Process for making microcomponents integrated circuits

A process for fabricating discrete electrical microcomponents, such as microtransformers, microautotransformers and microinductors, on a semiconductor substrate in which two patterned layers of electrically conductive material are electrically connected through vias in two interposed layers of electrically insulating material to form electrically conductive coils around a magnetic core formed by a patterned layer of magnetic material interposed between the two insulating layers. Laminated magnetic cores may be formed by patterning multiple layers of magnetic material. The microcomponents can also be formed without magnetic cores and can be formed on insulating substrates.

BACKGROUND OF THE INVENTION 
The present invention relates to integrated circuits and more particularly 
to microcomponents, such as microtransformers, microautotransformers and 
microinductors formed on substrates or as part of integrated circuits. 
Typically, discrete components such as inductors and transformers, are 
physically attached to an integrated circuit carrier and are electrically 
connected to the integrated circuit using standard wire bonding 
techniques. The problem with this arrangement is that relatively few 
discrete components can be used in connection with an integrated circuit. 
Accordingly, it is desirable to fabricate such components as part of the 
integrated circuit thereby increasing the density of such components and 
enabling them to be used in large numbers heretofore unavailable on VLSI 
integrated circuits. This will permit on-chip fabrication of integrated 
circuits, such as low pass, band pass and high pass filters, which require 
discrete components such as inductors; as well as on-chip fabrication of 
transformers and autotransformers which can be used to shift voltages and 
provide impedance matching on the chip. 
SUMMARY OF THE INVENTION 
A process for fabricating discrete electrical microcomponents such as 
microtransformers, microautotransformers and microinductors. The process 
includes the steps of disposing a layer of electrically insulating 
material over a semiconductor substrate having active devices disposed 
therein. Opening vias in the layer of insulating material to expose 
predetermined electrical contact areas on the underlying substrate. 
Disposing a first layer of electrically conductive material over the 
insulating layer into the vias contacting the exposed contact areas on the 
underlying substrate. Forming the first layer of electrically conductive 
material into a first predetermined pattern. 
Disposing a second layer of electrically insulating material over the first 
insulating layer and the patterned first metal layer. Disposing a first 
layer of a magnetic material on the second insulating layer. Forming the 
first layer of magnetic material into a predetermined pattern having a 
predetermined positional relationship with respect to the underlying 
patterned first layer of electrically conductive material. Disposing a 
third layer of electrically insulating material over the second layer of 
insulating material and the patterned first layer of magnetic material. 
Forming additional layers of patterned magnetic material and overlying 
insulating layers as required to reduce magnetic losses. 
Opening vias in the multiple layers of insulating material to expose 
predetermined electrical contact areas of the underlying patterned first 
electrically conductive layer. Disposing a second electrically conductive 
layer over the upper most insulating layer into the vias to contact the 
exposed electrical contact areas of the underlying patterned first 
electrically conductive layer. Forming the second electrically conductive 
layer into a second predetermined pattern having a predetermined spaced 
relationship with respect to the underlying patterned layer of magnetic 
material and the patterned first layer of electrically conductive 
material. Forming a final layer of electrically insulating material over 
the second patterned electrically conductive layer; then, if required by a 
particular application, opening contacts or vias to the second patterned 
electrically conductive layer to provide electrical access to the 
completed electrical component. 
An alternate embodiment of the process of the present invention includes 
the steps of disposing a layer of electrically conductive material over an 
insulating substrate. Forming the layer of electrically conductive 
material into a first predetermined pattern. Disposing a second layer of 
electrically insulating material over the first insulating layer and the 
patterned first metal layer then continuing on with the steps of disposing 
a first layer of a magnetic material on the second insulating layer and 
subsequent steps described above up to and including the steps of forming 
a final layer of electrically insulating material over the second 
patterned electrically conductive layer; then opening contacts or vias to 
the second metal layer and/or to the first metal layer to provide 
electrical access to the completed electrical component. The devices 
formed by this alternate embodiment of the present invention can then be 
electrically connected to other devices as desired. 
