - Se or Te 
(remainder) glass, and Ge (10 to 15 atomic %) - As (30 to 50 atomic %) - 
Se or Te (remainder) glass 
Oxide glass components (e.g., As.sub.2 O.sub.3) may be added to such a 
chalcogenide glass in an amount of 0 mol % to 20 mol% based on the 
chalcogenide glass. 
For forming a semiconductor device using such a chalcogenide glass bonding 
agent, the semiconductor element 15 is mounted to the base body 11, and 
the respective electrodes and the leads 18 are connected. Then, a mixture 
of a chalcogenide glass powder and a binder is applied to the surface of 
the base body 11 except for the recess 12, and to the surface of the lid 
body 13 except for the recess 14. The layers of the mixture are superposed 
and kept at a temperature higher than the softening point but lower than 
the melting point of the glass for 5 to 15 minutes. The layers are 
gradually cooled thereafter. A semiconductor device 5 as shown in FIGS. 1 
and 3 is thus obtained. These chalcogenide glasses may be sealed at 
temperatures lower than 300.degree. C. in most cases, so that the 
semiconductor element may not be adversely affected. Further, since the 
sealing may be performed in a non-oxidizing atmosphere (e.g., N.sub.2), 
the electrical characteristics of the semiconductor element and the 
bonding wires may not be degraded. Furthermore, with a semiconductor 
device thus obtained, it has been confirmed that no electrical leaks occur 
and no problem of capacity (problem of soft error) by alpha-ray is caused 
with a D-RAM (dynamic random access memory). 
The present invention is also applicable to a frit seal type semiconductor 
device as shown in FIG. 5. Referring to the Fig., a base body 51 having a 
recess 52 is hermetically sealed with a lid body 53 using a chalcogenide 
glass 54. A semiconductor element 55 is mounted in the recess 52 of the 
base body 51, and its electrodes are connected to leads 57 with bonding 
wires 56. The leads 57 extend through and outside the base body 51.