Depending upon the predetermined patterns of the first and second 
electrically conductive layers, the microcomponents formed by the process 
of the present invention can be, for example, microinductors, 
microtransformers and/or microautotransformers. In addition, although the 
above summary describes the fabrication of microcomponents having 
laminated magnetic cores, they can be fabricated with solid magnetic cores 
or without magnetic cores.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The various stages of the processing of a microtransformer on a integrated 
circuit in accordance with the present invention are depicted in FIGS. 1A 
through 1M. Referring now to FIG. 1A, there is schematically depicted, in 
cross section, a substrate 12, for example a silicon substrate having 
active devices (not shown) formed therein. It should be noted that the 
substrate 12 could be any type of material which could be used to make 
active devices, for example gallium arsenide or aluminum oxide. It should 
also be noted that substrate 12 could also comprise a substrate of 
insulating material for supporting the devices formed in accordance with 
the present invention. In this alternate embodiment of the present 
invention, the components formed as hereinafter described can be 
electrically connected to semiconductor devices and/or other components as 
necessary to construct the desired circuits. 
A layer 14 of insulating material, for example silicon dioxide, is formed 
over the silicon substrate 12, to a thickness preferably of about 10,000 
.ANG. (1 micron) preferably by plasma enhanced chemical vapor deposition 
(PECVD). At least one opening (not shown) is formed in the insulating 
layer 14 to expose predetermined electrical contact areas on the upper 
surface of the silicon substrate 12. The openings are preferably defined 
using a known photoresist method, then etched using an etchant which 
attacks the insulating material but which is unreactive with and stops at 
the underlying layer. In the embodiment where the microcomponents of the 
present invention are formed on an insulating substrate, neither the layer 
of insulating material 14 nor the openings in this layer are required. In 
such an embodiment, it is preferred that contacts to the microcomponents 
be made through the upper most insulating layer. A first layer 16 of an 
electrically conductive material, such as aluminum or a tungsten alloy, is 
formed over the first insulating layer 14 into the openings formed therein 
and into contact with the exposed contact areas, preferably by sputtering 
the aluminum to a predetermined thickness in the range of from about 3,000 
.ANG. to about 15,000 .ANG. (1.5) microns), preferably to a thickness of 
approximately 7,500 .ANG.. Referring now to FIG. 1B, the first 
electrically conductive layer 16 is formed into a predetermined pattern of 
electrically conductive segments 18 using, for example, known photoresist 
and etching techniques. FIG. 1C is a cross section through line C--C of 
FIG. 1B. 
Referring now to FIG. 1D, a second layer 20 of insulating material, for 
example silicon dioxide, is formed over the first insulating layer and the 
electrically conductive segments 18 to a thickness of approximately 10,000 
.ANG. preferably by PECVD. A first layer 22 of magnetic material, such as 
iron, nickel or an iron-nickel alloy, is disposed over the second 
insulating layer 20 to a thickness of approximately 5,000 .ANG. preferably 
by sputtering. The magnetic material could also be an insulating magnetic 
material such as, for example, a ferrite material which is useful for 
reducing losses at higher frequencies. The first layer of magnetic 
material 22 is formed into a predetermined pattern having a predetermined 
positional relationship with respect to the underlying segments 18 of 
electrically conductive material using, for example, known photoresist and 
etching techniques. One embodiment of this predetermined pattern 24 is 
depicted in FIG. 1E. As can be seen in FIG. 1E, the predetermined pattern 
24 of the magnetic material is preferably rectangular in shape. Two 
opposing sides of the rectangular shaped pattern 24 are positioned over 
the underlying segments 18 in substantially bisecting relationship 
thereto. The reason for this positional relationship between the patterned 
magnetic material 24 and the underlying segments 18 will become apparent 
later on in this detailed description. FIG. 1F is a cross sectional view 
taken along lines F--F of FIG. 1E. 
Referring now to FIG. 1G, a third electrically insulating layer 26, 
preferably comprising SiO.sub.2, is formed over the second electrically 
insulating layer 20 and the first patterned magnetic layer 24 preferably 
by PECVD to a thickness of layer 26 is approximately 10,000 .ANG.. 
Additional layers of patterned magnetic material are formed as required to 
reduce magnetic losses, each of which is formed preferably by sputtering 
and each of which has a thickness of approximately 5,000 .ANG.. Each layer 
of patterned magnetic material is covered by a layer of electrically 
insulating material, preferably SiO.sub.2. Each layer of electrically 
insulating material is preferably formed by PECVD to a thickness of 
approximately 10,000 .ANG.. in the embodiment depicted in FIG. 1G, there 
are three additional layers 28, 30 and 32 of patterned magnetic material; 
each of which has a layer of electrically insulating material, 34, 36 and 
38 respectively, formed thereover. The additional layers of patterned 
magnetic material each has substantially the same pattern and is 
substantially aligned with the underlying patterned magnetic material. 
Referring now to FIGS. 1H and 1I, vias 40 are opened through the insulating 
layers 20, 26, 34, 36 and 38 to expose electrical contact areas on the 
underlying patterned segments 18. The vias are opened using known 
photoresist and etching techniques. That is, for example, the openings are 
defined using a known photoresist method, then etched using an etchant 
which etches the insulating material but which stops on the surface of the 
underlying patterned segments 18. In those embodiments where the via 
openings are deep, for example, deeper than approximately 3 microns, the 
openings can be formed in each insulating layer following the formation of 
such layer or can be formed in groups of insulating layers (depending upon 
the thickness of each insulating layer) in order to prevent the etch depth 
from becoming excessive. The exposed electrical contact areas are 
preferably at the ends of the segments 18 for reasons which will become 
apparent later on in this detailed description. A nucleating layer of 
material, such as titanium/tungsten (TiW) is disposed over the sixth 
insulating layer 18 into the vias 40 and into electrical contact with the 
electrical contact areas exposed on the underlying segments 18. In the 
preferred embodiment, the nucleating layer is formed by sputtering the TiW 
material to a thickness of approximately 1,000 .ANG.. 
Referring to FIG. 1J, a second layer 42 of electrically conductive 
material, such as tungsten, is disposed over the nucleating layer 
previously disposed over the sixth insulating layer 38 into the vias 40 
and into electrical contact with the electrical contact areas exposed on 
the underlying segments 18 through the nucleating layer. The second layer 
42 is preferably formed by CVD to a thickness of approximately 7,500 
.ANG.. The second layer 42 of electrically conductive material is 
patterned into electrically conductive segments 44 as shown in FIGS. 1K 
and 1L, preferably using known photoresist and etching techniques. In the 
preferred embodiment shown in FIG. 1L, the end of each electrically 
conductive segment 44 terminates in an electrically conductive vertical 
member 46 which extends down through the via 40 into contact with the 
underlying electrically conductive segment 18. As shown in FIG. 1M, a 
layer 48 of electrically insulating material, such as silicon dioxide, 
phosphosilicate glass (PSG), undoped silicate glass (USG), or silicon 
nitride is disposed over the sixth layer 38 of insulating material and the 
electrically conductive segments 44 preferably by PECVD to a thickness of 
approximately one micron, to passivate the device from external attack. 
Referring now to FIG. 2, there is depicted, schematically in perspective, 
the transformer which has been formed in accordance with the method 
described above. As can be seen in FIG. 2, the transformer 100 comprises a 
primary segment 102 and a secondary segment 104. The primary segment 102 
comprises a plurality of coils 106 (two are shown for example in FIG. 2) 
each of which is formed by a portion of two electrically conductive 
segments 18, two vertically conductive members 46 and one electrically 
conductive segment 44. Each coil surrounds a portion of the patterned 
magnetic segments 24, 28, 30 and 32 as a result of the predetermined 
positional relationship between the patterned magnetic material and the 
underlying segments 18; the positioning of the vias 40; and the 
predetermined positional relationship between the segments 44, the vias 40 
and the underlying segments 18 as shown in FIGS. 1L-1M. The secondary 
portion 104 of the transformer 100 is formed of a plurality of coils 108 
(three are shown for example in FIG. 2) comprising portions of 
electrically conductive segments 18, vertical electrically conductive 
segments 46 and electrically conductive segments 44 which surround a 
portion of the patterned magnetic layers 24, 28, 30 and 32. 
Although, in the embodiment depicted in FIG. 2 there are two coils in the 
primary and three coils in the secondary, the electrically conductive 
layers 16 and 42 and the vias 40 can be patterned to accommodate different 
number of primary and secondary coils as required by the desired 
electrical characteristics of a particular transformer. It should also be 
noted that although the preferred embodiment described above includes a 
laminated core of magnetic material, the core could consist of a single 
layer of magnetic material or the transformer could be constructed without 
a core of magnetic material and these alternate embodiments are considered 
to be within the scope of contemplation of the present invention. It 
should be further noted that, although the process described in this 
detailed description utilizes thin film technology for constructing the 
inductive microcomponents, including microtransformers, 
microautotransformers and microinductors; in accordance with the present 
invention; thick film technology, for example forming the metal layers by 
plating, can also be effectively employed. 
The transformer depicted in FIG. 2 has been constructed such that the axis 
of primary and secondary coils are substantially parallel with respect to 
the surface of the underlying substrate. In this configuration, the 
transformer spreads out over the surface of the substrate and could occupy 
a relatively substantial portion of real estate of the integrated circuit 
depending upon the number of coils in the primary and/or secondary and/or 
the positional relationship between the primary and secondary. In order to 
conserve the area occupied by the device, it could be constructed such 
that the axes of the coils are substantially perpendicular to the surface 
of the underlying substrate, for example as shown schematically in 
perspective in FIG. 3. In the configuration depicted in FIG. 3, the axis 
of the primary coils 106 and the secondary coils 108 are substantially 
perpendicular to the underlying substrate (not shown). Two segments, 110 
and 112, of the magnetic core 114 extend through the primary 106 and 
secondary 108 coils respectively in a direction which is substantially 
perpendicular to the underlying substrate. The other two segments, 116 and 
118 of the coil 114 connect the first two segments 110 and 112 and extend 
in a direction which is substantially parallel to the underlying 
substrate. 
The various stages of the processing of a microtransformer on an integrated 
circuit in accordance with the embodiment of the present invention 
depicted in FIG. 3 are shown in FIGS. 4A through 4R. The methods employed 
for forming the various layers, the thicknesses of the layers, and the 
methods employed for forming the vias and the predetermined patterns in 
the electrically conductive and magnetic layers are preferably the same as 
those described above in connection with FIGS. 1A-1M. Referring now to 
FIG. 4A, there is schematically depicted, in cross section, a substrate 
412, for example a silicon substrate having active devices (not shown) 
formed therein. The substrate 412 can be any type of material which could 
be used to make active devices for example, silicon or gallium arsenide; 
or just a passive substrate like aluminum oxide. It should be noted that 
substrate 412 could also comprise a substrate of insulating material for 
supporting the devices formed in accordance with the present invention. In 
this alternate embodiment of the present invention, the components formed 
can be electrically connected to semiconductor devices and/or other 
components as necessary to construct the desired circuits. 
A layer 414 of insulating material, for example silicon dioxide, is formed 
over the silicon substrate 412. In the embodiment where the microdevices 
of the present invention are formed on an insulating substrate, the layer 
414 of insulating material is not required. A first layer 416 of magnetic 
material, such as iron, nickel or an iron-nickel alloy, is disposed over 
the first insulating layer 414. The magnetic material could also be an 
insulating magnetic material such as, for example, a ferrite material 
which is useful for reducing losses at higher frequencies. The first layer 
of magnetic material 416 is formed into a predetermined pattern having a 
predetermined positional relationship with respect to the underlying 
active devices (not shown) using, for example, known photoresist and 
etching techniques. One form of this predetermined pattern is shown in 
plan view in FIG. 4B and in cross sectional view in FIG. 4C. The segments 
418 of the predetermined pattern of magnetic material each forms a lower 
segment of a magnetic core corresponding to segment 118 of the transformer 
depicted in FIG. 3. 
Referring now to FIG. 4D and to FIG. 4E, which is a cross section of FIG. 
4D through lines E--E, a second electrically insulating layer 420 is 
formed over the first electrically insulating layer 414 and the first 
patterned magnetic layer 418. Openings, or vias 422, are formed in the 
electrically insulating layers 414 and 420 to expose predetermined 
electrical contact areas on the upper surface of the silicon substrate 
412. The vias 422 are formed using, for example, known photoresist and 
etching techniques. A first layer 424 of an electrically conductive 
material, such as aluminum, is formed over the second insulating layer 420 
into the vias 422 and into contact with the exposed contact areas on the 
surface of the semiconductor substrate 412. 
Referring now to FIG. 4G and to FIG. 4H which is a cross section of FIG. 4G 
through lines H--H, the first electrically conductive layer 424 is formed 
into a predetermined pattern of segments 426 using, for example, known 
photoresist and etching techniques. The segments 426 form a portion of the 
bottom coil 108 of the transformer depicted in FIG. 3. A third 
electrically insulating layer 428 is formed over the segments 426 and the 
second electrically insulating layer 420. Vias 430 are formed in the third 
electrically insulating layer 428 to expose contact areas on the 
underlying segments 426; for example, at one end of each segment 426 as 
shown in FIGS. 4G and 4H. The vias 430 are formed using, for example, 
known photoresist and etching techniques. 
A second layer of an electrically conductive material such as aluminum, is 
formed over the fourth insulating layer 428 into the vias 430 and into 
contact with the exposed areas on the underlying segments 426. The second 
electrically conductive layer is formed into a predetermined pattern of 
segments 432, as shown in FIG. 4I and in FIG. 4J which is a cross section 
of 4I taken along lines J--J. The predetermined pattern of segments 432 is 
formed using, for example, known photoresist and etching techniques. A 
fourth insulating layer 434 is formed over the segments 432 and the third 
insulating layer 428. Vias 436 are formed in the fourth insulating layer 
434 exposing contact areas on the underlying segments 432. The vias 436 
are formed using, for example, known photoresist and etching techniques. 
Each segment 432 corresponds to a segment of the lower coil 108 of a 
transformer of the type depicted in FIG. 3. 
Referring now to FIG. 4K and to FIG. 4L which is a cross section of FIG. 4K 
taken along lines L--L, a third layer of an electrically conductive 
material, such as aluminum, is formed over the fourth insulating layer 434 
into the vias 436 into contact with the exposed areas on the underlying 
segments 432. The third electrically conductive layer is formed into a 
predetermined pattern of electrically conductive segments 438 and 444 
using, for example, known photoresist and etching techniques. Each of the 
segments 438 corresponds to a portion of the middle coil 108 of the 
secondary of the microtransformer depicted in FIG. 3. Each of the segments 
440 corresponds to a portion of the lower coil 106 of the primary of the 
microtransformer depicted in FIG. 3. This process is continued until 
segments which correspond to portions of the top coils of the primary and 
secondary coils of the microtransformer, for example, the top coils of the 
primary 106 and secondary 108 of the microtransformer depicted in FIG. 3 
have been constructed. A top layer 446 (see FIGS. 4M and 4N) of 
electrically insulating material such as silicon dioxide is formed over 
the segments corresponding to the top coils of the primary 106 and 
secondary 108 of the microtransformer depicted in FIG. 3. 
Referring to FIG. 4M and to FIG. 4N which is a cross section of FIG. 4M 
taken along lines N--N, vias 448 are formed through the insulating layers 
446 down through 420 to expose contact areas on the underlying segments 
418 of magnetic material, preferably at the ends of each segment 418. In 
those embodiments where the vias 448 are deep, for example deeper than 
approximately 3 microns, the vias 448 can be formed in each insulating 
layer following the formation of such layer or can be formed in groups of 
insulating layers (depending upon the thickness of each insulating layer) 
in order to prevent the etch depth from becoming excessive. 
A second layer of magnetic material, preferably the same material as that 
of the first layer 416 of magnetic material, is formed over the top 
insulating layer 446 into the vias 448 in contact with the exposed areas 
of the underlying magnetic segments 418. Once again, if the number and 
thickness of the overlying insulating layers is such that formation of the 
magnetic material into the vias 448 and into contact with the underlying 
segments 418 becomes difficult or impractical, segments of the vertical 
portions (posts) of magnetic material can be formed into vias which are 
formed into individual insulating layers of groups of insulating layers 
depending upon the thicknesses. The second layer of magnetic material is 
formed into a predetermined pattern having a predetermined positional 
relationship with respect to the vertical segments (posts) of magnetic 
material and the underlying segments 418 of magnetic material such that 
resultant is a closed core of magnetic material as shown FIG. 40 and in 
FIG. 4P which is a cross section of FIG. 40 taken through lines P--P. 
Referring now to FIG. 4Q and to FIG. 4R which is a cross section of FIG. 4Q 
taken through lines R--R, a final layer 454 of electrically insulating 
material such as silicon dioxide is formed over the top insulating layer 
446 and the magnetic segments 450. Vias 456 are formed in the final 
insulating layer 454 to expose contact areas on the underlying segments of 
the top coils of the microtransformers. A final layer of electrically 
conductive material, for example aluminum, is. formed over the final 
insulating layer 454 into the vias 456 into contact with the exposed areas 
on the underlying segments. The final layer of electrically conductive 
material can be etched back to the surface of the final insulating layer 
454 in order to form contact posts 458, the tops of which are 
substantially co-planar with the surface of final layer 454. However, it 
is preferred that the final electrically conductive layer be patterned and 
formed into interconnects as desired to interconnect the microtransformers 
and/or other devices. 
Referring now to FIG. 5, there is shown an alternate embodiment of a 
microtransformer in accordance with the present invention, generally 
designated 300. The microtransformer 300 comprises a plurality of primary 
coils. Two primary coils 302 and 304 are shown for example in FIG. 5. In 
the configuration depicted in FIG. 5, the first primary coil 302 comprises 
an upper horizontal segment 306; a first vertical segment 308; a lower 
horizontal segment 310; and a second vertical segment 312. Similarly, the 
second primary coil 304 comprises an upper horizontal segment 314; a first 
vertical segment 316; a lower horizontal segment 318; and a second 
vertical segment 320, all of which are electrically connected in series. 
Accordingly, the electrical circuit between the upper portion of the 
second vertical segment 320, designated electrical contact 322; and the 
end of the upper horizontal segment 306 opposite the end electrically 
contacting the upper portion of the vertical segment 308, designated 
electrical contact 324, includes two electrically conductive loops which 
surround, in the embodiment depicted in FIG. 5, a magnetic core 326. 
The secondary portion of the exemplary transformer 300 depicted in FIG. 5 
comprises three secondary coils 328, 330 and 332. The first secondary coil 
328 comprises an upper horizontal segment 334; a first vertical segment 
336; a lower horizontal segment 338; and a second vertical segment 340. 
The second secondary coil 330 comprises an upper horizontal segment 342; a 
first vertical segment 344; a lower horizontal segment 346; and a second 
vertical segment 348. The third secondary coil 332 comprises an upper 
horizontal segment 350; a first vertical segment 352; a lower horizontal 
segment 354; and a second vertical segment 356. All of the aforementioned 
segments are electrically connected in series. Accordingly, the electrical 
circuit between the upper portion of the second vertical segment 356 of 
the third secondary coil 332, designated electrical contact 358; and the 
end of the upper horizontal segment 334 of the first secondary coil 328 
opposite the first vertical segment 336, designated electrical contact 
360, comprises three coils which surround the magnetic core 326. It should 
be noted that the magnetic core 326 could be a solid piece or could 
comprise a lamination of layers of magnetic materials as previously 
described and depicted in FIG. 2; and could also take the form of a closed 
loop and such configurations are considered within the scope and 
contemplation of the present invention. Furthermore, the magnetic core 326 
could be eliminated entirely and such is also considered to be within the 
scope contemplation of the present invention. 
Referring now to FIG. 6, there is shown an autotransformer in accordance 
with the present invention, generally designated 600. The autotransformer 
600 comprises a plurality of primary coils 602 and secondary coils 604. 
The primary coils 602 and secondary coils 604 are inductively coupled by 
means of a magnetic core 606. The autotransformer 600 is constructed in 
accordance with the present invention using the process described with 
respect to construction of the microtransformers depicted in FIGS. 2 and 
3. The magnetic core 606 can either be a solid magnetic core or it can be 
laminated as previously described in the detailed description. The 
autotransformer 600 can be constructed on a semiconductor substrate having 
active devices formed therein or can be formed on an insulating substrate 
as previously described in this detailed description. 
In operation as a step down transformer, an alternating voltage is applied 
across contact points 608 and 610 of the primary coil 602. Secondary 
voltages can be tapped from the autotransformer 600 at different locations 
depending upon the ratio of the secondary voltage to the primary voltage 
desired. For example, the secondary voltage between contact points 612 and 
614 of the secondary coils 604 will have a magnitude which is one-quarter 
the magnitude of the voltage input across the primary coils between 
contact points 608 and 610. Similarly the voltage output between contact 
points 612 and 616 of the secondary coils 604 will be one-half the 
magnitude of the primary voltage across contacts 608 and 610. The voltage 
across contact points 618 and 612 of the secondary coils 604 will have a 
magnitude which is three-quarters the magnitude of the primary voltage 
applied across contacts 608 and 610. The magnitude of the voltage across 
contact points 612 and 620 of the secondary coils 604 will be 
substantially equal to the magnitude of the voltage applied across contact 
points 608 and 610 of the primary coils. In operation as a step up 
transformer, the input voltage can be applied across the transformer taps 
as desired to obtain the desired output voltage across contact points 608 
and 611. 
Although the above detailed description sets forth the preferred embodiment 
of the process for fabricating microtransformers and 
microautotransformers, it is apparent to those skilled in the art that 
microinductors, with or without magnetic cores, can also be constructed 
using the process of the present invention, and such is considered to be 
within the scope and contemplation of the present invention. For example, 
either the primary segment 102 or the secondary segment 104 of the 
transformer 100 depicted in FIG. 2 could be a micro inductor having a 
magnetic core which is disposed only within the coils of either the 
primary segment 102 or the secondary segment 104; or each could be a micro 
inductor without any core material within their respective coils at all. 
It will be understood that various changes in the details, materials and 
arrangements of the parts which have been described and illustrated in 
order to explain the nature of this invention may be made by those skilled 
in the art without departing from the principle and scope of the invention 
as expressed in the claims.